阅读说明：本技术 异形溅射靶及其制备方法 (Special-shaped sputtering target and preparation method thereof ) 是由 林世遥 斯蒂芬·费拉泽 金在研 弗兰克·C·奥尔福德 于 2018-04-17 设计创作，主要内容包括：本发明公开了一种溅射靶,该溅射靶包括溅射材料并且在通过在溅射系统中使用进行侵蚀之前具有非平面溅射表面,该非平面溅射表面具有圆形形状并且包括中心轴线区域,该中心轴线区域在中心轴线区域处包括凹曲率特征部。中心轴线区域在通过在溅射系统中使用至少1000kWhr进行侵蚀之后具有磨损轮廓,该磨损轮廓包括隆起,该隆起包括具有第一斜率的第一外周边磨损表面。在同时溅射使用之后的基准靶的基准突出凸曲率特征部包括具有第二斜率的第二外周边磨损表面。隆起相对于基准突出凸曲率特征部提供具有减小的遮蔽的溅射靶,其中第一斜率比第二斜率较不陡峭。(A sputtering target includes a sputtering material and has a non-planar sputtering surface prior to erosion by use in a sputtering system, the non-planar sputtering surface having a circular shape and including a central axis region including a concave curvature feature at the central axis region. The central axis region has a wear profile after erosion by use of at least 1000kWhr in a sputtering system, the wear profile including a protuberance including a first outer peripheral wear surface having a first slope. The datum protruding convex curvature feature of the datum target after simultaneous sputtering use includes a second outer peripheral wear surface having a second slope. The protuberance protrudes relative to the reference convex curvature feature to provide the sputtering target with reduced shadowing, wherein the first slope is less steep than the second slope.)

1. A sputtering target comprising a sputtering material and having a non-planar sputtering surface prior to erosion by use in a sputtering system, the non-planar sputtering surface having a circular shape and comprising:

A central axis region having a central axis;

A concave curvature feature at the central axis region, the concave curvature feature symmetrically disposed about the central axis and having a first point that coincides with the central axis, the concave curvature feature corresponding to a reference protruding convex curvature feature of an erosion profile of a reference sputtering target and coinciding with the central axis after erosion by use of at least 1000 kwr in a sputtering system, the reference sputtering target comprising a sputtering material having the same composition as the sputtering material of the sputtering target, the reference sputtering target further comprising a planar sputtering surface prior to erosion by use in a sputtering system;

The central axis region has a wear profile after erosion by use of at least 1000kWhr in a sputtering system, the wear profile comprising a crown comprising a first height and a first outer peripheral wear surface having a first slope, and the reference convex curvature feature comprises a second height and a second outer peripheral wear surface having a second slope, the crown providing a sputtering target with reduced shadowing relative to the reference convex curvature feature, wherein:

The first height is less than the second height, the datum protruding convex curvature feature having the second height, the second height blocking more sputtered atoms having trajectories directed radially inward toward the central axis and redepositing onto the target; and the number of the first and second electrodes,

The first slope is less steep than the second slope, the second outer peripheral wear surface having the second slope directing more sputtered atoms having trajectories radially outward away from the wafer relative to the central axis.

2. a method of designing a sputtering target for use in a sputtering chamber, the method comprising:

Forming a sputter target having a surface profile with concave curvature features symmetrically about a central axis of the sputter target;

Measuring a sputtering profile of the sputtering target after sputtering at least 1000kWhr in a sputtering chamber;

Designing a modified surface profile based on the measurement of the sputtering profile to reduce shadowing at a central axis region of the sputtering target; and

Forming a modified sputter target having said modified surface profile.

3. The method of claim 2, further comprising measuring a sputtering profile of a reference sputtering target after using at least 1000kWhr, the reference sputtering target comprising a sputtering material having the same composition as the sputtering material of the sputtering target, the reference sputtering target further comprising a planar sputtering surface prior to erosion by use in a sputtering system, wherein:

The measured sputtering profile of the sputtering target comprises a first outer peripheral wear surface having a first slope; and is

The measured reference sputter target comprises a second peripheral wear surface having a second slope, wherein said first slope is less steep than said second slope.

4. A sputter target according to claim 1 or a method according to claim 3, wherein the percentage reduction between the first slope and the second slope is at least about 40%.

5. The sputter target of claim 1, said central axis region further comprising a total target thickness at said central axis, wherein said total target thickness is about 10% to about 30% less than a total target thickness at said central axis of said baseline sputter target comprising said planar sputtering surface prior to erosion.

6. The sputter target of claim 1 or the method of claim 2, wherein the sputter target further comprises at least one concave groove in the surrounding area.

7. A sputter target according to claim 1 or a method according to claim 2, wherein the sputter material comprises at least one material selected from the group consisting of Ti, Al, Cu, Ta, Ni, Co, Mo, Au, Ag, Pt, W, Cr, Ti alloys, Al alloys, Cu alloys, Ta alloys, Ni alloys, Co alloys, Mo alloys, Au alloys, Ag alloys, Pt alloys, W alloys and Cr alloys.

8. A sputter target according to claim 1 or a method according to claim 2, wherein the target is monolithic.

9. A sputter target according to claim 1 or a method according to claim 2, wherein the target is diffusion bonded.

10. The method of claim 2, wherein the steps of measuring, designing and forming a modified sputter target are repeated to optimize the modified surface profile.

Technical Field

The field of the present subject matter is the design and use of sputtering systems that include targets having a central axis zone geometry to provide longer target life and uniform film deposition.

Description of the Related Art

Electronic and semiconductor components are used in an increasing number of consumer and commercial electronic products, communication products and data exchange products. Examples of some of these consumer and commercial products are televisions, computers, mobile phones, pagers, handheld organizers, portable music players and radios, car stereos, and remote controls. As the demand for these consumer and commercial electronic devices increases, there is also a need for these same products to become smaller and more portable for consumers and businesses.

As the size of these products decreases, the components that make up the products must also become smaller and/or thinner. Examples of some of those components that need to be reduced in size or scaled down are microelectronic chip interconnects, semiconductor chip components, resistors, capacitors, printed circuit boards or wiring boards, wires, keyboards, touch pads, and chip packages.

As the size of electronic and semiconductor components is reduced or scaled down, any defects present in the larger components will be magnified in the scaled down components. Thus, defects that are or may be present in larger components should be identified and corrected, if possible, before the components are scaled down for smaller electronic products.

In order to identify and correct defects in electronic parts, semiconductor parts and communication parts, the materials used and the manufacturing processes for preparing these parts should be decomposed and analyzed. In some cases, electronic components, semiconductor components, and communication/data exchange components are composed of layers of materials, such as metals, metal alloys, ceramics, inorganic materials, polymers, or organometallic materials. The material layers are typically thin (on the order of less than a few tens of angstroms thick). To improve the quality of a layer of material, the process of forming the layer (such as physical vapor deposition of a metal or other compound) should be evaluated and, if possible, modified and improved.

To improve the process of depositing a layer of material, it is necessary to measure, quantify the surface and/or material composition, and detect defects or flaws. In the case of depositing one or more layers of material, not the actual layer or layers of material that should be monitored, but the material used to create the layer of material on the substrate or other surface and the surface of that material. For example, when a layer of a metal is deposited onto a surface or substrate by sputtering a target containing the metal, atoms and molecules deflected or released from the target must travel a path to the substrate or other surface that will allow for uniform and consistent deposition. Atoms and molecules that travel natural and desired paths after deflection and/or release from the target may be unevenly deposited on the surface or substrate, including grooves and pores in the surface or substrate. For certain surfaces and substrates, it may be necessary to redirect atoms and molecules away from the target in order to obtain a more uniform deposition, coating and/or film on the surface or substrate.

In DC magnetron sputtering systems, the accumulation of insulating layers on poorly eroded racetrack tracks and the subsequent arcing of such layers is an important issue for both process engineers and target manufacturers. Due to the nature of the magnet configuration, well-eroded and poorly-eroded "racetrack" were developed. On a poorly eroded racetrack, the insulating layer slowly accumulates with the use of the target (i.e., oxide or nitride films of Al, Ta, and Ti targets). Eventually, the charge buildup on the dielectric layer leads to arcing and particle generation. The tendency to arcing increases with target use due to the accumulation of dielectric layers.

A schematic view of a portion of an exemplary physical vapor deposition apparatus 10 is shown in fig. 1. The sputtering assembly 10 includes a backing plate 12 having a sputtering target 14 bonded thereto. Sputtering target 14 has a planar sputtering surface 16. A wafer 18 of semiconductor material is located within the assembly 10 and is disposed spaced apart from the sputtering surface 16 of the target 14. In operation, particles or sputtered material 22 are displaced from the surface 16 of the target 14 and used to form a coating (or film) 20 on the wafer 18.

Typically, the target forms part of a cathode assembly containing a process gas, such as argon, in a PVD chamber. An electric field is applied in the chamber between the cathode assembly and the anode (typically the sidewall of the PVD apparatus) and, as a result, the gas is ionized by collisions with electrons ejected from the surface of the cathode. This generates a plasma of positively charged gas ions accelerated towards the negatively charged target surface. The positive gas ions affect the target and dislodge particles from the target material. Once released from the target, these displaced (and substantially neutral) particles travel through the plasma and deposit themselves as a thin film on the wafer substrate.

There are several important parameters that control the effectiveness of sputtering. These parameters include uniformity and reflectivity of the deposited film, the number of defects (foreign particles) on the substrate, the deposition rate, current-voltage (I-V) characteristics during deposition, and target lifetime.

Deposition by sputtering may be non-uniform for various reasons. The plasma density can be influenced by the geometry of the PVD apparatus. The magnetic field may vary non-uniformly due to variations between magnets that are in motion or in a magnet to target relationship. Finding the optimal placement and rotation speed of the magnets behind the back of the target to affect the path taken by the electrons within the sputtering chamber, increase the rate of gas impingement and achieve better sputtering rates and uniformity of the deposited film can be challenging. In some cases, temperature variations at different locations on the target and grain size and texture of the target material can also lead to non-uniform deposition.

generally, atoms are ejected from the target surface with a wide angular distribution. However, collisions with other particles and gas scattering randomize the trajectory of the atoms, since the average path of the ejected metal atoms is small relative to the total travel distance between the target and the wafer. Therefore, low pressure (high vacuum) has been implemented to limit the number of collisions and reduce randomization.

Another source of non-uniform deposition arises from the changing shape of the target surface as the target is eroded away during sputtering. This erosion profile can also be affected by magnet placement and movement. Conventional target designs at the beginning of life typically include a planar surface geometry at the center of the sputtering target, as shown in fig. 1. There is a need to extend target life to improve film uniformity.

Disclosure of Invention

These and other needs are addressed by the various aspects, embodiments, and configurations of the present disclosure.

Embodiments of the present disclosure include a sputtering target comprising a sputtering material and having a non-planar sputtering surface prior to erosion by use in a sputtering system, the non-planar sputtering surface having a circular shape and comprising: a central axis region having a central axis; a concave curvature feature at a central axis region, the concave curvature feature being symmetrically disposed about the central axis and having a first point that coincides with the central axis, the concave curvature feature corresponding to a reference protruding convex curvature feature of an erosion profile of a reference sputtering target after erosion by use of at least 1000kWhr in the sputtering system and coinciding with the central axis, the reference sputtering target comprising a sputtering material having the same composition as the sputtering material of the sputtering target, the reference sputtering target further comprising a planar sputtering surface before erosion by use in the sputtering system; the central axis region has a wear profile after erosion by use of at least 1000kWhr in a sputtering system, the wear profile comprising a crown comprising a first height and a first outer peripheral wear surface having a first slope, and the reference protruding convex curvature feature comprises a second height and a second outer peripheral wear surface having a second slope, the crown providing a sputtering target with reduced shadowing relative to the reference protruding convex curvature feature, wherein: the first height is less than the second height, the datum protruding convex curvature feature has a second height that blocks more sputtered atoms that have trajectories directed radially inward toward the central axis and are redeposited onto the target; and, the first slope is less steep than the second slope, the second outer peripheral wear surface having a second slope that directs more sputtered atoms having trajectories away from the wafer radially outward relative to the central axis.

The sputtering target of paragraph [0016], wherein the percentage reduction between the first slope and the second slope is at least about 40%.

the sputtering target according to any of paragraphs [0016] or [0017], wherein the percentage reduction between the first slope and the second slope is from about 40% to about 100%.

The sputtering target of any one of paragraphs [0016] - [0018], the central axis region further comprising a total target thickness at the central axis, wherein the total target thickness is about 10% to about 30% less than a total target thickness at the central axis of a baseline sputtering target comprising the planar sputtering surface prior to erosion.

The sputtering target of any one of paragraphs [0016] - [0019], wherein the total target thickness is about 15% to about 25% less than the total target thickness of the baseline sputtering target at the central axis.

The sputtering target according to any one of paragraphs [0016] - [0020], wherein the sputtering target further comprises at least one concave groove in the peripheral region.

the sputtering target according to any one of paragraphs [0016] - [0021], wherein the sputtering material comprises at least one material selected from the group consisting of Ti, Al, Cu, Ta, Ni, Co, Mo, Au, Ag, Pt, W, Cr, Ti alloy, Al alloy, Cu alloy, Ta alloy, Ni alloy, Co alloy, Mo alloy, Au alloy, Ag alloy, Pt alloy, W alloy, and Cr alloy.

The sputtering target according to any one of paragraphs [0016] to [0022], wherein the target is monolithic.

The sputtering target according to any one of paragraphs [0016] - [0023], wherein the target is diffusion bonded.

Embodiments of the present disclosure also include a method of designing a sputtering target for use in a sputtering chamber, the method comprising: forming a sputtering target having a surface profile with concave curvature features symmetrically about a central axis of the sputtering target; measuring a sputtering profile of the sputtering target after sputtering at least 1000kWhr in the sputtering chamber; designing a modified surface profile based on the measurement of the sputtering profile to reduce shadowing at the central axis region of the sputtering target; and forming a modified sputtering target having a modified surface profile.

The method of paragraph [0025], further comprising: measuring a sputtering profile of a reference sputtering target after using at least 1000kWhr, the reference sputtering target comprising a sputtering material having the same composition as the sputtering material of the sputtering target, the reference sputtering target further comprising a planar sputtering surface prior to erosion by use in a sputtering system, wherein: the measured sputtering profile of the sputtering target includes a first outer peripheral wear surface having a first slope; and, the measured reference sputtering target includes a second peripheral wear surface having a second slope, wherein the first slope is less steep than the second slope.

The method of any of paragraphs [0025] or [0026], wherein the percentage reduction between the first slope and the second slope is at least about 40%.

The method of any of paragraphs [0025] to [0027], wherein the steps of measuring, designing, and forming a modified sputtering target are repeated to optimize the modified surface profile.

Embodiments of the present disclosure include a sputtering target comprising a sputtering material having a non-planar sputtering surface prior to erosion by use in a sputtering system, the non-planar sputtering surface having a circular shape and comprising: a central axis region having a central axis; the central axis region comprises at least one non-protruding concave curvature feature symmetrically disposed about the central axis and having a first point coincident with the central axis, the at least one non-protruding concave curvature feature corresponding to a reference protruding convex curvature feature of an erosion profile of a reference sputtering target and coincident with the central axis after erosion by use in the sputtering system, the reference sputtering target comprising a sputtering material having the same composition as the sputtering material of the sputtering target, the reference sputtering target further comprising a planar sputtering surface prior to erosion by use in the sputtering system; a line perpendicular to the central axis and collinear with a reference sputter target planar sputter surface prior to erosion by use in a sputtering system; a first point at a first axial distance from the line; a peripheral region disposed around the central axis region; the surrounding area comprises a second point coinciding with the line and at a first radial distance from the central axis; the central axis region has a wear profile after erosion by use in a sputtering system, the wear profile including a protuberance having a third point coincident with the central axis and at a second axial distance from the axis and a fourth point at a first radial distance from the central axis and at a third axial distance from the axis, wherein the third axial distance is greater than or equal to the first axial distance and greater than or equal to the second axial distance.

The sputter target of paragraph [0029], wherein the reference sputter target has a wear profile after use, the wear profile including a fifth point coincident with the central axis at a fourth axial distance from the line, wherein the first and second axial distances are greater than the fourth axial distance.

The sputtering target according to any one of paragraphs [0029] or [0030], wherein the bulge comprises a first outer peripheral wear surface having a first slope and the datum protruding convex curvature feature comprises a second outer peripheral wear surface having a second slope, wherein the first slope is less steep than the second slope.

the sputtering target of any one of paragraphs [0029] - [0031], wherein the at least one non-protruding concave curvature feature comprises an inner peripheral surface and a bottom surface comprising a first point.

The sputtering target according to any one of paragraphs [0029] - [0032], wherein the bottom surface is flat, rounded, concave, or convex.

The sputtering target of any one of paragraphs [0029] - [0033], wherein the sputtering target has an overall target radius and an overall target thickness, wherein relative to the overall target radius, the first radial distance is from about 5% to about 40%, and the first axial distance is from about 5% to about 50% of the overall target thickness.

The sputtering target according to any one of paragraphs [0029] - [0034], wherein the sputtering material comprises at least one material selected from the group consisting of Ti, Al, Cu, Ta, Ni, Co, Mo, Au, Ag, Pt, W, Cr, Ti alloy, Al alloy, Cu alloy, Ta alloy, Ni alloy, Co alloy, Mo alloy, Au alloy, Ag alloy, Pt alloy, W alloy, and Cr alloy.

Drawings

The accompanying drawings are incorporated in and form a part of the specification to illustrate several examples of the present disclosure. The drawings together with the description serve to explain the principles of the disclosure. The drawings simply illustrate preferred and alternative examples of how the disclosure may be made and used, and should not be construed as limiting the disclosure to only the examples shown and described. Additional features and advantages will become apparent from the following more detailed description of various aspects, embodiments, and configurations of the present disclosure, as illustrated below with reference to the accompanying drawings.

FIG. 1 is a schematic view of a portion of an exemplary physical vapor deposition apparatus 10.

FIG. 2 is a schematic diagram showing a system using a collimator as shown in the prior art at the beginning of target life (BOL) and at the end of target life (EOL).

Figure 3 is a surface profile of a prior art sputtering target after about 2000kWhr use.

Figure 4A is a profile at BOL of a sputtering target having a modified profile at a central region of the target according to one embodiment of the present disclosure.

Figure 4B is a surface profile of the sputtering target of figure 4A after about 1500kWhr sputtering use.

figure 5 is a surface profile of a prior art sputtering target after 1500kWhr use.

Figure 6 is a surface profile of a sputtering target having a modified profile at the central region after about 1500kWhr use.

Fig. 7 is a flow diagram illustrating a method for forming a target including a modified central axis region according to an embodiment of the present disclosure.

Figure 8 illustrates a sputtering target having a modified profile according to one embodiment of the present disclosure.

Figure 9 shows a surface profile of the sputtering target of figure 8 before and after use in 3950kWhr sputtering according to one embodiment of the present disclosure.

Fig. 10A shows the surface profile of the reference target and the modified profile shown in fig. 8 and a comparative surface profile of the reference target and the modified profile after 3000kWhr sputtering use.

Fig. 10B shows the surface profile of the reference target and the modified profile shown in fig. 8 and a comparative surface profile of the reference target and the modified profile after 3500kWhr sputtering use.

Fig. 10C shows the surface profile of the reference target and the modified profile shown in fig. 8 and a comparative surface profile of the reference target and the modified profile after 3950kWhr sputtering use.

figure 11A illustrates a surface profile and a prior art profile of a sputtering target having a modified profile according to one embodiment of the present disclosure prior to sputtering use.

Figure 11B shows the surface profile of the sputtering target of figure 10A before and after use in 3950kWhr sputtering.

Fig. 12A shows the surface profile of the reference target and the modified profile shown in fig. 11A and a comparative surface profile of the reference target and the modified profile after 3000kWhr sputtering use.

Fig. 12B shows the surface profile of the reference target and the modified profile shown in fig. 11A and a comparative surface profile of the reference target and the modified profile after 3500kWhr sputtering use.

Fig. 12C shows the surface profile of the reference target and the modified profile shown in fig. 11A and a comparative surface profile of the reference target and the modified profile after 3950kWhr sputtering use.

figure 13 illustrates a sputtering target having a modified profile and a baseline profile according to another embodiment of the present disclosure.

Fig. 14 shows the surface profile of the modified profile as shown in fig. 13 after 1650kWhr and 1860kWhr sputtering use and the reference profile after 1350kWhr sputtering use.

Fig. 15 is a flow chart illustrating a method for designing a target including a modified central axis region according to one embodiment of the present disclosure.

Detailed Description

Physical vapor deposition ("PVD") processes are widely used to form thin film materials on a variety of substrates. Various metals and alloys can be deposited using PVD techniques, including, for example, Al, Ti, Cu, Ta, Ni, Mo, Au, Ag, Pt, and alloys of these elements. In one PVD process, known as sputter deposition or sputtering, particles are ejected from the surface of a sputtering target by bombardment with gas ions, such as plasma. Thus, a sputtering target is a source of particles that are deposited onto a substrate (such as a semiconductor wafer). As the target is eroded during sputtering use, the surface geometry is altered. Changes in target surface geometry lead to difficulties in depositing uniform thin films by sputtering, and such wear limits target life.

Previously, problems associated with depositing uniform thin films and/or extending target life have been addressed in various ways. Those include: i) an increase in the distance between the target and the wafer to allow only certain atoms having a particular spray angle to reach the wafer; ii) using a filtering device also known as a collimator or flux optimizer; for selecting only atoms with a particular trajectory; iii) using magnets with new design, arrangement and movement; iv) applying an RF bias at the wafer, the RF bias capable of establishing a negative charge at the wafer and forcing the deposition of metal ions at an angle close to the wafer normal. All of the above solutions have limitations. For example, increasing the distance between the target source and the substrate or using a collimator is less efficient and results in more waste of ejected atoms trapped in the chamber or on the collimator walls. Additionally, applying a Radio Frequency (RF) bias may result in electrical stress of the wafer components.

Problems are also encountered with the latest systems using collimators and/or new magnet designs and motions. For the example using a collimator as shown in the prior art, as schematically shown in fig. 2, the film uniformity decreases (or, equally, the non-uniformity increases) through the lifetime. Generally, deposition is characterized by thinning at the center of the wafer compared to the edge, from the beginning of life (BOL) to the end of life (EOL) of the sputter target. This is due, at least in part, to the change in target erosion profile from target center 14a at BOL to target center 14b at EOL. This affects the direction in which atoms are ejected from the sputter target relative to the position of the collimator wall 24 throughout life. For the example using the new magnet design and motion, there is a degradation of the I-V sputtering characteristics. In particular, the voltage follows two trends as the target lifetime increases: i) voltage increase due to changes in erosion target profile and spacing between magnets; in fact, the target surface is on average closer to the magnets positioned near the target backside; and ii) an increase in voltage fluctuations as the magnet moves in and out of position under the target area with deeper or shallower erosion grooves. As the lifetime continues, the target erosion profile becomes more non-uniform, which exacerbates the local voltage differences.

Embodiments of the present disclosure address the problem of uniform thin film deposition by addressing the target center profile and proposing new geometries for sputtering the target in the center region of the target. According to the present disclosure, the initial (i.e., pre-sputtering) target surface is strategically modified at the center of the target. The center of the strategically modified target is interchangeably referred to herein as a center region, a central axis region, a modified central axis region, and a modified profile comprising the central axis region. Sputtering is sensitive to target shape and surface profile. The electric field distribution in the vicinity of the plasma discharge depends on the target shape and/or surface profile, since the target profile represents the boundary conditions of the magnetic and electric fields described by the known electromagnetic laws. Thus, the target shape will affect the local intensity and distribution of the electromagnetic field lines, which in turn controls the deposition rate and orientation of the ejected atoms.

Furthermore, the interaction and interaction between the sputtering target and the electromagnetic field is constantly evolving over the life of the target, as the profile of the target surface changes as the material is eroded. This results in a continuous redistribution of the local intensity of the electromagnetic field and a change in the direction of the sputtered atoms.

It was found that the mechanism that helps to thin the film deposited at the center of the wafer is at least partially impacted or affected by the center of the target during the life of the sputtering target, with little local erosion during use and corresponding to a low sputtering rate in the center. Thus, a conventional planar (i.e., flat or non-profiled surface) 300mm target having a thickness of 25.4mm (1 inch) and a radius of 221mm (8.7 inches) maintains nearly the same height at the center, while erosion in the surrounding area near the center, but typically at least about 25mm to about 50mm (1 to 2 inches) away from the center, is typically high and results in deep erosion grooves in the target at the end of life. For example, there may be a groove at the end of life having a depth of about 7.6mm to about 12.7mm (0.3-0.5 inch). An exemplary end-of-life erosion profile 26 for a 300mm sputter target having an initial flat or planar surface is shown in FIG. 3. As shown, after about 2000kWhr use, the target's erosion profile 26 (also referred to as a wear profile) has a significant hump (also referred to as a hump or bump) 30 at the central region 28. The central region 28 has a radius of about 50mm (2 inches). A 300mm target herein refers to the wafer size onto which the target is sputtered.

The bulge 30 develops during the entire life of the target. The central bumps 30, which have a height of about 10mm (0.4 inch) or about 40% of the initial target thickness, disadvantageously block at least some atoms during sputtering, such as those having trajectories represented by the first set of arrows 32, because their trajectories pass through the central profile. This results in the undesirable redeposition of atoms into the central region of the target. The most affected are those atoms removed from the surrounding area adjacent to the ridge 30 corresponding to the bottom 36 or side 38 of the erosion groove.

When the central bump 30 is formed by erosion, the slope 40 of the central bump 30 increases in steepness with further sputtering use, as shown by the erosion profile 26 of fig. 3. Thus, at least some of the atoms represented by the second set of arrows 34 are sputtered in a direction away from the axis 42, rather than in a direction toward the wafer, as shown from the original planar target surface in the central region. Thus, atoms traveling in the direction of the second set of arrows 34 (which should have reached the central region of the wafer from the original target surface) now sputter toward the sides of the wafer substrate. The traces 32 and 34 are not desirable in sputtering.

Further, referring again to FIG. 2, the local geometric relationship and spacing between the target surface and the collimator shows that the target surface 16a at the beginning of the target life and the surface 16b at the end of the target life change the most in the profile region with the greatest difference between the local maxima and minima of erosion. This difference is highest near the central bump and results in more atoms having a change in sputtering direction between the beginning of life and the end of life, and therefore a larger proportion of the atoms are observed to be trapped in the central portion 25 of the collimator 24, as shown in fig. 2. Thus, at least those atoms captured by the collimator and adhering to the collimator walls do not reach the wafer and contribute to wafer thinning.

To address the issue of wafer thinning, at least some embodiments of the present disclosure modify the profile of the central region of the target. Referring to fig. 4A and 4B, the target is modified at the central region in such a way that: a) the central bump of the comparative erosion profile is smaller in height at the end of life, and b) the slope on both sides of the central bump at the end of life is not as steep as the reference target. In at least some embodiments, this is achieved by fabricating a cavity 150 (also interchangeably referred to herein as a "concave curvature" or a "concave feature") in a central portion of the target profile 100 of fig. 4A. The profile 60 is a reference profile made of the same target material but having a planar profile at the central region. It is noted that the modified target profile 100 and the reference target profile 60 are different in the central portion, as shown, but overlap or coincide in the remaining portion, i.e., at a radial distance greater than about ± 58.4mm (about 2.3 inches). For a 25.4mm (1 inch) thick target, the depth d1 of the cavity can vary between about 1.3mm and about 12.7mm (about 0.050 inch and about 0.5 inch). In other words, the cavity depth can be about 5% to about 50% of the total target thickness, or about 10% to about 30% of the total target thickness, or about 15% to about 20% of the total target thickness. For example, in FIG. 4A, the cavity 150 has a maximum depth d1 of 4.6mm (about 0.18 inches). The radius of the absolute value where the center portion is modified depends on the particular initial target profile, target source material, and dimensions. For targets having an overall target radius of 221mm (8.7 inches), the modified central region generally includes a radius in the range of about 1.27mm up to about 89mm (about 0.050 inches up to about 3.5 inches). In FIG. 4A, for example, the maximum radius rmax where the central target profile is changed is about 58.4mm (about 2.3 inches). In other words, the cavity radius may be 5% to about 40% relative to the total target radius, or 20% to about 30% relative to the total target radius, or about 23% to about 27% relative to the total target radius. The specific profile of the cavity may vary, but is primarily determined by the central shape of the erosion profile at the end of life, as shown in FIG. 4B.

Fig. 4B shows a modified profile 110 corresponding to profile 100 of fig. 4A after sputtering use at about 1500kWhr according to an embodiment of the present disclosure. The profile 110 after 1500kWhr corresponds to near the end of life, which for a conventional target is about 2000 kWhr. For comparison, a profile 70 is shown in FIG. 4B, showing the reference target (with the initial planar center profile 60). Notably, after 1500kWhr, the profile 110 is similar to the baseline profile 70, except for the central region, where the hump 120 of the profile 110 is significantly less pronounced in width and height than the hump 80 of the baseline profile 70.

The beneficial effect on the trajectory of sputtered atoms using the modified profile 100 of fig. 4A after 1500kWhr use is schematically illustrated in fig. 6. The baseline target profile after use is shown in fig. 5 for comparison. As shown in fig. 5, for a prior art reference target profile 70 after 1500kWhr, the atoms include problematic trajectories represented by arrows 32 and 34, including redeposited atoms and atoms directed from a center region of the wafer (customary toward the side of the wafer), as similarly discussed in fig. 3. This is because the raised bumps 80 block the desired trajectory that will direct atoms from the central region of the target to the central region of the wafer. In contrast, fig. 6 shows the modified profile 110 after 1500kWhr, where the smaller protuberances 120 in height and width do not block the desired trajectory, as shown by arrows 62 and 64, so that sputtered atoms from the central region of the target are directed to the central region of the wafer. In other words, the modified profile 100 (as shown in fig. 4A) including the cavity 150 disposed in the central region provides two benefits to the trajectory of the central sputtered atoms as the lifetime of the target progresses: (a) fewer atoms are hindered in their trajectory by the central bump 120 (of fig. 4B and 6) because the bump 120 is not as high and as wide as the fiducial bump 80 (of fig. 4B and 5), resulting in a higher number of atoms that may reach the center of the wafer; and, (b) the shape of the central bump 120 changes the angular direction of the overall distribution of sputtered atoms and their trajectories, in other words, sputtered atoms exiting the bump region 120 are directed more toward the center of the wafer due to the smaller slope on each side of the central bump, resulting in the central atoms being directed vertically and a higher proportion of the central atoms passing through the flux collimator. Both of these effects reduce thinning of the wafer at the center and promote more uniform deposition onto the wafer, resulting in improved wafer film uniformity at the end of life.

Referring again to fig. 4A, 4B, and 6, a sputtering target, according to an embodiment of the present disclosure, includes a sputtering material having a non-planar sputtering surface prior to erosion by use in a sputtering system. The non-planar sputtering surface has a circular shape and includes a central axis region 152 having a central axis 42. The central axis region 152 includes at least one non-protruding concave curvature feature 150 symmetrically disposed about the central axis 42 and having a first point (point 1) coincident with the central axis. The at least one non-protruding concave curvature feature 150 corresponds to the baseline protruding convex curvature feature 72 of the erosion profile 70 of a baseline sputtering target after erosion by use in the sputtering system and coincides with the central axis 42, the baseline sputtering target comprising a sputtering material having the same composition as the sputtering material of the sputtering target, the baseline sputtering target further comprising a planar sputtering surface 60 before erosion by use in the sputtering system. The line 35 is perpendicular to the central axis 42 and is collinear with a reference sputter target planar sputtering surface 60 prior to erosion by use in a sputtering system. Point 1 is at a first axial distance 44 from line 35. A peripheral region 155 is disposed about the central axis region 152, in other words, the peripheral region is remote from the central axis 42 and does not overlap the central axis region 152. The surrounding area 155 includes a second point (point 2) coincident with the line 35 and at a first radial distance 156 from the central axis 42. The central axis region 152 has a wear profile 110 after erosion by use in a sputtering system, the wear profile including a protuberance 115 having: a third point (point 3) coincident with the central axis 42 and at a second axial distance 46 from the line 35; and a fourth point (point 4) at a first radial distance 156 from the central axis 42 and at a third axial distance 48 from the line 35; wherein the third axial distance 48 is greater than or equal to the first axial distance 44 and greater than or equal to the second axial distance 46.

The baseline sputter target having a wear profile 70 after use includes a fifth point (point 5) that coincides with the central axis 42 at a fourth axial distance 50 from the line 35, wherein the first axial distance 44 and the second axial distance 46 are greater than the fourth axial distance 50. The protuberance 115 comprises a first outer peripheral wear surface 118 having a slope m1, and the post-erosion reference convex curvature feature 72 comprises a second outer peripheral wear surface 78 having a slope m2, wherein m1 is less abrupt than m 2. In at least some embodiments of the present disclosure, the non-protruding concave curvature feature 150 includes an inner circumferential surface 145 and a bottom surface 148 that includes point 1. The bottom surface 148 may be flat. Alternatively, the bottom surface 148 may be rounded, concave, or convex. In other examples, bottom surface 148 may be pointed or angled (not shown).

The non-protruding concave curvature features 150 of the sputtering target have a total target radius and a total target thickness. The shape and size of the non-protruding concave curvature features may vary. In some embodiments, the first radial distance 156 is about 5% to about 40% relative to the total target radius, and the first axial distance 44 is about 5% to about 50% of the total target thickness. In other embodiments, the first radial distance 156 is about 20% to about 30% relative to the total target radius, and the first axial distance 44 is about 10% to about 30% of the total target thickness. In other embodiments, the first radial distance 156 is about 23% to about 27% relative to the total target radius, and the first axial distance 44 is about 15% to about 20% of the total target thickness.

Sputtering targets according to embodiments of the present disclosure can also include at least one recessed groove, such as grooves 82 and/or 84, in the surrounding area, as shown in figure 4A. The surrounding area may include the area between the central axis area 152 beyond the radial edge 86 of the target.

Referring again to fig. 4A, 4B, and 6 in accordance with an embodiment of the present disclosure, a sputtering target includes a sputtering material and has a non-planar sputtering surface prior to erosion by use in a sputtering system, the non-planar sputtering surface having a circular shape and including a central axis region 152 having a central axis 42. The central axis region 152 includes a concave curvature feature 150 disposed symmetrically about the central axis 42 and having a first point (point 1) coincident with the central axis 42. The concave curvature features 150 correspond to the baseline protruding convex curvature features 72 of the erosion profile 70 of a baseline sputtering target that includes a sputtering material having the same composition as the sputtering material of the sputtering target after erosion by use in the sputtering system of at least 1000kWhr and that coincides with the central axis 42, the baseline sputtering target further including a planar sputtering surface 60 before erosion by use in the sputtering system. The central axis region 152 has a wear profile 110 after erosion by use of at least 1000kWhr in a sputtering system, the wear profile including the protuberance 115. Protuberance 115 includes a first height, which is shown in fig. 4B as distance 48, which is less than distance 46. The protuberance 115 further comprises a first outer peripheral wear surface 118 having a first slope m 1. The reference projecting convex curvature feature 72 includes a second height, which is shown in fig. 4B as distance 48 being less than distance 50. The reference projecting convex curvature feature 72 also includes a second peripheral wear surface 78 having a second slope m 2. The protuberances 115 provide the sputtering target with reduced shadowing relative to the datum convex curvature feature 72, as shown in fig. 5 and 6. The first height (distance 48 is less than distance 46 in fig. 4B) is less than the second height (distance 48 is less than distance 50 in fig. 4B) because the datum protruding convex curvature feature 72 having the second height blocks more of the sputtered atoms that have trajectories that are directed radially inward toward the central axis 42 and are redeposited onto the target. It is also shown that the first slope m1 is less steep than the second slope m2 such that the second outer peripheral wear surface 78 directs more sputtered atoms having trajectories radially outward away from the wafer relative to the central axis 42. The sputtering material includes at least one material selected from the group consisting of Ti, Al, Cu, Ta, Ni, Co, Mo, Au, Ag, Pt, W, Cr, Ti alloy, Al alloy, Cu alloy, Ta alloy, Ni alloy, Co alloy, Mo alloy, Au alloy, Ag alloy, Pt alloy, W alloy, and Cr alloy. In some embodiments, the target is monolithic, as known in the art. In other embodiments, the target is diffusion bound, as is known in the art. The percent reduction between the slope of the outer peripheral wear surface of the inventive targets of the present disclosure (e.g., the first slope m1 as shown in fig. 4B) and the slope of the outer peripheral surface of the reference target (e.g., the second slope m2 in fig. 4B) is at least about 40% in at least some of the embodiments of the present invention. In other embodiments, the percent reduction between the slope of the outer peripheral wear surface of the inventive targets of the present disclosure and the slope of the outer peripheral surface of the reference target is at least about 45%, or at least about 50%, or at least about 55%, or at least about 60%, or at least about 65%, or at least about 70%, or at least about 75%, or at least about 80%, or at least about 85%, or at least about 90%, or at least about 95%. In at least some embodiments, the percentage reduction between the first slope and the second slope is from about 40% to about 100%. In these and other embodiments of the present disclosure, the central axis region 152 further includes a total target thickness at the central axis 42 in the central axis region 150 of the target prior to sputtering use, as shown in fig. 4A, the distance tT is less than the distance 44, which is less than the total target thickness tT of a reference target having a planar surface at the central axis region. In some embodiments, the total target thickness of the target of the present invention is about 10% to about 30% less than the total target thickness at the central axis of a reference sputtering target comprising a planar sputtering surface prior to erosion. In other embodiments, the total target thickness is about 15% to about 25% less than the total target thickness of the reference sputtering target at the central axis. In other embodiments, the total target thickness is about 18% to about 22% less than the total target thickness of the baseline sputtering target at the central axis. In some embodiments, the sputter target further comprises at least one concave trough in the peripheral region 155.

At least some embodiments of the present disclosure include a method for forming a target including a modified central axis region as shown in the flow diagram of fig. 7. The method can be tailored to specific target configurations and source materials as desired. A method of manufacturing a sputter target comprising a sputter material having a non-planar sputter surface before erosion by use in a sputtering system, the non-planar surface having a circular shape, the method comprising the steps shown in the context of fig. 7. In step 1000, a target having a central axis region is formed. The central axis region includes non-protruding concave curvature features symmetrically disposed about the central axis and having a first point (point 1 of fig. 4A) coincident with the central axis, wherein after erosion by use in a sputtering system, at least one of the non-protruding concave curvature features corresponds to a baseline protruding convex curvature feature of an erosion profile of a baseline sputtering target and coincides with the central axis. The reference sputtering target comprises a sputtering material having the same composition as the sputtering material of the sputtering target, and the reference sputtering target further comprises a planar sputtering surface before erosion by use in a sputtering system. A first point at a first axial distance from the line is perpendicular to the central axis and collinear with the reference sputter target planar sputtering surface prior to erosion by use in a sputtering system. Step 1010 includes forming a peripheral region disposed about the central axis region; the surrounding area includes a second point (point 2 of fig. 4A) coincident with the line and at a first radial distance from the central axis. The method also includes optimizing the first axial distance and the first radial distance. In step 1020, the erosion rates of the corresponding central axis region and the corresponding peripheral region of the reference sputter target are measured. In other words, the through-life erosion rate at various radii along the profile is experimentally measured and recorded by sputtering the reference target until the entire life of the through-life target. In at least some embodiments, the measurements are made in about 2.54mm (0.100 inch) increments from edge to edge of the target surface. In step 1020, it is assumed that the through-life erosion rate of any potential new candidate profile is similar to that of the prior art target. This assumption remains acceptable to a first degree, especially for the low sputtering central region of the target for most target designs. The potential new candidate and the reference target are made of the same material or alloy. Step 1030 includes calculating an erosion profile at the end of life of the non-protruding concave curvature feature based on the erosion rate determined in step 1020. Calculating as in step 1030 may further include calculating a plurality of erosion profiles for the plurality of non-salient concave feature candidates at the end of life to generate a profile dataset as in step 1040. An optimized target central axis region having a concave feature that includes a point coincident with the central axis is formed using the best candidate selected from the plurality of non-salient concave feature candidates based on the profile dataset, as in step 1050, as in step 1060. According to embodiments of the method, the sputtering target can have an overall target radius and an overall target thickness, wherein the first radial distance is from about 5% to about 40% relative to the overall target radius and the first axial distance is from about 5% to about 50% of the overall target thickness. In other embodiments, the first radial distance is from about 20% to about 30% relative to the total target radius, and the first axial distance is from about 10% to about 30% of the total target thickness. In other embodiments, the first radial distance is from about 23% to about 27% relative to the total target radius, and the first axial distance is from about 15% to about 20% of the total target thickness.

Materials suitable for use in sputtering targets according to embodiments of the present disclosure include pure elements and alloys. For example, suitable sputtering materials for the sputtering target include at least one material selected from the group consisting of Ti, Al, Cu, Ta, Ni, Co, Mo, Au, Ag, Pt, W, Cr, Ti alloy, Al alloy, Cu alloy, Ta alloy, Ni alloy, Co alloy, Mo alloy, Au alloy, Ag alloy, Pt alloy, W alloy, and Cr alloy. In some embodiments, the sputtering target is substantially pure or pure for targets made of a single element, such as a material selected from the elements Ti, Al, Cu, Ta, Ni, Co, Mo, Au, Ag, Pt, W, and Cr. Substantially pure means an element content of almost pure or at least 99.9% by weight. For example, a suitable sputtering material for the sputtering target can comprise at least one substantially pure material selected from the group consisting of Ti, Al, Cu, Ta, Ni, Co, Mo, Au, Ag, Pt, W, and Cr. In other embodiments, the sputter material of the sputter target is an alloy. The alloy includes a primary element mixed with at least one other element from the periodic table, wherein the sputtered material contains a higher amount of the primary element than the one or more elements mixed therewith. According to standard naming conventions, an alloy may be referred to as an alloy of the primary elements. For example, an alloy in which the main element is Al is referred to as an Al alloy. Suitable sputtering materials for the sputtering target may comprise at least one main element selected from the group consisting of Ti, Al, Cu, Ta, Ni, Co, Mo, Au, Ag, Pt, W and Cr. Such materials may be referred to as Ti alloys, Al alloys, Cu alloys, Ta alloys, Ni alloys, Co alloys, Mo alloys, Au alloys, Ag alloys, Pt alloys, W alloys, and Cr alloys, respectively.

In step 1020, the plurality of varying contours at the central region are designed to represent candidate designs. Step 1020 further includes determining a profile of the predicted candidate design at the central region at a plurality of life stages (progressively related to the time of use (kWhr)) of the plurality of variation profiles as determined in step 1000 using baseline calculations for a corresponding plurality of life stages of the baseline target, experimental measurements of the erosion rate as a function of time of use. In step 1030, the predicted contours of the candidate design over life are evaluated, and the best candidate design is selected based on the size and shape of the central portion of the contour toward the end of life. Further, step 1040 optionally includes modeling the interaction between the local electromagnetic field and the target surface to determine the angular distribution of sputtered atoms at the target center.

Advantageously, and in accordance with at least some embodiments of the present disclosure, the modified profile with the central region cavity can be used with a monolithic target design or a diffusion bonded target design.

In some embodiments, a sputtering target including non-protruding concave curvature features according to the present disclosure is monolithic. In other words, a sputtering target having a central region cavity can be formed from a single piece. These targets are interchangeably referred to herein as monoliths and/or monolithic assemblies. A monolithic design composed of a single material allows better control of electromagnetic properties, including voltage variations within the sputtering target.

In other embodiments according to the present disclosure, the sputtering target is coupled or attached to the backing plate by, for example, diffusion bonding. At least some embodiments of the present disclosure include wherein the target is diffusion bonded. The sputtering target can also include a backing plate. As with diffusion bonded targets, the use of a backing plate can provide support for the sputtering target during the sputtering process to advantageously reduce, for example, sputtering target warpage during the life of the target. One non-limiting example of a method of attaching a sputter target to a backing plate is hot isostatic pressing ("HIPing" or "hipping"). Hipping can be used to diffusion bond the sputtering target to the backing plate by pressing the sputtering target and backing plate together after heating to the Hipping temperature. Targets made of Ti are examples of diffusion bonded targets having a central region cavity. In terms of diffusion bonding design, the backing plate material is different from the core target material and thus can have different electromagnetic and other physical properties, such as CTE, electrical resistivity, and thermal conductivity. These differences between the core material and the backplane material can exacerbate the local voltage differences. Thus, the backing plate selection must carefully consider the electromagnetic and physical properties to complement those of the target core material. In general, controlling and predicting local fluctuations during erosion in diffusion bonded designs is more challenging than monolithic designs. The sputtering target can also include a backing plate that includes a grooved flange, wherein the grooved flange can also be recessed to provide cooling, for example.

With both monolithic and backing plate designs, the target material can be treated, for example, with a Thermodynamic (TMP) process to enhance the strength of the target. For example, when the grain size is large (typically 30-100 microns), Al alloys, Cu and Cu alloys with low strength can be processed with the TMP process to increase the strength of the material.

One particularly effective TMP process is Equal Channel Angular Extrusion (ECAE), the technique of which is disclosed in US 5,850,755, US 7,191,630 and US 7,767,043, which are incorporated herein by reference in their entirety. ECAE, according to at least some embodiments of the present disclosure, may be advantageously used to impart severe plastic deformation in bulk metals and alloys, and impart additional strength to these materials. ECAE is an extrusion technique consisting of two channels of roughly equal cross-section that intersect at a specific angle in the angular range of about 90 ° to about 140 °. In one embodiment, the angle is 90 °. Uniform simple shear deformation occurs layer by layer at the intersection plane between the two channels, providing good lubrication of the blank and the wall. The main process characteristics of ECAE are (i) high distortion per pass (true strain at 90 ° 1.17); (ii) after each pass, the multi-pass ECAE can achieve extreme levels of deformation without changing the shape and volume of the billet, (ii) rotation or turning of the billet between each pass can achieve various strain paths to control grain shape and crystallographic texture. Two main mechanisms for reinforcement during ECAE are described herein. First, the structural units (e.g., units, sub-grains and grains) are refined to a sub-micron level. This is also known as hall etch hardening:

Where σ y is the yield stress, σ o is the material constant of the initial stress of dislocation motion (or the resistance of the crystal lattice to dislocation motion), ky is the strengthening coefficient (constant specific to each material), and d is the average grain diameter. Based on this equation, strengthening becomes particularly effective when the grain diameter d is less than 1 μm. The second major mechanism for strengthening during ECAE is the presence of multiple dislocations within cells, sub-grains, and grains due to high strain.

other effective TMP processes to impart strength in the material include a hardening step by conventional methods such as rolling, drawing, extrusion or forging performed in the material after the recrystallization heat treatment step. In some embodiments of the present disclosure, the hardening produces a target having a central region cavity with an average grain size in a range of about 30 microns to about 100 microns; such targets include Al alloys and Cu alloys, and the strength that can be practically achieved is in the mid-range between low-strength fully-recrystallized materials and high-strength submicron ECAE materials. For some Al and especially Cu alloys and harder materials such as Ti, Ta, Co, Cr, W, Ni such as solution may provide sufficient strength for monolithic designs.

Generally, high strength materials (such as obtained, for example, via ECAE) are particularly advantageous in monolithic designs, as stronger materials can be sputtered deeper and thus more durable. For example, depending on design, the lifetime of a 200mm/300mm monolithic target can typically be extended by 20% -100% compared to a standard diffusion bonded target when using ECAE materials.

High strength ECAE materials having submicron grain structures and, to a lesser extent, conventional hardened materials can provide a reduction in voltage fluctuations. These reductions in voltage fluctuations may include a reduction in eddy currents due to slightly higher resistivity. This helps to actively reduce voltage fluctuations, plasma instabilities, and DC power failures. Further, the reduction in voltage fluctuations may include better resistance to target warping throughout life, a phenomenon that increases with age. The smaller warpage results in better consistency of the distance between the magnet and the erosion profile throughout life, which in turn is directly related to the local voltage. Thus, a better control of the voltage fluctuations may be obtained. Further, it should also be noted that the use of a central region cavity in a target profile according to at least some of the embodiments of the present disclosure weakens the overall mechanical strength of the target assembly. Thus, to limit target deflection, it becomes even more important and beneficial to promote higher strength in the target material.

In at least some of the embodiments of the present disclosure, various geometries of the backside of the target assembly are suitable. For example, the backside of the target assembly can include channels that improve cooling efficiency and help reduce target deflection. Another advantage of features such as channels at the back of the target is that eddy currents are reduced, which also helps to reduce plasma instability.

The following non-limiting examples illustrate at least some embodiments of the present disclosure.