阅读说明：本技术 薄膜沉积方法 (Thin film deposition method ) 是由 王宽冒 于 2020-07-15 设计创作，主要内容包括：本申请提供一种薄膜沉积方法,包括：主沉积步骤,进行薄膜沉积工艺,在晶片上沉积指定厚度的金属薄膜,并在沉积过程中采用第一流量的冷却气体对晶片进行冷却；应力转变步骤,将冷却气体由第一流量降低至第二流量,使晶片在沉积粒子的作用下温度提高至预设温度,在预设温度下,金属薄膜中的应力转变为拉应力。应用本申请,通过其主沉积步骤获得具有压应力的指定厚度的金属薄膜,然后在应力转变步骤中,通过沉积粒子撞击晶片对金属薄膜进行均匀加热,可以迅速将热量传递至晶片的内部,从而短时间内将晶片整体温度提高至预设温度,以使金属薄膜具有拉应力。(The application provides a thin film deposition method, which comprises the following steps: a main deposition step, namely performing a film deposition process, depositing a metal film with a specified thickness on the wafer, and cooling the wafer by adopting a first flow of cooling gas in the deposition process; and a stress conversion step of reducing the flow rate of the cooling gas from the first flow rate to a second flow rate to increase the temperature of the wafer to a preset temperature under the action of the deposited particles, wherein the stress in the metal film is converted into tensile stress at the preset temperature. By applying the method, the metal film with the specified thickness and compressive stress is obtained through the main deposition step, then in the stress transformation step, the deposited particles impact the wafer to uniformly heat the metal film, the heat can be rapidly transferred to the inside of the wafer, and therefore the integral temperature of the wafer is increased to the preset temperature in a short time, and the metal film has tensile stress.)

1. A thin film deposition method, comprising:

a main deposition step, namely performing a film deposition process, depositing a metal film with a specified thickness on a wafer, and cooling the wafer by adopting a first flow of cooling gas in the deposition process;

and a stress conversion step of reducing the cooling gas from the first flow rate to a second flow rate, so that the temperature of the wafer is increased to a preset temperature under the action of the deposited particles, and the stress in the metal film is converted into tensile stress at the preset temperature.

2. The thin film deposition method of claim 1, wherein the main deposition step and the stress transformation step are both performed in the same deposition chamber;

in the main deposition step, introducing process gas into the deposition chamber, applying power to a metal target, exciting the process gas into plasma, and attracting the plasma to bombard the metal target so as to deposit the metal film with the specified thickness on the wafer;

in the stress conversion step, continuously introducing the process gas into the deposition chamber, applying power to the metal target, exciting the process gas into plasma, and attracting the plasma to bombard the metal target so as to continuously perform deposition, so that the thickness of the metal film reaches a target thickness; and simultaneously, reducing the cooling gas from the first flow rate to the second flow rate, so that the temperature of the wafer is increased to the preset temperature under the action of the deposited particles.

3. The thin film deposition method according to claim 1 or 2, wherein in the main deposition step, the cooling gas is introduced into a gap between a susceptor carrying the wafer and the wafer through a gas passage in the susceptor, and back-blown against the wafer to cool the wafer.

4. The thin film deposition method according to claim 3, wherein the first flow rate has a value ranging from 1sccm to 50sccm, and the second flow rate has a value ranging from 0sccm to 10 sccm.

5. A thin film deposition method according to claim 1 or 2, wherein the predetermined temperature is greater than or equal to 130 ℃.

6. The thin film deposition method of claim 2, wherein the main deposition step comprises:

a gas inlet step, wherein the process gas is introduced into the deposition chamber, and the wafer is cooled by adopting the cooling gas with the first flow rate;

a glow starting step of applying a first power to the metal target through an excitation power supply, exciting the process gas into plasma, and simultaneously keeping cooling the wafer by using the cooling gas with the first flow rate;

a deposition step of increasing the first power to a second power and applying a bias power to the susceptor through a bias power supply to deposit a metal film on the wafer while keeping the wafer cooled by the cooling gas of the first flow rate;

a cooling step of turning off the excitation power supply and the bias power supply and keeping the wafer cooled by the cooling gas of the first flow rate;

and circularly executing the steps until the circularly executed times reach a preset numerical value.

7. The thin film deposition method of claim 2, wherein the stress transforming step comprises:

a turning starting step of applying a first power to the metal target through an excitation power supply, exciting the process gas into a plasma, and simultaneously reducing the cooling gas from the first flow rate to the second flow rate;

and a transition deposition step, namely increasing the first power to a second power, applying bias power to the base through a bias power supply to deposit a metal film on the wafer, and simultaneously keeping cooling the wafer by adopting the cooling gas with the second flow rate, so that the temperature of the wafer is increased to the preset temperature under the action of deposited particles, and the stress in the metal film is converted into tensile stress at the preset temperature.

8. The thin film deposition method of claim 7, wherein the stress transforming step further comprises:

and a cooling step of turning off the excitation power supply and the bias power supply and increasing the cooling gas from the second flow rate to the first flow rate to cool the wafer.

9. The thin film deposition method according to claim 6, wherein a process time of the deposition step is in a range of 1s to 300s, and the first power and the second power are both in a range of 1kW to 60 kW.

10. The thin film deposition method of claim 7, wherein a process time of the transition deposition step is in a range of 5s to 120s, and the first power and the second power are both in a range of 1kW to 60 kW.

Technical Field

The invention relates to the technical field of semiconductors, in particular to a thin film deposition method.

Background

In the manufacturing process of the semiconductor, the advanced packaging process of the semiconductor can realize multi-pin connection, has high speed and high practicability, and ensures the miniaturization and the multifunctionality of electronic products and communication equipment. The preparation of a redistribution layer (RDL) in the advanced semiconductor packaging process is an important process, and the performance control (conductivity, adhesion, stress control, etc.) and the preparation method of the conductive material applied to the redistribution layer are particularly important. Because aluminum materials have good electrical conductivity and are inexpensive, aluminum (Al) thin films are now commonly used for RDL layers.

Disclosure of Invention

The present invention is directed to at least one of the problems of the prior art, and provides a thin film deposition method, which can make a metal thin film deposited on a wafer have tensile stress.

To achieve the object of the present invention, there is provided a thin film deposition method including:

a main deposition step, namely performing a film deposition process, depositing a metal film with a specified thickness on a wafer, and cooling the wafer by adopting a first flow of cooling gas in the deposition process;

and a stress conversion step of reducing the cooling gas from the first flow rate to a second flow rate, so that the temperature of the wafer is increased to a preset temperature under the action of the deposited particles, and the stress in the metal film is converted into tensile stress at the preset temperature.

Optionally, the main deposition step and the stress conversion step are both performed in the same deposition chamber;

in the main deposition step, introducing process gas into the deposition chamber, applying power to a metal target, exciting the process gas into plasma, and attracting the plasma to bombard the metal target so as to deposit the metal film with the specified thickness on the wafer;

in the stress conversion step, continuously introducing the process gas into the deposition chamber, applying power to the metal target, exciting the process gas into plasma, and attracting the plasma to bombard the metal target so as to continuously perform deposition, so that the thickness of the metal film reaches a target thickness; and simultaneously, reducing the cooling gas from the first flow rate to the second flow rate, so that the temperature of the wafer is increased to the preset temperature under the action of the deposited particles.

Optionally, in the main deposition step, the cooling gas is introduced into a gap between the susceptor and the wafer through a gas passage in the susceptor carrying the wafer, and back-blows the wafer to cool the wafer.

Optionally, the first flow rate has a value in a range of 1sccm to 50sccm, and the second flow rate has a value in a range of 0sccm to 10 sccm.

Optionally, the preset temperature is greater than or equal to 130 ℃.

Optionally, the main deposition step comprises:

a gas inlet step, wherein the process gas is introduced into the deposition chamber, and the wafer is cooled by adopting the cooling gas with the first flow rate;

a glow starting step of applying a first power to the metal target through an excitation power supply, exciting the process gas into plasma, and simultaneously keeping cooling the wafer by using the cooling gas with the first flow rate;

a deposition step of increasing the first power to a second power and applying a bias power to the susceptor through a bias power supply to deposit a metal film on the wafer while keeping the wafer cooled by the cooling gas of the first flow rate;

a cooling step of turning off the excitation power supply and the bias power supply and keeping the wafer cooled by the cooling gas of the first flow rate;

and circularly executing the steps until the circularly executed times reach a preset numerical value.

Optionally, the stress transforming step comprises:

a turning starting step of applying a first power to the metal target through an excitation power supply, exciting the process gas into a plasma, and simultaneously reducing the cooling gas from the first flow rate to the second flow rate;

and a transition deposition step, namely increasing the first power to a second power, applying bias power to the base through a bias power supply to deposit a metal film on the wafer, and simultaneously keeping cooling the wafer by adopting the cooling gas with the second flow rate, so that the temperature of the wafer is increased to the preset temperature under the action of deposited particles, and the stress in the metal film is converted into tensile stress at the preset temperature.

Optionally, the stress transforming step further comprises:

and a cooling step of turning off the excitation power supply and the bias power supply and increasing the cooling gas from the second flow rate to the first flow rate to cool the wafer.

Optionally, the process time of the deposition step ranges from 1s to 300s, and the first power and the second power both range from 1kW to 60 kW.

Optionally, the process time of the conversion deposition step ranges from 5s to 120s, and the first power and the second power both range from 1kW to 60 kW.

The invention has the following beneficial effects:

according to the film deposition method provided by the invention, the metal film with the specified thickness is obtained through the main deposition step, and the wafer is cooled in the deposition process so as to ensure the surface quality of the wafer, so that the metal film with the compressive stress is obtained; then, in the stress transformation step, the deposited particles impact the wafer to uniformly heat the metal film, so that heat can be rapidly transferred to the inside of the wafer, and the overall temperature of the wafer is increased to a preset temperature in a short time, so that the metal film has tensile stress.

Drawings

FIG. 1 is a graph of stress of an Al film as a function of wafer temperature;

FIG. 2 is a flowchart of a thin film deposition method according to an embodiment of the present invention;

FIG. 3 is a graph showing the relationship between the stress of the Al thin film obtained by the thin film deposition method according to the embodiment of the present invention and the wafer temperature.

Detailed Description

Reference will now be made in detail to the present application, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar parts or parts having the same or similar functions throughout. In addition, if a detailed description of the known art is not necessary for illustrating the features of the present application, it is omitted. The embodiments described below with reference to the drawings are exemplary only for the purpose of explaining the present application and are not to be construed as limiting the present application.

It will be understood by those within the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

The following describes the technical solutions of the present application and how to solve the above technical problems in specific embodiments with reference to the accompanying drawings.

At present, in the deposition process of a metal thin film, in order to prevent the wafer temperature from being too high, the wafer is usually cooled while the deposition process is performed, and thus, the obtained wafer temperature is generally low. Taking the Al thin film as an example, the temperature is mostly less than 100 ℃, and the stress of the Al thin film is expressed as compressive stress due to the lower temperature. For advanced packaging, a conductive metal film generally grows on an insulating oxide or nitride film, and the compressive stress of the metal film easily causes micro-cracks in the underlying insulating film, which results in failure of a circuit. In order to solve the above technical problems, the present embodiment has conducted a research experiment on the relationship between the stress of the metal thin film and the wafer temperature, and found that the stress of the metal thin film has a direct mapping relationship with the temperature, as shown in fig. 1, which is a relationship between the stress of the Al thin film and the wafer temperature, and as can be seen from fig. 1, when the wafer temperature is 130 ℃ or higher, the Al thin film with tensile stress can be obtained. In view of the above, the present embodiment provides a film deposition method to make the metal film have tensile stress.

The thin film deposition method provided in the present application is described in detail below by taking only an aluminum thin film as an example, but it should be noted that the present embodiment is not limited to an aluminum thin film, and the present invention can also be applied to thin film deposition of other metals, such as copper, tantalum, titanium, and the like, that is, a metal thin film having a tensile stress obtained by the thin film deposition method is within the protection scope of the present application.

Referring to fig. 2, a schematic flow chart of a thin film deposition method according to an embodiment of the present disclosure includes the following steps:

the main deposition step S1 is to perform a film deposition process to deposit a metal film with a specified thickness on the wafer, and to cool the wafer during the deposition process using a first flow rate of cooling gas.

This main deposition step S1 is mainly used for obtaining the metal film of appointed thickness, and in the deposition process except that the wafer is heated, the clamping ring for preventing the wafer from taking place the displacement also can be heated to along with the time accumulation of the continuous deposition process of board, the temperature of clamping ring also can be higher and higher, this embodiment adopts the cooling gas of first flow to carry out cooling treatment to the wafer in the deposition process, can prevent that wafer itself from being heated and because the temperature transmission of clamping ring makes the wafer temperature too high, even burn out wafer etc.. Wherein the value of the specified thickness is slightly less than the value of the target thickness.

Specifically, the first flow rate can be set to a value ranging from 1sccm to 50sccm (standard state cubiccentimeter per minute).

More specifically, the wafer may be cooled by back-blowing, and a gas channel may be formed in the susceptor for supporting the wafer, and a cooling gas may be introduced into a gap between the susceptor and the wafer through the gas channel to back-blow the wafer, so as to cool the wafer. In the deposition process, a whole-process back blow molding mode is adopted, so that the temperature of the wafer and the pressure ring is ensured to be transmitted to the base in time, and the wafer is cooled. And the cooling degree of the wafer can be adjusted by adjusting the flow of the cooling gas, so that the temperature of the wafer can be effectively controlled, and the deposited aluminum film usually has compressive stress in order to ensure that the temperature of the wafer cannot be too high. Wherein the cooling gas may be, but is not limited to, the same as the process gas to facilitate the provision of the gas source and the gas path. Further, the cooling gas and the process gas may be (but are not limited to) helium, argon, etc.

And a stress conversion step S2, reducing the flow rate of the cooling gas from the first flow rate to a second flow rate, so that the temperature of the wafer is increased to a preset temperature under the action of the deposited particles, and the stress in the metal film is converted into tensile stress at the preset temperature.

The second flow rate can be significantly smaller than the first flow rate, or even zero, for example, the second flow rate can be in a range of 0sccm to 10sccm to prevent the cooling gas from decreasing the temperature of the wafer. The specific preset temperature can be set according to the stress and temperature relationship of the specific metal film type, for example, the preset temperature of the aluminum film can be greater than or equal to 130 ℃ to ensure that the aluminum film has tensile stress.

In the stress transition step S2, the deposition particles generally have a high temperature, the aluminum thin film can be uniformly heated by the impact of the deposition particles against the wafer, and heat can be rapidly transferred to the inside of the wafer due to the impact of the deposition particles, so that the temperature of the entire wafer can be raised to a predetermined temperature in a short time, and the aluminum thin film has a tensile stress. It should be noted that the preset temperatures of different metal films may be the same or different, and this embodiment is not limited in detail.

In one embodiment of the present application, the main deposition step S1 and the stress transition step S2 may be performed in the same deposition chamber, and accordingly, the main deposition step S1 may be performed as follows: and introducing process gas into the deposition chamber, applying power to the metal target, exciting the process gas into plasma, and attracting the plasma to bombard the metal target so as to deposit a metal film with a specified thickness on the wafer. The process of the stress transition step S2 may be as follows: continuously introducing process gas into the deposition chamber, applying power to the metal target, exciting the process gas into plasma, attracting the plasma to bombard the metal target so as to continuously perform deposition, and enabling the thickness of the metal film to reach the target thickness; meanwhile, the cooling gas is reduced from the first flow rate to the second flow rate, so that the temperature of the wafer is increased to a preset temperature under the action of the deposited particles.

The specified thickness of the metal film may be calculated according to the thickness of the film deposited in the stress conversion step S2 and the overall target thickness of the film (the specified thickness may be equal to the difference between the target thickness and the thickness of the film deposited in the stress conversion step S2), and different target thicknesses may be set according to different metal films, which is not particularly limited in this embodiment.

In this embodiment, the main deposition step S1 and the stress transition step S2 may be performed in the same deposition chamber, so that the aluminum thin film with a specified thickness may be obtained in the main deposition step S1, and after the main deposition step S1 is performed, the operation in the main deposition step S1 may be continued (i.e., the process gas is continuously introduced into the deposition chamber, power is applied to the metal target, the process gas is excited into plasma, and the plasma is attracted to bombard the metal target, so as to continue deposition), so as to obtain the aluminum thin film with a target thickness. Meanwhile, the deposition process of the stress transition step S2 adopts the cooling gas with the second flow rate, and the wafer is not cooled, so that the temperature of the wafer can be rapidly increased when the deposited particles impact the wafer, and since the deposition process of the stress transition step S2 is faster and shorter, the temperature of the wafer is not too high, and even the wafer is burned out. In addition, the main deposition step S1 and the stress conversion step S2 are carried out in the same deposition chamber in sequence, so that the utilization rate of equipment can be improved, the wafer transferring and conveying time can be shortened, and the processing efficiency of single wafers can be improved. In particular, the deposition chamber may be, but is not limited to, a magnetron sputtering chamber.

It should be noted that the main deposition step S1 and the stress transition step S2 may be performed in different process chambers, that is, the main deposition step S1 is performed in a deposition chamber (the specific implementation procedure may be the same as that in the above embodiment), and then the wafer is moved from the deposition chamber into a plasma generation chamber, or into a high temperature or low temperature plasma etching apparatus, and then the stress transition step S2 is performed in the plasma generation chamber, so that a plurality of apparatuses may be used to perform different processes on a batch of wafers at the same time, thereby improving the efficiency of mass production.

In another embodiment of the present application, the main deposition step S1 may further include the following steps: a gas inlet step, namely introducing process gas into the deposition chamber, and cooling the wafer by adopting cooling gas with a first flow rate; a glow starting step, namely applying first power to the metal target through an excitation power supply, exciting the process gas into plasma, and simultaneously keeping cooling the wafer by adopting cooling gas with first flow; a deposition step of increasing the first power to a second power and applying a bias power to the susceptor through a bias power supply to deposit a metal film on the wafer while keeping cooling the wafer with a first flow of cooling gas; a cooling step, namely closing the excitation power supply and the bias power supply and keeping cooling the wafer by adopting the cooling gas with the first flow rate; and circularly executing the steps until the circularly executed times reach a preset numerical value.

Wherein, the value range of the process time of the deposition step can be 1s-300s, and the value range of the first power and the second power can be 1kW-60 kW.

In this embodiment, a first smaller power is applied to the metal target to excite the process gas into a plasma, a second larger power is applied to the metal target to attract the plasma excited by the process gas to the metal target, so that the plasma bombards the metal target, metal particles are sputtered from the metal target, a bias power is applied to the pedestal to move the metal particles toward the wafer, a metal film is deposited on the surface of the wafer, and the wafer is cooled during the deposition process to prevent the wafer from being heated too fast, at too high a temperature, and even burning out the wafer. To further cool the wafer, the energizing power and the bias power may be turned off after a certain time or thickness of deposition, and the cooling process may be continued with the first flow of cooling gas to rapidly cool the wafer, thereby ensuring the temperature of the wafer (often below 130 ℃). Then, the above steps are repeated to obtain the metal film with the specified thickness.

In another embodiment of the present application, the stress transforming step S2 may further include the following steps: a turning starting step, namely applying first power to the metal target through an excitation power supply, exciting the process gas into plasma, and simultaneously reducing the cooling gas from the first flow to the second flow; and a transition deposition step, namely increasing the first power to a second power, applying bias power to the base through a bias power supply to deposit a metal film on the wafer, and simultaneously keeping cooling the wafer by adopting cooling gas with a second flow rate to increase the temperature of the wafer to a preset temperature under the action of deposited particles, wherein the stress in the metal film is converted into tensile stress at the preset temperature.

Wherein, the value range of the process time of the conversion deposition step can be 5s-120s, and the value range of the first power and the second power can be 1kW-60 kW.

In the present embodiment, the transition initiation step is similar to the initiation step of the main deposition step S1, in that a first, relatively small power is first applied to the metal target to excite the process gas into a plasma. In contrast, this step reduces the cooling gas from the first flow rate to the second flow rate, preventing effective cooling of the wafer, to enable the temperature of the wafer to be increased in the below-described transition deposition step. The transition deposition step is similar to the deposition step of the main deposition step S1, and applies a second higher power to the metal target, attracts the plasma excited by the process gas to the metal target, causes the plasma to bombard the metal target, sputters metal particles from the metal target, and applies a bias power to the susceptor, causes the metal particles to move toward the wafer, and deposits a metal film on the surface of the wafer. In the step, the wafer is kept cooled by the cooling gas with the second flow rate with a smaller value (even zero) to prevent effective cooling of the wafer, so that the temperature of the wafer can be increased to a preset temperature (often greater than or equal to 130 ℃) under the action of the deposited particles, and the internal stress of the metal film is converted into the tensile stress at the preset temperature.

Further, in the stress transforming step S2, after the stress of the wafer is transformed into the tensile stress, a transformation cooling step of turning off the excitation power supply and the bias power supply and raising the cooling gas from the second flow rate to the first flow rate to cool the wafer may be further included. The step of converting and cooling is carried out after the stress of the wafer is converted into the tensile stress, so that the tensile stress in the metal film is ensured, and the wafer can be rapidly cooled so as to be convenient for subsequent treatment of the wafer.

Typical examples of the present application (deposition of Al thin film) are as follows:

a main deposition step S1, which adopts a whole-course back-blowing mode to ensure that the temperatures of the wafer and the pressure ring are transmitted to the base in time, the flow rate of the cooling gas in the deposition process can be 1sccm-50sccm, the values of the power applied to the metal target (including the first power and the second power) and the bias power applied to the base in the step can be 1kW-60kW (kilowatt), the single-step deposition time can be set according to the specific conditions of the wafer temperature, and the wafer temperature can be effectively controlled in the step to ensure that the deposited Al film has compressive stress.

And a stress conversion step S2, adopting small back blowing or no back blowing deposition, wherein the flow rate of the cooling gas in the deposition process can be 0-10sccm, the power (including the first power and the second power) applied to the metal target and the bias power applied to the base in the step can still be 1-60 kW, and under the plasma environment, the wafer temperature is increased by means of the impact effect of deposited particles, so that the high-temperature treatment under the plasma environment of the wafer is realized, and the stress of the Al film is converted from compressive stress to tensile stress.

The above exemplary embodiments are described in detail below with reference to specific process parameters in table 1 as an example:

table 1 specific process parameters of the thin film deposition method provided in the embodiments of the present application

Taking the above table 1 as an example, the steps 1-40 are the main deposition step S1, and an Al thin film with a specified thickness is obtained. The process comprises the following steps:

step 1, introducing argon (process argon) into the magnetron sputtering chamber from the top or the side, and introducing the argon (back argon) by adopting the back blowing mode, wherein the flow rate of the introduced process argon is 8sccm, the flow rate of the introduced back argon is 20sccm, and the time for introducing the process argon and the back argon can be 20s so as to ensure the pressure in the chamber and enough cooling gas and process gas.

And 2, starting an excitation power supply, applying a first small power, such as 1000W, to the Al target to excite argon gas into Ar positive ions, and simultaneously keeping cooling the wafer by adopting 20sccm back argon, wherein the process time in the step can be 1 s.

And 3, increasing the first power to a second power, such as 35000W, attracting the excited Ar positive ions to bombard the Al target material, enabling the deposited particles to escape, applying bias power to the pedestal through a bias power supply, and attracting the deposited particles to the pedestal to deposit the Al thin film on the wafer, wherein the process time in the step can be 10 s. In the process of depositing the film, the back argon of 20sccm is continuously adopted to cool the wafer, the temperature of the wafer can be increased due to the fact that deposited particles impact the wafer, and meanwhile the wafer is cooled through the back argon, so that the temperature of the wafer is guaranteed to be lower, and temperature accumulation cannot be caused.

And 4, turning off the excitation power supply and the bias power supply, and simply cooling the wafer, wherein the process time in the step can be 10 s. The plasma disappears and the wafer heating is terminated and the wafer is cooled by means of 20sccm of back argon.

5-40, repeating the steps 2-4 for twelve times to obtain an Al film with the specified thickness;

1-40, back argon (20sccm) with a large flow is arranged, the cooling effect of the back argon on the wafer exists all the time in the whole process, and the air valve of the magnetron sputtering chamber is kept fully opened, so that the heat transferred to the wafer by the pressure ring can be effectively released due to the effective cooling effect, and the problem of temperature accumulation in the prior art can be avoided; however, the wafer temperature is always in a low temperature state due to the strong cooling effect of the back argon on the wafer, and the deposited Al thin film shows compressive stress.

Steps 41 to 44 are the stress conversion step S2, which can remove or reduce the cooling gas between the wafer and the susceptor in a short time, rapidly raise the temperature of the wafer due to the impact of the deposited particles, and simultaneously turn on the excitation power supply to apply a certain power to the Al target, thereby providing a necessary plasma environment, and achieving a high temperature treatment of the wafer in the plasma environment in a short time, so as to convert the stress of the Al thin film from compressive stress to tensile stress. Meanwhile, the process processing time of the stress conversion step S2 is short, so that the problem of serious cumulative temperature rise in the prior art is not caused. The process can be carried out in the same magnetron sputtering chamber as steps 1-40, and specifically comprises the following steps:

in step 41, argon gas (process argon) is introduced into the magnetron sputtering chamber only from the top or the side, wherein the flow rate of the introduced process argon can be 28sccm, and the time can also be 20s, so as to ensure the pressure in the chamber and sufficient process gas.

Step 42, similar to step 2 above, the excitation power is turned on, and a first small power, for example 1000W, is applied to the Al target to excite the argon gas into Ar positive ions. Except that this step was maintained at 28sccm of process argon in step 41. The process time in this step may also be 1 s.

And step 43, similar to the step 3, increasing the first power to a second power, for example 35000W, attracting the excited Ar positive ions to bombard the Al target material, allowing the deposited particles to escape, and applying bias power to the susceptor through the bias power supply to attract the deposited particles to the susceptor so as to deposit an Al thin film on the wafer, wherein the process time in this step can also be 10 s. Except that this step also holds 28sccm of process argon, without back argon, in step 41. Because the deposited particles impact the wafer and no back argon is available (the back argon with small flow can be set in practical application) to cool the wafer (or the cooling effect is very weak), the temperature of the wafer can be rapidly increased, the high-temperature treatment of the wafer in a plasma environment is realized, and the stress in the Al film is converted into tensile stress.

In step 44, referring to step 4, the excitation power supply and the bias power supply are turned off, and the wafer is simply cooled, and the process time in this step may also be 10 s. This step, the deposition particle strike, disappeared, wafer heating was terminated, and the wafer was cooled by 20sccm of back argon (8sccm of process argon was used to ensure the pressure in the chamber).

And step 45, closing all valves and power supplies, and ending the step.

In the stress conversion step S2, since the plasma environment is obtained by applying power from the dc excitation power source, the application of dc power will cause the Al target in the sputtering chamber to be bombarded, which results in a certain amount of film deposition, in steps 42 and 43, therefore, the number of the cycle steps in the main deposition step S1 can be reduced according to practical situations to ensure that the Al film thickness is the target thickness, and as shown in table 1 of this application, the number of the cycle steps can be reduced from the original 14 to 12.

Steps 41-44 achieve high temperature processing of the wafer in a plasma environment, so that the stress of the Al film is converted from compressive stress to tensile stress, the sum of the process time of steps 41-45 is much less than the sum of the process time of steps 1-40, steps 1-40 provide sufficient susceptor cooling efficiency for a long time, and steps 41-44 provide high temperature processing of a short plasma environment to rapidly heat the wafer. The stable cooling in the steps 1-40 for a long time can ensure that the temperature accumulation of the wafer can be removed to obtain the Al film with stable temperature and pressure stress, the plasma environment high-temperature treatment in the steps 41-44 for a short time can not cause serious temperature accumulation, and the plasma high-temperature treatment for a short time can ensure that the Al film is converted from the pressure stress to the tensile stress.

With the exemplary embodiment, an Al thin film was continuously deposited on 50 wafers, and the temperature of the stressed wafer (before the transition cooling step in the stress transition step S2) of the obtained Al thin film was tested, and the test results are shown in fig. 3, and it can be seen from fig. 3 that 50 wafers with Al thin films obtained with the exemplary embodiment all have tensile stress at a wafer temperature between 130 ℃ and 160 ℃, and from the 20 th wafer, the temperature of the wafer and the stress of the Al thin film both tend to be stable, the temperature of the wafer is stable at 149 ℃, and the tensile stress of the Al thin film is about 110 MPa.

In the film deposition method provided by this embodiment, the metal film with a specified thickness is obtained through the main deposition step S1, and the wafer is cooled during the deposition process to ensure the surface quality of the wafer, so that the metal film with compressive stress is obtained; then, in the stress transition step S2, by striking the wafer with the deposited particles to uniformly heat the metal thin film, heat can be rapidly transferred to the inside of the wafer, thereby raising the temperature of the entire wafer to a preset temperature in a short time to impart tensile stress to the metal thin film.

It is to be understood that the above embodiments are merely exemplary embodiments that are employed to illustrate the principles of the present application, and that the present application is not limited thereto. It will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the application, and these changes and modifications are to be considered as the scope of the application.

In the description of the present application, it is to be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience in describing the present application and simplifying the description, but do not indicate or imply that the referred device or element must have a particular orientation, be constructed in a particular orientation, and be operated, and thus should not be construed as limiting the present application.

The terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more unless otherwise specified.

In the description of the present application, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood in a specific case by those of ordinary skill in the art.

In the description herein, particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples.

The foregoing is only a partial embodiment of the present application, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present application, and these modifications and decorations should also be regarded as the protection scope of the present application.