阅读说明：本技术 蚀刻方法及等离子体处理装置 (Etching method and plasma processing apparatus ) 是由 箕浦佑也 于 2021-05-24 设计创作，主要内容包括：本发明的课题在于提供一种提高掩膜选择比,并且抑制形成于被蚀刻膜的各开口的形状产生差异的技术。作为解决本发明课题的手段为提供一种蚀刻方法,其特征在于,包括下述工序：工序(A),准备基板,所述基板具有第1膜和第2膜交替地层叠的层叠膜以及上述层叠膜上的掩膜；以及工序(B),通过包含含有碳和氟的气体的处理气体的等离子体,将上述层叠膜进行蚀刻,上述含有碳和氟的气体具有C的不饱和键和CF-(3)基。(The invention provides a technique for improving the mask selection ratio and inhibiting the shape difference of each opening formed on a film to be etched. An etching method according to an aspect of the present invention includes: a step (A) of preparing a substrate having a laminated film in which a 1 st film and a 2 nd film are alternately laminated and the laminated filmA mask on the substrate; and a step (B) of etching the laminated film by plasma of a process gas containing a gas containing carbon and fluorine, the gas containing carbon and fluorine having an unsaturated bond of C and CF 3 And (4) a base.)

1. An etching method, comprising the steps of:

a step (A) of preparing a substrate having a laminated film in which a 1 st film and a 2 nd film are alternately laminated and a mask on the laminated film; and

a step (B) of etching the laminated film by plasma of a process gas containing a gas containing carbon and fluorine,

the gas containing carbon and fluorine has C unsaturated bond and CF₃And (4) a base.

2. The etching method according to claim 1,

the gas containing carbon and fluorine is dissociated into carbon fragments having unsaturated bonds of the C and carbon fragments having the CF in the plasma₃The fluorocarbon segment of the group (a) is,

the carbon fragments are preferentially attached to the upper side of the mask in the step (B),

the fluorocarbon segments are transferred through the mask by the etching in the step (B) to the bottom of the concave portion formed in the laminated film, and the laminated film is further etched.

3. The etching method according to claim 2,

the depth-to-width ratio of the recess is 40 or more.

4. The etching method according to any one of claims 1 to 3,

the gas containing carbon and fluorine is fluorocarbon gas or hydrofluorocarbon gas.

5. The etching method according to claim 4,

the hydrofluorocarbon gas is C₃H₂F₄A gas.

6. The etching method according to any one of claims 1 to 5,

the process gas comprises a hydrogen-containing gas,

the hydrogen-containing gas is H₂。

7. The etching method according to any one of claims 1 to 6,

the 1 st film is a silicon oxide film, and the 2 nd film is a silicon nitride film.

8. The etching method according to any one of claims 1 to 7,

the mask has a plurality of No. 1 opening parts and a plurality of No. 2 opening parts,

the 2 nd opening is located around the outer periphery of the 1 st opening, and the outer periphery of the 2 nd opening has no opening.

9. The etching method according to any one of claims 1 to 8,

the process gas further comprises a hydrogen-containing gas.

10. The etching method according to any one of claims 1 to 9,

in the step (B) of etching the laminated film, the surface temperature of the substrate is controlled to 0 ℃ or lower.

11. A plasma processing apparatus is characterized in that the plasma processing apparatus is provided with a chamber and a control part,

the control unit controls the following steps:

a step (A) of preparing a substrate in the chamber, the substrate having a laminated film in which a 1 st film and a 2 nd film are alternately laminated, and a mask on the laminated film;

a step (B) of etching the laminated film by plasma of a process gas containing a gas containing carbon and fluorine,

in the step (B), the gas containing carbon and fluorine supplied into the chamber has an unsaturated bond of C and CF₃And (4) a base.

Technical Field

The present disclosure relates to an etching method and a plasma processing apparatus.

Background

Patent document 1 discloses a technique of etching openings such as holes and grooves with a high aspect ratio.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2016-

Disclosure of Invention

Problems to be solved by the invention

The present disclosure provides a technique for improving the mask selection ratio and suppressing the occurrence of variations in the shape of each opening formed in an etched film.

Means for solving the problems

According to an aspect of the present disclosure, there is provided an etching method including: a step (A) of preparing a substrate having a laminated film in which a 1 st film and a 2 nd film are alternately laminated and a mask on the laminated film, and a step (B) of etching the laminated film by plasma of a process gas containing a gas containing carbon and fluorine having a C unsaturated bond and a CF₃And (4) a base.

ADVANTAGEOUS EFFECTS OF INVENTION

According to one aspect, the mask selection ratio can be increased, and the occurrence of variations in the shape of each opening formed in the film to be etched can be suppressed.

Drawings

Fig. 1 is a schematic cross-sectional view showing an example of a plasma processing apparatus according to an embodiment.

Fig. 2 is a diagram illustrating an example of an etching method according to the embodiment.

Fig. 3 is a diagram showing a structure of a mask and a laminated film of etched films according to an embodiment.

Fig. 4 is a diagram showing an example of an opening according to the embodiment.

Fig. 5 is a diagram showing an example of the problem of etching.

Fig. 6 is a diagram for explaining a mechanism of etching an opening portion.

FIG. 7 is a graph showing an example of the depth to which radicals reach an opening of a film to be etched by an adhesion coefficient.

Fig. 8 is a diagram showing an example of the relationship between the gas type and the deposition adhesion position on the mask.

Fig. 9 is a diagram showing a precursor generation and a surface reaction model on a substrate according to an embodiment.

Fig. 10 is a diagram showing the configuration of each gas type according to the embodiment.

Fig. 11 is a diagram showing a mask selection ratio and a difference in depth between a central portion and a peripheral portion of a pattern according to the embodiment.

Fig. 12 is a diagram showing a mask selection ratio and an etching rate of a laminated film according to an embodiment.

Fig. 13 is a graph showing the etching rate of the laminated film with respect to the surface temperature of the substrate according to the embodiment and the mask selection ratio with respect to the surface temperature of the substrate according to the embodiment.

Fig. 14 is a table showing mask selection ratios of respective gas types and etching rates of the laminated film according to the embodiment.

Detailed Description

In the etching process, a plurality of holes (or lines) are etched in an etched film using a patterned mask. At this time, although the holes (or lines) to be patterned are densely formed in a certain region, the etching depth differs between the central portion and the peripheral portion of the region after the etching is completed. The Inner-Outer loading phenomenon is a significant problem under the condition that the mask selection ratio is high, that is, the deposition property is high, and causes a circuit failure. Therefore, the mask front side width dimensions of the central portion and the peripheral portion of the pattern are required to be the same etching method. The mask selection ratio is a ratio of an etching rate of an etching target film to an etching rate of a mask (mask E/R) in an etching process.

The present embodiment is a method for etching a laminated film (ON layer) of a silicon oxide film (SiOx) and a silicon nitride film (SiN) by generating plasma from a gas containing a hydrogen-containing gas and a carbon-and-fluorine-containing gas containing a double bond having C and CF₃A hydrofluorocarbon gas based on a polyhydric compound.

Reactive species supplied to each dense and dense region of mask pattern, and reaction of generationThe amount of the product varies, and the Critical Dimension (CD) of the front width of the central portion and the peripheral portion of the pattern region differs. This causes a difference in the shape of the etched film after etching. Therefore, carbon gas is used as much as possible, so that the deposition adhered to the mask becomes uniform and vertical. The radicals generated from the fluorocarbon gas have a higher adhesion coefficient than the radicals generated from the fluorocarbon gas, and the higher the adhesion coefficient of the polymer. The double bond of C contributes to the deposition on the mask, CF₃The radicals help to ensure the etch rate of the ON layer (ON E/R), thus achieving a high mask selectivity.

According to the etching method of the present embodiment, it is possible to suppress the occurrence of variations in the shape of each opening formed in the film to be etched.

Hereinafter, specific embodiments will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted.

[ plasma processing apparatus ]

First, an example of the plasma processing apparatus 1 used in the etching method according to the present embodiment will be described with reference to fig. 1. Fig. 1 is a schematic cross-sectional view showing an example of a plasma processing apparatus 1 according to the embodiment. The plasma processing apparatus 1 shown in fig. 1 is a capacity-coupled type apparatus.

The plasma processing apparatus 1 has a chamber 10. The chamber 10 provides an inner space 10s therein. The chamber 10 includes a chamber body 12. The chamber body 12 has a generally cylindrical shape. An inner space 10s is provided inside the chamber body 12. The chamber body 12 is formed of, for example, aluminum. A corrosion-resistant film is provided on the inner wall surface of the chamber body 12. The film having corrosion resistance is formed of ceramics such as aluminum oxide (alumina oxide) and yttrium oxide, and may be an oxide film subjected to anodic oxidation treatment.

A passage 12p is formed in a side wall of the chamber body 12. The substrate W passes through the passage 12p while being transported between the internal space 10s and the outside of the chamber 10. The passage 12p can be opened and closed by a gate valve 12 g. The gate valve 12g is disposed along a sidewall of the chamber body 12.

A support portion 13 is provided on the bottom of the chamber body 12. The support portion 13 has a substantially cylindrical shape and is formed of an insulating material. The support portion 13 extends upward from the bottom of the chamber body 12 in the internal space 10 s. An edge ring 25 (also referred to as a focus ring) surrounding the periphery of the substrate is provided on the support portion 13. The edge ring 25 has a substantially cylindrical shape and may be formed of silicon or the like.

The plasma processing apparatus 1 further includes a mounting table 14. The mounting table 14 is supported by the support portion 13. The mounting table 14 is provided in the internal space 10 s. The stage 14 is configured to support the substrate W in the chamber 10, i.e., in the internal space 10 s.

The mounting table 14 includes a lower electrode 18 and an electrostatic chuck 20 according to an exemplary embodiment. Table 14 may further include an electrode plate 16. The electrode plate 16 is formed of a conductor such as aluminum, and has a substantially disk shape. The lower electrode 18 is disposed on the electrode plate 16. The lower electrode 18 is formed of a conductor such as aluminum, and has a substantially disk shape. The lower electrode 18 is electrically connected to the electrode plate 16. The outer peripheral surface of the lower electrode 18 and the outer peripheral surface of the electrode plate 16 are surrounded by the support portion 13.

An electrostatic chuck 20 is disposed on the lower electrode 18. The electrode of the electrostatic chuck 20 is connected to a dc power supply 20p via a switch 20 s. If a voltage from the dc power supply 20p is applied to the electrode, the substrate W is held by the electrostatic chuck 20 due to the electrostatic attraction. The electrostatic chuck 20 supports the substrate W and the edge ring 25.

A flow channel 18f is provided inside the lower electrode 18. In the flow path 18f, a heat exchange medium (for example, a cooling medium) is supplied from a cooling unit provided outside the chamber 10 through the pipe 22 a. The heat exchange medium supplied to the flow path 18f is returned to the cooling unit through the pipe 22 b. In the plasma processing apparatus 1, the temperature of the substrate W placed on the electrostatic chuck 20 is adjusted by heat exchange between the heat exchange medium and the lower electrode 18.

In the plasma processing apparatus 1, a heat transfer gas supply line 24 is provided. The heat transfer gas supply line 24 supplies a heat transfer gas (e.g., He gas) from the heat transfer gas supply mechanism between the upper surface of the electrostatic chuck 20 and the lower surface of the substrate W.

The plasma processing apparatus 1 further includes an upper electrode 30. The upper electrode 30 is disposed above the mounting table 14 to face each other. The upper electrode 30 is supported on the upper portion of the chamber body 12 via a member 32. The member 32 is made of an insulating material. The upper electrode 30 and member 32 close the upper opening of the chamber body 12.

The upper electrode 30 may include a top plate 34 and a support 36. The lower surface of the top plate 34 is the lower surface on the side of the internal space 10 s. The top plate 34 may be formed of a low-resistance conductor or semiconductor with little joule heat. The top plate 34 is formed with a plurality of gas discharge holes 34 a. The gas discharge holes 34a penetrate the top plate 34 in the plate thickness direction.

Support 36 supports top plate 34 detachably. The support 36 is formed of a conductive material such as aluminum. A gas diffusion chamber 36a is provided inside the support body 36. The support body 36 is formed with a plurality of gas holes 36 b. The plurality of gas holes 36b extend downward from the gas diffusion chamber 36 a. The plurality of gas holes 36b communicate with the plurality of gas discharge holes 34a, respectively. The support 36 has a gas inlet 36 c. The gas inlet 36c is connected to the gas diffusion chamber 36 a. The gas inlet 36c is connected to a gas supply pipe 38.

A gas supply unit GS including a gas source group 40, a flow rate controller group 44, and a valve group 42 is connected to the gas supply pipe 38. The gas source group 40 is connected to the gas supply pipe 38 via a flow rate controller group 44 and a valve group 42. The gas source set 40 includes a plurality of gas sources. The valve group 42 includes a plurality of opening/closing valves. The flow controller group 44 includes a plurality of flow controllers. The plurality of flow rate controllers of the flow rate controller group 44 are each a mass flow rate controller or a pressure control type flow rate controller. The plurality of gas sources of the gas source group 40 are connected to the gas supply pipe 38 via corresponding flow rate controllers of the flow rate controller group 44 and corresponding on-off valves of the valve group 42, respectively. The power source 70 is connected to the upper electrode 30. The power supply 70 applies a voltage for introducing positive ions present in the internal space 10s into the top plate 34 to the upper electrode 30.

In the plasma processing apparatus 1, a shield (shield)46 is detachably provided along an inner wall surface of the chamber body 12. The shield 46 is also provided on the outer periphery of the support portion 13. The shield 46 prevents reaction products, such as etch byproducts, from adhering to the chamber body 12. The shield 46 is formed by forming a corrosion-resistant film on the surface of a member made of aluminum, for example. The film having corrosion resistance may be an oxide film such as alumina or yttria.

A buffer plate 48 is provided between the support portion 13 and the side wall of the chamber body 12. The buffer plate 48 is formed by forming a corrosion-resistant film on the surface of a member made of aluminum, for example. The film having corrosion resistance may be an oxide film such as alumina or yttria. The buffer plate 48 is formed with a plurality of through holes. An exhaust port 12e is provided at the bottom of the chamber body 12 below the buffer plate 48. The exhaust port 12e is connected to an exhaust device 50 via an exhaust pipe 52. The exhaust device 50 includes a vacuum pump such as a pressure regulating valve and a turbo molecular pump.

The plasma processing apparatus 1 includes a 1 st high-frequency power supply 62 for applying power of high-frequency HF for plasma excitation. The 1 st high-frequency power supply 62 is configured to generate electric power of high-frequency HF in order to generate plasma from the gas in the chamber 10. The frequency of the high-frequency HF is, for example, a frequency in the range of 40MHz to 100 MHz. The high-frequency HF may be a pulse-like voltage having a rectangular waveform.

The 1 st high-frequency power source 62 is electrically connected to the electrode plate 16 and the lower electrode 18 via a matching unit 66. The matcher 66 has a matching circuit. The matching circuit of the matching unit 66 is configured to match the impedance of the load side (lower electrode side) of the 1 st high-frequency power source 62 with the output impedance of the 1 st high-frequency power source 62. In another embodiment, the 1 st high frequency power source 62 may be electrically connected to the upper electrode 30 via the matching unit 66.

The plasma processing apparatus 1 may further include a 2 nd high-frequency power supply 64 for applying power of the high frequency LF for bias voltage. The 2 nd high frequency power supply 64 is configured to generate power of a high frequency LF. The high frequency LF mainly has a frequency suitable for introducing ions to the substrate W, and is, for example, a frequency in the range of 400kHz to 3 MHz. The high frequency LF may be a pulse-like voltage having a rectangular waveform.

The 2 nd high-frequency power supply 64 is electrically connected to the electrode plate 16 and the lower electrode 18 via a matching unit 68. The matcher 68 has a matching circuit. The matching circuit of the matching unit 68 is configured to match the impedance of the load side (lower electrode side) of the 2 nd high-frequency power supply 64 with the output impedance of the 2 nd high-frequency power supply 64.

The plasma processing apparatus 1 may further include a control unit 80. The control unit 80 may be a computer including a storage unit such as a processor and a memory, an input device, a display device, a signal input/output port, and the like. The control unit 80 controls each part of the plasma processing apparatus 1. The control unit 80 can use an input device, and an operator can perform an input operation of a command to manage the plasma processing apparatus 1. The control unit 80 can visually display the operating state of the plasma processing apparatus 1 through a display device. Further, a storage unit of the control unit 80 stores a control program and recipe data. The control program is executed by the processor of the control unit 80 in order to execute various processes by the plasma processing apparatus 1. The processor of the control section 80 controls each section of the plasma processing apparatus 1 in accordance with recipe data by executing a control program, so that various processes, for example, a plasma processing method, are executed by the plasma processing apparatus 1.

The temperature of the electrostatic chuck 20 is adjusted to a desired temperature by a heat exchange medium supplied from a cooling unit through a pipe 22a, and the surface temperature of the substrate (for example, the wafer temperature) is adjusted by heat transfer to the substrate W through the surface of the electrostatic chuck 20 and a heat transfer gas. However, the substrate W is exposed to plasma generated by the power of the high-frequency HF for plasma excitation, and the substrate W is irradiated with ions introduced by the light from the plasma or the power of the high-frequency LF for bias voltage. Therefore, the temperature of the substrate W, particularly, the surface temperature of the substrate W facing the plasma is higher than the temperature of the adjusted electrostatic chuck 20. In addition, the surface temperature of the substrate W may also rise due to radiant heat from the temperature-adjusted counter electrode and the side wall of the chamber 10. Therefore, when the temperature of the actual substrate W during the etching process can be measured, or when the temperature difference between the adjustment temperature of the electrostatic chuck 20 and the surface temperature of the actual substrate W can be estimated from the process conditions, the adjustment temperature of the electrostatic chuck 20 may be set to be lower in order to adjust the surface temperature of the substrate W within a predetermined temperature range.

[ etching method ]

The etching method according to the present embodiment will be described with reference to fig. 2 and 3. Fig. 2 is a diagram illustrating an example of an etching method according to the embodiment. Fig. 3 is a diagram showing a structure of a mask and a laminated film of etched films according to an embodiment.

As shown in fig. 2, in the etching method according to the present embodiment, a substrate W having a laminated film 100 in which a silicon oxide film and a silicon nitride film are alternately laminated and a mask 101 on the laminated film 100 as shown in fig. 3(a) is prepared (step S1). The silicon oxide film is an example of the 1 st film, and the silicon nitride film is an example of the 2 nd film.

Next, the film to be etched is etched by the plasma generated by the plasma processing apparatus 1 (step S2). The etching of step S2 is also referred to as main etching.

Fig. 3(a) shows the initial state before etching, which is the film structure of the laminated film 100 and the mask 101 as the etched films. The substrate W includes a laminated film 100, a mask 101 on the laminated film 100, and a base film 102 under the laminated film 100. The mask 101 is made of an organic material and has an opening HL. The base film 102 is formed of, for example, polysilicon. However, the base film 102 is not limited to polycrystalline silicon and may be formed of amorphous silicon or single crystal silicon.

In the main etching in step S2, as shown in fig. 3(b), the laminated film 100 is etched into the pattern of the mask 101 to form a concave portion. Further, as shown in fig. 3(c), etching is performed until the base film 102 is exposed.

In this way, in the main etching, the laminated film 100 is etched through the opening HL of the mask 101 by the plasma of the gas supplied to the plasma processing apparatus 1, and the laminated film 100 forms a concave portion having an etched shape. The hole-shaped recess formed in the laminated film 100 is also referred to as an opening HL.

Fig. 4 is a diagram illustrating an example of the opening HL according to the embodiment. As shown in fig. 4(a), the opening HL includes a plurality of 1 st openings HL1 and a plurality of 2 nd openings HL 2. The 2 nd opening HL2 is located around the periphery of the 1 st opening HL1, and the 2 nd opening HL2 has no opening at its periphery. The 1 st opening HL1 and the 2 nd opening HL2 have the same CD (critical dimension) value. The distance between the 2 nd opening HL2 in the outermost region 2 and the 1 st opening HL1 in the region 1 adjacent to the 2 nd opening HL2 is wider than or equal to the distance between the adjacent 1 st openings HL1 in the region 1.

In the above configuration, the pattern of the mask 101 is defined to have a density relationship in the opening HL of the present embodiment. That is, if comparing the region 1 where the plurality of 1 st opening parts HL1 are formed with the region 2 where the plurality of 2 nd opening parts HL2 are formed (the region outside the region 1), the pattern of the mask 101 of the region 1 is denser than the pattern of the mask 101 of the region 2. In other words, the pattern of the mask 101 of the region 2 is sparser than the pattern of the mask 101 of the region 1.

The recess formed by the laminate film 100 may have a linear shape. In FIG. 4(b), the linear recesses are shown by the 1 st opening LN1 and the 2 nd opening LN 2. A2 nd opening LN2 is located so as to surround the outer periphery of the 1 st opening LN1, and the outer periphery of the 2 nd opening LN2 has no opening.

As shown in fig. 4(b), the pattern of the mask 101 has a density relationship between the region 1 where the 1 st opening LN1 is formed and the region 2 where the 2 nd opening LN2 is formed, and the pattern of the mask 101 is dense in the region 1 and the pattern of the mask 101 is sparse in the region 2. Although the opening HL is described below as an example of the pattern of the mask 101, the etching method according to the present embodiment can be applied to the pattern of the mask 101 in which the recess is linear.

As shown in fig. 3, the laminated film 100 is etched to form a recess, and the thickness of the mask 101 decreases and becomes thinner as the depth of the recess becomes deeper. In addition, in the case where the laminated film 100 is further used, the aspect ratio of the concave portion becomes high, and the etching rate of the laminated film 100 is lowered due to the depth load effect. In particular, in the etching shape processing with a high aspect ratio of 40 or more, the mask 101 may disappear before the base film 102 is exposed, and the etching may not be completed. Therefore, etching of the laminated film 100 having a high mask selection ratio is required.

Fig. 5 shows a mask selection ratio and a depth difference between a central portion and a peripheral portion of a pattern. In fig. 5(a), the horizontal axis represents the mask selection ratio, and the vertical axis represents the depth difference (Δ ON depth) between the 1 st opening HL1(inner) and the 2 nd opening HL2 (outer).

Generally, as shown in FIG. 5(a), by using CF₄Gas, C₃F₈Gas phase ratio, C₄F₈Gas, C₄F₆A gas having a high C/F ratio such as a gas, that is, a gas having a high ratio of carbon (C) to fluorine (F), thereby obtaining an etching result having a high mask selectivity. When the mask selection ratio is about 4 or less, or 4 or less, the depth difference (Δ ON depth) of all gases is close to 0. At this time, as shown in fig. 5(b), the depths of the 1 st opening HL1 and the 2 nd opening HL2 are almost the same.

However, when the mask selection ratio of these gases is 4 or more, the difference in depth of all the gases is drastically increased. At this time, as shown in fig. 5(c), the depth of the 1 st opening HL1 is deeper than the depth of the 2 nd opening HL 2. That is, the etched multilayer film 100 has a difference in depth between the 1 st opening HL1 and the 2 nd opening HL2 with respect to the density of the pattern of the mask 101.

Fig. 6 is a diagram for explaining a mechanism of etching of the 1 st opening portion HL1 and the 2 nd opening portion HL 2. In fig. 6, a 1 st opening HL1 at the left end shown in fig. 4(a) and a 2 nd opening HL2 adjacent to the right side thereof are shown. In the region 1 where the 1 st opening HL1 is formed, the mask 101 has a dense pattern, and in the region 2 where the 2 nd opening HL2 is formed, the mask 101 has a sparse pattern.

As shown in fig. 6, the depth of the 2 nd opening HL2 of the etched laminated film 100 is shallower than the depth of the 1 st opening HL1 with respect to the density of the pattern of the mask 101.

In an initial state where etching is started, the depths of the 1 st opening HL1 and the 2 nd opening HL2 formed in the laminated film 100 are almost the same. However, if the etching of the laminated film 100 progresses, the radicals containing O, which are reaction products generated during the etching, are vaporized and pass through the 1 st openingThe HL1 and the 2 nd opening HL2 were discharged to the outside of the mask 101. The gas used for the main etching does not contain O radicals, and therefore no O-containing radicals are present in the generated plasma. Therefore, it is understood that the generated radicals containing O are SiO in the multilayer film 100₂Radicals generated from reaction products generated during etching.

On the other hand, the etching gas contains C radicals and F radicals, and thus the C radicals and the F radicals exist in the generated plasma. Among them, the F radicals are mainly consumed by etching the laminated film 100, and the C radicals are accumulated on the mask 101.

At this time, in the region 1, the plurality of 1 st opening portions HL1 are densely present, and in the region 2, the plurality of 2 nd opening portions HL2 are sparsely present. Therefore, the radicals containing O discharged from the plurality of 2 nd openings HL2 of the region 2 to the outside of the mask 101 are less than the radicals containing O discharged from the plurality of 1 st openings HL1 of the region 1 to the outside of the mask 101.

As a result, in the region 1, the radical containing O reacts with the radical containing C to become CO_xAnd volatilizing. In this way, since the C radicals are consumed in the region 1, the C radicals can be prevented from accumulating in the opening portion of the mask 101, and the opening of the mask can be narrowed. Therefore, in the region 1, the CD size of the opening portion of the mask 101 is not narrowed, and radicals containing F sufficiently enter the 1 st opening HL1 from the opening of the mask 101 and reach the bottom, thereby promoting etching.

On the other hand, in region 2, since the plurality of 2 nd opening portions HL2 are sparsely present, the proportion of radicals containing O generated is also lower than in region 1. Therefore, in the region 2, the C-containing radicals consumed by the reaction with the O-containing radicals are less than in the region 1, and the C radicals accumulated in the opening portion of the mask 101 are more than in the region 1. Therefore, in the region 2, the CD size of the opening portion of the mask 101 is narrowed by the deposition of the C radicals, and from the narrowed opening of the mask 101, sufficient F-containing radicals are less likely to enter the 2 nd opening HL2, and the F-containing radicals reaching the bottom are reduced, so that the etching rate is lowered.

As a result, etching was promoted in the plurality of 1 st openings HL1 in the region 1, etching was not promoted in the plurality of 2 nd openings HL2 in the region 2, and the depth of the recess of the 2 nd opening HL2 was shallower than the depth of the recess of the 1 st opening HL 1.

However, regardless of the density of the pattern of the mask 101, high throughput due to a high etching rate and a high mask selection ratio are required. In order to obtain high throughput, it is desirable to make it difficult to perform etching in which the difference between the depth of the recess of the 2 nd opening HL2 and the depth of the recess of the 1 st opening HL1 is generated.

Therefore, in the present embodiment, an etching method is proposed that can realize etching shape processing with a high throughput and a high mask selection ratio, for example, a high aspect ratio of 40 or more, regardless of the density of the pattern of the mask 101 when the laminated film 100 is etched.

In the etching method according to the present embodiment, high throughput and high mask selection ratio are realized by etching. Further, when C radicals are attached to the mask 101, a gas is selected in which the CD dimension of the front width of the 2 nd opening HL2 is not easily reduced.

Specifically, the laminated film 100 is etched by plasma of a process gas containing a gas containing carbon and fluorine. In the present embodiment, the gas containing carbon and fluorine has an unsaturated bond of C and CF₃And (4) a base. Examples of the gas containing carbon and fluorine include a fluorocarbon gas and a hydrofluorocarbon gas. The hydrofluorocarbon gas is, for example, C₃H₂F₄A gas. In the present embodiment, the process gas may further include a hydrogen-containing gas, and one example of the hydrogen-containing gas is H₂A gas.

Thus, an etching process is realized in which the CD size of the front width of the mask 101 is uniformly maintained regardless of the density of the pattern of the mask 101, and a difference in etching depth is less likely to occur in the 1 st opening HL1 of the region 1 and the 2 nd opening HL2 of the region 2. The etching method according to the present embodiment will be described in detail below.

When a gas whose CD size of the front width of the 2 nd opening HL2 is not easily reduced is selected when C radicals are attached to the mask 101, the gas attachment coefficient (reaction probability) is preferably low. FIG. 7 is a graph showing an example of the depth to which radicals reach an opening of a film to be etched by using the sticking coefficient.

As shown in fig. 7, if the radical adhesion coefficient is low, the radicals adsorbed to the side surface in the middle of the opening are small, and the radicals reach the bottom of the opening or the deep portion of the opening. On the other hand, as the adhesion coefficient is higher, radicals are adsorbed to the side surface in the middle of the opening, and it is difficult to supply radicals to the bottom of the opening or the deep portion of the opening.

That is, the lower the adhesion coefficient of the low molecular gas, the less the reaction product adheres to the mask 101, the opening of the mask 101 is not narrowed, and etching proceeds. However, in this case, the mask selection ratio becomes low.

Fig. 8 is a diagram showing an example of the relationship between the gas type and the deposit adhesion on the mask. FIG. 8(a) shows supply H₂/CF₄The state of the opening of the mask 202 in the mixed gas (c). FIG. 8(b) shows supply H₂/CHF₃The state of the opening of the mask 204 in the mixed gas (c). FIG. 8(c) shows supply H₂/CH₂F₂The state of the opening of the mask 203 in the mixed gas of (3). FIG. 8(d) shows supply H₂/CH₃The state of the opening of the mask 205 in the mixed gas of F. The masks 202-205 may be the same organic material as the mask 101.

Accordingly, the hydrofluorocarbon gas (fig. 8(b) to 8(d)) has a higher adhesion coefficient and a higher mask selectivity than the fluorocarbon gas (fig. 8(a)), and therefore, in fig. 8(b) to 8(d), C radicals tend to adhere to the upper portion of the mask and the opening of the mask tends to be less narrow than in fig. 8 (a). That is, a gas having a low adhesion coefficient has a high etching rate but a low mask selection ratio, and a gas having a high adhesion coefficient has a high mask selection ratio but a low etching rate.

In contrast, in the etching method according to the present embodiment, it is desired to achieve both the etching rate and the mask selection ratio in a trade-off relationship, and to realize the etching with respect to the mask 101The pattern has dense openings HL, and poor etching hardly occurs in the etching depth. Therefore, as the gas used for etching, unsaturated bond having C and CF are used₃Hydrofluorocarbon based gases.

Fig. 9 is a diagram showing a precursor generation and a surface reaction model on the substrate W according to the present embodiment. In FIG. 9, the etching shows C₃H₂F₄Gas as unsaturated bond having C and CF₃Hydrofluorocarbon-based gases are illustrated. In the present embodiment, the unsaturated bond of C is a double bond of C as an example, but the unsaturated bond is not limited thereto, and may be a gas having a triple bond or the like.

As shown in fig. 9, C contained in the process gas supplied in the etching method according to the present embodiment₃H₂F₄The gas is supplied to the inner space 10s of the chamber 10 and dissociated in the plasma 2.

Fig. 10 is a diagram showing the configuration of each gas type according to the embodiment. C₃H₂F₄The gas had the structure shown in FIG. 10(f), at CF₃The linking part of the radical and the unsaturated bond of C is easily cleaved, and dissociated into a compound having the unsaturated bond of C (here, the double bond of C) and a compound having CF in the plasma 2₃A compound of formula (I). Hereinafter, a compound having an unsaturated bond of C will be referred to as a carbon fragment A, and CF will be referred to as a carbon fragment A₃The compound of the radical is referred to as fluorocarbon segment B.

In FIG. 9, C is shown in the plasma 2₃H₂F₄Gas (CHF ═ CH-CF)₃) Dissociate into carbon fragments A (CHF ═ CH) and fluorocarbon fragments B (CF)₃) The state of (1).

During etching, carbon segment a (CHF ═ CH) preferentially adheres to the upper side of mask 101 during main etching (see 103 in fig. 9). This is because the carbon fragment a having a double bond of C is unstable and highly reactive, and therefore has a high adhesion coefficient and tends to adhere preferentially to the upper side of the mask 101. On the other hand, the fluorocarbon segment B is transported through the mask 101 by the main etching up to the bottom of the opening HL (concave portion) formed by the laminated film 100, and further, has a large amount of F with respect to C, thereby advancing the laminated film 100 furtherAnd (4) etching. That is, the carbon segment A having a double bond of C contributes to a high mask selection ratio, with CF₃The fluoro-carbon segments B of the radicals contribute to a high etch rate. Thus, in the etching method according to the present embodiment, C is included by the supply₃H₂F₄The processing gas is a gas capable of achieving both high throughput and high mask selection ratio due to a high etching rate.

In contrast, C in FIG. 10(a)₄F₈It is difficult to obtain a high mask selectivity ratio for the gas. Thereby, for using C₄F₈It is difficult to achieve both high throughput and high mask selectivity for gas etching.

C in FIG. 10(b)₄F₆The gas has 2C double bonds, but no CF₃And (4) a base. Therefore, a high mask selection ratio is obtained, but it is difficult to obtain a high etching rate. Thereby, for using C₄F₆It is difficult to achieve both high throughput and high mask selectivity for gas etching.

C of FIG. 10(C)₃F₈The gas having CF₃Accordingly, a high etching rate is obtained, but it is difficult to obtain a high mask selection ratio because it does not have an unsaturated bond of C. Thereby, for using C₃F₈It is difficult to achieve both high throughput and high mask selectivity for gas etching. CH of FIG. 10(e)₂F₂Similarly, since the gas does not have an unsaturated bond of C, it is difficult to obtain a high mask selection ratio. Thereby, for using CH₂F₂It is difficult to achieve both high throughput and high mask selectivity for gas etching.

C of FIG. 10(d)₃F₆Gas due to having CF₃Thus, a high etching rate is obtained. In addition, since the double bond of C is present, a high mask selection ratio is obtained. Thereby, for using C₃F₆The gas etching can achieve both high throughput and high mask selection ratio. However, in the laminated film 100 in which the silicon oxide film and the silicon nitride film are alternately laminated, hydrogen is required for etching the silicon nitride film. Thereby, for using C₃F₆For the etching of gases, inIt is desirable to include C in the process gas₃F₆Gases and gases containing hydrogen.

Furthermore, if C in FIG. 10(d) is added₃F₆Gas and C of FIG. 10(f)₃H₂F₄Comparison of the gases then C₃H₂F₄With C₃F₆The fluorocarbon gas has a higher adhesion coefficient. Thus, C₃H₂F₄Gas and C₃F₆The C radicals are more likely to adhere to the upper portion of the mask 101 than the gas, and the mask selection ratio can be further improved.

However, the gas containing carbon and fluorine used in the etching method according to the present embodiment is not limited to C₃H₂F₄Gas, C₃F₆A gas. For example, the gas containing carbon and fluorine is dissociated into a fragment containing an unsaturated bond having C and a CF when the gas is dissociated in the plasma 2₃The gas of the compound of the fragment of the substrate may be any gas.

[ test results 1: difference in depth between the 1 st opening and the 2 nd opening due to the gas type ]

Next, C is used in the etching method according to the present embodiment₃H₂F₄In comparison with the case of using a plurality of other gas species, an experiment was performed in which the difference in depth (difference in depth) between the 1 st opening HL1 and the 2 nd opening HL2 was measured for each gas species.

The etching conditions in this embodiment are as follows.

< etching Condition of experiment result 1 >

Pressure in the treatment vessel: 20mT (2.67Pa)

High-frequency HF power: on

High-frequency LF power: on

Treating gas: c₃H₂F₄Gas, C₄F₈Gas, C₄F₆Gas, CH₂F₂Gas (es)

Adding gas: hydrogen (H)₂) Gas (es)

Surface temperature of substrate: 0 deg.C

Fig. 11 is a diagram showing a mask selection ratio and a difference in depth between a central portion and a peripheral portion of a pattern according to the embodiment. In experimental result 1, etching was performed using 4 gases shown in fig. 11. In fig. 11, the horizontal axis represents the mask selection ratio, and the vertical axis represents the depth difference (Δ ON depth) between the 1 st opening HL1(inner) and the 2 nd opening HL2 (outer). In addition, use C₄F₈Gas, C₄F₆The gas case is the same as that shown in fig. 5.

According to experiment result 1 of FIG. 11, C was used₄F₈Gas, C₄F₆In the case of gas, when the mask selection ratio is about 4 or less, the difference in depth (Δ ON depth) of all gases is close to 0. At this time, as shown in fig. 5(b), the depths of the 1 st opening HL1 and the 2 nd opening HL2 are almost the same.

However, when the mask selection ratio of these gases is 4 or more, the difference in depth of all the gases becomes large. At this time, as shown in fig. 5(c), the depth of the 1 st opening HL1 is deeper than the depth of the 2 nd opening HL 2.

In the use of CH₂F₂In the case of gas, when the mask selection ratio is about 4.5 or less, the depth difference is close to 0. However, if the mask selection ratio is 4.5 or more, the difference in depth is large, and the etching is in the state shown in fig. 5 (c).

In contrast, in the use of C₃H₂F₄In the case of gas, when the mask selection ratio is about 4.8 to 4.9 or less, the depth difference is close to 0, and etching proceeds in the state shown in fig. 5 (b).

From the above results, it is clear that C is used₃H₂F₄In the case of gas, the carbon segment A having an unsaturated bond of C contributes to a high mask selection ratio, and CH having no unsaturated bond of C is used₂F₂The mask selection ratio is improved compared to the case of gas. In addition, since the carbon segment a having an unsaturated bond of C preferentially adheres to the upper side of the mask 101 and it is difficult to narrow the opening of the mask 101, the 1 st openingThe etching of the opening part HL1 and the 2 nd opening part HL2 did not cause a difference, and a recess part having substantially the same depth could be formed.

[ test results 2: mask selection ratio and etching Rate of laminated film ]

Then, the calculation of the use of C is performed₃H₂F₄Experiments of the relationship between the mask selection ratio in the case of a gas and a plurality of other gas species and the etching rate of the laminated film 100. Fig. 12 is a graph showing a relationship between the mask selection ratio and the etching rate of the laminated film 100 according to the embodiment. The process conditions other than the gas according to experiment result 2 are as shown in the above-mentioned etching conditions < experiment result 1 >.

From experiment result 2 of FIG. 12, it is understood that C is used even when C is used₄F₈Gas, C₄F₆Gas, C₃F₈Gas, C₃H₂F₄In the case of any of the gases, the mask selection ratio and the etching rate of the laminated film 100 also have a trade-off relationship.

In use C₄F₆In the case of a gas, the etching rate of the laminated film 100 is lower than that of other gases, and the throughput is reduced. In addition, in the use of C₄F₆In the case of gas, the mask selection ratio is relatively lowered compared to other gases. In use C₃F₈In the case of a gas, although the etching rate of the laminated film 100 is high, the mask selection ratio cannot be 3.4 or more, and it is not possible to achieve both the mask selection ratio and the etching rate.

In use C₃H₂F₄In the case of gas, with C₄F₈In comparison with the case of gas, the relationship of the mask selectivity to the etching rate is improved, a high mask selectivity can be obtained, and a decrease in the etching rate can be suppressed. The reason for this is that C is used₃H₂F₄In the case of gas, the carbon segment A having an unsaturated bond of C contributes to a high mask selection ratio and has CF₃The fluoro-carbon segments B of the radicals contribute to a high etch rate.

[ test results 3: etching Rate of laminated film relative to surface temperature of substrate and mask selection ratio

Then, the calculation of the use of C is performed₃H₂F₄An experiment of a relationship between an etching rate of the laminated film in the case of gas with respect to a surface temperature of the substrate and a mask selection ratio with respect to the surface temperature of the substrate. Fig. 13 is a graph showing a relationship between an etching rate of a laminated film and a surface temperature of a substrate according to an embodiment and a mask selection ratio with respect to the surface temperature of the substrate according to the embodiment. The process conditions other than the gas and substrate surface temperatures according to experiment result 3 are as shown in the above-mentioned etching conditions < experiment result 1 >.

As shown in fig. 13(a), the etching rate of the laminated film 100 is increased by lowering the surface temperature of the substrate. As shown in fig. 13(b), the mask selection ratio is also increased by lowering the surface temperature of the substrate. In the comparison of the gas types in experimental result 1 (fig. 11) and experimental result 2 (fig. 12), the surface temperature of the substrate is 0 ℃, and therefore, in order to obtain the condition of higher mask selection ratio, it is desirable to control the surface temperature of the substrate to 0 ℃ or less.

[ summary of the Experimental results ]

A summary of the experimental results is shown in fig. 14. Fig. 14 is a table showing the mask selection ratio of each gas type and the etching rate of the laminated film according to the embodiment. In the table entry, "mask selection ratio" indicates a mask selection ratio obtained in a state where the opening properties of the 2 nd opening HL2 are maintained. "ON E/R" is an etching rate obtained in a state where the difference between the depths of the 1 st opening HL1 and the 2 nd opening HL2 is maintained at substantially 0, and indicates an etching rate of the laminated film 100 when the mask selection ratio is fixed to 4.

Among the 5 gas species, H is used₂/C₄F₈The etching rate of the laminated film 100 is good, but since the mixed gas of (1) has no unsaturated bond of C, the mask selectivity is low, and the mask selectivity and the etching rate of the laminated film 100 are not achieved at the same time.

In use H₂/CH₂F₂The etching rate of the laminated film 100 is good, but since the mixed gas of (1) does not have an unsaturated bond of C, the improvement of the mask selectivity is small, and the mask selectivity and the etching rate of the laminated film 100 are not achieved at the same time.

In use H₂/C₃H₂F₄Has C unsaturated bond and CF during etching₃Accordingly, both the etching rate and the mask selection ratio of the laminated film 100 become good, and the mask selection ratio and the etching rate of the laminated film 100 are achieved at the same time.

In use H₂/C₄F₆Does not have CF in etching of the mixed gas₃Accordingly, the etching rate of the laminated film 100 is low, and the mask selection ratio cannot be improved, and the mask selection ratio and the etching rate of the laminated film 100 cannot be achieved at the same time.

In use H₂/C₃F₈The mask selectivity ratio in the etching of the mixed gas (2) is not 3.4 or more, and the mask selectivity ratio and the etching rate cannot be achieved at the same time.

As is clear from the above, in the etching method according to the present embodiment, the etching solution containing H is used₂Gas and C₃H₂F₄The processing gas is a gas, and thus both the mask selection ratio and the etching rate of the laminated film 100 can be achieved.

In addition, regardless of the density of the pattern of the mask 101 when the multilayer film 100 having the openings HL whose outermost periphery is sparse and whose inside is dense is etched, it is possible to achieve a high throughput and a high mask selection ratio.

For example, radicals generated from fluorocarbon gas have a larger adhesion coefficient than radicals generated from fluorocarbon gas, and the higher the adhesion coefficient of polymer. The double bond of C is easily deposited on the mask 101, and a high mask selectivity is obtained. Further, CF₃The radicals help to ensure the etching rate of the laminated film 100. This can suppress the occurrence of a difference in depth (shape) between the openings (the 1 st opening HL1 and the 2 nd opening HL2) formed in the multilayer film 100 as an etched film.

The etching method according to the embodiment disclosed here is illustrative in all respects and should not be considered as being limiting. The embodiments can be modified and improved in various forms without departing from the claims and the gist thereof.

The plasma processing apparatus of the present disclosure can also be applied to any type of apparatus of an Atomic Layer Deposition (ALD) apparatus, a Capacitively Coupled Plasma (CCP), an Inductively Coupled Plasma (ICP), a Radial Line Slot Antenna (RLSA), an electron cyclotron resonance plasma (ECR), and a Helicon Wave Plasma (HWP).