Plasma processing method

Abstract

A plasma processing method for plasma etching a film to be etched of a substrate to be processed (301) having the film to be etched (201) and a sacrificial layer (200) formed in a pattern above the film to be etched, the plasma processing method comprising: a first step for depositing a silicon element-containing film (204) on the sacrificial layer; a second step of nitriding, after the first step, the silicon element-containing film deposited on the sacrificial layer and the silicon element-containing film deposited on the film to be etched using plasma generated from a nitrogen element-containing gas; and a third step in which, after the second step, the silicon-containing film is oxidized using plasma generated from the oxygen-containing gas.

Description

Technical Field

[0001] The invention relates to a plasma processing method for a semiconductor substrate. Background Art

[0002] Currently, since it is difficult to directly analyze by exposure, the method of reducing the pattern by 2 times the pitch and 4 times the pitch is widely used. These are called Self-Aligned Double Patterning (SADP) and Self-Aligned Quadruple Patterning (SAQP), and have become essential technologies in the semiconductor manufacturing process for forming fine patterns.

[0003] For example, in patent document 1 or non-patent document 1, the process flow of SADP is shown. First, the film to be etched, the sacrificial film, and the resist are formed and coated in the order of the film to be etched, and the resist is developed and patterned. Next, the sacrificial layer is etched using the resist as a mask. After removing the resist, an oxide film or the like is formed on the sacrificial layer pattern using ALD (Atomic Layer Deposition) or the like. The formed oxide film or the like is called a spacer. Next, the portion deposited between the upper part of the sacrificial layer pattern and the bottom of the sacrificial layer pattern (i.e., on the etched film) is selectively removed from the spacer by etching. Furthermore, by removing the sacrificial layer, a structure is formed on the etched film in which only the spacer formed on the side wall of the sacrificial layer pattern remains. Then, the remaining spacer is used as a mask to process the etched film. By using such a method, a pattern with a size of 1 / 2 of the original pitch (2 times the pitch) can be formed.

[0004] Prior Art Literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2010-114424

[0007] Non-patent literature

[0008] Non-patent document 1: T.Shibata et al., "ALD-SiO2 deposition and CD slimmingtechniques for double patterning and a heater-less batch tool", 201 0International Symposium on Semiconductor Manufacturing (ISSM) Summary of the invention

[0009] Problems to be solved by the invention

[0010] In the SADP embodiment shown in the prior art document, a silicon oxide film or the like is formed as a mask around the sacrificial layer using a method such as ALD. Since the formation of the silicon oxide film using ALD and the etching after the film formation are processed by different devices, the film forming device and the etching device are repeatedly moved back and forth. As a result, the equipment dedicated area (floor area) becomes larger, and it takes time to transport between devices.

[0011] Solutions to Solve Problems

[0012] A plasma processing method as an embodiment of the present invention performs plasma etching on an etched film of a processed substrate having an etched film and a sacrificial layer formed in a pattern above the etched film, wherein the plasma processing method includes: a first step, which uses plasma generated by a silicon-containing gas to deposit a silicon-containing film on the sacrificial layer; a second step, which after the first step, uses plasma generated by a nitrogen-containing gas to nitride the silicon-containing film deposited on the sacrificial layer and the silicon-containing film deposited on the etched film; a third step, which after the second step, uses plasma generated by an oxygen-containing gas to oxidize the silicon-containing film; a fourth step, which after the third step, removes the silicon nitride film on the etched film or the sacrificial layer; a fifth step, which after the fourth step, removes the sacrificial layer; and a sixth step, which after the fifth step, uses a silicon oxide film formed on the etched film as a mask to perform plasma etching on the etched film.

[0013] Effects of the Invention

[0014] A plasma processing method capable of continuously performing a SADP process in a vacuum. Other problems and novel features will become apparent from the description of this specification and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the process flow of this embodiment.

[0016] Figure 2A FIG. 4 is a diagram schematically illustrating the processing process by taking the SADP process as an example.

[0017] Figure 2B FIG. 4 is a diagram schematically illustrating the processing process by taking the SADP process as an example.

[0018] Figure 2C FIG. 4 is a diagram schematically illustrating the processing process by taking the SADP process as an example.

[0019] Figure 2D FIG. 4 is a diagram schematically illustrating the processing process by taking the SADP process as an example.

[0020] Figure 2EFIG. 4 is a diagram schematically illustrating the processing process by taking the SADP process as an example.

[0021] Figure 2F FIG. 4 is a diagram schematically illustrating the processing process by taking the SADP process as an example.

[0022] Figure 2G FIG. 4 is a diagram schematically illustrating the processing process by taking the SADP process as an example.

[0023] Figure 2H FIG. 4 is a diagram schematically illustrating the processing process by taking the SADP process as an example.

[0024] Figure 3 This is a schematic diagram of the structure of a plasma processing device.

[0025] Figure 4 It is a diagram schematically showing the shape of a mask (silicon oxide film) of a comparative example. DETAILED DESCRIPTION

[0026] Figure 3 An example of a plasma processing apparatus for performing the plasma processing of the present embodiment is shown in FIG. Here, as an example of a plasma processing apparatus, an example of a plasma processing apparatus for generating electron cyclotron resonance (ECR) excited plasma is shown. In an ECR excited plasma processing apparatus, microwaves are used as an excitation source, and plasma is generated by applying an external magnetic field.

[0027] The plasma processing apparatus includes a sample stage 303 on which a substrate (wafer) 301 to be processed is placed in a vacuum container 300, and plasma processing is performed on the substrate 301 to be processed using plasma generated in the vacuum container 300. A high-frequency power supply 310 for substrate bias is connected to the sample stage 303. By controlling the applied substrate bias (high-frequency power), the directionality and energy of ions incident on the substrate 301 to be processed can be controlled. An exhaust pipe 307 is connected to the vacuum container 300, and a pressure control valve 308 and a pump 309 for adjusting the pressure inside the vacuum container 300 are connected to the exhaust pipe 307. The pump 309 exhausts the interior of the vacuum container 300 via the exhaust pipe 307 and the pressure control valve 308, and maintains the vacuum container 300 in a low pressure state during plasma processing.

[0028] The microwave generating source 321 generates microwaves by receiving power from the microwave power source (plasma generating power source) 304. The microwave power generated by the microwave generating source 321 is adjusted by the microwave matching device 323, and propagates from the rectangular waveguide 322 to the circular waveguide 325 and the cavity 326 via the converter 324, and the cavity 326 causes the propagated microwave power to resonate.

[0029] The cavity 326 and the vacuum container 300 are separated by a partition plate 328. The partition plate 328 is formed of a dielectric that allows microwave power to pass through and maintains the vacuum state inside the vacuum container 300. An electromagnet 327 is provided outside the vacuum container 300 and the cavity 326 for forming a magnetic field inside the cavity 326 and the vacuum container 300 to generate electron cyclotron resonance.

[0030] A shower plate 302 having a plurality of holes for supplying gas is provided inside the vacuum container 300, and a gas pipeline 306 for supplying gas is provided between the partition plate 328 and the shower plate 302. The gas is supplied to the inside of the vacuum container 300 through the gas pipeline 306 by adjusting the flow rate through a mass flow controller (Mass Flow Controller: MFC) 305. In order to obtain the desired film quality, it is preferred that the MFC 305 is mounted on each gas system. The gases supplied by each gas system are, for example, silicon-containing (Si) gas, nitrogen-containing (N) gas, oxygen-containing (O) gas, and inert gas. It should be noted that inert gas can be used for switching of gas and improving uniformity. As an example, argon can be used.

[0031] The control unit 311 controls the microwave power source 304 , the electromagnet 327 , the MFC 305 , the pressure control valve 308 , the pump 309 , and the high-frequency power source 310 for substrate bias to perform plasma processing on the substrate 301 to be processed.

[0032] use Figure 1 and Figure 2A ~H illustrate the process flow of this embodiment. Figure 2A 1 to 2 H show the SADP process as an example. First, an etched film 201 and a sacrificial layer 200 are sequentially formed on a semiconductor substrate 202 ( S01 ). Figure 2A The state of step S01 is shown. The sacrificial layer is preferably a silicon nitride (SiN) film or a polysilicon (Poly-Si) film. In addition, the semiconductor substrate 202 can be a bare wafer, or a state in which a certain base film is formed on the bare wafer. Next, a resist 203 is applied on the sacrificial layer 200, and patterning is performed by exposure and development (S02). Figure 2B The state in which step S02 is completed is shown. The substrate to be processed 301 that has completed the processing up to step S02 is introduced Figure 3 The plasma processing apparatus shown performs the following processing.

[0033] First, the sacrificial layer 200 is processed (anisotropic etching) using the resist 203 as a mask ( S03 ), and then the resist 203 is removed ( S04 ). Figure 2C3 shows the state where step S04 is completed. Next, silicon is deposited on the sacrificial layer 200 formed in a pattern. By supplying Si-containing gas from the gas pipeline 306, a Si-containing film is deposited, and a Figure 2D The structure shown. The silicon film 204 has an amorphous structure and is formed isotropically. However, a shoulder 205 is generated at the corner of the sacrificial layer 200. As the silicon-containing gas, for example, tetrachlorosilane, dichlorosilane, trichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, methyltrichlorosilane, monosilane, disilane, trisilane and other gases can be used.

[0034] Next, nitrogen-containing gas is supplied from the gas pipeline 306, and nitrogen ions (S06) generated by nitrogen plasma are vertically irradiated on the silicon film 204. As the nitrogen-containing gas, for example, a gas such as nitrogen or ammonia can be used. A substrate bias is applied from a substrate bias high-frequency power supply 310, and nitrogen ions are irradiated from a direction perpendicular to the sample mounting surface of the sample stage 303, thereby causing a reaction between silicon and nitrogen ions from the upper surface of the silicon film 204. As a result, the silicon film 204 above and below the sacrificial layer pattern (i.e., on the etched film 201) is selectively nitrided to become a silicon nitride film 206, while the silicon film 204 deposited on the side of the sacrificial layer pattern remains intact. Thus, Figure 2E The structure shown. It should be noted that Figure 2E In the figure, a plane parallel to the sample mounting surface of the sample stage 303 is shown as a horizontal plane H.

[0035] exist Figure 2E In the structure shown, the shoulder 205 also becomes the silicon nitride film 206. Since the upper surface of the shoulder 205 is at an angle with respect to the horizontal plane H, the proportion of nitrogen ions incident on the silicon film 204 is reduced, so that the boundary between the silicon nitride film 206 on the upper surface of the sacrificial layer pattern and the silicon film 204 on the side of the sacrificial layer pattern is at least smoother than the upper surface of the shoulder 205 (at Figure 2E The boundary is depicted as being parallel to the horizontal plane H, but is not limited to being horizontal).

[0036] Next, oxygen-containing gas is supplied from gas line 306, oxygen radicals generated by oxygen plasma are irradiated to oxidize silicon on the sidewall of the sacrificial layer pattern (S07). As the oxygen-containing gas, for example, a gas containing oxygen such as oxygen, carbon monoxide, carbon dioxide, or nitrogen oxide (NO2) can be used. Figure 2F The state in which step S07 is completed is shown. The silicon film 204 remaining at the stage in which step S06 is completed is oxidized to become a silicon oxide film 207 .

[0037] The temperature at which the ion bombardment by the plasma of the nitrogen-containing gas in step S06 and the sidewall oxidation by the plasma of the oxygen-containing gas in step S07 can be effectively performed is about 100° C. or less. Figure 3 The process flow of this embodiment is implemented using the ECR excitation plasma processing apparatus shown.

[0038] Then, the silicon nitride film 206 on the upper part and the bottom part of the sacrificial layer pattern is removed ( S08 ), and then the sacrificial layer is removed ( S09 ). Figure 2G The state in which step S09 is completed is shown. Then, the etched film 201 is processed (anisotropic etching) using the remaining silicon oxide film 207 as a mask (S10). Figure 2H The state in which step S10 is completed is shown.

[0039] It should be noted that steps S05 to S07 in the process flow may not be treated as a single process, but steps S05 to S07 may be treated as a cycle and repeated for multiple cycles to obtain Figure 2F Thus, a high-density silicon oxide film 207 can be obtained, and the etching resistance as a mask can be improved.

[0040] The effect of the plasma treatment of this embodiment is described below. In the conventional SADP process, a shoulder is generated when a silicon oxide film is formed as a mask. This case is shown as a comparative example. Figure 4 . Figure 4 An example of a case where a silicon oxide film 401 is formed on an etched film 201 by ALD as a mask. In this case, a gap A where the shoulder portions of the mask face each other and a gap B where the non-shoulder portions of the mask face each other are generated, and when etching the etched film 201, the amount of ions incident on the gap A and the amount of ions incident on the gap B become larger. Therefore, a deviation occurs in the processing width of the etched film 201 between the gap A and the gap B. Such a deviation in the processing width cannot be ignored in a fine pattern.

[0041] In contrast, in the process flow of this embodiment, Figure 2G As shown, after the shoulder formed during the deposition of the silicon film is removed, a silicon oxide film 207 is formed as a mask. As a result, at least the top surface of the silicon oxide film 207 is more inclined relative to the horizontal plane than the shoulder during the deposition of the silicon film, which can reduce the dimensional deviation of the pattern of the etched film 201 finally obtained.

[0042] Furthermore, the silicon oxide film serving as a mask is formed by oxidation using oxygen radicals, whereby the film quality is enhanced and a highly resistant oxide film mask can be formed.

[0043] The present invention is not limited to the above-mentioned embodiments, and includes various variations. For example, the above-mentioned embodiments and variations are described in detail to facilitate understanding of the present invention, and are not necessarily limited to having all the structures described. In addition, a part of the structure of a certain embodiment or variation can be replaced with the structure of other embodiments or variations, and the structure of other embodiments or variations can be added to the structure of a certain embodiment or variation. In addition, with respect to a part of the structure of each embodiment or variation, other structures can be added, deleted, or replaced.

[0044] Description of reference numerals:

[0045] 200: sacrificial layer, 201: etched film, 202: semiconductor substrate, 203: resist, 204: silicon film, 205: shoulder, 206: silicon nitride film, 207: silicon oxide film, 300: vacuum container, 301: processed substrate, 302: shower plate, 303: sample stage, 304: microwave power supply, 305: mass flow controller, 306: gas pipeline, 307: exhaust pipe, 308: pressure control valve, 309: pump, 310: high-frequency power supply for substrate bias, 311: control unit, 321: microwave generation source, 322: rectangular waveguide, 323: microwave matching device, 324: converter, 325: circular waveguide, 326: cavity, 327: electromagnet, 328: partition plate.

Claims

1. A plasma processing method, wherein a plasma etching is performed on a substrate to be processed which has a film to be etched and a sacrificial layer formed in a pattern on the film to be etched, wherein: The plasma treatment method comprises: In a first step, a silicon-containing film is deposited on the sacrificial layer using plasma generated from a silicon-containing gas; A second step, after the first step, nitriding the silicon-containing film deposited on the sacrificial layer and the silicon-containing film deposited on the etched film using plasma generated from nitrogen-containing gas; A third step, after the second step, oxidizing the silicon-containing film using plasma generated from an oxygen-containing gas; A fourth step, after the third step, removing the silicon nitride film on the etched film or the sacrificial layer; A fifth step, after the fourth step, removing the sacrificial layer; and In the sixth step, after the fifth step, the film to be etched is subjected to plasma etching using the silicon oxide film formed on the film to be etched as a mask.

2. The plasma treatment method according to claim 1, characterized in that: The sacrificial layer is a silicon nitride film or a polysilicon film.

3. The plasma treatment method according to claim 1, characterized in that: The first step to the third step are repeated a specified number of times.

4. The plasma treatment method according to claim 2, characterized in that: The first step to the third step are repeated a specified number of times.

5. The plasma processing method according to claim 1, characterized in that: The second step is performed while supplying high frequency power to a sample stage on which the substrate to be processed is placed.

6. The plasma treatment method according to claim 2, characterized in that: The second step is performed while supplying high frequency power to a sample stage on which the substrate to be processed is placed.

7. The plasma processing method according to claim 1, characterized in that: The silicon oxide film is a film formed by oxidizing the silicon-containing film deposited on the side surface of the sacrificial layer through the third step.

8. The plasma processing method according to claim 2, characterized in that: The silicon oxide film is a film formed by oxidizing the silicon-containing film deposited on the side surface of the sacrificial layer through the third step.

9. The plasma processing method according to claim 1, characterized in that: The plasmas in the first step to the third step are plasmas generated by electron cyclotron resonance.

10. The plasma processing method according to claim 2, characterized in that: The plasmas in the first step to the third step are plasmas generated by electron cyclotron resonance.

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