JP2005216960A - Manufacturing method for semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pattern forming method for forming a pattern having a highly precise size on a film containing nitrogen. <P>SOLUTION: The resist pattern forming method includes a coat forming process, a thin film forming process, and a resist pattern forming process. In the coat forming process, a coat containing nitrogen is formed on a board. In the thin film forming process, the coat is subjected to a plasma process to form a thin film on the coat. In the resist pattern forming process, a resist pattern is formed on the thin film formed by the plasma process. The thin film does not react with the resist pattern. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pattern forming method, and more particularly to a method for forming a pattern on a substrate.

  In order to realize a multifunctional and high-performance LSI, a high integration technique for forming a fine pattern is essential. Photolithography technology is the center of miniaturization technology that has enabled more advanced design standards and promoted higher integration of LSIs. Photolithographic technology forms a circuit pattern on a material film. Specifically, a photoresist film is formed on a material film to be processed, and after pattern exposure, a resist pattern is formed through a development process.

  In recent years, the wavelength of exposure light has been shortened, and the mainstream of exposure light is changing from KrF excimer laser light (wavelength 248 nm) to ArF excimer laser light (wavelength 193 nm). By exposing with exposure light having a short wavelength, the resolution of the resist can be improved. However, even with exposure using ArF excimer laser light, there are many technical problems to be overcome in order to mass-produce products. For example, in the exposure with short wavelength light, a chemically amplified resist is used as a resist material. The chemically amplified resist has a feature that it has high light sensitivity with little light absorption by the resist.

  Hereinafter, a conventional method for forming a pattern of a semiconductor device by photolithography will be described (Non-Patent Document 1). Here, FIGS. 3A to 3D are cross-sectional views of the semiconductor device at each step in the conventional pattern forming method. First, the insulating film 31 is formed on the surface of the semiconductor device (not shown). The insulating film 31 is a silicon oxide film, for example, and is formed by, for example, a plasma CVD (Chemical Vapor Deposition) method. Next, as illustrated in FIG. 3A, a TiN film 33 is formed on the insulating film 31. The TiN film 33 is formed by, for example, a plasma CVD method.

  Next, as illustrated in FIG. 3B, a resist film 37 is formed on the TiN film 33. The material of the resist film 37 is typically a chemically amplified resist. Thereafter, as shown in FIG. 3C, the resist film 37 is exposed to an excimer laser and developed to form a resist pattern.

Then, as shown in FIG. 3D, the TiN film 33 is etched using the resist pattern as a mask to form a wiring pattern. As described above, the pattern formation of the TiN film 33 by etching is completed through the steps shown in FIGS.
Kang Tan Wu, Semiconductor Engineering Series 9 Semiconductor Process Technology, Baifukan, November 1998, P.C. 97

When the TiN film 33 is formed using the plasma CVD method, titanium chloride (TiCl ₄ ) and ammonia (NH ₃ ) are generally used as reaction gases. However, the TiN film 33 formed by nitriding ammonia with titanium chloride contains nitrogen. Nitrogen contained in the TiN film 33 traps and neutralizes the acid generated in the resist during exposure of the positive chemically amplified resist, so that the resist is difficult to dissolve in the developer. Accordingly, there is a problem that a shape abnormality occurs in the resist pattern when the resist pattern is formed.

  Specifically, as shown in FIG. 3C, a so-called resist pattern tailing 39 is generated, in which the resist does not completely dissolve but remains undissolved during development. When the skirt 39 is generated in the resist pattern, as shown in FIG. 3D, variations occur in the pattern dimensions during etching of the TiN film 33 using the resist pattern as a mask. Therefore, the pattern accuracy is lowered and a pattern having a desired dimension cannot be formed. Note that the resist pattern formation abnormality may occur not only in the TiN film but also in a film containing a nitrogen component other than the TiN film.

  Therefore, an object of the present invention is to provide a pattern forming method capable of forming a pattern with high step accuracy on a film containing nitrogen.

  The present invention is a resist pattern forming method, and includes a film forming step, a thin film forming step, and a resist pattern forming step. In the film forming step, a film containing nitrogen is generated on the substrate. In the thin film forming step, plasma treatment is performed on the coating to form a thin film. In the resist pattern forming step, a resist pattern is formed on the plasma-treated thin film. The thin film is non-reactive with the resist pattern.

  The resist pattern forming method may further include a sputtering process step immediately before the plasma process step. In the sputtering process, sputtering is performed with an inert gas.

  The plasma treatment may be performed using a gas containing oxygen, or may be performed using a gas containing fluorocarbon.

  Further, the present invention is directed not only to a resist pattern forming method but also to a pattern forming method. The pattern forming method includes a film forming process, a thin film forming process, a resist pattern forming process, an etching process, a resist pattern removing process, and a thin film removing process. In the film forming step, a film containing nitrogen is generated on the substrate. In the thin film forming step, plasma treatment is performed on the coating to form a thin film. In the resist pattern forming step, a resist pattern is formed on the plasma-treated thin film. In the etching step, the film is etched using the resist pattern as a mask. In the resist pattern removing step, the resist pattern is removed. In the thin film removal step, the thin film is removed.

  In the resist pattern forming method according to the present invention, a plasma treatment is performed on a film containing nitrogen to form a thin film that is non-reactive with respect to the resist film. Therefore, it is possible to prevent the nitrogen component contained in the coating from being exposed to the surface. Thereby, the neutralization reaction with the acid generated by exposure to the resist film can be prevented, and the occurrence of so-called resist pattern tailing can be prevented.

  Moreover, when a film contains chlorine, it can prevent that chlorine is exposed to the surface of a film by performing plasma treatment. Thereby, the production | generation of ammonium chloride which is a reaction material of chlorine and ammonia in air | atmosphere can be prevented.

  Furthermore, if sputtering treatment is performed, ammonium chloride can be removed even when ammonium chloride is already deposited on the coating.

  Further, in the pattern forming method, if a thin film removing step is provided, a pattern of a film having a clean surface can be formed. Further, by removing the thin film, deterioration of transistor characteristics due to the presence of OH groups can be prevented.

  Hereinafter, a pattern formation method for a semiconductor device according to an embodiment of the present invention will be described with reference to the drawings. 1A to 1G show a cross-sectional structure of a semiconductor device at each step in the pattern forming method.

  In the resist pattern forming method according to this embodiment, first, the insulating film 11 is formed on the surface of a semiconductor substrate (not shown). The semiconductor substrate is typically a Si substrate, and the insulating film 11 is, for example, a silicon oxide film. Next, as illustrated in FIG. 1A, a TiN film 13 is formed on the insulating film 11. The TiN film 13 is formed by, for example, a plasma CVD method using titanium chloride and ammonia gas as reaction gases.

  Next, a sputtering process is performed on the surface of the TiN film 13. The sputtering process is performed using, for example, a dual frequency power supply type microwave etching apparatus. When performing a sputtering process with an etching apparatus, a semiconductor substrate is installed in the chamber, and the surface of the TiN film 13 is subjected to a sputtering process using Ar gas. The operating conditions of the etching apparatus are, for example, a bias power of 120 W and a pressure of 5 Pa. When the sputtering process is performed for 13 seconds under this operating condition, the surface of the TiN film 13 is removed by about 5 nm. As a result, the surface of the TiN film 13 can be cleaned, the residual chlorine component remaining on the surface of the TiN film 13 and the N—H bond structure contained in the TiN film 13 can be removed. Furthermore, ammonium chloride deposited on the surface of the TiN film 13 can be removed by performing a sputtering process. Note that sputtering treatment may be performed using He gas, Ne gas, or other inert gas, which are other rare gases, instead of Ar gas.

Thereafter, as shown in FIG. 1B, an inert layer 15 is formed on the surface of the sputtered TiN film 13. The inert layer 15 is formed by oxygen plasma treatment. The oxygen plasma may be performed using not only oxygen gas but also gas containing oxygen. The gas containing oxygen is, for example, an oxidizing gas such as CO _X gas, H _X O gas, or SO _X gas.

By the oxygen plasma treatment, hydrogen of ammonia (NH ₃ ) used as a reaction gas when depositing the TiN film 13 and oxygen of oxygen plasma are combined to generate OH groups. The OH group is adsorbed at a high concentration and becomes the inactive layer 15. When oxygen plasma treatment is performed for 5 seconds under an operating condition of microwave power of 2000 W and oxygen pressure of 5 Pa, an inert layer 15 having a thickness of about 2 to 3 nm is formed. Note that it is desirable that the sputtering process and the oxygen plasma process be continuously performed in the same chamber. Further, only the oxygen plasma treatment may be performed without performing the sputtering treatment.

  Next, as shown in FIG. 1C, a resist film 17 is formed on the surface of the TiN film 13. The material of the resist film 17 is, for example, a chemically amplified KrF resist, and the resist film 17 is formed by spin coating the chemically amplified KrF resist.

  Thereafter, as shown in FIG. 1D, a resist pattern is formed on the resist film 17. The resist pattern is formed by exposing the resist film 17 through a photomask using, for example, a KrF excimer laser stepper.

After the formation of the resist pattern, as shown in FIG. 1E, the TiN film 13 is subjected to a dry etching process to form a wiring pattern. Dry etching is performed using, for example, a parallel plate RIE apparatus. When the parallel plate RIE apparatus is used, the dry etching operation conditions are, for example, a flow rate of Cl ₂ gas of 50 sccm and a pressure of 5 Pa. By dry etching, not only the TiN film 13 not masked by the resist film 17 but also the inactive layer 15 can be easily etched.

  After the dry etching, as shown in FIG. 1F, the resist film 17 is removed by ashing the semiconductor device. Thereafter, as shown in FIG. 1G, wet etching of the substrate is performed. The wet etching process is performed using, for example, a buffered hydrofluoric acid solution. By this wet etching, the inactive film covered with the resist film 17 is removed in the step shown in FIG. 1E. Thereby, the pattern of the TiN film 13 having a clean surface can be formed. Further, by removing the inactive film, it is possible to prevent deterioration of transistor characteristics due to the presence of OH groups.

  FIG. 2 is a diagram showing the dependence of the resist pattern dimension variation 3σ (σ is the standard deviation of dimensions) formed on the TiN film 13 on the resist pattern formation method. The vertical axis represents the resist pattern dimension variation 3σ, and the horizontal axis represents the processing performed before forming the resist pattern. By changing the pretreatment conditions performed before applying the resist film 17 on the TiN film 13 and measuring the resist pattern dimensions after forming the resist pattern, the relationship between the pretreatment conditions and variations in the dimensions of the resist pattern can be obtained. evaluated.

  There are three types of pretreatments before application of the resist film 17: no pretreatment, oxygen plasma treatment, sputtering treatment, and oxygen plasma treatment. The method of applying the resist film 17 without pretreatment and forming a resist pattern is the same as the conventional photolithography method. The resist pattern dimensions were measured using a scanning electron microscope (S-9220, manufactured by Hitachi, Ltd.).

  As a result, when the pattern was formed by the conventional method, the dimensional variation 3σ was 18.5. When the pattern was formed after performing the oxygen plasma treatment without performing the sputtering treatment, the dimensional variation 3σ was 8.7. When pattern formation was performed after Ar sputtering treatment and oxygen plasma treatment, the dimensional variation 3σ was 5.3.

  From the above results, the dimensional accuracy is increased about twice as much by performing oxygen plasma treatment as compared with the case where the pattern is formed by the conventional method, and about three times by combining oxygen plasma treatment and sputtering treatment. It was found that it would increase.

  As described above, according to the present embodiment, sputtering is performed on a film having an activated surface such as the TiN film 13 having a surface formed by a plasma CVD method before resist formation. Residual chlorine component and N—H bond structure at the time of film formation are removed. Thereby, precipitation of ammonium chloride that causes contamination of the semiconductor substrate can be prevented.

  Further, the inert plasma layer 15 is formed by performing oxygen plasma treatment, thereby preventing the N—H bonds and residual chlorine components contained in the TiN film 13 from being exposed to the surface. Thereby, the neutralization reaction with the acid generated by the exposure of the resist film 17 can be prevented, and the occurrence of so-called resist pattern tailing can be prevented. Therefore, as shown in FIG. 1D, a pattern having a good cross-sectional shape and high dimensional accuracy can be formed.

  Furthermore, even when ammonium chloride is already deposited on the surface of the TiN film 13, the deposited ammonium chloride can be removed by the sputtering process. Hereinafter, the removal of ammonium chloride by the sputtering process will be described.

  A residual chlorine component at the time of forming the TiN film 33 exists on the TiN surface formed by the CVD method. Since this residual chlorine component reacts with the ammonia component in the atmosphere, ammonium chloride is deposited on the surface of the TiN film 33. Since ammonium chloride has a low vapor pressure and is difficult to vaporize, the ammonium chloride deposited on the TiN film 33 causes contamination of the semiconductor substrate and particles.

  However, according to this embodiment, ammonium chloride is removed by performing the sputtering process. Therefore, it is possible to prevent the substrate from being contaminated and the generation of particles caused by the precipitation of ammonium chloride.

  In the present embodiment, the resist film 17 is formed on the TiN film 13. Here, the film may be a film other than the TiN film as long as it includes a nitrogen component. The film containing a nitrogen component is, for example, a SiN film. Even in this case, it is possible to prevent the resist pattern from being abnormal, that is, resist pattern tailing.

  In this embodiment, the inert layer 15 is formed on the TiN film 13 by oxygen plasma treatment, but a fluorocarbon polymer film may be formed instead of the inert layer 15. Hereinafter, a method for forming a fluorocarbon polymer film will be described.

The fluorocarbon-based polymer film is formed using, for example, a CHF ₃ gas in a dual frequency power source type microwave etching apparatus. When forming a fluorocarbon polymer film with a frequency power source type microwave etching apparatus, a substrate is placed in the chamber, and CHF ₃ gas is introduced into the chamber and discharged. When discharged for 10 seconds under operating conditions of microwave power 2000 W and pressure 70 Pa, a polymer film having a thickness of about 1 to 3 nm is formed. After the formation of the polymer film, a KrF resist is spin-coated on the surface of the TiN film 13 to form a resist film 17. The method of forming and etching the following resist pattern is almost the same as the method described in this embodiment, but the wet etching process is unnecessary because the polymer film is removed together with the resist by the ashing process. Sputtering may be performed before the formation of the fluorocarbon polymer film.

  Fluorocarbon films are generally known to cause contamination of substrates. However, since the fluorocarbon polymer film can be removed by ashing, there is no problem of contaminating the substrate.

  As described above, the fluorocarbon polymer film covers the surface of the TiN film 13, thereby preventing residual chlorine components and N—H bond structures existing in the TiN film 13 from being exposed on the surface of the TiN film 13. Thereby, even when the resist film 17 is formed and the resist pattern is formed, it is possible to prevent the adverse effect on the resist development due to ammonia or the like, and to form the resist pattern with high dimensional accuracy.

  According to this method, the effect of improving the dimensional accuracy of the resist pattern can be obtained as in the present embodiment. Furthermore, since the wet etching process is unnecessary, the semiconductor device can be manufactured at a lower manufacturing cost.

  INDUSTRIAL APPLICATION This invention is useful as a pattern formation method etc. which can form a pattern with a high step accuracy in the film | membrane containing nitrogen.

Sectional drawing of a semiconductor device when an insulating film is formed in the pattern formation method which concerns on one Embodiment of this invention Sectional drawing of a semiconductor device when an inactive layer is formed in the pattern formation method which concerns on one Embodiment of this invention Sectional drawing of a semiconductor device when a resist film is formed in the pattern formation method which concerns on one Embodiment of this invention Sectional drawing of a semiconductor device when a resist pattern is formed in the pattern formation method which concerns on one Embodiment of this invention Sectional drawing of a semiconductor device when a wiring pattern is formed in the pattern formation method which concerns on one Embodiment of this invention Sectional drawing of a semiconductor device when a resist film is removed in the pattern formation method which concerns on one Embodiment of this invention Sectional drawing of a semiconductor device when an inactive layer is removed in the pattern formation method which concerns on one Embodiment of this invention The figure which shows the dimension variation of a resist pattern in the pattern formation method which concerns on one Embodiment of this invention. Sectional drawing of a semiconductor device when an insulating film is formed in the conventional pattern formation method Sectional drawing of a semiconductor device when a resist film is formed in the conventional pattern formation method Sectional drawing of a semiconductor device when a resist pattern is formed in the conventional pattern formation method Sectional drawing of a semiconductor device when a wiring pattern is formed in a conventional pattern formation method

Explanation of symbols

11, 31 Insulating film 13, 33 TiN film 15 Inactive layer 17, 37 Resist film 19 Footing of resist pattern

Claims (8)

A film forming step of generating a film containing nitrogen on the substrate;
A thin film forming step of performing a plasma treatment on the coating to form a thin film;
A resist pattern forming step of forming a resist pattern on the plasma-treated thin film,
The method for forming a resist pattern, wherein the thin film is non-reactive with the resist pattern.   The resist pattern forming method according to claim 1, further comprising a sputtering treatment step of performing a sputtering treatment with an inert gas immediately before the plasma treatment step.   The resist pattern forming method according to claim 2, wherein the film is a film containing chlorine.   The resist pattern forming method according to claim 1, wherein the plasma treatment is performed using a gas containing oxygen.   The resist pattern forming method according to claim 1, wherein the coating is a film containing a metal element.   The pattern forming method according to claim 5, wherein the plasma treatment is performed using a gas containing a fluorocarbon.   The pattern forming method according to claim 1, wherein the coating is a titanium nitride film. A film forming step of generating a film containing nitrogen on the substrate;
A thin film forming step of performing a plasma treatment on the coating to form a thin film;
Forming a resist pattern on the plasma-treated thin film; and
An etching step of etching the film using the resist pattern as a mask;
A resist pattern removing step for removing the resist pattern;
A pattern formation method comprising: a thin film removal step of removing the thin film.

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