JP5402860B2 - Resist pattern transfer method and photomask manufacturing method - Google Patents

Description

  The present invention is formed on a photomask blank suitable for manufacturing a photomask used for fine processing of a semiconductor integrated circuit, a CCD (charge coupled device), a color filter for LCD (liquid crystal display device), a magnetic head, etc. The present invention relates to a method for transferring a resist pattern to a film and a photomask manufacturing method to which this transfer method is applied.

  In recent years, in semiconductor processing, circuit pattern miniaturization has become more and more necessary, especially due to high integration of large-scale integrated circuits. There is an increasing demand for miniaturization technology of contact hole patterns for wiring. For this reason, even in the manufacture of photomasks with circuit patterns written thereon, which are used in photolithography to form these wiring patterns and contact hole patterns, a technique capable of writing circuit patterns more finely and accurately along with the above-mentioned miniaturization. Is required.

  In order to form a photomask pattern with higher accuracy on the photomask substrate, it is first necessary to form a high-precision resist pattern on the photomask blank. Photolithography when processing an actual semiconductor substrate performs reduction projection, so the photomask pattern is about four times as large as the actually required pattern size, but that does not mean that the accuracy is reduced. Rather, the original photomask is required to have higher accuracy than that required for the pattern accuracy after exposure.

  Furthermore, in the lithography that is currently being performed, the circuit pattern to be drawn is a size that is considerably smaller than the wavelength of the light to be used. If a photomask pattern in which the circuit shape is four times as it is is used, Due to the influence of light interference or the like that occurs during photolithography, the shape as in the photomask pattern is not transferred to the resist film. Therefore, in order to reduce these influences, it may be necessary to process the photomask pattern into a more complicated shape than an actual circuit pattern (a shape to which so-called OPC: Optical Proximity Correction (optical proximity effect correction) or the like is applied). Therefore, even in lithography technology for obtaining a photomask pattern, a highly accurate processing method is currently required. Lithographic performance may be expressed with a limit resolution, but this resolution limit is equivalent to or higher than the resolution limit required for optical lithography used in semiconductor processing processes using photomasks. Limiting resolution accuracy is required for the lithography technique in the photomask processing process.

  In the formation of a photomask pattern, a photoresist film is usually formed on a photomask blank having a light shielding film on a transparent substrate, a pattern is drawn with an electron beam, a resist pattern is obtained through development, and Using the resist pattern as an etching mask, the light-shielding film is etched to be processed into a light-shielding pattern. However, when miniaturizing the light-shielding pattern, keep the film thickness of the resist film as it was before miniaturization. If so, the ratio of film thickness to the pattern, the so-called aspect ratio, becomes large, the pattern shape of the resist deteriorates, and pattern transfer does not work well, and in some cases the resist pattern collapses or peels off. . Therefore, it is necessary to reduce the resist film thickness with miniaturization.

  On the other hand, as a light-shielding film material, silicon-based materials such as silicon-containing materials and silicon-and-transition metal-containing materials have superior light-shielding properties against exposure light of 200 nm or less, compared to conventionally used chromium-based materials. In addition, it can be processed by fluorine-based dry etching that hardly damages the resist pattern, and higher-precision processing can be performed (Patent Document 1: Japanese Patent Application Laid-Open No. 2007-244105). Further, it has been found that, in order to perform processing with higher accuracy, it is possible to perform more precise processing by combining with a technique using a hard mask made of a chromium-based material (Patent Document 2: Japanese Patent Application Laid-Open No. 2007-2007). -24060 publication). For this reason, not only a silicon-based material as a film material for a conventional halftone phase shift film (for example, Patent Document 3: Japanese Patent Laid-Open No. 7-140635) but also a silicon-based material as a next-generation light-shielding film material A light-shielding film using a film is considered promising.

JP 2007-2441065 A JP 2007-2441060 A JP-A-7-140635 JP-A 63-85553 Japanese Patent Laid-Open No. 2001-27799 JP-A-9-167733 JP-A-4-7829 Japanese Patent Laid-Open No. 5-283375 Japanese Patent Laid-Open No. 10-312991 Japanese Patent Laid-Open No. 10-312992 Japanese Patent Laid-Open No. 10-312993 JP 2003-303789 A

  When further miniaturization and high precision are required for the photomask, the resist film used for processing the photomask is required to increase etching resistance in order to obtain high resolution and high transfer performance. At the same time, the resist film must be thinned as described above.

  On the other hand, patterning of a light-shielding film made of a silicon-based material using an etching mask made of a chromium-based material described above requires the use of a chlorine-based gas containing oxygen that has a large load on the resist film during etching. When the above-described resist thinning and high accuracy are required, there is a possibility that the request cannot be met.

  The present invention has been made to solve the above-described problems, and has a light shielding film and a halftone phase shift mainly composed of a silicon-based material containing a transition metal having more preferable optical characteristics and capable of high-precision processing. In patterning of an optical functional film in a photomask blank or the like having a film, a resist pattern transfer method and photomask manufacturing capable of precise processing with higher accuracy, particularly when a thinner resist is used. It aims to provide a method.

Silicon oxide is known as an etching mask film that can be used for processing of a light shielding film using a silicon-based material other than a chromium-based material. In Japanese Patent Laid-Open No. 63-85553 (Patent Document 4), when processing a molybdenum silicide light-shielding film, silicon oxide (Si _m O _n ) is used as a hard mask, but for industrial production purposes. Since silicon oxide is a material that is liable to generate fine foreign matters during sputter film formation, it is difficult to apply it for producing a photomask having a fine structure for use in lithography with a minimum pattern line width of 50 nm or less.

  On the other hand, in the processing of the halftone phase shift film disclosed in Japanese Patent Application Laid-Open No. 2001-27799 (Patent Document 5), although the detailed composition is unknown, the MoSiON film is considerably wide under chlorine-based dry etching conditions containing oxygen. It has been shown that etching is possible in the oxygen-containing range. This data indicates that a silicon-based material film containing oxygen and / or nitrogen and containing a transition metal can be etched under chlorine-based dry etching conditions containing oxygen, while oxygen and / or nitrogen is used. It is also expected that it is difficult to obtain etching selectivity between silicon-containing materials containing transition metals.

  In contrast, the present inventor can perform selective etching by setting and combining materials and dry etching conditions even for silicon-based materials containing oxygen and / or nitrogen and containing transition metals. I thought it would be.

  Accordingly, as a result of intensive studies to solve the above problems, if the silicon-based material film containing a transition metal contains sufficient oxygen, it contains oxygen and / or nitrogen and contains a transition metal. It has been found that it functions as an etching mask for silicon-based materials.

  In addition, based on the above knowledge, as a method for etching by applying a thinner resist pattern, as a result of examining a method for reducing the load during dry etching on the resist pattern as much as possible, an optical function formed on a photomask blank or the like A resist pattern is formed on the film, an oxidation treatment is performed on a portion not protected by the resist pattern, the resist pattern is peeled off, and the oxidation treatment is performed on the oxidized portion and the resist pattern is protected. The resist pattern is transferred (reverse transfer) by etching the portion protected by the resist pattern by chlorine-based dry etching containing oxygen using the difference in the etching rate due to the difference in the degree of oxidation from the unexposed portion. I found out that I can do it.

  And, in this method, unlike the conventional resist pattern transfer method, the portion protected by the resist pattern is removed by etching, and the resist pattern functions as a mask for a portion not subjected to oxidation treatment, Since the resist pattern is not used as an etching mask, the thickness of the resist pattern can be reduced to the minimum necessary level as a mask for oxidation treatment, and precise processing is possible even with a thinner resist. As a result, the inventors have made the present invention.

Accordingly, the present invention provides the following resist pattern transfer method and photomask manufacturing method.
Claim 1:
Forming a resist pattern on a film containing a silicon-based material containing a transition metal formed on a substrate;
A step of oxidizing the surface layer of the part where the resist pattern of the film is not formed to increase the oxygen content ratio of the surface layer material composition;
After the oxidation step, the step of stripping the resist pattern under non-oxidizing conditions, and the portion where the resist pattern is formed using the oxidized surface layer as an etching mask after the resist pattern stripping step and is not oxidized in the oxidation step A method for transferring a resist pattern, comprising: a step of etching by oxygen-containing chlorine-based dry etching.
Claim 2:
2. The resist pattern transfer method according to claim 1, wherein the oxidation is gas phase oxidation.
Claim 3:
2. The resist pattern transfer method according to claim 1, wherein the oxidation is liquid phase oxidation.
Claim 4:
The resist pattern transfer method according to claim 1, wherein an organic solvent is used as a resist stripping solution in the resist pattern stripping step.
Claim 5:
5. A step of transferring a resist pattern to the film of a photomask blank having a film containing a silicon-based material containing a transition metal formed on a transparent substrate by the method according to claim 1. A method of manufacturing a photomask characterized by the above.

  By using the resist pattern transfer method of the present invention, a finer pattern can be transferred with a thinner resist pattern with high precision in the processing of a silicon-based material containing a transition metal. In manufacturing a photomask for processing an optical functional film formed on a mask blank, high precision processing can be applied.

6 is a graph showing a change in reflectance of a film with respect to etching time, measured by changing an O ₂ flow rate in Experimental Example 1. 6 is a graph showing a change in reflectance of a film with respect to etching time, measured by changing an O ₂ flow rate in Experimental Example 2. It is the schematic which shows the dry etching apparatus used by the experiment example and the Example.

Hereinafter, the present invention will be described in detail.
In the resist pattern transfer method of the present invention,
(1) forming a resist pattern on a film containing a silicon-based material containing a transition metal formed on a substrate;
(2) A step of oxidizing the surface layer of a portion of the film containing a silicon-based material containing a transition metal where the resist pattern is not formed to increase the oxygen content ratio of the surface layer material composition;
(3) A step of stripping the resist pattern under non-oxidizing conditions after the oxidation step,
(4) After the resist pattern peeling step, using the oxidized surface layer as an etching mask, the step of etching the portion where the resist pattern is formed but not oxidized in the oxidation step by chlorine-based dry etching containing oxygen is included. Yes.

[Step (1)]
Step (1) is a step of forming a resist pattern on a film containing a silicon-based material containing a transition metal formed on a substrate.

  When the resist pattern is transferred to the optical functional film formed on the photomask blank, a transparent substrate such as a quartz substrate used for the photomask blank is used as the substrate. As the film containing a silicon-based material containing a transition metal, specifically, a silicon-based material containing a transition metal, preferably further containing oxygen and / or nitrogen is used. Examples of optical function films include phase shift films such as light shielding films, antireflection films, and halftone phase shift films. Any film of a silicon-based material containing a transition metal may be used. Good. These films may be entirely silicon-based materials containing a transition metal, or a part (particularly, the surface layer on the side away from the substrate) may be a silicon-based material containing a transition metal.

  In the silicon-based material containing the transition metal, the surface layer of the portion where the resist pattern is not formed is oxidized in the oxidation step of step (2) described later. For this reason, at least the surface layer of the silicon-based material containing the transition metal to be oxidized needs to be in a state that can be oxidized, in particular, in a saturated oxidation state. Therefore, even in the case of a silicon-based material containing a transition metal that cannot be oxidized (particularly in a saturated oxidation state), the surface material (degree of oxidation) can be changed by oxidation treatment. Because it is not possible, it is not eligible.

  Here, when describing the saturated oxidation state, it means the case where the transition metal and silicon and the light elements (especially oxygen and nitrogen) are in a predetermined ratio with respect to the oxidation degree of the silicon-based material containing the transition metal, For transition metals such as molybdenum, 3 equivalents of oxygen (3 moles of oxygen atom per mole of molybdenum atom), 2 equivalents of nitrogen (2 moles of nitrogen atom per mole of molybdenum atom), silicon Is equivalent to 2 equivalents of oxygen (2 moles of oxygen atom to 1 mole of silicon atom) and 4/3 equivalents of nitrogen (4/3 mole of nitrogen atom to 1 mole of silicon atom). It corresponds to a state, and a composition containing a transition metal, silicon, and a light element at this ratio is a saturated oxidation state. When the amount of transition metal and silicon is larger than the above ratio, it is in a state where further oxidation is possible, and such a composition is a silicon-based material containing a transition metal that is not in the saturated oxidation state targeted by the present invention. It is.

  The resist pattern may be formed by any known method, but in order to form a fine pattern for a photomask, a resist film obtained from a chemically amplified photoresist composition is usually used, and an electron beam or After performing pattern exposure with an ultraviolet beam, a resist pattern is obtained through a development operation. However, in the pattern transfer method of the present invention, the position where the resist pattern is provided on the film to be processed is etched, and the resist pattern is reversely transferred to the film to be processed. Therefore, if a positive resist is used, the exposed part remains as a silicon-based material pattern containing a transition metal, and if a negative resist is used, the silicon-based material containing the transition metal in the exposed part is etched away. become.

[Step (2)]
Step (2) is a step of increasing the oxygen content ratio of the surface layer material composition by oxidizing the surface layer of the portion of the film containing the silicon-based material containing the transition metal where the resist pattern is not formed.

  This step is a step of oxidizing the film to be processed on which the resist pattern obtained in the step (1) is formed. In this step, the resist film opening is selectively oxidized with respect to the silicon-based material containing the transition metal on which the resist pattern is formed, and the surface layer of the film containing the silicon-based material containing the transition metal in the resist opening To increase the degree of oxidation (the oxygen content ratio in the atomic composition of the material constituting the surface layer).

  As this oxidation method, treatment by gas phase oxidation (dry conditions) can be employed. In this case, a method using oxygen plasma, a method using ozone gas, a method using thermal oxidation in oxygen gas, and the like are known, and any of them can be adopted. Of these, thermal oxidation is performed at a temperature exceeding 150 ° C. In such a case, it may be difficult to remove the resist. Therefore, it is preferable to carry out the resist at a high oxygen concentration of, for example, 50% by volume or more with an increased oxygen concentration.

  In addition, since the method using oxygen plasma and the method using ozone gas, particularly the method using oxygen plasma, removes the resist film in a short time, it is necessary to test in advance how long the thickness of the resist film to be used is removed. It is preferable to perform the oxidation treatment in a time shorter than the time for removing the entire resist film.

  When the oxidation method by vapor phase oxidation is used, a highly oxidized layer of about 1 to 10 nm can be provided on the surface layer of the silicon-based material film containing a transition metal.

  The method using oxygen plasma is a method known as oxygen ashing that is usually used for stripping a resist film. This method is known to enable etching with high anisotropy from above without degrading the shape of the resist pattern by adopting high-density plasma. (Patent Document 6: JP-A-9-167733). In this method using oxygen plasma, the oxidation process may be terminated before the resist film disappears.

  Note that an atmosphere gas containing a chlorine-containing compound, for example, a halogen atom in an oxygen plasma (Patent Document 7: JP-A-4-7829), an atmosphere gas containing a halogen atom and a carbon atom (Patent Document 8: JP-A-5-283375). ), An atmospheric gas containing a halogen atom and a carbonyl group (Patent Document 9: Japanese Patent Laid-Open No. 10-312991), an atmospheric gas containing a halogen atom, a nitrogen atom and an oxygen atom (Patent Document 10: Japanese Patent Laid-Open No. 10-312992) Patent Document 11), an atmospheric gas containing halogen atoms and sulfur atoms (Patent Document 11: Japanese Patent Laid-Open No. 10-312993), and the like provide an organic film that can provide a thin protective film on the resist pattern side wall and suppress the thinning of the resist pattern However, when these methods are applied to the oxidation treatment of the present invention, It is effective in controlling the reduction of the thickness of the resist pattern, to slow down the film reduction of the resist pattern, it is possible to proceed the oxidation of the resist opening portion with high accuracy.

For example, when the atmospheric gas is Cl ₂ and O ₂ , it is preferable to contain oxygen gas at a level that does not allow etching of the film to be processed, and it depends on the composition of the film to be processed, but preferably oxygen gas / chlorine gas When the oxidation treatment is performed with a (molar ratio) of 0.01 to 10, more preferably 0.05 to 5, and particularly preferably 0.1 to 1, the film thickness of the resist is greatly reduced compared to the case where the oxidation treatment is performed only with oxygen. The film to be processed can be oxidized at a reduced speed, and the surface layer of the silicon-based material film containing the target transition metal can be oxidized with high process accuracy and high dimensional accuracy.

  Further, as an oxidation method, a treatment by liquid phase oxidation (wet conditions) can be employed. Specific examples of a method for providing a highly oxidized layer on a silicon-based material film containing a transition metal by liquid phase oxidation include a method using an oxidizing agent solution such as ozone water or hydrogen peroxide solution.

  Even in this liquid phase oxidation method, since the resist film is subjected to wet etching to some extent, it is preferable to determine processing conditions in advance according to the physical properties of the resist to be used. When ozone water is used, if the concentration is too high, the etching rate to the resist film is increased. Therefore, it is preferable to use ozone water having a concentration of about 1 to 30 ppm, and the processing temperature is 0 to 30 ° C., 1 to 10 ° C. If the process is of the order of minutes, the etching of the resist film can be suppressed and an oxidation process with high dimensional accuracy can be performed. Further, when using hydrogen peroxide solution, it is preferable to use a hydrogen peroxide solution having a concentration of about 0.1 to 3%. If the processing temperature is 0 to 30 ° C. and about 10 to 10 minutes, the resist Oxidation with high dimensional accuracy can be achieved by suppressing film etching.

  In this liquid phase oxidation, an oxidant solution is supplied onto the film to be processed, heated as necessary, and when the reaction on the surface is completed, rinsing with pure water or the like is performed to remove the oxidant, What is necessary is just to dry. According to this method, a highly oxidized layer of about 1 to 10 nm can be provided on the surface layer of the silicon-based material film containing a transition metal.

In the oxidation treatment, in order to obtain etching selectivity by chlorine-based dry etching containing oxygen, which will be described later, the oxygen content C ₀ (mol%) in the silicon-based material containing the transition metal before being oxidized, and oxidation It is necessary that a sufficient difference is given to the silicon-based material containing the transition metal after being formed, that is, the oxygen content C ₁ (mol%) in the surface layer. Therefore, the oxidation treatment is preferably performed so that the difference (C ₁ −C ₀ ) between the content ratios C ₀ and C ₁ is preferably 2 or more, more preferably 5 or more, and even more preferably 10 or more.

[Step (3)]
Step (3) is a step of stripping the resist pattern under non-oxidizing conditions after the oxidation step.

  This step is a step of exposing a region to be removed by etching of the silicon-based material film containing the transition metal. For the resist stripping, any known method may be used as long as it is under non-oxidizing conditions. Oxidation conditions such as ashing with oxygen plasma, stripping with hot concentrated sulfuric acid, and the use of high-concentration hydrogen peroxide solution oxidize the surface of the resist-protected region. Although it is necessary to avoid use in the exposure stage, the resist film thickness is reduced by the oxidation condition treatment before the surface of the resist protected area is exposed, and then the remaining resist film is subjected to non-oxidation conditions. It is possible to remove with.

  As a resist peeling method under non-oxidizing conditions, a method in which an organic solvent is used and the resist is dissolved and peeled is mentioned as a preferred method. Specific examples of the organic solvent include polar solvents such as isopropyl alcohol, acetone, DMF, THF, dioxane, ethyl lactate and the like, and mixtures thereof, methanol, ethanol, toluene and the like. For example, other solvents may be mixed and used. In addition, hydroxylamine, ethanolamine, or the like may be added to promote the dissolution of the resist with an organic solvent.

  Resist stripping using an organic solvent can be performed by immersing a film to be processed formed on a substrate in an organic solvent or spraying it on a shower. The temperature can be 10 to 60 ° C. for 1 to 20 minutes, and a physical method such as surface scrubbing or ultrasonic treatment may be combined.

  Further, a method using laser irradiation in an inert gas (Patent Document 12: Japanese Patent Application Laid-Open No. 2003-303789) or a physical method such as surface scrub may be used alone.

[Step (4)]
In step (4), after the resist pattern peeling step, using the oxidized surface layer as an etching mask, a portion where the resist pattern is formed but not oxidized in the oxidation step is etched by chlorine-based dry etching containing oxygen. It is.

  This step is performed by using the surface layer of the silicon-based material film containing the transition metal oxidized in the step (2) as an etching mask and containing the transition metal in the region not oxidized in the step (3) exposed in the step (3). This is a step of selectively etching the material. This selective etching is oxidized in a chlorine-based dry etching with a controlled concentration of oxygen in the etching gas, that is, a highly oxidized composition that forms the surface layer of a silicon-based material containing an oxidized transition metal. It can be carried out by adding oxygen at a concentration that can be selectively etched by chlorine-based dry etching, depending on the composition of the silicon-based material containing a transition metal that is not present.

  The appropriate oxygen concentration for obtaining the selection ratio varies depending on the composition of the silicon-based material containing the transition metal. Therefore, the relationship between the oxygen addition ratio and the etching rate when etching the material used in advance under chlorine-based dry etching conditions. Check it out.

Specifically, a silicon-based material film containing a transition metal to be processed and a film obtained by subjecting this material to oxidation treatment are prepared, and etching is performed under a plurality of chlorine-based dry etching conditions with different oxygen contents. And measure the etch rate of each film. The chlorine-based dry etching used here can be based on the general dry etching conditions used when etching the chromium-based material film of the photomask blank, and using chlorine gas (Cl ₂ ) or the like, oxygen As the amount of addition (the ratio of oxygen gas to chlorine gas) is decreased, the silicon-based material film containing the transition metal on the substrate that has not been oxidized first exhibits an effective etching rate. By this method, the minimum oxygen concentration necessary for performing selective etching is obtained. Also, if the amount of oxygen added is too small, the silicon-based material film containing the transition metal that has undergone the oxidation process will also be etched, so check the minimum oxygen concentration required for selective etching. It is also necessary to keep it.

  Specifically, in the selective etching, the ratio of chlorine gas to oxygen gas (oxygen gas / chlorine gas (molar ratio)) is preferably 0.0001 to 1, more preferably 0.0003 to 0. .5, particularly preferably between 0.0005 and 0.3, a ratio capable of selective etching is found. The flow rates of chlorine gas and oxygen gas may be, for example, 100 to 300 sccm for chlorine gas, 0.1 to 100 sccm for oxygen gas, or 1 to 20 sccm for helium gas. The gas pressure is preferably 1 to 10 mtorr.

  The resist pattern transfer method of the present invention can be suitably used for processing a photomask blank having a film containing a silicon-based material containing a transition metal formed on a transparent substrate, and is formed on the photomask blank. A photomask can be manufactured by the method of transferring the resist pattern described above to the optical functional film.

  Specific examples of the optical functional film of a silicon-based material containing a transition metal formed on a photomask blank include phase shift films such as an antireflection film, a light shielding film, and a halftone phase shift film.

  When the film to be processed is an antireflection film made of a silicon-based material containing a transition metal, the composition of silicon is preferably 20 atomic% to 70 atomic%, oxygen is preferably 0 atomic% to 60 atomic%, Nitrogen is preferably 0 atomic% or more and 50 atomic% or less, and the total of oxygen and nitrogen is 10 atomic% or more. Further, the transition metal is preferably 1 atom% or more and 20 atom% or less, and may further contain other elements such as carbon if it is 5 atom% or less.

  When the film to be processed is a light-shielding film made of a silicon-based material containing a transition metal, the composition of silicon is preferably 30 atomic% to 95 atomic%, and oxygen is preferably 0 atomic% to 60 atomic%. Nitrogen is preferably 0 atomic% or more and 50 atomic% or less, transition metal is preferably 1 atomic% or more and 20 atomic% or less, and if it is 5 atomic% or less, other elements such as carbon may be included. .

  Further, when the film to be processed is a halftone phase shift film made of a silicon-based material containing a transition metal, the composition of silicon is preferably 20 atomic% to 80 atomic%, and oxygen is preferably 0 atomic% to 60 atomic%. Atomic% or less, nitrogen is preferably 0 atomic% or more and 50 atomic% or less, transition metal is preferably 1 atomic% or more and 20 atomic% or less, and if it is 5 atomic% or less, other elements such as carbon are included. May be.

  As the transition metal, one or more selected from titanium, vanadium, cobalt, nickel, zirconium, niobium, molybdenum, hafnium, tantalum and tungsten are suitable metals, and in particular, molybdenum from the viewpoint of dry etching processability. Preferably there is.

  When the photomask blank is, for example, a binary photomask blank, the optical density is 2.0 or more by combining the light shielding film and the antireflection film (which may be sandwiched between the light shielding films on both sides of the antireflection film). Each film thickness is designed in accordance with the optical density and refractive index of the material to be used, preferably 2.5 or more, more preferably 3.0 or more.

  When the photomask blank is a halftone phase shift mask blank, the halftone phase shift film is designed so that the necessary optical density and phase shift amount can be obtained. When an antireflection film is provided, the optical density of the phase shift film, the light shielding film, and the antireflection film when there is an antireflection film is 2.0 or more, preferably 2.5 or more, more preferably Each film thickness is designed according to the optical density and refractive index of the material used so that it may become 3.0 or more.

  Further, when a photomask is manufactured from a photomask blank using the resist pattern transfer method of the present invention, in a binary photomask blank, the content ratio of oxygen and / or nitrogen is usually higher in the light-shielding film than in the antireflection film. Therefore, if dry etching conditions that can selectively transfer a pattern to the antireflection film are used, the light shielding film can also be dry etched under the same conditions as the etching conditions of the antireflection film.

  On the other hand, in the halftone phase shift mask blank having a light shielding film, the antireflection film and the halftone phase shift film are subjected to the antireflection process by applying the etching condition of the film having the higher oxygen and / or nitrogen content ratio. A pattern can be simultaneously transferred under the same etching conditions to three kinds of films, a film, a light shielding film, and a halftone phase shift film.

  Furthermore, in the process of removing the unnecessary light shielding film, which is usually carried out after patterning of the halftone phase shift film, a resist film is provided again, and the portion where the light shielding film is left is protected with a resist pattern, thereby preventing the reflection of unnecessary portions. The film is removed by chlorine-based dry etching with an oxygen amount that can be etched, and the oxygen amount is increased when the light shielding film is continuously etched and removed, so that the halftone phase shift film is not damaged. The light shielding film can be removed.

  EXAMPLES Hereinafter, although an experiment example and an Example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

[Experimental Example 1]
Contains a transition metal made of MoSiON (Mo: Si: O: N = 1: 4: 1: 4 (molar ratio), total content of oxygen and nitrogen is 50 mol%) formed on a quartz substrate with a thickness of 75 nm. In order to evaluate the amount of oxygen in the etching gas and the etching rate under the chlorine-based dry etching conditions using the silicon-based material film, the oxygen amount was changed between 0 and 10.0 sccm according to the following conditions, and the wavelength was 675 nm. The change in reflectance with respect to the inspection light was measured over time. The obtained results are shown in FIG. FIG. 3 shows an outline of the etching apparatus used. In FIG. 3, 1 is a chamber, 2 is a ground, 3 is a lower electrode, 4 is an antenna coil, 5 is a substrate to be processed, and RF1 and RF2 are high-frequency power supplies.
RF1 (RIE: reactive ion etching): Pulse 700V
RF2 (ICP: inductively coupled plasma): CW (continuous discharge) 400W
Pressure: 6mTorr
Cl ₂ : 185 sccm
O ₂ : 0 to 10.0 sccm
He: 9.25 sccm

  From the change in reflectivity with respect to the dry etching time shown in FIG. 1, the reflectivity of the film surface before etching is about 40, whereas the reflectivity decreases as the etching progresses, and the etching of the film ends. It can be seen that the reflectance is about 10. In addition, in the MoSiON film in which the total content of oxygen and nitrogen used here is 50 mol%, the oxygen amount of the atmospheric gas in dry etching is 1 sccm or more (oxygen gas / chlorine gas (molar ratio) is 1/185 or more) ), It can be seen that the film is hardly etched.

[Experiment 2]
Silicon-based material containing a transition metal made of MoSiN having a film thickness of 46 nm (Mo: Si: N = 1: 3: 1.5 (molar ratio), the total content of oxygen and nitrogen being 27 mol%) The change in reflectance of the film was measured over time in the same manner as in Experimental Example 1. The obtained results are shown in FIG.

  As shown in FIG. 2, when the oxygen amount is 2 sccm (oxygen gas / chlorine gas (molar ratio) is 2/185), etching is performed at about 5 nm / min, and 55 sccm (oxygen gas / chlorine gas ( When the molar ratio was 55/185), it was confirmed that etching did not proceed at all.

  As shown in Experimental Examples 1 and 2, the oxygen ratio of the atmospheric gas and the etching rate in dry etching can be obtained according to the material used, and the optimum conditions for selectively etching each material can be determined.

[Example 1]
A photomask blank in which a light-shielding film made of MoSiN (Mo: Si: N = 1: 3: 1.5 (atomic ratio)) with a film thickness of 60 nm is formed on a quartz substrate, and a spin mask is formed on the light-shielding film. A chemically amplified resist film for EB exposure having a film thickness of 150 nm was formed using a coater. On this resist film, a pattern having a line width of 400 nm was drawn by an EB exposure apparatus and then developed to form a resist pattern that protects a portion where the light shielding film is etched.

Next, the light shielding film surface part of the resist non-protection part was oxidized by the method using oxygen plasma under the following conditions.
RF1 (RIE): Pulse 700V
RF2 (ICP): CW 400W
Pressure: 6mTorr
Cl ₂ : 185 sccm
O ₂ : 55 sccm
He: 9.25 sccm
Etching time: 10 minutes

  Next, the resist pattern on the light shielding film was immersed in acetone together with the transparent substrate, irradiated with ultrasonic waves, and held for 5 minutes to peel off the resist pattern.

Next, using the highly oxidized layer formed by the oxidation treatment as a mask, the exposed light shielding film is etched by peeling off the resist pattern by chlorine-based dry etching containing oxygen under the following conditions. Formed.
RF1 (RIE): Pulse 700V
RF2 (ICP): CW 400W
Pressure: 6mTorr
Cl ₂ : 185 sccm
O ₂ : ₂ sccm
He: 9.25 sccm
Etching time: 18 minutes

  By applying the steps (1) to (4) of the present invention, the resist pattern was transferred to the light shielding film, and the light shielding film could be accurately formed into a predetermined pattern shape.

1 Chamber 2 Ground 3 Lower electrode 4 Antenna coil 5 Substrate RF1 and RF2 High frequency power supply

Claims (5)

Forming a resist pattern on a film containing a silicon-based material containing a transition metal formed on a substrate;
A step of oxidizing the surface layer of the part where the resist pattern of the film is not formed to increase the oxygen content ratio of the surface layer material composition;
After the oxidation step, the step of stripping the resist pattern under non-oxidizing conditions, and the portion where the resist pattern is formed using the oxidized surface layer as an etching mask after the resist pattern stripping step and is not oxidized in the oxidation step A method for transferring a resist pattern, comprising: a step of etching by oxygen-containing chlorine-based dry etching.   2. The resist pattern transfer method according to claim 1, wherein the oxidation is gas phase oxidation.   2. The resist pattern transfer method according to claim 1, wherein the oxidation is liquid phase oxidation.   The resist pattern transfer method according to claim 1, wherein an organic solvent is used as a resist stripping solution in the resist pattern stripping step.   5. A step of transferring a resist pattern to the film of a photomask blank having a film containing a silicon-based material containing a transition metal formed on a transparent substrate by the method according to claim 1. A method of manufacturing a photomask characterized by the above.

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