JP2010164779A - Method of dry etching - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable high-accuracy etching on a light-shielding film without giving damages to a phase shift film, even when no etching stopper film is used or even when a laminate of the same type of silicon-based materials is used, for example, the laminate of the light-shielding film of a silicon-based material as a phase shift film on the phase shift film of a silicon-based material is used. <P>SOLUTION: A laminate is prepared, comprising: a single or multilayer first silicon-based material layer containing oxygen and/or nitrogen and optionally containing a transition metal; and a single or multilayer second silicon-based material layer formed adjacent to the first silicon-based material layer, optionally containing a transition metal and having a smaller total content of nitrogen and oxygen than that of the first silicon-based material layer. The second silicon-based material layer is selectively etched away by chlorine-based dry etching by setting a ratio of chlorine gas to oxygen gas so as to control the etching rate of the second silicon-based material layer to be larger than the etching rate of the first silicon-based material layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is a method for processing a photomask blank, which is a material for a photomask used for fine processing, such as a semiconductor integrated circuit, a CCD (charge coupled device), a color filter for an LCD (liquid crystal display device), a magnetic head, etc. into a photomask. The present invention relates to a suitable dry etching method.

  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 Effect 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). In addition, even when combined with technology that uses an etching mask to perform higher-precision processing, it is better to process a silicon-based light-shielding film using a chromium-based material as an etching mask. As a result, it has been found that pattern errors and processing errors due to side etching are smaller than when processing a chromium-based material (Patent Document 2: Japanese Patent Application Laid-Open No. 2007-24410). For this reason, as a next-generation light-shielding film material, a light-shielding film using a film made of a silicon-based material is considered promising.

JP 2007-2441065 A JP 2007-2441060 A Japanese Patent Laid-Open No. 2001-27799 JP 2004-333653 A JP-A 63-85553 JP-A-7-140635 JP 2006-317665 A

  By the way, a silicon-based compound containing a transition metal is commonly used as a preferable material in terms of processing characteristics and chemical stability even as a halftone phase shift film material. Therefore, when using a photomask blank having a silicon-based light-shielding film on a silicon-based halftone phase shift film, the light-shielding film on the halftone phase-shift film is etched away without damaging the halftone phase-shift film. For this purpose, it is preferable to provide an etching stopper film made of a material that can be selectively etched, for example, a chromium-based material, between the light shielding film and the halftone phase shift film.

  This etching stopper film not only enables the light-shielding film on the halftone phase shift film to be etched away without damaging the halftone phase shift film, but also has the effect of allowing the halftone phase shift film to be precisely processed. It is a thing. However, the presence of this film requires three etching processes in the order of the light shielding film, the etching stopper film, and the halftone phase shift film even if only the pattern of the halftone phase shift film is formed. Become. When the above-described chromium-based etching mask film is used for processing with higher accuracy, the etching process is performed four times in order to process the halftone phase shift film including the etching process of the etching mask film. In addition, including the process of removing the light-shielding film on the halftone phase shift film by etching, five etching processes are required even if a method of simultaneously etching different layers is used.

  However, the etching process is a process that easily causes the generation of mask defects, and the method using the etching stopper film as described above is disadvantageous in that the number of etching processes is increased.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide an etching method capable of selectively etching one of two layers made of a silicon-based material.

  In order to reduce the number of etching steps, for example, if a photomask blank without an etching stopper film disclosed in Japanese Patent Application Laid-Open No. 2007-244105 (Patent Document 1) is used, during pattern formation processing of the phase shift portion, This can be achieved by performing processing of the light shielding film and the phase shift film as one step by dry etching with fluorine. However, in order for the phase shift unit to function, it is necessary to remove the light shielding film on the phase shift unit, and the problem is whether at this time, only the light shielding film can be removed with high precision selectivity.

  In contrast to this selective etching, the present inventors focused on chlorine-based dry etching. Japanese Patent Laid-Open No. 2001-27799 (Patent Document 3) shows that the MoSiON film can be etched under chlorine-containing dry etching conditions containing oxygen. From a specific example, the oxygen content is about 20%. Until now, it has been shown that the etching rate is effective, and the etching rate gradually decreases as the amount of oxygen increases. However, in this case, since the etching rate does not change rapidly, it has been considered that selective etching is difficult even if the oxygen content is adjusted.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive studies, produced various test samples, and pursued the possibility of selective etching. It has been found that selective etching is possible by adjusting the amount of oxygen added to the etching gas if the materials are different materials.

  In addition, the present inventors include a single or multilayer first silicon-based material layer that contains oxygen and / or nitrogen and may contain a transition metal, and is adjacent to the first silicon-based material layer. A layer formed of a single layer or a multilayer of a second silicon-based material layer that may contain a transition metal and has a lower total content of nitrogen and oxygen than the first silicon-based material layer By selecting the composition of the silicon-based material layer and the etching conditions, the body can selectively etch the second silicon-based material layer by one chlorine-based dry etching. Even when a chromium-based material layer adjacent to the chromium-based material layer is provided, the second silicon-based material layer together with the chromium-based material film is selectively etched by a single chlorine-based dry etching by selecting the etching conditions. Is possible Heading the door, the present invention has been accomplished.

That is, the present invention provides the following dry etching method.
Claim 1:
A single-layer or multilayer first silicon-based material layer that contains oxygen and / or nitrogen and may contain a transition metal;
A single layer formed of a silicon-based material layer formed adjacent to the first silicon-based material layer, which may contain a transition metal, and has a lower total content of nitrogen and oxygen than the first silicon-based material layer Or a method of selectively etching away the second silicon-based material layer from the laminate composed of a plurality of second silicon-based material layers, leaving the first silicon-based material layer,
Using a chlorine-based dry etching gas containing oxygen, the ratio of the chlorine-based gas to the oxygen gas is set so that the etching rate of the second silicon-based material layer with respect to the etching rate of the first silicon-based material layer is increased. A dry etching method comprising: setting and selectively removing the second silicon material layer by chlorine dry etching.
Claim 2:
The dry etching method according to claim 1, wherein the second silicon-based material layer includes a silicon-based material layer containing nitrogen and / or oxygen and optionally containing a transition metal.
Claim 3:
The second silicon-based material layer further includes a silicon-based material layer that does not contain nitrogen and oxygen and may contain a transition metal on the side in contact with the first silicon-based material layer. The dry etching method according to claim 2.
Claim 4:
The total content C ₁ (mol%) of nitrogen and oxygen in the _first silicon-based material layer, the nitrogen and / or oxygen in the second silicon-based material layer, and a transition metal. The difference (C ₁ -C ₂ ) with respect to the total content C ₂ (mol%) of nitrogen and oxygen in the silicon-based material layer that may be 5 or more, according to claim 2 or 3, Dry etching method.
Claim 5:
5. The ratio of chlorine gas to oxygen gas (oxygen gas / chlorine gas (molar ratio)) is set to 0.0001 to 1 in the chlorine dry etching. The dry etching method according to Item.
Claim 6:
For each of the first silicon-based material layer formed on the substrate, and the second silicon-based material layer formed on the substrate or the silicon-based material layer constituting the second silicon-based material layer, chlorine-based gas and While changing the ratio with oxygen gas (oxygen gas / chlorine gas (molar ratio)), a chlorine-based dry etching operation with a chlorine-based dry etching gas containing oxygen is performed, and the first silicon material layer and the first It is possible to obtain the etching rate of each of the two silicon-based material layers, and to selectively remove the second silicon-based material layer from the stacked body, leaving the first silicon-based material layer, by comparing these etching rates. 6. The dry etching method according to claim 1, wherein a dry etching is performed by determining a ratio between a chlorine-based gas and an oxygen gas and setting the ratio.
Claim 7:
The laminate is further provided with a chromium-based material layer adjacent to the second silicon-based material layer, and both the chromium-based material layer and the second silicon-based material layer are subjected to the chlorine-based dry etching. The dry etching method according to claim 1, wherein the etching is removed.
Claim 8:
The first silicon-based material layer and the second silicon-based material layer are layers that are formed on a transparent substrate and constitute a functional film of a photomask blank. 2. A dry etching method according to item 1.
Claim 9:
The first silicon-based material layer is a layer constituting part or all of the phase shift film of the photomask blank, and the second silicon-based material layer is part or all of the light shielding film of the photomask blank. The dry etching method according to claim 8, wherein the dry etching method is a layer constituting the layer.

  By using the dry etching method of the present invention, the same type of silicon-based material laminate, for example, a silicon-based material light-shielding film that is a phase shift film can be used without phase shift of the silicon-based material without using a so-called etching stopper film. Even when a layer laminated on the film is used, the light shielding film can be etched with high accuracy without damaging the phase shift film.

  Further, when pattern processing of the lower layer of the laminate, for example, pattern processing of the phase shift film, the silicon-based light shielding film and the silicon-based phase shift film can be processed by one dry etching, and the upper layer of the laminate For example, even when an etching mask film made of a chromium-based material is used on the light-shielding film, or when a chromium-based material layer having an antireflection function is used as an upper layer in the light-shielding film, these and the silicon-based material in the light-shielding film Since the material layer can be processed by one dry etching, the dry etching process is reduced and the generation of mask defects can be prevented.

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. 10 is a graph showing changes in the reflectance of a film with respect to etching time, measured at an O ₂ flow rate of ₂ sccm in Experimental Example 3. 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 more detail.
When processing a photomask blank having a phase shift film on a transparent substrate and further having a light-shielding film thereon into a photomask having a light-shielding part and a phase-shifting part, from the relationship of the order in which those films were laminated In general, in order to obtain the required phase shift portion pattern, the light shielding film and the phase shift film are removed in this order in a portion where the phase shift film is unnecessary, and then the remaining portion is obtained to obtain the light shielding portion pattern. By removing an unnecessary light shielding film on the phase shift portion pattern, a desired photomask can be obtained.

  In order to perform highly accurate processing of the phase shift portion, conventionally, materials having different etching characteristics such as a chromium-based material for the light shielding film and a silicon-based material with or without a transition metal for the phase shift film are conventionally used. Using a photoresist pattern, a chromium-based material light-shielding film is patterned, and the resulting light-shielding part pattern is used as an etching mask to process a silicon-based material phase shift film (for example, Patent Documents). 4: Refer to JP 2004-333653 A).

  However, as described above, as the target semiconductor pattern rule is miniaturized to 65 nm or less, if a chromium film having a thickness necessary for ensuring light shielding properties is used, pattern accuracy is increased when the chromium film is processed. Is significantly reduced, and it is effective to use a silicon-based material containing or not containing a transition metal in the main layer of the light-shielding film (for example, Patent Document 1: Japanese Patent Application Laid-Open No. 2007-244105, (Patent document 2: Japanese Patent Application Laid-Open No. 2007-241060).

  However, if a silicon-based material, which is a similar material, is also used for the light-shielding film, only the silicon-based material of the light-shielding film is selectively used in the photomask processing process in order to remove unnecessary light-shielding films on the phase shift film. A method of etching is required. Therefore, the selective etching method using the chromium-based material and the silicon-based material as described above is used for etching between the phase shift film of the silicon-based material and the light-shielding film of the silicon-based material. It is effective to provide an etching stopper film of a chromium-based material having etching characteristics different from that of a silicon-based material, as disclosed in Japanese Patent Application Laid-Open No. 2007-244105 (Patent Document 1), between the silicon-based material and the light-shielding film. become.

  In the case of this method, various variations can be adopted in the processing method of the phase shift film, and although it is an advantageous method, in order to obtain the phase shift portion pattern as described above, etching with the etching stopper film is performed. Since the characteristics are different from the etching characteristics of the light-shielding film and the phase shift film, three etching steps are required in the order of the silicon-based light shielding film, the chromium-based material etching stopper film, and the silicon-based material phase shift film. Therefore, there has been a demand for a method capable of selectively etching one layer from a laminate of adjacent silicon-based material layers without an etching stopper film.

A method of selectively etching one of the two layers containing silicon in contact with each other is disclosed in Japanese Patent Laid-Open No. 63-85553 (Patent Document 5). Here, when a silicon film containing a transition metal formed on a quartz substrate is etched under chlorine-based dry etching conditions containing oxygen using silicon oxide (Si _m O _n ) as an etching mask, Quartz substrates have been shown to be able to selectively etch silicon films containing transition metals without being damaged. However, a specific method for selectively removing silicon oxide is not disclosed here, and silicon oxide used here is a material that easily generates foreign matters during sputtering film formation. Convenience is not good.

  Further, in the processing of the halftone phase shift film disclosed in Japanese Patent Laid-Open No. 2001-27799 (Patent Document 3), although the composition is unknown, the MoSiON film has a considerably wide oxygen under chlorine-based dry etching conditions containing oxygen. It has been shown that etching is possible in the range of the content. This indicates that the MoSiON film can be etched under chlorine-containing dry etching conditions containing oxygen, but it is expected that it is difficult to achieve selectivity between the MoSiON films.

  On the other hand, in Japanese Patent Application Laid-Open No. 2007-244102 (Patent Document 2), a silicon-based material light-shielding film is used on a phase shift film made of silicon-based material, and both layers are formed in one step by fluorine-based dry etching. Although it is shown that pattern processing is performed and a chromium-based compound film is formed on the light-shielding film, removal of the unnecessary light-shielding film of the chromium-based material film is different from the conditions for the silicon-based material film The dry etching process is performed.

  In the present invention, a first silicon-based material layer that contains oxygen and / or nitrogen and may contain a transition metal, and is formed adjacent to the first silicon-based material layer and contains a transition metal. The first silicon-based material layer, the second silicon-based material layer, and the second silicon-based material layer including a single layer or a multi-layer having a silicon-based material layer may be provided. By appropriately combining these, the second silicon layer formed on the first silicon-based material layer is left without damaging the first silicon-based material layer without providing a chromium material etching stopper film therebetween. This silicon-based material layer can be selectively removed by dry etching.

  In such a laminate of the first silicon-based material layer and the second silicon-based material layer, the light shielding film and the phase shift film of the photomask blank in which these layers are formed on the transparent substrate. The first silicon-based material layer is a layer constituting a part or all of the phase shift film of the photomask blank, and the second silicon-based material layer is preferably a layer constituting a functional film such as A layer constituting part or all of the light shielding film of the photomask blank is preferable.

  For example, in a photomask blank in which a phase shift film is formed on a transparent substrate and a light shielding film is further formed on the phase shift film, each of the phase shift film and the light shielding film contains oxygen and / or nitrogen. And a silicon-based material layer that may contain a transition metal, and when the silicon-based material layer of the phase shift film and the silicon-based material layer of the light-shielding film are adjacent to each other (both are other films) The silicon-based material layer of the phase shift film as the first silicon-based material layer and the silicon-based material of the light-shielding film as the second silicon-based material layer. By properly combining the layers, the etching stopper film of chromium material is not provided between them, and the silicon-based material layer of the phase-shift film is left without being damaged, and is formed on the silicon-based material layer of the phase-shift film. The silicon base material layer of the light-shielding film which is, can be selectively removed by dry etching.

  Furthermore, the light-shielding film may be provided with a silicon-based material layer that does not contain oxygen and nitrogen and may contain a transition metal, and does not contain oxygen and nitrogen. In the case where the silicon-based material layer that may be contained is provided on the side of the light shielding film in contact with the phase shift film, each of the phase shift film and the light shielding film contains oxygen and / or nitrogen, and may contain a transition metal. Good silicon-based material layers may be adjacent to each other via a silicon-based material layer that does not contain oxygen and nitrogen but may contain a transition metal. Also in this case, in order to selectively etch the entire light-shielding film with respect to the phase shift film by one dry etching by the selectivity mechanism of the present invention described later, oxygen and / or Appropriate silicon-containing material layer containing nitrogen and containing a transition metal and oxygen and / or nitrogen which is the outermost layer of the phase shift film and containing a transition metal Selection of combination and dry etching conditions is important.

  In the present invention, the silicon-based material layer of the phase shift film as the first silicon-based material layer and the silicon-based light shielding film as the second silicon-based material layer while realizing high-precision processing. Since there is no etching stopper film between the material layers, the silicon-based material of the light-shielding film and the silicon-based material of the phase shift film can be processed by fluorine-based dry etching in the same process. It is advantageous for shortening.

  Furthermore, in the present invention, oxygen and / or nitrogen may be included as a combination of a light-shielding film and a phase shift film that can obtain a high-performance film while ensuring an antireflection function, and may contain a transition metal. A silicon-based material layer is used in the light-shielding film, and a silicon-based material layer that contains oxygen and / or nitrogen and may contain a transition metal is the outermost layer of the phase shift film, and further, as a part of the light-shielding film, Alternatively, even if the chromium-based material film is on the silicon-based material layer of the light-shielding film as a film different from the light-shielding film, by selecting the composition of the silicon-based material layer and the etching conditions, one chlorine-based dry etching can be performed. The silicon material layer of the light shielding film can be etched together with the chromium material film, and the silicon material layer of the light shielding film can be selectively etched.

  The first silicon-based material layer (the silicon-based material layer of the phase shift film) containing the oxygen and / or nitrogen of the present invention, which may contain a transition metal (that is, contains or does not contain a transition metal) and the first The selective etching conditions of the laminate of the two silicon-based material layers (silicon-based material layer of the light shielding film) can be determined by the following method, for example.

  First, a predetermined amount of a silicon-based material film is formed on a substrate such as a quartz substrate used as a photomask substrate, and the oxygen gas content is predetermined (oxygen gas and chlorine) with respect to the silicon-based material film. By performing dry etching with chlorine-based gas (with a predetermined ratio with the system gas) by changing the oxygen gas content (changing the ratio of oxygen gas and chlorine-based gas), and obtaining the etching clear time The etching rate with respect to the oxygen addition amount can be obtained.

  This etching clear time can be obtained by measuring the reflectance of the silicon-based material film during etching. In addition, when the silicon-based material film can be observed during etching, a visual method is used, and the plasma in the etching chamber is measured. A method based on analysis of ions or elements in plasma by analysis of emission spectrum or the like may be used. Also, instead of etching clear time, a part of the silicon-based material is masked, and after etching for a predetermined time, it is etched away by optical methods such as stylus type film thickness meter and transmittance, and ellipsometry. The etching rate can also be obtained by a method of measuring the film thickness, which may be applied in combination.

The chlorine-based dry etching used here uses chlorine gas (Cl ₂ ) or the like and is typically added under the general dry etching conditions used when etching a chromium-based material film of a photomask blank. (Adjusting the ratio of oxygen gas and chlorine-based gas) can be carried out.

  Specifically, 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, and particularly preferably 0. .0005 to 0.3. More specifically, for example, conditions such as chlorine gas 100 to 300 sccm, oxygen gas 0.1 to 100 sccm, and gas pressure 1 to 10 mtorr can be applied. Further, helium gas may be added at 1 to 20 sccm.

  Japanese Patent Laid-Open No. 2001-27799 (Patent Document 3) shows that when the MoSiON film is dry etched, the etching rate gradually decreases as the amount of oxygen added to the chlorine-based dry etching gas increases. However, if there is a difference in the total content of oxygen and nitrogen in the two layers of silicon-based material in contact with each other (in the first silicon-based material layer (silicon-based material layer in the phase shift film)) If the total content of nitrogen and oxygen in the second silicon-based material layer (the silicon-based material layer of the light-shielding film) is made smaller than the total content of nitrogen and oxygen, the above chlorine-based dry etching is performed. Etching selectivity can be obtained.

For example, a first silicon-based material layer and a second silicon-based material layer (a silicon-based material layer constituting the second silicon-based material layer), for example, a silicon-based material layer of a phase shift film and a silicon-based light shielding film It is sufficient that there is a sufficient difference in the total content of oxygen and nitrogen between the material layer and the total content of nitrogen and oxygen in the first silicon-based material layer (silicon-based material layer in the phase shift film). difference rate C ₁ and (mole%), and total content of nitrogen and oxygen in the (silicon-based material layer of the light-shielding film) second silicon base material layer C ₂ (mol%) (C ₁ -C ₂ ) Is 5 or more, preferably 10 or more, and more preferably 20 or more, the first silicon-based material layer (phase shift) is adjusted by adjusting the amount of oxygen to be added using the method as described above. From the etching rate of the silicon-based material layer in the film, the second silicon-based material layer (light shielding) The etching rate of the silicon base material layer) of the large, in particular it is possible to obtain an etching rate difference of 10 times or more, it is possible to obtain a sufficient etching rate difference obtaining selectivity.

  As will be described later, a laminate of a first silicon-based material layer and a second silicon-based material layer in which the dry etching method of the present invention is preferably used (a silicon-based material for a phase shift film and a silicon for a light-shielding film) Since the photomask blank having a laminate with the system material layer preferably has a chromium material layer on the laminate, the chromium material layer and the second silicon material layer are simultaneously formed. It is preferable that etching can be removed, but this simultaneous etching is also possible within the range of the above-mentioned ratio of chlorine gas to oxygen gas (oxygen gas / chlorine gas (molar ratio)).

  The dry etching in the present invention can be usefully used for processing a photomask blank as described below into a photomask.

  First, in order to selectively etch the light shielding film by one dry etching using the above etching selectivity, the silicon-based material layer of the light shielding film may be a single layer or a multilayer. However, a sufficient etching rate difference is necessary in the relationship between the silicon-based material layer of the phase shift film and all the layers constituting the silicon-based material layer of the light shielding film. Therefore, the light shielding film used in the present invention is such that the total content of nitrogen and oxygen is as described above for all the silicon-based material layers of the light-shielding film and the silicon-based material layer of the phase shift film. Set to

  When the photomask blank of the present invention is completed, as described in, for example, Japanese Patent Application Laid-Open No. 2007-241060 (Patent Document 2), so that precise processing can be performed even using a thinner resist film. Etching mask film of chromium-based material that is completely peeled off (hereinafter referred to as an etching mask film that is used as an etching mask for such precision processing and is completely peeled off by the time the photomask is completed) Is provided on the light-shielding film as a film different from the light-shielding film, or as a part of the light-shielding film, a chromium-based material having an etching mask function with respect to a silicon-based material, and preferably an antireflection function It is preferable to provide this layer.

  As a preferred embodiment of the light shielding film used in the photomask blank of the present invention, first, the light shielding film in the case of using an etching mask film will be described.

  As described in Japanese Patent Application Laid-Open No. 2007-241060 (Patent Document 2), the etching mask film made of the chromium-based material causes a problem of side etching or a pattern density dependency problem as shown in Japanese Patent Application Laid-Open No. 2007-241402 (Patent Document 2). Therefore, in order to perform highly accurate etching processing, it is preferably 20 nm or less, more preferably 10 nm or less, and the material is metal chromium or chromium and at least one light element of oxygen, nitrogen, and carbon. It is preferable to use a material containing.

  As a preferable composition of the chromium-based material, for example, chromium is 50 atom% to 100 atom%, particularly 60 atom% to 100 atom%, oxygen is 0 atom% to 50 atom%, particularly 0 atom% to 40 atom. %, Nitrogen is 0 atom% or more and 50 atom% or less, particularly 0 atom% or more and 40 atom% or less, and carbon is 0 atom% or more and 20 atom% or less, particularly 0 atom% or more and 10 atom% or less. Thus, the etching mask film can be a film that provides high etching selectivity during the fluorine-based dry etching between the etching mask film, the light shielding film, and the phase shift film.

  In order to suppress poor formation of the resist pattern, it is preferable that at least the outermost surface portion of the etching mask film in contact with the resist contains oxygen and / or nitrogen in an amount of about 5 atomic% or more. Oxygen and / or nitrogen may be contained, and after the film formation, the film surface may be oxidized to adjust the oxygen concentration in the outermost surface portion.

  In the photomask blank of this aspect, a silicon-based material layer is used for the entire light shielding film. In addition, the required reflectance control for exposure light is adjusted by the content of nitrogen or nitrogen and oxygen, the film thickness, or both, but when an etching mask film is used, a silicon-based material layer is used. Since high processing accuracy can be ensured even when the film thickness of the film becomes relatively large, the optical density when combined with the phase shift film disposed under the light-shielding film is 2 or more, preferably 2.5 or more and 4 or less. The degree of freedom of material selection to satisfy this is great.

  In addition, the light-shielding film may be a single layer or a multilayer (including only a layer having a composition gradient in the film thickness direction) as long as this is satisfied. Some of the layers may be silicon or a layer made of silicon and a transition metal. In order to adjust the reflectivity, it is necessary to provide a layer containing oxygen and / or nitrogen. As described above, the layer containing oxygen and / or nitrogen is a silicon-based phase shift film. The content is made lower than the nitrogen and oxygen content of the uppermost layer of the material layer. The light-shielding film preferably has a reflectance with respect to exposure light controlled to 30% or less, more preferably 20% or less.

  The material used for the silicon-based material layer that contains oxygen and / or nitrogen and may contain a transition metal contained in the light-shielding film contains at least one selected from oxygen and nitrogen in addition to silicon. Further, it is a silicon compound that may further contain a transition metal, and may further contain a small amount of carbon or the like. Specific examples include silicon oxide, silicon nitride, silicon oxynitride, silicon oxycarbide, silicon oxynitride carbide, silicon oxynitride carbide, and compounds containing a transition metal.

  Further, as a silicon-based material layer constituting the light shielding film other than the above, silicon alone, transition metal silicon, silicon carbide, or transition metal silicon carbide may be added.

  As the transition metal, at least one selected from titanium, vanadium, cobalt, nickel, zirconium, niobium, molybdenum, hafnium, tantalum and tungsten is a suitable material, and in particular, molybdenum from the viewpoint of dry etching processability. It is preferable.

  The composition of the light shielding film is 10 atomic% to 100 atomic%, particularly 30 atomic% to 95 atomic%, oxygen is 0 atomic% to 50 atomic%, especially 0 atomic% to 30 atomic%, and nitrogen is included. 0 atom% to 40 atom%, particularly 1 atom% to 20 atom%, provided that the total amount of nitrogen and oxygen is 0 atom% to 60 atom%, particularly 0 atom% to 50 atom%, especially 1 Atomic% to 40 atomic%, further 1 atomic% to 30 atomic%, carbon is 0 atomic% to 20 atomic%, especially 0 atomic% to 5 atomic%, transition metal is 0 atomic% to 35 atomic% In particular, the content is particularly preferably 1 atom% or more and 20 atom% or less.

  On the other hand, as another preferred embodiment of the light shielding film used in the photomask blank of the present invention, a light shielding film having a chromium-based material layer contributing to an antireflection function as a part of the light shielding film on the outermost layer of the light shielding film. Can be mentioned. As a material of the chromium-based material layer, it is preferable to use metal chromium or a material containing chromium and at least one light element of oxygen, nitrogen, and carbon.

  As with the etching mask film, the chromium-based material layer provided on the outermost layer of the light shielding film has a risk of causing side etching problems and pattern density dependency problems when the film thickness is increased. The film thickness is preferably not more than necessary. Therefore, also in this case, the film thickness is preferably 30 nm or less, more preferably 20 nm or less, and particularly preferably 10 nm or less. Also, if a film that emphasizes the antireflection function (mainly a film that plays the role of antireflection function) is not sufficient as a hard mask layer, a chrome-based material layer is a layer that focuses on the antireflection function (mainly antireflection function). It is possible to make the layers multi-layered, for example, two layers of a layer that assigns a function) and a layer that emphasizes the hard mask function (mainly a layer that assigns a hard mask function), or to change the composition in a gradient. When changing the composition, it is preferable to increase the metal composition on the substrate side rather than on the surface.

  Moreover, since it is preferable that an outermost layer is a layer which bears a part of antireflection function, it is preferable to contain oxygen and / or nitrogen.

  The composition of the layer that places importance on the antireflection function is such that chromium is 30 atomic% to 90 atomic%, particularly 30 atomic% to 70 atomic%, especially 35 atomic% to 50 atomic%, and oxygen is 0 atomic% to 60 atomic%. Atomic% or less, especially 20 atomic% or more and 60 atomic% or less, Nitrogen is 0 atomic% or more and 50 atomic% or less, especially 3 atomic% or more and 30 atomic% or less, Carbon is 0 atomic% or more and 20 atomic% or less, especially 0 atomic% The content is preferably 10 atomic% or less. The composition of the layer placing emphasis on the hard mask function is 50 atomic% to 100 atomic%, particularly 60 atomic% to 100 atomic%, and oxygen is 0 atomic% to 50 atomic%, especially 0 atomic%. 40 atom% or less, nitrogen is 0 atom% or more and 50 atom% or less, particularly 0 atom% or more and 40 atom% or less, and carbon is 0 atom% or more and 20 atom% or less, particularly 0 atom% or more and 10 atom% or less. Is preferred.

  In the light-shielding film used for the photomask blank of this aspect, a silicon-based material layer is used for all the remaining layers other than the chromium-based material layer. The above-mentioned chromium-based material layer may be independently controlled in reflectivity, but as mentioned above, there is a limitation on the film thickness due to the demand for highly accurate etching processing, and the reflectivity depends on the combination with the silicon-based material layer. The rate may be adjusted. Therefore, the silicon-based material layer of the light shielding film may be a single layer or a multilayer, and may be a layer having a gradient in composition, but they are reflected by the content of nitrogen or nitrogen and oxygen, the film thickness, or both. The rate can also be adjusted. Then, it is preferable that the reflectance with respect to the exposure light is controlled to 30% or less, more preferably 20% or less by the silicon-based material layer and the chromium-based material layer, and it is combined with the phase shift film disposed under the light shielding film. In this case, the optical density is designed to be 2 or more, preferably 2.5 or more and 4 or less.

  Here, as in the case of the above-described embodiment, a layer made of silicon or silicon and a transition metal can be provided as the silicon-based material layer. However, in order to suppress the reflectance, a layer containing nitrogen or nitrogen and oxygen is used. This is necessary, and as described above, the layer containing nitrogen or nitrogen and oxygen has a value lower than the nitrogen and oxygen content of the uppermost layer of the silicon-based material layer of the phase shift film. Therefore, it is more preferable to use a silicon-based material (silicon nitride-based material or silicon nitride oxide-based material) containing nitrogen or nitrogen and oxygen for all layers.

  The material preferably used is basically the same as that of the above-described one embodiment, and the composition range of the light-shielding film is 10 atomic% to 100 atomic%, particularly 30 atomic% of silicon. 95 atomic% or less, oxygen is 0 atomic% or more and 50 atomic% or less, particularly 0 atomic% or more and 30 atomic% or less, and nitrogen is 0 atomic% or more and 40 atomic% or less, particularly 1 atomic% or more and 20 atomic% or less, provided that The total amount of nitrogen and oxygen is 0 atomic percent to 60 atomic percent, particularly 0 atomic percent to 50 atomic percent, particularly 1 atomic percent to 40 atomic percent, more preferably 1 atomic percent to 30 atomic percent, It is preferably 0 to 20 atom%, particularly 0 to 5 atom%, and the transition metal is preferably 0 to 35 atom%, particularly 1 to 20 atom%.

  In the present invention, the phase shift film is a film having a silicon-based material layer having excellent optical properties such as chemical resistance and refractive index on the outermost layer. This silicon-based material contains oxygen and / or nitrogen, and may contain a transition metal. This phase shift film may be a perfect transmission phase shift film or a halftone phase shift film, for example, a halftone phase shift film having a transmittance of 1 to 40%, particularly 5 to 40%. Various types of such phase shift films are already known, and in particular, a single layer (for example, see JP-A-7-140635 (Patent Document 6)) or a multilayer made of a silicon-based material containing a transition metal. The halftone phase shift film according to, for example, JP-A-2006-317665 (Patent Document 7) is used as a halftone phase shift film that can be etched under a single dry etching condition together with a light shielding film. It is advantageously used in the present invention with the purpose of reducing.

  JP-A-2001-27799 (Patent Document 3) describes that some of the above-described conventionally used halftone phase shift film materials can be etched by chlorine-based dry etching. As described above, the phase shift film in the present invention may be a film etched under chlorine-based dry etching conditions as defined in JP-A-2001-27799 (Patent Document 3). In the present invention, the etching selectivity of the phase shift film and the light shielding film can also be adjusted by adjusting the amount of oxygen gas in etching (ratio of oxygen gas to chlorine gas). Is preferably selected from the viewpoint of stress of the phase shift film, laser irradiation resistance, and optical characteristics.

  The material used for the silicon-based material layer that contains oxygen and / or nitrogen and may contain a transition metal of the phase shift film contains, in addition to silicon, at least one selected from oxygen and nitrogen, It is a silicon compound that may contain a transition metal, and may contain a small amount of carbon or the like. Specific examples include silicon oxide, silicon nitride, silicon oxynitride, silicon oxycarbide, silicon oxynitride carbide, silicon oxynitride carbide, and compounds containing a transition metal.

  Further, as a silicon-based material layer constituting the phase shift film other than the above, silicon alone, transition metal silicon, silicon carbide, or transition metal silicon carbide may be added.

  As the transition metal, at least one selected from titanium, vanadium, cobalt, nickel, zirconium, niobium, molybdenum, hafnium, tantalum and tungsten is a suitable material, and in particular, molybdenum from the viewpoint of dry etching processability. It is preferable.

  In the phase shift film of the present invention, at least the layer in contact with the light shielding film (outermost layer) is preferably a silicon-based material layer that contains oxygen and / or nitrogen and may contain a transition metal. A chromium-based material layer may be used on the side in contact with the substrate as long as it does not cause a problem of side etching (for example, 30 nm or less, more preferably 20 nm or less). If the chromium-based material at that position is used, the etching mask film or the light shielding film outermost layer having the etching mask function can be etched and removed at the same time in the photomask manufacturing process, which increases the etching process. Because it must not.

  The method for processing the photomask blank of the present invention into a photomask is performed, for example, in the following steps.

  As the first step, first, a resist pattern for protecting a region where the phase shift film is left as a phase shift portion is formed. For this purpose, a resist film is formed on a photomask blank, pattern exposure is performed with a high-energy beam such as an electron beam, a short wavelength light beam, EUV, and development is performed after a predetermined post-treatment depending on the resist film. By doing so, a resist pattern is obtained. The resist film used here may be either a negative type or a positive type as long as it can resolve the required pattern rule, and the material is not particularly limited, but basically a high resolution can be expected. A chemically amplified resist is used, and the film thickness is preferably 50 nm to 250 nm, particularly 50 nm to 150 nm.

  Next, in the case of having a chromium-based material etching mask film on the silicon-based material layer in the light-shielding film or a chromium-based material layer having an antireflection function that forms a part of the light-shielding film, chlorine containing oxygen The resist pattern is transferred to the chromium-based material layer by dry etching using a system gas.

Here, dry etching using a chlorine-based gas containing oxygen is conventionally used when dry-etching a chromium compound film. For example, a mixture ratio of chlorine gas and oxygen gas (Cl ₂ gas: O _{2). 2} gas) is set to a volume flow ratio of 1: 2 to 20: 1, and an inert gas such as helium is mixed and used as necessary. Etching conditions may be, for example, chlorine gas 100 to 300 sccm, oxygen gas 30 to 100 sccm, and gas pressure 1 to 10 mtorr. Further, helium gas may be added at 1 to 20 sccm.

  A part of the silicon-based material layer in contact with the chromium-based material layer that forms part of the etching mask film or the light-shielding film may be etched away by this dry etching. Attempts to completely remove the material layer may cause problems of pattern dimensional errors due to side etching and pattern density dependence, and silicon in contact with the chromium-based material layer that forms part of this etching mask film or light-shielding film It is particularly preferable that the dry etching with the chlorine-based gas containing oxygen is terminated under the condition that a part of the system material layer remains.

  When there is no chromium-based material etching mask film as described above, and when there is no chromium-based material layer having an antireflection function that forms a part of the light-shielding film, the resist pattern is used as an etching mask. If there is a chromium-based material etching mask film or a chromium-based material layer having an antireflection function that forms a part of the light-shielding film, dry etching with a fluorine-based dry etching gas is used as an etching mask. Depending on the conditions, pattern transfer is performed on the entire silicon-based material layer of the light-shielding film, or the remaining silicon-based material layer of the light-shielding film and the silicon-based material layer of the phase shift film. In this case, the resist film may be peeled off. However, since there is no need to remove the resist film here, if the resist film is left, the remaining resist pattern can also function as an etching mask. it can.

  In addition, Ta, W, Ti, etc. that can be etched by fluorine-based dry etching, when the entire phase shift film is composed of a silicon-based material layer that contains oxygen and / or nitrogen and may contain a transition metal Even when a metal compound layer containing these metals and a metal compound layer containing these metals and oxygen, nitrogen or both, a layer made of silicon or silicon and a transition metal, etc. are included, the pattern of the phase shift portion is formed by this fluorine-based dry etching. be able to. Therefore, in the photomask manufacturing method of the present invention, even when a layer having an etching mask function is used, the pattern processing of the phase shift portion can be performed in two dry etching steps.

The fluorine-based dry etching used here is a dry etching method commonly used for etching a silicon-containing material in the production of a photomask. This is a dry etching using a gas containing fluorine and contains fluorine. The gas may be a gas containing elemental fluorine, such as fluorine gas, gas containing carbon and fluorine such as CF ₄ and C ₂ F ₆ , gas containing sulfur and fluorine such as SF ₆ , and hydrogen atom Further, it may be a mixed gas of a gas not containing fluorine such as helium and a gas containing fluorine. Moreover, you may add gas, such as oxygen, as needed. As the etching conditions, for example, the ratio of the gas containing fluorine to the oxygen gas (oxygen gas / gas containing fluorine (molar ratio)) can be 0.001 to 1000, specifically, fluorine is included. The gas may be 1-1000 sccm, preferably 10-100 sccm, the oxygen gas 1-1000 sccm, preferably 10-100 sccm, and the gas pressure may be 1-20 mtorr.

  Next, if the above resist pattern remains in the above steps, the resist pattern is completely peeled off, and then a resist film for protecting the pattern of the portion where the light shielding pattern remains is formed. . Further, in accordance with the above-described method, a resist pattern is formed so that the resist pattern remains on the portion where the light shielding film remains.

  Next, using the resist pattern as an etching mask, unnecessary light shielding on the phase shift film is performed by dry etching conditions using a chlorine-based gas containing oxygen that gives an extremely slow etching rate to the outermost layer of the phase shift film described later. Remove the membrane. At this time, if there is a chromium-based material layer that forms part of the above-described chromium-based material etching mask film or light-shielding film, these layers can also be etched away at the same time.

  If there is no chromium-based material layer having an antireflection function that forms part of the above-described chromium-based compound etching mask film or light-shielding film, patterning can be completed at this stage. Even when there is a chromium-based material layer having an antireflection function that forms part of the light-shielding film, pattern formation can be completed by three times of dry etching.

  Further, if there is a chromium compound etching mask film, it is necessary to finally remove this etching mask film. However, the removal of this chromium compound etching mask film requires cerium ammonium nitrate and perchloric acid. Even if it performs by the well-known wet etching used, dry etching may be performed on the chlorine type dry etching conditions containing oxygen enough for the etching rate with respect to a silicon-type material layer to become very slow. In this case, even if dry etching is used here, pattern formation can be completed by four times of dry etching.

  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]
MoSiON (Mo: Si: O: N = 1: 4: 1: 4 (molar ratio)) having a film thickness of 75 nm with a transmittance of 6% and a phase difference of 180 ° formed with light having a wavelength of 193 nm formed on a quartz substrate, oxygen and In order to evaluate the amount of oxygen in the etching gas and the etching rate under chlorine-based dry etching conditions using a film of silicon-based material composed of a total nitrogen content of 50 mol%, The change in reflectance with respect to the inspection light having a wavelength of 675 nm was measured over time by changing between 10.0 sccm. The obtained results are shown in FIG. FIG. 4 shows an outline of the etching apparatus used. In FIG. 4, 1 is a chamber, 2 is 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]
The experiment was conducted using a silicon-based material film of MoSiN (Mo: Si: N = 1: 3: 1.5 (molar ratio), the total content of oxygen and nitrogen being 27 mol%) having a film thickness of 46 nm. The change in reflectance was measured over time in the same manner as in 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.

[Experiment 3]
The film was made of a chromium-based material composed of 44 nm of CrN (Cr: N = 9: 1 (molar ratio)), and the change in reflectance was measured over time in the same manner as in Experimental Example 1. The obtained results are shown in FIG.

  As shown in FIG. 3, it was confirmed that the etching was performed at about 4 nm / min when the oxygen amount was 2 sccm (oxygen gas / chlorine gas (molar ratio) was 2/185). This film is easily etched as the amount of oxygen increases.

  From the above results, in this case, by setting the amount of oxygen to 2 sccm, a MoSiN film (Mo: Si: N = 1: 3: 1.5 (molar ratio)) that can be used as a layer constituting the light shielding film, oxygen and MoSiON film (Mo: Si: O: N = 1: 4: 1: 4 (molar ratio)), oxygen which can be used as a layer constituting the phase shift film only with a total content of nitrogen of 27 mol%) And the total content of nitrogen and nitrogen were 50 mol%), it was shown that the etching can be selectively removed by chlorine dry etching.

  In this case, by setting the amount of oxygen to 2 sccm, the CrN film (Cr: N = 9: 1 (molar ratio)) that can be used as an etching mask film and the MoSiN film can be used without damaging the MoSiON film. It has been shown that etching can be simultaneously removed.

  Furthermore, it has been shown that when only the CrN film is to be removed by dry etching, the MoSiN film can be removed without damage by setting the oxygen amount to 55 sccm.

[Example 1]
A phase made of MoSiON (Mo: Si: O: N = 1: 4: 1: 4 (molar ratio)) having a film thickness of 75 nm having a transmittance of 6% and a phase difference of 180 ° with a light of wavelength 193 nm on a quartz substrate. A photomask blank having a shift film formed thereon and a light-shielding film made of MoSiN (Mo: Si: N = 1: 3: 1.5 (molar ratio)) having a film thickness of 31 nm is prepared, and A chemically amplified resist film for EB exposure having a thickness of 1500 mm was formed thereon using a spin coater. The resist film was developed after pattern drawing with an EB exposure apparatus, and a resist pattern was formed to protect the portion where the phase shift film remains.

[Etching step 1-1]
Next, using the resist pattern as an etching mask, the portion not leaving the phase shift film was etched by fluorine-based dry etching under the following conditions to form a light shielding film and a phase shift film in a predetermined phase shift pattern shape.
RF1 (RIE): CW 54V
RF2 (ICP): CW 325W
Pressure: 5mTorr
SF ₆ : 18 sccm
O ₂ : 45 sccm
Etching time: 2 min

[Etching step 1-2]
Next, when the light shielding film was etched using chlorine-containing dry etching conditions containing oxygen under the following conditions, only the light shielding film was selectively removed.
RF1 (RIE): Pulse 700V
RF2 (ICP): CW 400W
Pressure: 6mTorr
Cl ₂ : 185 sccm
O ₂ : ₂ sccm
He: 9.25 sccm
Etching time: 12 min

  When partially leaving the light shielding film by the etching step 1-2, before the chlorine-based dry etching, a resist is applied again, and exposure and development are performed to form a resist pattern that protects the portion that leaves the light shielding film. Later, if chlorine-based dry etching is performed, only an unnecessary light-shielding film can be selectively removed. By this method, a light shielding film pattern on the phase shift portion and a light shielding band around the pattern can be provided.

[Example 2]
A phase made of MoSiON (Mo: Si: O: N = 1: 4: 1: 4 (molar ratio)) having a film thickness of 75 nm and having a transmittance of 6% and a phase difference of 180 ° with light having a wavelength of 193 nm on a quartz substrate. A shift film is formed, and a light shielding film made of MoSiN (Mo: Si: N = 1: 3: 1.5 (molar ratio)) with a film thickness of 31 nm is formed thereon, and an etching mask film (hard mask film) ) A photomask blank having a 10 nm CrN film (Cr: N = 9: 1 (molar ratio)) formed thereon, and a 1500 nm thick chemically amplified resist for EB exposure using a spin coater thereon A film was formed. The resist film was developed after pattern drawing with an EB exposure apparatus, and a resist pattern was formed to protect the portion where the phase shift film remains.

[Etching step 2-1]
Next, using the resist pattern as an etching mask, portions of the hard mask film and the light shielding film that did not leave the phase shift film were etched by chlorine-based dry etching under the following conditions.
RF1 (RIE): Pulse 700V
RF2 (ICP): CW 400W
Pressure: 6mTorr
Cl ₂ : 185 sccm
O ₂ : ₂ sccm
He: 9.25 sccm
Etching time: 5 min

[Etching step 2-2]
Next, using the hard mask film as an etching mask, etching was performed by fluorine-based dry etching under the following conditions to form the remaining part of the light shielding film and the phase shift film in a predetermined phase shift pattern shape.
RF1 (RIE): CW 54V
RF2 (ICP): CW 325W
Pressure: 5mTorr
SF ₆ : 18 sccm
O ₂ : 45 sccm
Etching time: 2 min

[Etching step 2-3]
Next, after re-applying resist, exposing and developing, forming a resist pattern that protects the part that leaves the light-shielding film, etching with chlorine-based dry etching under the following conditions, without damaging the phase shift film Only the hard mask film and the light shielding film were selectively removed by one etching. By this method, a light shielding film pattern on the phase shift portion and a light shielding band around the pattern can be provided.
RF1 (RIE): Pulse 700V
RF2 (ICP): CW 400W
Pressure: 6mTorr
Cl ₂ : 185 sccm
O ₂ : ₂ sccm
Etching time: 15 min

[Etching step 2-4]
Next, when etching was performed by chlorine-based dry etching under the following conditions, only the hard mask film was selectively removed.
RF1 (RIE): Pulse 700V
RF2 (ICP): CW 400W
Pressure: 6mTorr
Cl ₂ : 185 sccm
O ₂ : 55 sccm
He: 9.25 sccm
Etching time: 2 min

[Example 3]
A phase made of MoSiON (Mo: Si: O: N = 1: 4: 1: 4 (molar ratio)) having a film thickness of 75 nm and having a transmittance of 6% and a phase difference of 180 ° with light having a wavelength of 193 nm on a quartz substrate. A shift film is formed, and a light shielding film made of MoSiN (Mo: Si: N = 1: 3: 1.5 (molar ratio)) with a film thickness of 31 nm is formed thereon, and an etching mask film (hard mask film) ) A photomask blank having a 10 nm CrN film (Cr: N = 9: 1 (molar ratio)) formed thereon, and a 1500 nm thick chemically amplified resist for EB exposure using a spin coater thereon A film was formed. The resist film was developed after pattern drawing with an EB exposure apparatus, and a resist pattern was formed to protect the portion where the phase shift film remains.

[Etching step 3-1]
Next, using the resist pattern as an etching mask, a portion of the hard mask film that does not leave the phase shift film was etched by chlorine dry etching 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: 2 min

[Etching step 3-2]
Next, using the hard mask film as an etching mask, etching was performed by fluorine-based dry etching under the following conditions to form a light shielding film and a phase shift film in a predetermined phase shift pattern shape.
RF1 (RIE): CW 54V
RF2 (ICP): CW 325W
Pressure: 5mTorr
SF ₆ : 18 sccm
O ₂ : 45 sccm
Etching time: 2 min

[Etching step 3-3]
Next, after re-applying resist, exposing and developing, forming a resist pattern that protects the part that leaves the light-shielding film, etching with chlorine-based dry etching under the following conditions, without damaging the phase shift film Only the hard mask film and the light shielding film were selectively removed by one etching.
RF1 (RIE): Pulse 700V
RF2 (ICP): CW 400W
Pressure: 6mTorr
Cl ₂ : 185 sccm
O ₂ : ₂ sccm
Etching time: 15 min

[Etching step 3-4]
Next, when etching was performed by chlorine-based dry etching under the following conditions, only the hard mask film was selectively removed. By this method, a light shielding film pattern on the phase shift portion and a light shielding band around the pattern can be provided.
RF1 (RIE): Pulse 700V
RF2 (ICP): CW 400W
Pressure: 6mTorr
Cl ₂ : 185 sccm
O ₂ : 55 sccm
He: 9.25 sccm
Etching time: 2 min

  In either case, before and after etching, a cleaning step can be performed as necessary. After etching, residual resist is removed with sulfuric acid-hydrogen peroxide solution as necessary. You may implement the process to do.

  In the above-described example, the case where the etching mask film (hard mask film) of the chromium-based material is provided on the light-shielding film is shown, but when the chromium-based material layer that functions as an antireflection film is provided as a part of the light-shielding film, The chromium-based material has a higher content of nitrogen or oxygen and nitrogen than the CrN film (Cr: N = 9: 1) used as the chromium-based material of the etching mask film in the above example in order to increase the transmittance. Therefore, when etching is performed under the same etching conditions, the etching rate is higher than that of the CrN film. Therefore, even the chromium-based material layer functioning as the antireflection film can be etched in a shorter etching time under the above-described chlorine-based dry etching etching conditions, and the above-described process conditions can be applied as they are. .

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

Claims (9)

A single-layer or multilayer first silicon-based material layer that contains oxygen and / or nitrogen and may contain a transition metal;
A single layer formed of a silicon-based material layer formed adjacent to the first silicon-based material layer, which may contain a transition metal, and has a lower total content of nitrogen and oxygen than the first silicon-based material layer Or a method of selectively etching away the second silicon-based material layer from the laminate composed of a plurality of second silicon-based material layers, leaving the first silicon-based material layer,
Using a chlorine-based dry etching gas containing oxygen, the ratio of the chlorine-based gas to the oxygen gas is set so that the etching rate of the second silicon-based material layer with respect to the etching rate of the first silicon-based material layer is increased. A dry etching method comprising: setting and selectively removing the second silicon material layer by chlorine dry etching.   The dry etching method according to claim 1, wherein the second silicon-based material layer includes a silicon-based material layer containing nitrogen and / or oxygen and optionally containing a transition metal.   The second silicon-based material layer further includes a silicon-based material layer that does not contain nitrogen and oxygen and may contain a transition metal on the side in contact with the first silicon-based material layer. The dry etching method according to claim 2. The total content C ₁ (mol%) of nitrogen and oxygen in the _first silicon-based material layer, the nitrogen and / or oxygen in the second silicon-based material layer, and a transition metal. The difference (C ₁ -C ₂ ) with respect to the total content C ₂ (mol%) of nitrogen and oxygen in the silicon-based material layer that may be 5 or more, according to claim 2 or 3, Dry etching method.   5. The ratio of chlorine gas to oxygen gas (oxygen gas / chlorine gas (molar ratio)) is set to 0.0001 to 1 in the chlorine dry etching. The dry etching method according to Item.   For each of the first silicon-based material layer formed on the substrate, and the second silicon-based material layer formed on the substrate or the silicon-based material layer constituting the second silicon-based material layer, chlorine-based gas and While changing the ratio with oxygen gas (oxygen gas / chlorine gas (molar ratio)), a chlorine-based dry etching operation with a chlorine-based dry etching gas containing oxygen is performed, and the first silicon material layer and the first It is possible to obtain the etching rate of each of the two silicon-based material layers, and to selectively remove the second silicon-based material layer from the stacked body, leaving the first silicon-based material layer, by comparing these etching rates. 6. The dry etching method according to claim 1, wherein a dry etching is performed by determining a ratio between a chlorine-based gas and an oxygen gas and setting the ratio.   The laminate is further provided with a chromium-based material layer adjacent to the second silicon-based material layer, and both the chromium-based material layer and the second silicon-based material layer are subjected to the chlorine-based dry etching. The dry etching method according to claim 1, wherein the etching is removed.   The first silicon-based material layer and the second silicon-based material layer are layers that are formed on a transparent substrate and constitute a functional film of a photomask blank. 2. A dry etching method according to item 1.   The first silicon-based material layer is a layer constituting part or all of the phase shift film of the photomask blank, and the second silicon-based material layer is part or all of the light shielding film of the photomask blank. The dry etching method according to claim 8, wherein the dry etching method is a layer constituting the layer.

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