JP4579728B2 - Photomask blank manufacturing method, photomask blank and photomask manufacturing method, and photomask - Google Patents

Description

  The present invention relates to a photomask blank manufacturing method, a photomask blank, a photomask manufacturing method, and a photomask. More specifically, the present invention is used in an exposure apparatus used for manufacturing a semiconductor device or the like, and can suppress precipitation of ammonium sulfate particularly when irradiated with high energy exposure light such as ArF excimer laser light. Photomask blank manufacturing method for manufacturing a photomask with high cleanliness capable of suppressing a change in pattern dimension due to cleaning treatment, a photomask blank obtained by the method, and a photomask having the above characteristics The present invention relates to a manufacturing method and a photomask obtained by the method.

  Formation of a transfer pattern in the manufacture of a semiconductor device is performed, for example, by irradiating exposure light through a photomask.

  As such a photomask, a light-shielding film pattern formed on a transparent substrate has been conventionally used. The material of the light-shielding film is a chromium-based material (chromium alone or chromium, nitrogen, oxygen, carbon, etc. In general, or a laminated film of these material films) is generally used. The film composition includes hydrogen but is often omitted.

  Furthermore, in recent years, phase shift masks have been put into practical use as those capable of improving the resolution of transfer patterns. Various types of phase shift masks (Levenson type, auxiliary pattern type, self-alignment type, etc.) are known, and one of them is halftone suitable for high resolution pattern transfer of holes and dots. There is a type phase shift mask. This halftone phase shift mask is obtained by forming a light semi-transmissive film pattern having a phase shift amount of approximately 180 ° on a transparent substrate.

  As a photomask having such a light semi-transmissive film, a halftone phase shift mask in which the light semi-transmissive film pattern is formed of a thin film made of a material mainly composed of metal such as silicon, nitrogen and molybdenum is disclosed. (For example, refer to Patent Document 1). Again, the film composition includes hydrogen but is often omitted. In addition to being able to control the predetermined phase shift amount and transmittance with a single layer, a light semi-transmissive film made of such a material is excellent in acid resistance and light resistance. Moreover, such a pattern using the characteristics of the light semi-transmissive film is also used for a phase shift mask other than the halftone phase shift mask.

  On the other hand, an exposure light source used for forming a transfer pattern in the manufacture of a semiconductor device is gradually required to have a shorter wavelength as the transfer pattern becomes finer. In general, as the light has a shorter wavelength, its optical energy gradually increases. For example, the optical energy of excimer laser light is 114.1 kcal / mol for KrF (248 nm) and 147.2 kcal / mol for ArF (193 nm). On the other hand, the bond dissociation energy of the molecule is 84 kcal / mol for a CC bond, for example. The magnitude of optical energy in such a wavelength region corresponds to the bond dissociation energy of various substances. Therefore, when a substance is irradiated and light is absorbed, a photochemical reaction is likely to occur. In addition, the photochemical reaction is more likely to occur as the light source having a shorter wavelength is used.

  In such an exposure wavelength region of short wavelength light, there is a problem that decomposition of a substance existing on a photomask or an exposure optical path or generation of a new substance occurs due to a photochemical reaction. For this reason, when the photomask is used, substances on the optical path of the exposure light generate foreign matter on the photomask or cause fogging. A representative example of such generated foreign matter is ammonium sulfate. Ammonium sulfate is produced from sulfuric acid and ammonia, and a substance similar in molecular structure to sulfuric acid or ammonia may produce ammonium sulfate crystals by reaction. The produced ammonium sulfate crystal is a foreign substance and becomes a defect during pattern transfer.

  The photomask may be subjected to an acid cleaning process including resist stripping using a sulfuric acid-based cleaning agent during the manufacturing process. The cleaning agent is removed by various methods, but a slight amount of acid or acid-based ions derived from the cleaning process remains on the photomask. In addition, sulfurous acid gas generated from a member such as a mask case may be adsorbed to the photomask. For this reason, if there are ammonium ions or ammonia gas on the photomask or the optical path of the exposure light, the reaction to react and form crystals of ammonium salt such as ammonium sulfate by the excimer laser of the exposure light is promoted.

  In order to create a state in which ammonium sulfate is hardly generated by this photochemical reaction, it is only necessary to reduce the amount of sulfuric acid-based substances and ammonia-based substances until they are sufficiently reduced from the mask surface or the optical path of exposure light. It is sufficient that either the sulfuric acid-based material or the ammonia-based material is completely eliminated.

  In other words, in order to make it difficult for ammonium sulfate to be generated, it is better to sufficiently remove the sulfuric acid-based cleaning agent adhered during the mask cleaning process. For example, a method generally used as a method for removing sulfuric acid is to bring a mask into contact with warm water or an alkaline solution. By removing the sulfuric acid detergent until the chemical concentration on the mask surface becomes sufficiently small, ammonium sulfate is hardly generated.

  By the way, it is known that when the MoSiON film is washed with an alkaline chemical, the transmittance and the phase difference change greatly (for example, refer to Patent Document 2). This publication indicates that the MoSiON film is etched by bringing the mask into contact with an alkaline solution. As a result, it is difficult to remove sulfuric acid and foreign matter using an alkaline solution, and there is a problem that the pattern size of a photomask formed of a MoSiON film is changed by washing with an alkaline solution. The phase-shifting photomask used in short-wavelength exposure equipment needs to be manufactured with high accuracy and high cleanliness, so if the pattern dimensions change due to cleaning with alkaline liquid, Highly clean patterns are difficult to produce.

  Therefore, also in the above-mentioned Patent Document 1, in the photomask in which the light semi-transmissive film pattern made of a material mainly composed of metal such as silicon, nitrogen and molybdenum is formed, sulfuric acid adsorbed on the surface is sufficiently removed. The removal process is difficult. If the removal of sulfuric acid is insufficient, ammonium sulfate is generated. In the cleaning, an alkali solution is used for the purpose of removing foreign substances in addition to the removal of acid. However, since the light semi-transmissive film is weak against alkali, the dimension width patterned in the alkali cleaning is cut and narrowed. For this reason, it cannot be washed sufficiently. Moreover, the accuracy of the dimensional width is deteriorated by the treatment with the alkali cleaning liquid.

  Furthermore, it is described that a film containing nitrogen detects a larger amount of ammonium ions on the film surface than a film not containing nitrogen (see, for example, Patent Document 3). Naturally, the surface of the MoSiON film contains nitrogen. Therefore, ammonium ions are present on the pattern of the semi-transmissive film made of such a MoSiON film, so that the photomask can easily generate ammonium sulfate. That is, if there are ammonium ions generated from the MoSiON film, sulfuric acid remaining in the photomask after washing, or exposure light having a short wavelength used for forming a transfer pattern, ammonium sulfate is generated and formed on the mask. Crystalline foreign matter is generated or cloudiness is generated.

As described above, the case where ammonium sulfate is generated at the time of exposure has been described in a limited manner. However, in the mask manufacturing process, a chemical solution such as a surfactant containing a phosphoric acid substance, a chemical solution containing hydrofluoric acid, a chlorine gas that easily forms hydrochloric acid, Residues on the mask surface also form ammonium salts such as ammonium phosphate, ammonium fluoride, and ammonium chloride, respectively, but these salts are also easily formed in the presence of ammonia and ammonium ions.
Japanese Patent Laid-Open No. 10-148929 JP 2000-330262 A WO2004 / 059384

  Under such circumstances, the present invention is used in an exposure apparatus used for manufacturing a semiconductor device and the like, and suppresses precipitation of ammonium sulfate particularly when irradiated with high energy exposure light such as ArF excimer laser light. A method of manufacturing a photomask blank for manufacturing a photomask with high cleanliness capable of suppressing a change in pattern dimensions due to cleaning treatment, a photomask blank obtained by the method, and the characteristics described above It is an object of the present invention to provide a photomask manufacturing method and a photomask obtained by the method.

The inventors of the present invention have made extensive studies in order to achieve the above object, and have obtained the following knowledge.
In Patent Document 3, ammonium ions are generated by detecting ammonium ions from the surface of a halftone phase shift mask having a light semi-transmissive film and by performing heat treatment on the light semi-transmissive film to reduce the nitrogen content on the surface. It is described that a photomask blank difficult to manufacture can be manufactured. However, even with a halftone mask manufactured using this blank, the generation of ammonium on the upper surface of the film can be suppressed, but in the photomask manufacturing process, the side cross section of the light translucent film is renewed by patterning. It is difficult to suppress the formation of ammonium ions exposed to the surface. For this reason, it is thought that the production | generation of ammonium needs to be performed not only by the method of patent document 3, but the photomask manufacturing process.

  Further, even when a process for dissolving the upper surface of the light semi-transmissive film is performed in the mask manufacturing process, the generation of ammonia on the upper surface of the light semi-transmissive film cannot be suppressed. The treatment that dissolves the upper surface of the light semi-transmissive film is a treatment that removes contamination such as foreign matter and sulfuric acid on the surface by, for example, dissolving the surface layer of the light semi-transmissive film.

  As a result of further research based on such knowledge, the present inventors contacted a silylating agent at a predetermined site of the light semi-transmissive film, and further subjected to an oxidation treatment to provide a deteriorated layer. It has been found that changes in pattern dimensions due to precipitation of ammonium sulfate and cleaning treatment can be effectively suppressed, and the present invention has been completed.

That is, the present invention
(1) In an exposure apparatus using a KrF excimer laser light or an ArF excimer laser light , which has a patternable light semi-transmissive film made of a material containing at least silicon atoms, nitrogen atoms and metal atoms on a transparent substrate. When manufacturing a photomask blank for manufacturing a photomask to be used,
After forming the semi-transmission film made of a material containing the silicon atoms and nitrogen atoms and the metal atom, the light semi-transmitting film surface is contacted with a silylating agent, followed by performing an oxidation treatment, the light semi-transmitting film Forming a denatured layer in which NH bonded hydrogen on the outermost surface of the light semitransmissive film is replaced with silicon or oxygen at the upper surface exposed portion of the photomask blank,
(2) The method for producing a blank for a photomask according to (1), wherein the metal atom is at least one selected from molybdenum, tantalum, tungsten, chromium, titanium, nickel, palladium, hafnium, and zirconium,
(3) The method for producing a photomask blank according to (1) or (2), wherein the photomask is a halftone phase shift mask,
( 4 ) The silylating agent is at least one selected from hexamethyldisilazane, vinyltrimethylsilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, methyldichlorosilane, isopropoxytrimethylsilane, acetoxytrimethylsilane, and polysilazane. The manufacturing method of the blank for photomasks of any one of said (1) thru | or (3) which are these ,
( 5 ) The method for producing a blank for a photomask according to the above ( 4 ), wherein the silylating agent is hexamethyldisilazane,
( 6 ) Light comprising a photomask blank obtained by the method according to any one of (1) to ( 5 ) above and (A) a material comprising at least a silicon atom, a nitrogen atom, and a metal atom. The semi-permeable membrane is etched using the layer above it as a mask to expose the desired side cross section, and then the exposed portion of the side cross section is contacted with a silylating agent, followed by oxidation treatment. Forming an altered layer in which the hydrogen of the NH bond on the outermost surface of the light translucent film is replaced with silicon or oxygen at the exposed side cross section; and (B) a layer above the light translucent film. Removing and exposing the pattern layer upper surface of the light semi-transmissive film having an exposed side cross-section, sequentially, a photomask manufacturing method,
( 7 ) Exposure of KrF excimer laser light or ArF excimer laser light having a pattern layer formed of a light semi-transmissive film made of a material containing at least silicon atoms, nitrogen atoms and metal atoms on at least the uppermost layer on the transparent substrate When manufacturing a photomask used in an exposure apparatus using light ,
After forming a pattern of a light semi-transmissive film made of a material containing at least silicon atoms, nitrogen atoms, and metal atoms , a silylating agent is brought into contact with the exposed surface of the light semi-transmissive film on which the pattern is formed, and then oxidized. To form a denatured layer in which NH bonded hydrogen on the outermost surface of the light-semitransmissive film is replaced with silicon or oxygen on the exposed surface of the pattern,
( 8 ) Exposure of KrF excimer laser light or ArF excimer laser light having a pattern layer formed of a light semi-transmissive film made of a material containing at least silicon atoms, nitrogen atoms and metal atoms on at least the uppermost layer on the transparent substrate When manufacturing a photomask used in an exposure apparatus using light ,
(X) A light translucent film made of a material containing at least silicon atoms, nitrogen atoms, and metal atoms is etched using the upper layer as a mask to expose a desired side section, and then the side section By contacting the exposed portion with a silylating agent and then subjecting it to an oxidation treatment, an altered layer in which the hydrogen of the NH bond on the outermost surface of the light-semitransmissive film is replaced with silicon or oxygen is exposed to the side cross-sectional exposed portion. And (Y) removing the layer above the light semi-transmissive film and exposing the upper surface of the pattern layer of the light semi-transmissive film having an exposed side section, and then patterning the light semi-transmissive film. By contacting the upper surface with a silylating agent and then performing an oxidation treatment, an altered layer in which the hydrogen of NH bonds on the outermost surface of the light translucent film is replaced with silicon or oxygen is formed on the upper surface of the pattern layer. The process is performed sequentially. A method of manufacturing a photomask and,
(9) The photomask according to any one of (6) to (8), wherein the metal atom is at least one selected from molybdenum, tantalum, tungsten, chromium, titanium, nickel, palladium, hafnium, and zirconium. Manufacturing method,
(10) The method for producing a photomask according to any one of (6) to (9), wherein the photomask is a halftone phase shift mask,
( 11 ) The silylating agent is at least one selected from hexamethyldisilazane, vinyltrimethylsilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, methyldichlorosilane, isopropoxytrimethylsilane, acetoxytrimethylsilane, and polysilazane. The method for producing a photomask according to any one of (6) to (10) ,
( 12 ) The method for producing a photomask according to the above ( 11 ), wherein the silylating agent is hexamethyldisilazane.
( 13 ) A blank for a photomask manufactured by the method according to any one of (1) to ( 5 ), and ( 14 ) any of the above ( 6 ) to ( 12 ) A photomask manufactured by the method according to claim 1,
Is to provide.

  According to the present invention, it is used in an exposure apparatus used for manufacturing a semiconductor device or the like, and in particular, when irradiated with high energy exposure light such as ArF excimer laser light, precipitation of ammonium sulfate can be suppressed, and a cleaning process is performed. Method of manufacturing a photomask blank for manufacturing a photomask having a high cleanliness capable of suppressing a change in pattern dimension due to the above, a blank for a photomask obtained by the method, and a method of manufacturing a photomask having the above characteristics And a photomask obtained by the method can be provided.

First, the manufacturing method of the blank for photomasks of this invention is demonstrated.
The manufacturing method of the blank for photomasks (henceforth only called a mask blank) of this invention has the light translucent film | membrane which can be patterned and consists of a material containing at least a silicon atom and a nitrogen atom on a transparent substrate. In manufacturing a photomask blank for manufacturing a photomask used in an exposure apparatus,
After forming the light semi-transmissive film made of the material containing silicon atoms and nitrogen atoms, the surface of the light semi-transmissive film is exposed by contacting the surface of the light semi-transmissive film with a silylating agent and then performing oxidation treatment. It is characterized by forming an altered layer.

  The mask blank manufacturing method of the present invention is a method for manufacturing a halftone phase shift mask blank having a phase shift film including at least one light semi-transmissive film on a transparent substrate, and the light semi-transmissive film comprises: It is made of a material containing at least silicon atoms and nitrogen atoms.

  The phase shift film composed of a light semi-transmissive film having a single layer structure is made of, for example, a material that contains metal, silicon, and nitrogen atoms, and may further contain atoms such as oxygen, fluorine, carbon, and hydrogen. Can be mentioned. Here, as the metal atom, for example, one containing at least one selected from molybdenum, tantalum, tungsten, chromium, titanium, nickel, palladium, hafnium, zirconium, and the like, particularly molybdenum is preferable.

  In addition, as the phase shift film having a multilayer structure, for example, a laminate of two or more single-layer light semi-transmissive films, or chromium, tantalum, hafnium, magnesium, aluminum, titanium, panadium, yttrium, zirconium, niobium, For example, a light-shielding film such as a metal film containing at least one selected from molybdenum, tin, lanthanum, tungsten, silicon, and the like, and the single-layer light semi-transmissive film are stacked.

  The phase shift film in the present invention is set so that the phase difference is approximately 180 ° in order to obtain the phase shift effect.

  Examples of the light semi-transmissive film include a MoSiN film and a MoSiON film. A method for forming the light semi-transmissive film on the transparent substrate is not particularly limited, but a conventionally known method such as sputtering, EB vapor deposition using a tablet in which the composition of metal element and silicon element is adjusted, and ion plating. The method can be appropriately selected depending on the situation, and among these, the reactive sputtering method is particularly preferable.

  The material for the transparent substrate is not particularly limited, and is conventionally used as a material for a transparent substrate in a halftone phase shift mask blank, for example, soda lime glass such as soda lime glass or white crown; Low expansion glass such as acid glass, alkali-free glass, aluminosilicate glass; quartz glass such as synthetic lime, plastic film such as polyester film, etc. are used as substrate materials for LSI and LCD masks. Soda lime glass and quartz glass are preferred.

  In the mask blank manufacturing method of the present invention, after forming the light semi-transmissive film on the transparent substrate in this manner, the surface of the light semi-transmissive film is contacted with a silylating agent and then subjected to an oxidation treatment.

  Examples of the silylating agent include hexamethyldisilazane, nonamethyltrisilazane, polysilazane, vinyltrimethylsilane, methyltriethoxysilane, dimethyldiethoxysilane, trimethylethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, Trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, methyldichlorosilane, trichlorosilane, isopropoxytrimethylsilane, trimethoxysilane, triethoxysilane, acetoxytrimethylsilane, acetoxysilane, diacetoxydimethylsilane, methyltriacetoxysilane, phenyltri Acetoxysilane, diphenyldiacetoxysilane, methylsilane, dimethylsilane, trimethylsilane, hexa Chill disiloxane, trimethyl silanol, triethyl silanol, triphenyl silanol, t- butyl-dimethyl silanol, and diphenyl silanols like.

  Among these, hexamethyldisilazane, vinyltrimethylsilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, methyldichlorosilane, isopropoxytrimethylsilane, acetoxytrimethylsilane, and polysilazane are preferable. These may be used individually by 1 type and may be used in combination of 2 or more type. Among these silylating agents, hexamethyldisilazane is particularly preferable in terms of operability and effects.

  In the present invention, when hexamethyldisilazane is used, the contact treatment and the subsequent oxidation treatment can be carried out, for example, as follows.

  FIG. 1 is an explanatory view showing an example of a method of bringing hexamethyldisilazane into contact with a light semi-transmissive film. The transparent substrate 3 on which the light semi-transmissive film 2 is formed is installed in the sealed container 10 as shown in the figure, and the container 12 containing the hexamethyldisilazane 11 is installed as shown in the figure. Next, the sealed container is heated or heated under reduced pressure to evaporate hexamethyldisilazane, and the vapor is brought into contact with the light semitransmissive film.

  The surface of the light translucent film thus subjected to the contact treatment with hexamethyldisilazane is subjected to acid cleaning / oxidation treatment with, for example, sulfuric acid / hydrogen peroxide solution, and then washed with water and ammonia / hydrogen peroxide solution. Apply a treatment such as washing with water, followed by further drying.

  By the treatment, the light semi-transmissive film made of a material containing at least silicon atoms and nitrogen atoms can reduce the amount of ammonium ions on the film surface. Regarding this mechanism, for example, when a MoSiON film is used as the light semi-transmissive film, it can be considered as follows.

There is hydrogen at the bonding terminal on the surface of the MoSiON film, and there are NH group, hydroxyl group and the like. When hexamethyldisilazane comes into contact with the surface of the MoSiON film, silylation occurs, and the hydroxyl group on the surface is substituted with a trimethylsilyl group ((CH ₃ ) ₃ Si group). In the subsequent acid cleaning / oxidation treatment, CH _{3 at the} trimethylsilyl group terminal is further substituted with hydroxyl groups, oxygen, and the like by the oxidizing power of acid cleaning and rinsing with pure water after acid cleaning. By the reaction so far, the MoSiON film grows by approximately one silicon atom and becomes a deteriorated layer. The NH bond on the outermost surface forms an oxide layer on the surface, which slows the rate at which ammonium ions are formed on the surface. Thus, the mechanism that the surface generation amount of ammonium ion decreases can be considered.

The following can also be considered.
When hexamethyldisilazane comes into contact with the NH group of the MoSiON film, silylation occurs, and the hydrogen of the NH group is substituted with a trimethylsilyl group ((CH ₃ ) ₃ Si group). In the subsequent acid cleaning / oxidation treatment, CH _{3 at the} trimethylsilyl group terminal is further substituted with hydroxyl groups, oxygen, and the like by the oxidizing power of acid cleaning and rinsing with pure water after acid cleaning. As a result, the NH bond on the outermost surface disappears, and the partner bonded to nitrogen of the NH bond is changed to silicon or oxygen. Nitrogen, which is the source of ammonium ions, loses the bond with hydrogen and is taken in between the bonds with silicon and oxygen, so that ammonium ions cannot be made unless the bond is broken. Thus, the mechanism that the surface generation amount of ammonium ion decreases can be considered.

  Thus, the ammonium ion reduction effect is caused by contact between the MoSiON film surface and hexamethyldisilazane, and further contact between the MoSiON film surface after hexamethyldisilazane treatment and the acid cleaning solution. If the contact occurs not only on the upper surface but also on the side surface of the MoSiON film exposed to the surface by patterning, the same effect can be obtained and the amount of ammonium ions can be reduced.

  Due to the above mechanism, the surface of the light translucent film that has undergone silylation and acid cleaning has been transformed into a form in which NH bonds that are the source of ammonium ions are reduced or not exposed on the outermost surface. That is, a deteriorated layer is formed. Since the altered layer is composed of silicon, oxygen, and hydrogen, it is more stable than a film containing nitrogen chemically and has excellent chemical resistance. Therefore, the light semi-transmissive film capped with the altered layer has improved resistance to alkaline chemicals.

  In this way, after forming a deteriorated layer on the exposed surface of the light semi-transmissive film, a thin film having a desired function such as a light-shielding film is provided thereon if desired, thereby obtaining a desired photomask blank. .

  The contact treatment with hexamethyldisilazane is not limited to the method of contacting the hexamethyldisilazane vapor as described above, but the method of bubbling, the method of contacting the heated semi-transparent film with hexamethyldisilazane vapor, For example, a method of spin-coating a liquid of methyldisilazane onto the light semi-transmissive film can be used. Moreover, the method of mixing hexamethyldisilazane with a suitable solvent, spraying or gasifying with a solvent, and contacting is also considered.

  In addition, the acid cleaning following the hexamethyldisilazane treatment is a treatment that decomposes the organic functional groups of hexamethyldisilazane in an oxidizing chemical solution or oxidizing atmosphere that decomposes organic substances, and then replaces the surface with oxygen or hydroxyl groups. Anything other than acid cleaning is acceptable. In addition to the above-mentioned acid cleaning treatment such as sulfuric acid hydrogen peroxide solution, such treatment includes cleaning treatment using other acids, cleaning treatment using ozone water instead of acid cleaning liquid, and oxygen plasma as a dry treatment. A treatment, UV ozone treatment, light semi-transmissive film heat treatment in an atmosphere containing moisture and oxygen, and the like are conceivable.

The hexamethyldisilazane treatment used in the present invention is known as a treatment in which a hydrophilic surface of a glass substrate such as a semiconductor wafer or a photomask is hydrophobized and a resist is brought into close contact by a silane coupling reaction. However, as can be seen from the fact that the treatment of the present invention does not have a substance to be coupled to the light semi-transmissive film, the principle, the action, and the process procedure before and after the treatment are clearly different from the technique for improving the adhesion. Furthermore, the present invention is a series of treatments that are completed by removing the acid cleaning chemical solution with pure water when oxidation treatment such as acid washing and acid washing are performed after the hexamethyldisilazane treatment, It differs from surface modification by a single treatment.
These are features that can be clearly distinguished from the known techniques of mask processing.

FIG. 2 is a manufacturing process diagram of an example in the method for manufacturing a photomask blank of the present invention.
First, a transparent substrate 3 is prepared (cross section A), and a light semitransmissive film 2 made of a material containing at least silicon atoms and nitrogen atoms is formed thereon (cross section B). Next, the surface of the light semi-transmissive film 2 is contacted with a silylating agent, preferably a vapor of hexamethyldisilazane (HMDS), and after the trimethylsilyl group is bonded (cross section C), an aqueous solution of sulfuric acid / hydrogen peroxide, etc. Is used to form an altered layer 5 capable of reducing the amount of ammonium ions in the exposed portion of the upper surface of the light translucent film (section D).
Next, a light-shielding layer 1 is provided on the altered layer (section E), and further a resist layer 4A is provided to obtain a desired photomask blank with a resist film (section F).

Next, the manufacturing method of the photomask of this invention is demonstrated.
The photomask manufacturing method of the present invention has three modes, photomask manufacturing method 1 to manufacturing method 3, which will be described in order.

  First, in the photomask manufacturing method 1 of the present invention, a photomask blank obtained by the above-described method is used, and (A) a light translucent film made of a material containing at least silicon atoms and nitrogen atoms is disposed thereon. Etching is performed using the above layer as a mask to expose a desired side cross section, a silylating agent is brought into contact with the exposed portion of the side cross section, and then subjected to oxidation treatment, whereby the altered layer is applied to the exposed side cross section. And (B) removing the layer above the light semi-transmissive film and exposing the upper surface of the pattern layer of the light semi-transmissive film having an exposed side section. .

  The silylating agent, its contact treatment and oxidation treatment in this method are as described in the above-mentioned method for producing a photomask blank.

  In this photomask manufacturing method 1, hexamethyldisilazane is brought into contact with a halftone mask in which only the side surface of the light semi-transmissive film is exposed after the etching of the light semi-transmissive film is completed, and further acid cleaning is performed. As a result, an altered layer that reduces the amount of ammonium ions is formed on the side cross-section of the patterned light-semitransmissive film. That is, when a mask is manufactured using a photomask blank in which only the upper surface of the light translucent film is protected against ammonium ions, an altered layer that reduces the amount of ammonium ions is formed only on the side surface of the light translucent film. This is the method to do in the case where it is sufficient.

  In this case, the process of etching the upper layer film of the light translucent film is performed by providing the chemical resistance to the exposed portion of the side cross section of the light translucent film before the formation of the altered layer of the side cross section is performed before the light shielding film etching. The effect that the pattern of the light translucent film can be prevented from being thinned by etching is added.

FIG. 3 is a manufacturing process diagram of an example in the photomask manufacturing method 1 of the present invention.
First, a mask blank manufactured by the manufacturing process shown in FIG. 2 described above, that is, a mask blank in which the light semitransmissive film 2, the altered layer 5, the light shielding layer 1, and the resist layer 4A are sequentially formed on the transparent substrate 3 is prepared. (Section A). Next, after patterning the resist layer 4A (cross section B), etching is performed using the resist layer as a mask to expose a side cross section of the light semi-transmissive film (cross section C).

  Next, the exposed portion of the side cross section is contacted with a silylating agent, preferably a vapor of hexamethyldisilazane (HMDS), and after the trimethylsilyl group is bonded (cross section D), an aqueous solution of sulfuric acid / hydrogen peroxide is added. By using this to perform an oxidation treatment by acid cleaning, an altered layer 5 capable of reducing the amount of ammonium ions is formed on the exposed side section of the light translucent film (section E). Next, after providing the resist layer 4B (cross section F), patterning (cross section G), and etching using the resist layer as a mask, after removing the light shielding film (cross section H), the remaining resist layer is removed, By exposing the upper surface of the pattern layer of the light semitransmissive film, a desired photomask can be obtained (section I).

The photomask manufacturing method 2 of the present invention is used in an exposure apparatus having a pattern layer formed of a light semi-transmissive film made of a material containing at least silicon atoms and nitrogen atoms on at least the uppermost layer on a transparent substrate. When manufacturing photomasks,
After forming a pattern of a light semi-transmissive film made of a material containing at least silicon atoms and nitrogen atoms, a silylating agent is brought into contact with the exposed surface of the light semi-transmissive film on which the pattern is formed, and then an oxidation treatment is performed. Thus, an altered layer is formed on the exposed surface of the pattern.

  In addition, the transparent substrate, the material of the light translucent film and the formation method thereof, the silylating agent, the contact treatment method thereof, and the oxidation treatment in this method are as described in the above-described photomask blank manufacturing method.

FIG. 4 is a manufacturing process diagram of an example in the photomask manufacturing method 2 of the present invention.
First, a mask blank, that is, a mask blank in which the light semitransmissive film 2, the light shielding film 1, and the first resist layer 4A are sequentially formed on the transparent substrate 3 is prepared (section A). Next, after patterning the first resist layer (section B), etching is performed using the mask as a mask (section C), and the remaining resist layer is removed (section D). Next, after providing the second resist layer 4B (section E), the second resist layer is patterned (section F), and etching is performed using the second resist layer as a mask (section G). The layer is removed to form a pattern of a light semi-transmissive film with the upper surface and side surfaces exposed (cross section H).

  Next, the exposed surface of the light-semitransmissive film is contacted with a vapor of a silylating agent, preferably hexamethyldisilazane (HMDS), and after the trimethylsilyl group is bonded (cross section I), an aqueous solution of sulfuric acid / hydrogen peroxide is used. By performing oxidation treatment by acid cleaning, a desired photomask is obtained by forming the altered layer 5 capable of reducing the amount of ammonium ions on the pattern exposed surface of the light translucent film (section J).

  In this method, the etching of the light translucent film using the first resist 4A ends in the cross section D, and then the etching of the light shielding film by the second resist 4B is completed in the cross section H. Both sides are in the state where the same part as when the mask is completed is exposed after processing. Hexamethyldisilazane is brought into contact with the halftone mask in this state, and the surface of the light semi-transmissive film is washed with acid and rinsed with water, whereby an altered layer is formed on the surface of the patterned light semi-transmissive film. Form.

  Formation of the altered layer makes it difficult for ammonium ions to be extracted from the surface, and as a result, it is difficult for ammonium salts to be generated during exposure of the photomask.

  Further, since the resistance to alkali chemicals is improved, it is possible to sufficiently remove acidic substances that form alkali salts such as sulfuric acid. Therefore, also in this respect, the ammonium salt is less likely to be generated upon exposure.

  Furthermore, since the chemical resistance of the surface of the light translucent film is improved, the difficulty of the cleaning operation is reduced, repeated cleaning is facilitated, the cleanliness of the photomask is improved, and the mask line width is not changed by the cleaning. There is also an advantage that the line width accuracy is improved.

  After the pattern is completed, the mask is finally cleaned to remove foreign matters. However, since the cross section H in FIG. 4 does not change until the end, hexamethyldisilazane treatment and subsequent acid cleaning are performed after the pattern is completed until the mask is completed. You may go. However, when a pellicle is mounted on the mask, the order of processes for hexamethyldisilazane treatment and subsequent acid cleaning is limited before mounting the pellicle. Also, the hexamethyldisilazane treatment and the subsequent acid cleaning in the state of the cross section G in FIG.

  Further, even after the pellicle is mounted, if the pellicle is removed, the section returns to the cross-section H in FIG. 4 and the processing of the present invention can be repeated.

The photomask manufacturing method 3 of the present invention is used in an exposure apparatus having a pattern layer formed of a light semi-transmissive film made of a material containing at least silicon atoms and nitrogen atoms on at least the uppermost layer on a transparent substrate. When manufacturing photomasks,
(X) A light translucent film made of a material containing at least silicon atoms and nitrogen atoms is etched using the upper layer as a mask to expose a desired side section, and then exposed to the exposed portion of the side section. A step of forming a deteriorated layer in the exposed portion of the side cross section by contacting a silylating agent and then performing an oxidation treatment; and (Y) removing the layer above the light translucent film and exposing the exposed side cross section After exposing the upper surface of the pattern layer of the light translucent film having a contact with the silylating agent on the upper surface of the pattern layer of the light translucent film and then performing an oxidation treatment, an altered layer is formed on the upper surface of the pattern layer Are sequentially performed.

  In addition, the transparent substrate, the material of the light translucent film and the formation method thereof, the silylating agent, the contact treatment method thereof, and the oxidation treatment in this method are as described in the above-described photomask blank manufacturing method.

FIG. 5 is a manufacturing process diagram of an example in the photomask manufacturing method 3 of the present invention.
First, a mask blank in which a light semi-transmissive film 2, a light shielding film 1, and a first resist layer 4A are sequentially formed on a transparent substrate 3 is prepared (cross section A). Next, after patterning the first resist layer (cross section B), etching is performed using the first resist layer as a mask to expose a desired side cross section of the light translucent film (cross section C). Next, a silylating agent, preferably hexamethyldisilazane (HMDS) vapor is brought into contact with the exposed portion of the side cross section to bind the trimethylsilyl group (cross section D), and then a sulfuric acid / hydrogen peroxide aqueous solution or the like is used. By performing oxidation treatment by acid cleaning, an altered layer 5 capable of reducing the amount of ammonium ions is formed on the pattern exposed surface of the light translucent film, and the remaining resist layer is peeled off (section E).

  Then, after providing the second resist layer 4B (cross section F), the resist layer 4B is patterned (cross section G), and the light shielding film is etched using the resist layer 4B as a mask, thereby having an exposed side cross section. The upper surface of the pattern layer of the light semitransmissive film is exposed (cross section H). Next, after vapor contact of a silylating agent, preferably hexamethyldisilazane (HMDS), is performed on the upper surface of the pattern layer of the light-semitransmissive film and a trimethylsilyl group is bonded (cross section I), an aqueous solution of sulfuric acid / hydrogen peroxide is used. By performing an oxidation treatment using acid cleaning, an altered layer 5 capable of reducing the amount of ammonium ions is formed on the upper surface of the pattern layer of the light translucent film, thereby obtaining a desired photomask (cross section J).

  This production method 3 is characterized in that a deteriorated layer for reducing the amount of ammonium ions is formed in two portions on each of the upper surface and the side surface of the light translucent film. According to this method, it is possible to produce an effect that it is possible to prevent the pattern of the light semi-transmissive film from being etched and thinned by only the photomask manufacturing process as compared with the process shown in FIG.

In the photomask blank manufacturing method and photomask manufacturing methods 1 to 3 of the present invention, the silylating agent is not limited to hexamethyldisilazane, and other materials may be used as appropriate. When another silylating agent is used, a bond containing Si that is not a trimethylsilyl group ((CH ₃ ) ₃ Si group) may be formed on the light translucent film, but the terminal in the functional group containing Si may be formed. Is bonded to a functional group containing carbon such as a methyl group. The terminal in this case is decomposed by an oxidation treatment subsequent to the silylation treatment, and in short, the oxidation treatment is appropriately selected according to the silylating agent.

  In the photomask manufactured by the method of the present invention, a contact process using a silylating agent and a subsequent oxidation process are performed on an upper surface and a side cross section of a light semitransmissive film made of a material containing at least silicon atoms and nitrogen atoms in the manufacturing process. By applying this to form a deteriorated layer, the amount of ammonium ions generated on the surface is reduced and chemical resistance such as alkali resistance is improved. By improving chemical resistance, it is possible to suppress changes in pattern dimensions, phase differences, and transmittances caused by chemicals used in the manufacturing process. As a result, the present invention provides a photomask that is highly resistant to phase difference and transmittance and has less ammonium ions on the surface, so that it is less likely to generate ammonium salts when used for exposure. it can.

  Further, in actual photomask manufacturing, cleaning that starts with acid cleaning is generally used for cleaning for the purpose of removing extracted foreign matters by patterning. Simply add a treatment step with a silylating agent before such acid washing.

  In the present invention, the application target of the technology is limited to the halftone phase shift mask and the blank. However, as long as it has a film made of a material containing at least silicon atoms and nitrogen atoms on the surface, The present invention can be applied not only to a phase shift film but also to a mask using MoSi as a light shielding film, an optical glass product having a film containing at least silicon atoms and nitrogen atoms on its surface, and a semiconductor silicon wafer having an oxynitride film.

  The present invention also provides a photomask blank manufactured by the above-described photomask blank manufacturing method of the present invention and a photomask manufactured by the above-described photomask manufacturing methods 1 to 3 of the present invention. .

  The photomask blank obtained by the method of the present invention can provide a photomask that is excellent in chemical resistance and hardly generates an ammonium salt during exposure. In addition, the photomask obtained by the method of the present invention is excellent in chemical resistance and hardly generates an ammonium salt when used for exposure.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
Production Example 1 Production of Photomask Blank Mixed gas of argon (Ar) and nitrogen (N ₂ ) using a mixed target (Mo: Si molar ratio = 8: 92) of molybdenum (Mo) and silicon (Si) In an atmosphere (Ar: 10%, N ₂ : 90%, pressure: 0.2 Pa), a light translucent film having a thickness of about 80 nm made of MoSiN is formed on a quartz substrate, which is a transparent substrate, by reactive sputtering. A plurality of blanks for halftone photomasks were produced.

Example 1
The photomask blank (transparent substrate 3, light translucent film 2) obtained in Production Example 1 is placed in a sealed container 10 as shown in FIG. 1, and a container 12 containing hexamethyldisilazane 11 is further provided. As shown in FIG. Next, hexamethyldisilazane vapor was brought into contact with the surface of the MoSiN film for 2 minutes at 100 ° C. and atmospheric pressure.
Next, the photomask blank treated with hexamethyldisilazane in this manner is taken out from the sealed container, washed with sulfuric acid-hydrogen peroxide solution at a temperature of 80 ° C., and washed with warm pure water, ammonia-peroxygenated. After washing with an aqueous hydrogen solution, the substrate was rinsed with pure water and dried.
Next, for comparison, the same treatment as described above was performed except that the hexamethyldisilazane treatment was not performed.
The amount of ammonium ions present on the surface of the MoSiN film of these photomask blanks was determined by ion chromatography. As a result, when the amount of ammonium ion in the blank that was not treated with hexamethyldisilazane was 10, the amount of ammonium ion in the blank of Example 1 was 1.7.

Example 2
A light-shielding film with a thickness of 80 nm made of a chromium-based metal was formed on the light semi-transmissive film made of the MoSiN film of the photomask blank obtained in Production Example 1 to produce a photomask blank with a light-shielding film.
Using this photomask blank with a light-shielding film, a first resist layer was provided thereon, and a photomask shown in section H was manufactured according to the manufacturing process diagram shown in FIG. This photomask has a transflective film part and a transmissive part in which the phase difference between the light shielding part and the transmissive part is approximately 180 ° at the ArF wavelength.

  After measuring the phase difference and transmittance of the photomask, the photomask was subjected to the same hexamethyldisilazane treatment as in Example 1 and acid cleaning / oxidation treatment with a sulfuric acid-hydrogen peroxide aqueous solution. After the ammonia-hydrogen peroxide aqueous solution was washed, it was rinsed with pure water and dried.

The phase difference and transmittance of the photomask processed in this way were measured.
As a result, it was confirmed that the phase difference and the transmittance hardly changed by a series of processes, and the optical characteristics that can be used as a halftone mask were maintained.

  The amount of change in phase difference caused by the treatment of the present invention in which a deteriorated layer is provided is reduced by 0.23 degrees, and the change in transmittance is increased by 0.02%. When using a photomask, the amount of change is almost negligible. Things were made.

Next, the chemical resistance of the photomask subjected to the hexamethyldisilazane treatment and the acid cleaning treatment in this way was evaluated.
Phase difference and transmission when both the photomask of the present invention that has been subjected to hexamethyldisilazane treatment and acid cleaning treatment and the conventional method, that is, the untreated photomask, are washed with alkali washing that is usually used for photomask washing. The amount of change in rate was confirmed. The results are shown in Table 1.

表１で示されるように、本発明の処理により洗浄時の位相差、透過率変化量は小さくなる。すなわち本発明の処理によってフォトマスクの耐薬品性が向上したことが分かる。

As shown in Table 1, the processing of the present invention reduces the phase difference and transmittance change during cleaning. That is, it can be seen that the chemical resistance of the photomask is improved by the treatment of the present invention.

  The photomask manufacturing method of the present invention can suppress precipitation of ammonium sulfate, particularly when irradiated with high-energy exposure light such as ArF excimer laser light, and can suppress changes in pattern dimensions due to cleaning treatment. A clean photomask can be manufactured.

It is explanatory drawing which shows one example of the method of making hexamethyldisilazane contact a light semipermeable film. It is a manufacturing-process figure of an example in the manufacturing method of the blank for photomasks of this invention. It is a manufacturing-process figure of an example in the manufacturing method 1 of the blank for photomasks of this invention. It is a manufacturing process figure of an example in the manufacturing method 2 of the photomask of this invention. It is a manufacturing process figure of an example in the manufacturing method 3 of the photomask of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light shielding film 2 Light semi-transmissive film 3 Transparent substrate 4A 1st resist layer 4B 2nd resist layer 5 Alteration layer 10 Sealed container 11 Hexamethyldisilazane 12 Hexamethyldisilazane container

Claims (14)

Used for an exposure apparatus using a KrF excimer laser light or an ArF excimer laser light , which has a patternable light transmissive film made of a material containing at least silicon atom, nitrogen atom and metal atom on a transparent substrate. When manufacturing a photomask blank for manufacturing a photomask,
After forming the semi-transmission film made of a material containing the silicon atoms and nitrogen atoms and the metal atom, the light semi-transmitting film surface is contacted with a silylating agent, followed by performing an oxidation treatment, the light semi-transmitting film A modified layer in which NH-bonded hydrogen on the outermost surface of the light-semitransmissive film is replaced with silicon or oxygen is formed on the exposed upper surface of the photomask blank. The method for producing a photomask blank according to claim 1, wherein the metal atom is at least one selected from molybdenum, tantalum, tungsten, chromium, titanium, nickel, palladium, hafnium, and zirconium. The photomask blank manufacturing method according to claim 1 or 2, wherein the photomask is a halftone phase shift mask. The silylating agent is at least one selected from hexamethyldisilazane, vinyltrimethylsilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, methyldichlorosilane, isopropoxytrimethylsilane, acetoxytrimethylsilane and polysilazane. Item 4. A method for manufacturing a blank for a photomask according to any one of Items 1 to 3 . The method for producing a blank for a photomask according to claim 4 , wherein the silylating agent is hexamethyldisilazane. To produce a blank off Otomasuku in claims 1 to according to any one of 5 method, using the blank obtained photomask made of a material containing at least (A) a silicon atom and a nitrogen atom and a metal atom The light translucent film is etched using the layer above it as a mask to expose the desired side cross section, and then the exposed portion of the side cross section is contacted with a silylating agent, followed by oxidation treatment. Forming an altered layer in which the hydrogen of NH bonds on the outermost surface of the light translucent film is replaced with silicon or oxygen at the exposed side cross section, and (B) a layer above the light translucent film And a step of exposing the upper surface of the pattern layer of the light-semitransmissive film having an exposed side cross section. Exposure light of KrF excimer laser light or ArF excimer laser light having a pattern layer formed of a light semi-transmissive film made of a material containing at least silicon atoms, nitrogen atoms and metal atoms is used as at least the uppermost layer on the transparent substrate . When manufacturing photomasks used in conventional exposure equipment,
After forming a pattern of a light semi-transmissive film made of a material containing at least silicon atoms, nitrogen atoms, and metal atoms , a silylating agent is brought into contact with the exposed surface of the light semi-transmissive film on which the pattern is formed, and then oxidized. To form an altered layer in which NH-bonded hydrogen on the outermost surface of the light translucent film is replaced with silicon or oxygen on the exposed surface of the pattern. Exposure light of KrF excimer laser light or ArF excimer laser light having a pattern layer formed of a light semi-transmissive film made of a material containing at least silicon atoms, nitrogen atoms and metal atoms is used as at least the uppermost layer on the transparent substrate . When manufacturing photomasks used in conventional exposure equipment,
(X) A light translucent film made of a material containing at least silicon atoms, nitrogen atoms, and metal atoms is etched using the upper layer as a mask to expose a desired side section, and then the side section By contacting the exposed portion with a silylating agent and then subjecting it to an oxidation treatment, an altered layer in which the hydrogen of the NH bond on the outermost surface of the light-semitransmissive film is replaced with silicon or oxygen is exposed to the side cross-sectional exposed portion. And (Y) removing the layer above the light semi-transmissive film and exposing the upper surface of the pattern layer of the light semi-transmissive film having an exposed side section, and then patterning the light semi-transmissive film. By contacting the upper surface with a silylating agent and then performing an oxidation treatment, an altered layer in which the hydrogen of NH bonds on the outermost surface of the light translucent film is replaced with silicon or oxygen is formed on the upper surface of the pattern layer. The process is performed sequentially. Manufacturing method of a photomask to be. 9. The method of manufacturing a photomask according to claim 6, wherein the metal atom is at least one selected from molybdenum, tantalum, tungsten, chromium, titanium, nickel, palladium, hafnium, and zirconium. The photomask manufacturing method according to claim 6, wherein the photomask is a halftone phase shift mask. The silylating agent is at least one selected from hexamethyldisilazane, vinyltrimethylsilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, methyldichlorosilane, isopropoxytrimethylsilane, acetoxytrimethylsilane and polysilazane. Item 11. A method for producing a photomask according to any one of Items 6 to 10 . The method for producing a photomask according to claim 11 , wherein the silylating agent is hexamethyldisilazane. A photomask blank manufactured by the method according to any one of claims 1 to 5 . Photomask characterized in that it is produced by the method according to any one of claims 6 to 12.

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