JP2011215404A - Photo mask blank and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the following problems: pattern dimension (reduction in dimensional linearity) in a fine pattern is reduced by a micro loading phenomenon during dry etching in manufacturing a photomask, or a difference in the pattern dimension occurs between regions with different aperture ratios due to a global loading phenomenon, or it is impossible to reduce the thickness of a resist or chromium (Cr) to be formed into an etching mask, because of the limitations of a dry etching selection ratio.SOLUTION: In a photomask blank, a material containing silicon such as silicon molybdenum (MoSi) is used for a phase shift layer or a light-shielding layer is provided. In the photomask blank, the above material is doped with a minute amount of group 15 elements such as phosphorus (P) and arsenic (As) as an impurity by an ion injection method or a diffusion method. A dry etching rate in manufacturing a photomask is increased, and a photomask with high quality can be manufactured.

Description

  The present invention relates to a photomask blank in which an etching rate of an etching mask material is improved as compared with a conventional photomask blank in a dry etching process for forming a photomask pattern, and a manufacturing method thereof.

  In recent years, as semiconductor devices such as large-scale integrated circuits (LSIs) are highly integrated, circuit patterns are further miniaturized. In order to realize such a fine circuit pattern, it is required to thin the wiring pattern and contact hole pattern constituting the circuit. Since these patterning are formed by photolithography using a photomask, a technique for forming a photomask pattern serving as an original plate with high precision is required.

  In optical lithography in semiconductor device manufacturing, it is common to use a light exposure device called a stepper or scanner to reduce the photomask pattern to 1/4 and transfer the pattern to the semiconductor device. The photomask pattern size is about four times as large as the semiconductor device pattern.

  However, the size of the circuit pattern transferred by recent optical lithography is smaller than the exposure wavelength (wavelength of 193 nm with the leading exposure equipment), and the effects of light interference, diffraction, aberration, etc. that occur during exposure Thus, it has been difficult to transfer the shape according to the photomask pattern to the resist film on the semiconductor substrate.

  For this reason, a photomask pattern (so-called OPC pattern) with a more complicated shape than the actual semiconductor device pattern or a fine auxiliary pattern (eg SRAF: Sub Resolution Assist Feature) that is not directly transferred to the semiconductor device is required. It is said. Thus, in practice, the photomask pattern is required to have high pattern processing accuracy and resolution equivalent to or higher than the semiconductor pattern.

  As a method for manufacturing a photomask which is a source of a semiconductor device, there are roughly classified a binary type photomask and a halftone type phase shift photomask.

  As a method for manufacturing a binary type photomask having a conventional structure, the one shown in Non-Patent Document 1 is known. In this manufacturing method, a photomask is manufactured by the following procedure. First, an electron beam resist film is applied on a photomask blank provided with a light shielding layer such as Cr on a transparent substrate, a pattern is drawn on the resist film with an electron beam, and a resist pattern is obtained by developing this. Next, using this resist pattern as an etching mask, a photomask pattern composed of a light shielding portion and a light transmitting portion is formed by dry etching.

  Incidentally, in recent years, with the miniaturization of the mask pattern, it has become necessary to improve the resolution of the resist pattern by thinning the resist. However, in the above-described conventional method for producing a binary type photomask, the dry etching selectivity between the light shielding layer and the resist (light shielding layer etching rate / resist etching rate) is small, so there is a limit to the thinning of the resist. is there. In order to solve this, as shown in Patent Document 1, a binary photomask having a new structure has been proposed. This is because the light shielding layer is mainly composed of MoSi instead of conventional Cr, and a thin layer made of an inorganic material (Cr-based material) different from the light shielding layer is provided between the resist and the light shielding layer.

  This type of binary photomask is manufactured by the following procedure. First, an electron beam resist film is applied on a photomask blank provided with an upper layer film and a lower layer film (light shielding layer) made of different inorganic materials on a transparent substrate, and a pattern is drawn on the resist film with an electron beam. This is developed to obtain a resist pattern. Next, the upper layer film is patterned by dry etching using this resist pattern as an etching mask. Next, the lower layer film (light shielding layer) is patterned by dry etching using the patterned upper layer film as an etching mask. Finally, the remaining upper layer film is peeled off to obtain a photomask pattern composed of a light shielding portion and a light transmitting portion.

  According to this manufacturing method, since the materials of the upper layer film and the lower layer film (light-shielding layer) are different, the dry etching selectivity of the lower layer film and the upper layer film in the dry etching of the lower layer film (etching rate of the lower layer film / resist etching rate) Becomes very large, the upper layer film can be made sufficiently thin. Further, since the upper layer film can be made thin, the resist film can be made sufficiently thin when the upper layer film is dry-etched using the resist as an etching mask. Therefore, the resolution of the resist pattern can be greatly improved, and as a result, the resolution and dimensional accuracy of the photomask pattern can be greatly improved.

  On the other hand, the halftone phase shift photomask fabrication method has the same basic fabrication procedure as that of the above-described binary photomask having a new structure having an upper layer film and a lower layer film. This is because the basic structures (such as the order of materials) of the resist film, the upper layer film, the lower layer film, and the transparent substrate are the same. However, since the composition and film thickness of each layer are different, the processing conditions (gas type, pressure, power, etc.) need to be optimized according to the blank.

  Now, with the miniaturization of the mask pattern, a technical problem in dry etching has arisen. When patterning the upper layer film by dry etching using the resist pattern as an etching mask, or when patterning the lower layer film by dry etching using the upper layer film as an etching mask, the finer openings are less likely to be dry etched. A microloading phenomenon occurs (see Non-Patent Document 2).

  The reason for the occurrence of this microloading phenomenon is that the finer opening portion or the opening portion having a higher aspect ratio has a tendency that the etching rate decreases because radicals serving as an etchant do not easily reach the bottom of the opening portion. In other words, this is a phenomenon in which a difference occurs in the etching rate between the fine opening and the large opening. Due to the occurrence of this microloading phenomenon, the dimensional linearity is lowered and the dimensional accuracy of the photomask is lowered.

In general, in etching of silicon-based materials such as molybdenum silicon (MoSi), silicon oxide film / nitride film, and silicon simple substance, fluorine-based gases such as CF ₄ , C 2 F ₆ , C ₄ F ₈ , CHF ₃ , SF ₆ , CL ₂ , HCL A mixed gas in which oxygen or an inert gas is added to a chlorine-based gas such as BCL ₃ or SiCL ₄ as required is used, but the microloading phenomenon occurs regardless of which gas type is used. Therefore, for miniaturization of the mask pattern, it is required to reduce the microloading phenomenon in the dry etching process (see Non-Patent Document 1).

  Conventional countermeasures against the microloading phenomenon include lowering the dry etching conditions and reducing the resist thickness. As a measure to reduce the dry etching conditions, if the dry etching conditions are reduced, the mean free path in the chamber becomes longer (the probability of collision with other particles decreases), and radicals easily reach the bottom of the opening. Therefore, the microloading phenomenon is reduced (see Non-Patent Document 2). On the other hand, however, there is a problem in that the selection ratio with respect to an etching mask such as a resist or an upper layer film is lowered due to the low pressure. Further, in the countermeasure for reducing the thickness of the resist, since radicals easily reach the bottom of the opening, there is an effect of reducing the microloading phenomenon. On the other hand, a resist as an etching mask requires a certain thickness, so that there is a limit to reducing the resist thickness.

  As another method for reducing the microloading phenomenon, a method of increasing the dry etching rate by changing the composition of the material to be etched of the photomask has been proposed (see Patent Document 2). According to this method, since the dry etching time can be shortened as a whole, even if there is a difference in etching rate between the fine opening and the large opening, the difference can be reduced.

  However, in this method, since it is necessary to adjust the content of oxygen and nitrogen, there is also a problem that it becomes difficult to maintain the optical characteristics necessary for the photomask.

  Another technical problem in dry etching processing is that a dimensional difference occurs between regions having different aperture ratios due to a global loading phenomenon. This global loading phenomenon is a phenomenon that occurs because the supply amount of the etchant (radicals or ions) is insufficient with respect to the material to be etched such as MoSi. For example, in a region where the aperture ratio is small (most parts are covered with an etching mask material), the etching rate does not decrease because the etchant is sufficient, but a region where the aperture ratio is large (mostly MoSi or the like) In the case where the material to be etched is exposed), the etching rate is lowered because the etchant is insufficient. Due to this phenomenon, since the dimensions are different between regions having different aperture ratios, the dimensional uniformity in the photomask plane is degraded. Therefore, it is also required to reduce the global loading phenomenon.

  In order to reduce the conventional global loading phenomenon, a large flow rate of etching gas and high-speed exhaust are effective in the dry etching process. This makes it possible to eliminate the shortage of etchant supply. However, this requires a large flow rate gas supply system and a large-capacity vacuum pump. In addition, since the etching characteristics are greatly changed, there may be a problem that good etching characteristics (dimensions and selection ratio) cannot be obtained.

  As another method for reducing the global loading phenomenon, a method for adjusting the aperture ratio by arranging a dummy pattern for adjusting the aperture ratio around the pattern has also been proposed (patent) Reference 3). However, this method requires an area where a dummy pattern can be placed, and therefore, in an actual product in which such an area does not exist, the practical possibility is low.

Story of photomask technology, Industrial Research Committee (1996) H.C. Jones et al .: Proc. 8th Plasma Processing (1990) p.45

JP 2008-257274 A JP 2007-178498 A Japanese Patent Laid-Open No. 2001-183809

  As described above, there is a problem that the dimensional accuracy of the photomask is reduced due to the microloading phenomenon and the global loading phenomenon that occur during the dry etching of the photomask, but the conventional methods proposed to solve these problems are as follows. These are methods such as lowering the dry etching conditions, reducing the thickness of the resist, changing the composition of the film to be etched, increasing the flow rate and speed of the etching gas, and arranging dummy patterns for adjusting the aperture ratio.

  However, these methods cause deterioration in dimensional characteristics (CD linearity, CD uniformity, etc.) and optical characteristics (transmittance, reflectance, phase difference, etc.) necessary for a photomask, and further on the apparatus or pattern design. In many cases, this is difficult.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a photomask blank and a method for manufacturing the photomask blank that prevent a reduction in dimensional accuracy of a photomask caused by a microloading phenomenon or a global loading phenomenon without reducing dimensional characteristics and optical characteristics.

In order to solve the above problems, the present invention has the following configuration.
In a photomask blank using a material containing silicon for a phase shift layer or a light shielding layer, these materials are doped with a Group 15 element such as phosphorus (P) or arsenic (As) as a trace amount of impurities. A photomask blank.

  The method for producing a photomask blank according to claim 1 is characterized in that a quartz substrate for a photomask is formed on a light shielding layer and / or a phase shift layer by sputtering or CVD, and then an impurity such as an ion implantation method or a thermal diffusion method is added. A photomask blank manufacturing method comprising a doping step and then a heat treatment step.

In the ion implantation method according to claim 2, the acceleration energy is in the range of 10 keV to 200 keV, and the ion implantation amount per unit area is in the range of 10 7 atoms / cm ^{2 to} 10 17 atoms / cm ² . A method of manufacturing a photomask blank, which is performed.

2. The photomask blank according to claim 1, wherein the impurity concentration in the unit volume of the Group 15 element is 10 10 or more and atoms / cm ³ or more.

  The photomask blank of claim 1 is a photomask blank characterized by MoSi, TaSi, ZrSi, Si, HfSi and oxides, nitrides, and oxynitrides thereof.

  According to the present invention, a light etching layer and a halftone layer of a photomask blank are doped with a small amount by an ion implantation method or a diffusion method using a Group 15 element as an impurity, thereby increasing a dry etching rate at the time of manufacturing a photomask. It is possible to provide a photomask blank that can reduce the loading phenomenon and the global loading phenomenon, and that can provide good pattern dimensional accuracy, and a manufacturing method thereof.

It is the photomask structure of this invention, Comprising: (a) is a phase shift type halftone mask blank, (b) is sectional drawing which shows a MoSi binary type mask blank. Explanatory drawing which shows the manufacturing process of the MoSi binary type | mold mask blank in Example 1 of this invention. Explanatory drawing which shows the process of the etching rate measurement of the MoSi binary mask blank in Example 1 of this invention. The graph of the ion implantation amount and etching rate of the MoSi binary mask blank in Example 1 of this invention. Explanatory drawing which shows the manufacturing process of the MoSi binary type photomask in Example 2 of this invention. The graph which shows the dimensional linearity of the MoSi binary type photomask in Example 2 of this invention. Explanatory drawing of the dimensional uniformity of the MoSi binary type photomask in Example 2 of this invention. Explanatory drawing of the manufacturing process of the phase shift type halftone blank in Example 3 of this invention. Explanatory drawing which shows the process of the etching rate measurement of the phase shift type halftone blank in Example 3 of this invention. The graph of the ion implantation amount and etching rate of the phase shift type halftone blank in Example 3 of the present invention. Explanatory drawing which shows the manufacturing process of the phase shift type halftone mask in Example 4 of this invention. 10 is a graph showing dimensional linearity of a phase shift photomask in Example 4 of the present invention. 10 is a graph showing dimensional uniformity of a phase shift photomask in Example 4 of the present invention.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  As shown in FIG. 1A, the photomask blank of the present invention is a phase shift type halftone mask blank composed of a halftone layer 002 and a light shielding layer 003 on a transparent quartz substrate 001, or FIG. As shown in the figure, a binary mask blank comprising a light shielding layer 004 and a hard mask layer 005 on a transparent quartz substrate 001 is shown.

  The halftone layer 002 of the phase shift type halftone mask blank of the present invention is made of a material containing at least Si such as MoSi, and the halftone layer 002 has a transmittance of 4 to 30% with respect to exposure light. It has a phase shift amount of 180 °.

  The content of Si atoms in the halftone layer 002 is 40% or more. This is because a sufficient amount is necessary for a substitution reaction with a Group 15 element described later.

In the halftone layer 002, a Group 15 element such as phosphorus (P) or arsenic (As) is doped in the unit volume by 10 10 or more atoms / cm ³ or more.

  The light shielding layer 004 of the binary mask blank of the present invention is made of a material containing at least Si such as MoSi, and the OD value (Optical Density: optical density) of the light shielding layer with respect to exposure light has a value of 3 or more. Is.

  The content of Si atoms in the light shielding layer 004 is 40% or more. This is because a sufficient amount is necessary for a substitution reaction with a Group 15 element described later.

In the light shielding layer 004, a group 15 element such as phosphorus (P) or arsenic (As) is doped in a unit volume of 10 10 or more atoms / cm ³ or more.

  When a Group 15 element is doped into a material containing Si as an impurity, one more outermost electron of an impurity atom is left and can move around in the material as a free electron. As a result, the material to be etched has a negative charge in the dry etching process during the manufacture of the photomask, and it is considered that the charge exchange with the fluorine radical and the chlorine radical is promoted and the etching rate is increased.

  The manufacturing method for realizing the mask blank of the present invention includes at least (1) a film forming step by sputtering or CVD (Chemical Vapor Deposition / Chemical Vapor Deposition) on a quartz substrate, and (2) a blank after film formation. It comprises an impurity doping step by ion implantation or thermal diffusion, and (3) a heat treatment step for diffusing or activating the doped impurity.

  The film forming step (1) may be the same as the film forming conditions of a light shielding film, a halftone film, and a hard mask film in a normal photomask blank.

In the ion implantation process which is one of the doping processes (2), there are two parameters, the ion implantation amount and the acceleration voltage. In order to increase the etching rate, the ion implantation amount is 10 7 atoms / cm. Must be ² or more. On the other hand, if the amount of ion implantation is too large, it is necessary to set it to 10 17 atoms / cm ² or less in order to keep the optical characteristics (transmittance, reflectance, and phase difference) of the photomask as unchanged. .

  The acceleration voltage of the ion implantation is a parameter that determines the depth of the implanted ions, and thus depends on the material and film thickness of the implanted side, but in the case of a photomask, a light shielding layer, a halftone layer, Since the hard mask layer has a thickness of approximately 100 nm or less, the acceleration voltage is preferably set to 10 keV to 200 keV. This is because, at an acceleration voltage higher than that, ions penetrate through the layer to be implanted and are implanted into the quartz substrate.

  The heat treatment step (3) may be any heat treatment method such as electric annealing, lamp annealing, laser annealing, and electron beam annealing. However, in order to electrically activate the doped impurities, the heat treatment step (3) is performed at 800 to 1300 degrees. It is better to process in the range.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(MoSi binary mask blank)
In Example 1, the manufacturing method of a MoSi binary mask blank produced by the method of the present invention and the results of measuring the dry etching rate are shown.

(Preparation of MoSi binary mask blank)
As shown in FIG. 2, a method of manufacturing a binary mask blank using MoSi as the main material of the light shielding layer will be described. First, the MoSi film 102 is formed to a thickness of 45 nm on the quartz substrate 101 with a multi-source sputtering apparatus (see FIG. 2B). The conditions for forming the MoSi film were as follows: pressure 10 mTorr, DC power 250 W, Ar flow rate 30 sccm, O 2 flow rate 5 sccm, N ₂ flow rate 15 sccm.

Next, phosphorus 104 (P) is applied to the MoSi light-shielding layer by an ion implantation apparatus, the acceleration voltage is 25 keV (fixed), and the ion implantation amount is a plurality of ions in the range of 10 12 to 10 15 atoms / cm ^2. Doping was performed under conditions (see FIG. 2C).

Next, heat treatment was performed at 900 ° C. for 10 minutes in the heat treatment apparatus 105 (see FIG. 2D), and finally a Cr film 103 was formed to a thickness of 10 nm in the multi-source sputtering apparatus (see FIG. 2E). ). The Cr film formation conditions were a pressure of 50 mTorr, a current of 4.0 A, an Ar flow rate of 45 sccm, an O ₂ flow rate of ₂ sccm, and an N ₂ flow rate of 1 sccm.

(MoSi binary mask blank etching rate)
In this way, only the Cr layer was removed from the entire surface of the MoSi binary mask blank by wet etching (see FIG. 3B), and then the MoSi light-shielding layer was removed from the ICP type dry etching apparatus Tetra2 (Applied Material). (FIG. 3 (c), and the MoSi etching rate was measured from the time until the MoSi layer completely disappeared. The conditions at this time were pressure 5 mTorr, SF6 flow rate 20 sccm, O ₂ flow rate 10 sccm, Source power. It was set to 400W and Bias power 70W.

  A graph showing the correlation between the ion implantation amount and the etching rate in this case is shown in FIG. According to this, as a result, the etching rate increased as the ion implantation amount increased.

(MoSi binary type photomask production)
In the present Example 2, a photomask is produced with the mask blank produced by Example 1, and the comparison with the conventional blank is shown about the dimension characteristic (dimension linearity, dimension uniformity).

FIG. 5 shows the manufacturing process. A positive electron beam resist FEP171 (Fuji Film Electronics Materials) is coated at 1500 mm on the mask blank (phosphorus doping amount of 10 14 atoms / cm ² ) produced in Example 1 using a spin coater (MTC). , PAB (Post Applied Bake) was processed at 130 degrees 10 minutes (see FIG. 5B). Next, a test pattern is drawn with a variable shaping electron beam drawing machine EBM5000 (New Flare Technology) with an acceleration voltage of 50 kV, and processed with a PEB / developing machine (Sigma Meltech) at 120 degrees 10 minutes and spray development 120 seconds. A resist pattern was formed (see FIG. 5C).

Next, Cr etching processing was performed in a dry etching apparatus Tetra2 (Applied Material) (see FIG. 5D) (conditions: pressure 3 mTorr, Cl ₂ flow rate 80 sccm, O ₂ flow rate 33 sccm, Source power 400 W, Bias power 10 W). Etching time 250 seconds).
Next, the resist residue was peeled off by washing with sulfuric acid / aqueous ammonia (see FIG. 5E).

  Next, MoSi etching treatment was performed using Tetra2 (Applied Material) (see FIG. 5F). The conditions at this time were a pressure of 5 mTorr, an SF6 flow rate of 20 sccm, an O2 flow rate of 10 sccm, a source power of 400 W, a bias power of 70 W, and an etching time that was twice as long as the MoSi layer was completely removed.

  Finally, the residual Cr film was stripped by wet treatment with a Cr etchant solution to produce a mask pattern (see FIG. 5G).

(Dimension comparison with conventional blank)
The dimensional linearity was compared between the MoSi binary type mask blank (phosphorus doping amount of 10 14 atoms / cm 2) and the conventional MoSi binary type mask blank. The result is shown in FIG. For the dimension measurement, LWM9000 (Leica) of a photomask length measurement SEM was used. According to this, it was confirmed that the pattern was formed with an accuracy close to the design dimension because the drop in the minute dimension was small compared to the conventional blank.

  Further, the dimensional uniformity was measured by arranging patterns having different aperture ratios over a wide range in the mask surface. FIG. 7A shows a schematic diagram of the pattern layout. Area A has an aperture ratio of 0%, B has an aperture ratio of 25%, C has an aperture ratio of 50%, D has an aperture ratio of 75%, and an LS (line and space) pattern having a pattern size of 1 μm is arranged therein. . FIG. 7B is a bubble diagram of the dimensional uniformity of a mask produced with a conventional blank, and FIG. 7C is a bubble diagram of the dimensional uniformity of a mask produced with the blank of Example 2 of the present invention. . In these bubble diagrams, the larger the bubble (circle), the greater the deviation from the average value. Fill (black) is more positive than the average value, and the hollow (white) is more than the average value. It means that it is shifted to the minus side.

  From this measurement result, it is known that the blank produced in Example 2 of the present invention has better dimensional uniformity when producing a photomask than the conventional blank. Further, the uniformity range value was 6.2 nm for the blank in the related art, whereas it was 2.4 nm in this Example 2.

(Phase shift type halftone blank)
In Example 3, the manufacturing method of the phase shift type halftone blank manufactured by the method of the present invention and the result of measuring the dry etching rate are shown.

A method of manufacturing a phase shift mask blank using MoSi as the main material of the halftone layer will be described (see FIG. 8). A MoSi film 302 with a thickness of 70 nm was formed on the quartz substrate 301 with a multi-source sputtering apparatus (see FIG. 8B). The conditions for forming the MoSi film were as follows: pressure 8 mTorr, DC power 300 W, Ar flow rate 30 sccm, O ₂ flow rate 5 sccm, N ₂ flow rate 15 sccm.

Next, incident ions 304 of arsenic (As) are applied to the MoSi light-shielding layer by an ion implantation apparatus, the acceleration voltage is 30 keV (fixed), and the ion implantation amount is in the range of 10 12 to 10 15 atoms / cm ² . And doping under a plurality of conditions (see FIG. 8C).

  Next, heat treatment was performed at 1100 ° C. for 10 minutes in the heat treatment apparatus 305 (see FIG. 8D), and finally a Cr film 303 was formed to a thickness of 10 nm in the multi-source sputtering apparatus (FIG. 8E). reference). The Cr film formation conditions were a pressure of 50 mTorr, a DC power of 250 W, an Ar flow rate of 45 sccm, an O2 flow rate of 10 sccm, and an N2 flow rate of 5 sccm.

(Etching rate of phase shift type halftone blank)
In this way, only the Cr layer was peeled off by wet etching from the manufactured phase shift halftone blank (see FIG. 9B), and then the MoSi light-shielding layer was removed from the ICP type dry etching apparatus Tetra2 (Applied Material). ) (See FIG. 9C), and the MoSi etching rate was measured from the time until the MoSi layer disappeared completely. The conditions at this time were a pressure of 5 mTorr, an SF6 flow rate of 20 sccm, an O2 flow rate of 10 sccm, a Source power of 400 W, and a Bias power of 70 W.

  A graph showing the correlation between the ion implantation amount and the etching rate is shown in FIG. As a result, the etching rate was increased as the ion implantation amount increased.

(Phase shift type halftone mask fabrication)
In this Example 4, a photomask is produced with the mask blank produced in Example 3, and the dimensional characteristics (dimensional linearity, dimensional uniformity) are compared with those of a conventional blank.

  On the mask blank of Example 3, a positive type electron beam resist FEP171 (Fuji Film Electronics Materials) is coated with 2000 mm using a spin coater (MTC) and processed at PAB (Post Applied Bake) 130 degrees 10 minutes. (See FIG. 11B). Next, a test pattern is drawn with a variable shaping electron beam drawing machine EBM5000 (New Flare Technology) with an acceleration voltage of 50 kV, and processed with a PEB / developing machine (Sigma Meltech) at 120 degrees 10 minutes and spray development 120 seconds. A resist pattern was formed (see FIG. 11C).

Next, Cr etching processing was performed in a dry etching apparatus Tetra2 (Applied Material) (see FIG. 11D) (conditions: pressure 5 mTorr, Cl2 flow rate 80 sccm, O ₂ flow rate 20 sccm, Source power 300 W, Bias power 5 W, Etching time was 240 seconds), and then the resist residue was removed by washing with sulfuric acid / aqueous ammonia (see FIG. 11 (e)).

Next, MoSi etching treatment was performed using Tetra 2 (Applied Material) (see FIG. 11F). The conditions at this time were a pressure of 5 mTorr, an SF ₆ flow rate of 20 sccm, an O ₂ flow rate of 10 sccm, a source power of 400 W, a bias power of 70 W, and an etching time that was twice as long as the MoSi layer was completely removed.

  Finally, the Cr residual film was peeled off by wet treatment with a Cr etchant solution to produce a mask pattern (see FIG. 11G).

(Dimension comparison with conventional blank)
The dimensional linearity was compared between the phase shift type mask blank (the arsenic doping amount of 10 14 atoms / cm ² ) and the conventional phase shift type mask blank thus manufactured (see FIG. 12). For the dimension measurement, LWM9000 (Leica) of a photomask length measurement SEM was used. According to this, it was confirmed that the pattern was formed with an accuracy close to the design dimension because the drop in the minute dimension was small compared to the conventional blank.

  Further, the dimensional uniformity was measured by arranging patterns having different aperture ratios over a wide range in the mask surface. FIG. 13A shows a schematic diagram of a pattern layout. Area A has an aperture ratio of 0%, B has an aperture ratio of 25%, C has an aperture ratio of 50%, D has an aperture ratio of 75%, and an LS (line and space) pattern having a pattern size of 1 μm is arranged therein. . FIG. 13B is a bubble diagram of the dimensional uniformity of a mask produced with a conventional blank, and FIG. 13C is a bubble diagram of the dimensional uniformity of a mask produced with the blank of Example 2 of the present invention. In this bubble diagram, the larger the bubble (circle), the greater the deviation from the average value. Fill (black) is on the positive side of the average value, and the hollow (white) is negative on the average value. It means that it is shifted to the side.

  From this result, it can be seen that the blank produced in Example 4 of the present invention has better dimensional uniformity when the photomask is produced than the conventional blank. The range value of uniformity was 4.9 nm in Example 4 compared to 9.6 nm for the conventional blank.

  The above-described invention can be used as a photomask blank serving as a photomask master and a manufacturing method thereof.

001 ... Photomask quartz substrate 002 ... Ion implanted halftone layer 003 ... Light shielding layer 004 ... Ion implanted light shielding layer 005 ... Hard mask layer 101 ... Photomask quartz substrate 102 ... MoSi light shielding layer 103 ... Cr hard mask layer 104 ... incident ions 105 ... heat treatment apparatus 106 ... etchant 107 during dry etching ... ion-implanted light-shielding layer 201 ... photomask quartz substrate 202 ... ion-implanted MoSi light-shielding layer 203 ... Cr hard mask layer 204 ... resist 301 ... photomask Quartz substrate 302 ... MoSi light shielding layer 303 ... Cr hard mask layer 304 ... Incident ions 305 ... Heat treatment apparatus 306 ... Etchant 307 during dry etching ... Ion implanted light shielding layer 401 ... Photomask quartz substrate 402 ... Ion implanted MoSi shielding Layer 403 ... Cr hard mask layer 404 ... resist

Claims (5)

In a photomask blank using a material containing silicon for a phase shift layer or a light shielding layer, these materials are doped with a Group 15 element such as phosphorus (P) or arsenic (As) as a trace amount of impurities. A photomask blank. 2. The photomask blank according to claim 1, wherein the impurity concentration in the unit volume of the Group 15 element is 10 <10> or more atoms / cm < ³ >. The photomask blank according to claim 1, wherein the photomask blank is MoSi, TaSi, ZrSi, Si, HfSi and oxides, nitrides, and oxynitrides thereof. The photomask blank manufacturing method according to claim 1, wherein a photomask quartz substrate is formed by sputtering or CVD to form a light shielding layer and / or phase shift layer, and then impurities such as ion implantation and thermal diffusion. A method of manufacturing a photomask blank, comprising a doping step and then a heat treatment step. In the ion implantation method according to claim 2, the acceleration energy is in the range of 10 keV to 200 keV, and the ion implantation amount per unit area is in the range of 10 7 atoms / cm ^{2 to} 10 17 atoms / cm ² . A method of manufacturing a photomask blank, which is performed

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