JP6564734B2 - Photomask blank and photomask manufacturing method - Google Patents

Description

  The present invention relates to a photomask blank that is a photomask material suitable for pattern transfer with exposure light having a wavelength of 200 nm or less, and a photomask manufacturing method using the photomask blank.

  High integration of large-scale integrated circuits is progressing for high-speed operation and low power consumption of semiconductor electronic devices, and advanced semiconductor microfabrication technology is an extremely important factor in the miniaturization of circuit patterns. It has become a technology. As such an elemental technology, for example, a thinning technology for a wiring pattern constituting a circuit and a miniaturizing technology for a contact hole pattern for wiring between layers constituting a cell are essential.

  High-level microfabrication is performed by a photolithography technique using a photomask, and the photomask is an important technique for miniaturization together with an exposure apparatus and a resist material. Therefore, for the purpose of realizing a photomask having the above-described thinned wiring pattern or miniaturized contact hole pattern, technological development for forming a finer and more accurate pattern on the photomask has been carried out. It has been advanced.

  Since photolithography when finely processing a semiconductor substrate uses a reduction projection method, the size of the pattern formed on the photomask is about four times the size of the pattern formed on the semiconductor substrate. This does not mean that the accuracy of the pattern formed on the photomask is relaxed, and it is required to form the photomask pattern with high accuracy.

  At present, the size of a circuit pattern drawn on a semiconductor substrate by photolithography has become considerably smaller than the wavelength of exposure light, so a photomask pattern in which the circuit pattern is enlarged four times as it is. Even if reduction exposure is performed using a photomask having a pattern formed thereon, the shape does not match the photomask pattern due to the influence of exposure light interference or the like.

  Therefore, as a super-resolution mask, so-called optical proximity effect correction (OPC) is performed, and an OPC mask to which an optical proximity effect correction technique that deteriorates transfer characteristics is applied, or the phase of adjacent patterns. A phase shift mask that makes the intensity distribution of incident light steep by changing the angle 180 ° is used. For example, some OPC masks are formed with an OPC pattern (hammer head, assist bar, etc.) having a size that is ½ or less of the circuit pattern. The phase shift mask includes a halftone phase shift mask, a Levenson type, and a chromeless type.

  In order to form a high-precision photomask pattern on a photomask substrate, it is necessary to pattern a resist film formed on the photomask blank with high accuracy. In order to form a mask pattern, generally, a photoresist film is formed on a photomask blank having a light-shielding film on a transparent substrate, and patterning is performed by irradiating the photoresist film with an electron beam or light. The photoresist film is developed to obtain a photoresist pattern. Then, the photomask pattern is obtained by patterning the light-shielding film using this photoresist pattern as an etching mask. In order to obtain a fine photomask pattern, it is effective to reduce the thickness of the photoresist film for the following reasons.

  If only the resist pattern is miniaturized without reducing the thickness of the resist film, the aspect ratio (ratio of resist film thickness to pattern width) of the resist portion that functions as an etching mask for the light-shielding film increases. In general, when the aspect ratio of a resist pattern increases, the pattern shape tends to deteriorate, and the pattern transfer accuracy to the light-shielding film decreases. In extreme cases, a part of the resist pattern may fall down or peel off, resulting in pattern omission. Therefore, as the photomask pattern becomes finer, it is necessary to reduce the film thickness of the resist used as an etching mask for light shielding film patterning so that the aspect ratio does not become too high. The aspect ratio is desirably 3 or less. For example, in order to form a resist pattern having a width of 70 nm, the resist film thickness is desirably 210 nm or less.

  By the way, many materials have been proposed as a light-shielding film material when patterning is performed using a photoresist pattern as an etching mask. In particular, a chromium simplex film or a chromium compound film containing chromium and at least one of nitrogen, oxygen, and carbon is used as a general light-shielding film material. For example, JP 2003-195479 A (Patent Document 1), JP 2003-195383 A (Patent Document 2), and Registered Utility Model No. 3093632 (Patent Document 3) disclose a photo for ArF excimer laser exposure. A configuration example of a photomask blank in which a light-shielding film having a light-shielding characteristic required for a mask blank is formed of a chromium compound film is disclosed.

  A light-shielding film that is a chromium compound film is generally patterned by chlorine-based dry etching containing oxygen, but in dry etching, an organic film such as a photoresist is often etched to a degree that cannot be ignored. For this reason, when a light-shielding film, which is a chromium-based compound film, is etched using a relatively thin resist film as a mask, the resist is damaged during this etching, and the shape of the resist pattern changes, and the original resist pattern is changed. It becomes difficult to accurately transfer the light-shielding film.

  As described above, there is a high technical barrier to simultaneously satisfy both high resolution, high patterning accuracy, and etching resistance in a photoresist that is an organic film. Therefore, in order to obtain high resolution, the photoresist film must be thinned. On the other hand, in order to ensure etching resistance in the etching process of the light-shielding film, the thinning of the photoresist film is limited. As a result, a trade-off relationship occurs between the high resolution and high patterning accuracy and the etching resistance. Therefore, in order to reduce the load on the photoresist to reduce the thickness and form a more accurate photomask pattern, the structure (film thickness, composition, etc.) of the light-shielding film to be patterned is improved. It is necessary to do.

  There have already been many studies on light-shielding film materials. For example, Japanese Patent Laid-Open No. 2001-312043 (Patent Document 4) discloses an example in which a metal film is used as a light-shielding film for ArF excimer laser exposure. Have been described. Among these, for example, tantalum is used as a light-shielding film and tantalum oxide is used as an antireflection film. In order to reduce the load on the photoresist when etching these two layers, These two layers are etched with a fluorine-based gas plasma with relatively little damage. However, even if such an etching condition is selected, there is a limit to reducing the load on the photoresist in order to etch the light shielding film and the antireflection film using only the photoresist as an etching mask. It is difficult to sufficiently satisfy the requirement for forming a photomask pattern with high accuracy.

As described above, in the conventional photomask blank structure, it is difficult to satisfactorily meet the demand for forming a fine photomask pattern on the light-shielding film with high accuracy. This is particularly serious in photolithography in which light having a wavelength of 200 nm or less (ArF excimer laser: 193 nm, F ₂ laser: 157 nm, etc.), which requires a short exposure wavelength and high resolution, is used as exposure light.

  In addition, in order to reduce the load on the photoresist and form a fine photomask pattern with high accuracy, a light-shielding film that has a high etching rate in chlorine-based dry etching is mainly composed of chromium and is made of a light element. A light-shielding film to which certain O and N are added has been proposed (Japanese Patent Laid-Open No. 2007-33470 (Patent Document 5)). However, in a chromium film containing a light element, as the light element content increases, The conductivity is reduced.

On the other hand, an exposure method using an electron beam (EB) has become the mainstream in patterning a resist when manufacturing a photomask. Further, for the electron beam, a high acceleration voltage of 50 keV is adopted in order to enable further miniaturization. Further, while the resist proceeds to lower sensitivity in order to obtain high resolution, the electron beam current density of the electron beam lithography system is increased from 40 A / cm ² to 800 A / cm ² from the viewpoint of improving productivity. Remarkably higher density is being promoted.

  When an electron beam is irradiated to an electrically floating photomask blank, the surface of the photomask blank is charged to a negative potential due to the accumulation of electrons, and the electron beam trajectory is bent due to the electric field due to the charging, The drawing position accuracy decreases. Therefore, in the electron beam drawing apparatus that performs high-energy and high-density electron beam drawing as described above, the photomask blank is grounded to perform electron beam drawing. For example, Japanese Unexamined Patent Application Publication No. 2014-216407 ( Patent Document 6) proposes a mechanism for grounding (grounding) a photomask blank using a ground pin.

However, when the grounding resistance (earth resistance) is large, the potential on the surface of the photomask blank increases by the product of the current flowing through the ground and the grounding resistance, and the drawing position accuracy decreases. In addition, for example, when the grounding is not sufficiently ensured or when the photomask blank is not conductive, the grounding resistance becomes very large or infinite, and it is not possible to perform electron beam drawing in this state. There is a possibility that the apparatus will be contaminated by causing abnormal discharge or substrate damage in the drawing vacuum chamber. Therefore, the electron beam drawing apparatus has a mechanism for measuring the earth resistance before drawing, and when the threshold value of the earth resistance is set to 1.5 × 10 ⁵ Ω, for example, and the earth resistance exceeds the threshold value, before the drawing is performed. It has a function to stop the drawing process.

  Further, in the portion that contacts the photomask blank and is grounded, particles generated when penetrating the electron beam resist are a problem. Many proposals have also been made for this problem. For example, in the above-mentioned Japanese Patent Application Laid-Open No. 2014-216407 (Patent Document 6), studies are made to suppress scattering of particles by a cover surrounding the ground pin. . In general, for grounding, a smaller ground mark left when penetrating an electron beam resist is superior in terms of suppressing particles. Therefore, for example, the shape of the ground pin has been improved from a blade type that obtains grounding by line contact to a pin type that obtains grounding by point contact, and even after contact of the ground pin, the expansion of ground marks due to misalignment is suppressed. Improvements are underway.

JP 2003-195479 A JP 2003-195483 A Registered Utility Model No. 3093632 JP 2001-312043 A JP 2007-33470 A JP, 2014-216407, A JP-A 63-85553

  In the electron beam drawing apparatus, when the earth pin is brought into contact with the photomask blank, in the conventional method, the photomask blank, the earth pin, or both of the photomask blank and the earth pin are mechanically moved by a motor or the like to be brought into contact. At the time of contact and after contact, scratch marks of several μm are generated in the laminated film on the photomask blank surface due to the influence of mechanical vibration or the like. In this case, since the laminated film on the surface of the photomask blank is broken at the contact portion by the ground pin, if the ground pin is brought into contact with the conductive layer included in the laminated film, grounding is ensured with a sufficiently low resistance value required. It was easy. On the other hand, in an electron beam lithography system in which ground marks are observed as small spots and particle scattering is small, even if the laminated film of the photomask blank includes a conductive layer, the grounding is performed with a sufficiently low resistance value. It was confirmed that there are cases where it cannot be secured.

  However, regarding photomask blanks and photomasks, as a countermeasure against charge-up in an electron beam lithography system, a conductive layer satisfying the recommended value of the sheet resistance measurement value by the four-terminal method has been included in the laminated film so far. Although many proposals have been made, there has been no example of examining grounding securing in an electron beam lithography apparatus from the relationship between resistivity and film thickness of a resistive layer in a laminated film having a resistive layer formed on a conductive layer.

  The present invention has been made in order to solve the above-described problems. Optical characteristics required when a photomask is used, for example, a sufficient optical density at the exposure wavelength and a wavelength region longer than the exposure wavelength. When drawing a mask pattern on a photomask blank with sufficient reflectivity using an electron beam drawing device, for example, an electron beam drawing device in which grounding is point contact and earth marks are observed as dots is used. It is an object of the present invention to provide a photomax blank that can ensure grounding with a sufficiently low resistance value required, and a photomask manufacturing method using the photomask blank.

As a result of intensive studies in order to solve the above problems, the present inventors, as a result, a transparent substrate, a resistance layer having a resistivity of 0.1 Ω · cm or more formed on the outermost portion on the side away from the transparent substrate, In a photomask blank having a resistivity formed in contact with the transparent substrate side of the resistance layer of less than 0.1 Ω · cm and having a conductive layer formed of a material containing chromium , the resistance layer and the conductive layer If each of the resistivity and thickness is configured to satisfy a predetermined formula and a photomask is manufactured from such a photomask blank, the optical characteristics required when the photomask is formed, for example, at the exposure wavelength With a sufficient optical density and sufficient reflectivity in the wavelength range longer than the exposure wavelength, when drawing a mask pattern using an electron beam lithography system, the ground is used as a point contact. Scratches are seen as dots Even when using the observed electron beam lithography system, grounding can be secured with a sufficiently low resistance value required, and pattern transfer is performed with exposure light having a wavelength required to form a fine pattern of 200 nm or less. The present invention has been found to be effective for the production of a photomask.

Accordingly, the present invention provides the following photomask blank and photomask manufacturing method.
Claim 1:
It is a photomask blank that is a material for manufacturing a photomask in which pattern transfer is performed with exposure light having a wavelength of 200 nm or less,
The photomask blank is in contact with a transparent substrate, a resistance layer having a resistivity of 0.1 Ω · cm or more formed on the outermost part on the side away from the transparent substrate, and the transparent substrate side of the resistance layer. Having a formed resistivity of less than 0.1 Ω · cm , and a conductive layer formed of a material containing chromium ,
The resistance layer is composed of a single layer or a multilayer composed of two or more sublayers,
Resistivity of each of the single layer or sub-layer (unit is Ω · cm, if the value of resistivity is 7.5 × 10 ⁵ (Ω · cm) or less, the value is 7.5 × 10 ⁵ If the resistance layer is a single layer, the resistivity and the thickness are 7.5 × 10 ⁵ (Ω · cm) if it exceeds (Ω · cm) and the thickness (unit is cm). When the resistance layer is a multilayer, the resistance index A, which is the sum of the product of resistivity and thickness in each sub-layer, is expressed by the following formula (1)
1.5 × 10 ⁵ ≧ A × α + ρ _C / d _C (1)
(Where α is a constant (unit is cm ⁻² ), ρ _C is the resistivity of the conductive layer (unit is Ω · cm), d _C is the thickness of the conductive layer (unit is cm) Is)
A photomask blank characterized by satisfying
Claim 2:
The photomask blank according to claim 1, wherein the conductive layer has a sheet resistance value of 1 × 10 ⁴ Ω / □ or less.
Claim 3:
3. The photomask blank according to claim 1, further comprising a phase shift film formed of a material containing silicon or a material containing silicon and molybdenum between the transparent substrate and the conductive layer.
Claim 4:
The photomask blank according to claim 1 or 2, further comprising a light shielding film formed of a material containing silicon or a material containing silicon and molybdenum between the transparent substrate and the conductive layer.
Claim 5:
5. The photomask blank according to claim 1, wherein the resistance layer is formed of a material obtained by adding a light element selected from oxygen, nitrogen, and carbon to a metal or an alloy.
Claim 6:
In the process of processing into a photomask, the grounding terminal is brought into contact with the resistance layer, and the grounding terminal is grounded by pressing the resistance layer to such an extent that conduction between the grounding terminal and the conductive layer is obtained. The photomask blank according to any one of claims 1 to 5, wherein the photomask blank is a photomask blank to be performed.
Claim 7:
A transparent substrate, a resistance layer having a resistivity of 0.1 Ω · cm or more formed on the outermost portion on the side away from the transparent substrate, and a resistivity formed in contact with the transparent substrate side of the resistance layer And a conductive layer made of a material containing chromium, and the resistance layer is a single layer or a multilayer composed of two or more sublayers. A method of manufacturing a photomask in which pattern transfer is performed with exposure light having a wavelength of 200 nm or less from a mask blank,
Resistivity of each of the single layer or sub-layer (unit is Ω · cm, if the value of resistivity is 7.5 × 10 ⁵ (Ω · cm) or less, the value is 7.5 × 10 ⁵ If the resistance layer is a single layer, the resistivity and the thickness are 7.5 × 10 ⁵ (Ω · cm) if it exceeds (Ω · cm) and the thickness (unit is cm). When the resistance layer is a multilayer, the resistance index A, which is the sum of the product of resistivity and thickness in each sub-layer, is expressed by the following formula (1)
1.5 × 10 ⁵ ≧ A × α + ρ _C / d _C (1)
(Where α is a constant (unit is cm ⁻² ), ρ _C is the resistivity of the conductive layer (unit is Ω · cm), d _C is the thickness of the conductive layer (unit is cm) Is)
Preparing a photomask blank that satisfies
The step of forming a photoresist film on the resistance layer, and the ground terminal is brought into contact with the resistance layer, and the ground layer is grounded by pressing the resistance layer to such an extent that conduction between the ground terminal and the conductive layer is obtained. A method of manufacturing a photomask comprising the step of drawing an electron beam on the photoresist film.

  According to the present invention, when a mask pattern is drawn using an electron beam drawing apparatus on a photomask blank in which a required optical characteristic when a photomask is formed is secured with a laminated film of a thinner film, the ground is point-contacted. Even when using an electron beam lithography system, the grounding is secured with a sufficiently low resistance value, and the pattern is transferred with high drawing position accuracy by suppressing the charging of the resist film during electron beam lithography. can do.

It is sectional drawing which shows an example of a structure of the photomask blank of this invention. It is sectional drawing which shows the other example of a structure of the photomask blank of this invention. It is sectional drawing which shows another example of a structure of the photomask blank of this invention. The main flow of current when the probe is brought into contact with the surface of the resistance layer and the electrical characteristics are measured is shown, (A) is a plan view showing a state where two probes are in contact with the surface of the resistance layer, (B) FIG. 3 is a longitudinal sectional view passing through the centers of two probes. It is a schematic diagram of the equivalent circuit of the circuit which flows through the surface part of a photomask blank.

Hereinafter, the present invention will be described in detail.
The photomask blank of the present invention is used as a material for manufacturing a photomask on which pattern transfer is performed with exposure light having a wavelength of 200 nm or less, for example, ArF excimer laser (193 nm), F ₂ laser (157 nm), or the like. In a photomask in which pattern transfer is performed with exposure light having a wavelength of 200 nm or less, for example, light with a wavelength of 257 nm is used for defect inspection, and light with a wavelength of 405 nm (solid laser diode) is used for reading an alignment mark. Applies.

In the photomask blank of the present invention, in the process of processing into a photomask, a ground terminal (ground pin) is brought into contact with the resistance layer, and the resistance layer is pressed to such an extent that conduction between the ground terminal and the conductive layer is obtained with the ground terminal. Accordingly, for example, the resistance value is set to 1.5 × 10 ⁵ Ω or less, which is suitable for a photomask blank for performing electron beam drawing by grounding.

  The photomask blank of the present invention includes a transparent substrate such as a quartz substrate, a resistance layer having a resistivity of 0.1 Ω · cm or more formed on the outermost portion on the side away from the transparent substrate, and a transparent substrate side of the resistance layer And a conductive layer having a resistivity of less than 0.1 Ω · cm formed in contact with the substrate. As long as the combination of the resistance layer and the conductive layer satisfies the above-mentioned range and satisfies the positional relationship between the transparent substrate and the transparent substrate, the film constituting the resistance layer and the conductive layer may be a film having any function. For example, an optical film such as a light-shielding film, an antireflection film, a phase shift film such as a halftone phase shift film, or a processing auxiliary film such as an etching mask film or an etching stopper film may be used.

In the present invention, in particular, the layer in contact with the ground terminal of the electronic drawing apparatus, specifically, the case where the resistivity of the layer on which the electron beam resist film is formed is high, the resistance layer is the most from the substrate. Those arranged on the outermost part apart from each other are targeted. The resistance layer may be composed of a single layer or a multilayer composed of two or more sub-layers, and in the case of a single layer, the layer is composed of multiple layers. In this case, the resistivity of each sublayer is 0.1 Ω · cm (1 × 10 ⁻¹ Ω · cm) or more, but ¹ Ω · cm or more, and further 10 Ω · cm (1 × 10 10). ¹ Ω · cm) or more.

On the other hand, since the conductive layer is a layer that provides conductivity for preventing charging during electronic drawing when the ground terminal of the electronic drawing device contacts the resistance layer, the resistivity is 0.1 Ω · cm (1 × 10 ⁻¹ Ω · cm), preferably 1 × 10 ⁻² Ω · cm or less, more preferably 1 × 10 ⁻³ Ω · cm or less, and must be disposed in contact with the resistance layer. It is. The sheet resistance value of this conductive layer is preferably 1 × 10 ⁴ Ω / □ or less, particularly preferably 5 × 10 ³ Ω / □ or less. The conductive layer may be a part of the multilayered film, that is, a part of the multilayered film formed in contact with the resistive layer on the side of the resistive layer. The conductive layer may be formed directly on the transparent substrate without any other film, or may be formed via another film, and the conductivity of the other film is not limited.

  The material of the optical film and processing auxiliary film constituting the photomask blank can be chromium (Cr), zirconium (Zr), tantalum (depending on required optical characteristics, etching characteristics, and electrical characteristics such as conductivity). Transition metals such as Ta), titanium (Ti), molybdenum (Mo), tungsten (W), iron (Fe), nickel (Ni), cobalt (Co), silicon (Si), germanium (Ge), aluminum (Al And the like, and alloys thereof, oxides of these metals or alloys, nitrides, carbides, oxynitrides, oxycarbides, nitride carbides, oxynitride carbides, and other materials are used. Among these metals, chromium (Cr), molybdenum (Mo), and silicon (Si) are particularly preferably used.

  In general, a metal or an alloy, a compound of a metal or alloy with a small amount of light elements such as oxygen, nitrogen, and carbon has a low resistivity, and it is preferable to use a film made of such a material as a conductive layer. Yes, the photomask blank can be made conductive by including such a conductive layer in the photomask blank.

  However, the optical characteristics and etching characteristics of the metal material or the alloy material can be changed by increasing the addition amount of the light element. For example, in a photomask blank for manufacturing a photomask for which pattern transfer is performed with exposure light having a wavelength of 200 nm or less, a material containing chromium is used. Among the materials containing chromium, chromium alone, A chromium compound with a small amount of light elements such as oxygen, nitrogen, and carbon is preferably used as a light shielding film because it effectively provides light shielding properties.

  On the other hand, a chromium-containing material can increase the etching rate in oxygen-containing chlorine-based dry etching that is commonly used for etching a chromium-containing material by adding a light element. This enables high-speed etching of the light-shielding film, and can advantageously reduce the load on a photoresist film such as a chemically amplified resist used as an etching mask during etching using the photoresist film.

  Furthermore, a film having a high transmittance can be obtained by increasing the amount of light element added to the chromium-containing material. A film formed of a chromium compound with a small amount of chromium alone or a light element added has a high reflectance, which may be disadvantageous in photomask blank or photomask defect inspection. Therefore, in general, a film formed of a material containing chromium in which the amount of light element added is increased is used as an antireflection film. Specifically, an antireflection film is provided on one or both of the transparent substrate side and the side away from the transparent substrate of the light shielding film.

  However, when a light element is added to a metal material or an alloy material, the resistivity increases and the conductivity decreases as the addition amount increases. Therefore, a film formed using such a material is a photomask. When it is formed on the outermost part on the side away from the blank transparent substrate, specifically, when it is formed as a layer on which the electron beam resist film is formed, charge-up occurs during electron beam exposure. The problem is that the drawing accuracy is lowered. In particular, when oxygen is added as a light element, the resistivity is remarkably increased and a high resistance film is likely to be obtained.

  The photomask blank shown in FIG. 1 is a cross-sectional view of an example of the photomask blank having such a configuration. The photomask blank 10 is a phase shift mask blank, and a phase shift film 2, a back surface side antireflection film 3, a light shielding film 4, and a surface side antireflection film 5 are sequentially laminated on the transparent substrate 1. In this case, for example, the light-shielding film 4 can be a conductive layer and the front-side antireflection film 5 can be a single resistance layer. In this case, the phase shift film 2 and the back-side antireflection film 3 can be It corresponds to the film. As the photomask blank having such a configuration, specifically, a conductive layer formed of a material containing chromium is suitable. For example, silicon is contained on the transparent substrate 1 such as a quartz substrate. Or a phase shift film 2 formed of a material containing silicon and molybdenum, a back-side antireflection film 3 formed of a chromium compound, a light shielding film 4 formed of chromium alone or a chromium compound, and a chromium compound. A phase shift mask blank in which the formed front-side antireflection film 5 is sequentially laminated is mentioned.

  Further, a hard mask film may be further provided as a processing auxiliary film in etching the light shielding film or the antireflection film. By using the hard mask film, the photoresist film can be thinned, and it becomes possible to cope with further miniaturization of the pattern. In addition, it is preferable to make the photoresist thin, because the electron beam drawing time can be shortened and, therefore, charge-up is suppressed. For example, when the light-shielding film and the antireflection film are formed of a material containing chromium, the hard mask film is etched quickly by fluorine-based dry etching, and the etching rate is extremely slow by chlorine-based dry etching containing oxygen. A material, i.e. a material that is not substantially etched, is used. As a material of such a hard mask film, a material containing silicon is suitable, for example, a silicon simple substance, a compound containing silicon and a light element such as oxygen, nitrogen, carbon, etc., and in addition to chromium A compound to which a transition metal such as molybdenum, tantalum, tungsten, zirconium, titanium or the like is added is preferable.

  However, in the case of the hard mask film, the etching characteristics may be advantageous due to the increase in the amount of light elements added to the metal material or alloy material, as in the case of the light shielding film or antireflection film described above. The problem of becoming scarce arises.

  The photomask blank shown in FIG. 2 is a cross-sectional view of an example of the photomask blank having such a configuration. The photomask blank 10 is a phase shift mask blank, and a phase shift film 2, a back surface side antireflection film 3, a light shielding film 4, a surface side antireflection film 5, and an etching mask film 6 are sequentially laminated on the transparent substrate 1. Has been. In this case, for example, the light-shielding film 4 can be a resistance layer having a two-layer structure in which the conductive layer and the surface-side antireflection film 5 and the etching mask film 6 are composed of two sublayers. 2 and the back side antireflection film 3 correspond to other films. As the photomask blank having such a configuration, specifically, a conductive layer formed of a material containing chromium is suitable. For example, silicon is contained on the transparent substrate 1 such as a quartz substrate. A phase shift film 2 made of a material to contain or silicon and molybdenum, a back side antireflection film 3 made of a chromium compound, a light shielding film 4 made of chromium alone or a chromium compound, and made of a chromium compound There may be mentioned a phase shift mask blank in which the surface side antireflection film 5 and the etching mask film 6 formed of silicon oxide (SiO) are sequentially laminated.

  Furthermore, when a hard mask film is provided on these as a processing auxiliary film in etching of a light shielding film or an antireflection film, the etching mask film is made of a metal or an alloy or a compound of a metal or an alloy with a small amount of light elements added. When formed, the film formed of such a material can ensure conductivity, but becomes a highly reflective film, which may be disadvantageous in photomask blank and photomask defect inspection, etc. An antireflection film may be further formed on the substrate. In the antireflection film in this case, similarly to the antireflection film formed of the above-described chromium-containing material, a material with an increased content of light elements is used. The increase in the amount causes a problem of poor conductivity.

  The photomask blank shown in FIG. 3 is a cross-sectional view of an example of the photomask blank having such a configuration. The photomask blank 10 is a photomask blank for a binary mask or a Levenson type phase shift mask, and a light shielding film 4, an etching mask film 6, and a surface side antireflection film 5 are sequentially laminated on the transparent substrate 1. Yes. In this case, for example, the etching mask film 6 can be a conductive layer, and the front-side antireflection film 5 can be a single resistance layer. In this case, the light shielding film 4 corresponds to another film. As the photomask blank having such a configuration, specifically, a conductive layer formed of a material containing chromium is suitable. For example, silicon is contained on the transparent substrate 1 such as a quartz substrate. A light-shielding film 4 made of a material containing silicon or molybdenum, an etching mask film 6 made of chromium alone or a chromium compound, and a surface-side antireflection film 5 made of a chromium compound. Photomask blanks.

In the photomask blank of the present invention, in the photomask blank having such a resistance layer and a conductive layer, the resistance layer is a single layer with respect to the resistivity and thickness of each single layer or sublayer constituting the resistance layer. If the resistance layer is a multilayer, the sum of the product of the resistivity and thickness in each sub-layer is the resistance index A, and the resistance index A is expressed by the following formula (1).
1.5 × 10 ⁵ ≧ A × α + ρ _C / d _C (1)
(Where α is a constant (unit is cm ⁻² ) and, as will be described later, is a constant related to the cross-sectional area S across the path of current flow through the resistance layer, and ρ _C is the conductive layer. (The unit is Ω · cm), d _C is the thickness of the conductive layer (unit is cm))
The resistance layer and the conductive layer are configured to satisfy the above. Here, as for the resistivity of the resistance layer, the unit is Ω · cm, and when the resistivity value is 7.5 × 10 ⁵ (Ω · cm) or less, the value is applied as it is. When it exceeds 5 × 10 ⁵ (Ω · cm), 7.5 × 10 ⁵ (Ω · cm) is applied as the resistivity value. The unit of thickness is cm.

When the resistance index A is shown more specifically, the following formula (1-1)
A = ρ _I1 × d _I1 +... + Ρ _In × d _In (1-1)
(Where ρ _I1 is the resistivity of the first layer (Ω · cm), d _I1 is the thickness of the first layer (cm), ρ _In is the resistivity of the nth layer (Ω · cm), _dIn is the thickness (cm) of the nth layer)
It can be expressed as That is, when the number of layers constituting the resistance layer is n, there is a product of resistivity and thickness according to the number n, and the sum of these is the resistance index A. By configuring the resistance layer and the conductive layer so as to satisfy the above formula (1), when processing with an electron beam lithography apparatus, a photomask blank is obtained in which high-precision rendering performance is ensured. If a photomask is manufactured from a blank, a photomask having a mask pattern with higher dimensional accuracy can be obtained.

  FIG. 4 shows the main flow of current when the probe is brought into contact with the surface of a resistive layer such as the photomask blank shown in FIG. 1 and the electrical characteristics are measured. 4A is a plan view showing a state in which the two probes 21 and 22 are in contact with the surface of the resistance layer 32 (surface-side antireflection film 5) of the photomask blank 10, and FIG. It is a longitudinal cross-sectional view which passes through the center of the probes 21 and 22. In this case, the position where the two probes 21 and 22 are brought into contact is the outer peripheral edge of the surface of the photomask blank 10, that is, the surface of the resistance layer 32, and a pair of opposing two pieces of the square resistance layer 32. It is near the center part of each. When the two probes 21 and 22 contact the surface of the resistance layer 32 without mechanically penetrating the resistance layer 32, the current path 23 between the two probes 21 and 22 is directly below the one probe 21. It passes through the resistance layer 32 toward the conductive layer 31 (light-shielding film 4), reaches the conductive layer 31, flows in the conductive layer 31 toward the other probe 22, and further directly under the other probe 22. And flows to the other probe 22. The current flowing through the resistance layer 32 can be ignored because the resistance of the resistance layer 32 is higher than that of the conductive layer 31.

FIG. 5 shows a schematic diagram of an equivalent circuit (resistance circuit) of a circuit flowing on the surface portion of such a photomask blank. In FIG. 4, the resistance (R _I1 (Ω)) of the path from one probe 21 to the conductive layer 31 vertically passing through the resistance layer 32 is 24a, and the resistance (R of the path passing through the conductive layer 31 is R _C (Ω)) is 24b, and the resistance (R _I1 ′ (Ω)) of the path from the conductive layer 31 to the other probe 22 through the resistance layer 32 vertically is 24c. Here, if the contact areas of the two probes 21 and 22 to the resistance layer 32 are the same, the thickness of the resistance layer 32 is constant, and therefore R _I1 = R _I1 ′.

Here, the equivalent circuit is a series resistance circuit of each resistor, and the resistance value of the photomask blank needs to be 1.5 × 10 ⁵ Ω or less.
1.5 × 10 ⁵ ≧ 2 × R _I1 + R _C (2)
It is necessary to satisfy.

Further, in the case of a two-layer structure in which the resistance layer is composed of two sublayers as in the photomask blank shown in FIG. 2, the resistance of the path passing through each sublayer and the inside of the conductive layer are passed. Since the sum of the resistance of the path is 5 × 10 ⁵ Ω or less, the following formula (2-1)
1.5 × 10 ⁵ ≧ 2 × (R _I1 + R _I2 ) + R _C (2-1)
In the case of a multilayer structure in which the resistance layer is composed of n sublayers, the following formula (2-2)
1.5 × 10 ⁵ ≧ 2 × (R _I1 +... + R _In ) + R _C (2-2)
It will be sufficient if it satisfies. In the formula, R _I2 and R _In correspond to R _I1 and R _I1 ′ and are the resistance (Ω) of the second layer and the resistance (Ω) of the nth layer, respectively.

Substituting into the above equation (2-2) the resistivity, film thickness, and cross-sectional area S through which the current flows through the resistance layer, the following equation (2-3)
1.5 × 10 ⁵ ≧ 2 × (ρ _I1 × d _I1 +... + Ρ _In × d _In ) / S + ρ _C / d _C (2-3)
Then, 2 / S = α, and the above formula (1) of the present invention is derived from the above formula (1-1). Here, the contact areas of the two probes with the resistance layer are usually the same, and the cross-sectional area S coincides with the contact area of one or the other probe. For example, assuming that the contact surfaces of the two probes with the resistance layer are circular surfaces each having a diameter of 50 μm, the cross-sectional area S is about 2 × 10 ⁻⁵ (cm ² ), and α is 1 × 10 ⁵ (cm ² ). ^-2 ) The value of α can be determined, for example, from the size of the contact area of the ground pin of the electron beam drawing apparatus to the photomask blank, and may be, for example, 1 × 10 ² to 1 × 10 ⁸ (cm ⁻² ). As the contact area between the probe and the photomask blank is smaller, defects are suppressed. However, if the contact area is too small, the probe life may be shortened. For example, in a photomask blank corresponding to a photomask of a generation of 30 nm or less, the resistance index is 1 × 10 ⁴ to 1 × 10 ⁶ (cm ⁻² ), particularly 1 × 10 ⁵ (cm ⁻² ). It is preferable to configure the resistance layer and the conductive layer so that A satisfies the above formula (1).

  Other films that may be provided between the transparent substrate and the conductive layer include optical films such as light shielding films, antireflection films, and phase shift films such as halftone phase shift films. A film that functions as an optical film remaining on the photomask is also included as a film that functions as an etching stopper film or an etching mask film.

  Specifically, as the phase shift film provided between the transparent substrate and the conductive layer, for example, when the conductive layer is made of a material containing chromium, or the conductive layer and the resistance layer are partially or entirely made of chromium. In the case of a material containing silicon, a phase shift film formed of a material containing silicon or a material containing silicon and a transition metal other than chromium, particularly molybdenum, is preferable. Examples of such a material include silicon alone, silicon, and a compound containing light elements such as oxygen, nitrogen, and carbon, in particular, one or both of oxygen and nitrogen, and further, transition metals other than chromium, for example, Molybdenum, tantalum, tungsten, zirconium, titanium, and the like, preferably a compound to which molybdenum is added is suitable. In the case of a photomask blank having such a phase shift film, the thickness of the light shielding film or the antireflection film can be further reduced as compared with a photomask blank not using the phase shift film. In this case, the light shielding property necessary for the photomask can be obtained by setting the total optical density of the light shielding film or the light shielding film and the antireflection film and the phase shift film to 2.0 or more, preferably 3.0 or more. Can do.

  Further, as a light shielding film provided between the transparent substrate and the conductive layer, specifically, for example, when the conductive layer is made of a material containing chromium, or a part or all of the conductive layer and the resistance layer In the case of using a material containing chromium, a light-shielding film formed of a material containing silicon or a material containing silicon and a transition metal other than chromium, particularly molybdenum, is preferable. As such a material, the same material as the phase shift film mentioned above is mentioned.

  As a method for forming a thin film such as an optical film or a processing auxiliary film on a photomask blank, film formation by sputtering is preferable because a film having high in-plane uniformity of optical characteristics and few defects can be obtained.

  In addition, an organic conductive film may be provided on the surface of the resist film when patterning by forming a chemically amplified resist film or the like on the photomask blank in order to perform drawing with an electron beam during photomask fabrication. In this way, it is possible to further suppress charge-up during electron beam drawing.

  In the present invention, the photomask includes a step of preparing the above-described photomask blank, a step of forming a photoresist film on the resistance layer, a ground terminal in contact with the resistance layer, the ground terminal, the ground terminal and the conductive layer. And a step of drawing an electron beam by grounding by pressing the resistance layer to such an extent that conduction with the electrode can be obtained. In addition, from a photoresist film drawn with an electron beam, a resist pattern can be formed by a conventional method, and patterning of thin films such as an optical film and a processing auxiliary film formed on a photomask blank using the resist pattern, It can be carried out by a known method such as chlorine dry etching or fluorine dry etching.

In order to escape the charge on the surface of the photomask blank during electron beam drawing, the ground terminal is brought into contact with the outer peripheral edge of the surface of the photomask blank installed in the electron beam drawing apparatus. In order to prevent this, the resist film on the outer peripheral edge of the photomask blank surface may be peeled off. When an organic conductive film is provided, the resist film and the organic conductive film on the outer peripheral edge of the photomask blank surface are peeled off. do it. If it does in this way, a ground terminal and a resistance layer can be made to contact directly and a charge will be removed rapidly. Specifically, for example, a resist film is formed on the surface of the photomask blank, that is, on the surface of the resistance layer , the resist film on the outer peripheral edge of the surface of the resistance layer is peeled off, and further, an organic conductive film And the outer peripheral edge of the surface of the organic conductive film may be peeled off.

  In addition, the ground terminal is connected by forming an organic conductive film up to the outer peripheral edge of the photomask blank, and without removing the organic conductive film at the edge, the ground terminal of the electron beam exposure machine is connected to this portion. It can also be set as the structure made to contact, or it can also be set as the structure which makes a grounding terminal contact a resistance layer, without providing an organic electroconductive film | membrane.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

[Examples 1 to 3, Comparative Examples 1 and 2]
By DC magnetron sputtering film formation, a metal chromium target is used on a 152 mm square, 6 mm thick quartz substrate, Ar gas is introduced at 10 sccm, O ₂ gas is introduced at 15 sccm, and N ₂ gas is introduced at a flow rate of 30 sccm. Thus, a high-resistance translucent antireflection film was formed. Next, a metal chromium target is used, Ar gas is introduced as a sputtering gas at a flow rate of 10 sccm, O ₂ gas is introduced at ₂ sccm, and N ₂ gas is introduced at a flow rate of 15 sccm. A light-shielding film was formed. Furthermore, a metal chromium target is used, and Ar gas is introduced at a flow rate of 11 sccm, O ₂ gas is introduced at 16 sccm, and N ₂ gas is introduced at a flow rate of 30 sccm, which corresponds to a single resistance layer (I1 layer). A high-resistance translucent antireflection film was formed to obtain a photomask blank having a laminated film composed of three layers.

[Example 4]
By DC magnetron sputtering film formation, a metal chromium target is used on a 152 mm square and 6 mm thick quartz substrate, Ar gas is introduced at 10 sccm, O ₂ gas is introduced at 11 sccm, and N ₂ gas is introduced at a flow rate of 20 sccm. Thus, a high-resistance translucent antireflection film was formed. Next, a metal chromium target is used, Ar gas is introduced at 20 sccm, O ₂ gas is introduced at a flow rate of ₂ sccm, and N ₂ gas is introduced at a flow rate of ₂ sccm as a sputtering gas. A light-shielding film was formed. Furthermore, using a metal chromium target, Ar gas is introduced at a flow rate of 12 sccm, O ₂ gas is introduced at 11 sccm, and N ₂ gas is introduced at a flow rate of 30 sccm, which corresponds to a single resistance layer (I1 layer). A high-resistance translucent antireflection film was formed to obtain a photomask blank having a laminated film composed of three layers.

[Example 5]
By DC magnetron sputtering film formation, a metal chromium target is used on a 152 mm square, 6 mm thick quartz substrate, Ar gas is introduced at 10 sccm, O ₂ gas is introduced at 15 sccm, and N ₂ gas is introduced at a flow rate of 30 sccm. Thus, a high-resistance translucent antireflection film was formed. Next, a metal chromium target is used, Ar gas is introduced as a sputtering gas at a flow rate of 10 sccm, O ₂ gas is introduced at ₂ sccm, and N ₂ gas is introduced at a flow rate of 15 sccm. A light-shielding film was formed. Next, a metal chrome target is used as a sputtering gas, Ar gas is introduced at a flow rate of 11 sccm, O ₂ gas is introduced at 16 sccm, and N ₂ gas is introduced at a flow rate of 30 sccm. A corresponding high-resistance translucent antireflection film was formed. Further, a high resistance etching mask film corresponding to a sublayer (I2 layer) of the resistance layer is formed by using a silicon target and introducing Ar gas at a flow rate of 18 sccm and O ₂ gas as a sputtering gas at a flow rate of 5 sccm. And a photomask blank having a laminated film consisting of four layers was obtained.

[Comparative Example 3]
By DC magnetron sputtering film formation, a metal chromium target is used on a 152 mm square and 6 mm thick quartz substrate, Ar gas is introduced at 10 sccm, O ₂ gas is introduced at 11 sccm, and N ₂ gas is introduced at a flow rate of 20 sccm. Thus, a high-resistance translucent antireflection film was formed. Next, a metal chromium target is used, Ar gas is introduced at 20 sccm, O ₂ gas is introduced at a flow rate of ₂ sccm, and N ₂ gas is introduced at a flow rate of ₂ sccm as a sputtering gas. A light-shielding film was formed. Next, a metal chromium target is used thereon, and Ar gas is introduced at a flow rate of 12 sccm, O ₂ gas is introduced at 11 sccm, and N ₂ gas is introduced at a flow rate of 30 sccm, thereby forming a sublayer (I1 layer) of the resistance layer. A corresponding high-resistance translucent antireflection film was formed. Further, a high resistance etching mask film corresponding to the sublayer (I2 layer) of the resistance layer is formed by using a silicon target and introducing Ar gas as sputtering gas at a flow rate of 5 sccm and O ₂ gas at 50 sccm. And a photomask blank having a laminated film consisting of four layers was obtained.

In the above examples and comparative examples, the thicknesses of the C layer, the I1 layer, and the I2 layer were adjusted to the thickness shown in Table 1 by adjusting the film formation time. Table 1 shows the results of the resistivity and sheet resistance of the C layer, the I1 layer, and the I2 layer obtained from the electrical characteristics measured using the four-terminal method. Table 1 also shows the result of calculating the value corresponding to the right side of the above formula (1) from the thickness and resistivity of each layer. The constant α in the above formula (1) was set to 1 × 10 ⁵ (cm ⁻² ) based on the contact area of the ground pin of the electron beam drawing apparatus to the photomask blank. As shown in Table 1, all the examples satisfy the formula (1), but none of the comparative examples satisfies the formula (1).

Next, the resistance value between earth | grounds was measured by making an earth pin contact with a photomask blank using the electron beam drawing apparatus. This electron beam drawing apparatus is an electron beam drawing apparatus in which grounding is observed as a point contact and an earth mark is observed as a point. As a result, in each example, a resistance value of 1.5 × 10 ⁵ Ω or less was obtained, and grounding was ensured with a sufficiently low resistance value required. On the other hand, in each of the comparative examples, the resistance value was higher than 1.5 × 10 ⁵ Ω or the resistance value could not be measured correctly. This means that the required grounding with a sufficiently low resistance value has not been obtained and the electrical characteristics are in a poor state. In such a photomask blank, abnormal discharge or a substrate is generated in the drawing vacuum chamber. It can cause damage and contaminate the equipment.

  From the above results, the resistivity and thickness of the conductive layer and the resistivity and thickness of the resistive layer provided on the conductive layer satisfy the above formula (1), so that the required sufficiently low resistance value can be obtained. It can be grounded and it can be seen that electron beam drawing can be performed with high accuracy.

  The present invention has been described with reference to the embodiments. However, the above-described embodiments are merely examples for carrying out the present invention, and the present invention is not limited thereto. It is apparent from the above description that various modifications of this embodiment are within the scope of the present invention, and that various other embodiments are possible within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Phase shift film 3 Back surface side antireflection film 4 Light shielding film 5 Surface side antireflection film 6 Etching mask film 10 Photomask blanks 21, 22 Probe 23 Current path 24a, 24b, 24c Resistance 31 Conductive layer 32 Resistance layer

Claims (7)

It is a photomask blank that is a material for manufacturing a photomask in which pattern transfer is performed with exposure light having a wavelength of 200 nm or less,
The photomask blank is in contact with a transparent substrate, a resistance layer having a resistivity of 0.1 Ω · cm or more formed on the outermost part on the side away from the transparent substrate, and the transparent substrate side of the resistance layer. Having a formed resistivity of less than 0.1 Ω · cm , and a conductive layer formed of a material containing chromium ,
The resistance layer is composed of a single layer or a multilayer composed of two or more sublayers,
Resistivity of each of the single layer or sub-layer (unit is Ω · cm, if the value of resistivity is 7.5 × 10 ⁵ (Ω · cm) or less, the value is 7.5 × 10 ⁵ If the resistance layer is a single layer, the resistivity and the thickness are 7.5 × 10 ⁵ (Ω · cm) if it exceeds (Ω · cm) and the thickness (unit is cm). When the resistance layer is a multilayer, the resistance index A, which is the sum of the product of resistivity and thickness in each sub-layer, is expressed by the following formula (1)
1.5 × 10 ⁵ ≧ A × α + ρ _C / d _C (1)
(Where α is a constant (unit is cm ⁻² ), ρ _C is the resistivity of the conductive layer (unit is Ω · cm), d _C is the thickness of the conductive layer (unit is cm) Is)
A photomask blank characterized by satisfying The photomask blank according to claim 1, wherein the conductive layer has a sheet resistance value of 1 × 10 ⁴ Ω / □ or less.   3. The photomask blank according to claim 1, further comprising a phase shift film formed of a material containing silicon or a material containing silicon and molybdenum between the transparent substrate and the conductive layer.   The photomask blank according to claim 1 or 2, further comprising a light shielding film formed of a material containing silicon or a material containing silicon and molybdenum between the transparent substrate and the conductive layer. 5. The photomask blank according to claim 1, wherein the resistance layer is formed of a material obtained by adding a light element selected from oxygen, nitrogen, and carbon to a metal or an alloy.   In the process of processing into a photomask, the grounding terminal is brought into contact with the resistance layer, and the grounding terminal is grounded by pressing the resistance layer to such an extent that conduction between the grounding terminal and the conductive layer is obtained. The photomask blank according to any one of claims 1 to 5, wherein the photomask blank is a photomask blank to be performed. A transparent substrate, a resistance layer having a resistivity of 0.1 Ω · cm or more formed on the outermost portion on the side away from the transparent substrate, and a resistivity formed in contact with the transparent substrate side of the resistance layer And a conductive layer made of a material containing chromium, and the resistance layer is a single layer or a multilayer composed of two or more sublayers. A method of manufacturing a photomask in which pattern transfer is performed with exposure light having a wavelength of 200 nm or less from a mask blank,
Resistivity of each of the single layer or sub-layer (unit is Ω · cm, if the value of resistivity is 7.5 × 10 ⁵ (Ω · cm) or less, the value is 7.5 × 10 ⁵ If the resistance layer is a single layer, the resistivity and the thickness are 7.5 × 10 ⁵ (Ω · cm) if it exceeds (Ω · cm) and the thickness (unit is cm). When the resistance layer is a multilayer, the resistance index A, which is the sum of the product of resistivity and thickness in each sub-layer, is expressed by the following formula (1)
1.5 × 10 ⁵ ≧ A × α + ρ _C / d _C (1)
(Where α is a constant (unit is cm ⁻² ), ρ _C is the resistivity of the conductive layer (unit is Ω · cm), d _C is the thickness of the conductive layer (unit is cm) Is)
Preparing a photomask blank that satisfies
The step of forming a photoresist film on the resistance layer, and the ground terminal is brought into contact with the resistance layer, and the ground layer is grounded by pressing the resistance layer to such an extent that conduction between the ground terminal and the conductive layer is obtained. A method of manufacturing a photomask comprising the step of drawing an electron beam on the photoresist film.

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