JP2015184453A - Method for manufacturing photomask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a photomask capable of correcting a defective part in shorter time, in a translucent mask pattern of a photomask blank having light fastness.SOLUTION: A method for manufacturing a photomask includes: a thin film pattern formation process (S2, S3) of forming a thin film pattern by etching a thin film of a photomask blank having a transparent substrate and the thin film formed on the transparent substrate; a metal ion irradiation process (S5) of irradiating an area including a defective part of the thin film pattern with metal ion; and a thin film pattern correction process (S6) of irradiating, with electron beam, the defective part of the thin film pattern irradiated with the metal ion while supplying assist gas to remove the defective part by etching.

Description

  The present invention relates to a photomask manufacturing method used for manufacturing a semiconductor.

  Conventionally, as a material for a translucent mask pattern in a phase shift mask, a compound mainly containing molybdenum silicide (MoSi), for example, molybdenum oxynitride silicide (MoSiON) is used (see Patent Document 1). A compound containing molybdenum silicide (MoSi) is used not only as a semi-transparent mask pattern but also as a material for a light shielding film.

  In a photomask such as a phase shift mask, an excess portion of etching called a black defect or a missing portion of etching called a white defect may be generated in the mask pattern in the manufacturing stage. Hereinafter, a black defect that is an excess part of the mask pattern is referred to as a “residue defect”.

  In general, the production of photomasks such as phase shift masks involves many complicated processes and the fact that the mask pattern is extremely fine. Is technically and difficult to manufacture. Accordingly, in the manufacture of a photomask such as a phase shift mask, the removal of the defective portion is an essential process (see Patent Document 2).

  An EB (electron beam) correcting device is mainly used for correcting the defective portion. The EB correcting device is a device that performs partial etching using an assist gas and an electron beam, and is generally widely used for correcting defective portions.

JP2013-11900A JP 2004-294613 A

  A conventional translucent mask pattern made of a MoSi-based material has a problem that the dimension of the mask pattern changes when transfer exposure using an ArF excimer laser is repeated. In addition, the conventional translucent mask pattern made of a MoSi-based material has a problem that when the transfer exposure and cleaning are repeated, the film thickness of the translucent mask pattern is reduced and the transmittance and phase difference are changed. There was also. Therefore, various improvements have been attempted in order to improve the light resistance of the translucent mask pattern.

  At present, it has been elucidated that the light resistance of a translucent mask pattern is improved by reducing the Mo content in a translucent mask pattern made of a MoSi-based material or by forming a film that does not contain Mo. Such a translucent mask pattern having light resistance is formed, for example, by subjecting a photomask blank formed with a translucent layer with a reduced or no Mo content to a dry etching process similar to the conventional one. can do. Hereinafter, the photomask blank formed with a translucent layer with or without the Mo content is also referred to as “photomask blank having light resistance”.

  However, in photomask blanks having light resistance, the etching rate (etching rate) of the semi-transparent pattern is slow, so that it has become clear that it is very difficult to correct a defective portion by partial etching using an EB correcting device. That is, in the semi-transparent mask pattern of photomask blanks having light resistance, when the defective part is corrected by the conventional partial etching method, the defective part is not etched, and the defective part is corrected in the same time as before. The problem of not being able to be completed was found.

  An object of the present invention is to provide a photomask manufacturing method capable of correcting a defective portion in a shorter time in a translucent mask pattern of a photomask blank having light resistance.

  The present invention solves the problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected and demonstrated, it is not limited to this. In addition, the configuration described with reference numerals may be improved as appropriate, or at least a part thereof may be replaced with another configuration.

-1st invention etches the said thin film of the photomask blanks (10) which has a transparent substrate (11) and the thin film (12A, 13A) formed on the said transparent substrate, and is thin film pattern (12, 13) ) Forming a thin film pattern (S2, S3), a metal ion irradiation step (S5) for irradiating a region including the defect portion (23) of the thin film pattern, and the thin film irradiated with metal ions And a thin film pattern correcting step (S6) for etching and removing the defective portion by irradiating an electron beam while supplying an assist gas to the defective portion of the pattern.

-2nd invention is a photomask manufacturing method of 1st invention, The density distribution of the depth direction of the metal ion irradiated to the said thin film pattern in the said metal ion irradiation process becomes the maximum value in a transparent substrate area | region. This is a method for manufacturing a photomask.

-3rd invention is a photomask manufacturing method of 1st or 2nd invention, and irradiates an electron beam, supplying assist gas to the said defect part of the said thin film pattern as a pre-process of the said metal ion irradiation process. Thus, the photomask manufacturing method includes a thin film pattern preliminary correction step (S15) in which a part of the defective portion is etched away in advance.

The fourth invention is the photomask manufacturing method according to any one of the first to third aspects, wherein the atomic ratio (A _Mo / A _Si ) of molybdenum (Mo) to silicon (Si) in the thin film is 0 ≦ A _Mo This is a photomask manufacturing method satisfying the relationship of / A _Si ≦ 1/10.

  ADVANTAGE OF THE INVENTION According to this invention, the photomask manufacturing method which can correct a defect part in the translucent mask pattern of the photomask blanks which has light resistance can be provided.

It is a flowchart which shows the process sequence of the photomask manufacturing method in 1st Embodiment. It is a schematic block diagram which shows the photomask manufacturing apparatus 1 in 1st Embodiment. It is a schematic process drawing which shows the photomask manufacturing method in 1st Embodiment. It is a schematic process drawing which shows the photomask manufacturing method in 1st Embodiment. It is a graph which shows the relationship between the etching time at the time of dry-etching a translucent mask pattern, and an etching depth. It is a graph which shows the simulation result which computed the distribution of the ion concentration in the depth direction of the semi-transparent pattern by FIB irradiation according to the acceleration voltage of FIB. It is a flowchart which shows the process sequence of the photomask manufacturing method in 2nd Embodiment. It is a schematic process drawing which shows a part of photomask manufacturing method in 2nd Embodiment.

  Hereinafter, embodiments of a photomask manufacturing method according to the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a flowchart showing a processing procedure of the photomask manufacturing method according to the first embodiment. As shown in FIG. 1, the photomask manufacturing method in the first embodiment includes a photomask blank preparation step (S1), a second thin film pattern formation step (S2), a first thin film pattern formation step (S3), and a first step. The thin film pattern defect inspection step (S4), the FIB irradiation step (S5), and the first thin film pattern defect correction step (S6) are sequentially provided. Hereinafter, each process will be briefly described.

The photomask blank preparation step (S1) is a step of preparing a photomask blank in which a first thin film is formed on a transparent substrate and a second thin film is formed on the first thin film.
The second thin film pattern forming step (S2) is a step of forming a second thin film pattern by etching the second thin film of the photomask blank prepared in the step (S1).
The first thin film pattern forming step (S3) is a step of forming the first thin film pattern by etching the first thin film exposed from the second thin film pattern.

  The defect inspection step (S4) of the first thin film pattern is a step of detecting a defect portion of the first thin film pattern formed in the step (S3). If a defective portion is detected in this step (S4), the process proceeds to the FIB irradiation step (S5) described later. Moreover, when a defective part is not detected, it transfers to another processing process.

  The FIB irradiation step (S5) is a step of irradiating a region including the defect portion of the first thin film pattern with FIB (focused ion beam) by Ga ions. As will be described later, the etching rate of the first thin film pattern can be increased by performing the FIB irradiation step.

  The defect correction step (S6) of the first thin film pattern is a step of correcting (removing) the defective portion of the first thin film pattern detected in the step (S4). Although not shown, a cleaning step is performed after the step (S6), and the first thin film pattern is cleaned. Thereafter, defect inspection is performed by a lithography simulation microscope. In this defect inspection, when a defective part is detected, the process returns to the step (S6) and the defect part is corrected again. Moreover, when a defective part is not detected, it transfers to the next processing process.

  Here, when the photomask blank is a halftone phase shift mask, the translucent film corresponds to the first thin film. On the other hand, when the photomask blank is a binary mask, the light shielding film corresponds to the first thin film.

  The second thin film functions as an etching mask when the first thin film is etched to form the first thin film pattern. The second thin film pattern is removed after the step (S3) of forming the first thin film pattern.

  Next, the photomask manufacturing apparatus in the first embodiment will be described. This photomask manufacturing apparatus is an apparatus for carrying out the photomask manufacturing method. FIG. 2 is a schematic configuration diagram showing the photomask manufacturing apparatus 1 in the first embodiment. In the following description, constituent elements shown in FIG. 3 and FIG.

  As shown in FIG. 2, the photomask manufacturing apparatus 1 includes a thin film pattern forming unit 2, a first inspection unit 3, a metal ion irradiation unit 4, a thin film pattern correction unit 5, and a second inspection unit 6. Prepare.

  The thin film pattern forming unit 2 is an apparatus for forming a first thin film pattern 12 by etching a two-layer thin film formed on the photomask blank 10. As will be described later, the photomask blank 10 includes a transparent substrate 11, and a first thin film 12A (semi-transparent film) and a second thin film 13A (light shielding film) formed on the transparent substrate 11. The thin film pattern forming unit 2 includes a resist coating device, an electron beam drawing device, an etching device, a resist stripping device, a cleaning device, etc. (all not shown).

  The first inspection unit 3 is an apparatus that inspects a photomask blank (hereinafter, also referred to as “intermediate product”) 10 on which the first thin film pattern 12 is formed, and detects a defective portion 23.

  The metal ion irradiation unit 4 is an apparatus that irradiates a region including the defect portion 23 of the first thin film pattern 12 with Ga (gallium) ions as metal ions. In the present embodiment, an FIB correction device is used as the metal ion irradiation unit 4. As the metal ion irradiation unit 4, an ion implantation apparatus or the like may be used instead of the FIB correction apparatus.

  The thin film pattern correction unit 5 is an apparatus that etches and removes the defective portion 23 by irradiating an electron beam while supplying an assist gas to the defective portion 21 of the first thin film pattern 12. In the present embodiment, an EB correction device is used as the thin film pattern correction unit 5.

The second inspection unit 6 is an apparatus for evaluating the first thin film pattern 12 corrected by the EB correction apparatus. In the present embodiment, a lithography simulation microscope is used as the second inspection unit 6.
In addition, the function of each part constituting the photomask manufacturing apparatus 1 will be described in more detail in a photomask manufacturing method described later.

  Next, a photomask manufacturing method according to the first embodiment will be described with reference to FIGS. 3A to 3E are schematic process diagrams showing the photomask manufacturing method according to the first embodiment. FIGS. 4F to 4I are schematic process diagrams illustrating the photomask manufacturing method according to the first embodiment. 3A to 3E and FIGS. 4F to 4I are a series of continuous process diagrams. In this embodiment, a case where a halftone type phase shift mask is manufactured as a photomask will be described. Hereinafter, the manufacturing process of the photomask in the first embodiment will be described in the order of (1) to (5).

<Preparation process of photomask blanks>
(1) As shown in FIG. 3A, a photomask blank 10 is prepared. The photomask blank 10 is installed in the thin film pattern forming unit 2. The photomask blank 10 includes a transparent substrate 11, a first thin film 12A formed on the transparent substrate 11, and a second thin film 13A formed on the first thin film 12A.

  The transparent substrate 11 is preferably a material that transmits an ArF excimer laser with high transmittance. Examples thereof include synthetic quartz glass, fluorite, and calcium fluoride. Among these, synthetic quartz glass is preferably used from the results of conventional phase shift masks.

  In the present embodiment, the first thin film 12A corresponds to a translucent film that controls the phase and transmittance of an ArF excimer laser. The film thickness of the first thin film 12A is such that the phase of the 193 nm wavelength ArF excimer laser light transmitted through the first thin film 12A portion and the wavelength of the 193 nm excimer laser light transmitted through the portion where the transparent substrate 11 is exposed. Is set to invert. The first thin film 12A is normally set so that the transmittance of an ArF excimer laser with a wavelength of 193 nm is 6% or more.

  When the photomask is a binary mask, the first thin film 12A is a light shielding film. In this case, the first thin film 12A is normally set so that the optical density value for an ArF excimer laser with a wavelength of 193 nm is approximately 3.

  Examples of the material of the first thin film 12A include materials used for a semi-transparent film of a conventional halftone phase shift mask for ArF excimer laser and a light shielding film of a binary mask. For example, as the first thin film 12A, it is preferable to use a compound such as molybdenum silicide oxide film (MOSiO), molybdenum silicide nitride film (MoSiN), molybdenum silicide oxynitride film (MoSiON), which is a molybdenum silicide (MoSi) -based material. In addition, a binary mask and a translucent film using a material such as Si, SiN, SiO, or SiON that is a silicide-based material that does not contain molybdenum (Mo) can be used.

The photomask blank 10 used in the present embodiment is configured as a photomask blank having a light resistance not including Mo or containing Mo. Therefore, in the present embodiment, the first thin film 12 _< / _b > A having an atomic ratio (A _Mo / A _Si ) between molybdenum (Mo) and silicon (Si) satisfying the relationship of A _Mo / A _Si ≧ 1/10 is used. . If the above relationship is satisfied, the first thin film 12A is etched to form a first thin film pattern 12 (described later) having high light resistance and excellent dimensional stability in ArF excimer laser exposure. Can do.

  The first thin film 12A can be formed by reactive sputtering using a mixed target of molybdenum and silicon in a mixed gas atmosphere of argon, nitrogen, and oxygen, for example.

  The second thin film 13A is a thin film for forming a second thin film pattern 13 (described later). The second thin film pattern 13 functions as an etching mask when the first thin film 12A is formed by etching the first thin film 12A.

  As described above, it is preferable to use a molybdenum silicide (MoSi) -based compound, a Si-based nitride, a Si-based nitride, or the like as the first thin film 12A. This molybdenum silicide (MoSi) -based compound or Si-based compound is processed mainly by dry etching using a fluorine-based gas. For this reason, the second thin film 13A serving as an etching mask is preferably made of a material having resistance to dry etching using a fluorine-based gas.

  Specific examples of the material forming the second thin film 13A include chromium-based materials such as Cr, CrO, CrN, and CrNO, and tantalum-based materials such as Ta, TaO, TaN, and TaNO. The second thin film 13A may have a single layer structure made of the same material or a multilayer structure made of two or more different materials.

  The film thickness of the second thin film 13A only needs to have a thickness sufficient for the function as an etching mask when the first thin film pattern 12 is formed. However, when the thickness of the second thin film 13A is excessively large, it is difficult to make the second thin film pattern 13 a fine pattern. Therefore, although the film thickness of the second thin film 13A depends on the size of the first thin film pattern 12, it is preferably in the range of about 3 nm to 50 nm.

  A known vacuum film forming method can be applied to the second thin film 13A. For example, when the second thin film 13A is a chromium film (Cr), it can be formed by a reactive sputtering method in a argon gas atmosphere using a chromium target.

<Second thin film pattern forming step>
(2) The photomask blank 10 prepared in the step (3) is set in a resist coating apparatus (not shown) of the thin film pattern forming unit 2 (see FIG. 2), and as shown in FIG. 3 (b). A resist layer 14A is formed on the second thin film 13A.

  As shown in FIG. 3B, in the present embodiment, an example is shown in which a residue defect occurs due to the foreign substance 21 mixed between the second thin film 13A and the resist layer 14A. In addition, in the form in which the residue defect occurs, there is a case where the foreign matter adheres to the surface of the resist layer 14A in addition to the foreign matter 21 being mixed. In this case, when an electron beam pattern is drawn in an electron beam drawing apparatus (not shown) of the thin film pattern forming unit 2 (see FIG. 2), the amount of electron beam irradiation at that portion is insufficient, and an unnecessary surplus portion. As a result, a resist pattern is formed. In addition, a residue defect may occur due to the formation of an unnecessary surplus portion due to a defective shape of the resist pattern. Note that FIG. 2 shows an example in which a residue defect is a single location, but the residue defect may occur at a plurality of locations.

  Next, the intermediate product 10 obtained in the steps up to FIG. 3B is set in an electron beam drawing apparatus (not shown) of the thin film pattern forming unit 2 (see FIG. 2). As shown, a resist pattern 14 is formed using a pattern forming method by electron beam pattern drawing.

  Subsequently, the intermediate product 10 on which the resist pattern 14 is formed is set in an etching apparatus (not shown) of the thin film pattern forming unit 2 (see FIG. 2), and as shown in FIG. 13A is etched and the 2nd thin film pattern 13 is formed. As a method for etching the second thin film 13A, for example, when the second thin film 13A is made of a chromium-based material, a dry etching method using a mixed gas of chlorine-based gas and oxygen gas is used. it can. When the second thin film 13A is made of a tantalum material, a dry etching method using a chlorine gas can be used.

  Next, the intermediate product 10 obtained in the steps up to FIG. 3 (d) is set in a resist stripping device (not shown) of the thin film pattern forming unit 2 (see FIG. 2), and shown in FIG. 3 (e). Thus, the resist pattern 14 is removed. Usually, the foreign matter 21 is also removed in the step of removing the resist pattern 14 or the subsequent cleaning step (not shown). However, when etching the second thin film 13A, a defective portion 22 that is an unnecessary surplus portion is formed in the portion of the second thin film 13A that is covered with the portion of the foreign material 21 exposed from the resist pattern 14. .

  The defective portion 22 is formed from the second thin film 13A. The material constituting the defect portion 22 is the same as the material constituting the second thin film pattern 13. However, in FIG. 3E and the like, the cross section of the defect portion 22 is indicated by diagonal lines different from the cross section of the second thin film pattern 13. In the present embodiment, the defect portion 22 of the second thin film pattern 13 is not removed in the defect correction step, and a defect portion 23 of the first thin film pattern 12 described later is removed in the defect correction step.

<First thin film pattern forming step>
(3) The intermediate product 10 obtained in the steps up to FIG. 3E is set in an etching apparatus (not shown) of the thin film pattern forming unit 2 (see FIG. 2). Then, as shown in FIG. 4F, the first thin film pattern 12 is formed by etching the first thin film 12 </ b> A exposed from the second thin film pattern 13. In addition, since the defect part 22 exists in the 2nd thin film pattern 13, the defect part 23 which is an unnecessary surplus part is formed in the 1st thin film pattern 12. FIG. In FIG. 4, the cross section of the defect portion 23 in the first thin film pattern 12 is indicated by oblique lines in a different direction from the cross section of the first thin film pattern 12.

<Defect inspection process of first thin film pattern>
(4) Although illustration is omitted, the intermediate product 10 obtained in the steps up to FIG. 4F is set in the first inspection section 3 (see FIG. 2) and formed in the first thin film pattern 12. A defect inspection for detecting the defect portion 23 is performed. In this defect inspection process, when the defect part 23 is not detected, the intermediate product 10 is conveyed to another processing process. On the other hand, when the defect part 23 is detected in the defect inspection process, the intermediate product 10 is conveyed to the FIB irradiation process described later.

<FIB irradiation process>
(5) The intermediate product 10 in which the defect 23 is detected in the step (4) is set in the metal ion irradiation unit 4 (see FIG. 2), and as shown in FIG. FIB 31 with Ga ions is irradiated to the region containing. In this step, the assist gas is not supplied when the FIB 31 is irradiated.

  This FIB irradiation process is a process performed to increase the etching rate of the first thin film pattern 12. Here, the relationship between the presence or absence of FIB irradiation and the etching time will be described with reference to FIG.

  FIG. 5 is a graph showing the relationship between etching time and etching depth when the semitransparent mask pattern is dry-etched. The graph shown in FIG. 5 is an experimental result obtained by measuring the etching time and the etching depth for each photomask blank to be described later when the semi-transparent mask pattern is dry-etched by irradiating an electron beam of a certain intensity from the EB correction device. is there. The graph shown in FIG. 5 schematically shows the characteristics of each photomask blank.

  In FIG. 5, the graph shown by a solid line shows the characteristics of a photomask blank having a translucent mask pattern made of a normal MoSi-based material whose Mo content is not lowered (hereinafter referred to as “normal photomask blanks”). ”).

  In FIG. 5, the graphs indicated by the broken lines and the one-dot chain lines are both photomask blanks (having light resistance) having a translucent mask pattern made of a MoSi-based material with a reduced Mo content. The characteristic of a photomask blank) is shown. Among these, a graph (without FIB) indicated by a broken line shows characteristics of photomask blanks (hereinafter also referred to as “photomask blanks without FIB”) in which the semitransparent pattern was not irradiated with FIB. A graph (with FIB 1.) indicated by a one-dot chain line shows characteristics of a photomask blank (hereinafter, also referred to as “FIB with 1. FIB 1”) irradiated with FIB on a semitransparent pattern.

  In FIG. 5, a graph (with FIB 2.) indicated by a two-dot chain line is a characteristic of a photomask blank in a second embodiment to be described later (hereinafter also referred to as “photomask blank with FIB 2.”). Indicates.

  As shown in FIG. 5, in the photomask blank without FIB, the etching rate is extremely slow, so that a longer etching time is required compared with a normal photomask blank. On the other hand, with FIB In this photomask blank, as shown in FIG. 5, the digging depth on the vertical axis with respect to the etching time on the horizontal axis is large, and it can be seen that the etching rate is high. From the experimental results shown in FIG. 5, it was confirmed that the etching rate can be increased by ion implantation. Although depending on the conditions for implanting ions, the etching rate can be increased by several times.

  As described above, by performing the FIB irradiation process, the etching rate of the first thin film pattern 12 can be increased. Therefore, in the defect repairing process of the first thin film pattern 12, the remaining defect portion can be removed in a shorter time. Can be corrected.

Next, the relationship between the intensity of FIB irradiation and the influence of the defect 23 in the depth direction will be described with reference to FIG.
In FIG. 6, a substrate made of SiO ₂ is laminated under a translucent film having a film thickness of 63 nm and a Mo content of 3%, a Si content of 44%, an O content of 1%, and an N content of 54%. It is a graph which shows the result simulated with the blank of a structure. In FIG. 6, the simulation which computed distribution of the ion concentration in the depth (depth from surface layer) direction of the translucent pattern (1st thin film pattern 12) by FIB irradiation according to the acceleration voltage (5-100 kV) of FIB. Results are shown. In FIG. 6, the acceleration voltage of FIB corresponds to the intensity of irradiated Ga ions. Moreover, in FIG. 6, ion concentration respond | corresponds to the influence degree by irradiation of Ga ion.

  As shown in FIG. 6, the ion concentration of the translucent pattern irradiated with FIB reaches a deeper region as the acceleration voltage of FIB increases, but the ion concentration is lower and the distribution range tends to diffuse. On the other hand, the ion concentration of the translucent pattern irradiated with FIB remains in a shallow region as the acceleration voltage of FIB decreases, but the ion concentration is high and the distribution range tends to be more focused.

In this embodiment, the FIB acceleration voltage applied to the first thin film pattern 12 as the semitransparent pattern is such that the depth of the defect 23 to be removed by etching is d ₁ , and the FIB irradiation is performed inside the first thin film pattern 12. the depth at which ion concentration is maximized when the d ₂ by,
d ₂ ≧ d ₁
It is preferable to set so that. More preferably, _{d 1} is set to be in the range of _{d 2} × 0.2 to 1.0. This is because Ga ions sufficiently pass through to the interface between the first thin film pattern 12 and the transparent substrate 11 and the defective portion 23 can be satisfactorily removed.

For example, as shown in FIG. 6, when the FIB acceleration voltage can be set to 5 kV, 10 kV to 100 kV, and the depth d ₁ of the defect 23 to be etched away is 63 nm, which is the same as the film thickness, the FIB acceleration voltage, as d ₂ is at the transparent substrate region is preferably set to 100 kV. More preferably, when d ₁ is set to be in the range of d ₂ × 0.2 to 1.0, correction is easier.

<Defect correction process of first thin film pattern>
(6) The intermediate product 10 obtained in the steps up to FIG. 4 (g) is set in the thin film pattern correcting section 5 (see FIG. 2), and the assist gas 41 is supplied as shown in FIG. 4 (h). However, the electron beam 32 is irradiated to the defect portion 23 of the first thin film pattern 12. As a result, as shown in FIG. 4I, a photomask from which the defect 23 has been removed by etching is obtained.

  In the photomask manufacturing method of the first embodiment described above, the FIB irradiation process is performed before the defect correction process of the first thin film pattern 12, and the FIB 31 made of Ga ions is formed in the region including the defect portion 23 of the first thin film pattern 12. Is irradiated. The first thin film pattern 12 in the region irradiated with the FIB 31 has a higher etching rate than other regions not irradiated with the FIB 31. Therefore, according to the photomask manufacturing method of the first embodiment, the defect portion 23 of the first thin film pattern 12 can be corrected in a shorter time in the photomask blank 10 having light resistance.

  Further, in the photomask blank 10 having light resistance, if the etching rate of the first thin film pattern 12 is slower than the etching rate of the transparent substrate 11 as a base, more time is required for etching of the defect portion 23. For this reason, it is considered that if the etching takes too much time at the interface between the defective portion 23 and the transparent substrate 11, the etching of the defective portion 23 proceeds more than necessary and damages the surface of the transparent substrate 11. It is done.

  However, in the photomask manufacturing method and the photomask manufacturing apparatus 1 of the first embodiment, the etching rate of the first thin film pattern 12 is increased by the irradiation of the FIB 31, so that the defect 23 can be etched in a shorter time. it can. According to this, since etching does not take too much time, the etching of the defect portion 23 does not proceed more than necessary at the interface between the defect portion 23 and the transparent substrate 11. Therefore, according to the photomask manufacturing method of the first embodiment, it is possible to suppress damage to the transparent substrate 11 when the defect portion 23 is removed.

Further, in the photomask manufacturing method in the first embodiment, the acceleration voltage of the FIB is irradiated to the first thin film pattern 12, the depth d ₁ of the defect portion 23 to be etched away is given the same as the thickness, FIB acceleration voltage is the depth to which ion concentration by irradiation with FIB inside the first thin film pattern 12 becomes maximum when the d _2, d ₂ is preferably set to come to the transparent substrate region. More preferably, _{d 1} is set to be in the range of _{d 2} × 0.2 to 1.0. According to this, the distribution in the depth direction of the ion concentration in the first thin film pattern 12, it is possible to set the range close to the depth d ₁ of the defect 23, while suppressing the side etching of the first thin film pattern 12 The defective part 23 can be corrected in a shorter time.

[Second Embodiment]
FIG. 7 is a flowchart showing a processing procedure of the photomask manufacturing method according to the second embodiment. As shown in FIG. 7, the photomask manufacturing method according to the second embodiment includes a photomask blank preparation step (S11), a second thin film pattern formation step (S12), a first thin film pattern formation step (S13), and a first step. The thin film pattern defect inspection step (S14), the first thin film pattern preliminary defect correction step (S15), the FIB irradiation step (S16), and the first thin film pattern defect correction step (S17) are sequentially provided.

  Steps (S11) to (S14) shown in FIG. 7 correspond to steps (S1) to (S4) shown in FIG. 1 (first embodiment). Moreover, the process (S16) and process (S17) shown in FIG. 7 correspond to the process (S5) and (S6) shown in FIG. In the second embodiment, the description of the corresponding steps in the first embodiment will be omitted as appropriate.

  The second embodiment is different from the first embodiment in that the preliminary defect correcting step (S15) of the first thin film pattern as the thin film pattern preliminary correcting step is performed before the FIB irradiation step (S16). The other steps are the same as the corresponding steps in the first embodiment. Moreover, since the structure of the photomask manufacturing apparatus 1A (refer FIG. 2) in 2nd Embodiment is the same as the photomask manufacturing apparatus 1 in 1st Embodiment, description is abbreviate | omitted.

  In the preliminary defect correction step (S15) of the first thin film pattern shown in FIG. 7, a part of the defect portion is etched away in advance by irradiating the electron beam while supplying the assist gas to the defect portion of the first thin film pattern. It is a process.

In the first embodiment, the FIB acceleration voltage applied to the first thin film pattern 12 is set to the depth d ₁ of the defect 23 to be etched, and the ion concentration due to the FIB irradiation is maximized inside the first thin film pattern 12. when the depth _{d 2,} an example was described _{in which d 1} is set to be in the range of _{d 2} × 0.2 to 1.0. However, depending on the depth d _{1 of} the defect 23 (first thin film pattern 12) or the limitation of the acceleration voltage of the apparatus, even if the acceleration voltage of the FIB is set to the maximum, d ₁ is d ₂ × 0.2 to It may not be in the range of 1.0. For example, in the example shown in FIG. 6, when the acceleration voltage of the FIB is 30 kV at the maximum, the depth d ₁ of the defect portion 23 is 63 nm, even if the acceleration voltage of the FIB is set to the maximum. It is considered that the etching rate cannot be sufficiently accelerated up to the interface between the pattern and the transparent substrate.

  Therefore, in the second embodiment, as a pre-process of the FIB irradiation step (S16), preliminary defect correction of the first thin film pattern in which a part of the defect portion 23 is removed by etching in advance by the thin film pattern correction unit 5 (see FIG. 2). A step (S15) is provided. In this preliminary defect correction step, by removing a part of the defect portion 23 in advance, the defect portion 23 can be easily corrected in the defect correction step (S17) of the first thin film pattern after the FIB irradiation step (S16). become.

For example, in the example shown in FIG. 6, when the depth d ₁ of the defect portion 23 is 63 nm, 40 nm of the defect portion 23 is previously removed by etching in the preliminary defect correction step (S15) of the first thin film pattern. Keep it. As a result, the remaining depth of the defect portion 23 becomes 23 nm. Therefore, in the subsequent defect correction step (S17) of the first thin film pattern, the remaining depth 23 nm of the defect portion 23 may be removed by etching. Become.

That is, since the depth d ₁ of the defect 23 in this case is about 23 nm, the etching rate of the remaining portion of the defect 23 can be increased even if the FIB acceleration voltage is 30 kV. Thus, if the metal ions have sufficiently reached the interface with the substrate, it can be corrected with a good shape.

  Even when a part of the defect portion 23 is removed by etching as in the present embodiment, there is FIB as shown in FIG. It can be seen that the photomask blank of FIG. 3 has a higher etching rate than that without ion implantation. In FIG. 5, there is FIB. This photomask blank shows characteristics from an etching depth of 40 nm.

  Next, a photomask manufacturing method according to the second embodiment will be described with reference to FIG. FIGS. 8F to 8J are schematic process diagrams illustrating a part of the photomask manufacturing method according to the second embodiment. Since the process leading to FIG. 8F is the same as FIGS. 3A to 3E of the first embodiment, the description thereof is omitted. In addition, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description overlapping with the first embodiment is appropriately omitted. Hereinafter, the manufacturing process of the photomask in 2nd Embodiment is demonstrated in order of (1)-(5).

<First thin film pattern forming step>
(1) The intermediate product 10A obtained through the steps up to FIG. 3 (e) is set in an etching apparatus (not shown) of the thin film pattern forming unit 2 (see FIG. 2). Then, as shown in FIG. 8 (f), the first thin film pattern 12 is formed by etching the first thin film 12 </ b> A exposed from the second thin film pattern 13. In FIG. 8, the cross section of the defect portion 23 is indicated by the same oblique lines as the cross section of the first thin film pattern 12.

<Defect inspection process of first thin film pattern>
(2) Although illustration is omitted, the intermediate product 10A obtained in the steps up to FIG. 8 (f) is set in the first inspection section 3 (see FIG. 2) and formed in the first thin film pattern 12. A defect inspection for detecting the defect portion 23 is performed.

<Preliminary defect correction process of first thin film pattern>
(3) The intermediate product 10A obtained in the steps up to FIG. 8 (f) is set in the thin film pattern correction section 5 (see FIG. 2), and the assist gas 41 is supplied as shown in FIG. 8 (g). However, the electron beam 32 is irradiated to the defect portion 23 of the first thin film pattern 12. Thereby, as shown in FIG. 8H, a part of the defect portion 23 is removed by etching.

<FIB irradiation process>
(4) The intermediate product 10A from which a part of the defective portion 23 has been removed is set in the metal ion irradiation portion 4 (see FIG. 2), and as shown in FIG. Irradiate FIB 31 with Ga ions.

<Defect correction process of first thin film pattern>
(5) The intermediate product 10A obtained in the steps up to FIG. 8 (h) is set in the thin film pattern correcting section 5 (see FIG. 2), and the assist gas 41 is supplied as shown in FIG. 8 (i). However, the remaining defect 23 of the first thin film pattern 12 is irradiated with the electron beam 32. As a result, as shown in FIG. 8J, a photomask from which the defect 23 has been removed by etching is obtained.

  According to the above-described photomask manufacturing method in the second embodiment, a part of the defect portion 23 is removed by etching in the preliminary defect correction process of the first thin film pattern before the FIB irradiation process. Therefore, even when the depth of the defect portion 23 (the film thickness of the first thin film pattern 12) is large, the defect portion 23 can be easily removed in the defect correction process of the first thin film pattern performed later. it can. Therefore, also in the photomask manufacturing method in the second embodiment, the defect portion 23 of the first thin film pattern 12 can be corrected in a shorter time in the photomask blank 10A having light resistance.

  Further, the etching rate of the first thin film pattern 12 may be slower than that of the underlying transparent substrate 11 before the FIB irradiation. However, in the preliminary defect correction process of the first thin film pattern performed before the FIB irradiation process, it is assumed that a part of the defect portion 23 (predetermined depth from the surface layer) is removed by etching, so that the etching takes too much time. However, the damage given to the transparent substrate 11 can be reduced as compared with the case where all the defective portions 23 are removed by etching.

[Example]
Hereinafter, specific examples of the method for producing a photomask blank according to the present invention will be described as examples. Here, photomasks made of photomask blanks having light resistance are referred to as Examples 1 to 5. Further, in photomask blanks having light resistance, Comparative Examples 1 and 2 are photomasks in which ion implantation by FIB irradiation was not performed.

Example 1
A photomask was prepared by the procedures (1) to (6) described below.
(1) As the transparent substrate 11, an optically polished 6-inch square, 0.25-inch thick synthetic quartz glass substrate was prepared. A molybdenum silicide oxynitride film (MoSiON) having a film thickness of 60 nm and an atomic ratio of Mo: Si: O: N of 3: 44: 1: 54 was formed on the substrate as the first thin film 12A. Next, a chromium film (Cr) having a film thickness of 48 nm was formed as the second thin film 13A on the first thin film 12A, and a photomask blank serving as a base was obtained (see FIG. 3A).

(2) An electron beam resist is applied on the chromium film (Cr) by a resist coating device (see FIG. 3B), and pattern drawing and development are performed by an electron beam drawing device to form a resist pattern. (See FIG. 3C).

(3) The chromium film exposed from the resist pattern was dry-etched with a mixed gas of chlorine and oxygen to form a chromium film pattern as the second thin film pattern 13 (see FIG. 3D). Thereafter, the resist pattern was removed by ashing with oxygen plasma in a resist stripping apparatus (see FIG. 3E). Next, after cleaning with a cleaning apparatus, the molybdenum silicide oxynitride film exposed from the chromium film pattern was dry-etched with SF ₆ gas to form a translucent mask pattern (see FIG. 4F). Thereafter, the chromium film pattern was removed with a mixed gas of chlorine and oxygen to obtain an intermediate product 10 having a semitransparent pattern of the first thin film pattern 12.

(4) The translucent mask pattern of the intermediate product 10 obtained in the above (3) was inspected using a defect inspection apparatus (MATRICS X700 manufactured by Lasertec Corporation).
(5) In Monte Carlo simulation, the acceleration voltage was changed in stages, and the simulation was performed, and the ion intensity distribution was confirmed with which acceleration voltage was sufficiently implanted for the film thickness of the defect to be corrected. . Since the peak of the ion concentration does not reach the substrate at the maximum acceleration voltage of 30 kV of the apparatus, the surface layer of the defect portion is removed in advance by 40 nm so that the peak in the depth direction of the ion concentration reaches the substrate.

  Next, the defect part 23 was irradiated with FIB 31 using Ga ions by an FIB correcting device (see FIG. 4G). The acceleration voltage of Ga ions was 30 kV (the same is true for the examples and comparative examples). By removing the surface layer of the defect portion in advance, even when the acceleration voltage of Ga ions was low, the ions could be sufficiently passed to the interface of the substrate.

(6) While supplying a mixed gas of xenon fluoride (XeF ₂ ) and water vapor (H ₂ O) as the assist gas 41, the electron beam 32 is irradiated to the defect detected in the inspection of (3) above. (Refer to FIG. 4 (h)), the defective portion was removed by etching. During etching, the end point of etching removal was detected by monitoring secondary electrons and reflected electrons. By implanting Ga ions, the etching rate of the translucent pattern can be increased, and the residual defects can be corrected satisfactorily. In addition, by allowing the ions to permeate, the etching rate of the semitransparent film was improved about 5 times. Table 1 shows the results obtained with the photomask of Example 1 (see FIG. 4I).

(Example 2)
As the first thin film 12A, a molybdenum silicide oxynitride film (MoSiON) having a film thickness of 63 nm with an atomic ratio of Mo: Si: O: N of 4: 42: 6: 46 is used, and the amount of the surface layer of the defective portion that is previously cut off The photomask of Example 2 was obtained in the same procedure as in Example 1 except that the thickness was changed to 45 nm. By implanting Ga ions, the etching rate of the translucent pattern can be increased, and the residual defects can be corrected satisfactorily. The results are shown in Table 1.

(Example 3)
As the first thin film 12A, a silicon oxide film (SiO) having a film thickness of 45 nm in which the atomic ratio of Mo: Si: O: N is 0: 81: 18: 0 is used, and an amount of previously removing the surface layer of the defect portion is 20 nm. A photomask of Example 3 was obtained by the same procedure as in Example 1 except that. By implanting Ga ions, the etching rate of the translucent pattern can be increased, and the residual defects can be corrected satisfactorily. The results are shown in Table 1.

Example 4
As the first thin film 12A, a 64 nm-thickness silicon oxide film (SiO) having an Mo: Si: O: N atomic ratio of 0: 45: 10: 45 is used, and the amount of the surface layer of the defective portion is previously reduced to 45 nm. A photomask of Example 4 was obtained by the same procedure as in Example 1 except that. By implanting Ga ions, the etching rate of the translucent pattern can be increased, and the residual defects can be corrected satisfactorily. The results are shown in Table 1.

(Example 5)
As the first thin film 12A, a silicon oxide film (SiO) having a film thickness of 57 nm in which the atomic ratio of Mo: Si: O: N is 0: 42: 0: 58 is used, and an amount of previously removing the surface layer of the defective portion is set to 35 nm. A photomask of Example 5 was obtained by the same procedure as in Example 1 except that. By implanting Ga ions, the etching rate of the translucent pattern can be increased, and the residual defects can be corrected satisfactorily. The results are shown in Table 1.

(Comparative Example 1)
As the first thin film 12A, an intermediate using a 57 nm-thick silicon nitride film (SiN) in which the atomic ratio of Mo: Si: O: N, which is the same material as in Example 5, is 0: 42: 0: 58 The product was prepared. Then, without irradiating Ga ions by the FIB correcting device, the defective portion was removed by etching according to the procedure of (6) shown in Example 1, and a photomask of Comparative Example 1 was obtained. The number of electron beam scans was the same as the total number of scans required to remove the residual defects in Example 5. The number of scans is the number of times the electron beam is scanned. In the photomask of Comparative Example 1, the defective part could not be removed and the remaining film remained, and the defect could not be removed satisfactorily. The results are shown in Table 1.

(Comparative Example 2)
The first thin film 12A is an intermediate using a 57-nm-thick silicon nitride film (SiN) in which the atomic ratio of Mo: Si: O: N, which is the same material as in Example 5, is 0: 42: 0: 58 The product was prepared. Then, without irradiating Ga ions by the FIB correcting apparatus, in the procedure of (6) shown in Example 1, the number of scans of the electron beam is set to 10 of the total number of scans required for removing the residual defects in Example 5. The defective part was removed by etching by doubling to obtain a photomask of Comparative Example 2. In the photomask of Comparative Example 2, the etching reached the interface, but the end point of the etching could not be detected and the transparent substrate 11 was scraped. Moreover, the bottom of the etched portion was rough, and the flatness of the surface was deteriorated. Further, large side etching also occurred, and the defective portion could not be removed with high accuracy. The results are shown in Table 1.

(Evaluation)
Atomic percentage of each atom constituting the first thin film of Examples 1 to 5 and Comparative Examples 1 and 2, atomic ratio of molybdenum (Mo) to silicon (Si) in the first thin film (A _Mo / A _Si ), The ease of correction of the first thin film and the selectivity with the transparent substrate in the correction process (etching selectivity before ion implantation) were evaluated. The results are shown in Table 1.

  The atomic percentage of each atom constituting the first thin film was calculated by XPS analysis. Moreover, the selection ratio with the transparent substrate in the correction process indicates the etching rate of the first thin film when the etching rate of the transparent substrate is 1.

  As shown in Table 1, in Comparative Examples 1 and 2, the defects could not be removed, or even when the number of etching scans was increased, the etching termination could not be detected, and the substrate was etched down. Also, the etched shape was rough at the bottom of the etched portion, resulting in poor surface flatness, side etching, and the defective portion could not be removed well.

On the other hand, as shown in Table 1, Example 1 in which the atomic ratio (A _Mo / A _Si ) of molybdenum (Mo) and silicon (Si) in the first thin film satisfies the relationship of A _Mo / A _Si ≧ 1/10. In the first to fifth thin films, the defect portion could be easily corrected by the partial etching correction method using the assist gas and the electron beam.

  As is apparent from the above-described embodiments, according to the photomask blank manufacturing method of the present invention, the defect portion can be corrected in a shorter time in the photomask blank having light resistance. Therefore, according to the photomask blank manufacturing method of the present invention, a photomask free from residual defects can be manufactured while maintaining the light resistance in ArF excimer laser exposure.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to embodiment mentioned above, A various deformation | transformation and change are possible, and they are also the technical scope of this invention. In addition, the effects described in the embodiments are merely a list of the most preferable effects resulting from the present invention, and the effects of the present invention are not limited to those described in the embodiments. In addition, although the structure of each embodiment mentioned above can also be used in combination suitably, detailed description is abbreviate | omitted.

DESCRIPTION OF SYMBOLS 1, 1A Photomask manufacturing apparatus 2 Thin film pattern formation part 3 1st test | inspection part 4 Metal ion irradiation part 5 Thin film pattern correction part 6 2nd test | inspection part 10 Photomask blanks 11 Transparent substrate 12 1st thin film pattern 12A 1st thin film 13 1st 2 Thin film pattern 13A 2nd thin film 22, 23 Defect part

Claims (4)

A thin film pattern forming step of forming a thin film pattern by etching the thin film of a photomask blank having a transparent substrate and a thin film formed on the transparent substrate;
A metal ion irradiation step of irradiating a region containing the defect portion of the thin film pattern with metal ions;
A thin film pattern correcting step of etching and removing the defective portion by irradiating an electron beam while supplying an assist gas to the defective portion of the thin film pattern irradiated with metal ions,
A photomask manufacturing method comprising: In the photomask manufacturing method of Claim 1,
In the metal ion irradiation step, the concentration distribution in the depth direction of the metal ions irradiated on the thin film pattern becomes a maximum value in the transparent substrate region. The photomask manufacturing method according to claim 1 or 2,
As a pre-process of the metal ion irradiation step, a thin film pattern preliminary correction step is performed in which a part of the defective portion is removed in advance by irradiating an electron beam while supplying an assist gas to the defective portion of the thin film pattern. A photomask manufacturing method characterized by the above. In the photomask manufacturing method of any one of Claim 1 to 3,
The atomic ratio (A _Mo / A _Si ) of molybdenum (Mo) and silicon (Si) in the thin film is
0 ≦ A _Mo / A _Si ≦ 1/10
The photomask manufacturing method characterized by satisfy | filling the relationship of these.

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