JP2006106253A - Phase shift mask and method for manufacturing phase shift mask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve resist resolution of a photomask while forming a finer light shielding pattern of the photomask and to prevent peeling of a light shielding pattern from the photomask to improve durability of the photomask. <P>SOLUTION: The phase shift mask has an engraved groove 200 for a phase shifter, wherein a light shielding pattern comprises a translucent film 203 applied on one principal surface of a transparent mask substrate and a light shielding film 202 applied on the translucent film and having a smaller width than that of the translucent film. The position of the light shielding film 202 in the light shielding pattern is deviated to the engraved groove nearest to the light shielding pattern. The transmittance of the translucent film for exposure light is lower than the transmittance of the transparent mask substrate for exposure light, and the transmittance of the light shielding film for exposure light is lower than the transmittance of the translucent film for exposure light. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a phase shift mask and a method for manufacturing the phase shift mask.

In recent years, miniaturization of semiconductor integrated circuit patterns has progressed, and the design rules for circuit elements and wiring have become one.
Design accuracy of the order of 00 nm or less is required. For processing the integrated circuit pattern, for example, a photolithography method is used in which the integrated circuit pattern on the photomask is transferred onto a semiconductor wafer with short wavelength light such as F ₂ laser light (wavelength: 157 nm).

FIG. 9 shows a structure of a general photomask used in this photolithography method (FIG. 9 (
It is a figure which shows light amplitude (FIG.9 (b)) and light intensity distribution (FIG.9 (c)) of exposure light through it a)). As shown in FIG. 9A, the photomask includes a transparent mask substrate 901 and a light shielding film 902 having a predetermined light shielding pattern provided on one main surface of the transparent mask substrate.

In order to process a resist pattern having a wavelength shorter than that of the exposure light using such a photomask, it is necessary to design the interval between the light shielding patterns to be equal to or smaller than the wavelength of the exposure light. When exposure light is irradiated to the photomask, the light transmitted through the transparent mask substrate portion where the light shielding film is not provided is diffracted, and as shown in FIG. 9B, these diffracted lights are emitted at the light shielding portion provided with the light shielding film. As shown in FIG. 9C, the light intensity distribution in the light shielding portion increases. Therefore, in such a general photomask, the contrast of the light projected onto the wafer through the mask is deteriorated, and the resist is designed according to the design light-shielding pattern of the photomask with a design dimension less than the wavelength of the exposure light. The pattern cannot be processed with high accuracy, that is, the resist resolution cannot be improved.

Here, in order to improve the resist resolution with a design dimension equal to or smaller than the exposure wavelength, there is a technique of providing a dug groove in a part of the mask substrate to form a phase shifter (see, for example, Non-Patent Document 1 or Patent Document 1). . More specifically, this technique adjusts the optical path length applied to a predetermined light transmitting portion and the optical path length applied to other light transmitting portions by providing the digging grooves, and transmits these pair of light transmitting portions. The exposure light projected onto the wafer through this mask is obtained by shifting the phase of the two lights 180 degrees relative to each other, canceling out the diffracted exposure light directly under the light shielding portion sandwiched between the pair of light transmission portions. The purpose is to increase the contrast of light.

However, in the phase shift mask according to the technique described in Patent Document 1, the exposure light transmitted through the transparent mask substrate portion where the digging grooves and the light shielding film are not provided, that is, the light transmitting portion where the digging grooves are not provided. The light amplitude and light intensity do not match the light amplitude and light intensity of the exposure light that has passed through the transparent mask substrate part where the digging grooves are provided, and the diffracted light to the light-shielding part cannot be offset sufficiently. The resist cannot be processed according to the design light-shielding pattern of the photomask.

Therefore, in order to correct such a shift in processing dimension, the digging groove 100 of the transparent mask substrate 101 as shown in FIG.
There is a technique with eight structures (see, for example, Patent Document 2).

JP 02-140743 A (page 2) JP 08-194303 A (2nd page) IEEE Transaction On Electron Devices, Vol. ED-29, No. 12, DECEMBER 1982, pp. 1828-1836 SPIE 2003, 5040-110

However, the phase shift mask according to the technique described in Patent Document 2 has a problem that the light shielding pattern cannot be stably miniaturized, and the durability of the photomask is inferior.
This problem will be further described with reference to FIG.

FIG. 4 is a diagram for explaining the processing size dependency of the light shielding pattern in the phase shift mask according to the technique described in Patent Document 2, and FIGS. 4B and 4C show the light shielding pattern size. And the transparent pattern size are 3/4 or 1/2 of that of FIG.
1 shows the structure of a miniaturized phase shift mask.

As shown in FIG. 4, in the phase shift mask according to the prior art, when the light shielding pattern size is miniaturized, the undercut amount of the transparent mask substrate must be increased in principle (for example, Non-Patent Document 2). Accordingly, the light shielding film 402 and the transparent mask substrate 4 are associated therewith.
Since the contact area with 01 is narrowed, the shading pattern is easily peeled off from the transparent mask substrate, as shown in FIG. 4C, and the durability of the photomask is inferior.

The present invention solves the above-described problems, and has an object to improve the resist resolution of a photomask while miniaturizing the light-shielding pattern of the photomask, and to prevent peeling of the light-shielding pattern from the photomask. .

In order to solve the above problems, a phase shift mask of the present invention is not provided with a transparent mask substrate, a light shielding pattern provided on one main surface of the transparent mask substrate, and the light shielding pattern of the transparent mask substrate. In the phase shift mask provided with the digging groove for the phase shifter provided on the one main surface portion and digging the one main surface portion, the light shielding pattern is formed on the one main surface of the transparent mask substrate. A semi-transparent film provided on the semi-transparent film, and a light-shielding film having a narrower width than the semi-transparent film, and the arrangement of the light-shielding film in the light-shielding pattern includes the light-shielding pattern. The exposure light transmittance of the semi-transparent film is lower than the exposure light transmittance of the transparent mask substrate, and the exposure light transmittance of the light-shielding film is lower than the semi-transparent film. Dew of And wherein the lower than the light transmittance.

Here, the “exposure light” means a light energy wave having a predetermined wavelength that is irradiated when a resist pattern is formed using a photomask.

In the above-described configuration according to the phase shift mask of the present invention, since the digging grooves for the phase shifter are arranged on one main surface portion where the light shielding pattern is not provided, the phase shift is processed by the conventional undercut process. The edge of the light-shielding pattern does not float from the transparent mask substrate like a mask, and the light-shielding pattern is reliably supported by the transparent mask substrate even when the photomask processing dimensions are miniaturized. Can do. Therefore, the light shielding pattern is hardly peeled off from the mask substrate, so that the durability of the photomask is improved.

Further, in the light shielding pattern composed of the light shielding film and the semi-transparent film, the light shielding film is disposed so as to be biased toward the digging groove closest to the light shielding pattern, so that the exposure light at the periphery of the digging groove is shielded from light. The pattern of transmitted exposure light of the transparent pattern portion provided with the digging groove can be defined with strong light shielding, and the phase of the exposure light is reversed by the semi-transparent film,
By adjusting the lateral width of the translucent film to increase or decrease the amount of light, the light intensity profile can be adjusted by causing interference with the transmitted exposure light of the transparent pattern portion where the digging groove is not provided.

As a result, the light intensity profile of the exposure light (phase -180 °) transmitted through the transparent pattern portion provided with the digging groove and the exposure transmitted through the transparent pattern portion provided with no digging groove. The light intensity profile of light (phase 0 °) can be made to exactly match, making it easy to correct the deviation between the resist processing width and the photomask design dimension, and finely processing the resist pattern below the exposure wavelength. Even in this case, the resolution of the resist can be remarkably improved.

In the phase shift mask of the present invention, the digging groove further has a vertical side surface formed by vertically digging one main surface of the transparent mask substrate, and the digging groove has a vertical side surface. All together, it can be set as the structure by which the one side surface of the said semi-transparent film | membrane and the one side surface of the said light shielding film are distribute | arranged.

If the edge of the shading pattern protrudes above the digging groove, the exposure light scattered on the side of the digging groove is transferred when the resist pattern is formed, and the resist processing pattern and the mask design shading pattern are masked. Deviation may occur. However, with the above configuration according to the phase shift mask of the present invention, the side surfaces of the semitransparent film and the light shielding film are arranged along the vertical side surface of the digging groove, and the light shielding pattern pops out with respect to the transmission exposure light. Absent. Therefore, such transfer of scattered exposure light is reliably prevented, and the resist resolution is further improved.

In the phase shift mask of the present invention, the thickness of the translucent film is 60 nm or more and 520.
It can be set as the structure below nm.

With this configuration, the phase of the exposure light transmitted through the portion provided with the semitransparent film is shifted by + 180 ° with respect to the exposure light transmitted through the transparent pattern portion where the digging groove is not formed. be able to.

In the phase shift mask of the present invention, the film thickness sum of the light shielding film and the translucent film is further
It can be set as the structure below the horizontal width of the transparent pattern which is the one main surface part in which the said light-shielding pattern is not provided.

When the thickness of the light shielding pattern is larger than the width of the transparent pattern portion, the amount of light absorbed by the adjacent light shielding pattern increases in the exposure light transmitted through the transparent pattern portion, and as a result, the light passes through the core transparent pattern. The amount of light to be exposed is reduced. However, with the above configuration according to the phase shift mask of the present invention, since the sum of the film thickness of the light shielding film and the semi-transparent film is less than the horizontal width of the transparent pattern portion, absorption of exposure light by the adjacent light shielding pattern can be reduced. In addition, a sufficient amount of exposure light can be obtained while suppressing a decrease in the amount of transmitted exposure light.

Here, in the phase shift mask of the present invention, the exposure light transmittance of the semitransparent film is lower than the exposure light transmittance of the transparent mask substrate, and the exposure light transmittance of the light shielding film is higher than the exposure light transmittance of the semitransparent film. More specifically, the exposure light transmittance of the transparent mask substrate is 80% or more,
It is preferable that the exposure light transmittance of the translucent film is greater than 0.5% and 30% or less, and the exposure light transmittance of the light shielding film is 0.5% or less.

When the light shielding film is made of chromium, the exposure light transmittance of the light shielding film can be adjusted to 0.5% or less. Further, when the translucent film is made of tantalum silicide, zircon silicide, molybdenum silicide, chromium fluoride, or silicon oxide, the exposure light transmittance of the translucent film is adjusted to more than 0.5% and 30% or less. be able to.

In the phase shift mask of the present invention, when the wavelength of the exposure light applied to the phase shift mask is λ and the numerical aperture of the lens that collects the exposure light is NA, the lateral width of the translucent film is: The width of the light-shielding film provided immediately above the translucent film may be wider than the width of 0.15λ / NA.

With this configuration, since the width of the semitransparent film is surely wider than that of the light shielding film, in addition to the light shielding film being stably disposed on the transparent mask substrate, the semitransparent film as described above Thus, the effect of correcting the light amplitude of the exposure light can be obtained with certainty.

The method for producing a phase shift mask of the present invention includes a transparent mask substrate and a translucent film layer formed on one main surface of the transparent mask substrate, the material being lower than the exposure light transmittance of the transparent mask substrate. And a phase shift mask precursor provided on the semitransparent film layer, and a light-shielding film layer made of a material lower than the exposure light transmittance of the semitransparent film, from the semitransparent film layer and the A part of the light-shielding film layer is etched to form a translucent film having a first light-shielding pattern;
A semi-transparent film forming step for forming a light-shielding film having a light-shielding pattern, and after the semi-transparent film forming step, a part of the light-shielding film having the first light-shielding pattern is further etched to form a second light-shielding film. A light-shielding film forming step to be processed into a pattern, and after the light-shielding film forming step, one main surface of the transparent mask substrate is etched and immediately below the opening shared by the first light-shielding pattern and the second light-shielding pattern And a step of forming a digging groove for a phase shifter, wherein the light shielding film forming step is configured such that the light shielding film is biased toward the digging groove. It is a process of etching from one light shielding pattern to a second light shielding pattern.

With this configuration, it is possible to manufacture a phase shift mask in which the resist resolution is improved while the light shielding pattern is miniaturized and the light shielding pattern is prevented from being peeled off. Further, with this configuration, unlike the conventional phase shift mask, a process for undercut processing is not required, so that the photomask manufacturing process can be simplified.

According to the present invention, the resist resolution of the photomask can be improved while miniaturizing the light-shielding pattern of the photomask, and the durability of the photomask can be improved by preventing peeling of the light-shielding pattern from the photomask.

  The best mode according to the phase shift mask of the present invention will be described.

<Embodiment 1>
FIG. 2 is a schematic cross-sectional view of the phase shift mask according to the first embodiment of the present invention. As shown in FIG. 2, this phase shift mask is provided on a transparent mask substrate 201, a semitransparent film 203 provided in contact with one main surface of the transparent mask substrate, and the semitransparent film 203. The light-shielding pattern 206 composed of the light-shielding film 202 having a narrower width than the semi-transparent film and the main surface portion where the light-shielding pattern is not provided have a predetermined depth in the vertical direction (details will be described later). And a digging groove 200 for a phase shifter.

Further, the light shielding film 202 in the light shielding pattern is arranged to be biased toward the digging groove closest to the light shielding pattern. Also, one side surface of the semitransparent film 203 on the digging groove side and one side surface of the light shielding film 202 on the digging groove side are arranged so as to be aligned with the vertical side surface of the digging groove 200, and each surface is arranged It has the same structure.

The opening pattern of the semitransparent film 202 is finely processed so that the narrowest opening width is equal to or less than the wavelength of exposure light used for resist processing. Specifically, the transparent pattern 207 is processed so that the narrowest width is equal to or less than the wavelength between the F ₂ laser light (wavelength: 157 nm) and the near infrared light (wavelength: 630 nm).

The transparent mask substrate 201, the semitransparent film 203, and the light shielding film 202 are composed of the semitransparent film 20.
3 satisfies the relative relationship that the exposure light transmittance of 3 is lower than the exposure light transmittance of the transparent mask substrate 201, and the light transmittance of the light shielding film 202 is lower than the exposure light transmittance of the semitransparent film 203. Each of the exposure light transmittances is specifically 80% or more of the transparent mask substrate 201, more than 0.5% and 30% or less of the translucent film 203, and the light shielding film 202. It is 0.5% or less.

As a material for the transparent mask substrate 201, specifically, F ₂ laser light (wavelength: 15).
7 nm) to near-infrared light (wavelength: 630 nm), and quartz glass showing an exposure light transmittance of 85% or more can be used.

Further, as the material of the light shielding film 202, specifically, a chromium (Cr) -based material having an exposure light transmittance of 0.5% or less in a wavelength region between the F ₂ laser light and the near infrared light is used. In addition to a single chromium film, a film made of chromium fluoride (CrF) or chromium oxide (CrO) may be used. Note that an exposure light transmittance of 0.5% or less can be said to be in a completely light-shielded state.

Further, as a material of the translucent film 203, specifically, a tantalum silicide that exhibits an exposure light transmittance of more than 0.5% and not more than 30% in a wavelength region between F ₂ laser light and near infrared light. (T
aSi), zircon silicide (ZrSi), molybdenum silicide (MoSi), chromium fluoride (CrF), silicon oxide (SiO ₂ ), or the like can be used.

In the following, a transparent mask substrate portion sandwiched between two semi-transparent films 203 is referred to as a transparent pattern 207. This transparent pattern is one main surface of the transparent mask substrate 201 on which the light shielding pattern 206 is not provided. It means a portion, and includes both one main surface portion where the digging groove 200 is provided and one main surface portion where the digging groove 200 is not provided.

FIG. 6A is a diagram showing the phase shift mask according to the first embodiment, and FIG. 6B is a diagram showing the light amplitude of the exposure light that has passed through the photomask, two types of 0 ° and −180 °. FIG. 6C is a diagram showing the light intensity distribution of the integrated exposure light that has passed through the photomask.

In addition, the solid curve drawn above the reference line in FIG. 6B represents the light amplitude of the exposure light having a relative phase of 0 °, and the solid line drawn below the reference line. The curve represents the light amplitude of the exposure light having a relative phase of −180 °.

In FIG. 6B, the broken line drawn above the reference line is transmitted when the light shielding pattern portion 606 composed of the light shielding film 602 and the semitransparent film 603 is not provided on the transparent mask substrate 601. The broken line drawn below the reference line represents the light amplitude of the exposure light (relative phase: 0 °) and passes only through the light shielding pattern portions 606 provided on both sides of the central transparent pattern portion 607. It represents the light amplitude of the coming exposure light (relative phase: + 180 °)
A solid line curve (relative phase: 0 °) drawn above the reference line in FIG. 6B described above is displayed in an integrated manner.

As shown in FIG. 6, the digging groove has a predetermined transparent pattern portion 607 on the mask.
And the optical path lengths applied to the other transparent pattern portions 607 on the mask are adjusted to shift the phases of light emitted from the respective transparent pattern portions 607 by 180 degrees (FIG. 6B). Thus, the exposure light that is diffracted directly below the light shielding pattern portion 606 composed of the light shielding film 602 and the semi-transparent film 603 is canceled, and it acts as a phase shifter that increases the contrast of the exposure light projected on the wafer. Yes (FIG. 6 (c)), the digging amount (d) is d = λ / {2 (2) where the wavelength of the exposure light is λ and the refractive index of the transparent mask substrate is n.
n-1)}.

Specifically, F ₂ laser light (wavelength: 157 nm) is used as exposure light, and quartz glass (refractive index n
: 2.0) is used as the material of the transparent mask substrate, the digging amount (d) is 100 to
130 nm.

Further, as described above, the semi-transparent film 603 is exposed through the portion provided with the semi-transparent film with respect to the exposure light transmitted through the transparent pattern portion 607 in which the digging groove is not formed. The relative phase of light is shifted by + 180 °, and the light amplitude of the transmitted exposure light of the transparent pattern portion 607 is corrected. The film thickness (m) is the wavelength of the exposure light is λ and the refraction of the translucent film. When the rate is n ′, it is defined by m = λ / {2 (n′−1)}.

Specifically, when the F ₂ laser beam (wavelength: 157 nm) is used as exposure light and the material of the transparent mask substrate is set as tantalum silicide (refractive index n ′: 1.7) as described above, this film is used. The thickness (m) is 60 nm or more and 150 nm or less. Further, near infrared light (wavelength: 630 nm) is used as exposure light, and the material of the transparent mask substrate is tantalum silicide (refractive index n ′:
In the case of 1.7), etc., the film thickness (m) is 420 nm or more and 520 nm or less.

The film thickness of the light shielding film 602 is defined such that the sum of the film thickness of the light shielding film 602 and the semitransparent film 603 is equal to or less than the lateral width of the transparent pattern portion 607, that is, the opening width of the opening of the semitransparent film. It is preferable. This is because, when the thickness of the light shielding pattern is larger than the width of the transparent pattern portion, the exposure light transmitted through the transparent pattern portion increases the amount of light absorbed by the adjacent light shielding pattern. This is because the amount of exposure light passing through the pattern is reduced, and the contrast of the exposure light projected onto the wafer cannot be sufficiently increased.

When the material of the light shielding film is Cr, if the film thickness is 60 nm or less, pinholes are easily generated in the film, and a sufficient light shielding effect cannot be obtained.
It is preferable to make it larger.

Further, when the wavelength of the exposure light applied to the phase shift mask is λ and the numerical aperture of the lens for condensing the exposure light is NA, the lateral width of the semitransparent film 603 is provided immediately above the semitransparent film. It is preferable that the width of the light shielding film 602 is defined to be wider in a range of 0.15λ / NA or less.

This range is preferable by ensuring that the width of the translucent film is wider than that of the light-shielding film, so that the light-shielding film can be stably disposed on the transparent mask substrate, and a part of the exposure light is formed by the translucent film. Adjusting the light intensity profile by adjusting the width of the translucent film while reversing the phase to increase or decrease the amount of light, thereby causing interference with the transparent exposure light of the transparent pattern part where the digging groove is not provided. It is because it can do.

A phase shift mask having the above structure was produced as follows. This manufacturing process will be described in detail with reference to the process diagram of FIG.

First, as shown in FIG. 3A, a translucent film 3 made of molybdenum silicide is in contact with one main surface of a transparent mask substrate 301 made of quartz glass by a sputtering method, a vacuum evaporation method, or the like.
03 is formed, and a light shielding film 302 made of chromium is formed on and in contact with the semitransparent film layer, and then a positive resist electron beam resist 304 is applied on the light shielding film layer. . Then, the electron beam 305 was irradiated to the electron beam resist part which covers the design position of the opening part of the semi-transparent film | membrane 303. FIG.

<Translucent film formation process>
Subsequently, using a developer, the electron beam resist portion irradiated with the electron beam 305 is removed,
After exposing a part of the light shielding film layer, the light shielding film layer and the semitransparent film layer are formed as shown in FIG. 3B by a dry etching method such as a parallel plate type reactive ion etching (RIE) method. Etching was performed in an island shape, and the lateral width and opening size of the translucent film were adjusted so that the first light-shielding pattern was as designed. Moreover, each was adjusted and processed so that the side surfaces of the etched light-shielding film and translucent film were aligned. In this semitransparent film forming step, the light shielding film layer is also etched into the first light shielding pattern.

Here, for etching of the light shielding film layer, tetrachloromethane (CCl ₄ ) and oxygen (O ₂ ) are used.
Or an etching gas (dichloromethane (CH ₂ Cl ₂ ) and oxygen adjusted at a flow rate ratio of 1: 3 was supplied. Tetrafluoromethane (C
An etching gas in which F ₄ ) and oxygen (O ₂ ) were adjusted to a flow rate ratio of 20: 1 was supplied. It should be noted that the selectivity of the etching target with these etching gases is high, and the non-target film, the electron beam resist, the transparent mask substrate, and the like are not unnecessarily etched. In addition, the etching gas and stripping solution used in the subsequent processes have high target selectivity as well.

Next, the electron beam resist 304 on the light shielding film etched into the first light shielding pattern was removed using a stripping solution in which sulfuric acid and hydrogen peroxide solution were mixed at a mass ratio of 3: 1. Subsequently, after cleaning the surface of the phase shift mask from which the electron beam resist was peeled and removed, FIG.
As shown in the figure, an electron beam resist 304 was newly applied so as to embed the light shielding film 302 and the semitransparent film 303. Thereafter, as shown in FIG. 3C, an electron beam 305 was irradiated to the electron beam resist portion covering the design position of the opening of the light shielding film 302.

<Light shielding film formation process>
Subsequently, using a developer, the electron beam resist portion irradiated with the electron beam 305 is removed,
After exposing a part of the light-shielding film, the first light-shielding pattern is formed by using the same etching gas as in the semitransparent film forming step by a dry etching method such as a parallel plate type reactive ion etching (RIE) method. As shown in FIG. 3D, the width and the arrangement of the light shielding film processed into the shape of the second light shielding pattern according to the design dimensions are further reduced. Adjusted. Below, the adjustment aspect of this light shielding film is demonstrated.

As described above, the width of the light-shielding film is the half of the light shielding film just below the light-shielding film, where λ is the wavelength of the exposure light applied to the phase shift mask during resist fabrication and NA is the numerical aperture of the lens that collects the exposure light. The width was adjusted to be narrower in the range of 0.15λ / NA or less than the transparent film.

Further, the etching process of the light shielding film from the first light shielding pattern to the second light shielding pattern is performed so that the light shielding film remains biased toward the design position side of the digging groove, that is, two adjacent island-shaped half It adjusted so that the light shielding film might remain unbalanced on the opposite end sides of the transparent film.

Next, the electron beam resist 304 on the light-shielding film adjusted to the second light-shielding pattern was removed using a stripping solution in which sulfuric acid and hydrogen peroxide water were mixed at a mass ratio of 3: 1. . Subsequently, after cleaning the surface of the phase shift mask from which the electron beam resist has been removed, as shown in FIG. 3E, a light shielding film 302 and a semi-transparent film 303 are embedded to newly form an electron beam resist 304. Was applied. Thereafter, as shown in FIG. 3E, an electron beam 305 was irradiated to the electron beam resist portion covering the design position of the digging groove of the transparent mask substrate 301.

Subsequently, using a developer, the electron beam resist portion irradiated with the electron beam 305 is removed,
After exposing a part of the transparent mask substrate, the flow rate ratio of tetrafluoromethane (CF ₄ ) and oxygen (O ₂ ) is 20: 1 by a dry etching method such as a parallel plate type reactive ion etching (RIE) method. As shown in FIG. 3 (f), the exposed transparent mask substrate was etched to form a digging groove using the etching gas adjusted to (1). In the above semi-transparent film etching process, an etching gas having the same composition as this process was used, but the environmental conditions such as plasma power and gas pressure were adjusted to prevent even the transparent mask substrate from being etched. did.

As described above, the depth of the digging groove (digging amount: d) is to act as a phase shifter, so that the wavelength of the exposure light applied to the phase shift mask during resist preparation is λ, and the refractive index of the transparent mask substrate When the rate is n, the depth is adjusted to d = λ / {2 (n−1)}.

Finally, the remaining electron beam resist 304 is completely removed using a stripping solution in which sulfuric acid and hydrogen peroxide are mixed at a mass ratio of 3: 1, and the phase shift mask according to the first embodiment is removed. Completed.

The phase shift mask 702 having the above structure is incorporated in a projection exposure apparatus including an exposure light source 701 and an exposure projection system lens 703 (numerical aperture (NA): 0.85) as shown in FIG.
Exposure light (wavelength: 157 nm) from the exposure light source 701 was applied to the phase shift mask 702 to transmit exposure light that matched the transparent pattern provided on the phase shift mask. And
After converging the transmitted exposure light to a size of 1/4 to 1/5 by the exposure projection system lens 703,
By exposing a uniform photoresist layer provided on the wafer 704, a photoresist pattern 80 is formed on the wafer 704 made of the silicon substrate 801 as shown in FIG.
2 was formed.

Resist pattern 80 processed using the phase shift mask according to the first embodiment
2 was observed, it was similar to the transparent pattern on the phase shift mask, and it was confirmed that a very fine resist pattern processing with a resolution equal to or lower than the exposure wavelength was applied with high resolution as designed.

As described above, in the phase shift mask according to the first embodiment, in the light shielding pattern composed of the light shielding film and the semi-transparent film, the light shielding film is biased toward the digging groove side closest to the light shielding pattern. Therefore, the exposure light at the periphery of the digging groove can be strongly shielded by the light-shielding film, so that the pattern of the transmitted exposure light in the transparent pattern portion provided with the digging groove can be defined, and a part of the exposure light can be half-finished. While the phase is reversed by the transparent film, the width of the translucent film is adjusted to increase or decrease the amount of light, thereby causing interference with the transmission light of the transparent pattern portion where the digging grooves are not provided, and the light intensity profile thereof. Can be adjusted.

As a result, the light intensity profile of the exposure light (phase -180 °) passing through the transparent pattern portion provided with the digging groove as the phase shifter and the transparent pattern portion not provided with the digging groove are transmitted. The light intensity profile of the incoming exposure light (phase 0 °) can be made to exactly match, making it easy to correct the deviation between the resist processing width and the photomask design dimension, and to reduce the resist pattern to below the exposure wavelength. Even when microfabricating
The resolution of the resist can be remarkably improved.

Furthermore, in the phase shift mask according to the first embodiment, since the digging grooves for the phase shifter are arranged on one main surface portion where the light shielding pattern is not provided, as shown in FIGS. This is a case where a part of the light-shielding pattern 406, such as a conventional undercut processed phase shift mask, does not have a structure floating from the transparent mask substrate (FIG. 4), and the photomask processing dimension is reduced. In addition, the light shielding pattern 506 can be reliably supported by the transparent mask substrate (FIG. 5). Therefore, the light shielding pattern 506 is difficult to peel off from the mask substrate,
Photomask durability is high.

FIG. 5 is a diagram for explaining the processing size dependency of the light shielding pattern 506 in the phase shift mask of the present invention. FIGS. 5B and 5C show the size of the light shielding pattern 506 and the transparency. The size of the pattern 507 is 3/4 or 1 / in comparison with that of FIG.
2 shows the structure of a miniaturized phase shift mask.

<Other matters>
(1) The arrangement of the light shielding pattern on the transparent mask substrate is aligned with the vertical side surface of the digging groove according to the first embodiment, and the side surface on the digging groove side of the semitransparent film and the light shielding film is arranged. The structure is not limited to the structure of the ridges in which each surface is coincident, and each side surface may be slightly shifted. However, if the side surface is completely aligned in this way, the light shielding pattern for the transmissive exposure light is used. Therefore, it is preferable that the scattered exposure light transfer due to the protruding light shielding pattern end can be surely prevented.

(2) In the phase shift mask according to the first embodiment, the light shielding pattern is hardly peeled off from the mask substrate, and the durability of the photomask is improved. In addition to not floating from the transparent mask substrate, the adhesive strength between the two can be increased by attaching a light shielding film on the transparent mask substrate via a semi-transparent film, compared to the case where the light shielding film is directly attached on the substrate. It is thought that the remarkably high level also contributes.

As described above, according to the present invention, while miniaturizing the light-shielding pattern of the photomask,
The exposure light contrast of the photomask can be improved, the peeling of the miniaturized light-shielding pattern from the photomask can be prevented, and it can also be used for microfabrication technology of semiconductor integrated circuits, so its industrial applicability Is big.

FIG. 1 is a schematic sectional view of a phase shift mask according to a conventional technique. FIG. 2 is a schematic sectional view of a phase shift mask according to the present invention. FIG. 3 is a conceptual diagram showing a manufacturing process of the phase shift mask according to the present invention. FIG. 4 is a conceptual diagram for explaining the processing size dependence of the light shielding pattern in the phase shift mask according to the conventional technique. FIG. 5 is a conceptual diagram for explaining the processing size dependence of the light shielding pattern in the phase shift mask according to the present invention. FIG. 6 is a conceptual diagram for explaining the light amplitude and light intensity distribution in the phase shift mask according to the present invention. FIG. 7 is a conceptual diagram of an optical lithography apparatus provided with a phase shift mask according to the present invention. FIG. 8 is a view showing a resist pattern after exposure and transfer produced using the phase shift mask according to the present invention. FIG. 9 is a conceptual diagram for explaining light amplitude and light intensity distribution in a photomask according to a conventional technique.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Transparent mask substrate 102 Light-shielding film 201 Transparent mask substrate 202 Light-shielding film 203 Semi-transparent film 206 Light-shielding pattern 207 Transparent pattern 301 Transparent mask substrate 302 Light-shielding film 303 Semi-transparent film 304 Electron beam resist 305 Electron beam 401 Transparent mask substrate 402 Light-shielding film 406 Light-shielding pattern 407 Transparent pattern 501 Transparent mask substrate 502 Light-shielding film 503 Semi-transparent film 506 Light-shielding pattern 507 Transparent pattern 601 Transparent mask substrate 602 Light-shielding film 603 Semi-transparent film 606 Light-shielding pattern 607 Transparent pattern 701 Exposure light source 702 Phase shift mask according to the present invention 703 Exposure projection system lens 704 Wafer 801 Silicon substrate 802 Photoresist 803 Transparent mask substrate 804 Light shielding film 805 Semitransparent film 901 Transparent mask substrate 9 2 shielding film

Claims (9)

A transparent mask substrate;
A light shielding pattern provided on one main surface of the transparent mask substrate;
In the phase shift mask provided with a digging groove for a phase shifter provided in the one main surface portion where the light shielding pattern of the transparent mask substrate is not provided, and the one main surface portion is digged,
The light-shielding pattern comprises a semi-transparent film provided on one main surface of the transparent mask substrate, and a light-shielding film provided on the semi-transparent film and having a narrower width than the semi-transparent film,
The arrangement of the light shielding film in the light shielding pattern is biased toward the digging groove side closest to the light shielding pattern,
The exposure light transmittance of the translucent film is lower than the exposure light transmittance of the transparent mask substrate,
An exposure light transmittance of the light shielding film is lower than an exposure light transmittance of the translucent film. The digging groove has a vertical side surface formed by vertically digging one main surface of the transparent mask substrate;
2. The phase shift mask according to claim 1, wherein one side surface of the semitransparent film and one side surface of the light shielding film are arranged in alignment with a vertical side surface of the digging groove. The phase shift mask according to claim 1, wherein a film thickness of the translucent film is 60 nm or more and 520 nm or less. 2. The phase shift mask according to claim 1, wherein a sum of film thicknesses of the light shielding film and the semitransparent film is equal to or less than a lateral width of a transparent pattern which is a main surface portion on which the light shielding pattern is not provided. The exposure light transmittance of the transparent mask substrate is 80% or more,
The exposure light transmittance of the translucent film is greater than 0.5% and 30% or less,
The phase shift mask according to claim 1, wherein the light shielding film has an exposure light transmittance of 0.5% or less. The phase shift mask according to claim 1, wherein the light shielding film is made of chromium. The translucent film is made of tantalum silicide, zircon silicide, molybdenum silicide,
The phase shift mask according to claim 1, wherein the phase shift mask is made of chromium fluoride or silicon oxide. When the wavelength of the exposure light applied to the phase shift mask is λ, and the numerical aperture of the lens that collects the exposure light is NA,
The width of the translucent film is less than the width of the light shielding film provided immediately above the translucent film.
. The phase shift mask according to claim 1, wherein the phase shift mask is wide in a range of 15λ / NA or less. A transparent mask substrate, a semitransparent film layer made of a material lower than the exposure light transmittance of the transparent mask substrate, provided on one main surface of the transparent mask substrate, and provided on the semitransparent film layer Etching a part of the semitransparent film layer and the light shielding film layer from a phase shift mask precursor comprising a light shielding film layer made of a material lower than the exposure light transmittance of the semitransparent film; A translucent film forming step of forming a translucent film having one light-shielding pattern and a light-shielding film having the first light-shielding pattern;
A light-shielding film forming step of further etching a part of the light-shielding film having the first light-shielding pattern after the semi-transparent film forming step to process into a second light-shielding pattern;
After the light shielding film forming step, one main surface of the transparent mask substrate is etched to form the first
A step of forming a dug groove for a phase shifter immediately below an opening shared by the light shielding pattern and the second light shielding pattern,
The step of forming a light shielding film is a process of etching from the first light shielding pattern to the second light shielding pattern so that the light shielding film is biased toward the digging groove side. Production method.

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