JPH06186728A - Production of photomask - Google Patents

Abstract

PURPOSE:To easily produce the photomask having shifter parts varying in the thickness of the edge parts of shifter parts from the other parts. CONSTITUTION:A shifter part forming material 31 is worked by a wet etching method to form the shifter parts. Prescribed side etching is, however, generated in the shifter part forming material 31 at the time of wet etching by controlling the adhesion of resist patterns 43 to be used as an etching mask at the time of wet etching to the shifter part forming material 31. Since the thickness and shape of the edge parts of the shifter parts are controllable simultaneously with the formation of the shifter parts, the photomask having the shifter parts different in the thickness of the edge parts of the shifter parts form the other parts is produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a photomask for a phase shift method, and more particularly to a method for manufacturing a photomask characterized by a method for forming a shifter portion.

[0002]

2. Description of the Related Art In the field of photolithography using a projection exposure method, various techniques have been proposed which can form a fine resist pattern that can be used for high integration of semiconductor devices. Among them, one of the technologies attracting attention is a technology called a phase shift method. This is a technique in which a portion (shifter portion) for shifting the phase of exposure light is partially provided on a photomask in order to increase the contrast of light on the wafer, thereby improving the resolution of the projection exposure method. However, in this method, for example, reference I (SPIE, Vol. 1464 (1991), pp.
327-335), the photomask used is, for example, the edge portion 13a of the shifter portion 13 on the light transmission region 11 as shown in the plan view of FIG.
A photomask 15 having a structure in which is located (in the figure, a photomask for line and space pattern is shown.
Is a light shielding part. ), The light intensity in the resist portion corresponding to the edge portion 13a is reduced even though it is a light transmitting region. As a result, when a positive resist is used as the resist, as shown in FIG. To
There is a problem that an unnecessary pattern 21 (resist remaining portion) is formed on the portion of the wafer 19 corresponding to the edge portion 13a. Therefore, in order to solve this, in Document I, the shifter portion 25 formed on the photomask substrate 23 as shown in the sectional view of FIG. 15 includes a first shifter layer 25a and a second shifter layer 25b. And the edge portion (P portion in FIG. 15) of the shifter portion 25 is constituted only by the first shifter layer 25a. However, the first shifter layer 25
a is a film that changes the phase of the exposure light by 90 degrees, and the second shifter layer 25b is formed by both the first and second shifter layers 25a and 25b so as to change the phase of the exposure light by 180 degrees. In this photomask, the edge portion of the shifter portion 25 is made of a film having a small rate of changing the phase of the exposure light (first
Since it is composed of the shifter layer 25a), the decrease in the intensity of the exposure light at the edge portion P can be made smaller than in the case where it is not formed, so that the above-mentioned problems can be solved.

[0003]

However, in the above-mentioned structure, the first shifter layer forming thin film is formed, the resist pattern is formed thereon, and the first shifter layer forming thin film is patterned using this as a mask. Then, it is necessary to remove the resist pattern, and then to perform the above-described series of steps such as the resist layer formation for the second shifter layer as well, which complicates the photomask manufacturing step. In order to avoid this, there is provided a structure in which the shifter portion is composed of one continuous body and the thickness of the edge portion of the shifter portion is different from that of the other portions of the shifter portion to adjust the amount of change in the phase of the exposure light at the edge portion. Conceivable.
However, for this purpose, a method for easily manufacturing a photomask having a shifter portion having such a structure is desired.

The present invention has been made in view of the above circumstances, and therefore an object of the present invention is to easily manufacture a photomask having a shifter portion in which an edge portion of the shifter portion has a thickness different from other portions. To provide a way to do it.

[0005]

In order to achieve this object, this application claims the method of the first invention and the method of the second invention below. The photomask in the first and second inventions also includes a reticle.

First, according to the first invention, when manufacturing a photomask for a phase shift method in which the thickness of the edge portion of the shifter portion is different from other portions of the shifter portion, the shifter portion is not formed. The shifter portion forming material is processed by processing the shifter portion forming material by a wet etching method, and the adhesion of the etching mask used for the wet etching to the shifter portion forming material is controlled to perform the shifter portion forming material during the etching. Is performed by causing a predetermined side etching to occur.

Here, in the first invention, the shifter portion forming material may be various materials as long as it can be used as the shifter portion and can be processed by wet etching. For example, a quartz-based substrate itself for forming a photomask or a SiO ₂ -based thin film for forming a shifter separately formed on this substrate is suitable as a shifter portion forming material. These are suitable as a shifter material from the viewpoint of durability and optical properties, and, for example, both the original etching of the shifter portion processing and the side etching according to the present invention can be performed with good controllability using a hydrofluoric acid-based etching solution. is there.

In implementing the first invention, the control of the adhesion of the above-mentioned etching mask to the above-mentioned material for forming the shifter portion is controlled by one or a plurality of means selected from the following means (a) to (d). It is preferable to carry out by means of.

(A) A resist is used as the above-mentioned etching mask, and the baking conditions of the resist are controlled. In addition, it is preferable to select a resist having weak adhesion to the shifter portion forming material.

(B) The resist and the light-shielding portion of the photomask are used as the etching mask, and the resist is brought into contact with the portion of the shifter portion forming material where the side etching is desired to occur predominantly. Form.

(C) The shifter portion forming material before or after the etching mask is formed is humidified.

(D) Ultrasonic waves are continuously or intermittently applied to the sample during etching for processing the shifter portion forming material into the shifter portion shape.

The second invention of this application is to manufacture a photomask for a phase shift method in which the thickness of the edge portion of the shifter portion is different from that of the other portions of the shifter portion. The step of forming a positive type resist on the shifter portion forming material, exposing the positive type resist to the first exposure and developing to expose a part of the shifter portion forming material, and exposing the exposed portion to a predetermined depth. First etching step, and second exposure and development of the positive resist on the sample that has been subjected to the first etching to newly expose the shifter portion forming material portion, and the newly exposed shifter portion. The step of second-etching the forming material portion and the first-etched portion by a predetermined depth and, if necessary, the same processing as the second-exposure and development and the second-etching described above are each performed a necessary number of times. And performing the step and the step.

[0014]

According to the structure of the first invention, when the shifter portion forming material is patterned into the shape of the shifter portion, the edge portion of the shifter portion is simultaneously processed to be thinner than the other portions of the shifter portion. Also, since side etching is used,
As a result, a shifter having a sloped edge portion can be obtained. The degree to which the edge portion is thinned (also referred to as edge shape control) can be adjusted mainly by controlling (decreasing or strengthening) the adhesion of the etching mask to the shifter portion forming material. A shifter portion having a sharp and shaped edge portion can be easily obtained.

Further, in the first aspect of the present invention, the adhesion of the etching mask to the shifter portion forming material is determined as described in (a) above.
In the case of a configuration in which one or more of the means (d) to (d) are used, each of the means can be carried out independently or in any combination, so that the desired adhesion can be easily obtained. In particular, in each of the means (a) and (b), the adhesion can be controlled with the process of the current photolithography technique, and in the means (c) and (d), the current photolithography technique can be controlled. The above adhesion can be controlled only by adding a simple step to the above process.

Further, according to the structure of the second invention, the positive resist formed once is patterned at least twice, and the shifter portion forming material is etched each time the patterning is performed. Therefore, a shifter portion having at least two portions having different thicknesses can be obtained. Therefore, the central portion of the shifter portion can be formed by the first exposure, development and etching, and the edge portion of the shifter portion can be formed by the second exposure, development and etching. Furthermore, by performing exposure, development and etching n times each, a shifter portion having n different thickness portions can be obtained.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Each embodiment of the photomask manufacturing method of this application will be described below with reference to the drawings. It should be noted that the drawings used in the description merely schematically show the dimensions, shapes, and arrangement relationships of the respective constituents to the extent that the present invention can be understood. Further, in each drawing used for the explanation, the same constituents are denoted by the same reference numerals, and the duplicated explanation thereof may be omitted.

1. Description of first invention 1-1. First Embodiment of the First Invention First, a difference in side etching when an etching mask for forming a shifter portion is formed by using materials having different adhesion to the shifter portion forming material will be described. Figure 1 (A)
(D) is a diagram which is used for the explanation, and the shifter portion is formed in each of the case where the etching mask is made of a resist and the etching mask is made of a chrome film which is generally used as a light shielding portion in a photomask. It is a process drawing of an experiment which looked at the difference in how the material was etched. Both are partial cross-sectional views of the sample.

In this experiment, a photomask forming substrate 31 (quartz glass substrate) is used as a shifter portion forming material. A chromium film is formed on the entire surface of the substrate 31 by a suitable film forming method. After forming a resist pattern on the chromium film, a portion of the chromium film not covered with the resist pattern is selectively removed. Thus, a sample in which the etching mask 33 made of a chromium film is formed on a part of the substrate 31 is obtained (FIG. 1A). If a commercially available photomask forming substrate with a chrome film formed in advance is used, the chrome film forming step can be omitted.

Next, on this sample (FIG. 1A), an electron beam resist OE manufactured by Tokyo Ohka Kogyo Co., Ltd. was used in this case.
BR-1000 is applied and then pre-exposure baked for 30 minutes in a bake oven at a temperature of 140 ° C. Next, a portion of the baked resist other than the portion where the chromium film 33 remains is selectively exposed by drawing with an electron beam drawing apparatus MEBESIII (manufactured by E-Tech Co., Ltd.), and then this sample is developed, Then, in a baking oven at a temperature of 140 ° C, 30
Bake after a minute exposure. As a result, a sample having the etching mask 31 made of the chromium film and the etching mask 35 made of the resist 35 on the substrate 31 is obtained (FIG. 1B).

Next, this sample was mixed with 15% by weight of NH ₄ F.
Etching is performed at room temperature for 5 minutes and 30 seconds with 5 wt% hydrofluoric acid (hereinafter referred to as experimental buffer hydrofluoric acid). Etching masks 33, 3 of the substrate (shifter portion forming material) 31
The portion not covered with 5 was etched to a depth of about 385 nm. Further, in the sample after etching, side etching marks (undercuts) 33a and 35a were observed in the portions of the substrate 31 which were below the edge portions of the etching masks 33 and 35, respectively (FIG. 1C).
(D)). Further, the side etching mark 35a under the edge of the etching mask 35 made of resist is
From the side etching mark 33a below the edge of the etching mask 33 made of a chrome film, it was confirmed that the amount of biting in the lateral direction was large and that it had a gentle slope. This is because the adhesion of the resist to the substrate (shifter forming material) 31 is weaker than that of the chrome film. Therefore, when etching is performed with the resist as an etching mask, the etching between the etching mask 35 and the substrate 31 is caused by surface tension. It is considered that this is because the liquid easily penetrates and undercut easily occurs. The above experimental buffer hydrofluoric acid was used because the controllability of the etching rate was good. Of course, this etching solution is an example, and other solutions may be used. However, hydrofluoric acid having an ammonium fluoride (NH ₄ F) concentration of 20 wt% or less and a hydrofluoric acid concentration of 10 wt% or less is preferable from the viewpoint of easy control of etching.

Here, in the structure of FIG.
There is a difference in thickness between the part marked with and the part marked with 31b. Therefore, it is possible to provide a phase difference between the exposure lights that pass through both the portions 31a and 31b, and it is possible to control the amount of change in the phase by the thickness difference. Therefore, these two parts 31a and 31b can be used as original shifter parts. However, only one of the two portions 31a and 31b, for example, the portion 31a formed by digging the substrate may be referred to as a shifter portion. Further, a portion 31c that is side-etched between the two portions 31a and 31b that can be used as the original shifter portion is an edge portion of the shifter portion and is an unnecessary pattern (indicated by 21 in FIG. 14B). It is a part that contributes to the prevention of the occurrence of things. However, the length a of the slope at the portion indicated by 31c (see FIG. 1D)
If is too small, the effect of preventing unnecessary pattern generation cannot be obtained (for details, refer to the third embodiment described later).

1-2. Second Embodiment of First Invention Next, when the etching mask for etching the shifter portion forming material is made of resist, how the bake condition after the development of the resist influences the side etching amount of the shifter portion. Will be explained. FIG. 2 (A)-
(D) is a figure used for the description.

Therefore, three samples are prepared by coating the OEBR-1000 used in the first embodiment on a quartz glass substrate 31 for forming a photomask similar to that used in the first embodiment. Next, these samples are pre-exposure baked under the same conditions as in the first embodiment, exposed, and further developed to obtain an etching mask 35 made of a resist (FIG. 2 (A)).
After that, the baking temperature after development is set to 140, 160 or 1
Bake in a baking oven for 30 minutes, each different from 80 ° C. Next, etching is performed under the same conditions as in the first embodiment. Then, the degree of side etching in each sample after etching is observed. As a result, in all of the samples, a side etching mark having a gentle slope was observed in the portion of the substrate 31 that hits below the edge portion of the etching mask 35. However, the slope length a of the side etching mark in each sample (FIGS. 2B to 2D)
(See FIG. 2B) is 0.8 μm for a sample having a bake temperature of 180 ° C. after development (FIG. 2B) and 1.6 μm for a sample having a bake temperature of 160 ° C. after development. It was found that the sample having a baking temperature of 140 ° C. had a thickness of 2.0 μm. From this, it is possible to adjust the side etching amount of the shifter portion forming material by configuring the etching mask when forming the shifter portion with resist and changing the baking conditions, and as a result, adjust the thickness and shape of the edge portion of the shifter portion. I know what I can do.

1-3. Third Embodiment of First Invention Next, based on the findings of the first and second embodiments, a photomask for line and space pattern, which is a photomask for the phase shift method, is manufactured as follows. This description will be given with reference to FIGS. here,
FIG. 3A is a plan view of a photomask being manufactured, and FIG.
FIGS. 3B to 3D are cross-sectional views of the manufactured photomask corresponding to line I-I, line II-II, and line III-III in FIG. 3A, respectively.

First, a resist pattern (not shown) for forming a line and space pattern of a chromium film is formed on the entire surface of the photomask forming substrate 31 on which the chromium film is formed. Next, the chromium film is selectively removed to obtain a line-and-space pattern 41 of the chromium film. Three such samples are prepared. In this case, this line-and-space pattern 41 has a width W ₁ (see FIG.
(See (A)), and the pitch P ₁ is 3 μm.

Next, in terms of the size on the photomask, the width W ₂ is 3 μm and the pitch P ₂ is on every other region of the space between the chromium films of the substrate 31 of each of the three samples. 6
A line and space pattern 43 of resist having a thickness of μm is formed. The resist pattern 43 is manufactured by the same procedure as the process using the OEBR-1000 described in the first embodiment. However, the baking temperatures after development of the three samples were 140 ° C., 160 ° C., and 180 ° C., respectively.

Then, each sample is etched with the experimental buffer hydrofluoric acid used in the first embodiment at room temperature for 5 minutes and 30 seconds. Chromium pattern 4 of substrate (shifter portion forming material) 31
1 and the part not covered with the resist pattern 43 is about 3
It was etched to a depth of 85 nm. Therefore, the etched portion 31a and the non-etched portion 3 of the substrate 31
The thickness difference from 1b (see FIG. 3B) is 385 nm. When the exposure light is the i-line, there is a phase difference of 180 degrees between the lights transmitted through both portions 31a and 31b having such a thickness difference. Further, in the substrate portion below the edge portion of the resist pattern 43, side etching traces S having slopes (see FIGS. 3C and 3D) are generated as in the second embodiment, and the length of the slope is long. Sa (Figure 3 (B)
For the sample whose bake temperature after development is 180 ° C., 0.8 μm, for the sample whose bake temperature after development is 160 ° C., 1.6 μm, for the sample whose bake temperature after development is 140 ° C. It was found that the thickness was 2.0 μm.

Next, each of these three types of photomasks was used for a positive type resist (PFI-24 manufactured by Sumitomo Chemical Co., Ltd.) formed on a silicon substrate, and
5: 1 reduction ratio i-line stepper (Nikon NSRi7E
(Numerical aperture NA 0.5)) and various exposure amounts are set to perform exposure. Then, the pattern obtained by developing this resist was observed.

In an experiment using a photomask manufactured by setting the baking temperature after resist development at the time of forming a photomask to 140 ° C., an unnecessary pattern (see FIG. 14) was obtained under the exposure condition where a 0.28 μm wide line could be formed on the wafer. It has been found that the remaining portion 13a described above can be eliminated and a resist pattern 45 for a desired line and space pattern as shown in FIG. 4 can be obtained. Further, in an experiment using a photomask manufactured by setting the baking temperature after resist development at the time of forming a photomask to 160 ° C., an unnecessary pattern can be erased under the exposure condition that a line of 0.26 μm width can be formed on a wafer. I knew I could do it. Further, in an experiment using a photomask manufactured by setting the baking temperature after the resist development at the time of forming the photomask to 180 ° C., an unnecessary pattern can be erased under the exposure condition that a line with a width of 0.22 μm can be formed on the wafer. I knew I could do it.

According to the results of the third embodiment, the case where the photomask manufactured by setting the baking temperature after resist development at the time of forming the photomask to 140 ° C. is used (that is, the case where the slope length a is 2 μm is used). In addition, it is possible to prevent the generation of unnecessary patterns with an exposure amount that can obtain a line of 0.28 μm, which is the closest to the line of 0.3 μm that should be normally obtained with a 5: 1 stepper. Therefore, when the exposure light is the i-line and the stepper has a reduction ratio of 5: 1 and the NA is 0.5, the slope length a (FIG. 3C) is formed at the edge portion of the shifter portion. It can be said that by using a photomask having a shifter portion having a side etching mark larger than 2 .mu.m, a desired line and space pattern can be obtained and an unnecessary pattern can be prevented. If a stepper with the same reduction ratio as NA 0.5 and a reduction ratio of 10: 1 is used, the slope length a is 4
It can be said that it must be larger than μm.

<Comparative Example> In addition, separately from FIG.
As shown in (C), the substrate 31 is etched by the same method as the third embodiment except that the etching is performed not by hydrofluoric acid but by dry etching using CF ₄ gas (see FIG. 5B). , A comparative photo mask (however,
A bake temperature after development of the resist for forming a photomask is 140 ° C.) is manufactured (FIG. 5C). Then, using the photomask of this comparative example, a pattern of a positive type resist is formed in the same manner as described above. However, in the case of this comparative example, an unnecessary pattern is generated even if the exposure is performed under the over-exposure condition that a line of 0.20 μm width can be formed on the wafer (the pattern shown in FIG. 14B). I knew that. From this, it can be said that wet etching is more preferable than dry etching as means for etching the shifter portion forming material in carrying out the first invention. This is considered to be because side etching is more likely to occur in wet etching than in dry etching.

1-4. Fourth Embodiment of First Invention Next, the result of confirming the effect of the humidifying process will be described. Among the experimental conditions described in the second embodiment, according to the condition that the baking temperature after development is 140 ° C.,
An etching mask 35 made of a resist is formed on the substrate 31 (see FIG. 2A). Next, this sample is exposed to a high humidity atmosphere (for example, an atmosphere equivalent to 100% humidity). In this example, this humidification treatment was performed by directly applying steam generated from the humidifier to the sample for 2 minutes. After that, etching with buffer hydrofluoric acid is performed as in the second embodiment. Observation of the sample after etching revealed that the length a of the slope, which was 2 μm in the second embodiment, spreads to almost 4 μm in the fourth embodiment.

1-5. Fifth Embodiment of First Invention Next, the result of confirming the effect of ultrasonic wave application will be described. Among the experimental conditions described in the second embodiment, according to the condition that the baking temperature after development is 160 ° C.,
An etching mask 35 made of a resist is formed on the substrate 31 (see FIG. 2A). Then, this sample is etched with buffer hydrofluoric acid as in the second embodiment,
Ultrasonic waves are applied to the sample every 5 minutes for 5 seconds during an etching period of 5 minutes and 30 seconds. In addition, the application of the ultrasonic wave,
The etching liquid containing the sample is placed in an ultrasonic generator for each container (in this case, BRANSONI manufactured by BRANSONIC).
It was carried out by intermittently driving this ultrasonic generator by placing it in a water tank of a device called C220). Observation of the sample after etching revealed that it was 1.6 in the second embodiment.
It was found that the length a of the slope, which was μm, extends to almost 4 μm in this fifth embodiment.

1-6. Sixth Embodiment of First Invention In each of the above-mentioned first to fifth embodiments, a shifter portion is formed on a quartz glass substrate for forming a photomask, and the thickness of the edge portion of the shifter portion is changed from other portions. However, the first invention is also applicable to the case where a thin film for forming the shifter portion is separately formed on the photomask forming substrate and the thin film is processed into the shape of the shifter portion. This sixth embodiment is such an example. This description will be given with reference to FIGS. In each figure, the state of the sample during the process is shown by a sectional view.

An etching stopper layer 51 and a shifter portion forming thin film 5 are formed on a quartz glass substrate 31 for forming a photomask.
3 and a resist layer 55 (for example, a layer composed of OEBR-1000 used in each of the above-described embodiments) are formed (FIG. 6).
(A)). Further, a resist pattern 55a is formed (FIG. 6 (B)). However, during this series of steps,
In order to control the adhesiveness of the resist pattern 55a to the shifter portion forming thin film 53, the treatment is performed under a preferable condition among the conditions of the above-described embodiments. Thin film 53 for forming shifter portion
If SOG (spin-on-glass) is used, the adhesion of the resist layer 55 to the SOG film is reduced by performing a humidification process on the SOG film as the shifter portion forming thin film before forming the resist layer 55. be able to. The humidifying process can be performed by, for example, the method using the humidifier described in the fourth embodiment.

After that, the shifter portion forming thin film 53 is selectively etched with a suitable etching liquid such as buffer hydrofluoric acid (FIG. 6C). Here, the shifter portion forming thin film 5
If 3 is composed of SOG (spin on glass),
By etching with a 2% by volume aqueous solution of hydrofluoric acid at room temperature for 30 seconds, it is possible to perform etching with a depth of 410 nm which becomes a phase shifter portion of 180 degrees at the i-line. Moreover,
Since the adhesion of the resist pattern 55a to SOG is weakened as described above, the resist pattern 5a of the SOG film is
Desired side etching can be generated in the portion of the lower edge 5a. By removing the resist pattern 55a, a shifter portion 53a in which the edge portion 53x is thin and has a slope shape is obtained (FIG. 6).
(D)).

2. Description of Second Invention Next, an example in which the photomask manufacturing method of the second invention is applied to manufacture of a photomask for a phase shift method for forming line and space patterns will be described.

2-1. First Embodiment of Second Invention FIGS. 7 to 11 are process diagrams for explaining the first embodiment of the second invention. In particular, FIGS. 7 to 9 are plan views showing the main part of the sample in the main steps of the process, and FIGS. 10 and 11 show the samples shown in FIGS. A) I
It is shown in a cross-sectional view at a position corresponding to the −I line.

First, a line-and-space pattern of 1.5 μm formed by a chromium film 61 on a photomask forming substrate 31 which also serves as a shifter portion forming material (a pattern of 0.3 L / S on a wafer is formed by a 5: 1 stepper). The resulting mask pattern) is formed. Positive resist layer 6 on this substrate
In this embodiment, the electron beam resister (OEBR)
-1000) layer is formed (plan view of FIG. 7A, cross-sectional view of FIG. 10A).

Next, in this embodiment, only the resist layer portion corresponding to every other space portion among the space portions between the adjacent chromium films 61 (actually the partial area resist portion on the chromium film is also included) is selected. Then, the resist layer is developed and exposed by an electron beam, and then the resist layer is developed to obtain a first resist pattern 63a. This resist pattern 63a exposes every other space portion among the space portions between the chromium films 61 and a part of the chromium film 61 (FIG. 7).
10B is a plan view and FIG. 10B is a cross-sectional view). In both figures, the area indicated by Q is the area exposed from the resist layer 63.

Next, the portion of the substrate 31 in the exposed region Q is selectively etched to a predetermined depth (plan view of FIG. 8A, sectional view of FIG. 10C). A region indicated by R in FIG. 8A is a region etched by the first etching.

In this case, the etching depth d ₁ (see FIG. 10)
(See (C)) is the depth that gives a phase difference of 90 degrees to the light transmitted through the etched portion and the non-etched portion of the substrate 31. This depth is, for example, 192 nm when the exposure light is i-line. This etching may be performed by a wet etching method or a dry etching method. For example, when a 5% by volume hydrofluoric acid aqueous solution is used, the depth of 192 nm can be obtained by etching at room temperature for 2 minutes and 45 seconds. In the case of dry etching, the exposed portion of the first resist pattern 63a may not be dissolved by the developer in the developing process after the second exposure (details will be described later) of the first resist pattern 63a. If this happens,
Development is possible by slightly etching the first resist pattern 63a with O ₂ gas before development.

Next, regions of the first resist pattern 63a which are continuous on both sides in the longitudinal direction of the space portion exposed by the first exposure are selectively exposed by electron beam exposure, and then the resist pattern 63a is developed. Then, the second resist pattern 63b is formed. This second resist pattern 63b
Exposes a region that is continuous on both sides in the longitudinal direction of the space portion exposed in the first exposure, that is, a region S where an edge portion is to be formed in the shifter portion (plan view of FIG. 8B, FIG. 1).
1 (A)). In this second exposure, it is necessary to perform alignment and exposure so as to be continuous with the area exposed in the first exposure. However, this alignment is easy because there is no inconvenience even if the exposure is performed over the exposure region in the first exposure.

Next, the portion of the substrate 31 in the exposed region S is selectively etched to a predetermined depth (plan view of FIG. 9A, sectional view of FIG. 11B). In FIG. 9A, T ₁
The region indicated by is the region etched for the first time in the etching of the substrate 31, and the region indicated by T ₂ is the region etched by both the first and second etching steps. Here, the depth of the newly etched region T ₁ is set to the same depth d ₁ as in the _first etching described above. As a result, the first and second
Region T ₂ etched in both of the second etching process
Has a depth of 2d ₁ . That is, if the exposure light is assumed to be the i-line, then 2d ₁ ≈385 nm, so this portion and the substrate 31
18 between the light passing through the non-etched part of
A phase difference of 0 degrees can be produced. After that, the photomask 31a is obtained by removing the resist pattern 63b (plan view of FIG. 9B, cross-sectional view of FIG. 11C).

According to the method of the first embodiment, the thickness of the edge portion of the shifter portion (that is, the region T _{1 in} this case) is made thinner than the other portions by using one positive resist layer. You can Further, in the method of this embodiment, the phase difference between the light transmitted through the region T ₂ of the substrate 31 and the light transmitted through the portion of the substrate 31 not etched at all is set to 1.
It can be seen that it is possible to easily obtain a photomask in which the phase difference between the light passing through the region T ₂ of the substrate 31 and the light passing through the portion of the substrate 31 not etched at all can be set to 90 °. .

A similar patterning experiment to a positive resist carried out in the third embodiment of the first invention was carried out using this photomask 31a. As a result, a line and space pattern of 0.3 μm was generated without generation of unnecessary patterns. It turns out that it can be formed.

2-2. Second Embodiment of Second Invention In the first embodiment, the same positive type resist layer is exposed and developed twice, and the shifter portion forming material is etched after each development. However, in this second invention, the same resist is exposed and developed three times or more, and the shifter portion forming material is etched after each development, thereby forming an edge portion that can change the phase difference stepwise in two or more steps. It is also possible to form the shifter portion having. The second embodiment is an example in which the same resist layer is exposed and developed three times and the shifter portion forming material is etched after each development. FIG. 12 (A)
10A to 10D are views used for the explanation, and are process diagrams shown by a cross section at the same position as in FIGS.

First, the positive type resist layer 63 is formed on the substrate 31 according to the procedure described with reference to FIGS. 10 and 11, and the resist layer 63 is subjected to the first exposure, development and etching, respectively, and then the second type. Are exposed, developed and etched (FIG. 12A). However, the etching depth during the first and second etching is the substrate 3
60 degrees (that is, 180 degrees / number of etchings n) between the light passing through the area where the etching was performed and the area where the etching was not performed.
In this case, n = 3) The depth is d ₂ which gives a phase difference.
When the exposure light is i-line, d ₂ ≈128 nm.
For example, if a 5% by volume hydrofluoric acid aqueous solution is used, the depth of 128 nm can be obtained by etching each at room temperature for 1 minute and 50 seconds.

Next, a new region of the second resist pattern 63b (a new region continuous with the region exposed by the second exposure) is selectively exposed by drawing with an electron beam (third exposure). Then, the exposed portion of the second resist pattern 63b is developed to form a third resist pattern 63c (FIG. 12 (B)). Then, the entire exposed portion of the substrate 31 is etched under the condition that the newly exposed substrate portion can be etched by the depth d ₂ . As a result, on the substrate 31, there can be formed an unetched portion, a portion etched to the depth d ₂ , a portion etched to the depth 2d ₂ , and a portion etched to the depth 3d ₂ ( FIG. 12C). Therefore, at the edge portion of the shifter portion, a photomask 31b capable of changing the phase difference in steps of 60 degrees and 120 degrees is obtained (FIG. 12).
(D)).

From this fact, in the positive resist layer for forming the shifter portion, the portions corresponding to the central portion formation planned area of the shifter portion and the edge portion formation planned area are exposed stepwise, developed, and etched after each development. It can be seen that by performing the process n times, it is possible to form a photomask in which an edge portion of the shifter portion is given a phase difference of n-1 steps.

2-3. Third Embodiment of Second Invention In the first and second embodiments described above, a positive type resist is formed on a quartz glass substrate for forming a photomask, this is exposed and developed a plurality of times, and the substrate is etched after each development. Then, the shifter portion was formed and the thickness of the edge portion of the shifter portion was changed stepwise.However, a thin film for forming the shifter portion was separately formed on the photomask forming substrate, and this thin film was formed. The second invention can also be applied to the case of processing into a shape.
This third embodiment is such an example. However, this is an example in which the number of exposures is set to 2 (an example corresponding to the first embodiment). This description will be given with reference to FIGS. In each figure, the state of the sample during the process is shown by a sectional view.

An etching stopper layer 51 and a shifter portion forming thin film 5 are formed on a quartz glass substrate 31 for forming a photomask.
3 and the resist layer (for example, the OE used in each of the above-described examples).
BR-1000). Then, the resist is selectively exposed so that the resist remains on the region of the thin film 53 where it is desired to remain as the shifter portion, and the resist is developed to obtain a first resist resist pattern 57 (FIG. 13).
(A)).

After that, the first etching is performed as in the first embodiment (FIG. 13B), and then the first resist pattern 57 is subjected to the second exposure and development, and the second resist pattern is performed. 57a is formed (FIG. 13C), second etching is then performed (FIG. 13D), and the resist pattern 57a is removed to obtain a photomask 31c (FIG. 13).
(E)).

Although the respective embodiments of the inventions of the present application have been described above, the inventions are not limited to the above-mentioned embodiments. For example, although the example of forming the phase shift mask for the line and space pattern has been described in the above embodiment,
The first and second inventions can be applied to the case of manufacturing another photomask for pattern formation, and the same effect as that of the embodiment can be obtained.
In addition, the resist used in the above examples, the etching solution,
The equipment and numerical conditions are examples within the scope of the invention,
Each invention is not limited to these conditions.

[0056]

As is apparent from the above description, according to the first invention of this application, when the shifter portion forming material is patterned into the shape of the shifter portion, the edge portion of the shifter portion is changed to the other edge portion of the shifter portion at the same time. Can be made thinner than the part.
The degree of thinning the edge portion (also referred to as edge shape control) can be adjusted mainly by controlling (decreasing or strengthening) the adhesion of the etching mask to the shifter portion forming material. Further, since the adhesion can be controlled by any of a plurality of means as shown in (a) to (d) above, a desired shifter portion can be formed substantially in one lithography and etching step. can get. Therefore, a shifter portion in which the edge portion of the shifter portion has a different thickness (thinner) from the other portions can be manufactured more easily than in the conventional method.

Further, according to the method of the first aspect of the present invention, since the edge portion of the shifter has a gentle slope, it is considered that the degree of change of the phase at the edge portion changes gently, and the unnecessary pattern can be effectively reduced. Can be done.

Further, according to the structure of the second invention, for example, the central portion of the shifter portion is formed by using the resist pattern obtained by subjecting the positive type resist once formed to the first exposure and development as an etching mask. Then, the resist pattern is subjected to second exposure and development to obtain a second resist pattern, and the edge portion of the shifter portion can be formed using this second resist pattern as an etching mask. Furthermore, by performing exposure, development and etching n times each, n-
It is possible to form one step having different thicknesses. And, although the thickness difference of a plurality of steps can be generated, the resist coating is required only once. Therefore, a shifter portion in which the edge portion of the shifter portion has a different thickness (thinner) from the other portions can be manufactured more easily than in the conventional method.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a first embodiment of the first invention.

FIG. 2 is a process drawing for explaining a second embodiment of the first invention.

FIG. 3 is a diagram for explaining a third embodiment of the first invention.

FIG. 4 is an explanatory diagram of a resist pattern obtained in a third embodiment of the first invention.

FIG. 5 is an explanatory diagram of a comparative example with respect to the third example of the first invention.

FIG. 6 is an explanatory diagram of a sixth embodiment of the first invention.

FIG. 7 is a plan view of the first embodiment of the second invention.

FIG. 8 is an explanatory view of the first embodiment of the second invention, following FIG. 7 in plan view.

FIG. 9 is an explanatory view of the first embodiment of the second invention, following FIG. 8 in plan view.

FIG. 10 is an explanatory view according to a sectional view of the first embodiment of the second invention.

FIG. 11 is a sectional view of the first embodiment of the second invention.
It is explanatory drawing following 0.

FIG. 12 is an explanatory view of a main part of a second embodiment of the second invention.

FIG. 13 is an explanatory diagram of the third embodiment of the second invention.

FIG. 14 is a diagram for explaining a conventional technique.

FIG. 15 is a diagram for explaining the conventional technique.

[Explanation of reference numerals] 31: shifter portion forming material (quartz glass substrate for photomask formation) 31a, 31b: portions that can be used as original shifter portions 31c: edge portion of shifter (portion that contributes to prevention of unnecessary patterns) 33: chromium Etching mask made of film 35: Etching mask made of resist 33a, 35a: Side etching trace a: Slope length of edge part of shifter part 55: Shifter part forming material (thin film (for example, SOG)) 55a: Shifter part 55x: Edge of shifter

Claims (3)

[Claims] 1. When manufacturing a photomask for a phase shift method in which the edge portion of the shifter portion has a thickness different from that of other portions of the shifter portion, the shifter portion is formed by a shifter portion forming material. By a wet etching method, and by controlling the adhesion of the etching mask used for the wet etching with the shifter portion forming material, a predetermined side etching is performed on the shifter portion forming material during the etching. A method of manufacturing a photomask, which comprises: 2. The method of manufacturing a photomask according to claim 1, wherein the control of the adhesion of the etching mask to the shifter portion forming material is selected from the following means (a) to (d): Alternatively, a method of manufacturing a photomask is performed by a plurality of means. (A) A resist is used as the etching mask, and the baking conditions of the resist are controlled. (B) A resist and a light-shielding portion of the photomask are used as the etching mask, and the resist is formed so as to come into contact with a portion of the shifter portion forming material where the side etching is desired to occur predominantly. (C) The shifter portion forming material before or after forming the etching mask is humidified. (D) Ultrasonic waves are applied to the sample continuously or intermittently during etching for processing the shifter portion forming material into a shifter shape. 3. When manufacturing a photomask for a phase shift method in which a thickness of an edge portion of the shifter portion is different from other portions of the shifter portion, the shifter portion is formed by a shifter portion forming material. A step of applying a positive resist on the upper surface, a step of first exposing and developing the positive resist to expose a part of the shifter portion forming material, and first etching the exposed portion to a predetermined depth; The positive type resist on the first-etched sample is secondly exposed and developed to newly expose the shifter portion forming material portion, and the newly exposed shifter portion forming material portion and the first etched portion. And a step of performing the same process as the second exposure and development and the second etching, respectively, a necessary number of times. Photomask manufacturing method of a.