JPH0440455A - Manufacture of phase shift mask - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention will be explained in the following order.

Industrial Application Field Overview of the Invention Conventional Technology Problems to be Solved by the Invention Means for Solving Problems Examples of Actions Example-1 Example-2 Example-3 Effects of the Invention [Industrial Applications] Field] Each invention of the present application relates to a method for manufacturing a phase shift mask. Each invention of the present application can be used as a method for manufacturing a phase shift mask used in various pattern forming techniques, for example, manufacturing a phase shift photomask used as a mask for forming a resist pattern in a semiconductor device manufacturing process. It can be used as a method.

[Summary of the invention]

Each of the inventions of the present application provides for a phase shift mask having a light shielding part, a light transmitting part, and a phase shift part on a transparent substrate. A phase shift mask can be easily obtained by forming a side wall made of a material and using this as a phase shift section.

[Conventional technology]

2. Description of the Related Art Devices formed using photomasks, such as semiconductor devices, tend to have smaller processing dimensions year by year.

Against this background, in order to further improve the resolution of photolithography technology for producing miniaturized semiconductor devices, so-called phase shift technology is used to impart a phase difference to the light passing through a mask, thereby improving the light intensity profile. is in the spotlight.

For example, the minimum feature size of semiconductor integrated circuits is approaching 0.5 μm or less at the research and development level, but lithography using conventional ultra-high pressure mercury lamps' G-line (436 nm) and i-line is still the mainstream. It has become. Therefore, in order to apply such lithography technology to achieve the above-mentioned fine processing, it will be difficult to achieve the desired processing unless various modifications are made to the process.

In this respect as well, the resist process itself can be carried out as before.
Phase shift mask technology, which only modifies the mask, is attracting attention as a way to easily improve resolution.

This technique was introduced by IBM's Levenson et al., and the conventional phase shift method is described in Japanese Patent Application Laid-open No. 173744/1983 and l'1ARc.
D.

LEVENSON and others “Improving Re5ol”
tion in Photolith.

graphy with a Phase-3h
ifting Mask'' IEEE TRANS
ACTIONS ON ELECTRON DE
VICES, VOL, ED-29No, 12D
ECEMBER1982, P1B28~1836, also MARCD, LEVENSON and others “The Phas”
e-5lifting MaskII: Imagi
ngSimulations and Submicr
ometer Re5ist Exposures Vow, ED-31, No. 6. JUNE 198
4. It is described in P2S5-763.

The conventionally known phase shift method will be explained using FIG. 5 as follows.

For example, when forming a line-and-space pattern, a typical conventional mask uses a light-shielding material such as Cr (chromium) on a transparent substrate l such as a quartz substrate, as shown in Figure 5(a). A light shielding part 10 is formed using a material, and a repeating pattern of lines and spaces is formed thereby to serve as an exposure mask. Ideally, the intensity distribution of the light transmitted through this exposure mask is zero at the light shielding part 10 and at other parts (transmissive parts 12a, 12b), as shown by the symbol AI in FIG. 5(a). Let's pass through. Considering one transmitting part 12a, the transmitted light given to the exposed material has a light intensity distribution with a hill-like maximum at the bottom of both sides, as shown by A2 in FIG. 5(a), due to light diffraction etc. become. The transmitted light toward the transmitting portion 12b is indicated by a dashed-dotted line. Combining the light from each transmission part 12a and 12b, A3
As shown in the figure, the light intensity distribution loses its sharpness and the image becomes blurred due to light diffraction, making it impossible to achieve sharp exposure. On the other hand, the light transmitting portion 12a of the repeating pattern.

If phase shift parts 11a (referred to as shifters) are provided on every other phase shift part 12b as shown in FIG. 5(b),
Image blur caused by light diffraction is canceled out by phase inversion, a sharp image is transferred, and resolution and focus latitude are improved. That is, as shown in FIG. 5(b), when a phase shift section 11a is formed in one of the transmission sections 12a, if the phase shift section 11a provides a phase shift of, for example, 180 degrees, the light passing through the phase shift section 11a is The light is inverted as shown by the symbol B1.

The light from the transmission section 12b adjacent to it is transmitted to the phase shift section 11.
Since it does not pass through a, such inversion does not occur. The light applied to the exposed material is inverted and cancels each other out at the bottom of the light intensity distribution at the position shown at 82 in the figure, resulting in the distribution of light applied to the exposed material as shown in Figure 5(b). As shown in 83, it has a sharp ideal shape.

In the above case, to make this effect most reliable, it is most advantageous to invert the phase by 180°. , λ is the exposure wavelength).

When forming a pattern by exposure, the one that performs reduced projection is sometimes called a reticle, and the one that projects one-to-one is called a mask, or the one that corresponds to the original is called a reticle, and the one that reproduces it is called a mask. However, in the present invention, masks and reticles in various meanings are collectively referred to as a mask.

Recently, in the above-mentioned phase shift technology, the method shown in FIG. 4 has been proposed as a technology that has good resolution and can easily form a phase shift film using a self-alignment method.
ch, Dig, 1989.3-3, also 1990
Spring Proceedings of the Japan Society of Applied Physics 28a-PD-2).

In this technique, chromium on the substrate 1 is patterned using an EB resist pattern 20 to obtain a chrome pattern 10b (FIG. 4(a)), and then, after appropriately removing the EB resist pattern 20, a photoresist which also serves as a phase shift material is applied. As shown in FIG. 4(b), PMM8 was coated to a thickness such that the phase of the transmitted light used as the exposure light of the phase shift mask is reversed by 180 degrees, and then the substrate was coated as shown by arrow P in the same figure. Exposure to far ultraviolet rays from the back side of 1. PMM
The A layer is designated by 11'. This results in chrome pattern 1
Transfer 0b onto PMMA and develop it to create PMMA pattern 11.
The structure of FIG. 4(C) having a PMMA pattern II" is obtained. Thereafter, the chromium pattern 10b is set back by side etching to obtain a ROM light shielding part 10c as shown in FIG. 4(d). A phase shift mask structure is obtained in which the portion where the chromium light shielding portion 10c is not present is used as the phase shift portion 11.

[Problem that the invention seeks to solve]

According to the above-mentioned conventional technology, it may be said that a self-aligned phase shift mask can be produced relatively easily, but since the phase shift portion 11 is obtained by recessing the chrome pattern 10b by etching, its width W is determined by controlling the regression, and it is difficult to control the regression due to etching well. Also, the process is still quite complex.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a method for manufacturing a phase shift mask that can obtain a phase shift portion with good controllability through a simple process.

[Means for solving problems]

The invention of claim 1 of the present application is a method for manufacturing a phase shift mask including a light shielding part, a light transmitting part, and a phase shift part on a transparent substrate, the method comprising: forming a light shielding material layer on the transparent substrate; The light-shielding material layer is patterned to form a light-shielding material pattern, a phase shift material film is formed on the entire surface, and a sidewall made of the phase shift material is formed on at least a sidewall of the light-shielding material pattern by etching back. This is a method for manufacturing a phase shift mask, characterized in that the phase shift portion is a phase shift portion. With this configuration, the above object has been achieved.

The invention of claim 2 of the present application is a method for manufacturing a phase shift mask including a light shielding part, a light transmitting part, and a phase shift part on a transparent substrate, the method comprising: forming a light shielding material layer on the transparent substrate; The light-shielding material layer is patterned to form a light-shielding material pattern, a resist pattern having a shape corresponding to the light-shielding material pattern is formed on the light-shielding material pattern, a phase shift material film is formed on the entire surface, and etching is performed. This method of manufacturing a phase shift mask is characterized in that a side wall made of a phase shift material is formed on the side wall of a light shielding material pattern and a resist pattern in the background, and this side wall is used as a phase shift portion.

With this configuration, the above object has been achieved.

In each invention of the present application, the phase shift portion refers to a portion that transmits exposure light at a phase different from that of the exposure light transmitted by the light transmission portion. The light shielding section is a section that blocks the exposure light used, and the light transmitting section is a section that transmits the exposure light used. It is desirable that the light-shielding part and the light-transmitting part have high light-blocking properties and high light-transmitting properties, respectively, but they do not necessarily completely or nearly completely block light or do not transmit light to the extent necessary to form the required pattern. Any material that blocks or transmits the light may be used.

Like the light transmitting part, the phase shift part is also desired to have a high light transmittance, but it may be of any type as long as it can perform the necessary phase inversion and exposure.

The material for the light shielding part is chromium, other chromium oxide,
Alternatively, all high melting point metals (W, Mo, Be, etc.) and their oxides can be used.

The light transmitting section can be configured to transmit light from a transparent substrate portion in which no light shielding section or phase shift section is formed, as it is.

As the transparent substrate, quartz, ordinary glass, glass containing various components as appropriate, and other appropriate materials can be used.

In each invention of the present application, any material can be used for the phase shift portion as long as it can form a sidewall by etching back and can produce the above-described phase shift effect. For example, silicon oxides such as 5iO7 and SiO, silicon nitrides, organic photosensitive compositions (resists), etc. can be used.

In the invention of claim 2 of the present application, the resist material of the resist pattern formed on the light-shielding material pattern is as follows:
Any material can be used as long as it can be patterned into a shape corresponding to the light-shielding material pattern.

The light-shielding material pattern and the resist pattern may be formed in the same process. Easily, after forming a light-shielding material pattern, a positive resist film is formed, the light-shielding material pattern is exposed to light through a mask by back exposure, and developed, and the positive resist is patterned into a shape that exactly corresponds to the light-shielding material pattern. Obtainable.

Regarding the structure of each invention of this application, FIGS.
) to (h) are as follows.

The invention of claim 1 of the present application provides a transparent substrate 1 with a light shielding part 10 (10b), a light transmitting part 12, and a phase shift part 11 (llb) as illustrated in FIG. 1(e). 1(a) is a manufacturing method for manufacturing a phase shift mask equipped with
), a light-shielding material layer 10a is formed on a transparent substrate 1, and the light-shielding material layer 10a is patterned to form a light-shielding material pattern 10b to obtain a structure as shown in FIG. 1(c). As shown in FIG. 1(d), a phase shift material film 11a is formed on the entire surface and etched back to form a side wall llb made of a phase shift material on at least the side wall of the light shielding material pattern 10b as shown in FIG. 1(e). This is used as the phase shift section 11.

The invention of claim 2 of the present application is to form a light shielding material layer 10a on a transparent substrate 1, as illustrated in FIGS. 2(a) to (h). The light-shielding material pattern 10b is formed by patterning on the light-shielding material pattern 10b (FIG. 2(c)).
A resist pattern 21 having a shape corresponding to the second pattern is formed.
The structure is as shown in FIG. (f), and then the phase shift material film 11
A is formed on the entire surface, and then etched back in FIG. Therefore, as illustrated in FIG. 2(h), a light shielding portion 10 (
10b), the light transmission section 12, and the phase shift section 11 (ll
b) A phase shift mask is obtained.

[Effect]

According to each invention of the present application, the phase shift portion etch-hacks the phase shift material film to form a sidewall on the sidewall of the light-shielding material pattern (or the light-shielding material pattern and the resist pattern), and phase-shifts the sidewall. Since the phase shift portion has a width, shape control such as the width of the phase shift portion can be controlled by etchback conditions. Therefore, according to each of the inventions of the present application, a phase shift mask can be formed with good controllability and by a conventionally well-known and easy process.

〔Example〕

Examples of the present invention will be described below. However, it goes without saying that the present invention is not limited to the examples described below.

Example 1 This example embodies the present invention in the case of manufacturing a phase shift mask used in manufacturing a miniaturized and integrated semiconductor device.

Please refer to FIGS. 1(a) to (e).

In this embodiment, quartz was used as the transparent substrate 1, and in particular, a thin tantalum film was formed on the quartz substrate 1 as the etching stopper film 1a. In this example, 5in2 is used as the phase shift material, so the 5i
This is to protect the underlying quartz during etching. In this example, the tantalum film as the etching stopper film 1a was formed to a thickness of 200 mm. In addition, a 5iN (silicon nitride) film can be used as the material for the etching stopper film 1a, and any material can be used as long as it serves as a stopper during SiO□ processing and notching. However, from the viewpoint of conductivity during EB writing, it is preferable to use a film of a conductive material such as tantalum or ITO (indium tin oxide).

In this embodiment, as described above, a blank having a thin etching stopper film 1a on a quartz substrate 1 is used, and a light shielding material layer 10a is formed thereon.

In this example, Cr was used as the light-shielding material, and the thickness of the Cr layer, which is the light-shielding material layer 10a, was 1300 layers.

This is generally thicker than when a Cr layer is attached as a light-shielding film, and is about twice as thick as a normal one. However, in this example, a sidewall is formed on the sidewall of this Cr layer using SiO Since the phase shift portion 11 is used, the thickness is set to correspond to the shifter film thickness in the case of exposure using excimer laser light (K r F 250 nm) as exposure light. Of course, this thickness is sufficient for the light shielding function.

The optimum thickness of the phase shift film can be theoretically determined from the above formula based on the wavelength of the exposure light used and the refractive index of the phase shift material, as described above. When the phase shift part is given in the form of a sidewall (see Fig. 1(e)), this is somewhat rounded, so this does not necessarily match the theoretical value, but in this example, the film thickness set above is It was just right.

Next, in this embodiment, a resist film is formed and patterned to form an opening 20' as shown in FIG. 1(b).
A resist pattern 20 was formed. Specifically, in this example, EB resist (product name: EBR-9,
(manufactured by Toshi ■), baked, and using MEABES (PerkinElmer) as an EB exposure device,
After exposure at an accelerating voltage of kV, development was performed with a developer suitable for the resist used to form a resist pattern 20. Set this to 0
Descum (removal of residue, etc.) was performed with □. Thereafter, the light-shielding material layer 10a was patterned using the resist pattern 20 as a mask. Here, a light-shielding material pattern 10b having an opening 10' was formed by etching with fuming nitric acid. The obtained structure is shown in FIG. 1(c).

Note that the etching means for patterning the light-shielding material layer 10b is also optional; in this example, since the light-shielding material is Cr, a means using commonly used fuming nitric acid was simply adopted, but other etching solutions for Cr may also be used. Furthermore, if the light-shielding material is other than Cr, it goes without saying that appropriate etching means should be used accordingly.

Next, a phase shift material film 1 is placed on the structure shown in FIG. 1(c).
1a is formed on the entire surface to obtain the structure shown in FIG. 1(d). In this specification, "forming on the entire surface" means forming on the entire surface of the required processed portion.

In this embodiment, 5iO7 is used as the phase shift material, and a SiO□ film is formed as the phase shift material film 11a. For forming the phase shift material film 11a such as a SiO□ film, CVD, sputtering, vapor deposition, or any other method may be used depending on the material. Generally, since the pattern size is large, there is no need to consider the problem of embedding of minute parts. Specifically, in this example, SiO□ was magnetron sputtered to form a film with a thickness of 4000 mm.

Next, perform an ecchi hack. As a result, Fig. 1(d)
As shown in FIG. 1(e), a structure is adopted in which a sidewall llb is formed on at least the sidewall of the light-shielding material pattern 10b. This sidewall Llb is obtained by etching the phase shift material film 11a, and is therefore made of the phase shift material.

In this example, the phase shift material film 11a is 5iOz
The entire surface of the film is etched, and in this case, the etching is performed under conditions that overetch by 30% compared to the just etching conditions, so that 5i02 is not left on the surface and only the sidewall llb is left on the sidewall of the light-shielding material pattern 10b. did. As specific etching conditions, DEA
-503, and a mixed gas of C2F6=503CCM8r=205CCM was used for etching. At this time, although the quartz that is the substrate 1 can also be etched under these conditions, in this example, the substrate 1 is provided with an etching stopper film 1a made of tantalum, so that the substrate 1 is protected from etching at this time.

In this example, the sidewall llb shown in FIG.
The sidewall l1b (phase shift part 11
) The exposed portion of the substrate 1 between the two portions is made into a light transmitting portion 12.

However, from the structure shown in Figure 1(e), the sidewall l
The desired phase shift portion 11 and light shielding portion 10 may be obtained by patterning the lb and the light shielding material pattern 10b.

In this example, the structure shown in FIG. 1(e) was used as the final phase shift mask. Using this phase shift mask, an exposure experiment was conducted as follows.

That is, KrF excimer laser stepper (NA: 0.37
) and 5AL601 manufactured by Shipley Co., Ltd. as a resist to form a film with a thickness of 0.7 μm.
After baking for seconds and exposing, a post-exposure bake was performed at 110° C. for 90 seconds to obtain a pattern.

When the above exposure experiment was carried out using the phase shift mask of this example having the phase shift section 11, a line and space pattern of 0.3 μm could be resolved. on the other hand,
For comparison, when we conducted a similar exposure experiment using a mask with the same structure but without a phase shift part, we found that the resolution was barely 0.4 μm line-and-space pattern at its finest. there were.

According to this embodiment, there is no need for combined exposure for EB drawing, and a phase shift mask can be easily created.

Example 2 This example embodies the invention of claim 2 of the present application.

Refer to FIGS. 2(a) to (h).

In this example as well, a blank was used in which a thin tantalum film was formed on a quartz substrate 1 to serve as an etching stopper film 1a, and a light shielding material layer 10a was formed thereon. In this example, Cr was used as the light-shielding material; however, in this example,
The thickness was thinner than in Example 1, and was approximately 2000 people.

Next, as shown in FIG. 2(b), <EB resist pattern 2
0 and pattern this light shielding material layer 10a,
A light-shielding material pattern 10b was formed as shown in FIG. 2(c).

Next, a resist pattern 21 having a shape corresponding to the light-shielding material pattern 10 is formed thereon, and this was realized in the following manner in this embodiment.

First, a positive resist layer 2 is formed as shown in FIG. 2(d). The film thickness was approximately 2000 people.

Next, the resist is irradiated with exposure light P from the back side (the side opposite to where the resist layer 2 is formed),
Expose (Fig. 2(e)). Here, exposure was performed using a mercury lamp at an exposure amount of 200 mJ/cfl. As a result of this back exposure, the light-shielding material pattern 10b serves as a mask, and only the portions that are not shielded by the light-shielding material pattern 10b are exposed. Thereafter, by performing baking or the like as appropriate and developing, a resist pattern 21 having a width exactly corresponding to the light-shielding material pattern 10b is formed as a self-aligned line, as shown in FIG. 2(f).

Specifically, in this example, TSMR88 was used as the resist.
00 (manufactured by Tokyo Ohka ■) to form a resist layer 2,
After prebaking at 90°C for 90 seconds, exposure was performed by irradiating with corresponding exposure light, and then post-baking was performed at 200°C for 60 seconds. Post-haking is performed at a fairly high temperature in order to strengthen the resist layer 2. Next, using a 2.8% aqueous solution of NASD-TD as a developer, development was carried out for 60 seconds, thereby forming the resist 1-pattern 21 corresponding to the light-shielding material pattern 10b as shown in FIG. 2(f).
I got it.

In this way, the structure shown in FIG. 2(f) is obtained in which the light-shielding material burnt 10b and the resist pattern 21 having the same planar shape are laminated.

Next, a phase shift material film 11a is formed thereon. This example is also the same as Example 1 (using 5i02 and having the structure shown in FIG. 2(g)).

Subsequently, the entire surface is etched back, and as shown in FIG. 2(h), a phase shift material (in this case, Si
A sidewall llb consisting of 0□) was formed.

The formation of the SiO□ film, which is the phase shift material film 11a, and the etchback conditions were the same as in Example-1.

As a result, as shown in Fig. 2 (h), the side wall l
lb, a light transmitting part between the phase shift parts 11, and a light shielding part 1 comprising a light shielding material pattern 10b.
A phase shift mask with 0 was obtained.

In this embodiment, the thickness of the laminated film of the light shielding material pattern 10b and the resist pattern 21 is
Therefore, the thickness of the phase shift portion 11 is determined by this. Therefore, by controlling the thickness of the laminated films of both 10b and 21, an appropriate phase shift effect can be obtained.

Example 3 In this example, Examples 1 and 2 were used as phase shift materials.
Since i02 was used, an etching stopper film is required when using a quartz substrate, but this is an example in which an organic film (resist, etc.) is used as the phase shift material and an etching stopper is not required.

Please refer to FIGS. 3(a) to 3(e).

In this embodiment, a light shielding material film 10a is directly formed on the quartz substrate 1.
form. In this example, the Cr film was formed to a thickness of 1800 mm (FIG. 3(a)).

A resist layer is formed on this and patterned by EB drawing or the like as appropriate to form a resist pattern 20 as shown in FIG. 3(b).
The light-shielding material film 10a is then patterned by etching or the like to obtain the light-shielding material pattern 10b (third
Figure (C)).

Thereafter, a phase shift material film 11a was formed as an organic film using a polyvinylphenol resist (FIG. 3(d)).

This was etched to obtain a structure having sidewalls Ilb as shown in FIG. 3(e). In this case, 0□ plasma etching was used as the etchback means. Since the quartz substrate 1 is not etched under these etching conditions, an etching stopper film is naturally unnecessary.

In this example as well, the sidewall llb formed by this etching is used as it is as the phase shift section 11.

In the above example, a polyvinylphenol film was used as the organic film, but other films such as novolac or PMMA may also be used.

〔Effect of the invention〕

As described above, according to the method for manufacturing a phase shift mask according to each invention of the present application, a phase shift portion can be obtained with good controllability through a simple process.

1... Substrate, 21... Resist pattern, 10...
- Light-shielding part, 10a... Light-shielding material layer, 10b... Light-shielding material pattern, 1st piece... Phase shift part, Ila...
Phase shift material film, llb...side wall, 12
...Light transmitting part.

Claims (1)

[Claims] 1. A method for manufacturing a phase shift mask including a light-shielding part, a light-transmitting part, and a phase-shifting part on a transparent substrate, the method comprising: forming a light-shielding material layer on the transparent substrate; Patterning the material layer to form a light-shielding material pattern, forming a phase-shifting material film over the entire surface, etching back to form a sidewall made of the phase-shifting material on at least the sidewall of the light-shielding material pattern, and shifting the phase. A method for manufacturing a phase shift mask, comprising: 2. A method for manufacturing a phase shift mask including a light-shielding part, a light-transmitting part, and a phase-shifting part on a transparent substrate, the method comprising: forming a light-shielding material layer on the transparent substrate; and patterning the light-shielding material layer. A light-shielding material pattern is formed, a resist pattern having a shape corresponding to the light-shielding material pattern is formed on the light-shielding material pattern, a phase shift material film is formed on the entire surface, and the sidewalls of the light-shielding material pattern and the resist pattern are etched back. 1. A method for manufacturing a phase shift mask, comprising forming a side wall made of a phase shift material on the surface of the mask, and using the side wall as a phase shift portion.