JPH0484411A - Preparation of x-ray mask structure - Google Patents

Abstract

PURPOSE:To enhance the density and absorption coefficient of X ray in an X-ray mask structure body by preparing an X-ray transmission film, followed by preparing a depressing layer on the surface of the X-ray transmission film, further followed by depositing X-ray absorptive material on the surface of the depressing layer by means of the gaseous phase development method, and furthermore followed by patterning the deposited film of X-ray absorptive material. CONSTITUTION:On a sufficiently flattened silicon wafer 11, SiNx film 12 to be used as X-ray transmission film is prepared until its thickness reaches 2mum by means of the LPCVD method. Next, like the above, TiN film as electronic sample is deposited until its thickness reaches 700Angstrom to prepare depression film 14 in a LPCVD apparatus. Next, silicon wafer is installed in a LPCVD apparatus to prepare deposit film 13 for X-ray absorptive material is prepared by silane conversion method of WF6. After that, SiO2 is deposited as intermediate layer 15 until its thickness reaches 1.0mum and is heated for later anisotropic etching to thicken the film. Next, the intermediate layer 15 is coated with resist and prebaked, followed by carrying out patterning on the intermediate layer 15 to prepare an exposure pattern of deposit film 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing an X-ray mask structure used in X-ray lithography.

[Conventional technology]

Conventionally, various methods have been used as lithography processing methods for electronic devices such as IC'P LSI, but among them, X-ray lithography has been the most popular method due to its unique properties such as high transmittance and short wavelength. It has many superior features compared to lithography methods using visible light and ultraviolet light, and is attracting attention as a powerful means of submicron lithography.

The X-ray mask structure used in these X-ray lithography has, for example, an X-ray transparent membrane 2 supported under tension on a support frame 1, as shown in FIGS. 1(a) and 1(b), Furthermore, a patterned X-ray absorber 3 is held on the X-ray transparent membrane 2.

Furthermore, in the manufacturing process of the X-ray mask structure shown in FIGS. 1(a) and 1(b), the patterning method of the X-ray absorber 3 has conventionally been carried out on the X-ray transparent film 2 made of X-ray absorbing material. In this method, deposition is performed by a sputtering method or an electrolytic plating method, and patterning is performed by using this in combination with a resist process and an electron beam lithography method.

[Problem that the invention is trying to solve]

However, when the X-ray absorbing material is deposited by sputtering or electrolytic plating when patterning the X-ray absorber as in the conventional example described above, the following problems occur.

First, in patterning an X-ray absorber using the sputtering method, ■ To control the grain boundary diameter of the particles that make up the X-ray absorber,
The only way to control the substrate temperature is during sputtering, which increases the variation in mass production.

(2) If an attempt is made to increase the grain boundary diameter of the material constituting the X-ray absorber, the internal stress of the X-ray absorber increases, resulting in warping after back etching (forming a support frame) of the base. There were problems such as.

Furthermore, in the patterning of the X-ray absorber using the electrolytic plating method, (1) Since it is a wet process, the frequency of defects in the X-ray absorber pattern due to minute foreign matter in the electrolytic plating solution is high.

■ Pinholes and protrusions are likely to occur on the electrode film (subbing film) (
For this reason, the electric field distribution during the deposition of the X-ray absorbing material becomes non-uniform, resulting in uneven film thickness and density of the X-ray absorber, and a distribution in the X-ray absorption rate.

There were problems such as.

Furthermore, in the X-ray absorber formed by the conventional method, the density decreases more than the bulk density of the material constituting the X-ray absorber, and the X-ray absorption rate decreases. Moreover, X
As the X-ray mask structure used in submicron lithography, the etched portion (side surface) of the radiation absorber is not sufficiently smooth, so burn-in is an undesirable problem such as a decrease in resolution and contrast. This caused problems.

An object of the present invention is to provide a novel method for manufacturing an X-ray mask structure, which solves the problems in the conventional methods for manufacturing an X-ray mask structure.

That is, an X-ray mask structure holding an X-ray absorber with high density and high X-ray absorption rate, and a method for manufacturing an X-ray mask structure capable of forming a pattern with high resolution, high definition, and printing with excellent contrast are required. It is about providing.

[Means for solving problems]

The above objects are achieved by the present invention as described below.

That is, the present invention provides a method for manufacturing an X-ray mask structure having an X-ray transparent membrane, an X-ray absorber patterned on the X-ray transparent membrane, and a support frame that supports the X-ray transparent membrane. , the step of patterning the X-ray absorber includes a) forming an undercoating layer on the surface of the X-ray transparent film after forming the X-ray transparent film, and b) applying air to the surface of the undercoating layer. A method for manufacturing an X-ray mask structure, comprising the steps of: depositing an X-ray absorbing material by a phase growth method; and C) patterning the deposited film of the X-ray absorbing material.

Hereinafter, the method for manufacturing an X-ray mask structure of the present invention (hereinafter referred to as the method of the present invention) will be described in detail.

First, in the method of the present invention, the X-ray transparent membrane and the support frame for supporting the X-ray transparent membrane are prepared by a conventionally known method. That is, regarding the X-ray transparent film, a vapor phase growth method or the like is used as the film forming method, and the film is formed to have a film thickness in the range of 1 to 3 μm. Here, the material for forming the X-ray transparent film is a material that can transmit X-rays, such as Be, B, C, and N.

Although it may be made of any combination of materials such as Af and Si, SiN is preferable in terms of Young's modulus, coefficient of thermal expansion, visible transmittance, etc. of the material.

It is preferable that it is made of SiC or the like. Furthermore, the above-mentioned X-ray transmitting film is not limited to a single-layer film, but may also be formed from a multilayer laminated film in which films made of materials such as 5i02 or polyimide are laminated for the purpose of anti-reflection film or film reinforcement. It's okay.

Regarding the support frame, after the formation of the X-ray transparent membrane (or even the X-ray absorber), there is a method of adhering it to the X-ray transparent membrane with an adhesive, or a method of attaching the X-ray transparent membrane to the X-ray transparent membrane with an adhesive, There are various methods for forming a transparent film (and even an X-ray absorber) into a frame shape (ring shape) by etching the film and the substrate. Here, the support frame is formed of a material such as glass such as Pyrex, single crystal silicon, metallic titanium, or an alloy thereof.

The method of the present invention includes the steps of manufacturing an X-ray mask structure.
In particular, the process of forming the X-ray absorber is characterized by having the following steps a), b) and C). That is, a) forming a subbing layer on the surface of the X-ray transparent film after forming the X-ray transparent film; b) depositing an X-ray absorbing material on the surface of the subbing layer by vapor phase growth. C) patterning the deposited film of the X-ray absorbing material.

First, in step a), an electron-donating material is used as the material constituting the undercoat layer.

An electron-donating material is one in which free electrons exist in the substrate or free electrons are intentionally generated.For example, a chemical reaction occurs through electron transfer with raw material gas molecules attached to the surface of the substrate. A material with a surface that is promoted. For example, metals and semiconductors generally correspond to this.

■Ga, In, AI as group elements! and P and As as group ■ elements.

A binary, ternary or quaternary m-v group compound semiconductor formed by combining N, dungesten, molybdenum,
Contains metals and alloys such as tantalum, tungsten silicide, titanium silicide, aluminum, aluminum silicon, titanium aluminum, titanium nitride, copper, aluminum silicon copper, aluminum palladium, titanium, molybdenum silicide, tantalum silicide gold, and their silicides. Further, in the method of the present invention, the thickness of the undercoat layer is preferably 100.lambda. to 1000.

Furthermore, the vapor phase growth method used in step b) above is
Preferably, the CVD method is used.

The mechanism of deposition of the X-ray absorbing material in step b) in the method of the present invention can be considered as follows.

That is, in the CVD method, the raw material gas molecules for forming the X-ray absorber undergo a chemical reaction on the surface of the undercoat layer made of an electron-donating material capable of transferring and accepting electrons, and are deposited with a certain crystal orientation ( .

Here, the X-ray absorbing material is a conventionally known material, such as Au.
, Ta, W, Mo, Cu, or other metal material having a high X-ray absorption rate, or an alloy material thereof.

In addition, in the method of the present invention, the ratio between the thickness of the deposited film of the X-ray absorbing material and the thickness of the subbing layer is such that, in particular, the thickness of the subbing layer is greater than the thickness of the deposited film of the X-ray absorbing material. It is preferable that the amount is 1% to 14%.

In the method of the invention, in particular, by having the above steps a) and b), that is, the X-ray absorbing material is deposited by a chemical reaction on the surface of the electron donating material as described above, so that the uniformity of the film is improved. A good and dense film can be obtained. In other words, an X-ray absorber with low internal stress and high X-ray absorption rate can be obtained.

Here, in the method of the present invention, as mentioned above, the material forming the X-ray transparent film may be Si, and some of this Si has electrical conductivity, that is, it corresponds to the above-mentioned electron-donating material. Something exists. However, in the method of the present invention, even when such a conductive Si material is used, it is essential to provide the undercoat layer. That is, the Si film has an oxide film (SiO
2) is likely to form, and this film reduces the deposition efficiency of the X-ray absorbing material by the above-mentioned chemical reaction. Therefore, in order for the X-ray absorber to have sufficient properties as described above, it is particularly preferable to include the formation of an undercoat layer as an essential step, as in the method of the present invention.

Furthermore, the method of the present invention is particularly effective when producing an X-ray mask structure in which the X-ray transparent film is made of SiN or SiC.

As mentioned above, it is preferable to form the X-ray transparent film with SiN or SiC from the viewpoint of the Young's modulus, thermal expansion coefficient, visible transmittance, etc. of the X-ray transparent film, but SiN.

Since SiC is a non-electron-donating material, it is not possible to deposit an X-ray absorbing material on the surface of such an X-ray transparent film by the above-mentioned vapor phase growth. In the method of the present invention, after forming a subbing layer on the surface of the X-ray transparent film, the X-ray absorbing material is deposited on the surface of the subbing layer by the chemical reaction described above.
While maintaining the above characteristics of the SiC X-ray transparent film,
Furthermore, it is possible to form an X-ray absorber having the above-mentioned desired characteristics.

Further, in the method of the present invention, the above step C) includes the above a),
The deposited film of the X-ray absorbing material formed on the surface of the undercoat layer in step b) is patterned in a desired manner by using a conventionally known resist process and an electron beam lithography method. However, when patterning the deposited film of the X-ray absorbing material, the undercoat layer may be patterned at the same time to form an exposed portion of the X-ray transparent film, or the undercoat layer may be patterned at the same time as the X-ray absorbing material is patterned and the undercoat layer is patterned at the same time. The layer may be left on the entire surface of the X-ray transparent membrane.

Hereinafter, the present invention will be explained in further detail by giving specific examples and comparative examples.

Example 1 Silicon wafer 11 with sufficiently good flatness (TIR2p
SiNxM12, which will become an X-ray transparent film, was formed to a thickness of 2 μm by the LPCVD method (Fig. 2-(a)).

The formation conditions are dichlorosilane 5iH2CI! 2 11005CC Ammonia NH3500SCCM Pressure
0.3 Torr deposition rate
180 people/min Deposition temperature 80
At 0°C, the internal stress of the formed X-ray transparent film 12 is:
The value was 5 to 7xlO'dyn/crrr, which was sufficiently small for use. Next, 700 TiN films as electron donors were deposited on the silicon wafer by CVD using Ti(N(CHs) 2 ) 4 and NH 3 in the same LPCVD apparatus to form an undercoat film 14 (second = (b) figure).

Next, place the silicon wafer in the LPCVD equipment,
Deposited film 13 of X-ray absorbing material by silane reduction method of WF6
was formed.

The formation conditions are: Partial pressure of WF6 2XIO-"TorrSiH4 partial pressure 1.5XIO-"Torr Growth temperature
360°C H296, 5 mTorr, and the deposited film 13 with a thickness of 0.85 μm is the undercoat layer]
4 (Fig. 2-(C)).

After this, SiH4 and 02
SiO3 is formed as the intermediate layer 15 by a reaction at 420°C.
was deposited to a thickness of 1.0 μm, and N
The film was densified by heat treatment at 950° C. for 30 minutes in two atmospheres.

Next, on the intermediate layer 15, a PMMA-based resist (trade name: Tokyo Ohka: DEBR-1000) was applied to a thickness of 1 μm, prebaked, and then exposed by electron beam lithography.
After developing and post-baking, SiO□ was developed in F plasma.
By dry etching the intermediate layer 1
5 was patterned to form an exposed pattern 16 of the deposited film 13 (FIG. 2 (d)).

Next, the deposited film 13 of the X-ray absorbing material is
5i021 of the intermediate layer is etched using a hydrofluoric acid etching solution.
After removing the TiN film 14, the exposed TiN film 14 was removed using fluorine plasma (No. 2-(e)).

Note that in this step, it is desirable to remove the 5iO2 15 and the TiN film 14 at the same time, preferably using fluorine plasma.

Finally, a support frame was formed by partially removing the silicon wafer 11 by back etching (No. 2-(f)
figure).

The X-ray mask structure of the present invention created as described above is referred to as an X-ray mask structure (A).

Examples 2-4 X-ray mask structures (B) ~
(D) was produced.

Example 5 In FIGS. 2(a) to 2(f), Mo was used as the undercoat film 14.
The film was formed by sputtering to a thickness of 500 mm, and the X-ray absorber 13 was made of M.

Partial pressure of (Co)a 2X10-'Torr, reaction gas H2
An X-ray mask structure (E) was produced in the same manner as in Example 1 except that a Mo film with a thickness of 0.85 μm was formed under conditions of (partial pressure 1.5 Torr) and a growth temperature of 450° C.

Example 6 In FIGS. 2(a) to 2(f), an X-ray mask was used in the same manner as in Example 1 except that a 5iCx film was formed as the X-ray transparent film 12 by the LPCVD method to a thickness of 2 μm. A structure (F) was created.

Comparative Example 1 Similar to Examples 1-6 described above, FIGS. 2(a) to (f)
), the step e) of forming the absorber was performed by conventional gold plating, and the final process was completed to form the X-ray mask structure (a). When the surface of the completed absorber was observed with a scanning electron microscope, unevenness with a height Pv value of 0.1 to 0.5 μm was observed. This greatly exceeded the specifications required for uneven thickness of the absorber.

Comparative Example 2 Silicon nitride film S serving as an X-ray transparent film similar to the example of the present application
iN was deposited to a thickness of 2 μm. Next, a tungsten film, which will become an X-ray absorber, is deposited using a magnetron sputtering device.
rlOmTorr, 0.85μm at N 23mTorr
A film was formed by sputtering to a thickness of . Thereafter, through a resist process, EB drawing and W etching with CF4 were performed to form an X-ray mask structure (b).

When the surface of the completed X-ray absorber was observed using a scanning electron microscope, it was found to be smooth and amorphous;
When the density was measured, it was only 78% of the bulk value.

Reference Example Regarding the X-ray mask structures (A) to (F), (a), and (b) produced in Examples 1 to 6 and Comparative Example 1.2, (1) Crystals constituting the X-ray absorber Grain boundary diameter of particles,
(2) The density of the X-ray absorber film was measured by the following method.

The crystal grain boundary diameter of the X-ray absorber can be determined from the results of ordinary X-ray diffraction, that is, from the measurement of the angular width B (radians) of the diffraction line profile obtained from the X-ray diffraction chart, as shown in (A) and (B) below. ) was used to calculate the grain boundary diameter t (μm) of the crystal grains constituting the X-ray absorber.

2dsin θB = m λ −
(A) t=0.9 λ/B cos θB
-(B) In the above formulas (A) and (B), d is the absorber crystal particle lattice spacing (nm), θB is the Bragg angle of the diffraction line (radians), and λ is the wavelength of the X-ray (n m ) shows.

(M=1.) Moreover, the value described in the ASTM card was used for the above d.

In addition, for those whose grain boundary diameter is thought to exceed 1 μm, the cross section of the film is observed using a high-resolution scanning electron microscope.
The average grain boundary diameter was determined by comparing it with a standard sample.

In addition, the density ρ^ (g/crtr) of the X-ray absorber is determined by The amount of radiation transmitted (I^ and 1m (%), respectively) and the thickness dA of the X-ray absorber
(μm) was measured, and the X-ray absorption coefficient μm (μm−1) of the X-ray absorber was calculated from the following formula (c), and calculated from the μA value using the following formula (D).

I m / I A = e#A''
−(C)ρA=(μ＾/μB)ρB...
(D) In addition, in the above formulas (C) and (D), μB1ρB
respectively indicate the bulk X-ray absorption coefficient (μm-1) and bulk density (g/crtr) of the material constituting the X-ray absorber, and these values used the values described in the ASTM card.

Table 1 shows the grain boundary diameter and density of the X-ray absorber determined by the above method.

As is clear from Table 1, the grain boundary diameter of the X-ray absorber produced by the conventional method is never larger than 1 μm, and the grain boundary diameter of the X-ray absorber produced by the present example is small (both 1 μm or larger).
Most of the particles had a particle size of 2 μm or more. In addition, the density of the X-ray absorber, which is important for fulfilling its function as an X-ray absorber, is conventionally less than 90% of the bulk value, but according to the method of the present invention, the density is 90% or less of the bulk value.
It was 0% or more.

In X-ray exposure equipment, the divergence of the exposure illumination light is often not fully absorbed, resulting in run-out errors. However, the thickness of the absorber is as thin as possible to reduce run-out errors and the penumbra caused by the thick absorber. The high density contributes to reducing the thickness of the X-ray absorber.

Since the transferred pattern size is about 1 μm or less and 0.2 μm, the large grain boundary diameter means that the pattern is formed within a single grain boundary diameter, and the XIs leaking through the X-ray absorber is sufficiently small ( ,-like.

〔effect〕

As described above in detail, the method of the present invention produces an X-ray mask structure having an X-ray absorber formed of crystal grains with a large grain boundary size and an X-ray absorber having a larger density. obtain. That is, it is possible to produce an X-ray mask structure in which the X-ray absorbability of the X-ray absorber is significantly improved, and the smoothness of the edge portion (side surface) of the X-ray absorber is also significantly improved.

Further, by using such an X-ray mask structure, it is possible to form a printing pattern with high resolution, high definition, and high contrast. Furthermore, the manufacturing method of the present invention is a method that can mass-produce X-ray mask structures excellent in the above-mentioned properties with good reproducibility.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are schematic configuration diagrams of an X-ray mask structure, with FIG. 1(a) showing its sectional view and FIG. 1(b) showing its plan view. FIGS. 2(a) to 2(f) are diagrams for explaining the method of manufacturing the X-ray mask structure of the present invention. 1.11... Support frame 2.12... X-ray transparent membrane 3.13... X-ray absorber 14... Subbing layer (a) (b)

Claims (3)

[Claims] (1) In a method for manufacturing an X-ray mask structure having an X-ray transparent film, an X-ray absorber patterned on the X-ray transparent film, and a support frame that supports the X-ray transparent film, the The step of patterning the radiation absorber includes a) forming an X-ray transparent film and then forming a subbing layer on the surface of the X-ray transparent film; and b) applying a vapor phase growth method to the surface of the subbing layer. 1. A method for manufacturing an X-ray mask structure, comprising: depositing an X-ray absorbing material; and c) patterning the deposited film of the X-ray absorbing material. (2) The method for manufacturing an X-ray mask structure according to (1), wherein the X-ray transparent film includes a silicon carbide film or a silicon nitride film. (3) Claim (1) in which the undercoat layer is made of an electron-donating material.
A method for manufacturing an X-ray mask structure according to .