JPS63250121A - Manufacture of x-ray mask - Google Patents

Abstract

PURPOSE:To obtain a membrane whose tensile stress is stable even after irradiation with X-rays by a method wherein, after a compound for the membrane is formed in a compressive stress state on a substrate, it is heat-treated to be transformed into a tensile stress state. CONSTITUTION:An amorphous BNC:H film 2 for membrane use is formed to be a thickness of 6 mum on a silicon substrate 1. A pressure inside a chamber during the formation is 60-200 Pa; high-frequency electric power at 13.56 MHz is impressed on an upper-part electrode in order to obtain an electric-power density of 0.1-0.3 W/cm<2>. By this setup, the BNC:H film 2 in a weak compressive stress state of -1.0X10<9>dyn/cm<2>--1.0X10<8>dyn/cm<2> is formed. Then, a specimen is taken out from a chamber, and is heat-treated at a temperature of 700-1000 deg.C for 30-60 min in a mixed atmosphere of nitrogen and hydrogen. By this process, the BNC:H film 2 is transformed into a film in the compressive stress state of 1X10<8>-2X10<9> dyn/cm<2>. After the central part on the rear surface of the silicon substrate is removed by etching, a mask pattern 3 composed of an X-ray absorber such as gold, tantalum or the like is patterned and formed on the membrane. The membrane of an X-ray mask obtained in this manner does not cause the segregation of boron and a fluctuation in a stress even when it is irradiated with X rays.

Description

[Detailed Description of the Invention] [Summary] When a compound film such as BNC:H for the membrane of an X-ray mask is grown on a substrate in a vapor phase, it is first formed in a compressive stress state and then heat-treated to make it into a tensile stress state. change x
Forms a stable membrane with no stress fluctuations caused by radiation irradiation.

[Industrial application field]

The present invention relates to a method for manufacturing an X-ray mask, and more particularly to a method for forming a membrane with excellent properties such as stress and X-ray transparency.

[Conventional technology]

For the formation of fine patterns in VLSI devices, X-ray exposure, which can draw finer patterns, has become an effective method, replacing light exposure, which has limitations on the size of fine patterns due to diffraction. There is.

In this type of X-ray exposure,
A line mask is used.

That is, a membrane 2 is formed on a silicon substrate 1, and the silicon substrate 1 below the mask pattern 3 is etched away, and X-rays coming from below in the figure are transmitted through the membrane, and the X-rays are absorbed in a certain part of the mask pattern. In areas where there is no mask pattern, a pattern corresponding to the mask pattern is transferred by passing the X-rays.

The following conditions must be met by the membrane in such an X-ray mask.

That is, ■High X-ray transmittance, ■High rigidity, ■High optical transparency, ■Moderate tensile stress It is to have.

It is an obvious condition that the X-ray transmittance of (2) must be high. Regarding the tensile stress (2), in use, an X-ray mask is placed above a wafer coated with resist in an upside-down state as shown in FIG. 2, and irradiates X-rays to transfer a pattern onto the resist.

At this time, if the tensile stress of the membrane is low, the pattern may move in the vertical direction and shift, so the membrane must be stretched to the extent that it can resist such movement of the pattern, so the membrane does not self-destruct. It is required that the tensile stress is relatively high.

Regarding the rigidity of (2), the membrane has a Young's modulus of 3 to prevent the pattern from moving laterally when the membrane is stretched due to the stress relationship between the membrane and the pattern.
Rigidity of approximately XIO" dyn/cm2 is required.

Regarding optical transparency (2), the X-ray mask must be aligned at - before use, and this requires passing light through the membrane, so the membrane has optical transparency to improve alignment accuracy. High demands are required.

Membrane materials that have been proposed so far include B
There are compounds with less than three elements, such as N:H, SiN:H, and SiC, but it has been difficult to form thin films that simultaneously satisfy the above conditions with good control and with a certain level of productivity. .

Therefore, the present inventor proposed amorphous BNC in Japanese Patent Application No. 61-219217 and No. 61-219781:
) has proposed an X-ray mask having a membrane made of a quaternary or more compound such as I.

In such membranes, for example, amorphous BNC
: H: X-ray transmittance is 80% or more, Young's modulus is IX
IO"dyn/cm" or more, visible light transmittance (optical band gap) 3eV or more, tensile stress lXl0"~2
X 10'dyn/Cl1l'' was realized.

[Problem that the invention seeks to solve]

However, if a film with the above-mentioned tensile stress is directly formed in the formation of such a membrane, the film becomes an off-stoichiometric film rich in boron, and when irradiated with X-rays, boron segregation occurs, and It was found that stress fluctuates.

The reason for the stress fluctuation is that the membrane is a film formed by plasma chemical vapor deposition.
Although the film contains 0% hydrogen, this is thought to be because hydrogen is desorbed by irradiation with X-rays.

An object of the present invention is to provide a method for obtaining a membrane having stable tensile stress even when irradiated with X-rays.

[Means for solving problems]

In order to solve the above problems, the present invention first forms a membrane compound on a substrate in a compressive stress state, and then
It is characterized by heat treatment to change it to a tensile stress state.

[Effect]

A film formed in a stoichiometric state that is not boron-rich has weak compressive stress, but by heat treatment to remove hydrogen from the film, it can be controlled to a tensile stress state, and the stress changes even when exposed to X-rays. There isn't.

〔Example〕

FIG. 1 is a process-order sectional view showing an embodiment of the present invention.

On a silicon substrate 1 shown in FIG. 1(a), an amorphous BNC:If film 2 for a membrane is formed as shown in FIG.
is formed to a thickness of 6 μm.

The method is to first use a plasma vapor phase epitaxy device,
Diborane (Bg) (16) diluted with argon (4%) and ammonia (N143) diluted with argon (4%) together for 200-400 sec, methane (CH,) for 5-50 sec, and NH3/Bzt16 The ratio is 0.
5 to 2.0 and introduced into the chamber. At this time, the pressure inside the chamber was 60 to 200 Pa, and the upper electrode was supplied with a high frequency power of 13.56 MHz at a power density of 0.1 to 0.
．． 3W/cm".The substrate temperature is 35
0 to 500°C. In this example, CH4 was used as the carbon supply source, but in addition, cp, ccg, halogenated hydrocarbons, i.e., CHCE z, cHzc l
z, Cll3Cl, CHFx, CHJ'z, CH3
F may also be used.

In this way -1,OXl09dyn 7cm”~
A BNC:H film 2 with a weak compressive stress of -1,0XIO' dyn 7 cm'' is formed.

The sample is then removed from the chamber and exposed to nitrogen (N2) and hydrogen (
Heat treatment is performed at a temperature of 700 to 1,000° C. for 30 to 60 minutes in a mixed atmosphere of 30 to 1000° C. (Hz).

As a result, the BNC:H film 2 is 1×108 to 2×109
A film with a tensile stress state of dyn 7 cm" is obtained. After forming the membrane in this manner, the central portion of the lower surface of the silicon substrate is etched away as shown in FIG.

Next, as shown in FIG. 4(d), a mask pattern 3 made of an X-ray absorber such as gold or tankle is patterned for the membrane. In this case, a ring made of silicon carbide (SiC), for example, may be provided under the silicon substrate.

In this way, the X-ray transmittance is 80% or more, and the Young's modulus is I.
Xl09dyn/cm2 or more, visible light transmittance (optical band gap) 3eV or more, 1×108dyn 7c
An X-ray mask membrane with a tensile stress of more than m" was obtained, and it was confirmed that there was no boron segregation or stress fluctuation even when irradiated with X-rays.

In the above examples, the case where amorphous BNC:H was used as the membrane material was explained, but in addition, amorphous 5iNC:H, amorphous BNSi:1
1. Amorphous BC5i: H, amorphous BN
CSi:H can also be used.

[Effects of the Invention] As explained above, according to the present invention, the conditions for a membrane are sufficiently provided, and there is no change in stress due to X-ray irradiation. An x-ray mask having a stable membrane is provided.

[Brief explanation of drawings]

FIG. 1 is a process-order sectional view showing one embodiment of the present invention, and FIG.
The figure is a sectional view showing the structure of an X-ray mask. In the figure, 1 is a silicon substrate, 2 is a membrane, and 3 is a mask pattern. 5 Mask Hahoon Showing the actual sales sequence of the invention car! yT plane drawing 1 figure x cross section showing green mask βa tongue 2 figure

Claims (4)

[Claims] (1) A method for manufacturing an X-ray mask, which comprises forming a compound film for a membrane of an X-ray mask on a substrate in a compressive stress state, and then subjecting the compound film to a heat treatment to bring the compound film into a tensile stress state. (2) The compound film is amorphous BNC:H, amorphous SiNC:H, amorphous BNSi:H, amorphous BCSi:H, amorphous BNCSi:H
2. The method of manufacturing an X-ray mask according to claim 1, wherein the film is made of one selected from the following. (3) The method for manufacturing an X-ray mask according to claim 1, wherein the compound film is a quaternary or more compound formed by chemical vapor deposition. (4) The compound film contains carbon and is formed by chemical vapor deposition using a hydrocarbon or a halogenated hydrocarbon as a carbon supply source.
A method for manufacturing an X-ray mask as described in .