JPH07307328A - Pattern forming method - Google Patents

Abstract

PURPOSE:To obtain an optimum dimension for patterning a resist film on an antireflection film and of the etching pattern of the antireflection film, in a photolithography process. CONSTITUTION:In a process wherein a resist film 4 having an antireflection film 3 whose main component is carbon or hydrocarbon as the lower layer is used as a mask, and a film 2 on a substrate 1 is etched, the exposed and developed resist film 4 and the antireflection film 3 are etched by using etching gas 5 wherein halogen hydrocarbon containing fluorine is mixed in oxygen.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor manufacturing process for resist patterning and etching on an antireflection film containing carbon or hydrocarbon as a main component.
The present invention relates to an etching method for obtaining an optimum pattern size.

In recent years, the miniaturization of devices has been remarkable, and when forming a fine resist pattern on a semiconductor substrate, it has become essential to use an antireflection film as a base of the resist film.

[0003]

2. Description of the Related Art Conventionally, in patterning a resist film on a highly reflective film of a substrate, the line width of the resist film pattern is jagged, narrowed on a step, or varied in line width under the influence of halation. For this reason, a carbonaceous substance is used as the antireflection film under the resist film.

[0004]

However, when the antireflection film is used, the resist film pattern line width varies the most even if the resist film is subjected to a pivotal shift (pivotal exposure dose is defocused). This refers to a difficult exposure amount, and the dimension shift of the resist film pattern from the line width of the mask pattern at that time is called a pivotal shift.) Or, the pivotal shift after etching may be as large as about ± 0.1 μm. There is a problem that it is far from the size of.

Therefore, it is necessary to adjust the finished dimension of the device pattern after etching. Actually, as the miniaturization of semiconductor devices progresses and sub-micron size patterning becomes mainstream, the point where the resist film pattern of 0.35 μm width is desired to be obtained with a mask of 0.35 μm pattern width, the pivotal shift is 0.1 μm. In that case, the influence is large, and in order to obtain a pattern with a width of 0.35 μm, it is necessary to perform exposure with an exposure amount deviated from the pivotal, which impairs the focus margin.

In view of the above points, the present invention controls the etching shift amount in the direction in which the pivotal shifts in the resist pattern are canceled in the base etching including the antireflection film, and makes the finished product after etching the mask size. It is a thing.

[0007]

FIG. 1 is a diagram for explaining the principle of the present invention. In the figure, 1 is a substrate, 2 is a film to be etched, 3 is an antireflection film, 4 is a resist film, and 5 is an etching gas.

According to the present invention, in order to solve the above problems,
When etching the antireflection film under the resist film, a halogen-containing hydrocarbon gas containing fluorine represented by Freon and O
_It is better to use a mixed gas of ₂ . This is done by etching the antireflection film or the underlayer including the antireflection film while ashing the pivotal shift of the resist film by the effect of O ₂ gas to adjust the pivotal shifts deviating from the mask size. To do.

That is, as shown in FIG. 1A, the substrate 1
When the upper etching target film 2 is etched by using the resist film 4 as a mask, even if the antireflection film 3 is provided, the pivotal shift is included in the resist film 4 when the resist film 4 is exposed, because the focal shift due to the warp of the substrate is included. When the shift is required to be about 0.1 μm, the line width a of the mask pattern of the resist film which is originally necessary is thickly exposed, and the line width of the resist film 4 after development becomes thicker by the pivotal shift of 2b, and the line of c. It becomes a width.

Therefore, when the antireflection film 3 or the film to be etched 2 is anisotropically dry-etched, the required mask pattern line width of the resist film 4 is set to a.
In addition to the conventional etching gas for the antireflection film 3 of halogen hydrocarbon containing fluorine, O ₂ gas is added as a resist ashing gas that reduces the line width of the resist film 4. As a result, the resist width can be set to the original mask pattern width a of the resist film 4 as shown in FIG. 1B, and the anisotropic dry etching is applied to the lower antireflection film 3 and further on the substrate 1. The etching target film 2 can be etched to a desired pattern width a.

As the halogen-containing hydrocarbon gas containing fluorine, CF ₄ is generally often used, but chlorine (C
Of course, a gas containing l) or hydrogen (H) may be used. That is, as shown in FIG. 1, the object of the present invention is to etch the etching target film 2 on the substrate 1 by using the resist film 4 having the antireflection film 3 mainly composed of carbon or hydrocarbon as an underlying layer as a mask. By etching the exposed and developed resist film 4 and antireflection film 3 with an etching gas 5 which is a mixture of fluorine-containing halogenated hydrocarbon and oxygen, and by using CF ₄ and O ₂ as the etching gas 5. To be achieved.

[0012]

As described above, in the present invention, the portion of the line width of the pattern formed by exposure and development thickened by the focus margin is used as a CF ₄ etching gas for etching the resist film during etching of the antireflection film. The line width of the resist film pattern is adjusted by mixing O ₂ to reduce the thick line width and achieve the originally designed mask pattern width. As a result, it becomes possible to etch the SiO ₂ film and the conductive film for electrodes to a line width as designed by anisotropic etching or the like.

Basically, the etching gas may be a mixed gas of a halogen-containing hydrocarbon gas containing fluorine and oxygen, or a plurality of mixed gases containing at least both of them.

[0014]

2 to 5 are explanatory views of an embodiment of the present invention. In the figure, 11 is a Si substrate, 12 is a field SiO ₂ film,
13 is a gate SiO ₂ film, 14 is a poly-Si film, 15 is a WSi film, 16 is Si
O ₂ film, 17 is an amorphous carbon film, 18 is a resist film,
19 is an etching gas (CF ₄ + O ₂ ), 20 is an etching gas (Cl ₂ + O ₂ ), and 21 is an ashing gas (O ₂ ).

FIG. 2 shows changes in the line width of the resist film pattern on the underlying structure shown in FIG. 1 with respect to defocus (defocus) at the time of exposure, with the exposure amount as a parameter.

From FIG. 2, it is understood that the condition for obtaining the maximum focus margin in this system is that the line width dimension of the resist pattern, which is the mask dimension, is 0.42 μm.

Next, as compared with in the line width results resist pattern using the conventional CF ₄ only etching gas as shown in FIG. 3 is 0.4 .mu.m, the CF ₄ of the present invention O ₂ In the case of the mixed system, the line width of the resist film is 0.35 μm when the antireflection film is etched as shown in FIG.
It can be seen that the state where the focus margin is maximized can be obtained in the vicinity, and the dimensions are designed as intended, and the design dimensions can be reproduced most accurately.

An example in which the film to be etched (eg, SiO ₂ film or W silicide film) and the antireflection film are etched using the above results will be described with reference to FIG. A gate formed on the Si substrate 11 as shown in FIG.
A film to be etched such as a poly-Si film 14, a WSi film 15 and a SiO ₂ film 16 is laminated on the SiO ₂ film 12, an amorphous carbon film 17 is further coated as an antireflection film, and then a resist film 18 is applied,
When exposure and development are performed under the condition that the focus margin is maximized, a pattern of the resist film 18 for forming a gate electrode having a line width of 0.42 μm is formed.

Next, as shown in FIG. 5B, the Si substrate 11
Is set in a cathode coupling type RIE device, the degree of vacuum in the chamber of the device is 0.3 Torr, the output is 500 W,
Frequency 13.56MHz, CF as etching gas 19
₄ 90 sccm, O ₂ at 10sccm etching conditions, the resist film 18 as a mask, the amorphous carbon film 17 and the Si
The O ₂ film 16 is continuously dry-etched. At this time, 0.
The surface of the resist film 18 having a width of 42 μm is also etched and ashed to have a width of 0.35 μm as designed.

Subsequently, the Si substrate 11 is set in the RIE apparatus, the vacuum degree in the chamber of the apparatus is 0.1 Torr, and the output is 20.
Anisotropic dry etching of the WSi film 15 and the poly-Si film 14 is continuously performed under the etching conditions of 0 W, a frequency of 13.56 MHz, and an etching gas of Cl ₂ 90 sccm and O _{2 10} sccm, using the SiO ₂ film 16 as a mask. .

After that, the resist film and the amorphous carbon film 17 and the resist film 18 are removed by plasma stripping with an ashing apparatus to obtain a MOS element having a WSi gate electrode.

In one embodiment of the present invention, an etching gas in which CF ₄ and O ₂ are mixed is used, but basically, a halogen-containing hydrocarbon gas containing fluorine for etching the antireflection film,
For example a CHF ₃ or CClF ₃ gas such as a mixed gas of O ₂ ashing of the resist film surface, or may be a plurality of mixed gas containing at least the two.

[0023]

As described above, according to the present invention,
Using a mixed gas of Freon-based gas and oxygen for ashing the resist film surface, the dimension deviation from the original mask resist film pattern due to the focus margin is used, and the mixed gas of Freon-based gas and oxygen for ashing the resist film surface By matching the dimension as a mask pattern by using, it greatly contributes to significantly improve the patterning accuracy of the fine element pattern.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of the present invention.

FIG. 2 is an explanatory diagram of an embodiment of the present invention (No. 1)

FIG. 3 is an explanatory diagram of an embodiment of the present invention (No. 2)

FIG. 4 is an explanatory diagram of an embodiment of the present invention (No. 3)

FIG. 5 is an explanatory diagram of an embodiment of the present invention (Part 4).

[Explanation of symbols]

In the figure, 1 substrate 2 film to be etched 3 antireflection film 4 resist film 5 etching gas 11 Si substrate 12 field SiO ₂ film 13 gate SiO ₂ film 14 poly Si film 15 WSi film 16 SiO ₂ film 17 amorphous carbon film 18 resist film 19 Etching gas (CF ₄ + O ₂ ) 20 Etching gas (Cl ₂ + O ₂ ) 21 Ashing gas (O ₂ )

Claims (2)

[Claims] 1. A process of etching a film (2) to be etched on a substrate (1) using a resist film (4) having an antireflection film (3) mainly composed of carbon or hydrocarbon as an underlying layer as a mask, The resist film (4) exposed and developed and the antireflection film
A method for forming a pattern, characterized in that (3) is etched with an etching gas (5) in which a halogen-containing hydrocarbon containing fluorine and oxygen are mixed. 2. The pattern forming method according to claim 1, wherein carbon tetrafluoride (CF ₄ ) and oxygen (O ₂ ) are used as the etching gas (5).