KR20060106548A - Method for semiconductor device - Google Patents

Abstract

Even when a thin photoresist pattern is used as an etching mask, a dry etching method capable of obtaining a high resolution and a good etching profile is provided. The dry etching method includes forming a photoresist pattern on an etched film of a semiconductor substrate, a first etching step of etching the etched film to a first depth using the photoresist pattern as an etching mask, an etching stop step, and an etching stop step. And a second etching step of etching from the etching surface etched to the first depth of the etched film to the second depth.

ArF, Photoresist, Tissue, Profile

Description

Method for manufacturing a semiconductor device {Method for semiconductor device}

1 is a flowchart illustrating a dry etching method according to an embodiment of the present invention.

2 is a cross-sectional view of a semiconductor substrate on which a photoresist pattern is formed by a dry etching method according to an exemplary embodiment of the present invention.

3 to 5 are cross-sectional views of respective first and second etching steps of the dry etching method according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

20: semiconductor substrate 21: etched film

22, 22 ': photoresist pattern

The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a method for manufacturing a semiconductor device by dry etching using an ArF light source.

As the manufacturing process of semiconductor devices becomes complicated and the degree of integration increases, individual semiconductor devices formed on a substrate must be formed in a finer pattern. In the photolithography process, the development of a new photoresist suitable for forming such a fine pattern has become an essential task.

As the degree of integration of semiconductor devices increases, it becomes more difficult to form fine patterns by a general photolithography process. As the degree of integration of semiconductor devices increases, the line width of the pattern to be formed becomes smaller than the exposure limit resolution. This is because it becomes more difficult to form a photoresist pattern having a desired profile.

As one method for forming a fine pattern, a method of using an exposure beam having a shorter wavelength is known to improve the resolution in forming a photoresist pattern.

For example, a KrF excimer laser with a wavelength of 248 μm is used instead of an existing 365 μm wavelength i-line as a light source for exposure when manufacturing a 256 M bit dynamic random access memory (DRAM) having a 0.25 μm design rule. The method has been proposed.

In addition, the fabrication of 1G bit DRAMs with 0.2µm design rules requiring high fine patterning techniques requires the use of light sources with shorter wavelengths than those with KrF excimer lasers. For this purpose, an ArF excimer laser having a wavelength of 193 nm is used as the light source for exposure.

However, since the deep UV, KrF or ArF excimer laser light in a very short wavelength region for processing the ultrafine pattern is absorbed in the photoresist film during exposure, when the photoresist film is formed thick, the light is photoresisted. It becomes difficult to reach the bottom of the membrane.

For example, in the case of using ArF excimer laser light having a short wavelength of 193 nm (= 0.193 μm) as a light source for high resolution patterning, the thickness of the photoresist film should be thinly formed to be 1930 Å (= 0.193 μm) or less in consideration of beam absorption. do.

However, the thinly formed photoresist pattern has low resistance to etching during the etching of the underlying etching and is very sensitive to heat, so that the photoresist pattern may be wiggled or collapsed when the etching reaction is performed at high temperature. Stripe-shaped deformation occurs in the etched pattern.

An object of the present invention is to provide a dry etching method that can obtain a high resolution and a good etching profile even when using a thin photoresist pattern as an etching mask.

Technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

The dry etching method according to an embodiment of the present invention for achieving the above technical problem is to form a photoresist pattern on the etched film quality of the semiconductor substrate, removing the etched film quality by using the photoresist pattern as an etching mask And a second etching step of etching to the second depth from the etching surface etched to the first depth of the etched film after the first etching step, the etching stop step, and the etching stop step of etching to the first depth.

Specific details of other embodiments are included in the detailed description and the drawings.

Advantages and features of the present invention, and methods for achieving them will be apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention, and those skilled in the art to which the present invention pertains. It is provided to fully inform the scope of the invention, and the invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

The dry etching method according to an embodiment of the present invention will be well understood by referring to FIGS. 1 to 5.

First, a dry etching method according to an embodiment of the present invention is as follows. 1 is a flowchart illustrating a dry etching method according to an embodiment of the present invention.

Referring to FIG. 1, a photoresist pattern is formed on an etched film (S11).

Specifically, referring to FIG. 2, an etching target film 21 is formed on the semiconductor substrate 20. The type of the etched film is not particularly limited as long as dry etching is possible.

Thereafter, a photoresist is applied to the entire surface of the etching target film 21. When the ArF excimer laser is used as the light source to maximize the resolution, the thickness of the photoresist may be thinly formed to about 0.5 to 1.2 μm, for example, 0.7 μm.

In order to pattern the photoresist, i-line, KrF, ArF excimer laser light source and the like can be used as the light source. For example, when the thickness of the photoresist is thin, the photoresist is exposed and developed using an ArF excimer laser light source. A resist pattern can be formed.

Subsequently, the film to be etched is etched using the photoresist pattern as an etching mask. This is called a first etching step (S12).

This etching step may be performed using a source / bias power system or a dual frequency power system, but is not limited thereto.

The first etching step may be performed by placing a wafer W including an etched film having a photoresist pattern in the reactor, applying power, and supplying an etching gas. In this case, the etching gas may be a C _x F _y or C _a H _b F _c gas, for example, CF ₄ , CHF ₃ , C ₂ F ₆ , C ₄ F ₈ , CH ₂ F ₂ , CH ₃ F, CH ₄ , C ₂ H ₂ , C ₄ F ₆ and the like may be used, but are not limited to the above-described types of etching gases.

In addition, an inert gas such as He, Ar, Xe, I, etc. may be further supplied into the reactor to stably generate a plasma for etching the etched film.

Referring to FIG. 3, under the process conditions as described above, the photoresist pattern 22 is used as an etching mask to a predetermined depth h ₁ of the etched film 21, for example, 20 to 50% of an etching target depth. Etching may be performed to a depth corresponding to, but is not limited to this depth.

In the case of forming the contact hole, the etching target depth may be all of the etched film, but in the case of forming the trench, the etching target depth may be a part of the etched film.

In addition, a portion of the photoresist pattern may be etched in the etching step as described above. Reference numeral 22 ′ denotes a photoresist pattern partially etched.

Subsequently, the semiconductor substrate is left for a predetermined time. This is called a pause (S13).

During the first etching step as described above, the temperature inside the reactor is increased to several hundred degrees, and the etching gas and the photoresist pattern react on the photoresist pattern to deposit a byproduct polymer. Since the photoresist pattern and the polymer are composed of different materials, their respective coefficients of thermal expansion are different, and therefore their behavior toward heat is different. That is, the photoresist pattern of the middle portion or the lower portion is thinner than the upper portion of the photoresist pattern on which the polymer is deposited. If this phenomenon is severe, the photoresist pattern may be collapsed by heat.

Therefore, in the dry etching method according to the exemplary embodiment of the present invention, an etching pause step is provided between the first etching step and the second etching step to be described later. The etch stop step is a step of lowering the temperature in the elevated reactor to lower the temperature of the etched film by leaving the wafer W in the reactor without applying power to the reactor and supplying the etching gas. . Through this rest step, thermal deformation of the photoresist pattern may be minimized.

Although the time of the idle step is not particularly limited, when the time of the idle step is too long, the total etching process time increases by the idle time, and the temperature in the reactor may be too low. In this case, the time required for the entire etching process until the temperature of the reactor is raised back to a predetermined temperature may be longer, and the process efficiency may be lowered. Thus, the time of rest phase can be 20 seconds or more, for example 20 to 40 seconds.

Subsequently, etching is continuously performed in the etching surface of the etched film. This is called a second etching (S14).

Referring to FIG. 4, the power applied to the reactor is restored to the level of the first etching step for each of the semiconductor substrates that have been subjected to the above-described rest and rest steps to the etching surface of the etched film 21 formed by the first etching step. The second etching is performed.

In the second etching step, the etched film quality 21 may be etched up to a desired depth h ₁ + h ₂ at a time, but as described above after etching to the predetermined depth h ₂ ′ as shown in FIG. 5. After repeating the same dozens of rest steps, the etching process may be performed again to etch the etched film 21 to the etching target depth h ₁ + h ₂ '+ h ₃ .

In the process of etching the etching target membrane 21 by placing a resting stage between the etching stages as described above, the number of repetitions of the resting stage and the etching stage is the thickness and type of the etching target membrane 21, and the etching target membrane 21. The thickness and type of photoresist formed on the substrate and the light source used for etching are not particularly limited.

By the etching process, as shown in FIGS. 4 and 5, the photoresist pattern 32 ′ is used as an etch film as a mask, and the etching target depth (h ₁ + h ₂ or h ₁ + h ₂ '+ h ₃ ) can be etched.

In accordance with one embodiment of the present invention, a 20-second rest phase between the first and second etch steps was able to form a trench of good profile with a depth of 5000 microns of SiOF film quality. In addition, when the continuous etching process was performed without a rest step, the SiOF etch rate was 3709 Å / min, while the etching rate was 4166 Å / min according to one embodiment of the present invention.

The dry etching method according to the present invention may be used, for example, when patterning an active region, a gate, a contact hole, a trench, a metal wiring, etc. using an ArF excimer laser, but is not limited thereto.

Although embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains may implement the present invention in other specific forms without changing the technical spirit or essential features thereof. I can understand that. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

According to the dry etching method of the present invention as described above, even when a thin photoresist pattern is used as an etching mask, a high resolution and a good etching profile can be obtained, thereby improving process efficiency.

Claims (5)

Forming a photoresist pattern on the etched film of the semiconductor substrate; A first etching step of etching the etched film to a first depth by using the photoresist pattern as an etching mask; Etch stop step; And And a second etching step of etching from the etched surface etched to the first depth of the etched film to the second depth after the etching stop step. The method of claim 1, The etching stop step is a dry etching method that proceeds for 20 seconds or more. The method of claim 2, The etching rest step is a dry etching method that proceeds for 20 to 40 seconds. The method of claim 1, The first etching step is a dry etching method of the first depth is 20 to 50% of the depth corresponding to the etching target depth. The method of claim 1, And performing the at least one resting step and the second etching step at least once to etch the etched film to an etching target depth.

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