JPH06349790A - Pattern-forming method for laminated film - Google Patents

Abstract

PURPOSE:To obtain the cross section of a laminated film excellent in the properties of covering a difference in level without causing lowering of a productivity by the increase of the number of processes at the time of pattern-forming a laminated film composed of a plurality of layers by the use of one resist pattern. CONSTITUTION:In a method for forming the pattern of a laminated film 14 by etching the upper layer film 13 of the laminated film 14 composed of a plurality of layers with the use of a resist film 15 having a desired pattern, by causing the resist film 15 to remain and by using the resist film 15 again to each the lower layer film 12 of the laminated film 14, the upper layer film 13 of the laminated film 14 is first etched by isotropic etching. Subsequently, the lower layer film 12 of the laminated film 14 is etched by anisotropic etching so that overetching is brought about at the time of etching the upper layer film 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern forming method for forming island-shaped portions and openings of a laminated film composed of a plurality of layers by patterning by etching in a manufacturing process of a semiconductor device such as a thin film transistor.

[0002]

2. Description of the Related Art When a laminated film composed of an upper layer film and a lower layer film is patterned with a photoresist pattern of one kind formed on the upper part of the laminated film to form islands or openings, When each of the lower layer films is sequentially etched, the pattern of the upper layer film may have a so-called overhang shape that protrudes from the pattern of the lower layer film in the horizontal plane direction. When a coating film is further deposited on such an overhang-shaped laminated film, the step coverage of the overhang portion by this coating film deteriorates, cracks occur in the coating film, or There is a problem that the metal wiring pattern formed on the film is broken.

Therefore, in order to solve the above problem, FIG.
As shown in (a) to (d), when the opening 36 is formed in the laminated film 33 composed of the upper layer film 32 and the lower layer film 31 deposited on the silicon substrate 30, the following method is used. Proposed. That is, after applying a resist 34 on the laminated film 33 (FIG. 3A), a resist pattern 35 is formed, and the upper layer film 32 and the lower layer film 31 of the laminated film 33 are etched by this resist pattern 35 to form an opening. 36 is formed (FIG. 3B). After that, only the upper layer film 32 is selectively etched again while leaving the resist pattern 35, thereby etching away the protruding portion of the upper layer film 32 (FIG. 3C), and then removing the resist pattern 35 (FIG. 3). (D)), avoiding the overhang shape and obtaining a cross section of the laminated film 33 having excellent step coverage (see Japanese Patent Publication No. 64-4662).

[0004]

However, according to the above method, the upper layer film 32 of the laminated film 33 is etched twice, resulting in an increase in the number of etching steps in the semiconductor manufacturing process. In particular, the laminated film 3
When the upper layer film 32 and the lower layer film 3 of 3 need to be etched by separate etching steps, the etching steps are required three times in total, which causes a problem that productivity is reduced due to an increase in the number of steps.

The present invention has been made in view of the above circumstances, and when patterning a laminated film composed of a plurality of layers using one resist pattern, the productivity is not lowered due to an increase in the number of steps, An object of the present invention is to provide a method for forming a pattern of a laminated film, which can obtain a cross section of the laminated film having excellent step coverage.

[0006]

In order to solve the above-mentioned problems of the conventional example, the present invention uses an upper layer film of a laminated film composed of a plurality of layers by using a resist film having a desired pattern formed on the laminated film. In the method of forming a pattern of the laminated film by etching the lower layer film of the laminated film again by using the resist film while remaining the resist film, first, the etching of the upper layer film of the laminated film is isotropic. It is characterized in that the etching is performed by etching, and subsequently the lower layer film of the laminated film is etched by anisotropic etching.

[0007]

According to the method of the present invention, isotropic etching is used for etching the upper layer film of the laminated film. Therefore, by controlling the overetching amount, the undercut of the upper layer film with respect to the resist pattern on the laminated film is controlled. Form a minute. Then, since anisotropic etching is used for etching the lower layer film of the laminated film, the undercut amount of the lower layer film is suppressed to be smaller than the undercut amount of the upper layer film with respect to the resist pattern on the laminated film.

[0008]

EXAMPLES As an example of pattern formation of a laminated film by the method of the present invention, a case of applying to a method of manufacturing a sandwich type photodiode formed by a thin film process,
A description will be given with reference to FIGS. 1 (a) to 1 (d). A titanium (Ti) film 11 having a film thickness of 200 nm is formed on the glass substrate 10 as a metal thin film to be a lower electrode of the photodiode. Subsequently, the amorphous silicon (a-Si) film 12 having a film thickness of 1.3 μm which becomes the photoelectric conversion layer of the photodiode, and the film thickness 60 nm which becomes the upper electrode of the photodiode.
A transparent conductive (ITO) film 13 is sequentially formed to form a laminated film 14 having a two-layer structure. A resist is applied on the laminated film 14 and patterned into a desired pattern to form a resist pattern 15 (FIG. 1A).

Next, as a first etching step, the upper film 13a of the laminated film 14 is etched by an isotropic etching method such as wet etching to form an upper electrode 13a. By using the isotropic etching, the etching progresses in the horizontal direction from point A directly below the side surface of the resist pattern 15, so that an undercut portion is easily formed in the resist pattern 15 (see FIG. 1).
(B)). The undercut amount of the ITO film 13 corresponding to the undercut amount with respect to the resist pattern 15 can be adjusted by appropriately performing overetching in wet etching.

Next, in a second etching step, the a-Si film 12 which is the lower layer film of the laminated film 14 is etched by an anisotropic etching method such as reactive ion etching (RIE) to form the photoelectric conversion layer 12a. Form. By using the anisotropic etching, the a-Si film 12 is etched in the vertical direction with respect to the resist pattern 15, so that an undercut amount with respect to the resist pattern 15 is suppressed (FIG. 1C). In this anisotropic etching, from the pattern of the ITO film 13 (upper electrode 13a) already etched in the previous step, aS
Various etching parameters (etching gas ratio, RF power) and overetching are adjusted so that the pattern of the i film 12 (photoelectric conversion layer 12a) becomes large.

Next, the resist pattern 15 is removed by ashing with oxygen plasma and a resist stripper (FIG. 1 (d)). Then, a resist pattern is newly formed (not shown), the Ti film 11 is etched to form a lower electrode, and the photodiode is completed.

According to the above embodiment, the ITO film forming the upper electrode 13a of the photodiode and the photoelectric conversion layer 1 are formed.
The cross section of the laminated film 14 made of the a-Si film that constitutes 2a has a shape (overhang shape) in which the upper electrode 13a, which is an upper layer film (ITO film), protrudes from the photoelectric conversion layer 12a, which is a lower layer film. Therefore, the ITO film 13 can be formed into a shape having excellent step coverage without etching twice. Therefore, when the coating layer is formed on the photodiode, it is possible to prevent the coating layer from cracking, prevent the disconnection of the wiring formed on the coating layer, and improve the reliability.

Next, as another example of pattern formation of a laminated film, a case of applying the formation of an opening in a thin film process will be described with reference to FIGS. 2 (a) to 2 (d). A wiring electrode 21 is formed on the insulating substrate 20, and a laminated film 24 having a two-layer structure including an upper insulating film 23 and a lower insulating film 22 is formed on the wiring electrode 21. A resist is applied on the laminated film 24 and patterned into a desired pattern to form a resist pattern 25 (FIG. 2A).

Next, as a first etching step, the upper insulating film 23 of the laminated film 24 is etched by an isotropic etching method such as wet etching to form an upper contact hole 26. By using the isotropic etching, the etching proceeds in the horizontal direction from the point A directly below the side surface of the resist pattern 25.
5 is likely to form an undercut (Fig. 2
(B)). The amount of undercut of the upper insulating film 23 corresponding to the amount of undercut with respect to the resist pattern 25 is
It can be adjusted by appropriately performing overetching in wet etching.

Next, as a second etching step, the lower insulating film 22 of the laminated film 24 is etched by an anisotropic etching method such as reactive ion etching (RIE) to form a lower contact hole 27 to form a contact hole. Two
8 is formed. By using anisotropic etching,
Since the lower insulating film 22 is etched in the vertical direction with respect to the resist pattern 25, an undercut amount with respect to the resist pattern 25 is suppressed (FIG. 2).
(C)). In this anisotropic etching, various etching parameters (etching are performed so that the opening area of the lower contact hole 27 is smaller than the opening area of the upper contact hole 26 already obtained by etching the upper insulating film 23 in the previous step. Adjust gas ratio, RF power) and overetching.

Next, the resist pattern 25 is removed by ashing with oxygen plasma and a resist stripping solution (FIG. 2 (d)). After that, a metal film is deposited and patterned to form a wiring (not shown), and the wiring and the wiring electrode 21 are connected through the contact hole 28.

According to the above embodiment, the contact hole 28 of the laminated film 24 composed of the upper insulating layer 23 and the lower insulating layer 22.
The cross section of the portion is the upper contact hole 26 of the upper insulating layer
The opening is larger than the opening of the lower contact hole 27 of the lower insulating layer 22, so that the upper insulating layer 23 can be formed into a shape having excellent step coverage without etching twice. Therefore, it is possible to prevent a crack or the like from being generated in the wiring formed so as to cover the contact hole 28, and it is possible to improve reliability without increasing the manufacturing process.

Further, in each of the above embodiments, the pattern formation of the laminated film composed of two layers of the upper layer film and the lower layer film has been described, but the method of the present invention can be applied to a laminated film of three layers or more.

[0019]

According to the method of the present invention, isotropic etching is used for etching the upper film of the laminated film.
By controlling the amount of over-etching, an undercut portion of the upper layer film is formed with respect to the resist pattern on the laminated film, and anisotropic etching is used for subsequent etching of the lower layer film of the laminated film. The undercut amount of the lower layer film with respect to the resist pattern on the film can be suppressed to be smaller than the undercut amount of the upper layer film. Therefore, a cross-sectional shape with excellent coverage that does not cause the cross-section of the laminated film to have an overhang shape can be realized in a process with excellent productivity without etching the same film twice.

[Brief description of drawings]

1A to 1D are cross-sectional explanatory views showing a method of manufacturing a photodiode to which the method of the present invention is applied.

2A to 2D are cross-sectional explanatory views showing a method of forming an opening to which the method of the present invention is applied.

3A to 3D are cross-sectional explanatory views showing a method of forming an opening according to a conventional technique.

[Explanation of symbols]

10 ... Glass substrate, 11 ... Ti film, 12 ... a-Si
Film (lower layer film), 12a ... Photoelectric conversion layer, 13 ... ITO
Film (upper layer film), 13a ... upper electrode, 14 ... laminated film,
15 ... Resist pattern, 20 ... Insulating substrate, 2
DESCRIPTION OF SYMBOLS 1 ... Wiring electrode, 22 ... Lower insulating layer, 23 ... Upper insulating layer, 24 ... Laminated film, 25 ... Resist pattern, 2
8 ... Contact hole

Claims (1)

[Claims] 1. An upper layer film of a laminated film composed of a plurality of layers is etched by using a resist film having a desired pattern formed on the laminated film, and the resist film is left to be laminated again using this resist film. In the method of forming a pattern of a laminated film by etching the lower film of the film, the upper film of the laminated film is etched by isotropic etching, and the lower film of the laminated film is etched by anisotropic etching. A method for forming a pattern of a laminated film, comprising: