JPH07135201A - Pattern forming method for multilayer film - Google Patents

Abstract

PURPOSE:To obtain the cross section of a multilayer film having excellent step coverage without lowering productivity due to increase in number of processes in the formation of pattern on a multilayer film consisting of a plurality of layers using a resist pattern. CONSTITUTION:In this pattern forming method in which the upper layer film 13 of a multilayer film 14, consisting of a plurality of layers, is etched using the resist film 15 having the desired pattern, the resist film 15 is left, and the lower layer film 12 of the multilayer film 14 is etched using the resist film 15 again, first, the upper layer film 13 of the multilayer film 14 is etched using an isotropic etching method. The resist film is excessively removed while the etching amount for the resist film is being controlled, subsequently, the pattern form of the lower layer film 12 is etched into a tapered shape by conducting isotropic dry etching on the lower layer film of the multilayer film.

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 cross-sectional shape of the pattern edge may be a steep shape close to a right angle, or the pattern of the upper layer film may be a shape protruding from the pattern of the lower layer film, that is, a so-called overhang shape. . When a coating film is further deposited on the laminated film having such a steep pattern edge shape or overhang shape, the step coverage by the coating film at the steep pattern edge portion or the overhang portion deteriorates,
There are problems that the coating film is cracked, and if the coating film is for metal wiring, the metal wiring pattern 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.

As a method of forming a tapered cross section for a metal thin film, a layer to be etched (for example, an aluminum thin film) on a substrate and an upper thin film (for example, a molybdenum thin film) having a large selection ratio with respect to the layer to be etched are provided.
When the aluminum thin film and the molybdenum thin film are simultaneously etched by sequentially laminating the aluminum thin film and the molybdenum thin film with the resist pattern formed on the upper thin film, the side surface of the aluminum thin film pattern can be tapered due to the difference in etching rate (JP-A-1-151236). See the bulletin).

However, according to the above method, the molybdenum thin film is provided in order to make the lower aluminum thin film into a tapered shape, and it is necessary to remove it thereafter. Therefore, when it is used in the manufacturing process of a semiconductor device. However, there is a problem that productivity is reduced due to an increase in the number of processes.

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.

[0008]

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. The method of forming a pattern of a laminated film by etching the lower layer film of the laminated film again by using the resist film as described above, wherein the resist film is left, and the following steps are provided. As the first etching step, the upper layer film of the laminated film is etched by isotropic etching, and is removed excessively while controlling the etching amount with respect to the resist film. As the second etching step, the lower layer film of the laminated film is etched by isotropic dry etching.

[0009]

According to the method of the present invention, isotropic etching is used for etching the upper layer film of the laminated film, and the amount of over-etching is controlled so that the upper layer film is underexposed to the resist film pattern on the laminated film. Form cuts. Then, since isotropic dry etching is used for etching the lower layer film of the laminated film, the etching radical species in the etching gas enters the undercut portion of the upper layer film to etch the pattern shape of the lower layer film into a tapered shape. be able to. At this time, since the amount of the etching radical species changes depending on the undercut amount, the taper angle can be controlled by the undercut amount.

[0010]

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 ITO film 13 which is the upper layer film 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, as a second etching step, the a-Si film 12 which is the lower layer film of the laminated film 14 is etched by a dry etching method of isotropic etching to form a photoelectric conversion layer 12a. At this time, the starting point at the time of isotropic etching is the point B immediately below the resist edge. Therefore, due to the presence of the undercut formed on the resist pattern 15 of the upper electrode 13a during the first etching step,
A gap between the resist pattern 15 and the upper electrode 13a (ITO
The etching radical species in the etching gas easily enter the undercut portion of the film 13 and the pattern shape of the photoelectric conversion layer 12a of the lower layer film can be etched into a tapered shape (FIG. 1C). The angle of the taper shape (taper angle) can be controlled by changing the amount of etching radical species that enters the gap between the resist pattern 15 and the upper electrode 13a (the undercut portion of the ITO film 13) depending on the undercut amount. .

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 a dry etching method of isotropic etching to form the lower contact hole 2.
7 is drilled to form a contact hole 28. At this time, the starting point during the isotropic etching is the point B immediately below the resist edge, so that the upper insulating film 23 is formed during the first etching step.
Due to the presence of the undercut formed in the resist pattern 25, the etching radical species in the etching gas easily enter the undercut portion of the upper insulating film 23, and the pattern shape of the lower insulating film 22 is etched into a tapered shape. It is possible (FIG. 2 (c)). The angle of the taper shape (taper angle) can be controlled by changing the amount of etching radical species that enters the undercut portion of the upper insulating film 23 depending on the undercut amount.

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-mentioned 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 the laminated film of three layers or more.

[0021]

According to the method of the present invention, isotropic etching is used for etching the upper layer film of the laminated film, and the amount of over-etching is controlled, so that the upper layer film with respect to the pattern of the resist film on the laminated film is controlled. Is formed, and subsequently, isotropic dry etching is used for etching the lower layer film of the laminated film, so that etching radical species in the etching gas enter the undercut portion of the upper layer film, The pattern shape can be etched into a tapered shape. 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

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location H05K 3/06 A H01L 21/88 C

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. A method of etching a lower layer film of a film to form a pattern of a laminated film, wherein the upper layer film of the laminated film is etched by isotropic etching, and is removed excessively while controlling an etching amount with respect to the resist film. And a second etching step in which the lower layer film of the laminated film is isotropically dry-etched, the pattern forming method of the laminated film.