JPH05267254A - Pattern formation for semiconductor element - Google Patents

Abstract

PURPOSE:To provide a method capable of forming a pattern, particularly an aperture, narrower than the conventional one while using the conventional resist patterning with respect to a patterning method for the manufacture of a semiconductor element. CONSTITUTION:A method is to use a fluid material as an etching mask for a film 2 to be etched. In an embodiment, BPSG4 is used. At first, the BPSG4 is patterned with a resist 1, and then, is expanded mainly in the transverse direction by a heat treatment (glass flow, expansion (a)). With this as a mask, the film 2 to be etched is patterned.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming an etching mask for patterning.

[0002]

2. Description of the Related Art A conventional example of a method of forming an etching mask at the time of patterning in manufacturing a semiconductor device is shown in FIG. 5 and will be described below.

For example, when patterning an insulating film 52 grown and formed on a silicon substrate (hereinafter simply referred to as a substrate) 53 as shown in FIG. 5, that is, etching into a predetermined pattern, a photoresist ( Hereinafter, a resist 51 will be simply applied, and the resist 51 will be patterned by photolithography (hereinafter abbreviated as photolithography) technique.
Etching is performed by the (Reactive Ion Etching) method. In such an etching method, as can be seen from the figure, the opening width of the insulating film 52 by etching is determined by the finished opening width A of the resist 51 shown, and cannot be smaller than that width.

The same applies to any patterning in the manufacture of semiconductor devices, an example of which is shown in FIGS. 6 to 8 including defects and will be briefly described below.

FIG. 6 shows an example of an element isolation structure by forming a trench. As is well known, in this structure, a trench (groove) 60 is opened in the substrate 53 and an insulator is buried in the trench 60 (not shown) for element isolation. Since the trench 60 is formed by the same method as the patterning described above, the opening width thereof is determined by the pattern opening width A of the resist 51 shown in the figure, and cannot be less than the width A. Therefore, the width B of the element formation region also depends on it. That is, no further reduction is possible.

FIG. 7 shows an example of forming the contact hole 61 in the multilayer wiring structure (the upper layer wiring is not shown). As is well known, in the case of a multi-layer wiring structure, generally, a first insulating film 56 is formed on a substrate 53 as shown in FIG.
A first conductive layer (wiring) 58 is formed thereon and patterned, and a second insulating film 59 is further formed thereon, and then a contact hole 61 up to the first insulating film 56 is patterned to form a resist 51. Is used as a mask for etching. At this time as well, the opening width is determined by the opening width A of the resist 51, the opening width D of the contact hole cannot be smaller than A, and the first conductive layer 58 has the above-mentioned opening width A as shown in FIG. When the contact hole 61 is formed so as to reach the side wall of the contact hole 61 formed with the opening width A, when the contact hole 61 is filled with a conductive material (not shown), the first conductive layer 58 which is not necessary is formed. They come into contact with each other (the contact hole 61 is for contact with the substrate 53). When this happens
If the contact hole 61 is formed narrower than the opening width A, there is no such case.

FIG. 8 shows an element isolation structure similar to that of FIG. 6 in which a trench is formed, and an insulating film 70 is formed by CVD so as to fill the opened trench 60 by the method described in FIG.
When formed by the (chemical vapor deposition) method or sputtering,
At the time of its formation, the growth film overhangs, so-called voids such as the E portion shown in FIG. 8 occur, and the step coverage is not good.

As described above, the reason why the opening in patterning cannot be smaller than the opening width A of the resist is
This is because the etching shape becomes almost vertical in ordinary etching by RIE or the like.

[0009]

As described above, the conventional resist patterning method cannot reduce the opening width of the pattern. As is well known, there is a limit to the patterning of the resist, that is, the opening width here, and therefore it cannot be made smaller than the minimum dimension.

Therefore, even in the element isolation, a wider element region cannot be taken and the contact hole cannot be made smaller. In addition, when the open groove is filled, the voids described above are likely to occur, and the step coverage is poor.

In order to eliminate the above problems, the present invention uses a fluid material such as BPSG (boron / phosphorus / silicate glass) or PSG as an etching mask to form a groove having a smaller width. The purpose is that.

[0012]

To achieve the above object, the present invention is designed to perform etching by using a material having fluidity such as BPSG or PSG, particularly a material exhibiting a flow shape in the lateral direction, as an etching mask. Is.

[0013]

As described above, according to the present invention, since a fluid material is used as an etching mask, when the material is patterned and heat-treated, the material expands in the lateral direction and becomes narrower than the width of the first pattern (opening). If it is used as a mask, a smaller pattern can be formed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention, which will be described below.

First of all, as shown in FIG.
The insulating film 2 is formed on the silicon substrate 3, and the insulating film 2
In order to pattern the insulating film 2 as a fluid material which is a feature of the present invention, in this embodiment, BP is used.
The SG4 is grown to a thickness of about 8000 Å (hereinafter not referred to as a thickness). In this example, B ₂ O ₃ / P ₂ O ₅ =
12/15 (wt%) concentration of BPSG was used.

After that, a normal resist 1 is applied on the BPSG 4, and predetermined patterning is performed in the same manner as in the conventional case, and using it as a mask, the BPSG is formed by the RIE method or the like.
Etch 4. Then, as shown in Fig. 1 (a),
Resist 1 and BPSG 4 patterned on insulating film 2
The structure will remain.

After that, when the resist 1 is removed and a heat treatment is performed, the remaining BPSG 4 swells particularly in the lateral direction (so-called glass flow) because it has fluidity, as shown in FIG. 1 (b). That is, the bulge a, that is, 2a is narrower than the opening width A at the time of patterning with the resist 1.

Therefore, when the BPSG 4 thus bulged is used as a mask and the insulating film 2 thereunder is etched, as shown in FIG. 1B, an opening narrowed by 2a of the bulge of the BPSG 4 is formed. It The etching at this time is generally performed by the RIE method, but as a matter of course, the etching rate is such that the insulating film 2 is etched and the BPSG 4 is not etched.

The fluidity of the BPSG 4, that is, the bulge, can be controlled by the concentration of impurities added to the BPSG 4, the film thickness of the BPSG, and the heat treatment conditions.

For example, in the experiment of this embodiment, BPS having the concentration of B ₂ O ₃ / P ₂ O ₅ = 12/15 (wt%) was used.
After G was grown to 1000 Å, it was patterned as described above and RTA (Rpid Th) at 950 ° C. for 20 sec.
(1) with an opening diameter of 8600Å and a = 140 with 5800Å.
With 0Å and 3000Å, a = 500Å is obtained.

The film growth is performed at 900 ° C. for 30 seconds.
Almost no bulge occurs when the RTA treatment is carried out in (1).

An application example of the above-described embodiment is shown in FIGS. 2 to 4 and will be described below.

FIG. 2 shows an example of a trench type element isolation structure similar to that of FIG. 6 described in the prior art.

In this case as well, if the heat treatment is carried out using BPSG4 as the etching mask in exactly the same manner as the method described in the above embodiment, as shown in the figure, a trench having a width narrower than the original pattern (a bulge 2a of BPSG4) is formed. Can be opened. The element forming region becomes wider accordingly.

FIG. 3 shows the BPS as described above.
Although G is used as an etching mask, this example is an example in which taper etching can be performed by the same method.

As shown in the figure, B formed on the substrate 3
When the PSG 4 is heat-treated after patterning in the same manner as described above, it expands in the vertical and horizontal directions to form a pattern 4a. This BPSG
When the etching is performed under the following conditions using 4a as a mask, the side wall of the opening of the substrate 3 is tapered.

That is, when etching is performed under the condition that the etching rate between the BPSG 4a and the substrate 3 is about 1: 1 to 1: 5, the bulge b of the BPSG 4a is gradually etched, that is, the BPSG 4a.
Since the opening width as a mask of is widened, the etching shape of the substrate 3 etched accordingly is
As shown in the figure, the side wall is tapered.

FIG. 4 also shows an example in which taper etching is performed as in the above. In the case of this figure, the film to be etched is the insulating film 11, on which B is patterned and heat treated.
The PSG 4a is formed, and the insulating film 11 is etched using the PSG 4a as a mask as described above. In this case, if the insulating film 11 is the same material as the mask, such as BPSG, the etching rates are the same, and if etching is performed at that rate, the insulating film 11 is the same as the above-described situation.
The etching shape of is a taper shape.

[0029]

As described above, according to the present invention, a material having fluidity as an etching mask, B in the embodiment, is used.
Since PSG is used to heat it to expand it and to pattern the film to be etched using it as a mask, a narrower patterning (opening) can be made than before and taper etching can be performed easily. Patterning in all aspects contributes to reducing the size of the opening (and eventually enlarging the required portion), and also contributes to the generation of voids and the improvement of step coverage.

[Brief description of drawings]

FIG. 1 Example of the present invention

FIG. 2 Example of application to trench element isolation structure

FIG. 3 Example of application to taper etching (1)

FIG. 4 Example of application to taper etching (Part 2)

FIG. 5 Conventional example

FIG. 6 Conventional example of trench element isolation

FIG. 7 Conventional example of contact hole

FIG. 8 is an explanatory diagram of void generation.

[Explanation of symbols]

 1 resist 2 insulating film 3 substrate 4 BPSG

Claims (3)

[Claims] 1. A material is formed on a semiconductor substrate or a film to be etched formed on the semiconductor substrate, which serves as a mask for etching the substrate or the film to be etched and which is fluid to heat treatment. A step of: (b) applying a photoresist on the formed material and patterning it; (c) patterning the fluid material using the patterned photoresist as a mask; (d) the patterning A step of heat-treating the fluid material with a glass flow, and (e) etching the substrate or the film to be etched using the heat-treated fluid material as a mask. A method for forming a pattern of a characteristic semiconductor device. 2. A mask of the fluid material,
In the step of etching the substrate or the film to be etched, the mask of the fluid material is gradually etched, and etching is performed at an etching rate such that the etching shape of the film to be etched becomes a tapered side wall. The method for forming a pattern of a semiconductor device according to claim 1, which is characterized in that. 3. The method for forming a pattern of a semiconductor device according to claim 1, wherein BPSG or PSG is used as the fluid material.