JPS6119132A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To restrain resist from deterioration and undercut by a method wherein an insulating film containing no oxygen is formed on another insulating film mainly comprising SiO2 and a conductive film deposited on the former insulating film is plasma-etched. CONSTITUTION:An SiO2 film 17 is formed on a semiconductor substrate 11 to deposit an Si3N4 film 18 on the film 17. Next a contact hole 19 passing through a source region 15 and a drain region 16 is opened by etching the films 18 and 17. Firstly after depositing an Al film 20 on overall surface, a resist pattern 21 is formed on the film 20. Secondly the film 20 is plasma-etched utilizing the pattern 21 as a mask. Thus the film 20 is patterned to be removed at the opening of pattern 21. Resultantly a wiring 21' connecting to the regions 15, 16 through the intermediary of the hole 19 is patterned. Through these procedures, the film 17 may be prevented from producing oxygen atoms while restraining the resist 21 from deterioration and undercut in case of plasma etching process by means of forming the film 18.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides a method for preventing the separation of oxygen atoms in a base insulating film when processing a metal film formed on an insulating film on a semiconductor substrate by plasma etching. The present invention relates to a method for manufacturing a semiconductor device.

[Technical background of the invention and its problems] In recent years, with the increasing integration of semiconductor devices, advanced micro-line processing technology has become required, and as an etching method, the conventional isotropic wet etching has been replaced. , plasma etching methods that enable anisotropic etching have come to be widely used. In addition, multilayer wiring is often used, and CVD-8i 02 YaPSG (!,
5i02 is mainly used, such as D/glass silicide), and Aβ (aluminum) is mainly used for metal wiring.

Therefore, in order to achieve high integration of a semiconductor device and to obtain high reliability of the device, a technique is required that can process and form the Aρ wiring on the SiO2 film with good controllability.

By the way, plasma etching is used to process the metal (here AQ) on an insulating film whose main component is SiO2 with good control, but it is usually , overetching of about 30 to 50% is required. However, since the underlying 5iO211 is etched during overetching, the oxygen atoms in 5102 are separated, and the separated oxygen atoms cause the resist to Significant deterioration (film reduction)
Otherwise, undercuts may occur in Aβ, resulting in a significant decrease in dimensional controllability.

[Object of the Invention] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a semiconductor device in which a metal film on an insulating film can be plasma etched with good controllability. .

[Summary of the Invention] In order to achieve the above object, the present invention deposits a conductive film on the surface of an insulating film formed on a semiconductor substrate, forms a resist pattern on the conductive film, and masks the resist pattern. In the manufacturing process of a semiconductor device in which the conductive film is patterned by plasma etching, a film of an insulating material that does not contain oxygen atoms is formed on the insulating film, and a conductive film is deposited on the surface of the film. After that, a resist pattern is formed on the conductive film, and the conductive film is patterned by plasma etching using the resist pattern as a mask. According to the present invention, based on the fact that resist deterioration and undercuts that occur during overetching are due to the influence of oxygen atoms generated from the etched SiO2 film, an insulating film mainly composed of SiO2 is used. An insulating film that does not contain oxygen on top, e.g.
After forming i3N4, a conductive film to be processed was formed on its surface, and this conductive film was plasma-etched using a resist as a mask.This prevented the generation of oxygen atoms. Deterioration of the resist and occurrence of undercuts can be suppressed.

[Embodiments of the invention] Embodiments of the present invention will be described below with reference to the drawings.

First, FIG. 3 shows an outline of a plasma etching apparatus for etching the Aβ film for wiring used in the manufacturing process of the present invention. That is, as shown in the figure, the plasma etching apparatus includes a pair of flat electrodes 41 .
Of these electrodes, the lower electrode 41 is grounded, the upper electrode 42 is connected to a high frequency power source 43, and a wafer is placed on the electrode 41. Then, etching gas is passed through the container 40, and the electrodes 41.
42, a high frequency current is applied to generate plasma to perform etching.

Embodiment First, a thick field oxide layer 1112 is formed on a semiconductor substrate 11 to isolate the device region into islands, a gate insulating film 13 on the surface of the device region, a gate electrode 14 on the gate insulating film 13, and other source and drain regions 15° and 16. Then, on this semiconductor substrate 11, a 3000 silicon oxide m < s +02 film) 17 is formed as an interlayer insulating film by thermal oxidation, and then a silicon nitride film ( S i: + N4 Ilri 18
500 people were deposited (as shown in Figure 1(a)). Continuing,
5iaN+I1 using a resist pattern formed by applying resist to the entire surface and patterning it by photo-etching method.
Insulation between 18 and l1! [Etches 117 and sources.

A contact hole 19 communicating with the drain region was opened. Next, an An film 20 of 800O was deposited on the entire surface by sputtering.
After the Aβ film 20 is deposited, a positive photoresist is coated on the Aβ film 20 and patterned by photolithography to form a resist pattern 21 (as shown in FIG. 1B).

Next, the Aβ film 20 was plasma etched using the resist pattern 21 as a mask. For ARR2O3 etching, as shown in FIG.
The semiconductor substrate 11 was placed thereon, etching gas was passed through the container 40, and a high frequency current was applied between the electrodes 41 and 42 to generate plasma to perform etching. The etching conditions are as follows.

The etching gas supplied to the plasma etching equipment is C.
Cβ4 was used, the flow rate of CCβ4 was 2008 CCm, the high frequency power applied between the electrodes was 500 W, and the etching pressure was 350 mt.

It was set as rr.

As a result, the Aρ film 20 was patterned, and the H2 film 20 at the opening of the resist pattern 21 was removed. At this time, in order to prevent the β film 20 from remaining in the portion to be removed due to variations in the thickness of the A° C. film 20WA, overetching was performed by about 30%.

At that time, the exposed surface of 5iaN+l118 was also slightly etched. As a result, the wiring 22 connected to the source/drain region 15.16 via the contact hole 19
was patterned (as shown in FIG. 1(C)).

Furthermore, the etching rate of 82 at this time was 700 people/mi.
n, and the etching amount of 5i3N4WA17 during overetching was only 200. Therefore, 50
The 3i3N+ film 17 of 0 remains as much as 300 after overetching, and the underlying 8+02 film 17 is this 5ia
N41[118 was protected and not etched.

Comparative Example First, on a semiconductor substrate 11, a thick field oxide film 12 for isolating device regions into islands, a gate insulating film 13 on the surface of the device region, a gate electrode 14 on the gate insulating film 13, and other source and drain regions 15, . A silicon oxide film (Si0211) 17 of 3,500 layers was then formed as an interlayer insulating film on this semiconductor substrate 11 by thermal oxidation (as shown in FIG. 2(a)). Subsequently, the interlayer insulating film 17 is etched using a resist pattern formed by applying a resist to the entire surface and patterning it by photolithography, and forming contact holes 1 leading to the source and drain regions.
9 was opened. Next, Afil is applied to the entire surface by sputtering.
After depositing 8000 l#20, βN1120 to this
A positive photoresist is applied thereon and patterned by photolithography to form a resist pattern 21 (as shown in FIG. 2(1)).

Next, using the resist pattern 21 as a mask, the Aλ film 20 was plasma etched using the same plasma etching apparatus as in the example under the same conditions.

As a result, the A2 film 20 was patterned, and the Aj211120 in the opening of the resist pattern 21 was removed. As a result, the source can be connected via the contact hole 19.
Wiring 22 connected to drain regions 15 and 16 was formed by patterning. At this time, in order to prevent the A°C film 20 from remaining in the portion to be removed due to variations in the β film 20, overetching is performed.
211) The exposed surface of 17 was also slightly etched (second
Figure (C) (Illustrated).

Incidentally, the plasma etching conditions used in this comparative example were the same as in the example.

That is, the comparative example is a method of manufacturing a semiconductor device having a conventional structure, and has a structure in which S+3N418 is removed from the structure shown in FIG. 1, and an Aa film 20 is formed on an 8i02 film 17.

Therefore, in the present example and the comparative example, during the plasma etching process in their manufacturing process, the A°C film 20
In order to investigate the amount of etching of the resist pattern 21 during etching and overetching, the etching time was varied so that etching was completed before and after just etching. The etching amount of the resist pattern 21 was measured using a Talystep (stepped needle), and the cross-sectional shape was observed using a scanning electron microscope (SEM).

FIG. 4 is a characteristic diagram showing the results, in which examples are shown as A and comparative examples as B. That is, the figure shows the relationship between the amount of film loss of the resist pattern 21 and the etching time when etched with a plasma etching apparatus, and the position indicated by arrow J is the just etching time of the An film 20. As can be seen from the figure, in the comparative example with the conventional structure, the slope increases before and after the just etching time, indicating that the etching rate of the resist increases.
This clearly shows that oxygen atoms have an effect. On the other hand, in the method of the present invention indicated by A, no deterioration of the resist or abnormality in the cross-sectional shape was observed even after just etching the A2 film 20.

Therefore, when forming an A2 film on a SiO2 film and patterning this A°C film by plasma etching to form A°C wiring, etc., an Si3N4 film is formed as a protective film on the 3i3N41 film, and the Si3N4 film is formed on the 3i3N41 film. By forming an A°C film on the substrate and plasma etching it using the resist pattern as a mask, it is possible to prevent the etching of the 5102 film and the separation of oxygen atoms in the S+02 film, thereby reducing the thickness of the resist pattern. Since the occurrence of undercuts can be prevented, the patterning of the β film can be performed with good controllability so as to obtain the desired dimensions. Therefore, a high quality semiconductor device can be obtained.

Note that the thickness of the 513N4 film, which is a protective film for the 5iQ2 film, must be set to a level that reduces the thickness of the 513N4 film due to overetching during plasma etching. The film may be made of a heat-resistant insulating material other than the SI3N4 film that does not contain oxygen atoms. In the above embodiment, a He2 film is used as a conductive film for wiring, etc., but it may be an aluminum alloy, polycrystalline silicon, a high melting point metal, a silicide of a high melting point metal, or the like.

The SiO2 film on the semiconductor substrate is not only a thermal silicon oxide film but also a C
VD silicon oxide, phosphorus-doped silicide glass, or boron-doped silica glass can be used.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to suppress film thinning and undercut of a resist pattern for patterning a conductive film, and therefore pattern a conductive film with good controllability. Therefore, it is possible to provide a method for manufacturing a semiconductor device which has features such as being able to obtain a high quality semiconductor device.

[Brief explanation of the drawing]

Figures 1 (a) to (C) are manufacturing process diagrams showing examples of the present invention, Figures 2 (a) to (C) are manufacturing process diagrams of comparative examples, and Figure 3.
The figure shows the schematic structure of the plasma etching apparatus used for plasma etching, and the IN4 figure shows the structure shown in Figure 1.
3 is a diagram showing the relationship between the etching time of each sample in FIG. 2 by plasma etching and the amount of film loss of the resist pattern. FIG. 11... Semiconductor substrate, 12... Field oxide film,
13... Gate insulating film, 14... Gate electrode, 17
...Silicon oxide II (on SiO2 film), 18...
Silicon cave film (Si3N4 film), 20...A℃ film,
21...Resist pattern, β wiring to 22... Applicant's agent Patent attorney Takehiko Suzue 1st vi! J Figure 2

Claims (5)

[Claims] (1) After depositing a conductive film on the surface of an insulating film mainly composed of silicon oxide formed on a semiconductor substrate, a resist pattern is formed on the conductive film, and this is used as a mask to form the conductive film. In the manufacturing process of a semiconductor device in which the conductive film is patterned by plasma etching, a film of an insulating material that does not contain oxygen atoms is formed on the insulating film, a conductive film is deposited on the surface of the insulating film, and then the conductive film is patterned by plasma etching. 1. A method of manufacturing a semiconductor device, comprising forming a resist pattern on a conductive film, and patterning the conductive film by plasma etching the conductive film using the resist pattern as a mask. (2) The method of manufacturing a semiconductor device according to claim 1, wherein the thickness of the insulating material that does not contain oxygen atoms is greater than the amount of film reduction due to over-etching during plasma etching. (3) The method of manufacturing a semiconductor device according to claim 1, wherein the film of an insulating material that does not contain oxygen atoms is a silicon nitride film. (4) Manufacturing a semiconductor device according to claim 1, wherein the conductive film is any one of aluminum, an aluminum alloy, polycrystalline silicon, a high melting point metal, or a silicide of a high melting point metal. Method. (5) Manufacturing a semiconductor device according to claim 1, wherein the insulating film is any one of a thermal silicon oxide film, a CVD silicon oxide film, a phosphorous-doped silicide glass, and a boron-doped silica glass. Method.