JPS6041243A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To manufacture a semiconductor device in simple steps by forming a thin oxidized film portion including carbon and an oxidized film having a thick oxidized film portion including no carbon continued slowly to the thin oxidized film portion. CONSTITUTION:A carbon inclusion preventive film 23 is formed on the upper surface of a semiconductor substrate 21, the film 23 is patterned, and with the film 23 as a mask carbon is selectively introduced to the upper surface portion of the substrate 21, thereby forming a carbon including layer 25. After the film 23 is removed, an oxidized film 26 in which the upper surface of the substrate 21 is oxidized is formed. The oxygen diffusing speed is decelerated depending upon the quantity of the included carbon in the layer 25, with the result that a thin oxidized film portion 26c including carbon is formed at the portion corresponding to the layer 25, a thick oxidized film portion 26o continued slowly to the portion 26c is formed on the region except the layer 25. Then, it is etched at the same speed, and the remaining oxidize film 26o having slow opening section is formed on the region which does not correspond to the layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device having an insulating film that is free from breakage at contact hole portions.

[Technical background of the invention and its problems]

The outline of a conventionally used method for forming a wiring portion that connects elements in a semiconductor device is as follows. That is, as shown in FIG. 1, a predetermined element region 12 is formed in a semiconductor substrate 11 using selective diffusion or selective implantation technology of impurities, and an insulating film 13 such as a silicon oxide film is formed on the upper surface of the semiconductor substrate 11. Form. Then, a window is opened in this insulating film 13 as shown in FIG. 2, and an opening 14 is formed at a portion that will become an element connection portion. Next, in order to obtain good connectivity between the element region 12 in the semiconductor substrate 11 and the wiring layer to be formed later, high-concentration ion implantation (IJ) is performed using n (or p) ion implantation from the opening 14.
15 is formed directly below the opening 14.

Subsequently, as shown in FIG. 3, the ion implantation layer 15 is subjected to activation heat treatment, etc., and at the same time, a thin oxide film 138 is formed on the surface of the substrate 11 during this heat treatment.

Next, as shown in FIG. 4, a contact hole 14c of a predetermined shape is opened in the oxide film 13s.

Subsequently, as shown in FIG. 5, a metal film 16 is deposited on the upper surface of the substrate and turned by a predetermined amount. By turning, a wiring layer connecting each element region is formed.

In the device formed as described above, the opening 14 is formed in the insulating film 13, but since the cross section of the opening 14 is steep and has a large step, the metal film 16 formed on the step has a Wiring breaks, so-called step breaks, as shown by a in FIG. 5, were likely to occur.

As a countermeasure against breakage in such conventional equipment, for example,
As shown in FIG. 6, a silicon oxide film 13o is formed as an insulating film 13 on a semiconductor substrate 11, and a BSG (boron silicate glass) film 131, which is softened by low-temperature heat treatment, is formed on the semiconductor substrate 11.
11) There is also a method of laminating and depositing the layers on Ll and performing a post-heat treatment to smooth out the steps of the insulating film 13.

Although such a device can prevent the metal film 16 from breaking, it has the disadvantage that the process is complicated.

In addition, in these methods, n+(
(or p+) It is necessary to consider the accuracy of mask alignment between the opening 14 for ion implantation and the contact hole 14c, and to make the margin for the area of the contact portion considerably large, which hinders miniaturization of the device.

In addition to this, so-called LOCO8 (LOCalOx
There is also a method in which an oxide film is selectively formed on the surface of a silicon substrate by an oxidation of 5 silicon method.

This method involves depositing a silicon nitride film on the surface of a silicon substrate, turning the silicon nitride film, and then selectively oxidizing the silicon substrate surface using the silicon nitride film as an oxidation-resistant mask to form a pattern of silicon oxide film. is formed, and the unnecessary silicon nitride film is removed. According to this method, the cross section of the opening in the silicon oxide film becomes smooth, but it is difficult to apply the silicon nitride film in the deposition process and its patterning process, as well as remove unnecessary silicon nitride film and grooves after selective oxidation. It has the disadvantage that the removal process is cumbersome.

[Purpose of the invention]

The present invention was made in view of the above points, and its purpose is to provide a semiconductor device that can easily manufacture a device having an insulating film with a gradual stepped structure without the fear of step breakage. The aim is to provide a manufacturing method and improve productivity.

[Summary of the invention]

That is, in the method for manufacturing a semiconductor device according to the present invention, a carbon introduction prevention film made of, for example, a silicon oxide film or a resist film is formed on the upper surface of a semiconductor substrate, and this carbon introduction prevention film is subjected to main turning 5-. Using the blocking film as a mask, carbon is selectively introduced into the upper surface of the semiconductor substrate to form a carbon-introduced layer.

After removing the carbon introduction blocking film, the upper surface of the semiconductor substrate is oxidized to form an oxide film. Here, in the carbon-introduced layer, the oxygen diffusion rate decreases depending on the amount of introduced carbon.

In other words, by providing a region containing a large amount of carbon,
By reducing the amount of oxygen supplied to this carbon-containing region and the oxide film portion or silicon substrate interface located below it, compared to other regions, the amount of oxide film growth in that region can be suppressed. As a result, a thin oxide film portion containing carbon is formed in a portion corresponding to the carbon-introduced layer, and a thick oxide film portion that is loosely continuous with the thin oxide film portion is formed in a region other than the carbon-introduced layer.

After that, the thin oxide film part and the thick oxide film part are etched at the same speed so that the thin oxide film part is removed and the thick oxide film part remains, and a gentle opening cross section is formed in the region not corresponding to the carbon-introduced layer. There are 6 types that are designed to form a residual oxide film.

Here, the carbon-introduced layer may be formed on the surface region of the silicon substrate, or may be formed on an oxide film suitably formed in advance on the upper surface of the semiconductor substrate.

Furthermore, if the implantation blocking film formed in the ion implantation process for obtaining ohmic contact is used as the carbon introduction blocking film, a dedicated i! No need to turn.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below by taking an example of a resistance element with reference to the drawings.

First, as shown in FIG. 7, an n-type silicon semiconductor substrate 21
Then, a p-diffusion layer 22 which becomes a resistor is formed. Next, an injection blocking member film 23 made of a dielectric film such as a photoresist or a silicon oxide film is deposited on the substrate 21, and an opening 23c is formed at the contact position of the resistor.

Subsequently, as shown in FIG. 8, in order to obtain ohmic contact with the wiring layer to be formed later, p+ ions are implanted using the implantation blocking member film 23 as a mask, for example, at an acceleration voltage of 1.
The ridge injection layer 24 is formed under the conditions of 80 keV and a poron concentration of 2 x 1015c1n-2. Then, for example, the acceleration voltage is 501 CeV.

C″-injection (
carbon implantation) to form a carbon implantation layer 25 in a relatively shallow surface region of the substrate 21.

Next, after removing the injection blocking member film 23, the wafer is placed in a normal oxidation furnace as shown in FIG.
One surface is oxidized to form an oxide film 26. At this time,
When the carbon introduced into the substrate 21 is incorporated into the oxide film, the oxide film thickness on the carbon injection layer 25 becomes thinner than on other regions because the oxygen diffusion rate in the oxide film containing carbon is slow.

In this case, the thin oxide film portion 26 on the carbon injection layer 25
c is about 3000! The film thickness is a degree, and the thick oxide film portion 26. The film thickness is approximately 8,000 mm.

Read the oxide film part containing carbon (thin oxide film part) 26c
and oxide film part that does not contain carbon (thick oxide film part) 2
The above-mentioned oxide film 2 is etched by etching using, for example, an acid-based chemical such that the etching rate of 6o does not change substantially.
6 is removed by etching at a constant film thickness of about 3000X. As a result, as shown in FIG.
o remains on the semiconductor substrate 2 as a residual oxide film with a film thickness of about 5000×, and this is used as a field insulating film to separate it from other device regions.

Next, as shown in FIG.
A wiring layer for wiring each predetermined part is formed by vapor-depositing 7 on a wafer and performing varnishing.

In the oxidation process of the semiconductor substrate in the above method, the diffusion rate of oxygen in that part decreases depending on the amount of carbon injected into the carbon injection layer, so the amount of oxygen diffusion into the center of the carbon injection layer is small. , a large amount of oxygen is diffused into the periphery of the carbon-injected layer from the surrounding area. As a result, an oxide film 9- is formed on the semiconductor substrate, having a thin oxide film portion containing carbon and a thick oxide film portion not containing carbon, which is loosely continuous to the thin oxide film portion. Therefore, if the oxide film is etched to a constant thickness so as to remove the thin oxide film portion of the oxide film, the cross section of the opening of the residual oxide film remaining on the semiconductor substrate due to the thick oxide film portion will be gently sloped. It becomes what it is.

Thereby, a metal wiring layer can be uniformly formed from the opening of the residual oxide Ill over the residual oxide film,
The occurrence of disconnections in the wiring layer can be reduced.

However, if the implantation blocking material film used in the impurity ion implantation process to obtain ohmic contacts is used as a blocking film for carbon introduction, it is possible to repeat patterning on the contact area as in the conventional method, patterning of silicon nitride film, etc. There is no need to carry out 1) major shortening and simplification of the manufacturing process.

Furthermore, unlike in the past, there is no need to unnecessarily enlarge the contact area in anticipation of mask misalignment between the impurity implantation process for ohmic contact and the contact hole opening process. It is also effective.

In addition, in FIG. 11, the carbon injection layer 25 is shown to remain in the contact area under the metal film 27, but during the aluminum alloying process, that is, the sintering process, the substrate 2
Most of the carbon remaining on the surface of the substrate 21 is absorbed into the aluminum, and if the oxide film 26 is formed sufficiently thick in the oxidation process of the surface of the substrate 21 shown in FIG. Since the salt 9 is incorporated into the oxide film 26, almost no change in device characteristics due to the influence of carbon is observed.

Furthermore, although the above embodiment shows the case where the carbon injection layer 25 is formed on the surface region of the silicon substrate, a semiconductor substrate on which an oxide film is previously formed on the upper surface of the silicon substrate is used, and carbon is introduced onto this substrate. Carbon may be selectively introduced into the oxide film by forming a thick film with a predetermined pattern to prevent carbon from entering the oxide film, and then the same steps as in the above embodiments may be performed.

Furthermore, in the above embodiments, the selective ion implantation method is used as a method of introducing carbon into the upper surface of the semiconductor substrate, but this is not limited to ion implantation, and other introduction methods may be used.

〔Effect of the invention〕

As described above, according to the present invention, there is provided a method for manufacturing a semiconductor device that can manufacture a semiconductor device having an insulating film having a gentle opening cross section without fear of breakage of a metal wiring layer through a simple process. It is possible to improve productivity.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1 to 5 are cross-sectional views for explaining an example of a conventional method for manufacturing a semiconductor device, and FIG. 6 is a cross-sectional view for explaining another example of a conventional method for manufacturing a semiconductor device. FIGS. 7 to 11 are cross-sectional views for explaining a method of manufacturing a semiconductor device according to an embodiment of the present invention. 21... Semiconductor substrate, 23... Injection blocking member film, 2
5... Carbon injection layer (carbon introduction layer), 26... Oxide film, 26c... Thin oxide film portion, 26o... Thick oxide film portion, 27... Metal film. ward ward ward 246- @ ward `` taste bandit

Claims (1)

[Claims] A step of selectively forming a carbon introduction prevention film having openings at a predetermined portion on the upper surface of the semiconductor substrate, and a step of selectively introducing carbon into the upper surface portion of the semiconductor substrate using the carbon introduction prevention film as a mask to form a carbon introduction layer. By oxidizing the upper surface of the semiconductor substrate after removing the carbon introduction blocking film, a thin oxide film containing carbon is formed in the carbon introduction layer, and a region other than the carbon introduction layer contains carbon. a step of forming an oxide film having a thick oxide film portion, and a step of exposing the semiconductor substrate directly under the thin oxide film portion, and leaving a part of the thick oxide film formed in a region not corresponding to the carbon-introduced layer; 1. A method of manufacturing a semiconductor device, comprising: etching the thick oxide film portion and the thin oxide film portion at substantially the same etching rate.