JPS58188140A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a steplike electrode hole by a method wherein a resist film is selectively left on a hole partly removing an oxide film adjoining the resist only by HF plasma to etch any residual resist in the longitudinal and lateral directions. CONSTITUTION:An SiO2 film 12 is formed into a hole on n layer 13 on p type Si substrate 11 to be covered with another SiO2 film 14 further forming a rubber base resist mask 15 in the hole. After selectively etching the film 14 by means of activating HF heated in a furnace, HF is removed to etch the mask 15 isotropically by O2 plasma down to the contracted shape 15' of said mask 15. HF is again introduced to etch the film 14 and then HF is discharged to contract the mask 15' isotropically by O2 plasma repeatedly until Si surface comes into direct contact with the mask 15'. Consequently the hole becomes steplike and the reaction is stopped as soon as Si comes into direct contact with the resist. In this constitution, the dimensional difference in the lateral direction of the resist mask before and after etching may be decided by the size of hole at upper and lower edge of the connecting hole regardless of the adherence of the resist forming a steplike hole with excellent reproducibility.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a semiconductor device that improves the shape of a step in a contact opening and prevents disconnection of metal wiring at the contact opening.

As a conventional method for manufacturing a semiconductor device, a polycrystalline/reconverter MO/MOS transistor shown in FIG. 1 will be explained.

After forming a field oxide film 2 on the 11Ft type substrate 1, the oxide film 2 is selectively removed. Gate oxidation M3. A polycrystalline silicon layer 4 is formed. The polycrystalline silicon/layer selectively leaves only the areas that will become the gate electrodes and wiring, and
Drain diffusion layers 5a and 5b are formed by a self-alignment method. An oxide film or glue/glass (PSG) is applied to the entire surface using a vapor phase growth method.
) Membrane etc.OIl! Grow the membrane 6 and open the co/tact window 7a,
7b is opened, but if the step of the insulating film 6 at this opening is large, the metal wiring 8Ω disconnection may occur due to the steep step of the contact window. As a way to completely improve this, as shown in FIG. It was being prevented. This slope can be created by intentionally reducing the adhesion between the photosensitive film for tact opening (hereinafter referred to as photoresist) and the underlying insulating film.
There is a method of chemically or physically treating the surface of the substrate, which results in a large change in etching speed, and a method of forming a thin glass layer on the surface. By using this method, the amount of side etching during oxide film etching is greatly increased, and 9a, 9
As shown in b, the step of the contact part was sloped. But in such a way.

The amount of side etch becomes larger. There were cases in which the amount of side etching was not constant due to variations in adhesion. For this reason, when used in an IC manufacturing method that requires control of the size of one pattern, if there is not enough margin in the design around the contact window, disconnection of the metal wiring can be prevented, but the contact hole will expand and the contact hole will become larger. - There was a possibility that the drain electrode and gate electrode would be short-circuited, resulting in problems with yield stability.

The present invention provides a contact etching method that eliminates the above-mentioned drawbacks and can control the amount of side etching.

A feature of the present invention is a method for manufacturing a semiconductor device in which an insulating film is formed on a substrate and a hole is formed in the insulating film. A process of etching the main surface of the insulating film where the photoresist film is provided, and a process of etching the main surface and side surfaces of the insulating film where the photoresist film is not provided. For example, after forming a second conductive sleeve type diffusion layer on a part of the surface of the first conductivity type semiconductor substrate and coating the diffusion layer with a silicon oxide film, @1 A contact opening connecting the diffusion layer and the metal interconnection layer 1- is formed by a reaction using hydrogen fluoride gas plasma under the photosensitive coating, which is left on the area where the opening is formed. In the method of manufacturing a semiconductor device formed by a method of removing a photosensitive film, a first process of removing a part of the thickness of the oxidized film under the photosensitive film using hydrogen fluoride gas plasma and an oxygen plasma treatment are performed to remove the photosensitive film. Part of the thickness of the sex capsule from the top and side surfaces at the same time.

This method of manufacturing a semiconductor device includes a step of forming a contact window by alternately repeating a second process of removing the same film thickness a plurality of times.

This method requires seven etchings in the area of the contact window to be etched.
There is a process in which the photoresist is left behind by selective exposure, a process in which only a portion of the oxide film thickness is removed by using fluoride water bulk gas plasma from the oxide film in contact with the photoresist by a so-called reverse etching phenomenon, and a process in which the oxide film remaining in the contact opening is removed. By repeating the process of reducing part of the resist film thickness by the same thickness both vertically and horizontally by oxygen plasma treatment in the same reactor several times, the cross section of the etched portion is A contact opening having a stepped shape is formed.

An example will be described in which the method for manufacturing a semiconductor device according to the present invention is applied to the formation of a contact window between a diffusion layer and a metal wiring layer. FIG. 3 (11 to (e)) K Therefore, explanation will be given. FIG. 3 (al: First, an oxide film 12 is formed on the first conductivity type substrate ll, and a region where a diffusion layer is to be formed is selectively removed. , a second conductivity type diffusion layer 13 is formed.

Thereafter, an oxide layer 14 (including a glass film containing impurities) is formed on the entire surface of the substrate 11 by vapor phase growth. Next, a rubber-based photoresist is formed on the oxide film 14. The resulting thickness must be thicker than the film thickness that will be reduced in subsequent steps.

Thereafter, a step of positioning the contact window is performed, leaving a rubber photoresist 15 in the contact window opening.

! Next, the wafer is placed in a reactor, hydrogen fluoride gas is introduced, and when the wafer is heated and allowed to act on the wafer, only the oxidized m14 graded with rubber photolens 15 is etched. In addition, noholac type positive resist l
When used, etching hardly progresses.

This difference is thought to be due to the fact that the rubber resist is hydrophobic and the novolac resist is hydrophilic.

Hydrogen fluoride gas has no reactivity with an oxide film on which no H2O is attached, but it reacts with H2O to generate H+F- ions. The surface of S r 02 reacts with absorbed water and partially becomes kanranol 8i (OH) 2 , but hydrogen fluoride gas reacts with this to generate H 2 O. Under the rubber-based resist, in,o is maintained, H,0 increases as etching progresses, and the amount of F-io/ produced increases, allowing etching to proceed, but in the novo2c-based resist, H,0 increases. Since it passes through, the generated H2O moves to the resist surface and is lost, and almost no F- ions are generated and are not etched.

A portion of the thickness of the oxide film 14 below the photoresist 15 is removed by utilizing the phenomenon of one-inversion etching.

FIG. 3(C): Next, the HF gas in the reactor is exhausted, oxygen is introduced, and the photoresist 15 is isotropically reduced from the surface by a portion of the film thickness using oxygen plasma. At this time, the s-photoresist 15 is also removed in the lateral direction, so
7. on the contact. ) The size of the resist 15 becomes smaller (15).

FIG. 3(d): Next, hydrogen fluoride gas is introduced again and heated to proceed with etching only the oxide film under the photoresist 15' which has become smaller due to the previous oxygen plasma treatment. next,
Oxygen is introduced again to remove the photoresist 15' isotropically. A process like this.

This process is repeated several times until the silicon surface of the contact portion is in direct contact with the photoresist. As a result, the cross-sectional view of the contact opening becomes step-like.

When the oxide film is completely etched and the silicon is in direct contact with the resist, the reaction at the silicon-resist interface stops. This is thought to be because the resist acts as a buffer material to stop the reaction between Si and hydrogen fluoride.

Next, remove the leaking photoresist 15.

Golden fly? After forming IN, the result is shown in FIG. 3(e).

When the shape of the contact is formed by the manufacturing method of the present invention,
The size of the diameter of the contact 17 is determined by the size of the upper end of the contact 17 after development of the photoresist 15, and the size of the lower end of the contact 17 is determined by the size of the diameter of the photoresist remaining after tIk.

In this way, the size of the upper and lower ends of the contact is determined by the difference in shape between the beginning and end of the photoresist etch, that is, the amount of reduction in the film thickness of the photoresist, that is, the size of the lateral diameter.

For this reason, the cross-sectional shape of the contact is determined regardless of the adhesion between the oxide 11114 and the 7-photoresist 15, and there is no reproducibility.

Furthermore, since etching progresses only at the interface of the oxide film in contact with the photoresist, the area to be etched is determined by the size of the resist, and there is no side etching.

Furthermore, if the oxide film contains a high concentration of sulphur, the step-like cross-sectional shape will soften even with a short heat treatment of about 1000°C after the contact hole is formed, as shown in Fig. 4. It is also possible to make the stepped contact shape sloped.

According to the present invention, (1) the size of the contact diameter on the silicon/oxide film surface is determined by the size of the resist after resist development gII. (2) Divide the metal wiring into a staircase shape that prevents disconnection from occurring due to step differences in the contact area. There are percentages such as (18) good stem coverage and (3) good shape reproducibility.

Furthermore, it goes without saying that the same process can be applied to a substrate having a contact hole formed therein, in the case of a polycrystalline silicon layer or a metal wiring made of aluminum or the like.

[Brief explanation of the drawing]

FIG. 1 shows a cross-sectional view of a silicon/gate MO8) in which a metal wiring breakage has occurred in a conventional PC/tact portion. FIG. 2 shows a cross-sectional view of a MOS transistor/raster in which the step of the contact portion is tapered by conventional wet etching. FIG. 3 is a cross-sectional view of a semiconductor device, paying attention to the contact to the diffusion layer according to the embodiment of the present invention. FIG. 4 is another embodiment of the present invention. ...First conductivity type substrate, 2.
...Field oxide film, 3...Kate oxide film, 4...Gate polycrystalline, 5a,
5b... nce and tray/diffusion layer, 6...
...Oxide film, 7a, 7b...Contact opening, lO...Metal wiring, 11...First
411 [type substrate, 12... oxide film in field section, 13... diffusion #, 14... oxide film, 15... photoresist, 16. 17...
...Step part of contact part. 18...Metal wiring, 19...Contact opening portion sloppy due to heat treatment. n 34 5jihoko 1 figure strong 2 figures 13 1j 5 311 Figure 3

Claims (1)

[Claims] In a method of manufacturing a semiconductor device in which an insulating film is formed on a substrate and an opening is formed in the skeleton insulating film, step 1 of selectively forming a photoresist film on the scissor insulating film, and then a #photoresist film is provided. the main surface (I) of the insulating film in the part where the resist film is not provided; A method for manufacturing a semiconductor device.