JPS6226574B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device, and is particularly aimed at improving the adhesion between an insulating film on the surface of a semiconductor substrate and an electrode metal.

Conventionally, platinum silicide has been used as the electrode metal for transistors that require high reliability and high quality.
Multilayer electrodes made of titanium-platinum-gold have been used.

However, titanium has a drawback that the electrode metal peels off at the interface between the silicon oxide film and titanium because titanium does not adhere well to the surface of the semiconductor substrate and the silicon oxide film that protects the PN junction that reaches the surface.
Therefore, recently, a method has been adopted in which a silicon nitride film is formed by vapor phase growth on a silicon oxide film, and an electrode metal of titanium-platinum-gold is formed on the silicon nitride film.

That is, after semiconductor elements are formed and before electrodes are formed, a silicon nitride film is formed over the entire surface of the semiconductor substrate, and a reverse voltage equal to or higher than the breakdown voltage is applied for a long time between the front and back surfaces of the semiconductor substrate. Then, the silicon nitride film on the silicon surface, which is to become the electrode contact portion of the semiconductor element, becomes a chemically formed film. The chemically formed film can be easily removed with a hydrofluoric acid-based etchant, and if a metal electrode is formed on it, the electrode is formed on a clean nitride film, and the silicon nitride film and electrode are formed on a clean nitride film. The adhesion can also be improved.

However, when forming the silicon nitride film on the opening of the semiconductor element part, it is not easy to specify conditions such as applied voltage and time, and in some cases, the chemical formation film cannot be completely formed and the remaining silicon nitride film remains. It was occurring.
Furthermore, the formation of the nitride film progresses so much that the inside of the silicon surface is formed, and for this reason, when a platinum silicide layer is formed for ohmic contact with the electrode, it is difficult to form a platinum silicide layer, especially for devices with shallow emitter regions such as high frequency transistors. , the platinum penetrates the shallower emitter region and reaches the base region, causing an emitter-base short circuit. As described above, the conventional method has drawbacks such as poor electrode energization or bond breakdown, resulting in problems of reduced yield and reliability.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a manufacturing method that has improved yield, high reliability, and improved adhesion of multilayer electrodes.

According to the present invention, after forming an opening for contacting an electrode of a semiconductor element, platinum silicide is formed on the exposed semiconductor surface, and then covered with a silicon nitride film, and then the excess on the opening is formed. A method for manufacturing a semiconductor device is provided, which is characterized in that a silicon nitride film is removed by replacing it with a chemically formed film, and then a multilayer electrode is formed thereon.

According to the manufacturing method of the present invention, since the semiconductor interface at the opening is stable, it does not affect the characteristics in any way.
Moreover, since a multilayer electrode is formed on a clean silicon nitride film, its adhesion can also be improved.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

Figures 1 to 3 show the steps of the conventional manufacturing method described above, in which a silicon nitride film is formed on the entire surface after the element is formed, and the silicon nitride film on the opening of the semiconductor element is converted into a chemical film. FIG.

That is, after forming a base region 2 and an emitter region 3 on a semiconductor substrate 1, an opening for leading out an electrode is formed in a silicon oxide film 4 on the substrate by photolithography, and then a silicon nitride film 5 is formed on the entire surface. (Figure 1).

Next, when a reverse voltage is applied between the front surface and the back surface of the semiconductor substrate 1 (positive voltage on the back surface and negative voltage on the front surface since it is an NPN transistor), the silicon nitride film 5 in contact with the base region 2 and emitter region 3 is applied. is chemically converted to form a chemically formed film 6 (FIG. 2).

Then, the chemically formed film 6 formed on the semiconductor substrate 1 is removed (FIG. 3). However, at this time, the chemical film 6
Even if the chemical formation conditions for forming the nitride film 5 are uniform, the nitride film 5
Due to variations in the thickness of the substrate 1, not all of the silicon nitride film was formed, leaving a silicon nitride film 7, or the formation progressed too much, causing distortions 8 on the surface of the substrate 1. For this reason, there is no contact between the emitter region 3 and the electrode,
Furthermore, the surface strain 8 in the base region 2 had an adverse effect on the characteristics.

Therefore, in order to eliminate such drawbacks, the present invention first makes holes in the silicon oxide film 14 on the semiconductor substrate 1 on which the base region 12 and the emitter region 13 are formed, and makes electrode extraction portions in each region 12 and 13. Then, a platinum silicide layer 15 is formed in that portion (FIG. 4). In this method, approximately 100 Å of platinum is deposited on the entire surface of the silicon substrate 1 by vapor deposition or sputtering, and the temperature is approximately 450°C.
Heat treatment is performed for about 30 minutes in an argon atmosphere.
Then, the excess platinum on the silicon oxide film 14 is
When immersed in aqua regia for several minutes, it is dissolved and removed, forming platinum silicide 15.

Next, a silicon nitride film 16 is applied to the entire surface to a thickness of 300 Å.
A negative voltage is applied to the front surface of the semiconductor substrate 1 and a positive voltage is applied to the back surface of the semiconductor substrate 1, for example, a potential difference of 130 V,
Reverse bias is applied at 100 mA for 50 minutes to turn the nitride film 16 on the platinum silicide layer 15 into a chemically formed film 17 (fifth
figure). At this time, the platinum silicide layer 15 is
Furthermore, since this layer 15 is not chemically formed, even if the nitride film 16 is sufficiently formed, no strain will be generated on the semiconductor surface.

Thereafter, the chemical film 17 is removed by immersing it in a mixed solution of hydrofluoric acid and pure water at a ratio of 1:50 for about 1 minute (FIG. 6).

Then, a titanium-platinum-gold multilayer electrode 18 is formed on the clean silicon nitride film 16 (seventh
figure).

According to this manufacturing method, the silicon nitride film 16
When forming the silicon, the platinum silicide layer 15 prevents the formation from proceeding to the base region 12 and emitter region 13. Therefore, the nitride film 16 can be formed in an amount sufficient to eliminate the remaining nitride film, and moreover, the platinum silicide layer 15 prevents the formation of the base region 12 and the emitter region 13. No chemical formation occurs either. Therefore, since the multilayer electrode 18 is formed on the silicon nitride film 16 which has a stable semiconductor surface and is clean, a semiconductor device having the multilayer electrode 18 with high yield, high reliability, and good adhesion is provided. can.

It should be noted that the present invention is not limited to the above-mentioned embodiment. For example, the silicon nitride film 16 may be formed by anodic oxidation, and the collector electrode may also be taken out from the same surface. Furthermore, even in the case of the PNP type, the bias voltage may be reversed to that of this embodiment. Moreover, platinum silicide layer 15
It is not necessary to chemically form all of the upper nitride film 16, and a portion may be left.

[Brief explanation of the drawing]

1 to 3 are process sectional views showing a conventional manufacturing method, and FIGS. 4 to 7 are manufacturing process sectional views showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1, 11... Semiconductor substrate, 2, 12... Base region, 3, 13... Emitter region, 4, 14... Silicon oxide film, 5, 16... Silicon nitride film, 6, 17
...Chemical film, 7...Nitride film remaining, 8...Inside surface, 15
...Platinum silicide layer, 18...Titanium-platinum-gold multilayer electrode.

Claims (1)

[Claims] 1. A step of opening an electrode extraction portion of a silicon oxide film on a semiconductor substrate, a step of forming an alloy layer with platinum on the semiconductor substrate at the electrode extraction portion, a step of forming a silicon nitride film on the entire surface, and a step of forming a silicon nitride film on the entire surface. A method for manufacturing a semiconductor device, comprising the steps of chemically converting and removing at least a portion of the silicon nitride film on the alloy layer, and forming an electrode electrically connected to the alloy layer.