JPS5913326A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To permit a subsequent lithography process to be carried out successively, by regenerating a pattern on the semiconductor surface which has once disappeared in a diffusion pretreatment process or the like. CONSTITUTION:After a lithography process, an n type impurity 8 is doped by means of an ion implantation device or the like. If an oxide film is over-etched in a subsequent process of pretreatment for impurity diffusion, a pattern on the silicon surface becomes difficult or unable to observe. When the impurity 8 is thermally diffused, the pattern on the silicon surface becomes substantially unobservable. Therefore, the oxide film grown through the thermal diffusion is removed by etching the whole surface by means of hydrofluoric acid diluted with water. Then, a chemical etching is carried out with a hydrofluoric-nitric acid solution obtained by mixing a small amount of nitric acid into hydrofluoric acid diluted with water. After the impurity diffusion, the pattern is faintly observable. Even when the pattern becomes unobservable after the formation of the thermal oxide film, it becomes possible to effect a subsequent lithography process by removing the oxide film from the whole surface, carrying out the chemical etching, effecting a hot water cleaning treatment with an ammonia water and a hydrogen peroxide solution, and forming a thermal oxide film again.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves coating a semiconductor surface with a photosensitive polymer material (hereinafter referred to as resist) that is sensitive to ultraviolet rays, etc., overlaying a mask with a silver pattern on top of the photosensitive polymer material (hereinafter referred to as resist), After irradiating the resist, the resist is developed, and the resist is used as a mask to perform etching (hereinafter referred to as phosphorography process).In the intermediate process of the next phosphorography process, the existing pattern on the semiconductor surface disappears and becomes visible. The present invention relates to a method for manufacturing a semiconductor device that allows the existing pattern to be visibly reproduced to enable the next phosphorography process when the existing pattern is lost.

Conventionally, in order to manufacture semiconductor devices (for example, transistors and integrated circuits), it is necessary to locally diffuse impurities into a part of the substrate or locally oxidize it.
These microfabrications are performed using phosphorography technology. For example, when it is desired to partially diffuse impurities onto a silicon substrate of a type or P type, a process as shown in FIG. 1 is performed. First, a R-type or P-type silicon wafer 2 is thermally oxidized in high-temperature oxygen to form an oxide film 1 on the entire surface of the wafer 2. A resist 3 is applied onto this oxide film 1 and exposed to ultraviolet rays 6 through a mask pattern 5 on a glass substrate 4. The resist 3 is locally dissolved and removed by the subsequent development process, and when immersed in fluoric acid, which is an etching solution, only the part of the oxide film 1 where there is no resist film 3 is etched. A pattern is formed. Through the window of the oxide film 1 obtained by such a phosphorography step, impurities are diffused only into necessary portions to form an impurity diffusion layer 7.

Next, the wafer is thermally oxidized to form an oxide film 1 on the entire surface, and then the next phosphorography process is started. However, due to impurity doping during the process or excessive oxide film etching in the pretreatment process for impurity diffusion, the pattern may become difficult to see, or in severe cases, the total heat may not be visible. Furthermore, even if it appears blank after thermal diffusion, it may become invisible after the oxide film is formed. Therefore, in the next phosphorography process, the markers on the silicon wafer that are positioned with the mask cannot be seen, so mask alignment cannot be performed. In such cases, the semiconductor is often thrown away during the process.

The present invention eliminates this drawback by regenerating the pattern that has disappeared in the pre-diffusion process and allowing the phosphorography process to be carried out following the previous diffusion and oxidation process.

EXAMPLES Hereinafter, the present invention will be specifically described in detail with reference to Examples.

FIG. 2 is a diagrammatic representation of an embodiment of the present invention, and is a flowchart of a process for regenerating a pattern that has disappeared in the pre-diffusion process to enable the next phosphorography process. A P-type silicon wafer 2 is used as a semiconductor material. After the phosphorography step shown by the dotted line frame in FIG. 1, doping with a phosphor-type impurity 8 is performed using an ion implantation device or the like. If the oxide film is etched excessively in the pretreatment step for the next impurity diffusion, the pattern on the silicon surface becomes difficult to see or disappears. When the impurity 8 is thermally diffused, the pattern on the silicon surface becomes almost invisible.

Therefore, the oxide film that had grown by thermal diffusion was removed by etching the entire surface with hetamine diluted with water, and then a small amount of nitric acid (approximately 1% or less in concentration) was added to the diluted hetamine acid with water.
Chemical etching (hereinafter abbreviated as stain etching) is performed using a mixed fluoro-nitric acid solution. Due to this etching, the P-type and N-type regions are colored slightly differently, and a pattern appears after a few seconds. Next, after washing with water, washing is performed by heating a mixture of aqueous ammonia and hydrogen peroxide diluted with water, washing with water, drying, and thermal oxidation. In the first stain etching, a pattern appears depending on the strength and weakness of the coloring by the P type, but in the next hot water cleaning treatment with ammonia water and hydrogen peroxide, the stain film on the colored part is removed to the extent that this pattern is not very visible. is etched. However, the surface step at the boundary between the P-type and N-type regions on the silicon wafer, which was created during the first stain etching, cannot be removed even after the thermal oxide film is formed and the resist is applied in the next phosphorography process. The marker on the silicon wafer surface remains visible through the machine and can be exposed.

In addition, even if a floating turn is visible after impurity diffusion and disappears after thermal oxidation,
After removing the entire oxide film, perform stain etch,
The next phosphorography process becomes possible by performing hot water cleaning treatment with ammonia water and hydrogen peroxide solution and forming a thermal oxide film again.

As described above, the present invention not only reproduces the pattern on the semiconductor surface that has disappeared in the pre-diffusion process, etc., and enables the next phosphorography process, but also does not leave any color difference due to coloring on the pattern surface. It has an excellent effect. Although this embodiment uses stain etching as the chemical etching method, other chemical etching methods can be applied as well. Any semiconductor material that can be chemically etched can be used as long as it is a material that can be chemically etched, and in particular, bipolar transistors that have little effect due to the surface that does not significantly deteriorate the characteristics of semiconductor elements due to etching, It is fully applicable to diodes, thyristors, and field effect transistors that control bulk charge transfer. It can also be applied to a field effect transistor having a three-layer structure of metal-oxide-semiconductor, but it is necessary to consider the influence of charge transfer due to damage to the semiconductor surface.

[Brief explanation of drawings]

Fig. 1 is a flowchart of a semiconductor device manufacturing process including a conventional phosphorography process, and Fig. 2 is a flow chart of a semiconductor device manufacturing process including a conventional phosphorography process, and Fig. 2 is a flowchart of the present invention, which reproduces a pattern that has disappeared in the diffusion pretreatment process and makes it possible to perform the next phosphorography process. It is a flow chart of the process of making. 1 is a fermented film, 2 is a silicon wafer, 3 is a resist, 4
5 is a glass substrate, 5 is a mask pattern, 6 is an ultraviolet ray, 7 is an impurity diffusion layer, 8 is an impurity, and the dotted line frame is a phosphorography process. Applicant Suiwa Seikosha Co., Ltd. Agent Patent Attorney Mogami Tsutomu Figure 1 Figure 2

Claims (1)

[Claims] 1. A method for manufacturing a semiconductor device, characterized in that, in an intermediate step between a phosphorography step and a subsequent phosphorography step, a pattern on a semiconductor surface that has once disappeared is reproduced by a regeneration process.