JPS6119103B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device with excellent electrical characteristics.

In general, semiconductor devices are manufactured through a process of selectively thermally or physically doping elements with different valences into a semiconductor substrate, a process of creating a wiring metal to configure a desired function, and a process of doping the semiconductor substrate with elements of different valences, as necessary. It is well known that semiconductor devices are manufactured through a passivation process in which the surface of a semiconductor substrate is covered with an insulating thin film. For details of each of the above steps, individual conditions are generally set depending on the type of semiconductor device to be manufactured. The manufacturing process technology includes ion implantation technology, which was born from the need to precisely control the amount of impurity elements doped into the semiconductor substrate, and electron beam evaporation technology, which was developed to avoid contamination during the production of wiring metal. Sputtering technology has become popular due to the demand for producing special alloy wiring thin films and the demand for producing thin films with good mechanical properties. Also,
More recently, electron beam or X-ray exposure technology has been developed as a basic technology for submicron processing. These individual technologies are becoming increasingly critical to the reproducibility and reliability of the performance of semiconductor devices, as well as to the integration of unit elements.

However, many of these technologies generate many lattice defects and levels in the semiconductor substrate or the interface between the semiconductor substrate and the insulating film, which may reduce the current amplification factor of bipolar transistors, for example.
This has the adverse effect of so-called damage, such as increasing the leakage current of the PN junction and increasing the threshold voltage of the field effect transistor. Therefore, in each process of semiconductor device manufacturing,
The heat treatment method to recover these damages is
Although it has become more important than ever before to improve the performance of semiconductor devices, current amplification factors of lateral type bipolar transistors and substrate type bipolar transistors are extremely susceptible to damage due to sputtering, for example. It has been difficult to recover to a sufficient value by simply performing heat treatment, even if a semiconductor substrate free of crystal defects such as dislocations and schools is used.

The present invention provides a novel heat treatment method to overcome the above-mentioned drawbacks. According to the present invention, a semiconductor substrate on which at least one active element region is formed is provided, a thin film layer is formed by sputtering on the surface of the substrate on the side where the active element region is formed, and then the semiconductor substrate is A first heat treatment is performed in an atmosphere at a temperature of 400 to 550°C, and then a predetermined amount of charged particle beams, ionizing radiation, or electromagnetic waves is irradiated to this semiconductor substrate, and then this semiconductor substrate is heated again in an atmosphere at a temperature of 300 to 500°C. This invention proposes a method for manufacturing a semiconductor device characterized by performing a second heat treatment.

As a result, in the present invention, it is possible to eliminate crystal defects, etc., caused in the semiconductor substrate during various processing steps, especially the sputter processing step, and obtain a more stable substrate recovery state, and only by heat treatment after the sputter processing. It becomes possible to obtain a semiconductor device having significantly superior electrical characteristics compared to the previously obtained semiconductor device.

Hereinafter, the present invention will be explained in detail based on one example. A semiconductor device applicable to the present invention is a device including a semiconductor substrate having at least one active element region. A semiconductor device having a lateral bipolar transistor will be described below as a representative example. What is shown in FIG. 1 is a cross-sectional view of a semiconductor device including a lateral transistor. Reference numeral 1 denotes a semiconductor substrate body, which has an N-type silicon layer 2 grown epitaxially. 3
4 is a P+ type separation layer, and 4 is a P type layer for forming an emitter region and a collector region, which together with the N type layer 2 constitute a PNP type transistor. Reference numeral 5 indicates a silicon thermal oxide film, and reference numeral 6 indicates a wiring metal film made of aluminum, which in this case is formed using electron beam evaporation technology and then heat treated to establish ohmic contact. 7 is an insulating film, in this case a silicon dioxide film is formed by sputtering. 8 is an electrode extraction hole.

According to one embodiment of the present invention, the transistor having the above structure is manufactured by the following method. That is, after completing a predetermined impurity diffusion operation, each wiring metal 6 for the base, emitter, and collector is formed using an electron beam evaporation method,
After that, a heat treatment is performed to establish ohmic contact, and then a silicon dioxide coating 7 is formed by sputtering.
form. Then, holes are opened at necessary locations using a well-known photoetching technique to expose the wiring metal made of aluminum and form electrode extraction holes 8. After that, 5~
Heat treatment for 60 minutes, followed by an integrated dose of 20-200 mrad, e.g. using a tungsten tube.
The surface of the semiconductor substrate is irradiated with X-rays of about
Heat treatment is performed for 10 to 60 minutes in a thermal atmosphere of 300 to 500°C.

By the way, there are a variety of stable or unstable defects that remain on semiconductor element substrates that have completed the wiring metal forming process, such as lattice strain and thermal strain that occur during doping with impurity elements, or defects that occur during metal evaporation. There are interface levels and levels caused by lattice misfit between the metal/semiconductor compound and the substrate to establish ohmic contact, and furthermore, in the sputtering process, there are Lattice defects and levels occur at the interface, and the electrical properties expected theoretically cannot be obtained.

However, according to the method shown in the above example, the unstable defects remaining through the initial heat treatment are converted into a metastable form and brought into a state similar to other stable defects, and then X-ray Stable or metastable defects are uniformly dispersed at the same time by irradiation, followed by heat treatment at a relatively low temperature that does not generate thermally induced defects, thereby rearranging the lattice at the surface and interface. This makes it possible to obtain excellent electrical properties that could not be obtained by conventional heat treatment methods, such as significant improvements in current amplification factor and leakage current.

Here, the characteristic diagram shown in FIG. 2 shows the fluctuation of the current amplification factor and the reverse leakage current between the collector and emitter of the transistor for each processing step shown in the above embodiment. In FIG. 2, fluctuations in current amplification factor are shown in an arithmetic relationship, and fluctuations in leakage current are shown in a logarithmic relationship. According to this, when the current amplification factor after the formation of the wiring metal 6 is 100, if the substrate surface is protected by forming an insulating film in the sputtering process, the current amplification factor decreases to about 72%. After that, heat treatment will restore the recovery to about 80%, but if it was just heat treatment, the process would have ended at this point.
Recovery was about 80%. For it,
By successively irradiating with X-rays as in the present invention, it was reduced to a level of about 38%, but by subsequent heat treatment it was possible to significantly recover it to about 115%. On the other hand, the reverse leakage current between the collector and emitter after the wiring metal 6 is formed is 1
Compared to the case where heat treatment is only performed after the sputtering process, a single heat treatment is performed and then X
By applying radiation and subsequent heat treatment, we were able to significantly reduce the leakage current.

In addition, FIG. 3 shows the variation in the current amplification factor of the transistor for each step when no heat treatment is performed after the sputtering step, and similarly to FIG. 2, the current amplification factor after the formation of the wiring metal 6 is shown. is set as 100. In this case, the current amplification factor after heat treatment remains at a level of 92%. In contrast, as shown in FIG. 2, when uniform heat treatment was performed after the sputtering process, the current amplification factor could be recovered more greatly.

In the above embodiment, a lateral type PNP transistor was explained, but the PN transistor is not limited to this.
The present invention can be sufficiently applied to diodes that use junctions as functional parts, transistors with other structures, or field effect transistors that use surface field effects, although there are slight differences in effectiveness. Further, the semiconductor device can be similarly applied to either a single element structure or a composite structure having a plurality of elements.

Further, in the above embodiment, a silicon dioxide film was formed by sputtering or the like as a surface protection film of a semiconductor device, but the present invention is not limited to this, and other surface protection films may be used. It may be formed depending on the forming method or surface protection material. Further, the present invention can be similarly applied to semiconductor devices having a thin film layer required in place of the surface protective film.

Further, in the above embodiment, a case was described in which X-ray irradiation was performed using an X-ray tube with a tungsten target, but the present invention does not depend greatly on the quality of X-rays, and the type of X-ray source No question. Furthermore, it has been confirmed that the method is applicable not only to X-rays but also to other ionizing radiations such as gamma rays, electron beams, and ultraviolet rays, charged particle beams, and electromagnetic waves.

As described above, in the present invention, a semiconductor substrate on which at least one active element region is formed is provided, and a thin film layer is formed by sputtering on the surface of the substrate on the side where the active element region is formed. The semiconductor substrate is subjected to a first heat treatment in an atmosphere at a temperature of 400 to 550°C, and then the semiconductor substrate is irradiated with a predetermined amount of charged particle beams, ionizing radiation, or electromagnetic waves. In particular, it metastabilizes the unstable defects among the various defects caused in the sputtering process, and then destroys the stable or metastable defects remaining on the semiconductor substrate again by subsequent irradiation, making the defect state uniform. Try to disperse it, and then
By subjecting the semiconductor substrate to heat treatment again in a temperature atmosphere in the range of 300 to 500°C, the lattice on the substrate surface and interface can be effectively rearranged and a stable substrate recovery state can be obtained. This has the excellent effect of making it possible to obtain a semiconductor device with far superior electrical properties in terms of leakage current characteristics and current amplification factor, compared to those obtained by mere heat treatment after sputtering. .

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the main parts of a lateral type transistor using the method of the present invention, and FIGS. 2 and 3 are
FIG. 2 is a characteristic diagram showing electrical characteristics of the lateral transistor shown in FIG. 1; 1... Semiconductor substrate body, 2... N-type layer, 3...
P+ type layer, 4... P type layer, 5... Silicon thermal oxide film, 6... Wiring metal, 7... Insulating coating forming the main part of the thin film layer.

Claims (1)

[Claims] 1. A semiconductor substrate with at least one active element region formed thereon is provided, a thin film layer is formed by sputtering on the surface of the substrate on the side where the active element region is formed, and then this semiconductor substrate is heated at 400 to 550°C. A first heat treatment is performed in a temperature atmosphere, and then this semiconductor substrate is irradiated with a predetermined amount of charged particle beam, ionizing radiation, or electromagnetic waves, and then a second heat treatment is performed on this semiconductor substrate again in a temperature atmosphere of 300 to 500°C. 1. A method of manufacturing a semiconductor device, characterized in that: