JP2628814B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device such as an electronic device and an optical device formed on a compound semiconductor.

[0002]

2. Description of the Related Art Conventionally, when a semiconductor device is formed on a compound semiconductor substrate such as GaAs, a clean and stable surface of the compound semiconductor is formed in a manufacturing process before forming a thin film layer of a metal, an insulator or a semiconductor. Was difficult to obtain. Therefore, a semiconductor device formed on such a semiconductor surface that has not been sufficiently cleaned, for example, AlGaAs /
GaAs HBT (heterojunction bipolar transistor)
The problem is that the initial value of the current amplification factor β is small due to the influence of surface oxides, crystal defects, etc. on the emitter / mesa end face, and the deterioration with time in the operating state is large.
It has been difficult to obtain a semiconductor element having high performance and high reliability. One solution to this problem is to remove the native oxide film and compound semiconductor layer using an ammonium sulphide solution containing an excess of sulfur atoms while etching and removing a new semiconductor surface. By forming a thick sulfur layer and shielding from the atmosphere,
A method of preventing surface oxidation during transport in the atmosphere has been used. In this case, just before forming a thin film in the next step, excess sulfur atoms are removed by sublimation in the same vacuum to finally leave only one atomic layer of sulfur atoms on the surface, thereby stabilizing. Thus, a clean semiconductor surface is obtained. In addition, as a conventionally known example,
Japan Pan Applied Physics, 27
(7), (1988), L1331 [Jpn.
J. Appl. Phys. , 27 (7), L1331
(1988)].

[0003]

In the prior art described above, when only one type of ammonium sulfide solution having a high sulfur content is used for treatment, excessive sulfur atoms adhere to the semiconductor surface with an uneven thickness. However, there is a problem that it is difficult to obtain a uniform surface state over the entire surface of the wafer, and that the product yield is reduced. To remedy this problem,
Heretofore, attempts have been made to remove the excess sulfur layer by performing a water washing treatment immediately after the treatment with an ammonium sulfide solution having a high sulfur content. However, in this case, sulfur easily flows with water, and it is difficult to leave a moderately thick sulfur layer on the semiconductor surface with good controllability. However, there is a problem that is reduced.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art.
First, a treatment with an ammonium sulfide solution having a high sulfur content is performed, and then, a treatment is sequentially performed using an ammonium sulfide solution having a low sulfur content to form a clean and stable compound semiconductor surface. It is an object of the present invention to provide a method for manufacturing a high-performance and highly reliable semiconductor device at a high yield by preventing performance deterioration due to the above-mentioned problems.

[0005]

In order to achieve the object of the present invention, a method of manufacturing a semiconductor device by forming a metal layer, an insulating layer or a semiconductor layer on a compound semiconductor is described. A surface treatment with a first ammonium sulfide solution having a predetermined sulfur content,
And a step of performing a surface treatment using a second ammonium sulfide solution having a sulfur content lower than that of the first ammonium sulfide solution. If necessary, after the surface treatment step, the ammonium sulfide solution By performing at least the step of performing surface treatment by arbitrarily changing the sulfur content in the product, a clean and stable compound semiconductor surface is formed, preventing performance deterioration due to surface oxides and crystal defects, and ensuring high performance and reliability. It is intended to obtain a highly reliable semiconductor device.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in more detail with reference to the drawings. FIG. 1 shows that G is used as a compound semiconductor.
Using aAs or Al _0.3 Ga _0.7 As, the sulfur content of the ammonium sulfide solution used in the first stage treatment is 5%, the treatment temperature is 25 ° C., the treatment time is 10 minutes, and it is used in the next second stage treatment. FIG. 3 is a graph showing the KLL Auger peak intensity of oxygen obtained from the compound semiconductor surface when the sulfur content of the ammonium sulfide solution is 0.5%, the processing temperature is 25 ° C., and the processing time is 5 seconds. If the concentration of oxygen atoms on the semiconductor surface is not treated with ammonium sulfide solution,
And a drastically reduced water content after the first-stage ammonium sulfide solution treatment and a sulfur content of 5%.
It can be seen that it is almost the same as the case of only the treatment with the ammonium sulfide solution of 5%. That is, when the excess sulfur layer on the surface of the compound semiconductor is removed by the ammonium sulfide solution treatment (sulfur content: 0.5%) in the second step, the thick sulfur layer is uniformly formed as compared with the case where the conventional washing treatment is performed. Therefore, it can be said that the effect of the sulfur layer to prevent surface oxidation in the atmosphere is sufficient. The slightly detected oxygen atoms are considered to be due to adsorbed gas molecules that are not chemically bonded to Ga and As atoms on the surface of the compound semiconductor, and can be easily removed at a relatively low temperature. It seems that there is almost no effect on the characteristics. The semiconductor surface in this embodiment is formed by SEM (scanning electron microscope),
When analyzed by micro Auger, it was confirmed that the surface sulfur layer was flat and the composition was good in-plane uniformity. This processing step includes, for example, AlGaAs / GaAs.
Surface treatment of HBT emitter / mesa end surface before protective film formation, laser diode end surface treatment, substrate surface treatment before epitaxial growth on compound semiconductor, MISFET
The present invention can be applied to a semiconductor surface treatment before forming a gate insulating film of an (insulated gate type field effect transistor) and a semiconductor surface treatment before depositing a gate metal of a MESFET (metal gate type field effect transistor). According to the present embodiment,
Sufficient thickness of sulfur layer is formed over the entire surface of the semiconductor wafer to prevent oxidation in the atmosphere and at the same time the thickness is uniform in the plane. And the in-plane uniformity of device characteristics is improved. Therefore, there is an advantage that a semiconductor device having high performance and high reliability can be easily obtained at a high yield. In this example, the sulfur content of the ammonium sulfide solution used in the second stage treatment was set to 0.5%. However, even when this was changed in the range of about 0.2 to 2%,
A relatively uniform sulfur layer is formed on the entire surface of the wafer, thereby preventing surface oxidation. However, generally, as the value of the sulfur content of the ammonium sulfide solution decreases, the thickness of the sulfur layer remaining on the wafer surface decreases, and as the value of the sulfur content increases, the surface uniformity of the sulfur layer increases. Sex is reduced. Further, in the present embodiment, the treatment temperature with the ammonium sulfide solution was 25 ° C., but the same effect can be obtained when the treatment temperature is changed in the range of about 10 to 80 ° C., and the present invention is effective. However, the etching rate of the compound semiconductor and its oxide layer with the ammonium sulfide solution increases as the processing temperature increases. Further, in the present embodiment, the treatment time with the ammonium sulfide solution in the second stage treatment is set to 5 seconds, but the same effect as described above can be obtained even when the treatment time is changed in the range of about 1 second to 2 hours. The present invention was effective. However, in general, the shorter the treatment time, the lower the uniformity of the surface sulfur layer, and the longer the treatment time, the thinner the surface sulfur layer. Further, in the present embodiment, the treatment with the ammonium sulfide solution having a low sulfur content is added in one stage, and the treatment is performed in a total of two stages. However, the treatment with the ammonium sulfide solution with different conditions is further added thereto. The present invention is also effective when treated with a total of n stages (n ≧ 2) of ammonium sulfide solutions. in this case,
Generally, as n increases, the surface uniformity improves, but at the same time the thickness of the surface sulfur layer decreases. Further, in this embodiment, the case where GaAs and AlGaAs are used as semiconductors has been described.
Even in the case of using InP or the like, the same effect as in the present embodiment can be obtained, and the present invention is effective.

[0007]

As described above in detail, according to the method of manufacturing a semiconductor device of the present invention, the surface state can be controlled with good uniformity over the entire surface of a semiconductor wafer, and therefore, stable metal / semiconductor, insulator / semiconductor, and semiconductor can be obtained. / A semiconductor device having a high performance and a high reliability including a semiconductor interface can be manufactured with a high yield.

[Brief description of the drawings]

FIG. 1 is a graph showing the KLL Auger peak intensity of oxygen on a compound semiconductor surface treated with an ammonium sulfide solution under various conditions exemplified in Examples of the present invention.

Claims (1)

(57) [Claims] 1. A method of manufacturing a semiconductor device by forming a metal layer, an insulator layer or a semiconductor layer on a compound semiconductor, wherein the surface of the compound semiconductor is formed by first ammonium sulfide having a predetermined sulfur content. A surface treatment with a solution, and a surface treatment with a second ammonium sulfide solution having a sulfur content lower than that of the first ammonium sulfide solution, or after the surface treatment step, the sulfur of the ammonium sulfide solution is continuously A method for manufacturing a semiconductor device, comprising at least a step of performing a surface treatment by arbitrarily changing a content.