JPS63144512A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To unnecessitate a buffer layer, to reduce a surface blemish and to contrive improvement in mass productivity of the title semiconductor device by a method wherein high density impurities are introduced into the layer located in the vicinity at least of one interface adjoining to the interface of an epitaxial layer, and a doping distribution is formed in such a manner that the modified layer generating in the vicinity of the interface will be compensated. CONSTITUTION:An Si-doped n-type gallium-arsenide layer 2 of 1500Angstrom in thickness, for example, is epitaxially grown on the substrate 1 such as a non-doped semiinsulative gallium-arsenide substrate. At this time, an n<+> type interface proximity layer 2A having the Si density of 5X10<17>cm<-3> or thereabout in the initial stage is formed. The surface of the arsenide substrate 1 is etched using a sulfuric acid etchant in the amount of 10 mum or thereabout, and after washing by pure water, the substrate 1 is led to an MBE device, for example, and an n-type gallium-arsenide layer 2 is formed. Si density is increased in the vicinity of the interface, and the epitaxial layer having the constant donor density of 3X10<17>cm<-3> or thereabout of 1500Angstrom in thickness can be obtained. Even when there is no buffer layer as abovementioned, a steep doping region of fixed donor density can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device, and particularly to an epitaxial growth method.

[Conventional technology]

In recent years, semiconductor devices have become increasingly highly integrated and fast. In particular, in [1-V group compound-based betero bibolar transistors, its speed is increased.

High integration is important, and improvements in characteristics and uniformity are being sought by improving controllability of element size, impurity concentration, etc.

(2) Thin film growth is one of the extremely important steps in the method of manufacturing semiconductor devices using V-group compounds. Vapor phase epitaxy, liquid layer epitaxy, and molecular beam epitaxial (MBE) methods are used as thin film growth methods;
The vapor phase growth method and the molecular beam epitaxial (MBE) method are superior in terms of rFII control.

In the conventional molecular beam epitaxial method, for example, a crystal substrate is introduced into an ultra-high vacuum from outside the MBE apparatus and epitaxial growth is performed, but since the crystal substrate is exposed to the atmosphere, doping occurs at the interface between the crystal substrate and the epitaxial layer. Since sufficient electrons or holes corresponding to the impurities are not generated, a metamorphic layer is formed at the interface. To form an epitaxial layer with a controlled impurity concentration for this purpose, an epitaxial layer called a buffer layer is provided on a crystal substrate, and an impurity-doped epitaxial layer is formed thereon.

In this case, the thickness of the buffer layer is sufficiently larger than the metamorphic layer formed at the interface to eliminate any influence on the doped epitaxial layer. Normally, the thickness of one buffer layer is extremely thick compared to the epitaxial layer forming the active layer.

[Problem that the invention seeks to solve]

Therefore, for example, when manufacturing a field effect transistor (FET) of a compound semiconductor made of group II and group V atoms using the MBE method, oval defects occur because the buffer layer is formed thickly.
Defects called t) occur on the surface of the epitaxial layer.

Moreover, the surface defects increase and become larger as the epitaxial layer becomes thicker. Particularly when manufacturing integrated circuits (ICs) using FQTs, these surface defects reduce the yield.

Furthermore, in the MBE method, the growth rate of the epitaxial layer is 5000 to 20000 per hour, for example, 1000 per hour.
In the case of a growth rate of 0 people, it takes one hour of growth time to create a buffer layer of 10,000 people, so it is necessary to increase the growth rate to increase mass productivity. However, increasing the growth rate further increases the number of surface defects.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a semiconductor device that eliminates the above-mentioned drawbacks and can form an epitaxial layer with few surface defects and high productivity without reducing the doping level of impurities. .

[Means for solving problems]

The method of manufacturing a semiconductor device of the present invention is a method of manufacturing a semiconductor device in which an epitaxial layer containing impurities is formed on a semiconductor substrate, and the method includes forming a layer near the interface of at least one of the semiconductor substrate and the epitaxial layer in contact with the interface of the semiconductor substrate and the epitaxial layer. This method introduces a high concentration of impurities.

[Effect]

For example, when growing an n-type epitaxial layer on a semiconductor substrate, the surface of the semiconductor substrate is exposed to the atmosphere, so
Impurities in the epitaxial layer near the semiconductor substrate interface do not function as donors sufficiently, resulting in a decrease in donor concentration. However, by introducing a high concentration of n-type impurity into a layer near the interface between the semiconductor substrate and the epitaxial layer, it becomes possible to compensate for inactive donors and obtain the donor concentration necessary for the device.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a semiconductor chip for explaining a first embodiment of the present invention.

As shown in FIG. 1, an n-type gallium arsenide layer 2 doped with 1,500 N of St is epitaxially grown on a non-doped semi-insulating gallium arsenide substrate 1. At this time, in the initial stage, an n+ type near-interface layer 2A was formed with a Si concentration of 5.times.10.sup.17 cn.sup.-3 as shown by curve A in FIG. 3. The surface of the arsenic substrate 1 was etched by about 10 μm using lX acid etching solution, washed with pure water, and then subjected to MBE.
This was introduced into the device to form an n-type gallium arsenide layer 2.

Figure 3 shows the distribution of impurity concentration in the film thickness direction when epitaxially grown by the MBE method, curve A is for the first implementation, and curve B is for the epitaxial layer of the conventional method without a buffer layer. The concentration distribution of impurities is shown below. The Si concentration in this example, shown by curve A, is increased near the interface, and in the conventional method shown by curve B, it is 3X],
The Si concentration is 0.017 cm-3.

FIG. 4 shows the distribution of the donor concentration in the film thickness direction of the epitaxial layer thus prepared, where curve A is for this example and curve B is for the conventional method. Furthermore, curve C has the same impurity distribution as the conventional method and has a thickness of 800 mm.
This is the donor concentration when there is a buffer layer of 0 people.

As is clear from FIG. 4, in the conventional method without a buffer layer, a decrease in donor concentration was observed as shown in curve B, but in this example and in the case of the buffer layer shown in curves A and C, a decrease in donor concentration was observed. In the case of the conventional method, an epitaxial layer with a constant donor concentration of about 3.times.10@17 cn@-3 was obtained over a thickness of 1500 nanometers. In this way, in this example, it was possible to form a steeply doped region with a constant donor concentration even though there was no buffer layer. Therefore, an epitaxial layer with few surface defects and high productivity can be formed.

FIG. 2 is a sectional view of a semiconductor chip for explaining a second embodiment of the present invention.

As shown in FIG. 2, a layer of 1,500 layers of S is deposited on a semi-insulating gallium arsenide substrate 1 having an n+ type interfacial layer IA formed by doping the surface with St by ion implantation.
An n-type gallium arsenide layer 2 doped with i was epitaxially grown.

A gallium arsenide substrate 1 having an n+ type near-interface layer IA was introduced into an MBE apparatus without surface etching, and an n type gallium arsenide layer 2 was formed.

FIG. 5 is a distribution diagram of the impurity concentration in the film thickness direction in the second embodiment, where the curve E indicates the impurity distribution in the n+ type interface vicinity layer IA and the n type gallium arsenide layer 2, respectively. Further, FIG. 6 shows the distribution of donor concentration in the film thickness direction, where curve F is for the second embodiment, and curve G is for the case where the epitaxial layer shown in FIG. 5 is formed without ion implantation.

As is clear from FIG. 6, by using the second example, the metamorphic layer at the interface was compensated and an improved donor concentration distribution was obtained.

In the above embodiment, gallium arsenide was used for the semiconductor substrate and the epitaxial layer, and Si was used as the dopant, but other III-
Group V compounds and their root crystals may be used, and Dovan I and other impurities may be used. Furthermore, in the above embodiments, the case where the near-interface layer is formed only on one side of the interface between the substrate and the epitaxial layer has been described, but it may be formed on both sides.

Although the above explanation deals with the case where the impurity is a donor, the present invention is equally applicable to the case where the impurity is an acceptor. In this case, it is possible to compensate for the metamorphosed layer near the interface and form an epitaxial layer having the intended acceptor concentration by doping the acceptor and making the acceptor concentration in the layer near the interface higher than the impurity outside the interface.

〔Effect of the invention〕

As is clear from the above description, when forming an epitaxial layer containing impurities on a semiconductor substrate, the present invention introduces a high concentration impurity into at least one layer near the interface to compensate for the metamorphic layer generated near the interface. By forming such a doping distribution, an epitaxial layer having an intended impurity distribution can be formed. Therefore, there is an advantage that the conventionally used buffer layer is not required, and furthermore, it is possible to form an epitaxial layer with fewer surface defects and improved mass productivity.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of a semiconductor chip for explaining the first and second embodiments of the present invention, FIGS. 3 and 5 are distribution diagrams of impurity concentration in the film thickness direction, and FIG. and FIG. 6 is a distribution diagram of donor concentration in the film thickness direction. DESCRIPTION OF SYMBOLS 1...Semi-insulating gallium arsenide substrate, IA...n+ type interface vicinity layer, 2...n type gallium arsenide layer, 2A...
n+ type layer near the interface. Interface θ 5ρρ /l) ρθ lμ i
Needle 'y - Distance C Splint 3 Shoulder θ 5ρρ , /; Do: λ and 1 pin 2 /j
≦23BiU≧'shgararichu>nail Mc;+nbud 4M

Claims (1)

[Claims] A method for manufacturing a semiconductor device in which an epitaxial layer containing impurities is formed on a semiconductor substrate, characterized in that a high concentration of impurities is introduced into at least one layer near the interface that is in contact with the interface between the semiconductor substrate and the epitaxial layer. Method of manufacturing the device.