JPH02114520A - Diffusion mask for use in manufacture of semiconductor - Google Patents

Abstract

PURPOSE:To suppress diffusion in the interface direction and enable refinement of a semiconductor device by using one or more diffusion mask layers on a compound semiconductor and turning the main element of one layer on the compound semiconductor side to be silicon. CONSTITUTION:A silicon film 5 is provided as a first layer of a diffusion mask, and a silicon oxide film 6 is further provided on the silicon film 5 to form a two-layer diffusion mask. The silicon film scarcely produces a modified layer formed of oxide or the like at the interface of the compound semiconductor during the formation of the silicon film and forms a more dense film, and further the values of the thermal expansion coefficient and the lattice constant of the silicon film 5 are approximate to those of the compound semiconductor such as GaAs, InP, so that the thermal damage during the temperature rise or fall can be reduced. Thus, the diffusion in the direction along the interface between the compound semiconductor and the diffusion mask can be suppressed and the refinement of the semiconductor device is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a diffusion mask used for manufacturing semiconductor devices such as light emitting diodes or field effect transistors using compound semiconductors.

(Prior art) Impurity diffusion into compound semiconductors is used not only as a method for forming a 100% PN junction, but also as a high concentration technique to improve resistive contact, or as a partial method for optical semiconductor devices. It is also used as a current confinement method by increasing the concentration, and is also widely used as an element isolation method in which a PN junction formed by epitaxial growth is partially separated by diffusion to limit the light emitting region.

In the following, a case where an epitaxially grown layer of GaAGAs is used as a compound semiconductor and a pre-formed PN heterojunction is used will be described in more detail (prior art).

FIG. 2 shows the structure of a conventional diffusion mask. In Fig. 2, 1 is a P-type GaAs substrate, 2 is a P-type Ga□-xAQ
xAs (x = 0.75), 3 is P-type Ga, -xAGx
As (x=0.:15), 4 is N-type Ga, -xAllx
As (x = 0.75).

Reference numeral 6 denotes an insulating film, which is formed by a chemical vapor deposition method (hereinafter referred to as CVD method), and typically a silicon oxide film or a silicon nitride film is used.

This is a conventional diffusion mask. Using this diffusion mask, selectively impurities are added to P-type Ga, -, A(1, As(x
= 0.75) to change a part of the N-type region 4 into a P-type diffusion region 7. In the light emitting diode thus created, the N-type region 4 and the P-type expanded IF 1. Since the energy band barrier of the PN junction composed of the region 7 is high, the N-type region 4 which does not undergo diffusion and the P-type Ga, -, AU, As
(x = 0.35) Current concentrates at the PN junction composed of 3. This makes it possible to create a light emitting diode in which one light emitting region is limited to a region in which no diffusion is performed.

With the above method, an integrated light emitting semiconductor device having a plurality of light emitting parts on a flat surface can be realized, and a light emitting semiconductor'! AI
Demand is increasing as a means of expanding the application fields of W. In the future, there will be a strong demand for further narrowing the spacing between light emitting regions and increasing the degree of integration.

(Problem to be Solved by the Invention) However, in the above method, in the silicon oxide film or silicon nitride film that is the conventional diffusion mask, a metamorphosed layer, such as an oxide layer, is generated at the interface with a compound semiconductor such as GaAs. However, since the formation of a dense area is slow, there is a problem in that the diffusion progresses rapidly toward the interface between the compound semiconductor and the diffusion mask compared to the diffusion in the vertical direction. If the diffusion in the interface direction is large, the separation interval must be widened to ensure separation between the plurality of light emitting parts, and this makes it difficult to miniaturize semiconductor devices, which has been desired in recent years.

The present invention solves the above-mentioned conventional problems.

It is an object of the present invention to provide a diffusion mask used in manufacturing for suppressing diffusion in the interface direction and at the same time miniaturizing semiconductor devices.

(Means for Solving the Problems) In order to achieve the above object, the present invention is configured such that the diffusion mask on the compound semiconductor has one or more layers, and the main element of at least one layer on the compound semiconductor side is silicon.

(Function) When a silicon film is formed, a metamorphic layer such as oxide is generated at the compound semiconductor interface, resulting in a more dense film.
Furthermore, since the silicon film and compound semiconductors such as GaAs and InP have similar thermal expansion coefficients and lattice constants, thermal damage can be reduced when the temperature is raised or lowered.

Therefore, when the diffusion mask of the present invention is used in the GA fabrication of semiconductor devices, it becomes possible to suppress the diffusion toward the interface between the compound semiconductor and the diffusion mask, and it also becomes possible to miniaturize the semiconductor device. .

(Example) An example of the present invention in which the above-mentioned Ga1-xAQxAs epitaxial wafer is used as a substrate and zinc is used as a diffusion source will be described in more detail below with reference to FIG. FIG. 1 is a basic configuration diagram of a diffusion mask according to the present invention, which differs from the conventional one in that a silicon film 5 is provided in the first layer of the diffusion mask. First, P-type Ga, xAllxAs (x=0.75)2. P-type Ga
1-x1! , As (x = 0.35): 3 and N-type Ga, -xAQ ';a1-XAII
A silicon film 5 was formed on the XAS (x = O-75) 4. The silicon film 5 is formed by chemical vapor deposition using light irradiation (photo-CVD).

Semiconductor substrate temperature: 330°C, pressure: 400 Pa, disilane (Si, If, ) 2 cc/min, nitrogen (N, )
The thickness was set to 400 people under the condition of 100oc/min. In the embodiment of the present invention, since the growth rate of silicon film by photo-CVD method is slow, about 4000 silicon oxide films 6 are further grown on silicon film 5 by normal CVD method, and two layers are formed. I used it as a mask. That is, in the embodiment of the present invention, the diffusion mask has a two-layer structure, and the first layer is a silicon film and the second layer is a silicon oxide film. A diffusion pattern was formed on the diffusion mask thus prepared by photolithography, and diffusion was performed at a temperature of 800°C for 1 hour using a diarsenic subbutton as a diffusion source. A comparison was made between a case using only a silicon oxide film and a case using the method of the present invention. For comparison, the diffusion in the depth direction is
Diffusion in the direction of the interface will be expressed as S−X. When the thickness of N-type Ga, -XI As4 is 10μI, and the diffusion in the depth direction is constant X = = 201Jm, in contrast to the conventional method, which is 5-XJ = 15 to 20μ. In the invention, S-x,=to~13p@, and the diffusion rate toward the interface could be reduced by about 30%, and when converted to pattern width, it was possible to achieve a reduction of about 20%.

In the case of integrated light emitting devices actually used in LED printers, etc., the light emitting pattern is often already determined for other reasons, and a 30% reduction in interfacial direction diffusion is expressed in terms of fR manufacturing yield. The effect of the present invention was clearly confirmed.

(Effects of the Invention) According to the diffusion mask used for manufacturing the optical semiconductor device of the present invention, since a silicon layer is provided as the diffusion mask material,
Compared to conventional diffusion masks that do not have a silicon layer, diffusion in the interface direction is significantly suppressed.

We were able to advance the integration of light-emitting semiconductor devices.

[Brief explanation of drawings]

FIG. 1 shows a basic structure of a diffusion mask according to the present invention using a silicon film as a diffusion mask, and FIG. 2 shows a structure of a conventional diffusion mask using a piece of silicon oxide as a diffusion mask. 1 ・P-type GaAs substrate, 2-P-type Ga1-, AQ
xAs (x=0.75), 3 ・P-type Ga, -x
AllxAs (x = 0.35), 4-N type Ga
1-xAQ, ^s (x = 0.75). 5... Silicon film, 6... Silicon oxide film, 7...
P-type diffusion region. Patent Applicant: Matsushita Electric Industrial Co., Ltd. No. 1 Oxide 5L Silicone N -Gal -x Alx As P-Got-xALxAs P-Got-xALzAs P-GaAs base anti(X=0.75) (X= 0.353 (X=0.75) Figure

Claims (1)

[Claims] A diffusion mask for selectively diffusing impurities into a compound semiconductor, comprising one or more layers, and at least one layer on the compound semiconductor side having silicon as the main element, for use in manufacturing a semiconductor device.