JPS5851509A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To diffuse an impurity having a large optical absorption coefficient uniformly by forming an oxide film, to which the impurity is added, to the main surface of a substrate and irradiating laser beams from the back of the substrate. CONSTITUTION:Liquefied Sn and a silica film are applied onto the semi-ins- ulating GaAs substrate 1, and a film shaped in this manner is dried, and the oxide film 2 is formed. CO2 Laser pulses are irradiated from the arrow direction. The optical absorption coefficient of GaAs is extremely small to the CO2 laser beams. The optical absorption coefficient of the film 2 depends upon the quantity of the impurity added, and is large. Accordingly, only a section in the vicinity of the interface of the substrate 1 and the film 2 is heated, and a uniform impurity diffusion layer is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an electric conductor device, and more particularly to a method for diffusing an impurity, such as tin (1 m), into a gallium-arsenide substrate using laser annealing.

The 7-ring technology using laser light irradiation, which has become widely used in the manufacture of semiconductor devices, has the advantage of adding 5Φ impurities to a portion of the semiconductor substrate at a level higher than the solid solubility. Such I#lIk is much more effective in forming the source and drain of GaAm FET ICs than the conventional furnace seven-hole method.

However, in the case of laser 7-neel, a difficult problem is encountered in maintaining the substrate interface in a good condition without roughness, for example, to obtain the effect of 7-neel.

Methods currently being attempted to obtain a high degree impurity diffusion layer in a substrate include electrical activation of ion implanted atoms by laser/neal of a highly concentrated ion implanted layer, and G
There is a method of diffusing impurities from an impurity-doped oxide film grown on the aA1 & plate.This method is a modification of the previous method and utilizes the phenomenon of an increase in the light absorption coefficient due to defects introduced by ion implantation. Therefore, in order to obtain a good high concentration, one step is to electrically activate the implanted atoms and at the same time,
The defects introduced thereby need to be removed. For this purpose, the irradiation energy of the laser beam is 6 mm x J/l.
c is required, and as a result, the GaAs isolating plate surface may be damaged by a single irradiation.

On the other hand, in the latter method, the light absorption coefficient of the oxide film doped with C1 impurity is compared to that of the GaA-substrate.
It increases by several orders of magnitude depending on the amount of impurities added. Sara K is
In the case of laser irradiation, there is no problem of removing defects introduced by ion implantation.

Therefore, the irradiation energy is smaller compared to the case where the ion implantation layer is irradiated with a laser beam.The diffusion by the gold-impurity-doped oxide film will be explained with reference to FIG. As shown in the cross-sectional view of the semi-insulating GaAs substrate lf), the surface of the semi-insulating GaAs substrate lf) was coated with oxide 1ilk2 of tin-containing sil dioxide:l:/gv′aioa by spin coating (rotary coating) and heated at 150 °C. It is dried by scattering the organic solvent at a temperature of . 8m Due to diffusion, vc is as shown by the arrow on the surface of the oxide film 20.
Irradiate with laser light. During such annealing, in order to cause diffusion, the entire layer of the oxide film 2 is heated to a high temperature, i.e., 8!, by laser beam irradiation, as shown in FIG. ℃
Since it is necessary to heat the oxide film 2 to a higher temperature, the oxide film 2 is easily damaged.
- Depth into substrate 1 (horizontal axis) and temperature (vertical axis) according to laser beam irradiation;
s When irradiating the above-mentioned laser beam that indicates the interface of the substrate l, in order to obtain an irradiation energy of 117 cm, the temperature of the oxide film 2 in the direction a often exceeds the boiling point of Jlv'IIi, and the In this case, the surface of the oxide film becomes unstable as it tries to evaporate, and not only does the diffusion of 8n into the GaA1 substrate become uneven, but the oxide film 2
Due to thermal distortion? The surface of the GaAm substrate 1 deteriorates. In other words, it becomes rough or defects are introduced.

An object of the present invention is to solve the problems of the prior art described above.
To do this, a thin film of impurity-doped oxide film having a light absorption coefficient several orders of magnitude larger than that of the semiconductor substrate is grown on the main surface of the semiconductor substrate, and then a thin film of impurity-doped oxide film is grown on the back surface of the semiconductor substrate, that is, the oxide film. Impurities in the oxide film are removed by irradiating a laser beam with a wavelength that sufficiently transmits through the semiconductor substrate and causes absorption in the oxide film region from the back surface opposite to the surface on which the oxide is grown. A method for diffusion into a semiconductor substrate is provided.

An embodiment of the method of the present invention will be described below with reference to the accompanying drawings.

Referring to FIG. 2 (in this figure, the same parts as those shown in FIG. 1 are denoted by the same reference numerals).

On the semi-insulating GaAm substrate l, the liquid I described above is deposited.
I n7'II i (h (tin silica film) 3
Apply at tO00 rpm, 30 kicks, then 1
The 811/810m film is dried at 50° C. for 30 minutes to form an oxide film 2. Then, as indicated by the arrow in the figure, a CO quadrature laser pulse of about 0.6 J/ad, or 2
Irradiate with CW Cot v-za of 00 W/cm. By the way, for C or Nd YAG laser light,
The light absorption coefficient of GaA- is very small, less than 0.1 x 1. On the other hand, the light absorption coefficient of the oxide film 20 on the GaAg substrate 1 varies from 104 to 1G" country-1 depending on the amount of impurity addition.
That's all.

As a result, as shown in Figure 2 of the irises (note).

The same figure (in BL, the vertical axis represents temperature, and the horizontal axis represents the depth into substrate 1)%GaAs The temperature is only near the interface between substrate 1 and oxide@2 (indicated by the vertical dotted line in BLK) In this way, the entire layer of oxide film 2 does not reach a high temperature, so damage to oxide #12 due to laser light irradiation does not occur. The layers were obtained.

The results obtained by the above example are shown in diagram M3,
In the figure, the horizontal axis shows the depth of impurity diffusion into the GaA-substrate, and the vertical axis shows the temperature of the impurity. The figure color is clear 5i
C. In the above example, the surface concentration is about 10" cr
'', an impurity diffusion layer with a diffusion depth of approximately 10,001 mm was obtained. In the figure, the sandy area indicates an oxide film.

Using the above embodiment, a high electron mobility transistor (HI
CM? ) It was confirmed that the contact resistance was significantly reduced by forming a heavily doped 8n layer in the source and drain regions.

FIG. 44 shows a cross-sectional view of the main part of a high electron mobility transistor (HNMT) having a diffusion layer formed by the method described above. In the same figure, 11 is a GaAg substrate, 12 is a GaAs 14 is a source electrode.

15 is a drain electrode, 16 is a gate electrode (these electrodes are formed of gold/gel 1 (M@G@) or gold (MU1)), and the shaded area 17 is a highly concentrated 8n doped layer ( ~1G"or"), the source and drain regions K111 degrees In as shown in the figure.
By providing the doped layer, the contact resistance was significantly reduced.

When attempting to form a doped layer as high as 111 as described in CM using the conventional thermal diffusion method, sso'c#! Degree σ) − Kairi is required. At such high temperatures, n-mujGa
Mus / GaAs Hede structure electron e] Running path 13
In the example shown in the figure, the diffusion of Si:17 or aluminum is A high -.HRMT with high electron mobility was obtained without generation.

As explained above, according to the unconventional method, an oxide film is formed on a semiconductor (GaAg) substrate by doping an impurity (ILM) with an optical absorption coefficient several orders of magnitude larger than that of the semiconductor (GaAg) substrate. A thin layer (1000 to 30θ0λ) is grown, and later, laser light (for example, CWAr laser beam)
The impurities in the oxide film are uniformly diffused into the semiconductor, reducing the contact resistance. ~・It has the effect of increasing electron mobility.

[Brief explanation of the drawing]

1 is a diagram showing a laser beam 7 on a semi-insulating GaAs substrate according to the prior art, and FIG. 2 is a diagram showing a laser beam 7 on a semi-insulating G1S substrate according to the method of the present invention.
Figure (Diagram showing the results of the laser 7 needle shown in Figure I42,
FIG. 4 shows the height of the HEMT formed by the method of the present invention.
It is a sectional view of a part. l...Semi-insulating GaAs substrate, 2 ・= 8m / jiio* II! membrane, 11
- GaAm substrate, lj! -Mu-mujGaA more. 13... Two-dimensional electron gas travel path, 14... Source electrode, 1B-... Drain electrode, 16
・-Gate electrode, 17-High concentration 8n doped layer Patent applicant Fujitsu Limited ((1) (b) Figure 1 (a) (b) Figure 2

Claims (2)

[Claims] (1) On the main surface of the semiconductor substrate, a layer of an oxide film doped with an impurity having a large light absorption coefficient according to the single absorption coefficient of the semiconductor is formed, and the added semiconductor is transmitted through the backing of the semiconductor substrate. A method for manufacturing a semiconductor device, characterized in that impurities in the oxide film are diffused into the semiconductor substrate by irradiating the region of the oxide film with a laser beam that generates a delicate amount. (2) n-mujGaAs on GaA1 substrate
Claim 11: A method of forming a high electron mobility transistor in which a layer is formed, comprising doping a north region and a drain region thereof with a high concentration of impurity.
A method for manufacturing a semiconductor device according to Section 11EI.