JPS6039825A - Formation of semiconductor active layer - Google Patents

Abstract

PURPOSE:To enable to activate impurity ions implanted in a semiconductor with a high activation ratio at heat-treating time after ion implantation by a method wherein the surface of the compound semiconductor substrate is covered with a silicon oxynitride film. CONSTITUTION:Impurities enabled to act as conductive impurities in a GaAs substrate 1, silicon for example, are implanted under some condition to the semi- insulating GaAs substrate 1 to form an ion implante layer 2. Then after a silicon oxynitride (SiOxNy) film 3 is formed at the temperature of the GaAs substrate of 650 deg.C, for example, according to the thermal decomposition method at the reaction system of monosilane-ammonia-oxygen, for example, as to cover the ion implanted layer 2, heat treatment is performed for 15min at 800 deg.C to activate the Si impurities, and the ion implanted layer 2 is converted into a GaAs active layer 4. When the surface of the GaAs substrate is covered with the silicon oxynitride and heat-treated, the implanted silicon indicates a high activation ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a semiconductor active layer by implanting ions into a compound semiconductor and activating the same.

In recent years, with the aim of increasing the speed of semiconductor integrated circuits (abbreviated as IC), so-called compound semiconductor ICs using compound semiconductors, such as gallium arsenide (abbreviated as GaAs), have been actively conducted in various places. As an example of such a compound semiconductor IC (bAsIc will be explained.
In the production of aAs IC, in order to improve the performance of field effect transistors, diodes, etc., which are the basic elements of GaAs IC, we have developed a method for forming an active layer with high mobility and a high carrier concentration layer that achieves low resistance. Great efforts are being put into development. Conventionally, an ion implantation method has been used as a method for forming such active layers and high carrier concentration layers from the viewpoint of uniformity, controllability, and mass production. Generally, ion implantation requires a heat treatment process to activate the implanted impurities, and in the case of GaAs,
5 at temperatures between 700°C and 900°C, where GaAs thermally decomposes.
Requires heat treatment for 20 minutes to 20 minutes. In order to suppress such thermal decomposition, siliconite 2ide (abbreviated as 8i0y) and siliconite 2ide (B j
A heat treatment is performed by depositing an absolute R film such as N4), but when 5ins is used as a protective film, Ga diffuses through 510W during the heat treatment process. This has the drawback that the activation rate of the implanted impurity cannot be increased unless the stoichiometry of GaAs is scattered and the stoichiometry of GaAs is greatly shifted. Due to the large difference in thermal expansion coefficient between υ, a large strain occurs between them, and the activation rate of the /C impurity implanted in the same manner cannot be increased.

An object of the present invention is to provide a method for forming a semiconductor active layer that can activate impurities ion-implanted into the compound semiconducting body with a high activation rate.

According to the BAK of the present invention, in a method of forming a semiconductor active layer by implanting impurity ions into a compound semiconductor substrate and activating it by heat treatment, at least during the heat treatment after ion implantation, the surface of the compound semiconductor substrate is exposed to silicon oxide. A method for forming a semiconductor active layer is obtained, which is characterized in that heat treatment is performed while covered with a nitride film.

The present invention has been made based on new experimental findings by the inventor. Next, the present invention will be specifically explained using FIGS. FIG. 1, (a) to (c) are diagrams for explaining one embodiment of the present invention. Sunzu, 1st
As shown in Figure (a), an impurity, such as silicon (abbreviated as Si), which can become a -4, electrically undesirable substance in the GaAs substrate 1, is implanted under certain conditions into a semi-insulating GaAs substrate 1. Then, an ion implantation layer 2 is formed.

Next, as shown in FIG. 1(b), the ion-implanted layer 2 is covered with monosilane (abbreviated as S 14) - ammonia IIH) - oxygen (Oz!: FP'l). In the reaction system, for example, GaA
s Silicon oxynitride (S) at a substrate temperature of 650°C
After forming the IOxNy) film 3, B o o ”c, 1
Heat treatment is performed in 5 sections to activate the implanted impurity Si as shown in x+v (a) and form the ion-implanted layer (first
Figures (al and b12) are changed to GaAs active layer 4. In the reaction system of 8iH4NHsOs that forms silicon oxynitride (SiOxNy), 5iH
By changing the flux ratio of 0 to L, [13, j
) The values of X and y of 8i0xNy can be changed from 0 to 2 and from 0 to -i, respectively, and at this time, the refractive index of the formed SiOxNy will be from 1.45 to 2.
Changes to 0.

Therefore, silicon oxynitride (SIOx
Figure 2 shows the dependence of the activation rate of the implanted impurity St on the refractive index of SiOxNy when a Si ion-implanted layer formed in a GaAs substrate is activated using a Ny) film.
In the figure, the vertical axis is the activation rate, the horizontal axis is the A11Fr rate n, and N (nitrogen purple) for 0 (oxygen) in '8i0xNy.
As the ratio of n increases, the refractive index n increases.

810t refraction head 1, 45, aimN number refractive index is 2
．． It is 0. In Figure 2, curve A is semi-insulating GaA
5aSH+ on s substrate with 150 key energy,
Curve B shows the dependence of the activation rate of the implanted impurity S1 on the M refraction index n of the protective film when implanted at a dose of 7 x 10" tyn. Similarly, at an energy of 100 kev, the dose ft5
10'! cn1 → injection, curve A is used for forming a high carrier concentration layer in GaAs IC, and curve B is used for forming an active layer. (8i 0xN
y) When the GaAs substrate surface is covered with K and heat treated, the implanted 81 exhibits a high activity rate, for example, a refractive index of 18
silico;/oxynitride (S i 0xNy
), compared to the previously reported maximum peak carrier concentration of 2
The following four conditions can be considered as the reasons why such a high activation rate can be obtained.

(1) 8i0= does not significantly change the stoichiometry of GaAs during heat treatment through Oa, which deteriorates the crystallinity of GaAs, and 8i0x has τ! (Processing G
This causes a layer 1-1 stress on the RA s, and the
l: The activation rate of Si, which is an impurity, is higher than that of soil.

(2) S is N4 should not diffuse Oa:b/yohi As through Kng during heat treatment; GaAs
Although it does not degrade the crystallinity of Ll, 5raNa causes tensile stress in GaAsK during heat treatment, which increases the activation rate of Sl, which is not implanted.

(3) On the other hand, SiOxNy has properties intermediate between both 5iO- and 5rsNa, i.e., SiOx can suppress the diffusion of Ga in the film, and generates an appropriate amount of Ga vacancies in GaAs. The activation rate of 81 is increased because SiOxNy has a coefficient of thermal expansion similar to that of GaA, and does not cause both υ compressive stress and tensile stress. As described above, according to the present invention (Compound 1), there is a method for forming a semiconductor active layer that can activate impurities ion-implanted into a semiconductor with a high activation rate and completely solves the conventional drawbacks. The present invention is applicable not only to GaAs but also to other compound semiconductors.

In addition to this, for example, a silicon oxynitride film is first formed to cover the substrate surface, ions are implanted through the silicon oxynitride film, and the substrate is then covered with a silicon oxynitride film. A similar effect was obtained in so-called through implantation, in which heat treatment is performed in the state.

In the diagram, 1 is a semi-insulating GaAs, S plate, 2 is an ion implantation layer, 3 is a holding W5m, and 4 is a GaAs active layer.

FIG. 2 is a diagram showing the effect of the present invention. In the diagram, A is “S”.
When i+ is implanted at 150 KeV and 7 x 10"Crn-", B is 5 x 101 at 100 KeV! The dependence of the activation index on the refractive index of the CD-implanted g compound is shown.

/“ (S1 person group 11 Uchihara +jjf(”, , 1 range 1
Figure 2

Claims (1)

[Claims] In a method for forming a semiconductor active layer by ion-implanting impurities into a compound semiconductor substrate and then activating the impurities by heat treatment, at least seven times the surface of the compound semiconductor substrate is formed into a silicon oxynitride film during the heat treatment after ion implantation. 1. A method for forming a semiconductor active layer, the method comprising performing heat treatment while covered with a semiconductor active layer.