JPS59149023A - Method for introduction of impurity into semiconductor - Google Patents

Abstract

PURPOSE:To contrive improvement in reproducibility of impurity introduction by a method wherein a crystal layer, having the degree of resolution of introduced impurities smaller than that of an impurity introduction semiconductor, is formed on the surface of a compound semiconductor whereon impurities will be introduced. CONSTITUTION:A heterogeneous semiconductor layer AlGaAs thin film 12 is formed in advance on the surface of a GaAs wafer 11 as a compound semiconductor crystal by performing an epitaxial growing method using an MOCVD method or an MBE method. Subsequently, an ion-implanted layer 21 is provided by implanting Zn. Then, after an Si3N4 layer 31 has been formed on the AlGaAs layer 12 by performing a vapor-phase growing method, a high density Zn diffusion layer 32' is formed by performing a heat treatment at 800 deg.C for 20min in GaAs11. When the Si3N4 film 31 is removed using HF after performance of a heat treatment and subsequently an AlGaAs layer 12 is removed, the etching by HF is automatically stopped on the surface of the GaAs11, thereby enabling to obtain the compound semiconductor layer having a Zn diffusion layer on the surface.

Description

[Detailed Description of the Invention] The present invention relates to a method for introducing impurities into a semiconductor.
It is generally difficult to develop techniques for introducing impurities into compound semiconductors, such as group V compounds, with excellent reproducibility and controllability. This is because compound semiconductors such as GaAs crystals are easily damaged by ion implantation, etc., and surface thermal decomposition is also likely to occur during heat treatment after ion implantation.

A/203 Measures are taken to suppress the occurrence of surface non-stoichiometric defects as much as possible by attaching a film or the like and thermally decomposing the compound semiconductor. However, 8i02, 8iaN4゜Al2O3
When growing compound semiconductor crystals by CVD, etc., compound semiconductor crystals are grown at high temperatures (
300° to 700°C), at which time stoichiometric defects occur near the surface.

Also these 8 i02. a l 1IN4 or A
It is extremely difficult to control the interface between a film such as A'203 (hereinafter referred to as a blocking film) and a compound semiconductor crystal. Especially G
As is commonly done in ion implantation such as aAs, G
If ions are implanted with the aAs surface exposed, the implantation layer will be around ~1000A, so surface etching etc. cannot be performed sufficiently, and the above-mentioned blocking film must be formed on the surface, so the barrier film and the compound semiconductor crystal will be separated. Controlling the interface is difficult.

Due to the reasons mentioned above, it is extremely difficult to improve the reproducibility of ion implantation into GaAs or the like and the introduction of cine fine particles through subsequent heat treatment.

The purpose of the present invention is to eliminate the above-mentioned problems when introducing impurities into a compound semiconductor by ion implantation, and to provide an impurity introduction method with excellent reproducibility. The present invention makes it possible not only to produce high quality products, but also to perform surface treatment very accurately and cleanly before the process of introducing impurities, which ends at the activation stage such as ion implantation and heat treatment. Using this impurity introduction method significantly improves the stability of the device process and the reliability of the resulting device.

According to the invention, a step of epitaxially growing a crystal layer on the surface of a compound semiconductor into which an impurity is to be introduced, in which the solubility of the introduced impurity is smaller than that of the semiconductor to be introduced with the impurity, and forming a crystal layer on this epitaxially grown surface or on the epitaxially grown surface. a step of introducing a cine fine substance into the surface of the protective film for heat treatment, a step of transferring the introduced impurity to the semiconductor to be impurity-introduced by applying heat treatment, and an epitaxial layer formed on the semiconductor to be impurity-introduced. A method for introducing impurities into a semiconductor is obtained, the method comprising the step of removing.

Hereinafter, the present invention will be explained in detail based on an example, regarding the case of impurity introduction by Zn ion implantation into GaAs.

Figures 1 to 3 are diagrams explaining an embodiment of the invention in the order of steps. Figure 1 shows a GaAs wafer 11 as a compound semiconductor crystal into which impurities are to be introduced, and a foreign semiconductor layer AA! This is a cross section of a GaAsAlGaAs thin film grown epitaxially by a method such as MOCVD or MBE. After this, an ion implantation layer 21 is provided as shown in FIG. An example is shown in which Zn is used as the ion implantation layer and 2X10'' steel is introduced with an acceleration of 5QKeV and an ion implantation amount Ns.Since the thickness of the AAtGaAs layer 12 is 200OA in the example, the thickness of the ion implantation layer 21 is the same as the AJGaAa layer. Approximately 1 in 12 thickness
/2. Note that AA! in Examples! GaAsAlG
The composition ratio of the aAs layer 12 is 0.5:O15, and the solubility of the introduced impurity Zn is smaller than that of Zn in GaAs.

Thereafter, as shown in the cross section of FIG. 3, an 8i3N4 layer 31 was formed on the AlGaAs5 layer 12 to a thickness of 200 OA by vapor phase epitaxy, and after heat treatment at 800°C for 20 minutes, the implanted impurity layer was removed. 3. As shown in FIG. 32, the acceptor concentration due to the implanted ZnK was measured at room temperature after this heat treatment. FIG. 4 shows the depth distribution of the acceptor concentration measured from the surface of the AlGaAs layer 120. As shown in FIG. 4, a difference in acceptor concentration can be clearly seen at the interface between the AlGaAs 12 and the 5-GaAs wafer 11. The acceptor concentration on the AlGaAs 12 side is ~8X10 cm, whereas the G
a A s 1.2X10 an on the wafer 11 side
It becomes.

The fact that the rg acceptor concentration distribution fluctuates as shown in FIG. 4 after heat treatment can be qualitatively explained as follows. First, the Zn ion implantation amount N5 = 10 cm increases the solubility of Zn in the AlGaAs layer 12 (at a heat treatment temperature of 800°C) by approximately 1.
This is more than an order of magnitude higher. Therefore, when heat treatment is applied at 800°C, the implanted Zn becomes AA! GaAsAlGa
The As layer 12 is diffused as if removed. Zn diffusion is SI!
It is extremely difficult to form in the lN4 film 21, and inevitably GaAs
Zni is excluded in 1 l. This heat treatment results in rapid KA
A! The Zn removed from the GaAs layer 12 becomes GaAs1I.
It can be considered that a high concentration of Zn diffuses in the skin 32'. The thickness of the high concentration Zn diffusion layer 32' can be obtained with good reproducibility at ~1000 A by heat treatment at 800 DEG 020 minutes giving the results shown in FIG. 4 shown in the example.

The good reproducibility with 6- is because the interface involved in Zn diffusion is the hetero semiconductor junction interface of GaAs11 and A/GaAs12, which has a good crystallographic connection! It can be easily understood from a qualitative consideration that the concentration also decreases and the thickness increases. In this way, by setting the heat treatment time and temperature, the reproducibility was good (Zn in GaAs
An impurity-introduced layer 32' is obtained.

In the conventional technique, when Zni ions are implanted into GaAs and heat treated, Zn is added to the ion implantation layer at its implantation surface Vr, 5.
To2 film or Si8N4 film is attached to prevent thermal decomposition of the GaAs surface and to prevent Zn from scattering to the outside.
For 5iOz film SOO″C+ 8 i 3 N 4
In the case of membranes, heat treatment is performed at ~850°C for about 20 degrees.

In this case, phenomena such as a low activation rate or a low impurity concentration till are observed in the concentration and distribution of Zn acceptors activated in the Zn implanted layer after heat treatment.
Moreover, the problem was that the reproducibility was also lacking.◎However, the uninvented method can achieve impurity implantation that is extremely stable and has excellent reproducibility.

As mentioned above, the film 31 attached on the AlGaAs 12 must not melt or permeate a large amount of host constituent elements during heat treatment, but as mentioned above, 8i
It is sufficient to use an sNa film or the like.

This is because, as mentioned above, when the 8i3N4 film is heat-treated at about 850°C, some reaction occurs with the host element.
This is because the impurity introduction of the present invention is achieved at a relatively low temperature of about 800° C. or lower, so deterioration should not be a problem.

In addition, in the conventional technology, since the surface where impurities are introduced is exposed and ions are implanted, adhesion of hydride p, carbon, etc. is observed on the surface, and during heat treatment, an 8i3N4 film etc. is attached to the surface to activate it. Therefore, it is difficult to prevent and control impurity contamination in the layer near the GaAs surface, that is, in the ion-implanted layer itself.

However, in the impurity introduction method of the present invention, after ion implantation and heat treatment, p843N is
Etching by HF is automatically stopped on the surface of the GaAs 11 on the a film 21 and then on the AA'GaAsAlGaAs 12, and a clean surface is exposed. In other words, the surface of the GaAs introduced with the impurity Zn, which is carried over to the next process, has extremely high cleanliness, which increases the stability of the device fabrication process, improves the device manufacturing yield, and improves the finished product. The reliability of the device also becomes high.

The case where Zn is introduced into fGaAa of the present invention has been described in detail above, but this invention also applies to the introduction of Zn or Cd into other compound semiconductors such as InGaAa mixed crystals that are lattice-matched to InP. The installed system (in this case A
It is preferable to use InP instead of lGaAs. ), the key is to create a crystal layer epitaxially grown on the compound semiconductor into which impurities are to be introduced, and the solubility of the introduced impurities is smaller in the ridge crystal layer than in the former. If it can be obtained, it can be used as a technique for introducing impurities into any compound semiconductor. Furthermore, it is clear that there are no limitations regarding the 9- impurity.

In addition to highly reproducible production of impurity-introduced layers, the invention also makes surface treatment extremely reliable and clean before the process after impurity introduction, which ends in the activation stage such as ion implantation and heat treatment. It becomes possible to do so.

[Brief explanation of the drawing]

FIGS. 1, 2, and 3 are cross-sectional views illustrating the steps of an embodiment of the impurity introduction method according to the invention, and FIG. 4 shows the location distribution of the concentration at the time when the impurity introduction is completed. 11-...GaAa, 12-=AIGaAa layer, 2
1...Zn ion implantation layer, 31...5
iBN4 film, 32... Zn introduction layer of heat treatment. Agent Patent Attorney Susumu Uchihara 10- Fig. 2 Fig. 3 (front) S Gyori (A) Fig. 4

Claims (1)

[Claims] A step of epitaxially growing a crystal layer on the surface of a compound semiconductor into which an impurity is to be introduced, in which the solubility of the introduced impurity is smaller than that of the impurity-introduced semiconductor, and a process for heat treatment formed on the epitaxially grown surface or the epitaxially grown surface. a step of introducing a cine fine substance from the surface of a protective film; a step of moving the introduced impurity to the impurity-introduced semiconductor by applying heat treatment; and a step of removing an epitaxial layer formed on the impurity-introduced semiconductor. A method for introducing an impurity into a semiconductor, the method comprising: