JP2789262B2 - Method for forming an ion implantation active layer in a GaAs substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an ion implantation active layer having a uniform carrier concentration in a GaAs substrate with good reproducibility.

[0002]

2. Description of the Related Art Generally, a field effect transistor (hereinafter referred to as GaAsFET) using GaAs as a substrate is manufactured by ion-implanting a donor element into the surface of a semi-insulating substrate and heat-treating the donor element to form an active layer. It is. In order to activate the implanted ions, a heat treatment at a high temperature of about 800 ° C. is necessary, and during the treatment, a volatile element, A, is removed from the GaAs substrate.
In order to prevent s from evaporating and altering the surface of the GaAs substrate, an insulating film such as SiN or SiO ₂ is usually used as a protective film. Therefore, the state of adhesion of these films to the GaAs substrate greatly affects the characteristics of the active layer, that is , the FET characteristics.

When a GaAs FET is actually manufactured, the active layer is formed only at a required predetermined place, not on the entire surface of the GaAs substrate. This can be realized by ion implantation through a mask pattern made of a photoresist formed on a GaAs substrate . That is , Ga
A photoresist is left on the As substrate where no ion implantation is required, so that the ions do not reach the GaAs substrate. After the ion implantation, the photoresist mask pattern is removed by an ashing process using oxygen plasma or a dissolution process using an organic chemical, and a heat treatment protective film is deposited to perform a subsequent process. In this case, the photoresist is deteriorated by ion implantation, by ion implantation conditions that can not be completely removed photoresist above process, was conventionally often generated. Thermal protection film and GaAs
When a thin photoresist layer is interposed between the substrate and the heat treatment protective film, the heat treatment protective film partially peels off during the heat treatment, resulting in non-uniform active layer characteristics within the substrate or fluctuation of the active layer characteristics between the substrates. It had been.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to completely remove GaAs by completely removing the photoresist by heat treatment.
An object of the present invention is to provide a method for forming an ion-implanted active layer in a GaAs substrate, characterized in that the active layer to be formed is brought into close contact with the s substrate to make the characteristics of the active layer uniform.

[0005]

According to the prior art, a photoresist pattern used for ion implantation is formed directly on a GaAs substrate. On the other hand, in the present invention, a III-V film containing In as a constituent element is first formed on a GaAs substrate. A group compound semiconductor thin film is deposited, and thereafter, an active layer is formed by a process similar to the conventional one.
After the semiconductor thin film ion implantation, the photoresist is removed
Then, it is dissolved and removed with a hydrochloric acid solution. III including In
The group V compound semiconductor crystal is easily etched by hydrochloric acid, but the GaAs crystal is not etched at all. Therefore,
Even if the photoresist remains, it is removed from the surface of the GaAs substrate together with the group III-V compound semiconductor thin film by the hydrochloric acid-based solution, and the heat treatment protective film is completely adhered to the GaAs substrate. Therefore, the book
The configuration of the invention is as follows. That is, GaAs
Implantation of additive element (4) using crystal as substrate (1)
Then, the GaAs substrate (1) is heat-treated to
Method for forming an ion-implanted active layer (7) in a substrate (1)
In the above , the surface of the GaAs substrate (1) is
III-V compound semiconductor thin film containing n as a constituent element (2)
A first step of depositing a (FIG. 1), the III -V group compound
Of ion implantation mask (3) on semiconductor thin film (2)
A second step of patterning (Fig. 2), the GaA
a second step of ion-implanting the additional element (4) into the s substrate (1);
Step 3 (FIG. 2) and the III-V compound semiconductor thin film
(2) and a fourth step of removing the ion implantation mask (3).
(FIG. 3) and heat treatment on the GaAs substrate (1)
A fifth step of forming a protective film (6) and (4), wherein G
The sixth step of heat-treating the aAs substrate (1) (FIG. 4)
(1) in the GaAs substrate characterized by comprising
The structure as a method of forming the ion implantation active layer (7) is as follows.
Have

[0006]

EXAMPLE A GaAs crystal was used as a substrate, and III containing In was used.
FIGS. 1 to 4 show an example of a manufacturing process of an ion implantation active layer according to the present invention when InGaP is used for a -V compound semiconductor crystal thin film and Si is used for an ion implantation element. That is, FIG. 1 shows that an InGaP thin film is formed on a GaAs substrate.
FIG. 4 shows a longer process diagram (first process). Figure 2 is a photo register
After forming a mask pattern, an Si element ion implanted layer is formed.
(Steps 2 and 3) are shown. Figure 3 shows a cash register
Process diagram for removing stomach pattern and InGaP thin film
(4th process) is shown. Fig. 4 shows the SiN film as a heat treatment protection film.
Forming an ion-implanted active layer by heat treatment
The process diagram (fifth and sixth steps) is shown. Each process is explained below.
I will tell. An InGaP thin film 2 is grown on a GaAs substrate 1 ( first step ). A photoresist mask pattern 3 is formed thereon, Si elements 4 are ion-implanted, and an ion-implanted layer 5 is formed in the substrate ( second and third steps ). Thereafter, the photoresist mask pattern 3 is ashed and removed by oxygen plasma treatment, and then immersed in hydrochloric acid for 1-2 minutes to completely remove the photoresist mask pattern 3 and the InGaP thin film 2 ( fourth step ). In addition , 1500 ° SiN
Depositing a film 6 as heat treatment protective film, by performing a heat treatment for 10 minutes at 800 ° C. to activate the Si element 4 of the ion implantation layer 5 to manufacture an ion-implanted active layer 7 (fifth and sixth Engineering of
About ).

FIG. 5 is a diagram comparing the distribution of the carrier concentration in the substrate surface between the ion implantation active layer formed according to the above process and the ion implantation active layer formed by the conventional method. However, ion implantation was performed at an acceleration voltage of 30 keV and an area density of 1 × 1.
Under the condition of 0 ¹³ / cm ² , the InGaP thin film 2 is grown to a thickness of 50 ° by a vapor phase growth method (usually called MOCVD method) using an organic metal gas as a raw material. Also,
The ion implantation active layer 7 has a 300 μm square area of 400 μm.
It is formed on the entire surface of the GaAs substrate 1 at intervals of μm. Figure 5
Shows the results of measurement of these regions of the ion-implanted active layer 7 every five in the substrate diameter direction, that is , at intervals of 2 mm.

In the case of manufacturing by the conventional process, the carrier concentration is reduced at the outer peripheral portion of the GaAs substrate.
It can be seen that the carrier concentration is uniform over the entire surface of the GaAs substrate when the ion implantation active layer is formed in the GaAs substrate. This resist ashing with oxygen plasma starts from the center of the GaAs substrate 1, the outer circumference of the GaAs substrate 1 reflects the fact that hardly ashed and removed. That is , using the conventional process, Ga
In the outer peripheral portion of the As substrate 1 , the heat treatment protective film and the GaAs substrate 1
Since the resist thin layer is interposed between the surfaces of the GaAs substrate 1 , the heat treatment protective film is peeled off during the heat treatment step, so that the surface of the GaAs substrate 1 is deteriorated and the carrier concentration is reduced. On the other hand, of the present invention
When a method of forming an active layer for ion implantation in a GaAs substrate is used, the resist thin layer remaining on the outer peripheral portion of the GaAs substrate 1 is completely removed together with the InGaP thin film 2 .
No deterioration of the surface of the GaAs substrate 1 occurs, and the carrier concentration becomes uniform in the surface of the GaAs substrate 1 .

[0009]

As described above, the GaAs of the present invention can be used.
If a method of forming an ion-implanted active layer in a substrate is used, the heat treatment protective film and the GaAs substrate are completely adhered to each other, so that the surface of the GaAs substrate does not deteriorate during the heat treatment process, and the characteristics within the substrate surface or between the substrates are reduced. A uniform ion implantation active layer can be realized.

[Brief description of the drawings]

FIG. 1 shows a process diagram ( first process ) for growing an InGaP thin film on a GaAs substrate.

FIG. 2 is a process chart of forming a Si element ion-implanted layer after forming a photoresist mask pattern ( second and third steps ).
Is shown.

FIG. 3 is a process diagram ( fourth process ) for removing the resist mask pattern and the InGaP thin film.

FIG. 4 is a process chart for forming an ion-implanted active layer by a heat treatment step using a SiN film as a heat treatment protection film ( fifth and sixth steps).
Step ).

FIG. 5 shows a comparison of the in-plane distribution of the carrier concentration of the ion implantation active layer between the present invention and the conventional example.

[Explanation of symbols]

 Reference Signs List 1 GaAs substrate 2 InGaP thin film 3 photoresist mask pattern 4 Si element 5 ion implantation layer 6 SiN film 7 ion implantation active layer

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Suehiro Sugita 1-6, Uchisaiwai-cho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (56) References JP-A-57-21824 (JP, A) (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/265

Claims (1)

(57) [Claims] An GaAs crystal is used as a substrate to implant ions of an additional element, and the GaAs substrate is heat-treated to form the Ga.
Method for forming ion implantation active layer in As substrate
Te first step of depositing a III -V compound semiconductor thin film including the advance In the configuration element to the GaAs substrate surface
And an ion implantation mask on the III-V compound semiconductor thin film
A second step of forming and patterning, and a third step of ion-implanting the additive element into the GaAs substrate.
And the step of III-V compound semiconductor thin film and the ion implantation mask.
A fourth step of removing a mask, and a fifth step of forming a heat treatment protective film on the GaAs substrate.
And a sixth step of heat-treating the GaAs substrate.
How to form an ion-implanted active layer in the GaAs substrate, characterized in that it is.