JPS62274621A - Ion implantation - Google Patents

Abstract

PURPOSE:To form a thin ion implanted layer without decreasing implanted energy, by setting the incident angle of the ions to a semiconductor substrate at a specified value or more, and performing the ion implantation. CONSTITUTION:As a semiconductor substrate 1, GaAs is used. Si ions are implanted. Implantation energy is 30 keV. An incident angle THETA is 60 deg.. In this case, the thickness of an ion-implanted layer (d) becomes 338 Angstrom . In order to obtain the thickness of 338 Angstrom for the same ion-implanted layer 2, it is necessary to use implantation energy of 22 keV, which is close to the limit of an ion- implanting apparatus at the incident angle of 0 deg. of the ions. By setting the incident angle of the ions at 30 deg. or more in this way, the thin ion-implanted layer 2 can be readily obtained with good reproducibility without decreasing the implanted energy. When this method is applied to the formation of the operating layer of a GaAs field effect transistor, the thickness of the operating layer can be made thin. Therefore, a high-performance field-effect transistor having a large mutual conductance gm can be obtained.

Description

[Detailed description of the invention] 3. Detailed description of the invention [Industrial application field] The present invention relates to an ion implantation method.

[Conventional technology]

FIG. 3 is a cross-sectional view showing a conventional ion implantation method. In this figure, 1 is a semiconductor substrate, and 2 is this semiconductor substrate 1.
The ion implantation layer 3 formed on the main surface of the ion implantation layer 3) is the main ion implantation layer.

Next, the ion implantation method will be explained.

The incident angle of the ions 3 to the semiconductor substrate 1 is set near the critical angle of channeling for the desired implantation energy of the ions 3, and the ion implantation layer 26! Form. The critical angle for channeling is at most 15°.

[Problem that the invention seeks to solve]

In the conventional ion implantation method, the incident angle of ion 3 is at most 1
5 degrees, and the ions 3 are implanted almost perpendicularly to the semiconductor substrate 1 (incident angle of 0 degrees), so it was necessary to lower the implantation energy in order to form a shallow ion implantation layer. However, there have been problems in that conventional ion implanters have an equipment limit of at least 10 KeV when it comes to implantation energy, and that lower implantation energy tends to cause channeling.

This invention was made to solve the above-mentioned problems, and aims to provide an ion implantation method that can form a thin ion implantation layer without lowering the implantation energy.

[Means for solving problems]

The ion implantation method according to the present invention forms a thin ion implantation layer without lowering the implantation energy by setting the azimuth angle of incidence to the semiconductor substrate at 309 or more.

[Effect]

In this invention, by increasing the ion incidence angle to 30° or more, it is possible to form a very thin ion implantation layer.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In FIG. 1, 1 is a semiconductor substrate, 2 is an ion implantation layer,
3 is an ion. The incidence of the ions 3 on the semiconductor substrate 1 is assumed to be θ.

Next, the semiconductor substrate 1 is made of GaAs, and the implanted ions are made of Si.
.

Taking as an example the case where the implantation energy is 30 KeV and the incident angle θ is 600, the thickness d of the ion implantation layer 2 will be described in comparison with the conventional method with reference to FIG.

According to the LSS theory, the irradiation range RP of ion 3 is 262
people, standard deviation ΔRP is 170 people, lateral inward spread ΔX p
, is 226th.

When the incident angle is 0° according to the conventional method, the thickness d of the ion implantation layer 2 is as shown in FIG. 4, d = RP + ΔR.
1 = 432 people.

On the other hand, in the case of the incident angle of 60° according to the present invention, as shown in FIG. 2, the thickness d of the ion implantation layer 2 is d=Rpeoso+rd=3386.

In order to obtain the same thickness of 3386 for the ion implantation layer 2, the implantation energy must be set to 22KeV to perform implantation at an ion incidence angle of 0°, which is the conventional method, but such a low energy is close to the limit of the ion implanter, and it is difficult to perform implantation with good reproducibility. Further, the lower the implantation energy is, the more likely channeling is to occur, which causes problems such as variations in the thickness d of the ion implantation layer 2.

However, according to the present invention, a thin ion implantation layer 2 can be easily obtained with good reproducibility without lowering the implantation energy.

If this invention is applied to the formation of the active layer of a GaAs field-effect l-lanster, the thickness of the active layer can be reduced, and a high-performance field-effect transistor with a large mutual conductance gm can be obtained.

〔Effect of the invention〕

As explained above, this invention sets the incident angle of ions to the semiconductor substrate at 30° or more, so that it is possible to form a sufficiently thin ion implantation layer without lowering the implantation energy within the stable implantation energy range of the ion implanter. There is an effect that can be achieved.

[Brief explanation of drawings]

1 and 2 are diagrams showing an ion implantation method according to an embodiment of the present invention, and FIGS. 3 and 4 are diagrams showing a conventional ion implantation method. In the figure, 1 is a semiconductor substrate, 2 is an ion implantation layer, and 3 is an ion. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Masuo Oiwa (2 others) Figure 1 Figure 2 Figure 3 Figure 4 -

Claims (1)

[Claims] An ion implantation method characterized in that when implanting ions into a semiconductor substrate, the ion implantation is performed with an incident angle of the ions to the semiconductor substrate being 30° or more.