JPS61290716A - Ion implantation method - Google Patents

Abstract

PURPOSE:To obtain a conductive layer with good reproducibility, by implanting ions of an impurity from the family IV and ions of an impurity from the family VI both in the same region before performing a heat treatment for activation. CONSTITUTION:An N-type conductive layer is formed in crystals of a family III-V compound semiconductor by means of ion implantation. For that purpose, ions of an element from the family IV and subsequently ions of an element from the family VI are implanted in the same region of the crystals of the family III-V compound semiconductor, and they are heat-treated for activation. In the family III-V compound semiconductor, even if the elements from the families VI and IV change their densities or ratio of vacancies during the heat treatment, the elements from the families III and V show a reverse tendency thereto. As a result, the totality of the activated elements from the families IV and VI is not substantially changed. According to this method, a conductive layer with good reproducibility can be obtained.

Description

[Detailed Description of the Invention] [Summary] This is a method of forming a 5-type conductive layer in a ■-■ group compound semiconductor crystal by ion implantation. By performing an activation heat treatment after implanting group element ions and group (2) ions, an ion-implanted layer of a (1)-(2) group compound semiconductor with extremely good reproducibility can be obtained.

[Industrial application field]

The present invention relates to a method of forming a conductive layer with good reproducibility by ion implantation.

[Conventional technology]

Conventionally, m-v group compound semiconductor 1, for example, Ga Am, S4
GaA and S# are ion-implanted to form a conductive layer.
aDepending on crystal differences, 1 to 5 x 10”C between samples
There are differences in the activation of the three types.

This variation cannot be explained by variations in the compensation effect of these impurities, since the electrically active impurities in undoped GaAs are on the order of 10"6%-".

The present inventor found that this variation is based on a change in stoichiometry (Sto4a4ommtwy) within the GaAa crystal.

When manufacturing a semiconductor device such as a GaAaOFET, it is necessary to form a GaAs ion implantation layer with good reproducibility.

Conventionally, for this reason, as shown in Figure @2, semiconductor devices to be actually manufactured, such as GaAa ICs or power FETs,
A single device was manufactured under conditions as close to those as possible, and the required ion implantation dose was determined by measuring the device.

(AtN) 5 is deposited, source and drain electrodes 4 and 5 are formed by vapor deposition and alloying in (C), and a gate electrode 6 (At) is formed in (D).

In the above process, first, when a certain pinch-off voltage is desired, the injection amount is determined from experience, and the above (A) to CD>
After the process, the device characteristics were measured), and if the implantation amount was too large, the implantation amount was adjusted by decreasing it to bring it to the desired design value, thereby determining the implantation correction value.

[Problem that the invention seeks to solve]

However, with this conventional method, it is time-consuming and requires about one week to determine the injection amount.

It is necessary to determine the amount of implantation for each ingot, but it is very difficult because only about 100 wafers can be obtained from one GaAa ingot.

[Ninth Means for Solving the Problems] In the present invention, in a method of forming a 9S type conductive layer by ion implantation into an m-v group compound semiconductor crystal, An ion implantation method is provided, which comprises performing activation heat treatment after implanting group (1) group element ions and group (2) group element ions.

[Effect]

There are two types of impurities in group (1)-(2) compound semiconductors: those which are activated by substitution at the group (1) element position, and those which are activated by substitution at the group V element position.

Taking GaAa as an example, since Si is activated only after it is substituted in the Ga position, the greater the vacancy of Ga, the greater the probability of substitution and the greater the activation rate. G6
There is a relationship in which the lattice constant increases as the peacency increases.

On the other hand, since S# is activated only after being substituted at the Aa position, the activation rate is higher in cells with more As (lower Ga) sensitivity. That is, the larger the lattice constant, the smaller the activation rate.

The present invention was thus made by focusing on the fact that the direction of change in activation rate for group Ⅰ elements and ions of group Ⅰ elements is opposite to the change in the paycency of group Ⅰ elements 1, for example, Ga. Chiru.

Due to the presence of the pecanciency of the group elements, the group ■ elements are more likely to enter the lattice positions of the group element elements. By implanting approximately the same amount of ions to the same depth, even if the concentration and ratio of the peacancy of the ■ and ■ group elements in the m-v crystal changes, the ■ and ■ group elements will not respond to the change in their concentration ratio. , shows the opposite tendency, so the sum of the activated group ■ elements and group ■ elements does not change much.

〔Example〕

In this example, when ions are implanted into GaAa crystal, σαA
This method reduces changes in the activation of the ion-implanted layer due to variations in the growth of the s-crystal, thereby producing an ion-implanted layer with good reproducibility.

The impurity ion-implanted into GaAs will more easily enter the atomic position and the activation rate will be better if there is an elemental vacancy (for example, S (for example, Ga vacancy) that the impurity should occupy).

However, in actual GaAa crystals, Ga vacancy is also A.
1 vacancy exists, and its concentration and ratio change.

Therefore, when forming a % type layer by implanting S(ions), the activation rate changes.

As a result of examining many GaAs crystals, the present inventor found that tetravalent (
The activation rate of Si which is W group) and S- which is hexavalent (■ group)
We found that there is an inverse correlation between the activation rate of

FIG. 1 shows the results of investigating the relationship between changes in the lattice constant of GaAs and changes in the activation rates of Si and S-.

Figure 1 shows St and S# of 150 fsy and 55 fsy, respectively.
After ion implantation at 0 KgV, it was heat treated at 850°C for 220 minutes as an AINt'' wk retaining film. Here, it is difficult to measure the absolute value of the lattice constant, so
Based on one crystal, in this case #1, the difference in lattice constant from that of the standard crystal (α.-a) is determined for crystals #2 to #4. There is. This measurement uses the Bond method.
), XH is applied to the crystal to be measured, the angle at which the XH is reflected is accurately measured, and the lattice constant is calculated using a relational expression (Reference Aata Cryat.

1960, Vol. 13. (See P. 814).

Even for #1 to #4, under the above ion implantation conditions,
SN+ or S-” dose is 3 x 10” own
-2.

Then, for each sample, the concentration of the activated carriers was determined by the CV method.

In the C-Y method, a circular electrode with a diameter of 200μ is formed on the ion implantation layer, a voltage is applied to this, the relationship between the applied voltage and the capacitance is measured, and the carrier distribution within the implantation layer is determined based on this. especially) go 9.

According to Fig. 1, 5 x 1G12dm-
In contrast to the injection of St + f of ``, the concentration in the sheet is about A to 1/2.

It can be seen that as the lattice constant of the crystal increases (Gα peacency increases), the sheet carrier concentration increases and the activation rate increases.

On the other hand, when looking at S#, contrary to St, the sheet carrier concentration decreases as the lattice constant increases.

Next, an example of manufacturing a conductive layer according to this embodiment will be described.

113μ deep scratch on GaAa, peak carrier concentration 1.5
When creating a % scattering layer of X 10"ewh-", as conventionally,
Instead of injecting with 6g4-2, Si+t-150
KmF, 1.5 X 1011012a and Ss”t
-550KmV, 1.5 x 101211%-2 and ions are implanted.

Then, the implanted ions are activated by heat treatment using the VkAIM as a holding film.

At this time, as shown in Figure 1, the correlation between Si and S- with respect to the peacancy of the GaAa crystal is opposite, so it is compensated for.
It is possible to create an outer conductive layer with good reproducibility.

In the above, the injection of S (and S-) was shown in the present invention, but
The present invention is not limited to this, and combinations of other impurities having the opposite correlation to peacancy are possible. For example, Si as a group Ⅰ element impurity.

As G-1 group element impurities, S, Ss, Ta
A combination of the following can be applied.

In addition to GaAa, other l[-v group compounds such as I%P, AIAa, GaP, etc. can also be used for the semiconductor crystal.

〔Effect of the invention〕

As is clear from the above, according to the present invention, a conductive layer is actually fabricated by ion implantation, its electrical characteristics are measured, and a correction amount for plow implantation is also determined from this. It is possible to obtain a conductive layer with good reproducibility by simply implanting group (1) impurity ions and group (2) impurity ions into the same region and then performing activation heat treatment without any troublesome processing.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, and FIGS. 2(A) to (D) are process diagrams for explaining a conventional example. 1...5I-GaAa (substrate) 2-5-GaAa (ion implantation N) 3...AIN (ffi film) 4.5...source, drain electrode 6...gate electrode

Claims (1)

[Claims] In a method for forming an n-type conductive layer by ion implantation into a III-V compound semiconductor crystal, group IV element ions and group VI element ions are added to the same region of the III-V compound semiconductor crystal. An ion implantation method characterized by performing activation heat treatment after implanting.