JPH01212443A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To stabilize the deposition rate of an insulating film and to make it possible to control precisely the thickness of the operating layer of a FET by a method wherein a conducting layer other than the constituent elements of a device is locally formed before the insulating film for through-implantation is deposited by a plasma CVD method. CONSTITUTION:A maskless ion-implantation is performed in a prescribed region 9 of a semi-insulative GaAs substrate 1 using a convergent ion beam 10. Then, a laser beam 11 is selectively directed onto the region only implanted Si to perform an annealing and to form a conducting layer 12 and, moreover, an insulating film 2c for through-implantation is deposited. If the film 2c is deposited in such a way, the deposition rate of the insulating film can be stabilized and the thickness of an operating layer of a FET can be precisely controlled.

Description

Detailed Description of the Invention (Industrial Application Field) This invention relates to a method for manufacturing a compound semiconductor device that can improve the uniformity of the thickness distribution of an insulating film deposited on a semi-insulating G, A, or substrate. It is.

(Prior Art) Improving the driving ability of FETs constituting GaAsJC and uniformity of the formed FETs, especially V.

Precise control of (threshold voltage) is the most important technical issue in putting LSI-level digital ICs into practical use.

The active layer of a FET is usually formed by ion implantation, but in order to reduce the depth of the peak value of carrier concentration, that is, the thickness of the active layer (and improve the mutual conductance (gap)), it is necessary to make several hundred thin insulating films. It is well known that the through implantation method, in which ions are implanted through the ion implantation method, is effective.

As the insulating film, S51N4. S! Ox,S5O,N
.

(0/N to 0.6), etc. are used.

Methods for forming insulating films are broadly classified into CVD methods and sputtering methods, but plasma CVD is often employed because it allows low-temperature film formation and has excellent stability of the film itself.

The merits of the through-injection method through the insulating film include, in addition to the already mentioned effect of increasing g, it also alleviates the planar channeling effect caused by ion scattering within the insulating film.

However, on the other hand, there is a major problem in that variations in the thickness of the insulating film directly affect the thickness of the active layer formed by ion implantation. This variation in the thickness of the active layer is fatal for controlling the FET threshold voltage (V).

Figure 2 (al~ (The illusion is a conventional FE using the through injection method.
It is a sectional view showing an example of a T formation process. (a) shows the insulating film (2) for through injection deposited on a semi-insulating GaAs substrate (1) by plasma CVD method, (b) shows photolithography after coating the photoresist (3). The operating layer (
n layer) pattern openings are formed, and Smu ions (4a) are formed.
(C1 is the active layer (
The state is shown in which the through-injection insulating film (2a) and the photoresist +3) have been removed.

(al indicates the state in which the high melting point gate electrode (for example WSt) +61 is processed by the reactive ion etching (RIE) method.) Next, as shown in (al), the second through-implanted insulation for forming the n0 layer (7) is applied. Deposit film (2b) and photolithography.

After forming an opening for n9 implantation by reactive ion etching (RIE), S ions (4b) are implanted at a high concentration. Then, as shown in (f), a predetermined heat treatment is performed in an A s Hs atmosphere at around 800°C to activate the implanted ions.Finally, as shown in (8), an ohmic electrode (8) is formed. Then the FET is completed.

(What the invention attempts to solve!! la) When relying on the conventional example described in detail in FIG.
It is extremely difficult to control the thickness of the layer).

This is because the thickness of the plasma CVD film, which uniquely defines the thickness of the active layer, is subject to complex variation parameters (CVDIIR).
This is because it is controlled by the resistivity of the substrate on which it is deposited, the temperature distribution of the substrate, fluctuations in the flow of the source gas, stability of the plasma, minute fluctuations in the gas composition ratio, etc. Among these, substrates with particularly high resistivity have a very unstable film deposition rate. Therefore, it is considered that the technical limit is to suppress the film thickness variation within ±lθ%. However, depending on the process method, if the thickness of the through injection insulating film in active layer formation deviates by about 3% from the target value, αvtt+ will be about 10 mV.
It is said that the current fluctuation range of ±10% is not satisfactory, and it is important to take every possible measure to suppress film thickness fluctuations to the utmost when putting G, A, and LSI into practical use. This is an issue for the government.

This invention was made to solve the above-mentioned problems, and aims to stabilize the deposition rate of the insulating film and enable precise control of the thickness of the active layer. do.

[Means to solve the problem]

The method for manufacturing a semiconductor device according to the present invention improves the reproducibility of the active layer thickness of a compound semiconductor device, particularly G, A, FET, and locally forms a conductive layer other than the device constituent elements in order to reduce αVt1k. be.

(Function) The method for manufacturing a semiconductor device according to the present invention includes plasma C
Before depositing the through injection insulating film by the VD method, a conductive layer other than the device constituent elements is locally formed in advance.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing a semiconductor device according to the present invention will be described below with reference to the drawings. 1a) to 10) are cross-sectional views showing the steps up to the formation of an insulating film for through injection in the manufacturing process.
A focused ion beam OR (FIB; Focused Ion B@
avn) shows a state in which maskless ion implantation is being performed.

Si may be a good choice for the injection source; 1-31 s or A for the liquid metal ion source.

Eutectic alloys such as -3 and -B are easy to use due to their melting points.

Then, as shown in Fig. 2, the conductive layer (2) is annealed by selectively irradiating the SL implanted region with laser light I.
) to form. Furthermore (like 01, for through injection w
Deposit an Am film (2c). Figure 1 la) ~ (C)
i! This is the initial step of the FET formation process, and the subsequent steps are shown in Figures 2(b) to (g), which explain the conventional method.
Since the steps are similar to those in step 1, the explanation will be omitted.

Next, the effect will be explained. Through-injection insulation Il! by the above means! When (2c) is deposited, the film thickness variation is significantly reduced, and the uniformity between wafers and between lofts is significantly improved.

In order not to impede the high integration of devices, the area for maskless ion implantation is not inside the IC chip.
For example, a dicing line may be convenient.

Note that in the above embodiment, Ga is used as the semi-insulating semiconductor substrate.
Although the explanation was given using As as an example, 1. Similar effects can be obtained even with P. Furthermore, although a laser beam is used in the description as a heat source for beam annealing, it goes without saying that an electron beam may also be used.

〔Effect of the invention〕

As described above, according to the present invention, a conductive layer is selectively formed on the main surface of a semi-insulating substrate before depositing an insulating film for through injection by plasma CVD, so that ``the deposition of the insulating film This has the effect of stabilizing the speed and precisely controlling the thickness of the active layer of the FET.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing steps up to formation of an insulating film for through injection in a method for manufacturing a semiconductor device according to an embodiment of the present invention, and FIG. 2 shows steps in a conventional method for manufacturing a semiconductor device. In the cross-sectional view, (11 is a semi-insulating GaAs substrate, (2a) is also used for the manufacturing method in this invention.
). (2b) and (2c) are insulating films for through injection, (3)
are photoresists, (4a) and (4b) are St- ions 1.15) are active layers, (6) are high melting point gate electrodes,
(7) is an n''' layer, (8) is an ohmic electrode, (9) is a specific area, Q is a focused ion beam, aD is a laser beam,
(2) is a conductive layer. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Agent Masuo Oiwa Figure 1 Figure 2 Figure 2 Procedural amendment (voluntary) to μ 5F427I3 2, Title of invention Method for manufacturing semiconductor devices 3, Person making the amendment Representative Moriya Shiki 4, Agent 5 , Target of correction 6, Contents of correction-22

Claims (1)

[Claims] Plasma CVD (chemical vapor deposition) is applied to the main surface of a semi-insulating semiconductor substrate on which no conductive thin film is formed.
In the step of depositing an insulating film by a method (orDeposition), before depositing the insulating film, impurity ions that impart a desired conductivity type only to a specific region of the main surface of the semiconductor substrate are selectively implanted, and A method of manufacturing a semiconductor device, characterized in that a conductive layer is formed by selectively performing beam annealing.