JPH0472736A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enhance the controllability of life time and the reliability by a method wherein a semiconductor device is arranged in vacuum or inert gas atmosphere to be irradiated with a high energy electron beam or gamma rays. CONSTITUTION:A semiconductor device 10 having multiple main electrodes and at least one control electrode is arranged in vacuum or inert gas atmosphere to be irradiated with a high energy electron beam or gamma rays 50 in the atmosphere. Through these procedures, the chemically active species produced in open air can be prevented from entering the vacuum region 41 due to the irradiation with the electron beams 50 so that the surface of the semiconductor device 10 need not be oxidized and the new level need not be deeply led inside.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is applicable to lifetime control of power semiconductors.
Thyristor), SI Th (5Lat
istia Iduration Thyristor
), IGBT (In5ulat@d Gate
Elements based on various operating principles, such as BipolatTransiaLor), have been developed. These are Izun
Since minority carriers are also introduced, lifetime control is required to improve switching speed. In order to control the life stage and im, there are methods of diffusing heavy metals such as gold and platinum into the element, methods of irradiating heat radiation with high penetrating power such as electron beams and rdAs neutron beams, and methods of irradiating ions such as protons and helium. A method of irradiating is known. Among these, life time control by irradiation with electron beams or gamma rays is often performed because it has excellent reproducibility and uniformity and is relatively simple to manufacture.

FIG. 4 shows a schematic cross-sectional view when lifetime control of an IGBT is performed using conventional electron beam irradiation. This one is P
“An N-epitaxial layer is formed on the main surface of the collector layer (1).P-type impurities are selectively diffused into a part of the surface of the N-epitaxial layer (2). An N+ emifter region (4) is formed by N-.
The surface of the epitaxial layer (2) and the N+ emifter region (4)
A gate insulating film (5) is formed on the surface of the P well region (3) sandwiched between the surface of the gate insulating film (6) and the surface of the P well region (3).
) are also formed on the surface of the N-epitaxial layer (2) so as to be integrated between adjacent IGBT cells. A gate electrode (6) made of polysilicon, for example, is formed on the gate insulating film (5), and a P well region (3) is formed on the gate insulating film (5).
) and the N-shaped ivy region (4) (for example, an emitter layer (7) made of metal such as aluminum is formed so as to be electrically connected to the gate layer (6) and the emitter layer (7). J! (7) is an insulating film (by having a multilayer structure with a target in between, it has a structure in which it is electrically connected in common to all IGBT cells. In addition to the P collector layer (1) A metal collector electrode If (1) is formed on the main surface so as to be integral with all fGBT cells.

Next, the operation will be explained. N-epitaxial layer (2
) and the N-type vine region (4), the vicinity of the surface of the P-well region (3) has an n-channel MO5 structure, and a positive voltage is applied to the gate electrode (6) through the gate terminal G. By applying the gate voltage [P directly below (6)
Electrons flow from the N+ emitter region (4) to the N- epitaxial layer (2) through a channel formed near the surface of the well region (3). In the figure, ■. represents the electron current flowing in this way. On the other hand, holes, which are minority carriers, are injected from the P collector layer ω into the N″″″ epitaxial layer), a part of which recombines with the electrons and disappears, and the rest is the hole current 1 h in the figure. as the P-well region (
3). In this way, the IGBT basically operates in a bipolar manner, and the N epitaxial layer (2) has a lower on-voltage and larger current capacity than the conventional power MO5 because the conductivity increases due to the effect of conductivity modulation. It has the advantage of being able to achieve However, on the other hand, during turn-off, the decrease in hole current Ih is slower than in g□5FIT, so the operating frequency cannot be increased.

When the built-in PNP transistor is in the on state, the N- epitaxial layer (2) serving as its base region is filled with electrons and holes, which turns off the MOS) transistor and turns the N'''' This is because even if injection of electrons into the epitaxial layer is blocked, holes do not suddenly decrease because of their small mobility.

It is known that performing time-time control is effective in shortening this turn-off time. Several methods have been proposed, but they are not widely used.
This is done by irradiating it with an electron beam. Here, the electron MA trout has an acceleration energy of INhV or more. These electron beams are N-epitaxial layer (2)
Although lattice defects are generated within the lattice defect, since this n serves as a recombination center for carriers as a deep trap level, carriers can be annihilated within a short time at the time of turn-off. The high-energy electron edge has a large penetrating power, so the outside air
Even if the sample is completely in the atmosphere, there is no problem in uniformly irradiating the entire sample to be irradiated, and there is an advantage that the sample can be easily installed and recovered.

However, when irradiated with electron beam or T-ray in air,
The effects of ozone (0. It will become.

This will be explained in detail below.

Ozone is known to have a strong oxidizing power as a chemical property, and its reduction potential under acidic conditions is 2.07V, which is the second highest after fluorine when unstable substances such as free radicals and atoms are excluded, and under alkaline conditions. But it shows 1.24V. Therefore, it oxidizes all metals except gold and platinum and reacts with many other elements.

Various types of ozone decomposition reactions are known at firing ranges.
For example, depending on the ultraviolet light, 0, +b, / (λ>
8 10 n, )−+0(”P) 〇, (' Δ
g)-(1)03+bν(λ<810 nm) →Q
(ID) + 02 (Δg)...The reaction (2) occurs.

In reaction (1), an octet base oxygen atom and a singlet excited oxygen molecule are generated, and in reaction (2), a singlet excited state oxygen atom and a singlet excited oxygen molecule are generated.

In addition to the reaction path in which ozone is generated in the presence of an electron beam, Q2 +eleatron snsrgy →0 (”
P) +OCIF> ...(3)OH+s
l*etr*n @n@rgy −*O(”D) +O
(”P) −(4)OB + el*atron
@n@rgy→Oj+...(6
) reaction ξ occurs.

In particular, reaction (5) has a high threshold energy of 12 eV (02 has very high chemical activity. It is thought that it will become dominant in the presence of a high-energy electron beam as shown in Figure 4). nru.

The active ozone and active oxygen generated secondarily in this way
Figure 5 shows the results of examining the influence on i. 75 in advance
A Si substrate on which an oxide film was formed was exposed to heat in the air.
e V (7) Electron beam I X l g14~I X
Changes after irradiation at 10”m/r4 with positron
This is an evaluation using extinction property. Po5itro
The details of the n reduction method are described in, for example, "Monthly fQNI (S=Ion Science and Technology=July 1988 issue").Here, only the main points of FIG. 5 will be explained.

The vertical axis is S-param@*sr, and raw Si is approximately 0
．． It shows the value of 585. At the Sin, /Si interface, a value lower than this is shown. The horizontal axis is P-sit injected into the sample.
It is the acceleration energy of rom and reflects the parameters in the depth direction. Po5 from measurement data of unirradiated sample
When the acceleration energy of itr@n is 11KsV, S-
The value of piram@cer decreases the most, but it gives information on the interface of the SJO film with a thickness of n of 750. As the electron beam irradiation dose increases, C is 5-par.
It can be seen that the 5iQ film is growing from the fact that the point at which afflII&sr has decreased the most has moved to the higher energy side.

Next, to investigate the effect on the electrical characteristics of the device,
The same IGBT was irradiated with an electron beam under the same conditions, and the change in Vth was compared between the case in air and the case in vacuum related to the invention described later, as shown in FIG. From the figure, it can be seen that the Vtk of the sample irradiated in vacuum is lower overall. If this difference is due to active ozone or active oxygen, then the active species may be
There is a possibility that it may penetrate to the interface and form an interfacial unit.
Ru.

[Problem to be solved by the invention]

In this way, when electron beams or gamma rays are irradiated in the air, the effects of ozone (Os) and active oxygen atoms, which are generated as a result of collisions and reactions with oxygen molecules in the air, on the irradiated sample are There was a problem that it led to deterioration of characteristics or unstable factors in performing lifetime control.This invention was made to solve the above problems. The purpose is to prevent active ozone, active oxygen, and other active forms generated from the air from affecting the device.

[Means to solve the problem]

A method for manufacturing a semiconductor device according to the present invention includes placing a semiconductor device having a plurality of main electrodes and at least one control electric field in a vacuum or an inert gas atmosphere, and irradiating the semiconductor device with high-energy electron beams or gamma rays in that state. This is how it was done.

[Effect]

In this invention, the introduction of a vacuum or an inert gas atmosphere acts to insulate the semiconductor device from the active ozone, active oxygen, etc. generated as a by-product during irradiation with electron beams and γ-rays without contacting the semiconductor device. Electron beams and gamma rays only have the effect of forming lattice defects within the semiconductor device.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

In Figure 1, (g) is a semiconductor device, (2) is a support stand for this semiconductor device US, (7) is a chamber for processing the semiconductor device α0, and (Foundation) is an exhaust gas inside chamber 4. 4 is an irradiation window such as Mylar, - is a vacuum area, and ■ is a high-energy electric wire. #f The chemically active species generated in the outside air by the irradiation of the edge member are transferred to the vacuum region (transfer).
Since it cannot penetrate into the semiconductor device, there is no need to worry about oxidizing the surface of the semiconductor device or entering the inside and introducing new units.

FIG. 2 is a diagram showing another embodiment of the invention.

In the figure, (b) is an air supply port, - is an inert gas, and (2) is an exhaust port. Chemically active species generated in the outside air by electron @SO irradiation cannot enter the inert gas region, and no chemically active species are generated within the inert gas region. There is no need to worry about the surface of the device [phase] being oxidized or new units being introduced into the interior.

FIG. 8 is a diagram showing still another embodiment of the present invention.

In the figure, (2) is a conductive thick film material, and - is a vacuum region or an inert gas filled region. In this case, the semiconductor device (transfer) is sealed in advance with a conductive thick film material (2).

The subsequent steps are basically the same as the first method described above, and the simplicity of process work, which is one of the advantages of lifetime control using electron beams, is the same.

The electrical characteristics of the semiconductor device formed by these methods are shown in FIG. 6 in comparison with a conventional one.

〔Effect of the invention〕

As described above, according to the present invention, a semiconductor device is installed in a vacuum or an inert gas atmosphere, and a high-energy electron beam,
Or, since γ-rays are irradiated, the semiconductor device does not come into contact with the outside air affected by high-energy electron beams or γ-rays after irradiation, improving the controllability and reliability of lifetime control. A semiconductor device can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing a method for manufacturing a semiconductor device according to an embodiment of the present invention, FIG. 2 is a schematic cross-sectional view showing a method for manufacturing a semiconductor device according to another embodiment of the invention, and FIG. FIG. 4 is a schematic cross-sectional view showing a method for manufacturing a semiconductor device according to still another embodiment of the invention, FIG. 4 is a schematic cross-sectional view showing a method for manufacturing a semiconductor device according to the conventional technique, and FIG. , the secondary generated active species are 5i
Figure 6 shows the data of the influence on the surface measured using the POGF Ron extinction method. Figure 6 shows the data on the change in Vtb when an IGBT is irradiated with an electron beam in the air in the conventional example and in vacuum in the present invention. FIG. In the figure, QO is a semiconductor device, (1) is a chamber (
2) is a conductive membrane material, - is outside air, - is a vacuum, - is an inert gas, - is a vacuum region or an inert gas filled region, and the ring is a high-energy electron beam or gamma ray. Note that the same reference numerals in each figure indicate the same or equivalent parts.

Claims (1)

[Claims] A semiconductor device having a plurality of main electrodes and at least one control electrode is placed in a vacuum or an inert gas atmosphere, and is irradiated with high-energy electron beams or gamma rays in that state. Production method.