JPS61220339A - Control of characteristics of semiconductor material - Google Patents

Abstract

PURPOSE:To control space distribution of specific resistivity and conductive types by introducing an energy level created by a defect into a substrate crystal by local heat treatment. CONSTITUTION:A semiconductor substrate 2 is partially heated by a local heating source 1 such as a laser beam to create a defect in the heated region and the energy level created by the defect is introduced into the substrate crys tal. The silicon substrate is locally melted by the laser beam to create an oxy gen donor. The oxygen donor is one of the defects which form a donor potential in a band gap of silicon. A change of a specific resistivity is created by the defect. The specific resistivity is in inverse proportion to the donor concentra tion. As the concentration increases linearly in accordance with the increase of the laser power and the change of the oxygen donor concentration against the laser power is monotonous, it is easily controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for controlling semiconductor material properties by controlling resistivity and conductivity type of a semiconductor.

[Technical background of the invention and its problems]

The resistivity and conductivity type, which are the basic properties of semiconductors, are determined by the energy level within the band gap.Normally, donor impurities (for example, in silicon, group V elements) or accelerator impurities (also group The specific resistance and conduction type are controlled by using the energy level generated by the addition of (elements). In semiconductor devices such as LSI, resistivity and
It is necessary to be able to spatially and precisely control the conduction type, and element fabrication technology involves precisely applying the above impurities to the substrate.
It is required that it can be added locally. Conventionally, diffusion or ion implantation has been used as a method for introducing a cyene energy level into a substrate by locally heat-treating impurities. Although these methods have good controllability, they include a step of heat-treating the entire wafer at high temperature, which causes deterioration of material properties, and a complicated process including photolithography to form the surface coating fQ5 for localized impurity addition. However, since this method requires large-scale equipment, it has drawbacks such as high processing costs.

In order to eliminate the drawbacks of the above-mentioned methods, the following two methods have been proposed that utilize energy levels due to defects in silicon without using gold as a donor or acceptor impurity to introduce energy levels. In these methods, oxygen in silicon does not form an energy level by itself, but when multiple oxygen in silicon aggregates and forms crystal defects by heat treatment at around 450°C, it becomes a donor (
It takes advantage of the property of being an oxygen donor).

The first method is to periodically change the oxygen concentration in the p-type side-raised crystal depending on the growth conditions, and then perform heat treatment to generate oxygen donors. This is a region IRP type control. In this method, the oxygen concentration distribution is dominated by phenomena within the melt during crystal growth.

The controllability of the spatial distribution of oxygen donor concentration is poor, making it impossible to form fine semiconductor devices. Another proposed method is to implant oxygen ions into a silicon substrate and then perform heat treatment to generate oxygen donors in the ion implantation region. Although this method has good controllability over the spatial distribution of the oxygen donor concentration, it is no different from the conventional method in that it uses a large-scale ion implantation device, and when the amount of oxygen ion implantation is increased, defects may occur due to heat treatment. occurs, so the maximum donor concentration that can be obtained is 1015/cm'' and low resistance cannot be obtained.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and it is possible to improve the resistivity and specific resistance of semiconductors without using so-called donor or accelerator impurities.
The purpose of the present invention is to provide a method for controlling semiconductor material properties that can locally control conductivity type.

[Embodiments of the invention]

In the present invention, the normal lattice position Kl> does not form an energy level or does form an energy level K<or does an impurity form an energy level at a defect position, or does not form an energy level by itself or does it form an energy level. Impurities and point defects, which are difficult to form but only form energy levels when they become complex and become defects, are used to introduce energy levels.

In other words, the energy level caused by impurities occupying defect positions, or defects that are a combination of impurities and point defects (hereinafter referred to simply as defects), is reduced by local heat treatment (
(including cases involving melting) into the substrate crystal.
Therefore, the spatial distribution of resistivity and conduction type can be controlled.

FIG. 1 is a diagram illustrating the introduction of energy levels into a semiconductor substrate using a local heating source according to the present invention. By partially heating the semiconductor substrate 2 with a local heating source 1 such as Raded light, a defect is generated in the heated region and its energy level is introduced.

Hereinafter, the present invention will be explained based on Examples.

Figure 2 shows that by locally melting the silicon substrate with Rade light, oxygen donors, which are one of the defects that form donor levels in the band gap of silicon, are generated, and the resistivity changes due to this. This is an example of measurement using the resistance method.

The substrate is an n-type Cz wafer with a specific resistance of 0.830.

The laser light source is Nd:YAG radar multiplied light with a wavelength of 0.53 μm, and the irradiation conditions are: base frequency: 4 kHz, scanning speed: 10 vm/S, laser power: 0.3 W.
(Fig. 0)) In the Raded light irradiation area 3, the specific resistance is 0.
It has decreased to 090·α. Since resistivity and Donna concentration are in an inversely proportional relationship, it can be seen that Cydona concentration increases due to Raded light irradiation. The fact that the generated donor is an oxygen donor indicates the unique thermal behavior of oxygen donors, in which the donor disappears after short-time heat treatment at 650°C and is generated after long-time heat treatment at 450°C. This can be easily confirmed.

FIG. 3 shows the relationship between the oxygen donor concentration and the laser power when the laser power and power are changed under the above irradiation conditions. ), oxygen donor silicon begins to melt o, i
It occurs near JW, and its concentration increases linearly as the lede power increases.

As described above, since the oxygen donor concentration changes monotonically with respect to radar power, it is easy to control it. At Rede power〇, 30 W, oxygen donor concentration/I'i1.15
X 10 10n", the maximum donor concentration obtained by the oxygen ion implantation described above is 1.OX 10"7c
m'' is also higher by more than two orders of magnitude, and a low resistance region can be formed according to the present invention.The above is a case where an n-type silicon substrate is used, but a p-type silicon substrate can also be used with silicon nitride on the surface. It has been confirmed that the same effect can be achieved even when there is a thin film such as a silicon oxide film or a silicon oxide film.A similar effect can be obtained by changing the wavelength of the Raded light or by electron beam heating.

In the above example, the defect is an oxygen donor in silicon, but as mentioned at the beginning, other defects in silicon, such as acceptors, or defects in other semiconductor materials can also occur in the band gap. It goes without saying that the pottery method is effective for defects that form energy levels.
Further, although the embodiment deals with a case of local heat treatment accompanied by melting, the present method can be similarly applied to cases where melting is not involved.

〔Effect of the invention〕

As described above, according to the present invention, the spatial distribution of the donor or acceptor concentration caused by the energy level of defects can be controlled by simply performing local heat treatment on the semiconductor substrate. This is unnecessary, and since the substrate is not held at a high temperature for addition, there are great advantages such as no deterioration of the substrate properties. Furthermore, the maximum concentration of oxygen donors obtained by the present invention is more than two orders of magnitude higher than the maximum concentration obtained by the oxygen ion implantation described at the beginning. According to the present invention, which has the characteristic of widening the concentration control range, it is possible to form a pn junction as well as a low resistance layer for ohmic contact or a high resistance layer for element isolation.

[Brief explanation of drawings]

FIG. 1 is a block diagram for explaining the introduction of energy levels into a semiconductor substrate using a local heating source according to the present invention, and FIG. 2 is a diagram showing the ratio due to oxygen donors generated by laser beam irradiation according to an embodiment of the present invention. FIG. 3 is a diagram illustrating an example of foot measurement using the resistance method in which the spread of resistance change is measured, and FIG. DESCRIPTION OF SYMBOLS 1...Local heat source, 2...Semiconductor substrate, 3...Raed light irradiation area. Applicant's agent Patent attorney Takehiko Suzue Figure 2

Claims (3)

[Claims] (1) Generating defects that form energy levels in the band gap of the semiconductor by local heat treatment of the semiconductor substrate, and controlling the spatial distribution of donor or acceptor concentrations corresponding to the energy levels of the defects. A method for controlling semiconductor material properties characterized by: (2) A method for controlling semiconductor material properties according to claim 1, wherein the local heat treatment is performed under conditions that cause melting of the semiconductor substrate. (3) Claim 2 in which the defect is an oxygen donor in a silicon crystal, and the local heat treatment is performed using a laser beam.
Method for controlling semiconductor material properties as described in .