JPH06163596A - Method for formation of conductive layer of semiconductor substrate - Google Patents

Abstract

PURPOSE:To reduce thermal oxidation process extremely and to suppress poor influence to element characteristics by directly performing ion implantation of impurities into a semiconductor substrate which is manufactured by the floating zone method, eliminating a formed damage layer by alkali washing, and then performing thermal diffusion of impurities into the semiconductor substrate. CONSTITUTION:A mask oxide film 2 is formed on a semiconductor substrate 1 by thermal oxidation and a resist 3 is subjected to patterning on it. The mask oxide film 2 is etched with the resist 3 as a mask for eliminating the resist 3. Then, an impurity 4 is directly ion-implanted onto the semiconductor substrate 1 using the mask oxide film 2. Then, a damage layer 5 is eliminated by an alkali washing liquid. The entire surface is thermally oxidized and at the same time the impurity 4 is thermally diffused to the semiconductor substrate 1, thus forming a conductive layer 6 and hence eliminating formation of a buffer oxide film to absorb the damage of ion implantation and reducing possibility for poorly affecting an element such as increase in leakage current of a junction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a conductive layer on a semiconductor substrate manufactured by a floating zone method, and more particularly to improving the crystallinity of the conductive layer.

[0002]

2. Description of the Related Art Conventionally, there have been FZ (floating zone) method and CZ (Czochralski) method as methods for producing semiconductor silicon single crystals. In the FZ method, the raw material polycrystal is on the upper axis,
A method of holding a seed crystal on the lower shaft, heating and melting the contact part with a high-frequency coil, and lowering the vertical axis while rotating the seed crystal to grow a single crystal, because there is no contact with other substances A single crystal with high purity and high resistivity can be obtained.

For example, silicon produced by the FZ method
Oxygen concentration in single crystal is 10¹⁶cm ^-3CZ
Silicon single bond produced by (Czochralski) method
Oxygen concentration in crystals (10¹⁸cm^-3Value is lower than
It Therefore, in the manufacture of high withstand voltage devices, high resistivity half
Since it is necessary to use a conductor substrate, FZ (Floating
Section from a silicon single crystal produced by
It used the semiconductor substrate that was exposed.

On the other hand, the oxygen contained in the conductive layer formed on the semiconductor substrate causes a microcrystal defect such as an oxidation-induced stacking fault or a dislocation in a subsequent heat treatment,
It is considered that this may cause generation of oxygen precipitates and, as a result, adverse effects such as an increase in junction leakage current and a decrease in carrier lifetime are exerted on the device characteristics. Therefore, it is desirable that the oxygen concentration in the conductive layer is low.

A conventional method for forming a conductive layer on a semiconductor substrate will be described below with reference to the drawings. 2A to 2D are schematic process diagrams showing a conventional method for forming a conductive layer on a semiconductor substrate. In FIG. 2A, a mask oxide film 2 is formed by thermal oxidation on a silicon semiconductor substrate 1 manufactured by the FZ method, and a resist 3 is patterned on the mask oxide film 2.

Next, in FIG. 2B, the mask oxide film 2 is etched by using the resist 3 as a mask to remove the resist 3. Then, in FIG. 2C, after the buffer oxide film 20 is formed on the semiconductor substrate 1 by thermal oxidation, a desired conductive type impurity 4 is masked over the buffer oxide film 20 using the mask oxide film 2 as a mask. 1 is ion-implanted. In this case, the buffer oxide film 20 is for absorbing damage due to ion implantation. next,
In FIG. 2D, the entire surface is further thermally oxidized and the impurities 4 are thermally diffused into the semiconductor substrate 1 to form the conductive layer 60.

[0007]

In such a conventional technique, the step of forming the mask oxide film 2 (see FIG. 2).
(A)), a step of forming the buffer oxide film 20 (FIG. 2)
(C)), thermal oxidation step of thermally diffusing the impurities 4 (FIG. 2)
In a total of three steps (d)), when oxygen is taken into the surface portion forming the conductive layer 60 and a device is formed through heat treatment later, the leak current of the junction increases or the carrier lifetime is increased. The device characteristics were adversely affected by the decrease of the element.

On the other hand, oxygen in the silicon single crystal produces oxygen precipitates and minute defects inside the crystal by heat treatment, and produces a gettering effect of taking in and removing defects and impurities in the conductive layer 60. Since the semiconductor substrate 1 manufactured by the FZ method has a low oxygen concentration, this gettering effect cannot be expected. Therefore, it can be said that the larger the number of heat treatments, the higher the possibility that microcrystalline defects will occur in the conductive layer 60, that is, the possibility that the element characteristics will be adversely affected.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to reduce the thermal oxidation step until the formation of the conductive layer as much as possible and to give the device characteristics. An object of the present invention is to provide a more optimized conductive layer forming method for a semiconductor substrate while suppressing adverse effects.

[0010]

In order to achieve the above object, the present invention provides a step of directly ion-implanting an impurity of a desired conductivity type into a semiconductor substrate manufactured by a floating zone method, and forming by the ion implantation. And then thermally diffusing the impurities into the semiconductor substrate after removing the damaged layer by an alkali cleaning, the method for forming a conductive layer of a semiconductor substrate.

[0011]

In the present invention as described above, since the ions are directly implanted into the semiconductor substrate, the thermal oxidation step of forming the buffer oxide film for the ion implantation is unnecessary, and the alkali cleaning removes the damaged layer of the semiconductor substrate after the ion implantation. Remove.

[0012]

Embodiments of the present invention will now be described with reference to the drawings. In the following drawings, the same parts as those in FIG. 2 are designated by the same reference numerals, and the description thereof will be appropriately omitted. Figure 1
FIG. 3 is a process schematic view showing a method for forming a conductive layer on a semiconductor substrate according to the present invention. In FIG. 1A, a mask oxide film 2 is formed on a semiconductor substrate 1 of silicon manufactured by the FZ method by thermal oxidation, and a resist 3 is patterned on the mask oxide film 2.

Next, in FIG. 1B, the mask oxide film 2 is etched using the resist 3 as a mask to remove the resist 3. Then, impurities 4 of a desired conductivity type are directly ion-implanted into the semiconductor substrate 1 using the mask oxide film 2 as a mask.

Next, in FIG. 1 (c), the damage layer 5 due to the ion implantation is used as an alkaline cleaning solution, for example, NH ₄ O.
H + H ₂ O ₂ + H ₂ O was removed with a mixture, and HCl +
Wash with H ₂ O ₂ + H ₂ O. Then, in FIG. 1D, the entire surface is thermally oxidized and the impurities 4 are thermally diffused into the semiconductor substrate 1 to form the conductive layer 6.

According to the above steps, there is no step of forming the buffer oxide film for absorbing the damage of the ion implantation, so that the step of introducing oxygen into the surface portion forming the conductive layer 6 is performed by mask oxidation. Formation of membrane 2 (Fig. 1
(A)), a thermal oxidation step of thermally diffusing the impurities 4 (see FIG. 1).
(D)) is reduced twice in total, and when the element is formed after the heat treatment, it is less likely that the element is adversely affected such that the junction leakage current increases and the carrier lifetime decreases. can do.

[0016]

As described above, according to the present invention, impurities are directly ion-implanted into a semiconductor substrate manufactured by the floating zone method, and a damaged layer formed by ion-implantation is removed by alkali cleaning. Since it is configured to diffuse heat into the substrate, the thermal oxidation process until the conductive layer is formed can be minimized, and the adverse effect on the device characteristics can be suppressed to achieve a more optimized conductive layer forming method for a semiconductor substrate. Can be provided.

[Brief description of drawings]

FIG. 1 is a schematic process diagram showing a method for forming a conductive layer on a semiconductor substrate according to the present invention.

FIG. 2 is a process schematic view showing a conventional conductive layer forming method for a semiconductor substrate.

[Explanation of symbols]

 1 Semiconductor substrate 4 Impurity 5 Damage layer

Front page continuation (72) Inventor Toshiyuki Ueno 2-9-32 Nakamachi, Musashino-shi, Tokyo Yokogawa Electric Co., Ltd.

Claims (1)

[Claims] 1. A step of directly ion-implanting an impurity of a desired conductivity type into a semiconductor substrate manufactured by a floating zone method, and a step of removing a damaged layer formed by the ion-implantation by alkali cleaning, and then removing the impurity by the semiconductor. A method of forming a conductive layer on a semiconductor substrate, comprising: a step of thermally diffusing into the substrate.