JPH0927504A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce heavy metal contamination of a semiconductor device during a thermal processing step of semiconductor device manufacturing and to improve yield and reliability of the semiconductor device by suppressing leak current increase of junction and gate withstand voltage degradation. SOLUTION: Dummy gettering silicon substrates 15 having a big gettering effect are arranged between each silicon substrate 14, which is a semiconductor device to be made into a product, on a quartz boat 13. The gettering silicon substrates 15 are arranged in front and at the back of the silicon substrates, and after that a thermal processing step is performed. The step cam reduce heavy metal contamination of the semiconductor device and can improve yield and reliability of the semiconductor device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly to prevention of contamination in a heat treatment furnace in the process of manufacturing a semiconductor device.

[0002]

2. Description of the Related Art In a method of manufacturing a semiconductor device, when a semiconductor substrate is contaminated with heavy metal, the leak electrode at the junction increases, the junction breakdown voltage is insufficient, and the gate insulating film withstand voltage is insufficient. It causes defects and poor reliability. Therefore, in the manufacturing method of the semiconductor device, the cleanliness of the manufacturing equipment and the cleanliness of the manufacturing environment are important issues, and the semiconductor device manufacturing personnel and the semiconductor device manufacturing personnel aim to improve the cleanliness. Many efforts have been made. However, it is still inadequate even if the apparatus and environment of the current cleanliness are used, so that a method of giving a gettering action of heavy metal to the silicon substrate itself which becomes a semiconductor device is taken. As this gettering method, BMD (Bulk Micro De
IG (Intrinsic Ge)
tering) substrate to getter the heavy metal into the BMD, or the EG method (Extrinsic) to getter the heavy metal by forming a layer on the back surface of the silicon substrate in which high concentration phosphorus is diffused to generate dislocations.
Gettering method).

In these gettering methods, heavy metals mixed in the semiconductor substrate during the heat treatment process for manufacturing the semiconductor device are trapped in the inside of the silicon substrate separated from the surface portion of the silicon substrate, which is the operating region of the semiconductor device, or on the back surface of the silicon substrate. It is intended not to affect the characteristics of the semiconductor device. In manufacturing a semiconductor device, there are many heat treatment steps such as oxidation, impurity diffusion, and annealing for activation after ion implantation, and the gettering effect described above decreases with each heat treatment step. .

[0004]

As described above, in the conventional gettering method, there is a problem that the gettering effect decreases with each heat treatment process. Therefore,
INDUSTRIAL APPLICABILITY The present invention makes it possible to reduce the heavy metal contamination of the semiconductor device by reducing the heavy metal contamination in the semiconductor substrate placed in the heat treatment furnace in the heat treatment process in which the heavy metal contamination occurs in the semiconductor substrate. Accordingly, it is an object of the present invention to provide a method for manufacturing a semiconductor device capable of sustaining the above gettering effect.

[0005]

A method of manufacturing a semiconductor device according to the present invention proposes to reduce heavy metal contamination of a semiconductor device. In a heat treatment step in manufacturing a semiconductor device, a semiconductor device is mounted on a boat arranged in a heat treatment furnace. In addition, after the gettering silicon substrate is arranged before and after the product silicon substrate and the product silicon substrate, a heat treatment process is performed. Further, in a heat treatment step in the manufacture of a semiconductor device, a product silicon substrate and a gettering silicon substrate are alternately arranged on a boat arranged in a heat treatment furnace, and the two kinds of silicon substrates arranged alternately are disposed before and after the silicon substrate. After arranging the gettering silicon substrates, a heat treatment process is performed.

Further, as a gettering silicon substrate, an intrinsic getter substrate in which defects are formed in the silicon substrate, an extrinsic getter substrate in which dislocations are formed by applying processing strain to the surface of the silicon substrate, or a surface of the silicon substrate is often used. An extrinsic getter substrate on which a crystalline silicon film is formed is used as a gettering silicon substrate.

[0007]

According to the gist of the present invention, in a heat treatment process in which a heavy metal is mixed in a semiconductor substrate, a dummy silicon substrate having a large gettering effect is arranged around the silicon substrate of the product and the heat treatment is performed to obtain a semiconductor product. It is a method of manufacturing a semiconductor device that reduces heavy metal contamination of the device. Heavy metal contamination of semiconductor devices in the heat treatment furnace is caused by heavy metal substances contained in the reaction gas or carrier gas introduced into the heat treatment furnace,
Air near the outlet of the gas in the heat treatment furnace diffuses into the heat treatment furnace (so-called entrained air), the heavy metal substances contained in the air, the material of the heater of the heat treatment furnace (generally heavy metal substance) evaporates, and this substance Are diffused on the core tube wall, and further, heavy metal substances that evaporate from the core tube wall and mix into the atmosphere gas in the furnace, or heavy metal substances that adhere to the silicon substrate of the product before entering the heat treatment furnace are heat-treated on the semiconductor substrate. Due to being diffused.

Therefore, it is possible to take measures to prevent the above-mentioned heavy metal substances from entering the heat treatment furnace. However, the measures currently taken are not sufficient, and the characteristics of semiconductor devices are deteriorated due to heavy metal contamination. Therefore, the concentration of the heavy metal substance in the atmosphere of the core tube is reduced to suppress the diffusion amount of the heavy metal substance into the semiconductor substrate. This method places a dummy silicon substrate with a large gettering effect on the gas inlet side for heavy metal substances in the gas introduced into the core tube, and a getter on the gas discharge side for heavy metal substances in the entrained air. It is possible to reduce the concentration of heavy metal substances in the atmosphere of the core tube by arranging a dummy silicon substrate with a large ring effect and increasing the number of the above dummy silicon substrates for heavy metal substances coming in from the core tube wall. I chose

For heavy metal substances attached to the silicon substrate of the product, dummy silicon substrates having a large gettering effect are arranged on both sides of the silicon substrate, and the vaporized heavy metal substances are used as dummy silicon. By diffusing it into the substrate and reducing the concentration of heavy metal substances in the atmosphere, it is possible to reduce the heavy metal contamination of the silicon substrate that is the product.

[0010]

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

Embodiment 1 FIG. 1 is a schematic sectional view showing a state in which a silicon substrate 2 for oxidation treatment is inserted in an oxidation furnace 1 as an example of a heat treatment process of a semiconductor device. This oxidation furnace is an example of a simple oxidation furnace in which a heater 11 for heating and an opposite side of a gas introduction port are composed of an open type quartz furnace core tube 12 and a quartz boat 13. Silicon substrate 2 in oxidation furnace 1
In order to oxidize, the silicon substrate 2 is arranged in the quartz boat 13 and then inserted into the oxidation furnace. It is assumed that dummy gettering silicon substrates 15 having a large gettering effect are arranged.

As an example of this arrangement, ten dummy gettering silicon substrates 15 are continuously arranged in a portion on the gas inlet side of a quartz boat, and subsequently 100 silicon substrates 14 of a semiconductor device to be a product are arranged. 10 pieces of dummy gettering silicon substrates 15 are arranged continuously after that. When the silicon substrates 2 are arranged in the quartz boat 13 and oxidized in this manner, the heavy metal substance in the gas introduced into the quartz furnace tube 12 is arranged on the gas inlet side and is a dummy gettering silicon substrate having a large gettering effect. 15, the concentration of the heavy metal substance in the atmosphere near the region where the silicon substrate 14 of the product is arranged is reduced, and the heavy metal substance diffused to the semiconductor substrate is reduced.

Heavy metal substances in the entrained air are also diffused into the dummy gettering silicon substrate 15 arranged on the gas outlet side, and the heavy metal substances in the vicinity of the arranged region of the silicon substrate 14 of the semiconductor device to be manufactured are disposed. The concentration is reduced, and heavy metal contamination of the semiconductor device is reduced. Further, the concentration of the heavy metal substance mixed in the atmosphere in the furnace from the core tube wall is diffused to the gettering silicon substrates 15 arranged on both sides of the silicon substrate 14 of the product, whereby the concentration of the heavy metal substance in the atmosphere is lowered, and the semiconductor device is reduced. The heavy metal pollution of is reduced.

Here, as the dummy gettering silicon substrate, the IG substrate and the EG substrate (extrinsic getter substrate) described in the prior art are used.
In the former method of manufacturing an IG substrate, a normal silicon substrate is first used, heat treatment is performed at 700 to 800 ° C. for about 3 hours, and then heat treatment at about 1000 ° C. is performed for about 15 hours to produce an IG substrate. By doing so, a BMD of 5E9 / cm ³ or more is formed in the silicon substrate.
In addition, the latter method of manufacturing the EG substrate is one in which one surface or both surfaces of a normal silicon substrate is mechanically damaged by sandblasting or the like, or is produced by scanning with a laser beam to give thermal distortion. Generate dislocations. Furthermore, the latter method of manufacturing an EG substrate is such that polycrystalline silicon of about 500 nm is deposited on a normal silicon substrate by LPCVD.
It is manufactured by depositing a film having a certain thickness.

Embodiment 2 FIG. 2 is a schematic sectional view showing a state in which a silicon substrate 2 for oxidation treatment is inserted in an oxidation furnace 1 as an example of a heat treatment process for a semiconductor device. In the second embodiment, the silicon substrate 2
When arranging the wafers on the quartz boat 13, a dummy gettering silicon substrate 15 is provided before and after the silicon substrate 14 of the product.
And the dummy gettering silicon substrates 15 are arranged between the silicon substrates 14 of the product at the same time.
, And the product silicon substrate 14 and the gettering silicon substrate 15 are alternately arranged.

As an example of this arrangement, ten dummy gettering silicon substrates 15 are continuously arranged in a portion on the gas introduction port side of a quartz boat, and then the silicon substrate 14 of a semiconductor device to be a product is 50. One sheet and 49 gettering silicon substrates are alternately arranged, and subsequently 10 dummy gettering silicon substrates 15 are continuously arranged. When the silicon substrates 2 are arranged in the quartz boat 12 and subjected to heat treatment in this manner, the effect of reducing the concentration of heavy metal substances in the atmosphere in the solid heat treatment furnace in Example 1 is further increased, and heavy metal contamination of the semiconductor device is further enhanced. Not only is it reduced, but the contamination of the semiconductor device by the heavy metal substances attached to the silicon substrate 14 of the product is also reduced. Further, in the above arrangement, it is possible to reduce the problem that these impurities evaporated from the high-concentration boron or phosphorus impurity layer of the semiconductor substrate diffuse to the other surface of the silicon substrate of the product and the characteristics of the semiconductor device change.

In the above-described first and second embodiments, the number of gettering silicon substrates arranged before and after the product silicon substrate, the number of product silicon substrates, and the portion in which the product silicon substrate and the gettering silicon substrate are alternately arranged. The number of sheets can be appropriately changed within the scope of the technical idea of the present invention. In the oxidation process described in the first and second embodiments, the gettering silicon substrate is oxidized, so that not only the BMD portion and the dislocation portion are trapped in the gettering silicon substrate as a trap portion for the heavy metal substance. It is also trapped in the oxide film. In particular, a metal such as Fe having an enthalpy of oxide formation larger than Si is incorporated in the oxide film more than in the silicon substrate in the oxidation step. Furthermore, in the above-described first and second embodiments, the oxidation process is taken up as the heat treatment process, and only the arrangement of the product silicon substrate and the dummy gettering silicon substrate in the oxidation furnace is described, but other heat treatments are performed. It is obvious that the present invention can be applied to the process.

[0018]

As is apparent from the above description, in the heat treatment step of the semiconductor device, the silicon substrate of the product and the gettering silicon substrate are arranged on the quartz boat as described above and the heat treatment is performed. The heavy metal contamination of the semiconductor device can be reduced, and the getter effect can be maintained for a longer period in the manufacture of a normal semiconductor device using a getter substrate. Therefore, the leakage current at the junction of the semiconductor device increases. And gate breakdown voltage deterioration can be suppressed, and the production yield of semiconductor devices can be improved.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a semiconductor device manufacturing method to which the present invention is applied, in a state in which a silicon substrate for oxidation treatment is inserted in an oxidation furnace as an example of a heat treatment process of the semiconductor device. .

FIG. 2 is a schematic cross-sectional view of a semiconductor device manufacturing method to which the present invention is applied, in a state in which a silicon substrate for an oxidation treatment is inserted into an oxidation furnace as an example of a heat treatment process of the semiconductor device. .

[Explanation of symbols]

 1 Oxidation Furnace 2 Silicon Substrate 11 Heater 12 Quartz Furnace Tube 13 Quartz Boat 14 Product Silicon Substrate 15 Dummy Gettering Silicon Substrate

Claims (5)

[Claims] 1. In a heat treatment process in manufacturing a semiconductor device, a product silicon substrate and a gettering silicon substrate before and after the product silicon substrate are arranged on a boat placed in a heat treatment furnace, and then the heat treatment process is performed. A method of manufacturing a semiconductor device, comprising: 2. In a heat treatment step in the manufacture of a semiconductor device, a product silicon substrate and a gettering silicon substrate are alternately arranged on a boat arranged in a heat treatment furnace, and the product silicon substrates are alternately arranged. A method of manufacturing a semiconductor device, comprising: arranging gettering silicon substrates before and after the gettering silicon substrate, and then performing a heat treatment process. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the intrinsic getter substrate having a defect formed in the silicon substrate is a gettering silicon substrate. 4. The gettering silicon substrate is an extrinsic getter substrate in which dislocations are formed by applying processing strain to the surface of the silicon substrate.
A method for manufacturing a semiconductor device according to claim 2. 5. The method of manufacturing a semiconductor device according to claim 1, wherein an extrinsic getter substrate having a polycrystalline silicon film formed on a surface of the silicon substrate is a gettering silicon substrate.