JPH09283456A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to form a doped layer uniformly with good controllability by exposing a silicon semiconductor to a substance containing phosphorous or boron at a temperature which is at least a melting point of the substance and at most a specified temperature to attach the substance to the silicon semiconductor, and then heating the silicon semiconductor to dope the substance in the silicon semiconductor. SOLUTION: After washing the surface of a silicon semiconductor 4, the semiconductor is exposed to a substance containing a dopant such as phosphorus and boron at a temperature which is at least a melting point of the substance and at most 400 deg.C to attach the substance to the surface of the silicon semiconductor in a phosphorus processing chamber 6 and a boron processing chamber 7. After that, the silicon semiconductor 4 is heated in a heat-treatment chamber 8 and then the dopant is doped in a shallow region of the semiconductor 4 with the substance attached to the semiconductor as a source of diffusion. By this method, a doping layer can be formed uniformly in the semiconductor 4 with good controllability without damaging the semiconductor 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a high-performance semiconductor device, and more particularly to forming a uniform and well-controlled doping layer in a shallow region of a silicon semiconductor surface without damaging it. And a method for doping a silicon semiconductor that can be used.

[0002]

2. Description of the Related Art Conventionally, in order to form a doping layer in a shallow region of a silicon surface, for example, one of the following doping methods has been used. (1) A method of implanting ions of a dopant such as phosphorus (P) or boron (B) into a shallow region of the silicon surface, and then heating. (2) A method in which a film containing a dopant such as P or B is deposited on the silicon surface and then heated. (3) A method of exposing silicon to a gas containing P and B at a high temperature of about 800 to 1000 ° C. (4) A method of heating the silicon surface by laser irradiation while exposing the silicon surface to a gas containing a dopant such as P or B. Alternatively, (5) a method of exposing the silicon surface to plasma containing a dopant such as P or B. However, each of the conventional doping methods has the following problems. In the above method (1), when the dopant is ion-implanted into silicon, the dopant is deeply diffused in the subsequent heating due to crystal defects occurring around the doping layer in the silicon. In the above method (2), when a film containing a dopant such as P or B is deposited on silicon and a doping layer is formed in the silicon by a subsequent heat treatment, the doping concentration should be the same as the silicon surface treatment state performed immediately before. Since it depends strongly and its control is difficult, the controllability of the formed doping layer deteriorates. In the method of (3) above, silicon is added in the range of 800 to 100.
Even when exposed to a gas containing P or B at a high temperature of about 0 ° C., the doping concentration strongly depends on the silicon surface treatment state performed immediately before and its control is difficult, and therefore the controllability of the formed doping layer becomes poor. . In the above method (4), the intensity of the laser light to be applied is not spatially constant,
In addition, when scanning laser light, it is unavoidable that overlapping portions and non-overlapping portions occur,
Unevenness occurs in the dopant layer. In the above method (5),
Non-uniformity of plasma irradiation on a silicon wafer and damage to the silicon wafer due to plasma irradiation are essentially inevitable. In any of the conventional methods, it was not possible to uniformly form a doping layer in a shallow region of the silicon surface with good controllability. Also, these conventional methods
Since all of them require expensive equipment for vacuum exhaust or heating to a high temperature of 500 ° C. or more during doping, this has been a factor of increasing the manufacturing cost of the semiconductor device. Further, since the conventional doping process is a completely different process from the surface cleaning process, there is a problem that it is difficult to integrate the doping device and the surface cleaning device.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art, and to provide a doping method in a shallow region of the surface of a silicon semiconductor without causing damage to the silicon semiconductor and to make the doping layer uniform. An object of the present invention is to provide a high-performance and inexpensive semiconductor device manufacturing method that can be formed with good controllability.

[0004]

In order to achieve the above-mentioned object of the present invention, the present invention has a constitution as set forth in the claims. That is, according to the present invention, as described in claim 1, immediately after cleaning the surface of the silicon semiconductor to expose the clean surface, a substance containing phosphorus or boron is added.
A method of manufacturing a semiconductor device includes a step of exposing the semiconductor to a temperature of not less than a melting point of the substance and not more than 400 ° C. to deposit the substance, and then heating the semiconductor to dope the substance. As described above, according to the doping method of the present invention, as described in claim 1, immediately after cleaning the surface of the silicon semiconductor, a substance containing a dopant such as P or B is added to the substance at a temperature not lower than the melting point and not higher than 400 ° C. Is a simple method in which a substance containing a dopant is deposited on the surface of a silicon semiconductor by exposure with, and the silicon semiconductor is heated, and the dopant is introduced into a shallow region of the silicon semiconductor by using the deposit as a diffusion source. Moreover, a phosphorus (P) or boron (B) doping layer can be uniformly formed in a shallow region of the surface of a large-diameter silicon wafer with good controllability without damaging the silicon semiconductor. Therefore, an inexpensive semiconductor device can be easily realized.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION A method of manufacturing a semiconductor device according to the present invention is such that a dopant [phosphorus (P) or boron (B)] contained in a chemical solution or its vapor is adhered to the surface of a silicon semiconductor and then heat-treated. , A doping method for diffusing into a shallow portion (region) inside silicon, and the P doping method will be specifically described below. First, a silicon wafer was washed and oxidized, and further immersed in a hydrofluoric acid aqueous solution and pure water to remove the oxide film on the silicon surface. Subsequently, the wafer was dipped in a phosphoric acid aqueous solution at 155 ° C. for 10 minutes to attach phosphorus to the wafer surface and washed with water for 1 minute. This was heated at 1000 ° C. in oxygen for 1-3 minutes. As a result, it was possible to form a phosphorus doping layer having a thickness of 10 to 20 nm in silicon. The sheet resistance value of the phosphorus-doped layer is
For heating for 1, 2, 3 minutes, 6156, 4186,
3212Ω, and a phosphorus doping layer was obtained with a uniformity of 2 to 3% over the entire wafer having a diameter of 150 mm.
The average concentration of the phosphorus doped layer is about 10 ¹⁹ / c.
It became m ³ . Therefore, under these heating conditions,
Not all the phosphorus deposited on the silicon surface has diffused into the silicon. In other words, if the heating is performed at a higher temperature for a long time, a room for supplying a larger amount of phosphorus into the silicon remains in the phosphorus adhesion layer. The phosphorus adhesion layer could be easily removed by immersing the wafer in a hydrofluoric acid aqueous solution after heating.
The above results show that phosphorus attached to the wafer from the phosphoric acid aqueous solution is effective as a diffusion source of the shallow doping layer into silicon. When doping with boron (B), the phosphoric acid aqueous solution may be replaced with boric acid or its aqueous solution. Further, when the etching of silicon by these acids becomes a problem, hydrogen peroxide solution may be added to form a natural oxide film on the silicon surface which is generated by the strong oxidizing action of the hydrogen peroxide solution. By doing so, phosphorus or boron is taken into the natural oxide film, and a dopant layer similar to the above is formed,
This is the source of diffusion. Further, ozone (O ₃ ) gas may be bubbled instead of the above hydrogen peroxide solution. When an aqueous solution of boric acid or a mixed solution of boric acid and hydrogen peroxide is used, the step of attaching boron to the silicon surface can be performed at a temperature of about 100 to 150 ° C. In these examples, the chemical used was a chemical solution,
It may be vapor of this chemical solution. For example, when boric acid itself is heated and boron-containing water vapor released when boric acid is dehydrated is used to adhere boron to the silicon surface, the adhesion step should be performed at about 200 to 400 ° C. You can In the above example, an example of an experiment in which phosphorus or boron was adhered to the silicon surface and then heated in oxygen was introduced.However, a silicon oxide film or the like was deposited before heating, and a non-oxidizing atmosphere was used. You may go in. If the doping amount is small, the deposition of the silicon oxide film or the like can be omitted. The core steps of the semiconductor device manufacturing method of the present invention are summarized in FIG. In the present invention, immediately after the silicon semiconductor cleaning step, the surface of the silicon can be kept constant because phosphorus or boron is adhered to the surface of the silicon semiconductor by treating with a chemical solution or its vapor at a low temperature of 400 ° C. or lower. . Further, the dopant diffusion process into the silicon semiconductor is not a process of damaging the semiconductor such as ion implantation or plasma irradiation, but a process of only heat treatment. Therefore, problems such as accelerated diffusion and defect generation due to damage do not occur. Since this dopant attachment step utilizes the physical adsorption phenomenon of the dopant on the semiconductor surface, the dopant attachment amount hardly depends on the temperature. Therefore, the temperature control in the doping process may be extremely rough, and if the evaporation of phosphorus or boron from the silicon semiconductor surface is substantially negligible at 400 ° C. or lower, the substance containing the dopant may be in a liquid state or a gas state. So long as it is possible, any temperature is possible. Further, the diffusion source is attached to the surface of the silicon semiconductor by immersing the chemical solution or exposing it to the chemical solution vapor, and does not involve uneven beam irradiation or scanning thereof. Therefore, on the surface of a large-diameter silicon wafer,
The diffusion source can be easily attached uniformly.

FIG. 2 shows the structure of an example of a device in which the doping process and the cleaning process are integrated in the method for manufacturing a semiconductor device of the present invention. The reason why both are integrated is that the cleanliness of the silicon surface is extremely important in order to carry out the doping deposition with excellent uniformity and controllability. The dopant deposition process according to the present invention is very similar to the cleaning process, and the difference is that the liquid (vapor) exposed to the silicon surface is a dopant-containing liquid (vapor) or a cleaning liquid (vapor). Therefore, the devices that perform both processes can be integrated without a special intermediary device, and continuous processing becomes possible. The integrated device has two parts (1 ... Inlet cassette chamber, 2 ... Exit cassette chamber) in which wafer cassettes are placed, and four parts (5 ... Hydrofluoric acid treatment chamber) in which semiconductor wafers (silicon wafers) 4 are processed. , 6 ... Phosphorus processing chamber, 7 ... Boron processing chamber, 8 ...
Heat treatment room), and the part between each room,
A robot arm 3 for wafer movement is provided and filled with a non-oxidizing gas. The semiconductor wafer 4 taken out from the inlet cassette chamber 1 by the robot arm 3 is subjected to a hydrofluoric acid treatment chamber 5 in which the surface of the silicon wafer is treated with an aqueous solution of hydrofluoric acid or its vapor to be washed with water to expose the cleaned surface. Then, the robot arm 3
Is moved to the phosphorus processing chamber 6 or the boron processing chamber 7. In the phosphorus processing chamber 6, the surface of the silicon wafer is treated with an aqueous solution of phosphoric acid or its vapor, phosphorus is attached to the surface of the silicon wafer, and the surface is washed with water. Boron processing room 7
Then, the surface of the silicon wafer is treated with an aqueous solution of boric acid or its vapor, boron is attached to the surface of the silicon wafer and washed with water. Then, the silicon wafer enters the heat treatment chamber by the robot arm 3 and is heated in a predetermined gas such as oxygen or nitrogen. After heating, it is stored in the outlet cassette chamber 2 and cooled. As described above, in the present invention, the device for adhering the dopant to the surface of the silicon wafer and the device for diffusing the dopant into the silicon wafer can be easily integrated. In addition, since a toxic and expensive gas and high voltage are not required at the time of depositing the dopant on the surface of the silicon wafer, it is possible to achieve safety of the working environment and cost reduction of the process at the same time.
As described above, according to the present invention, the adhesion layer of the dopant used as the diffusion source can be stably formed on the surface of the silicon wafer, and further, the damage during the addition of the dopant inside the silicon does not occur. Therefore, the shallow dopant layer can be uniformly and easily formed in the silicon wafer by the subsequent heat treatment.

[0007]

As described in detail above, according to the method for manufacturing a semiconductor device of the present invention, the adhesion layer of the dopant used as the diffusion source can be stably formed on the surface of the silicon semiconductor, and the silicon semiconductor can be stably formed. Since no damage occurs when the dopant is added to the inside, a shallow dopant layer can be formed uniformly, with good controllability, and easily, for example, in a large-diameter silicon wafer by the subsequent heat treatment. effective.

[Brief description of drawings]

FIG. 1 is a diagram showing basic steps of a method for manufacturing a semiconductor device, which is exemplified in an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an example of the configuration of a semiconductor doping apparatus exemplified in the embodiment of the present invention.

[Explanation of symbols]

 1 ... Inlet cassette chamber 2 ... Exit cassette chamber 3 ... Robot arm 4 ... Semiconductor wafer (silicon wafer) 5 ... Hydrofluoric acid treatment chamber 6 ... Phosphorus treatment chamber 7 ... Boron treatment chamber 8 ... Heat treatment chamber

Claims (1)

[Claims] 1. Immediately after cleaning the surface of a silicon semiconductor to expose a clean surface, a substance containing phosphorus or boron is added,
A method of manufacturing a semiconductor device, comprising the steps of exposing the semiconductor to a temperature not lower than the melting point of the substance and not higher than 400 ° C. to deposit the substance, and then heating the semiconductor to dope the substance.