CN1278388C

CN1278388C - Method and device for preparing high power semiconductor device by open-tube diffusion

Info

Publication number: CN1278388C
Application number: CN 200310100117
Authority: CN
Inventors: 沈首良
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-10-10
Filing date: 2003-10-10
Publication date: 2006-10-04
Anticipated expiration: 2023-10-10
Also published as: CN1529345A

Abstract

The present invention relates to a method for producing large power semiconductor devices by open tube diffusion, which belongs to the technical field of the manufacture of semiconductor devices. Gallium deoxidized from Ga2O3 source powder in a reactor is diffused into a silicon chip under the protective atmosphere. The device of the present invention comprises a gas supply, a device for protecting against back fire, a diffusion furnace and a tail gas constant pressure bottle, wherein the device for protecting against back fire is arranged between the gas supply and the admission end of the diffusion furnace, and the tail gas constant pressure bottle is connected with the tail gas exit end of the diffusion furnace. The method and the device of the present invention are easy and feasible and are convenient to operate; during diffusion, the silicon chip can be taken out to measure parameters, and the diffusion time and the diffusion temperature can be adjusted at any time, so the parameters of final diffused parts are uniform; the products produced by the method have good consistency and good dynamic performance, a finished product rate is raised by more than 20 percent, and the present invention is especially suitable for mass production.

Description

Method and device for preparing high-power semiconductor device by open-tube diffusion

The invention relates to a method and a device for preparing a high-power semiconductor device by open-tube diffusion, belonging to the technical field of semiconductor device manufacture.

In the production of high-power semiconductor devices in the background art, one-time P-type impurity diffusion is a key process, the current domestic P-type impurity diffusion mostly adopts open-tube boron-aluminum latex source coating diffusion, and the defects of the boron-aluminum latex source coating diffusion are as follows: 1. the concentration gradient of the P-type impurity is large near the front edge of the PN junction, and the dispersion of the parameters of the device can be caused in the subsequent process parameters such as secondary diffusion, polishing and the like, so that the quality of the product is unstable. 2. The effective concentration of the front edge of the short base region of the PN junction of the semiconductor device is low, in order to meet the relationship between space charge broadening and withstand voltage, the width of the short base region must be very wide, the dynamic parameters of the device are greatly influenced by the width of the short base region, and therefore the dynamic parameters of the device are not ideal. The other process of P-type impurity diffusion is closed tube gallium diffusion, and the concentration distribution of impurities is ideal. But the disadvantages are: 1. the process is complicated. 2. The quartz tube in the diffusion equipment is difficult to seal. 3. A vacuum diffusion furnace is required. 4. The production cost is high, and the diffusion quality is greatly influenced by the quality of the quartz tube.

The invention aims to provide a method and a device for preparing a high-power semiconductor device by open-tube diffusion, which overcome the defects of poor diffusion uniformity of a currently universal boron-aluminum latex source coating, large finished parameter dispersibility and poor dynamic characteristics of the device, and overcome the defects that a vacuum diffusion furnace is needed by adopting vacuum closed-tube diffusion in the prior art, the production batch is small, and the method and the device are difficult to be suitable for the mass production of the high-power semiconductor device (such as a fast thyristor, a rectifier tube and the like). The open tube gallium diffusion process is simple and convenient to operate, diffusion parameters can be controlled and adjusted at will, the doping concentration is adjustable, the equipment universality is strong, and the method is suitable for batch production of high-power semiconductor devices.

The invention provides a method for preparing a high-power semiconductor device by open-tube diffusion, which comprises the following steps:

1. introducing nitrogen into the reactor, wherein the flow rate of the nitrogen is 1000-1500 ml/min, and the time is 10-15 minutes, so as to expel air in the system;

2. ga in the reactor₂O₃Heating the source powder to 850-1050 ℃, reducing the source powder into gallium in reduction protective gas hydrogen, wherein the flow rate of the hydrogen is 1000-1500 ml/min, the hydrogen is used for expelling nitrogen in the system and is used as a reduction gas source, the reduction time is 10-15 minutes, and then the gallium is reduced for 30-60 minutes at the flow rate of 400-600 ml/min;

3. and diffusing gallium into the silicon wafer under the hydrogen gas of a protective atmosphere, wherein the diffusion temperature is about 1250 ℃, the hydrogen flow is 400-600 ml/min, and the diffusion time is 10-16 hours.

The pressure of the tail gas can be kept at 200mm water column.

The nitrogen is introduced for 10-15 minutes in a range of 1000-1500 ml/min before introducing the hydrogen and after finishing diffusion.

The device for preparing the high-power semiconductor device by open-tube diffusion comprises an air source, an anti-backfire device, a diffusion furnace and a tail gas constant-pressure bottle; the anti-backfire device is arranged between the gas source and the gas inlet end of the diffusion furnace, and the tail gas constant-pressure bottle is connected with the tail gas outlet end of the diffusion furnace.

The diffusion furnace in the device comprises a quartz tube and heating wires, the diameter of the gas inlet end side of the quartz tube is larger than that of the tail gas outlet end side, the heating wires are respectively arranged on the outer sides of a small-diameter part and a large-diameter part, the quartz tube of the small-diameter part extends out of the diffusion furnace, an electromagnetic coil is arranged on the outer side of the extending part of the quartz tube, a source feeding bracket is arranged in the extending part of the quartz tube, the source feeding bracket comprises two mutually-connected quartz tubes, a diffusion source is placed in one end of the quartz tube, the other end of the quartz tube is an iron-carrying end, and the position of; a silicon wafer holder is arranged in the quartz tube of the large-diameterpart.

The anti-backfire device in the device consists of a shell, a porous metal partition plate and metal chips; the two sides of the shell are provided with gas inlets and gas outlets, the porous metal partition plates are arranged in the shell, and the metal chips are arranged between the two porous metal partition plates.

The method and the device for preparing the high-power semiconductor device by open-tube diffusion are simple and feasible, are convenient to operate, can take out the silicon wafer for parameter measurement in the diffusion process, adjust the diffusion time and temperature at any time, and have uniform diffusion final device parameters. The product has good parameter consistency and dynamic performance, the yield of the product can be improved by more than 20 percent, and the method is particularly suitable for batch production and has obvious economic benefit.

Drawings

FIG. 1 is a system diagram of a diffusion process.

Fig. 2 is a schematic view of the anti-backfire apparatus.

In fig. 1 and 2, 1 is a nitrogen fine adjustment valve, 2 is a hydrogen fine adjustment valve, 3 and 4 are gas flow meters, 5 is an anti-backfire device, 6 is a small quartz ground cap, 7 is an electromagnetic coil for moving a source-supply bracket, 8 is a source-supply bracket, 9 is a source temperature zone heating furnace wire, 10 is a double-ground quartz tube, 11 is a silicon wafer bracket, 12 is a main diffusion zone heating furnace wire, 13 is a large quartz ground cap, 14 is a tail gas constant pressure bottle, 15 is a double-temperature zone diffusion furnace, 16 is a gas inlet and outlet of the anti-backfire device, 17 is red copper chips for absorbing heat, 18 is a porous red copper partition plate, and 19 is an anti-backfire device shell.

Detailed Description

The structure of the device for preparing the high-power semiconductor device by open-tube diffusion designed by the invention is shown in figure 1, and the device comprises a gas source, an anti-backfire device 5, a diffusion furnace 15 and a tail gas constant-pressure bottle 14. The anti-backfire device 5 is arranged between the gas source and the gas inlet end of the diffusion furnace 15, and the tail gas constant-pressure bottle 14 is connected with the tail gas outlet end of the diffusion furnace 15. The gas source is hydrogen source and nitrogen source, which are respectively led in through the micro-adjusting valves 1 and 2 and the gas flow meters 3 and 4.

The diffusion furnace 15 in the device comprises a quartz tube 10, heating wires 9 and 12, the diameter of the gas inlet end side of the quartz tube is larger than that of the tail gas outlet end side, the outer sides of the small-diameter part and the large-diameter part are respectively provided with the heating wires 9 and 12, the quartz tube of the small-diameter part extends out of the diffusion furnace, the outer side of the extending part of the quartz tube is provided with an electromagnetic coil 7, a source feeding bracket 8 is arranged in the extending part of the quartz tube, the source feeding brackets are two mutually connected quartz tubes, a diffusion source is placed in the quartz tube at one end, the other end of the quartz tube is an iron-containing end, and the position of the iron; a silicon wafer holder 11 is provided in the quartz tube of the large diameter portion.

The structure of the anti-backfire device 5 in the above-mentioned device is shown in fig. 2, and is composed of a housing 19, a porous metal partition 18 and metal chips 17. The two sides of the shell 19 are provided with gas inlets and outlets 16, the porous metal partition plates are arranged in the shell, and the metal chips are arranged between the two porous metal partition plates. In one embodiment of the present invention, the metal separator used is a porous red copper separator, and the metal chips are red copper chips for absorbing heat.

While diffusing Ga₂O₃The source powder is arranged in a source temperature area, namely, a position corresponding to the heating wire 9, and the silicon wafer is arranged in a main diffusion constant temperature area, namely, a position corresponding to the heating wire 12.

When diffusing, use H₂As carrier gas and reaction gas, from solid Ga₂O₃Decomposing gallium atoms into gallium atoms, then separating from H₂The gallium atoms are brought to the main diffusion constant-temperature area and diffused into the silicon wafer. In order to prevent gallium atoms from forming alloy points and corrosion pits on the surface of the silicon wafer, an oxide layer is generated on the surface of the silicon wafer in advance. Due to gallium atom pair SiO₂Has extremely strong penetrating power, so that the realization of the penetration in SiO₂Doping under the protection of the film, and finally obtaining smooth symmetrical PN junctions on two sides of the N-type silicon wafer.

After the gallium source is decomposed, the gallium is attached to the wall of the quartz tube in the form of oxide at the temperature below 800 ℃, or is discharged out of the system along with the tail gas together with the water vapor, and the gallium source starts to react with H at the temperature above 800 DEG C₂Reaction of the formula

According to the diffusion requirement, the source temperature is 850-1050 ℃, and the silicon wafer diffusion temperature is 1250 ℃. By adjusting the temperature of the source region, the temperature of the main diffusion constant temperature region and the time of source connectionMeta and general formula H₂The flow rate of (2) can be controlled to meet a predetermined diffusion requirement.

According to the requirement of the diffusion parameters in the production of the high-power semiconductor device, the utility model discloses a special design and manufacture's two constant temperature zone diffusion furnaces, source warm area length are greater than 600mm, and the furnace temperature can reach 1260 ℃ at most, is fit for the requirement of high-power semiconductor device diffusion.

The diffusion source being Ga₂O₃The performance of the gallium sesquioxide is stable at low temperature, the gallium sesquioxide is placed in a source temperature region of 850-1050 ℃ during diffusion, the decomposition speed and the source flux are determined by the temperature, and the amount of the source flux is determined in H₂Reducing into gallium atoms, reaching the main diffusion constant-temperature area, and rapidly diffusing into the silicon wafer at high temperature.

Because the gallium atoms form alloy points and corrosion pits on the surface of the silicon wafer, an oxide layer is grown on the surface of the silicon wafer before the diffusion of the gallium to protect the surface of the silicon wafer. Due to gallium atom pair SiO₂Has extremely strong penetrating power, so that the realization of the penetration in SiO₂Doping is carried out under the protection of the film.

In order to keep a certain amount of saturated vapor pressure of impurities in the diffusion furnace tube, a tail gas constant pressure bottle 14 is arranged at the tail part of the furnace tube, and tail gas is discharged through the constant pressure bottle.

Because the reduction protective gas adopted by the process is H₂Therefore, safety is the first important, and three aspects are adopted in the process to ensure production safety.

1. Firstly, introducing nitrogen to flush the plastic pipeline and the quartz tube system;

2. hydrogen firstly passes through the anti-backfire device and then enters the quartz tube system;

3. the hydrogen-containing tail gas is discharged to high altitude or ignited.

In the diffusion process, the ground opening of the quartz tube cannot be opened in the diffusion process due to the introduction of hydrogen, and the operation can only be carried out in the closed quartz tube. Therefore, a prepared silicon wafer with an oxide layer is placed in the middle of the main diffusion constant temperature area in advance, a source is placed on a source-sending bracket, and the source-sending bracket is placed in the air inlet port of the double-ground quartz tube and does not enter the source constant temperature area. The quartz diffusion tube is designed into double ground, that is, two ends are opened, one end is used for feeding silicon chip, and the other end is used for placing source-carrying mopAnd (4) a frame. When the silicon chip and the source are put in operation, the front quartz ground and the rear quartz ground are covered tightly, then the gas is introduced for heating, (according to the operation rule, firstly the nitrogen is introduced and then the hydrogen is introduced), the temperature of the source region reaches the set temperature, at this time, the temperature of the main expansion region is also close to or reaches the preset temperature, at this time, the source can be sent into the constant temperature region, because the system is closed, the electromagnetic force source sending method is adopted, the method is characterized in that a special source sending bracket is made, the length of the bracket depends on the distance from the center of the constant temperature region to the furnace mouth, two sections of quartz tubes are respectively arranged at two ends of the bracket, openings at two ends of one quartz tube are₂O₃The other end of the source is a quartz tube which is sealed with an open annular iron ring and keeps low vacuum, and the quartz tube sealed with the open annular iron ring is moved by adopting an annular electromagnet outside the quartz diffusion tube, so that the source can be driven to enter and exit the source constant temperature area.

By adopting the process, P-type gallium diffusion can be completed in the same diffusion furnace through continuous diffusion, or pre-diffusion of gallium can be performed only in the furnace, and then main diffusion is performed. The impurity profile may be a residual error function profile or a gaussian profile, as desired.

One embodiment of the invention is as follows:

1. the source temperature is 930 ℃, the silicon wafer temperature is 1260 ℃, the diffusion time is 1 hour, and the gas flow is 500 ml/min. Diffusion result R_□800 Ω/square.

2. The source temperature is 1000 ℃, the silicon chip temperature is 1260 ℃, the source is connected for 2 hours, the hydrogen flow is 500 ml/min, the diffusion is continued for 12 hours after the source is removed, the diffusion result Xj is 33.9 μm, R_□400-480 omega/square.

3. In an extreme comparison test, the source temperature is 1080 ℃, the silicon wafer temperature is 1265 ℃, the diffusion time is 2 hours, and the gas flow is 800 ml/min. The diffusion results were as follows:

the surface of the silicon chip is protected by an oxide layer, Xj is 18 mu m, R_□The power is 5, 07-5.32 omega/square.

No oxide layer protection is provided on the surface of the silicon chip, Xj is 18 mu m, R_□4.29-4.55 omega/square. Surface alloy pitting and etch pits are severe.

Claims

1. The device for preparing the semiconductor device by open-tube diffusion is characterized by comprising a gas source, an anti-backfire device, a diffusion furnace and a tail gas constant-pressure bottle; the anti-backfire device is arranged between the gas source and the gas inlet end of the diffusion furnace, and the tail gas constant-pressure bottle is connected with the tail gas outlet end of the diffusion furnace; the diffusion furnace comprises a quartz tube and heating wires, the diameter of the gas inlet end side of the quartz tube is smaller than that of the tail gas outlet end side of the quartz tube, the heating wires are respectively arranged on the outer sides of a small-diameter part and a large-diameter part, the quartz tube of the small-diameter part extends out of the diffusion furnace, an electromagnetic coil is arranged on the outer side of the extending part of the quartz tube, a source feeding bracket is arranged in the extending part of the quartz tube, the source feeding bracket comprises two mutually-connected quartz tubes, a diffusion source is placed in the quartz tube at one end, an iron-containing end is arranged at the other end, and the; a silicon wafer rack is arranged in the quartz tube of the large-diameter part; the anti-backfire device consists of a shell, a metal partition plate and metal chips; the two sides of the shell are provided with gas inletsand gas outlets, the metal partition plates are arranged in the shell, and the metal chips are arranged between the two metal partition plates.