JPH11121389A - Vertical type diffusion furnace and diffusion method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize characteristics of a semiconductor device and improve yield and productivity, by independently controlling the amount of impurity gas jetted from the respective gas injectors jetting the impurity gas to semiconductor substrates positioned in the upper part, the central part and the lower part. SOLUTION: A first gas injector 11 in which a plurality of small holes 11S jetting impurity gas against a semiconductor substrate positioned in the upper part are arranged and formed in the longitudinal direction, a second gas injector 12 in which a plurality of small holes 12S jetting the impurity gas against a semiconductor substrate positioned in the central part are arranged and formed in the longitudinal direction, and a third gas injector 13 in which a plurality of small holes 13S jetting the impurity gas against a semiconductor substrate positioned in the lower part are arranged and formed in the longitudinal direction are installed. Since the respective gas injectors 11, 12, 13 are provided with mass flow controllers 21, 22, 23, each of the gas flow rate can be independently controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a vertical diffusion furnace and a diffusion method.

[0002]

2. Description of the Related Art In a conventional vertical diffusion furnace, as shown in FIG. 2, a large number of semiconductor substrates 2 housed in a quartz boat 3 are inserted into a furnace tube 1 heated to a high temperature by a heater 8, and phosphorus oxychloride is added. The nitrogen gas 45 is blown into the impurity source container 35 containing impurities such as gas to vaporize the gas, and the mass flow controller (hereinafter, referred to as MFC) 25 controls the flow rate through the many small holes 15S of the gas injector 15. Introduce a controlled main gas such as phosphorus oxychloride,
An auxiliary gas 40 such as oxygen or nitrogen is introduced from the outlet of the gas supply pipe 7 provided in the furnace core tube, and impurities such as phosphorus are diffused into the semiconductor substrate while rotating the quartz boat 3 loaded with the semiconductor substrate. Was performed.

[0003] Also, Japanese Patent Application Laid-Open No. Hei 4-329631 discloses that
As shown in FIG. 3, a U-shaped gas injector in which a gas mixing / heating unit 17 is provided in front of an ejection unit 16 in which a gas ejection small hole 16S is formed in order to mix gases and make the temperature uniform. Is disclosed.

[0004]

However, in any of the above-mentioned prior arts, the flow rate of the gas increases near the gas supply source (the lower one in FIG. 2 and the upper one in FIG. 3), The amount of gas blown off in the longitudinal direction (longitudinal direction) of the tube.

For this reason, the supply amount of gas to the surface of the semiconductor substrate is different between the upper part and the lower part of the furnace core tube, and the uniformity of the impurity diffusion amount in the batch is inferior.

For this reason, the yield as a semiconductor device has been reduced due to variations in the wiring resistance and gate length of the polysilicon gate of the transistor.

[0007] The reason is that in the batch (vertical direction of the furnace core tube)
As a result, the variation in the amount of impurity diffusion (impurity concentration) becomes large, and the variation in the amount of impurity diffused in the gate polysilicon film becomes large. This causes variation in the wiring resistance of the gate electrode formed by etching this. Because it was. Further, when the gate electrode is formed by etching the gate polysilicon film, the variation in the impurity concentration in the polysilicon film is large, so that the etching rate varies, and as a result, the gate length varies.

On the other hand, even if it is considered that the distribution of the small holes is changed in order to make the gas supply amount the same, this can be applied only to certain conditions. Switching to a gas injector is not practical in terms of productivity.

Accordingly, an object of the present invention is to provide a vertical diffusion furnace and a diffusion method which stabilize the characteristics of a semiconductor device, improve the yield, and improve the productivity.

[0010]

SUMMARY OF THE INVENTION The present invention is characterized in that a boat in which a large number of semiconductor substrates are vertically arranged at predetermined intervals from each other is placed in a furnace tube, and is provided in a lateral direction of the semiconductor substrates. In a vertical diffusion furnace in which an impurity gas is blown from a small hole of a gas injector onto the semiconductor substrate to perform a diffusion process, a first step of blowing the impurity gas onto an upper semiconductor substrate among the plurality of semiconductor substrates is performed. A gas injector, a second gas injector that blows the impurity gas onto a semiconductor substrate located at a central portion, and a third gas injector that blows the impurity gas onto a semiconductor substrate located at a lower portion; The amount of the impurity gas blown from the third gas injector is in an independently controlled vertical diffusion furnace. Here, it is preferable that the piping connected to the first to third gas injectors supply the impurity gas from each impurity container. Further, it is preferable that the flow rate of the impurity gas blown out from the first to third gas injectors is controlled by each MFC.

Another feature of the present invention is that a boat in which a number of semiconductor substrates are vertically arranged at a predetermined interval from each other is placed in a furnace tube, and a gas injector provided in a side direction of the semiconductor substrates. In a diffusion method of performing a diffusion process by spraying an impurity gas onto the semiconductor substrate from the small holes,
Among the many semiconductor substrates, the flow rate of the impurity gas controlled by a first mass flow controller is sprayed by a first gas injector onto a semiconductor substrate positioned at an upper portion, and the flow rate is sprayed onto a semiconductor substrate positioned at a central portion. Is blown by the second gas injector with the impurity gas controlled by the second mass flow controller, and the flow rate of the impurity gas controlled by the third mass flow controller is applied to the semiconductor substrate located at the lower central portion. In a diffusion method in which gas is blown by a third gas injector. Here, it is preferable that the piping connected to the first to third gas injectors supply the impurity gas from each impurity container. in this case,
Each of the impurity containers contains phosphorus oxychloride, and can diffuse phosphorus into the semiconductor substrate.

According to the present invention, by adjusting the amount of gas blown out in accordance with various conditions in the longitudinal direction (longitudinal direction) of the furnace core tube, the gas can be simultaneously processed in one process. The uniformity in the batch of the impurity diffusion amount diffused to the surface of up to 150 semiconductor substrates can be improved.

That is, for example, in a diffusion furnace having an exhaust port at the lower part of the furnace core tube, when the flow rate of the impurity gas at the lower part of the furnace core tube becomes insufficient due to the exhaust gas,
By intentionally increasing the gas flow rate in the lower portion, the amount of impurities adsorbed on the semiconductor surface can be made uniform.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an outline of a vertical diffusion furnace according to an embodiment.

The inside of the furnace tube is heated to a predetermined temperature by a heater 8 provided around the furnace tube 1. A large number of semiconductor substrates 2 are loaded in a quartz boat 3 while being arranged at a predetermined interval in the vertical direction. The quartz boat 3 can be moved up and down and rotated by an elevator 18 supporting the quartz boat 3.

A plurality of small holes 1 for blowing an impurity gas to an upper semiconductor substrate among many semiconductor substrates.
A first gas injector 11 in which 1S are formed in a vertical direction, and a plurality of small holes 12 for blowing an impurity gas to a semiconductor substrate located at a central portion among a large number of semiconductor substrates.
Second gas injector 1 in which S is formed in a vertical direction
2 and a third gas injector 13 in which a plurality of small holes 13S for forming a plurality of small holes 13S for spraying an impurity gas to a semiconductor substrate located at a lower position among a large number of semiconductor substrates are formed in a vertical direction.

The first gas injector 11 has a pipe connected to a first impurity source container 31 into which a nitrogen gas 41 is introduced through a first MFC 21, and the second gas injector 12 has a pipe connected to a second impurity injector vessel 31. MFC22
The third gas injector 13 is connected to a third impurity source container 33 into which the nitrogen gas 43 is introduced through the third MFC 23. doing.

As described above, each gas injector 1
Since the MFCs 21, 12, and 23 are provided with the MFCs 21, 22, and 23, respectively, the gas flow rate can be controlled independently. , Each gas injector 11,
Small holes 1 and 12 each having a plurality of outlets
1S, 12S, and 13S are formed, and an impurity gas as a main gas is supplied into the furnace core tube from the small holes. Further, a gas supply pipe 7 for supplying an auxiliary gas 40 such as oxygen and nitrogen gas is separately provided in the furnace core tube.

In the diffusion operation of the embodiment, the elevator 18 is raised into the furnace core tube 1 heated at a high temperature, and the quartz boat 3 loaded with the semiconductor substrate 2 is inserted and rotated.

Next, first, second and third impurity source containers 31 containing impurities such as phosphorus oxychloride, respectively,
Impurity sources are vaporized by blowing nitrogen gas 41, 42, 43 through MFCs 21, 22, 23 into 32, 33, and the gas injectors 11, 12, 13 supply impurity gas, which is the main gas, to the furnace core tube. The auxiliary gas 40 is introduced from the outlet of the gas supply pipe 7. At this time, the main gas is supplied to a plurality of small holes 11S, 12S, which are blowout ports provided in the gas injectors 11, 12, and 13.
13S, the diffusion process of impurities such as phosphorus into the semiconductor substrate 2 is performed. At this time, the diversion of the main gas is controlled independently by each MFC, whereby the gas having a uniform flow rate (or the effect of exhaust gas) is considered from each of the injectors for the upper part, the central part, and the lower part of the furnace core tube,
(The flow rate may be intentionally changed) can be supplied into the furnace core tube. As a result, the amount of impurities (phosphorus) supplied to the surface of the same batch of semiconductor substrates loaded on the boat can be uniformed, and the uniformity of the amount of impurity (phosphorus) diffused into the semiconductor substrates in the furnace core tube is improved. Thus, a phosphorus diffusion region having the same characteristics can be formed.

In the embodiment, the case of three gas injectors has been described.
Or more gas injectors and M coupled to each
FC and impurity source containers can also be provided.

[0023]

As described above, according to the present invention, a plurality of gas injectors are provided for the upper part, the central part, and the lower part of the furnace core tube, and the gas flow rate is controlled independently of each other so that the batch in the batch can be obtained. Thus, the amount of impurities adsorbed on the surface of the semiconductor substrate can be made uniform, so that the amount of impurities diffused to the surface of the semiconductor substrate in a batch can be made uniform.

As described above, since the uniformity of the diffusion amount (impurity concentration) of the impurities in the batch (longitudinal direction of the furnace core tube) can be improved, for example, the variation in the amount of impurities diffused in the gate polysilicon film can be reduced. It is possible to reduce the variation in the wiring resistance of the gate electrode formed by etching the gate electrode. Further, when the gate electrode is formed by etching the gate polysilicon film, the variation in impurity concentration in the polysilicon film can be reduced, so that the etching rate can be stabilized and the variation in gate length can be reduced. As a result, the wiring resistance and gate length of the polysilicon gate of the transistor can be stabilized, and the yield as a semiconductor device can be improved.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a vertical diffusion furnace according to an embodiment of the present invention.

FIG. 2 is a side sectional view showing a conventional vertical diffusion furnace.

FIG. 3 shows another prior art gas injector.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Furnace core tube 2 Semiconductor substrate 3 Quartz boat 7 Gas supply tube 8 Heater 11, 12, 13, 15 Gas injector 11S, 12S, 13S, 15S Small hole (gas outlet) 16 Spouting part 16S Small hole 17 Gas mixing / heating Part 18 Elevator 21, 22, 23, 25 MFC 31, 32, 33, 35 Impurity source container 40 Secondary gas (oxygen gas, nitrogen gas) 41, 42, 43, 45 Nitrogen gas

Claims (6)

[Claims] 1. A boat in which a number of semiconductor substrates are vertically arranged at a predetermined interval from each other is placed in a furnace tube, and impurity gas is passed through a small hole of a gas injector provided on a side surface of the semiconductor substrate. A first gas injector that sprays the impurity gas onto an upper semiconductor substrate among the plurality of semiconductor substrates, and a semiconductor device that is located at a central portion. A second step of spraying the impurity gas onto the substrate;
And a third gas injector that blows the impurity gas onto a semiconductor substrate located below, and the amount of the impurity gas blown from the first to third gas injectors is independently controlled. A vertical diffusion furnace. 2. The vertical diffusion furnace according to claim 1, wherein a pipe connected to the first to third gas injectors supplies the impurity gas from each impurity container. 3. The flow rate of the impurity gas blown out from the first to third gas injectors is different from each mass gas.
The vertical diffusion furnace according to claim 1, wherein the furnace is controlled by a flow controller. 4. A boat in which a number of semiconductor substrates are vertically arranged at predetermined intervals from each other is placed in a furnace tube, and impurity gas is passed through a small hole of a gas injector provided on a side surface of the semiconductor substrate. Is applied to the semiconductor substrate to perform a diffusion process, wherein the impurity gas whose flow rate is controlled by a first mass flow controller is supplied to a semiconductor substrate located at an upper portion of the plurality of semiconductor substrates. The impurity gas controlled by the second mass flow controller is blown by the second gas injector, and the flow rate is blown by the second gas injector to the semiconductor substrate located at the central portion. The impurity gas controlled by a third mass flow controller to a third gas injector. A diffusion method characterized by spraying more. 5. The diffusion method according to claim 4, wherein a pipe connected to the first to third gas injectors supplies the impurity gas from each impurity container. 6. The diffusion method according to claim 5, wherein each of the impurity containers contains phosphorus oxychloride, and the diffusion of phosphorus is performed on the semiconductor substrate.