JP4976111B2 - Vapor growth method - Google Patents

Description

  The present invention relates to a vapor phase growth apparatus and a vapor phase growth method for forming a semiconductor layer such as silicon on a wafer in a chamber by vapor phase growth.

Conventionally, as a manufacturing apparatus for forming a film on a wafer, a vapor phase growth apparatus (CVD: Chemical Vapor Deposition, which includes VPE: Vapor phase epitaxial growth) is generally used. For example, Japanese Patent Laid-Open No. 9-17734 (Patent) As shown in Document 1), silane (SiH ₄ ) and hydrogen (H ₂ ) are used as gases in Si film formation.
Here, depending on the properties of the substrate, a single-crystal Si or poly-Si film is formed. In this case, a single crystal Si film is usually formed on the Si single crystal substrate, and a poly Si film or an amorphous Si film is formed on an amorphous substrate.

As a specific example, as shown in FIG. 2, a semiconductor wafer 202 placed on a support table 201 is stored in a chamber 203. The stored semiconductor wafer 202 is heated to a temperature required for film formation by a heater 204.
Gas flow paths 205a and 205b (first flow paths) for supplying silane (SiH ₄ ) gas or dichlorosilane (SiH ₂ Cl ₂ ) and H ₂ gas are connected to the chamber 203, and the other of the gas flow paths is These are connected to gas cylinders 206a and 206b, respectively. Valves 207a and 207b for opening and closing the gas are connected in the middle of the flow paths 205a and 205b.

Valves 207a and 207b are opened from the cylinders 206a and 206b through the gas flow paths 205a and 205b, SiH ₄ gas and H ₂ gas are supplied into the chamber 203, and a single crystal Si film is formed on the semiconductor wafer. Be filmed. This film formation is often repeated several times. For example, as shown in Japanese Patent Application Laid-Open No. 2000-282241, when SiH ₄ gas contains boron, aluminum, gallium, phosphorus, or the like, P-type and N-type semiconductor single crystal layers can be formed. Further, as disclosed in Japanese Patent Application Laid-Open No. 2004-281673 (Patent Document 2), when SiH ₄ gas and O ₂ gas are supplied, the SiO ₂ film supplies SiH ₄ gas and HN ₃ gas. Then, a Si ₃ N ₄ film can be formed.

The chamber 203 is connected to a gas flow path 208 for supplying a ClF ₃ gas (a gas such as CF ₄ or C ₂ F _{6 in} the case of a SiO ₂ film or a Si ₃ N ₄ film). Is connected to a valve 209 for opening and closing the gas.

When the inside of the chamber 203 is cleaned after the film formation (single crystal Si film) is completed, the valve 209 is opened from the cylinder 210 via the gas flow path 208 to supply ClF 3 gas.
In the film formation on the wafer and the cleaning of the chamber, the gas is exhausted by a vacuum pump 212 connected to a gas flow path 211 for gas exhaust.

By the way, in the above-described vapor phase growth apparatus of FIG. 2, it is absolutely necessary to avoid mixing of SiH ₄ gas or SiH ₂ Cl ₂ used at the time of film formation and ClF ₃ gas used at the time of cleaning because of danger.
For this reason, in particular, the valve 206a connected to the flow path 205a for flowing SiH ₄ gas used during film formation is completely closed during cleaning. Further, after the film formation is completed, the inside of the chamber is purged with N ₂ or the like, and then the valve 311 is opened and vacuumed by the vacuum pump 313 connected to the gas flow path 312 for exhaustion, and the SiH ₄ gas is completely discharged. To exhaust.

  In the vapor phase growth apparatus shown in FIG. 2, the process gas after the vapor phase growth reaction is sequentially exhausted from an exhaust port 215 provided in the chamber 203. The closer to the exhaust port 215 from the vicinity of the wafer 202 where the vapor phase growth is performed, the farther away from the high temperature portion in the chamber 203 such as the heater 201 for heating the wafer 201 and the wafer 202, and the lower portion of the chamber 203. Because it is located, it is hard to become high temperature.

  Further, packing is used for sealing at the flange connecting portion of the chamber 203. The packing is made of fluoro rubber, and the heat-resistant temperature is up to about 300 ° C. Therefore, a water channel (not shown) for circulating cooling water for preventing deterioration of the packing is provided on the outer periphery of the chamber 203. The cooling water cools the packing, but at the same time, the chamber body and the quartz cover are also cooled, so that a local low temperature portion is created near the exhaust port 215 in the chamber.

The problem here is that when the process gas after the reaction when dichlorosilane (SiH ₂ Cl ₂ ) is used for the vapor phase growth reaction is placed in a low temperature atmosphere, the by-product reactive polysiloxane (chemical formula Si _x H _{2x + 2-y} Cl _y where y ≦ 2x + 2) is generated and deposited. By-product accumulation near the exhaust port reduces the flow rate of the process gas required for the vapor phase growth reaction and the exhaust pressure of the exhaust port 215, thereby reducing the process conditions necessary for the production of high-quality wafers. Problems such as being unable to satisfy will occur.

Further, when it becomes difficult to set process conditions in the chamber due to the generation of deposits, maintenance such as disassembling the chamber 203 and cleaning the inside must be performed once a month. . Also, doing this itself has a negative effect, and even after all maintenance work has been completed, even if the device is reassembled as before, the wafers that are manufactured afterwards will have quality such as crystal thickness and purity. It has been found that considerable time is required to return to the level before maintenance.
Furthermore, performing the maintenance work itself requires a considerable amount of time and labor, and a decrease in the operating rate of the vapor phase growth apparatus due to this time cannot be ignored.
As described above, in the conventional vapor phase growth apparatus, there are problems that the maintenance of the quality of the wafer to be manufactured by the deposition of by-products is hindered and the management of the apparatus is complicated.

  In the above-described vapor phase growth apparatus, it is desired that there is no decrease in the flow rate of reaction gas and variation in process conditions due to the deposition of by-products. Therefore, various means for maintaining this have been proposed. For example, as in JP-A-2001-226774 (Patent Document 3), temperature control inside the exhaust pipe, which is a portion where by-products are likely to accumulate as in the vicinity of the exhaust port of the reactor, It is common to create a fluidized bed in the vicinity of the inner cylinder surface and to smoothly exhaust the exhaust gas by not exposing the reacted process gas to the inner cylinder surface.

  Further, in the above-described vapor phase growth apparatus, the process gas after the reaction is exhausted from the exhaust port 215 of the chamber and heated by a heater when entering the exhaust pipe inner cylinder, thereby depositing by-products on the inner cylinder wall surface. prevent. At the same time, the inert gas flow layer does not expose the inner wall of the inner cylinder to the process gas after the reaction, thereby further reducing the accumulation of by-products, and the by-products generated in the chamber are carried to the exhaust gas. When it is likely to adhere to the cylinder, the inert gas is blown off to prevent the adhesion.

  The reason why such measures were taken was that the disadvantage of the generation and accumulation of by-products was that there was concern about an increase in the number of maintenances of this pipe and the vacuum pump provided after this pipe. Yes, it was mentioned that they were trying to improve this.

  However, no matter how much the portion constituting the process after the exhaust pipe is cleaned, deposition of by-products in the chamber is a problem that occurs in the method of Patent Document 3 as well. Maintenance of removal of accumulated by-products must be performed. Therefore, considering the complexity of maintenance and the operating rate of the vapor phase growth apparatus itself, it is possible to adopt a method that can achieve a reduction in the number of maintenance of the apparatus main body by suppressing the generation of by-products in the chamber. It is clear that this can contribute to higher utilization rates.

JP-A-9-17734 JP 2004-281673 A JP 2001-226774 A

As described above, the conventional method for suppressing the generation of by-products in the vapor phase growth apparatus is manufactured because the improvement in the operating rate of the apparatus main body and the variation in process conditions in the chamber are considered. However, this is not sufficient from the viewpoint of affecting the quality of the wafer, and there is still room for improvement.
The present invention addresses the above-mentioned points and suppresses the generation of by-products during vapor phase growth, thereby improving the operating rate of the vapor phase growth apparatus and stabilizing the process conditions during the vapor phase growth reaction. It is an object of the present invention to provide a novel vapor phase growth method capable of manufacturing a high quality wafer at a high operation rate.

In the vapor phase growth method of the present invention, a wafer placed on a support base is accommodated in a chamber, and a first flow path for supplying dichlorosilane, which is a gas for forming a film on the wafer, and a gas A second flow path for exhausting air is connected to the chamber, a cooling water circulation part for controlling the temperature in the chamber is provided around the chamber, and the temperature in the chamber is measured on the inner wall part of the chamber The temperature of the inner wall of the chamber is set to 15 ° C. or more during film formation on the wafer using a vapor phase growth apparatus provided with a temperature sensor for controlling the temperature of the cooling water. The film is formed on the wafer under the control of the temperature controller so that the temperature of the inner wall of the chamber becomes 21 ° C. or higher and 30 ° C. or lower after the film formation on the wafer at a temperature of ℃ or lower. .

According to the present invention, by addressing the above-mentioned points, by suppressing the generation of by-products during vapor phase growth, the operating rate of the vapor phase growth apparatus is improved and the environment during the vapor phase growth reaction is stabilized. It is possible to provide a new vapor phase growth method capable of manufacturing a high-quality wafer at a high operation rate.

The best mode for carrying out the present invention will be described below in detail with reference to the drawings.
In the first embodiment, similar to the conventional example described above, a Si single crystal wafer 102 placed on a support base 101 is accommodated in a chamber 103 as shown in FIG. The accommodated Si single crystal wafer 102 is heated by a heater 104 to a temperature necessary for film formation.

Gas flow paths 105a and 105b (first flow paths) for supplying SiH ₂ Cl ₂ gas and H ₂ gas are connected to the chamber 103, and the other gas flow paths are connected to gas cylinders 106a and 106b, respectively. Yes. Valves 107A, 107a, 107B, 107b for opening and closing the gas are connected in the middle of the flow paths 105a, 105b. That is, the valves are provided with 107A and 107a in series for H ₂ gas control and 107B and 107b in series for SiH ₄ gas control. Pressure switches 114A and 114B are connected between the valves 107A and 107a and 107B and 107b, and the other ends of the pressure switches (not shown) are connected to a control device (not shown). A valve 109 for controlling the cleaning gas is also connected to this control device.

Note that if the SiH ₂ Cl ₂ gas contains boron (B ₂ H ₆ gas), phosphorus (PH ₃ gas), or the like, P-type and N-type Si single crystal layers can be formed. The gas included in the SiH ₂ Cl ₂ gas is not limited to boron and phosphorus, but may be a gas including Al, As, and the like.

Valves 107A, 107a, 107B, and 107b are opened from cylinders 106a and 106b through gas flow paths 105a and 105b, and SiH ₄ gas and H ₂ gas are supplied into chamber 103. A Si single crystal film is formed. This film formation is often repeated several times. In the case of the present embodiment, first, a gas in which PH ₃ gas is mixed with SiH ₂ Cl ₂ gas, H ₂ gas, a gas in which SiH ₂ Cl ₂ gas is mixed with B ₂ H ₆ gas, and H By flowing _two gases, first an N-type Si single crystal layer and then a P-type Si single crystal layer are formed.

In addition, a gas flow path 108 (second flow path) for supplying ClF ₃ gas is connected to the chamber 103, and a valve 109 for opening and closing the gas is connected in the middle of the flow path 108. A controller 115 is connected to the valve 109. Of course, the cylinder 110 is connected to the other end of the gas flow path 108 for supplying the ClF ₃ gas.

After film formation (P-type Si single crystal layer, N-type Si single crystal layer) is completed, the inside of the chamber 103 is cleaned. In this case, the ClF ₃ gas is supplied from the cylinder 110 by opening the valve 109 via the gas flow path 108.
In the film formation on the wafer and the cleaning of the chamber, the exhaust of the gas is vacuumed by the vacuum pump 113 to which the gas channel 112 (third channel) for gas exhaust is connected ( Open the valve 111).

In this embodiment, during the transition from the vapor phase growth process to cleaning, in addition to the chamber 103, the SiH ₂ Cl ₂ gas supply side valves 107A (from the chamber to the valve 107A via the valve 107a), 107B (chamber To the valve 107B via the valve 107b) is vacuumed, and SiH ₄ gas is discharged from the pipe. After discharging the SiH4 gas, the valves 107a, 107A, 107b, and 107B are closed. Thereafter, ClF ₃ gas is introduced into the chamber 103 to perform cleaning.
As described above, in this embodiment, as shown in FIG. 1, the supply port 100 for introducing a process gas containing a reactive gas necessary for vapor phase growth is provided at the top of the chamber 103, and the process gas is exhausted at the bottom. A mouth 115 is provided. After the reaction environment such as the temperature of the wafer is settled, process gas is introduced into the chamber 103 from the supply port 100, and the process gas after reaction is exhausted from the exhaust port 115.

The process gas supply flow rate is set by, for example, carrier gas: H2 of ₂₀ to 100 SLM (Standard Liter per Minutes), film formation gas: dichlorosilane (SiH ₂ Cl ₂ ) of 50 sccm (standard cubic centimeter per). minutes · standard cc per minute) to 2 SLM, and other dopant gas: diborane (B ₂ H ₆ ) or phosphine (PH ₃ ) is set to be added in a minute amount. When diborane is introduced as described above, a p-type conductivity film is formed, and when phosphine is introduced, an n-type conductivity film is formed. Then, the pressure in the chamber 103 is controlled to, for example, 1333 Pa to normal pressure. The above conditions are satisfied and vapor phase growth is started.

  Generally, the inner wall of the chamber of the vapor phase growth apparatus is covered with a quartz cover so as not to expose a stainless steel casing. This is to prevent particles and metal contamination during the formation of a crystal film on the wafer surface, or corrosion of the chamber itself.

  While the wafer 102 is performing vapor phase growth reaction in the above-described environment, the heater 104 keeps heating the wafer 102 from about 1000 ° C. to about 1200 ° C., so that the temperature of the chamber 103 increases as a whole and approaches the heater 104. This is particularly noticeable at the location where the heat treatment occurs and at the top of the chamber 103 that is susceptible to heat radiation.

  If the temperature of the entire chamber 103 becomes too high, it may adversely affect the electrically controlled equipment, or may be used in a part that seals the flange joint of the chamber 103 or a gap between the holder 101 and the chamber 103. The packing (including the O-ring) that seals the inside of the chamber 103 and the outside air is deteriorated. The packing used here is made of fluororubber, and the heat-resistant temperature is about 300 ° C.

  At this time, in order to suppress breakage of equipment and deterioration of packing, circulation of cooling water having a water temperature of 20 ° C. to 45 ° C. in the cooling water flow path 116 provided on the outer periphery of the chamber 103 makes it close to the heater 104. The inside of the holder, the upper portion of the chamber 103 that is susceptible to heat radiation, packing (not shown), and the like are cooled by circulation of cooling water, and kept at a favorable temperature for the operation of the apparatus. Further, the cooling means at this time may be other than water, and there is no problem as long as heat can be effectively removed from the apparatus such as air or oil.

However, a quartz cover on the wall surface near the exhaust port at the bottom of the chamber 103, which is made of a quartz material that is difficult to be heated and is not easily affected by the second heater 114, or the inner lower surface of the chamber 103 By cooling a portion such as a circular quartz cover provided on the substrate, a by-product due to the process gas after the vapor phase growth reaction is deposited. The by-product of the process gas after the vapor phase growth reaction is reactive polysiloxane (Si _x H _{2x + 2-y} Cl _y where y ≦ 2x + 2), and its properties are slightly higher than room temperature, and are generally 40 ° C. to 50 ° C. It is generated and deposited when the process gas after vapor deposition is exposed to the following environment.

  In such a state, the cross-sectional area of the exhaust port 115 of the chamber 103 decreases, the flow rate of the process gas necessary for the vapor phase growth reaction introduced into the chamber 103 decreases, and the exhaust pressure from the chamber 103 decreases. Problems such as failure to satisfy process conditions necessary for production of high-quality wafers occur.

  In addition, the deposited reactive polysiloxane has a risk of ignition, explosion, and the like, and has a property of becoming hard when exposed to the outside air. For this reason, careful work is required for removal during maintenance, and time is required. Therefore, it becomes a problem which must be concerned as a cause of a reduction in the operating rate of the apparatus itself.

In order to solve this problem, the temperature is controlled by the cooling water control unit 117 by the cooling water flow path 116 provided on the outer periphery of the chamber 103, so that there is almost no accumulation of by-products embedded in the chamber. If the temperature of the inner wall of the chamber is set to 21 ° C. or higher and 43 ° C. or lower, adhesion of byproducts is hardly confirmed. The temperature of the inner wall of the chamber is measured by a thermometer 118 and fed back to the cooling water control unit to control the temperature of the cooling water.
The present invention is not limited to the above-described embodiments, and can be variously modified and implemented without departing from the scope of the invention.

Sectional drawing of the vapor phase growth apparatus in embodiment of this invention. Sectional drawing which showed the conventional vapor phase growth apparatus typically.

Explanation of symbols

100 ... Supply port 101 ... Support base 102 ... Si single crystal wafer 103 ... .. Chamber 104... Heater 105 a... SiH ₄ gas flow path 105 b... H ₂ gas flow path 106 a. ... SiH ₄ gas cylinder 106b ... H ₂ cylinders 107, 109, 111 ... Valve 108 ... ClF ₃ gas flow path (second Gas flow path)
110... ClF ₃ gas cylinder 112... Exhaust gas flow path (third gas flow path)
113 ... Vacuum pump 115 ... Exhaust port 116 ... Cooling water flow path 117 ... ... Cooling water control unit 118 ... thermometer

Claims (1)

In the chamber, a wafer placed on a support is accommodated, and a first flow path for supplying dichlorosilane, which is a gas for forming a film on the wafer, and a second flow path for exhausting the gas are provided. Connected to the chamber, a cooling water circulation unit for controlling the temperature in the chamber is provided around the chamber, a temperature sensor for measuring the temperature in the chamber is provided on the inner wall of the chamber, and the cooling Using a vapor phase growth apparatus provided with a temperature controller for controlling the temperature of water ,
During film formation on the wafer, the temperature of the inner wall portion of the chamber is 15 ° C. or more and 20 ° C. or less, and after film formation on the wafer, the temperature of the chamber inner wall portion is 21 ° C. or more and 30 ° C. or less. A vapor phase growth method comprising forming a semiconductor film on the wafer under the control of the temperature controller.

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