JP6524944B2 - Vapor phase etching method and epitaxial substrate manufacturing method - Google Patents

Description

  The present invention relates to a vapor phase etching method implemented in a vapor phase growth apparatus, and more particularly, to a vapor phase etching method for removing a wall deposit in a chamber of the vapor phase growth apparatus and manufacture of an epitaxial substrate using the same. On the way.

  A variety of devices such as computer memories and computing elements, digital cameras, video imaging elements, and the like are manufactured using a silicon wafer which is a semiconductor substrate (hereinafter referred to as a substrate). In particular, an epitaxial silicon wafer (epi wafer) in which a silicon layer is deposited by vapor deposition on the surface of a silicon wafer is used for a device for leading edge.

  In general, an epi-wafer is produced by vapor phase reaction of a raw material such as trichlorosilane at a high temperature of 1100 ° C. or higher to form an epitaxial silicon layer on a silicon substrate. In a vapor phase growth apparatus, a cold wall type apparatus is generally used which heats a wafer and a susceptor on which the wafer is placed with a heater and cools a furnace body.

FIG. 4 schematically shows the state of the chamber sealed with the transparent quartz member of the vapor phase growth apparatus.
The vapor phase growth apparatus has a chamber 1 equipped with a susceptor 2 supported by a susceptor support 6 for mounting a wafer W thereon. The chamber 1 is configured to be sealed by transparent quartz members 4 and 4 'placed at the top and bottom. In order to heat the wafer W and the susceptor 2 through the transparent quartz members 4 and 4 ', heaters 10 such as lamps are provided at the upper and lower portions of the chamber.

  The epitaxial growth reaction occurs on the wafer W, which is a silicon substrate, and also reacts on the susceptor 2 and the wall of the chamber 1 to deposit polysilicon and silicon compound as a by-product. Such by-products are called wall deposition (wall deposition). As shown in FIG. 4, when the wall deposit 14 adheres on the transparent quartz member 4 between the wafer W and the heater 10 as a heating lamp, it peels off from the wall during the epitaxial reaction and adheres on the wafer W. Become a particle.

  Further, when the wall deposit 14 is generated, as shown in FIG. 4, the irradiation light 15 of the heater 10 is blocked, and the temperature of the shadowed area is lowered by the wall deposit 14 and the temperature distribution is deteriorated. Therefore, the film thickness distribution and the resistance distribution of the epitaxial wafer are deteriorated and slip dislocations are easily generated.

  Furthermore, in the chamber 1 sealed with the transparent quartz member of the vapor phase growth apparatus, the wall deposit 14 formed on the transparent quartz members 4, 4 'is a light beam incident on the pyrometer for measuring the temperature of the silicon substrate. And degrade the accuracy of the measured temperature.

  Therefore, the wall deposits need to be removed regularly, and the removal of the wall deposits is carried out by vapor phase etching using hydrogen chloride gas (HCl). However, excessive etching reduces the life of the chamber members, increases the cycle time, and deteriorates the productivity.

JP-A-2013-051350

  As described above, in vapor deposition, it is necessary to remove the wall deposit periodically by vapor etching using HCl. The required etching time varies as the thickness of the reacted epitaxial film is accumulated. Evaluate the amount of wall deposit remaining in the chamber with various epitaxial film thickness and etching time, and calculate the required etching time.

  However, the evaluation of the remaining amount of the wall deposit is not always accurate because it is performed visually. Further, the required etching time is influenced not only by the accumulation of the reacted epitaxial film thickness but also by the epitaxial reaction conditions such as the source gas species, the process temperature and the carrier gas flow rate.

  As described above, the etching time is added to the total of the epitaxial film thickness, and in order to perform the etching reliably, the introduction of the over etching time is required. However, excessive etching damages the susceptor made of a SiC member. In addition, an increase in etching time deteriorates productivity.

  The present invention has been made in view of the above-mentioned problems of the prior art, and when removing the wall deposit deposited in the chamber of the vapor phase growth apparatus by etching, the etching time can be shortened and damage to the susceptor due to overetching can be reduced. It is an object of the present invention to provide a vapor phase etching method and an epitaxial substrate manufacturing method capable of improving the productivity.

  In order to solve the above problems, the vapor phase etching method of the present invention is provided on a susceptor on which a substrate is placed, a chamber containing the susceptor, sealed by a transparent quartz member, and outside the chamber. A susceptor temperature measuring pyrometer installed to measure a susceptor temperature in the chamber across a location where a measurement light path is expected to generate a wall deposit on the inner wall surface of the transparent quartz member A vapor phase etching method implemented in a growth apparatus, wherein the temperature in the chamber is raised, and a reference temperature is set by measuring in advance the susceptor temperature in the absence of the wall deposit; When the temperature of the susceptor with the temperature in the chamber raised is lower than the reference temperature, the wall deposit is generated. A vapor phase etching start step of performing vapor phase etching on the assumption that the gas phase etching is performed, and a vapor phase etching end step of terminating the vapor phase etching when the susceptor temperature reaches the reference temperature. .

  The cold wall type vapor phase growth apparatus heats the susceptor with a heater, and performs epitaxial reaction and vapor phase etching while cooling the furnace body. Since the reaction efficiency is high at a high temperature in the vapor phase etching, the wall deposits on the susceptor are easy to remove, whereas the wall deposits on the chamber wall surfaces need to be etched for a long time. In particular, the temperature of the transparent quartz member is hard to increase, and the wall deposit on the transparent quartz member tends to be unetched.

  For this reason, at the timing when the wall deposit on the transparent quartz member in the chamber is removed, it can be considered that the wall deposit deposited on a place other than on the transparent quartz member in the chamber has already been removed. Therefore, if the wall deposits on the transparent quartz member in the chamber are sequentially detected during the gas phase etching, and the gas phase etching is finished at the timing when the wall deposits are removed, the etching time is minimized. The damage to the susceptor can be reduced and the productivity can be improved.

  As a method for detecting a wall deposit on a transparent quartz member in the chamber, a pyrometer (a radiation thermometer) is used for susceptor temperature measurement. The susceptor temperature measurement pyrometer measures the temperature of the susceptor surface from the outside of the chamber through the transparent quartz member, and the place where generation of a wall deposit on the transparent quartz member in the chamber is predicted is the temperature of the susceptor surface It is installed at a position crossing the measurement light path between the measurement point and the detection unit of the susceptor temperature measurement pyrometer.

  When the wall deposit is generated on the transparent quartz member in the chamber, the wall deposit reflects and absorbs the radiation on the surface of the susceptor, and the measured value of the susceptor temperature measurement pyrometer is displayed lower than the actual temperature. When vapor phase etching is performed while heating the susceptor with a constant heater output, the wall deposit on the transparent quartz member is gradually removed, and the measured value of the susceptor surface temperature is increased.

  When the susceptor temperature at a predetermined heater output without wall deposition is measured in advance and a reference temperature is set, vapor phase etching is performed while controlling the heater to the output, and the susceptor reaches the reference temperature If the etching is finished, there is no residue left to remove the wall deposit in the chamber, and the etching time can be minimized.

  The portion of the inner wall surface where generation of a wall deposit of the chamber is predicted may be a portion on the inner wall surface of the transparent quartz member of the chamber which is likely to be formed. In particular, a susceptor temperature measurement pyrometer is installed on the inner wall surface of the transparent quartz member of the chamber where the wall deposit is most likely to be formed as a portion of the inner wall surface where generation of the wall deposit of the chamber is expected. It is suitable.

  In the vapor phase etching end step, the heater output is controlled so that the susceptor temperature becomes a predetermined temperature, and when the heater output becomes a predetermined value, it is considered that the susceptor temperature becomes the reference temperature The gas phase etching may be ended.

  That is, as described above, the vapor phase etching is performed while controlling the heater output constant, and the vapor phase etching is controlled constant as in the method of ending the etching when the susceptor reaches a predetermined temperature. The etching time can be shortened also by a method in which etching is performed and the etching is finished by regarding the susceptor temperature as the reference temperature at the timing when the heater output reaches a predetermined value.

  When there is deposition of a wall deposit on the transparent quartz member, the measured value of the susceptor temperature by the susceptor temperature measuring pyrometer decreases. When feedback control is performed on the heater output so that the susceptor temperature becomes constant, the heater output gradually decreases due to the vapor phase etching. When there is no wall deposit, the heater output when the susceptor temperature is controlled to a predetermined value is measured in advance, and vapor phase etching is performed while controlling the susceptor temperature constant, and when the susceptor reaches the heater output By completing the etching, it is possible to remove no wall deposit in the chamber and to minimize the etching time.

  In the method of manufacturing an epitaxial substrate according to the present invention, after the chamber of the vapor phase growth apparatus is cleaned by vapor phase etching by the vapor phase etching method, the substrate is placed on the susceptor in the cleaned chamber, and the substrate In the method of manufacturing an epitaxial substrate, an epitaxial layer is formed on the surface of the substrate by introducing a source gas into the chamber while raising the temperature with a heating device.

  According to the vapor phase etching method of the present invention, when the wall deposit deposited in the chamber of the vapor phase growth apparatus is removed by etching, the etching time can be shortened, damage to the susceptor due to over etching is reduced, and productivity is improved. A significant effect of providing a vapor phase etching method and an epitaxial substrate manufacturing method that can be performed is achieved.

It is sectional drawing which shows an example of the vapor phase growth apparatus with which the vapor phase etching method of this invention is implemented. It is the principal part schematic of the vapor phase growth apparatus with which the vapor phase etching method of this invention is implemented. It is transition of the susceptor temperature in vapor-phase etching in the Example of this invention. It is the principal part schematic of a vapor phase growth apparatus.

  Hereinafter, the embodiments of the present invention will be described with reference to the drawings, but these are shown as examples and it goes without saying that various modifications can be made without departing from the technical concept of the present invention.

  In the vapor phase etching method of the present invention, a cold wall type single wafer type vapor phase growth apparatus is provided which is equipped with a susceptor for mounting a wafer in a chamber and which has a chamber sealed with a transparent quartz member. FIG. 1 shows an example of a vapor phase growth apparatus in which the vapor phase etching method of the present invention is carried out.

  As shown in FIG. 1, the cold-wall type vapor deposition apparatus 13 includes a susceptor 2 for mounting a wafer W in a chamber 1. Further, transparent quartz members 4, 4 'for sealing the chamber 1 by sandwiching the chamber base 3, 3' made of SUS (stainless steel) from above and below, and the opaque quartz member 5 for covering the chamber base 3, 3 '. , 5 '. The susceptor 2 is supported by a susceptor support 6, and the susceptor support 6 is connected to a rotation mechanism 7.

In the chamber 1, a vapor phase gas is introduced into the upper region of the susceptor in which a vapor phase growth gas containing a source gas (eg, SiCl ₄ , SiHCl ₃ , SiH ₂ Cl ₂ , SiH ₄ , and a dopant) and a carrier gas (eg, hydrogen) is added. A growth gas inlet 8 is provided. Further, in the chamber 1, a gas discharge port 9 for discharging the gas is provided on the opposite side of the vapor growth gas introduction port 8.

  In order to heat the wafer W and the susceptor 2 through the transparent quartz members 4 and 4 ', heaters 10 and 10' such as lamps are provided at the upper and lower portions of the chamber. Further, a pyrometer 11 for wafer temperature measurement and a pyrometer 12 for susceptor temperature measurement are provided for measuring the temperatures of the wafer W and the susceptor 2 from the upper part of the wafer, respectively.

  The susceptor temperature measurement pyrometer 12 measures the temperature of the susceptor 2 in the chamber 1 across the portion where the measurement light path is expected to generate a wall deposit on the inner wall surface of the transparent quartz members 4 and 4 '. Install in In particular, it is preferable to set the susceptor surface temperature to be measured in a field of view where the measurement light path crosses the portion where the wall deposit is most likely to be deposited on the transparent quartz members 4 and 4 '.

  An epitaxial wafer is formed by forming a silicon epitaxial layer on, for example, a silicon wafer having a diameter of 300 mm using such a single wafer type vapor deposition apparatus. The epitaxial layer production flow of the epitaxial wafer will be described below.

  First, a wafer W is loaded into the chamber 1 by a substrate loading robot (not shown) or the like and placed on the susceptor 2. While supplying, for example, 50 slm of hydrogen from the vapor phase growth gas inlet 8 and rotating the wafer W at 50 rpm by the rotation mechanism 7, the wafer W is heated to, for example, 1100 ° C. by the heaters 10 and 10 'which is a heating device. The measured value of the wafer temperature measuring pyrometer 11 is fed back to control the output of the heaters 10 and 10 'so as to keep the temperature constant, and annealing is performed, for example, for 30 seconds. Thus, the natural oxide film on the surface of the wafer W is removed, and the surface of the wafer W is hydrogen-terminated.

After annealing, while maintaining the wafer temperature at 1100 ° C., for example, SiHCl ₃ as a source gas is diluted with hydrogen to, for example, 3%, and a reactive gas introduced with several ppb of dopant is introduced into, for example, 50 slm chamber 1. SiHCl ₃ is reduced on the wafer W to form a silicon epitaxial film, and an exhaust gas composed of unreacted gas and reaction byproducts is exhausted from the gas exhaust port 9. Then, the wafer is cooled to, for example, 600 ° C., and then the wafer W is unloaded from the chamber 1.

  By repeating such an epitaxial reaction, a wall deposit is deposited on the surfaces of the susceptor 2, the transparent quartz members 4 and 4 ′, and the opaque quartz members 5 and 5 ′. Therefore, when the accumulated film thickness of the epitaxial wafer becomes, for example, 20 μm or more, the wall deposit is removed by vapor phase etching. The flow of the vapor phase etching method according to the present invention is shown below.

  First, the temperature inside the chamber 1 is raised, the heater output is controlled to be constant, the temperature of the susceptor 2 in the absence of the wall deposit is measured in advance, and this is used as the reference temperature. The reference temperature is, for example, 1200 ° C.

  When the susceptor 2 is heated with a predetermined heater output and the temperature of the susceptor 2 is measured with the susceptor temperature measurement pyrometer 12, the radiation light 16 is not attenuated as shown in FIG. 2A. The measured temperature displayed will be correct.

  However, if there is a wall deposit 14 on the measurement light path between the susceptor 2 and the susceptor temperature measurement pyrometer 12, the radiation light 16 of the susceptor temperature measurement pyrometer 12 becomes attenuated radiation 16 'and the display The measured temperature is lowered. Therefore, the temperature in the chamber 1 is raised, the heater output is controlled to be constant, and the temperature of the susceptor 2 in the state where there is no wall deposit as shown in FIG. .

  Next, when the susceptor temperature in the state where the temperature in the chamber 1 is raised is lower than the reference temperature, it is considered that the wall deposit 14 is generated as shown in FIG. 2 (b). Start phase etching. If the reference temperature is, for example, 1200 ° C. and the susceptor temperature only reaches, for example, 1160 ° C. even if the temperature in the chamber 1 is raised, it is considered that a wall deposit is formed.

  In the vapor phase etching, the heater output is controlled to raise the temperature of the susceptor 2 to, for example, 1200 ° C. The temperature of the transparent quartz members 4, 4 'and the opaque quartz members 5, 5' is increased by maintaining the susceptor temperature for, for example, 60 seconds. Subsequently, while controlling the heater output to a constant level, HCl gas is introduced into, for example, the 25 slm chamber 1 to remove the wall deposit.

  In this way, the wall deposit on the chamber wall surface is removed, and when the susceptor temperature reaches a predetermined reference temperature is taken as the end point of the etching. Thereafter, the temperature inside the chamber 1 is lowered.

  An example showing the relationship between the elapsed time of vapor phase etching and the susceptor temperature is shown in FIG. In the example shown in FIG. 3, the measured value of the susceptor temperature rises by removing the wall deposit on the transparent quartz members 4, 4 'for 50 seconds after the start of etching, but there is no temperature change after 50 seconds , Over etching. In the example of the flow of the vapor phase etching method according to the present invention described above, since the etching is completed when the temperature change reaches 1200 ° C., the etching can be performed without excess or deficiency. In addition, since the vapor phase etching is conventionally performed for about 70 seconds, the vapor phase etching time is shortened by 20 seconds.

  As described above, according to the present embodiment, the susceptor surface temperature is measured by the susceptor temperature measurement pyrometer 12 at the time of vapor phase etching, and when the susceptor temperature reaches a predetermined value, the chamber is used as the etching end point. It is possible to reliably remove the wall deposits adhering to the wall deposits on the transparent quartz members 4 and 4 'of 1. In addition, the wall deposits generated on the members in the chamber 1 (the surface of the susceptor 2, the inner wall of the transparent quartz members 4, 4 ', the inner wall of the opaque quartz members 5, 5') are also removed.

  In the vapor phase etching method according to the present invention, since the vapor phase etching time is shortened compared to the conventional method, the damage to the SiC member due to the etching can be reduced, and the productivity can be improved.

  In the above embodiment, an example is described in which the etching is ended when the susceptor temperature reaches a predetermined temperature, but the heater output is feedback controlled so that the susceptor temperature becomes constant, and the heater output is predetermined. The gas phase etching may be ended assuming that the susceptor temperature has become the reference temperature when it reaches a value.

Next, a method of manufacturing the epitaxial substrate of the present invention will be described.
First, using the epitaxial growth apparatus 13 having the chamber 1 cleaned by the vapor phase etching method of the present invention as described above, the chamber 1 of the epitaxial growth apparatus 13 can be used as a substrate by a substrate loading robot (not shown) or the like. A silicon single crystal wafer W is loaded and placed on the susceptor 2.

  Thereafter, the raw material gas is introduced into the chamber while raising the temperature of the wafer W to, for example, 1100 ° C. by the heaters 10 and 10 ′, which are heating devices, in the same manner as the epitaxial layer manufacturing flow described above. Form layers and produce an epitaxial wafer. Thereby, a silicon epitaxial layer is formed on the main surface of wafer W, and a silicon epitaxial wafer can be manufactured.

1: Chamber 2, 2: Susceptor 3, 3 3: Chamber base 4, 4 ': Transparent quartz member 5, 5': Opaque quartz member 6: 6: Susceptor support, 7: Rotation mechanism, 8: Vapor phase growth Gas inlet, 9: gas outlet, 10, 10 ': heater, 11: pyrometer for wafer temperature measurement, 12: pyrometer for susceptor temperature measurement, 13: vapor phase growth apparatus, 14: wall deposition, 15: irradiation Light, 16: radiation, 16 ': attenuated radiation, W: wafer.

Claims (3)

A susceptor on which a substrate is mounted, and a chamber in which the susceptor is accommodated and sealed by a transparent quartz member;
Susceptor temperature measurement, provided outside the chamber, for measuring the temperature of the susceptor in the chamber across a location where a measurement light path is expected to generate a wall deposit on the inner wall surface of the transparent quartz member A vapor phase etching method implemented in a vapor phase growth apparatus having a pyrometer,
Setting the reference temperature by raising the temperature in the chamber and measuring the susceptor temperature in the absence of the wall deposit in advance;
A vapor phase etching start step of performing vapor phase etching on the assumption that the wall deposit is generated when the susceptor temperature in a state where the temperature in the chamber is raised is lower than the reference temperature;
A vapor phase etching termination step of terminating the vapor phase etching when the susceptor temperature reaches the reference temperature;
Vapor phase etching method including: In the vapor phase etching end step, the heater output when the susceptor temperature is controlled to a predetermined value when there is no wall deposition is measured in advance, and the heater output is fed back so that the susceptor temperature becomes a constant temperature. 2. The gas phase etching according to claim 1, wherein the vapor phase etching is terminated by controlling the susceptor temperature to be the reference temperature when the heater output reaches the previously measured heater output. Vapor phase etching method.   After cleaning a chamber of a vapor phase growth apparatus by vapor phase etching according to the vapor phase etching method according to claim 1 or 2, a substrate is placed on a susceptor in the cleaned chamber, and the substrate is heated. A method for producing an epitaxial substrate, comprising forming an epitaxial layer on the surface of the substrate by introducing a source gas into the chamber while raising the temperature.

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