Manufacturing equipment of SiC single crystal and method for manufacturing SiC single crystal

A method for manufacturing a SiC single crystal from a SiC seed crystal is provided. The method includes the steps of: measuring a diameter of the SiC single crystal during a crystal growth of the SiC single crystal; and controlling the diameter of the SiC single crystal to be a predetermined diameter on the basis of the measured diameter. The method provides the SiC single crystal with high quality and large size.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on Japanese Patent Applications No. 2004-248656 filed on Aug. 27, 2004, and No. 2005-195558 filed on Jul. 4, 2005, the disclosures of which are incorporated herein by references.

FIELD OF THE INVENTION

The present invention relates to manufacturing equipment of a SiC single crystal and a method for manufacturing a SiC single crystal.

BACKGROUND OF THE INVENTION

A SiC (silicon carbide) single crystal has high withstand voltage and high electron mobility. Therefore, the SiC single crystal is used for a semiconductor substrate of a power device. The SiC single crystal is formed by a sublimation method (i.e., a modified Lely method).

In the modified Lely method, raw material of SiC is mounted in a graphite crucible. A seed crystal of SiC is mounted on an inner wall of the crucible in such a manner that the seed crystal faces the raw material. Then, the raw material is heated at a temperature in a range between 2200° C. and 2400° C. so that a sublimation gas is generated. The sublimation gas reaches the seed crystal so that the gas is re-crystallized on the seed crystal. Here, the temperature of the seed crystal is set to be a temperature, which is lower than the raw material by a few tens degrees C. to a few hundreds degrees C. Thus, the SiC single crystal is grown on the seed crystal.

In this modified Lely method, as the SiC single crystal is grown, the SiC raw material is deteriorated, i.e., the composition of the raw material is changed. Thus, the growth amount of the SiC single crystal is limited. Even when additional raw material is added into the crucible during the crystal growth of SiC, the concentration of the sublimation gas is deviated from the initial composition so that the single crystal is not continuously grown with high quality. This is because the sublimation gas of SiC has the composition of silicon and carbon, which is not 1:1, i.e., stoichiometric.

A method for forming a SiC single crystal by a CVD method is disclosed in U.S. Pat. No. 6,030,661 and U.S. Pat. No. 5,704,985. Specifically, the SiC single crystal is grown by an epitaxial growth method. In this method, gas phase raw material is used for forming the SiC single crystal. Therefore, the composition of the raw material is controlled stably. Further, the raw material can be supplied continuously.

However, as the SiC single crystal is grown, environment around the growth surface of the seed crystal is changed so that crystal growth conditions are changed. Accordingly, the quality of the single crystal may be changed in a case where the single crystal is grown longer and larger. Specifically, it is difficult to perform the lengthy crystal growth with high crystal quality.

To improve the above problem, a raising growth method such as a CZ method is disclosed as a prior art. This method is such that the crystal is raised up from melted raw material liquid. The crystal growth is controlled at a boundary between solid and liquid. This technique can be applied to gas phase crystal growth. For example, in Japanese Patent Application Publication No. H06-298594, a crucible is moved down, and a seed crystal is moved up, independently. However, this method is the gas phase crystal growth; and therefore, the raw material gas diffuses everywhere. Thus, a SiC poly crystal is grown at everywhere. Thus, the crystalline of the single crystal is deteriorated, and equipment for manufacturing the SiC single crystal is also damaged.

To limit a raw material gas from diffusing, a method for crystal growth with using a guide is disclosed in Japanese Patent Application Publication No. 2001-226197. In this method, the guide is disposed near the side of the seed crystal so that the raw material gas is prevented from penetrating to the side of the seed crystal. Thus, the crystal growth is performed stably. However, the raw material gas is not completely protected, so that a part of the raw material gas penetrates to the side of the seed crystal. Thus, the diameter of the single crystal becomes larger. Therefore, the single crystal having a target diameter is not obtained.

SUMMARY OF THE INVENTION

In view of the above-described problem, it is an object of the present invention to provide manufacturing equipment of SiC single crystal and a method for manufacturing SiC single crystal.

A method for manufacturing a SiC single crystal from a SiC seed crystal is provided. The method includes the steps of: measuring a diameter of the SiC single crystal during a crystal growth of the SiC single crystal; and controlling the diameter of the SiC single crystal to be a predetermined diameter on the basis of the measured diameter.

The method provides the SiC single crystal having high quality and large size. Further, the SiC single crystal having the predetermined diameter is obtained.

Preferably, the step of controlling the diameter is performed together with the crystal growth of the SiC single crystal. Preferably, the crystal growth is performed together with pulling up the seed crystal. Preferably, the diameter of the SiC single crystal is measured on the basis of a combination of multiple measuring methods composed of a method by using X-ray, a method by using a plurality of X-ray generating devices and a plurality of X-ray detectors, a method by using a pair of X-ray generating device and a detector, which is capable of moving around the SiC single crystal, a method on the basis of a difference between a pressure of a downstream side of a raw material gas and a pressure of an upstream side of the raw material gas, a method on the basis of a gas flow amount of the raw material gas, a method on the basis of a gas flow speed of the raw material gas, a method on the basis of an amount of light, a method on the basis of an amount of a light wave or a sound wave, a method on the basis of a weight and a length of the SiC single crystal, and a method on the basis of change of a growth speed of the SiC single crystal. Preferably, the step of controlling the diameter is performed by changing an insertion amount of the SiC single crystal into the guide cover. More preferably, the diameter of the SiC single crystal becomes larger when the insertion amount of the SiC single crystal into a guide hole of the guide cover is large, and the diameter of the SiC single crystal becomes smaller when the insertion amount of the SiC single crystal into the guide hole of the guide cover is small. Preferably, the step of controlling the diameter is performed by changing a plurality of growth parameters. More preferably, the growth parameters include a high responsive growth parameter and a low responsive growth parameter, and the diameter of the SiC single crystal is controlled by changing both of the high responsive growth parameter and the low responsive growth parameter. More preferably, the crystal growth is performed in such a manner that a guide cover is disposed on a side of the SiC single crystal. The crystal growth is performed by supplying a raw material gas to the seed crystal continuously. The high responsive growth parameter is at least one of a group consisting of an insertion amount of the SiC single crystal into a guide hole of the guide cover, a partial pressure of the raw material gas reaching the SiC single crystal, a gas flow amount of the raw material gas reaching the SiC single crystal. Preferably, the low responsive growth parameter is at least one of a group consisting of a temperature of the guide cover and a pulling speed of the SiC single crystal

Further, manufacturing equipment of manufacturing a SiC single crystal from a SiC seed crystal includes: measuring means for measuring a diameter of the SiC single crystal during a crystal growth of the SiC single crystal; and controlling means for controlling the diameter of the SiC single crystal to be a predetermined diameter on the basis of the measured diameter. The equipment manufactures the SiC single crystal having high quality and large size. Further, the SiC single crystal having the predetermined diameter is obtained.

Furthermore, manufacturing equipment of manufacturing a SiC single crystal from a SiC seed crystal includes: a cylindrical member; a base including a columnar portion and a circular plate portion; a guide cover disposed on a side of the SiC single crystal; a measuring device for measuring a diameter of the SiC single crystal during a crystal growth of the SiC single crystal; and a controlling device for controlling the diameter of the SiC single crystal to be a predetermined diameter on the basis of the measured diameter. The circular plate portion is disposed on one end of the columnar portion. The circular plate portion has an outer diameter, which is larger than an outer diameter of the columnar portion. The seed crystal is disposed on the other end of the columnar portion. The base is capable of sliding in the cylindrical member in such a manner that an outer surface of the circular plate portion contacts an inner surface of the cylindrical member. The base is capable of sliding in a sliding direction, which is opposite to a growth direction of the SiC single crystal. The guide cover includes a guide hole. The guide cover is disposed on an opening of the cylindrical member. The guide hole has a diameter, which is smaller than an inner diameter of the cylindrical member. The guide hole is capable of passing a raw material gas therethrough toward the seed crystal. The equipment manufactures the SiC single crystal having high quality and large size. Further, the SiC single crystal having the predetermined diameter is obtained.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

Manufacturing equipment of a SiC (silicon carbide) single crystal according to a first embodiment of the present invention is shown inFIGS. 1A and 2.FIG. 2shows a main part of the equipment shown as II inFIG. 1A. The equipment performs to grow a SiC single crystal14from a seed crystal13.

The equipment includes a vacuum chamber1having a cylindrical shape. The vacuum chamber1is composed of a main chamber2, an upper chamber3and a lower chamber4. The upper chamber3is disposed on the main chamber2, and the lower chamber4is disposed under the main chamber2. The inside of the main chamber2, the inside of the upper chamber3and the inside of the lower chamber4are connected each other. A reaction chamber composed of a lower reaction chamber5and an upper reaction chamber6is disposed in the main chamber2. A raw material gas is introduced into the reaction chamber through the lower chamber4. Further, the SiC single crystal14after the crystal growth is retrieved from the upper chamber3.

The upper chamber3is made of, for example SUS (i.e., stainless steel). A retrieve outlet3ais disposed on the sidewall of the upper chamber3. The SiC single crystal14is retrieved from the retrieve outlet3a. An exhaust pipe7is connected to a cover3bof the upper chamber3. Further, the exhaust pipe7is connected to a vacuum pump (not shown). The vacuum pump or a vacuum pump system controls pressure of the vacuum chamber1, and further, performs purge of the vacuum chamber1.

The main chamber2and the lower chamber4are made of a quartz tube. The diameter of the lower chamber4is smaller than the diameter of the main chamber2. The main chamber2and the lower chamber4are connected through a plate2a. The lower chamber4includes a bottom plate4a, to which a gas introduction pipe8is connected. The gas introduction pipe8extends in a vertical direction, i.e., an up-and-down direction. The gas introduction pipe8is connected to another gas introduction pipe9. The other gas introduction pipe9extends in a horizontal direction.

A heat insulation member10is disposed inside of the main chamber2. The lower reaction chamber5having a cylindrical shape and having a bottom is disposed inside of the heat insulation member10in the main chamber2. The lower reaction chamber5is vertically arranged in the main chamber2. The lower reaction chamber5is made of graphite. The lower reaction chamber5has an upper opening. The upper reaction chamber6having a cylindrical shape and having a cover is disposed on the upper opening of the lower reaction chamber5. The lower reaction chamber5and the upper reaction chamber6have a positional relationship such that the upper reaction chamber6having the cylindrical shape and having the cover covers the lower reaction chamber5to cap from the lower opening side of the upper reaction chamber6. In this case, the outer surface of the lower reaction chamber5is separated from the inner surface of the upper reaction chamber6by a predetermined distance. The upper end of the lower reaction chamber5is separated from a cover as a guide cover6aof the upper reaction chamber6.

A guide hole11as a through hole for guiding the raw material gas is formed at the center of the cover6aof the upper reaction chamber6. The raw material gas passes through the guide hole11of the cover6a. Thus, the cover6aof the upper reaction chamber6provides a guide member for the raw material gas.

A base12is disposed over the upper reaction chamber6. The base12is composed of a columnar portion12aand a circular plate portion12bas a radial disk portion. The circular plate portion12bextends in a horizontal direction and has a plate shape. The columnar portion12aprotrudes from the center of the bottom of the circular plate portion12b. Specifically, the columnar portion12aprotrudes downwardly. The circular plate portion12bhaving a disk shape is formed on the top of the circular plate portion. The circular plate portion12bhas a diameter, which is larger than that of the columnar portion12a. A SiC semiconductor substrate13as a seed crystal is attached and fixed on the bottom of the columnar portion12a. The SiC single crystal14is grown from the substrate13as the seed crystal through the guide hole11. The SiC single crystal14is grown at the center of the guide hole11. Thus, the guide member as the guide cover6ais arranged on the side of the single crystal14.

In the vacuum chamber1, the heat insulation member15is disposed under the lower reaction chamber5. The heat insulation member15has a raw material gas supply passage15a. The raw material gas is introduced into the raw material gas supply passage15afrom the gas introduction pipes8,9. Then, the raw material gas passes through the raw material gas supply passage15aso that the raw material gas is supplied to the reaction chambers5,6, which are disposed over the supply passage15a. Specifically, the raw material gas includes a raw material gas such as a SiH4gas and a C3H8gas for providing the raw material of the SiC single crystal, an etching gas such as H2gas, CF4gas and O2gas, an inert gas such as Ar gas and He gas, and a dopant gas such as N2gas. Therefore, for example, a mixed gas of a silane gas and a propane gas is used as the raw material gas.

The raw material gas is continuously introduced and supplied into the main chamber2through the gas introduction pipes8,9. The base12is fixed on a bottom end of a shaft16. The shaft16extends in the vertical direction. The shaft16is connected to a vertical movement device17as a crystal raising device (i.e., crystal elevation device) so that the shaft16is movable upwardly and downwardly by the device17. Therefore, when the shaft16moves upwardly, the SiC single crystal14is moved to the upper chamber3as a specimen retrieve chamber. Further, after the seed crystal13is attached on the base12, the shaft16moves downwardly so that the seed crystal13is moved to the main chamber2. Further, the growing SiC single crystal14can be pulled up with any velocity during the crystal growth. Specifically, as shown inFIG. 2, the thickness of the cover6aas the guide member is defined as T1. A half of the thickness T1provides a standard height Ho of the growth surface of the SiC single crystal14. Here, the thickness T1of the cover6ais equal to the length of the guide hole11. The height of the base12, i.e., the height of the crystal14is controlled to set the growth surface of the crystal14, that is the bottom of the crystal14, to be disposed on the standard height Ho. The crystal growth is monitored by X-ray generation equipment21and an image tube22so that the bottom of the crystal14is controlled to be equal to the standard height Ho of the crystal growth. Here, a gas flow direction is from the lower reaction chamber5to the upper reaction chamber3. A growth direction of the SiC single crystal14is opposite to the gas flow direction. The seed crystal13is pulled up so that a pulling up direction as a moving direction of the seed crystal14is opposite to the growth direction.

A cylindrical member18is disposed on the upper reaction chamber6. The base12is disposed in the cylindrical member18. The cylindrical member18is made of graphite. The cylindrical member18includes multiple through holes18a, which are disposed under the circular plate portion12bof the base12. Each through hole penetrates the cylindrical member18in a radial direction. The raw material gas introduced from the guide hole11is discharged through the through holes18a. The inner surface of the cylindrical member18contacts the outer surface of the circular plate portion12bof the base12. The base12slides in the vertical direction with contacting the cylindrical member18to the circular plate portion12b.

InFIG. 1, a high frequency induction coil (i.e., RF coil)19as the first RF coil is winded to the outer surface of the vacuum chamber1. The RF coil19is disposed around the height of the guide hole11. The RF coil19works as heating means. The RF coil19is energized so that induction current flows through the RF coil19. The RF coil19is disposed around the height of the seed crystal13, the growing SiC single crystal14and the upper reaction chamber6. Thus, the upper reaction chamber6and the inside of the upper reaction chamber6are heated by the RF coil19. Further, another high frequency induction coil20as the second RF coil is winded on the outer surface of the vacuum chamber1. The second RF coil20is disposed under the first RF coil19. The second RF coil20is energized so that the lower reaction chamber5, the upper reaction chamber6and the inside of them are heated by the second RF coil20. The first and the second RF coils19,20can be independently controlled.FIG. 1Bshows a temperature profile of the inside of the equipment in the vertical direction when the SiC single crystal is grown. The temperature of the inside of the lower reaction chamber5is higher than the temperature of the guide hole side, which is disposed over the lower reaction chamber5.

The X-ray generating equipment21as X-ray generating means and the image tube22as X-ray detecting means, i.e., a X-ray detector, are disposed outside of the vacuum chamber1. The X-ray generating equipment21generates X-ray, and the image tube22detects the X-ray. The equipment21and the tube22observe the crystal14through the X-ray so that they work as diameter measurement means. The equipment21and the tube22are disposed outside of the RF coil19. The equipment21is opposite to the tube22so that they sandwich the guide hole11as a crystal growth chamber. The equipment21radiates the X-ray toward the guide hole11, i.e., the edge of the growth surface of the growing SiC single crystal14. The tube22receives the X-ray through the vacuum chamber1. Then, the tube22outputs a signal corresponding to the strength of the detected X-ray. Thus, the X-ray transmits the reaction chamber6and the crystal14so that the distribution of strength of the transmitted X-ray is detected by the image tube22. The edge of the growth surface of the growing crystal14can be observed as an image of the X-ray. Specifically, the absorption coefficient of X-ray of SiC is higher than that of carbon (i.e., C), which composes the reaction chamber6. Accordingly, the crystal14and the graphite reaction chamber6can be observed separately. The equipment21and the tube22provide X-ray generating and receiving apparatus for observing the diameter of the growing crystal14directly. The equipment21and the tube22provide the means for measuring the diameter of the crystal14.

A pyrometer23as the first pyrometer is disposed in the shaft16, and another pyrometer24as the second pyrometer is disposed under the gas introduction pipe8. The first and the second pyrometers23,24detects the temperature of the inside atmosphere of the base12and the reaction chambers5,6.

Next, a method for manufacturing the SiC single crystal14is described as follows. When the single crystal14is grown, the seed crystal13is mounted. Then, the vacuum chamber1is vacuumed, and an argon gas (i.e., Ar gas) is introduced into the chamber through the gas introduction pipes8,9. Then, the RF coils19,20are energized, so that the reaction chambers5,6are heated by an induction heating method. The temperature of the inside of the reaction chambers5,6is held at a predetermined temperature, and stabilized. Preferably, the temperature is held near 2400° C., which is a sublimation temperature of SiC. At the same time, a predetermined pressure is applied to the inside of the guide hole11. Thus, the raw material gas is introduced into the reaction chambers5,6through the raw material gas supply passage15aso that the pressure of the inside of the guide hole11is controlled to be a predetermined pressure. The raw material gas is supplied to the seed crystal13so that the crystal growth on the seed crystal13starts.

During the crystal growth, the base12is raised up to control the growth surface of the growing crystal14to be equal to the standard height Ho of growth surface. A part of the raw material gas flows through the guide hole11, and passes through a through hole18aof a cylindrical member18. Then, the gas flows toward the exhaust pipe7. Another part of the raw material gas passes through a clearance between the outer surface of the reaction chamber5and the inner surface of the reaction chamber6, and then, the gas flows toward the exhaust pipe7.

The SiC single crystal14is grown in accordance with supply of the raw material gas to the seed crystal13. When the length of the SiC single crystal14becomes a predetermined length, the supply of the raw material gas is stopped. Then, the single crystal14is retrieved from the retrieve outlet3a.

A control method of the diameter of the single crystal14is described as follows.FIGS. 4A to 4Cexplain a process in a case where the diameter of the crystal14expands during the crystal growth.FIGS. 5A to 5Cexplain another process in a case where the diameter of the crystal14shrinks during the crystal growth.

Firstly, the diameter of the crystal14is observed. The observation is performed by the X-ray generating equipment21and the image tube22. When the diameter of the crystal14expands, the diameter of the crystal14is controlled to shrink. This is, when the diameter of the crystal14becomes larger, the diameter of the crystal14is controlled to be smaller so that the diameter reaches the target diameter. Specifically, the insertion of the crystal14into the guide hole11becomes shallower, that is to pull up the crystal14. Thus, the raw material gas reached on the side of the crystal14is diffused to a top of the cover6a, so that the gas does not deposit on the side of the crystal14. Further, a part of the crystal14, which is a diameter expanding portion of the crystal14, is etched and sublimes. Thus, the diameter of the crystal14becomes smaller. The raw material gas reached on the bottom of the crystal14adheres on the bottom, i.e., the growth surface of the crystal14. Thus, the crystal growth on the growth surface of the crystal14is performed. Then, the insertion of the crystal14returns to a standard position, as shown inFIG. 4C.

When the diameter of the crystal shrinks, as shown inFIG. 5A, the diameter of the crystal14is controlled to expand. This is, when the diameter of the crystal14becomes smaller, the diameter of the crystal14is controlled to be larger so that the diameter reaches the target diameter. Specifically, the insertion of the crystal14into the guide hole11becomes deeper, that is to pull down the crystal14. Thus, the resistance of the raw material gas flowing toward the top of the guide hole11through the clearance between the inner surface of the guide hole11and the crystal14becomes larger. Thus, the retention time of the gas on the side of the crystal14becomes longer. As a result, the crystal growth in the radial direction proceeds at a diameter shrinking portion of the crystal14. Thus, the diameter of the crystal14becomes larger. The raw material gas reached on the bottom of the crystal14adheres on the growth surface of the crystal14. Thus, the crystal growth on the growth surface of the crystal14is performed. Then, the insertion of the crystal14returns to a standard position, as shown inFIG. 5C.

The above control is performed by a person or automatically during the crystal growth. Thus, the SiC single crystal ingot with high quality is obtained. In this embodiment, the diameter control means for controlling the diameter of the crystal14to be a predetermined diameter is provide by the cover6aand the vertical movement equipment17on the basis of the measurement result of the diameter of the crystal14measured by the diameter detecting means.

The detailed description of the control is described as follows.

Firstly, the seed crystal13is mounted on the base12. The seed crystal13has an initial diameter of φ1, which is 100 mm. The seed crystal is mounted at a predetermined position. The seed crystal13is mounted on the base12in such a manner that a C-surface, i.e., a (0001)-surface of 4H—SiC crystal structure faces the guide hole11. The inner diameter of the guide hole11is 102 mm. Therefore, a distance Δd between the inner surface of the guide hole11and the seed crystal13or the SiC single crystal14is 1 mm. The thickness of the cover6ais 20 mm. Therefore, in the standard position of the seed crystal13, the bottom, i.e., the growth surface of the seed crystal13is inserted into the guide hole11by 10 mm. The standard height Ho is disposed from the bottom of the cover6aby 10 mm.

Then, the vacuum chamber1is vacuumed, and the argon gas is introduced into the chamber1through the gas introduction pipes8,9with flowing amount of 10 SLM (i.e., standard liter per minute). Then, the RF coils19,20are energized, so that the temperature of the inside of the reaction chambers5,6is heated up to 2400° C. Then, when the temperature of the inside of the reaction chambers5,6is stabilized around 2400° C., the pressure of the chamber1is set to be 2.66×104Pa. Thus, the raw material gas is introduced into the reaction chambers5,6by using a mass flow controller and the like. Specifically, a SiH4gas is introduced with a flow rate of 1.2 SLM, a C3H8gas is introduced with a flow rate of 0.32 SLM, and an argon gas is introduced with a flow rate of 3.0 SLM. Then, the crystal growth starts. At the same time, the X-ray generating equipment21is driven so that the diameter of the crystal14and the crystal growth rate of the crystal14are measured. The base12, i.e., the crystal14is pull up in accordance with the growth rate, so that the edge of the crystal14is ordinary inserted into the guide hole11by 10 mm.

One example of the crystal growth is as follows. From the beginning of the crystal growth, the diameter of the crystal14becomes larger slightly. After the crystal growth is performed for five hours, the length of the grown crystal14becomes 7 mm. At that time, the diameter of the crystal14is 100.4 mm. Therefore, the radius of the crystal14expands by 0.2 mm. The expansion of the radius reaches about 20% of the distance Δd between the inner surface of the guide hole11and the crystal14. Here, the distance Δd is initially 1 mm. Accordingly, the crystal14is pulled up from the guide hole11by 5 mm so that the growth surface of the crystal14is inserted into the guide hole11by 5 mm. Then, the crystal growth is maintained for 30 minutes. After that, the diameter of the crystal14is reduced to 100 mm. Then, the growth surface of the crystal14is inserted into the guide hole11by 7 mm. Then, the crystal growth is continued for 7 hours. After that, the diameter of the crystal14becomes to be 99.6 mm. Then, the growth surface of the crystal14is pull down by 10 mm. Then, the crystal growth is continued. By repeating these steps, the crystal growth is performed for 50 hours with continuous growth. Then, the SiC single crystal having the growth length of 65 mm is obtained.

Thus, the crystal growth is performed with pulling the crystal14up and down. In general, the raw material of the SiC crystal is the raw material gas. Therefore, the raw material gas may penetrate around the seed crystal13, or the grown crystal14may be sublimed, so that the diameter of the crystal14becomes smaller or larger. To solve the above problem, in this embodiment, the diameter of the growing crystal14is observed, so that the diameter of the crystal is controlled to be a predetermined diameter. Specifically, the diameter of the crystal14is observed by using the transmitted X-ray so that the inside of the reaction chambers is observed. The control of the diameter is performed by an insertion amount of the crystal14into the guide hole11so that the raw material gas flowing to the side of the crystal14is controlled. These steps are repeated by multiple times. Then, the SiC single crystal having high quality and having large length is obtained. Thus, the crystal growth is continuously performed.

The method for manufacturing the SiC single crystal includes two steps. One is to measure the diameter of the growing crystal14directly. The other is to control the diameter of the growing crystal14to be a predetermined diameter as a target diameter. Thus, the crystal having a predetermined diameter is obtained. This is, the crystal having a large length can be grown without deviating the target diameter. By controlling the diameter to enlarge or to reduce, the SiC single crystal is grown without contacting the cover6a. Thus, by measuring the diameter of the crystal14, a direction of control of the diameter is determined.

Further, the diameter of the crystal14is controlled together with growing the crystal14, as shown inFIGS. 4B and 5B. Further, the raw material gas is continuously supplied, so that the crystal growth is effectively performed.

Further, since the crystal14is pulling up during the crystal growth, the growth condition is stable and substantially constant. Thus, the crystal growth is performed stably. Further, the diameter of the crystal14can be controlled easily by using the cover6aas the guide member. Here, the cover6ais disposed on the side of the crystal14.

The diameter of the crystal is controlled accurately on the basis of the observation of the diameter by using the X-ray. The X-ray observation can be performed from the bottom of the crystal14so that the crystal14is observed directly.

The measurement position of the diameter of the crystal14by using the X-ray is the edge of the growth surface of the crystal14. Therefore, even when the observation region is narrow, the diameter change is effectively observed. Therefore, the X-ray generating equipment21and the image tube22can be smaller.

Further, the diameter of the crystal14is controlled by the insertion of the crystal14into the cover6a. Therefore, the growth condition near the growth surface is not changed substantially. Thus, the diameter of the crystal14can be controlled with performing the crystal growth. Specifically, the crystal14is inserted into the cover6adeeply so that the diameter of the crystal14becomes larger. This is because the flowing resistance of the raw material gas is increase when the crystal14is inserted into the guide hole11deeply. Thus, the adhesion of the gas on the side of the crystal14proceeds so that the diameter of the crystal14increases. Further, the crystal14is inserted into the cover6ashallowly so that the diameter of the crystal14becomes smaller. This is because the flowing resistance of the raw material gas is decreased when the crystal14is inserted into the guide hole11shallowly. Thus, the adhesion of the gas on the side of the crystal14is reduced so that the diameter of the crystal14decreases. Thus, the diameter of the crystal14can be controlled without changing a main parameter such as temperature and pressure. Here, the main parameter affects the quality of the crystal14.

Here, the diameter of the crystal14is controlled as follows. As shown inFIG. 4B, a deviation Δt from a radius of a target diameter φ1is controlled to be in a range between +20% and −20% of the distance Δd between the inner surface of the guide hole11and the SiC single crystal14. The deviation Δt can be controlled in a range between +50% and −50% of the distance Δd. This is because the flowing resistance of the raw material gas penetrating to the top of the cover6abecomes larger when the diameter becomes larger. Thus, the diameter of the crystal14is rapidly increased. When the diameter of the crystal14becomes smaller, the flowing resistance of the gas becomes smaller. Thus, the diameter of the crystal14is rapidly reduced. As a result, when the deviation Δt is out of the range between +50% and −50% of the distance Δd, increasing amount or decreasing amount of the diameter of the crystal14becomes larger than speed of controlling the diameter. Therefore, it is difficult to control the diameter. Thus, it is required to control the deviation Δt to be in a range between +50% and −50% of the distance Δd.

Further, it is preferred that the deviation Δt is controlled to be in a range between +2% and −2% of the radius of the target diameter φ1of the crystal14. In this case, heat emission amount of the crystal14to the base12and heat radiation are not changed substantially. Therefore, the crystal growth condition can be maintained stably. Specifically, since the SiC single crystal14is grown at high temperature near 2000° C., the heat radiation affects the crystal growth. Therefore, when the diameter of the crystal14changes, the temperature distribution around the reaction chambers5,6also changes. Accordingly, when the deviation Δt is out of the range between +2% and −2% of the radius of the target diameter φ1of the crystal14, it is difficult to control the temperature distribution accurately. Further, when the deviation Δt is in a range between +2% and −2% of the radius of the target diameter φ1of the crystal14, it is easy to perform a later process such as wafer process.

Second Embodiment

Manufacturing equipment for manufacturing a SiC single crystal according to a second embodiment of the present invention is shown inFIG. 6A. Although the equipment shown inFIG. 1includes the X-ray generating equipment21and the image tube22, the equipment shown inFIG. 6Aincludes an optical detector30. The optical detector30measures amount of light passing through a guide hole32so that the optical detector30indirectly measures the diameter of the crystal14. Specifically, the optical detector30indirectly measures a distance between the crystal14and the cover6aby detecting leakage of the light. The optical detector30is fixed on the shaft16. A slit31for observing the light is formed on the circular plate portion12bof the base12. The light to be observed is, for example, radiation light from the top of the cover6aand radiation light from the reaction chambers5,6passing through a clearance between the crystal14and the cover6a. The radiation light from the reaction chambers5,6is emitted at high temperature higher than that of the radiation light from the top of the cover6a. Therefore, they can be separately observed. Accordingly, change of the distance between the crystal14and the cover6a, i.e., the inner surface of the guide hole32, can be estimated on the basis of change of the radiation light from the reaction chambers5,6. Thus, the diameter of the crystal14can be measured indirectly. The guide hole32has a tapered shape so that a diameter of the guide hole32becomes larger as it goes to upside. Here, the upside of the equipment is a pulling up direction. Thus, the diameter of the crystal14becomes a little larger as the crystal growth proceeds.FIG. 6Bshows an observed view of the optical detector30.FIG. 6Cshows a temperature distribution of the inside of the chambers5,6.

The control method for the diameter of the crystal14is described as follows.FIGS. 7A to 7Cexplain a process in a case where the diameter of the crystal14expands during the crystal growth.FIGS. 8A to 8Cexplain another process in a case where the diameter of the crystal14shrinks during the crystal growth.

Firstly, as shown inFIG. 7A, the diameter of the crystal14is observed. For example, when the diameter of the crystal14becomes larger than a target diameter, the crystal growth is controlled to reduce the diameter of the crystal14, as shown inFIG. 7B. In this case, the electricity of the RF coil19disposed upside of the equipment is increased so that the temperature of the cover6abecomes higher. Thus, the temperature of the side of the crystal14is increased intensively. As a result, the outer periphery of the bottom of the crystal14is etched so that the diameter of the crystal14is decreased. On the other hand, the temperature of the center of the bottom of the crystal14is not changed substantially, since the radiation from the power reaction chamber5and the emission to the base12mainly affect the temperature of the crystal14. Accordingly, the raw material gas reached to the bottom of the crystal14adheres on the bottom so that the crystal growth is performed on the bottom of the crystal14. Thus, as shown inFIG. 7C, the diameter of the crystal14is reduced, and then, the crystal growth continues.

As shown inFIG. 8A, when the diameter of the crystal14becomes smaller than the target diameter, the crystal growth is controlled to increase the diameter of the crystal14. In this case, the electricity of the RF coil19is reduced, so that the temperature of the cover6ais reduced. As a result, the temperature of the side of the crystal14is also reduced. Thus, the crystal growth on the side of the crystal14proceeds in the radial direction, so that the diameter of the crystal14becomes larger. Further, the raw material gas reached on the center of the bottom of the crystal14adheres on the bottom so that the crystal growth proceeds. Next, as shown inFIG. 8C, the crystal growth continues.

These operations are performed by an operator or automatically. Thus, the SiC single crystal ingot having high quality is obtained.

The detailed description of the equipment according to this embodiment is described as follows.

Firstly, the seed crystal13is mounted on the base12. The seed crystal13has a diameter of 100 mm, and disposed on a predetermined position. The C-surface of 4H—SiC crystal structure (i.e., a (0001)-surface) of the seed crystal13faces the guide hole32. The guide hole32has a lower side inner diameter of 102 mm, and an upper side inner diameter of 104 mm. Thus, the tapered shape of the guide hole32expands toward the pulling up direction. The thickness of the cover6a, i.e., the length of the guide hole32, is 20 mm. The growth surface (i.e., the bottom) of the seed crystal13is inserted into the guide hole32by 10 mm. The distance between the cover6aand the crystal13is 1.5 mm at the growth surface of the crystal13.

Then, the vacuum chamber1is vacuumed. Further, the argon gas is introduced into the chamber1through the gas introduction pipes8,9. The flowing amount of the gas is 10 SLM.

Then, the RF coils19,20are energized so that the reaction chambers5,6are heated up to 2400° C. When the temperature of the reaction chambers5,6are stabilized near 2400° C., the pressure of the vacuum chamber1is set to be 2.66×104Pa. The raw material gas is introduced into the reaction chambers5,6by controlling with using a mass flow controller and the like. The raw material gas includes the SiH4gas, the C3H8gas and the Ar gas. The flow rate of the SiH4gas is 1.2 SLM, the flow rate of the C3H8gas is 0.32 SLM, and the flow rate of the Ar gas is 3.0 SLM. The light through the guide hole32is detected by the optical detector30, so that the diameter of the crystal14is estimated.

During the crystal growth, the base12is pulled up in accordance with crystal growth speed so that the bottom of the crystal14is inserted into the guide hole32by 10 mm. Accordingly, the position of the bottom of the crystal14is maintained to be at the standard height Ho during the crystal growth.

From the beginning of the crystal growth, the diameter of the crystal14becomes larger. After the crystal growth is performed for seven hours, the length of the crystal14becomes 10 mm. At that time, the diameter of the crystal14becomes 101.2 mm. Thus, the radius of the crystal14becomes larger by 0.6 mm. Therefore, the increase of the radius of the crystal14is 40% of the initial distance between the crystal14and the cover6a. Here, the initial distance is 1.5 mm. Then, the electricity of the upper RF coil19is increased. After the crystal growth is continued for two hours, the diameter of the crystal14is reduced to 100 mm. In this case, the growth speed of the crystal14is reduced from 1.4 mm/hour to 1.1 mm/hour. After that, the electricity of the upper RF coil19is increased. The crystal growth is continued.

In a case where the guide hole32has the tapered shape, the crystal14can be pulled up even when the diameter of the crystal14is increased. Therefore, the controllable range of the crystal growth becomes larger, and therefore, it is easy to control the crystal growth.

Thus, the crystal growth is totally performed for 50 hours. The SiC single crystal ingot having the length of 60 mm is obtained.

Thus, the diameter of the growing crystal14is obtained by measuring the light amount passing through the guide hole32. Therefore, the measurement of the diameter can be performed apart from the growth surface of the crystal14, so that the measurement can be performed without affecting the crystal growth.

Further, the diameter of the crystal14is controlled by changing the temperature of the cover6a. This is, the crystal growth is controlled by the temperature of the crystal14so that the diameter of the crystal14is controlled. Thus, it is easy to control the diameter of the crystal14.

Although the measuring means of the diameter is the optical detector30, the means can be other methods as follows.

For example, as shown inFIG. 9, the equipment includes multiple X-ray generating equipments25a,26aas a generator of the X-ray and multiple image tubes25b,26bas a receiver of the X-ray. They are disposed around the crystal14. When the diameter of the crystal14is measured, multiple X-ray generating equipments25a,26aand multiple tubes25b,26bare used so that the diameter is measured from multiple directions.

Further, the equipment includes a pair of X-ray generator and an image tube, which are movable. When the diameter of the crystal14is measured, the X-ray generator and the image tube are moved so that the diameter is measured from different directions. Thus, the diameter is measured in different multiple directions, so that the diameter is controlled more accurately.

Further, as show inFIG. 10, the raw material gas flows along with an arrow F1. The pressure disposed downstream side of the gas flow is defined as P1, and the pressure disposed on upstream side of the gas flow is defined as P2. The diameter of the crystal14is estimated on the basis of the difference between the pressure P1and the pressure P2. Further, the diameter of the crystal14can be measured indirectly on the basis of a gas flow amount Q1of the gas flowing through the guide hole11. Furthermore, the diameter of the crystal14can be measured indirectly on the basis of a gas flow speed v of a gas flowing through the guide hole11. Thus, the diameter of the crystal14can be detected by using the gas flow F1of the gas flowing through the guide hole11from the reaction chambers5,6to the top of the cover6a. Specifically, the diameter is detected by a parameter of the gas flow F1. These methods can provide the measuring method of the diameter easily without complicated equipment.

Furthermore, as shown inFIG. 11, the equipment includes a light emission device41, which is embedded in the heat insulation member15. The light emission device41emits the light, and the light passes through a through holes5a,15btoward the guide hole11. Then, a light detector40detects the light passing through a slit42. The slit42is formed in the base12. Although the equipment includes the light emission device41, the equipment can include a sound wave emission device. Thus, the light amount or the sound wave amount passing through the guide hole11is detected so that the diameter of the crystal14is indirectly measured. Thus, the diameter can be measured without affecting the growth condition.

Further, as shown inFIG. 12, the diameter can be indirectly measured on the basis of the weight W and the length L of the crystal14. Specifically, as shown inFIG. 13, the determination whether the crystal14is grown with a columnar shape is decided on the basis of the length L and the weight W of the crystal14. The weight W and the length L of the crystal14can be easily measured. Thus, it is easy to estimate the diameter of the crystal14on the basis of the weight Wand the length L. The initial diameter of the crystal14is defined as φ1. A line XIIIB represents a relationship between the length L and the weight W in a case where the crystal14is grown with the columnar shape. When the diameter is increased from φ1to φ2, the relationship between the length L and the weight W is changed from the line XIIIB to a line XIIIA. Thus, the line XIIIA represents the crystal14having the tapered shape so that the diameter of the crystal14becomes larger. When the diameter is decreased from φ1, the relationship between the length L and the weight W is changed from the line XIIIB to a line XIIIC. Thus, the line XIIIC represents the crystal14having the inverse tapered shape so that the diameter of the crystal14becomes smaller.

Furthermore, the diameter can be measured on the basis of change of the growth speed. In this case, the growth speed of the crystal14can be detected by the X-ray generating equipment21and the image tube22. The diameter of the crystal14is indirectly measured on the basis of the change of the growth speed by using the X-ray. Specifically, when the distance between the crystal14and the cover6abecomes smaller, the raw material gas is accumulated so that the growth speed is increased. Thus, the growth speed and the diameter of the crystal14are measured at the same time.

The above described methods for measuring the diameter of the growing crystal14such as the means with using the X-ray and the means with using the light can be combined to detect the diameter. Thus, the diameter is detected more accurately, although the inside of the reaction chambers5,6made of graphite is not directly visible.

Although the diameter of the crystal14is controlled by changing the insertion amount of the crystal14into the cover6aor by changing the temperature of the cover6a, the diameter can be controlled by other methods.

For example, the diameter of the crystal14can be controlled by using multiple parameters. By changing multiple parameters, the diameter of the crystal14is controlled stably and responsively. Here, the parameters include at least a high responsive parameter and a low responsive parameter. By changing a combination of the high responsive parameter and the low responsive parameter, the diameter of the crystal14can be controlled to be a predetermined diameter. Thus, the diameter is controlled rapidly and stably. For example, the high responsive parameter is one of the insertion amount of the crystal14, the partial pressure of the raw material gas and the flow speed of the raw material gas flowing toward the crystal14. The insertion of the crystal14changes the gas flow, the partial pressure changes super-saturation degree directly, and the flow speed affects the boundary between the gas phase and the solid phase of the crystal14. These parameters affect the crystal growth responsively. Further, if these parameters are not largely changed, the crystalinity of the crystal14is not reduced. Thus, the diameter of the crystal14is controlled with high response.

On the other hand, the low responsive parameter is, for example, the temperature of the cover6aor the pulling up speed of the crystal14. The temperature of the cover6aprovides to heat the side of the crystal14by the radiation. It takes long time to heat the side of the crystal14after the cover6ais heated. However, when the difference between the temperature of the cover6aand the temperature of the crystal14becomes larger, the surface of the crystal14does not change largely. Therefore, the crystal growth is performed stably. The pulling up speed of the crystal14does not change the gas flow rapidly. Thus, the diameter of the crystal14is not rapidly changed. Thus, the response of control of the diameter is late. This point is different from that in a silicon crystal growth from melt. Further, when the pulling up speed is changed, the growth condition and the growth temperature are not changed rapidly. Thus, the crystal growth is performed stably.

Further, the diameter of the crystal14is controlled by the partial pressure of the raw material gas. Specifically, the raw material gas is diluted by the inert gas and/or the etching gas so that the partial pressure of the raw material gas at the side of the crystal14is reduced locally. Thus, the diameter of the crystal14is controlled to be smaller or larger.

Furthermore, the diameter of the crystal14is controlled by generation of discharge between the side of the crystal14and the cover6a, as shown inFIG. 14. The discharge causes the temperature increase of the side of the crystal14. Thus, the diameter of the crystal14is directly and positively controlled.

Further, the diameter of the crystal14is controlled by laser beam irradiation. The laser beam is irradiated on a part of the side of the crystal14, the diameter of the part of which is increased. The laser beam is irradiated on a clearance between the side of the crystal14and the cover6a. Thus, without changing the growth condition, the diameter of the crystal14is controlled.

As described in the second embodiment, when the diameter of the crystal14is controlled by the temperature of the cover6a, it is effective to etch the surface of the crystal14by the etching gas. Specifically, when the diameter of the crystal14is reduced, the surface of the crystal14is etched so that the diameter of the crystal14is rapidly reduced. This method is much effective in a case where the deviation of the diameter is large. Here, after the surface of the crystal14is etched, excess particles accumulating on the surface of the crystal14are removed by the gas flow having large gas flow amount, which is larger than that in case of etching. Thus, after the excess particle is removed, the crystal growth is continued. Thus, the crystal14can be formed with high quality. Further, in other methods for controlling the diameter, when the diameter of the crystal14is reduced, the surface of the crystal14can be etched by the etching gas.

Third Embodiment

Manufacturing equipment according to a third embodiment of the present invention is shown inFIG. 15. The base12includes the columnar portion12aand the circular plate portion12b. The circular plate portion12bis formed on one end of the columnar portion12a. The diameter of the circular plate portion12bis larger than that of the columnar portion12a. The seed crystal13is fixed on the bottom of the circular portion12a. The diameter of the columnar portion12ais almost the same as the seed crystal13and the SiC single crystal14. The seed crystal13is bonded to the bottom of the columnar portion12awith an adhesive.

The base12is capable of sliding in such a manner that the outer surface of the circular plate portion12bcontacts the inner surface of the cylindrical member18. Thus, the base slides in the vertical direction with adhering and contacting the cylindrical member18. The base12is pulled up so that the sliding direction of the base18is opposite to the growth direction of the crystal14.

The cover6ais disposed under the opening of the cylindrical member18. The cover6aincludes the guide hole11. The diameter of the guide hole11is defined as φ7. The inner diameter of the cylindrical member18is defined as φ5. The diameter φ7of the guide hole11is smaller than the inner diameter φ5of the cylindrical member18. The raw material gas passes through the guide hole11. The cover6ais disposed on the side of the crystal14.

The diameter of the growing crystal14can be measured by the diameter measuring means such as the X-ray generating equipment21and the image tube22. The diameter of the crystal14can be controlled by the diameter controlling means such as the vertical movement device17so that the diameter is controlled by moving the base12in the cylindrical member18in the vertical direction. Thus, the diameter of the crystal14is controlled to be a predetermined diameter.

InFIG. 15, the outer diameter D1of the circular plate portion12bis larger than the outer diameter D2of the columnar portion12a. Specifically, the difference between the outer diameter D1and the outer diameter D2is in a range between 10 mm and 150 mm.

The raw material gas passes through the guide hole11of the cover6atoward the seed crystal13. The base12includes the columnar portion12ahaving the same diameter as the seed crystal13and the growing crystal14and the circular plate portion12bhaving the large diameter larger than the columnar portion12a. Therefore, the sliding portion between the cylindrical member18and the circular plate portion12bis apart from the guide hole11, compared with a case where a base is formed of a columnar shape. Therefore, the raw material gas passing through the guide hole11is prevented from adhering to the sliding portion. Further, since the base12slides with contacting the inner surface of the cylindrical member18to the outer surface of the circular plate portion12b, the raw material gas is prevented from discharging from a clearance between the circular plate portion12band the cylindrical member18. Thus, excess SiC poly crystal is prevented from adhering the sliding portion.

Thus, since SiC poly crystal is prevented from adhering to the sliding portion between the cylindrical member18and the circular plate portion12bof the base12, the cylindrical member18is prevented from fixing to the base12. The circular plate portion12bof the base12can slide smoothly in the cylindrical member18by the shaft16and the vertical movement device17.

Since the difference between the outer diameter D1of the circular plate portion12band the outer diameter D2of the columnar portion12ais in a range between 10 mm and 150 mm, the sliding portion between the cylindrical member18and the circular plate portion12bis sufficiently separated from the guide hole11. Thus, the raw material gas is prevented from adhering to the sliding portion so that SiC poly crystal is prevented from depositing on the sliding portion. When the difference between the outer diameters D1, D2is larger than 150 mm, the dimensions of the equipment becomes larger. Thus, the manufacturing cost of the equipment becomes higher. When the difference between the outer diameters D1, D2is smaller than 10 mm, SiC poly crystal is easily deposited on the sliding portion.

Further, the length, i.e., the height H1of the columnar portion12aof the base12is in a range between 5 mm and 100 mm. In this case, the sliding portion is sufficiently separated from the guide hole11so that excess SiC poly crystal is prevented from depositing on the sliding portion. When the height H1of the columnar portion12ais larger than 100 mm, the dimensions of the equipment becomes larger. Thus, the manufacturing cost of the equipment becomes higher. When the height H1of the columnar portion12ais smaller than 5 mm, SiC poly crystal is easily deposited on the sliding portion.

The inner diameter φ6of the lower reaction chamber5is equal to or smaller than the diameter φ7of the guide hole11. Preferably, the difference (i.e., φ7-φ6) between the inner diameter06of the lower reaction chamber5and the diameter07of the guide hole11is equal to or smaller than 30 mm. The lower reaction chamber5is a cylindrical part for supplying the heated raw material gas to the guide hole11. The low reaction chamber5is disposed to separate from the cover6a. The raw material gas is heated in the lower reaction chamber5so that the raw material gas is thermally decomposed. In this case, the raw material gas is limited from reaching the cover6adirectly. Thus, SiC poly crystal is prevented from adhering to the cover6a. Thus, the cover6ais prevented from adhering to the SiC single crystal14through SiC poly crystal. The diameter of the crystal14is sufficiently controlled by using the cover6a, so that the crystal growth is performed for sufficiently long time and continuously. When the inner diameter φ6of the lower reaction chamber5is larger than the diameter φ7of the guide hole11, the raw material gas reaches the cover6adirectly. Thus, excess SiC poly crystal may be deposited on the cover6a, so that the excess SiC poly crystal is adhered to the SiC single crystal14. In this case, the crystal growth is prevented from performing for sufficiently longtime and continuously. Since the difference between the inner diameter φ6and the diameter φ7is equal to or smaller than 30 mm, the diameter of the crystal14is easily controlled by using the cover6a. Thus, the crystal growth can be performed for sufficient long time and continuously. When the difference between the inner diameter06and the diameter07is larger than 30 mm, the growth speed of the crystal14on the outer periphery of the crystal14becomes smaller although SiC poly crystal is effectively prevented from adhering to the cover6a. Thus, as shown a dashed line inFIG. 15, the crystal14abecomes a convexity shape. Thus, the quality and productivity of the crystal14is reduced.

The equipment can have a heat insulation member50. The heat insulation member50is disposed on the top of the cover6a, so that the heat insulation member50is disposed on the downstream side of the gas from the cover6a. The heat insulation member50is disposed in a space, which is surrounded with the cover6a, the circular plate portion12b, the columnar portion12aand the cylindrical member18. The heat insulation member50is made of porous material so that the raw material gas can pass through the heat insulation member50.

Since the heat insulation member50is disposed on the surface of the cover6a, the heat insulation member50prevents the heat from diffusing from the cover6ato other parts. Thus, the temperature of the cover6ais increased, so that excess SiC poly crystal is prevented from adhering to the cover6a. Thus, the SiC poly crystal is prevented from adhering to the SiC single crystal14. The diameter of the crystal14is sufficiently controlled by using the cover6a, so that the crystal growth is performed for sufficiently long time and continuously.