JP4418879B2 - Heat treatment apparatus and heat treatment method - Google Patents

Description

The present invention, the object to be treated the pressure 10 ^-2 Pa or less preferably 10 ^-5 Pa or less of vacuum is heat-treated object, or less preferably pre pressure 10 ^-2 Pa after reaching the following vacuum 10 ^-5 Pa The present invention relates to a heat treatment apparatus and a heat treatment method capable of heating to 1200 ° C. to 2300 ° C. in a short time in a rare gas atmosphere into which an inert gas is introduced.

  2. Description of the Related Art Conventionally, a heat treatment apparatus used in a semiconductor manufacturing process includes a heat treatment apparatus that heat-treats an object to be processed at a high speed in order to reduce the thermal history of the object to be processed and prevent slipping (for example, Patent Document 1). (See, for example, Patent Document 2) and the like that have been reported to be capable of high vacuum in a short time and epitaxial growth at a low temperature.

  These heat treatment apparatuses used in the conventional semiconductor manufacturing process are mainly used for Si epitaxial growth. Therefore, for example, the heat treatment apparatus described in Patent Document 1 has a high temperature portion of 950 ° C., and the heat treatment apparatus described in Patent Document 2 has a temperature of 800 to 900 ° C.

  However, in recent years, not only is it excellent in heat resistance and mechanical strength, but it is also resistant to radiation, and it is easy to control the valence electrons of electrons and holes by adding impurities, and has a wide band gap. (Incidentally, about 3.0 eV for a 6H-type SiC single crystal and 3.3 eV for a 4H-type SiC single crystal), there are existing ones such as silicon (hereinafter referred to as Si) and gallium arsenide (hereinafter referred to as GaAs). Single crystal silicon carbide (hereinafter referred to as SiC), which can realize high temperature, high frequency, withstand voltage and environmental resistance, which cannot be realized with any semiconductor material, is the next generation of power devices and semiconductors for high frequency devices. It is attracting attention and is expected as a material. Hexagonal SiC has a lattice constant close to that of gallium nitride (hereinafter referred to as GaN), and is expected as a GaN substrate.

  For example, as described in Patent Document 3, this type of single-crystal SiC has a seed crystal fixedly arranged on the low temperature side in the crucible, and a powder containing Si as a raw material is arranged on the high temperature side. A sublimation recrystallization method in which a single crystal is grown by sublimating a powder containing Si by heating to a high temperature of 1450 to 2400 ° C. in an inert atmosphere and recrystallizing on the surface of the seed crystal on the low temperature side (improved) Some are formed by the Rayleigh method.

  Further, for example, as described in Patent Document 4, a SiC single crystal substrate and a plate material composed of Si atoms and C atoms are opposed to each other in a state where they are opposed to each other in parallel with a minute gap therebetween. Si atoms and C atoms are sublimated and recrystallized in minute gaps by heat treatment in an active gas atmosphere and a SiC saturated vapor atmosphere with a temperature gradient so that the SiC single crystal substrate side is at a lower temperature than the plate material. In some cases, a single crystal is deposited on a SiC single crystal substrate.

  Further, for example, as described in Patent Document 5, after the first epitaxial layer is formed on the SiC single crystal by the liquid phase epitaxial growth method, the second epitaxial layer is formed on the surface by the CVD method, Some remove micropipe defects.

JP-A-8-70008 Japanese Patent Laid-Open No. 11-260738 JP 2001-158695 A JP 11-315000 A Japanese National Patent Publication No. 10-509943

However, the formation of these single crystal SiCs requires heat treatment at a high temperature of 1450 to 2400 ° C. as described in Patent Documents 3 to 5. For this reason, in the conventional heat treatment apparatus as described in Patent Document 1 or Patent Document 2, it is difficult to form single crystal SiC. In addition, for example, in the case of the sublimation recrystallization method described in Patent Document 3, the growth rate is very fast as several 100 μm / hr, but the SiC powder is once decomposed into Si, SiC ₂ and Si ₂ C during sublimation. Vaporizes and reacts with part of the crucible. For this reason, the types of gases that reach the surface of the seed crystal differ depending on the temperature change, and it is technically very difficult to control these partial pressures stoichiometrically accurately. Impurities are also likely to be mixed in, and crystal defects and micropipe defects are likely to occur due to the influence of the mixed impurities and strain caused by heat. In addition, performance such as generation of crystal grain boundaries due to many nucleation There is a problem that single crystal SiC stable in quality and quality cannot be obtained.

  On the other hand, in the case of the liquid phase epitaxial growth method (hereinafter referred to as LPE method) described in Patent Document 4 and Patent Document 5, the occurrence of micropipe defects and crystal defects as seen in the sublimation recrystallization method is small, and sublimation. Single crystal SiC superior in quality as compared with that manufactured by the recrystallization method can be obtained. On the other hand, since the growth process is rate-determined by the solubility of C in the Si melt, the growth rate is very slow, 10 μm / hr or less, and the productivity of single crystal SiC is low. The temperature must be precisely controlled. Further, the process becomes complicated, and the manufacturing cost of single crystal SiC becomes very expensive.

The present invention has been made in view of the above problems, and is suitable for the formation of next-generation single crystal SiC. The pressure is 10 ⁻² Pa or less, preferably 10 ⁻⁵ Pa or less, or the pressure is preferably 10 ⁻² Pa or less in advance. Is a heat treatment apparatus capable of heating to 1200 ° C. to 2300 ° C. in a short time even in a dilute gas atmosphere in which some inert gas is introduced after reaching a high vacuum of 10 ⁻⁵ Pa or less, and using the same An object is to provide a heat treatment method.

A heat treatment apparatus according to the present invention for solving the above problems is configured as follows. That is, a heating chamber capable of heating the object to be processed to 1200 ° C. to 2300 ° C. is provided, and this heating chamber is configured to be able to heat the object to be processed in a vacuum of a pressure of 10 ⁻² Pa or less. A heater is provided inside the heating chamber so as to cover the container containing the object to be processed, and a reflecting mirror is disposed around the heater. The container is formed by fitting an upper container and a lower container, and the object to be processed is heated by the heater while being accommodated in the container.
The heating chamber is preferably configured to heat the object to be processed in a vacuum of a pressure of 10 ⁻⁵ or less. Alternatively, the heating chamber, instead of a vacuum of the pressure 10 ^-2 Pa, the object to be processed in the lean gas atmosphere with an inert gas is introduced after reaching the following vacuum pressure 10 ^-2 Pa It is preferably configured to heat.

Moreover, the heat processing method which concerns on this invention is a heat processing method with the heat processing apparatus provided with the heating chamber which can heat a to-be-processed object at 1200 to 2300 degreeC, Comprising: It performs as follows. That is, the heating chamber is under vacuum pressure of less than 10 ^-2 Pa, or under a lean gas atmosphere with an inert gas is introduced after reaching the following vacuum pressure 10 ^-2 Pa, it can heat the object to be processed It is configured as follows. A heater is provided inside the heating chamber so as to cover the container containing the object to be processed, and a reflecting mirror is disposed around the heater. The container is formed by fitting an upper container and a lower container, and the object to be processed is heated by the heater while being accommodated in the container.

effect

The present invention is configured as described above, and is diluted with an inert gas after reaching a high vacuum of 10 ⁻² Pa or less, preferably 10 ⁻⁵ Pa or less, or a vacuum of 10 ⁻² Pa or less in advance. under a pressure of gas atmosphere, using a heating heater, it is possible to heat an object to be processed of the fitting in the container to high temperatures that short time 1 200 ° C. to 2300 ° C., could not be obtained in the conventional heat treatment apparatus and a heat treatment method and Ru can be created a new material.

BEST MODE FOR CARRYING OUT THE INVENTION

  Hereinafter, an embodiment of a heat treatment apparatus according to the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing an example of a heat treatment apparatus according to this embodiment. In FIG. 1, the heat treatment apparatus 1 includes a heating chamber 2, a preheating chamber 3, and a front chamber 4 that extends from the preheating chamber 3 to the heating chamber 2. And the to-be-processed object 5 can be heated to 1200 to 2300 degreeC in a short time because the to-be-processed object 5 moves sequentially from the preheating chamber 3 to the front chamber 4 and the heating chamber 2. FIG.

  As shown in FIG. 1, in the heat treatment apparatus 1, a heating chamber 2, a preheating chamber 3, and a front chamber 4 are in communication. For this reason, it becomes possible to control each chamber under a predetermined pressure in advance. As a result, even when the workpiece 5 is moved, the inside of the furnace under a predetermined pressure can be moved by a moving means (not shown) without touching the outside air, so that contamination of impurities and the like can be suppressed.

  The preheating chamber 3 is provided with a halogen lamp 6 and is a lamp-type heating furnace capable of rapidly heating to about 800 to 1000 ° C. In addition, a gate valve 7 is provided at a connection portion between the preheating chamber 3 and the front chamber 4 to facilitate pressure control of the preheating chamber 3 and the front chamber 4. The object to be treated 5 is preheated to 800 ° C. or higher in the state of being placed on the table 8 in the preheating chamber 3, and then the pressure adjustment between the preheating chamber 3 and the front chamber 4 is completed. 4 is moved so as to be installed on an elevating type susceptor 9 provided in 4.

The workpiece 5 moved to the front chamber 4 is moved from the front chamber 4 to the heating chamber 2 by a lifting / lowering moving means 10 partially shown. At this time, the inside of the heating chamber 2 is a predetermined pressure of 10 ⁻¹ Pa or less, preferably a pressure of 10 ⁻² Pa or less, more preferably 10 ⁻⁵ Pa or less, or a pressure of 10 ⁻ After reaching a high vacuum of ² Pa or less, preferably 10 ⁻⁵ Pa or less, a slight inert gas is introduced to form a dilute gas atmosphere of 10 ⁻¹ Pa or less, preferably 10 ⁻² Pa or less. It is preferable that the temperature is set to 1200 ° C to 2300 ° C. By setting the state in the heating chamber 2 in this way, the workpiece 5 is rapidly shortened to 1200 ° C. to 2300 ° C. by moving the workpiece 5 from the front chamber 4 into the heating chamber 2. Can be heated in time. In addition, a reflecting mirror 12 is disposed around the heater 11 in the heating chamber 2 so that the heat of the heater 11 is reflected and concentrated on the object 5 to be processed located inside the heater 11. ing. Even if the reflecting mirror 12 has a housing shape as shown in FIG. 1, for example, a dome-like reflecting mirror 12 as shown in FIG. 5 can be used. Thus, by making the reflecting mirror 12 into a dome shape, it is possible to use a flat heater as the heater 11, and even if the flat heater 11 is used, the heater 11 Can be efficiently concentrated on the workpiece 5.

  The fitting portion 25 between the moving means 10 and the heating chamber 2 is composed of a convex stepped portion 21 provided in the moving means 10 and a concave stepped portion 22 formed in the heating chamber 2. ing. And the heating chamber 2 will be in the state sealed by sealing members, such as an O-ring which is not shown in figure provided in each step part of the step part 21 of the moving means 10. FIG.

  Further, a contaminant removal mechanism 20 that removes impurities discharged from the workpiece 5 during the heat treatment so as not to come into contact with the heater 11 is provided inside the heater 11 in the heating chamber 2. Thereby, it can suppress that the heater 11 reacts with the impurity discharged | emitted from the to-be-processed object 5, and deteriorates. The contaminant removal mechanism 20 is not particularly limited as long as it can adsorb impurities discharged from the workpiece 5.

  The heater 11 is a resistance heater made of graphite, and includes a base heater 11a installed on the susceptor 9 and an upper heater 11b in which a side portion and an upper portion are integrally formed in a cylindrical shape. Thus, since the heater 11 is arrange | positioned so that the to-be-processed object 5 may be covered, it becomes possible to heat the to-be-processed object 5 equally. Note that the heating method of the heating chamber 2 is not limited to the resistance heater shown in the present embodiment, and may be a high frequency induction heating method, for example.

  In the case of processing single crystal SiC as the object 5 to be processed, for example, it is preferable to use a sealed container 5 ′ composed of an upper container 5 a and a lower container 5 b as shown in FIG. 2. As will be described later, the single crystal SiC substrate 16 and the polycrystalline SiC substrate are stacked in this sealed container 5 ', and heat treatment is performed (see FIG. 3).

  In this sealed container 5 ′, it is preferable that the play of the fitting portion when fitting the upper container 5 a and the lower container 5 b is 2 mm or less. As a result, contamination of impurities into the sealed container 5 ′ can be suppressed. Further, by setting the play to 2 mm or less, it is possible to control the Si partial pressure in the sealed container 5 ′ at 10 Pa or less during the heat treatment. For this reason, the SiC partial pressure and the Si partial pressure in the sealed container 5 ′ are increased to contribute to prevention of sublimation of the single crystal SiC substrate 16, the polycrystalline SiC substrates 14, 15 and the ultrathin metal Si melt 17. . When the play of the fitting portion when the upper container 5a and the lower container 5b are fitted is larger than 2 mm, it is difficult to control the Si partial pressure in the sealed container 5 ′ to a predetermined pressure. In addition, impurities may enter the sealed container 5 ′ through the fitting portion, which is not preferable. As shown in FIG. 2, the sealed container 5 ′ is not limited to a square shape but may be a circular shape.

  Moreover, as shown in FIG.3 and FIG.4, the three support parts 13 are provided in the lower container 5b. This support portion 13 supports a polycrystalline SiC substrate 14 that becomes a seed crystal to be described later. In addition, the support part 13 does not need to be a pin-shaped thing as shown in this embodiment, For example, the ring-shaped thing formed with SiC, graphite, etc. may be sufficient.

  FIG. 3 shows a 6H-type single crystal SiC substrate 16 serving as a seed crystal installed in an airtight container 5 ′ in a state where the upper container 5 a and the lower container 5 b are fitted, and a multi-layer sandwiching the single crystal SiC substrate 16. The state of the crystalline SiC substrate 15 and the ultrathin metal Si melt 17 formed therebetween is shown. The ultrathin metal Si melt 17 is formed at the time of heat treatment, and the Si source of the ultrathin metal Si melt 17 is preliminarily formed on the surface of the single crystal SiC substrate 16 to be a seed crystal on the surface of the metal Si. The method is not particularly limited, such as forming a film to 10 μm to 50 μm by CVD or placing Si powder.

  As shown in FIG. 3, the single crystal SiC substrate 16, the polycrystalline SiC substrates 14 and 15, and the ultrathin metal Si melt 17 are applied to the support portion 13 provided in the lower container 5 b constituting the sealed container 5 ′. It is placed and accommodated in the sealed container 5 ′. Here, the single crystal SiC substrate 16 is cut out to a desired size (10 × 10 to 20 × 20 mm) from a single crystal 6H—SiC wafer manufactured by a sublimation method. Further, the polycrystalline SiC substrates 14 and 15 can be made by cutting to a desired size from SiC used as a dummy wafer in the Si semiconductor manufacturing process manufactured by the CVD method. The surface of each of the substrates 16, 14, 15 is polished into a mirror surface, and oils, oxide films, metals, etc. adhering to the surface are removed by washing or the like. Here, the polycrystalline SiC substrate 14 located on the lower side prevents erosion of the single crystal SiC substrate 16 from the sealed container 5 ′, and improves the quality of single crystal SiC that is liquid phase epitaxially grown on the single crystal SiC substrate 16. It contributes to.

  The sealed container 5 'is preferably formed of isotropic graphite. If it does so, the inner surface exposed to Si vapor | steam will come to SiC equally, and the crack etc. accompanying SiC conversion at the time of a process can be suppressed. In order to prevent this inner surface from becoming SiC, SiC, pyrolytic carbon, or tantalum carbide can be coated on the inner surface of the sealed container 5 'in advance.

  Further, in this sealed container 5 ′, it can be installed together with Si pieces for controlling SiC sublimation and Si evaporation during heat treatment. By simultaneously installing the Si pieces, the SiC partial pressure and the Si partial pressure in the sealed container 5 'are increased by sublimation during the heat treatment, so that the single crystal SiC substrate 16 and the polycrystalline SiC substrates 14 and 15, ultrathin metal Si melt 17 contributes to prevention of sublimation. In addition, the pressure in the sealed container 5 ′ can be adjusted to be higher than the pressure in the heating chamber 2, and thereby, it is possible to always release Si vapor from the fitting portion between the upper container 5a and the lower container 5b. Intrusion into the sealed container 5 ′ can be prevented.

The airtight container 5 ′ thus configured is set to 10 ⁻⁵ Pa or less after being installed in the preheating chamber 3, and is preferably 800 ° C. or more, preferably by the lamp 6 provided in the preheating chamber 3. Heated to 1000 ° C. or higher. At this time, the inside of the heating chamber 2 is similarly set to a vacuum of 10 ⁻² Pa or less, preferably 10 ⁻⁵ Pa or less, and then preferably heated to 1200 to 2300 ° C.

  As described above, the sealed container 5 ′ preheated in the preheating chamber 3 opens the gate valve 7, moves to the susceptor 9 in the front chamber 4, and is raised to 1200 ° C. to 2300 ° C. by the elevating means 10. It is moved into the heating chamber 2 that is being heated. As a result, the sealed container 5 ′ is rapidly heated to 1200 ° C. to 2300 ° C. in a short time within 30 minutes. Although the heat processing temperature in the heating chamber 2 should just be a temperature which the metal Si piece currently installed in the airtight container 5 'melts | melts, it shall be 1200 to 2300 degreeC. As the processing temperature is increased, the wettability between the molten Si and SiC increases, and the molten Si easily penetrates between the single crystal SiC substrate 16 and the polycrystalline SiC substrates 14 and 15 by capillary action. Thereby, an ultrathin metal Si melt 17 having a thickness of 50 μm or less can be interposed between the single crystal SiC substrate 16 and the polycrystalline SiC substrates 14 and 15.

  In addition, according to the heat treatment apparatus according to the present embodiment, the temperature can be set to 1200 ° C. to 2300 ° C. in a short time, so that the crystal growth can be completed in a short time and the efficiency of the crystal growth can be improved.

By the way, the growth mechanism of single crystal SiC will be briefly described. As a result of the heat treatment, molten Si enters between the single crystal SiC substrate 16 and the upper polycrystalline SiC substrate 15 and enters the interface between the substrates 16 and 15. A metal Si melt layer 17 having a thickness of about 30 μm to 50 μm is formed. The metal Si melt layer 17 becomes thinner as the heat treatment temperature becomes higher, and becomes about 30 μm. The C atoms flowing out of the polycrystalline SiC substrate 2 are supplied to the single crystal SiC substrate 16 through the Si melt layer, and liquid phase epitaxial growth (LPE) is performed on the single crystal SiC substrate 1 as 6H—SiC single crystal. Thus, since the space between the single-crystal SiC substrate 16 serving as the seed crystal and the polycrystalline SiC substrate 14 is small, thermal convection is not generated during the heat treatment. Therefore, the interface between the formed single crystal SiC and the single crystal SiC substrate 16 serving as a seed crystal becomes very smooth, and no distortion or the like is formed at the interface. Therefore, very smooth single crystal SiC is formed. Moreover, since the nucleation of SiC is suppressed during the heat treatment, the generation of the fine crystal grain boundaries of the formed single crystal SiC can be suppressed. In the method for growing single crystal SiC according to the present embodiment, melted Si enters only between the single crystal SiC substrate 16 and the polycrystalline SiC substrate 15, and therefore, in the single crystal SiC where other impurities grow. Since it does not enter, high-purity single crystal SiC having a background of 5 × 10 ¹⁵ / cm ³ or less can be produced.

As described above, according to the heat treatment apparatus of the present embodiment, the pressure 10 ^-2 Pa or less preferably 10 ^-5 Pa or less high vacuum, or pre-pressure 10 ^-2 Pa or less preferably 10 ^-5 Pa or less high vacuum A slight amount of inert gas is introduced after reaching a temperature of 10 ⁻¹ Pa or less, preferably 10 ⁻² Pa or less in a dilute gas atmosphere. it is possible to heat the 1200 ° C. to 2300 ° C., the case of forming a single crystal SiC as an object to be treated was a flame-frame in the liquid phase growth method of a conventional single crystal SiC (LPE method), 10 [mu] m on the surface It becomes possible to form single crystal SiC having the above wide terrace.

  In addition, the heat treatment apparatus according to the present invention is not limited to the above-described embodiment example, and can be used other than the above-described single-crystal SiC liquid phase growth method. Utilizing the feature of heating to 2300 ° C, for example, after ions are implanted into the surface of the semiconductor substrate, the device is heated to a high temperature in a short time to crystallize the ion-implanted portion reliably and efficiently. And so on. Since the heat treatment apparatus according to the present invention is small and has a relatively simple structure, it can be easily connected to another apparatus such as an ion implantation apparatus.

  Conventionally, when high-speed heating is performed, a special method such as laser or plasma has been used. However, the heat treatment apparatus according to the present invention has a simple structure and can be connected to other apparatuses such as an electron microscope and an ion implantation apparatus. For this reason, there is a possibility that a novel material that cannot be obtained by the conventional method can be created.

1 is a schematic cross-sectional view of an embodiment of a heat treatment apparatus according to the present invention. It is the schematic of one Embodiment of the airtight container used for formation of the single crystal SiC which is one Embodiment using the heat processing apparatus which concerns on this invention. A 6H-type single crystal SiC substrate serving as a seed crystal installed in the hermetic container shown in FIG. 2, a polycrystalline SiC substrate sandwiching the single crystal SiC substrate, and an ultrathin metal Si melt formed therebetween. It is a figure which shows the state of a liquid. It is a figure which shows the state which installed the SiC substrate in the lower container of the airtight container shown in FIG. It is a partially expanded schematic view of another embodiment of the heat treatment apparatus according to the present invention.

Explanation of symbols

1 Heat treatment furnace 2 Heating chamber 3 Preheating chamber 4 Front chamber
5 Workpiece 5 'Sealed container 5a Upper container 5b Lower container 6 Lamp 7 Gate valve 8 Table 9 Susceptor 10 Moving means 11 Heater 12 Reflecting mirror 25 Fitting part

Claims (4)

A heating chamber capable of heating the object to be processed to 1200 ° C. to 2300 ° C. is provided , and this heating chamber is configured to heat the object to be processed in a vacuum of a pressure of 10 ⁻² Pa or less,
A heater is provided inside the heating chamber so as to cover the container containing the object to be processed, and a reflecting mirror is disposed around the heater ,
The heat treatment apparatus , wherein the container is formed by fitting an upper container and a lower container, and the object to be processed is heated by the heater in a state of being accommodated in the container . 2. The heat treatment apparatus according to claim 1, wherein the heating chamber is configured to heat the object to be processed in a vacuum of a pressure of 10 ⁻⁵ or less. The heating chamber, instead of a vacuum of the pressure 10 ^-2 Pa, heating the object to be processed in the lean gas atmosphere with an inert gas is introduced after reaching the following vacuum pressure 10 ^-2 Pa The heat treatment apparatus according to claim 1, wherein the heat treatment apparatus is configured as described above. In a heat treatment method using a heat treatment apparatus including a heating chamber capable of heating an object to be processed at 1200 ° C. to 2300 ° C.,
  The heating chamber has a pressure of 10 ^-2 Under vacuum of Pa or less or pressure 10 ^-2 It is configured so that the object to be processed can be heated in a rare gas atmosphere into which an inert gas is introduced after reaching a vacuum of Pa or less,
  A heater is provided inside the heating chamber so as to cover the container containing the object to be processed, and a reflecting mirror is disposed around the heater,
  The container is formed by fitting an upper container and a lower container, and the object to be processed is heated by the heater while being accommodated in the container.

Images