JP2005259854A - Method and device of film formation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film formation method and a film formation device by which a crystal film grown on an epitaxial substrate can be made uniform. <P>SOLUTION: The film formation device 10 is provided with a substrate receiver 18 wherein a substrate 16 for film formation is arranged, an NH<SB>3</SB>gas supply nozzle 28 and a gas supply nozzle 29 having a band-like blow-off port 32 facing the substrate receiver 18, a motor 20 to move at least either of the substrate receiver 18 and the nozzle relatively along the surface of the substrate receiver 18, and an NH<SB>3</SB>gas supply 47 and material gas supplies 14 and 15 to supply a material gas for film formation to the NH<SB>3</SB>gas supply nozzle 28 and the gas supply nozzle 29. In this case, the substrate receiver 18 is rotatable, and the nozzle is formed in a manner that the lengthwise direction of the blow-off port 32 is arranged in the radial direction of the substrate receiver 18, and the opening width of the blow-off port 32 gradually becomes larger from the center of the substrate receiver 18 toward its outer circumferential side. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a film forming method and a film forming apparatus capable of uniformly forming a thin film crystal of a compound semiconductor on a substrate surface.

  GaN (gallium nitride) compound semiconductors are attracting attention as blue light emitting diodes or raw materials for laser diodes, as well as materials for electronic devices in the high power / high frequency region. A GaN-based compound semiconductor is generally generated by an organic compound vapor phase growth method using sapphire, SiC or the like as a crystal growth substrate.

  In this case, dislocations occur due to lattice mismatch between the crystal growth substrate and the GaN compound semiconductor crystal, and dislocations in the thickness direction also propagate in the growth direction of the GaN compound semiconductor crystal, resulting in crystal defects. There was a problem. If a defect occurs in the initial stage of film formation, the direction vector in which the defect and the growth film grow is the same direction, so the defect also grows in the film thickness direction together with the crystal. Therefore, in the conventional vapor phase epitaxial film formation, threading dislocations (penetration defects) in which defects penetrate to the surface of the film are generated.

  In order to reduce the propagation of dislocations, Patent Document 1 discloses a method of growing a GaN-based nitride semiconductor crystal laterally with respect to the crystal growth substrate: ELO (Epitaxial Lateral Overgrowth).

In this crystal growth method using ELO, as shown in FIG. 5, first, slits 2 are formed with a certain gap made of SiO _{2 in} the substrate 1. During the crystal growth, the GaN-based nitride semiconductor crystal 3 does not grow on the slit. On the other hand, the GaN-based nitride semiconductor crystal 3 with the triangular crystal growing from between the slits 2 grows in the lateral direction. A portion grown from the opening 4 between the slits 2 is used as a seed for crystal growth. The crystal grown in the lateral direction fills the upper portion of the slit 2 to stop dislocation propagation, and the crystallinity of the upper portion of the slit 2 is dramatically improved.

The device characteristics are greatly influenced by slight variations in the thickness of the epitaxially grown layer. Therefore, it is desired to manufacture devices with high yield as well as high accuracy. Therefore, it is extremely important to uniformly form the epitaxial growth layer as well as to improve the crystal quality of the epitaxial growth layer.
JP 2000-91253 A

  However, in the epitaxial growth by ELO, since the source gas is sprayed uniformly on the substrate, it is necessary to make the reaction system such as a reaction vessel uniform with the source gas. In this case, it is difficult to uniformly supply the source gas to all regions on the surface of the substrate heating table. A uniform film cannot be formed unless all the conditions are uniform. If the conditions are not met, a non-uniform crystal film is formed on the substrate, causing crystal defects in film formation. In addition, since the source gas is supplied from the upper direction or the lateral direction of the substrate heating table and the excess source gas is discharged to the outside, the use efficiency of the source gas is poor. Furthermore, since it is necessary to previously form a slit in the substrate, it takes time and labor.

  In the method described in Patent Document 1, since the source gas is supplied to the entire substrate, the film grows in the vertical direction, which is the thickness direction of the film, and vertical penetration defects are likely to occur. On the other hand, as an application to a new device, there are cases where crystal films having different compositions such as GaN and AlN are stacked on a growth substrate so as to have a quantum well structure. In this case, since the source gas is supplied into the large reaction vessel, when the crystal films having different compositions are stacked on the substrate, the source gas used in the previous crystal film remains in the reaction vessel, and the next growth film When the layers are stacked, the remaining source gas is mixed and the boundary surface where the crystal films are stacked becomes unclear. Therefore, when the growth film is a diode or the like, the performance may deteriorate.

In order to solve the above-mentioned problems of the prior art, an object of the present invention is to make a crystal film grown on a substrate uniform.
Another object of the present invention is to form a crystal having a clear layer between the growth substrates and having no through defects.

  In the film forming method according to the present embodiment, the film forming source gas is blown onto the substrate in a strip shape, and the nozzle for blowing the film forming source gas and the substrate are relatively moved along the surface of the substrate. It is characterized by.

  In addition, the film forming apparatus according to the present embodiment includes a table on which a substrate for film formation is disposed, a nozzle having a strip-shaped outlet facing the table, and at least one of the table and the nozzle. It has a drive part moved relatively along the surface, and a source gas supply part for supplying a source gas for film formation to the nozzle.

In this case, the table is a rotary table, and the nozzle is arranged such that the longitudinal direction of the blowout port is arranged in the radial direction of the rotary table, and the opening width of the blowout port is on the outer peripheral side from the center side of the rotary table. You should make it gradually widen toward.
A plurality of nozzles may be arranged along the circumferential direction of the rotary table.

  In the film forming method and the film forming apparatus having the above configuration, the nozzle for blowing the film forming source gas and the substrate are relatively moved along the surface of the substrate. The film grows in the lateral direction. Therefore, the occurrence of penetration defects can be prevented. Moreover, the source gas spraying pressure for crystal growth can be locally increased, so that a high crystal growth rate can be obtained and the crystal growth location can be limited to a narrow place. Thereby, it is not necessary to make the whole reaction container uniform, and there is no waste of raw material gas.

  Further, the nozzle for blowing the raw material gas has a blowing port formed in a band shape, and the opening width is gradually formed wider from the center of the rotary table toward the outer periphery. Therefore, in addition to obtaining the same effect as described above, when the rotary table is rotated, the amount of spraying due to the difference in rotational speed between the center side and the outer peripheral side of the rotary table can be made uniform. As a result, the film formed on the substrate grows uniformly on the inner side and the outer side in the radial direction with respect to the rotary table, and can be formed with a uniform thickness.

  Further, a plurality of nozzles are provided on the substrate in accordance with the size or number of substrates placed on the rotary table. Thereby, in addition to obtaining the same effect as described above, the amount of the raw material gas sprayed can be controlled, and the growth rate of the growth film can be increased.

  Hereinafter, embodiments of a film forming method and a film forming apparatus according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of a film forming apparatus according to the present embodiment. FIG. 2 is an enlarged view in which the source gas is sprayed from the gas supply nozzle onto the substrate.

As shown in FIG. 1, the film forming apparatus 10 includes NH ₃ having a reaction vessel 12, a substrate receiver 18 serving as a table on which a substrate 16 for film formation is arranged, and a strip-shaped outlet 32 facing the substrate receiver 18. A motor 20 serving as a drive unit that relatively moves at least one of the gas supply nozzle 28 and the gas supply nozzle 29 and the substrate receiver 18 and the NH ₃ gas supply nozzle 28 and the gas supply nozzle 29 along the surface of the substrate receiver 18. And the NH ₃ gas supply unit 46 and the source gas supply units 14 and 15 for supplying the film forming source gas from the nozzle described above.

The inside of the reaction vessel 12 can be depressurized by a vacuum pump 11 connected to the side surface via a pressure regulating valve 13, and the vessel is a closed system in order to grow crystals under reduced pressure.
A substrate receiver 18 on which a substrate 16 is placed is installed at the bottom of the reaction vessel 12. As shown in FIG. 2, the substrate receiver 18 has a disk shape and has an opening so that a plurality of substrates 16 can be placed on the upper surface side. A heater 19 for heating the substrate is fixed to the lower surface of the substrate receiver 18. For example, sapphire, SiC, or the like can be used as the material of the substrate 16 placed on the substrate receiver 18.

A motor 20 is installed at the bottom of the reaction vessel 12. The shaft 22 of the motor 20 passes through the bottom of the reaction vessel 12 and its upper end is fixed to the lower surface of the substrate receiver 18. On the other hand, above the substrate 16, an NH ₃ gas supply nozzle 28 that serves as a nozzle that blows out ammonia (NH ₃ ) gas and a gas supply nozzle 29 that serves as a nozzle that blows out the source gas are arranged close to each other. In the present embodiment, description will be made using trimethylgallium (TMG) 34, trimethylaluminum (TMA) 36, and ammonia gas 47 as film forming source gases. The motor 20 serves as a driving unit, and rotates the substrate receiver 18 to relatively move the substrate receiver 18 and the NH ₃ gas supply nozzle 28 and the gas supply nozzle 29.

The NH ₃ gas supply nozzle 28 and the gas supply nozzle 29 are provided at a position where the outlet 32 faces the substrate receiver 18. The outlet 32 is formed in a band shape and is arranged in the radial direction of the substrate receiver 18. Further, the length of the outlet 32 is formed to be larger than the diameter of the substrate 16. Since the circumferential speed of the substrate receiver 18 is slow in the vicinity of the center and fast on the outside of the substrate, the opening width of the outlet 32 is directed from the center of the substrate receiver 18 toward the outer periphery so that the amount of film forming raw material gas sprayed is uniform. And gradually formed.

One end of a supply pipe 26 c is connected to the upper end of the NH ₃ gas supply nozzle 28. The other end of the supply pipe 26 c penetrates the upper part of the reaction vessel 12 and is connected to the NH ₃ gas supply unit 46. The NH ₃ gas supply unit 46 supplies ammonia gas 47 serving as a nitrogen source to the NH ₃ gas supply nozzle 28. An adjustment valve 45 is installed on the supply pipe 26c, and the adjustment valve 45 can arbitrarily adjust the flow rate of the ammonia gas 47.

  On the other hand, a supply pipe is connected to the upper end of the gas supply nozzle 29 and branches to supply pipes 26a and 26b via switching valves 38a and 38b. The other ends of the supply pipes 26a and 26b are connected to the source gas supply units 14 and 15, respectively.

  The source gas supply unit 14 supplies a source gas for forming a GaN film to the gas supply nozzle 29. The source gas supply unit 14 includes a TMG tank 40 in which trimethylgallium 34 is stored. The TMG tank 40 is provided with a heater 43a that heats and vaporizes the trimethylgallium 34 below. The above-described supply pipe 26a is connected to the upper portion of the TMG tank 40, and the carrier pipe 31a is connected. The other end of the carrier pipe 31a is connected to the carrier gas supply unit 44a via the flow rate adjustment valve 41a. The carrier gas supply unit 44a can adjust the concentration by diluting the vaporized source gas by controlling the flow rate using, for example, hydrogen, nitrogen gas or the like.

  The source gas supply unit 15 supplies source gas for forming an AlN (aluminum nitride) film to the gas supply nozzle 29. The source gas supply unit 15 includes a TMA tank 42 in which trimethylaluminum 36 is stored. The TMA tank 42 is provided with a heater 43b that heats and vaporizes the trimethylaluminum 36 below. The above-described supply pipe 26b is connected to the upper portion of the TMA tank 42, and the carrier pipe 31b is connected. The other end of the carrier pipe 31b is connected to the carrier gas supply unit 44b via the flow rate adjustment valve 41b. The carrier gas supply unit 44b can adjust the concentration by diluting the vaporized source gas by controlling the flow rate using, for example, hydrogen, nitrogen gas or the like.

With the above configuration, the film forming apparatus 10 operates as follows. The inside of the reaction vessel 12 is depressurized, and the substrate 16 is heated by a heater 19 fixed to the lower surface of the substrate receiver 18. In this embodiment, the heating temperature is set to 1000 ° C. to 1100 ° C. Next, the substrate receiver 18 on which the substrate 16 is placed is rotated. The switching valves 38a and 38b on the supply pipes 26a and 26b are closed in advance. Next, source gas is injected from the upper part of the reaction vessel 12. When growing GaN, the trimethylgallium 34 inside the TMG tank 40 of the source gas supply unit 14 is heated and vaporized by the heater 43a. The switching valve 38a is opened, and the carrier gas is introduced from the carrier gas supply unit 44a connected to the end of the source gas supply unit 14. The trimethyl gallium 34 is diluted with the carrier gas to adjust the concentration, and sent into the reaction vessel 12 together with the carrier gas. The ammonia gas 47 from the NH ₃ gas supply unit 46 and the trimethyl gallium 34 vaporized from the source gas supply unit 14 are supplied onto the heated substrate 16. Thermal decomposition of trimethylgallium 34 and ammonia gas 47 occurs on the substrate 16, and GaN crystals grow.

During the thermal decomposition reaction, the crystal substrate 16 on the substrate receiver 18 is revolved by a motor 20 connected to the substrate receiver 18. As a result, the NH ₃ gas supply nozzle 28 and the gas supply nozzle 29 move in the horizontal direction on the substrate 16, so that the film grows in the horizontal direction along the film surface. Therefore, the grown crystals are stacked in the lateral direction, and a laterally grown film is formed on the substrate. At this time, the growth film is formed by arbitrarily setting the rotation speed of the substrate 16 and the gas flow rate of the source gas supply unit 14. If the sprayed portions are uniform in this way, the layers are laminated as a whole, and a uniform film can be formed on the substrate.

When an AlN (aluminum nitride) film is deposited after GaN is deposited, the switching valve 38a installed in the supply pipe 26a is first closed to stop the supply of vaporized trimethylgallium 34. Next, the trimethylaluminum 36 is heated and vaporized by the heater 43b in the TMA tank 42 of the source gas supply unit 15. The switching valve 38b installed in the supply pipe 26b is opened and the vaporized trimethylaluminum 36 is sent into the reaction vessel 12 together with the carrier gas. The ammonia gas 47 from the NH ₃ gas supply unit 46 and the trimethylaluminum 36 vaporized from the source gas supply unit 15 are supplied onto the heated substrate 16. Thermal decomposition of trimethylaluminum 36 and ammonia gas 47 occurs on the substrate 16, and an AlN crystal grows on the substrate 16. The gas supply nozzle 29 can also supply the trimethylgallium 34 and the trimethylaluminum 36 simultaneously by opening both the switching valves 38a and 38b.

Next, a film forming apparatus according to the second embodiment will be described with reference to FIG. As shown in FIG. 3, one large-diameter substrate 16 is placed on the substrate receiver 18. An NH ₃ gas supply nozzle 28 and a gas supply nozzle 29 are installed in the radial direction of the substrate receiver 18, and these are also installed in the diameter direction. Thereby, the deposition rate of film formation on the substrate can be increased by controlling the amount of the source gas sprayed. The number and location of the nozzles are not limited to this, and can be arbitrarily set in consideration of the size or number of substrates placed on the substrate receiver or the growth rate of the film formation.

FIG. 4 is a view showing a film forming apparatus according to the third embodiment. As shown in FIG. 4, the NH ₃ gas supply nozzle 28 and the gas supply nozzle 29 can be reciprocated on the substrate 16 in the direction of arrow e by a drive unit (not shown) while the substrate 16 is placed on the substrate receiver 18. It is installed in. Also with this configuration, the NH ₃ gas supply nozzle 28 and the gas supply nozzle 29 move laterally on the substrate 16 as in the film formation described above. Therefore, a lateral growth film along the film surface on the substrate 16 can be formed. The NH ₃ gas supply nozzle 28 and the gas supply nozzle 29 may be fixed, and the substrate receiver 18 may be installed so as to be able to reciprocate in the direction of arrow e.

  On the other hand, since a plurality of crystal films on the substrate may be stacked, when forming a crystal film having a different composition on the substrate 16, the composition of the source gas must be changed. According to the conventional method, when the composition of the raw material gas is changed, it is necessary to make the composition of the entire reaction vessel 12 uniform. However, according to this embodiment, the spraying of the raw material is set in the vicinity of the substrate 16 and the discharge range of the raw material gas is narrow, so that the composition can be easily and quickly switched. Thereby, the source gas does not remain in the reaction vessel, and the layers to be stacked on the substrate 16 are clearly switched, and the boundary surface becomes clear.

  As described above, in this embodiment, the source gas is blown locally on the vicinity of the substrate 16 to form the growth film in the lateral direction, so that the generation of through defects on the substrate 16 is prevented and uniform growth is achieved. A film can be formed.

  Although the present embodiment has been described using GaN and AlN as the compound semiconductor to be formed, the compound semiconductor to be formed is not limited to this, and gallium arsenide (GaAs), gallium indium arsenide (GaInAs), and the like. The present invention can also be applied to other compound semiconductor manufacturing. Furthermore, the present invention can be applied to the general film formation of epitaxial films such as Si and SiC.

1 is a schematic configuration diagram of a film forming apparatus according to an embodiment. It is an enlarged view which sprays source gas on a board | substrate. It is a figure which shows the growth apparatus which concerns on 2nd Embodiment. It is a figure which shows the growth apparatus which concerns on 3rd Embodiment. It is a figure which shows the conventional epitaxial growth apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ......... Substrate, 2 ......... Slit, 3 ......... GaN-based nitride semiconductor crystal, 4 ......... Opening, 10 ...... Film forming apparatus, 11 ......... Vacuum pump, 12 ......... Reaction Container, 13 ......... Pressure regulating valve, 14 ......... Source gas supply unit, 15 ......... Source gas supply unit, 16 ...... Substrate, 18 ...... Substrate receptacle, 19 ...... Heater, 20 ... ... motor, 22 ......... shaft, 26 ......... supply pipe, 28 ......... NH ₃ gas supply nozzle, 29 ......... gas supply nozzle, 31 ......... carrier pipe, 32 ......... air outlet, 34 ... ...... Trimethyl gallium, 36 ......... Trimethyl aluminum, 38 ......... Switching valve, 40 ......... TMG tank, 41 ......... Flow control valve, 42 ......... TMA tank, 43 ......... Heater, 44 ... ... carrier gas supply unit, 45 ......... regulating valve, 46 ......... NH ₃ gas supply Part, 47 ......... ammonia gas.

Claims (4)

  A film forming method, wherein a film forming source gas is sprayed on a substrate in a band shape, and a nozzle for blowing the film forming source gas and the substrate are relatively moved along a surface of the substrate.   A table on which a substrate for film formation is arranged; a nozzle having a strip-shaped outlet facing the table; and a drive unit that relatively moves at least one of the table and the nozzle along the surface of the table; And a raw material gas supply unit for supplying a raw material gas for film formation to the nozzle.   The table is a rotary table, and the nozzle is arranged such that the longitudinal direction of the blowout port is arranged in the radial direction of the rotary table, and the opening width of the blowout port is directed toward the outer peripheral side from the center side of the rotary table. 3. The film forming apparatus according to claim 2, wherein the film forming apparatus is gradually widened.   The film forming apparatus according to claim 3, wherein a plurality of the nozzles are arranged along a circumferential direction of the rotary table.

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