JP2009221056A - Crystal growth method, crystal growth apparatus, and semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crystal growth method capable of growing a high-crystallinity and high-quality group III element nitride crystal without using any seed crystal. <P>SOLUTION: A sapphire substrate 7 is nitrided by annealing it for 5 min at 1,050°C in an ammonia atmosphere in an annealing furnace 20. Next, a raw material solution 8 comprising Ga as a raw material metal and Na as a flux and nitrogen as a raw material gas are brought into contact with each other on the nitrided sapphire substrate 7 to grow a GaN crystal thereon. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for growing a crystal of a material used for a light emitting device and the like, and an apparatus for growing the crystal. Moreover, it is related with the semiconductor device containing the crystal | crystallization obtained by this method.

Today, Group III element nitride crystals such as GaN (gallium nitride) are used as materials for light emitting devices such as LD (laser diode) and LED (light emitting diode). This crystal is produced by a vapor phase epitaxial growth method or the like. For example, a sapphire substrate is used as a substrate, and the crystal is heteroepitaxially grown on the substrate. The transition density of the group III element nitride crystal thus produced is about 10 ⁸ pieces / cm ² to 10 ⁹ pieces / cm ² . The crystal used as the material of the light-emitting device is desired to have a lower transition density in order to maintain the reliability of the device. Therefore, in the vapor phase epitaxial growth method which is one of crystal growth methods, it is an important issue to reduce the dislocation density.

As methods for solving this problem, Patent Document 1 discloses an ELOG (Epitaxial Lateral Over Growth) method, and Patent Document 2 discloses a facet growth method. According to these vapor phase growth methods, the crystal transition density can be lowered to about 10 ⁵ pieces / cm ² to 10 ⁷ pieces / cm ² .

Further, a method of growing crystals in a liquid phase instead of a vapor phase growth method has been studied, and a Na flux method using an alkali metal such as Na (sodium) as a flux is disclosed in Patent Document 3. Conventionally, group III element nitride crystals such as GaN and AlN (aluminum nitride) have an equilibrium vapor pressure of nitrogen at the melting point of 10,000 atmospheres or more. For this reason, in order to grow GaN in a liquid phase, conditions of 1,200 ° C. (1,473 K) and 8,000 atmospheres (8,000 × 1.01325 × 10 ⁵ Pa) are required. However, by using the Na flux method, a GaN crystal can be grown at a relatively low temperature and low pressure of 750 ° C. (1,023 K) and 50 atm (50 × 1.01325 × 10 ⁵ Pa).

Furthermore, Patent Document 4 and Non-Patent Document 1 disclose a method of liquid phase growth (LPE: Liquid Phase Epitaxy) of a GaN crystal by a Na flux method using a seed crystal. Note that the seed crystal is formed by forming a GaN crystal layer on a sapphire substrate by metal organic chemical vapor deposition (MOCVD). The transition density of a crystal produced using such a seed crystal is about 10 ⁴ pieces / cm ² to 10 ⁶ pieces / cm ^2, which is even lower than a crystal produced by a vapor phase growth method. can get.
JP 11-145516 A (published May 28, 1999) JP 2001-102307 A (published April 13, 2001) US Pat. No. 5,868,837 (published on February 12, 2004) WO 2004/013385 (published on February 12, 2004) Fumio Kawamura, Tomoya Iwahashi, Kunimichi Omae, Masanori Morishita, Masashi Yoshimura, Yusuke Mori and Takatomo Sasaki, "Growth of a Large GaN Single Crystal Using the Liquid Phase Epitaxy (LPE) Technique", Jpn. J. et al. Appl. Phys. , 2003, Vol 42, pp. 4-6

  However, the crystal growth method using the seed crystal as described above has a problem that the productivity of the seed crystal is poor because the preparation process of the seed crystal is complicated.

  Further, when crystal growth is performed on a substrate without using a seed crystal, wettability between the raw material solution and the substrate is important. If this wettability is poor, not only is it difficult to grow the crystal, but even if the crystal can be grown, the crystal axis is not aligned in a certain direction, etc. There is a risk of becoming.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a crystal growth method capable of producing high-quality crystals with high productivity without forming a seed crystal layer. It is in.

  In order to solve the above problems, the crystal growth method according to the present invention is a crystal growth method in which a source liquid and a source gas are brought into contact with each other on a substrate to grow a crystal of a compound of the source liquid and the source gas. In the crystal growth method including the steps, at least a part of the surface of the substrate is nitrided.

  According to the above configuration, since the crystal growth method according to the present invention grows a crystal on a nitrided substrate, it is possible to easily produce a crystal with crystal axes aligned in a certain direction.

  Specifically, the crystal growth method according to the present invention uses a substrate whose surface is at least partially nitrided. Therefore, a part of atoms constituting the target portion of the nitriding treatment in the surface of the substrate is replaced with nitrogen atoms. Thus, in the portion of the surface of the substrate where the atomic structure is changed, the wettability between the raw material liquid and the substrate is improved, so that it is easy to grow crystals on the substrate.

  In addition, when a crystal is grown using the substrate, a crystal nucleus is generated by combining a nitrogen atom introduced to the substrate surface by nitriding treatment and a crystal raw material atom. Thereafter, crystal growth starts preferentially from the crystal nucleus. Thus, since the position where crystal growth starts can be controlled by nitriding treatment, it is possible to produce a crystal with crystal axes aligned in a certain direction.

  In the crystal growth method according to the present invention, it is preferable that a region for generating the nucleus of the crystal in the surface of the substrate is nitrided.

  According to the above configuration, since the region in which crystal nuclei are generated is specified, it is possible to produce a crystal with aligned crystal axis directions.

  Specifically, by nitriding a specific region on the surface of the substrate, crystal nuclei can be preferentially generated in the region. Thus, by specifying the generation position of the crystal nucleus, the direction of the crystal growing from the nucleus can be controlled. Therefore, for example, by controlling so that the crystal grows preferentially in the lateral direction, a crystal having a uniform crystal axis direction can be obtained. Furthermore, by aligning the direction of the crystal axis, it is possible to produce a crystal with few crystal grain boundaries and excellent flatness.

  In the crystal growth method according to the present invention, the substrate is preferably nitrided in a circular shape.

  According to the above configuration, since the region to be nitrided is circular, the nuclei generated on the surface of the substrate are controlled to be circular. Therefore, for example, when a crystal is grown in the lateral direction, the crystal grows while spreading in a circular shape, so that a crystal with few crystal grain boundaries can be manufactured.

  In the crystal growth method according to the present invention, the substrate is preferably nitrided in a stripe shape.

  According to the above configuration, since the region to be nitrided has a stripe shape, the nuclei generated on the surface of the substrate are controlled to have a stripe shape. Therefore, when the crystal is grown in the lateral direction, not only can the time required for the crystals grown from the respective nuclei to associate with each other, but also a flat crystal can be produced on the entire surface of the substrate.

  In the crystal growth method according to the present invention, the source gas preferably contains nitrogen, and the source metal preferably contains a group III element.

  According to said structure, the group III element nitride suitable as a material of a light-emitting device can be manufactured by making the nitrogen in source gas react with the group III element in the raw material liquid which consists of source metals.

  In the crystal growth method according to the present invention, it is preferable to use an alkali metal as the flux in the crystal growth step.

  According to said structure, since the growth temperature of a crystal | crystallization and the pressure of a growth atmosphere can be reduced by containing an alkali metal in a raw material liquid, a crystal | crystallization can be obtained more simply.

  In the crystal growth method according to the present invention, the substrate is preferably a sapphire substrate.

  According to the above configuration, by using sapphire excellent in thermal stability and chemical stability as the material of the substrate, oxygen atoms, which are constituent elements of sapphire, can be converted into nitrogen atoms relatively easily during nitriding. Can be replaced.

  Furthermore, a semiconductor device according to the present invention is characterized by having the crystal produced by the crystal growth method.

  According to the above configuration, the semiconductor device according to the present invention is manufactured on the crystal whose manufacturing cost is suppressed by the crystal growth method according to the present invention, so that the cost performance of the final product semiconductor device is greatly increased. Can be improved.

  In order to solve the above problems, a crystal growth apparatus according to the present invention includes a nitriding treatment means for nitriding the surface of a substrate, and a raw material solution and a raw material on the substrate nitrided by the nitriding treatment means. Crystal growth means for growing a crystal of a compound of the raw material liquid and the raw material gas in contact with a gas is provided.

  According to said structure, there exists an effect similar to the crystal growth method concerning this invention.

  In the crystal growth apparatus according to the present invention, it is preferable that the nitriding treatment means nitrides the surface of the substrate by annealing in an ammonia atmosphere.

  According to the above configuration, since the nitriding means performs the annealing process in an ammonia atmosphere, the manufacturing cost of the crystal can be suppressed.

  Specifically, the nitrogen gas used for the annealing treatment can be used in the crystal growth process, and further, when ammonia is decomposed by high-temperature annealing, nitrogen atoms are generated, and the nitrogen atoms are also used in the crystal growth process. Available.

  Therefore, not only can the supply amount of the raw material gas be reduced, but also the effect of improving the reaction efficiency between the raw material liquid and the raw material gas can be achieved.

  In the crystal growth apparatus according to the present invention, it is preferable that the nitriding treatment means nitrides the surface of the substrate by plasma treatment in a nitrogen atmosphere.

  According to said structure, the nitriding process means can suppress the manufacturing cost of a crystal | crystallization by performing a plasma process in nitrogen atmosphere.

  Specifically, the nitrogen gas used for the plasma treatment can be used also in the crystal growth step, and further, nitrogen atoms generated by the plasma treatment can be used in the crystal growth step.

  Therefore, not only can the supply amount of the raw material gas be reduced, but also the effect of improving the reaction efficiency between the raw material liquid and the raw material gas can be achieved.

  As described above, in order to solve the above-described problem, the crystal growth method according to the present invention brings a raw material liquid and a raw material gas into contact with each other on a substrate to crystallize a compound of the raw material liquid and the raw material gas. In the crystal growth method including the crystal growth step of growing the substrate, at least a part of the surface of the substrate is nitrided. Further, the crystal growth apparatus according to the present invention comprises a nitriding treatment means for nitriding the surface of the substrate, and contacting the raw material liquid and the raw material gas on the substrate that has been nitrided by the nitriding treatment means, Crystal growth means for growing crystals of a compound of the raw material liquid and the raw material gas is provided.

  According to said structure, the crystal growth method and crystal growth apparatus which can produce a high quality crystal | crystallization with sufficient productivity can be provided, without using a seed crystal layer.

<1. Crystal Growth Method According to the Present Invention>
The crystal growth method according to the present invention is a crystal growth method including a crystal growth step of growing a compound crystal of the raw material liquid and the raw material gas by bringing the raw material liquid and the raw material gas into contact with each other on a substrate. It is sufficient that at least a part of the surface of the substrate is nitrided.

  As described above, the crystal growth method according to the present invention is characterized in that a crystal is grown on a substrate having a surface subjected to nitriding treatment.

  The nitriding process is a process of substituting, for example, oxygen atoms or the like, which are atoms constituting the substrate, with nitrogen atoms on the surface of the substrate.

  As an example of the nitriding treatment, first, a substrate is placed inside a nitriding treatment means for performing nitriding treatment. Next, the inside of the nitriding means is placed in a nitrogen atmosphere, and the nitriding means is heated by a heating device. Thereby, some of the atoms constituting the surface of the substrate are replaced with nitrogen atoms. Examples of the nitriding means for performing nitriding include, but are not limited to, an annealing furnace and a plasma processing furnace. For example, a gas containing nitrogen atoms such as an MOCVD apparatus is allowed to flow. It is possible to use a device that can be heated and heated.

  As described above, the change in the atomic structure on the surface of the substrate greatly improves the wettability between the substrate and the raw material liquid when the crystal is grown. Therefore, there is an effect that crystal growth is facilitated.

  The “surface of the substrate” means a surface on which a crystal is formed on the substrate. The material of the substrate used in the present invention is preferably sapphire, which is excellent in thermal stability and chemical stability, but is not limited thereto, and for example, silicon or silicon carbide can be used. It is.

  Further, the nitriding treatment is preferably performed on a region where crystal nuclei are generated on the surface of the substrate. The region may be at least a part of the surface of the substrate, but is preferably a circular region 71 as shown in FIG. 4 or a stripe-shaped region 72 as shown in FIG.

  Specifically, in the circular region 71 subjected to the nitriding treatment shown in FIG. 4, the wettability between the substrate 7 and the raw material liquid is improved, so that crystal nuclei are preferentially generated. Furthermore, for example, when a crystal is grown in the lateral direction after the generation of the nucleus, the crystal grows while spreading in a circular shape. Therefore, a crystal with few crystal grain boundaries can be manufactured. The above-mentioned “crystal grain boundary” means a surface where the crystal directions are not uniform at the interface where the crystals grown from these nuclei are joined together when a plurality of crystal nuclei are grown on the substrate 7. To do. At this crystal grain boundary, impurities are likely to remain, and defects such as dislocations are concentrated, so that crystallinity, electrical characteristics, etching resistance, and the like may change greatly. Therefore, it is preferable that the crystal grain boundary is smaller.

  Further, the size of the circular area 71 may be at least a part of the area on the surface of the substrate 7, but is preferably less than half the area of the surface of the substrate 7. By limiting to such a size, there is an effect that it is easy to produce a crystal with good crystallinity in which the directions of crystal axes are aligned.

  Further, by using the substrate 7 having the regions 72 nitrided in the stripe shape as shown in FIG. 5, a crystal having a flat shape in which the directions of the crystal axes are aligned can be obtained in a short time. .

  Specifically, in the stripe-shaped region 72 subjected to nitriding treatment, the wettability between the substrate 7 and the raw material liquid is improved, so that crystal nuclei are preferentially generated in a stripe shape. Therefore, for example, when a crystal is grown in the lateral direction after the generation of the nucleus, the time until the crystal is associated can be shortened.

  Further, by controlling the nitriding region in a stripe shape, a flat crystal can be formed on the entire surface of the substrate 7. Note that the optimum width and number of stripes may be appropriately selected according to the type of crystal to be grown and the reaction conditions.

  A raw material liquid is a solution obtained by heating and melting a raw material metal. The source metal may be any group III element metal. For example, a group III element metal such as aluminum (Al), indium (In), and thallium (Tl) can be used, but gallium (Ga). It is more preferable that When the source metal is gallium (Ga), it can be suitably used as a material for a semiconductor element.

The source gas is a gas in which crystals are synthesized by reacting with the source liquid. The source gas may be any gas that can react with the source liquid to synthesize crystals, but preferably contains nitrogen. When the source gas contains nitrogen, a nitride crystal suitable for a light emitting device is synthesized. As such a source gas, it is sufficient if it contains nitrogen atoms. For example, nitrogen (N ₂ ) gas, ammonia (NH ₃ ) gas, or the like can be used. These source gases can be used alone or in combination.

  In the crystal growth method according to the present invention, the crystal is grown by bringing the above-described raw material liquid and raw material gas into contact with each other on the nitrided substrate. Such a crystal growth method will be described in detail later. For example, in a state where the raw material liquid and the raw material gas are present in the reaction vessel, the reaction vessel is heated. As a result, the raw material liquid and the raw material gas react to grow crystals.

  Here, the crystal of the compound grown by the above reaction includes, for example, a nitride of a group III element metal, and among them, a gallium nitride crystal is more preferable. Thus, when the crystal is gallium nitride, there is an effect that it can be suitably used as a material for a light emitting device.

  The crystal growth step is a step in which a raw material liquid supplied on a substrate and a raw material gas are reacted to grow while synthesizing crystals of these compounds.

  As an example of the crystal growth step, details will be described later, but first, a nitrided substrate is placed in a reaction vessel. Next, the raw material liquid supplied on the substrate and the raw material gas are heated and reacted by a heating device. By this reaction, a compound crystal is synthesized from the raw material liquid and the raw material gas, and the crystal is grown to a desired size.

  As described above, in the crystal growth process, the use of the nitrided substrate significantly improves the wettability between the substrate and the raw material liquid, and the crystal growth is facilitated. Furthermore, as described above, since the region to be nitrided is circular or stripe-shaped, it is possible to produce a crystal with good crystallinity with aligned crystal axis directions.

<2. Crystal growth apparatus according to the present invention>
Next, the configuration of the crystal growth apparatus according to one embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a cross-sectional view showing a configuration of a crystal growth apparatus 1 according to the present embodiment. As shown in FIG. 1, the crystal growth apparatus 1 of the present invention includes a crystal growth unit 2 and a gas supply unit 10. The crystal growth unit 2 includes a heat and pressure resistant vessel 3, a heating device 4, and a reaction vessel 5. The gas supply unit 10 includes a gas storage unit 11, a pressure regulator 12, and a connection pipe 13.

  The periphery of the crystal growth unit 2 is surrounded by a heating device 4. In addition, a heat-resistant and pressure-resistant container 3 is disposed inside the crystal growth unit 2, and a reaction container 5 is disposed in the heat-resistant and pressure-resistant container 3.

  The reaction vessel 5 is not limited as long as a part of the reaction vessel 5 is open. For example, an alumina crucible or the like can be used. The reaction vessel 5 is installed inside the heat-resistant and pressure-resistant vessel 3, and a substrate 7 subjected to nitriding treatment is arranged inside the reaction vessel 5. Here, when the raw material liquid 8 is supplied onto the substrate 7, the raw material gas supplied from the gas supply unit 10 reacts with the raw material liquid 8. Thereby, a crystal of a compound of the raw material liquid 8 and the raw material gas is synthesized on the substrate 7.

  In addition, the heat-resistant and pressure-resistant container 3 may be any container that can be sealed, but for example, a SUS (stainless steel) container or the like can be used. The heat and pressure resistant container 3 is provided with a hermetic lid 6. Therefore, when the sealing lid 6 is opened, the reaction vessel 5 can be easily placed inside the heat-resistant and pressure-resistant vessel 3, and when the sealing lid 6 is closed, the heat-resistant and pressure-resistant vessel 3 can be sealed.

  The heating device 4 may be any device that can raise the inside of the reaction vessel 5 to a temperature equal to or higher than the crystal growth temperature and hold it for an arbitrary time. For example, an electric furnace or the like can be used. As described above, when the temperature inside the reaction vessel 5 is set to the growth temperature using the heating device 4, the reaction between the raw material liquid 8 and the raw material gas is promoted, so that crystals can be obtained efficiently. The heating device 4 is provided outside the heat-resistant pressure-resistant vessel 3, and when the heat-resistant pressure-resistant vessel 3 is heated by the heating device 4, the reaction vessel 5 can also be heated. The heating device 4 is not necessarily installed outside the heat-resistant pressure-resistant container 3, and may be installed between the heat-resistant pressure-resistant container 3 and the reaction container 5 or integrated with the heat-resistant pressure-resistant container 3 or the reaction container 5. May be used.

  Further, as shown in FIG. 1, the crystal growth unit 2 and the gas storage unit 11 are connected by a connection pipe 13. Specifically, the connection pipe 13 passes through the heating device 4 of the crystal growth unit 2 and reaches the inside of the heat and pressure resistant container 3. Here, as described above, a part of the reaction vessel 5 is open. Therefore, the raw material gas is also supplied to the inside of the reaction vessel 5 by supplying the raw material gas from the gas storage unit 11 to the heat and pressure resistant container 3. Thereby, the inside of the heat-resistant pressure-resistant container 3 and the reaction container 5 can be made into the atmosphere (pressure atmosphere) of source gas.

  At this time, the pressure regulator 12 provided in the connection pipe 13 can adjust the inside of the reaction vessel 5 to the pressure of the crystal growth atmosphere by sealing the heat and pressure resistant vessel 3 and can hold it for an arbitrary time. It becomes. Furthermore, the pressure can be higher or lower than the pressure of the crystal growth atmosphere. Such a pressure regulator 12 may be anything that adjusts the pressure of the growth atmosphere in the reaction vessel 5, but preferably has a configuration including, for example, a pressure sensor and a pressure regulating valve.

  Thus, the reaction between the raw material liquid 8 and the raw material gas is promoted by setting the pressure inside the reaction vessel 5 to the pressure of the crystal growth atmosphere using the pressure regulator 12. Therefore, crystals can be obtained efficiently.

  Further, the crystal growth apparatus 1 according to the present invention may further include a nitriding means as shown in FIGS.

  FIG. 2 is a diagram showing a crystal growth apparatus 1 provided with an annealing furnace 20 as nitriding treatment means. In the annealing furnace 20, the substrate 7 disposed in the furnace is subjected to a high temperature annealing process in an ammonia atmosphere. In this way, the surface of the substrate 7 is nitrided.

  Specifically, as shown in FIG. 2, the annealing furnace 20 is provided with a heater 24. The substrate 7 is placed in the heater 24, and the annealing furnace 20 is heated while supplying ammonia gas from the gas storage unit 11. Thereby, the surface of the substrate 7 can be nitrided.

  As another nitriding means, a plasma processing furnace 30 as shown in FIG. 3 can be used.

  Specifically, as shown in FIG. 3, the plasma processing furnace 30 is provided with an upper electrode 31 and a lower electrode 32 for generating plasma. A high frequency power source 33 is connected to the upper electrode 31, and the lower electrode 32 is grounded. In addition, as an electrode material, although not limited to this, carbon is mentioned, for example. A heater 34 is installed below the lower electrode 32, and the substrate 7 is installed above. As a specific nitriding method, first, nitrogen gas is supplied from the gas storage unit 11 while being heated by the heater 34. Next, nitriding treatment is performed on the surface of the substrate 7 by generating plasma between the upper electrode 31 and the lower electrode 32.

  Further, as described above, the annealing furnace 20 and the plasma processing furnace 30, which are nitriding means provided in the crystal growth apparatus 1 according to the present invention, are connected to the crystal growth unit 2 by the connection pipe 13. By being connected in this way, for example, ammonia gas or nitrogen gas used in the nitriding means can be introduced into the crystal growth unit 2 during nitriding. Therefore, since these gases can be used as source gases in the crystal growth step, the manufacturing cost of crystals can be further reduced.

  The crystal growth apparatus 1 according to the present invention can be manufactured, for example, by the following method. First, the heating device 4 is disposed outside the heat and pressure resistant container 3 using a conventionally known method. Thereafter, one end of the connection pipe 13 is connected so as to penetrate the heating device 4 and reach the inside of the heat and pressure resistant container 3, and the other end of the connection pipe 13 is connected to the gas storage unit 11. In this way, the crystal growth apparatus 1 may be manufactured.

<3. Crystal Growth Process According to the Present Invention>
Next, the crystal growth process according to the present invention will be described below with reference to the crystal growth apparatus 1 shown in FIG.

  First, the raw material metal weighed by a predetermined amount and the substrate 7 having at least a part of the surface nitrided are placed in the reaction vessel 5. In addition, if necessary, a substance that becomes a flux is also added.

  Next, the hermetic lid 6 of the heat and pressure resistant container 3 is opened, and the reaction container 5 is installed inside the heat and pressure resistant container 3. Then, the heat-resistant pressure-resistant container 3 is sealed by closing the sealing lid 6, and the inside of the heat-resistant pressure-resistant container 3 is shut off from the external atmosphere.

  Next, the heating device 4 is used to raise the temperature of the reaction vessel 5 until the crystal growth temperature is reached. Further, the source gas is supplied from the gas storage unit 11 as the supply unit 10 into the heat-resistant and pressure-resistant container 3 through the connection pipe 13. Further, the pressure regulator 12 is used to bring the inside of the reaction vessel 5 to a crystal growth pressure.

  At this time, by holding the growth temperature for a certain period of time, the raw material liquid 8 and the raw material gas can react to grow a crystal of the compound of the raw material liquid 8 and the raw material gas. Note that the growth temperature may be appropriately selected depending on the type of crystal to be grown.

  Further, by maintaining the growth pressure for a certain period of time, the raw material liquid 8 and the raw material gas react with each other, and the crystal of the compound of the raw material liquid 8 and the raw material gas can be grown more efficiently. The growth pressure may be appropriately selected according to the type of crystal to be grown.

  Thus, by holding the growth temperature and the growth pressure for a certain time, the raw material liquid 8 and the raw material gas react with each other, and a crystal of the compound of the raw material liquid 8 and the raw material gas grows on the substrate 7.

  At this time, for example, by using a group III element as a source metal, an alkali metal as a flux, a gas containing nitrogen as a source gas, and a nitrided sapphire substrate as a substrate, a group III element nitride crystal on the sapphire substrate Can grow.

  Next, after the crystal grows to a desired size, it is cooled until the temperature of the crystal reaches room temperature. The cooling method is not limited as long as the temperature of the crystal can be lowered to room temperature. For example, the crystal growth apparatus 1 is allowed to stand at room temperature, or a conventionally known cooling means such as a cooler is used. Can be applied.

  Further, after cooling the crystal, the hermetic lid 6 of the heat and pressure resistant container 3 is opened, and the crystal is taken out from the reaction container 5. At this time, since there is a solidified mass of the raw material liquid 8 inside the reaction vessel 5, this mass is removed. As a removing method, for example, there is a method of immersing in a solution of water, ethanol, hydrochloric acid or the like.

<4. Semiconductor Device According to the Present Invention>
Next, as an example of the semiconductor device according to the present invention, a light-emitting diode (LED) using a crystal obtained by the crystal growth method of the present invention will be described with reference to FIGS.

  FIG. 6 is a sectional view showing an intermediate member of the light emitting diode according to the present invention. As shown in this figure, a GaN crystal layer 7a grown by the crystal growth method according to the present invention is formed on a substrate 7. Further thereon, an n-type contact layer 7b, an active layer 7c, a p-type block layer 7d, and a p-type contact layer 7e are sequentially stacked. Each layer laminated on the GaN crystal layer 7a can be formed by a conventionally known method. Examples of such a method include metal organic chemical vapor deposition (MOCVD).

  FIG. 7 is a sectional view showing a light emitting diode according to the present invention. As shown in this figure, the configuration of the light emitting diode of the present invention differs from the configuration of the intermediate member described above in the following points. That is, a part of the substrate 7 and the GaN crystal layer 7a is removed, and an n-side electrode 7h is formed at that position. Further, a laminated layer 7f and a metal substrate 7g are formed on the p-type contact layer 7e. Although not shown in the figure, the laminate 7f includes a p-side electrode, a light reflection layer, and an adhesive layer.

  Moreover, the process of forming a light emitting diode from the intermediate member of a light emitting diode is formed by the following procedures, for example.

  First, the stack 7f is formed on the p-type contact layer 7e. Next, a metal substrate 7g is bonded onto the laminated 7f. Thereafter, the substrate 7 is peeled off. At this time, a part of the GaN crystal layer 7a is polished in order to prepare the surface from which the substrate 7 is peeled off. Furthermore, the LED element of this invention is produced by forming the n side electrode 7h under the GaN crystal layer 7a.

  As described above, the light-emitting diode according to the present embodiment uses the GaN crystal layer 7a having a low dislocation density manufactured by the crystal growth method of the present invention. For this reason, the active layer 7 formed on the GaN crystal layer 7a can keep the dislocation density low. Therefore, an LED with high emission intensity can be manufactured.

  In addition, the crystal obtained by the crystal growth method according to the present embodiment is not only used for a light emitting diode, but also for a light emitting device such as a laser diode, an electronic device such as a high output IC, or a high frequency IC. Applicable.

<Example 1>
In Example 1, a GaN crystal was grown using the crystal growth apparatus 1 shown in FIG.

  First, in the annealing furnace 20, the sapphire substrate 7 (1/4 of a 2-inch wafer) was nitrided by annealing at 1,050 ° C. in an ammonia atmosphere for 5 minutes. As a result of measuring the sapphire substrate 7 thus nitrided by X-ray photoelectron spectroscopy, it was found that about 15% of oxygen atoms constituting the sapphire were substituted with nitrogen atoms.

  Next, on the nitrided sapphire substrate 7, Ga (50 mg) as a raw material metal and Na (80 mg) as a flux were placed. Thereafter, they were put in an alumina crucible (reaction vessel) 5.

  Further, after placing the alumina crucible 5 in the SUS heat-resistant pressure vessel 3, the alumina crucible 5 was set in the electric furnace (heating device) 4. Furthermore, the nitrogen cylinder (gas storage part) 11 and the SUS heat-resistant pressure vessel 3 were connected by a SUS pipe (connection pipe) 13.

Here, the electric furnace 4 was heated and the temperature in the SUS heat-resistant pressure-resistant container 3 was adjusted to 850 ° C. (1,123 K). Moreover, the nitrogen atmosphere pressure in the heat-resistant pressure-resistant container 3 made from SUS was adjusted to 40 atmospheres (40 * 1.01325 * 10 < ⁵ > Pa) using the pressure regulator 12. FIG. And the temperature mentioned above was hold | maintained for 5 hours, and the GaN crystal was grown.

  After the growth of the crystal was completed, the temperature in the SUS heat-resistant pressure-resistant vessel 3 was cooled to room temperature and released to the atmosphere, and then the GaN crystal was taken out from the alumina crucible 5. Na adhered to the surface of the GaN crystal. Therefore, it was immersed in ethanol and water for 30 minutes to remove Na. Further, unreacted Ga metal and Ga—Na alloy adhering to the surface of the GaN crystal were removed by immersion in 12N hydrochloric acid for 20 minutes. As a result, a GaN crystal having a thickness of about 10 μm was obtained on the sapphire substrate 7.

  The GaN crystal obtained by the above steps was evaluated by a scanning electron microscope and an X-ray diffractometer. As a result, the obtained GaN crystal was colorless and transparent although crystal grain boundaries were observed everywhere. It was also found that the degree of fluctuation of the crystal axis in the crystal growth direction was small and the GaN crystal had good crystallinity.

  Next, using the GaN crystal obtained by the above method, an LED having the same device configuration as the LED shown in FIG. 7 was produced.

  First, the following layers were formed on the GaN crystal layer 7a using an MOCVD apparatus.

  That is, the n-type GaN contact layer 7b was made of trimethylgallium and ammonia as raw materials, and silane as a dopant. The In (indium) GaN active layer 7c was prepared by adding trimethylindium to the material used for the n-type contact layer 7b. Using these, the barrier layer and the well layer were repeatedly laminated while changing the growth temperature and the raw material supply amount. Further, on the In (indium) GaN active layer 7c, a p-type Al (aluminum) GaN blocking layer 7d using trimethylaluminum, trimethylgallium, and ammonia as raw materials and bisethylcyclopentadienylmagnesium as a dopant, and A p-type GaN contact layer 7e was sequentially laminated. Thereafter, a stacked layer 7f including a p-side electrode, a light reflecting layer, and an adhesive layer was formed on the p-type GaN contact layer 7e. Further, after adhering a Si (silicon) substrate 7g to the adhesive layer by reflow, the sapphire substrate 7 was peeled off by irradiating the GaN crystal layer 7a with a YAG laser having a wavelength of 355 nm from the sapphire substrate 7 side. Finally, by polishing a part of the GaN crystal layer 7a, the surface from which the sapphire substrate 7 was peeled was flattened to form an n-side electrode 7h. This produced the LED element.

  Here, the light emission intensity at 200 mA emitted from the LED produced in this example and the LED produced with the GaN buffer layer on the sapphire substrate 7 was compared using a MOCVD apparatus which is a conventionally known method. .

  As a result, it was found that the LED of the present invention has a light emission intensity 1.2 times that of an LED produced by a conventionally known method.

<Example 2>
In Example 2, a GaN crystal was grown using the crystal growth apparatus 1 shown in FIG. In the crystal growth apparatus 1 of the present embodiment, the nitriding means of the crystal growth apparatus 1 used in the first embodiment is replaced with a plasma processing furnace 30.

  In this example, a circular region having a radius of 0.5 cm was nitrided from the center of the sapphire substrate 7 having a diameter of 2 inches by performing plasma treatment using a rod-shaped carbon electrode having a diameter of 1 cm.

  First, the substrate 7 was heated to 400 ° C., subjected to a plasma treatment for 30 minutes at a high frequency power of 50 W and a nitrogen partial pressure of 10.5 Torr. A crystal was grown by the same method as in Example 1 using the sapphire substrate 7 thus nitrided.

  Here, when the GaN crystal obtained by the above method was measured by X-ray diffraction, it was found that the degree of fluctuation of the crystal axis in the crystal growth direction was smaller.

  In addition, an LED element was produced using this crystal by the same method as in Example 1. The emission intensity at 200 mA was compared between the LED manufactured in this way and the LED manufactured by a conventionally known method. As a result, it was found that the LED of this example had a light emission intensity 1.3 times that of an LED produced by a conventionally known method.

<Example 3>
In Example 3, a GaN crystal was grown using the crystal growth apparatus 1 shown in FIG.

  In the present embodiment, a mask made of alumina is manufactured and placed on the substrate 7, and then plasma treatment is performed using a rod-like carbon electrode having a diameter of 2 inches, whereby the sapphire substrate 7 having a diameter of 2 inches is obtained. Above, a stripe-shaped region was nitrided. At this time, the width of the stripe shape was 2 mm, and the interval was 3 mm.

  First, the substrate 7 was heated to 400 ° C., subjected to plasma treatment for 40 minutes under a high frequency power of 50 W and a nitrogen partial pressure of 10.5 Torr. When a crystal was grown by the same method as in Example 1 using the sapphire substrate 7 thus nitrided, a flat GaN crystal was obtained in 4 hours.

  In addition, an LED element was produced using this crystal by the same method as in Example 1. The emission intensity at 200 mA was compared between the LED manufactured in this way and the LED manufactured by a conventionally known method. As a result, it was found that the LED of this example had a light emission intensity 1.2 times that of an LED produced by a conventionally known method.

  According to the crystal growth method of the present invention, a crystal of high quality and low cost can be produced, so that the practical value is extremely high. For example, it can be widely used in the semiconductor manufacturing industry by using it as a material for a semiconductor element. it can.

It is sectional drawing which shows the structure of the crystal growth apparatus which concerns on one Embodiment of this invention. It is sectional drawing which shows the structure of the crystal growth apparatus which concerns on one Embodiment of this invention. It is sectional drawing which shows the structure of the crystal growth apparatus which concerns on one Embodiment of this invention. It is the top view which showed the nitridation process area | region of the board | substrate nitrided circularly by the crystal growth method which concerns on one Embodiment of this invention. It is the top view which showed the nitridation process area | region of the board | substrate nitrided in the stripe shape by the crystal growth method which concerns on one Embodiment of this invention. It is sectional drawing which shows the structure of the intermediate member of the light emitting diode using the crystal produced in the crystal growth method concerning one Embodiment of this invention. It is sectional drawing which shows the structure of the light emitting diode using the crystal produced in the crystal growth method concerning one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Crystal growth apparatus 2 Crystal growth part (crystal growth means)
DESCRIPTION OF SYMBOLS 3 Heat-resistant pressure vessel 4 Heating apparatus 5 Reaction container 6 Sealed lid 7 Substrate 8 Raw material liquid 10 Gas supply part 11 Gas storage part 12 Pressure regulator 13 Connection pipe 20 Annealing furnace (nitriding treatment means)
24 Heater 30 Plasma processing furnace (nitriding treatment means)
31 Upper electrode 32 Lower electrode 33 High frequency power supply 34 Heating heater 71 Nitriding region (circular shape)
72 Nitrided region (stripe shape)
7a GaN (gallium nitride) crystal layer 7b n-type contact layer 7c active layer 7d p-type block layer 7e p-type contact layer 7f lamination (p-side electrode, light reflecting layer, adhesive layer)
7g metal substrate 7h n-side electrode

Claims (11)

In a crystal growth method including a crystal growth step of growing a compound crystal of the raw material liquid and the raw material gas by bringing the raw material liquid and the raw material gas into contact with each other on the substrate,
A crystal growth method, wherein at least a part of the surface of the substrate is nitrided.   2. The crystal growth method according to claim 1, wherein a region for generating the nucleus of the crystal is nitrided in the surface of the substrate.   3. The crystal growth method according to claim 1, wherein the substrate is nitrided in a circular shape.   3. The crystal growth method according to claim 1, wherein the substrate is nitrided in a stripe shape.   5. The crystal growth method according to claim 1, wherein the source gas contains nitrogen, and the source metal contains a group III element.   6. The crystal growth method according to claim 1, wherein an alkali metal is used as a flux in the crystal growth step.   The crystal growth method according to claim 1, wherein the substrate is a sapphire substrate.   A semiconductor device comprising the crystal produced by the crystal growth method according to claim 1. Nitriding means for nitriding the surface of the substrate;
Crystal growth means for growing a compound crystal of the raw material liquid and the raw material gas by bringing the raw material liquid and the raw material gas into contact with each other on the substrate nitrided by the nitriding means. A crystal growth apparatus.   10. The crystal growth apparatus according to claim 9, wherein the nitriding means performs a nitriding process on the surface of the substrate by an annealing process in an ammonia atmosphere.   11. The crystal growth apparatus according to claim 9, wherein the nitriding means performs nitriding treatment on the surface of the substrate by plasma treatment in a nitrogen atmosphere.

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