JP2006156454A - Method of crystal growing and method of manufacturing gallium nitride compound thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To grasp exactly a generation state of a warpage when a gallium nitride compound semiconductor is crystal grown on a sapphire substrate and to cope with this. <P>SOLUTION: When a crystal layer made of a gallium nitride compound semiconductor is crystal grown on a sapphire substrate, the sapphire substrate is laid on a supporting fixture which performs mirror polishing of the front surface, and the warpage is grasped by observing a Newton ring. In the case of the crystal growth of the gallium nitride compound semiconductor on the sapphire substrate, the thickness of the sapphire substrate is increased to the thickness of the crystal layer which performs the crystal growth. More particularly, when the thickness of the sapphire substrate is d, the diameter of the sapphire substrate is r (numerical value when expressing with inches), and the thickness of the crystal layer is t, the thickness of the sapphire substrate is set so that d≥50×r×t is satisfied. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a crystal growth method of a gallium nitride compound semiconductor and a method of manufacturing a gallium nitride compound thin film used in a light emitting diode (LED) or the like, and in particular, a gallium nitride compound semiconductor is formed on a sapphire substrate. The present invention relates to an improvement of a crystal growth method for growing a crystal layer.

  Gallium nitride compound semiconductors are widely used for light emitting diodes (LEDs), laser diodes (LDs), and the like, and particularly LEDs are expected to be used explosively in the field of displays and lighting. Collecting.

  By the way, a gallium nitride compound semiconductor is generally grown on a substrate made of a material such as SiC, Si, or sapphire, for example, but there is no lattice-matched substrate, and further, a gallium nitride compound semiconductor and Since the coefficient of thermal expansion differs greatly from that of the substrate, there is a problem that warpage or the like occurs and temperature distribution occurs in the substrate.

  For example, as a crystal growth method for a gallium nitride compound semiconductor, a metal organic chemical vapor deposition method (MOCVD), a molecular beam epitaxial growth method (MBE), or the like is generally used. A substrate is placed on a support (so-called susceptor) made of graphite or the like, and the substrate is heated by heat conduction from the susceptor. At this time, the susceptor itself is controlled to a very uniform temperature so that the temperature distribution becomes about 1 ° C. by a temperature control method using a divided heater, a thermocouple, a radiation thermometer, etc. There is a possibility that warpage occurs due to the stress in between, and a part of the substrate is lifted from the susceptor, and the substrate surface temperature is not uniform. Further, for example, in general crystal growth of a light emitting device, it is necessary to sequentially grow a first cladding layer, an active layer, and a second cladding layer. These layers have different growth temperatures. The stress due to the difference in expansion coefficient tends to become remarkable. The warpage of the substrate greatly varies depending on the temperature, and the temperature change as described above is a major cause of the warpage and may cause a large temperature distribution on the substrate surface.

  If a temperature distribution is generated on the substrate surface due to the above factors, uniform crystal growth may be hindered, which may cause a serious problem in characteristics. For example, in a light-emitting element (such as an LED or LD), the temperature distribution during growth of the active layer is a distribution of emission wavelength and emission efficiency, so the yield is greatly reduced. For this reason, it is difficult to manufacture a high-quality device with a high yield, particularly in a substrate having a large area.

Therefore, as a countermeasure against such a problem, it has been studied to reduce the thickness of the crystal layer (see, for example, Patent Document 1). In the invention described in Patent Document 1, the generation of cracks in the crystal layer and the warpage of the sapphire substrate are eliminated by setting the thickness of the gallium nitride compound semiconductor layer to 2.5 μm or less.
JP 2003-179263 A

  However, in a light emitting diode or the like, in order to improve the light extraction efficiency, it is necessary to increase the thickness of the crystal layer made of a gallium nitride compound semiconductor. I can't respond. Further, in the laser diode, it is necessary to reduce the defect density by using selective growth. In this case as well, the film thickness of the crystal layer made of the gallium nitride compound semiconductor is increased, which is also described in Patent Document 1. Technology cannot handle it. A thick crystal layer has a large warp and causes a distribution in the growth temperature on the substrate surface, particularly affecting the wavelength distribution and the like. However, the technique described in Patent Document 1 is a drastic countermeasure. I don't get it.

  The present invention has been proposed in view of such a conventional situation. That is, according to the present invention, first, when a gallium nitride compound semiconductor is crystal-grown on a sapphire substrate, it is possible to accurately grasp the state of occurrence of warpage, and to cope with it appropriately. The object is to provide a possible crystal growth method. Second, the present invention provides a crystal growth method and gallium nitride that can reduce warpage even when the film thickness of the crystal layer is large and can produce a device having uniform characteristics with a high yield. An object of the present invention is to provide a method for producing a system compound thin film.

  In order to achieve the above object, the crystal growth method of the present invention places a sapphire substrate on a support whose surface is mirror-polished when a crystal layer made of a gallium nitride compound semiconductor is grown on the sapphire substrate. The warp is grasped by observing the Newton ring.

  The sapphire substrate during crystal growth is warped due to various factors such as stress due to the combination of substrate and crystal material, stress due to differences in thermal expansion coefficient due to temperature, etc., and differences in strain due to substrate thickness and crystal layer thickness. The state changes. Therefore, in the present invention, the state of warping of the sapphire substrate is monitored by Newton ring observation during crystal growth. Thereby, speeding up of various feedbacks is realized. For example, if temperature control of the support is performed according to the state of warp grasped by observation of Newton rings, the temperature distribution in the sapphire substrate is eliminated, and crystal growth of a crystal layer with uniform characteristics is realized.

Further, as a result of repeated studies by the present inventors, in the case of crystal growth of a gallium nitride compound semiconductor on a sapphire substrate, the thickness of the sapphire substrate is increased relative to the thickness of the crystal layer to be crystal-grown. For example, it has been found that the wavelength distribution in the crystal layer is reduced. This is defined in the invention according to claim 9, and when the crystal layer made of the gallium nitride compound semiconductor is grown on the sapphire substrate, the thickness of the sapphire substrate is d and the diameter of the sapphire substrate is r ( (Value in inches), where t is the thickness of the crystal layer,
d ≧ 50 × r × t
The thickness of the sapphire substrate is selected so that

  If the thickness of the sapphire substrate is increased, the occurrence of warpage can be suppressed even when the crystal layer is thick, the temperature distribution in the substrate surface is suppressed, and the characteristic distribution such as the wavelength distribution is eliminated. In a semiconductor, using a large substrate is effective in reducing the cost. However, in a large substrate, the influence of warpage is increased accordingly. Even in such a case, if the thickness of the sapphire substrate is selected so as to satisfy the above formula, a high yield can be realized.

  Furthermore, the present invention provides a manufacturing method capable of manufacturing a gallium nitride-based compound thin film with a high yield based on the above knowledge. This is the invention according to claim 10, and in the method for producing a gallium nitride compound thin film comprising a gallium nitride compound semiconductor made of a gallium nitride compound semiconductor on a sapphire substrate, the surface is placed on a support whose surface is mirror-polished. The thin film made of the gallium nitride compound semiconductor is grown on the double-side polished sapphire substrate by changing the thickness of the sapphire substrate, and the thickness of the sapphire substrate is selected so that the Newton ring appears on almost the entire surface of the thin film. And a thin film forming step of growing a thin film made of the gallium nitride compound semiconductor on a sapphire substrate having a thickness greater than or equal to the thickness selected in the substrate selecting step.

  In the above manufacturing method, “Newton ring appears almost on the entire surface of the thin film” means, for example, that the Newton ring is not observed only in the vicinity of the central portion or only in the outer peripheral portion of the thin film. The pattern is not localized, and the state is observed such that Newton rings spread over the entire surface of the thin film. In this case, the pattern observed as a Newton ring is not necessarily a perfect concentric circle.

  According to the present invention, when a gallium nitride compound semiconductor is crystal-grown on a sapphire substrate, it is possible to accurately grasp the state of occurrence of warping, and it is possible to appropriately cope with temperature control and the like accordingly. It is. As a result, it is possible to realize crystal growth of a crystal layer with uniform characteristics.

  Further, according to the present invention, warpage can be reduced even when the crystal layer is thick, and for example, even when a large substrate is used, a crystal layer having uniform characteristics can be formed with a high yield. It is possible to manufacture a device having uniform characteristics. The reduction of the warp is suitable for applying the laser ablation technique, and is very effective for effectively using the sapphire substrate by peeling off.

  Hereinafter, a crystal growth method to which the present invention is applied will be described in detail with reference to the drawings.

  First, an example of a growth sequence of a light emitting device using a gallium nitride compound semiconductor is shown in FIG. This growth sequence is an example of a growth sequence in a light emitting diode (LED) having a peak wavelength of 525 nm.

  As shown in FIG. 1, in the crystal growth of the gallium nitride compound semiconductor constituting the light emitting diode, first, the temperature is raised and thermal cleaning is performed. This thermal cleaning is an operation for cleaning the surface of the sapphire substrate.

  Next, the base layer L1 made of GaN is formed on the sapphire substrate at a relatively low temperature, and the first cladding layer L2 made of GaN: Si is crystal-grown thereon. GaN: Si constituting the first cladding layer L2 is n-type GaN, and therefore the first cladding layer L2 is an n-cladding layer. Note that the crystal growth temperature of the first cladding layer L2 is higher than the crystal growth temperature of the previous underlayer L1.

  After crystal growth of the first cladding layer l2, an active layer (InGaN / GaN multiple quantum well) L3 and a second cladding layer (GaN: Mg) L4 are crystal-grown thereon. The crystal growth temperature of the active layer L3 is lower than the crystal growth temperature of the first cladding layer L2, and the crystal growth temperature of the second cladding layer L4 is higher than the crystal growth temperature of the active layer L3.

  The growth sequence described above is performed in a state where the sapphire substrate is placed on a susceptor as a support, but in the present invention, the surface of the susceptor is mirror-polished and the Newton ring is observed to warp the sapphire substrate. By grasping the state and feeding back to various crystal growth condition settings, uniform crystal growth is realized.

  FIG. 2 shows the state of Newton's ring before crystal growth (point A in FIG. 1). As shown in FIG. 2A, when a sapphire substrate 2 having a diameter of 2 inches and a thickness of 430 μm is placed on a susceptor 1 made of SiC-coated graphite, the Newton ring is as shown in FIG. there were. Although the pattern is different due to slight warpage and adhesion difference, a Newton ring was seen on the entire surface of the sapphire substrate 2. This indicates that the sapphire substrate 2 is in close contact with the susceptor 1 with a very small gap on the entire surface. In order to see the state of the Newton ring, the surface of the susceptor 1 was polished to a mirror surface in advance, and the sapphire substrate 2 was also polished to a mirror surface.

  FIG. 3 shows the state of the Newton ring after the formation of the first cladding layer L2 (point B in FIG. 1). As shown in FIG. 3A, when the gallium nitride compound semiconductor film 3 was grown on the sapphire substrate 2, the Newton ring was as shown in FIG. The crystal-grown gallium nitride compound semiconductor film (first cladding layer L2) was a Si-doped GaN layer, and was grown with a thickness of 5 μm.

  As apparent from FIG. 3B, when the first cladding layer L2 is crystal-grown, a dense Newton ring is generated almost in the vicinity of the center, and no Newton ring is seen in the periphery of the sapphire substrate 2. This indicates that the sapphire substrate 2 is greatly warped, and the sapphire substrate 2 is in contact with the susceptor 1 only at the center.

  FIG. 4 shows the state of the Newton ring after the formation of the active layer L3 (point C in FIG. 1). As shown in FIG. 4A, when the active layer L3 is grown on the sapphire substrate 2 as the gallium nitride compound semiconductor film 3 in addition to the first cladding layer L2, the Newton ring is shown in FIG. 4B. It was as shown. The crystallized active layer L3 is an active layer having an InGaN / GaN multiple quantum well structure.

  Although the warpage is reduced as compared with the state shown in FIG. 3B, it can be seen that the sapphire substrate 2 is in contact with the susceptor 1 only at the center as shown in FIG. 4B.

  FIG. 5 shows the state of the Newton ring after the formation of the second cladding layer L4 (point D in FIG. 1). As shown in FIG. 5A, when a second cladding layer L4 is further grown as a gallium nitride compound semiconductor film 3 on the sapphire substrate 2, the Newton ring is as shown in FIG. 5B. there were. The second clad layer L4 that has been crystal-grown is an Mg-doped GaN layer. The Newton ring in this case is substantially the same as FIG. 3B, as shown in FIG.

  Further, FIG. 6 shows a state of Newton ring when the temperature is lowered to room temperature after crystal growth (point E in FIG. 1). When the temperature is lowered to room temperature, a dense Newton ring is generated only in the peripheral portion of the sapphire substrate 2, and no Newton ring is seen in the central portion of the sapphire substrate 2. This indicates that the warpage is reversed from that during the crystal growth, and only the peripheral portion of the sapphire substrate 2 is in contact with the susceptor 1.

  In the case of the above growth sequence, the wavelength distribution of the crystal-grown gallium nitride compound semiconductor film (gallium nitride light emitting device) on the entire surface of the sapphire substrate 2 was about 10 nm with a standard deviation. If the state of warping at each stage of the growth sequence is grasped by observing the Newton ring, the temperature of the sapphire substrate 2 can be controlled by controlling the temperature of the susceptor 1 according to crystal growth conditions, for example, the state of warping. Distribution is eliminated and crystal growth with uniform characteristics can be realized. By observing the Newton ring as described above, quick feedback is possible.

  By the way, in the sapphire substrate 2 during crystal growth, there are various factors such as stress due to the combination of the substrate and crystal material, stress due to the difference in thermal expansion coefficient due to temperature, etc., difference in strain due to the thickness of the substrate and the thickness of the crystal layer, etc. The state of the warp changes depending on. As a result of various studies by the present inventors, if the thickness of the sapphire substrate 2 is increased with respect to the thickness of the crystal layer (gallium nitride compound semiconductor film 3), the wavelength distribution in the surface of the sapphire substrate 2 is obtained. It was found that the distribution of characteristics such as could be greatly reduced.

  FIG. 7 shows the state of Newton rings during active layer growth when the thickness of the sapphire substrate 2 is 900 μm. It can be seen that by increasing the thickness of the sapphire substrate 2, Newton rings are seen on the entire surface, although not concentric, and warpage is reduced as compared with the above condition (the thickness of the sapphire substrate 2 is 430 μm). The wavelength distribution at this time was about 5 nm with a standard deviation.

  In the case of the above growth sequence, it was found that the characteristic distribution in the plane of the sapphire substrate 2 can be reduced by setting the thickness of the sapphire substrate 2 to 500 μm or more. When other film thicknesses of the gallium nitride-based compound semiconductor film were also examined, the effect was obtained by setting the thickness of the sapphire substrate 2 to 100 times or more, preferably 120 times or more the thickness of the gallium nitride-based compound semiconductor film. Admitted.

  The effect of increasing the thickness of the sapphire substrate 2 is remarkable when the thickness of the gallium nitride compound semiconductor film, which is a crystal layer, is large, for example, 2.5 μm or more. In particular, when the thickness of the crystal layer is 5 μm or more, the yield is very low unless the thickness of the sapphire substrate 2 is set to 100 times or more the thickness of the crystal layer as described above.

  In general, in a semiconductor manufacturing process, it is effective to use a large substrate to reduce process costs. However, the influence of warpage becomes large in a large substrate. In order to avoid the influence of warpage even in a large substrate, the thickness of the sapphire substrate 2 is d, the diameter of the sapphire substrate 2 is r (numerical value expressed in inches), the crystal layer It is considered that a high yield can be realized by setting d ≧ 50 × r × t, preferably d ≧ 60 × r × t, where t is the thickness of the (gallium nitride compound semiconductor film).

  Explaining the reason why the above equation is derived, first, the amount of warpage of the sapphire substrate 2 is proportional to the thickness t of the crystal layer (gallium nitride compound semiconductor film 3) both elastically and experimentally. On the other hand, since the amount of warpage is determined by the stress ratio between the crystal layer and the sapphire substrate 2, it can be considered that the thickness is approximately inversely proportional to the thickness d of the sapphire substrate 2 from similar elastic theoretical predictions. Further, it is considered to be approximately proportional to the diameter r of the sapphire substrate 2. Therefore, the warpage of the entire wafer (sapphire substrate + crystal layer) in the sapphire substrate on which the crystal layer is grown can be expressed as C × r × t / d using a certain proportionality constant C.

Here, if the upper limit of the amount of warpage that provides a good in-plane distribution during crystal growth is B,
B ≧ C × r × t / d
d ≧ C2 × r × t (where C2 = C / B)
The following inequality holds. In the observation of the Newton's ring, if the diameter of the sapphire substrate 2 is 2 inches and the thickness of the crystal layer (gallium nitride compound semiconductor film 3) is 5 μm, it is at least necessary to realize a good in-plane distribution. Since the thickness was 500 μm or more, C2 = 50 (/ inch) can be obtained by substituting these values. Therefore, when a crystal layer made of a gallium nitride compound semiconductor is grown on a sapphire substrate, the thickness of the sapphire substrate is d, the diameter of the sapphire substrate is r (numerical value expressed in inches), and the thickness of the crystal layer. Where t is
d ≧ 50 × r × t
The thickness of the sapphire substrate should be selected so that

  In a gallium nitride-based compound semiconductor, the composition and film thickness of a mixed crystal change depending on the temperature distribution due to warping. The most sensitive is a mixed crystal containing In. The emission wavelength of the light-emitting element varies depending on the composition. In particular, the uniformity of the emission wavelength is important for LEDs used in displays and the like. Further, even in an optical disk laser or the like, it is required to control the emission wavelength with high accuracy.

  On the other hand, in applications where a gallium nitride-based compound semiconductor is used for a photodetection element, the detection wavelength varies depending on the mixed crystal composition, and therefore, control of the composition is important for a highly accurate detection element. Even in an electronic device, the characteristics greatly depend on the composition of the mixed crystal. Therefore, ascertaining the warp by observing the Newton ring as described above and reducing the warp by increasing the thickness of the sapphire substrate 2 are light emitting elements such as a light emitting diode (LED) and a semiconductor laser (LD), and a light detecting element. It is effective in manufacturing electronic devices and the like.

  Increasing the thickness of the sapphire substrate as described above causes an increase in the price of the substrate. Further, in the method of thinning and dicing a sapphire substrate by a technique such as polishing for element isolation, the time required for thinning the substrate becomes longer by the thickness of the substrate, and the cost increases. In order to eliminate such inconvenience, it is effective to use a method (so-called ablation) in which an electromagnetic wave such as an excimer laser is irradiated from the sapphire substrate side without peeling the sapphire substrate and peeled off at the interface with the crystal layer. It is. In this method, the peeled sapphire substrate can be reused only by polishing and cleaning the surface.

  In the method of peeling the crystal layer by the laser ablation, it is important to accurately control the light density and the spot diameter of the laser irradiation portion. If the light density is too low, the film cannot be peeled off. If it is too high, the crystal layer may be damaged and cracks may occur. Further, if the spot diameter is small, the back surface of the element cannot be peeled cleanly, and if it is too large, the adjacent element may be peeled off.

  When this laser ablation peeling technique is used for a wafer with a large warp, there is a problem that the focal point shifts depending on the location, and the peeling yield decreases. In addition, when element transfer to another substrate is performed at the same time as peeling, the parallelism between the wafer and the counter substrate is important, but it is also important here to reduce the warpage of the wafer.

  In the present invention, since the warpage is suppressed to be small by the above-described method, such a shift in focus is reduced, and the yield of crystal layer peeling by laser irradiation is improved. At the same time, when the transfer to the counter substrate is performed, the parallelism is good and the transfer can be performed with high accuracy.

  Hereinafter, a method for reusing a sapphire substrate in a light emitting diode manufacturing example will be described.

  In order to fabricate the light emitting diode, as shown in FIG. 8A, the first cladding layer 12, the active layer 13, and the second cladding layer 14 are crystal-grown on the sapphire substrate 11. The first cladding layer 12 is formed, for example, by crystal growth of Si-doped GaN, and is an n-type GaN layer. The active layer 13 is a layer having an InGaN / GaN multiple quantum well structure. The second cladding layer 14 is formed by crystal growth of Mg-doped GaN, and is a p-type GaN layer.

  The crystal growth is performed while placing the sapphire substrate 11 on a susceptor (not shown) and controlling the temperature. At this time, the warp is grasped by observing the Newton ring, and a quick feedback is made to the temperature control or the like, and a thick substrate is used as the sapphire substrate 11. That is, the first clad layer 12, the active layer 13, and the second clad layer 14 are grown on the sapphire substrate 11 that is mounted on a mirror-polished support and the thickness of the sapphire substrate 11 is changed. Let Then, the Newton ring after crystal growth is observed for each thickness of the sapphire substrate 11, and the thickness of the sapphire substrate 11 is selected so that the Newton ring appears on substantially the entire surface of the thin film. Thereafter, a sapphire substrate 11 having a thickness greater than the thickness selected here is used, and a thin film (first cladding layer 12, active layer 13, second cladding layer 14) made of the gallium nitride compound semiconductor is formed thereon. Grow)

  After crystal growth, the p-type GaN layer (second cladding layer 14) is thermally activated, and as shown in FIG. 8B, a gallium nitride compound semiconductor film (first cladding layer 12, active layer 13, second layer). The cladding layer 14) is etched corresponding to the individual light emitting diodes using photolithography. Further, an n electrode 15 is formed in contact with the first cladding layer 12, and a p electrode 16 is formed in contact with the second cladding layer 14. Note that the n-electrode 15 is formed, for example, by forming a film of Ti / Al or the like and patterning it with a photolithography technique. The p-electrode 16 is formed by depositing Ag or the like and patterning it with a photolithography technique.

  Next, as shown in FIG. 8C, a solder connection metal 17 is formed on the n electrode 15, and a solder connection metal 18 is also formed on the p electrode 16. The solder connecting metals 17 and 18 are formed with the same height.

  Next, as shown in FIG. 8D, the sapphire substrate 11 on which the crystal layer and the electrode are formed is turned upside down and flip-chip bonded onto the submount 19. The submount 19 is made of, for example, Si, and mount electrodes 20 and 21 are provided corresponding to the solder connecting metals 17 and 18.

  After bonding to the submount 19, as shown in FIG. 8E, an energy beam is irradiated from the back side of the sapphire substrate 11, so-called ablation (in the case of using laser light as the energy beam, laser ablation). And the sapphire substrate 11 is peeled off.

  As an energy beam used for ablation, a laser beam such as an excimer laser or a YAG laser can be used. For example, in the case of a gallium nitride-based light-emitting diode, the crystal layer of the gallium nitride-based compound semiconductor is decomposed into metallic Ga and nitrogen at the interface with the sapphire substrate 11 and is easily separated from the sapphire substrate 11.

  Note that after the sapphire substrate 11 is peeled off by the laser ablation, metallic Ga generated during ablation adheres to the surface of the crystal layer. Therefore, after the laser ablation, it is preferable to remove metal Ga deposited on the surface by a technique such as wet etching. For example, if wet etching is performed using a mixed acid solution of hydrochloric acid and nitric acid, the deposited metal Ga can be easily removed.

  The peeled sapphire substrate 11 is reused for crystal growth after polishing and washing. That is, it is used again as a substrate in the process shown in FIG. On the other hand, the submount 19 is separated into light emitting diodes by separating the submount 19 for each element.

  According to the above manufacturing process, the sapphire substrate 11 can be reused, and an increase in cost can be suppressed. In addition, since it is not necessary to polish a thick sapphire substrate at the time of element isolation, the processing time can be reduced.

It is a figure which shows an example of the growth sequence of a gallium nitride system light emitting element. (A) is typical sectional drawing which shows the state of the curvature in A point of FIG. 1, (b) is a typical top view which shows the mode of the Newton ring at that time. (A) is typical sectional drawing which shows the state of the curvature in B point of FIG. 1, (b) is a typical top view which shows the mode of the Newton ring at that time. (A) is typical sectional drawing which shows the state of the curvature in C point of FIG. 1, (b) is a typical top view which shows the mode of the Newton ring at that time. (A) is typical sectional drawing which shows the state of the curvature in D point of FIG. 1, (b) is a typical top view which shows the mode of the Newton ring at that time. (A) is typical sectional drawing which shows the state of the curvature in E point of FIG. 1, (b) is a typical top view which shows the mode of the Newton ring at that time. (A) is typical sectional drawing which shows the state of the curvature at the time of thickening a sapphire substrate, (b) is a typical top view which shows the mode of the Newton ring at that time. The example of manufacture of a light emitting diode is shown, (a) is typical sectional drawing which shows a crystal growth process, (b) is typical sectional drawing which shows an electrode formation process, (c) is metal formation for solder connection Schematic sectional view showing a process, (d) is a schematic sectional view showing a bonding process to a submount, (e) is a schematic sectional view showing a sapphire substrate peeling process, and (f) is an element isolation process. It is a typical sectional view showing.

Explanation of symbols

1 susceptor, 2,11 sapphire substrate, 3 gallium nitride compound semiconductor film, 12 first cladding layer, 13 active layer, 14 second cladding layer, 15 n electrode, 16 p electrode, 17, 18 metal for solder connection, 19 Submount, 20, 21 Mount electrode

Claims (11)

When growing a crystal layer made of a gallium nitride compound semiconductor on a sapphire substrate,
A crystal growth method, comprising: mounting a sapphire substrate that has been mirror-polished on both sides on a support that has been mirror-polished and observing a Newton ring to grasp warpage.   2. The crystal growth method according to claim 1, wherein the thickness of the sapphire substrate is 100 times or more the thickness of the crystal layer.   The crystal growth method according to claim 2, wherein the thickness of the crystal layer is 2.5 μm or more.   2. The crystal growth method according to claim 1, wherein the crystal layer includes a crystal layer made of a gallium nitride compound semiconductor containing indium.   2. The crystal growth method according to claim 1, wherein the first cladding layer, the active layer, and the second cladding layer are sequentially grown as the crystal layer.   6. The crystal growth method according to claim 5, wherein the active layer is made of a gallium nitride compound semiconductor containing indium.   2. The crystal growth method according to claim 1, wherein after the crystal layer is grown, the sapphire substrate is peeled off and reused.   The crystal growth method according to claim 7, wherein the sapphire substrate is peeled off by laser ablation. When growing a crystal layer made of a gallium nitride compound semiconductor on a sapphire substrate,
When the thickness of the sapphire substrate is d, the diameter of the sapphire substrate is r (numerical value when expressed in inches), and the thickness of the crystal layer is t,
d ≧ 50 × r × t
A crystal growth method, wherein the thickness of the sapphire substrate is selected so that In the method for producing a gallium nitride compound thin film, a gallium nitride compound thin film comprising a gallium nitride compound semiconductor is formed on a sapphire substrate.
A thin film made of the gallium nitride compound semiconductor is grown on a sapphire substrate polished on both sides and placed on a support whose surface is mirror-polished, and the Newton ring is formed on almost the entire surface of the thin film. A substrate selection step of selecting the thickness of the sapphire substrate to appear;
A thin film forming step of growing a thin film made of the gallium nitride compound semiconductor on a sapphire substrate having a thickness greater than or equal to the thickness selected in the substrate selecting step;
A method for producing a gallium nitride-based compound thin film characterized by comprising:   The method for producing a gallium nitride compound thin film according to claim 10, further comprising a step of peeling the nitride gallium compound thin film grown in the thin film forming step from the sapphire substrate by a laser ablation method.