JP5223112B2 - Method for producing group III nitride compound semiconductor - Google Patents

Description

The present invention relates to a method for producing a group III nitride compound semiconductor on a group III nitride compound semiconductor substrate. In particular, the present invention relates to a surface treatment of a group III nitride compound semiconductor substrate prior to epitaxial growth. The substrate is a substrate on which a group III nitride compound semiconductor element is formed, or a base substrate for forming a thicker group III nitride compound semiconductor as an ingot.
In the present application, the group III nitride compound semiconductor is a semiconductor represented by Al _x Ga _y In _1-xy N (where x, y, and x + y are each 0 or more and 1 or less), and n-type / p-type. Including those added with any element for conversion. Furthermore, it includes those in which a part of the composition of the group III element and the group V element is substituted with B, Tl; P, As, Sb, Bi.

  In recent years, for example, a group III nitride compound semiconductor substrate has become available as a substrate for forming a group III nitride compound semiconductor light emitting device. In other words, GaN ingots are obtained by various methods, and are sold in a desired thickness. At this time, since the cut surface becomes the main surface of the substrate, mechanical polishing or so-called chemical mechanical polishing is performed.

By the way, there is no simple method for smoothing the surface of a GaN substrate or other group III nitride compound semiconductor substrate with high accuracy. This is because the group III nitride compound semiconductor is very resistant to general wet etching, and the pits are deepened when a strong etching solution such as an alkaline aqueous solution is used.
Therefore, an attempt has been made to combine heat treatment or heat treatment with another treatment. Examples of such a technique include Patent Documents 1 to 3.
JP 2003-327497 A JP-A-2005-136311 JP 2004-273484 A

  In Patent Documents 1 and 2, the process includes heat-treating the GaN substrate surface at a temperature of 1000 ° C. or more for 10 minutes or more in an atmosphere of ammonia and hydrogen. In addition, the method of Patent Document 3 is such that the substrate temperature is lower than the growth temperature before the vapor phase growth of GaN, and the supply of the source gas of the group 3B element is stopped or epitaxial growth is performed. In this method, the surface of the GaN substrate is cleaned by lowering the supply amount in the process.

  Substrate The inventors of the present application conducted the processing disclosed in Patent Documents 1 and 2, and then observed the surface of the GaN substrate with an atomic force microscope (AFM) or a metallographic microscope. As a result, solidified Ga droplets were found. It was done. This indicates that GaN was decomposed during heating of the GaN substrate surface and nitrogen molecules were detached, and then the remaining Ga was aggregated. If such a Ga droplet solidified GaN substrate is used as an epitaxial growth substrate, an epitaxially grown film with good crystallinity cannot be obtained over the entire wafer. That is, in the surface treatment method for a GaN substrate described in Patent Documents 1 and 2, the epitaxial growth film formed thereafter does not have good crystallinity, and it is also good even if a semiconductor element layer is formed thereon. Characteristics are not obtained. Further, the method of Patent Document 3 has a problem that decomposition of the GaN substrate and generation of Ga particles occur in order to increase the temperature when shifting from the cleaning process to the epitaxial growth process.

  Accordingly, an object of the present invention is to provide a surface treatment that removes polishing flaws on the substrate surface and does not leave a solidified Ga droplet on the surface so that the epitaxially grown film formed on the substrate has good crystallinity. Is to realize. Furthermore, in addition to these effects, another object is to realize a surface treatment of the substrate that can obtain a smooth flat surface with a good step state.

According to a first aspect of the present invention, a polished semiconductor substrate surface made of a group III nitride compound semiconductor is heated in an atmosphere containing an organic compound of a group III element, ammonia, and hydrogen to cause unevenness on the surface of the semiconductor substrate. And a growth step for epitaxially growing a group III nitride compound semiconductor after the surface treatment step. The conditions in the surface treatment step are the formation and decomposition of the group III nitride. This is a method for producing a group III nitride compound semiconductor characterized by being in the vicinity of an equilibrium state .

The group III nitride compound semiconductor substrate polished here includes mechanical polishing using a grindstone, fine powder, and the like, and chemical mechanical polishing using a liquid material in which fine powder is dispersed. The group III nitride compound semiconductor substrate in which the polishing scratches remain has a step, and an approximate height difference means a root mean square (RMS) of 10 nm or less .

In the second invention, the temperature in the surface treatment step and the supply amount of the organic compound of the group III element are set in the vicinity of an equilibrium state between the growth and decomposition of the group III nitride, and the group III nitride compound semiconductor is manufactured. The condition is that the growth is not performed. The present invention is to perform the surface treatment in an equilibrium state in which growth and decomposition are balanced. In addition, it is desirable that the surface treatment be performed in a state in which it tends to decompose somewhat rather than an equilibrium state. By maintaining the conditions for not growing the group III nitride compound semiconductor for a predetermined time, the polishing scratches can be eliminated without generating Ga droplets. Thereby, the RMS of the level difference of the unevenness | corrugation of the board | substrate surface can be made small.

The third invention is characterized in that the temperature during heating is 1000 ° C. or higher and 1250 ° C. or lower. The temperature during the heating is more preferably 1100 ° C. or higher and 1200 ° C. or lower.
Furthermore, the temperature at the time of heating is 1100 ° C. or higher, and the temperature is preferably equal to or higher than the optimum growth temperature of the group III nitride compound semiconductor to be carried out following the surface treatment step. The higher the temperature, the larger the mass transport and the higher the effect of eliminating polishing scratches.

In the fourth invention, the group III nitride compound semiconductor substrate is a GaN substrate, and the growth temperature of gallium nitride after the surface treatment step is in the range of 0 ° C. or more and 400 ° C. or less than the temperature in the surface treatment step. It is characterized by lowering by. In such a condition, the surface treatment step can be set in the vicinity of the equilibrium state of the growth and decomposition of the group III nitride.
According to a fifth invention, in the fourth invention, the organic compound of the group III element is trimethyl gallium, and the amount of trimethyl gallium supplied when growing the gallium nitride after the surface treatment step is trimethyl gallium in the surface treatment step. It is characterized by making it increase rather than the supply amount. In such a condition, the surface treatment step can be set in the vicinity of the equilibrium state of the growth and decomposition of the group III nitride.

The sixth invention is characterized in that the supply amount of trimethylgallium is 15 μmol / min or more and 2 mmol / min or less. The supply amount is more preferably 150 μmol / min or more and 200 μmol / min or less.
In the seventh invention, the group III nitride compound semiconductor substrate is a GaN substrate, the organic compound of the group III element is trimethylgallium, and the supply amount of trimethylgallium is set in a range in which gallium nitride does not substantially grow. It is characterized by being.
Furthermore, it is desirable that the supply amount of trimethylgallium is in the vicinity of an equilibrium state where the growth and decomposition of gallium nitride are balanced and the decomposition of gallium nitride occurs.

In the eighth aspect of the invention, the ratio of the supply amount of ammonia and trimethylgallium is such that the ratio of the number of nitrogen atoms supplied as ammonia to the number of gallium atoms supplied as trimethylgallium (so-called V / III ratio) is 1200 or more and 4000 or less. It is characterized by being. The ratio of supply amount (V / III ratio) is more preferably 1800 or more and 3600 or less, and further preferably 2000 or more and 3000 or less. Under such conditions, a substrate surface having a good step state can be obtained.

The ninth invention is characterized in that the temperature of the surface treatment step is equal to or higher than the temperature at which the group III nitride compound semiconductor is epitaxially grown thereafter. That is, by treating the surface of the semiconductor at a temperature higher than the temperature at which a group III nitride compound semiconductor with good crystal quality can be epitaxially grown, the polishing flaws are more effectively eliminated, uneven steps, Ga droplets The crystallinity of the group III nitride compound semiconductor that is epitaxially grown thereafter can be improved. Note that the temperature of the surface treatment step is desirably higher in the range of 0 ° C. or higher and 400 ° C. or lower than the temperature at which the subsequent group III nitride compound semiconductor is epitaxially grown. In such a condition, the surface treatment step can be set in the vicinity of the equilibrium state of the growth and decomposition of the group III nitride.

According to a tenth aspect of the present invention, in the ninth aspect of the invention, the supply amount of the organic compound of the group III element in the surface treatment step is the group III element organic compound when the group III nitride compound semiconductor is epitaxially grown thereafter. It is characterized by being smaller than the supply amount. In such a condition, the surface treatment step can be set in the vicinity of the equilibrium state of the growth and decomposition of the group III nitride.

In the eleventh aspect of the invention, the temperature of the surface treatment process minimizes the area density of polishing scratches on the surface of the semiconductor substrate, and the supply amount of the organic compound of the group III element determines the area density of Ga droplets on the surface of the semiconductor substrate. It is characterized by being controlled to a minimum value. Here, the area density of polishing scratches means the product of the number of scratches per unit area and the area occupied by one scratch. The area of one flaw means the sum of the surface areas of the bottom and side surfaces of the flaw recess. The area density of Ga droplets means the product of the number of Ga droplets per unit area and the area occupied by one droplet. As the temperature of the surface treatment process increases, the area density of the processing scratches tends to decrease, but the area density of the Ga droplets tends to increase. Further, the area density of Ga droplets tends to decrease as the supply amount of the organic compound of group III element increases. Therefore, by optimally controlling the temperature of the surface treatment and the supply amount of the organic compound of the group III element, the area density of processing flaws and the area density of Ga droplets can be minimized.

In the twelfth aspect of the present invention, the temperature of the surface treatment step, the supply amount of the organic compound of the group III element, and the supply amount of ammonia are the area density of the polishing scratches on the semiconductor substrate surface, and the Ga liquid on the semiconductor substrate surface. It is characterized in that the drop area density is minimized and the step state is controlled to the best value. The step state means the degree of order of the step that is the starting point of crystal growth in the atomic order of the crystal structure. When the step state of the substrate is good, the quality of crystals grown on the substrate can be improved. As the amount of ammonia supplied is increased, the step average can be improved by reducing the mean square of the height difference of the surface irregularities. However, when Annimore increases beyond a certain value, a convex portion appears on the surface, the root mean square of the unevenness of the surface unevenness increases, and the step state deteriorates. Therefore, in addition to the surface treatment temperature and the supply amount of the organic compound of the group III element, the ammonia supply amount is optimally controlled, so that the area density of the polishing scratches and the area of the Ga droplet are more effectively controlled. The density can be minimized and the step state can be best.

According to a thirteenth aspect of the present invention, the temperature of the surface treatment step, the supply amount of the organic compound of the group III element, and the supply amount of ammonia are such that the root mean square of the unevenness on the semiconductor surface is 2.2 nm or less. It is characterized by being controlled. Furthermore, desirably, the root mean square of the height difference of the irregularities on the semiconductor surface is 1.3 nm or less. By optimally controlling the temperature of the surface treatment step, the supply amount of the organic compound of the group III element, and the supply amount of ammonia, the root mean square of the unevenness on the semiconductor surface is preferably 2.2 nm or less. Can be controlled to 1.3 nm or less.

  It is preferable that among the irregularities due to polishing on the surface of the group III nitride compound semiconductor substrate, the convex portions are actively decomposed, and group III atoms generated by the decomposition are supplied to the concave portions to become nitrides. However, it was found that when heated in the presence of ammonia alone, group III atoms generated by decomposition aggregate as droplets and do not contribute to filling the recesses by renitriding. When cooling with group III atoms agglomerated as droplets, the part remains on the surface of the semiconductor substrate as metal grains, so when used as an epitaxial growth substrate, epitaxial growth occurs with the metal grains remaining, and the resulting group III nitride This adversely affects the crystallinity of the compound semiconductor film.

  As shown below, the present inventors have found that the group III atom droplets can be eliminated by supplying an organic compound of a group III element together with ammonia during heating. At this time, hydrogen as a carrier gas is considered to contribute to the decomposition of the protrusions on the surface of the group III nitride compound semiconductor substrate.

The action of the present invention has the following two possibilities.
The first possibility is that by supplying an organic compound of a group III element together with ammonia at the time of heating, the partial pressure of the group III atom or the group III element compound in the gas phase increases, and the group III nitridation on the substrate surface The decomposition of the physical compound semiconductor is suppressed. According to this, the group III nitride compound semiconductor moves from the convex portion to the concave portion by the mass transport without being decomposed into nitrogen and group III atoms, and the concave and convex portions are flattened.

The second possibility of the action of the present invention is as follows.
When a group III atom droplet is generated due to rapid decomposition of a group III nitride compound semiconductor, such as a convex portion on the surface of a substrate, and elimination of a nitrogen atom as a nitrogen molecule at a high temperature. Only the reaction between the surface group III atom and ammonia does not sufficiently consume the group III atom droplet. That is, even if a bond of group III atom-nitrogen atom-group III atom or the like occurs, it is considered that the rate of decomposition and elimination of the nitrogen atom (as a nitrogen molecule) wins.

  Here, by mixing the organic compound of the group III element, the nitride precursor having a plurality of group III atoms helps the consumption of the group III atoms from the droplets of the group III atoms. That is, when a nitride precursor having a plurality of group III atoms attacks the surface of a group III atom droplet at a high temperature, the nitride precursor having a higher molecular weight is obtained by further taking in the group III atom from the droplet. It is considered that a GaN crystal is finally formed. At this time, the nitride precursor having a plurality of group III atoms has a large number of group III atoms-nitrogen atoms, and also has a number of group III atoms surrounded by three nitrogen atoms. Even if a part of is decomposed, it becomes only a “low molecular weight” nitride precursor, and it is considered that not all nitrogen atoms are eliminated as nitrogen molecules.

The heating temperature is preferably 1000 ° C. or higher and 1250 ° C. or lower. If it is less than 1000 ° C., the decomposition rate of the convex portion becomes too slow to obtain the effect of the present invention. If it exceeds 1250 ° C., the decomposition rate of the convex portion becomes too fast and the effect of the present invention cannot be obtained. The temperature during the heating is more preferably 1100 ° C. or higher and 1200 ° C. or lower.
In particular, the surface treatment temperature is preferably equal to or higher than the growth temperature of the group III nitride compound semiconductor to be epitaxially grown in a later step. That is, by setting the temperature to be equal to or higher than the optimum growth temperature of the group III nitride compound semiconductor, it becomes easy to maintain the flatness of the substrate surface until the subsequent epitaxial growth step.

  The group III nitride compound semiconductor substrate currently available as a general-purpose product is a GaN substrate, and the present invention can be easily implemented using trimethylgallium which is readily available. When the supply amount of trimethylgallium is less than 15 μmol / min, it is difficult to renitride Ga droplets generated by decomposition. The upper limit of the supply amount is preferably set to 2 mmol / min or less from the point that the convex portion of the GaN substrate should be sufficiently decomposed and the point that no unnecessary thick epi film is formed. The supply amount is more preferably 150 μmol / min or more and 200 μmol / min or less. According to an atomic force microscope (AFM) observation, when the so-called V / III ratio is less than 1200, the steps on the GaN surface are rough, and when 4000 or more, irregularities in a large region of 10 μm square or more are likely to be formed. According to the observation with an atomic force microscope (AFM), the V / III ratio is more preferably 1800 or more and 3600 or less, and further preferably 2000 or more and 3000 or less.

  In addition, if the supply amount of trimethylgallium is too small, Ga droplets are likely to be generated, and if the supply amount of trimethylgallium is too large, the group III nitride semiconductor grows on the substrate, so that the polishing scratches disappear. Before performing the process, a nitride film is formed while leaving a polishing flaw. Therefore, the supply amount of trimethylgallium is in the vicinity of an equilibrium state where the growth and decomposition of the group III nitride semiconductor are balanced at the set surface treatment temperature, and the group III nitride semiconductor is decomposed. A supply amount is desirable.

  The carrier gas is preferably hydrogen. At this time, argon or other rare gas may be mixed. Although it is not preferable to use only nitrogen as a carrier gas, it is expected that the effect of the present invention will not be reduced even if it is mixed at 50% or less.

  In the following examples, the polished GaN substrate surface is heated in the presence of trimethylgallium and ammonia to perform surface treatment. However, the present invention provides a desired group III nitride compound semiconductor substrate surface having an arbitrary composition. And those subjected to surface treatment by heating in the presence of an organic compound of group III element and ammonia.

  In this example, the so-called Ga surface side of the GaN substrate was used. As a result of AFM image analysis of the surface of the Ga surface, the root mean square (RMS) of the height difference of the unevenness at 50 μm □ was 3.0 nm. Moreover, when the unevenness | corrugation of the surface was observed with the metal microscope, many linear recessed parts in which many directions did not align were seen. That is, many polishing scratches remained on the surface of the GaN substrate. This is shown in FIG. The three photographs in FIG. 1 are a 50 μm square AFM image, a 2 μm square AFM image, and a metal micrograph from the left. Although the RMS in the 2 μm square region was 0.58 nm, no step state was observed, and it could not be said that the substrate was suitable for crystal growth.

  First, heat treatment was performed in an atmosphere of hydrogen and ammonia without flowing trimethylgallium (hereinafter abbreviated as TMG). The supply amount of hydrogen was 29 SLM, the supply amount of ammonia was 7 SLM, each of which was held at the following temperature for 7 minutes, and then cooled to room temperature. The RMS of unevenness in 50 μm □ and 2 μm □ by AFM image analysis and the presence or absence of Ga droplets were as follows.

Experiment 1: At a temperature of 1160 ° C., the RMS at 50 μm □ is 45.21 nm, the RMS at 2 μm □ is 0.21 nm, and most of the irregularities are due to Ga droplets.
Experiment 2: At a temperature of 1100 ° C., RMS at 50 μm □ is 9.25 nm, RMS at 2 μm □ is 0.17 nm, and most of the irregularities are due to Ga droplets. The Ga droplets in Experiment 2 were smaller and fewer in number than the Ga droplets in Experiment 1.
Experiment 3: At a temperature of 1050 ° C., RMS at 50 μm □ is 7.43 nm, RMS at 2 μm □ is 0.17 nm, and most of the irregularities are due to Ga droplets. Although the Ga droplets in Experiment 3 were smaller than the Ga droplets in Experiment 2, the number was larger.
Experiment 4: At a temperature of 1000 ° C., RMS at 50 μm □ was 2.45 nm, RMS at 2 μm □ was 0.13 nm, and fine Ga droplets were found.
In Experiments 2 and 3, the RMS at 2 μm □ was 0.17 nm, and an atomic scale step was observed. In particular, in Experiment 3, the step state is good. However, in Experiments 1 and 4, no atomic scale step was observed or the step state was poor.

  When the temperature in Experiment 4 was 1000 ° C., the surface was observed with a metal microscope, and the polishing scratches were not lost. On the other hand, when the surface was observed with a metallographic microscope at a temperature of 1160 ° C. in Experiment 1, many solidified Ga droplets were generated, but polishing scratches were not present. This is shown in FIG. The twelve photos in FIG. 2 are AFM images of 50 μm square on the top four, AFM images of 2 μm square on the middle four, and metal microscope photographs on the bottom four, from Experiment 1 to Experiment 4 from left to right. ing.

  From this experiment, it is understood that as the temperature of the surface treatment process is increased, the processing flaws tend to decrease, but the area density of Ga droplets tends to increase. For this reason, it is desirable that the temperature is lower in the temperature range where the processing scratches disappear. However, in this temperature condition, in the state where TMG is not flowed, it was impossible to eliminate the processing flaws and not to generate Ga droplets.

Next, the untreated GaN substrate was treated for 7 minutes with the following TMG supply amount, with a heating temperature of 1160 ° C., a hydrogen supply amount of 29 SLM, and an ammonia supply amount of 7 SLM.
Experiment 1: When the supply amount of TMG is 0, the RMS at 50 μm □ is 45.21 nm, the RMS at 2 μm □ is 0.21 nm, and most of the irregularities are Ga droplets (described above).
Experiment 5: When the supply amount of TMG was 120 μmol / min, the RMS at 50 μm □ was 6.00 nm, the RMS at 2 μm □ was 0.22 nm, and Ga droplets were found.
Experiment 6: When the supply amount of TMG was 173 μmol / min, the RMS at 50 μm □ was 2.24 nm, the RMS at 2 μm □ was 0.23 nm, and no Ga droplet was found.

  From the above, it was found that the TMG supply rate of 120 μmol / min in Experiment 5 was insufficient for Ga droplets not to remain, and that the Ga droplets were not observed when the TMG supply rate of Experiment 6 was 173 μmol / min or more. As apparent from the above temperature change and TMG supply amount change experiments 1 to 6, by setting the surface treatment temperature appropriately and supplying TMG in an appropriate amount, the polishing flaws can be effectively removed, and Ga It turns out that generation | occurrence | production of a droplet can be suppressed. This is because mass transport does not cause GaN to grow in a state in which the generation of Ga droplets is prevented by heat treatment in an equilibrium state in which growth and decomposition are balanced, and in a state where there is a slight tendency to decomposition. This is because the concave portion of the polishing scratch was filled.

  However, when the TMG supply amount in Experiment 6 is 173 μmol / min, according to the AFM image analysis, the GaN step state on the processed surface of the GaN substrate is a portion where no Ga droplet is generated when the TMG supply amount is 120 μmol / min. Worse than the step state at. This is shown in FIG. In the photograph 6 of FIG. 3, the upper three images are 50 μm square AFM images, and the lower three images are 2 μm square AFM images, which are Experiment 1, Experiment 5, and Experiment 6 from left to right.

  From the above experiments, it is understood that the area density of Ga droplets tends to decrease as the supply amount of the organic compound of the group III element increases, but the step state tends to deteriorate.

Next, the untreated GaN substrate was treated for 7 minutes with the following supply amount of ammonia at a heating temperature of 1160 ° C. and a TMG supply amount of 173 μmol / min. The hydrogen supply amount was set to 36 SLM with ammonia.
Experiment 6: Ammonia supply was 7 SLM, ie, 0. At 31 mol / min, the RMS at 50 μm □ was 2.24 nm, the RMS at 2 μm □ was 0.23 nm, and the step state was poor (described above).
Experiment 7: When the supply amount of ammonia was 10.5 SLM, that is, 0.47 mol / min, the RMS at 50 μm □ was 1.31 nm, the RMS at 2 μm □ was 0.24 nm, and the step state was good.
Experiment 8: When the supply amount of ammonia is 14 SLM, that is, 0.63 mol / min, the RMS at 50 μm □ is 3.47 nm, the RMS at 2 μm □ is 0.21 nm, and the surface has irregularities of about 10 μm □. Been formed.

  From the above, it was found that the step state was poor when the ammonia supply amount was 7 SLM (V / III ratio 1806), and the surface was uneven when the ammonia supply amount was 14 SLM (V / III ratio 3613). On the other hand, when the supply amount of ammonia was 10.5 SLM (V / III ratio 2710), the step state was good and no irregularities were formed on the surface. This is shown in FIG. In the photograph 6 in FIG. 4, the upper three images are 50 μm square AFM images, and the lower three images are 2 μm square AFM images, which are Experiment 6, Experiment 7, and Experiment 8 from left to right.

  From this experiment, as the ammonia supply amount increases, the RMS of the unevenness tends to decrease and the step state tends to improve, but when the value exceeds a certain value, the RMS of the unevenness increases, It is understood that the condition tends to worsen. Therefore, in addition to the temperature of the surface treatment and the supply amount of the organic compound of the group III element, the supply amount of ammonia is optimally controlled, so that the polishing scratches can be eliminated more effectively and the surface density of the Ga droplets can be reduced. It will be appreciated that the step value can be best with a minimum value.

Next, LEDs were formed on the two surface-treated GaN substrates as follows, and photoluminescence and electroluminescence were measured. An LED 110 having the structure shown in FIG. 5 was manufactured. On the treated GaN substrate 100 obtained by the experiment 7, an n-type contact layer 101 made of GaN is grown at a growth temperature of 1160 ° C., a TMG supply amount of 346 μmol / min, and an ammonia supply amount of 7.0 SLM, that is, 0.0. 31 mol / min, the V / III ratio 903, and the supply amount of hydrogen 25.5SLM, the sum of the supply amount of hydrogen and ammonia is grown at a growth condition of 36SLM. Subsequently, TMI was supplied, and the n-type cladding layer 102 made of InGaN was grown at 850 ° C. Next, a light emitting layer 103 made of an InGaN / GaN MQW structure, a p-type cladding layer 104 made of p-type AlGaN, and a p-type contact layer 105 made of p-type GaN were grown in this order. Next, part of the p-type contact layer 105 to the n-type contact layer 101 was removed by etching. A light-transmitting or reflective p-electrode 106 was deposited on the upper surface of the p-type contact layer 105, and an n-electrode 107 was deposited on the exposed upper surface of the n-type contact layer 101 to form an LED 110.
As a comparative example, the LED 11 was formed in exactly the same manner on the GaN substrate 10 obtained in Experiment 1 and having many Ga droplets on the surface.

When the photoluminescence (PL) intensities of these two LEDs 110 and 11 are compared, the PL intensity of the LEDs 110 formed on the treated GaN substrate 100 according to the embodiment of the present invention is the GaN in which Ga droplets according to the comparative example remain. The PL intensity of the LED 11 formed on the substrate 10 was 1.5 times.
Further, when comparing the electroluminescence (EL) intensity of these two LEDs, the EL intensity of the LED 110 formed on the treated GaN substrate 100 according to the example of the present invention is the GaN in which Ga droplets according to the comparative example remain. The EL intensity of the LED 11 formed on the substrate 10 was 1.1 times.

  These results indicate that the surface of the processed GaN substrate 100 was flattened by the surface treatment process of the present invention, and thus, on the GaN substrate 10 in which a large number of Ga droplets existed on the surface, obtained in Experiment 1. This is because the crystallinity of each layer constituting the LED 110 formed on the treated GaN substrate 100 is improved rather than the crystallinity of each layer constituting the formed LED 11.

In this embodiment, the growth temperature of the n-type contact layer made of GaN may be lowered in the range of 0 ° C. to 400 ° C. with respect to the substrate processing temperature of 1160 ° C. The supply amount of the source gas may be increased before the temperature is lowered or after the temperature is lowered.

Further, crystal growth on the GaN substrate may be performed as follows. With the LED having the structure shown in FIG. 6, the surface of the n-type GaN substrate 120 is heat-treated for a predetermined time under the conditions of Experiment 7. Next, after the source gas is switched from TMG to TMI and the supply amount of other gases is maintained, the substrate temperature is lowered from 1160 ° C. to 850 ° C. Thereby, an n-type cladding layer 122 made of InGaN is grown on the n-type GaN substrate 120. Next, a light emitting layer 123 composed of an InGaN / GaN MQW structure, a p-type cladding layer 124 composed of AlGaN, and a p-type contact layer 125 composed of GaN were grown in this order. Next, a translucent or reflective p-electrode 126 was formed on the p-type contact layer 125, and a reflective or translucent n-electrode 127 was formed on the back surface of the n-type GaN substrate 120 to form the LED 200. The growth temperature of the n-type cladding layer 122 made of InGaN is lower than 300 ° C. compared to the surface treatment temperature of 1160 ° C. of the n-type GaN substrate 120. The state is not impaired. In addition, since the surface treatment of the present invention provides an extremely high-quality GaN surface, the n-type InGaN made of n-type InGaN is directly formed on the GaN substrate without forming the n-type contact layer made of GaN. Even if the mold cladding layer is grown, the crystal quality after the light emitting layer is not adversely affected. It has been confirmed that the EL intensity of the LED 200 thus obtained is equal to or greater than the EL intensity of the LED 110.

  In the present invention, as described above, the surface treatment of the substrate is performed under the conditions of the substrate temperature and the supply amount of the organometallic gas containing the group III element so that the growth and decomposition are in an equilibrium state. It is characterized by. During this surface treatment, scratches on the substrate surface are eliminated. Therefore, the conditions for the subsequent growth of the group III nitride semiconductor with respect to the surface treatment conditions are the temperature, the supply amount of the organometallic gas containing the group III element, You can do it. One method that satisfies this condition is to lower the substrate temperature or increase the supply amount of the organometallic gas containing a group III element. Further, in order to eliminate the polishing scratches, it is desirable to perform the treatment at a high temperature. In the subsequent growth of the group III nitride semiconductor, the surface-treated substrate is maintained by maintaining the temperature or decreasing the temperature. It is characterized by maintaining the surface state of the product with high quality. Further, by performing the surface treatment with the V / III ratio set appropriately, the step state of the substrate surface can be made favorable.

  By the surface treatment process of the present invention, a group III nitride compound semiconductor substrate having a very flat surface can be obtained, and a group III nitride compound semiconductor having good crystallinity can be grown on the group III nitride compound semiconductor substrate. The group III nitride compound semiconductor substrate that has undergone the surface treatment step is extremely useful as an epitaxial growth substrate for forming a light emitting element, an FET, and other semiconductor elements.

3 is a photograph of three GaN substrates before surface treatment according to an embodiment of the present invention. FIG. The photograph figure of 3 each of the GaN substrate after the surface treatment of Experiment 1 thru | or 4 shown in the Example of this invention. The photograph figure of 2 sheets each of the GaN board | substrate after the surface treatment of Experiment 1, 5 and 6 shown in the Example of this invention. The photograph figure of two each GaN substrates after the surface treatment of Experiment 6 thru | or 8 shown in the Example of this invention. Sectional drawing which showed the structure of LED concerning the Example of this invention. Sectional drawing which showed the structure of LED concerning the other Example of this invention.

10: GaN substrate processed by Experiment 1 11: LED formed on GaN substrate 10 on which many Ga droplets existed on the surface
100: GaN substrate processed in Experiment 7 110: LED formed on the processed GaN substrate 100

Claims (18)

The polished surface of the semiconductor substrate made of a group III nitride compound semiconductor is heated in an atmosphere containing a group III element organic compound, ammonia, and hydrogen to flatten the irregularities on the surface of the semiconductor substrate. Processing steps;
After the surface treatment step, a growth step of epitaxially growing a group III nitride compound semiconductor ,
Have
The method for producing a group III nitride compound semiconductor characterized in that the conditions in the surface treatment step are in the vicinity of an equilibrium state between the formation and decomposition of a group III nitride. The polished surface of the semiconductor substrate made of a group III nitride compound semiconductor is heated in an atmosphere containing a group III element organic compound, ammonia, and hydrogen to flatten the irregularities on the surface of the semiconductor substrate. Processing steps;
After the surface treatment step, a growth step of epitaxially growing a group III nitride compound semiconductor,
Have
The temperature in the surface treatment step and the supply amount of the organic compound of the group III element are set in the vicinity of an equilibrium state between the growth and decomposition of the group III nitride, and are the conditions under which the group III nitride compound semiconductor is not grown. A method for producing a group III nitride compound semiconductor. 3. The method for producing a group III nitride compound semiconductor according to claim 1, wherein a temperature in the heating is 1000 ° C. or more and 1250 ° C. or less. The group III nitride compound semiconductor substrate is a GaN substrate, and the growth temperature of gallium nitride after the surface treatment step is lowered in a range of 0 ° C. or more and 400 ° C. or less than the temperature in the surface treatment step. The method for producing a group III nitride compound semiconductor according to any one of claims 1 to 3 , characterized in that: The organic compound of the group III element is trimethyl gallium, and the supply amount of trimethyl gallium when the gallium nitride is grown after the surface treatment step is increased more than the supply amount of trimethyl gallium in the surface treatment step. A method for producing a Group III nitride compound semiconductor according to claim 4 . The method for producing a group III nitride compound semiconductor according to claim 5 , wherein the supply amount of the trimethylgallium is 15 μmol / min or more and 2 mmol / min or less. The polished surface of the semiconductor substrate made of a group III nitride compound semiconductor is heated in an atmosphere containing a group III element organic compound, ammonia, and hydrogen to flatten the irregularities on the surface of the semiconductor substrate. Processing steps;
After the surface treatment step, a growth step of epitaxially growing a group III nitride compound semiconductor,
Have
The group III nitride compound semiconductor substrate is a GaN substrate, the organic compound of the group III element is trimethyl gallium, and the supply amount of the trimethyl gallium is set in a range in which gallium nitride does not substantially grow. A method for producing a group III nitride compound semiconductor characterized by the following . The group III nitride compound semiconductor substrate is a GaN substrate, the organic compound of the group III element is trimethyl gallium, and the supply amount of the trimethyl gallium is set in a range in which gallium nitride does not substantially grow. The method for producing a group III nitride compound semiconductor according to any one of claims 1 to 6 , wherein: The ratio of the ammonia and the supply amount of trimethylgallium, the ratio of the number of nitrogen atoms to be supplied as ammonia to the number of gallium atoms supplied as trimethyl gallium, claims 5 to, characterized in that at 1200 to 4,000 9. A method for producing a group III nitride compound semiconductor according to any one of 8 above. The polished surface of the semiconductor substrate made of a group III nitride compound semiconductor is heated in an atmosphere containing a group III element organic compound, ammonia, and hydrogen to flatten the irregularities on the surface of the semiconductor substrate. Processing steps;
After the surface treatment step, a growth step of epitaxially growing a group III nitride compound semiconductor,
Have
Temperature of the surface treatment step, then, II I nitride compound semiconductor process for manufacturing which is characterized in that the temperature than epitaxially growing a Group III nitride compound semiconductor. The group III nitride compound semiconductor according to any one of claims 1 to 9, wherein a temperature of the surface treatment step is equal to or higher than a temperature at which a group III nitride compound semiconductor is epitaxially grown thereafter. Manufacturing method. The supply amount of the group III element organic compound in the surface treatment step is smaller than the supply amount of the group III element organic compound when the group III nitride compound semiconductor is epitaxially grown thereafter. The manufacturing method of the group III nitride compound semiconductor of Claim 10 or Claim 11 . The polished surface of the semiconductor substrate made of a group III nitride compound semiconductor is heated in an atmosphere containing a group III element organic compound, ammonia, and hydrogen to flatten the irregularities on the surface of the semiconductor substrate. Processing steps;
After the surface treatment step, a growth step of epitaxially growing a group III nitride compound semiconductor,
Have
The temperature of the surface treatment step minimizes the area density of polishing scratches on the surface of the semiconductor substrate, and the supply amount of the organic compound of the group III element is a value that minimizes the area density of Ga droplets on the surface of the semiconductor substrate. A method for producing a group II nitride compound semiconductor, characterized by being controlled by: The temperature of the surface treatment step minimizes the area density of polishing scratches on the surface of the semiconductor substrate, and the supply amount of the organic compound of the group III element is a value that minimizes the area density of Ga droplets on the surface of the semiconductor substrate. The method for producing a group III nitride compound semiconductor according to any one of claims 1 to 12 , wherein the method is controlled. The polished surface of the semiconductor substrate made of a group III nitride compound semiconductor is heated in an atmosphere containing a group III element organic compound, ammonia, and hydrogen to flatten the irregularities on the surface of the semiconductor substrate. Processing steps;
After the surface treatment step, a growth step of epitaxially growing a group III nitride compound semiconductor,
Have
The temperature of the surface treatment step, the supply amount of the organic compound of the group III element, and the supply amount of the ammonia are the area density of polishing flaws on the surface of the semiconductor substrate, and the area of Ga droplets on the surface of the semiconductor substrate. A method for producing a group III nitride compound semiconductor, characterized in that the density is controlled to a value that minimizes the step state and is the best. The temperature of the surface treatment step, the supply amount of the organic compound of the group III element, and the supply amount of the ammonia are the area density of polishing flaws on the surface of the semiconductor substrate, and the area of Ga droplets on the surface of the semiconductor substrate. The method for producing a group III nitride compound semiconductor according to any one of claims 1 to 12 , wherein the density is controlled to a value that minimizes the step state and the step state is optimal. The polished surface of the semiconductor substrate made of a group III nitride compound semiconductor is heated in an atmosphere containing a group III element organic compound, ammonia, and hydrogen to flatten the irregularities on the surface of the semiconductor substrate. Processing steps;
After the surface treatment step, a growth step of epitaxially growing a group III nitride compound semiconductor,
Have
The temperature of the surface treatment step, the supply amount of the organic compound of the group III element, and the supply amount of the ammonia are controlled so that the root mean square of the unevenness of the unevenness of the semiconductor surface is 2.2 nm or less. A method for producing a Group III nitride compound semiconductor, characterized in that : The temperature of the surface treatment step, the supply amount of the organic compound of the group III element, and the supply amount of the ammonia are controlled so that the root mean square of the unevenness of the unevenness of the semiconductor surface is 2.2 nm or less. The method for producing a group III nitride compound semiconductor according to any one of claims 1 to 16 , wherein: