JP2015167201A - Method for manufacturing nitride semiconductor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To regrow a nitride semiconductor layer having high crystallinity using a template substrate.SOLUTION: A method for manufacturing a nitride semiconductor element comprises the steps of: (a) preparing a template substrate in which a nitride semiconductor layer is laminated on a crystal substrate; (b) arranging the template substrate in a furnace and raising the temperature in the furnace till it reaches the regrowth temperature of the nitride semiconductor layer; (c) starting supply of a first material gas containing a group V element if the temperature in the furnace reaches a prescribed first temperature lower than the regrowth temperature when the step (b) is in progress; and (d) starting supply of a second material gas containing a group III element if the temperature in the furnace reaches a prescribed second temperature lower than the regrowth temperature and higher than the first temperature when the step (b) is in progress. The method continuously supplies the first and second material gases even after the temperature in the furnace has reached the regrowth temperature.

Description

  The present invention relates to a method for manufacturing a nitride semiconductor device, and more particularly to a method for manufacturing a nitride semiconductor device by re-growing a nitride semiconductor layer on a template substrate in which a nitride semiconductor layer is laminated on a crystal substrate. .

  For example, as a method of growing a nitride semiconductor layer on a crystal substrate such as sapphire (also referred to as “growth substrate”), it is abbreviated as “Metal Organic Chemical Vapor Deposition” (hereinafter referred to as “MOCVD method”). )It has been known. In the MOCVD method, a carrier gas containing group III and group V source gases is supplied to a crystal substrate heated in a furnace (reactor), and the semiconductor crystal is thermally decomposed on the crystal substrate. It is a way to grow.

  In the MOCVD method, an organic metal is used as a gas material. An organic metal refers to a compound having a direct bond between a metal atom and a carbon atom, and is liquid or solid at room temperature but has a property of relatively high saturation vapor pressure. For this reason, by supplying a source gas using a gas such as nitrogen as a carrier gas, a sufficient amount of a growth source for crystal growth can be stably supplied.

  Generally, trimethylgallium (TMG), trimethylindium (TMI), trimethylaluminum (TMA) or the like is used as the group III source gas. Further, ammonia or the like is generally used as the group V source gas.

  By the way, in order to form an LED structure on a substrate, a method in which semiconductor layers are continuously laminated by epitaxial growth by MOCVD on the upper surface of a crystal substrate such as sapphire is generally used. On the other hand, as another method, a substrate (hereinafter referred to as “template substrate”) in which a nitride semiconductor layer made of GaN or the like is laminated on a crystal substrate is prepared, and the nitride semiconductor is formed on the template substrate. A method of regrowing a semiconductor layer including a layer is also performed. If a template substrate is purchased and utilized, part of the process for forming the semiconductor layer can be omitted, leading to a reduction in man-hours.

  For example, Patent Document 1 discloses a method for regrowing a nitride semiconductor layer on a template substrate in which a GaN layer is stacked on sapphire.

JP 2001-44126 A

  FIG. 6 schematically shows a conventional regrowth process profile when an undoped second GaN layer is regrown on a template substrate in which an undoped first GaN layer is formed on a c-plane sapphire substrate as a crystal substrate. It is shown as an example. The horizontal axis indicates the time axis, and the vertical axis indicates the furnace temperature. In FIG. 6, the timing of starting the supply of the source gas and the carrier gas is also shown along the time axis. Hereinafter, a conventional method will be described with reference to FIG.

  The temperature rise is started with the template substrate placed in the furnace. At this time, supply of hydrogen gas and nitrogen gas as carrier gases and ammonia as group V source gas is started from around room temperature. As an example, supply of hydrogen gas with a flow rate of 15 SLM, nitrogen gas with a flow rate of 20 SLM, and ammonia gas with a flow rate of 5 SLM is started. Then, after the furnace temperature (temperature on the substrate if the temperature on the substrate is measurable) reaches 1150 ° C. which is the regrowth temperature of GaN, annealing is performed for about 5 minutes, and then the group III material Supply of TMG as gas is started.

  However, according to the earnest study of the present inventors, after the second GaN layer is regrown on the template substrate by the above method, the n-type semiconductor layer, the active layer, and the p-type semiconductor layer are sequentially stacked. The formed semiconductor light emitting device has significantly higher emission intensity than the semiconductor light emitting device formed by sequentially stacking a GaN layer, an n-type semiconductor layer, an active layer, and a p-type semiconductor layer directly on a crystal substrate such as sapphire. It turns out that it falls.

  The present inventor made two hypotheses as the cause. The first hypothesis is that dislocation defects generated in the active layer are increasing, and the second hypothesis is that some impurities increase in the active layer to form non-luminescent centers.

  However, the upper surface was observed in a state where the active layer was formed on both the semiconductor layer formed directly on the crystal substrate and the semiconductor layer formed after the GaN layer was regrown on the template substrate. However, there was no significant difference in the number of pits. Further, for both of the above, the density of C and O impurities was observed by secondary ion mass spectrometry (SIMS), but there was no significant difference. As a result, the present inventors have found that the semiconductor light-emitting element formed using the template substrate has a lower emission intensity than the semiconductor light-emitting element formed directly on the crystal substrate. I conclude, however, the exact reason is unknown at this time.

  FIG. 7 schematically shows a regrowth process profile disclosed in Patent Document 1. In the process of placing the template substrate having the same structure as described above in the furnace and raising the temperature, the group III source gas and the group V source gas are reached from the stage before the temperature at which the crystal re-grows (re-growth temperature). The contents for starting the supply are disclosed. More specifically, according to the same literature, when the regrowth temperature is 1100 ° C., the temperature on the substrate is lower than 800 ° C. (specifically, it is described as 760 ° C.). There is a disclosure that the supply of the source gas and the group V source gas is started. According to Patent Document 1, it is described that when the supply of the source gas is started after reaching 800 ° C., a conical protrusion is generated on the surface of the regrown crystal, which is not preferable.

  However, according to the diligent research of the present inventors, in the method described in this document, since the supply start temperature of the raw material gas is lower than 800 ° C., when the GaN crystal is regrown at this temperature, it is amorphous. It became clear that the crystallinity deteriorated. When a GaN regrowth layer with deteriorated crystallinity is formed, when a semiconductor light emitting device is formed by sequentially growing an n-type semiconductor layer, an active layer, and a p-type semiconductor layer thereon, the crystal of each layer Since the state deteriorates, the emission intensity is remarkably reduced, and it is assumed that no light is emitted at all depending on the element.

  In the case of manufacturing a semiconductor light emitting device by re-growing a nitride semiconductor layer on a template substrate and then growing the semiconductor layer on the re-grown layer, the present invention provides a semiconductor light emitting device having higher emission intensity than the conventional one The object is to realize an element.

The method for producing a nitride semiconductor device of the present invention includes:
Preparing a template substrate in which a nitride semiconductor layer is laminated on a crystal substrate (a);
Placing the template substrate in a furnace and raising the temperature until reaching the regrowth temperature of the nitride semiconductor layer (b),
During the execution of the step (b), when the temperature in the furnace reaches a predetermined first temperature lower than the regrowth temperature, the step (c) of starting the supply of the first source gas containing the group V element,
When the temperature in the furnace reaches a predetermined second temperature lower than the regrowth temperature and higher than the first temperature during the execution of the step (b), the supply of the second source gas containing a group III element Having a step (d) of starting
The supply of the first source gas and the second source gas is continued after the temperature in the furnace reaches the regrowth temperature.

  According to the above method, when a semiconductor light emitting device is manufactured by forming a semiconductor layer on the upper surface of the regrowth layer after regrowth using the template substrate, higher light emission intensity than before is realized.

  Further, according to the above method, when the furnace temperature reaches the first temperature, the supply of the first source gas containing the group V element is started, and when the furnace temperature reaches the second temperature higher than the first temperature, the group III element is contained. The supply of the second source gas has started. For this reason, the temperature at which both the group III material and the group V material constituting the nitride semiconductor layer are supplied to the template substrate can be higher than that of the method of Patent Document 1. This avoids the possibility of forming an amorphous nitride semiconductor layer and improves crystallinity.

  In the above method, the first source gas containing a group V element is supplied first, and the second source gas containing a group III element is supplied later. It is known that nitrogen, which is a group V element, has a high vapor pressure, and is easily desorbed from the crystal surface at a high temperature as compared with a group III element. When the group V element is desorbed, the group III element remains in the form of a metal drop on the crystal surface. When crystal growth is performed by supplying group III and group V element source gases in this state, the crystal quality is degraded by the drop-like portion. According to this method, since the first source gas containing the group V element is supplied first, deterioration of crystal quality due to the above-described reason is prevented.

In the above method,
And (e) starting the supply of hydrogen gas and inert gas from a temperature lower than the first temperature in the furnace,
Even after the temperature in the furnace reaches the regrowth temperature, the supply of hydrogen gas and inert gas may be continued.

  Patent Document 1 describes that nitrogen gas is used as a carrier gas and hydrogen gas is not used. According to the same literature, when hydrogen gas is used as a carrier gas, since hydrogen has an etching effect on a nitride-based semiconductor at a high temperature, the surface of the nitride crystal constituting the substrate is roughened. It is described that there is a possibility of causing irregularities on the surface of the regrown crystal grown thereon.

  However, when hydrogen gas is not used as the carrier gas, the oxide film formed during the epitaxial growth cannot be removed, and there is a region where the crystal information of the nitride semiconductor layer located under the growth layer cannot be correctly inherited and grown. As a result, it was found that the crystal surface might be disturbed.

  According to the above method, by supplying the hydrogen gas and the inert gas before the first source gas, the oxide film formed on the upper surface of the nitride semiconductor layer in the temperature rising process by the etching function of the hydrogen gas And impurities can be removed, and high crystallinity is ensured. Further, by using not only hydrogen gas but also inert gas as the carrier gas, etching damage to the nitride semiconductor layer due to hydrogen can be suppressed.

  In particular, when nitrogen gas is used as the inert gas, it can play an auxiliary role for correctly supplying the source gas to the substrate surface at a high temperature exceeding 1000 ° C. in the furnace. When the temperature in the furnace exceeds 1000 ° C., intense convection occurs, and a sufficient amount of source gas may not reach the upper surface of the substrate as it is. By including the nitrogen gas in the carrier gas, the raw material gas to escape from the substrate can be suppressed by the nitrogen gas. In particular, this effect can be enhanced by increasing the flow rate of the inert gas as compared with the hydrogen gas in the step (e). As an example, when the nitride semiconductor layer is made of GaN, it is preferable that the flow rate ratio of hydrogen gas to nitrogen gas is 0.3 or less.

  In the above method, the nitride semiconductor layer can be made of GaN. In this case, the second temperature is preferably 800 ° C. or higher and 1050 ° C. or lower, and more preferably 850 ° C. or higher and 1050 ° C. or lower.

  According to the method of the present invention, a semiconductor light emitting device exhibiting high light emission intensity can be realized even if a template substrate in which a nitride semiconductor layer is laminated on a crystal substrate is used. Thereby, it is possible to realize a semiconductor light emitting device exhibiting an equivalent light emission intensity while reducing the number of steps compared to a method of manufacturing a semiconductor light emitting device by directly growing a nitride semiconductor layer on the upper surface of the crystal substrate.

  Note that the present invention is characterized by a process of re-growing a nitride semiconductor layer on a template substrate in which a nitride semiconductor layer is laminated on a crystal substrate. In other words, the technology of the present invention can be applied to the case where an element is manufactured by re-growing a nitride semiconductor layer using a template substrate and forming a semiconductor layer on the nitride semiconductor layer. It is not specific to the method.

It is sectional drawing which shows the structure of a semiconductor light-emitting device typically. FIG. 2 schematically shows a regrowth process profile of the method of the present invention when a nitride semiconductor layer is regrowth on a template substrate. 6 is a graph showing IL characteristics of Example 1 and Comparative Example 1. 6 is a graph showing IL characteristics of Example 1 and Comparative Example 2. It is the table | surface which compared the light emission output when a predetermined amount of electric current is supplied with respect to each element of Examples 1-4 and Comparative Examples 1-4. It is a graph which shows typically the process profile of the conventional method at the time of regrowing a nitride semiconductor layer on a template substrate. It is a graph which shows typically the process profile of the method described in patent documents 1 at the time of regrowing a nitride semiconductor layer on a template substrate.

  A method for manufacturing a nitride semiconductor device of the present invention will be described with reference to the drawings. In the following drawings, the dimensional ratios in the drawings do not necessarily match the actual dimensional ratios.

  FIG. 1 is a cross-sectional view schematically showing an example of the configuration of a semiconductor light emitting device manufactured using the method of the present invention. The semiconductor light emitting element 20 has a template substrate 10, and a semiconductor layer is formed on the template substrate 10. The template substrate 10 is configured by laminating an undoped first GaN layer 2 on a crystal substrate 1 composed of a c-plane sapphire substrate or the like.

  In the semiconductor light emitting device 20, the undoped second GaN layer 3 is formed on the template substrate 10, and the n-type semiconductor layer 4 made of, for example, AlGaN is formed on the second GaN layer 3. An active layer 5 composed of, for example, InGaN / AlGaN periodically is formed on the n-type semiconductor layer 4. A p-type semiconductor layer 6 composed of, for example, AlGaN is formed on the active layer 5. A part of the n-type semiconductor layer 4 is exposed, and an n-side electrode 7 made of, for example, Cr / Ni / Au is formed on a part of the exposed surface. A p-side electrode 8 made of, for example, Ni / Au is formed on the upper surface of the p-type semiconductor layer 6.

  Hereinafter, the method for manufacturing the semiconductor light emitting device 20 will be described as an example with respect to the method for manufacturing the nitride semiconductor device of the present invention. FIG. 2 schematically shows the regrowth process profile of the method of the present invention when the undoped second GaN layer 3 is regrowth on the template substrate 10.

(Step S1)
First, the template substrate 10 is prepared. The template substrate 10 having the first GaN layer 2 formed on the upper surface of the crystal substrate 1 such as c-plane sapphire is distributed in the market and can be procured. The template substrate 10 is appropriately placed in the furnace of the MOCVD apparatus. This step S1 corresponds to the step (a).

(Step S2)
Raise the furnace temperature. An example of the rate of temperature increase is 100 ° C./min. This temperature raising step is performed until reaching a temperature at which the GaN layer re-grows (re-growth temperature). This step S2 corresponds to the step (b). In addition, the following steps S4 and S5 are performed under the temperature raising process according to step S2. Step S3 is performed before the start of the temperature raising process according to Step S2 or under the temperature raising process.

(Step S3)
Supply of hydrogen gas and nitrogen gas as a carrier gas is started. Here, the flow rate of the nitrogen gas is preferably larger than the flow rate of the hydrogen gas. As an example, the flow rate of hydrogen gas can be 0.1 SLM or more and 10 SLM or less, and the flow rate of nitrogen gas can be 1 SLM or more and 100 SLM or less.

  As described above, the start time of the supply of the carrier gas may be such that the furnace temperature is at room temperature, that is, before the start of temperature increase, or during the temperature increase. However, it is preferable to start supplying the carrier gas when the furnace temperature is 300 ° C. or lower. By supplying a carrier gas containing hydrogen from a point in time at a low temperature, it becomes possible to effectively remove excess moisture, oxide film, and organic matter adhering to the surface of the template substrate 10 without damaging the crystal. .

  Step S3 corresponds to step (e).

(Step S4)
When the furnace temperature reaches a predetermined first temperature T1, supply of the first source gas containing the group V element is started. As an example of the first source gas, an organic compound containing ammonia or hydrazine-based nitrogen can be used.

  As 1st temperature T1, it can be about 300 degreeC, for example. In addition, when ammonia is used as the first source gas, the flow rate of ammonia is preferably 1 SLM or more and 100 SLM or less. By supplying ammonia gas at a predetermined flow rate, roughening of the GaN crystal surface can be prevented. This is because a part of the first GaN layer 2 is etched by the supplied ammonia gas, and a part of Ga is precipitated, and this is combined with N contained in ammonia, and a portion roughened by the re-formed GaN. This is to show the effect of filling. The first temperature T1 is preferably 300 ° C. or more and 500 ° C. or less.

  Step S4 corresponds to step (c).

(Step S5)
When the furnace temperature reaches the second temperature T2 higher than the first temperature T1, the supply of the second source gas containing the group III element is started. As an example of the second source gas, TMG, triethylgallium (TEG), trimethylaluminum (TMA), trimethylindium (TMI), or the like can be used.

  The second temperature T2 is preferably 850 ° C. or higher and 1050 ° C. or lower. The temperature of 1050 ° C. is lower than 1150 ° C., which is the regrowth temperature T3 of the GaN layer. The flow rate of TMG can be set to 5 to 300 μmol / min when the substrate to be processed is, for example, an MOCVD apparatus having a size of 2 inches.

  Step S5 corresponds to step (d).

(Subsequent steps)
When the furnace temperature reaches the GaN re-growth temperature T3, the temperature raising process according to step S2 is stopped. Note that the carrier gas, the first source gas, and the second source gas are continuously supplied even after the furnace temperature reaches T3. The supply time is appropriately changed according to the film thickness of the second GaN layer 3. For example, after the furnace temperature reaches T3, the supply of each gas is continued for 40 minutes, whereby the second GaN layer 3 having a thickness of about 2 μm is formed. An example of the regrowth temperature T3 is 1150 ° C.

  When the second GaN layer 3 having a desired film thickness is formed on the template substrate 10, the semiconductor layer and the electrode are sequentially formed by the same method as the method for manufacturing a normal semiconductor light emitting device. Hereinafter, an example thereof will be described.

An n-type semiconductor layer 4 is formed on the second GaN layer 3. A more specific formation method is as follows, for example. Subsequently, the furnace pressure of the MOCVD apparatus is set to 30 kPa in a state where the furnace temperature is 1150 ° C. Then, while supplying nitrogen gas having a flow rate of 20 SLM and hydrogen gas having a flow rate of 15 SLM as a carrier gas in the processing furnace, tetraethylsilane for doping TMG, trimethylaluminum (TMA), ammonia and n-type impurities as source gases. Is fed into the processing furnace for 30 minutes. Thereby, for example, an n-type semiconductor layer 4 having a composition of Al _0.06 Ga _0.94 N and a thickness of 1.7 μm is formed on the second GaN layer 3.

  In addition to Si, Ge, S, Se, Sn, Te, etc. can be used as the n-type impurity contained in the n-type semiconductor layer 4.

  Next, the active layer 5 is formed on the n-type semiconductor layer 4. A more specific formation method is as follows, for example. The furnace temperature is lowered to about 830 ° C., and the furnace pressure of the MOCVD apparatus is set to about 100 kPa. Then, while flowing nitrogen gas having a flow rate of 15 SLM and hydrogen gas having a flow rate of 1 SLM as a carrier gas, TMG having a flow rate of 10 μmol / min, trimethylindium (TMI) having a flow rate of 12 μmol / min, and a flow rate are supplied into the processing furnace. Performs a step of supplying ammonia of 300,000 μmol / min into the processing furnace for 48 seconds. Thereafter, TMG having a flow rate of 10 μmol / min, TMA having a flow rate of 1.6 μmol / min, tetraethylsilane having a flow rate of 0.002 μmol / min, and ammonia having a flow rate of 300,000 μmol / min are supplied into the processing furnace for 120 seconds. Hereinafter, by repeating these two steps, the active layer 5 in which the light emitting layer made of InGaN having a thickness of 2 nm and the barrier layer made of n-type AlGaN having a thickness of 7 nm are formed in a multi-period form the n-type semiconductor layer 4. It is formed in the upper layer.

Next, the p-type semiconductor layer 6 is formed on the active layer 5. A more specific formation method is as follows, for example. The furnace pressure of the MOCVD apparatus is maintained at 100 kPa, and the furnace temperature is raised to 1025 ° C. while flowing 15 SLM nitrogen gas and 25 SLM hydrogen gas as carrier gases into the processing furnace. Thereafter, as source gases, TMG with a flow rate of 35 μmol / min, TMA with a flow rate of 20 μmol / min, ammonia with a flow rate of 250,000 μmol / min, and biscyclopentadiene with a flow rate of 0.1 μmol / min for doping p-type impurities. Enilmagnesium (Cp ₂ Mg) is fed into the processing furnace for 60 seconds. As a result, a hole supply layer having a composition of Al _0.3 Ga _0.7 N having a thickness of 20 nm is formed on the active layer 5. After that, by changing the flow rate of TMG to 9 μmol / min and supplying the source gas for 360 seconds, a hole supply layer having a composition of Al _0.13 Ga _0.87 N having a thickness of 120 nm is formed. A p-type semiconductor layer 6 is formed by these hole supply layers.

  As the p-type impurity contained in the p-type semiconductor layer 6, Be, Zn, C, or the like can be used in addition to Mg.

After the formation of the p-type semiconductor layer 6, the supply of TMA is stopped, the flow rate of Cp ₂ Mg is changed to 0.2 μmol / min, and the source gas is supplied for 20 seconds. Thereby, a high Mg concentration p-type GaN layer made of p-type GaN having a thickness of 5 nm is formed. Thereafter, after annealing, etching is performed to expose a part of the upper surface of the n-type semiconductor layer 4. Then, an n-side electrode 7 made of, for example, Cu / Ni / Au is formed on the exposed upper surface of the n-type semiconductor layer 4, and a p-side electrode 8 made of, for example, Ni / Au is formed on the upper surface of the high-concentration p-type GaN layer. .

  Hereinafter, the performance of the semiconductor light emitting device manufactured using the method of the present invention will be verified in comparison with the semiconductor light emitting device manufactured by the conventional method.

[Verification 1]
The light emission intensity of the semiconductor light emitting device manufactured by the conventional method using the c-plane sapphire substrate 1 and the semiconductor light emitting device 20 manufactured by the method of the present invention using the template substrate 10 were compared.

Example 1
The semiconductor light emitting device 20 manufactured by the method of the present invention described above was taken as Example 1. In addition, temperature T2 which starts supply of 2nd source gas (here TMG) was 1050 degreeC.
(Comparative Example 1)
A semiconductor light emitting device in which an n-type semiconductor layer 4, an active layer 5, and a p-type semiconductor layer 6 were sequentially formed on a c-plane sapphire substrate 1 by directly forming an undoped GaN layer 2 by a conventional MOCVD method was used as Comparative Example 1. .

  FIG. 3 is a graph showing the IL characteristics (current light intensity characteristics) of Example 1 and Comparative Example 1. As can be seen from FIG. 3, the semiconductor light emitting device 20 of Example 1 can achieve the light emission intensity equivalent to that of the conventional semiconductor light emitting device in which the LED is formed on the c-plane sapphire substrate 1.

[Verification 2]
The light emission intensity of the semiconductor light emitting device manufactured by the conventional method using the template substrate 10 and the semiconductor light emitting device 20 manufactured by the method of the present invention using the template substrate 10 were compared.

(Comparative Example 2)
Semiconductor light emission in which an n-type semiconductor layer 4, an active layer 5, and a p-type semiconductor layer 6 are sequentially formed after the second GaN layer 3 is grown on the template substrate 10 under the conventional process profile shown in FIG. The device was referred to as Comparative Example 2.

  FIG. 4 is a graph showing IL characteristics (current light intensity characteristics) of Example 1 and Comparative Example 2. FIG. 4 shows that the device of Comparative Example 2 has significantly lower emission intensity than the device 1 of the example. When a light emitting device is manufactured using the template substrate 10, only a device having a very low light emission intensity can be realized by the conventional manufacturing method. However, according to the method of the present invention, as shown in FIGS. In addition, an element exhibiting high emission intensity can be realized.

[Verification 3]
The light emission intensity of the light emitting device 20 manufactured by the method of the present invention using the template substrate 10 was compared while changing the temperature T2 at which the supply of the second source gas was started.

(Example 2)
Example 2 corresponds to the semiconductor light emitting device 20 manufactured by the same method as Example 1 except that the temperature T2 at which the supply of the second source gas is started is 950 ° C.
(Example 3)
Example 3 corresponds to the semiconductor light emitting element 20 manufactured by the same method as Example 1 except that the temperature T2 at which the supply of the second source gas is started is 850 ° C.
Example 4
Example 4 corresponds to a semiconductor light emitting device manufactured by the same method as Example 1 except that the temperature T2 at which the supply of the second source gas is started is 800 ° C.

(Comparative Example 3)
Comparative Example 3 corresponds to a semiconductor light emitting device manufactured by a method common to Example 1 except that the temperature T2 at which the supply of the second source gas is started is 1150 ° C. which is the regrowth temperature of GaN. .
(Comparative Example 4)
In Comparative Example 4, after the second GaN layer 3 was grown on the template substrate 10 under the process profile described in Patent Document 1 shown in FIG. 7, the n-type semiconductor layer 4, the active layer 5, p This corresponds to a semiconductor light emitting element in which the type semiconductor layer 6 is formed. As shown in FIG. 7, the supply start temperature of ammonia as the first source gas and TMG as the second source gas was set to 760 ° C., and only nitrogen gas was used as a carrier gas without containing hydrogen gas.

  In each of the elements of Examples 1 to 4 and Comparative Examples 1 to 4, after the furnace temperature reached the regrowth temperature T3, each source gas and carrier gas was supplied for 40 minutes, and then sequentially. An n-type semiconductor layer 4, an active layer 5, and a p-type semiconductor layer 6 were formed and manufactured.

  FIG. 5 is a table comparing the light emission outputs when a current of 20 mA is supplied to each of the elements of Examples 1 to 4 and Comparative Examples 1 to 4. According to FIG. 5, each of the elements of Examples 1 to 3 can achieve substantially the same emission intensity as the element of Comparative Example 1 manufactured by the conventional method using the c-plane sapphire substrate 1. Although the element of Example 4 has lower emission intensity than the element of Comparative Example 1, a higher light output is realized than the elements of Comparative Examples 2 to 4. On the other hand, each element of Comparative Examples 2 to 4 manufactured using a template substrate 10 by a method different from the method of the present invention has lower emission intensity than each element of Examples 1 to 4, and in particular, It can be seen that the light emission intensity is remarkably low as compared with the elements of Examples 1 to 3.

  In the element of Comparative Example 3 in which the supply start temperature T2 of the second source gas is 1150 ° C., which is the GaN re-growth temperature, the furnace temperature becomes extremely high before the second source gas is supplied. It is considered that the crystallinity is lowered because the upper surface of the first GaN layer 2 is thermally decomposed and Ga is precipitated on the surface. As a result, the second GaN layer 3 grows on the upper surface of the first GaN layer 2 having low crystallinity, so that the crystallinity of the second GaN layer 3 also decreases, and the crystallinity of the active layer 5 formed thereafter also increases. It is considered that the emission intensity was reduced.

  Moreover, also in the element of the comparative example 4 which started supply of both the 1st source gas and the 2nd source gas when the furnace temperature reached 760 degreeC, the emitted light intensity is lower than each element of Examples 1-4. . One reason for this is that since the supply of the second source gas is started at a temperature as low as 760 ° C., the GaN layer grown in the initial stage of regrowth becomes amorphous and crystallinity is lowered. Is considered.

  Furthermore, in the element of Comparative Example 4, the film thickness of the second GaN layer 3 was about 1/5 as compared with the elements of Examples 1 to 4. This is considered to be due to the fact that the comparative example 4 is manufactured using only nitrogen gas without using hydrogen gas as the carrier gas. Nitrogen gas has a larger mass than hydrogen gas and ammonia gas. For this reason, nitrogen gas is excessively blown onto the surface of the substrate, which inhibits the formation of the second GaN layer 3. For this reason, it is considered that the second GaN layer 3 having a sufficient thickness was not formed in the element of Comparative Example 4.

  Since the second GaN layer 3 functions as a base layer for the n-type semiconductor layer 4 formed thereafter, a film thickness of a certain level or more is required to improve the film quality of the nitride semiconductor layer formed thereafter. It becomes. The second GaN layer 3 provided in the element of Comparative Example 4 is insufficient in film thickness, and the fact that the film quality of the semiconductor layer formed thereafter is also deteriorated is considered to be the cause of the lower emission intensity.

  The element of Example 4 in which the supply start temperature T2 of the second source gas was set to 800 ° C. was the same as Example 1 in which the supply start temperature T2 was set to 1050 ° C., Example 2 in which the supply start temperature T 2 was set to 950 ° C. The light output is lower than each of the three elements. This is presumably because the emission intensity decreased because the temperature at the initial stage of regrowth of the GaN layer was lower than that of each of the devices of Examples 1 to 3. More specifically, the GaN layer grown at the initial stage of the regrowth becomes amorphous and the crystallinity is lowered, and the active layer 5 takes over the defects generated in association therewith. It is considered that a non-emission center is formed in the light emission and the emission intensity is lowered. Therefore, if the supply start temperature T2 is further lower than 800 ° C., it is considered that the emission intensity is further reduced as compared with the element of Example 4. Therefore, the supply start temperature of the second source gas is preferably 800 ° C. or more, and 850 ° C. More preferably.

  As a result of the above verification, the supply of the first source gas containing the group V element is started first in the temperature raising step, and the furnace temperature is 800 ° C. or higher and 1050 ° C. or lower, more preferably 850 ° C. or higher and 1050 ° C. or lower. When the temperature reaches the second temperature T2, the supply of the second source gas containing the group III element is started. After the furnace temperature reaches the regrowth temperature T3 (1150 ° C.), the temperature rise is stopped and the carrier gas and the source gas are supplied. By adopting the method of continuing the supply of gas, it can be seen that even when the template substrate 10 is used, a high emission intensity equivalent to that of a light-emitting element manufactured using a crystal substrate can be realized.

  Further, by using hydrogen gas in addition to nitrogen gas as an inert gas as a carrier gas, an effect of improving the film quality of GaN formed on the upper surface of the template substrate 10 can be obtained. Furthermore, in this case, by making the flow rate of nitrogen gas larger than that of hydrogen gas, the source gas can be suppressed to the substrate side even at a high temperature exceeding 1000 ° C., and a sufficient amount of source gas can be reduced. It can be supplied to the upper surface of the template substrate 10.

  In the above-described embodiment, the furnace temperature T2 at which the supply of the second source gas is started is set to 800 ° C. or more and 1050 ° C. or less. This is the nitride semiconductor layer GaN layer (on the crystal substrate 1 ( The temperature is suitable when the nitride semiconductor layer formed on the upper layer of the first GaN layer 2) is a GaN layer (second GaN layer 3). In particular, the temperature T2 may be appropriately selected according to the material of the nitride semiconductor layer grown on the upper surface of the template substrate 10.

[Another embodiment]
Hereinafter, another embodiment will be described.

  <1> In the above-described embodiment, the template substrate 10 in which the first GaN layer 2 is stacked on the upper surface of the crystal substrate 1 made of c-plane sapphire is used. However, as the crystal substrate 1, materials other than c-plane sapphire, such as SiC, can be used.

  <2> In the above-described embodiment, the case where the second GaN layer 3 is formed on the upper surface of the template substrate 10 has been described, but the same applies to the case where a nitride semiconductor layer other than the GaN layer (for example, an AlGaN layer) is formed. This method can be used. In the case of AlGaN, the regrowth temperature T3 is higher than that of GaN.

  <3> The profile of the method of the present invention shown in FIG. 3 is merely schematically shown. In FIG. 3, the furnace temperature is depicted as if it rose linearly, but this is an example, and the way of temperature rise is selected as appropriate. That is, it is sufficient that the furnace temperature T rises continuously or intermittently from the room temperature to the regrowth temperature T3 during the temperature raising process according to step S2, and the pattern of the temporal change of the furnace temperature T is as follows: It doesn't matter.

  <4> In the above-described embodiment, a nitride semiconductor layer (on the second GaN layer 3) is formed on the template substrate 10 in which a nitride semiconductor layer (corresponding to the first GaN layer 2) is laminated on the upper surface of the crystal substrate 1. The method of manufacturing a semiconductor light emitting device by further forming a semiconductor layer after regrowth was described. However, the present invention is characterized by a process of re-growing a nitride semiconductor layer on the template substrate 10. That is, the method of the present invention can be applied to the case where an element is manufactured by re-growing a nitride semiconductor layer using the template substrate 10 and forming a semiconductor layer on the nitride semiconductor layer. It is not specialized in the manufacturing method.

1: Crystal substrate 2: First GaN layer 3: Second GaN layer 4: n-type semiconductor layer 5: active layer 6: p-type semiconductor layer 7: n-side electrode 8: p-side electrode 10: template substrate 20: semiconductor light emitting element

Claims (6)

Preparing a template substrate in which a nitride semiconductor layer is laminated on a crystal substrate (a);
Placing the template substrate in a furnace and raising the temperature until reaching the regrowth temperature of the nitride semiconductor layer (b),
During the execution of the step (b), when the temperature in the furnace reaches a predetermined first temperature lower than the regrowth temperature, the step (c) of starting the supply of the first source gas containing the group V element,
When the temperature in the furnace reaches a predetermined second temperature lower than the regrowth temperature and higher than the first temperature during the execution of the step (b), the supply of the second source gas containing a group III element Having a step (d) of starting
The method of manufacturing a nitride semiconductor device, wherein the supply of the first source gas and the second source gas is continued after the temperature in the furnace reaches the regrowth temperature. And (e) starting the supply of hydrogen gas and inert gas from a temperature lower than the first temperature in the furnace,
2. The method for manufacturing a nitride semiconductor device according to claim 1, wherein the supply of the hydrogen gas and the inert gas is continued after the temperature in the furnace reaches the regrowth temperature.   The method for manufacturing a nitride semiconductor device according to claim 2, wherein the inert gas is nitrogen gas.   The method for manufacturing a nitride semiconductor device according to claim 3, wherein in the step (e), the flow rate of the inert gas is larger than that of hydrogen gas.   The method for manufacturing a nitride semiconductor device according to claim 1, wherein the nitride semiconductor layer is made of GaN.   The method for manufacturing a nitride semiconductor device according to claim 5, wherein the second temperature is 850 ° C. or higher and 1050 ° C. or lower.

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