JP7066178B2 - Manufacturing equipment and method for group III nitride semiconductor devices and manufacturing method for semiconductor wafers - Google Patents

Description

The technical field of the present specification relates to a manufacturing apparatus and a manufacturing method of a group III nitride semiconductor element using plasma, and a manufacturing method of a semiconductor wafer.

In the group III nitride semiconductor represented by GaN, the band gap changes from 0.6 eV to 6 eV by changing the composition. Therefore, group III nitride semiconductors are applied to light emitting devices, laser diodes, light receiving elements, etc., which correspond to a wide range of wavelengths from near infrared to deep ultraviolet.

In addition, group III nitride semiconductors have high breaking field strength and high melting point. Therefore, group III nitride semiconductors are expected as materials for high-power, high-frequency, high-temperature semiconductor devices to replace GaAs-based semiconductors. Along with this, HEMT elements and the like have been researched and developed.

As a method for epitaxially growing a group III nitride semiconductor, for example, there is a metalorganic chemical vapor deposition method (MOCVD method). The MOCVD method uses a large amount of ammonia gas. Therefore, it is necessary to equip the MOCVD furnace with an abatement device that excludes ammonia. Also, the running cost of ammonia is high. Then, a semiconductor layer is formed by the reaction between the organometallic gas and ammonia. In order to cause this reaction, it is necessary to raise the substrate temperature to a high temperature. When the substrate temperature is high, it is difficult to grow an InGaN layer having a high In concentration with high quality. In addition, warpage is likely to occur due to the difference in thermal expansion difference between the growth substrate and the semiconductor layer.

Further, as a method for epitaxially growing a group III nitride semiconductor, for example, a molecular beam epitaxy method (MBE method) can be mentioned. In the MBE method, group III nitride semiconductors can be grown at a low growth temperature. However, the RF-MBE method using a radical source has a slow growth rate. That is, the RF-MBE method is not suitable for mass production. The MBE method using ammonia gas uses a large amount of ammonia gas, so that the manufacturing cost is high.

Japanese Unexamined Patent Publication No. 2015-99866

Therefore, the present inventors have developed a REMOCVD (Radical Enhanced Metalal Organic Chemical Vapor Deposition) method in which a gas containing a nitrogen atom is converted into plasma and supplied to a growth substrate without converting an organic metal gas containing a group III metal into plasma. (Patent Document 1). In the technique of Patent Document 1, GaN and the like can be grown at a low temperature. Therefore, the stress caused by the difference in the coefficient of thermal expansion can be suppressed.

By the way, in order to grow a group III nitride semiconductor, a group III organometallic gas is often used. Group III organometallic gases have carbon atoms (eg, methyl groups). Therefore, the carbon atom of the group III organometallic gas may be mixed in the crystal of the group III nitride semiconductor. From the viewpoint of the crystallinity of the group III nitride semiconductor, it is preferable that carbon atoms are not mixed in the group III nitride semiconductor. The lower the growth temperature, the more carbon atoms tend to be mixed in the group III nitride semiconductor. That is, although the technique of Patent Document 1 can relieve the strain and stress of the substrate, there is a possibility that a relatively large amount of carbon atoms are mixed in the group III nitride semiconductor.

The technique described in the present specification has been made to solve the problems of the above-mentioned conventional technique. The problem is the manufacturing apparatus and manufacturing method of the group III nitride semiconductor element and the manufacturing method of the semiconductor wafer, which can be grown at a relatively low temperature and can suppress the mixing of carbon atoms into the group III nitride semiconductor. Is to provide.

The apparatus for manufacturing a group III nitride semiconductor element in the first aspect is for epitaxially growing a group III nitride semiconductor. In this manufacturing apparatus, a first electrode, a potential applying portion for applying a potential to the first electrode, a substrate support portion for supporting the growth substrate, and a group III metal as a first gas in the substrate support portion are used. A first gas supply pipe for supplying an organic metal gas containing the gas, a second gas supply pipe for supplying a gas containing nitrogen gas as a second gas to the substrate support portion, and a first electrode and a substrate support portion. It has a metal mesh member arranged at a position in between. The first gas supply pipe has at least one first gas outlet. The first gas outlet is arranged at a position between the substrate support portion and the metal mesh member. The second gas supply pipe allows the second gas to pass through the space between the first electrode and the metal mesh member. The first gas supply pipe and the potential applying unit alternately repeat the first period and the second period. The first gas supply pipe supplies the first gas in the first period and does not supply the first gas in the second period. The potential-imparting unit generates plasma at the first output in the first period, and generates plasma at the second output smaller than the first output in the second period.

This group III nitride semiconductor device manufacturing apparatus epitaxially grows a group III nitride semiconductor on a growth substrate. This manufacturing apparatus supplies the first gas to the growth substrate without passing it through the plasma generation region, and supplies the second gas to the growth substrate after passing it through the plasma generation region. This manufacturing apparatus alternately repeats the first period and the second period. In the first period, the output of the plasma generator is increased while flowing the first gas. In the second period, the output of the plasma generator is reduced without flowing the first gas. As a result, the group III nitride semiconductor is formed in the first period, and the carbon atom is separated from the group III nitride semiconductor in the second period. Therefore, this manufacturing apparatus can manufacture a group III nitride semiconductor having a low carbon atom content.

In the present specification, an apparatus and a method for manufacturing a group III nitride semiconductor element and a method for manufacturing a semiconductor wafer, which can be grown at a relatively low temperature and can suppress the mixing of carbon atoms into a group III nitride semiconductor. Is provided.

It is a figure which shows the structure of the semiconductor wafer of 1st Embodiment. It is a figure which shows the schematic structure of the manufacturing apparatus in 1st Embodiment. 6 is a timing chart showing the relationship between the supply of the first gas and the output of the high frequency potential applied to the shower head electrode by the RF power supply. It is a timing chart explaining the conventional pulse type CVD method. It is a figure which shows the structure of the MIS type semiconductor element of 2nd Embodiment. It is a figure which shows the structure of the light emitting element of 3rd Embodiment. It is a graph which shows the analysis result by the secondary ion mass spectrometry (SIMS) in Example 1 and Comparative Example 1. 6 is an SEM photograph showing a cross section of GaN in Example 1. 6 is an SEM photograph showing the surface of GaN in Example 1. 6 is an SEM photograph showing a cross section of GaN in Comparative Example 1. 6 is an SEM photograph showing the surface of GaN in Comparative Example 1. It is a graph (the 1) which shows the temperature dependence of the phase difference Δ when the surface of a GaN layer is measured by an ellipsometer. It is a graph (No. 2) which shows the temperature dependence of the phase difference Δ when the surface of a GaN layer is measured by an ellipsometer.

Hereinafter, specific embodiments will be described with reference to the drawings, taking as an example a manufacturing apparatus and manufacturing method for a group III nitride semiconductor element and a manufacturing method for a semiconductor wafer.

(First Embodiment)
1. 1. Semiconductor Wafer FIG. 1 is a diagram showing the structure of the semiconductor wafer Wa1 of the present embodiment. The semiconductor wafer Wa1 has a substrate Sa1 and a semiconductor layer F1. The substrate Sa1 is a growth substrate. The semiconductor layer F1 is a single crystal semiconductor layer made of a group III nitride semiconductor. As described above, the semiconductor wafer Wa1 is obtained by epitaxially growing a group III nitride semiconductor on the main surface of the wafer.

2. 2. Group III Nitride Semiconductor Device Manufacturing Equipment FIG. 2 is a schematic configuration diagram of a group III nitride semiconductor device manufacturing device 1000 according to the present embodiment. The manufacturing apparatus 1000 is for epitaxially growing a group III nitride semiconductor. The manufacturing apparatus 1000 is a plasma generator that generates a plasma generation region inside the chamber. The manufacturing apparatus 1000 supplies an organic metal gas containing a group III metal (first gas) to the growth substrate without passing it through the plasma generation region, and supplies a gas containing nitrogen atoms (second gas) to the plasma generation region. After passing through, it is supplied to the growth substrate.

The manufacturing apparatus 1000 includes a furnace body 1001, a shower head electrode 1100, a susceptor 1200, a heater 1210, a first gas supply pipe 1300, a gas introduction chamber 1410, a second gas supply pipe 1420, and a metal. Mesh 1500, RF power supply 1600, matching box 1610, plasma power pulse control unit 1620, first gas supply unit 1810, second gas supply unit 1710, gas containers 1910, 1920, 1930, and constant temperature. It has tanks 1911, 1921, 1931, mass flow controllers 1720, 1820, 1830, 1840, and a pulse valve 1850. Further, the manufacturing apparatus 1000 has an exhaust port (not shown).

The shower head electrode 1100 is a first electrode to which a periodic potential is applied. The shower head electrode 1100 is made of, for example, stainless steel. Of course, other metals may be used. The shower head electrode 1100 is a flat plate-shaped electrode. The shower head electrode 1100 is provided with a plurality of through holes (not shown) penetrating from the front surface to the back surface. The plurality of through holes communicate with the gas introduction chamber 1410 and the second gas supply pipe 1420. Therefore, the second gas supplied from the gas introduction chamber 1410 to the inside of the furnace body 1001 is preferably plasma-ized.

The RF power supply 1600 is a potential applying unit that applies a high frequency potential to the shower head electrode 1100. The plasma power pulse control unit 1620 is a device for applying a high frequency pulse to the shower head electrode 1100.

The susceptor 1200 is a substrate support portion for supporting the substrate Sa1. The material of the susceptor 1200 is, for example, graphite. Further, it may be a conductor other than this. Here, the substrate Sa1 is a growth substrate for growing a group III nitride semiconductor.

The first gas supply pipe 1300 is for supplying the first gas to the susceptor 1200. Actually, the first gas is supplied to the substrate Sa1 supported by the susceptor 1200. Here, the first gas is an organometallic gas containing a Group III metal. It may also contain other carrier gases. The first gas supply pipe 1300 has a ring-shaped ring portion 1310. The ring portion 1310 of the first gas supply pipe 1300 is provided with 12 through holes (not shown) inside the ring portion 1310. As described above, the first gas supply pipe 1300 has at least one through hole. These through holes are outlets from which the first gas is ejected. Therefore, the first gas will be ejected toward the inside of the ring portion 1310. Further, these through holes are arranged at positions between the susceptor 1200 and the metal mesh 1500. Therefore, the first gas supply pipe 1300 is located at a position away from the plasma generation region.

The second gas supply pipe 1420 is for supplying the second gas to the susceptor 1200. In reality, the second gas is supplied to the space between the shower head electrode 1100 and the metal mesh 1500, and the second gas is supplied to the substrate Sa1 supported by the susceptor 1200. Here, the second gas is a gas containing nitrogen gas. The second gas may be a mixed gas of nitrogen gas and hydrogen gas.

The gas introduction chamber 1410 is for temporarily accommodating a mixed gas of nitrogen gas and hydrogen gas, and for supplying this mixed gas to the through hole of the shower head electrode 1100.

The metal mesh 1500 is a metal mesh member for capturing charged particles. The metal mesh 1500 is made of, for example, stainless steel. Of course, other metals may be used. The metal mesh 1500 is arranged at a position between the shower head electrode 1100 and the susceptor 1200. Therefore, the metal mesh 1500 can suppress the charged particles generated in the plasma generation region from heading toward the growth substrate Sa1 supported by the susceptor 1200, as will be described later. Further, the metal mesh 1500 is arranged at a position between the shower head electrode 1100 and the ring portion 1310 of the first gas supply pipe 1300. Therefore, it is possible to prevent the charged particles from colliding with the organic metal molecules including the group III metal ejected from the ring portion 1310 of the first gas supply pipe 1300. Further, in the metal mesh 1500, a large number of meshes are overlapped with each other by shifting them little by little. That is, the linear portion of the second mesh is arranged at the position of the opening of the first mesh. Therefore, the light traveling linearly cannot pass through the metal mesh 1500. That is, the metal mesh 1500 does not allow electrons, ions, or light to pass through, but allows neutral radicals to pass through.

The furnace body 1001 houses at least a shower head electrode 1100, a susceptor 1200, a ring portion 1310 of the first gas supply pipe 1300, and a metal mesh 1500. The furnace body 1001 is made of, for example, stainless steel. The furnace body 1001 may be a conductor other than the above.

The furnace body 1001, the metal mesh 1500, and the first gas supply pipe 1300 are conductive members, and all of them are grounded. Therefore, when a potential is applied to the shower head electrode 1100, a voltage is applied between the shower head electrode 1100, the furnace body 1001, and the metal mesh 1500. Then, it is considered that an electric discharge is generated between at least one or more of the furnace main body 1001 and the metal mesh 1500 and the shower head electrode 1100. Immediately below the shower head electrode 1100, a high-frequency and high-intensity electric field is formed. Therefore, the position directly below the shower head electrode 1100 is the plasma generation region.

Here, the second gas is turned into plasma in this plasma generation region. Then, a plasma product is generated in the plasma generation region. The plasma product in this case is, for example, a nitrogen radical, a hydrogen radical, a hydrogen nitride-based compound, an electron, other ions, or the like. Here, the hydrogen nitride-based compound includes NH, NH ₂ , NH ₃ , their excited states, and others.

Further, the shower head electrode 1100 and the susceptor 1200 are sufficiently separated from each other. The distance between the shower head electrode 1100 and the susceptor 1200 is 40 mm or more and 200 mm or less. More preferably, it is 40 mm or more and 150 mm or less. If the distance between the shower head electrode 1100 and the susceptor 1200 is short, the plasma generation region may extend to the location of the susceptor 1200. If the distance between the shower head electrode 1100 and the susceptor 1200 is 40 mm or more, there is almost no possibility that the plasma generation region extends to the susceptor 1200. Therefore, it is possible to prevent the charged particles from reaching the substrate Sa1. Further, if the distance between the shower head electrode 1100 and the susceptor 1200 is large, it becomes difficult for nitrogen radicals, hydrogen nitride-based compounds, and the like to reach the substrate Sa1 held by the susceptor 1200. It should be noted that these distances also depend on the size of the plasma generation region and other plasma conditions.

The shower head electrode 1100 is arranged at a position far from the through hole of the ring portion 1310 of the first gas supply pipe 1300 when viewed from the susceptor 1200. The distance between the shower head electrode 1100 and the through hole of the ring portion 1310 of the first gas supply pipe 1300 is 30 mm or more and 190 mm or less. More preferably, it is 30 mm or more and 140 mm or less. This is to prevent charged particles from being mixed into the first gas and to make it easier for nitrogen radicals, hydrogen nitride-based compounds, and the like to reach the substrate Sa1. Therefore, the semiconductor layer is laminated on the substrate Sa1 by the second gas that has been plasmatized and the first gas that has not been plasmatized. It should be noted that these distances also depend on the size of the plasma generation region and other plasma conditions.

The heater 1210 is for heating the substrate Sa1 supported by the susceptor 1200 via the susceptor 1200.

Mass flow controllers 1720, 1820, 1830, 1840 are for controlling the flow rate of each gas. The pulse valve 1850 is for supplying an organometallic gas containing a group III metal in synchronization with a pulse having a high frequency potential. The constant temperature baths 1911, 1921, 1931 are filled with antifreeze liquids 1912, 1922, 1932. Further, the gas containers 1910, 1920, and 1930 are containers for accommodating organometallic gas containing Group III metal. The gas containers 1910, 1920, and 1930 contain trimethylgallium, trimethylindium, and trimethylaluminum, respectively. Of course, it may be an organometallic gas containing other group III metals such as triethyl gallium.

3. 3. Manufacturing conditions of the manufacturing equipment Table 1 shows the manufacturing conditions of the manufacturing equipment 1000. The numerical range shown in Table 1 is just a guide, and does not necessarily have to be this numerical range. The RF power is in the range of 100 W or more and 1000 W or less. The frequency of the periodic potential applied to the shower head electrode 1100 by the RF power supply 1600 is in the range of 30 MHz or more and 300 MHz or less. The substrate temperature is in the range of 0 ° C. or higher and 900 ° C. or lower. Preferably, it is 400 ° C. or higher and 900 ° C. or lower. The internal pressure of the manufacturing apparatus 1000 is in the range of 1 Pa or more and 10000 Pa or less.

[Table 1]
RF power 100W or more 1000W or less Frequency 30MHz or more 300MHz or less Board temperature 0 ° C or more 900 ° C or less Internal pressure 1Pa or more 10000Pa or less

4. First gas supply and potential imparting unit (RF power supply)
FIG. 3 is a timing chart showing the relationship between the supply of the first gas and the output of the high frequency potential applied to the shower head electrode 1100 by the RF power supply 1600. The horizontal axis of FIG. 3 is time. The vertical axis in the upper figure of FIG. 3 is the flow rate of trimethylgallium (TMG). The vertical axis in the lower figure of FIG. 3 is RF power.

As shown in FIG. 3, the supply of the first gas and the supply of power by the RF power supply 1600 are repeated at regular intervals. As shown in FIG. 3, the manufacturing apparatus 1000 forms a film while alternately repeating the first period T1 and the second period T2.

4-1. First Period As shown in FIG. 3, in the first period T1, the first gas supply pipe 1300 supplies the first gas to the susceptor 1200, and the RF power supply 1600 receives the first output W1. Generate plasma. Therefore, during the first period T1, Group III elements and nitrogen atoms (including radicals and excited states) are supplied to the substrate Sa1 of the susceptor 1200. Therefore, in the first period T1, a group III nitride semiconductor is formed.

4-2. Second Period As shown in FIG. 3, during the second period T2, the first gas supply pipe 1300 does not supply the first gas to the susceptor 1200, and the RF power supply 1600 has a second output. Plasma is generated at W2. Therefore, during the second period T2, nitrogen atoms (including radicals and excited states) are supplied to the substrate Sa1 of the susceptor 1200, but Group III elements are not supplied to the substrate Sa1. Therefore, in the second period T2, the group III nitride semiconductor is not formed.

4-3. Outputs of the first period and the second period The first output W1 in the first period T1 is, for example, 600 W or more and 1000 W or less. The second output W2 in the second period T2 is, for example, 200 W or more and 500 W or less. The ratio (W1 / W2) of the first output W1 to the second output W2 is 1.5 or more and 5 or less. More preferably, it is 1.6 or more and 4 or less. The RF power supply 1600 generates plasma at the first output W1 in the first period T1 and generates plasma at the second output W2 in the second period T2. As described above, the second output W2 is smaller than the first output W1.

4-4. Time of the first period and the second period The first period T1 is, for example, 5 seconds or more and 60 seconds or less. The second period T2 is, for example, 0.5 seconds or more and 5 seconds or less. These numerical ranges are examples and may be numerical values other than the above.

4-5. Effects of the first period and the second period Thus, the manufacturing apparatus 1000 forms a group III nitride semiconductor in the first period T1 and forms a group III nitride semiconductor in the second period T2. Does not film. Since the group III nitride semiconductor is not formed during the second period T2, it is considered that the carbon atom is separated from the surface of the group III nitride semiconductor. Therefore, the number of carbon atoms mixed in the group III nitride semiconductor is reduced.

As described above, the first output W1 is larger than the second output W2. Further, the second output W2 is larger than 0. Therefore, plasma is generated in both the first period T1 and the second period T2. The second plasma density of the plasma of the second period T2 is smaller than the first plasma density of the plasma of the first period T1. In this way, high-power and low-power plasmas are alternately generated.

The plasma in the first period T1 produces particles derived from nitrogen atoms used for film formation. The plasma in the second period T2 produces particles derived from nitrogen atoms as in the first period T1. In the second period T2, the particles derived from the nitrogen atom are not used for film formation, and it is considered to prevent the nitrogen atom from being desorbed from the film-formed semiconductor layer. In this way, in the second period T2, the carbon atom is evaporated from the semiconductor layer and the nitrogen atom is not evaporated. Therefore, in the second period T2, nitrogen radicals that prevent the desorption of nitrogen atoms may reach the surface of the substrate Sa1 or the semiconductor layer F1.

5. Differences from the Conventional Technique FIG. 4 is a timing chart for explaining the conventional pulse type CVD method. As shown in FIG. 4, as shown in FIG. 4, conventionally, the third period T3 and the fourth period T4 are alternately carried out. That is, the generation of high-output plasma and the supply of the raw material gas such as TMG are alternately carried out. As described above, when generating high-power plasma, it is different from the technique of the present embodiment in which the raw material gas is supplied.

Further, in the present embodiment, the group III nitride semiconductor can be grown without setting the substrate temperature to a high temperature. Therefore, it is suitable for growing an InGaN layer having a high In concentration, which is difficult to grow crystals when the substrate temperature is high. Moreover, it is not necessary to flow a large amount of ammonia gas. Therefore, it is not necessary to provide an abatement device for removing ammonia gas. Therefore, the cost of the manufacturing apparatus itself is low. In addition, running costs can be suppressed.

6. Method for Manufacturing a Semiconductor Wafer In the method for manufacturing a semiconductor wafer of the present embodiment, a semiconductor layer is grown by a REMOCVD (Radical Enchanted Metalal Organic Chemical Vapor Deposition) method. That is, the group III nitride semiconductor is epitaxially grown on the main surface of the wafer by using the manufacturing apparatus 1000 of the present embodiment.

6-1. Cleaning the Substrate Here, a method of manufacturing a semiconductor wafer using the manufacturing apparatus 1000 of the present embodiment will be described. First, the substrate Sa1 is prepared. As the substrate Sa1, for example, a c-plane sapphire substrate can be used. Further, other substrates may be used. The substrate Sa1 is arranged in the susceptor 1200 inside the manufacturing apparatus 1000, and the substrate temperature is raised to about 900 ° C. while supplying hydrogen gas. As a result, the surface of the substrate Sa1 is reduced and the surface of the substrate Sa1 is cleaned. The substrate temperature may be higher than this.

6-2. Semiconductor layer forming step Next, the first gas and the second gas are supplied to the inside of the furnace body 1001 and the RF power supply 1610 is turned on. At this time, as described above, the plasma power pulse control unit 1620 is used to alternately repeat the first period T1 and the second period T2.

The first gas supply unit 1810 supplies the first gas from the first gas supply pipe 1300 to the inside of the furnace body 1001. The through hole of the ring portion 1310 of the first gas supply pipe 1300 is outside the plasma generation region. Therefore, the first gas is supplied to the substrate Sa1 without passing through the plasma generation region. That is, the first gas supply pipe 1300 supplies the organometallic gas containing the Group III metal as the first gas to the substrate Sa1 without passing through the plasma generation region.

The second gas supply unit 1710 supplies the second gas from the second gas supply pipe 1420 to the inside of the furnace body 1001. The second gas is supplied from the shower head electrode 1100 to the inside of the furnace body 1001. Immediately below the shower head electrode 1100 is a plasma generation region. The second gas supply pipe 1420 allows the second gas to pass through the space between the shower head electrode 1100 and the metal mesh 1500. That is, the second gas supply pipe 1420 supplies the second gas to the substrate Sa1 after passing it through the plasma generation region.

As described above, the RF power supply 1610 generates plasma at a high output (first output W1) in the first period T1 and generates plasma at a low output (second output W2) in the second period T2.

In the first period T1, particles derived from nitrogen atoms such as nitrogen radicals are generated in the plasma generation region. When the second gas contains hydrogen gas, a hydrogen radical and a hydrogen nitride-based compound are generated. Also, electrons and other charged particles are generated. Charged particles such as electrons disappear by colliding with the metal mesh 1500. Therefore, a nitrogen atom or a hydrogen atom and a hydrogen nitride-based compound derived from these atoms pass through the metal mesh 1500.

The particles that have passed through the metal mesh 1500 are supplied to the substrate Sa1 together with the first gas. The first gas is supplied to the substrate Sa1 without passing through the plasma generation region. Then, the particles derived from the nitrogen atom and the organic metal gas containing the group III metal react on the substrate Sa1 to form a group III nitride semiconductor.

In the second period T2, the first gas is not supplied to the substrate Sa1 and only the second gas is supplied to the substrate Sa1. The second gas is plasmatized with low power plasma. Therefore, nitrogen radicals and the like fall on the substrate Sa1. As a result, it is considered that nitrogen atoms are not easily desorbed from the surface of the semiconductor layer F1.

During this second period T2, no film is formed on the surface of the semiconductor layer F1. It is considered that the nitrogen atom is not desorbed from the surface of the semiconductor layer F1 and the carbon atom is desorbed from the surface of the semiconductor layer F1.

6-3. Semiconductor wafer In this way, the semiconductor layer F1 is epitaxially grown on the main surface of the substrate Sa1. As a result, the semiconductor wafer Wa1 is manufactured. Since the semiconductor layer F1 contains almost no carbon atom, the crystallinity of the group III nitride semiconductor in this semiconductor wafer Wa1 is good.

7. Modification 7-1. Through hole of the ring portion In the present embodiment, the first gas supply pipe 1300 has a through hole inside the ring portion 1310. However, the position of this through hole may be inside the ring and pointing downwards. The angle formed by the surface including the ring portion 1310 and the direction of the opening of the through hole is, for example, 45 °. The angle of this angle may be changed, for example, within the range of 0 ° or more and 60 ° or less. This angle, of course, also depends on the diameter of the ring portion 1310 and the distance between the ring portion 1310 and the susceptor 1200. Further, the number of through holes may be 1 or more. Of course, it is preferable that through holes are formed in the ring portion 1310 at equal intervals.

8. Summary of the present embodiment The manufacturing apparatus 1000 of the present embodiment epitaxially grows a group III nitride semiconductor on a growth substrate. During the first period T1, the first gas is supplied and the second gas is passed through the high-power plasma generation region. Then, the semiconductor layer F1 is formed on the substrate Sa1. On the other hand, during the second period T2, the first gas is not supplied and the second gas is passed through the low output plasma generation region. Carbon atoms are separated from the surface of the semiconductor layer F1 without forming a film. Therefore, this manufacturing apparatus can form a semiconductor layer having few carbon atoms.

(Second embodiment)
The second embodiment will be described. The semiconductor device of this embodiment is a MIS type semiconductor device having a group III nitride semiconductor layer.

1. 1. MIS type semiconductor element FIG. 5 is a schematic configuration diagram showing the structure of the MIS type semiconductor element 100 of the present embodiment. As shown in FIG. 5, the MIS type semiconductor element 100 includes a substrate 110, a buffer layer 120, a GaN layer 130, an AlGaN layer 140, an insulating film 150, a source electrode S1, a gate electrode G1, and a drain electrode. It has D1 and. The source electrode S1 and the drain electrode D1 are formed on the AlGaN layer 140. There is an insulating film 150 between the gate electrode G1 and the groove 141 of the AlGaN layer 140.

2. 2. Method for Manufacturing MIS-Type Semiconductor Device In the method for manufacturing the MIS-type semiconductor device 100 of the present embodiment, the semiconductor layer is grown by a REMOCVD (Radical Enhanced Metall Organic Chemical Vapor Deposition) method. That is, the semiconductor layer is grown using the manufacturing apparatus 1000 of the first embodiment.

2-1. Semiconductor layer forming step The group III nitride semiconductor layer is formed on the substrate 110 by using the manufacturing apparatus 1000 of the first embodiment. The conditions used here are almost the same as the method for manufacturing a semiconductor wafer described in the first embodiment. A buffer layer 120, a GaN layer 130, and an AlGaN layer 140 are formed on the substrate 110. In order to form each of the above semiconductor layers, the raw material gas may be switched as appropriate.

2-2. Recessed portion forming step Next, a groove 141 is formed in the AlGaN layer 140 by etching with ICP or the like.

2-3. Insulating film forming step Next, the insulating film 150 is formed in the groove 141.

2-4. Electrode forming step Next, the source electrode S1 and the drain electrode D1 are formed on the AlGaN layer 140. Further, the gate electrode G1 is formed at the groove 141 via the insulating film 150. The source electrode S1 and the drain electrode D1 may be formed before the insulating film 150 is formed. As described above, the MIS type semiconductor element 100 is manufactured.

(Third embodiment)
A third embodiment will be described. The semiconductor device of this embodiment is a semiconductor light emitting device having a group III nitride semiconductor layer.

1. 1. Semiconductor light emitting device FIG. 6 is a schematic configuration diagram showing the structure of the light emitting device 200 of the present embodiment. As shown in FIG. 6, the light emitting device 200 has a group III nitride semiconductor layer. The light emitting element 200 includes a substrate 210, a buffer layer 220, an n-GaN layer 230, a light emitting layer 240, a p-AlGaN layer 250, a p-GaN layer 260, a p electrode P1, and an n electrode N1. Has. The light emitting layer 240 has a well layer and a barrier layer. The well layer has, for example, an InGaN layer. The barrier layer has, for example, an AlGaN layer. These laminated structures are examples, and may be a laminated structure other than the above.

2. 2. Manufacturing Method of Semiconductor Light-emitting Device In the manufacturing method of the light-emitting device 200 of the present embodiment, the semiconductor layer is grown by a REMOCVD (Radical Enhanced Metall Organic Chemical Vapor Deposition) method. That is, the semiconductor layer is grown using the manufacturing apparatus 1000 of the first embodiment.

2-1. Semiconductor layer forming step The group III nitride semiconductor layer is formed on the substrate 210 by using the manufacturing apparatus 1000 of the first embodiment. The conditions used here are almost the same as the method for manufacturing a semiconductor wafer described in the first embodiment. A buffer layer 220, an n-GaN layer 230, a light emitting layer 240, a p-AlGaN layer 250, and a p-GaN layer 260 are formed on the substrate 210. In order to form each of the above semiconductor layers, the raw material gas may be switched as appropriate.

2-2. Recessed portion forming step Next, by etching an ICP or the like, a concave portion extending from the p-GaN layer 260 to the middle of the n-GaN layer 230 is formed. As a result, the exposed portion of the n-GaN layer 230 is exposed.

2-3. Electrode forming step Next, the n electrode N1 is formed on the exposed portion of the n-GaN layer 230. Further, the p electrode P1 is formed on the p-GaN layer 260.

2-4. Other Steps Other steps such as an annealing step and a step of forming an insulating film may be carried out.

1. 1. Example 1
In this experiment, the experiment was performed using the manufacturing apparatus 1000 shown in FIG. As the plasma gas, a mixed gas in which nitrogen gas 750 sccm and hydrogen gas 250 sccm were mixed was supplied. That is, the volume flow rate ratio of hydrogen gas in the mixed gas was 25%. The internal pressure of the manufacturing apparatus 1000 was 300 Pa. As the growth substrate, a GaN / Si substrate having an 8 mm square shape and a thickness of 400 μm was used.

First, the temperature of the GaN / Si substrate was raised to 800 ° C., and then GaN was formed for 1 hour under normal film formation conditions. Next, GaN was pulse-grown for 2 hours as in the first embodiment. The first period T1 was 25 seconds. The second period T2 was 1 second. The first output W1 in the first period T1 was 700 W. The second output W2 in the second period T2 was 400 W. The ratio W1 / W2 of the first output W1 to the second output W2 is 1.75. In the first period T1, TMG was supplied in an amount of 0.1 sccm. During the second period T2, TMG was not supplied.

2. 2. Comparative Example 1
In Comparative Example 1, GaN was formed under almost the same conditions as in Example 1. The difference from Example 1 is that pulse growth was not performed. That is, GaN was grown for 6 hours while keeping the RF power at 700 W.

3. 3. SIMS
FIG. 7 is a graph showing the analysis results by the secondary ion mass spectrometry (SIMS) in Example 1 and Comparative Example 1. The horizontal axis of FIG. 7 is the depth from the surface. That is, it shows the distance from the surface. The vertical axis of FIG. 7 is the concentration of each element. In FIG. 7, the solid line shows Example 1 and the broken line shows Comparative Example 1.

The concentration of carbon atoms in the vicinity of the surface provided with the first period T1 and the second period T2 in Example 1 is about 2.4 × 10 ¹⁸ cm ^-3 . The concentration of carbon atoms in the region where the first period T1 and the second period T2 are not provided is about 4.2 × 10 ²⁰ cm ^-3 . The concentration of carbon atoms in the pulse-grown semiconductor layer is about two orders of magnitude smaller than the concentration of carbon atoms in the normally-grown semiconductor layer.

In Comparative Example 1, the concentration of carbon atoms is about 4.2 × 10 ²⁰ cm ^-3 from the surface to the back of the GaN. As described above, in the semiconductor layer in which pulse growth was not performed, the concentration of carbon atoms remains uniformly high.

4. SEM photograph FIG. 8 is an SEM photograph showing a cross section of GaN in Example 1. FIG. 9 is an SEM photograph showing the surface of GaN in Example 1. As shown in FIG. 9, in this case, the surface of GaN is sufficiently flat.

FIG. 10 is an SEM photograph showing a cross section of GaN in Comparative Example 1. FIG. 11 is an SEM photograph showing the surface of GaN in Comparative Example 1. As shown in FIG. 11, in the comparative example, the surface of GaN is rough.

5. First period For the first period T1, the experiment was performed with 10 seconds and 18 seconds. Similarly, in these cases, GaN in a relatively flat surface state was obtained.

6. Decomposition temperature of trimethylgallium The surface of the GaN layer was measured with an ellipsometer while changing the substrate temperature. The phase difference Δ is the phase difference between the s polarization and the p polarization. This phase difference Δ changes due to the reflection of light on the surface of the GaN layer. That is, the phase difference Δ changes according to the surface state of the GaN layer.

The substrate was a Si (111) substrate. As the plasma gas, a mixed gas in which nitrogen gas 750 sccm and hydrogen gas 250 sccm were mixed was supplied. The supply of TMG was 0.1 sccm.

FIG. 12 is a graph (No. 1) showing the temperature dependence of the phase difference Δ when the surface of the GaN layer is measured with an ellipsometer. FIG. 13 is a graph (No. 2) showing the temperature dependence of the phase difference Δ when the surface of the GaN layer is measured with an ellipsometer. FIG. 13 is an enlarged graph of FIG.

As shown in FIG. 12, it can be seen that the surface state of the GaN layer changes between 300 ° C and 400 ° C.

As shown in FIG. 13, trimethylgallium is considered to be decomposed into monomethylgallium at about 328 ° C. It is considered that monomethylgallium is decomposed into gallium at about 400 ° C.

7. Summary of Experiment As described above, in Example 1, the concentration of carbon atoms is low in the pulse-grown GaN region. In Comparative Example 1, since the pulse is not grown, the concentration of carbon atoms remains uniformly high. Further, as shown in FIGS. 9 and 11, it is presumed that there is a certain degree of correlation between the relatively high concentration of carbon atoms near the surface of GaN and the roughness of the surface of GaN.

As shown in FIGS. 12 and 13, when the substrate temperature is 300 ° C. or lower, it is considered that Ga of trimethylgallium binds to nitrogen on the surface of the semiconductor layer and the methyl group is desorbed with the passage of time. .. When the substrate temperature is 400 ° C. or higher, it is considered that the methyl group is instantly desorbed by thermal decomposition as soon as Ga of trimethylgallium is bonded to nitrogen on the surface of the semiconductor layer. Therefore, the substrate temperature is preferably 400 ° C. or higher and 900 ° C. or lower.

A. Supplementary note The apparatus for manufacturing a group III nitride semiconductor element in the first aspect is for epitaxially growing a group III nitride semiconductor. In this manufacturing apparatus, a first electrode, a potential applying portion for applying a potential to the first electrode, a substrate support portion for supporting the growth substrate, and a group III metal as a first gas in the substrate support portion are used. A first gas supply pipe for supplying an organic metal gas containing the gas, a second gas supply pipe for supplying a gas containing nitrogen gas as a second gas to the substrate support portion, and a first electrode and a substrate support portion. It has a metal mesh member arranged at a position in between. The first gas supply pipe has at least one first gas outlet. The first gas outlet is arranged at a position between the substrate support portion and the metal mesh member. The second gas supply pipe allows the second gas to pass through the space between the first electrode and the metal mesh member. The first gas supply pipe and the potential applying unit alternately repeat the first period and the second period. The first gas supply pipe supplies the first gas in the first period and does not supply the first gas in the second period. The potential-imparting unit generates plasma at the first output in the first period, and generates plasma at the second output smaller than the first output in the second period.

In the apparatus for manufacturing the group III nitride semiconductor element in the second aspect, the potential applying unit sets the ratio of the first output to the second output to 1.5 or more and 5 or less.

The method for manufacturing a group III nitride semiconductor element in the third aspect is a method for epitaxially growing a group III nitride semiconductor. In this method, a plasma generator that generates a plasma generation region is used. An organic metal gas containing a group III metal as the first gas is supplied to the growth substrate without passing through the plasma generation region, and a gas containing nitrogen gas as the second gas is passed through the plasma generation region and then the growth substrate. Supply to. The film is formed by alternately repeating the first period and the second period. When supplying the first gas, the first gas is supplied in the first period and the first gas is not supplied in the second period. The plasma generator generates plasma at the first output in the first period and generates plasma at the second output smaller than the first output in the second period.

In the method for manufacturing a group III nitride semiconductor device according to the fourth aspect, the plasma generator has a ratio of the first output to the second output of 1.5 or more and 5 or less.

The method for manufacturing a wafer in the fifth aspect is a method for epitaxially growing a group III nitride semiconductor on the main surface of the wafer. In this method, a plasma generator that generates a plasma generation region is used. An organic metal gas containing a group III metal as the first gas is supplied to the growth substrate without passing through the plasma generation region, and a gas containing nitrogen gas as the second gas is passed through the plasma generation region and then the growth substrate. Supply to. The film is formed by alternately repeating the first period and the second period. When supplying the first gas, the first gas is supplied in the first period and the first gas is not supplied in the second period. The plasma generator generates plasma at the first output in the first period and generates plasma at the second output smaller than the first output in the second period.

1000 ... Manufacturing equipment 1001 ... Furnace body 1100 ... Shower head electrode 1200 ... Scepter 1210 ... Heater 1300 ... First gas supply pipe 1410 ... Gas introduction chamber 1420 ... Second gas supply pipe 1500 ... Metal mesh 1600 ... RF power supply 1610 … Matching box

Claims (5)

In the equipment for manufacturing group III nitride semiconductor devices that epitaxially grow group III nitride semiconductors.
With the first electrode
A potential applying portion that applies a potential to the first electrode,
A substrate support for supporting the growth substrate and
A first gas supply pipe for supplying an organometallic gas containing a group III metal as a first gas to the substrate support portion,
A second gas supply pipe that supplies a gas containing nitrogen gas as a second gas to the substrate support portion,
A metal mesh member arranged at a position between the first electrode and the substrate support portion,
Have,
The first gas supply pipe is
It has at least one first gas outlet and
The first gas outlet is
It is arranged at a position between the substrate support portion and the metal mesh member.
The second gas supply pipe is
The second gas is passed through the space between the first electrode and the metal mesh member.
The first gas supply pipe and the potential applying portion are
The first period and the second period are repeated alternately,
The first gas supply pipe is
The first gas is supplied during the first period,
The first gas was not supplied during the second period,
The potential applying portion is
Plasma is generated at the first output during the first period.
A device for manufacturing a group III nitride semiconductor device, characterized in that plasma is generated at a second output smaller than the first output during the second period. In the apparatus for manufacturing a group III nitride semiconductor device according to claim 1.
The potential applying portion is
A device for manufacturing a group III nitride semiconductor element, wherein the ratio of the first output to the second output is 1.5 or more and 5 or less. In the method for manufacturing a group III nitride semiconductor device for epitaxially growing a group III nitride semiconductor,
Using a plasma generator that generates a plasma generation region,
As the first gas, an organometallic gas containing a group III metal is supplied to the growth substrate without passing through the plasma generation region, and is also supplied.
A gas containing nitrogen gas as a second gas is passed through the plasma generation region and then supplied to the growth substrate.
Film formation was performed by alternately repeating the first period and the second period.
When supplying the first gas,
The first gas is supplied during the first period,
The first gas was not supplied during the second period,
The plasma generator is
Plasma is generated at the first output during the first period.
A method for manufacturing a group III nitride semiconductor device, which comprises generating plasma at a second output smaller than the first output during the second period. In the method for manufacturing a group III nitride semiconductor device according to claim 3.
The plasma generator is
A method for manufacturing a group III nitride semiconductor element, wherein the ratio of the first output to the second output is 1.5 or more and 5 or less. In a method for manufacturing a semiconductor wafer in which a group III nitride semiconductor is epitaxially grown on the main surface of the wafer.
Using a plasma generator that generates a plasma generation region,
As the first gas, an organometallic gas containing a group III metal is supplied to the growth substrate without passing through the plasma generation region, and is also supplied.
A gas containing nitrogen gas as a second gas is passed through the plasma generation region and then supplied to the growth substrate.
Film formation was performed by alternately repeating the first period and the second period.
When supplying the first gas,
The first gas is supplied during the first period,
The first gas was not supplied during the second period,
The plasma generator is
Plasma is generated at the first output during the first period.
A method for manufacturing a semiconductor wafer, characterized in that plasma is generated at a second output smaller than the first output during the second period.

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