JP2019212714A - Apparatus and method for manufacturing group iii nitride semiconductor element and method for manufacturing semiconductor wafer - Google Patents

Abstract

To provide an apparatus and a method for manufacturing a group III nitride semiconductor element and a method for manufacturing a semiconductor wafer, which can perform growing at a relatively low temperature and can suppress the incorporation of carbon atoms into a group III nitride semiconductor.SOLUTION: A second gas supply pipe 1420 allows a second gas to pass through a space between a showerhead electrode 1100 and a metal mesh 1500. A first gas supply pipe 1300 and a RF power supply 1600 alternately repeat a first period T1 and a second period T2. The first gas supply pipe 1300 supplies the first gas during a first period T1, and does not supply the first gas during a second period T2. The RF power supply 1600 generates plasma with the first output W1 during the first period T1, and generates plasma with the second output W2 smaller than the first output W1 during the second period T2.SELECTED DRAWING: Figure 3

Description

  The technical field of this specification relates to an apparatus and method for manufacturing a group III nitride semiconductor device using plasma, and a method for manufacturing a semiconductor wafer.

  In a group III nitride semiconductor typified by GaN, the band gap changes from 0.6 eV to 6 eV by changing its composition. Therefore, group III nitride semiconductors are applied to light-emitting elements, laser diodes, light-receiving elements and the like corresponding to a wide range of wavelengths from near infrared to deep ultraviolet.

  Further, the group III nitride semiconductor has a high breakdown electric field strength and a high melting point. Therefore, the group III nitride semiconductor is expected as a material for a semiconductor device for high output, high frequency, and high temperature that replaces a GaAs semiconductor. Along with this, research and development of HEMT elements and the like is underway.

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

  Moreover, 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, a group III nitride semiconductor can be grown at a low growth temperature. However, the growth rate is slow in the RF-MBE method using a radical source. That is, the RF-MBE method is not suitable for mass production. In the MBE method using ammonia gas, since a large amount of ammonia gas is used, the manufacturing cost is high.

JP-A-2015-99866

  Therefore, the present inventors have developed a REMOCVD (Radial Enhanced Metal Organic Vapor Deposition) method in which an organic metal gas containing a group III metal is not made into a plasma, but a gas containing a nitrogen atom is made into a plasma and supplied to a growth substrate. (Patent Document 1). With the technique of Patent Document 1, GaN or the like can be grown at a low temperature. Therefore, the stress resulting from the difference in thermal expansion coefficient can be suppressed.

  By the way, in order to grow a group III nitride semiconductor, a group III organometallic gas is often used. The group III organometallic gas has a carbon atom (for example, a methyl group). For this reason, the carbon atom of the group III organometallic gas may be mixed into 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 do not enter the group III nitride semiconductor. The lower the growth temperature, the more carbon atoms tend to enter the group III nitride semiconductor. In other words, the technique of Patent Document 1 can relieve the strain and stress of the substrate, but there is a possibility that a relatively large amount of carbon atoms may be mixed into the group III nitride semiconductor.

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

  The group III nitride semiconductor device manufacturing apparatus according to the first aspect is for epitaxially growing a group III nitride semiconductor. The manufacturing apparatus includes a first electrode, a potential applying unit that applies a potential to the first electrode, a substrate support unit for supporting the growth substrate, and a group III metal as a first gas in the substrate support unit. A first gas supply pipe for supplying an organic metal gas containing; a second gas supply pipe for supplying a gas containing nitrogen gas as a second gas to the substrate support; and a first electrode and a substrate support. And a metal mesh member disposed at a position therebetween. The first gas supply pipe has at least one or more first gas outlets. The 1st gas jet nozzle is arrange | positioned in the position between a board | substrate support part and a 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 during the first period and does not supply the first gas during the second period. The potential applying unit generates plasma with a first output in a first period, and generates plasma with a second output smaller than the first output in a second period.

  This group III nitride semiconductor device manufacturing apparatus epitaxially grows a group III nitride semiconductor on a growth substrate. In this manufacturing apparatus, the first gas is supplied to the growth substrate without passing through the plasma generation region, and the second gas is supplied to the growth substrate after passing through the plasma generation region. This manufacturing apparatus repeats the first period and the second period alternately. In the first period, the first gas is flowed and the output of the plasma generator is increased. In the second period, the first gas is not flowed and the output of the plasma generator is reduced. Thereby, a group III nitride semiconductor is formed in the first period, and carbon atoms are detached from the group III nitride semiconductor in the second period. Therefore, this manufacturing apparatus can manufacture a group III nitride semiconductor having a small carbon atom content.

  In the present specification, a group III nitride semiconductor device manufacturing apparatus and method, and a semiconductor wafer manufacturing method capable of growing at a relatively low temperature and suppressing the mixing of carbon atoms into the 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 schematic structure of the manufacturing apparatus in 1st Embodiment. It is a timing chart which shows the relationship between supply of 1st gas, and the output of the high frequency electric potential which RF power supply provides to a shower head electrode. It is a timing chart explaining the conventional CVD method of a pulse form. It is a figure which shows the structure of the MIS type | mold 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. 2 is a SEM photograph showing a cross section of GaN in Example 1. 3 is a SEM photograph showing the surface of GaN in Example 1. 4 is a SEM photograph showing a cross section of GaN in Comparative Example 1. 4 is a SEM photograph showing the surface of GaN in Comparative Example 1. It is a graph (the 1) which shows the temperature dependence of phase difference (DELTA) at the time of measuring the surface of a GaN layer with an ellipsometer. It is a graph (the 2) which shows the temperature dependence of phase difference (DELTA) at the time of measuring the surface of a GaN layer with an ellipsometer.

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

(First embodiment)
1. Semiconductor Wafer FIG. 1 is a view showing the structure of a semiconductor wafer Wa1 of this 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. Thus, the semiconductor wafer Wa1 is obtained by epitaxially growing a group III nitride semiconductor on the main surface of the wafer.

2. Group III Nitride Semiconductor Device Manufacturing Apparatus FIG. 2 is a schematic configuration diagram of a group III nitride semiconductor element manufacturing apparatus 1000 according to this 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 a chamber. The manufacturing apparatus 1000 supplies an organic metal gas containing a Group III metal (first gas) to the growth substrate without passing through the plasma generation region, and supplies a gas containing nitrogen atoms (second gas) to the plasma generation region. After passing, it is supplied to the growth substrate.

  The manufacturing apparatus 1000 includes a furnace main 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, a metal Mesh 1500, RF power source 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, constant temperature Tanks 1911, 1921, 1931, mass flow controllers 1720, 1820, 1830, 1840, and a pulse valve 1850 are included. Moreover, 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 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. For this reason, the second gas supplied from the gas introduction chamber 1410 to the inside of the furnace main body 1001 is preferably converted into plasma.

  The RF power source 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 showerhead electrode 1100.

  The susceptor 1200 is a substrate support unit for supporting the substrate Sa1. The material of the susceptor 1200 is, for example, graphite. Other conductors may be used. 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. Moreover, the other carrier gas may be included. 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 twelve through holes (not shown) inside the ring portion 1310. Thus, the first gas supply pipe 1300 has at least one or more through holes. These through holes are jet outlets from which the first gas is jetted. Therefore, the first gas is ejected toward the inside of the ring portion 1310. Further, these through holes are arranged at a position 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. Actually, 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 storing a mixed gas of nitrogen gas and hydrogen gas and supplying the mixed gas to the through hole of the showerhead electrode 1100.

  The metal mesh 1500 is a metal mesh member for capturing charged particles. The metal mesh 1500 is made of stainless steel, for example. Of course, other metals may be used. The metal mesh 1500 is disposed 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 moving toward the growth substrate Sa1 supported by the susceptor 1200, as will be described later. In addition, the metal mesh 1500 is disposed at a position between the shower head electrode 1100 and the ring portion 1310 of the first gas supply pipe 1300. Therefore, the charged particles can be prevented from colliding with an organometallic molecule containing a group III metal ejected from the ring portion 1310 of the first gas supply pipe 1300. Further, the metal mesh 1500 is overlapped by shifting a large number of meshes little by little. That is, the linear part of the second mesh is arranged at the position of the opening of the first mesh. Therefore, light that travels linearly cannot pass through the metal mesh 1500. That is, the metal mesh 1500 does not pass electrons, ions, and light, but allows neutral radicals to pass.

  The furnace body 1001 accommodates 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 stainless steel, for example. 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 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 a discharge occurs between at least one of the furnace body 1001 and the metal mesh 1500 and the shower head electrode 1100. A high-frequency and high-intensity electric field is formed immediately below the showerhead electrode 1100. Therefore, the position immediately below the shower head electrode 1100 is a plasma generation region.

Here, the second gas is turned into plasma in this plasma generation region. A plasma product is generated in the plasma generation region. The plasma products in this case are, for example, nitrogen radicals, hydrogen radicals, hydrogen nitride compounds, electrons, and other ions. Here, the hydrogen nitride-based compound includes NH, NH ₂ , NH ₃ , their excited states, and others.

  Moreover, the shower head electrode 1100 and the susceptor 1200 are sufficiently separated. The distance between the showerhead 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 showerhead electrode 1100 and the susceptor 1200 is short, the plasma generation region may spread to the susceptor 1200. If the distance between the showerhead 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 suppress the charged particles from reaching the substrate Sa1. Further, when the distance between the showerhead electrode 1100 and the susceptor 1200 is large, nitrogen radicals, hydrogen nitride-based compounds, and the like hardly reach the substrate Sa1 held by the susceptor 1200. These distances depend on the size of the plasma generation region and other plasma conditions.

  The shower head electrode 1100 is disposed at a position farther 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 showerhead 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 because charged particles are prevented from being mixed into the first gas, and nitrogen radicals, hydrogen nitride-based compounds, and the like can easily reach the substrate Sa1. For this reason, the semiconductor layer is stacked on the substrate Sa1 by the second gas converted into plasma and the first gas not converted into plasma. These distances 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.

  The mass flow controllers 1720, 1820, 1830, and 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 of a high-frequency potential. The thermostats 1911, 1921, and 1931 are filled with antifreeze liquids 1912, 1922, and 1932. Further, the gas containers 1910, 1920, and 1930 are containers for storing an organometallic gas containing a group III metal. The gas containers 1910, 1920, and 1930 contain trimethyl gallium, trimethyl indium, and trimethyl aluminum, respectively. Of course, organic metal gas containing other group III metals such as triethylgallium may be used.

3. Manufacturing conditions of manufacturing apparatus Table 1 shows manufacturing conditions in the manufacturing apparatus 1000. The numerical ranges given in Table 1 are only a guide and are not necessarily limited to these numerical ranges. The RF power is in the range of 100 W to 1000 W. The frequency of the periodic potential applied to the shower head electrode 1100 by the RF power source 1600 is in the range of 30 MHz to 300 MHz. The substrate temperature is in the range of 0 ° C. or higher and 900 ° C. or lower. Preferably, it is 400 degreeC or more and 900 degrees C or less. The internal pressure of the manufacturing apparatus 1000 is in the range of 1 Pa to 10,000 Pa.

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

4). First gas supply and potential application 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 source 1600. The horizontal axis of FIG. 3 is time. In FIG. 3, the vertical axis represents the flow rate of trimethylgallium (TMG). The vertical axis in the lower diagram of FIG. 3 is the RF power.

  As shown in FIG. 3, the supply of the first gas and the supply of power by the RF power source 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 source 1600 has the first output W1. Generate plasma. Therefore, in 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, a group III nitride semiconductor is formed in the first period T1.

4-2. Second Period As shown in FIG. 3, in the second period T2, the first gas supply pipe 1300 does not supply the first gas to the susceptor 1200, and the RF power source 1600 outputs the second output. Plasma is generated by W2. Therefore, in the second period T2, nitrogen atoms (including radicals and excited states) are supplied to the substrate Sa1 of the susceptor 1200, but no group III element is supplied to the substrate Sa1. Therefore, the group III nitride semiconductor is not formed in the second period T2.

4-3. Output in First Period and Second Period The first output W1 in the first period T1 is, for example, not less than 600 W and not more than 1000 W. The second output W2 in the second period T2 is, for example, not less than 200 W and not more than 500 W. 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 source 1600 generates plasma with the first output W1 during the first period T1, and generates plasma with the second output W2 during the second period T2. As described above, the second output W2 is smaller than the first output W1.

4-4. Time of first period and second period The first period T1 is, for example, not less than 5 seconds and not more than 60 seconds. The second period T2 is, for example, not less than 0.5 seconds and not more than 5 seconds. These numerical ranges are exemplary, and numerical values other than those described above may be used.

4-5. Effects of the First Period and the Second Period As described above, 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. I don't film. During the period of the second period T2, the group III nitride semiconductor is not formed, so it is considered that the carbon atoms are detached 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. The second output W2 is greater than zero. Therefore, plasma is generated in both the first period T1 and the second period T2. Then, the second plasma density of the plasma in the second period T2 is smaller than the first plasma density of the plasma in the first period T1. In this way, high-power and low-power plasmas are generated alternately.

  The plasma in the first period T1 generates particles derived from nitrogen atoms used for film formation. The plasma in the second period T2 generates particles derived from nitrogen atoms as in the first period T1. In the second period T2, the particles derived from the nitrogen atoms are not used for film formation, and it is considered that the nitrogen atoms are prevented from being detached from the formed semiconductor layer. Thus, in the second period T2, carbon atoms are evaporated from the semiconductor layer, and nitrogen atoms are not evaporated. Therefore, in the second period T2, nitrogen radicals that prevent the elimination of nitrogen atoms may reach the surface of the substrate Sa1 or the semiconductor layer F1.

5. FIG. 4 is a timing chart for explaining a 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 performed. That is, generating high output plasma and supplying a source gas such as TMG are alternately performed. Thus, when generating high output plasma, it differs from the technique of this embodiment which supplies source gas.

  In the present embodiment, the group III nitride semiconductor can be grown without increasing the substrate temperature. Therefore, it is suitable for growing a high In concentration InGaN layer or the like, which is difficult to grow 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 a detoxifying device for removing ammonia gas. Therefore, the cost of the manufacturing apparatus itself is low. Also, the running cost can be suppressed.

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

6-1. Cleaning of Substrate Here, a method for manufacturing a semiconductor wafer using the manufacturing apparatus 1000 of the present embodiment will be described. First, the substrate Sa1 is prepared. For example, a c-plane sapphire substrate can be used as the substrate Sa1. Other substrates may also be used. The substrate Sa1 is placed on 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 into the furnace main body 1001 and the RF power source 1610 is turned on. At this time, as described above, using the plasma power pulse control unit 1620, the first period T1 and the second period T2 are alternately repeated.

  The first gas supply unit 1810 supplies the first gas from the first gas supply pipe 1300 to the inside of the furnace main 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 an organometallic gas containing a 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 main body 1001. The second gas is supplied from the shower head electrode 1100 into 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 showerhead 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 the second gas through the plasma generation region.

  Thus, the RF power source 1610 generates plasma with a high output (first output W1) in the first period T1, and generates plasma with 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, hydrogen radicals and a hydrogen nitride-based compound are generated. Electrons and other charged particles are also generated. Particles having charges such as electrons disappear when they collide with the metal mesh 1500. Therefore, a nitrogen atom or a hydrogen atom and a hydrogen nitride-based compound derived therefrom 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. Note that the first gas is supplied to the substrate Sa1 without passing through the plasma generation region. Then, particles derived from nitrogen atoms and an organometallic gas containing a 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 turned into plasma by low-power plasma. Therefore, nitrogen radicals or the like pour onto the substrate Sa1. Thereby, it is considered that nitrogen atoms are hardly detached from the surface of the semiconductor layer F1.

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

6-3. Semiconductor wafer Thus, the semiconductor layer F1 is epitaxially grown on the main surface of the substrate Sa1. Thereby, the semiconductor wafer Wa1 is manufactured. Since the semiconductor layer F1 contains almost no carbon atoms, the crystallinity of the group III nitride semiconductor in the semiconductor wafer Wa1 is good.

7). Modification 7-1. Through-hole of ring part In the present embodiment, the first gas supply pipe 1300 has a through-hole inside the ring part 1310. However, the position of the through-hole may be set to the inside of the ring and downward. 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 °. For example, the angle may be changed within a range of 0 ° to 60 °. Of course, this angle also depends on the diameter of the ring portion 1310 and the distance between the ring portion 1310 and the susceptor 1200. Moreover, the number of through-holes should just be one 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. In 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, in the second period T2, the first gas is not supplied and the second gas is passed through the low-power plasma generation region. Without forming the semiconductor layer F1, carbon atoms are released from the surface. Therefore, this manufacturing apparatus can form a semiconductor layer with few carbon atoms.

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

1. MIS Type Semiconductor Device FIG. 5 is a schematic configuration diagram showing the structure of the MIS type semiconductor device 100 of this embodiment. As shown in FIG. 5, the MIS type semiconductor device 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. D1. 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. Manufacturing Method of MIS Type Semiconductor Device In the manufacturing method of the MIS type semiconductor device 100 of this embodiment, a semiconductor layer is grown by a REMOCVD (Radially Enhanced Metal Organic Vapor Deposition) method. That is, the semiconductor layer is grown using the manufacturing apparatus 1000 of the first embodiment.

2-1. Semiconductor Layer Formation Step A group III nitride semiconductor layer is formed on the substrate 110 using the manufacturing apparatus 1000 of the first embodiment. The conditions used here are almost the same as those of the semiconductor wafer manufacturing method 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 semiconductor layers, the source gas may be switched as appropriate.

2-2. Next, a groove 141 is formed in the AlGaN layer 140 by etching such as ICP.

2-3. Insulating Film Formation Step Next, the insulating film 150 is formed in the trench 141.

2-4. Electrode Formation Step Next, the source electrode S1 and the drain electrode D1 are formed on the AlGaN layer 140. In addition, the gate electrode G <b> 1 is formed at the location of the trench 141 through the insulating film 150. Note that the source electrode S1 and the drain electrode D1 may be formed before the insulating film 150 is formed. Thus, 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 element having a group III nitride semiconductor layer.

1. Semiconductor Light Emitting Element FIG. 6 is a schematic configuration diagram showing the structure of the light emitting element 200 of the present embodiment. As shown in FIG. 6, the light-emitting element 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, an n electrode N1, Have 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 laminated structures other than the above may be used.

2. Manufacturing Method of Semiconductor Light-Emitting Element In the manufacturing method of the light-emitting element 200 of the present embodiment, a semiconductor layer is grown by a REMOCVD (Radial Enhanced Metal Organic Vapor Deposition) method. That is, the semiconductor layer is grown using the manufacturing apparatus 1000 of the first embodiment.

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

2-2. Next, a recess that reaches from the p-GaN layer 260 to the middle of the n-GaN layer 230 is formed by etching such as ICP. As a result, the exposed portion of the n-GaN layer 230 is exposed.

2-3. Next, an n-electrode N1 is formed on the exposed portion of the n-GaN layer 230. In addition, the p-electrode P <b> 1 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 performed.

1. Example 1
In this experiment, the experiment was performed using the manufacturing apparatus 1000 shown in FIG. As a plasma gas, a mixed gas obtained by mixing 750 sccm of nitrogen gas and 250 sccm of hydrogen gas was supplied. That is, the volume flow 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 and a thickness of 400 μm was used.

  First, after heating the GaN / Si substrate to 800 ° C., GaN was formed for 1 hour under normal film forming conditions. Next, GaN was pulse-grown over 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 700W. The second output W2 in the second period T2 was 400W. The ratio W1 / W2 of the first output W1 to the second output W2 is 1.75. In the first period T1, 0.1 sccm of TMG was supplied. In the second period T2, TMG was not supplied.

2. Comparative Example 1
In Comparative Example 1, GaN was deposited under substantially 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. SIMS
FIG. 7 is a graph showing analysis results by secondary ion mass spectrometry (SIMS) in Example 1 and Comparative Example 1. The horizontal axis in FIG. 7 is the depth from the surface. That is, the distance from the surface is shown. The vertical axis in FIG. 7 represents the concentration of each element. In FIG. 7, the solid line indicates Example 1, and the broken line indicates 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 lower 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 of GaN to the back. Thus, the concentration of carbon atoms remains uniformly high in the semiconductor layer that has not been subjected to pulse growth.

4). SEM photograph FIG. 8 is a SEM photograph showing a cross section of GaN in Example 1. FIG. 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, the surface of GaN is rough in the comparative example.

5. First Period For the first period T1, the experiment was performed with 10 seconds and 18 seconds. Also in these cases, GaN having 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 a phase difference between s-polarized light and p-polarized light. This phase difference Δ changes due to 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 a plasma gas, a mixed gas obtained by mixing 750 sccm of nitrogen gas and 250 sccm of hydrogen gas was supplied. The supply amount of TMG was 0.1 sccm.

  FIG. 12 is a graph (part 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 (part 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, it is considered that trimethylgallium is decomposed into monomethylgallium at about 328 ° C. Monomethylgallium is considered to be 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 GaN region grown by pulse growth. In Comparative Example 1, since the pulse growth is not performed, the concentration of carbon atoms remains high uniformly. 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 rough 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 is bonded to nitrogen on the surface of the semiconductor layer, and the methyl group is desorbed over time. . When the substrate temperature is 400 ° C. or higher, it is considered that methyl groups are instantaneously detached 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. Appendix The group III nitride semiconductor device manufacturing apparatus according to the first aspect is for epitaxially growing a group III nitride semiconductor. The manufacturing apparatus includes a first electrode, a potential applying unit that applies a potential to the first electrode, a substrate support unit for supporting the growth substrate, and a group III metal as a first gas in the substrate support unit. A first gas supply pipe for supplying an organic metal gas containing; a second gas supply pipe for supplying a gas containing nitrogen gas as a second gas to the substrate support; and a first electrode and a substrate support. And a metal mesh member disposed at a position therebetween. The first gas supply pipe has at least one or more first gas outlets. The 1st gas jet nozzle is arrange | positioned in the position between a board | substrate support part and a 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 during the first period and does not supply the first gas during the second period. The potential applying unit generates plasma with a first output in a first period, and generates plasma with a second output smaller than the first output in a second period.

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

  The method for producing a group III nitride semiconductor device according to 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 organometallic gas containing a Group III metal as a first gas is supplied to the growth substrate without passing through the plasma generation region, and a growth substrate after passing a gas containing nitrogen gas as the second gas into the plasma generation region. To supply. Film formation is performed while alternately repeating the first period and the second period. When supplying the first gas, the first gas is supplied during the first period, and the first gas is not supplied during the second period. The plasma generator generates plasma with a first output in a first period and generates plasma with a second output smaller than the first output in a second period.

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

  The wafer manufacturing method according to the fifth aspect is a method of 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 organometallic gas containing a Group III metal as a first gas is supplied to the growth substrate without passing through the plasma generation region, and a growth substrate after passing a gas containing nitrogen gas as the second gas into the plasma generation region. To supply. Film formation is performed while alternately repeating the first period and the second period. When supplying the first gas, the first gas is supplied during the first period, and the first gas is not supplied during the second period. The plasma generator generates plasma with a first output in a first period and generates plasma with a second output smaller than the first output in a second period.

1000 ... Manufacturing apparatus 1001 ... Furnace body 1100 ... Shower head electrode 1200 ... Susceptor 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 a group III nitride semiconductor device manufacturing apparatus for epitaxially growing a group III nitride semiconductor,
A first electrode;
A potential applying unit that applies a potential to the first electrode;
A substrate support for supporting the growth substrate;
A first gas supply pipe for supplying an organometallic gas containing a group III metal as a first gas to the substrate support;
A second gas supply pipe for supplying a gas containing nitrogen gas as a second gas to the substrate support;
A metal mesh member disposed at a position between the first electrode and the substrate support;
Have
The first gas supply pipe is
Having at least one or more first gas outlets;
The first gas outlet is
It is arranged at a position between the substrate support part and the metal mesh member,
The second gas supply pipe is
Passing the second gas through a space between the first electrode and the metal mesh member;
The first gas supply pipe and the potential applying unit are:
Alternately repeating the first period and the second period,
The first gas supply pipe is
Supplying the first gas in the first period;
Without supplying the first gas in the second period;
The potential applying unit includes:
Generating a plasma with a first output during the first period;
The apparatus for producing a group III nitride semiconductor device, wherein plasma is generated at a second output smaller than the first output during the second period. In the group III nitride semiconductor device manufacturing apparatus according to claim 1,
The potential applying unit includes:
The apparatus for manufacturing a group III nitride semiconductor device, wherein a ratio of the first output to the second output is 1.5 or more and 5 or less. In a method of 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,
While supplying an organometallic gas containing a Group III metal as a first gas to the growth substrate without passing through the plasma generation region,
Supplying a gas containing nitrogen gas as the second gas to the growth substrate after passing through the plasma generation region;
The film formation is performed while alternately repeating the first period and the second period,
When supplying the first gas,
Supplying the first gas in the first period;
Without supplying the first gas in the second period;
The plasma generator comprises:
Generating a plasma with a first output during the first period;
A method of manufacturing a group III nitride semiconductor device, wherein plasma is generated at a second output smaller than the first output during the second period. In the manufacturing method of the group III nitride semiconductor device according to claim 3,
The plasma generator comprises:
The method of manufacturing a group III nitride semiconductor device, wherein a 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,
While supplying an organometallic gas containing a Group III metal as a first gas to the growth substrate without passing through the plasma generation region,
Supplying a gas containing nitrogen gas as the second gas to the growth substrate after passing through the plasma generation region;
The film formation is performed while alternately repeating the first period and the second period,
When supplying the first gas,
Supplying the first gas in the first period;
Without supplying the first gas in the second period;
The plasma generator comprises:
Generating a plasma with a first output during the first period;
A method of manufacturing a semiconductor wafer, wherein plasma is generated at a second output smaller than the first output during the second period.