JP6187167B2 - Compound semiconductor device and manufacturing method thereof - Google Patents

Description

  The present invention relates to a compound semiconductor device and a manufacturing method thereof.

  One of the indexes representing the performance of a GaN-based high electron mobility transistor (HEMT) using GaN as an electron transit layer and AlGaN as an electron supply layer is power added efficiency (PAE). is there. For example, PAE can be improved by reducing the dimension of the gate electrode in the gate length direction.

  However, the manufacturing yield decreases as the size of the gate electrode in the gate length direction decreases. On the contrary, the PAE may decrease due to the short channel effect.

JP 2000-174260 A JP 2003-338510 A

  An object of the present invention is to provide a compound semiconductor device capable of improving power added efficiency and a method for manufacturing the same.

  In one embodiment of the compound semiconductor device, a channel layer, a carrier supply layer formed above the channel layer, a gate electrode, a source electrode and a drain electrode formed above the carrier supply layer, and an electric current to the drain electrode The drain electrode is formed between the gate electrode and the drain electrode in plan view, and the channel layer and the carrier supply layer are provided in a non-conductive metal film. The lower surface of the metal film is located below the upper surface of the channel layer immediately below the gate electrode.

  In the method for manufacturing a compound semiconductor device, a carrier supply layer is formed above a channel layer, a gate electrode, a source electrode, and a drain electrode are formed above the carrier supply layer, and the drain electrode is disposed between the gate electrode and the gate electrode in plan view. A metal film electrically connected to the drain electrode and non-conductive with the channel layer and the carrier supply layer is formed at a position sandwiched between the channel layer and the carrier supply layer. The lower surface of the metal film is positioned below the upper surface of the channel layer immediately below the gate electrode.

  According to the above-described compound semiconductor device or the like, power added efficiency can be improved by the action of an appropriate metal film. It is not necessary to reduce the dimension of the gate electrode in the gate length direction.

It is sectional drawing which shows the structure of the compound semiconductor device which concerns on 1st Embodiment. It is sectional drawing which shows the structure of a reference example. It is a figure which shows the characteristic of 1st Embodiment and a reference example. It is sectional drawing which shows the structure of the compound semiconductor device which concerns on 2nd Embodiment. It is sectional drawing which shows the manufacturing method of the compound semiconductor device which concerns on 2nd Embodiment to process order. FIG. 5B is a cross-sectional view illustrating the method of manufacturing the compound semiconductor device in the order of steps, following FIG. 5A. FIG. 5B is a cross-sectional view showing the method of manufacturing the compound semiconductor device in order of processes, following FIG. 5B. It is sectional drawing which shows the structure of the compound semiconductor device which concerns on 3rd Embodiment. It is sectional drawing which shows the manufacturing method of the compound semiconductor device which concerns on 3rd Embodiment to process order. FIG. 7B is a cross-sectional view illustrating the method of manufacturing the compound semiconductor device in order of processes subsequent to FIG. 7A. It is a figure which shows the discrete package which concerns on 4th Embodiment. It is a connection diagram which shows the PFC circuit which concerns on 5th Embodiment. It is a connection diagram which shows the power supply device which concerns on 6th Embodiment. It is a connection diagram which shows the amplifier which concerns on 7th Embodiment.

  Hereinafter, embodiments will be described in detail with reference to the accompanying drawings.

(First embodiment)
First, the first embodiment will be described. The first embodiment is an example of a GaN-based HEMT. FIG. 1 is a cross-sectional view showing the structure of the compound semiconductor device according to the first embodiment.

  In the first embodiment, as shown in FIG. 1, a carrier supply layer 102 is formed above the channel layer 101, and a gate electrode 103, a source electrode 104, and a drain electrode 105 are formed above the carrier supply layer 102. The source electrode 104 and the drain electrode 105 are in ohmic contact with the carrier supply layer 102. A metal film 106 that is electrically connected to the drain electrode 105 and is not electrically connected to the channel layer 101 and the carrier supply layer 102 is formed at a position sandwiching the drain electrode 105 with the gate electrode 103 in plan view. The lower surface of the metal film 106 is positioned below the upper surface of the channel layer 101 immediately below the gate electrode 103.

  In the first embodiment, when a voltage is supplied to the drain electrode 105, this voltage is also supplied to the metal film 106. For this reason, the electric field also spreads from the lower end of the metal film 106 on the gate electrode 103 side, and the electric field tends to concentrate in the region on the drain electrode 105 side in the gate electrode 103. Therefore, PAE, particularly PAE during high frequency operation is improved. Further, since a depletion layer is easily formed in a pinch-off state, a short channel effect is hardly generated.

  Here, the operation of the first embodiment will be further described in comparison with a reference example. FIG. 2 is a sectional view showing the structure of a reference example. In the first reference example, as shown in FIG. 2A, a drain electrode 115 is provided in place of the drain electrode 105 and the metal film 106 in the first embodiment. The entire drain electrode 115 is above the carrier supply layer 102, and in the gate length direction, the size of the drain electrode 115 matches the sum of the size of the drain electrode 105 and the size of the metal film 106. In the second reference example, as shown in FIG. 2B, a gate electrode 113 is provided instead of the gate electrode 103 in the first reference example. In the gate length direction, the dimension of the gate electrode 113 is half of the dimension of the gate electrode 103.

  The relationship between the gate length Lg and the effective gate length Leff in each of the first embodiment, the first reference example, and the second reference example is schematically shown in FIG. FIG. 3B schematically shows the relationship between the input power Pin and the PAE in each of the first embodiment, the first reference example, and the second reference example. That is, the gate length Lg matches between the first embodiment and the first reference example, and the effective gate length Leff of the first embodiment is smaller than the effective gate length Leff of the first reference example. The effective gate length Leff is approximately the same between the first embodiment and the second reference example, and the gate length Lg of the second reference example is half the gate length Lg of the first embodiment. Therefore, as shown in FIG. 3B, in the first embodiment and the second reference example, the electric field concentrates in the region on the drain electrode side in the gate electrode 103 as compared with the first reference example. Easy and high efficiency is obtained. Also. In the first embodiment, since the gate length Lg is large compared to the second reference example, the gate electrode can be formed with a high yield, and the short channel effect can be suppressed.

(Second Embodiment)
Next, a second embodiment will be described. The second embodiment is an example of a GaN-based HEMT. FIG. 4 is a diagram illustrating the structure of the compound semiconductor device according to the second embodiment.

In the second embodiment, as illustrated in FIG. 4A, the buffer layer 212 is formed on the substrate 211, and the channel layer 201 is formed on the buffer layer 212. A spacer layer 213 is formed on the channel layer 201, a carrier supply layer 202 is formed on the spacer layer 213, and a cap layer 214 is formed on the carrier supply layer 202. The substrate 211 is, for example, a SiC substrate. The buffer layer 212 is an AlN layer, for example, and is an example of a compound semiconductor layer. The channel layer 201 is, for example, an i-GaN layer having a thickness of about 3 μm and not intentionally doped with impurities. The spacer layer 213 is, for example, an i-AlGaN layer having a thickness of about 5 nm and not intentionally doped with impurities. The carrier supply layer 202 is an n-type n-AlGaN layer having a thickness of about 30 nm, for example. The carrier supply layer 202 is doped with, for example, Si as an n-type impurity at a concentration of about 5 × 10 ¹⁸ cm ⁻³ . The cap layer 214 is an n-type n-GaN layer having a thickness of about 10 nm, for example. The cap layer 214 is doped with, for example, Si as an n-type impurity at a concentration of about 5 × 10 ¹⁸ cm ⁻³ .

  An element isolation region 215 that defines an element region is formed in a stacked body of the channel layer 201, the spacer layer 213, the carrier supply layer 202, and the cap layer 214. In the element region, an opening 216 and an opening 217 are formed in the cap layer 214, a source electrode 204 is formed in the opening 216, and a drain electrode 205 is formed in the opening 217. The source electrode 204 and the drain electrode 205 are in ohmic contact with the carrier supply layer 202. In the element region, an opening 218 is formed in the cap layer 214, the carrier supply layer 202, the spacer layer 213, and the channel layer 201 at a position sandwiching the drain electrode 205 with the source electrode 204 in plan view. The lower surface of the opening 218 is positioned below the upper surface of the channel layer 201 between the source electrode 204 and the drain electrode 205. For example, the opening 218 reaches the lower surface of the channel layer 201. A metal film 206 electrically connected to the drain electrode 205 is formed in the opening 218. For example, the metal film 206 contains Al, preferably includes an Al film, and is in direct contact with the channel layer 201 and the carrier supply layer 202. In the present embodiment, the metal film 206 is ensured to be highly non-conductive with the channel layer 201, the spacer layer 213, and the carrier supply layer 202. That is, the metal film 206 is not in ohmic contact or Schottky contact with the channel layer 201, the spacer layer 213, and the carrier supply layer 202.

  An insulating film 219 that covers the source electrode 204, the drain electrode 205, and the metal film 206 is formed on the cap layer 214. In the insulating film 219, an opening 220 is formed between the source electrode 204 and the drain electrode 205, and a gate electrode 203 that is in Schottky contact with the cap layer 214 is provided through the opening 220. . An insulating film 221 that covers the gate electrode 203 is formed over the insulating film 219. The material of the insulating film 219 and the insulating film 221 is not particularly limited, and for example, a silicon nitride film is used. For example, the thickness of the insulating film 219 is approximately 10 nm to 5000 nm (for example, 100 nm).

  In the second embodiment, when a voltage is supplied to the drain electrode 205, this voltage is also supplied to the metal film 206. For this reason, the electric field also spreads from the lower end of the metal film 206 on the gate electrode 203 side, and the electric field tends to concentrate in the region on the drain electrode 205 side in the gate electrode 203. Therefore, PAE, particularly PAE during high frequency operation is improved. Further, since a depletion layer is easily formed in a pinch-off state, a short channel effect is hardly generated.

  4B, an insulating film 222 may be formed between the metal film 206 and the channel layer 201, the spacer layer 213, and the carrier supply layer 202.

  Next, a method for manufacturing a compound semiconductor device according to the second embodiment will be described. 5A to 5C are cross-sectional views illustrating the method of manufacturing the compound semiconductor device according to the second embodiment in the order of steps.

  First, as shown in FIG. 5A (a), a buffer layer 212, a channel layer 201, a spacer layer 213, a carrier supply layer 202, and a cap layer 214 are formed on a substrate 211. The buffer layer 212, the channel layer 201, the spacer layer 213, the carrier supply layer 202, and the cap layer 214 can be formed by, for example, a metal organic vapor phase epitaxy (MOVPE) method.

In forming these compound semiconductor layers, for example, a mixed gas of trimethylaluminum (TMA) gas that is an Al source, trimethylgallium (TMG) gas that is a Ga source, and ammonia (NH ₃ ) gas that is an N source is used. At this time, whether or not trimethylaluminum gas and trimethylgallium gas are supplied and the flow rate are appropriately set according to the composition of the compound semiconductor layer to be grown. The flow rate of ammonia gas, which is a common material for each compound semiconductor layer, is, for example, about 100 ccm to 10 LM. Further, for example, the growth pressure is about 50 Torr to 300 Torr, and the growth temperature is about 1000 ° C. to 1200 ° C. Further, when growing an n-type compound semiconductor layer (for example, the carrier supply layer 202 and the cap layer 214), for example, SiH ₄ gas containing Si is added to the mixed gas at a predetermined flow rate, and Si is added to the compound semiconductor layer. Doping. The doping concentration of Si is about 1 × 10 ¹⁸ cm ^{−3 to} about 1 × 10 ²⁰ cm ⁻³ , for example, about 5 × 10 ¹⁸ cm ⁻³ .

  Next, as shown in FIG. 5A (b), an element isolation region 215 that defines an element region in the cap layer 214, the carrier supply layer 202, the spacer layer 213, and the channel layer 201 is formed. In the formation of the element isolation region 215, for example, a photoresist pattern exposing the region where the element isolation region 215 is to be formed is formed on the cap layer 214, and ion implantation of Ar or the like is performed using this pattern as a mask. Dry etching using a chlorine-based gas may be performed using this pattern as an etching mask.

  Thereafter, as shown in FIG. 5A (c), a region where the source electrode 204 is to be formed and a region where the drain electrode 205 is to be formed are exposed, and a resist pattern 251 covering the other region is formed on the cap layer 214. To do. Subsequently, the opening 216 and the opening 217 are formed in the cap layer 214 by dry etching using the resist pattern 251 as a mask.

  Next, as shown in FIG. 5B (d), the resist pattern 251 is removed, the source electrode 204 is formed in the opening 216, and the drain electrode 205 is formed in the opening 217. The source electrode 204 and the drain electrode 205 can be formed by, for example, a lift-off method. That is, a region where the source electrode 204 is to be formed and a region where the drain electrode 205 is to be formed are exposed, and a photoresist pattern covering the other region is formed, and a metal film is formed by vapor deposition using this pattern as a growth mask. Then, the pattern is removed together with the metal film thereon. In the formation of the metal film, for example, the Al film is formed after the Ti film is formed. Next, for example, heat treatment is performed at 400 ° C. to 900 ° C. (for example, 580 ° C.) in a nitrogen atmosphere to establish ohmic characteristics.

  After the formation of the source electrode 204 and the drain electrode 205, as shown in FIG. 5B (e), a region where the metal film 206 is to be formed is exposed, and a resist pattern 252 covering the other region is used as the source electrode 204 and the drain electrode. 205 and the cap layer 214. Thereafter, openings 218 are formed in the cap layer 214, the carrier supply layer 202, the spacer layer 213, and the channel layer 201 by dry etching using the resist pattern 252 as a mask.

  Subsequently, as shown in FIG. 5B (f), the resist pattern 252 is removed, and a metal film 206 is formed in the opening 218. The metal film 206 can be formed by, for example, a lift-off method. That is, a region where the metal film 206 is to be formed is exposed, a photoresist pattern covering the other region is formed, and a metal film is formed by vapor deposition using this pattern as a growth mask. Remove with membrane. In the formation of the metal film, for example, the Al film is formed after the Ti film is formed.

  After the formation of the metal film 206, the insulating film 219 covering the source electrode 204, the drain electrode 205, and the metal film 206 is capped as shown in FIG. 5C (g) without performing heat treatment that establishes ohmic characteristics. Form on layer 214. The insulating film 219 can be formed by, for example, a chemical vapor deposition (CVD) method, an atomic layer deposition (ALD) method, or a sputtering method.

  Next, as illustrated in FIG. 5C (h), an opening 220 is formed in a region where the gate electrode 203 of the insulating film 219 is to be formed. The opening 220 can be formed by dry etching, for example. The opening 220 may be formed by wet etching or ion milling. Thereafter, the gate electrode 203 is formed in the opening 220. The gate electrode 203 can be formed by, for example, a lift-off method. That is, a photoresist pattern exposing a region where the gate electrode 203 is to be formed is formed, a metal film is formed by vapor deposition using this pattern as a growth mask, and the pattern is removed together with the metal film thereon. In the formation of the metal film, for example, the Au film is formed after the Ni film is formed. Subsequently, for example, heat treatment is performed at 100 ° C. to 500 ° C. (for example, 290 ° C.) to establish Schottky characteristics.

  After the gate electrode 203 is formed, an insulating film 221 that covers the gate electrode 203 is formed over the insulating film 219. As with the insulating film 219, the insulating film 221 can be formed by, for example, a CVD method, an ALD method, or a sputtering method.

  And a protective film, wiring, etc. are formed as needed and a compound semiconductor device is completed. As described above, in this embodiment, after the formation of the metal film 206, heat treatment that establishes ohmic characteristics between the metal film 206, the channel layer 201, the spacer layer 213, and the carrier supply layer 202 is not performed. Therefore, although the metal film 206 is in direct contact with the channel layer 201 or the like, neither the ohmic contact nor the Schottky contact is made with the channel layer 201 or the like. For example, the state of the interface between the metal film 206 and the channel layer 201 is maintained as it was when the metal film 206 was formed.

  When the insulating film 222 is included as shown in FIG. 4B, for example, the insulating film 222 may be formed between the formation of the opening 218 and the formation of the metal film 206.

(Third embodiment)
Next, a third embodiment will be described. The third embodiment is an example of a GaN-based HEMT. FIG. 6 is a diagram illustrating the structure of the compound semiconductor device according to the third embodiment.

  In the third embodiment, as shown in FIG. 6A, an opening 316 is formed instead of the opening 216 in the second embodiment, and the source electrode 304 is placed in the opening 316 instead of the source electrode 204. Is formed. The source electrode 304 is in ohmic contact with the carrier supply layer 202. In the element region, an opening 318 is formed in the cap layer 214, the carrier supply layer 202, the spacer layer 213, and the channel layer 201 at a position sandwiching the source electrode 304 with the drain electrode 205 in plan view. The lower surface of the opening 318 is located below the upper surface of the channel layer 201 between the source electrode 304 and the drain electrode 205. For example, the opening 318 reaches the lower surface of the channel layer 201. A metal film 306 electrically connected to the source electrode 304 is formed in the opening 318. For example, the metal film 306 contains Al, preferably includes an Al film, and is in direct contact with the channel layer 201 and the carrier supply layer 202. In this embodiment, the metal film 306 is ensured to be highly non-conductive with the channel layer 201, the spacer layer 213, and the carrier supply layer 202. That is, the metal film 306 is not in ohmic contact or Schottky contact with the channel layer 201, the spacer layer 213, and the carrier supply layer 202. Other configurations are the same as those of the second embodiment.

  Also in the third embodiment, when a voltage is supplied to the drain electrode 205, this voltage is also supplied to the metal film 206. For this reason, the electric field also spreads from the lower end of the metal film 206 on the gate electrode 203 side, and the electric field tends to concentrate in the region on the drain electrode 205 side in the gate electrode 203. Therefore, PAE, particularly PAE during high frequency operation is improved. Further, since a depletion layer is easily formed in a pinch-off state, a short channel effect is hardly generated.

  Furthermore, in the third embodiment, an electric field concentration occurs on the drain electrode 205 side at the end of the gate electrode 203 due to the voltage applied to the drain electrode 205. Since the region where the electric field concentration at the gate electrode end occurs is narrower than in the second embodiment, the drain electrode voltage can be more efficiently linked to the improvement of PAE.

  6B, an insulating film 222 may be formed between the metal film 206 and the channel layer 201, the spacer layer 213, and the carrier supply layer 202, and the metal film 306 and the channel layer may be formed. An insulating film 322 may be formed between the spacer 201, the spacer layer 213, and the carrier supply layer 202.

  The metal film 206 and the metal film 306 need not be in contact with the buffer layer 212.

  Next, a method for manufacturing a compound semiconductor device according to the third embodiment will be described. 7A to 7B are cross-sectional views illustrating the method of manufacturing the compound semiconductor device according to the third embodiment in the order of steps.

  First, as shown in FIG. 7A (a), processing up to the formation of the element isolation region 215 is performed in the same manner as in the second embodiment. Next, as shown in FIG. 7A (b), a region where the source electrode 304 is to be formed and a region where the drain electrode 205 is to be formed are exposed, and a resist pattern 351 is formed on the cap layer 214 to cover the other regions. To do. Thereafter, an opening 316 and an opening 217 are formed in the cap layer 214 by dry etching using the resist pattern 351 as a mask.

  Subsequently, as shown in FIG. 7A (c), the resist pattern 351 is removed, the source electrode 304 is formed in the opening 316, and the drain electrode 205 is formed in the opening 217. The source electrode 304 and the drain electrode 205 can be formed by, for example, a lift-off method. Also in the formation of the source electrode 304 and the drain electrode 205, heat treatment is performed to establish ohmic characteristics.

  After the formation of the source electrode 304 and the drain electrode 205, as shown in FIG. 7B (d), the region where the metal film 206 is to be formed and the region where the metal film 306 is to be formed are exposed and the other regions are covered. A resist pattern 352 is formed on the source electrode 304, the drain electrode 205, and the cap layer 214. Next, an opening 218 and an opening 318 are formed in the cap layer 214, the carrier supply layer 202, the spacer layer 213, and the channel layer 201 by dry etching using the resist pattern 352 as a mask.

  Thereafter, as shown in FIG. 7B (e), the resist pattern 352 is removed, a metal film 206 is formed in the opening 218, and a metal film 306 is formed in the opening 318. The metal film 206 and the metal film 306 can be formed by, for example, a lift-off method.

  After the formation of the metal film 206 and the metal film 306, without performing a heat treatment that establishes ohmic characteristics, as shown in FIG. 7B (f), after the formation of the insulating film 219, as in the second embodiment. Perform the process.

  And a protective film, wiring, etc. are formed as needed and a compound semiconductor device is completed. As described above, in this embodiment, the ohmic characteristics of the metal film 206 and the metal film 306, the channel layer 201, the spacer layer 213, and the carrier supply layer 202 are established after the metal film 206 and the metal film 306 are formed. No heat treatment is performed. Therefore, although the metal film 206 and the metal film 306 are in direct contact with the channel layer 201 and the like, neither ohmic contact nor Schottky contact is made with the channel layer 201 or the like. For example, the state of the interface between the metal film 206 and the metal film 306 and the channel layer 201 is maintained as it was when the metal film 206 and the metal film 306 were formed.

  When the insulating film 222 is included as shown in FIG. 6B, for example, the insulating film 222 may be formed between the formation of the opening 218 and the formation of the metal film 206 and the metal film 306. .

The resistance between the metal film 106 and the channel layer 101 and the carrier supply layer 102, and the resistivity between the metal film 206 and the metal film 306 and the channel layer 201, the spacer layer 213, and the carrier supply layer 202 are 1 × It is preferably 10 ⁻¹ (Ω · cm ² ) or more. This is because when the resistivity is less than 1 × 10 ⁻¹ (Ω · cm ² ), a current path is easily formed in the lower layer portion of the channel layer, and desired characteristics may not be obtained. Because.

  The presence or absence of heat treatment for establishing ohmic contact after the formation of the metal film 106 and the presence or absence of heat treatment for establishing ohmic contact after the formation of the metal film 206 and the metal film 306 are, for example, a transmission electron microscope (TEM). Judgment can be made based on observation of these interfaces using a transmission electron microscope. That is, the determination can be made based on the presence or absence of a change in the interface accompanying the heat treatment.

(Fourth embodiment)
The fourth embodiment relates to a GaN-based HEMT discrete package. FIG. 8 is a diagram illustrating a discrete package according to the fourth embodiment.

  In the fourth embodiment, as shown in FIG. 8, the back surface of the GaN-based HEMT HEMT chip 1210 of either the second or third embodiment is land (die pad) using a die attach agent 1234 such as solder. 1233 is fixed. Further, a wire 1235d such as an Al wire is connected to the drain pad 1226d to which the drain electrode 205 is connected, and the other end of the wire 1235d is connected to a drain lead 1232d integrated with the land 1233. A wire 1235 s such as an Al wire is connected to the source pad 1226 s connected to the source electrode 204 or 304, and the other end of the wire 1235 s is connected to a source lead 1232 s independent of the land 1233. A wire 1235g such as an Al wire is connected to the gate pad 1226g connected to the gate electrode 203, and the other end of the wire 1235g is connected to a gate lead 1232g independent of the land 1233. The land 1233, the HEMT chip 1210, and the like are packaged with the mold resin 1231 so that a part of the gate lead 1232g, a part of the drain lead 1232d, and a part of the source lead 1232s protrude.

  Such a discrete package can be manufactured as follows, for example. First, the HEMT chip 1210 is fixed to the land 1233 of the lead frame using a die attach agent 1234 such as solder. Next, by bonding using wires 1235g, 1235d, and 1235s, the gate pad 1226g is connected to the gate lead 1232g of the lead frame, the drain pad 1226d is connected to the drain lead 1232d of the lead frame, and the source pad 1226s is connected to the source of the lead frame. Connect to lead 1232s. Thereafter, sealing using a mold resin 1231 is performed by a transfer molding method. Subsequently, the lead frame is separated.

(Fifth embodiment)
Next, a fifth embodiment will be described. The fifth embodiment relates to a PFC (Power Factor Correction) circuit including a GaN-based HEMT. FIG. 9 is a connection diagram illustrating a PFC circuit according to the fifth embodiment.

  The PFC circuit 1250 is provided with a switch element (transistor) 1251, a diode 1252, a choke coil 1253, capacitors 1254 and 1255, a diode bridge 1256, and an AC power supply (AC) 1257. The drain electrode of the switch element 1251 is connected to the anode terminal of the diode 1252 and one terminal of the choke coil 1253. A source electrode of the switch element 1251 is connected to one terminal of the capacitor 1254 and one terminal of the capacitor 1255. The other terminal of the capacitor 1254 and the other terminal of the choke coil 1253 are connected. The other terminal of the capacitor 1255 and the cathode terminal of the diode 1252 are connected. A gate driver is connected to the gate electrode of the switch element 1251. An AC 1257 is connected between both terminals of the capacitor 1254 via a diode bridge 1256. A direct current power supply (DC) is connected between both terminals of the capacitor 1255. In this embodiment, the GaN-based HEMT according to any one of the second and third embodiments is used for the switch element 1251.

  In manufacturing the PFC circuit 1250, the switch element 1251 is connected to the diode 1252, the choke coil 1253, and the like using, for example, solder.

(Sixth embodiment)
Next, a sixth embodiment will be described. The sixth embodiment relates to a power supply device including a GaN-based HEMT. FIG. 10 is a connection diagram illustrating the power supply device according to the sixth embodiment.

  The power supply device is provided with a high-voltage primary circuit 1261 and a low-voltage secondary circuit 1262, and a transformer 1263 disposed between the primary circuit 1261 and the secondary circuit 1262.

  The primary circuit 1261 is provided with an inverter circuit connected between both terminals of the PFC circuit 1250 according to the fifth embodiment and the capacitor 1255 of the PFC circuit 1250, for example, a full bridge inverter circuit 1260. The full bridge inverter circuit 1260 is provided with a plurality (here, four) of switch elements 1264a, 1264b, 1264c, and 1264d.

  The secondary side circuit 1262 is provided with a plurality (three in this case) of switch elements 1265a, 1265b, and 1265c.

  In this embodiment, the switch element 1251 of the PFC circuit 1250 and the switch elements 1264a, 1264b, 1264c, and 1264d of the full bridge inverter circuit 1260 that constitute the primary circuit 1261 are either of the second and third embodiments. A GaN-based HEMT is used. On the other hand, normal MIS type FETs (field effect transistors) using silicon are used for the switch elements 1265a, 1265b, and 1265c of the secondary side circuit 1262.

(Seventh embodiment)
Next, a seventh embodiment will be described. The seventh embodiment relates to an amplifier including a GaN-based HEMT. FIG. 11 is a connection diagram illustrating an amplifier according to the seventh embodiment.

  The amplifier is provided with a digital predistortion circuit 1271, mixers 1272a and 1272b, and a power amplifier 1273.

  The digital predistortion circuit 1271 compensates for nonlinear distortion of the input signal. The mixer 1272a mixes the input signal compensated for nonlinear distortion and the AC signal. The power amplifier 1273 includes the GaN-based HEMT according to any of the second and third embodiments, and amplifies the input signal mixed with the AC signal. In the present embodiment, for example, by switching the switch, the signal on the output side can be mixed with the AC signal by the mixer 1272b and sent to the digital predistortion circuit 1271. This amplifier can be used as a high-frequency amplifier or a high-power amplifier.

  Note that the composition of the compound semiconductor layer used in the compound semiconductor stacked structure is not particularly limited, and for example, GaN, AlN, InN, or the like can be used. These mixed crystals can also be used.

  In any of the embodiments, a silicon carbide (SiC) substrate, a sapphire substrate, a silicon substrate, a GaN substrate, a GaAs substrate, or the like may be used as the substrate. The substrate may be conductive, semi-insulating, or insulating.

  Further, the structures of the gate electrode, the source electrode, and the drain electrode are not limited to those of the above-described embodiment. For example, these may be composed of a single layer. Moreover, these formation methods are not limited to the lift-off method. Furthermore, if ohmic characteristics can be obtained, the heat treatment after the formation of the source electrode and the drain electrode may be omitted. The gate electrode may contain Pd and / or Pt in addition to Ni and Au.

  Hereinafter, various aspects of the present invention will be collectively described as supplementary notes.

(Appendix 1)
A channel layer;
A carrier supply layer formed above the channel layer;
A gate electrode, a source electrode and a drain electrode formed above the carrier supply layer;
A metal film that is electrically connected to the drain electrode and is sandwiched between the drain electrode and the gate electrode in a plan view;
Have
The lower surface of the metal film is located below the upper surface of the channel layer immediately below the gate electrode.

(Appendix 2)
The compound semiconductor device according to appendix 1, wherein the lower surface of the metal film reaches the lower surface of the channel layer.

(Appendix 3)
The channel layer and the carrier supply layer contain a GaN-based compound semiconductor,
The compound semiconductor device according to appendix 1 or 2, wherein the metal film contains Al.

(Appendix 4)
The compound semiconductor device according to any one of appendices 1 to 3, wherein the channel layer, the carrier supply layer, and the metal film are in direct contact with each other.

(Appendix 5)
The compound semiconductor device according to appendix 4, wherein the metal film is not in ohmic contact or Schottky contact with the channel layer and the carrier supply layer.

(Appendix 6)
4. The compound semiconductor device according to claim 1, further comprising an insulating film between the channel layer and the carrier supply layer and the metal film.

(Appendix 7)
The compound semiconductor device according to any one of appendices 1 to 6, wherein the metal film is not heat-treated.

(Appendix 8)
8. The compound semiconductor device according to any one of appendices 1 to 7, further comprising a compound semiconductor layer formed below the channel layer.

(Appendix 9)
A second metal film electrically connected to the source electrode, formed at a position sandwiching the source electrode with the gate electrode in plan view, and non-conductive with the channel layer and the carrier supply layer; Item 8. The compound semiconductor device according to appendix 8.

(Appendix 10)
A power supply device comprising the compound semiconductor device according to any one of appendices 1 to 9.

(Appendix 11)
An amplifier comprising the compound semiconductor device according to any one of appendices 1 to 9.

(Appendix 12)
Forming a carrier supply layer above the channel layer;
Forming a gate electrode, a source electrode and a drain electrode above the carrier supply layer;
Forming a metal film electrically connected to the drain electrode at a position sandwiching the drain electrode between the gate electrode and the channel layer and the carrier supply layer in a plan view; and
Have
A method of manufacturing a compound semiconductor device, wherein the lower surface of the metal film is positioned below the upper surface of the channel layer immediately below the gate electrode.

(Appendix 13)
13. The method of manufacturing a compound semiconductor device according to appendix 12, wherein the lower surface of the metal film reaches the lower surface of the channel layer.

(Appendix 14)
The channel layer and the carrier supply layer contain a GaN-based compound semiconductor,
14. The method of manufacturing a compound semiconductor device according to appendix 12 or 13, wherein the metal film contains Al.

(Appendix 15)
15. The method of manufacturing a compound semiconductor device according to any one of appendices 12 to 14, wherein the metal film is formed so as to be in direct contact with the channel layer and the carrier supply layer.

101, 201: Channel layer 102, 202: Carrier supply layer 103, 203: Gate electrode 104, 204: Source electrode 105, 205: Drain electrode 106, 206, 306: Metal film

Claims (10)

A channel layer;
A carrier supply layer formed above the channel layer;
A gate electrode, a source electrode and a drain electrode formed above the carrier supply layer;
A metal film that is electrically connected to the drain electrode and is sandwiched between the drain electrode and the gate electrode in a plan view;
Have
The lower surface of the metal film is located below the upper surface of the channel layer immediately below the gate electrode.   The compound semiconductor device according to claim 1, wherein a lower surface of the metal film reaches a lower surface of the channel layer. The channel layer and the carrier supply layer contain a GaN-based compound semiconductor,
The compound semiconductor device according to claim 1, wherein the metal film contains Al.   4. The compound semiconductor device according to claim 1, wherein the channel layer, the carrier supply layer, and the metal film are in direct contact with each other. 5. 5. The compound semiconductor device according to claim 1, wherein the metal film is not in ohmic contact or Schottky contact with the channel layer and the carrier supply layer. 6. Forming a carrier supply layer above the channel layer;
Forming a gate electrode, a source electrode and a drain electrode above the carrier supply layer;
Forming a metal film electrically connected to the drain electrode at a position sandwiching the drain electrode between the gate electrode and the channel layer and the carrier supply layer in a plan view; and
Have
A method of manufacturing a compound semiconductor device, wherein the lower surface of the metal film is positioned below the upper surface of the channel layer immediately below the gate electrode. The method of manufacturing a compound semiconductor device according to claim 6 , wherein the lower surface of the metal film reaches the lower surface of the channel layer. The channel layer and the carrier supply layer contain a GaN-based compound semiconductor,
The metal film production method of a compound semiconductor device according to claim 6 or 7, characterized in that it contains Al. The method of manufacturing a compound semiconductor device according to any one of claims 6 to 8, characterized by forming the metal film in direct contact with the channel layer and the carrier supply layer. 10. The method of manufacturing a compound semiconductor device according to claim 6, wherein the metal film is not in ohmic contact or Schottky contact with the channel layer and the carrier supply layer. 11.

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