JP2016119463A - High-electron-mobility transistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-electron-mobility transistor that includes field plates.SOLUTION: A high-electron-mobility transistor 100 includes a first semiconductor material 105 and a second semiconductor material 110 disposed to form a heterojunction 115 at which a two-dimensional electron gas 120 arises, a source electrode 125, a drain electrode 130, and a gate electrode 135. The gate electrode 135 is disposed to regulate conduction in the heterojunction 115 between the source electrode 125 and the drain electrode 130. The gate electrode 135 has a drain-side edge. A gate-connected field plate 140 is disposed above the drain-side edge of the gate electrode 135 and extends laterally toward a drain. A source-connected field plate 145 is disposed above a drain-side edge of the gate-connected field plate 140 and extends laterally toward the drain.SELECTED DRAWING: Figure 1

Description

CROSS REFERENCE TO RELATED APPLICATIONS Under United States Patent Act Section 119, this application claims priority to US Provisional Patent Application No. 61 / 921,140, filed December 27, 2013. The entire contents are hereby incorporated by reference.

TECHNICAL FIELD This specification relates to high electron mobility transistors, and more particularly to the design of field plates and other components of high electron mobility transistors.

  A high electron mobility transistor (HEMT), also called a heterostructure field effect transistor (HFET), is a field effect transistor including a heterojunction that functions as a transistor channel. In HEMTs, the conduction of the “two-dimensional electron gas” in the heterojunction channel is regulated by the gate.

  Despite being an invention in the late 1970s and the commercial success of HEMTs in applications such as, for example, millimeter waveband switches, commercialization of some HEMTs (eg, gallium nitride type HEMTs for power electronics) Development is slower than expected.

  A field plate is a conductive element commonly used to change the appearance of an electric field in a semiconductor device. In general, the field plate is designed to reduce the peak value of the electric field in the semiconductor device, thereby improving the breakdown voltage and lifetime of the device including the field plate.

  In HEMTs (eg, gallium nitride type HEMTs), the field plate is further believed to reduce parasitic effects commonly referred to as “dc-rf dispersion” or “drain current collapse”. During operation at a relatively high frequency (eg, radio frequency), devices that experience this parasitic effect reach a drain current level that is less than the drain current level reached during direct current (dc) operation. The parasitic effect is considered to be caused by a relatively slow response time of the interface state.

  Experimental studies on the length of field plates in HEMT have been conducted. For example, researchers have described that in some HEMT devices, the breakdown voltage approaches a maximum value (ie, “saturates”) after the gate-connected field plate extends a certain distance toward the drain. doing. In addition, the extension of the gate connection field plate beyond the saturation length towards the drain has little or no improvement in breakdown voltage. As the gate connection field plate approaches the drain, the gate input capacitance increases, so it is recommended that the extension of the gate connection field plate toward the drain should be limited if the saturation length is reached. Has been.

  A high electron mobility transistor including a field plate is described. In the first embodiment, the HEMT includes a first semiconductor material and a second semiconductor material disposed so as to form a heterojunction at a position where a two-dimensional electron gas is generated, a source electrode, and a drain electrode. And a gate electrode, wherein a two-dimensional electron gas is generated at the heterojunction, the gate electrode is arranged to regulate conduction at the heterojunction between the source electrode and the drain electrode, and the gate is connected to the drain side An end, a gate connection field plate disposed above the drain side end of the gate electrode and extending laterally toward the drain, and disposed above the drain side end of the gate connection field plate. And a second field plate extending laterally toward the drain.

  In the second embodiment, the HEMT includes a first semiconductor material and a second semiconductor material disposed so as to form a heterojunction at a position where a two-dimensional electron gas is generated, a source electrode, and a drain electrode. And a gate electrode, wherein the gate electrode is disposed to regulate conduction at a heterojunction between the source electrode and the drain electrode, the gate includes a drain side end, and a drain side end of the gate electrode And a gate connection field plate extending laterally toward the drain, and a gate connection field plate extending above the drain side end of the gate connection field plate and extending laterally toward the drain. Two field plates. In the off state, the first electric field at the heterojunction extends the drain section from the drain side end of the gate connection field plate and the second electric field at the heterojunction extends from the drain side end of the second field plate to the source section. And the first electric field is applied only at a source-drain potential difference that exceeds the source-drain potential difference where the charge carriers are depleted from a portion of the heterojunction in the vicinity of the drain side end of the second field plate. First, it overlaps with the second electric field.

  In the third embodiment, the semiconductor device includes a substrate, a first active layer disposed above the substrate, and a lateral conductive channel generated between the first active layer and the second active layer. A second active layer disposed on the first active layer, source and drain electrodes, a first passivation layer disposed above the second active layer, and disposed above the first passivation layer. A gate electrode, a second passivation layer disposed above the gate electrode, a gate field plate extending a first distance beyond the end of the gate electrode closest to the drain electrode, and disposed above the first metal pattern. A third passivation layer provided and a second end extending beyond the end of the gate field plate electrically connected to one of the source and gate electrodes and closest to the drain electrode by a second distance. 2 Including a field plate. The end of the second field plate is spaced a third distance from the first extension of the drain electrode adjacent to the second field plate. For a first drain bias greater than the absolute value of the available gate amplitude above the smaller threshold, a gradual increase in the electric field at the gate edge when a portion of the lateral conduction channel below the gate electrode is pinched off. The first distance is selected so that becomes a peak.

  Each of the first, second, and third embodiments may include one or more of the following features.

  In the off-state and with the source-drain potential difference exceeding the absolute value of the gate amplitude, the charge carriers are depleted from part of the heterojunction near the drain side end of the gate connection field plate, and the charge carriers are depleted. Is effective in saturating the lateral electric field at the heterojunction in the vicinity of the drain side end of the gate electrode. Charge carriers can be depleted with a source-drain potential difference of 2-5 times the absolute value of the gate amplitude. For example, charge carriers are depleted with a source-drain potential difference of 3 to 4 times the absolute value of the gate amplitude.

  In the off state and with the source-drain potential difference exceeding the potential difference at which the charge carriers are depleted from that portion of the heterojunction in the vicinity of the drain side end of the gate connection field plate, the charge carriers are in contact with the second field plate. Can be depleted from part of the heterojunction in the vicinity of the drain side end of the gate, and charge carrier depletion is effective in saturating the lateral electric field in the heterojunction near the drain side end of the gate connection field plate Is. For example, the potential difference in which charge carriers are depleted from a part of the heterojunction in the vicinity of the drain side end of the second field plate is caused by the charge carrier from a part of the heterojunction in the vicinity of the drain side end of the gate connection field plate. Is 3 to 5 times the potential difference of depletion. For example, in the off state, the first electric field at the heterojunction extends the drain section from the drain side end of the gate connection field plate, and the second electric field at the heterojunction is from the drain side end of the second field plate. The source / drain is widened and the first electric field first exceeds the source-drain potential difference where the charge carriers are depleted from a portion of the heterojunction near the drain side end of the second field plate. It overlaps with the second electric field only in the inter-potential difference.

  The HEMT or semiconductor device may include a third field plate disposed above the drain side end of the second field plate and extending laterally toward the drain. In the off-state, the source-drain potential difference exceeds the source-drain potential difference where the charge carriers are depleted from a part of the heterojunction in the vicinity of the drain side end of the second field plate. A portion of the junction is depleted due to the longitudinal voltage difference between the heterojunction and the third field plate. The third field plate can be a source connection field plate.

  In the HEMT or semiconductor device in the off state, the first electric field at the heterojunction can extend the drain section from the drain side end of the gate connection field plate, and the second electric field at the heterojunction can be applied to the second field plate. The source section is expanded from the drain side end, and the first electric field first causes the potential difference between the source and drain where charge carriers are depleted from a part of the heterojunction in the vicinity of the drain side end of the second field plate. It overlaps with the second electric field only when the source-drain potential difference is higher. The first electric field is generated only when the source-drain potential difference exceeds the source-drain potential difference where the charge carriers are depleted from a part of the heterojunction in the vicinity of the drain side end of the second field plate. Can overlap with electric field.

  The HEMT or semiconductor device can include one or more insulating material layers above the first and second semiconductor materials, and certain sheet carrier densities can occur at the heterojunction. After reaching a steady state after long-term operation with specific operating parameters, the number of charge defects per unit area in the insulating material layer is less than the sheet carrier density. For example, the number of charge defects per unit area in the insulating material layer can be less than 10% of the sheet carrier density.

  The HEMT or semiconductor device can include GaN and AlGaN. The HEMT or semiconductor device may include an aluminum silicon nitride layer that insulates the gate electrode from the second semiconductor material.

  In the HEMT or semiconductor device in the off state, and with a source-drain potential difference exceeding the source-drain potential difference where charge carriers are depleted from a part of the heterojunction in the vicinity of the drain side end of the second field plate A part of the heterojunction in the vicinity of the drain is depleted due to a vertical voltage difference between the heterojunction and the third field plate.

  In the HEMT or semiconductor device in the off state, the source and drain electrodes may be disposed above the second active layer. The gate field plate may be defined by a first metal pattern disposed on the second passivation layer, the first metal pattern extending laterally over the entire gate electrode. The second field plate can be a source field plate defined by a second metal pattern disposed on the third passivation layer. The second metal pattern can be electrically connected to the source electrode and extends laterally above the entire first metal pattern and the end of the first metal pattern closest to the drain electrode The second distance is further extended beyond. The end of the second metal pattern may be separated from the first extension of the drain electrode adjacent to the second metal pattern by a third distance.

  The HEMT or semiconductor device may include a fourth passivation layer disposed over the second metal pattern that is a shield wrap defined by a third metal pattern disposed on the fourth passivation layer. The third metal pattern may be electrically connected to the source electrode, and the third metal pattern ends at a third distance from the second extension of the drain electrode adjacent to the third metal pattern. So that it extends laterally over the majority of the lateral conducting channels. The distance from end to end between the third metal pattern and the second extension of the drain electrode may be 2 to 6 micrometers. The thickness of the fourth passivation layer can be 0.5-2 micrometers. The first drain bias can be about 2-5 times greater than the absolute value of the available gate amplitude above the threshold. The second distance is relative to the second drain bias, which is greater than the gate edge field peaking bias provided by the gate field plate when a portion of the lateral conductive channel below the gate electrode is pinched off. It may be sufficient to provide a heading to the field plate end field. For example, the second drain bias can be about 2.5 to 10 times greater than the first drain bias. The second distance is at least a lateral depletion extension below the second metal pattern before the lateral conduction channel is vertically pinched off below the edge of the second metal pattern closest to the drain edge. It can be long enough that the part never reaches the end of the second metal pattern. The first distance can be between 1.5 and 3.5 micrometers. The second distance can be between 2.5 and 7.5 micrometers, and the third distance can be between 2 and 6 micrometers. The end-to-end distance between the gate electrode and the drain electrode can be 8-26 micrometers. The thickness of the third passivation layer can be 0.35 to 0.75 micrometers.

FIG. 1 is a schematic view of a cross section of a lateral channel HEMT. FIG. 2 is a schematic view of a cross section of a lateral channel HEMT. FIG. 3 is a schematic view of a cross section of a lateral channel HEMT. 4A and 4B are graphs that schematically represent the voltage and electric field at the heterojunction between the source and drain, respectively, of some embodiments of the HEMT in the off state. 5A and 5B are graphs that schematically represent the voltage and electric field at the heterojunction between the source and drain, respectively, of some embodiments of the HEMT in the on state. FIGS. 6A and 6B show the heterogeneity between the source and drain of some embodiments of the HEMT in the off state for fixed source and gate potentials, respectively, for various different discrete drain potential cases. It is a graph which represents roughly the voltage and electric field in junction. Same as above FIG. 7 shows the electric field at the heterojunction between the source and drain of some embodiments of the HEMT in the off state for a fixed source and gate potential, for various different discrete drain potential cases. Is a graph schematically representing FIG. 8 shows the electric field at the heterojunction between the source and drain of some embodiments of the HEMT in the off state for a fixed source and gate potential, for various different discrete drain potential cases. Is a graph schematically representing FIG. 9 schematically represents the electric field at the heterojunction of some embodiments of the HEMT in the off state for fixed source and gate potentials and for various different discrete drain potential cases. It is a graph.

  FIG. 1 is a schematic view of a cross section of a lateral channel HEMT 100. The HEMT 100 includes a first semiconductor material 105 and a second semiconductor material 110 that are in contact with each other to form a heterojunction 115. A two-dimensional electron gas 120 is generated at the heterojunction 115 due to the material properties of the semiconductor materials 105 and 110. The HEMT 100 further includes a source electrode 125, a drain electrode 130, and a gate electrode 135. The selective bias application of the gate electrode 135 adjusts the conductivity between the source electrode 125 and the drain electrode 130.

  The HEMT 100 further includes a field plate structure 135 that is layered vertically. In the illustrated embodiment, the field plate structure 135 is a dual field plate structure that includes a gate connection field plate 140 and a source connection field plate 145. The gate connection field plate 140 is electrically connected to the gate electrode 135. The source connection field plate 145 is electrically connected to the source electrode 125.

  In the illustrated embodiment, the gate electrode 135, the gate connection field plate 140, and the source connection field plate 145 each have a substantially rectangular cross section. The gate electrode 135 includes a bottom drain side end 150. The drain-side end 150 is disposed at a lateral distance d0 from the side of the source electrode 125 toward the drain electrode 130 and at a longitudinal distance d5 above the second semiconductor material 110. The drain side end portion 150 is vertically separated from the second semiconductor material 110 by the first insulating material layer 155. The gate connection field plate 140 includes a bottom drain side end 160. The drain side end portion 160 is disposed at a lateral distance d0 + d1 from the side portion of the source electrode 125 toward the drain electrode 130 and at a longitudinal distance d5 + d6 above the second semiconductor material 110. The drain-side end portion 160 is vertically separated from the second semiconductor material 110 by both the first insulating material layer 155 and the second insulating material layer 165. The source connection field plate 145 includes a bottom drain side end 170. The drain side end 170 is disposed at a lateral distance d0 + d1 + d3 from the side of the source electrode 125 toward the drain electrode 130 and a vertical distance d5 + d6 + d7 above the second semiconductor material 110. The drain side end 170 is vertically separated from the second semiconductor material 110 by the first insulating material layer 155, the second insulating material layer 165, and the third insulating material layer 175. As described further below, the electric field between each of the gate electrode 135, the gate connection field plate 140 and the source connection field plate 145, and the heterojunction 115 is subject to a respective end 150, 160 under a particular bias condition. , 170 is the largest.

  The gate electrode 135 can be electrically connected to the gate connection field plate 140 in a variety of different ways. In the illustrated embodiment, the connection between the gate electrode 135 and the gate connection field plate 140 is outside the cross section. In other embodiments, the gate electrode 135 and the gate connection field plate 140 may be formed by a single member having a generally L-shaped cross section when viewed in the illustrated embodiment.

  The source electrode 125 can be electrically connected to the source connection field plate 145 in a variety of different ways. In the illustrated embodiment, the source electrode 125 is electrically connected to the source connection field plate 145 by a source via member 180. In other implementations, the source electrode 125 may be electrically connected to the source connection field plate 145 outside the illustrated cross section.

  In the illustrated embodiment, the drain 130 is electrically connected to a set of drain via members 185, 190. The drain via members 185 and 190 extend through the third insulating material layer 175 to the same vertical level as the source connection field plate 145, and as a result, function as an extension of the drain 130. Since the via member 190 is at the same vertical level as the source connection field plate 145, it is the extension of the drain 130 closest to the source connection field plate 145. The side of the source connection field plate 145 including the bottom drain side end 170 is disposed at a lateral distance d4 from the drain via member 190 at the same vertical level. In some embodiments, the lateral distance d4 is less than or equal to the distance required to maintain the device specific lateral breakdown voltage for the device specific device lifetime. In the illustrated embodiment, the source connection field plate 145 and the drain via member 190 are covered by a fourth insulating material layer 195. The fourth insulating material layer 195 extends a distance d8 from the upper surface of the third insulating material layer 175.

  In the illustrated embodiment, both the source electrode 125 and the drain electrode 130 are mounted directly on the top surface of the second semiconductor material 110 and are in electrical contact therewith. This is not necessarily the case. For example, in some implementations, the source electrode 125 and / or the drain electrode 130 penetrates into the second semiconductor material 110. In some implementations, this penetration is deep enough that the source electrode 125 and / or the drain electrode 130 contact the heterojunction 115 or even penetrate the heterojunction 115. As another example, in some implementations, one or more interstitial adhesive metals or other conductive materials can be formed between the source electrode 125 and / or the drain electrode 130 and one or both of the semiconductor materials 105, 110. Between the two.

  In the illustrated embodiment, the gate electrode 135 is electrically isolated from the second semiconductor material 110 by a single electrically insulating layer 155 having a uniform thickness d5. This is not necessarily the case. For example, in other embodiments, multiple layers can be used to insulate the gate electrode 135 from the second semiconductor material 110. As another example, single or multiple layers with non-uniform thicknesses can be used to insulate the gate electrode 135 from the second semiconductor material 110.

Various features of the lateral channel HEMT 100 may be formed by a variety of different materials. For example, the first semiconductor material 105 can be GaN, InN, Aln, AlGaN, InGaN, AlIn—GaN. In some embodiments, the first semiconductor material 105 can further include a compound semiconductor containing arsenic, such as, for example, one or more of GaAs, InAs, AlAs, InGaAs, AlGaAs, InAlGaAs. The second semiconductor material 110 can be, for example, AlGaN, GaN, InN, Aln, InGaN, AlIn—GaN. The second semiconductor material 110 may further include a compound semiconductor containing arsenic, such as one or more of GaAs, InAs, AlAs, InGaAs, AlGaAs, InAlGaAs. The compositions of the first and second semiconductor materials 105, 110 (which may also be referred to as “active layers”) are adjusted so that the two-dimensional electron gas 120 is formed at the heterojunction 115. For example, in some embodiments, the composition of the first and second semiconductor materials 105, 110 is 10 ¹¹ to 10 ¹⁴ cm ⁻² at the heterojunction 115, for example, 5 × 10 ^{12 to} 5 × 10 ¹³ cm at the heterojunction 115. ⁻² or 8 × 10 ^{12 to} 1.2 × 10 ¹³ cm ⁻² of sheet carrier density. The semiconductor material 105, 110 may be formed over the substrate, for example, over gallium nitride, gallium arsenide, silicon carbide, sapphire, silicon, or other substrate. The semiconductor material 105 can either be in direct contact with such a substrate or there can be one or more intervening layers.

Source electrode 125, drain electrode 130, and gate electrode 135 may be formed from various conductors including metals such as, for example, Al, Ni, Ti, TiW, TiN, TiAu, TiAlMoAu, TiAlNiAu, TiAlPtAu, or the like. The first insulating material layer 155 includes, for example, aluminum oxide (Al ₂ O ₃ ), zirconium dioxide (ZrO ₂ ), aluminum nitride (Aln), hafnium oxide (HfO ₂ ), silicon dioxide (SiO ₂ ), silicon nitride ( It can be formed from a variety of dielectrics suitable for forming a gate insulator, including Si ₃ N ₄ ), aluminum silicon nitride (AlSiN), or other suitable gate dielectric material. The second, third, and fourth insulating material layers 165, 175, 195 may be formed from a variety of dielectrics including, for example, silicon nitride, silicon oxide, silicon oxynitride, or the like. The first, second, third, and fourth insulating material layers 155, 165, 175, 195 further include a second semiconductor material in which each of the layers 155, 165, 175, 195 is below. 110 or layers 155, 165, 175 may also be referred to as "passivation layers" in that they prevent or prevent the formation of surface states and / or charging.

  In some embodiments, the second, third, and fourth layers of insulating material 165, 175, 195 are made of insulating material (so that steady state is reached after prolonged operation at certain operating parameters). The quality and composition are adjusted such that the number of charge defects per area in layers 165, 175, 195 is less than the sheet carrier density at the heterojunction. In other words, the sum of the products of the three-dimensional defect density of each of the insulating material layers 165, 175, 195 and the thickness of each of the layers is less than the (two-dimensional) sheet carrier density at the heterojunction 115. For example, in some embodiments, the number of charge defects per area in the insulating material layers 165, 175, 195 is less than 20% or less than 10% of the sheet carrier density in the heterojunction 115. In some embodiments, the HEMT 100 and other HEMTs described herein include an intermediate layer, eg, an Aln intermediate layer.

  The source electrode 125 is disposed at a lateral distance from the drain electrode 130 to d2. In some embodiments, the lateral distance d2 is 5-50 micrometers, such as 9-30 micrometers. In some embodiments, the lateral distance d1 is 1-5 micrometers, such as 1.5-3.5 micrometers. In some embodiments, the thickness of the third insulating material layer 175 is 0.2-1 micrometer, such as 0.35-0.75 micrometers. In some embodiments, the lateral distance d4 is 1-8 micrometers, such as 2-6 micrometers. In some embodiments, the thickness of the fourth insulating material layer 195 is 0.4-3 micrometers, such as 0.5-2 micrometers. In some embodiments, the lateral distance d3 is 1-10 micrometers, such as 2.5-7.5 micrometers.

  FIG. 2 is a schematic diagram of a cross-section of the lateral channel HEMT 200. In addition to the semiconductor materials 105, 110, electrodes 125, 130, 135 and via members 180, 185, 190, the HEMT 200 includes a field plate structure 205 that is layered vertically. The field plate structure 205 is a triple field plate structure including not only the gate connection field plate 140 and the source connection field plate 145 but also the second source connection plate 210. The second source connection plate 210 is electrically connected to the source electrode 125. The second source connection plate 210 covers the gate electrode 135, the gate field plate 140, and the source connection field plate 145.

  In some embodiments, the second source connection plate 210 functions as a so-called “shield wrap”. As mentioned above, some HEMTs are subject to parasitic dc-rf dispersion that is believed to occur at least in part due to surface charge exchange with the high operating ambient environment. In particular, the surface states are charged and discharged with a relatively slow response time, and the high-frequency operation of the HEMT is affected. The metal shield wrap may mitigate or eliminate these effects by improving the surface level shield and preventing surface charge exchange. In some implementations, the second source connection plate 210 includes an electric field in the HEMT 200, eg, a heterojunction 115, and a bottom drain side end 170 of the source connection field plate 145 or a bottom drain of the gate connection field plate 310, for example. It functions as a field plate that reduces the peak value of the electric field between the side end portions 320 (FIG. 3). As will be described further below, in some embodiments, the second source connection plate 210 further functions to deplete the charge carriers of the heterojunction 115. In some embodiments, the second source connection plate 210 serves multiple functions, ie, as two or more shield wraps, as a field plate, and to deplete the heterojunction 115. The particular function of the second source connection plate 210 in any device will be a function of any of a number of different geometric parameters, material parameters, and operating parameters. Since the source connection plate 210 may perform more than one role, the source connection plate 210 is simply referred to herein as a “source connection plate”.

  In the illustrated embodiment, the second source connection plate 210 has a generally rectangular cross section. The second source connection plate 210 includes a bottom drain side end 220. The drain side end portion 220 is disposed at a lateral distance d0 + d1 + d3 + d11 from the side portion of the source electrode 125 toward the drain electrode 130 and at a vertical distance d5 + d6 + d7 + d8 above the second semiconductor material 110. In some embodiments, the lateral distance d0 + d1 + d3 + d11 is at least twice the longitudinal distance d5 + d6 + d7 + d8. For example, the lateral distance d0 + d1 + d3 + d11 may be three times or more than d5 + d6 + d7 + d8. The drain-side end portion 220 extends vertically from the second semiconductor material 110 by the first insulating material layer 155, the second insulating material layer 165, the third insulating material layer 175, and the fourth insulating material layer 195. Are spaced apart. As will be described further below, the electric field between the second source connection plate 210 and the heterojunction 115 is greatest at the bottom drain side end 220 under certain bias conditions.

  The second source connection plate 210 can be electrically connected to the source electrode 125 in a variety of different ways. In the illustrated embodiment, the source electrode 125 is electrically connected to the second source connection plate 210 by a source via member 225. In other embodiments, the source electrode 125 may be electrically connected to the second source connection plate 210 outside the illustrated cross section.

  In the illustrated embodiment, the drain 130 is electrically connected to another drain via member 230 via via members 185, 190. The drain via member 230 extends through the fourth insulating material layer 195 to the same vertical level as the second source connection plate 210, and as a result, functions as an extension of the drain 130. Since the via member 230 is at the same vertical level as the second source connection plate 210, the via member 230 is an extension portion of the drain 130 closest to the second source connection plate 210. The side portion of the second source connection plate 210 including the bottom drain side end portion 220 is disposed at the same vertical level by a lateral distance d9 from the drain via member 230. In the illustrated embodiment, the second source connection plate 210 and the drain via member 230 are covered with a fifth insulating material layer 245. The fifth insulating material layer 245 extends a distance d10 from the upper surface of the fourth insulating material layer 195.

  In some embodiments, d1 + d3 + d4 is 5-35 micrometers, such as 8-26 micrometers. In some embodiments, the lateral distance d9 is 1-10 micrometers, such as 2-6 micrometers. In some embodiments, the second, third, fourth, and fifth layers of insulating material 165, 175, 195, 245 are in steady state (after prolonged operation at certain operating parameters. With the quality and composition adjusted so that the number of charge defects per area in the insulating material layers 165, 175, 195, 245 is less than the sheet carrier density at the heterojunction. In other words, the sum of the products of the three-dimensional defect density of each of the insulating material layers 165, 175, 195, 245 and the thickness of each of the layers is less than the sheet carrier density at the (two-dimensional) heterojunction 115. For example, in some embodiments, the number of charge defects per area in the insulating material layers 165, 175, 195, 245 is less than 20% of the sheet carrier density in the heterojunction 115, such as less than 10%.

  FIG. 3 is a schematic view of a cross section of a lateral channel HEMT 300. In addition to the semiconductor materials 105, 110, the electrodes 125, 130, 135 and the via members 180, 185, 190, 225, 230, the HEMT 300 includes a field plate structure 305 that is layered vertically. The field plate structure 205 is a triple field plate structure including not only the gate connection field plate 140 and the second source connection plate 210 but also the second gate connection field plate 310. The second gate connection field plate 310 is electrically connected to the gate electrode 135.

  In the illustrated embodiment, the second gate connection field plate 310 has a substantially rectangular cross section. The second gate connection field plate 310 includes a bottom drain side end 320. The drain-side end portion 320 is disposed at a lateral distance d0 + d1 + d3 from the side portion of the source electrode 125 toward the drain electrode 130 and at a longitudinal distance d5 + d6 + d7 above the second semiconductor material 110. The drain side end portion 320 is vertically separated from the second semiconductor material 110 by the first insulating material layer 155, the second insulating material layer 165, and the third insulating material layer 175. As will be described further below, the electric field between the second connection field plate 310 and the heterojunction 115 is greatest at the bottom drain side end 320 under certain bias conditions.

  The second gate connection field plate 310 can be electrically connected to the gate electrode 135 in a variety of different ways. In the illustrated embodiment, the second gate connection field plate 310 is electrically connected to the gate connection field plate 140 by a gate via member 325. Furthermore, the gate connection field plate 140 is connected to the gate 125 outside the cross section shown. In other embodiments, the second gate connection field plate 310 may be electrically connected to the gate connection field plate 140 outside the illustrated cross section and / or the gate electrode 135 and the gate connection field plate 140 Can be connected in the illustrated cross section.

  In operation, the HEMTs such as the HEMTs 100, 200, 300 are switched between an on state and an off state by applying a bias to each gate electrode 135. In general, the HEMTs 100, 200, and 300 are depletion type devices that conduct when the potential difference between the gate and the source is zero. To switch the depletion type device to the off state, the gate is negatively biased with respect to the source. In many applications, it is desirable in practice to have a low on-resistance of the HEMT to such an extent that the power loss of the HEMT does not become undesirably high and / or does not become too high. In general, the gate is positively biased with respect to the source to reduce the on-resistance of the HEMT.

  In practice, even though theoretically an excessively large gate-source potential difference has some beneficial effects, such as further reducing the on-resistance of the HEMT, such an excessively large gate-source It is impossible to apply an inter-potential difference. In particular, the gate-source potential difference is constrained by the interaction of the HEMT's geometric parameters, material parameters, and operating parameters. For example, an excessive gate-source potential difference can cause degradation and / or breakdown of intervening materials having a specific thickness and density, leakage of electrons into the second semiconductor layer 110, and trapping in the second semiconductor layer 110, In addition, hot electron capture in the first insulating material layer 155 may be brought about. For this reason, the operating range of the gate-source potential difference is limited to a range of values for a given device, with a range of temperatures and other operating parameters. The operating range of this gate-source potential difference is called the available gate amplitude. In many GaN HEMT devices, a potential difference on the order of 1 digit to 10 volts is applied between the gate and the source. Thus, the available gate amplitude is generally on the order of 10 volts. For example, in some GaN HEMT devices, the available gate amplitude is 30 volts or less, such as 20 volts or less. In the depletion type HEMT, the usable gate amplitude is in a range from a smaller threshold value in the negative off state to a positive upper limit. In enhancement-type devices that are in the off state when the gate-source potential difference is zero, the available gate amplitude ranges from the smaller threshold, which is the zero potential difference, to the maximum, which is a positive value. It can take.

In contrast, in many power switching applications, the HEMT source-drain potential difference ΔV _SD can be on the order of about 100 volts, eg, above 500 V _DC , eg, about 650 V _DC . In such an application, when the applied gate amplitude is about 10 volts, both the source-drain potential difference magnitude ΔV _SD and the source-gate potential difference magnitude ΔV _SG are both the gate-source potential difference. It is significantly larger than the size. Considering this, the schematic representation of the following graph is the interchangeable ends 170, 320 despite the fact that there will be a difference (in a real device).

  4A and 4B are graphs 405 and 410, respectively, that schematically represent the voltage and electric field at the heterojunction between the source and drain of the HEMTs of some embodiments in the off state. HEMT embodiments include at least a double field plate structure (eg, FIG. 1), or a triple or more field plate structure (eg, FIGS. 2, 3). Graphs 405, 410 include, but are not limited to, geometric parameters (including, but not limited to, the number, dimensions, and configuration of HEMT features), material parameters (eg, material permittivity, material density, Functions of various parameters including work function, dopant concentration, defect concentration, surface state composition, and surface state concentration), and operating parameters (eg, including temperature, gate voltage, and source-drain voltage) It is understood that this is a very schematic diagram. Furthermore, even in the case of a single device, such parameters change over time, e.g., as the device ages or as operating conditions change. obtain. Thus, the slope of the line, the peak size, the number of peaks, and other characteristics will vary depending on, for example, the particular device and operating conditions. Accordingly, the graphs 405, 410 should be construed as schematic for normative and exemplary purposes.

  Graph 405 includes axis 410 and abscissa 415. The vertical position along axis 410 represents the voltage. The lateral position along the abscissa 415 represents the lateral position along the HEMT heterojunction between the source and drain. Graph 420 includes axis 425 and abscissa 430. The vertical position along axis 425 represents the magnitude of the electric field. The lateral position along the abscissa 430 represents the lateral position along the HEMT heterojunction between the source and drain. The lateral positions along the abscissas 415, 430 correspond to the ends 150, 160, 170, 320 of the HEMTs 100, 200, 300 (FIGS. 1, 2, 3) for purposes of illustration.

  Under the parameters shown, it is observed that the heterojunction is substantially conductive in the vicinity 420 of the source and is a voltage approximately equal to the source voltage VS. Therefore, the electric field in the vicinity 420 of the source is about zero. Under the indicated bias conditions (the gate is biased to locally deplete charge carriers from the heterojunction), the electrical impedance per unit length of the heterojunction increases in the vicinity of the gate, and The local maximum value is reached almost directly below the bottom drain side end 150 of the gate. Local depletion of charge carriers in the vicinity of the bottom drain side edge 150 of the gate generates a voltage change 425 and a local value 430 of the electric field.

  Depletion of charge carriers from the heterojunction by the gate decreases towards the drain. Therefore, both the change in potential per unit length and the electric field of the heterojunction are reduced. However, under exemplary parameters (where the gate connection field plate is further disposed and biased to locally deplete charge carriers from the heterojunction), the electrical per unit length of the heterojunction The impedance increases as well and reaches a local value almost directly below the bottom drain side edge 160 of the gate connection field plate. The increase in electrical impedance in the vicinity of the gate connection field plate results in a relatively large change 435 in voltage per unit length and a local value 440 of the electric field.

  Charge carrier depletion from the heterojunction by the gate-connected field plate is also reduced towards the drain. Therefore, both the change in potential per unit length and the electric field at the heterojunction are reduced. However, the electrical impedance per unit length of the heterojunction under the exemplary parameters (source connection field plate is further disposed and biased to locally deplete charge carriers from the heterojunction) Increases similarly and reaches a local value almost directly below the bottom drain side end 170 of the source connection field plate 145 or the bottom drain side end 320 of the gate connection field plate 310. An increase in electrical impedance in the vicinity of the source connection field plate results in a relatively large change 445 in voltage per unit length and a local value 450 of the electric field.

Under the exemplary parameters, charge carrier depletion from the heterojunction by the source connected field plate is also reduced towards the drain. It is observed that the heterojunction becomes substantially conductive near the drain 455 and is at a voltage approximately equal to the drain voltage V _D. Therefore, the electric field in the vicinity 455 of the drain is about zero. The total source-drain potential difference ΔV _SD is supported over the lateral length of the heterojunction and the HEMT is in the off (non-conductive) state. As described above, FIGS. 4A and 4B are schematic diagrams for exemplary and exemplary purposes. Other HEMTs under other operating conditions may have additional or fewer peaks, different sloped peaks, and various peak peaks, as well as other methods, including other characteristics. Potential difference ΔV _SD can be supported.

  5A and 5B are graphs 505 and 510, respectively, that schematically represent the voltage and electric field at the heterojunction between the source and drain of the HEMTs of some embodiments in the on state. HEMT embodiments may include a dual field plate structure (eg, FIG. 1), or a triple or more field plate structure (eg, FIGS. 2, 3). Graphs 505, 510 are also schematic, with voltage and electric field being a function of various parameters, and such parameters may change over time.

  The graph 505 includes an axis 510 and an abscissa 515. The vertical position along axis 510 represents the voltage. The lateral position along the abscissa 515 represents the lateral position along the heterojunction of the HEMT between the source and drain. The graph 520 includes an axis 525 and an abscissa 530. The vertical position along axis 525 represents the magnitude of the electric field. The lateral position along the abscissa 530 represents the lateral position along the heterojunction of the HEMT between the source and drain. The lateral positions along the abscissas 515, 530 correspond to the ends 150, 160, 170, 320 of the HEMTs 100, 200, 300 (FIGS. 1, 2, 3) for purposes of illustration.

  In the on state under the indicated geometric, material, and operating parameters, the heterojunction is conductive and the source and drain are at substantially the same voltage. However, even under the parameters shown, the heterojunction has a finite non-zero resistance and the source and drain voltages are not the same. For purposes of illustration, voltage 535 has a slight but uniformly rising slope and a minimal but uniform non-uniformity, as is reasonable if the heterojunction has an ideally uniform resistivity over the entire length of the channel. And a zero value electric field 540. This is not necessarily the case. For example, the finite resistivity of a heterojunction may vary depending on the lateral position, even though it is conductive, due to local differences in contact potential difference, carrier density, defect density, and / or other parameters. There may be.

As another example, for example, if the number of carriers in a heterojunction is relatively small compared to the current that would be conducted by an ideal conductor, the current in the heterojunction may be a specific geometric parameter, material parameter, And can be limited space charge under operating parameters. A relatively large source-drain potential difference ΔV _SD and an electric field may occur. For example, under certain parameters, for a given drain current level, at or above the knee voltage (ΔV _SD ≧ V _knee ), a relatively large electric field may be generated from the non-depleted region toward the drain below the gate electrode. Also extends laterally.

In some embodiments, the distance d3 (characterizing the lateral extension of the field plates 145, 310 from the bottom drain side edge 160 of the gate connection field plate 140 to the drain) is this relatively large toward the drain. Less than the lateral spread of the electric field. Such a limitation on the lateral extension of the field plates 145, 310 may reduce the electric field generated between the field plates 145, 310 and the heterojunction 115. In particular, for the source connection field plate 145, the total source-drain potential difference ΔV _SD has a first insulating material layer 155, a second insulating material layer 165, and a third insulating material layer 175 along the length d3. It will not be supported by the whole part. For the gate connection field plate 310, the total potential difference between the gate and the drain is the entire portion of the first insulating material layer 155, the second insulating material layer 165, and the third insulating material layer 175 along the length d3. Will not be supported by. By reducing the electric field in this region, the breakdown voltage and lifetime of the HEMT can be improved.

  Thus, as described above, FIGS. 5A and 5B are also schematic diagrams for normative and exemplary purposes. The vertical position of voltage 535 along axis 510 will depend on the HEMT placement, eg, whether the HEMT is placed on the high load side or on the low side.

  FIGS. 6A and 6B show several embodiments of HEMTs in the off state for a fixed source and gate potential, respectively, for various different distinct drain potentials VD1, VD2, VD3, VD4. 6 are graphs 605 and 620 schematically showing a voltage and an electric field at the heterojunction between the source and the drain of the semiconductor device. Graphs 605, 620 are very schematic diagrams shown for normative and exemplary purposes. HEMT embodiments may include a dual field plate structure (eg, FIG. 1), or a triple or more field plate structure (eg, FIGS. 2, 3).

  The graph 605 includes an axis 610 and an abscissa 615. The vertical position along axis 610 represents the voltage. The lateral position along the abscissa 615 represents the lateral position along the heterojunction of the HEMT between the source and drain. Graph 620 includes axis 625 and abscissa 630. The vertical position along axis 625 represents the magnitude of the electric field. The lateral position along the abscissa 630 represents the lateral position along the heterojunction of the HEMT between the source and drain. The lateral positions along the abscissas 615, 630 correspond to the ends 150, 160, 170, 320 of the HEMTs 100, 200, 300 (FIGS. 1, 2, 3) for purposes of illustration.

In the off state, a source-drain potential difference ΔV _SD is supported throughout the lateral length of the heterojunction. However, depending on the HEMT's geometric parameters, material parameters, and operating parameters, the degree of local depletion of charge carriers can vary. Correspondingly, since the source-drain potential difference ΔV _SD changes, the voltage change 425 and the local value 430 near the bottom drain side end 150, and the voltage change 435 near the bottom drain side end 160. Also, the local value 440 and the voltage change 445 and the local value 450 in the vicinity of the bottom drain side ends 170, 320 may be different.

Although the graphs 605 and 620 are very schematic diagrams, the local value 430 of the electric field in the vicinity of the bottom drain side end 150 of the gate 135 is larger than the larger source-drain potential difference ΔV displayed in the graph 620. Note that at _SD , it begins to saturate. In other words, with a relatively small source-drain potential difference ΔV _SD (eg, at a drain voltage less than VD1 and between VD1 and VD2), an increase in the source-drain potential difference ΔV _SD is also caused by the bottom drain of the gate 135 This results in an increase in the local value 430 of the electric field in the vicinity of the side edge 150. In contrast, at a relatively large source-drain potential difference ΔV _SD (eg, a drain voltage between VD3 and VD4), an increase in the source-drain potential difference ΔV _SD is caused at the bottom drain side end 150 of the gate 135. There is a smaller increase or even no increase in the local value 430 of the electric field in the vicinity. This saturation or “heading” of the incremental change in field magnitude 430 with increasing drain potential results in complete depletion of charge carriers near the bottom drain side edge 160 of the gate connection field plate 140. Correspond.

  In some embodiments, for example, the geometry of the HEMT, such that the gate edge field ramps up at typical operating conditions within a room temperature of 150 degrees Celsius or 125 degrees Celsius, and The properties of the material can be adjusted. For example, the geometry and material properties of the HEMT can be adjusted so that the gate edge field increases gradually with a drain potential relative to the source that is greater than the absolute value of the gate amplitude. Thus, at least some of the geometrical and material properties that define the gate amplitude are related to the ramping-up of the gate edge field, which itself is at least some of its same geometrical and material properties. Is partly defined by the interaction. By adjusting the geometric and material properties in this manner, the maximum electric field in the channel near the drain side end 150 of the gate 135 can be limited, and thus deeper in the center in the semiconductor material 105 and / or 110. Reduce or prevent ionization of This provides a reduction or even prevention of the associated dispersion or collapse effect and reduces or eliminates the possibility of avalanche breakdown occurring in the semiconductor material 105 and / or 110.

  As another example, in some embodiments, the geometry and material properties of the HEMT are greater than twice the absolute value of the gate amplitude, eg, the drain potential relative to the source, eg, 2 to 2 of the absolute value of the gate amplitude. At 5 times or 3-4 times the absolute value of the gate amplitude, the gradual increase of the gate edge field at the same operating condition can be adjusted to peak. By adjusting such geometrical properties and material properties in this way, the above benefits are more likely to be achieved.

  FIG. 7 shows the source and drain of some embodiments of the HEMT in the off state for a fixed source and gate potential, for various different discrete drain potentials VD4, VD5, VD6, VD7. 7 is a graph 720 schematically representing the electric field at the heterojunction between the two. Graph 720 is a very schematic diagram shown for normative and exemplary purposes. HEMT embodiments may include a dual field plate structure (eg, FIG. 1), or a triple or more field plate structure (eg, FIGS. 2, 3).

  The graph 720 includes an axis 725 and an abscissa 730. The vertical position along axis 725 represents the magnitude of the electric field. The lateral position along the abscissa 730 represents the lateral position along the heterojunction of the HEMT between the source and drain. The lateral position along the abscissa 730 corresponds to the ends 150, 160, 170, 320 of the HEMTs 100, 200, 300 (FIGS. 1, 2, 3) for illustrative purposes.

In the off state, a source-drain potential difference ΔV _SD is supported throughout the lateral length of the heterojunction. However, depending on the HEMT's geometric parameters, material parameters, and operating parameters, the degree of local depletion of charge carriers can vary.

The graph 720 is a very schematic illustration, but note the following:
The local value 430 of the electric field in the vicinity of the bottom drain side end 150 of the gate 135 saturates in all of the illustrated source-drain potential differences ΔV _SD . And the local value 440 of the electric field in the vicinity of the bottom drain side end 160 of the gate connection field plate 140 starts to saturate with a larger source-drain potential difference ΔV _SD shown in the graph 720.

In other words, with a relatively small source-drain potential difference ΔV _SD (eg, at a drain voltage less than VD4 and between VD4 and VD5), an increase in the source-drain potential difference ΔV _SD is also caused by the gate connection field plate 140. This results in an increase in the local value 440 of the electric field in the vicinity of the bottom drain side end 160 of the. In contrast, with a relatively large source-drain potential difference ΔV _SD (eg, with a drain voltage between VD6 and VD7), an increase in the source-drain potential difference ΔV _SD increases with the bottom drain side of the gate connection field plate 140. This results in a smaller or no increase in the local value 440 of the electric field in the vicinity of the end 160. This saturation or “heading” of the incremental change in field magnitude 440 with increasing drain potential corresponds to complete depletion of charge carriers in the vicinity of the bottom drain side ends 170, 320, respectively. .

  In some implementations, the geometry of the HEMT is such that the gate edge field ramps up at normal operating conditions, eg, room temperature of 150 degrees Celsius or room temperature of 125 degrees Celsius. And material properties (including distance d3) can be adjusted. For example, the geometry and material properties (including distance d3) of the HEMT are adjusted so that the gradual increase of the gate connection field plate reaches a peak at a drain potential greater than the drain potential at which the gate end electric field increases. Can be done. For example, the potential difference may be a potential difference that is greater than twice the drain potential at which the gradual increase in the gate end electric field reaches a peak, for example, a potential difference that is 3 to 5 times the drain potential at which the gradual increase in the gate end electric field reaches a peak. Thus, at least some of the geometrical and material properties that define the ramping-up of the gate edge field are related to the ramping-up of the gate connection field plate, which itself has its same geometrical properties and It is defined in part by at least some interactions of the material properties. By adjusting the geometry and material properties in this way, the maximum electric field in the channel near the drain end 160 of the gate connection field plate 140 can be limited, and thus the semiconductor material 105 and / or 110. Reduce or prevent deep ionization at the center. This reduces or even prevents the associated dispersion or collapse effect and reduces or eliminates the possibility of avalanche breakdown occurring in the semiconductor material 105 and / or 110.

  As another example, in some embodiments, a gradual increase in the gate end field is greater than 2.5 times the drain potential at which it peaks, for example, 5 times the drain potential at which the gradual increase in the gate end field peaks, Alternatively, the geometry and material properties of the HEMT so that the gradual increase of the gate connection field plate peaks at the drain potential relative to the source, where the gradual increase of the gate edge electric field is 10 times the peak drain potential. (Including the distance d3) can be adjusted. By adjusting the geometric and material properties in this way, the above benefits are more likely to be achieved.

  FIG. 8 shows the source and drain of some embodiments of the HEMT in the off state for a fixed source and gate potential, for various different and distinct drain potentials VD4, VD5, VD6, VD7. It is the graph 820 which represents roughly the electric field in a heterojunction in between. Graph 720 is a very schematic diagram shown for normative and exemplary purposes. HEMT embodiments may include a dual field plate structure (eg, FIG. 1), or a triple or more field plate structure (eg, FIGS. 2, 3).

  The graph 820 includes an axis 825 and an abscissa 830. The vertical position along axis 825 represents the magnitude of the electric field. The lateral position along the abscissa 830 represents the lateral position along the heterojunction of the HEMT between the source and drain. The lateral position along the abscissa 830 corresponds to the ends 150, 160, 170, 320 of the HEMTs 100, 200, 300 (FIGS. 1, 2, 3) for purposes of illustration.

In the off state, a source-drain potential difference ΔV _SD is supported throughout the lateral length of the heterojunction. However, although the graph 820 is a very schematic diagram, the local value 440 of the electric field in the vicinity of the bottom drain side end 160 of the gate connection field plate 140 is saturated at a larger source-drain potential difference ΔV _SD . The electric field extending in the lateral direction from the bottom drain side end 160 of the gate connection field plate 140 toward the drain until the start of the electric field extends in the lateral direction from the bottom drain side end 170, 320 toward the source. Note that this is not reached. In other words, with a relatively small source-drain potential difference ΔV _SD (eg, below VD4 and at a drain voltage between VD4 and VD5), the heterojunction portion 805 remains substantially conductive, and , The electric field in the portion 805 is about zero. Symmetrically, the drain side edge 160 and the drain side edges 170, 320 overlap with a relatively large source-drain potential difference ΔV _SD (eg, between VD6 and VD7 and at a drain voltage greater than VD7). Local depletion (and associated electric field) arising from the, and the conductivity of the portion 805 is reduced.

Until the local value 440 of the electric field near the bottom drain side end 160 of the gate connection field plate 140 begins to saturate (in the case of general operating conditions) As the potential difference ΔV _SD increases, the geometry and material properties (including distance d3) of the HEMT can be adjusted to remain substantially conductive. An example of such operating conditions is, for example, in a room temperature of 150 degrees Celsius or in a room temperature of 125 degrees Celsius. By adjusting the geometric and material properties, the maximum electric field in the channel near the drain end 160 of the gate connection field plate 140 can be limited, and thus in the semiconductor material 105 and / or 110. Reduce or prevent ionization deep in the center.

  FIG. 9 shows the heterojunction between the source and drain of some embodiments of the HEMT in the off state for a fixed source and gate potential, for various different discrete drain potential cases. 2 is a graph 920 schematically representing an electric field. Graph 920 is a very schematic diagram shown for normative and exemplary purposes. HEMT embodiments include triple or more field plate structures (eg, FIGS. 2, 3).

  The graph 920 includes an axis 925 and an abscissa 930. The vertical position along axis 925 represents the magnitude of the electric field. The lateral position along the abscissa 930 represents the lateral position along the heterojunction of the HEMT between the source and drain. The lateral position along the abscissa 930 corresponds to the ends 150, 160, 170, 320, 220 of the HEMTs 200, 300 (FIGS. 2, 3) for purposes of illustration.

In the off state, a source-drain potential difference ΔV _SD is supported throughout the lateral length of the heterojunction. Under the exemplary parameters, the bottom drain side end 220 of the second source connection plate 210 further depletes charge carriers from the heterojunction and generates an electric field near the drain 455. Therefore, due to the vertical voltage difference between the heterojunction and the second source connection plate 210 (in the case of typical operating conditions), a portion of the heterojunction near the drain 455 is depleted. As such, the geometry and material properties of the HEMT can be adjusted. An example of such operating conditions is, for example, in a room temperature of 150 degrees Celsius or in a room temperature of 125 degrees Celsius.

By adjusting the geometry and material properties in this way, the potential difference between the heterojunction and the second source connection plate 210 and, as a result, the electric field is reduced while the device is in the off state. Can be reduced. In particular, since a part of the source-drain potential difference ΔV _SD decreases along the heterojunction 115 in the vicinity 455 of the drain, the total source-drain potential difference ΔV _SD is reduced between the second source connection plate 210 and the second source connection plate 210. It is not applied between the heterojunction 115 below the source connection plate 210. Instead, there is a smaller potential difference, for example, reducing the likelihood of charge injection and / or dielectric breakdown into the intervening insulating material (s).

In some embodiments, the HEMT is tuned to operate at least a specified source-drain potential difference ΔV _SD between the heterojunction and the second source connection plate 210 for at least a short period of time. It has the following geometrical properties and material properties. In particular, HEMTs can consume a relatively large percentage of their operating lifetime in the off state, but during switching, a potential close to the maximum operational source-drain potential difference ΔV _SD is transiently Appears between the heterojunction and the second source connection plate 210. While not intending to be bound by any theory, the depletion and (re) accumulation process at the heterojunction may not occur uniformly along the entire lateral length of the heterojunction. Conceivable. For example, in the context of switching between an off state and an on state, some of the heterojunction 115 near the drain 455 may (re) accumulate charge faster than other parts of the heterojunction 115. In this case, the heterojunction in the vicinity 455 of the drain can become conductive prior to other parts of the heterojunction 115. During this transient state, the drain voltage V _D can spread within the neighborhood 455, and the total source-drain potential difference ΔV _SD is below the portion of the second source connection plate 210 and the heterojunction 115. Will be supported.

  Several embodiments have been described. However, it is understood that various changes apply. For example, the illustrated embodiments are all lateral channel HEMTs, but the same techniques can be applied to the longitudinal channel HEMTs as long as longitudinal heterojunctions can be formed. Accordingly, other embodiments are within the scope of the appended claims.

Claims (27)

A first semiconductor material and a second semiconductor material arranged to form a heterojunction at a position where a two-dimensional electron gas is generated;
A source electrode, a drain electrode, and a gate electrode, wherein the gate electrode is arranged to regulate conduction in the heterojunction between the source electrode and the drain electrode, and the gate is connected to a drain side end The source electrode, the drain electrode, and the gate electrode having a portion;
A gate connection field plate disposed above a drain side end of the gate electrode and extending laterally toward the drain; and a gate connection field plate disposed above a drain side end of the gate connection field plate A second field plate extending laterally toward the drain;
With
In an off state and with a potential difference between the source and the drain that exceeds the absolute value of the gate amplitude, charge carriers are removed from a portion of the heterojunction in the vicinity of the drain side end of the gate connection field plate. Depleted and the depletion of charge carriers is effective to saturate a lateral electric field at the heterojunction in the vicinity of the drain side end of the gate electrode;
HEMT.   The HEMT of claim 1, wherein charge carriers are depleted by a potential difference between the source and the drain that is 2-5 times the absolute value of the gate amplitude.   The HEMT of claim 1, wherein charge carriers are depleted with a potential difference between the source and the drain of 3 to 4 times the absolute value of the gate amplitude.   In the off-state and in the vicinity of the drain side end of the gate connection field plate, the potential difference between the source and drain exceeds the potential difference where the charge carriers are depleted from the part of the heterojunction. Charge carriers are depleted from a portion of the heterojunction in the vicinity of the drain side end of the second field plate, and the depletion of charge carriers is the drain side end of the gate connection field plate The HEMT of claim 1, which is effective to saturate a lateral electric field at the heterojunction in the vicinity of.   The potential difference at which charge carriers deplete from a part of the heterojunction in the vicinity of the drain side end of the second field plate is the heterojunction in the vicinity of the drain side end of the gate connection field plate. The HEMT of claim 4, wherein the potential difference is 3 to 5 times the potential difference at which charge carriers are depleted from the portion. In the off state:
A first electric field at the heterojunction widens the drain compartment from the drain side end of the gate connection field plate;
A second electric field at the heterojunction unfolds the source section from the drain side end of the second field plate; and
The first electric field first exceeds the potential difference between the source and the drain, where charge carriers are depleted from a portion of the heterojunction in the vicinity of the drain side end of the second field plate. Only the potential difference between the source and the drain overlaps the second electric field;
The HEMT of claim 4. A third field plate disposed above the drain side end of the second field plate and extending laterally toward the drain;
The HEMT of claim 1, further comprising: The source exceeding the potential difference between the source and the drain in which the charge carriers are depleted from a portion of the heterojunction in the off state and in the vicinity of the drain side end of the second field plate; A potential difference between the drain and a portion of the heterojunction in the vicinity of the drain is depleted due to the longitudinal voltage difference between the heterojunction and the third field plate;
The HEMT of claim 7. The third field plate is a source connection field plate;
The HEMT of claim 7. In the off state:
A first electric field at the heterojunction widens the drain compartment from the drain side end of the gate connection field plate;
A second electric field at the heterojunction unfolds the source section from the drain side end of the second field plate; and
The first electric field first exceeds a potential difference between the source and the drain where charge carriers are depleted from a portion of the heterojunction in the vicinity of the drain side end of the second field plate. Only the potential difference between the source and the drain overlaps the second electric field;
The HEMT of claim 1. The first electric field first exceeds the source that exceeds the potential difference between the source and the drain where charge carriers are depleted from a portion of the heterojunction in the vicinity of the drain side end of the second field plate; Only the potential difference with the drain overlaps the second electric field,
The HEMT of claim 10. The HEMT includes one or more layers of insulating material over the first and second semiconductor materials;
A sheet carrier density occurs at the heterojunction; and
After reaching steady state after long-term operation with specific operating parameters, the number of charge defects per unit area in some of the insulating material layers is less than the sheet carrier density,
The HEMT of claim 1. The number of charge defects per unit area in the insulating material layer is less than 10% of the sheet carrier density.
The HEMT of claim 12. The first and second semiconductor materials are GaN and AlGaN, respectively;
The HEMT of claim 1. The gate electrode is separated from the second semiconductor material by an aluminum silicon nitride layer;
The HEMT of claim 14. A first semiconductor material and a second semiconductor material arranged to form a heterojunction at a position where a two-dimensional electron gas is generated;
A source electrode, a drain electrode, and a gate electrode, wherein the gate electrode is disposed to regulate conduction at the heterojunction between the source electrode and the drain electrode, and the gate is at a drain side end. The source electrode, the drain electrode, and the gate electrode;
A gate connection field plate disposed above a drain side end of the gate electrode and extending laterally toward the drain; and a gate connection field plate disposed above a drain side end of the gate connection field plate A second field plate extending laterally toward the drain;
With
In the off state:
A first electric field at the heterojunction widens the drain compartment from the drain side end of the gate connection field plate;
A second electric field at the heterojunction unfolds the source section from the drain side end of the second field plate; and
The first electric field first exceeds a potential difference between the source and the drain where charge carriers are depleted from a portion of the heterojunction in the vicinity of the drain side end of the second field plate. Overlaps the second electric field only at the potential difference between the source and the drain;
HEMT.   17. The HEMT of claim 16, further comprising a third field plate disposed above the drain side end of the second field plate and extending laterally toward the drain.   The source exceeding the potential difference between the source and the drain in which the charge carriers are depleted from a portion of the heterojunction in the off state and in the vicinity of the drain side end of the second field plate; A potential difference between the drain and a portion of the heterojunction in the vicinity of the drain is depleted due to the longitudinal voltage difference between the heterojunction and the third field plate; The HEMT of claim 17. substrate;
A first active layer disposed over the substrate;
A second active layer disposed on the first active layer such that a lateral conductive channel is generated between the first active layer and the second active layer. Two active layers;
Source and drain electrodes;
A first passivation layer disposed above the second active layer;
A gate electrode disposed above the first passivation layer;
A second passivation layer disposed above the gate electrode;
A gate field plate extending a first distance beyond an end of the gate electrode closest to the drain electrode;
A third passivation layer disposed over the first metal pattern; and an end of the gate field plate electrically connected to one of the source electrode and the gate electrode and closest to the drain electrode A second field plate extending a second distance beyond the section,
With
An end of the second field plate is spaced a third distance from a first extension of the drain electrode adjacent to the second field plate;
When a portion of the lateral conduction channel below the gate electrode is in a pinch-off state for a first drain bias greater than the absolute value of the available gate amplitude above the smaller threshold, The first distance is selected such that the gradual increase peaks.
A semiconductor device comprising: The source and drain electrodes are disposed above the second active layer;
The gate field plate is defined by a first metal pattern disposed on the second passivation layer, the first metal pattern extending laterally above the entire gate electrode;
The second field plate is a source field plate defined by a second metal pattern disposed on the third passivation layer, and the second metal pattern is electrically connected to the source electrode. Connected and extends laterally above the entire first metal pattern and extends further by the second distance beyond the end of the first metal pattern closest to the drain electrode. And an end of the second metal pattern is separated from the first extension of the drain electrode adjacent to the second metal pattern by the third distance.
The semiconductor device according to claim 19. A fourth passivation layer disposed above the second metal pattern; and
A shield wrap defined by a third metal pattern disposed on the fourth passivation layer;
The third metal pattern is electrically connected to the source electrode and at a third distance from a second extension of the drain electrode adjacent to the third metal pattern. Extending laterally above a majority of the lateral conductive channel such that the metal pattern has an end,
21. The semiconductor device according to claim 20. The distance from the end to the end between the third metal pattern and the second extension of the drain electrode is 2-6 micrometers; and the thickness of the fourth passivation layer Is 0.5 to 2 micrometers,
The semiconductor device according to claim 21. The first drain bias is about 2-5 times greater than the absolute value of the available gate amplitude above a threshold;
21. The semiconductor device according to claim 20.   The second distance is a second drain bias that is greater than a gate edge field top bias provided by the gate field plate when a portion of the lateral conductive channel below the gate electrode is pinched off. 24. The semiconductor device of claim 23, wherein the semiconductor device is sufficient to provide a peak to the edge field of the gate field plate.   25. The semiconductor device of claim 24, wherein the second drain bias is approximately 2.5 to 10 times greater than the first drain bias.   At least a lateral depletion extension below the second metal pattern before the lateral conductive channel is pinched off vertically below the end of the second metal pattern closest to the drain end. 21. The semiconductor device according to claim 20, wherein the second distance is long enough to never reach an end of the second metal pattern. The first distance is 1.5 to 3.5 micrometers;
The second distance is 2.5 to 7.5 micrometers;
The third distance is 2-6 micrometers;
The distance between the gate electrode and the drain electrode is 8 to 26 micrometers; and the thickness of the third passivation layer is 0.35 to 0.75 micrometers. Is,
The semiconductor device according to claim 19.

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