Patent ID: 12237409

DETAILED DESCRIPTION

According to one embodiment, a semiconductor device includes a first electrode, a second electrode, a third electrode, a semiconductor member, a first conductive member, a first insulating member, a second insulating member, and a first nitride member. A position of the third electrode in a first direction from the first electrode to the second electrode is between a position of the first electrode in the first direction and a position of the second electrode in the first direction. The semiconductor member includes a first semiconductor region and a second semiconductor region. The first semiconductor region includes Alx1Ga1-x1N (0≤x1<1). The first semiconductor region includes a first partial region, a second partial region, a third partial region, a fourth partial region, and a fifth partial region. A second direction from the first partial region to the first electrode crosses the first direction. A direction from the second partial region to the second electrode is along the second direction. A direction from the third region to the third electrode is along the second direction. A position of the fourth partial region in the first direction is between a position of the first partial region in the first direction and a position of the third partial region in the first direction. A position of the fifth partial region in the first direction is between the position of the third partial region in the first direction and a position of the second partial region in the first direction. The second semiconductor region includes Alx2Ga1-x2N (0≤x2≤1, x1<x2). The second semiconductor region includes a first semiconductor portion and a second semiconductor portion. A direction from the fourth partial region to the first semiconductor portion is along the second direction. A direction from the fifth partial region to the second semiconductor portion is along the second direction. The second semiconductor portion includes a first portion, a second portion, and a third portion between the first portion and the second portion. A position of the second portion in the first direction is between a position of the first portion in the first direction and the position of the second electrode in the first direction. The first conductive member includes a first conductive region and a second conductive region. The first conductive region overlaps the third electrode in the second direction. The first portion is between the fifth partial region and a part of the first conductive region. The first conductive member is electrically connected with one of the first electrode and the third electrode, or the first conductive member is configured to be electrically connected with the one of the first electrode and the third electrode. The first insulating member includes a first insulating region. The first insulating region is between the third partial region and the third electrode in the second direction. The second insulating member includes a first insulating portion and a second insulating portion. The first insulating portion is between the first portion and the first conductive region in the second direction. The second portion is between the fifth partial region and the second insulating portion. The first nitride member includes Alx3Ga1-x3N (0≤x3<1) or Iny1Aly2Ga1-y1-y2N (0<y1≤1, 0≤y2≤1, y1+y2≤1). The first nitride member includes a first nitride region. The first nitride region is between the first insulating portion and the second insulating portion in the first direction. The first nitride region is between the third portion and the second conductive region in the second direction.

Various embodiments are described below with reference to the accompanying drawings.

The drawings are schematic and conceptual; and the relationships between the thickness and width of portions, the proportions of sizes among portions, etc., are not necessarily the same as the actual values. The dimensions and proportions may be illustrated differently among drawings, even for identical portions.

In the specification and drawings, components similar to those described previously or illustrated in an antecedent drawing are marked with like reference numerals, and a detailed description is omitted as appropriate.

First Embodiment

FIG.1is a schematic cross-sectional view illustrating a semiconductor device according to a first embodiment.

As shown inFIG.1, a semiconductor device110according to the embodiment includes a first electrode51, a second electrode52, a third electrode53, a semiconductor member10M, a first conductive member61, a first insulating member41, and a second insulating member42.

A direction from the first electrode51to the second electrode52is a first direction D1. The first direction D1is defined as an X-axis direction. One direction perpendicular to the X-axis direction is defined as a Z-axis direction. The direction perpendicular to the X-axis direction and the Z-axis direction is defined as a Y-axis direction.

A position of the third electrode53in the first direction D1is between a position of the first electrode51in the first direction D1and a position of the second electrode52in the first direction D1. For example, at least a part of the third electrode53is located between the first electrode51and the second electrode52in the first direction D1.

The semiconductor member10M includes a first semiconductor region10and a second semiconductor region20. In this example, the semiconductor device110includes a base body10sand a nitride semiconductor layer10B. The nitride semiconductor layer10B is provided between the base body10sand the semiconductor member10M. For example, the nitride semiconductor layer10B is provided on the base body10s. The semiconductor member10M is provided on the nitride semiconductor layer10B. For example, the first semiconductor region10is provided on the nitride semiconductor layer10B. The second semiconductor region20is provided on the first semiconductor region10. The first to third electrodes51to53are provided on the semiconductor member10M. The base body10smay be, for example, a silicon substrate or a SiC substrate. The nitride semiconductor layer10B includes, for example, AlGaN.

The first semiconductor region10includes Alx1Ga1-x1N (0≤x1<1). The first semiconductor region10is, for example, a GaN layer. The composition ratio x1 of Al in the first semiconductor region10may be, for example, not less than 0 and not more than 0.1.

For example, the first semiconductor region10includes GaN. The first semiconductor region10includes a first partial region11, a second partial region12, a third partial region13, a fourth partial region14, and a fifth partial region15. The second direction D2from the first partial region11to the first electrode51crosses the first direction D1. The second direction D2may be, for example, the Z-axis direction.

A direction from the second partial region12to the second electrode52is along the second direction D2. A direction from the third partial region13to the third electrode53is along the second direction D2.

A portion of the first semiconductor region10that overlaps the first electrode51in the second direction D2corresponds to the first partial region11. A portion of the first semiconductor region10that overlaps the second electrode52in the second direction D2corresponds to the second portion region12. A portion of the first semiconductor region10that overlaps the third electrode53in the second direction D2corresponds to the third portion region13.

A position of the fourth partial region14in the first direction D1is between a position of the first partial region11in the first direction D1and a position of the third partial region13in the first direction D1. A position of the fifth partial region15in the first direction D1is between a position of the third partial region13in the first direction D1and a position of the second partial region12in the first direction D1. The first to fifth subregions11to15may be continuous with each other. The boundaries between the first to fifth subregions11to15may be clear or unclear.

The second semiconductor region20includes Alx2Ga1-x2N (0<x2≤1, x1<x2). The second semiconductor region20is, for example, an AlGaN layer. The composition ratio x2 of Al in the second semiconductor region20may be, for example, not less than 0.25 and not more than 0.4.

The second semiconductor region20includes a first semiconductor portion21and the second semiconductor portion22. A direction from the fourth partial region14to the first semiconductor portion21is along the second direction D2. A direction from the fifth partial region15to the second semiconductor portion22is along the second direction D2. The second semiconductor portion22includes a first portion22a, a second portion22b, and a third portion22c. The third portion22cis between the first portion22aand the second portion22b. A position of the second portion22bin the first direction D1is between a position of the first portion22ain the first direction D1and the position of the second electrode52in the first direction D1. The first to third portions22ato22cmay be continuous with each other. The boundary between the first to third portions22ato22cmay be clear or unclear.

For example, the first electrode51is electrically connected with the first semiconductor portion21. For example, the second electrode52is electrically connected with the second semiconductor portion22.

The first conductive member61includes a first conductive region61aand a second conductive region61b. The first conductive region61aoverlaps the third electrode53in the second direction D2. The second conductive region61bdoes not overlap the third electrode53in the second direction D2. A position of the second conductive region61bin the first direction D1is between the position of the third electrode53in the first direction D1and the position of the second electrode52in the first direction D1. The second conductive region61bcorresponds to a protruding portion protruding toward a side of the second electrode52with reference to the third electrode53. The second conductive region61bcorresponds to, for example, the eaves.

The first portion22ais located between the fifth partial region15and a part of the first conductive region61ain the second direction D2. In this example, the third electrode53is located between the fifth partial region15and the first conductive region61ain the second direction D2. At least a part of the second portion22bdoes not overlap the first conductive member61in the second direction D2.

In the embodiment, the first conductive member61is electrically connected with one of the first electrode51and the third electrode53. Alternatively, the first conductive member61is configured to be electrically connect with one of the first electrode51and the third electrode53. In the first embodiment, the first conductive member61is electrically connected with the first electrode51. A terminal electrically connected with the first conductive member61and a terminals electrically connected with the first electrode51may be provided, and these terminals may be electrically connected when the semiconductor device is used.

For example, the first conductive member61includes a first conductive end portion61e. The first conductive end portion61eis an end on the side of the second electrode52in the first direction D1. A position of the first conductive end portion61ein the first direction D1is between the position of the third electrode53in the first direction D1and the position of the second electrode52in the first direction D1.

The first insulating member41includes a first insulating region41a. The first insulating region41ais located between the third partial region13and the third electrode53in the second direction D2.

The second insulating member42includes a first insulating portion42aand a second insulating portion42b. The first insulating portion42ais located between the first portion22aand the first conductive region61ain the second direction D2. The second portion22bis between the fifth portion region15and the second insulating portion42b.

The first nitride member31includes Alx3Ga1-x3N (0≤x3<1). The first nitride member31is, for example, a GaN layer or an AlGaN layer. The composition ratio x3 of Al in the first nitride member31may be, for example, not less than 0 and not more than 0.5. For example, the composition ratio x3 of Al in the first nitride member31is lower than the composition ratio x2 of Al in the second semiconductor region20(for example, the second semiconductor portion22).

The first nitride member31includes a first nitride region31a. The first nitride region31ais located between the first insulating portion42aand the second insulating portion42bin the first direction D1. The first nitride region31ais between the third portion22cand the second conductive region61bin the second direction D2. The first nitride region31aoverlaps the second conductive region61bin the second direction D2.

A current flowing between the first electrode51and the second electrode52can be controlled by a potential of the third electrode53. The potential of the third electrode53may be, for example, a potential based on a potential of the first electrode51. For example, the first electrode51functions as a source electrode. The second electrode52functions as a drain electrode. The third electrode53functions as a gate electrode. The first insulating region41afunctions as a gate insulating film. The semiconductor device110is, for example, a transistor. For example, a distance between the first electrode51and the third electrode53is shorter than a distance between the third electrode53and the second electrode52.

A carrier region10C is formed in a portion of the first semiconductor region10facing the second semiconductor region20. The carrier region10C is, for example, a two-dimensional electron gas. The semiconductor device110is, for example, a HEMT (high electron mobility transistor).

The first conductive member61functions as, for example, a field plate. As described above, in the embodiment, the first conductive member61is provided with the second conductive region61b(protruding portion or eaves portion). The first nitride region31a(GaN or AlGaN) is provided at a position overlapping the second conductive region61b. As a result, the carrier concentration in the carrier region10C locally decreases in the region overlapping the second conductive region61b.

Generally, the electric field is concentrated at the end (first conductive end61e) of the second conductive region61b(protruding portion or eaves). The breakdown voltage tends to decrease due to the concentration of the electric field. In the embodiment, the carrier concentration can be locally reduced in the region overlapping the second conductive region61b. As a result, high breakdown voltage can be easily obtained. According to the embodiment, it is possible to provide a semiconductor device whose characteristics can be improved.

In this example, the first nitride member31includes a second nitride region31band a third nitride region31c. The first insulating portion42ais between the first portion22aand the second nitride region31b. The second insulating portion42bis between the second portion22band the third nitride region31c. The first nitride region31a, the second nitride region31b, and the third nitride region31cmay be continuous with each other. The boundaries between the first nitride region31a, the second nitride region31b, and the third nitride region31cmay be clear or unclear. By continuously providing the first nitride region31a, the second nitride region31b, and the third nitride region31c, the formation of the first nitride member31is easy.

A portion of the first nitride member31that overlaps the second conductive region61bin the second direction D2corresponds to the first nitride region31a. In the first nitride member31, a portion between the first insulating portion42aand the second insulating portion42bin the first direction D1corresponds to the first nitride region31a. In this example, the first nitride region31ais in contact with the third portion22c. As will be described later, another layer (for example, an AlN layer) may be provided between the first nitride region31aand the third portion22c.

For example, the crystallinity of the first nitride region31amay be higher than the crystallinity of the second nitride region31band may be higher than the crystallinity of the third nitride region31c. At least a part of the first nitride region31amay include crystals. At least a part of the second nitride region31bmay be amorphous. At least a part of the third nitride region31cmay be amorphous.

The thickness t1of the first nitride region31aalong the second direction D2is, for example, not less than 1 nm and not more than 10 nm. When the thickness t1is not less than 1 nm, for example, a homogeneous first nitride region31acan be easily obtained. When the thickness t1is not more than 10 nm, it is easy to suppress crystal defects such as misfit dislocations caused by film stress, for example. The thickness t1may be not less than 3 nm and not more than 5 nm. When the thickness t1is not less than 3 nm, for example, a homogeneous first nitride region31acan be more easily obtained. When the thickness t1is not less than 3 nm, for example, the carrier concentration can be stably controlled. When the thickness t1is not more than 5 nm, it is easier to suppress crystal defects such as misfit dislocations caused by film stress, for example.

In the embodiment, the second insulating member42includes silicon and nitrogen. The second insulating member42includes, for example, SiN. With such a second insulating member42, high quality can be easily obtained in the semiconductor member10M under the second insulating member42.

For example, the first insulating member41includes silicon and oxygen. The first insulating member41includes, for example, silicon oxide (SiO2). For example, the first insulating member41does not nitrogen substantially. Alternatively, the concentration of nitrogen in the first insulating member41is lower than the concentration of nitrogen in the second insulating member42. With such a first insulating member41, for example, a stable threshold voltage can be easily obtained.

As shown inFIG.1, the first insulating member41may further include a second insulating region41band a third insulating region41c. The second insulating region41bis located between the first semiconductor portion21and the third electrode53in the first direction D1. The third insulating region41cis located between the third electrode53and the second semiconductor portion22in the first direction D1. At least a part of the third electrode53is between the first semiconductor portion21and the second semiconductor portion22in the first direction D1.

At least a part of the first insulation region41ais between the fourth partial region14and the fifth partial region15in the first direction D1. For example, the semiconductor member10M is provided with a recess, and at least a part of the third electrode53is filled in the recess. The semiconductor device110is a gate recess type transistor.

As shown inFIG.1, the second insulating member42may include a third insulating portion42c. The first semiconductor portion21is between the fourth portion region14and the third insulating portion42c.

As shown inFIG.1, the first insulating member41further includes a fourth insulating region41d. At least a part of the fourth insulating region41dis between the third electrode53and the first conductive member61.

The first insulating member41may include a fifth insulating region41eand a sixth insulating region41f. The first semiconductor portion21is between the fourth partial region14and the fifth insulating region41e. The second semiconductor portion22is between the fifth portion region15and the sixth insulating region41f.

As shown inFIG.1, a length of the first nitride region31aalong the first direction D1is defined as a first length w1. The second semiconductor portion22includes an end22pon the side of the third electrode53. The second semiconductor portion22includes a portion22qthat overlaps the second electrode52in the second direction D2. A distance in the first direction D1between the end22pon the side of the third electrode53of the second semiconductor portion22and the position of the portion22qof the second semiconductor portion22that overlaps the second electrode52in the second direction D2is defined as a second length w2. The first length w1is, for example, note less than 0.035 times and not more than 0.5 times the second length w2. With such a first length w1, for example, a region in which the carrier concentration is controlled is appropriately formed, and a high breakdown voltage can be effectively obtained.

FIG.2is a schematic cross-sectional view illustrating a semiconductor device according to the first embodiment.

As shown inFIG.2, a semiconductor device111according to the embodiment includes a second nitride member32. Except for this, the configuration of the semiconductor device111is the same as the configuration of the semiconductor device110. For example, in the semiconductor device111, the configurations of the first electrode51, the second electrode52, the third electrode53, the semiconductor member10M, the first conductive member61, the first insulating member41, the second insulating member42, and the first nitride member31may be the same as those in the semiconductor device110.

The second nitride member32includes Alx4Ga1-x4N (0<x4≤1, x3<x4). The second nitride member32may be, for example, an AlN layer. The composition ratio x4 of Al in the second nitride member32may be, for example, not less than 0.5 and not more than 1.0.

At least a part of the second nitride member32is between the first portion22aand the first insulating portion42a, and between the second portion22band the second insulating portion42b. A part of the second nitride member32may be provided between the third portion22cand the first nitride region31a.

By providing the second nitride member32as described above, high quality can be obtained in the second semiconductor portion22. For example, damage to the second semiconductor portion22by the second insulating member42can be suppressed.

Also in the semiconductor device111, the carrier concentration can be locally reduced in the region overlapping the second conductive region61b. High breakdown voltage is easy to obtain. It is possible to provide a semiconductor device whose characteristics can be improved.

For example, the second nitride member32may be in contact with the third portion22cand the first nitride region31a.

As shown inFIG.2, a part of the second nitride member32may be provided between the first semiconductor portion21and the third insulating portion42c. For example, damage to the second semiconductor portion22by the second insulating member42can be suppressed.

The thickness t2of the second nitride member32along the second direction D2is, for example, not less than 1 nm and not more than 10 nm. When the thickness t2is not less than 1 nm, for example, damage to the second semiconductor region20can be effectively suppressed. When the thickness t2is not more than 10 nm, for example, in the second nitride member32, it is easy to suppress crystal defects such as misfit dislocations due to film stress. The thickness t2may be, for example, not less than 3 nm and not more than 5 nm. When the thickness t2is not less than 3 nm, damage to the second semiconductor region20can be suppressed more effectively. When the thickness t2is not more than 5 nm, it is easier to suppress crystal defects such as misfit dislocations due to film stress.

Second Embodiment

FIG.3is a schematic cross-sectional view illustrating a semiconductor device according to a second embodiment.

As shown inFIG.3, in a semiconductor device112according to the embodiment, the first conductive member61is electrically connected with the third electrode53. Except for this, the configuration of the semiconductor device112is the same as the configuration of the semiconductor device110. For example, in the semiconductor device112, the configuration of the first electrode51, the second electrode52, the third electrode53, the semiconductor member10M, the first insulating member41, the second insulating member42, and the first nitride member31may be the same as those in the semiconductor device110.

In the semiconductor device112, a terminal electrically connected with the first conductive member61and a terminal electrically connected with the third electrode53are provided, and these terminals may be electrically connected when the semiconductor device is used.

The first nitride region31ais also provided in the semiconductor device112. The first nitride region31ais located between the first insulating portion42aand the second insulating portion42bin the first direction D1. The first nitride region31ais between the third portion22cand the second conductive region61bin the second direction D2. The first nitride region31aoverlaps the second conductive region61bin the second direction D2.

As a result, the carrier concentration in the carrier region10C locally decreases in the region overlapping the second conductive region61b. As a result, high breakdown voltage can be easily obtained. According to the embodiment, it is possible to provide a semiconductor device whose characteristics can be improved.

FIG.4is a schematic cross-sectional view illustrating a semiconductor device according to the second embodiment.

As shown inFIG.4, a semiconductor device113according to the embodiment includes the second nitride member32. Except for this, the configuration of the semiconductor device113is the same as the configuration of the semiconductor device112. For example, in the semiconductor device113, the configurations of the first electrode51, the second electrode52, the third electrode53, the semiconductor member10M, the first conductive member61, the first insulating member41, the second insulating member42, and the first nitride member31may be the same as those in the semiconductor device112.

Also in the semiconductor device113, the carrier concentration can be locally lowered in the region overlapping the second conductive region61b. High breakdown voltage is easy to obtain. It is possible to provide a semiconductor device whose characteristics can be improved.

In the embodiment, information on crystallinity can be obtained, for example, by an X-ray diffraction pattern image. Information on the composition ratio can be obtained by, for example, X-ray photoelectron spectroscopy.

Un the semiconductor devices110to113according to the embodiment, the first nitride member31may include In, Ga and nitrogen. For example, the first nitride member31may include Alx3Ga1-x3N (0≤x3<1) or Iny1Aly2Ga1-y1-y2N (0<y1≤1, 0≤y2<1, y1+y2≤1). For example, the first nitride member31may include Iny1Ga1-y1N (0<y1≤1). On the other hand, the second nitride member32includes Alx4Ga1-x4N (0<x4≤1, x3<x4). For example, the first nitride member31includes InGaN, and the second nitride member32includes AlGaN or AlN.

Third Embodiment

FIG.5is a schematic cross-sectional view illustrating a semiconductor device according to a third embodiment.

As shown inFIG.5, in a semiconductor device121, the first nitride member31includes fourth to seventh nitride regions31dto31gin addition to the first to third nitride regions31ato31c. The second nitride member32includes first to seventh nitride portions32ato32g.

The first nitride portion32ais between the third portion22cand the first nitride region31a. The second nitride portion32bis between the first portion22aand the second nitride region31b. The third nitride portion32cis between the second portion22band the third nitride region31c.

The fourth nitride region31dis located between the third partial region13and the third electrode53in the second direction D2. The fifth nitride region31eis, for example, between the first semiconductor portion21and at least a part of the third electrode53in the first direction D1. The fifth nitride region31eis, for example, between the first semiconductor portion21and at least a part of the second insulating region41bin the first direction D1. The sixth nitride region31fis, for example, between at least a part of the third electrode53and the first portion22ain the first direction D1. The sixth nitride region31fis, for example, between at least a part of the third insulating region41cand the first portion22ain the first direction D1.

The fourth nitride portion32dis located between the third partial region13and the fourth nitride region31din the second direction D2. The fifth nitride portion32eis located between the first semiconductor portion21and the fifth nitride region31ein the second direction D2. The sixth nitride portion32fis located between the sixth nitride region31fand the first portion22ain the second direction D2.

The first semiconductor portion21is located between the fourth partial region14and the seventh nitride region31gin the second direction D2. The third insulating portion42cis located between the seventh nitride portion32gand the seventh nitride region31gin the second direction D2.

The configuration of the semiconductor device121other than the above may be the same as that of the semiconductor device111. By providing the first nitride member31and the second nitride member32as described above, for example, a lower subthreshold swing can be easily obtained.

FIG.6is a schematic cross-sectional view illustrating a semiconductor device according to the third embodiment.

As shown inFIG.6, in a semiconductor device122, the first nitride member31includes the first to seventh nitride regions31ato31g. The second nitride member32includes the first to seventh nitride portions32ato32g. The configuration of the semiconductor device122other than the above may be the same as that of the semiconductor device112. By providing the first nitride member31and the second nitride member32as described above, for example, a lower subthreshold swing can be easily obtained.

In the semiconductor devices112and122, for example, the first nitride member31may include Alx3Ga1-x3N (0≤x3<1) or Iny1Aly2Ga1-y1-y2N (0<y1≤1, 0≤y2≤1, y1+y2≤1). For example, the first nitride member31may include Iny1Ga1-y1N (0<y1≤1). On the other hand, the second nitride member32includes Alx4Ga1-x4N (0<x4≤1, x3<x4). For example, the first nitride member31includes InGaN, and the second nitride member32includes AlGaN or AlN.

According to the embodiments, it is possible to provide a semiconductor device whose characteristics can be improved.

In the specification, “nitride semiconductor” includes all compositions of semiconductors of the chemical formula BxInyAlzGa1-x-y-zN (0≤x≤1, 0≤y≤1, 0≤z≤1, and x+y+z≤1) for which the composition ratios x, y, and z are changed within the ranges respectively. “Nitride semiconductor” further includes group V elements other than N (nitrogen) in the chemical formula recited above, various elements added to control various properties such as the conductivity type and the like, and various elements included unintentionally.

In the specification of the application, “perpendicular” and “parallel” refer to not only strictly perpendicular and strictly parallel but also include, for example, the fluctuation due to manufacturing processes, etc. It is sufficient to be substantially perpendicular and substantially parallel.

Hereinabove, exemplary embodiments of the invention are described with reference to specific examples. However, the embodiments of the invention are not limited to these specific examples. For example, one skilled in the art may similarly practice the invention by appropriately selecting specific configurations of components included in semiconductor devices such as electrodes semiconductor members, compound members, nitride members, insulating members, etc., from known art. Such practice is included in the scope of the invention to the extent that similar effects thereto are obtained.

Further, any two or more components of the specific examples may be combined within the extent of technical feasibility and are included in the scope of the invention to the extent that the purport of the invention is included.

Moreover, all semiconductor devices practicable by an appropriate design modification by one skilled in the art based on the semiconductor devices described above as embodiments of the invention also are within the scope of the invention to the extent that the purport of the invention is included.

Various other variations and modifications can be conceived by those skilled in the art within the spirit of the invention, and it is understood that such variations and modifications are also encompassed within the scope of the invention.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.