JP2009253126A - Semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device which can reduce a current collapse and leakage current, softening an electric field concentration and improving a dielectric resistance. <P>SOLUTION: The semiconductor device 1 includes a control electrode 5 and second main electrode 4 which are separately located on a nitride semiconductor 2 each other, a first insulator 6 which is located between the control electrode 5 and second main electrode 4 on the nitride semiconductor 2, a first field plate 5FP whose one edge is electrically connected with the control electrode 5 and another edge is located between the control electrode 5 and the second main electrode 4 on the first insulator 6, and a resistive field plate 7 whose one edge is connected with the first field plate 5FP on the first insulator 6, another edge is extended towards the second main electrode 4, and has a higher sheet resistance in comparison with the first field plate 5FP. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a semiconductor device, and more particularly to a semiconductor device having a resistive field plate.

  In a device using a gallium nitride (GaN) compound semiconductor, ideal device characteristics such as a high melting point, a high breakdown electric field, and a high saturation electron velocity can be realized. Therefore, it is expected that the gallium nitride compound semiconductor is applied to a low-loss high-voltage power device and a high-frequency device. Application to power devices used in power supply circuits and the like requires not only high breakdown voltage and low on-resistance device characteristics, but also low manufacturing costs.

  The breakdown voltage of the device is determined by the distance between the gate and the drain and the electric field distribution between the gate and the drain. For this reason, in order to obtain a high breakdown voltage device, it is important to increase the distance between the gate and the drain, or to adopt an electric field relaxation structure such as a field plate (FP) to reduce the electric field concentration and control the electric field distribution to be uniform. It is.

  On the other hand, a device using a gallium nitride compound semiconductor has a problem of current collapse. Current collapse is a phenomenon in which electrons trapped at the surface level of a gallium nitride-based compound semiconductor act as a virtual gate and reduce the drain current. To reduce current collapse. There are methods such as adopting a protective film that can reduce the distance between the gate and the drain or reduce the surface state.

In such a device using a gallium nitride compound semiconductor, paying attention to the gate-drain distance, there is a trade-off relationship between the breakdown voltage and the current collapse. As an electric field relaxation method and a current collapse reduction method, there are an invention in which the field plate disclosed in the following Patent Document 1 has a multistage structure and an invention in which the semiconductor surface disclosed in the following Patent Document 2 is covered with a silicon nitride film. It is valid.
JP 2005-93864 A JP 2004-200248 A

  In the invention disclosed in Patent Document 1 and the invention disclosed in Patent Document 2, the following points have not been considered.

  In the invention disclosed in Patent Document 1, electric field concentration can be reduced by making the field plate multi-stage as compared with a device adopting a single structure of the field plate. However, the multi-stage field plate has limitations in the manufacturing process, and furthermore, since a metal film having a low resistance is usually used for the field plate, electric field concentration occurs at the end of the field plate. There is a limit to the relaxation of electric field concentration.

  Further, in the invention disclosed in Patent Document 2, there is a limit to reducing surface state traps by the silicon nitride film. In particular, in the case of a power device, since the distance between the gate and the drain is long, the number of electrons trapped at the surface level increases, and the influence of the trapped electrons tends to remain. Furthermore, the current collapse can be reduced by employing the silicon nitride film, but the leakage current increases conversely.

  The present invention has been made to solve the above problems. Accordingly, an object of the present invention is to provide a semiconductor device that can alleviate electric field concentration and improve breakdown voltage, reduce current collapse, and reduce leakage current.

  In order to solve the above-described problem, a first feature according to an embodiment of the present invention is that a semiconductor device includes a nitride semiconductor and a first electrode disposed on the nitride semiconductor so as to be spaced apart from each other. And the second electrode, the insulator disposed between the first electrode and the second electrode on the nitride-based semiconductor, one end electrically connected to the first electrode, and the other end A field plate disposed between the first electrode and the second electrode on the insulator; one end connected to the field plate on the insulator; the other end extending toward the second electrode; And a resistive field plate having a sheet resistance higher than that of the field plate.

  According to a second aspect of the present invention, in the semiconductor device, a nitride-based semiconductor, and a first main electrode and a second main electrode that are spaced apart from each other on the nitride-based semiconductor, and A control electrode disposed between the first main electrode and the second main electrode on the nitride-based semiconductor; a control electrode between the first main electrode and the control electrode on the nitride semiconductor; One end is electrically connected to the insulator disposed between the second main electrode and the control electrode, and the other end is disposed between the control electrode and the second main electrode on the insulator. One end of the first field plate and the first main electrode is closer to the first main electrode than the other end of the first field plate and is electrically connected to the first main electrode, and the other end is A second electrode disposed between the other end of the first field plate and the second main electrode on the insulator on the control electrode. Comprising a I over field plate is disposed between the control electrode and second main electrode on the insulator, and a resistive field plate having a high sheet resistance than the sheet resistance of at least the control electrode.

  In the semiconductor device according to the second feature, it is preferable that one end of the resistive field plate is connected to the control electrode and the other end is connected to the second main electrode.

  In the semiconductor device according to the second feature, it is preferable that one end of the resistive field plate is connected to the second main electrode and the other end extends beyond the second field plate toward the control electrode. .

  In the semiconductor device according to the second feature, it is preferable that one end of the resistive field plate is connected to the second field plate and the other end is extended toward the second main electrode.

  According to the present invention, it is an object to provide a semiconductor device that can alleviate electric field concentration and improve withstand voltage, reduce current collapse, and reduce leakage current.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, the drawings are schematic and different from actual ones. In addition, there may be a case where the dimensional relationships and ratios are different between the drawings.

  Further, the following embodiments exemplify apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention is to arrange the components and the like as follows. Not specific. The technical idea of the present invention can be variously modified within the scope of the claims.

(First embodiment)
In the first embodiment of the present invention, an example in which the present invention is applied to a semiconductor device including a high electron mobility transistor (HEMT) composed of a gallium nitride semiconductor will be described. .

[Structure of semiconductor device]
As shown in FIG. 1, a semiconductor device 1 according to the first embodiment includes a nitride-based semiconductor 2, a first main electrode 3 and a first main electrode 3 that are spaced apart from each other on the nitride-based semiconductor 2. Two main electrodes 4, a control electrode 5 disposed on the nitride-based semiconductor 2 between the first main electrode 3 and the second main electrode 4, and a first on the nitride-based semiconductor 2. One end of the first insulator 6 disposed between the main electrode 3 and the control electrode 5 and between the control electrode 5 and the second main electrode 4 is electrically connected to the control electrode 5. A first field plate 5FP having an end disposed between the control electrode 5 and the second electrode 4 on the first insulator 6, and the control electrode 5 and the second electrode on the first insulator 6 A resistive field plate (resistive) which is disposed between the main electrode 4 and has a sheet resistance higher than at least the sheet resistance of the control electrode 5 And the first main electrode 3 and the second main electrode 4 on the first insulator 6, the control electrode 5, and the first field plate 5 FP. A second insulator 8 functioning as an interlayer insulating film between the field plate 3FP and the control electrode 5, the first field plate 5FP and the resistive field plate 7, and one end electrically connected to the first main electrode 3. And the other end of the second insulator 8 includes a second field plate 3FP disposed between the first field plate 5FP and the second main electrode 4 on the second insulator 8.

  Although the detailed cross-sectional structure is not shown here, the nitride-based semiconductor 2 is a device functional layer that constructs a HEMT. The nitride-based semiconductor 2 is disposed on a substrate (not shown) such as a silicon carbide (SiC) substrate, a silicon (Si) substrate, or a sapphire substrate, and an aluminum nitride (AlN) buffer layer, undoped gallium nitride, for example, is provided on the substrate. (GaN) layers, undoped aluminum gallium nitride (AlGaN) layers, n-type AlGaN layers, and undoped AlGaN layers are sequentially stacked. The two-dimensional electron gas channel (or two-dimensional electron gas layer) of the HEMT is generated near the heterojunction between the n-type AlGaN layer and the undoped AlGaN layer.

  In the first embodiment, the first main electrode 3 is a source electrode, and the second main electrode 4 is a drain electrode. Although the HEMT shown in FIG. 1 is schematically described, the first main electrode 3 and the second main electrode 4 are both connected to the two-dimensional electron gas channel of the nitride-based semiconductor 3. It reaches the n-type AlGaN layer. The first main electrode 3 is constituted by a laminated film of, for example, a titanium (Ti) layer and an aluminum (Al) film that make ohmic connections.

  The control electrode 5 is a gate electrode. The control electrode 5 is composed of a laminated film of, for example, a nickel (Ni) layer and a gold (Au) layer that perform Schottky connection.

  In the first insulator 6, a silicon oxide film capable of generating compressive stress and reducing leakage current as compared with a silicon nitride film is used at least in a layer directly in contact with the surface of the nitride-based semiconductor 2. For the second insulator 8, for example, at least one of a silicon oxide film and a silicon nitride film can be used.

  The first field plate 5FP is a gate field plate. In the first embodiment, the first field plate 5FP is made of the same conductive material as that of the control electrode 5, and is integrally formed on the same conductive layer.

  The other end of the first field plate 5FP extends toward the second main electrode (drain electrode) 4 and is disposed between the control electrode 5 and the second main electrode 4. The first field plate 5FP has a function of shielding the electric field from the second main electrode 4 and suppressing the occurrence of electric field concentration at the control electrode 7 end. The length of the first field plate 5FP is set to a length within a range of 10% to 40% of the distance between the control electrode 5 and the second main electrode 4. The first field plate 5FP may be provided on the surface of the first insulator 6 with an inclination and disposed on the first insulator 6 along the inclination. In this case, the angle formed between the bottom surface of the first field plate 5FP and the surface of the nitride semiconductor 2 is set within a range of 10 degrees to 60 degrees.

  The second field plate 3FP is a source field plate. One end of the second field plate 3FP is closer to the first main electrode 3 than the other end of the first field plate 5FP and is electrically connected to the first main electrode 3. In the first embodiment, second field plate 3FP is made of an upper layer conductive material different from first main electrode 3. For the second field plate 3FP, for example, a conductive material composed of a laminated film of a Ti layer, a Ni layer, and an Au layer can be used.

  The other end of the second field plate 3FP is extended to the second main electrode (drain electrode) 4 side beyond the control electrode 5 and the first field plate 5FP, and the first feed plate 5FP and the second main plate 3FP are extended. The electrode is disposed up to the resistive field plate 7 between the electrodes 4. The second field plate 3FP has a function of shielding the electric field from the second main electrode 4 and suppressing the occurrence of electric field concentration at the end of the control electrode 7. The length of the second field plate 3FP is the same as that between the control electrode 5 and the second main electrode 4 because the semiconductor device 1 according to the first embodiment includes the first field plate 5FP. The length is set within a range of 20% to 60% of the distance. When the first field plate 5FP is not provided, the length of the second field plate 3FP is within a range of 10% to 40% of the distance between the control electrode 5 and the second main electrode 4. Set to length.

  In the first embodiment, the resistive field plate 7 is disposed between the first insulator 6 and the second insulator 8, one end is electrically connected to the control electrode 5, and the other end Is connected to the second main electrode 4. The resistive field plate 7 is composed of a conductive film that is several orders of magnitude thinner than the thickness of the control electrode 5, and has a sheet resistance much higher than that of the control electrode 5. Specifically, the resistive field plate 7 is composed of a metal film such as a Ti layer, a Ni layer, a copper (Cu) layer, a chromium (Cr) layer, a tungsten (W) layer, and the like. It is set within the range of 1 nm to several tens of nm. The sheet resistance value is set to 1 MΩ / □ or more, for example. In the first embodiment, the resistive field plate 7 has a single-layer structure. However, the present invention is not limited to such a structure, and a conductive material having a changed length and sheet resistance. You may comprise by the composite film which laminated | stacked the film | membrane.

[Operation principle of resistive field plate]
In the semiconductor device 1 according to the first embodiment described above, in order to achieve a high breakdown voltage, the other end of the first field plate 5FP on the second main electrode 4 side, the second field plate 3FP second It is necessary to alleviate the electric field concentration at the other end on the main electrode 4 side.

  When a reverse voltage is applied, a minute leak current flows through the resistive field plate 7. At this time, since the semiconductor device 1 is in the off state, the voltage between the first main electrode 3 and the control electrode 5 is sufficiently smaller than that between the second main electrode 4 and the control electrode 5. One end of the resistive field plate 7 is closer to the control electrode 5 than the other end of the first field plate 5FP, and the potential gradient of the resistive field plate 7 gradually decreases as the distance from the first field plate 5FP increases. Therefore, the electric field concentration in the second field plate 3FP is relaxed. Therefore, the high breakdown voltage of the HEMT can be realized.

  In order to reduce current collapse, it is necessary to further extract electrons trapped on the surface of the nitride-based semiconductor 2.

  When a reverse voltage is applied, electrons are trapped on the surface of the nitride semiconductor 2 between the second main electrode 4 and the control electrode 5. The trapped electrons are also extracted by the resistive field plate 7. be able to. Therefore, the current collapse phenomenon that occurs in the HEMT can be improved.

  In the HEMT that does not include the resistive field plate 7 according to the first embodiment, only the extraction of electrons by the first field plate 5FP and the second field plate 3FP can be performed. That is, since electrons trapped in a region slightly away from the end of the first field plate 5FP on the second main electrode 4 side cannot be extracted, the current collapse phenomenon generated in the HEMT cannot be sufficiently improved. .

[Features of semiconductor devices]
The semiconductor device 1 according to the first embodiment described above includes the resistive field plate 7 and can suppress electric field concentration on the second main electrode 4 side of the second field plate 3FP. Since the distribution can be relaxed uniformly and gently, a high breakdown voltage can be realized.

  Furthermore, in the semiconductor device 1 according to the first embodiment, electrons trapped at the surface level of the nitride-based semiconductor 2 can be effectively extracted when a reverse voltage is applied. The occurrence of collapse can be reduced. Therefore, in the semiconductor device 1, it is possible to suppress an increase in on-resistance after applying a reverse voltage.

  Furthermore, in the semiconductor device 1 according to the first embodiment, the surface of the nitride-based semiconductor 2 is covered with the first insulator 6 formed of the silicon oxide film under the condition that causes compressive stress, and the stress On-resistance is lowered by generating a compressive stress on the surface of the nitride-based semiconductor 2 having piezoelectric polarization. Further, the silicon oxide film can reduce the leakage current more than the silicon nitride film.

  Furthermore, in the semiconductor device 1 according to the first embodiment, electric field concentration can be relaxed and it is difficult to break down, so that the gap between the control electrode 5 and the second main electrode 4 (gate electrode-drain electrode) Distance) can be shortened, and the on-resistance can be reduced.

[First Modification]
The first modification of the first embodiment is that the structure of the first main electrode 3 and the second field plate 3FP is changed in the semiconductor device 1 according to the first embodiment shown in FIG. An example will be described.

  As shown in FIG. 2, in the semiconductor device 1 according to the first modification, the second field plate 3FP is made of the same conductive material as that of the first main electrode 3, and is formed in the same conductive layer. It is constructed integrally.

  In the semiconductor device 1 according to the first modified example configured as described above, the same operational effects as those obtained by the semiconductor device 1 according to the first embodiment described above can be obtained.

[Second Modification]
The second modification of the first embodiment is an example in which the structures of the resistive field plate 7 and the second main electrode 4 are changed in the semiconductor device 1 according to the first modification shown in FIG. Is described.

  As shown in FIG. 3, the semiconductor device 1 according to the second modification example has one end electrically connected to the second main electrode 4 and the other end on the first insulator 6. 4 and the control electrode 5, more specifically, a third field plate 4PF disposed between the second field plate 3FP is further provided. In the second modification, the third field plate 4FP is made of the same conductive material as that of the second main electrode 4 and is integrally formed in the same conductive layer.

  The resistive field plate 7 has one end electrically connected to the second main electrode 4 and the other end extending beyond the other end of the second field plate 3FP toward the first field plate 5FP. .

  In the semiconductor device 1 according to the second modified example configured as described above, the same operational effects as those obtained by the semiconductor device 1 according to the first embodiment described above can be obtained.

(Second Embodiment)
In the second embodiment of the present invention, an example in which the structure of the resistive field plate 7 is changed in the semiconductor device 1 according to the first modification of the first embodiment shown in FIG. 2 will be described. Is.

  As shown in FIG. 4, in the semiconductor device 1 according to the second embodiment, the resistive field plate 7 is disposed on the second insulator 8 and has one end connected to the second field plate 3FP. The other end is connected to the second main electrode 4.

  In the semiconductor device 1 according to the second embodiment configured as described above, the same operational effects as those obtained by the semiconductor device 1 according to the first embodiment described above can be obtained.

[Modification]
The modification of the second embodiment is for explaining an example in which the structure of the resistive field plate 7 is changed in the semiconductor device 1 according to the second embodiment shown in FIG.

  As shown in FIG. 5, in the semiconductor device 1 according to the modification, the resistive field plate 7 is disposed on the second insulator 8, one end is connected to the second field plate 3FP, and the other end Is extended toward the second main electrode 4.

  In the semiconductor device 1 according to the modified example configured as described above, the same operational effects as the operational effects obtained by the semiconductor device 1 according to the second embodiment described above can be achieved.

(Third embodiment)
In the third embodiment of the present invention, an example in which the present invention is applied to a semiconductor device including Schottky barrier diodes (SBD) made of a gallium nitride semiconductor will be described.

  As shown in FIG. 6, the semiconductor device 1 according to the third embodiment includes a nitride-based semiconductor 2, a first main electrode 3 and a first main electrode 3 that are spaced apart from each other on the nitride-based semiconductor 2. Two main electrodes 4, a first insulator 6 disposed between the first main electrode 3 and the second main electrode 4 on the nitride semiconductor 2, and one end of the first main electrode 3 Are electrically connected, and the other end is disposed on the first insulator 6 between the first main electrode 3 and the second main electrode 4 (extends toward the second main electrode 4). The first main electrode 3 and the second main electrode 4 are connected to the second field plate 3FP and the second main electrode 4 at one end, and the other ends on the first insulator 6. And a third field plate 4FP (stretched toward the first main electrode 3) disposed between and one end of the second field on the first insulator 6 A resistance electrically connected to the rate 3FP and having the other end extending toward the third field plate 4FP and having a sheet resistance higher than that of the first main electrode 3 and the second main electrode 4 And a field plate 7.

  Although the detailed cross-sectional structure is not shown here, the nitride-based semiconductor 2 is a device functional layer that constructs an SBD.

  In the third embodiment, the first main electrode 3 is an anode electrode, and the second main electrode 4 is a cathode electrode. Although the SBD shown in FIG. 6 is schematically shown, the first main electrode 3 is disposed on the anode region (p-type semiconductor region) of the nitride-based semiconductor 2, and the Schottky is formed in the anode region. It is connected. The second main electrode 4 is disposed on the cathode region (n-type semiconductor region) of the nitride-based semiconductor 2 and is ohmically connected to the cathode region.

  The first main electrode 3 is made of the same conductive material as that of the control electrode 5 of the semiconductor device 1 according to the first embodiment. For the second main electrode 4, the same conductive material as that of the first main electrode 3 or the second main electrode 4 of the semiconductor device 1 according to the first embodiment is used. Similarly, a silicon oxide film is used for the first insulator 6.

  In the third embodiment, the second field plate 3FP is an anode field plate. The second field plate 3FP is made of the same conductive material as that of the first main electrode 3, and is integrally formed on the same conductive layer. The third field plate 4FP is a cathode field plate. The third field plate 4FP is made of the same conductive material as that of the second main electrode 4, and is integrally formed on the same conductive layer.

  Similar to the resistive field plate 7 according to the first embodiment, the resistive field plate 7 has a conductive property that is several orders of magnitude thinner than the film thickness of the first main electrode 3 and the second main electrode 4. It is composed of a film and has a sheet resistance much higher than that of the first main electrode 3 and the second main electrode 4.

  In the semiconductor device 1 according to the third embodiment configured as described above, the same operational effects as those obtained by the semiconductor device 1 according to the first embodiment described above can be obtained.

[Modification]
The modification of the third embodiment is for explaining an example in which the structure of the resistive field plate 7 is changed in the semiconductor device 1 according to the third embodiment shown in FIG.

  As shown in FIG. 7, in the semiconductor device 1 according to the modification, the resistive field plate 7 has one end electrically connected to the third field plate 4FP on the first insulator 6 and the other end connected to the third field plate 4FP. It extends toward the second field plate 3FP.

  In the semiconductor device 1 according to the modified example configured as described above, the same operational effects as the operational effects obtained by the semiconductor device 1 according to the second embodiment described above can be achieved.

(Other embodiments)
As described above, the present invention has been described according to the first embodiment, the second embodiment, and the third embodiment. However, the description and drawings constituting a part of this disclosure limit the present invention. Not. The present invention can be applied to various alternative embodiments, examples, and operational technologies. For example, although the HEMT is formed in the semiconductor device 1 according to the first embodiment and the second embodiment described above, the present invention is not limited to this transistor. For example, a MESFET (metal It can be applied to a transistor using a nitride semiconductor such as a semiconductor field effect transistor) or a heterojunction bipolar transistor (HBT).

1 is a cross-sectional view of a semiconductor device according to a first embodiment of the present invention. It is sectional drawing of the semiconductor device which concerns on the 1st modification of 1st Embodiment. It is sectional drawing of the semiconductor device which concerns on the 2nd modification of 1st Embodiment. It is sectional drawing of the semiconductor device which concerns on the 2nd Embodiment of this invention. It is sectional drawing of the semiconductor device which concerns on the modification of 2nd Embodiment. It is sectional drawing of the semiconductor device which concerns on the 3rd Embodiment of this invention. It is sectional drawing of the semiconductor device which concerns on the modification of 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Semiconductor device 2 ... Nitride-type semiconductor 3 ... 1st main electrode 3FP ... 2nd field plate 4 ... 2nd main electrode 4FP ... 3rd field plate 5 ... Control electrode 5FP ... 1st field plate 6 ... first insulator 7 ... resistive field plate 8 ... second insulator

Claims (5)

A nitride-based semiconductor;
A first electrode and a second electrode which are spaced apart from each other on the nitride-based semiconductor;
An insulator disposed between the first electrode and the second electrode on the nitride-based semiconductor;
A field plate having one end electrically connected to the first electrode and the other end disposed between the first electrode and the second electrode on the insulator;
A resistive field plate having one end connected to the field plate on the insulator and the other end extending toward the second electrode and having a sheet resistance higher than the sheet resistance of the field plate;
A semiconductor device comprising: A nitride-based semiconductor;
A first main electrode and a second main electrode which are spaced apart from each other on the nitride-based semiconductor;
A control electrode disposed between the first main electrode and the second main electrode on the nitride-based semiconductor;
An insulator disposed between the first main electrode and the control electrode on the nitride semiconductor and between the control electrode and the second main electrode;
A first field plate having one end electrically connected to the control electrode and the other end disposed between the control electrode and the second main electrode on the insulator;
One end of the first main electrode is closer to the first main electrode than the other end of the first field plate and is electrically connected to the first main electrode, and the other end is on the control electrode A second field plate disposed on the insulator between the other end of the first field plate and the second main electrode;
A resistive field plate disposed between the control electrode and the second main electrode on the insulator and having a sheet resistance higher than at least the sheet resistance of the control electrode;
A semiconductor device comprising:   The semiconductor device according to claim 2, wherein one end of the resistive field plate is connected to the control electrode, and the other end is connected to the second main electrode.   The one end of the resistive field plate is connected to the second main electrode, and the other end extends beyond the second field plate toward the control electrode. Semiconductor device.   3. The semiconductor device according to claim 2, wherein one end of the resistive field plate is connected to the second field plate, and the other end is extended toward the second main electrode.

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