TW201733137A - Power diode device - Google Patents

Abstract

A power diode device is provided. The power diode device includes a substrate, an epitaxial layer, a RESURF layer, a highly-doped contact region, and an isolation structure. The epitaxial layer disposed on the substrate has the same conductivity type as the substrate. The RESURF layer disposed on the epitaxial layer and having a top surface defines an active region. The highly-doped contact region having the same conductivity type as the RESURF layer is formed in the active region of the RESURF region and exposed at the top surface. The isolation structure is formed in the RESURF layer and surrounds the active region. A continuous PN junction among the RESURF layer, the epitaxial layer, and the isolation structure is formed.

Description

Power diode component

The present invention relates to a semiconductor component, and more particularly to a power diode component for rectification.

A power diode is a widely used electronic component and an important component of an electronic circuit. A good power diode must have low turn-on voltage, high switching speed, and high breakdown voltage.

Referring to Figure 1, a schematic cross-sectional view of a conventional power diode is shown. A conventional power diode element 1 includes a substrate 10, a semi-insulating layer 11, a glass passivation layer 12, and an electrode layer 13. Specifically, the substrate 10 has a p-type doping region 101 and an n-type doping region 102 respectively to form a PN junction in the substrate 10, wherein the p-type doping region 101 is exposed to the substrate 10 Top surface. The electrode layer 13 is located on the top surface of the substrate 10 to electrically contact the p-type doping region 101.

In addition, the sides of the substrate 10 are partially etched such that the upper portion of the substrate 10 forms a mesa and the PN junctions are exposed to both side surfaces of the platform. A semi-insulating layer 11 covers both side surfaces of the platform to protect the PN junction. In addition, a glass passivation layer 12 is overlaid on the semi-insulating layer 11.

Since the power diode 1 described above is subjected to an etching process to form a three-dimensional structure, in the etching process, the etching rate of the etching liquid to different positions of the substrate 10 may not be completely uniform, thereby making the side surface of the platform Gradient cannot be precisely controlled. However, the gradient of the side surface of the platform affects the breakdown voltage of the power diode 1, and thus the measured breakdown voltage is not as expected. In addition, when the semi-insulating layer 11 and the glass passivation layer 12 and the electrode layer 13 are formed by the yellow lithography process, the alignment accuracy is also affected.

Next, referring to FIG. 2, a schematic cross-sectional view of another power diode of the prior art is shown. Another conventional power diode 2 includes a substrate 20, a protective layer 21, an upper electrode layer 22, and a lower electrode layer 23. The upper electrode layer 22 and the lower electrode layer 23 are respectively located on the upper surface and the lower surface of the substrate 20.

In addition, the substrate 20 has an n-type heavily doped region 201 for forming an ohmic contact with the lower electrode layer 23, a p-type heavily doped region 203 for forming an ohmic contact with the upper electrode layer 22, and an n-type heavily doped region. An n-type lightly doped region 202 between the 201 and the p-type heavily doped region 203. When the power diode 2 is applied with a reverse bias, in order to laterally extend the electric field to increase the breakdown voltage of the power diode 2, there are a plurality of ring-shaped p-type dopings around the p-type heavily doped region 203. Zones to form a plurality of guard rings 204.

However, in order to increase the breakdown voltage of the power diode 2, it is necessary to increase the number of guard rings. Therefore, the proportion of the area occupied by the guard ring also increases, which is disadvantageous for the size reduction of the component. In addition, since the guard ring usually has a narrow line width, when the guard ring is prepared by a line width process such as yellow lithography and etching, the process cleanliness and the line width process limitation easily affect the yield of the power diode 2.

Accordingly, the development of a power diode with a simple process and a large breakdown voltage is still a goal of research by those skilled in the art.

The invention provides a power diode element, which reduces the surface electric field of the power diode element by reducing the surface electric field layer, thereby improving the breakdown voltage of the power diode element.

One embodiment of the present invention provides a power diode component including a substrate, an epitaxial layer, a reduced surface electric field layer, a heavily doped contact region, and an isolation structure. The epitaxial layer is on the substrate and has the same conductivity type as the substrate. The reduced surface electric field layer is located on the epitaxial layer and has a top surface, wherein the reduced surface electric field layer defines an active region. The heavily doped contact region is formed in the active region of the reduced surface electric field layer and exposed to the top surface, wherein the heavily doped contact region and the reduced surface electric field layer have the same conductivity type. Isolation structure formed in the lower The low surface electric field layer surrounds the active region, wherein a reduced PN junction is formed between the surface electric field layer and the epitaxial layer and the isolation structure.

In summary, the power diode element provided by the present invention can reduce the surface electric field layer so that the withstand voltage control of the power diode element can be determined by reducing the thickness of the surface electric field layer. In addition, the PN junction is formed between the surface electric field layer, the epitaxial layer and the isolation structure, and when the power diode element is reversely biased, the surface electric field can be laterally extended, thereby improving the power diode component. The breakdown voltage. In addition, since the power diode element provided by the present invention does not need to be provided with a guard ring and does not have a three-dimensional structure, the power diode device of the embodiment of the present invention is simpler and easier to manufacture than the prior art. control.

The above described features and advantages of the present invention will be more apparent from the following description.

1, 2‧‧‧Learning power diodes

10, 20‧‧‧ substrate

101‧‧‧p-doped region

102‧‧‧n-doped region

11‧‧‧Semi-insulating layer

12‧‧‧ glass passivation layer

13‧‧‧Electrode layer

21‧‧‧Protective layer

22‧‧‧Upper electrode layer

23‧‧‧ lower electrode layer

201‧‧‧n type heavily doped area

203‧‧‧p type heavily doped area

202‧‧‧n type lightly doped area

204‧‧‧ guard ring

3‧‧‧Power diode components

30‧‧‧Base

30a‧‧‧ upper surface

30b‧‧‧back

31‧‧‧Elevation layer

32‧‧‧Reducing the surface electric field layer

321‧‧‧ top surface

AR‧‧‧Active Area

33‧‧‧ heavily doped contact area

34‧‧‧Isolation structure

35‧‧‧ Passivation layer

36‧‧‧ positive electrode layer

37‧‧‧Back electrode layer

S1‧‧‧ first PN junction

S2‧‧‧ second PN junction

351‧‧‧Electrical neutral insulation

352‧‧‧hard protective layer

D‧‧‧Predetermined distance

DR‧‧‧ Vacant Zone

Peak P1, P2‧‧‧

L1~L4‧‧‧ position

FIG. 1 is a schematic cross-sectional view of a conventional power diode.

2 is a schematic cross-sectional view of another conventional power diode.

3 is a top plan view of a power diode component in accordance with an embodiment of the present invention.

4 is a cross-sectional view of the power diode component of FIG. 3 taken along line IV-IV.

FIG. 5 is a partial enlarged view of the power diode element of FIG. 4.

FIG. 6 is a graph showing electric field intensity along the line X-X of the power diode element of FIG. 5.

FIG. 7 is a graph showing the electric field intensity along the line Y-Y of the power diode element of FIG. 5.

Please refer to FIG. 3 and FIG. 4. 3 is a schematic top view of a power diode component according to an embodiment of the invention, and FIG. 4 is a cross-sectional view of the power diode component of FIG. 3 taken along line IV-IV.

The power diode element 3 of the embodiment of the present invention includes a substrate 30, an epitaxial layer 31, a reduced surface electric field layer 32, a heavily doped contact region 33, an isolation structure 34, a passivation layer 35, a positive electrode layer 36, and a back electrode layer 37. .

In this embodiment, the substrate 30 is a semiconductor material, which may be germanium (Si) or nitrided. Gallium (GaN), gallium arsenide (GaAs), aluminum nitride (AlN), tantalum carbide (SiC), indium phosphide (InP), zinc selenide (ZnSe) or other Group VI, III-V or II- Group VI semiconductor materials. The substrate 30 has a high concentration of the first type of conductive impurities and may be an N-type or P-type conductive impurity. It is assumed that the substrate 30 is a germanium substrate, the N-type conductive impurities are pentavalent element ions such as phosphorus ions or arsenic ions, and the P-type conductive impurities are trivalent element ions such as boron ions, aluminum ions or gallium ions.

Further, the substrate 30 has an upper surface 30a and a back surface 30b opposed to the upper surface 30a. An epitaxial layer 31 is located on the upper surface 30a of the substrate 30 and has a low concentration of first type conductivity impurities. In the present embodiment, the substrate 30 is a high concentration of N-type doping (N+), and the epitaxial layer 31 is a low concentration of N-type doping (N-).

The back surface 30b of the substrate 30 is in electrical contact with the back electrode layer 37. In this embodiment, the substrate 30 having the N-type doping has a resistance range of less than 0.01 ohm. Cm to form an ohmic contact with the back electrode layer 37. Also, when the substrate 30 is N-type doped, the back electrode layer 37 is a cathode electrode layer and is electrically connected to an external control circuit.

The reduced surface electric field layer 32 is located on the epitaxial layer 31 and has a conductivity type opposite to that of the epitaxial layer 31. In the present embodiment, the epitaxial layer 31 has a low concentration of the N-type doped region, and the surface electric field layer 32 is lowered to have a low concentration of the P-type doped region. In one example, the reduced surface electric field layer 32 is a P-type epitaxial layer. Therefore, the first PN junction S1 is formed between the surface electric field layer 32 and the epitaxial layer 31.

It should be noted that the thickness of the epitaxial layer 31 and the reduced surface electric field layer 32 and the doping concentration affect the breakdown voltage of the power diode element 3, and therefore, the thickness of the epitaxial layer 31 and the surface electric field reducing layer 32 and the doping. The concentration can be adjusted according to the preset breakdown voltage.

In the embodiment of the present invention, the preset breakdown voltage is 200V to 1000V, and the thickness of the epitaxial layer 31 is between 10 and 65 μm, and the resistance value is between 5 and 25 ohms. Between cm. In addition, the thickness of the surface electric field reducing layer 32 is between 10 and 45 μm, and the resistance value is between 15 and 75 ohms. Between cm. It should be noted that the thickness of the surface electric field layer 32 is generally reduced to be substantially the same as the thickness of the epitaxial layer 31. In one embodiment, the difference between the thickness of the reduced surface electric field layer 32 and the thickness of the epitaxial layer 31 is less than 10 [mu]m.

In addition, the reduced surface electric field layer 32 has a top surface 321 and defines an active area AR. The heavily doped contact region 33 is formed in the active region AR of the reduced surface electric field layer 32 and is exposed on the top surface 321. In detail, the heavily doped contact region 33 has the same conductivity type as the reduced surface electric field layer 32, but the doping concentration of the heavily doped contact region 33 is greater than the doping concentration of the reduced surface electric field layer 32. Additionally, the depth of the heavily doped contact region 33 is less than the thickness of the reduced surface electric field layer 32.

Thus, when the power diode element 3 is applied with a reverse bias, the range of the depletion region DR can be confined as much as possible within the reduced surface electric field layer 32, and the carrier in the heavily doped contact region 33 can be avoided. Do it.

Referring to FIG. 3, it can be seen from the top view that the isolation structure 34 is formed in the reduced surface electric field layer 32 and surrounds the active area AR. Additionally, as shown in FIG. 4, the isolation structure 34 extends downwardly from the top surface 321 of the reduced surface electric field layer 32 into the epitaxial layer 31.

In detail, the isolation structure 34 is formed by an ion implantation or a thermal diffusion process in an isolated doped region in the reduced surface electric field layer 32, and the isolation doped region has the same conductivity type as the epitaxial layer 31, and The reduced surface electric field layer 32 has an opposite conductivity type. Therefore, a second PN junction S2 is formed between the reduced surface electric field layer 32 and the isolation structure 34.

In addition, the diffusion depth of the isolation structure 34 may be greater than the thickness of the surface electric field layer 32, and the isolation structure 34 is extended into the epitaxial layer 31. Therefore, the first PN junction S1 formed between the surface electric field reducing layer 32 and the epitaxial layer 31 and the second PN junction S2 formed between the surface electric field layer 32 and the isolation structure 34 are connected to each other. That is to say, a continuous PN junction is formed between the surface electric field layer 32, the epitaxial layer 31 and the isolation structure 34.

In an embodiment of the invention, the concentration of the isolation structure 34 may be greater than the reduction of the doping concentration of the surface electric field layer 32. In the present embodiment, the doping concentration of the isolation structure 34 is greater than 10 ¹⁹ cm ^-3 . In addition to this, the isolation structure 34 and the heavily doped contact regions 33 are separated from each other by a predetermined distance D. It should be noted that if the predetermined distance D between the foregoing isolation structure 34 and the heavily doped contact region 33 is too small, the effect of soothing the surface electric field cannot be effectively achieved, and it is possible to make the power diode element 3 close to the surface (also It is the place where the top surface 321) is broken, and the breakdown voltage of the power diode element 3 cannot be effectively improved.

Therefore, the predetermined distance D between the isolation structure 34 and the heavily doped contact region 33 can be designed according to the breakdown voltage of the power diode element 3. The higher the breakdown voltage that is required to withstand, the greater the predetermined distance D needs to be. In an embodiment, the predetermined distance D is at least greater than the sum of the thickness of the reduced surface electric field layer 32 and the thickness of the epitaxial layer 31. In an embodiment, if the preset breakdown voltage is 200V to 1000V, the total thickness of the epitaxial layer 31 and the reduced surface electric field layer 32 may be between 20 and 105 μm.

In one embodiment, when the breakdown voltage is 200V, the total thickness of the epitaxial layer 31 and the reduced surface electric field layer 32 is between 20 and 40 μm, and when the breakdown voltage is 1000 V, the epitaxial layer 31 and the surface electric field are lowered. The total thickness of layer 32 is between 85 and 105 μm. The predetermined distance D can be adjusted according to the preset breakdown voltage value and the total thickness of the epitaxial layer 31 and the reduced surface electric field layer 32.

Referring to FIGS. 3 and 4, a passivation layer 35 is formed on the top surface 321 of the reduced surface electric field layer 32 to cover the second PN junction S2 exposed to the top surface 321. Additionally, passivation layer 35 has an opening 350 that is coupled to heavily doped contact region 33. The passivation layer 35 covers the second PN junction S2 exposed to the top surface 321 and exposes the heavily doped contact region 33 located in the active region AR through the opening 350. As shown in FIG. 3, the passivation layer 35 is over the top surface 321 of the reduced surface electric field layer 32 around the active area AR.

In detail, the passivation layer 35 has an electrically neutral insulating layer 351 and a hard protective layer 352 which are sequentially stacked on the top surface 321 . The electrically neutral insulating layer 351 is, for example, a borophosphorus bismuth glass (BPSG) or a semi-insulating polycrystalline germanium film (SIPOS), which prevents electrons or holes from accumulating on the surface of the power diode element 3, and It is avoided that when the power diode element 3 is biased, the accumulated electrons or holes generate leakage current, which affects the electrical performance of the power diode element 3. The hard protective layer 352 is, for example, a dense insulating layer such as nitride, which can be used to insulate moisture or contamination.

In addition, the positive electrode layer 36 is disposed on the top surface 321 of the surface electric field reducing layer 32, and electrically contacts the heavily doped contact region 33 through the opening of the passivation layer 35. In this embodiment, the positive electrode layer 36 can form an ohmic contact with the heavily doped contact region 33 and function as a power diode component. The anode of 3 is connected to an external control circuit.

Please refer to FIG. 5. FIG. 5 is a partial enlarged view of the power diode component of FIG. 4. When the power diode element 3 is reversely biased, a depletion region DR is formed between the reduced surface electric field layer 32, the epitaxial layer 31, and the isolation structure 34. It should be noted that since the isolation structure 34 contains a high concentration doped first conductivity type impurity and the surface electric field reduction layer 32 contains a low concentration doped second conductivity type impurity, the load in the surface electric field layer 32 can be reduced. The sub-depletion is completely depleted, and the depletion region DR can be laterally extended to the heavily doped contact region 33. The depletion region DR formed near the surface of the power diode element 3 can relieve the electric field distribution, thereby increasing the breakdown voltage of the power diode element 3.

Please refer to FIG. 6 and FIG. 7 first. 6 is a graph showing the electric field intensity along the line X of the power diode element of FIG. 5, and FIG. 7 is a graph showing the electric field intensity along the line Y of the power diode element of FIG. 5. 6 and 7 are diagrams showing the electric field distribution simulated under the condition that a reverse bias voltage of 750 V is applied to the power diode element of the embodiment of the present invention.

The position L1 of Fig. 6 corresponds to the position of L1 of Fig. 5, and the position L2 is the position corresponding to L2 of Fig. 5. Similarly, the position L3 of FIG. 7 is the position corresponding to L3 of FIG. 5, and the position L4 is the position corresponding to L4 of FIG.

As can be seen in FIG. 6, the reduced surface electric field layer 32 can relieve the electric field originally concentrated on the isolation structure 34 and the heavily doped contact region 33. In Fig. 6, the maximum value P1 of the electric field strength is 1.6 × 10 ⁵ Newtons / Coulomb. Referring to FIG. 7, the maximum value P2 of the electric field intensity is shown in FIG. 7 to be 2.3×10 ⁵ Newtons/Coulomb, and the position of the electric field intensity maximum value P2 is the position corresponding to the first PN junction S1. That is, when a larger reverse bias is continuously applied to the power diode element 3, the collapsed region will be substantially located at the first PN junction S1 formed between the epitaxial layer 31 and the reduced surface electric field layer 32, It is not located on the surface of the power diode element 3.

Referring to Table 1 below, the power diode elements (Embodiment 1 and Embodiment 2) of the embodiment of the present invention and the conventional power diodes (Comparative Example 1, Comparative Example 2) are applied with a reverse bias of 600 V. Electrical performance under. The structure of a conventional power diode is shown in FIG.

As shown in Table 1, Example 1 and Example 2 can be applied at a high temperature of 175 ° C and have a high single pulse collapse energy (EAS) compared to Comparative Examples 1 and 2. In addition, Example 1 and Example 2 have smaller leakage currents than Comparative Examples 1 and 2, and in particular, after more than 125 ° C, Example 1 and Comparative Examples 1 and 2 The increase in leakage current of Embodiment 2 is not large.

In summary, in summary, the power diode device provided by the present invention forms a continuous PN junction between the surface electric field layer, the epitaxial layer and the isolation structure, and the power diode element is reversely applied. When biased, the surface electric field can be laterally extended to increase the breakdown voltage of the power diode component. Through the above test results, it is apparent that the power diode element provided by the embodiment of the present invention has better electrical performance than the conventional power diode.

In addition, since the power diode element provided by the present invention does not need to be provided with a guard ring and does not have a three-dimensional structure, the power diode of the embodiment of the present invention is compared with the prior art. The process of the body components is relatively simple and easy to control.

Although the embodiments of the present invention have been disclosed as above, the present invention is not limited to the above-described embodiments, and those skilled in the art can make some modifications without departing from the scope of the present invention. The scope of protection of the present invention is therefore defined by the scope of the appended claims.

3‧‧‧Power diode components

30‧‧‧Base

30a‧‧‧ upper surface

30b‧‧‧back

31‧‧‧Elevation layer

32‧‧‧Reducing the surface electric field layer

321‧‧‧ top surface

AR‧‧‧Active Area

33‧‧‧ heavily doped contact zone

34‧‧‧Isolation structure

35‧‧‧ Passivation layer

36‧‧‧ positive electrode layer

37‧‧‧Back electrode layer

S1‧‧‧ first PN junction

S2‧‧‧ second PN junction

351‧‧‧Electrical neutral insulation

352‧‧‧hard protective layer

D‧‧‧Predetermined distance

Claims (10)

A power diode component comprising: a substrate; an epitaxial layer on the substrate and having the same conductivity type as the substrate; a reduced surface electric field layer on the epitaxial layer and having a top surface, wherein the reduced surface electric field layer defines an active region; a heavily doped contact region is formed in the active region of the reduced surface electric field layer and exposed to the top surface, wherein the weight The doped contact region and the reduced surface electric field layer have the same conductivity type; and an isolation structure formed in the reduced surface electric field layer and surrounding the active region, wherein the reduced surface electric field layer and the epitaxial layer A continuous PN junction is formed between the layer and the isolation structure. The power diode component of claim 1, further comprising a passivation layer disposed on the top surface, wherein the passivation layer has an opening connecting the heavily doped contact regions. The power diode component of claim 2, further comprising a positive electrode layer disposed on the top surface, wherein the positive electrode layer electrically contacts the heavily doped contact region through the opening. The power diode component of claim 2, wherein the passivation layer comprises an electrically neutral insulating layer on the top surface and a hard protective layer on the electrically neutral insulating layer. The power diode device of claim 1, wherein the isolation structure is an isolation doping region formed in the reduced surface electric field layer, and a doping concentration of the isolation doping region is greater than the reduction The doping concentration of the surface electric field layer. The power diode component of claim 1, wherein the isolation structure is from the top The face extends into the epitaxial layer. The power diode component of claim 1, wherein the isolation structure and the heavily doped contact regions are separated from each other by a predetermined distance. The power diode component of claim 7, wherein the predetermined distance is at least greater than a sum of a thickness of the epitaxial layer and a thickness of the reduced surface electric field layer. The power diode component of claim 1, further comprising a back electrode layer disposed on a back surface of the substrate. The power diode component of claim 1, wherein the heavily doped contact region has a depth less than a thickness of the reduced surface electric field layer.