A high voltage fast soft recovery diode

Abstract

The invention is a high-voltage fast soft recovery diode. It belongs to the field of high-voltage semiconductor diode design and manufacturing technology. It mainly solves the problem that the existing high-voltage diode cannot meet the reverse freewheeling requirements of high-voltage semiconductor devices above 4000V. Its main features are: the semiconductor chip is composed of an anode P + Block or anode P + Region, anode P region, long base region N, cathode N + Ring, cathode P + Block and cathode N + Block composition; the anode P + Block or anode P + The area is distributed on the surface of the anode P area. + Block or anode P + Zone and anode P + Block or anode P + The anode P region between the regions constitutes the anode region; the cathode N + The blocks are spaced apart on the long base N surface, and the cathode P + The block is located at the cathode N + Between blocks, cathode P + Block and cathode N + The blocks are isolated by a long base region N. The invention has the characteristics of higher reverse blocking voltage, shorter reverse recovery time and improved diode softness factor, and is mainly used for reverse freewheeling of devices such as IGBT, IGCT, and IEGT.

Description

Technical Field

[0001] The present invention relates to the technical field of high-voltage semiconductor diode design and manufacturing, and in particular to a high-voltage fast soft recovery diode, which is mainly used for reverse freewheeling of devices such as IGBT, IGCT, and IEGT. Background Art

[0002] Traditional semiconductor diodes use P + PNN + Structure, its P + and N + Distributed on the anode and cathode surfaces, such as Figure 1 and Figure 2 As shown in the figure, the thickness of the P region and the N region and the impurity concentration distribution are adjusted according to different voltage requirements; when improving the fast recovery characteristics, the thickness of the N region is often thinned to form a PIN-type structure diode, which reduces the carrier base transit time and reduces the base minority carrier lifetime through electron irradiation or heavy metal diffusion. Although this method reduces the reverse recovery time, it is easy to generate a high reverse voltage in the circuit and damage the device because the recovery characteristics are relatively "hard" (that is, the softness factor S is small); for high-voltage (≥3000V) fast recovery diodes, the effect of reducing the reverse recovery time is limited, and continuing to reduce the base minority carrier lifetime will cause the on-state voltage drop to deteriorate.

[0003] Adopt fast soft recovery diode SIOD tube core structure, such as Figure 3 As shown, the anode diffuses high concentration impurities P from the surface of the P region. + The cathode region is composed of a plurality of strip-shaped high-concentration N + Block, two adjacent N + In this structure, the Schottky region (the contact area between the N layer and the metal) provides an extraction channel for holes. Under high voltage, a large number of carriers gather in the NN + High and low junction, N + The layer forms a barrier to holes. Although the Schottky region provides an extraction channel, the holes still need to pass through the wider low-doping concentration N layer, so the extraction time is still relatively long and the optimal reverse recovery time cannot be achieved.

[0004] The SPEED diode die structure with self-adjusting emission efficiency is adopted, such as Figure 4 As shown, the anode region is composed of low-concentration P-type impurities and multiple uniformly distributed high-concentration P-type impurities P + The base region is composed of low-concentration N-type impurities, and the cathode region is composed of high-concentration impurities cathode N + The low-concentration P region on the anode side increases the speed of electrons passing through the diode during reverse recovery and improves the diode softness factor. However, under high voltage conditions, since the base region and the P region are still relatively thick, the improvement effect is limited and the reverse recovery time of the diode is still not ideal.

[0005] With the continuous increase in the voltage of semiconductor devices and the continuous increase in chip diameter, especially for high-voltage IGBT, IGCT, and IEGT with a follow current of more than 4000V, it is urgent to adopt new semiconductor high-voltage fast soft recovery diode device structures and new semiconductor diode process technologies to meet new demands. Summary of the invention

[0006] In order to overcome the shortcomings of the prior art, the present invention proposes a diode structure with better high-voltage reverse fast soft recovery. The diode manufactured by this structure and the optimal parameter matching can increase the reverse blocking voltage, have a shorter reverse recovery time, and greatly improve the diode softness factor. It can meet the reverse freewheeling requirements of high-voltage semiconductor devices above 4000V.

[0007] The technical solution of the present invention can be: a high-voltage fast soft recovery diode, including a tube shell lower sealing member, a lower molybdenum disc, a glue injection ring, a semiconductor wafer, an upper molybdenum disc and a tube shell upper sealing member, characterized in that: the semiconductor wafer is composed of an anode P + block, anode P region, long base region N, cathode N + Ring, cathode P + Block and cathode N + Block composition; wherein the anode P + The blocks are spaced apart on the surface of the anode P region. + Block and anode P + The anode P region between the blocks constitutes the anode region; the base region is a low-concentration impurity N region, and the cathode region is on the surface of the N region; the cathode N + The blocks are spaced apart on the long base N surface, and the cathode P + The block is located at the cathode N + Between blocks, cathode P + Block and cathode N + The blocks are isolated by a long base region N.

[0008] The technical solution of the present invention can also be: a high-voltage fast soft recovery diode, comprising a tube shell lower sealing member, a lower molybdenum disc, a glue injection ring, a semiconductor wafer, an upper molybdenum disc and a tube shell upper sealing member, wherein: the semiconductor wafer is composed of an anode P + Region, anode P region, long base region N, cathode N + Ring, cathode P + Block and cathode N + Block composition; wherein the anode P + The anode P region is evenly distributed on the surface of the anode P region. + The anode region is constituted by the base region, the base region is a low-concentration impurity N region, and the cathode region is on the surface of the N region; the cathode N + The blocks are spaced apart on the long base N surface, and the cathode P +The block is located at the cathode N + Between blocks, cathode P + Block and cathode N + The blocks are isolated by a long base region N.

[0009] The cathode N described in the technical solution of the present invention + The block occupies 50-90% of the total cathode area. + The block is cylindrical or square, and the cathode P + The block occupies 10-30% of the total cathode area. + The block is at cathode P + The block is surrounded by the cathode P + The junction depth of the block is less than that of the cathode N + The block is deep.

[0010] The cathode P described in the technical solution of the present invention + The blocks are straight strips or frame strips with a width of 20∽80μm.

[0011] The anode P described in the technical solution of the present invention + The block occupies 40-88% of the total area of ​​the anode area. + The block spacing is 50∽200μm, the anode P + The block is cylindrical or square.

[0012] The semiconductor wafer described in the technical solution of the present invention is N-type <100> Crystal orientation high resistance single crystal silicon wafer or N-type <111> Crystalline high-resistance single-crystal silicon wafer; Semiconductor wafer The internal microscopic longitudinal structure of the wafer is composed of P + PNN + P + The structure consists of a P region formed by high-concentration Al diffusion, and an anode P + The cathode P is formed by high concentration boron diffusion. + Block adopts anode P + Counter-diffusion is formed.

[0013] The semiconductor wafer anode P described in the technical solution of the present invention + The surface concentration of the block is 5×10 19 ∽3×10 21 / cm 3 , the junction depth is 15∽31μm; the impurity concentration on the surface of the anode P region is 0.1∽9.8×10 16 / cm 3 , junction depth is 60∽125μm; cathode N + Ring and cathode N + The impurity concentration on the block surface is 0.5∽8×10 21 / cm3 , junction depth is 18∽35μm; cathode P + The impurity concentration on the block surface is 0.4∽8.5×10 20 / cm 3 , the junction depth is 4∽16μm.

[0014] The semiconductor wafer anode P described in the technical solution of the present invention + The surface concentration of the area is 5×10 19 ∽3×10 21 / cm 3 , the junction depth is 15∽31μm; the impurity concentration on the surface of the anode P region is 0.1∽9.8×10 16 / cm 3 , junction depth is 60∽125μm; cathode N + Ring and cathode N + The impurity concentration on the block surface is 0.5∽8×10 21 / cm 3 , junction depth is 18∽35μm; cathode P + The impurity concentration on the block surface is 0.4∽8.5×10 20 / cm 3 , the junction depth is 4∽16μm.

[0015] The present invention has the following effects:

[0016] 1. Two adjacent cathode N + Add a narrow strip of high-concentration cathode P between the zones + Block area, cathode N + and P + The blocks are isolated by low-concentration impurities N, which greatly reduces the reverse recovery time of the diode;

[0017] 2. Wafer edge N + Ring, which can reduce the thickness of N to achieve high blocking voltage, reduce the number of carriers in the base region, and also reduce the reverse recovery time of the diode;

[0018] 3. Two adjacent anodes P + The narrow strip-shaped low-concentration P region is formed between the blocks, which can reduce the reverse recovery time of the diode and optimize the P + The block ratio can significantly improve the recovery softness factor without affecting the on-state voltage drop;

[0019] 4. The diameter of the semiconductor wafer of the present invention can be Φ38∽Φ125, the blocking voltage of the product can reach 3000∽8500V, the reverse recovery time is 1.0∽10μS, the softness factor is increased to above 0.7; the reverse recovery current is about 50% of that of a conventional fast recovery diode.

[0020] The present invention increases the reverse blocking voltage of the diode, that is, has a shorter reverse recovery time, and also greatly improves the diode softness factor. It has the diode characteristics of high voltage, fast soft recovery, and low reverse recovery current, and can be used for reverse freewheeling devices such as IGBT, IGCT, IEGT and other devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the structure of a traditional welded fast diode chip.

[0022] Figure 2 This is a schematic diagram of the structure of a traditional press-fit fast diode chip.

[0023] Figure 3 It is a schematic diagram of the chip anode P+ and cathode local N+ structure.

[0024] Figure 4 This is a schematic diagram of the local P+ structure of the anode and N+ structure of the cathode of the chip.

[0025] Figure 5 The figure is a schematic diagram of a high-voltage fast soft recovery diode of the present invention.

[0026] Figure 6 Schematic diagram of the anode P+ structure of a semiconductor wafer according to an embodiment of the present invention.

[0027] Figure 7 It is a schematic structural diagram of the edge of a semiconductor wafer and a silicone ring according to an embodiment of the present invention.

[0028] Figure 8 It is a schematic structural diagram of the edge of a semiconductor wafer and a silicone ring with a groove according to an embodiment of the present invention.

[0029] Fig. 9 Schematic diagram of the arrangement structure of cathode P+ and N+ of a semiconductor wafer according to an embodiment of the present invention.

[0030] Fig.10 This is a schematic diagram of the assembled product of the present invention.

[0031] In the figure, A-anode, K-cathode, 1-tube shell lower sealing part, 2-lower molybdenum disc, 3-glue injection ring, 4-semiconductor wafer, 5-upper molybdenum disc, 6-tube shell upper sealing part, 7-positioning column, 30-glue injection ring, 41-anode area metal layer, 42-anode P + block, 43-anode P region, 44-long base region N, 45-cathode N+ ring, 46-cathode P+ Block, 47-cathode N + Block, 48-cathode metal layer, 49-groove, 420-anode P + Zone, 450-cathode N + district. DETAILED DESCRIPTION

[0032] Combine the following Figures 5 to 10 , a complete description of the embodiments of the present invention is given. Obviously, the described embodiments are only a part of the present invention rather than all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0033] Embodiment 1 is a high voltage fast soft recovery diode, such as Figure 5 , Figure 7 , Fig. 9 , Fig.10 As shown, it is packaged by the lower sealing part 1 of the tube shell, the lower molybdenum disc 2, the injection ring 3, the semiconductor chip 4, the upper molybdenum disc 5, and the upper sealing part 6 of the tube shell. The semiconductor chip 4 is made of anode P + Block 42, anode P region 43, long base region N44, cathode N + Ring 45, cathode P + Block 46 and cathode N + The anode region is composed of a low-concentration anode P region 43 and a high-concentration impurity anode P uniformly distributed in the anode P region 43. + The base region is a low-concentration impurity N region, and the cathode region is on the surface of the N region, which is composed of a uniformly distributed high-concentration cathode N + Block 47 and cathode N + Ring 45, two adjacent cathodes N + The high concentration cathode P is formed between the blocks 47 in a narrow strip shape. + Block 46 area, cathode N + Block 47 and cathode P + The blocks 46 are isolated by a low-concentration impurity long base region N44. + Block 47 occupies 50-90% of the total cathode area. + Block 47 is cylindrical or square, and cathode P + Block 46 occupies 10-30% of the total cathode area. + Block 47 is at cathode P + The cathode P is surrounded by a block 46. + The block 46 is a straight strip or a frame strip with a width of 20 to 80 μm. + Block 42 occupies 40-88% of the total area of ​​the anode region. + The spacing between blocks 42 is 50∽200μm, and the anode P +The block 42 is cylindrical or square. + The area of ​​block 42 is less than or equal to the cathode N + Block 47 area, improve the effectiveness of the flow area. Anode P + Block 42 should not be too wide, otherwise it will occupy the cathode flow area.

[0034] The semiconductor wafer 4 is N-type <100> Crystal orientation high resistance single crystal silicon wafer or N-type <111> Crystalline high-resistance single crystal silicon wafer, semiconductor wafer 4 The microscopic longitudinal structure inside the wafer is composed of P + PNN + P + The structure is composed of a P region formed by high-concentration Al diffusion, and the anode P + The cathode P is formed by high concentration boron diffusion. + Block adopts anode P + Back diffusion is formed. The cathode doping distribution is as follows Fig. 9 As shown, cathode N + Blocks 47 are evenly distributed on the cathode P + The block 46 is surrounded to ensure uniformity of carrier extraction during reverse recovery.

[0035] Anode P + The surface concentration of block 42 is 5×10 19 ∽3×10 21 / cm 3 The junction depth is 15 to 31 μm. The surface impurity concentration of the anode P region 43 is 0.1 to 9.8 × 10 16 / cm 3 , the junction depth is 60∽125μm. Cathode N + Ring 45 and cathode N + The impurity concentration on the surface of block 47 is 0.5∽8×10 21 / cm 3 , the junction depth is 18∽35μm. Cathode P + The impurity concentration on the surface of block 46 is 0.4∽8.5×10 20 / cm 3 , the junction depth is 4∽16μm. Cathode P + The impurity concentration on the surface of block 46 is less than that of anode P + Block 42 and cathode N + Block 47 surface impurity concentration, cathode P + Block 46 junction depth is less than cathode N + Ring 45 and cathode N + Block 47 knots deep.

[0036] A sealed cavity is formed inside the tube shell lower sealing member 1 and the tube shell upper sealing member 6. The sealed cavity is filled with an inert gas whose pressure is lower than the external atmospheric pressure, thereby ensuring good contact between the components and preventing high-voltage sparking of the wafer.

[0037] The edge of the semiconductor wafer 4 is as Figure 7 As shown, the two double negative angled mesas are provided with an annular right-angle cylindrical insulating protection injection ring 3, and the double-sided surface mesas are protected by multi-layer high-purity high-insulating polyester imide, polyimide, or silicone rubber for surface passivation. The anode and cathode surfaces of the semiconductor wafer 4 are coated with a metal conductive layer with a thickness of 10∽40μm.

[0038] The surfaces of the upper molybdenum disc 5 and the lower molybdenum disc 2 are coated with a passivation layer, wherein the passivation layer is rhodium, ruthenium or silver, which prevents the upper and lower molybdenum discs from thermal oxidation and improves the device characteristic stability and long-term reliability.

[0039] Positioning holes are provided in the center of the lower molybdenum disc 2 and the upper molybdenum disc 5, and installation positioning holes are provided in the center of the lower sealing part 1 of the tube shell and the upper sealing part 6 of the tube shell. Positioning columns 7 are installed in the positioning holes to prevent the chip from being displaced and worn due to thermal stress during operation.

[0040] The upper and lower surfaces of the upper molybdenum disc 5 and the lower molybdenum disc 2 and the inner and outer surfaces of the upper and lower sealing parts 6 and 1 of the tube shell are polished surfaces with a flatness or parallelism of ≤10 microns, which can reduce thermal resistance and improve overcurrent capacity.

[0041] Example 2 Figure 6 , Figure 7 , Fig. 9 , Fig.10 As shown, the difference from embodiment 1 is that the semiconductor wafer 4 is provided with an anode P + Region 420, anode P region 43, long base region N44, cathode N + Ring 45, cathode P + Block 46, cathode N + The anode region is composed of a low-concentration impurity P region and anode P uniformly distributed on the surface of the anode P region 43. + The region 420 is formed. The anode carrier injection area is increased, the diode on-state voltage drop can be reduced, the reverse recovery time is shorter, and the reverse blocking voltage is increased.

[0042] Example 3 Figure 5 , Figure 7 or Figure 8 , Fig. 9 , Fig.10 As shown, different from implementation 1, the outer surface of the injection ring 3 is provided with a groove 49 to increase the creepage distance, which can be applied to higher voltage solutions.

[0043] As a high-voltage fast soft recovery diode implemented by the present invention, it can be used for reverse freewheeling devices such as IGBT, IGCT, IEGT and other devices.

[0044] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Therefore, any modification, equivalent replacement, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the content of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A high-voltage fast soft recovery diode, used for reverse freewheeling of high-voltage semiconductor devices above 4000V, characterized by: A semiconductor wafer (4) is composed of an anode P+ block (42), an anode P region (43), a long base region N (44), a cathode N+ ring (45), a cathode P+ block (46) and a cathode N+ block (47); the anode P+ blocks (42) are distributed at intervals on the surface of the anode P region (43); the anode P+ blocks (42) and the anode P region (43) between the anode P+ blocks (42) constitute an anode region; the cathode N+ blocks (47) are distributed at intervals on the surface of the long base region N (44) , the cathode P+ block (46) is located between the cathode N+ block (47), and the cathode P+ block (46) and the cathode N+ block (47) are isolated by a long base region N (44); wherein the P region is formed by high-concentration Al diffusion, the anode P+ is formed by high-concentration boron diffusion, and the cathode P+ block is formed by anode P+ reverse diffusion; the cathode P+ block junction depth is less than the cathode N+ ring and cathode N+ block junction depth; the anode P+ block (42) area is less than or equal to the cathode N+ block (47) area.

2. A high voltage fast soft recovery diode according to claim 1, characterized in that: The surface concentration of the anode P+ block (42) of the semiconductor wafer (4) is 5×10 19 ∽3×10 21 / cm 3 , the junction depth is 15∽31μm; the surface impurity concentration of the anode P region (43) is (0.1∽9.8)×10 16 / cm 3 , the junction depth is 60∽125μm; the surface impurity concentration of the cathode N+ ring (45) and the cathode N+ block (47) is (0.5∽8)×10 21 / cm 3 , the junction depth is 18∽35μm; the surface impurity concentration of the cathode P+ block (46) is (0.4∽8.5)×10 20 / cm 3 , the junction depth is 4∽16μm.

3. A high voltage fast soft recovery diode according to claim 1, characterized in that: The anode P+ block (42) occupies 40-88% of the total area of ​​the anode region, the spacing between the anode P+ blocks (42) is 50-200 μm, and the anode P+ blocks (42) are cylindrical or square columnar.

4. A high-voltage fast soft recovery diode, used for reverse freewheeling of high-voltage semiconductor devices above 4000V, characterized by: A semiconductor wafer (4) is composed of an anode P+ region (420), an anode P region (43), a long base region N (44), a cathode N+ ring (45), a cathode P+ block (46) and a cathode N+ block (47); the anode P+ region (420) is evenly distributed on the surface of the anode P region (43), and the anode P region (43) and the anode P+ region (420) constitute an anode region; the cathode N+ block (47) is distributed at intervals on the surface of the long base region N (44), the cathode P+ block (46) is located between the cathode N+ blocks (47), and the cathode P+ block (46) and the cathode N+ block (47) are isolated by the long base region N (44); the P region is formed by high-concentration Al diffusion, the anode P+ is formed by high-concentration boron diffusion, and the cathode P+ block is formed by anode P+ reverse diffusion; the junction depth of the cathode P+ block is smaller than the junction depth of the cathode N+ ring and the cathode N+ block.

5. A high voltage fast soft recovery diode according to claim 1 or 4, characterized in that: The cathode N+ block (47) occupies 50-90% of the total area of ​​the cathode region, the cathode N+ block (47) is cylindrical or square, the cathode P+ block (46) occupies 10-30% of the total area of ​​the cathode region, the cathode N+ block (47) is surrounded by the cathode P+ block (46); the cathode P+ block (46) is a straight bar or a frame bar with a width of 20-80 μm.

6. A high voltage fast soft recovery diode according to claim 4, characterized in that: The surface concentration of the anode P+ region (420) of the semiconductor wafer (4) is 5×10 19 ∽3×10 21 / cm 3 , the junction depth is 15∽31μm; the surface impurity concentration of the anode P region (43) is (0.1∽9.8)×10 16 / cm 3 , the junction depth is 60∽125μm; the surface impurity concentration of the cathode N+ ring (45) and the cathode N+ block (47) is (0.5∽8)×10 21 / cm 3 , the junction depth is 18∽35μm; the surface impurity concentration of the cathode P+ block (46) is (0.4∽8.5)×10 20 / cm 3 , the junction depth is 4∽16μm.

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