Silicon carbide power device with base region lateral doping concentration gradient and preparation method thereof

Abstract

The present invention provides a silicon carbide power device with a base region having a laterally gradient doping concentration and a preparation method thereof. The prepared silicon carbide power device with a laterally gradient doping concentration in the base region comprises a p+ epitaxial layer 1, a P-base region 2, an N+ substrate 3, a passivation layer 4, a back electrode 5, and a front electrode 6. The P-base region 2 of the present invention uses a laterally variable doping base region, which can increase the doping concentration of the P-base region at the P+ / P-junction, reduce the concentration gradient at the negative corner of the device, suppress the surface electric field, and improve the operating reliability of the device.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology, and in particular relates to a silicon carbide power device with a base region having a gradient lateral doping concentration and a preparation method thereof. Background Art

[0002] Traditional silicon carbide power devices improve their breakdown efficiency by adding various surface terminations to the outside of the device cell to expand the space charge region. Commonly used planar terminations, such as JTE and FLR, offer some improvements, but they still present the problem of surface electric field concentration. Consequently, technicians must continuously adjust the termination design to improve breakdown efficiency, and ion implantation is also required. These processes introduce additional defects and are significantly affected by interface charge.

[0003] Existing technologies propose a bevel-etched termination method that doesn't require ion implantation. However, this method creates both positive and negative angles on the surface of silicon carbide power devices. The surface electric field at the negative angle is greater than the bulk electric field, and the device is significantly affected by the doping concentration gradient and etching angle at this location, resulting in reduced stability. Summary of the Invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a silicon carbide power device with a base region laterally doped with a gradient concentration and a method for manufacturing the same. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0005] In a first aspect, the present invention provides a silicon carbide power device with a base region laterally doped with a gradient concentration, comprising:

[0006] p+ epitaxial layer 1, P-base region 2, N+ substrate 3, passivation layer 4, back electrode 5 and front electrode 6;

[0007] The P-base region 2 is located on the N+ substrate 3, and the doping concentration of the P-base region 2 changes regularly from the inside to the outside, so that the concentration of the P-base region at the slope is higher than the concentration inside the P-base region; the side close to the N+ substrate 3 is lower than the side close to the p+ epitaxial layer 1; the p+ epitaxial layer 1 is located on the P-base region 2, and the front electrode 6 is located on the p+ epitaxial layer 1; the p+ epitaxial layer 1, the P-base region 2 and the N+ substrate 3 are in a trapezoidal step structure; the passivation layer 4 wraps the p+ epitaxial layer 1, the P-base region 2 and the N+ substrate 3 from top to bottom to form a trapezoidal step structure, and exposes the front electrode 6 on the upper surface of the trapezoidal step structure; a step surface is provided on the outside of the N+ substrate 3, and the step surface makes the upper part of the N+ substrate 3 trapezoidal and the lower part rectangular; the back electrode 5 is located on the lower surface of the rectangle, and the passivation layer 4 wraps the upper part of the N+ substrate 3 and the step surface.

[0008] Among them, the doping concentration of the P-base region 2 increases gradually from the inside to the outside in a gradient pattern, and the doping concentration of the P-base region 2 follows a Gaussian distribution continuous change pattern from the inside to the outside. The metals deposited to form the back electrode 5 and the front electrode 6 include Ti and Ni.

[0009] Optionally, the N+ substrate 3 includes a first step surface and a second step surface, the first step surface is in contact with the lower surface of the P-base region 2, and the second step surface is located on both sides of the junction of the trapezoid and the matrix, and the passivation layer 4 wraps the N+ substrate 3 from top to bottom until it completely wraps the second step surface, exposing the portion of the N+ substrate 3 below the second step surface.

[0010] In a second aspect, the present invention provides a method for preparing a silicon carbide power device with a base region laterally doped with a gradient concentration, comprising:

[0011] Step 1: Obtain an N+ substrate 3;

[0012] Step 2: growing a P-base region 2 with a regularly varying lateral doping concentration on the surface of the N+ substrate 3 by a CVD method;

[0013] Step 3: growing a P+ epitaxial layer 1 on the surface of the P-base region 2 by a CVD method;

[0014] Step 4: Etching away the outer edges of the P-base region 2, the P+ epitaxial layer 1 and part of the N+ substrate 3 so that the P+ epitaxial layer 1, the P-base region 2 and the N+ substrate 3 have a trapezoidal step structure, and etching the step surface on the N+ substrate 3 so that the upper part of the N+ substrate 3 has a trapezoidal structure and the lower part has a rectangular structure;

[0015] Step 5: Etching a portion of the upper surface of the P+ epitaxial layer 1;

[0016] Step 6: Grow a SiO2 passivation layer 4 from bottom to top on the step surface of the N+ substrate 3 until the SiO2 passivation layer 4 covers the etched portion of the P+ epitaxial layer 1, the P-base region 2 and the step surface of the N+ substrate 3;

[0017] Step 7: Deposit metal on the lower surface of the lower rectangular structure of the N+ substrate 3 to form a back electrode 5 , and deposit metal on the upper surface of the P+ epitaxial layer 1 to form a front electrode 6 .

[0018] The growth temperature of the P-base region 2 is 1600° C. to 1900° C., and the growth temperature of the P+ epitaxial layer 1 is 1600° C. to 1900° C.

[0019] Optionally, the metal deposited in step 7 includes Ti and Ni; the preparation method of the present invention further includes annealing the back electrode 5 and the front electrode 6 at a temperature of 400° C. to 1000° C.

[0020] Optionally, the doping concentration of the P-base region 2 changes regularly in a gradient-increasing manner from the inside to the outside or in a Gaussian distribution that changes continuously from the inside to the outside.

[0021] Beneficial effects of the present invention:

[0022] The present invention provides a silicon carbide power device with a base region with a laterally gradient doping concentration and a preparation method thereof. The prepared silicon carbide power device with a laterally gradient doping concentration in the base region includes a p+ epitaxial layer 1, a P-base region 2, an N+ substrate 3, a passivation layer 4, a back electrode 5 and a front electrode 6. The P-base region 2 of the present invention uses a laterally variable doping base region, which can increase the doping concentration of the P-base region at the P+ / P- junction, reduce the concentration gradient at the negative angle of the device, suppress the surface electric field, and improve the working reliability of the device.

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of a silicon carbide power device with a base region lateral doping concentration gradient provided by an embodiment of the present invention;

[0025] Figure 2 This is a flow chart for preparing a silicon carbide power device with a base region lateral doping concentration gradient provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0027] like Figure 1 As shown, the present invention provides a silicon carbide power device with a base region laterally doped with a gradient concentration, comprising:

[0028] p+ epitaxial layer 1, P-base region 2, N+ substrate 3, passivation layer 4, back electrode 5 and front electrode 6;

[0029] The P-base region 2 is located on the N+ substrate 3, and the doping concentration of the P-base region 2 changes regularly from the inside to the outside, so that the concentration of the P-base region at the slope is higher than the concentration inside the P-base region; the p+ epitaxial layer 1 is located on the P-base region 2, and the front electrode 6 is located on the p+ epitaxial layer 1; the p+ epitaxial layer 1, the P-base region 2 and the N+ substrate 3 are in a trapezoidal step structure; the passivation layer 4 wraps the p+ epitaxial layer 1, the P-base region 2 and the N+ substrate 3 from top to bottom to form a trapezoidal step structure, and exposes the front electrode 6 on the upper surface of the trapezoidal step structure; a step surface is provided on the outside of the N+ substrate 3, and the step surface makes the upper part of the N+ substrate 3 trapezoidal and the lower part rectangular; the back electrode 5 is located on the lower surface of the rectangle, and the passivation layer 4 wraps the upper part of the N+ substrate 3 and the step surface.

[0030] The doping concentration of the P-base region 2 increases gradually from the inside out in a gradient pattern or changes continuously from the inside out in a Gaussian distribution pattern. The metals deposited to form the back electrode 5 and the front electrode 6 include Ti and Ni.

[0031] refer to Figure 1 The N+ substrate 3 of the present invention includes a first step surface and a second step surface. The first step surface is in contact with the lower surface of the P-base region 2, and the second step surface is located on both sides of the junction of the trapezoid and the matrix. The passivation layer 4 wraps the N+ substrate 3 from top to bottom until it completely wraps the second step surface, exposing the portion of the N+ substrate 3 below the second step surface.

[0032] It is worth noting that the decrease in area from the lightly doped side to the heavily doped side of the PN junction is defined as a negative bevel, and Figure 1 The area from the base region 2 to the P+ epitaxial layer 1 side is reduced. Since the negative angle removes more charge from the P+ side than the P-type side, the depletion region will expand in the P+ epitaxial layer 1 and shrink on the side of the base region 1. Therefore, the depletion region width of the negative angle junction on the surface is smaller than the depletion width of the body region. This means that the terminal surface electric field will be higher than that in the body, resulting in unstable surface breakdown. In order to suppress this situation where the surface electric field is high, a higher doping concentration can be introduced near the surface of the device to reduce the concentration gradient at the negative angle. At the same time, the lower doping concentration in the body can ensure that the depletion region of the device in the body widens normally. This lateral variable doping method can also effectively increase the negative bevel angle of the device and effectively reduce the device area.

[0033] The present invention provides a silicon carbide power device with a laterally gradient doping concentration in the base region, comprising a p+ epitaxial layer 1, a P-base region 2, an N+ substrate 3, a passivation layer 4, a back electrode 5, and a front electrode 6. The P-base region 2 of the present invention uses a laterally variable doping base region, which can increase the doping concentration of the P-base region at the P+ / P- junction, reduce the concentration gradient at the negative corner of the device, suppress the surface electric field, and improve the operating reliability of the device.

[0034] like Figure 2 As shown, the present invention provides a method for preparing a silicon carbide power device with a base region laterally doped with a gradient concentration, comprising:

[0035] Step 1: Obtain an N+ substrate 3;

[0036] Step 2: growing a P-base region 2 with a regularly varying lateral doping concentration on the surface of the N+ substrate 3 by a CVD method;

[0037] The doping concentration of the P-base region 2 changes regularly in the lateral direction, and changes gradually from the inside to the outside or changes continuously from the inside to the outside in a Gaussian distribution.

[0038] Step 3: growing a P+ epitaxial layer 1 on the surface of the P-base region 2 by a CVD method;

[0039] Step 4: Etching away the outer edges of the P-base region 2, the P+ epitaxial layer 1 and part of the N+ substrate 3 so that the P+ epitaxial layer 1, the P-base region 2 and the N+ substrate 3 have a trapezoidal step structure, and etching the step surface on the N+ substrate 3 so that the upper part of the N+ substrate 3 has a trapezoidal structure and the lower part has a rectangular structure;

[0040] Step 5: Etching a portion of the upper surface of the P+ epitaxial layer 1;

[0041] Step 6: Grow a SiO2 passivation layer 4 from bottom to top on the step surface of the N+ substrate 3 until the SiO2 passivation layer 4 covers the etched portion of the P+ epitaxial layer 1, the P-base region 2 and the step surface of the N+ substrate 3;

[0042] Step 7: Deposit metal on the lower surface of the lower rectangular structure of the N+ substrate 3 to form a back electrode 5 , and deposit metal on the upper surface of the P+ epitaxial layer 1 to form a front electrode 6 .

[0043] The growth temperature of the P-base region 2 is 1600° C. to 1900° C.; the growth temperature of the P+ epitaxial layer 1 is 1600° C. to 1900° C.; and the metal deposited in step 7 includes Ti and Ni.

[0044] After depositing metal to form the back electrode 5 and the front electrode 6 , the preparation method provided by the present invention further comprises: annealing the back electrode 5 and the front electrode 6 at a temperature of 400° C. to 1000° C.

[0045] The present invention provides a method for preparing a silicon carbide power device with a base region with a laterally gradient doping concentration. The prepared silicon carbide power device with a laterally gradient doping concentration in the base region includes a p+ epitaxial layer 1, a P-base region 2, an N+ substrate 3, a passivation layer 4, a back electrode 5 and a front electrode 6. The P-base region 2 of the present invention uses a laterally variable doping base region, which can increase the doping concentration of the P-base region at the P+ / P- junction, reduce the concentration gradient at the negative corner of the device, suppress the surface electric field, and improve the working reliability of the device.

[0046] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A silicon carbide power device with a base region laterally doped with a gradient concentration, characterized in that: include: p+ epitaxial layer (1), P-base region (2), N+ substrate (3), passivation layer (4), back electrode (5) and front electrode (6); The P-base region (2) is located on the N+ substrate (3), and the doping concentration of the P-base region (2) changes regularly from the inside to the outside, so that the concentration of the P-base region located at the slope is higher than the concentration inside the P-base region; the side close to the N+ substrate (3) is lower than the side close to the p+ epitaxial layer (1); the p+ epitaxial layer (1) is located on the P-base region (2), and the front electrode (6) is located on the p+ epitaxial layer (1); the p+ epitaxial layer (1), the P-base region (2) and the N+ substrate (3 ) presents a trapezoidal step structure; the passivation layer (4) wraps the p+ epitaxial layer (1), the P-base region (2) and the N+ substrate (3) from top to bottom to form the periphery of the trapezoidal step structure, and exposes the front electrode (6) on the upper surface of the trapezoidal step structure; a step surface is provided on the outer side of the N+ substrate (3), and the step surface makes the upper part of the N+ substrate (3) trapezoidal and the lower part rectangular; the back electrode (5) is located on the lower surface of the rectangle, and the passivation layer (4) wraps the upper part of the N+ substrate (3) and the step surface.

2. The silicon carbide power device with a base region laterally doped with a gradient concentration according to claim 1, characterized in that: The doping concentration of the P-base region (2) increases from the inside to the outside in a gradient manner.

3. The silicon carbide power device with a base region laterally doped with a gradient concentration according to claim 1, characterized in that: The doping concentration of the P-base region (2) changes continuously from the inside to the outside following the Gaussian distribution rule.

4. The silicon carbide power device with a base region laterally doped with gradient concentration according to claim 1, characterized in that: The metals deposited to form the back electrode (5) and the front electrode (6) include Ti and Ni.

5. The silicon carbide power device with a base region laterally doped with gradient concentration according to claim 1, characterized in that: The N+ substrate (3) includes a first step surface and a second step surface, the first step surface is in contact with the lower surface of the P-base region (2), and the second step surface is located on both sides of the junction of the trapezoid and the matrix, and the passivation layer (4) wraps the N+ substrate (3) from top to bottom until it completely wraps the second step surface, exposing the portion of the N+ substrate (3) below the second step surface.

6. A method for preparing a silicon carbide power device with a base region laterally doped with a gradient concentration, characterized in that: The preparation method comprises: Step 1: Obtain an N+ substrate (3); Step 2: growing a P-base region (2) with a regularly changing lateral doping concentration on the surface of the N+ substrate (3) by a CVD method; the doping concentration of the P-base region (2) regularly changes in a gradient increasing manner from the inside to the outside or in a Gaussian distribution with a continuous change from the inside to the outside; Step 3: growing a P+ epitaxial layer (1) on the surface of the P-base region (2) by a CVD method; Step 4: etching away the outer edges of the P-base region (2), the P+ epitaxial layer (1) and a portion of the N+ substrate (3) so that the P+ epitaxial layer (1), the P-base region (2) and the N+ substrate (3) have a trapezoidal step structure, and etching a step surface on the N+ substrate (3) so that the upper portion of the N+ substrate (3) has a trapezoidal structure and the lower portion has a rectangular structure; Step 5: etching a portion of the upper surface of the P+ epitaxial layer (1); Step 6: growing a SiO2 passivation layer (4) from bottom to top on the step surface of the N+ substrate (3) until the SiO2 passivation layer (4) covers the etched portion of the P+ epitaxial layer (1), the P-base region (2) and the step surface of the N+ substrate (3); Step 7: depositing metal on the lower surface of the lower rectangular structure of the N+ substrate (3) to form a back electrode (5), and depositing metal on the upper surface of the P+ epitaxial layer (1) to form a front electrode (6).

7. The method for preparing a silicon carbide power device with a base region laterally doped with a gradient concentration according to claim 6, characterized in that: The growth temperature of the P-base region (2) is 1600°C~1900°C.

8. The method for preparing a silicon carbide power device with a base region laterally doped with a gradient concentration according to claim 6, characterized in that: The growth temperature of the P+ epitaxial layer (1) is 1600°C~1900°C.

9. The method for preparing a silicon carbide power device with a base region laterally doped with gradient concentration according to claim 6, characterized in that: The metal deposited in step 7 includes Ti and Ni, and the preparation method further includes: The back electrode (5) and the front electrode (6) are annealed at a temperature of 400°C to 1000°C.

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