Edge charge balanced sic super junction structure and method of fabricating the same

Abstract

The application relates to a SiC super-junction structure with balanced edge charges and a preparation method thereof. The SiC super-junction structure comprises an N-epitaxial region and a plurality of p-type column regions, the plurality of p-type column regions are arranged in parallel and at intervals in the N-epitaxial region, the N-epitaxial region between each two adjacent p-type column regions serves as an n-type column region, the plurality of p-type column regions and the plurality of n-type column regions are alternately arranged to form a super-junction structure; wherein edge ion implantation regions are formed at both ends close to the p-type column regions, and the doping concentration of the edge ion implantation regions is lower than the doping concentration of the p-type column regions between the two edge ion implantation regions. The SiC super-junction structure with balanced edge charges can realize the charge balance at the edges of a single strip-shaped floating junction cell by reducing the doping concentration at both ends of the p-type column region in the super-junction structure, so that the charge balance of the device is improved, the breakdown voltage and the reliability of the device are improved, and the terminal design difficulty is reduced.

Description

Technical Field

[0001] This invention belongs to the field of microelectronics technology, specifically relating to a SiC superjunction structure with balanced edge charge and its preparation method. Background Technology

[0002] SiC power devices can reduce converter losses, increase power density, reduce heat dissipation requirements, and reduce system size and complexity, significantly improving system performance. Their high temperature, high pressure, and low loss characteristics make SiC power devices suitable for power supplies, rail transportation, motor control, electric vehicles, aerospace, and other systems. SiC power devices have a natural advantage over other types of switching devices in low-to-medium power applications. As a novel structural device, SiC superjunction devices, by incorporating continuous P- and N-column structures within a traditional pressure-bearing layer, transform the electric field within the depletion layer from a triangular shape to a rectangular shape when the device is reverse-biased. This effectively balances the relationship between the characteristic on-resistance and breakdown voltage of the power device, breaking the theoretical limit of one-dimensional unipolar materials. Currently, common SiC superjunction structures are continuous P- and N-column strip structures with uniform concentration, resulting in the inability to achieve charge balance at the edges of the source region of the strip cells. Summary of the Invention

[0003] To address the aforementioned problems in the prior art, this invention provides a SiC superjunction structure with balanced edge charge and its fabrication method. The technical problem to be solved by this invention is achieved through the following technical solution:

[0004] This invention provides a SiC superjunction structure with edge charge balance, comprising: an N-epitaxial region and a plurality of p-type pillar regions, wherein the plurality of p-type pillar regions are arranged in parallel and spaced apart within the N-epitaxial region, and the N-epitaxial region between each two adjacent p-type pillar regions is a n-type pillar region, and the plurality of p-type pillar regions and the plurality of n-type pillar regions are arranged alternately to form a superjunction structure;

[0005] Among them, edge ion implantation regions are formed near both ends of the p-type pillar region, and the doping concentration of the edge ion implantation regions is lower than the doping concentration of the p-type pillar region between the two edge ion implantation regions.

[0006] In one embodiment of the present invention, the doping concentration of the N-epipolar region is 1×10⁻⁶. 15 ~5×10 17 cm -3 .

[0007] In one embodiment of the present invention, the width of the p-type column region is 1 μm to 5 μm.

[0008] In one embodiment of the present invention, the spacing between two adjacent p-type column regions is 1 μm to 5 μm.

[0009] In one embodiment of the present invention, the doping concentration of the p-type pillar region between the two edge ion implantation regions is 1 × 10⁻⁶. 15 ~1×10 18 cm -3 .

[0010] In one embodiment of the present invention, the doping concentration of the edge ion implantation region is 15% to 50% lower than the doping concentration of the p-type pillar region between the two edge ion implantation regions.

[0011] This invention provides a method for preparing a SiC superjunction structure with balanced edge charge, comprising:

[0012] Step 1: Select an N+ substrate and epitaxially grow an N- epitaxial region on the upper surface of the N+ substrate;

[0013] Step 2: Perform p-type ion implantation in the N-epitaxial region to form several ion implantation regions that are parallel and spaced apart within the N-epitaxial region;

[0014] Step 3: Perform p-type ion implantation again on the middle region of each ion implantation region, and obtain several p-type column regions after two ion implantations;

[0015] In this structure, the N-extension region between each pair of adjacent p-type column regions is an n-type column region, and multiple p-type column regions and multiple n-type column regions are arranged alternately to form a superjunction structure;

[0016] Edge ion implantation regions are formed near both ends of the p-type pillar region, and the doping concentration of the edge ion implantation regions is lower than the doping concentration of the p-type pillar region between the two edge ion implantation regions.

[0017] In one embodiment of the present invention, the doping concentration of the p-type pillar region between the two edge ion implantation regions is 1 × 10⁻⁶. 15 ~1×10 18 cm -3 .

[0018] In one embodiment of the present invention, the doping concentration of the edge ion implantation region is 15% to 50% lower than the doping concentration of the p-type pillar region between the two edge ion implantation regions.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] The SiC superjunction structure with edge charge balance of the present invention achieves charge balance at the edge of a single strip-shaped floating junction cell by reducing the doping concentration at both ends of the p-type pillar region in the superjunction structure, thereby improving the charge balance of the device, increasing the breakdown voltage and reliability of the device, and reducing the difficulty of terminal design.

[0021] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0022] Figure 1 This is a top view of a SiC superjunction structure with balanced edge charge provided in an embodiment of the present invention;

[0023] Figure 2 This is a three-dimensional diagram of a SiC superjunction structure with balanced edge charge provided in an embodiment of the present invention;

[0024] Figure 3 This is a side view of the p-type column region of a SiC superjunction structure provided in an embodiment of the present invention. Detailed Implementation

[0025] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a method for preparing an edge charge balanced SiC superjunction structure based on the present invention.

[0026] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a more in-depth and concrete understanding can be gained of the technical means and effects adopted by the present invention to achieve its intended purpose. However, the accompanying drawings are for reference and illustration only and are not intended to limit the technical solutions of the present invention.

[0027] Example 1

[0028] Please see Figure 1 , Figure 1 This is a top view of a SiC superjunction structure with edge charge balance provided in an embodiment of the present invention. Figure 2 This is a three-dimensional diagram of a SiC superjunction structure with balanced edge charge provided in an embodiment of the present invention; Figure 3 This is a side view of a p-type pillar region of a SiC superjunction structure provided in an embodiment of the present invention. Generally, the superjunction structure is applied to SiCMOS transistors to form a superjunction MOS transistor with a superjunction structure. The superjunction MOS transistor includes an N-type heavily doped silicon substrate and an N-epitaxial region 1 thereon. A plurality of p-type pillar regions 2 are disposed in parallel and spaced apart in the N-epitaxial region 1. The N-epitaxial region 1 between each two adjacent p-type pillar regions 2 is a n-type pillar region 1a. The plurality of p-type pillar regions 2 and the plurality of n-type pillar regions 1a are arranged alternately to form a superjunction structure.

[0029] As shown in the figure, the p-shaped column area 2 extends a relatively long length along the paper direction based on the rectangle in the top view, and the overall shape is roughly a cuboid.

[0030] Typically, the N-extended region with p-type column region 2 is set as the active region, and the periphery of the active region is the terminal region 3. The terminal region 3 is also set with terminal p-column region (not shown in the figure), and the area between the active region and the terminal region is set as the transition region 4.

[0031] Among them, edge ion implantation regions 2a (the dark part of p-type pillar region 2 in the figure) are formed near both ends of p-type pillar region 2. The doping concentration of edge ion implantation regions 2a is lower than that of p-type pillar region 2 between the two edge ion implantation regions 2a.

[0032] It should be noted that there is no limit to the length of the edge ion implantation region 2a in the p-type column region 2. It is necessary to ensure that the doping concentration of the region of the p-type column region 2 adjacent to the transition region 4 is lower than the doping concentration of the middle region of the p-type column region 2, so that the edge ion implantation region 2a formed has the same width and spacing as the p-type column region 2.

[0033] In one optional embodiment, the doping concentration of the N-epitaxial region is 1 × 10⁻⁶. 15 ~5×10 17 cm -3 .

[0034] Optionally, the width of the p-type column region is 1μm to 5μm, and the spacing between two adjacent p-type column regions is 1μm to 5μm.

[0035] In one optional embodiment, the doping concentration of the p-type pillar region 2 between the two edge ion implantation regions is 1 × 10⁻⁶. 15 ~1×10 18 cm -3 .

[0036] In an optional embodiment, the doping concentration of the edge ion implantation region is 15% to 50% lower than the doping concentration of the p-type pillar region 2 between the two edge ion implantation regions.

[0037] For a superjunction structure, the middle region of the p-type pillar region of the active region only needs to achieve charge balance between the n-type pillar regions on both sides. For the edge region of the p-type pillar region, it is necessary to achieve charge balance between the n-type pillar regions on both sides, the edge of the p-type pillar region, and the transition region connected to the p-type pillar region. In the SiC superjunction structure with edge charge balance in the embodiment of the present invention, by reducing the doping concentration at both ends of the p-type pillar region in the superjunction structure, charge balance at the edge of a single strip floating junction cell can be achieved, thereby improving the charge balance of the device, increasing the breakdown voltage and reliability of the device, and reducing the difficulty of terminal design.

[0038] Example 2

[0039] This embodiment provides a method for preparing a SiC superjunction structure with balanced edge charge, including:

[0040] Step 1: Select an N+ substrate and epitaxially grow an N- epitaxial region on the upper surface of the N+ substrate;

[0041] In an optional embodiment, an N-epitaxial region is epitaxially grown on the upper surface of an N+ substrate using a CVD method at a growth temperature of 1600°C-1900°C.

[0042] Step 2: Perform p-type ion implantation in the N-epitaxial region to form several ion implantation regions that are parallel and spaced apart within the N-epitaxial region;

[0043] In one alternative implementation, the implanted ion is Al, and the implantation energy ranges from 10 KeV to 1000 KeV.

[0044] Step 3: Perform p-type ion implantation again on the middle region of each ion implantation region. After two ion implantations, several p-type column regions are obtained.

[0045] In one alternative implementation, the implanted ion is Al, and the implantation energy ranges from 10 KeV to 1000 KeV.

[0046] In this structure, the N-epitaxial region between each pair of adjacent p-type pillar regions is considered as an n-type pillar region, and multiple p-type pillar regions and multiple n-type pillar regions are arranged alternately to form a superjunction structure; edge ion implantation regions are formed near the two ends of the p-type pillar regions, and the doping concentration of the edge ion implantation regions is lower than that of the p-type pillar regions between the two edge ion implantation regions.

[0047] Accordingly, in an optional embodiment, during the first ion implantation, the entire p-type column region is doped at the same concentration as the edge ion implantation region. Then, a second ion implantation is performed on the middle region of the p-type column region to form the final p-type column region.

[0048] In an optional embodiment, the doping concentration of the p-type pillar region between the two edge ion implantation regions is 1 × 10⁻⁶. 15 ~1×10 18 cm -3 .

[0049] Optionally, the doping concentration of the edge ion implantation region is 15% to 50% lower than the doping concentration of the p-type pillar region between the two edge ion implantation regions.

[0050] It should be noted that the p-type pillar region is prepared in layers. That is, an N- epitaxial region is grown on the upper surface of the N+ substrate, and then the p-type pillar region of this N- epitaxial region is prepared by step 2-3. Then, a second N- epitaxial region is grown on the N- epitaxial region that has been ion implanted by CVD. Step 2-3 is repeated to prepare the p-type pillar region of this N- epitaxial region until an active region with balanced edge charge is formed.

[0051] Optionally, the doping concentration of the N+ substrate region is 1×10⁻⁶. 18 cm -3 ~1×10 20 cm -3 Thickness 50μm~400μm.

[0052] Optionally, the doping concentration of the N-epitaxial region is 1×10⁻⁶. 15 ~5×10 17 cm -3 The thickness of each N-epitaxial region is 2μm to 20μm.

[0053] Optionally, the width of the p-type column region is 1 μm to 5 μm, and the spacing between two adjacent p-type column regions is 1 μm to 5 μm. The edge ion implantation region maintains the same width and spacing as the p-type column region 2.

[0054] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that an article or device comprising a list of elements includes not only those elements but also other elements not expressly listed. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device comprising said element. Terms such as "connected" or "linked" are not limited to physical or mechanical connections but can include electrical connections, whether direct or indirect. The orientations or positional relationships indicated by terms such as "upper," "lower," "left," and "right" are based on the orientations or positional relationships shown in the accompanying drawings and are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0055] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A SiC superjunction structure with balanced edge charge, characterized in that, include: The N-epipolar region and multiple p-type pillar regions are arranged in parallel and spaced apart within the N-epipolar region. The N-epipolar region between each two adjacent p-type pillar regions is an n-type pillar region. The multiple p-type pillar regions and multiple n-type pillar regions are arranged alternately to form a superjunction structure. Among them, edge ion implantation regions are formed near both ends of the p-type pillar region, and the doping concentration of the edge ion implantation regions is lower than the doping concentration of the p-type pillar region between the two edge ion implantation regions. The width of the p-type column region is 1μm to 5μm; The spacing between two adjacent p-type column regions is 1 μm to 5 μm; The doping concentration of the edge ion implantation region is 15% to 50% lower than the doping concentration of the p-type pillar region between the two edge ion implantation regions; The active region is defined as the N-epipolar region with a p-type column region, the periphery of the active region is the terminal region, the region between the active region and the terminal region is the transition region, and the edge ion implantation region is located within the active region and adjacent to the transition region.

2. The SiC superjunction structure with edge charge balance according to claim 1, characterized in that, The doping concentration of the N-epitaxial region is 1×10⁻⁶. 15 ~5×10 17 cm -3 .

3. The SiC superjunction structure with edge charge balance according to claim 1, characterized in that, The doping concentration of the p-type pillar region between the two edge ion implantation regions is 1 × 10⁻⁶. 15 ~1×10 18 cm -3 .

4. A method for preparing a SiC superjunction structure with balanced edge charge, characterized in that, include: Step 1: Select an N+ substrate and epitaxially grow an N- epitaxial region on the upper surface of the N+ substrate; Step 2: Perform p-type ion implantation in the N-epitaxial region to form several ion implantation regions that are parallel and spaced apart within the N-epitaxial region; Step 3: Perform p-type ion implantation again on the middle region of each ion implantation region, and obtain several p-type column regions after two ion implantations; In this structure, the N-extension region between each pair of adjacent p-type pillar regions is considered as an n-type pillar region, and multiple p-type pillar regions and multiple n-type pillar regions are arranged alternately to form a superjunction structure; Edge ion implantation regions are formed near both ends of the p-type pillar region, and the doping concentration of the edge ion implantation regions is lower than the doping concentration of the p-type pillar region between the two edge ion implantation regions. The width of the p-type column region is 1μm to 5μm; The spacing between two adjacent p-type column regions is 1 μm to 5 μm; The doping concentration of the edge ion implantation region is 15% to 50% lower than the doping concentration of the p-type pillar region between the two edge ion implantation regions; The active region is defined as the N-epipolar region with a p-type column region, the periphery of the active region is the terminal region, the region between the active region and the terminal region is the transition region, and the edge ion implantation region is located within the active region and adjacent to the transition region.

5. The method for preparing the SiC superjunction structure with edge charge balance according to claim 4, characterized in that, The doping concentration of the p-type pillar region between the two edge ion implantation regions is 1 × 10⁻⁶. 15 ~1×10 18 cm -3 .

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