Method for improving reverse recovery capability of FRD structure in RC-IGBT

Abstract

The invention provides a method for improving the reverse recovery capability of an FRD structure in an RC-IGBT, and the method comprises the steps: providing a substrate of a first conductive type, and forming an epitaxial layer of the first conductive type on the substrate; a first well of a second conductive type of an IGBT device and a second well of a second conductive type of a fast recovery diode are formed on a substrate, a gate trench is formed on the first well, trench gate structures are formed in the gate trench, a first doped region of a first conductive type is formed on the upper surface of the first well between the trench gate structures, and a second doped region of a second conductive type is formed on the upper surface of the second well between the trench gate structures. Forming an ion implantation protection layer on the epitaxial layer; a third doped region of the second conductive type is formed at the bottom of the first contact hole through ion implantation, a second doped region of the second conductive type is formed at the bottom of the second contact hole, and the doping concentration of the third doped region is higher than that of the second doped region. According to the invention, different dosage requirements of doping the contact holes of the active regions of the two parts of the RC-IGBT can be met, and the reverse recovery capability of an FRD (Fast Recovery Diode) part is improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for improving the reverse recovery capability of an FRD structure in an RC-IGBT. Background Art

[0002] RC-IGBT integrates IGBT and diode on the same chip to reduce chip area, module power consumption and overall cost. For the IGBT part, the ion implantation (usually P+ implantation) of the active area contact hole requires a larger dose to reduce the contact resistance. For the diode part, in order to improve the reverse recovery performance (called fast recovery diode FRD), the ion implantation of the active area contact hole requires as small an implantation dose as possible while satisfying the ohmic contact, to control the excess minority carrier distribution in the forward conduction state. In other words, for high-performance RC-IGBT, the ion implantation dose of the active area contact holes of the IGBT / FRD parts needs to be one thick and one thin.

[0003] In order to solve the above problems, it is necessary to propose a new method to improve the reverse recovery capability of the FRD structure in the RC-IGBT. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a method for improving the reverse recovery capability of the FRD structure in the RC-IGBT, so as to solve the problem that there is a lack of a method for improving the reverse recovery capability of the FRD structure in the RC-IGBT in the prior art.

[0005] To achieve the above objectives and other related objectives, the present invention provides a method for improving the reverse recovery capability of an FRD structure in an RC-IGBT, comprising:

[0006] Step 1, providing a substrate of a first conductivity type, including a formation area of ​​an IGBT device and a fast recovery diode on the substrate, a first buried layer of a second conductivity type of the IGBT device and a second buried layer of a first conductivity type of the fast recovery diode are respectively formed on the substrate, and an epitaxial layer of a first conductivity type is formed on the substrate;

[0007] Step 2: forming a first well of a second conductivity type of the IGBT device and a second well of a second conductivity type of the fast recovery diode on the substrate, wherein a gate trench is formed on the first well, a trench gate structure is formed in the gate trench, a first doped region of the first conductivity type is formed on the upper surface of the first well between the trench gate structures, and an ion implantation protection layer is formed on the epitaxial layer;

[0008] Step three: Use the first and second contact hole masks to form the first contact hole of the IGBT device and the second contact hole of the fast recovery diode, use ion implantation to form a third doped region of the second conductivity type at the bottom of the first contact hole, and form a second doped region of the second conductivity type at the bottom of the second contact hole, wherein the third doped region has a higher doping concentration than the second doped region.

[0009] Preferably, in step one, the first and second buried layers are formed by back ion implantation.

[0010] Preferably, in step 2, the gate trench is formed by photolithography and etching.

[0011] Preferably, the trench gate structure in step 2 comprises: a gate dielectric layer formed on the gate trench; and a gate polysilicon layer filling the gate trench.

[0012] Preferably, the method for forming the trench gate structure in step 2 comprises: depositing the gate dielectric layer; depositing the gate polysilicon layer; and grinding the gate polysilicon layer onto the epitaxial layer.

[0013] Preferably, the method of grinding the gate polysilicon layer in step 2 is chemical mechanical planarization grinding.

[0014] Preferably, the material of the ion implantation protection layer in step 2 is borophosphosilicate glass.

[0015] Preferably, in step 2, the ion implantation protection layer is formed by deposition and grinding.

[0016] Preferably, the method of grinding the ion implantation protection layer in step 2 is chemical mechanical planarization grinding.

[0017] Preferably, the method for forming the second and third doped regions in step three includes: using the first and second contact hole masks to form the first contact hole of the IGBT device and the second contact hole of the fast recovery diode; the first contact hole extends from the upper surface of the ion implantation protection layer to the first well, and the second contact hole extends from the upper surface of the ion implantation layer to the second well, and the depths of the first and second contact holes are the same; using the first ion implantation to simultaneously form the second doped region of the second conductivity type at the bottom of the first and second contact holes; forming a photoresist layer covering the ion implantation protection layer, using the first mask to open the photoresist layer on the first contact hole, using the second ion implantation to form the third doped region of the second conductivity type at the bottom of the first contact hole, and then removing the photoresist layer.

[0018] Preferably, the method for forming the second and third doped regions in step three includes: forming a first photoresist layer on the ion implantation protection layer, and opening the first photoresist layer using a second contact hole mask; forming a second contact hole of the fast recovery diode by etching, and the second contact hole extends from the upper surface of the ion implantation layer to the upper surface of the second well; forming the second doped region of the second conductivity type at the bottom of the second contact hole by a first ion implantation; removing the first photoresist layer to form a second photoresist layer covering the ion implantation protection layer, opening the second photoresist layer on the first contact hole by using the first mask, forming a first contact hole of the IGBT device by etching, forming a third doped region of the second conductivity type at the bottom of the first contact hole by a second ion implantation, and then removing the second photoresist layer.

[0019] Preferably, the first conductivity type is N-type, and the second conductivity type is P-type; or the first conductivity type is P-type, and the second conductivity type is N-type.

[0020] As described above, the method of improving the reverse recovery capability of the FRD structure in the RC-IGBT of the present invention has the following beneficial effects:

[0021] The present invention can meet the different doping dosage requirements of the contact holes of the two active regions of the RC-IGBT, and improve the reverse recovery capability of the FRD (fast recovery diode) part. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Shown is a schematic diagram of the process flow of the present invention;

[0023] Figure 2 It is a schematic diagram of forming an ion implantation protection layer according to the present invention;

[0024] Figure 3 It is a schematic diagram showing the formation of the first and second contact holes according to the first embodiment of the present invention;

[0025] Figure 4 It is a schematic diagram of the first ion implantation according to the first embodiment of the present invention;

[0026] Figure 5 It is a schematic diagram of the second ion implantation according to the first embodiment of the present invention;

[0027] Figure 6 It is a schematic diagram showing the formation of a second contact hole according to the second embodiment of the present invention;

[0028] Figure 7 It is a schematic diagram of the first ion implantation according to the second embodiment of the present invention;

[0029] Figure 8It is a schematic diagram showing the formation of a first contact hole according to a second embodiment of the present invention;

[0030] Fig. 9 It is a schematic diagram of the second ion implantation according to the second embodiment of the present invention. DETAILED DESCRIPTION

[0031] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0032] See also Figure 1 The present invention provides a method for improving the reverse recovery capability of the FRD structure in the RC-IGBT, comprising:

[0033] Step 1, providing a substrate of the first conductivity type, that is, forming a doped region 103 on the substrate by ion implantation, including a formation region of an IGBT device and a fast recovery diode on the substrate, forming a first buried layer 102 of the second conductivity type of the IGBT device and a second buried layer 112 of the first conductivity type of the fast recovery diode on the substrate, and forming an epitaxial layer 103 of the first conductivity type on the substrate;

[0034] In some embodiments, in step 1, the first and second buried layers are formed by back ion implantation.

[0035] Step 2: forming a first well 104 of the second conductivity type of the IGBT device and a second well 105 of the second conductivity type of the fast recovery diode on the substrate, a gate trench is formed on the first well 104, a trench gate structure 106 is formed in the gate trench, a first doping region 108 of the first conductivity type is formed on the upper surface of the first well 104 between the trench gate structures 106, and an ion implantation protection layer 107 is formed on the epitaxial layer 103 to form a structure as shown in FIG. Figure 2 The structure shown;

[0036] In some embodiments, in step 2, a gate trench is formed by photolithography and etching.

[0037] In some embodiments, the trench gate structure 106 in step 2 includes: a gate dielectric layer formed on the gate trench, the material of the gate dielectric layer may be an oxide layer or other known materials; and a gate polysilicon layer filling the gate trench.

[0038] In some embodiments, the method for forming the trench gate structure 106 in step 2 includes: depositing a gate dielectric layer; depositing a gate polysilicon layer; and grinding the gate polysilicon layer onto the epitaxial layer 103 .

[0039] In some embodiments, the method of polishing the gate polysilicon layer in step 2 is chemical mechanical planarization polishing.

[0040] In some embodiments, the material of the ion implantation protection layer 107 in step 2 is borophosphosilicate glass or other known materials.

[0041] In some embodiments, in step 2, the ion implantation protection layer 107 is formed by deposition and grinding.

[0042] In some embodiments, the method of polishing the ion implantation protection layer 107 in step 2 is chemical mechanical planarization polishing.

[0043] Step three: Use the first and second contact hole masks to form the first contact hole of the IGBT device and the second contact hole of the fast recovery diode, use ion implantation to form a third doped region of the second conductivity type at the bottom of the first contact hole, and form a second doped region of the second conductivity type at the bottom of the second contact hole, wherein the doping concentration of the third doped region is higher than that of the second doped region.

[0044] In some embodiments, the method for forming the second and third doped regions in step three includes: using the first and second contact hole masks to form the first contact hole C1 of the IGBT device and the second contact hole C2 of the fast recovery diode, specifically, forming a photoresist layer on the ion implantation protection layer, using the first and second contact hole masks to define the formation positions of the first and second contact holes, and then using etching to form the first and second contact holes; the first contact hole C1 extends from the upper surface of the ion implantation protection layer 107 to the first well 104, and the second contact hole C2 extends from the upper surface of the ion implantation layer 107 to the second well 105. The depths of the first and second contact holes are the same, and they can be deep contact holes or shallow contact holes, forming as shown in FIG. Figure 3 The structure shown; using the first ion implantation at the same time at the bottom of the first and second contact holes to form a second conductivity type of the second doping region 109, forming as Figure 4 The structure shown in FIG. 1 can also be formed with a protective layer (such as a photoresist) as a mask to protect other regions; a photoresist layer 111 is formed to cover the ion implantation protective layer 107, the photoresist layer 111 on the first contact hole C1 is opened by a first mask, and a third doped region 110 of a second conductivity type is formed at the bottom of the first contact hole C1 by a second ion implantation, so as to form a structure as shown in FIG. Figure 5 The structure shown is then removed from the photoresist layer 111.

[0045] In some embodiments, the method for forming the second and third doped regions in step three includes: forming a first photoresist layer 112 on the ion implantation protection layer 107, opening the first photoresist layer 113 using a second contact hole mask; forming a second contact hole C2 of the fast recovery diode by etching, wherein the second contact hole C2 extends from the upper surface of the ion implantation layer 107 to the upper surface of the second well 105, forming Figure 6 The structure shown in FIG. 1; using the first ion implantation to form a second doped region of the second conductivity type at the bottom of the second contact hole C2, forming a second doped region of the second conductivity type at the bottom of the second contact hole C2; Figure 7 The structure shown; removing the first photoresist layer 113, forming a second photoresist layer 114 covering the ion implantation protection layer 107, using the first mask to open the second photoresist layer 114 on the first contact hole C1, using etching to form the first contact hole C1 of the IGBT device, forming as Figure 8 The structure shown in FIG. 1 is formed by a second ion implantation at the bottom of the first contact hole C1 to form a third doping region 110 of the second conductivity type. Fig. 9 The structure shown is then removed from the second photoresist layer 114. In this embodiment, the depths of the first and second contact holes are also different, that is, the distances from the recombination center are different, and the ratio is more optimal.

[0046] In some embodiments, the first conductivity type is N-type and the second conductivity type is P-type; or the first conductivity type is P-type and the second conductivity type is N-type.

[0047] It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner. Therefore, the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0048] In summary, the present invention can meet the different doping requirements of the contact holes in the two active regions of the RC-IGBT and improve the reverse recovery capability of the FRD (fast recovery diode). Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0049] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for improving the reverse recovery capability of an FRD structure in an RC-IGBT, characterized in that: At least: Step 1, providing a substrate of a first conductivity type, including a formation area of ​​an IGBT device and a fast recovery diode on the substrate, a first buried layer of a second conductivity type of the IGBT device and a second buried layer of a first conductivity type of the fast recovery diode are respectively formed on the substrate, and an epitaxial layer of a first conductivity type is formed on the substrate; Step 2: forming a first well of a second conductivity type of the IGBT device and a second well of a second conductivity type of the fast recovery diode on the substrate, wherein a gate trench is formed on the first well, a trench gate structure is formed in the gate trench, a first doped region of the first conductivity type is formed on the upper surface of the first well between the trench gate structures, and an ion implantation protection layer is formed on the epitaxial layer; Step three: Use the first and second contact hole masks to form the first contact hole of the IGBT device and the second contact hole of the fast recovery diode, use ion implantation to form a third doped region of the second conductivity type at the bottom of the first contact hole, and form a second doped region of the second conductivity type at the bottom of the second contact hole, wherein the third doped region has a higher doping concentration than the second doped region.

2. The method for improving the reverse recovery capability of the FRD structure in the RC-IGBT according to claim 1, characterized in that: In step one, the first and second buried layers are formed by back ion implantation.

3. The method for improving the reverse recovery capability of the FRD structure in the RC-IGBT according to claim 1, characterized in that: In step 2, the gate trench is formed by photolithography and etching.

4. The method for improving the reverse recovery capability of the FRD structure in the RC-IGBT according to claim 1, characterized in that: The trench gate structure in step 2 includes: a gate dielectric layer formed on the gate trench; and a gate polysilicon layer filling the gate trench.

5. The method for improving the reverse recovery capability of the FRD structure in the RC-IGBT according to claim 3, characterized in that: The method for forming the trench gate structure in step 2 includes: depositing the gate dielectric layer; depositing the gate polysilicon layer; and grinding the gate polysilicon layer onto the epitaxial layer.

6. The method for improving the reverse recovery capability of the FRD structure in the RC-IGBT according to claim 4, characterized in that: The method of grinding the gate polysilicon layer in step 2 is chemical mechanical planarization grinding.

7. The method for improving the reverse recovery capability of the FRD structure in the RC-IGBT according to claim 1, characterized in that: The material of the ion implantation protection layer in step 2 is borophosphosilicate glass.

8. The method for improving the reverse recovery capability of the FRD structure in the RC-IGBT according to claim 1, characterized in that: In step 2, the ion implantation protection layer is formed by deposition and grinding.

9. The method for improving the reverse recovery capability of the FRD structure in the RC-IGBT according to claim 7, characterized in that: The method of grinding the ion implantation protection layer in step 2 is chemical mechanical planarization grinding.

10. The method for improving the reverse recovery capability of the FRD structure in the RC-IGBT according to claim 1, characterized in that: The method for forming the second and third doped regions in step three includes: using the first and second contact hole masks to form the first contact hole of the IGBT device and the second contact hole of the fast recovery diode; the first contact hole extends from the upper surface of the ion implantation protection layer to the first well, and the second contact hole extends from the upper surface of the ion implantation layer to the second well, and the depths of the first and second contact holes are the same; using the first ion implantation to simultaneously form the second doped region of the second conductivity type at the bottom of the first and second contact holes; forming a photoresist layer covering the ion implantation protection layer, using the first mask to open the photoresist layer on the first contact hole, using the second ion implantation to form the third doped region of the second conductivity type at the bottom of the first contact hole, and then removing the photoresist layer.

11. The method for improving the reverse recovery capability of the FRD structure in the RC-IGBT according to claim 1, characterized in that: The method for forming the second and third doped regions in step three includes: forming a first photoresist layer on the ion implantation protection layer, and opening the first photoresist layer using a second contact hole mask; forming a second contact hole of a fast recovery diode by etching, wherein the second contact hole extends from the upper surface of the ion implantation layer to the upper surface of the second well; forming the second doped region of the second conductivity type at the bottom of the second contact hole by a first ion implantation; removing the first photoresist layer to form a second photoresist layer covering the ion implantation protection layer, opening the second photoresist layer on the first contact hole by using the first mask, forming a first contact hole of an IGBT device by etching, forming a third doped region of the second conductivity type at the bottom of the first contact hole by a second ion implantation, and then removing the second photoresist layer.

12. The method for improving the reverse recovery capability of the FRD structure in the RC-IGBT according to claim 1, characterized in that: The first conductivity type is N type, and the second conductivity type is P type; or the first conductivity type is P type, and the second conductivity type is N type.

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