A device structure and process manufacturing method for improving the forward conduction characteristic of a small-size RC-IGBT diode

Abstract

The application relates to the technical field of RC-IGBT diode, and discloses a device structure for improving the forward conduction characteristic of a small-size RC-IGBT diode, which is divided into an IGBT region and an FWD region and comprises a MOS gate structure and an n-type drift layer located on the front face of the RC-IGBT device, an n-type magnetic field stop layer, a p+ type collector region and an n+ type cathode region and a collector located on the back face of the RC-IGBT device, and the IGBT region and the FWD region are in ohmic contact with the MOS gate structure; the contact hole one is filled with a contact plug composed of a titanium layer, a titanium nitride layer and a tungsten layer, and the contact hole two is filled with an emitter electrode, so that the ohmic contact performance of the IGBT region is ensured, the direct degradation problem caused by the contact between titanium and silicon is eliminated, the forward voltage characteristic of the FWD region is remarkably improved; at the position of the contact hole two of the FWD region, the contact plug material is removed through etching, so that the emitter electrode is directly in contact with the semiconductor of the FWD, a small amount of residual contact plug has little influence on the forward conduction characteristic of the FWD and can be ignored, and the contact path causing degradation is cut off.

Description

Technical Field

[0001] This invention relates to the field of RC-IGBT diode technology, specifically to a device structure and manufacturing process for improving the forward conduction characteristics of small-size RC-IGBT diodes. Background Technology

[0002] An RC-IGBT diode is a power semiconductor device that integrates an IGBT and a freewheeling diode (FRD) onto the same chip. Its core feature is its bidirectional conductivity, allowing it to conduct as an IGBT in the forward direction and also to provide reverse freewheeling current through the built-in diode.

[0003] As the cell size of RC-IGBTs becomes smaller and smaller, tungsten needs to be used instead of traditional aluminum as the contact metal for through holes (as the through hole size decreases, aluminum through holes have poor filling performance, while tungsten has better filling performance for small through holes) in order to ensure good electrode contact and good electrical characteristics.

[0004] Due to the poor contact (electrical contact) between tungsten and silicon, a titanium layer or similar material is formed between the tungsten layer and the semiconductor in a typical IGBT as a barrier metal layer. However, when the contact vias in the FWD region inside the RC-IGBT are filled with titanium and semiconductor contacts, the contact performance deteriorates, resulting in contact degradation. This leads to a deterioration in the forward voltage (Vf) characteristics of the FWD inside the RC-IGBT. Therefore, we need to propose a device structure and manufacturing process to improve the forward conduction characteristics of small-size RC-IGBT diodes. Summary of the Invention

[0005] The purpose of this invention is to provide a device structure and manufacturing method for improving the forward conduction characteristics of small-size RC-IGBT diodes. By filling a contact plug composed of a titanium layer, a titanium nitride layer, and a tungsten layer in the first contact hole and filling the emitter electrode in the second contact hole, the ohmic contact performance of the IGBT region is ensured, the direct degradation problem caused by the contact between titanium and silicon is eliminated, and the forward voltage characteristics of the FWD region are significantly improved, thereby solving the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a device structure for improving the forward conduction characteristics of a small-size RC-IGBT diode, comprising an IGBT region and an FWD region, including a MOS gate structure and an n-type drift layer on the front side of the RC-IGBT device, an n-type magnetic field stop layer on the back side of the RC-IGBT device, a p+ type collector region and an n+ type cathode region, and a collector, wherein both the IGBT region and the FWD region are in ohmic contact with the MOS gate structure;

[0007] An interlayer insulator is disposed above the MOS gate structure. A resistor mask is fabricated on the interlayer insulator. After selective etching of the surface of the interlayer insulator under the cover of the resistor mask, a contact hole 1 located in the IGBT region and a contact hole 2 located in the FWD region are formed.

[0008] It also includes a contact plug deposited on the front side of the RC-IGBT device, wherein a recessed area is formed above the contact plug corresponding to the second contact hole, and an emitter electrode is deposited on the contact plug in the recessed area after etching.

[0009] Preferably, the MOS gate structure includes a p-type base region, a plurality of trenches are formed on the p-type base region, a gate insulator is provided on the inner wall of the trenches, and a gate electrode is inserted into the inside of the trenches.

[0010] Preferably, two n+ type emitter regions and one p+ type contact region are respectively provided between two adjacent trenches in the IGBT region, and the p+ type contact region is located between the two n+ type emitter regions.

[0011] Preferably, the contact plug is composed of a titanium layer, a titanium nitride layer and a tungsten layer, wherein the titanium layer in the IGBT region forms an ohmic contact with the p+ type contact region, and the titanium layer in the FWD region does not contact the p-type base region.

[0012] Preferably, the spacing between the trenches in the IGBT region is smaller than the spacing between the trenches in the FWD region; an intermediate region is also provided between the IGBT region and the FWD region, and the spacing between the trenches in the intermediate region is equal to the spacing between the trenches in the IGBT region.

[0013] Preferably, the width of the contact hole in the intermediate area is equal to the width of the first contact hole, and the width of the contact hole in the intermediate area is smaller than the width of the second contact hole.

[0014] Preferably, the width of the second contact hole is greater than the thickness of the interlayer insulator, and the deposition thickness of the tungsten layer is less than the width of the second contact hole.

[0015] Based on the device structure described above for improving the forward conduction characteristics of a small-size RC-IGBT diode, this invention also provides a manufacturing method for improving the forward conduction characteristics of a small-size RC-IGBT diode, comprising the following steps:

[0016] S1. A resistor mask is fabricated on the interlayer insulator, and the interlayer insulator is selectively etched under the shielding effect of the resistor mask to form contact hole one and contact hole two.

[0017] S2. A titanium layer, a titanium nitride layer and a tungsten layer are sequentially deposited on the front side of the RC-IGBT device to form a contact plug, making the surface of the contact plug flush with the surface of the IGBT area, and the contact plug has a recessed area at the corresponding position of the contact hole 2.

[0018] S3. Wafer heating and annealing enhances the electrical adhesion between the contact plug and the wafer, and in the IGBT region, the titanium layer and the p+ type contact area form an ohmic contact.

[0019] S4. Etch the contact plug to expose the interlayer insulator. The contact plug at the first contact hole is flush with the interlayer insulator. The contact plug at the second contact hole is etched away, and the contact plug remains on the inner wall of the second contact hole.

[0020] S5. Evaporate the emitter electrode onto the surface of the contact plug.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] 1. This invention ensures the ohmic contact performance of the IGBT region by filling the first contact hole with a contact plug composed of a titanium layer, a titanium nitride layer, and a tungsten layer, and filling the second contact hole with an emitter electrode, thereby eliminating the direct degradation problem caused by the contact between titanium and silicon and significantly improving the forward voltage characteristics of the FWD region.

[0023] 2. In this invention, at the second contact hole position in the FWD region, the contact plug material is removed by etching, so that the emitter electrode directly contacts the semiconductor of the FWD. The small amount of residual contact plug has little impact on the forward conduction characteristics of the FWD and can be ignored, thus cutting off the contact path that leads to degradation.

[0024] 3. The present invention provides an intermediate region between the IGBT region and the FWD region, with the trench spacing of the intermediate region being the same as that of the IGBT region. The width of the contact hole in the intermediate region is smaller than that of the second contact hole, thereby increasing the anode contact resistance of the intermediate region, reducing the hole injection rate, and reducing the carrier interference of the FWD region on the IGBT region. Attached Figure Description

[0025] Figure 1 This is a cross-sectional view of the RC-IGBT semiconductor device in Embodiment 1 of the present invention;

[0026] Figure 2 This is a flowchart illustrating the fabrication process of the RC-I GBT semiconductor device in Embodiment 1 of the present invention.

[0027] Figure 3 This is a cross-sectional view of the fabrication of a resistor mask on an RC-IGBT semiconductor device according to Embodiment 1 of the present invention;

[0028] Figure 4This is a schematic diagram showing the widths of contact hole one and contact hole two in Embodiment 1 of the present invention;

[0029] Figure 5 This is a cross-sectional view of the deposition of contact plugs on an RC-I GBT semiconductor device according to Embodiment 1 of the present invention;

[0030] Figure 6 This is a cross-sectional view of the contact plug after etching in Embodiment 1 of the present invention;

[0031] Figure 7 This is a cross-sectional view of the fabrication of a second resistor mask on an RC-IGBT semiconductor device according to Embodiment 2 of the present invention;

[0032] Figure 8 This is a schematic diagram showing the widths of contact hole one and contact hole two in Embodiment 2 of the present invention;

[0033] Figure 9 This is a cross-sectional view of the deposition of contact plugs on an RC-I GBT semiconductor device according to Embodiment 2 of the present invention;

[0034] Figure 10 This is a cross-sectional view of the contact plug after etching in Embodiment 2 of the present invention;

[0035] Figure 11 This is a cross-sectional view of the RC-I GBT semiconductor device in Embodiment 3 of the present invention;

[0036] Figure 12 This is a schematic diagram showing the widths of contact hole one and contact hole two in Embodiment 3 of the present invention;

[0037] Figure 13 This is a schematic diagram of ion implantation into the p+ type contact region in Embodiment 3 of the present invention;

[0038] Figure 14 This is a schematic diagram of the diode forward voltage characteristics of the RC-IGBT semiconductor device prepared in Embodiment 2 of the present invention.

[0039] In the diagram: 1. n-type drift layer; 2. p-type base region; 3. Trench; 4. Gate insulator; 5. Gate electrode; 6. n+ type emitter region; 7. p+ type contact region one; 8. Emitter electrode; 9. Interlayer insulator; 9a. Contact hole one; 9b. Contact hole two; 10. n-type magnetic field stop layer; 11. p+ type collector region; 12. n+ type cathode region; 13. Collector; 14. Contact plug; 15. Titanium layer; 16. Titanium nitride layer; 17. Tungsten layer; 18. p+ type contact region two; 20. MOS gate structure; 21. IGBT region; 22. FWD region; 23. Intermediate region; 31. Resistor mask one; 32. Resistor mask two; 33. Resistor mask three; 34. Resistor mask four. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Example 1

[0042] Please see Figure 1-6 The present invention provides a technical solution: a device structure for improving the forward conduction characteristics of a small-size RC-IGBT diode, which is divided into an IGBT region 21 and an FWD region 22, including a MOS gate structure 20 and an n-type drift layer 1 on the front side of the RC-IGBT device, an n-type magnetic field barrier layer 10, a p+ type collector region 11 and an n+ type cathode region 12 on the back side of the RC-IGBT device, and a collector 13. Both the IGBT region 21 and the FWD region 22 are in ohmic contact with the MOS gate structure 20.

[0043] The p+ type collector region 11 is located in the IGBT region 21, and the n+ type cathode region 12 is located in the FWD region 22.

[0044] An interlayer insulator 9 is disposed above the MOS gate structure 20. A resistor mask 31 is fabricated on the interlayer insulator 9. After selective etching of the surface of the interlayer insulator 9 under the cover of the resistor mask 31, a contact hole 9a located in the IGBT region 21 and a contact hole 9b located in the FWD region 22 are formed.

[0045] It also includes a contact plug 14 deposited on the front side of the RC-IGBT device. A recessed area is formed on the contact plug 14 above the position corresponding to the contact hole 9b. After the wafer is heated and annealed, the electrical adhesion between the contact plug 14 and the wafer can be enhanced. After the contact plug 14 in the recessed area is etched, an emitter electrode 8 is deposited. The emitter electrode 8 is the anode of the FWD region, and the contact plug 14 in the IGBT region 21 is in ohmic contact with the emitter electrode 8.

[0046] After the contact plug 14 in the recessed area is etched, the second contact hole 9b is exposed again. A small amount of contact plug 14 will remain on the inner wall of the second contact hole 9b. This small amount of contact plug 14 residue has little impact on the forward conduction characteristics of the FWD area and can be ignored.

[0047] In order to ensure that the aforementioned morphology is formed after etching, the tungsten layer 17 is embedded in the contact holes (9a and 9b) by making the width of the contact holes (9a and 9b) almost equal to or less than the thickness of the interlayer insulator 9.

[0048] The MOS gate structure 20 includes a p-type base region 2, which penetrates the IGBT region 21 and the FWD region. Multiple trenches 3 are formed on the p-type base region 2. The spacing between the multiple trenches 3 is not all the same. A gate insulator 4 is provided on the inner wall of the trenches 3. A gate electrode 5 is inserted into the inside of the trenches 3.

[0049] Two n+ type emitter regions 6 and one p+ type contact region 7 are respectively arranged between two adjacent trenches 3 in IGBT region 21. The p+ type contact region 7 is located between the two n+ type emitter regions 6. The p+ type contact region 7 is located at the center position between two adjacent trenches 3 in IGBT region 21, and the two n+ type emitter regions 6 are symmetrically arranged about the p+ type contact region 7.

[0050] The contact plug 14 is composed of a titanium layer 15, a titanium nitride layer 16 and a tungsten layer 17. After filling the contact plug 14, the surface of the IGBT region 21 can be made flat. The titanium layer 15 in the IGBT region 21 forms an ohmic contact with the p+ type contact region 7. The titanium layer 15 in the FWD region 22 does not contact the p type base region 2.

[0051] The spacing between the grooves 3 in the IGBT region 21 is smaller than the spacing between the grooves 3 in the FWD region 22; an intermediate region 23 is also provided between the IGBT region 21 and the FWD region 22, and the spacing between the grooves 3 in the intermediate region 23 is equal to the spacing between the grooves 3 in the IGBT region 21.

[0052] The width of the contact hole in the intermediate region 23 is equal to the width of the first contact hole 9a, and the width of the contact hole in the intermediate region 23 is smaller than the width of the second contact hole 9b. This increases the anode contact resistance of the intermediate region 23, reduces the hole injection rate when the diode is working, and makes the carrier concentration in the intermediate region 2 lower than that in the FWD region 22, thereby reducing the interference to the IGBT region 21.

[0053] If the width of contact hole 9b is greater than the thickness of interlayer insulator 9, tungsten layer 17 will not be fully embedded. If the deposition thickness of tungsten layer 17 is less than the width of contact hole 9b, the surface of the n-type semiconductor substrate will be exposed in contact hole 9b after etching tungsten layer 17 and barrier metal (titanium nitride layer 16 and titanium layer 15).

[0054] Based on the device structure described above for improving the forward conduction characteristics of a small-size RC-IGBT diode, this invention also provides a manufacturing method for improving the forward conduction characteristics of a small-size RC-IGBT diode, comprising the following steps:

[0055] S1. A resistance mask 31 is fabricated on the interlayer insulator 9, and the interlayer insulator 9 is selectively etched under the shielding effect of the resistance mask 31 to form contact hole 9a and contact hole 9b.

[0056] S2. A titanium layer 15, a titanium nitride layer 16, and a tungsten layer 17 are sequentially deposited on the front side of the RC-IGBT device to form a contact plug 14, making the surface of the contact plug 14 flush with the surface of the IGBT region 21, and the contact plug 14 has a recessed area at the corresponding position of the contact hole 9b.

[0057] S3. Wafer heating and annealing enhances the electrical adhesion between the contact plug 14 and the wafer, and in the IGBT region 21, the titanium layer 15 forms an ohmic contact with the p+ type contact region -7.

[0058] S4. Etch contact plug 14 to expose interlayer insulator 9, and make contact plug 14 at contact hole 1 9a flush with interlayer insulator 9, and contact plug 14 at contact hole 2 9b is etched away, and contact plug 14 remains on the inner wall of contact hole 2 9b.

[0059] S5. Evaporate the emitter electrode 8 onto the surface of the contact plug 14.

[0060] Example 2

[0061] The similarities with Example 1 will not be repeated here; the differences are...

[0062] like Figure 7-10 and Figure 14 Contact holes 9a and 9b are formed separately on the interlayer insulator 9 of the RC-IGBT device using different resistive masks. Specifically, contact hole 9a is formed using resistive mask 32 and contact hole 9b is formed using resistive mask 33. After contact holes 9a and 9b are formed separately, contact plug 14 is filled separately inside contact hole 9a and emitter electrode 8 is filled separately inside contact hole 9b. The structure of the RC-IGBT device in Example 1 is then formed by etching. It is worth mentioning that the RC-IGBT device prepared in this example has no residual contact plug 14 inside contact hole 9b.

[0063] Figure 14 This is a schematic diagram of the forward voltage characteristics of an RC-IGBT structure in this embodiment, where the contact hole 9a of the IGBT region 21 is filled with a contact plug 14 and the contact hole 9b of the FWD region 22 is filled with an emitter electrode 8. It can be observed that it has better forward voltage characteristics than the conventional RC-IGBT structure (where both the IGBT part 9a and the FWD part 9b are filled with 14).

[0064] Example 3

[0065] The similarities with Examples 1 and 2 will not be repeated here; the differences are as follows:

[0066] like Figure 11-13This embodiment is applicable to the case where both IGBT region 21 and FWD region 22 are designed with small size, that is, both contact hole 1 9a and contact hole 2 9b are small size;

[0067] On the interlayer insulator 9 of the RC-IGBT device, a resistor mask 34 is used to form contact holes 9a and 9b, and contact plugs 14 are filled in both contact holes 9a and 9b.

[0068] It is worth noting that a p+ type contact area 7 is provided below the contact hole 9a in the IGBT region 21, and a p+ type contact area 18 is provided on the p-type base area 2 in the middle region 23 and the FWD region 22.

[0069] Therefore, even though the contact hole 29b is filled with contact plug 14 to make the titanium layer 15 contact with the semiconductor, the FWD region 22 can still achieve good ohmic contact because the p+ type contact region 28 is in contact with the titanium layer 15, which can also improve the forward conduction characteristics of the FWD region 22.

[0070] The fabrication process of the RC-IGBT device in this embodiment is as follows: Figure 12-13 As shown, firstly, the interlayer insulator 9 is selectively etched using a resistor mask 34 to form contact hole 9a and contact hole 9b. Then, p+ type contact region 18 is selectively implanted using the resistor mask 34. The p+ type contact region 18 can also be formed synchronously with the p+ type contact region 7 (the first p+ type contact region) of the IGBT region 21.

[0071] Ion implantation 35 to form p+ type contact region 2 18 can be performed using boron fluoride (BF2) ions at an implantation energy of 30 keV. The depth of p+ type contact region 2 18 can be 0.5 μm or less. Annealing is then performed, for example, heat treatment at approximately 650°C for approximately 30 minutes, to activate p+ type contact region 2 18.

[0072] Then, a contact plug 14 is deposited on the surface to fill the contact hole 9a and the contact hole 9b. Finally, the contact plug 14 is etched to expose the interlayer insulator 9, and then the emitter electrode 8 is deposited on the surface.

[0073] Of course, the p+ type contact area 218 can also be made in the same way in Embodiment 1 and Embodiment 2, thereby further improving the performance.

[0074] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A device structure for improving the forward conduction characteristics of a small-size RC-IGBT diode, comprising an IGBT region (21) and a FWD region (22), characterized in that: The device includes a MOS gate structure (20) and an n-type drift layer (1) on the front side of the RC-IGBT device, an n-type magnetic field stop layer (10) on the back side of the RC-IGBT device, a p+ type collector region (11) and an n+ type cathode region (12), and a collector (13). The IGBT region (21) and the FWD region (22) are both in ohmic contact with the MOS gate structure (20). An interlayer insulator (9) is disposed above the MOS gate structure (20). A resistor mask (31) is fabricated on the interlayer insulator (9). After selective etching of the surface of the interlayer insulator (9) under the shielding of the resistor mask (31), a contact hole (9a) located in the IGBT region (21) and a contact hole (9b) located in the FWD region (22) are formed. It also includes a contact plug (14) deposited on the front side of the RC-IGBT device. A recessed area is formed on the contact plug (14) above the position corresponding to the second contact hole (9b). The contact plug (14) in the recessed area is etched and then deposited with an emitter electrode (8).

2. The device structure for improving the forward conduction characteristics of a small-size RC-IGBT diode according to claim 1, characterized in that: The MOS gate structure (20) includes a p-type base region (2), a plurality of trenches (3) are formed on the p-type base region (2), a gate insulator (4) is provided on the inner wall of the trenches (3), and a gate electrode (5) is inserted into the inside of the trenches (3).

3. The device structure for improving the forward conduction characteristics of a small-size RC-IGBT diode according to claim 2, characterized in that: Two n+ type emitter regions (6) and one p+ type contact region (7) are respectively provided between two adjacent trenches (3) in the IGBT region (21), and the p+ type contact region (7) is located between the two n+ type emitter regions (6).

4. The device structure for improving the forward conduction characteristics of a small-size RC-IGBT diode according to claim 3, characterized in that: The contact plug (14) is composed of a titanium layer (15), a titanium nitride layer (16) and a tungsten layer (17). The titanium layer (15) in the IGBT region (21) forms an ohmic contact with the p+ type contact region (7). The titanium layer (15) in the FWD region (22) does not contact the p-type base region (2).

5. The device structure for improving the forward conduction characteristics of a small-size RC-I GBT diode according to claim 4, characterized in that: The spacing between the grooves (3) of the IGBT region (21) is smaller than the spacing between the grooves (3) of the FWD region (22); an intermediate region (23) is also provided between the IGBT region (21) and the FWD region (22), and the spacing between the grooves (3) of the intermediate region (23) is equal to the spacing between the grooves (3) of the IGBT region (21).

6. The device structure for improving the forward conduction characteristics of a small-size RC-I GBT diode according to claim 5, characterized in that: The width of the contact hole in the intermediate region (23) is equal to the width of contact hole one (9a), and the width of the contact hole in the intermediate region (23) is smaller than the width of contact hole two (9b).

7. The device structure for improving the forward conduction characteristics of a small-size RC-I GBT diode according to claim 6, characterized in that: The width of the second contact hole (9b) is greater than the thickness of the interlayer insulator (9), and the deposition thickness of the tungsten layer (17) is less than the width of the second contact hole (9b).

8. A manufacturing method for improving the forward conduction characteristics of a small-size RC-IGBT diode, based on the device structure for improving the forward conduction characteristics of a small-size RC-IGBT diode as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. A resistor mask (31) is fabricated on the interlayer insulator (9), and the interlayer insulator (9) is selectively etched under the shielding effect of the resistor mask (31) to form contact hole 1 (9a) and contact hole 2 (9b). S2. A titanium layer (15), a titanium nitride layer (16) and a tungsten layer (17) are sequentially deposited on the front side of the RC-IGBT device to form a contact plug (14). The surface of the contact plug (14) is flush with the surface of the IGBT region (21). The contact plug (14) has a recessed area at the corresponding position of the contact hole (9b). S3. Wafer heating and annealing enhances the electrical adhesion between the contact plug (14) and the wafer, and in the I GBT region (21), the titanium layer (15) forms an ohmic contact with the p+ type contact region (7). S4. Etch the contact plug (14) to expose the interlayer insulator (9), and make the contact plug (14) at the contact hole one (9a) flush with the interlayer insulator (9), and etch away the contact plug (14) at the contact hole two (9b), and leave the contact plug (14) on the inner wall of the contact hole two (9b). S5. Evaporate an emitter electrode (8) onto the surface of the contact plug (14).

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