RC-IGBT and manufacturing method thereof

Abstract

On the basis of a traditional RC-IGBT, the RC-IGBT and the manufacturing method thereof are provided, a convex n region is introduced between and below two Pbody regions of the manufactured RC-IGBT, and a p-type transparent anode region is designed between two planar grids on the surface of the n region. When the RC-IGBT is reversely conducted, electrons injected into the n + short circuit region can directly flow to the p-type transparent anode region of the n region after sequentially passing through the nFS region and the n-drift region under the low current density, the hole injection efficiency of the lightly doped p-type transparent anode region is low, the hole concentration of the anode side of the integrated diode is reduced, the reverse recovery peak current is obviously reduced, and the reliability of the RC-IGBT is improved. Therefore, the reverse recovery characteristic is improved; under high current density, holes are mainly injected into the n-drift region by the p + ohmic contact region, the hole injection efficiency of the heavily doped p + ohmic contact region is improved, and the surge current resistance of the device is improved.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology, and particularly relates to an RC-IGBT and a manufacturing method thereof. Background Art

[0002] An RC-IGBT (Reverse Conducting Insulated Gate Bipolar Transistor) is a device that integrates an IGBT (Insulated Gate Bipolar Transistor) and a freewheeling diode (FWD) on the same chip.

[0003] Reference Figure 1 As shown, a traditional RC-IGBT adds an n + short-circuit region on the collector side. The n + short-circuit region and the p-type region on the emitter side form a PN junction diode, and its reverse conduction ability is provided by the integrated PN junction diode. The p + ohmic contact region on the emitter side serves as the anode region of the diode, and the n + short-circuit region on the collector side serves as the cathode region of the diode. When reverse conducting, a reverse voltage VCE<0 is applied between the collector and the emitter, the diode is forward-biased, the p + anode region injects holes into the n - drift region, and the n + cathode region injects electrons into the n - drift region, thereby realizing the conduction of the diode. However, due to the heavy doping of the p + anode region, the concentration on the anode side is very high when the diode conducts, which causes a high peak reverse recovery current when the diode turns off, slows down the reverse recovery speed, and increases the reverse recovery charge. Therefore, its reverse recovery characteristics are generally worse than those of an independent fast recovery diode (FRD) or a SiC diode. Summary of the Invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides an RC-IGBT and a manufacturing method thereof. The technical problems to be solved by the present invention are realized through the following technical solutions: In a first aspect, the present invention provides an RC-IGBT including: an n region disposed on the n-drift region, an emitter, and a collector disposed on the back surface of the n-drift region. The n region is provided with two Pbody regions, a p+ ohmic contact region, and an n +An emitter region is provided such that the n-region appears convex; two planar gates with a spacing are provided above the left and right Pbody regions. Except for the bottom surface, the other three sides of the planar gate are wrapped by an interlayer dielectric layer, and a p-type transparent anode region is provided below the spacing between the two planar gates.

[0005] In a second aspect, the present invention provides a manufacturing method of an RC-IGBT. An RC-IGBT as in the first aspect is prepared, and the manufacturing method includes: S1, Select an n-type silicon wafer as the drift region of the RC-IGBT; S2, Inject phosphorus ions on the upper surface of the drift region to form an n-region; S3, Thermally oxidize SiO2 on the upper surface of the n-region to form a gate oxide layer, deposit heavily doped polysilicon on the gate oxide layer, and etch to form two planar gates with a spacing in the middle; S4, Inject boron ions into the n-region from both sides of the upper surface of the n-region to form two Pbody regions with a spacing in the middle, and inject phosphorus ions into the two Pbody regions from the upper surface of the n-region to form two n+ emitter regions; S5, Deposit borophosphosilicate glass on the upper surface and side surfaces of the two planar gates, and etch to form two interlayer dielectric layers; S6, Inject boron ions into the two Pbody regions from the upper surface of the two Pbody regions to form two p+ ohmic contact regions; S7, Inject boron ions into the n-region from the upper surface of the n-region and in the spacing area between the two planar gates to form a p-type transparent anode region; S8, Deposit aluminum metal from top to bottom on the two interlayer dielectric layers, p+ ohmic contact regions, p-type transparent anode region, and n+ emitter regions to form an emitter covering the interlayer dielectric layers, p+ ohmic contact regions, p-type transparent anode region, and n+ emitter regions; S9, Form an nFS region on the back surface of the drift region, form a p+ collector region and an n+ short-circuit region in the nFS region, and then deposit aluminum metal to form a collector covering the p+ collector region and the n+ short-circuit region.

[0006] Beneficial effects: Based on the traditional RC-IGBT, the present invention provides an RC-IGBT and a manufacturing method thereof. In the manufactured RC-IGBT, a convex n-region is introduced between and below two Pbody regions, and a p-type transparent anode region is designed between two planar gates on the surface of the n-region. When the RC-IGBT of the present invention conducts in the reverse direction, at low current density, the electrons injected into the n+ short-circuit region can flow directly to the p-type transparent anode region of the n-region after passing through the nFS region (n-field stop layer) and the n-drift region in sequence. The hole injection efficiency of the lightly doped p-type transparent anode region is relatively low, and the hole concentration on the anode side of the integrated diode decreases, resulting in a significant reduction in the reverse recovery peak current, thereby improving the reverse recovery characteristics. At high current density, mainly holes are injected from the p+ ohmic contact region into the n-drift region. The hole injection efficiency of the heavily doped p+ ohmic contact region is relatively high, which helps to improve the surge current resistance of the device.

[0007] The following will further elaborate on the present invention in conjunction with the accompanying drawings and embodiments. Description of the Drawings

[0008] Figure 1 is a schematic structural diagram of a traditional RC-IGBT.

[0009] Figure 2 is a schematic diagram of an RC-IGBT provided by the present invention.

[0010] Figure 3 is a schematic flow diagram of a manufacturing method of an RC-IGBT provided by the present invention.

[0011] Figure 4 is a schematic diagram of forming a drift region provided by the present invention.

[0012] Figure 5 is a schematic diagram of forming an n-region provided by the present invention.

[0013] Figure 6 is a schematic diagram of forming two planar gates with a spacing provided by the present invention.

[0014] Figure 7 is a schematic diagram of forming two Pbody regions with a spacing in the middle provided by the present invention.

[0015] Figure 8 is a schematic diagram of forming two n+ emitter regions provided by the present invention.

[0016] Figure 9 is a schematic diagram of forming two interlayer dielectric layers provided by the present invention.

[0017] Figure 10 is a schematic diagram of forming two p+ ohmic contact regions provided by the present invention.

[0018] Figure 11 It is a schematic diagram of forming a p-type transparent anode region provided by the present invention.

[0019] Figure 12 It is a schematic diagram of forming an emitter provided by the present invention.

[0020] Figure 13 It is a schematic diagram of forming an nFS region provided by the present invention.

[0021] Figure 14 It is a schematic diagram of forming a p+ collector region provided by the present invention.

[0022] Figure 15 It is a schematic diagram of forming an n+ short-circuit region provided by the present invention.

[0023] Figure 16 It is a comparative curve graph of the reverse conduction characteristics of the RC-IGBT provided by the present invention and the traditional RC-IGBT at room temperature (300K).

[0024] Figure 17 It is a comparative curve graph of the reverse recovery characteristics of the RC-IGBT provided by the present invention and the traditional RC-IGBT at room temperature (300K). Detailed implementation manners

[0025] The following further describes the present invention in detail with reference to specific embodiments, but the implementation manners of the present invention are not limited thereto.

[0026] In a first aspect, as Figure 2 shown, the present invention provides an RC-IGBT including: an n region disposed on an n-drift region, an emitter, and a collector disposed on the back surface of the n-drift region. The n region is provided with two Pbody regions on the left and right, a p+ ohmic contact region, and an n + emission region, such that the n region presents a convex shape; two planar gates with a spacing are disposed above the two Pbody regions on the left and right. Except for the bottom surface, the other three sides of the planar gate are wrapped by an interlayer dielectric layer, and a p-type transparent anode region is disposed below the spacing facing the two planar gates.

[0027] Wherein, each p+ ohmic contact region is disposed above the Pbody region and adjacent to the side wall of the RC-IGBT; each n + emission region is disposed adjacent to the p+ ohmic contact region; the emitter is disposed above the two planar gates, and the emitter and the planar gate are isolated by an interlayer dielectric layer; an nFS region is disposed below the n-drift region; a p+ collector region is disposed on the left side in the nFS region, and an n+ short-circuit region is disposed on the right side; the collector is disposed on the back surfaces of the p+ collector region and the n+ short-circuit region.

[0028] In Figure 2In it, the planar gate includes a gate oxide layer and polysilicon. The polysilicon is disposed above the gate oxide layer, and the gate oxide layer is disposed above the Pbody region. There is a spacing between the two planar gates and the sidewalls of the RC-IGBT. There is a spacing between the lower surfaces of both Pbody regions and the n-region. The spacing between the two Pbody regions is greater than the spacing between the two planar gates. Each planar gate is not flush with the Pbody region below it.

[0029] Among them, the width of the planar gate is 5 µm to 15 µm, and the spacing between the two planar gates is 0.5 µm to 3 µm. The junction depth of the n-region is 6 µm to 10 µm, and the doping concentration is 1×10 15 cm -3 ~1×10 17 cm -3 ; the junction depth of the Pbody region is 5 µm to 9 µm, and the doping concentration is 2×10 17 cm -3 ~ 5×10 17 cm -3 ; the junction depth of the p-type transparent anode region is 0.5 µm to 1 µm, and the doping concentration is 5×10 16 cm -3 ~2×10 17 cm -3 .

[0030] Based on the traditional RC-IGBT, the present invention provides an RC-IGBT and a manufacturing method thereof. The manufactured RC-IGBT introduces a convex n-region between and below the two Pbody regions, and designs a p-type transparent anode region between the two planar gates on the surface of the n-region. When the RC-IGBT of the present invention is reversely conducting, at low current density, the electrons injected into the n+ short-circuit region flow through the nFS region (n-field stop layer) and the n-drift region in sequence, and can directly flow to the p-type transparent anode region of the n-region. The hole injection efficiency of the lightly doped p-type transparent anode region is relatively low, and the hole concentration on the anode side of the integrated diode decreases, resulting in a significant reduction in the reverse recovery peak current, thereby improving the reverse recovery characteristics; at high current density, mainly the p+ ohmic contact region (integrated diode anode region) injects holes into the n-drift region. The hole injection efficiency of the heavily doped p+ ohmic contact region (integrated diode anode region) is relatively high, which helps to improve the surge current resistance ability of the device.

[0031] As Figure 3 shown, the present invention provides a manufacturing method of an RC-IGBT, for preparing the RC-IGBT as in the first aspect. The manufacturing method includes: S1, selecting an n-type silicon wafer as the drift region of the RC-IGBT.

[0032] In this step, an n-type silicon wafer with appropriate resistivity is selected as the drift region. As Figure 4as shown

[0033] S2, Inject phosphorus ions on the upper surface of the drift region to form an n-region, as Figure 5 shown

[0034] S3, Thermally oxidize SiO2 on the upper surface of the n-region to form a gate oxide layer, deposit heavily doped polysilicon on the gate oxide layer, and etch to form two planar gates with a spacing in between, as Figure 6 shown

[0035] S4, Inject boron ions into the n-region from both sides of the upper surface of the n-region to form two Pbody regions with a spacing in between, as Figure 7 shown. And inject phosphorus ions from the upper surface of the n-region into the two Pbody regions to form two n+ emitter regions, as Figure 8 shown

[0036] S5, Deposit borophosphosilicate glass on the upper surface and sides of the two planar gates, and etch to form two interlayer dielectric layers, as Figure 9 shown

[0037] S6, Inject boron ions into the two Pbody regions from the upper surface of the two Pbody regions to form two p+ ohmic contact regions, as Figure 10 shown

[0038] S7, Inject boron ions into the n-region from the upper surface of the n-region and in the spacing area between the two planar gates to form a p-type transparent anode region, as Figure 11 shown

[0039] S8, Deposit aluminum metal from top to bottom on the two interlayer dielectric layers, p+ ohmic contact regions, p-type transparent anode region, and the emitters of the n+ emitter regions to form a covering layer on the interlayer dielectric layers, p+ ohmic contact regions, p-type transparent anode region, and the emitters of the n+ emitter regions, as Figure 12 shown

[0040] S9, Form an nFS region on the back surface of the drift region, form a p+ collector region and an n+ short-circuit region in the nFS region, and then deposit aluminum metal to form a collector covering the p+ collector region and the n+ short-circuit region.

[0041] Specifically, S9 includes: S91, Inject phosphorus ions into the drift region from the lower surface of the drift region to form an nFS region, as Figure 13 shown

[0042] S92, Inject boron ions into the nFS region at a position close to the lower surface on the left side inside the nFS region to form a p+ collector region, as Figure 14 shown

[0043] S93. Inject phosphorus ions into the nFS region at a position adjacent to the lower surface on the right side inside the nFS region to form an n+ short-circuit region, as Figure 15 shown.

[0044] S94. Deposit aluminum metal on the lower surfaces of the p+ collector region and the n+ short-circuit region to form a collector covering the p+ collector region and the n+ short-circuit region, as Figure 2 shown.

[0045] The working process and specific characteristics of the RC-IGBT of the present invention are described as follows.

[0046] 1) When the RC-IGBT of the present invention is in the blocking state, the planar gate-emitter is connected to zero potential (i.e., U GE = 0), and a positive bias voltage is applied between the collector-emitter (U CE > 0). The Pbody / n-junction is reverse-biased, and the n-drift region is completely depleted and bears the applied forward voltage.

[0047] 2) When the RC-IGBT of the present invention is in the forward conduction state, a forward voltage is applied between the collector-emitter (U CE > 0), and the positive voltage applied between the planar gate-emitter is greater than the threshold voltage (U GE > U T ), electrons in the n + emission region will flow through the lateral channel under the planar gate and directly enter the n - drift region, and then flow to the n + short-circuit region. At this time, the device conducts in the single-pole mode of the power MOSFET. When the voltage drop generated by the electron current above the p + collector region is greater than the turn-on voltage of the p + / nFS junction, the p+ collector region injects holes into the n-drift region. At this time, the device conducts in the bipolar mode of the IGBT and has a lower saturation voltage.

[0048] 3) When the RC-IGBT of the present invention is turned off, a negative voltage is applied between the planar gate-emitter (U GE ≤ 0), and the lateral channel will disappear, making it impossible for electrons in the emission region to be injected into the n-drift region. Then the IGBT starts to turn off. During turn-off, the n+ short-circuit region can quickly extract electrons, making the turn-off speed faster. 4) When a reverse voltage is applied between the collector-emitter of the RC-IGBT of the present invention (U CEWhen V < 0, the integrated diode conducts (the RC-IGBT conducts reversely). At low current density, the electrons injected into the n+ short-circuit region can directly flow to the p-type transparent anode region in the n region after passing through the nFS region (n-field stop layer) and the n-drift region in sequence. The hole injection efficiency of the lightly doped p-type transparent anode region is relatively low, and the hole concentration on the anode side of the integrated diode decreases, resulting in a significant reduction in the reverse recovery peak current, thus improving the reverse recovery characteristics. At high current density, mainly holes are injected from the p+ ohmic contact region (the anode region of the integrated diode) into the n-drift region, and the hole injection efficiency of the heavily doped p+ ohmic contact region (the anode region of the integrated diode) increases, which helps to improve the surge current resistance ability of the device.

[0049] 5) When a positive voltage (U CE > 0) is applied between the collector and emitter of the RC-IGBT of the present invention, and a negative voltage (U GE < 0) is applied between the planar gate and emitter, the integrated diode enters the reverse recovery stage. During conduction, a large number of non-equilibrium carriers stored in the n - -drift region continuously recombine, and the applied voltage can accelerate the extraction of non-equilibrium carriers, shortening the reverse recovery time of the integrated diode.

[0050] To verify the characteristics of the RC-IGBT of the present invention, taking the 1200V voltage level as an example, the reverse conduction characteristics and reverse recovery characteristics of the RC-IGBT of the present invention at room temperature (300K) are respectively simulated using simulation software.

[0051] 1) Reverse conduction characteristics.

[0052] Referring to Figure 16 , it is the reverse conduction characteristic curves of the RC-IGBT of the present invention and the traditional RC-IGBT at room temperature (300K). At room temperature (300K), when the anode current density is 100A / cm 2 , the reverse conduction voltage drop of the traditional RC-IGBT is about 1.07V, and the reverse conduction voltage drop of the RC-IGBT of the present invention is about 1.16V.

[0053] 2) Reverse recovery characteristics.

[0054] Referring to Figure 17 , it is the reverse recovery characteristic curves of the RC-IGBT of the present invention and the traditional RC-IGBT at room temperature (300K). Under the same test conditions, the peak value of the reverse recovery current density of the traditional RC-IGBT is 293A / cm 2 , the reverse recovery charge is about 22.5µC / cm 2 , and the peak value of the reverse recovery current density of the RC-IGBT of the present invention is 234A / cm 2, the reverse recovery charge is about 16.5 µC / cm 2 , which are 20.1% and 27.1% lower than those of traditional RC-IGBTs respectively.

[0055] It should be noted that the terms "first" and "second" in the present invention are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality of" means two or more, unless otherwise specifically defined.

[0056] The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. An RC-IGBT, characterized in that, Comprising: An n-region, an emitter disposed on the n-drift region, and a collector disposed on the back surface of the n-drift region, wherein the n-region is provided with two left and right Pbody regions, a p+ ohmic contact region, and an n + emission region, such that the n-region presents a convex shape; two planar gates with a spacing are disposed above the two left and right Pbody regions, and except for the bottom surface, the other three sides of the planar gate are wrapped by an interlayer dielectric layer, and a p-type transparent anode region is disposed below the spacing facing the two planar gates.

2. The RC-IGBT according to claim 1, wherein Each of the p+ ohmic contact regions is disposed above the Pbody region and adjacent to the sidewall of the RC-IGBT; each of the n + emitting region is disposed adjacent to the p+ ohmic contact region; the emitter is disposed above the two planar gates, and an interlayer dielectric layer is used for isolation between the emitter and the planar gates; an nFS region is disposed below the n-drift region; a p+ collector region is disposed on the left side within the nFS region, and an n+ short-circuit region is disposed on the right side; the collector is disposed on the back surface of the p+ collector region and the n+ short-circuit region.

3. The RC-IGBT according to claim 1, wherein The planar gate includes a gate oxide layer and polysilicon. The polysilicon is disposed above the gate oxide layer, and the gate oxide layer is disposed above the Pbody region.

4. The RC-IGBT according to claim 1, wherein There is a spacing between the two planar gates and the sidewalls of the RC-IGBT. There is a spacing between the lower surfaces of the two Pbody regions and the n region. The spacing between the two Pbody regions is greater than the spacing between the two planar gates.

5. The RC-IGBT according to claim 4, wherein Each planar gate is not flush with the Pbody region below it.

6. The RC-IGBT according to claim 4, wherein The width of the planar gate is 5 µm to 15 µm, and the spacing between the two planar gates is 0.5 µm to 3 µm.

7. The RC-IGBT according to claim 1, wherein The junction depth of the n-region is 6 µm to 10 µm, and the doping concentration is 1×10 15 cm -3 ~ 1×10 17 cm -3 ; the junction depth of the Pbody region is 5 µm to 9 µm, and the doping concentration is 2×10 17 cm -3 ~ 5×10 17 cm -3 ; the junction depth of the p-type transparent anode region is 0.5 µm to 1 µm, and the doping concentration is 5×10 16 cm -3 ~ 2×10 17 cm -3 .

8. A manufacturing method of an RC-IGBT, characterized in that, Fabricating the RC-IGBT according to any one of claims 1 to 7, the manufacturing method comprising: S1, selecting an n-type silicon wafer as the drift region of the RC-IGBT; S2, implanting phosphorus ions on the upper surface of the drift region to form an n region; S3. Thermally oxidize and grow SiO on the upper surface of the n region 2， to form a gate oxide layer, deposit heavily doped polysilicon on the gate oxide layer, and etch to form two planar gates with a spacing in between; S4, implanting boron ions into the n region from both sides of the upper surface of the n region to form two Pbody regions with a spacing therebetween, and implanting phosphorus ions into the two Pbody regions from the upper surface of the n region to form two n+ emitter regions; S5, depositing borophosphosilicate glass on the upper surface and sides of the two planar gates, and etching to form two interlayer dielectric layers; S6, implanting boron ions into the two Pbody regions from the upper surface of the two Pbody regions to form two p+ ohmic contact regions; S7, implanting boron ions into the n region from the upper surface of the n region and in the spacing region between the two planar gates to form a p-type transparent anode region; S8, depositing aluminum metal on the two interlayer dielectric layers, the p+ ohmic contact regions, the p-type transparent anode region, and the n+ emitter regions from top to bottom to form an emitter covering the interlayer dielectric layers, the p+ ohmic contact regions, the p-type transparent anode region, and the n+ emitter regions; S9, forming an nFS region on the back surface of the drift region, forming a p+ collector region and an n+ short-circuit region in the nFS region, and then depositing aluminum metal to form a collector covering the p+ collector region and the n+ short-circuit region.

9. The manufacturing method of the RC-IGBT according to claim 8, characterized in that, S9 includes: S91, implanting phosphorus ions into the drift region from the lower surface of the drift region to form an nFS region; S92, implanting boron ions into the nFS region at a position adjacent to the lower surface on the left side inside the nFS region to form a p+ collector region; S93, implanting phosphorus ions into the nFS region at a position adjacent to the lower surface on the right side inside the nFS region to form an n+ short-circuit region; S94, depositing aluminum metal on the lower surfaces of the p+ collector region and the n+ short-circuit region to form a collector covering the p+ collector region and the n+ short-circuit region.

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