Heat dissipation trench gate IGBT structure

Abstract

The present invention provides a heat-equalizing trench gate IGBT structure, comprising: an effective IGBT cell and a gate thermal control unit; the effective IGBT cell is set as a trench gate IGBT cell; the gate thermal control unit includes two thermistors and two diodes; one thermistor and a diode are connected in series to form a first series branch for controlling the gate opening speed, one end of the first series branch is connected to the trench gate, and the other end is connected to the gate metal; another thermistor and another diode are connected in reverse series to form a second series branch for controlling the gate turning off speed, one end of the second series branch is connected to the trench gate, and the other end is connected to the gate metal. The present invention realizes that a single cell adjusts the switching speed according to its own temperature by independently setting the trench gate and the thermal gate resistor, so that the cell with high temperature reduces the loss, thereby achieving the purpose of reducing its own junction temperature. Thermal balance is achieved for the entire IGBT chip.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor power devices, in particular to a heat-averaging trench gate IGBT structure. Background Art

[0002] The IGBT structure was invented by introducing the P+ region on the back substrate of the power MOSFET. Therefore, it can be regarded as a new type of power device that combines the power MOSFET and BJT. It has the advantages of the MOS structure driving power and fast switching speed, as well as the BJT device's reduced saturation voltage drop and strong load capacity. It gradually replaces MOSFET and BJT devices in the DC voltage conversion system of 600V and above. Therefore, IGBT is widely used in various fields such as motor control, induction cooker, air filter frequency conversion, locomotive traction, high-voltage DC transmission, etc., and has become the most popular power device.

[0003] The current mainstream IGBT structure is the trench gate field stop IGBT, which has a better turn-on and turn-off compromise characteristic, higher current density, better area and conduction ratio. In order to enhance the in-plane consistency and improve the parallel characteristics of the device, a polysilicon gate resistor is integrated between the gate metal and the cell gate. The gate resistance value can be set arbitrarily according to design requirements. The process is simple and has strong process compatibility. No additional photolithography or process steps are required. At present, IGBT chips with integrated gate resistors have been widely used.

[0004] Limitations of existing technologies:

[0005] 1. The gate resistor controls the switching speed of the entire chip cell; therefore, cells that are far away from the gate metal may have a switching lag, which can easily cause the first-turned-on cells to bear most of the current, causing current concentration during the IGBT switching process; current concentration can easily cause heat concentration, causing device failure under high-voltage current conditions; especially for chips with larger areas, in-plane consistency is particularly important.

[0006] 2. The heat distribution within the chip surface is very important for reliability. Generally speaking, the center temperature is high and the edge temperature is low. For long-term use, the failure rate of high-temperature areas is higher than that of low-temperature areas. Currently, there is no very effective design method to achieve temperature regulation of a single cell and optimize temperature consistency within the surface. Summary of the invention

[0007] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a heat-balanced trench gate IGBT structure, which achieves thermal balance for the entire IGBT chip and reduces the risk of failure caused by chip heat concentration. To achieve the above technical objectives, the technical solution adopted in the embodiment of the present invention is:

[0008] The embodiment of the present invention provides a heat-equalizing trench gate IGBT structure, including: an effective IGBT cell and a gate thermal control unit;

[0009] The effective IGBT cell is configured as a trench gate IGBT cell;

[0010] The gate thermal control unit includes two thermistors and two diodes; one of the thermistors and one of the diodes is connected in series to form a first series branch for controlling the gate turn-on speed, one end of the first series branch is connected to the trench gate, and the other end is connected to the gate metal; another thermistor and another diode are connected in reverse series to form a second series branch for controlling the gate turn-off speed, one end of the second series branch is connected to the trench gate, and the other end is connected to the gate metal.

[0011] Furthermore, the trench gate of each cell is independent and separate, and is not connected to the trench gates of other cells.

[0012] Further, the thermistor in the first series branch has a negative temperature coefficient, and the thermistor in the second series branch has a positive temperature coefficient.

[0013] Furthermore, the two thermistors and the two diodes are both arranged on one side of the top of the cell and are independently isolated by an insulating dielectric layer and isolated from the cell body area;

[0014] The first series branch includes a thermistor Rg2 and a diode D2, one end of the thermistor Rg2 is connected to the anode of the diode D2, and the cathode of the diode D2 is contact-connected to the trench gate in the cell; the second series branch includes a thermistor Rg1 and a diode D1, one end of the thermistor Rg1 is connected to the cathode of the diode D1, and the anode of the diode D1 is contact-connected to the trench gate in the cell.

[0015] Furthermore, the other end of the thermistor Rg1 and the other end of the thermistor Rg2 are connected to the gate metal through the G-pole contact holes, respectively.

[0016] Specifically, the trench gate IGBT cell includes a heavily doped P-type collector region, a collector metal is connected below the heavily doped P-type collector region, an electric field stop layer is arranged above, an N-type base region is arranged above the electric field stop layer, a trench gate of the cell is arranged in the N-type base region, and a gate oxide layer is arranged between the trench gate and the N-type base region; a first P-type body region is arranged on the upper part of the N-type base region on one side of the trench gate, and the insulating dielectric layer is arranged above the first P-type body region; a carrier storage layer, a second P-type body region and a deep P region are distributed from bottom to top on the other side of the N-type base region; the doping concentration of the deep P region is higher than the concentration of the P-type body region; and an N+ type source region is also arranged above the second P-type body region and close to the gate oxide layer.

[0017] Furthermore, the N+ type source region and the deep P region are short-circuited and connected; the N+ type source region and the deep P region are connected to the emitter metal through an E-pole contact hole.

[0018] Furthermore, the depths of the first P-type body region and the second P-type body region are 3 μm to 6 μm, and the depth of the N+ type source region is 0.1 μm to 1 μm.

[0019] The technical solution provided by the embodiment of the present invention has the following beneficial effects: in the structure of the present application, the resistance of a thermistor Rg2 decreases as the temperature of the cell region increases, thereby increasing the cell turn-on speed and reducing the turn-on loss; the resistance of another thermistor Rg1 increases as the temperature of the cell region increases, thereby reducing the cell turn-off speed, thereby reducing the Vce peak voltage to avoid thermal failure; and the IGBT turn-off loss is generally not significantly affected by the gate resistance change, so even if the resistance of the thermistor Rg1 increases, the turn-off loss does not increase significantly; in general, when the temperature rises, the switching speed of a single cell is controlled by the thermistor gate resistor to achieve a total loss reduction, and reduce the Vce peak voltage to avoid the appearance of a dangerous point. Thus, the overall loss of the cell is reduced to achieve the purpose of reducing the junction temperature. Since the temperature of each region directly controls the thermistor value, and each gate thermal control unit controls a single cell separately, the switching speed and switching loss of a single cell can be controlled by its own temperature, and the higher the temperature, the lower the loss, preventing the junction temperature from further increasing; thermal balance is achieved for the entire IGBT chip, further reducing the risk of failure caused by chip heat concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the IGBT structure in an embodiment of the present invention.

[0021] Figure 2 Schematic diagram of the electrical principle in the embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0023] like Figure 1 As shown, an embodiment of the present invention provides a heat-equalizing trench gate IGBT structure, including: an effective IGBT cell and a gate thermal control unit;

[0024] The effective IGBT cell is configured as a trench gate IGBT cell;

[0025] The gate thermal control unit comprises two thermistors and two diodes; one of the thermistors and one diode are connected in series to form a first series branch for controlling the gate turn-on speed, one end of the first series branch is connected to the trench gate, and the other end is connected to the gate metal; another thermistor and another diode are connected in reverse series to form a second series branch for controlling the gate turn-off speed, one end of the second series branch is connected to the trench gate, and the other end is connected to the gate metal;

[0026] It should be noted that, in this embodiment, the trench gate of each cell is independent and separate, and is not connected to the trench gates of other cells; thereby, each cell is independently controlled by its own series thermistor; whereas in the existing IGBT structure, the trench gates of at least one row (or one column) of multiple cells are integrated, that is, directly connected;

[0027] Since the thermistor adopts a thermosensitive material, its resistance value changes with temperature, thereby realizing that the IGBT turn-on speed and turn-off speed change with temperature; as an optimization of this embodiment, the thermistor in the first series branch has a negative temperature coefficient, and the thermistor in the second series branch has a positive temperature coefficient; the resistance of the thermistor with a negative temperature coefficient decreases with increasing temperature, thereby causing the IGBT to turn on faster, and the turn-on loss is significantly reduced, thereby reducing its own temperature rise; the resistance of the thermistor with a positive temperature coefficient increases with increasing temperature, and the turn-off di / dt is reduced, thereby reducing the Vce peak voltage, avoiding the appearance of a dangerous point, and reducing the risk of IGBT thermal failure;

[0028] The two thermistors and the two diodes are both arranged on one side of the top of the cell, and are independently isolated by the insulating dielectric layer 12 and isolated from the cell body area; in a specific embodiment, the first series branch includes a thermistor Rg2 and a diode D2, one end of the thermistor Rg2 is connected to the anode of the diode D2, and the cathode of the diode D2 is in contact with the trench gate 5 in the cell; in some embodiments, one end of the thermistor Rg2 and the anode of the diode D2 can be connected by a wire; in a specific embodiment, the second series branch includes a thermistor Rg1 and a diode D1, one end of the thermistor Rg1 is connected to the cathode of the diode D1, and the anode of the diode D1 is in contact with the trench gate 5 in the cell; in some embodiments, one end of the thermistor Rg1 and the cathode of the diode D1 can be connected by a wire;

[0029] As an optimization of this embodiment, the other end of the thermistor Rg1 and the other end of the thermistor Rg2 are connected to the gate metal through the G-pole contact hole 13 respectively;

[0030] Specifically, Figure 1As shown, the trench gate IGBT cell includes a collector heavily doped P-type region 2, a collector metal 1 is connected below the collector heavily doped P-type region 2, an electric field stop layer 3 is arranged above, an N-type base region 4 is arranged above the electric field stop layer 3, a cell trench gate 5 is arranged in the N-type base region 4, a gate oxide layer 6 is arranged between the trench gate 5 and the N-type base region 4; a first P-type body region 7 is arranged on the upper part of the N-type base region 4 on one side of the trench gate 5, and the depth of the first P-type body region 7 is 3 μm~6μm; the insulating dielectric layer 12 is arranged above the first P-type body region 7; a carrier storage layer 8, a second P-type body region 9 and a deep P region 10 are distributed from bottom to top on the other side of the N-type base region 4; the depth of the second P-type body region 9 is 3μm~6μm; the doping concentration of the deep P region 10 is higher than the concentration of the P-type body region; an N+ type source region 11 is also arranged above the second P-type body region 9 near the gate oxide layer 6; the depth of the N+ type source region 11 is 0.1μm~1μm;

[0031] The N+ source region 11 and the deep P region 10 are short-circuited, for example, by a wire; the N+ source region 11 and the deep P region 10 are connected to the emitter metal through the E-pole contact hole 14; in some embodiments, the N+ source region 11 and the deep P region 10 can be short-circuited by a wire, and then connected to the emitter metal through their respective E-pole contact holes, or the N+ source region 11 and the deep P region 10 can be short-circuited by a communicating E-pole contact hole, and simultaneously connected to the emitter metal;

[0032] In the above specific embodiments, the thermistor Rg2 is connected to the anode of the diode D2, and the cathode of the diode D2 is in contact with the trench gate 5 in the cell to control the gate turn-on speed. The thermistor Rg2 decreases with increasing temperature, thereby causing the IGBT to turn on faster and the turn-on loss to be significantly reduced, thereby reducing its own temperature rise; the thermistor Rg1 is connected to the cathode of the diode D1, and the anode of the diode D1 is in contact with the trench gate 5 in the cell to control the gate turn-off speed. The thermistor Rg1 increases with increasing temperature, and the turn-off di / dt is reduced, thereby reducing the Vce peak voltage, avoiding the occurrence of dangerous points, and reducing the risk of IGBT thermal failure; and because the IGBT turn-off loss is not greatly affected by the gate resistance, the turn-off loss will not increase even if the gate resistance increases.

[0033] The embodiments of the present invention use independently set trench gates and thermistor gate resistors to achieve the goal of reducing the junction temperature of a single cell by adjusting the switching speed according to its own temperature, thereby reducing the loss of cells with high temperatures. Thermal balance is achieved for the entire IGBT chip, reducing the risk of failure caused by chip heat concentration.

[0034] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A heat-saturated trench gate IGBT structure, characterized in that: include: An active IGBT cell and a gate thermal control unit; The effective IGBT cell is configured as a trench gate IGBT cell; The gate thermal control unit includes two thermistors and two diodes; one of the thermistors and one diode are connected in series to form a first series branch for controlling the gate turn-on speed, one end of the first series branch is connected to the trench gate, and the other end is connected to the gate metal; another thermistor and another diode are connected in reverse series to form a second series branch for controlling the gate turn-off speed, one end of the second series branch is connected to the trench gate, and the other end is connected to the gate metal; The two thermistors and the two diodes are both arranged on one side of the top of the cell and are independently isolated by an insulating dielectric layer and isolated from the cell body area; The first series branch includes a thermistor Rg2 and a diode D2, one end of the thermistor Rg2 is connected to the anode of the diode D2, and the cathode of the diode D2 is contact-connected to the trench gate in the cell; the second series branch includes a thermistor Rg1 and a diode D1, one end of the thermistor Rg1 is connected to the cathode of the diode D1, and the anode of the diode D1 is contact-connected to the trench gate in the cell; The trench gate IGBT cell includes a heavily doped P-type collector region, a collector metal is connected below the heavily doped P-type collector region, an electric field stop layer is arranged above, an N-type base region is arranged above the electric field stop layer, a trench gate of the cell is arranged in the N-type base region, and a gate oxide layer is arranged between the trench gate and the N-type base region; a first P-type body region is arranged on the upper part of the N-type base region on one side of the trench gate, and the insulating dielectric layer is arranged above the first P-type body region; a carrier storage layer, a second P-type body region and a deep P region are distributed from bottom to top on the other side of the N-type base region; the doping concentration of the deep P region is higher than that of the P-type body region; and an N+ type source region is also arranged above the second P-type body region and close to the gate oxide layer.

2. The heat-saturated trench gate IGBT structure according to claim 1, characterized in that: The trench gate of each cell is independent and separate, and is not connected to the trench gates of other cells.

3. The heat-saturated trench gate IGBT structure according to claim 1, characterized in that: The thermistor in the first series branch has a negative temperature coefficient, and the thermistor in the second series branch has a positive temperature coefficient.

4. The heat-saturated trench gate IGBT structure according to claim 1, characterized in that: The other end of the thermistor Rg1 and the other end of the thermistor Rg2 are connected to the gate metal through the G-pole contact holes respectively.

5. The heat-saturated trench gate IGBT structure according to claim 1, characterized in that: The N+ type source region and the deep P region are short-circuited and connected; the N+ type source region and the deep P region are connected to the emitter metal through an E-pole contact hole.

6. The heat-saturated trench gate IGBT structure according to claim 1, characterized in that: The depth of the first P-type body region and the second P-type body region is 3 μm to 6 μm, and the depth of the N+ type source region is 0.1 μm to 1 μm.

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