Radiation-proof reinforced power MOSFET (metal-oxide-semiconductor field effect transistor) structure

Abstract

The invention discloses an anti-radiation reinforced power MOSFET structure and belongs to the technical field of power semiconductor devices. Comprising drain metal, an N + substrate, an N-type buffer layer, an N-drift region, an N-type current expansion layer, a P-type base region, a P-type doped channel region, an N + source region, a P + contact region, a gate oxide layer, a polysilicon gate and an isolation oxide layer, the hole shunting region is jointly formed by a P-type floating hole shunting region making contact with the upper side of the current expansion layer and an N-type hole shunting region making contact with the upper side of the P-type floating hole shunting region, and the shunting region metal and the source electrode metal keep equipotential. The radiation-proof reinforced power MOSFET structure provided by the invention has good single particle resistance, and can maintain small on-resistance at the same time.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and particularly to an anti-radiation hardened power MOSFET structure. Background Art

[0002] In aerospace applications, unhardened power MOSFETs have poor single-event immunity. After experiencing heavy ion radiation, the performance of the devices will deteriorate severely, which directly threatens the safety of aerospace equipment. When a heavy ion penetrates into the device, a large number of electron-hole pairs will be generated along the ion incident path. Under the action of an applied voltage, the electrons generated by radiation move towards the drain while the holes move towards the source to form a current. When the lateral resistance of the P-type base region of the power MOSFET is large, a voltage drop will be generated when the holes flow through the P-type base region. This voltage drop will cause the PN junction between the N + source region and the P-type base region to conduct, resulting in a large number of electrons being injected from the N + source region into the N - drift region and converging towards the single-particle incident path, causing single-point current concentration. Furthermore, the large current density is coupled with the strong electric field near the upper surface of the N + substrate, resulting in a rapid increase in local temperature, and finally causing the device to burn out. Summary of the Invention

[0003] In order to solve the above existing problems, the present invention proposes an anti-radiation hardened power MOSFET structure, which is realized through the following technical solutions:

[0004] The present invention provides an anti-radiation hardened power MOSFET structure, including a drain metal, an N + substrate, an N-type buffer layer, an N - drift region, an N-type current spreading layer located between two adjacent P-type base regions, a P-type base region, a P-type doped channel region, an N + source region, a P + contact region, a gate oxide layer, a polysilicon gate, an isolation oxide layer, a hole shunt region composed of a P-type floating hole shunt region in contact with the upper side of the N-type current spreading layer and an N-type hole shunt region in contact with the upper side of the P-type floating hole shunt region, a source metal, and a shunt region metal having the same potential as the source metal. An ohmic contact or a Schottky contact can be formed between the shunt region metal and the N-type hole shunt region.

[0005] Preferably, the width of the polysilicon gate and the gate oxide layer is greater than that of the P-type doped channel region.

[0006] Preferably, the interface between the P-type hole shunt region and the N-type current spreading layer is higher than the upper side of the P-type doped channel region, and the vertical gap is 0 to 1.5 μm.

[0007] Preferably, in the hole shunt region, the total amount of P-type doping per unit area in the P-type floating hole shunt region is greater than the total amount of N-type doping per unit area in the N-type hole shunt region.

[0008] Preferably, the P-type floating hole shunt region is P-type doped with a doping concentration of 1×10 18 ~1×10 20 cm -3 , with a thickness of 0.3 - 1.2 μm and a width of 1 μm - 10 μm.

[0009] Preferably, the N-type hole shunt region is N-type doped with a doping concentration of 1×10 16 ~5×10 18 cm -3 , with a thickness of 0.1 - 0.5 μm and a width of 1 μm - 10 μm.

[0010] Preferably, the N-type current spreading layer is N-type doped with a doping concentration of 5×10 16 ~1×10 18 cm -3 .

[0011] Compared with the prior art, a radiation-hardened power MOSFET structure of the present invention has the following advantages:

[0012] The present invention proposes a radiation-hardened power MOSFET structure. The hole shunt region in this structure consists of a P-type floating hole shunt region and an N-type hole shunt region. When the device is in the blocking state, the parasitic NPN transistor formed by the N-type hole shunt region, the P-type floating hole shunt region, and the N-type current spreading layer is in a state of small-current amplification. And because the amount of N-type doping per unit area in the N-type hole shunt region is lower than the amount of P-type doping per unit area in the P-type floating hole shunt region, the electron injection efficiency of the emitter junction of this parasitic NPN transistor is low (the hole current passing through the emitter junction is much larger than the electron current). Therefore, when a heavy ion causing a single event effect enters the device, especially when the incident position is in the middle of two adjacent P-type base regions, most of the generated holes will be drawn away through the current spreading layer - P-type floating hole shunt region - N-type hole shunt region - shunt region metal electrode and do not significantly cause electron injection. A small portion of the generated holes, like in a conventional MOSFET structure, will pass through the current spreading layer - P-type base region - P + -contact region - source metal, or N-type current spreading layer - P-type base region - N +The source region—the source metal is removed. The implantation of the hole shunt region plays a role in shunting holes. The existence of the N-type hole shunt region is the key to the present invention. Although the electron injection it provides is weak, it is sufficient to attract holes to continuously inject into the N-type hole shunt region, thus maintaining the shunting effect throughout the single-event effect process. If the hole shunt region is only composed of a P-type region, or other structures are included in the P-type region but it is still connected to the shunt region metal electrode, at this time, since there is no electron injection in the hole shunt region, the holes originally moving towards the hole shunt region are attracted by the electrons injected into the N + source region and disperse and move towards the adjacent P-type base regions on the left and right, so that the continuous shunting of holes via the hole shunt region cannot be achieved. The hole shunt region structure parasitic with an NPN transistor proposed by the present invention well solves this problem. After the holes are shunted, on the one hand, the holes themselves can be cleared faster. On the other hand, the hole current density flowing through the P-type base region will decrease, and the generated lateral voltage drop will decrease, and the PN junction between the N + source region and the P-type base region becomes difficult to turn on, thereby reducing the injection of electrons from the N + source region, effectively reducing the electron convergence and current density increase on the single-event incident path caused by electron injection, and further reducing the N + local electric field enhancement near the upper surface of the substrate, and finally effectively improving the single-event immunity of the device. For a device with a breakdown voltage of 1200V, the single-event burnout threshold of the radiation-hardened power MOSFET structure proposed by the present invention can reach more than 900V, which is more than twice that of a conventional planar-gate MOSFET. In addition, since the upper interface of the P-type floating hole shunt region and the current spreading layer is higher than the upper side of the channel region, the depletion region of the PN junction formed by the P-type floating hole shunt region and the N-type current spreading layer does not affect the electron conduction path in the on state when the device is turned on, so the on-resistance of the device will not be affected. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A radiation-hardened power MOSFET structure proposed by the present invention.

[0014] Figure 2 A radiation-hardened superjunction power MOSFET structure proposed by the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] The principles and features of the present invention are described in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention. It can be seen from the drawings that both embodiments are axisymmetric structures, but are not limited to axisymmetric structures, and the protection scope of the claims shall prevail.

[0016] Embodiment 1 Please refer to Figure 1, this embodiment provides a specific implementation scheme of an anti-radiation hardened power MOSFET structure, and its structural parameters are as follows: N+ substrate 11, N-type buffer layer 10, N - drift region 9, N - P-type base region 8 in contact with the upper side of the drift region 9, the upper side of the P-type base region 8 is in contact with the lower side of the P + contact region 7, the lower side of the N + source region 6, the lower side of the P-type doped channel region 15, N + the left side of the source region 6 is in contact with the P + right side of the contact region 7, N + the right side of the source region 6 and the left side of the P-type doped channel region 15 are in contact, P + the upper side of the contact region 7, N + a part of the upper side of the source region 6 is in contact with the source metal 14, N + a part of the upper side of the source region 6, the upper side of the P-type doped channel region 15 are in contact with the lower side of the gate oxide layer 5, the polysilicon gate 1 located above the gate oxide layer 5 is wrapped by the isolation oxide layer 4, the N-type current spreading layer 13 is surrounded by the N-type drift region 9, the P-type base region 8, the P-type doped channel region 15, the isolation oxide layer 4, the P floating hole shunt region 2-1 and is in contact with their boundaries, the lower side of the P-type floating hole shunt region 2-1 is in contact with the upper side of the current spreading layer 11, the upper side of the P-type floating hole shunt region 2-1 is in contact with the lower side of the N-type hole shunt region 2-2, the upper side of the N-type hole shunt region 2-2 is in contact with the shunt region metal electrode 3; the P floating hole shunt region 2-1 and the N hole shunt region 2-2 together form the hole shunt region 2.

[0017] Furthermore, the polysilicon gate is N-type doped, and the doping concentration is 1×10 19 cm -3 .

[0018] Furthermore, the protruding length of the polysilicon gate compared to the P-type doped channel region is 0.2 μm.

[0019] Furthermore, the N drift region is N-type doped, and the doping concentration is 1.5×10 16 cm -3 , and the thickness is 10 μm.

[0020] Furthermore, the buffer layer is N-type doped, and the doping concentration is 2×10 17 cm -3 , and the thickness is 2 μm.

[0021] Furthermore, the N+ substrate is N-type doped, and the doping concentration is 1×10 19 cm -3 .

[0022] Further, the N+ source region is N-type doped with a doping concentration of 5×10 18 cm -3 , and has a thickness of 0.3 μm.

[0023] Further, the P-base region is P-type doped with a doping concentration of 1.5×10 18 cm -3 , and has a thickness of 0.3 μm.

[0024] Further, the P + contact region is P-type doped with a doping concentration of 8×10 18 cm -3 , and has a thickness of 0.3 μm.

[0025] Further, the P-channel region is P-type doped with a doping concentration of 5×10 16 cm -3 , and has a thickness of 0.3 μm.

[0026] Further, the P-type floating hole shunt region is P-type doped with a doping concentration of 5×10 18 cm -3 , has a thickness of 0.3 μm, and a width of 4 μm.

[0027] Further, the N-type hole shunt region is N-type doped with a doping concentration of 5×10 16 cm -3 , has a thickness of 0.3 μm, and a width of 4 μm.

[0028] Further, the interface between the P-type hole shunt region and the N-type current spreading layer is higher than the upper side of the channel region, and the vertical gap is 0.5 μm.

[0029] Further, the current spreading layer is N-type doped with a doping concentration of 1.5×10 17 cm -3 .

[0030] The threshold voltage of single event burnout of an anti-radiation hardened power MOSFET structure according to an embodiment of the present invention reaches 900 V, and the on-resistance is 2.2 mΩ. While the threshold voltage of single event burnout of a traditional MOSFET structure is only 400 V, and the on-resistance is 2.5 mΩ.

[0031] Embodiment 2 Please refer to Figure 2 , this embodiment provides a specific implementation scheme of an anti-radiation hardened superjunction power MOSFET structure, and the differences in its structural parameters from those of Embodiment 1 are as follows: The upper side of the buffer layer (10) is in contact with the lower side of the superjunction structure (9) composed of P pillars (9-1) and N pillars (9-2). The upper side of the superjunction structure (9) is in contact with the lower side of the P-type base region (8) and the lower side of the current spreading layer (13), respectively.

[0032] Further, the P pillars are P-type doped with a doping concentration of 5×10 16 cm -3 , a thickness of 8 μm, and a width of 2.5 μm.

[0033] Further, the N pillars are N-type doped with a doping concentration of 5×10 16 cm -3 , a thickness of 8 μm, and a width of 2.5 μm.

[0034] An anti-radiation hardened superjunction power MOSFET structure according to an embodiment of the present invention. The presence of the superjunction structure enables the device to have a lower on-resistance while not changing the breakdown voltage. At the same time, in combination with the hole shunt region structure proposed by the present invention, a strong anti-single-particle radiation ability can also be obtained. The threshold voltage of single-particle burnout reaches 900 V while the on-resistance is reduced to 1.9 mΩ.

[0035] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. 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 still be made, which should all be regarded as belonging to the protection scope of the present invention.

Claims

1. An anti-irradiation reinforced power MOSFET structure, characterized in that: The anti-radiation hardened power MOSFET structure includes a drain metal (12), N + substrate (11), an N-type buffer layer (10), N - drift region (9), an N-type current spreading layer (13), a P-type base region (8), a P-type doped channel region (15), N + source region (6), P + contact region (7), a gate oxide layer (5), a polysilicon gate (1), an isolation oxide layer (4), a hole shunt region (2) composed of a P-type floating hole shunt region (2-1) in contact with the upper side of the N-type current spreading layer (13) and an N-type hole shunt region (2-2) in contact with the upper side of the P-type floating hole shunt region (2-1), a source metal (14), and a shunt region metal (3) kept at the same potential as the source metal (14); The left and right sides of the N-type current spreading layer (13) are in contact with two adjacent P-type base regions, the upper side of the N-type current spreading layer (13) is in contact with the lower side of the P-type floating hole shunt region (2-1), the upper side of the P-type floating hole shunt region (2-1) is in contact with the lower side of the N-type hole shunt region (2-2), and the upper side of the N-type hole shunt region (2-2) is in contact with the shunt region metal (3).

2. The anti-radiation hardened power MOSFET structure according to claim 1, wherein: The interface between the P-type hole shunt region (2-1) and the N-type current spreading layer (13) is higher than the upper side of the P-type doped channel region (15), and the vertical gap is 0 to 1.5 μm.

3. A radiation-hardened power MOSFET structure according to claim 1, characterized in that: In the hole shunt region (2), the total amount of P-type doping per unit area of the P-type floating hole shunt region (2-1) is greater than the total amount of N-type doping per unit area of the N-type hole shunt region (2-2).

4. A radiation-hardened power MOSFET structure according to claim 1, characterized in that: The P-type floating air hole shunt region is P-type doped, and the doping concentration is 1×10 18 ~1×10 20 cm -3 , the thickness is 0.3 - 1.2 μm, and the width is 1 μm - 10 μm.

5. An anti-radiation hardened power MOSFET structure according to claim 1, characterized in that: The N-type hole shunt region is N-type doped with a doping concentration of 1×10 16 ~5×10 18 cm -3 , with a thickness of 0.1 - 0.5 μm and a width of 1 μm - 10 μm.

Images