The lateral double-diffused metal-oxide-semiconductor transistor of N type silicon-on-insulator
Technical field
The present invention relates to the power semiconductor field, in particular, is the new construction that is applicable to the lateral double-diffused metal-oxide-semiconductor transistor (SOI LDMOS) of the silicon-on-insulator of high-voltage applications about a kind of.
Background technology
Because the device that adopts silicon-on-insulator material to make can be realized full dielectric isolation, its parasitic capacitance and leakage current are little, and drive current is big, so be well suited for making power IC device and circuit.For making SOI device that better effect be arranged, the puncture voltage that improves SOI device is an important research project.As everyone knows, withstand voltage its laterally withstand voltage and vertical withstand voltage reckling that depends on of silicon-on-insulator power device, the horizontal withstand voltage of device can be adopted field plate techniques, falls a layer technology, and the knot terminal technology of body silicon such as RESURF technology solves.But, become a difficult point in the research of silicon-on-insulator lateral power device because how the restriction of technology and structure improves the vertically withstand voltage of device.
Vertical puncture voltage of conventional soi structure is mainly born jointly by insulating barrier and active semiconductor layer, and the vertically withstand voltage V that is is arranged
B=E (3D
1+ 0.5D
2), wherein E is the critical breakdown electric field of semiconductor layer, D
1And D
2Be respectively the thickness of insulation material layer and silicon epitaxial layers, obviously vertically withstand voltage with D
1And D
2Increase and improve.But if insulation material layer do too thick, one side process implementing difficulty is big and be unfavorable for that device dispels the heat, can cause the silicon warp distortion on the other hand, integrity problem appears in the high accuracy photoetching, if it is too thick that silicon epitaxial layers is done, then similar with the body silicon device, bring difficulty for simultaneously follow-up dielectric isolation technology.
Abroad the someone proposes to insert one deck N between insulation material layer and silicon epitaxial layers
+Withstand voltage layer, the electric field that it can the shielding insulation material layer, the electric field of device silicon epitaxial layers subcritical breakdown electric field still when making electric field on insulation material layer reach very high, thus avoided device to cross as far back as Si/SiO
2Puncture on the interface, but on technology to N
+When heat-treating, Withstand voltage layer has serious anti-expansion phenomenon.
The domestic people of having proposes the channel insulation structure of voltage-sustaining layer in a kind of silicon-on-insulator power device, it can introduce interface charge on the interface of silicon epitaxial layers and insulation material layer, full continuity according to electric displacement increases substantially the insulating barrier internal electric field, thereby it is vertically withstand voltage to improve device.But it makes most of zone of insulation material layer have bigger thickness, is unfavorable for the heat radiation of device, has also reduced bond strength, and the etching of required big measuring tank has also been brought the complexity of whole manufacture craft in addition.
Summary of the invention
The invention provides and a kind ofly can effectively improve vertically withstand voltagely, and help improving the lateral double-diffused metal-oxide-semiconductor transistor of N type silicon-on-insulator of the heat dispersion of power device.
The present invention adopts following technical scheme:
A kind of lateral double-diffused metal-oxide-semiconductor transistor of N type silicon-on-insulator, comprise: Semiconductor substrate, on Semiconductor substrate, be provided with and bury oxide layer, be provided with N type doped semiconductor area on the oxide layer burying, on N type doped semiconductor area, be provided with P trap and N type drain region, on the P trap, be provided with N type source region and P type contact zone, be provided with gate oxide and gate oxide on the surface of P trap and extend to N type doped semiconductor area from the P trap, N type source region on P trap surface, the N type drain region with exterior domain and N type doped semiconductor area surface of P type contact zone and gate oxide is provided with field oxide with exterior domain, be provided with the surface that polysilicon gate and polysilicon gate extend to field oxide on the surface of gate oxide, at field oxide, P type contact zone, N type source region, the surface in polysilicon gate and N type drain region is provided with oxide layer, in N type source region, P type contact zone, be connected with metal level respectively on polysilicon gate and the N type drain region, in N type doped semiconductor area, be provided with first oxide layer of floating, and first oxide layer of floating is positioned at the below in N type drain region.
Compared with prior art, the present invention has following advantage:
(1) structure of the present invention has the first oxide layer structure 121 of floating below drain region 10, the horizontal withstand voltage employing RESURF technical optimization of device is handled, only need to consider vertical pressure drop, reduce gradually and device is vertically anti-from drain terminal to the source end, first of the face that the leaks down oxide layer 121 of floating can be born higher field intensity, thus improve the whole withstand voltage of device.With reference to accompanying drawing 4, to float after the oxide layer structure 121 having added first, the electric field strength that oxide layer 8 is buried in the below, drain region obviously reduces, and first float and shared part electric field strength on the oxide layer 121, the area that curve enclosed is also bigger, and with reference to accompanying drawing 5, puncture voltage has improved greatly as can be seen.
(2) in the structure of the present invention, the first oxide layer structure 121 of floating is arranged under the drain terminal, reduced charge carrier ionization integration lengths, make disruptive critical voltage increase in silicon and the silicon dioxide, thereby can reduce to bury the thickness of oxide layer 8 greatly, certainly also reduce the technology difficulty that cutting in the silicon epitaxial layers and dielectric isolation realize.
(3) structure of the present invention only need be carried out the injection of window oxygen on the lateral double-diffused metal-oxide-semiconductor transistor surface of N type silicon-on-insulator, and do not need its lower zone is done any processing, this has just been avoided making buried structure or the special photoetching contraposition problem that can occur when burying oxide structure, has highly also kept heat dispersion preferably in withstand voltage bearing.
(4) structure of the present invention is except that window oxygen injects, and other processing step is compatible mutually with complementary bilateral diffusion metal oxide transistor (CDMOS) technology of standard, does not therefore need to revise intrinsic technological process.
Description of drawings
Fig. 1 is the lateral double-diffused metal-oxide-semiconductor transistor structural representation of high voltage N type SOI that does not add the conventional structure of the oxide layer structure of floating.
Fig. 2 has added the first lateral double-diffused metal-oxide-semiconductor transistor structural representation of high voltage N type SOI of oxide layer structure 121 of floating among the present invention.
Fig. 3 is the lateral double-diffused metal-oxide-semiconductor transistor structural representation that has added the high voltage N type SOI of two-layer float oxide layer 121 and 122 among the present invention.(allowing more multi-layered)
Fig. 4 does not add to have added first below, the drain region longitudinal electric field distribution comparison diagram of lateral double-diffused metal-oxide-semiconductor transistor of high voltage N type SOI of oxide layer 121 of floating among the lateral double-diffused metal-oxide-semiconductor transistor of high voltage N type SOI of conventional structure of the oxide layer of floating and the present invention, interpreting blueprints for convenience, the part of below, device drain region is placed the left side of longitudinal electric field distribution comparison diagram among the figure, the ordinate and the device lengthwise position of longitudinal electric field distribution comparison diagram are one to one.
Fig. 5 does not float to have added first the float puncture voltage of lateral double-diffused metal-oxide-semiconductor transistor of high voltage N type SOI of oxide layer 121 and the analog result figure of epitaxial silicon layer thickness relation among the lateral double-diffused metal-oxide-semiconductor transistor of high voltage N type SOI of conventional structure of oxide layer and the present invention.
Embodiment
With reference to Fig. 2, a kind of lateral double-diffused metal-oxide-semiconductor transistor of N type silicon-on-insulator, comprise: Semiconductor substrate 9, on Semiconductor substrate 9, be provided with and bury oxide layer 8, be provided with N type doped semiconductor area 7 on the oxide layer 8 burying, on N type doped semiconductor area 7, be provided with P trap 6 and N type drain region 10, on P trap 6, be provided with N type source region 11 and P type contact zone 13, be provided with gate oxide 3 and gate oxide 3 on the surface of P trap 6 and extend to N type doped semiconductor area 7 from P trap 6, N type source region 11 on P trap 6 surfaces, the N type drain region 10 with exterior domain and N type doped semiconductor area 7 surfaces of P type contact zone 13 and gate oxide 3 is provided with field oxide 1 with exterior domain, be provided with the surface that polysilicon gate 4 and polysilicon gate 4 extend to field oxide 1 on the surface of gate oxide 3, at field oxide 1, P type contact zone 13, N type source region 11, the surface in polysilicon gate 4 and N type drain region 10 is provided with oxide layer 5, in N type source region 11, P type contact zone 13, be connected with metal level 2 respectively on polysilicon gate 4 and the N type drain region 10, in N type doped semiconductor area 7, be provided with first float oxide layer 121 and first float oxide layer 121 be positioned at N type drain region 10 below.
Present embodiment also adopts following technical measures further to improve performance of the present invention:
With reference to Fig. 3, in N type doped semiconductor area 7, be provided with second oxide layer 122 of floating, and second oxide layer 122 of floating is positioned at first below of floating oxide layer 121.
First float the upper surface of oxide layer 121 apart from the lower surface in N type drain region 10 between 0.5 micron to 1 micron.
First floats oxide layer 121 thickness between 0.2 micron to 0.5 micron.
Second oxide layer 122 and first distance of floating between the oxide layer 121 of floating is no more than 0.5 micron.
First length of floating oxide layer 121 is 1 to 1.5 times of drain region 10 width.
Though present embodiment has adopted the two-layer oxide layer of floating, in the reality, allow below the drain region, to be provided with the multilayer oxide layer of floating, make the longitudinal electric field in device drain region further optimize, thereby further improve device electric breakdown strength.
The present invention adopts following method to prepare:
1, make needed silicon-on-insulator SOI substrate, it can adopt and annotate the oxygen partition method, other methods such as wafer bonding method (following is example to annotate the oxygen isolation method).Can adopt the special-purpose oxonium ion implanter of big line that oxonium ion is injected in the Silicon Wafer, implantation dosage is about 1E18/cm
2, in inert gas, carried out 〉=1300 ℃ of high annealings then 3 to 5 hours, thereby form thickness silicon epitaxial layers and insulation material layer as thin as a wafer uniformly at the Silicon Wafer top.
2, make buried oxide layer, it need cover the part that does not need to carry out the oxygen atom injection with a mask, adopts the high concentration oxygen atom to inject with the energy of counting million-electron-volt again.For one deck lateral double-diffused metal-oxide-semiconductor transistor of high voltage N type SOI of oxide layer structure of floating only is set, only need carry out an oxygen atom and inject (1Mev is to 2Mev), in inert gas, carried out 〉=1300 ℃ of high annealings then 3 to 5 hours, thereby form continuous oxide layer in vivo, and for the two-layer or multilayer lateral double-diffused metal-oxide-semiconductor transistor of high voltage N type SOI of oxide layer of floating is set, then need to carry out twice or the injection of oxygen atom repeatedly, note twice or repeatedly inject the difference (3Mev is to 4Mev for the first time, and 1Mev is to 2Mev for the second time) of energy.Then carry out high annealing,, polish, make it the thickness that reaches required then with wafer thinning.
3, be the making of the lateral double-diffused metal-oxide-semiconductor transistor of routine, it comprises that P type trap injects, the preparation of field oxygen, the growth of grid oxygen, etching, the deposit of polysilicon, etching are exactly that leakage injection region, high concentration source contacts the injection region preparation with substrate then, be fairlead at last, the preparation of aluminum lead and Passivation Treatment.