Background technology
The electronics of semiconductor Ge and hole mobility are respectively 2.8 times and 4.2 times of Si, and its hole mobility is the highest in all semiconductors.Si is similar to strain, and the carrier mobility of strain Ge also has larger lifting, and the hole mobility of buried channel strain Ge can improve 6-8 doubly.Therefore, Ge and strain Ge are by the best channel material that is 16 nanometers and following technique Si based CMOS devices and integrated circuit.Still extremely excellent photoelectric material of Ge, has very widely and applies at detector (visible ray is to near-infrared), modulator, fiber waveguide, optical transmitting set, solar cell etc.
Because energy gap only has 0.67eV, the greatest weakness of Ge device and circuit is that the electric leakage of substrate is larger.And GeOI develops for solution substrate leakage currents just, be widely used in the manufacture of semiconductor device and integrated circuit at present.
The strain GeOI that combines strain Ge and GeOI advantage provides a kind of new solution for researching and developing novel ultrahigh speed, low-power consumption, radioresistance, high integration silicon-based devices and chip, and there is important application prospect the aspect such as, system level chip integrated at photoelectricity.
Traditional strain GeOI is the Biaxial Compressive strain based on SOI wafer, at SOI (SilicOn On Insulater, silicon on insulating barrier) direct growth strain Ge on wafer, or the SiGe layer of the Ge content gradually variational of first growing on SOI wafer makes empty substrate, then on this SiGe layer the required strain Ge layer of epitaxial growth.The major defect of tradition strain GeOI is that dislocation density is high, can only to be that Biaxial Compressive strain, mobility promote not high, the empty substrate of SiGe has increased hot expense and cost of manufacture, the empty substrate of SiGe have had a strong impact on device and circuit heat radiation, strain Ge layer critical thickness are subject to that Ge component limits, hole mobility lifting under High-Field can be degenerated etc.
C.Himcinschi has proposed the manufacturing technology of uniaxial strain SOI wafer in 2007, referring to [1] C.Himcinschi., I.Radu, F.Muster, R.SiO2gh, M.Reiche, M.Petzold, U.Go ¨ sele, S.H.Christiansen, Uniaxially strained silicon by wafer bonding and layertransfer, Solid-State electronics, 51 (2007) 226-230; [2] C.Himcinschi, M.Reiche, R.Scholz, S.H.Christiansen, and U.
compressive uniaxially strainedsilicon on insulator by prestrained wafer bonding and layer transferAPPLIeD, PHYSICS LeTTeRS 90,231909 (2007).As depicted in figs. 1 and 2, the manufacturing process steps of its single shaft tensile strain GeOI is described below for the technological principle of this technology and step:
1. first by 4 inches of Si sheet 1 thermal oxidations, then this oxidation sheet 1 is injected to H
+(hydrogen ion).
2. will note H
+oxidation sheet 1 be placed on arc-shaped bend platform,, fit tightly with arc-shaped table board its bending by outer depression bar; Subsequently 3 inches of Si sheets 2 are placed on to 4 inches of bending note H along same flexure direction
+oxidation sheet 1 on, by interior depression bar by its bending, with note H
+oxidation sheet 1 fits tightly;
3. bending platform is placed in annealing furnace, at 200 DEG C, anneals 15 hours.
4. take off bending and two Si wafers of bonding from bending platform, be reentered in annealing furnace, at 500 DEG C, anneal 1 hour, complete smart peeling, and finally form uniaxial strain GeOI wafer.
The major defect of this technology is: 1) processing step complexity: the method must experience thermal oxidation, H
+implantation, peel off requisite main technique and the correlation step thereof such as annealing.2) flexure temperature is limited: because being advances at smart peeling that line unit closes and bending annealing, noted H
+the restriction of exfoliation temperature, its bending annealing temperature can not be higher than 300 DEG C, otherwise will in bending annealing process, peel off, and make the fragmentation of Si sheet.3) fabrication cycle is long: extra thermal oxidation, H
+implantation, peel off the processing steps such as annealing and increased the time of its making.4) rate of finished products is low: the method is to carry out mechanical bend and bonding by two overlapping silicon wafer, and under case of bending, carries out again high temperature and peel off, and silicon wafer is easy to fragmentation.
Summary of the invention
The object of the invention is to overcome the deficiency of above-mentioned prior art, the manufacture method that a kind of machinery causes uniaxial strain GeOI wafer is proposed, with reduce strain GeOI wafer cost of manufacture, improve heat dispersion, insulation property and the integrated level of strain GeOI device and integrated circuit, meet microelectronics technology, particularly ultrahigh speed, low-power consumption, anti-irradiation and high power device and the demand of integrated circuit to strain GeOI wafer.Adopt following technical scheme:
Machinery causes a manufacture method for uniaxial strain GeOI wafer, comprises the following steps: 1) GeOI wafer top layer Ge aspect is placed on arc-shaped bend platform up or down; 2) two cylindrical stainless steel depression bars lie in a horizontal plane in respectively GeOI wafer two ends, apart from GeOI crystal round fringes 1cm; 3) slow turn connects the nut of depression bar, makes GeOI wafer bending gradually along arc-shaped table board, until GeOI wafer is complete and arc-shaped table board laminating; 4) the arc-shaped bend platform that is loaded with GeOI wafer is placed in annealing furnace anneals, and annealing temperature can be selected arbitrarily within the scope of 200 DEG C to 900 DEG C.For example, can at 200 DEG C, anneal 10 hours, also can at 600 DEG C, anneal 5 hours; 5) annealing finishes rear slow cooling to room temperature, takes out the arc-shaped bend platform that is loaded with GeOI wafer; 6) turn connects the nut of depression bar, depression bar is slowly promoted, until bending GeOI wafer reinstatement.Being loaded with temperature that the bending platform of GeOI wafer anneals in annealing furnace minimum is 200 DEG C, to ensure the SiO in GeOI wafer
2the deformation of enterree in this process can exceed its yield strength, and plastic deformation occurs; The highest annealing temperature is 900 DEG C, approaches the fusing point of Ge.But the highest annealing temperature must not be higher than the deformation temperature of mechanical bend platform
Described manufacture method, the radius of curvature of described arc-shaped bend platform can change continuously from 1.2m to 0.35m, the uniaxial strain GeOI wafer of the differently strained amount of its respective production.
Described manufacture method, described step 4) annealing process be: at 200 DEG C, anneal 10 hours; Or at 400 DEG C, anneal 5 hours; Or at 900 DEG C, anneal 2.2 hours.
Described manufacture method, described GeOI wafer is the GeOI wafer of 3 inches, 4 inches, 5 inches, 6 inches, 8 inches.
Know-why of the present invention:
The GeOI sheet top layer Ge aspect of finished product is upwards placed on carries out mechanical bend, then thermal annealing on circular arc table top.According to material plastoelasticity principle, be subject to the heat treated effect of long-time Bending Deformation, SiO2 layer in GeOI wafer neutral surface top and top layer Ge layer will be along bending direction generation uniaxial tensile deformations, and its lattice constant will become greatly, and so-called single shaft tensile strain occurs.Meanwhile, stored certain elastic potential energy at GeOI inside wafer.When annealing finishes to remove after mechanical external force, under this elastic potential energy effect, can there is resilience in GeOI wafer, be returned to ortho states by case of bending, as shown in Figure 3.
But in the GeOI wafer restoring, top layer Ge layer has retained a certain amount of tensile strain.This is because in the time of bending thermal anneal process, has set suitable annealing temperature and time, ensures that the mechanical external force applying can exceed SiO
2yield strength but be less than the yield strength of Si substrate, make SiO
2plastic deformation occurs, and Si substrate is elastic deformation all the time.The SiO of plastic deformation
2enterree is resilience completely in the time that the resilience of GeOI wafer is restored, and still keeps a certain amount of tensile strain.And top layer Ge layer is subject to plastic deformation SiO
2the effect that pulls and supports of enterree, resilience completely, finally forms single shaft tensile strain GeOI wafer.
In like manner, if GeOI wafer top layer Ge aspect is placed on downwards on circular arc table top and carries out mechanical bend and thermal annealing, due to the bottom of top layer Si Ge layer in GeOI wafer neutral surface, in the time that bending is annealed, its lattice is by compressed, lattice constant diminishes, and finally can obtain single shaft compressive strain GeOI wafer.
With respect to existing uniaxial strain GeOI technology, the present invention has the following advantages:
1) raw material is easy to get: the present invention adopts finished product GeOI wafer, on market, can buy in batch at any time, greatly reduces process complexity and equipment cost.
2) cost of manufacture is low: because manufacture craft is simple, equipment investment is few, thereby cost of manufacture is low.
3) manufacture craft is simple: compared with existing similar technology, do not have thermal oxidation, Implantation, high temperature the extra technique such as to peel off, only have mechanical bend and thermal annealing twice technical process.
4) technological temperature scope is wide: 200 DEG C to 300 DEG C annealing regions of relatively existing similar technique, annealing temperature of the present invention from minimum 200 DEG C to the highest 900 DEG C, can select arbitrarily.
5) rate of finished products is high: prior art adopts two Si wafers to carry out the bending annealing of bonding, and peels off to obtain uniaxial strain SOI wafer by high temperature under case of bending, thereby Si sheet is very easy to broken.And the present invention only carries out bending annealing with the GeOI wafer of a slice finished product and obtains uniaxial strain GeOI wafer, be difficult for brokenly, thereby rate of finished products is high.
6) surface roughness is little: the present invention is without make strain GeOI by stripping technology, thus the surface roughness of its top layer Ge film monocrystalline much smaller than with existing similar technique.
7) strain effects is good: compared with existing similar technology, under same flexibility, dependent variable of the present invention is high, thereby can obtain higher carrier mobility.
8) good in thermal property: compared with the strain GeOI wafer of tradition based on the empty substrate of SiGe, the uniaxial strain GeOI wafer that the present invention makes without the empty substrate of SiGe, thereby both can greatly reduce the hot expense of device and circuit, be conducive to again the heat radiation of its device and circuit.
Embodiment
Below in conjunction with specific embodiment, the present invention is described in detail.
The preparation of embodiment 1:3 inch uniaxial strain GeOI wafer
1, GeOI wafer is selected: 3 inches (100) or (110) wafer ((100) or (110) refer to certain crystal face of GeOI wafer plane of crystal), the thick 0.4mm of Si substrate, SiO
2the thick 500nm of enterree, top layer Ge bed thickness 500nm.
GeOI diameter wafer is selected: the brilliant diameter of a circle of GeOI is larger, its bending minimum bending radius is just less, the dependent variable of the uniaxial strain GeOI wafer obtaining is also just larger, and the final electron mobility of uniaxial strain GeOI wafer and the enhancing of hole mobility are also just higher.For made of the present invention based on SiO
2the uniaxial strain GeOI wafer of enterree, according to the different process of its GeOI device and circuit, can select the different-diameter GeOI wafer from 3 inches to 8 inches.
GeOI wafer crystal face and crystal orientation are selected: for the tensile strain GeOI wafer of made of the present invention, should select (100) crystal face, bending direction should be selected <110> crystal orientation, and (<110> refers to certain crystal orientation of wafer surface, conventionally be also the channel direction of device), can obtain maximum electron mobility and promote.For the compressive strain GeOI wafer of made of the present invention, should select (110) crystal face, bending direction should be selected <100> crystal orientation, can obtain maximum hole mobility and promote.
GeOI wafer Si substrate thickness is selected: the thickness of Si substrate is thinner, and the minimum bending radius of its GeOI wafer is just little, and the dependent variable of the single shaft tensile strain GeOI wafer obtaining is also just larger.For made of the present invention based on SiO
2the uniaxial strain GeOI wafer of enterree, according to different structure and the technique thereof of its GeOI device and circuit, can select the GeOI wafer of different Si substrate thickness.
GeOI wafer top layer Ge layer thickness is selected: according to the different structure of its GeOI device and circuit, can select the GeOI wafer of different top layer Ge layer thickness.If made of the present invention based on SiO
2the strain GeOI wafer of enterree is applied to cmos device and circuit, requires top layer Ge thickness can not exceed 30nm; If be applied to photo-detector, require the top layer Ge thickness can not be lower than 700nm;
GeOI wafer SiO2 enterree thickness is selected: according to the different structure of GeOI device and circuit, can select the GeOI wafer of different SiO2 thickness of insulating layer.If made of the present invention based on SiO
2the strain GeOI wafer of enterree is applied to cmos device and circuit, requires SiO2 thickness of insulating layer to be not less than 250nm; If be applied to photo-detector, require SiO2 thickness of insulating layer to be no more than 200nm;
Bending platform material is selected: bending platform material is mainly to select according to annealing temperature, ensure that bending platform is indeformable under the highest annealing temperature.For of the present invention based on SiO
2the GeOI wafer of enterree, its highest annealing temperature is 900 DEG C, therefore bending platform material can adopt resistant to elevated temperatures ZG35Cr26Ni12 heat-resisting steel material.
2, bending platform radius of curvature is selected: according to the GeOI wafer of selecting, selecting bending platform radius of curvature is 1m.The radius of curvature of bending platform is to select according to the diameter of GeOI wafer and thickness.Under identical GeOI wafer size, the minimum bending radius of thin GeOI wafer is less than thick GeOI wafer.Under same thickness, the minimum bending radius of large scale GeOI wafer is less than small size GeOI wafer.For the tensile strain GeOI wafer based on SiO2 enterree of made of the present invention, the bending radius scope of its 4 inches of GeOI wafers is 0.50m-1.2m, the bending radius scope of its 6 inches of GeOI wafers is 0.45m-1.2m,, its 8 inches of GeOI wafer bending radius scopes are 0.4m-1.2m.
3, GeOI wafer bending process step:
1) by GeOI wafer top layer Ge aspect upwards (or downwards, it is upwards tensile strain, as Fig. 3, it is downwards compressive strain, as Fig. 4, lower same) be placed on arc-shaped bend platform, its bending direction is parallel with <110> or <100> direction;
2) two cylindrical horizontal depression bars on bending platform lie in a horizontal plane in respectively GeOI wafer two ends, apart from 1 centimetre, its edge;
3) the push rod nut of one of them depression bar on the bending platform of turn, makes GeOI wafer one end first fixing;
4) the slow push rod nut of another depression bar of turn again, makes GeOI wafer bending gradually along arc-shaped bend platform table top, until GeOI wafer completely and arc-shaped bend platform table top fit completely.
4, annealing process step:
1) annealing temperature: 200 DEG C;
2) heating rate: 5 DEG C/min;
3) annealing time: 10 hours;
4) rate of temperature fall: 5 DEG C/min;
5, unload frame: treat that furnace temperature is down to room temperature, take out bending platform.The push rod nut of two depression bars in the bending platform two ends of simultaneously slow turn slowly promotes horizontal struts, until depression bar departs from GeOI wafer completely simultaneously.
By above-mentioned processing step, can obtain 3 inches of uniaxial strain GeOI wafers.
The preparation of embodiment 2:4 inch uniaxial strain GeOI wafer
1, GeOI wafer is selected: 4 inches (100) or (110) crystal face, the thick 0.55mm of Si substrate, SiO
2the thick 300nm of enterree, top layer Ge bed thickness 50nm.
2, bending curvature radius is selected: according to the GeOI wafer of selecting, selecting bending platform radius of curvature is 0.75m.
3, GeOI wafer bending process step:
1) by GeOI wafer top layer Ge aspect upwards (or downwards) be placed on clean stainless steel arc-shaped bend platform, its <110> or <100> direction are parallel with bending direction, as shown in Figure 3 or Figure 4;
2) two cylindrical horizontal depression bars on bending platform lie in a horizontal plane in respectively GeOI wafer two ends, apart from 1 centimetre, its edge;
3) the push rod nut of one of them depression bar on the bending platform of turn, makes GeOI wafer one end first fixing;
4) the slow push rod nut of another depression bar of turn again, makes GeOI wafer bending gradually along arc-shaped bend platform table top, until GeOI wafer completely and arc-shaped bend platform table top fit completely.
4, annealing process step:
1) annealing temperature: 400 DEG C;
2) heating rate: 4 DEG C/min;
3) annealing time: 5 hours;
4) rate of temperature fall: 4 DEG C/min;
5, unload frame: treat that furnace temperature is down to room temperature, take out bending platform.The push rod nut of two depression bars in the bending platform two ends of simultaneously slow turn slowly promotes horizontal struts, until depression bar departs from GeOI wafer completely simultaneously.
By above-mentioned processing step, can obtain 4 inches of uniaxial strain GeOI wafers.
The preparation of embodiment 3:6 inch uniaxial strain GeOI wafer
1, GeOI wafer is selected: 6 inches (100) or (110) crystal face, O.68mm Si substrate thick, the thick 1000nm of SiO2 enterree, top layer Ge bed thickness 1000nm.
2, bending curvature radius is selected: according to the GeOI wafer of selecting, selecting bending platform radius of curvature is 0.5m.
3, GeOI wafer bending process step:
1) by GeOI wafer top layer Ge aspect upwards (or downwards) be placed on arc-shaped bend platform, its bending direction is parallel with <110> or <100> direction, as shown in Figure 3 or Figure 4;
2) two cylindrical horizontal depression bars on bending platform lie in a horizontal plane in respectively GeOI wafer two ends, apart from 1 centimetre, its edge;
3) the push rod nut of one of them depression bar on the bending platform of turn, makes GeOI wafer one end first fixing;
4) the slow push rod nut of another depression bar of turn again, makes GeOI wafer bending gradually along arc-shaped bend platform table top, until GeOI wafer completely and arc-shaped bend platform table top fit completely.
4, annealing process step:
1) annealing temperature: 900 DEG C;
2) heating rate: 3 DEG C/min;
3) annealing time: 2.2 hours;
4) rate of temperature fall: 3 DEG C/min;
5, unload frame: treat that furnace temperature is down to room temperature, take out bending platform.The push rod nut of two depression bars in the bending platform two ends of simultaneously slow turn slowly promotes horizontal struts, until depression bar departs from GeOI wafer completely simultaneously.
By above-mentioned processing step, can obtain 6 inches of uniaxial strain GeOI wafers.
In order to make narration of the present invention more clear, below will many details be made and being illustrated.For example concrete structure, composition, material, size, technical process and technology.
The present invention's arc-shaped bend platform used adopts ZG35Cr26Ni12 heat-resisting steel material, and this is indeformable under the highest annealing temperature in order to ensure bending platform.In addition, the present invention's bending platform used also can adopt other to be easy to higher and resistant to elevated temperatures all materials of machining, fineness to make.
Strain GeOI wafer base semiconductor substrate 1 of the present invention can be also other semi-conducting materials, semi-conducting material as all possible in Ge, GaAs etc.
Strain GeOI wafer top layer semi-conducting material 3 of the present invention is not limited to Ge semi-conducting material, also the semi-conducting materials of all applicable making GeOI wafer top layer semiconductive thin films such as Si, SiGe, GaAs.
The GeOI wafer that any process is made is all suitable for the present invention and makes uniaxial strain GeOI wafer, and these processes comprise smart peeling (Smart-cut), note oxygen isolation (SIMOX), bonding and back of the body corrosion (BeGeOI), layer transfer (eLRANT), epitaxial growth based on GeOI wafer etc.
The selection principle of the bending annealing temperature of the present invention and annealing time is, ensures that in GeOI crystal circle structure, plastic deformation occurs SiO2 film in annealing process, but Si substrate in GeOI wafer, in annealing, elastic deformation can only occur.Therefore, according to SiO
2the Material Thermodynamics characteristic of film, its minimum annealing temperature must not be lower than 200 DEG C.According to the characteristic of GeOI wafer top layer Ge layer, the highest annealing temperature can reach 900 DEG C, approaches the fusing point of Ge.But the highest annealing temperature must be considered the thermodynamic property of bending platform material, can not be higher than its deformation temperature.
Detailed description of the present invention and describing all based on optimization test scheme, but person of skill in the art will appreciate that, the variation of above and other form and details can't depart from essence of the present invention and scope.For those skilled in the art; understanding after content of the present invention and principle; can be in the situation that not deviating from the principle and scope of the present invention; the method according to this invention is carried out various corrections and the change in form and details, but these based on correction of the present invention and change still within claim protection range of the present invention.
Should be understood that, for those of ordinary skills, can be improved according to the above description or convert, and all these improvement and conversion all should belong to the protection range of claims of the present invention.