CN102912449B - A kind of bonding method improving bonded crystals linkage force and optical characteristics - Google Patents
A kind of bonding method improving bonded crystals linkage force and optical characteristics Download PDFInfo
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- CN102912449B CN102912449B CN201210387960.9A CN201210387960A CN102912449B CN 102912449 B CN102912449 B CN 102912449B CN 201210387960 A CN201210387960 A CN 201210387960A CN 102912449 B CN102912449 B CN 102912449B
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Abstract
The present invention relates to a kind of bonding method improving bonded crystals linkage force and optical characteristics, can be used for preparing quasi-phase matched nonlinear crystal, belong to non-linear optic crystal field, mainly solve the problem that quasi-phase-matching crystals optical loss is large, linkage force is little that conventional bonding obtains, have selected gallium arsenide as bonding material, utilize ultrahigh vacuum ion source cleaning equipment, reduce the loss of bonded interface by technology such as solution cleaning, Ion Cleaning, ultrahigh vacuum(HHV) low-temperature bonding, low-pressure heat treatment, improve the linkage force of bonded crystals.The method is mainly used in the preparation of infrared band nonlinear frequency transformation quasi-phase matched gallium arsenide.
Description
Technical field
The present invention relates to a kind of bonding method improving bonded crystals linkage force and optical characteristics, can be used for preparing quasi-phase matched nonlinear crystal, belong to non-linear optic crystal field.
Background technology
Wafer bonding techniques is through surface cleaning and activation treatment by the homogeneity of two panels surface cleaning, atomic roughness or dissimilar materials, do not use any adhesive substance, directly laminating is integral under certain condition, and two panels crystal is by Van der Waals force, molecular force, and even atomic power combines.Wafer bonding techniques has great superiority, and the interface obtained by this technology has firm, level and smooth, optically transparent advantage, and this interface has very important significance for the innovation of optical device.Quasi-phase matched is the effective optical nonlinearity frequency conversion way of one grown up in recent years, quasi-phase-matching crystals internal polarization direction needs mechanical periodicity, utilize wafer bonding can by contrary for direction of polarization two wafer bondings together, reach the object of phase matched, this material of gallium arsenide infrared band transmitance is high, be applicable to infrared band nonlinear frequency transformation, also have that damage threshold is high simultaneously, nonlinear factor is large, thermal conductivity high.As far back as 1976, the people such as the Thompson of Luo Keweier international corporation of the U.S. just provide the theoretical explanation of gallium arsenide for quasi-phase matched, because this material is not ferroelectric material, cannot puncture period polarized with electrode, method main is at present epitaxy, but epitaxially grown quasi-phase-matching crystals clear aperature is little, can not play the advantage of crystal, and the quasi-phase-matching crystals clear aperature prepared with bonding pattern is large, can easily exceed 1cm
2, but there is zone of oxidation in gallium arsenide surface, not only can reduce second order nonlinear effect, affects the efficiency of frequency inverted, and oxide compound has stronger absorption to infrared band, and larger on frequency translation impact.
The existence of zone of oxidation makes the poor effect of gallium arsenide quasi-phase matched device, therefore be restricted with the application of bonding pattern acquisition quasi-phase matched device, the diffusion interlinked research work of gallium arsenide mainly concentrates on eighties of last century nineties, up to the present this diffusion interlinked gallium arsenide is not still used widely, and gallium arsenide quasi-phase matched device mainly still adopts epitaxially grown mode to obtain.In order to remove oxide compound, reduce the optical loss of diffusion interlinked gallium arsenide, people study discovery, the oxide compound of gallium arsenide starts volatilization in 500 DEG C, when temperature is greater than 850 DEG C, oxide compound effectively volatilizees, (document 1, Wu YS, Feigelson RS, Route RK, Zheng D, Gordon LA, Fejer MM, Byer RL.Improved GaAs bonding process for quasi-phase-matched second harmonic generation, Journal of the Electrochemical Society, 1998, 145 (1): 366 ~ 371).Adopt the diffusion interlinked of high temperature evaporation oxide compound, evaporative process is carried out in pre-bonding process, crystal interface oxide compound is caused to evaporate not exclusively, crystal edge transmitance is higher than germ nucleus, and gallium is different from the oxide content of arsenic, volatilization causes surface component to be lacked of proper care, have a strong impact on frequency-doubling conversion efficiency (document 2, E. Lallier, M. Brevignon, and J. Lehoux. Efficient second-harmonic generation of a CO2 laser with a quasi-phase-matched GaAs crystal, 1998, 23 (19): 1511 ~ 1513).
What the present invention proposed removes oxide on surface with the purging method of hydrogen ion bombardment plane of crystal, the optical loss of bonded crystals can be reduced, bombardment does not increase surfaceness, after pre-bonding, crystal is annealed, the arrangement of bonded interface atom is recombinated, form firmly covalent, increase linkage force.
Summary of the invention
The object of the invention is to overcome the problem that current diffusion interlinked gallium arsenide linkage force is little, optical loss is large, propose a kind of hydrogen ion and remove oxide on surface, the pre-bonding of ultrahigh vacuum(HHV), the method of high-temperature heat treatment, increase the linkage force of the diffusion interlinked crystal of gallium arsenide, reduce bonded interface optical loss.
Improve a bonding method for bonded crystals linkage force and optical characteristics, it is characterized in that: the arsenide gallium monocrystal of twin polishing, remove surface organic matter impurity with chemical solvents, use deionized water rinsing afterwards; Wafer is placed in vacuum effects on surface and carries out H rays bombardment processing, vacuum tightness during bombardment processing is less than 5*10
-5pa, ion beam current energy is 300-500eV, ion beam current density 2-10 μ A/cm
2, under room temperature, bombardment time is 15-25 minute, is heated to 150 DEG C, bombards 5 minutes; Ingress of air does not move to vacuum tightness and is less than 10
-7pre-bonding in the vacuum chamber of Pa, in pre-bonding process, wafer entirety is evenly warmed to 150-200 DEG C, and wafer surface evenly applies 10kg/cm
2-15kg/cm
2pressure, keep 1-2 hour; Finally wafer is placed in Ar compression ring border to heat-treat, by room temperature to 650-800 DEG C, applies 20 kg/cm simultaneously
2-60 kg/cm
2pressure, insulation 2-3 hour, Temperature fall is to room temperature.
With the arsenide gallium monocrystal of twin polishing as bonded crystals, surface organic matter impurity is removed with chemical solvents, after through deionized water rinsing, wafer is placed in vacuum effects on surface and carries out H rays bombardment processing, ingress of air does not move to pre-bonding in high vacuum, finally wafer is placed in Ar compression ring border and heat-treats.
Do not remove the bonding method of gallium arsenide surface oxide compound, optical loss is excessive, cannot be applied to optical nonlinearity frequency transformation field; And high temperature removes the method for oxide compound, can there is volatilization not exclusively, the shortcoming of surface component imbalance, optical loss is large; The method that the present invention adopts hydrogen ion to clean, effectively can remove oxide on surface, does not increase plane of crystal roughness simultaneously.Hydrogen ion cleaning while can also increase surface dangling bonds quantity, be conducive to increase bonding area, improve crystal interface in conjunction with energy, be bonded in advance in high vacuum and carry out, can avoid the residual of bonded interface gas, anneal after pre-bonding, annealing process can improve the linkage force of crystal.
The present invention has substantial feature and marked improvement, and method of the present invention has following advantage relative to current conventional diffusion interlinked method:
Effective elimination oxide on surface, improves the optical property of bonded crystals;
Add surface dangling bonds quantity, improve bonding area and linkage force;
In high vacuum, pre-bonding, avoids the entrap bubble problem between bonded interface;
The method of annealing, can improve the linkage force of crystal.
Accompanying drawing explanation
Fig. 1 is bonding ultrahigh vacuum(HHV) hydrogen ion washing unit used.
Fig. 2 is the Ga3d(A without hydrogen ion cleaning gallium arsenide) and As3d(B) spectral line photoelectron collection of illustrative plates.
Fig. 3 is the Ga3d(A of gallium arsenide after hydrogen ion cleaning) and As3d(B) spectral line photoelectron collection of illustrative plates.
Fig. 4 is the high-resolution-ration transmission electric-lens image of bonded interface.
Fig. 5 is the diffraction pattern in bonded crystals cross section.
Embodiment
The present invention's arsenide gallium monocrystal carries out diffusion interlinked, and device fabrication process can be divided into four key steps.The first step needs gallium arsenide to carry out twin polishing, and removes surface organic matter impurity with chemical solvents, and deionized water rinsing is clean; Second step carries out hydrogen ion bombardment in a vacuum; 3rd step is pre-bonding wafer in high vacuum; 4th step the high temperature anneal.
Embodiment 1:
Wafer is after surface finish process, chemical solution cleans is carried out to wafer surface, cleaning the solution used is: tetracol phenixin, acetone, ethanol, deionized water, soak pending subsequent technique in deionized water after wafer cleaning, all operations carries out in clean room.
After sample nitrogen dries up, ultrahigh vacuum(HHV) hydrogen ion washing unit (CN201010279377.7, ultrahigh vacuum ion source chip cleaning system authorize day: 2012-05-02) is used to complete cleaning and pre-bonding process, as shown in Figure 1.Sample is placed on specimen holder 7, and is put in sputtering vacuum chamber B, treat that vacuum tightness reaches 10
-5during Pa, produce H rays by hydrogen ion source 5, start to carry out hydrogen ion cleaning to sample 6 to be cleaned, ion beam current energy 350eV is set, ion beam current density 10 μ A/cm
2, bombard 20 min under room temperature, reduce most of oxide compound, and B room entirety is heated to 150 DEG C, then bombard 5 min, remove residual oxide, and heat reduzate is evaporated.
After end of bombardment, utilize driven rod 8 that the wafer 6 after cleaning is passed to A room through valve 4, before transmitting, the vacuum tightness of A room need reach 5*10
-8pa, specimen holder 7 and sample 6 are together fixed in sample table 2, valve-off 4 is evacuated to the vacuum tightness before setting-out again, the cleaning of another wafer is carried out in B room simultaneously, after cleaning terminates, wafer 6 is passed to A room, by locating device two wafer are fit together and obtain two-layer sample 3 to be bonded, recover vacuum tightness 5*10
-8after Pa, magnetic force pressurizing device 1 is utilized to apply 10 kg/cm
2pressure, B room entirety is heated to 200 DEG C, is incubated 1 hour, completes pre-bonding.
Wafer through pre-bonding can better fit together, and in order to increase linkage force further, is arranged in high temperature resistant fixture by wafer, be put in be full of Ar gas heat treatment furnace in, from room temperature, be warming up to 700 DEG C, pressure is 40kg/cm
2, be incubated 2 hours, Temperature fall, to room temperature, completes whole bonding process.
The situation of oxide compound is removed in order to detect hydrogen ion, photoelectron spectrum detection is carried out to hydrogen ion bombardment front and rear surfaces, Fig. 2, Fig. 3 are respectively the Ga3d(A of gallium arsenide before and after hydrogen ion cleaning) and As3d(B) spectral line photoelectron collection of illustrative plates, can find that the oxide compound cleaning rear surface arsenic and gallium obviously reduces.Use contourgraph measure surface roughness, the r.m.s. roughness that result shows to bombard front sample is 0.37nm, after bombardment, the r.m.s. roughness of sample is 0.40nm, and before and after bombardment, roughness is all less than the lattice parameter of gallium arsenide, does not make surfaceness obviously change before and after bombardment.
In order to detect the impact of hydrogen ion cleaning on optical property and linkage force, carried out stretching experiment to pre-bonding wafer, the crystal without hydrogen ion cleaning Direct Bonding ruptures from bonding face, and bonded energy is 0.34J/cm
2; The crystal of pre-bonding after hydrogen ion cleaning, stretched experimental crystal has the area of more than 50% to rupture from crystals, and bonded energy is 0.55J/cm
2.Can increase bond strength further through Overheating Treatment, according to the wafer of the pre-bonding of embodiment 1, after annealing, bonding area can reach 95%, and it is 0.85J/cm that stretching experiment records bonded energy
2, close to crystal self in conjunction with energy.Measure the optical property of crystal with infrared transmission, the average optical loss of bonded layer is 0.3% at wavelength 5.3 μm of places, and at wavelength, 10.6 μm of places are 0.2%.
By transmission electron microscope observing bonded interface pattern, as shown in Figure 4, bonded interface does not observe amorphous layer, illustrates that oxide compound is efficiently removed, not there is dislocation in crystals, because pre-bonding process carries out in high vacuum environment, bonded interface does not observe bubble, and interface crystal lattice marshalling runs through bonded interface, para-linkage layer entirety carries out diffraction imaging, as shown in Figure 5, after diffraction pattern display bonding, entirety is single crystal structure, illustrates that two-layer gallium arsenide wafer combines in high quality.
Embodiment 2:
Wafer is after surface finish process, chemical solution cleans is carried out to wafer surface, cleaning the solution used is: tetracol phenixin, acetone, ethanol, deionized water, soak pending subsequent technique in deionized water after wafer cleaning, all operations carries out in clean room.
After sample nitrogen dries up, sample is placed on specimen holder 7, and is put in sputtering vacuum chamber B, treat that vacuum tightness reaches 10
-5during Pa, produce H rays by hydrogen ion source 5, start to carry out hydrogen ion cleaning to sample 6 to be cleaned, ion beam current energy 500eV is set, ion beam current density 5 μ A/cm
2, bombard 15 min under room temperature, reduce most of oxide compound, and B room entirety is heated to 150 DEG C, then bombard 5 min.
After end of bombardment, utilize driven rod 8 that the wafer 6 after cleaning is passed to A room through valve 4, before transmitting, the vacuum tightness of A room need reach 5*10
-8pa, specimen holder 7 and sample 6 are together fixed in sample table 2, valve-off 4 is evacuated to the vacuum tightness before setting-out again, the cleaning of another wafer is carried out in B room simultaneously, after cleaning terminates, wafer 6 is passed to A room, by locating device two wafer are fit together and obtain two-layer sample 3 to be bonded, recover vacuum tightness 5*10
-8after Pa, magnetic force pressurizing device 1 is utilized to apply 10 kg/cm
2pressure, B room entirety is heated to 150 DEG C, is incubated 1 hour, completes pre-bonding.
Wafer is arranged in high temperature resistant fixture, be put in be full of Ar gas heat treatment furnace in, from room temperature, be warming up to 650 DEG C, pressure is 20kg/cm
2, be incubated 2 hours, Temperature fall, to room temperature, completes bonding process.
Measuring bonding area after annealing is 92%, and it is 0.82J/cm that stretching experiment records bonded energy
2, close to crystal self in conjunction with energy.Measure the optical property of crystal with infrared transmission, the average optical loss of bonded layer is 0.2% at wavelength 5.3 μm of places, and at wavelength, 10.6 μm of places are 0.1%.
Embodiment 3:
Wafer is after surface finish process, chemical solution cleans is carried out to wafer surface, cleaning the solution used is: tetracol phenixin, acetone, ethanol, deionized water, soak pending subsequent technique in deionized water after wafer cleaning, all operations carries out in clean room.
After sample nitrogen dries up, sample is placed on specimen holder 7, and is put in sputtering vacuum chamber B, treat that vacuum tightness reaches 10
-5during Pa, produce H rays by hydrogen ion source 5, start to carry out hydrogen ion cleaning to sample 6 to be cleaned, ion beam current energy 300eV is set, ion beam current density 10 μ A/cm
2, bombard 15 min under room temperature, reduce most of oxide compound, and B room entirety is heated to 150 DEG C, then bombard 5 min.
After end of bombardment, utilize driven rod 8 that the wafer 6 after cleaning is passed to A room through valve 4, before transmitting, the vacuum tightness of A room need reach 5*10
-8pa, specimen holder 7 and sample 6 are together fixed in sample table 2, valve-off 4 is evacuated to the vacuum tightness before setting-out again, the cleaning of another wafer is carried out in B room simultaneously, after cleaning terminates, wafer 6 is passed to A room, by locating device two wafer are fit together and obtain two-layer sample 3 to be bonded, recover vacuum tightness 5*10
-8after Pa, magnetic force pressurizing device 1 is utilized to apply 15kg/cm
2pressure, B room entirety is heated to 200 DEG C, is incubated 2 hours, completes pre-bonding.
Wafer is arranged in high temperature resistant fixture, be put in be full of Ar gas heat treatment furnace in, from room temperature, be warming up to 800 DEG C, pressure is 60kg/cm
2, be incubated 3 hours, Temperature fall, to room temperature, completes bonding process.
Measuring bonding area after annealing is 98%, and it is 0.86J/cm that stretching experiment records bonded energy
2.Measure the optical property of crystal with infrared transmission, the average optical loss of bonded layer is 0.6% at wavelength 5.3 μm of places, and at wavelength, 10.6 μm of places are 0.4%.
Claims (1)
1. improve a bonding method for bonded crystals linkage force and optical characteristics, it is characterized in that: the arsenide gallium monocrystal of twin polishing, remove surface organic matter impurity with chemical solvents, use deionized water rinsing afterwards; Wafer is placed in vacuum effects on surface and carries out H rays bombardment processing, vacuum tightness during bombardment processing is less than 5*10
-5pa, ion beam current energy is 300-500eV, ion beam current density 2-10 μ A/cm
2, under room temperature, bombardment time is 15-25 minute, is heated to 150 DEG C, bombards 5 minutes; Ingress of air does not move to vacuum tightness and is less than 10
-7pre-bonding in the vacuum chamber of Pa, in pre-bonding process, wafer entirety is evenly warmed to 150-200 DEG C, and wafer surface evenly applies 10kg/cm
2-15kg/cm
2pressure, keep 1-2 hour; Finally wafer is placed in Ar compression ring border to heat-treat, by room temperature to 650-800 DEG C, applies 20 kg/cm simultaneously
2-60 kg/cm
2pressure, insulation 2-3 hour, Temperature fall is to room temperature.
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| CN211999987U (en) * | 2020-04-17 | 2020-11-24 | 中国电子科技南湖研究院 | Device for preparing large-size single crystal |
| CN111270314A (en) * | 2020-04-17 | 2020-06-12 | 中国电子科技南湖研究院 | Method for preparing large-size single crystal |
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| CN115161770A (en) * | 2021-04-06 | 2022-10-11 | 中国科学院福建物质结构研究所 | Rare earth ion doped gallium tetraborate crystal, bonded crystal, and preparation method and application of crystal |
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