CN1152635A - Hole conduction tellurium-cadimium-mercury epitaxy material heat treatment process and device thereof - Google Patents

Abstract

The present invention provides a heat treatment process for long-wave Te-Cd-Hg epitaxial material and its equipment. Said heat treatment process consists of six portions of sample surface treatment, heat treatment device treatment, chip-charging, system vacuum-pumping, heat treatment condition selection and quenching-taking-out. Said invention can be used for regulating N-type material grown up by using molecular beam epitaxy (MBE) technology, and its hole concentration is regulated to (77K working temp.)_ 0.8-2X10 to the power 16 cm to the power 13 or so, and its hole mobility is greater than 500 cm to the power 2/VS, so that it can make the long-wave Te-Cd-Hg MBE material meet the requirements for application of infrared focal plane device of N-on-P structure.

Description

Technology and device bury in hole conduction tellurium-cadimium-mercury epitaxy material heat place

The present invention relates to monocrystalline or have the post-processing technology of the homogeneous polycrystalline material of a fixed structure, particularly a kind of hole conduction type (P type) Te-Cd-Hg (HgCdTe) molecular beam epitaxy (MBE) material heat treatment process and device.

The HgCdTe epitaxial material is used to prepare infrared focal plane detector; the infra-red imaging photoelectron Detection Techniques that grow up with infrared focal plane detector are in space flight; airborne remote sensing; weather-forecast; military; medical science and biotechnology, information technology has a wide range of applications in the fields such as industrial remote sensing thermometric, environment protection.

According to the structure that infrared focal plane detector adopted, the HgCdTe material there are P type and two kinds of requirements of N type, P type and N type are divided into two kinds on doping type and lattice imperfection type again, in the technology of preparing of semiconductor material, the electric property of material generally all needs to adjust by thermal treatment process, then rely on thermal treatment process fully for lattice imperfection section bar material, therefore, thermal treatment process is a very important technology in the semiconductor fabrication technology.

Be to obtain big area component uniform HgCdTe layer material, people's researchdevelopment successively liquid phase epitaxial technique (LPE), molecular beam epitaxy technique (MBE) and metal organic chemical vapor deposition technology (MOCVD).The component uniformity and the thickness evenness of MBE technology gained epitaxial material are best in various epitaxy technology, and MBE technology has advantages such as preparing PN junction, introducing component heterojunction and CdTe surface passivation layer in epitaxy technique, and very big development potentiality is arranged.But because the temperature range very little (180 ℃～200 ℃) of MBE technology growth HgCdTe material, the material that grows is uneven N type, and material can't need to adjust to the required electrical parameter of focal plane device through Overheating Treatment directly for device uses.And device is very harsh to the requirement of material electric property, and general requirement P type carrier concentration is 0.8～2 * 10 ¹⁶Cm ^-3, mobility is greater than 500cm ²/ vs, this just requires to provide effective thermal treatment process for MDE technology growth HgCdTe material.

HgCdTe material hot treatment work in the past, mostly concentrate on body material and the liquid-phase epitaxial material, the annealed method all is traditional stopped pipe two warm area annealing methods, and promptly sample is placed in the high-temperature zone, utilizes the mercury dividing potential drop in the saturated vapo(u)r pressure-controlled annealing system in cold zone mercury source.H.R Vydyanath is at J.Electrochem, Soc, in 128 (1981) 2609 to Hg _0.8Cd _0.2Relation in the Te body material between mercury room and the heat-treat condition is studied, because selected thermal treatment temp is higher, the concentration in mercury room is bigger, is not suitable for the requirement that focal plane device is made.Body material and liquid-phase epitaxial material are after the thermal treatment of P type, and the mobility in hole can reach 800～1000cm in the material ²/ vs is (as P.H shl is at Phys.Stat.Sol (b) Vol.145, result who provides in 637 (1988) and E Finkman are in J.Appl.PHys.Vol.59 (4), the result who provides in 1205 (1986)), but, adopt annealing technology present maximum that reaches under the 77K temperature in two warm area stopped pipe mercury sources only to be 400cm from the hole mobility of P type HgCdTe-MBE material of report ²/ vs (seeing J.Cryst.Growth such as T.Sasaki, Vol.117,222 (1992)).

The object of the present invention is to provide a kind of thermal treatment process and device that forms mercury vacancy defect type long wave molecular beam epitaxial TeCdHg material.This technology and device can adjust to 0.8～2 * 10 with the hole concentration of long wave molecular beam epitaxial TeCdHg material under the 77K working temperature ¹⁶Cm ^-3About, hole mobility is greater than 500cm ²/ vs, and can keep the epitaxial material surface integrity.

Thermal treatment process is one and requires very strict process, the factor that influences the technology success or failure is a lot, processing as sample surfaces, the clean of thermal treatment unit, the quality of load process, the mode of choosing and getting sheet of heat-treat condition etc., each is dealt with improperly all can produce very big influence to heat treated result, at the technological line of the characteristics of MBE epitaxial material and thermal treatment itself design thermal treatment process, it is handled by sample surfaces, thermal treatment unit is handled, load, system vacuumizes, heat-treat condition selection and thermal treatment and taking-up six parts of quenching are formed.In these operations, the inventor has found out the cleaning that can remove surface contamination effectively, after cleaning, increased the operation of hydrochloric acid removal metal ion, take high-temperature degassing to obtain the purpose of silica tube purifying treatment to the silica tube that thermal treatment is used, correctly choosing of heat-treat condition makes thermal treatment reach its intended purposes.Adopt the quenching-in water that inserts room temperature that the mercury room that forms in the as-heat-treated condition can at room temperature be remained.

Description of drawings of the present invention is as follows:

Fig. 1 is the schema of thermal treatment process of the present invention.

The sample temperature that Fig. 2 tries to achieve for the present invention and the graph of relation of mercury source temperature.

Fig. 3 is the structural representation of thermal treatment unit of the present invention.

Fig. 4 is the Wilson seal synoptic diagram in the thermal treatment unit of the present invention

Fig. 5 is the specimen holder sample socket synoptic diagram in the thermal treatment unit of the present invention.

Fig. 6 is the synoptic diagram of the anti-mercury cover of the specimen holder in the thermal treatment unit of the present invention.

Below in conjunction with accompanying drawing the present invention is specifically addressed:

(1). sample surfaces cleans and handles

Sample surfaces is because ingress of air is easy to form on the surface oxide compound, and adsorb a large amount of impurity elements (as C, Cu, Ca, K, Na, etc.), it is one of principal element that causes the material contamination that these surface impurity elements are diffused in heat treatment process in the material bodies, therefore, the sample surfaces cleaning is the important step of thermal treatment process before the thermal treatment, for this reason, adopt strict process of surface treatment in technology, processing step is:

A). divide pure toluene ultrasonic cleaning (each 8 minutes of secondary),

B). divide pure ether ultrasonic cleaning (each 5 minutes of secondary),

C) .MOS grade acetone ultrasonic cleaning (each 5 minutes of secondary),

D). the pure methyl alcohol ultrasonic cleaning of top grade (each 5 minutes of secondary),

E). greater than the deionized water rinsing of 8M Ω 10 minutes,

F). to cleaned slice, thin piece with 46% salt acidleach 2 minutes,

G). the pure water rinsing of usefulness 18.2M Ω 10 minutes;

Above technology can make surperficial natural oxidizing layer reduce to about 10A from 20A more, reduces compact oxide to the inhibition of atom exchange between the solid and gas two-phase in the heat treatment process.Concentrated hydrochloric acid has removal effect preferably to the metal ion of surface adsorption simultaneously.Use the pure water rinsing 10 minutes of 18.2M Ω at last, guarantee the clarity of sample surfaces.

(2). the degasification of thermal treatment silica tube

Degassing process is extensive use of in epitaxial growth technology, but does not come into one's own as yet in thermal treatment process.Experiment shows, degassing process is crucial in thermal treatment, clean silica tube generally has certain impurity atoms in surface adsorption, in this technology, with heat treatment furnace the part that silica tube inserts in the stove is carried out vacuum stripping, the degasification condition be 500 ℃ 4 hours, valve-off when degasification finishes prevents that the external world from staiing the silica tube inwall again.

(3). load

To in 100 grades clean work station, open except that the thermal treatment unit of good gas, the humidity in room is controlled in 50%, then the sample of handling well is installed on the specimen holder, close the valve of thermal treatment unit after shelving, whole process is all finished in 100 grades environment, prevents the contamination of outer bound pair sample to greatest extent.

(4). system vacuumizes

Adopt the combination vacuum system of mechanical pump, molecular pump and isolation cold-trap that the thermal treatment silica tube is evacuated to 10 ^-4More than the Pa, valve-off.

(5). heat-treat condition is selected and thermal treatment

The heat treated principle of this technology P type realizes by regulating material internal mercury vacancy concentration, about more existing researchs of the relation of mercury dividing potential drop size in mercury vacancy concentration and thermal treatment temp, the gas phase and report, but these work all are to design for the purpose of studying, heat treated temperature is than higher, the mercury vacancy concentration is also bigger, can not be directly used.For this reason, divide folding to set about, obtain complete description Hg from theory _1-xCd _xThe thermodynamical equilibrium equation of Te solid and gas two-phase system: $\mathrm{NokT}\ln \left(P_{\mathrm{<figure-callout\; id="2"\; label="Hg\; P\; Te"\; filenames="A9611634000151.png"\; state="\{\{state\}\}">Hg</figure-callout>}}{P}_{\mathrm{Te}}^{}{2}_{1/2}^{}\right)=K_1(x,T),$ $\mathrm{Nokt}\ln \left(P_{\mathrm{<figure-callout\; id="2"\; label="Cd\; P\; Te"\; filenames="A9611634000151.png"\; state="\{\{state\}\}">Cd</figure-callout>}}{P}_{\mathrm{Te}}^{}{2}_{1/2}^{}\right)=K_2(x,T),$

p ²[V _Hg]/P _Hg＝K ₃(x，T)，

p ²[V _Cd]/P _Cd＝K ₄(x，T)，

pn＝K ₅(x，T)，

([V _Hg]+[V _cd])[V _Te]＝K ₆(x，T)，

2([V _Hg]+[V _cd])+n＝2[V _Te]+p，

P wherein _Hg, P _Cd, P _Te2Be the dividing potential drop of each element, [V _Hg], [V _Cd], [V _Te] be the vacancy concentration of each element, x is the component of Cd, and T is a temperature, and n and p are the concentration in electronics and hole, and No is an Avogadro constant, k is a Boltzmann constant, K ₁, K ₂, K ₃, K ₄, K ₅, K ₆, be the thermodynamic equilibrium constant of each defect chemistry reaction.The contriver collects existing thermodynamic data and estimate, and therefrom summarizes they and component relation, and they are: K ₁(x, T)=NokTln (1-x)+(1.384-8.452 * 10 ^-4T) x ²

-41.66+0.04271T, (kcal/mole, (each dividing potential drop adopts atm unit) K ₂(x, T)=NokTlnx+ (1.384-8.452 * 10 ^-4T) (1-x) ²

-68.64+0.04494T, (kcal/mole, (each dividing potential drop adopts atm unit) K ₃=(1-x) T ³Exp (139.47-10.13x-42.02x ²-2.07eV/kT), (atm cm ^-9) K ₄=xT ³Exp (72.1+94.2x-42.0x ²-2.8leV/kT), (atm cm ^-9) K ₅=T ³Exp (72.25-27.77x+29.5x ²-(0.182-0.0775x+1.596x ²) eV/kT],

(cm ^-6)K ₆＝exp(95.005-1.52eV/kT)，(cm ^-6)

These constant substitution thermodynamical equilibrium equations can be tried to achieve the numerical value of the mercury vacancy concentration of depressing to fixed temperature and given mercury.Obtain 1 * 10 as hope ¹⁶Cm ^-3With 2 * 10 ¹⁶Cm ^-3The material of P type current carrier, its mercury vacancy concentration is 5 * 10 ¹⁵Cm ^-3With 1 * 10 ¹⁶Cm ^-3, can try to achieve the relation that temperature and mercury are pressed according to formula, utilize the relation of pure mercury equilibrium vapor pressure and temperature to convert the mercury pressure to balance each other mercury source temperature, thereby try to achieve the relation curve of sample temperature and mercury source temperature with it.The relation shown in the curve of pressing is selected heat treated concrete sample temperature and mercury source temperature.Because in this technology, the mercury in the thermal treatment silica tube around the sample forces down in the equilibrium vapor pressure in mercury source, the mercury source temperature than calculated value slightly higher (because of the distance in sample and mercury source different), with the thermal treatment silica tube of our design, about about high 10K.For example, choosing sample temperature is 573K, and the temperature in mercury source is got 443K, and annealing time is 8 hours, has obtained good effect.The sample thief temperature is 523K, and the temperature 373K in mercury source, annealing time are 24 hours, have also obtained effect preferably.

(6). quench and take out

For the mercury room that forms in the as-heat-treated condition can at room temperature be remained, need after thermal treatment finishes to adopt quick refrigerative mode that the mercury room " is freezed " in material, this process using carry out quenching method in the insertion room temperature water, take out sample then.

Except that groping new thermal treatment process, also be an importance that guarantees that thermal treatment produces a desired effect to the design of thermal treatment unit.This thermal treatment unit adopts rectilinear structure, be that sample is above mercury source 7, the upper end of placing the quartz annealing pipe 4 in sample and mercury source 7 is in the outer room temperature state of process furnace, and link to each other with stainless steel diaphragm valve 2 by Wilson seal 3, diaphragm valve 2 directly is welded on inferior close the end socket 3 of Weir, diaphragm valve 2 the other ends stainless steel extraction pipe 1 of burn-oning.Mercury source 7 is laid in the silica tube bottom.The sample socket 6 and the anti-mercury cover 5 of sample placed at the silica tube middle part.Packing into by opening the inferior head of Weir in sample and mercury source, puts in order after this system vacuumizes valve closes, and make system keep closed state in whole heat treatment process.In this covering device, following 2 characteristics are arranged:

(1). the Wilson seal head

General vertical thermal treatment apparatus adopts full quartz construction; the ingress adopts the frosted structure to add the vacuum grease sealing; vacuum is taken out by quartzy piston (also being with grease), and the shortcoming of this structure is the pollution of vacuum grease to system, and grease consumption xeromenia regular meeting causes the sand-ground opening end socket not open.Adopt the inferior end socket of Weir can overcome these shortcomings fully, use also more convenient.The Wilson seal circle adopts the viton material, and stopping property can be better than 1.33 * 10 ^-4Pa.See also Fig. 4, after inserting quartzy annealing pipe 4, stainless steel sieve cap 304 is screwed on the stainless steel sleeve pipe 301, and the centre is added with stainless steel gasket 303 and fluororubber O shape circle 302, tightening nuts 304 and extruding fluororubber O shape circle 302 on stainless steel tube 301 and 4 of quartzy annealing pipes form sealing.

(2). the specimen holder of anti-return mercury solution

The rectilinear advantage of opening heat treatment system is that technology is simple, device can use repeatedly, but the problem that such system certainly will exist mercury to reflux, the mercury solution that refluxes drips as if producing the effect of mercury precipitation to HgCdTe on the HgCdTe epitaxial film that drops on sample surfaces, destroy the sample surfaces perfection of crystal, for this reason, inventor's specialized designs prevent that the mercury phegma from dropping onto the specimen holder of epi-layer surface, concrete structure is as follows:

See also Fig. 3, Fig. 5 and Fig. 6, specimen holder is made up of sample socket 6 and anti-mercury cover 5, and sample is placed in the silica tube 601 of cutting skewed slot 602, prevents mercury cover 5 a quartzy spillikin 603 of twisting on the sample socket 6 gently on the cover, by the 504 card posts of the bayonet socket on the anti-mercury cover 5.Sample promptly is in the protection of little bell jar 503.Anti-mercury cover 5 is equipped with baffle plate 502 can prevent mercury upwards evaporation in large quantities, and is equipped with quartzy suspension hook 501 and can lifts the entire sample frame in the annealing pipe.

Employing the invention provides a kind of processing method of adjusting long wave HgCdTe-MBE material Hg vacancy concentration, can obtain the P type HgCdTe material with certain performance that satisfies the infrared focal plane device requirement.Can develop and produce the infrared focal plane detector of N-on-P structure with P-type material, be used for the room temperature target is carried out thermal imaging.The purposes of infrared thermography comprises: practical night vision technology is provided, is equipped on the instrument and facility of executing the task various nights; Can diagnose the position of pathology the human organ thermal imaging,, can provide the ability of following the tracks of fast and following the trail of the thermal imaging of military target; Be used for the thermal imaging of space technology, can be on a surface target realize the observation of high definition, for the detection and the weather forecast of earth resources provides reliable data with cloud atlas.

Adopt the present invention to have following beneficial effect:

(1). the electrical parameter of material reaches the theoretical expected value of calculating, satisfied the demand of the HgCdTe infrared focal plane detector making of Hg room type N-on-P structure, following table is the situation of material electrical parameter after the part material processed:

Sample number into spectrum	Component X	Mobility cm2/vs	P type carrier concentration 1E16cm-3
				95009	0.233	598	2.2
95014	0.243	784	0.85
				95015	0.223	1159	1.25
95016	0.222	866	1.14
				95019	0.231	696	1.48
95020	0.226	795	1.34
				95021	0.241	654	2.0
95022	0.238	978	1.27

The ability of obtaining P-type material has reached 100%.

(2). surface integrity remains unchanged, and the high integrity of material surface is the characteristics of MBE material, and the sheet sub-surface after this art breading still can keep the integrity of this height.

(3). any change does not take place in the optical property through heat treatment material, has kept MBE material interface integrity.

(4). manufactured experimently out 32 * 32 LONG WAVE INFRARED focus planardetectors with the P-type material that this technology obtains, and realized the imaging of staring the room temperature target.

Claims (2)

1. hole conduction tellurium-cadimium-mercury epitaxy material heat treatment process, it by sample surfaces processing, thermal treatment unit processing, load, system vacuumize, heat-treat condition selection and thermal treatment and quench and take out six parts and form, it is characterized in that:

1-1 surface cleaning and processing:

1-1-1 divides pure toluene ultrasonic cleaning (each 8 minutes of secondary);

1-1-2 divides pure ether ultrasonic cleaning (each 5 minutes of secondary);

1-1-3MOS grade acetone ultrasonic cleaning (each 5 minutes of secondary);

The pure methyl alcohol ultrasonic cleaning of 1-1-4 top grade (each 5 minutes of secondary);

1-1-5 was greater than the deionized water rinsing of 8M Ω 10 minutes;

1-1-6 to cleaned slice, thin piece with 46% salt acidleach 2 minutes;

The pure water rinsing of 1-1-7 employing 18.2M Ω 10 minutes; The degasification of 1-2 thermal treatment silica tube:

With heat treatment furnace the part that silica tube inserts in the stove is carried out vacuum stripping, the degasification condition be 500 ℃ 4 hours, valve-off when degasification finishes; The 1-3 load:

To open in 100 grades clean work station except that the thermal treatment unit of good gas, the humidity in room is controlled in 50%, then the sample of handling well is installed on the specimen holder, closes the valve of thermal treatment unit after shelving; The 1-4 system vacuumizes:

Color combination vacuum system with mechanical pump, molecular pump and isolation cold-trap is evacuated to 10 to the thermal treatment silica tube ^-4More than the Pa, valve-off; The 1-5 heat-treat condition is selected and thermal treatment:

Complete description Hg _1-xCd _xThe thermodynamical equilibrium equation of Te solid and gas two-phase system: $\mathrm{NokT}\ln \left(P_{\mathrm{Hg}}{P}_{\mathrm{Tc}2}^{1/2}\right)=K_1(x,T),$ $\mathrm{NokT}\ln \left(P_{\mathrm{Cd}}{P}_{\mathrm{Te}2}^{1/2}\right)=K_2(x,T),$

p ²[V _Hg]/P _Hg＝K ₃(x，T)，

p ²[V _Cd]/P _Cd＝K ₄(x，T)，

pn＝K ₅(x，T)，

([V _Hg]+[V _Cd])[V _Te]＝K ₆(x，T)

2([V _Hg]+[V _Cd])+n＝2[V _Te]+p，

P wherein _Hg, P _Cd, P _Te2Be the dividing potential drop of each element, [V _Hg], [V _Cd], [V _Te] be the vacancy concentration of each element, x is the component of Cd, and T is a temperature, and n and p are the concentration in electronics and hole, N _oBe Avogadro constant, k is a Boltzmann constant, K ₁, K ₂, K ₃, K ₄, K ₅, K ₆Thermodynamic equilibrium constant for each element defect chemistry reaction.Existing thermodynamic data is summarized the relation of they and component, and they are:

K ₁(x，T)＝NokTln(1-x)+(1.384-8.452×10 ^-4T)x ²

-41.66+0.04271T, (kcal/mole, pressure atm unit)

K ₂(x，T)＝NokTlnx+(1.384-8.452×10 ^-4T)(1-x) ²

-68.64+0.04494T, (kcal/mole, pressure atm unit)

K ₃＝(1-x)T ³exp(139.47-10.13x-42.02x ²-2.07eV/kT)，(atm?cm ^-9)

K ₄＝xT ³exp(72.1+94.2x-42.0x ²-2.81eV/kT)，(atm?cm ^-9)

K ₅＝T ³exp(72.25-27.77x+29.5x ²-(0.182-0.0775x+1.596x ²)eV/

kT]，(cm ^-6)

K ₆＝exp(95.005-1.52eV/kT)，(cm ^-6)

These constant substitution thermodynamical equilibrium equations can be tried to achieve the numerical value of the mercury vacancy concentration of depressing to fixed temperature and given mercury; Can try to achieve the relation that temperature and mercury are pressed according to formula, utilize the relation of pure mercury equilibrium vapor pressure and temperature to convert the mercury pressure to balance each other mercury source temperature, thereby try to achieve the relation curve of sample temperature and mercury source temperature with it; Again per sample with the distance in mercury source and revise; Be chosen under the appropriate condition by curved line relation, as to choose sample temperature be 573K that the mercury source temperature is 443K,

Anneal and heat-treated in 8 hours; The 1-6 taking-up of quenching:

Adopt and insert the back taking-up of quenching in the room temperature water.

2. hole conduction tellurium-cadimium-mercury epitaxy material thermal treatment unit, sample places the top of mercury source (7), the upper end of placing the quartz annealing pipe (4) of sample and mercury source (7) is in the outer room temperature state of process furnace, and link to each other with stainless steel diaphragm valve (2) by Wilson seal head (3), every valve (2) the other end stainless steel extraction pipe (1) of burn-oning, mercury source (7) is laid in the silica tube bottom, and the sample socket (6) and the anti-mercury cover (5) of sample placed in the middle part lifting; After total system vacuumizes valve (2) is closed, and in whole heat treatment process, makes system keep closed state, it is characterized in that:

2-1. Wilson seal head

After inserting quartzy annealing pipe (4), stainless steel sieve cap (304) is screwed on the stainless steel sleeve pipe (301), the centre is added with stainless steel gasket (303) and fluororubber O shape circle (302), tightening nuts (304) and extruding fluororubber O shape circle (302) stainless steel tube (301) go up and quartzy annealing pipe (4) between form and seal;

2-2. the specimen holder of anti-return mercury solution

Specimen holder is made up of sample socket (6) and anti-mercury cover (5), sample is placed in the silica tube (601) of cutting skewed slot (602), anti-mercury cover (5) on the cover, a quartzy spillikin (603) of twisting on the sample socket (6) is blocked by the bayonet socket (504) on the anti-mercury cover (5) gently; Sample is in the protection of little bell jar (503); Anti-mercury cover (5) is equipped with baffle plate (502) to prevent mercury upwards evaporation in large quantities, is equipped with quartz hook (501) the entire sample frame is lifted in the annealing pipe.

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