CN100483626C - P type doping method for cubic boron nitride thin film - Google Patents

Abstract

The invention relates to a p-type doping method of heteroepitaxial cubic boron nitride thin film, belonging to the wide band-gap semiconductor thin film doping field. The invention overcomes the difficulty that wide band-gap superhard material c-BN thin film is difficult to realize the p-type doping, and realize the effective p-type doping of the c-BN thin film. The invention comprises the following steps: firstly, low pressure gas phase thin film is used to deposit a layer of intrinsic c-BN thin film on growth equipment, the thickness of the intrinsic c-BN thin film is 200 to 800 nm, the content of cubic phase is 40 to 95 percent, the electrical conductivity is 10<-9> to 10<-11> ohm<-1> cm<-1>; secondly, metal beryllium ions are chosen as p-type dopant, the energy range of the ion-implanted beryllium is 80 to 200 kiloelectronvolt; the dosage range of the ion-implanted beryllium is 5 x 10<15> to 1 x 10<17>ion/cm<2>; secondly, slow rate annealing: the slow rate annealing temperature is 600 to 900 DEG C; the constant temperature time is 40 to 60 minutes; fourthly, the thin film which is annealed through the step three is irradiated by laser and the second impurity activation process is operated to the thin film, the annealing temperature is1000 to 1050 DEG C, and the annealing time is 20 to40 minutes. The invention leads the electrical conductivity of the c-BN thin film with above 40 percent of the cubic phase content is increased by about hundred thousand times.

Description

The p type doping method of cubic boron nitride film

Technical field

The present invention relates to the p type method for manufacturing thin film of a kind of broad stopband, high rigidity semi-conducting material-cubic boron nitride (c-BN).This p N-type semiconductor N film will be used for high-power, high pressure resistant, high-frequency electron device, belong to the compound semiconductor materials field.

Background technology

Boron nitride (BN) belongs to third generation semi-conducting material, is the Wideband gap semiconductor material that grows up after first generation semi-conducting material (is representative with the silicon-based semiconductor) and second generation semi-conducting material (is representative with GaAs (GaAs) and indium phosphide (InP)).In the BN system, cubic boron nitride (c-BN) has very outstanding physics, chemistry, mechanical performance.Therefore, about its material preparation and characteristic research, and the exploration of device is various countries' researcher in recent years always, and such as U.S. G.E, IBM, the research topic of well-known semiconductor company common concerns such as Britain DeBeers.Hardness, the thermal conductivity of c-BN are only second to diamond; And its resistance to chemical corrosion and high temperature oxidation resistance obviously are better than diamond, and especially it has affinity with iron family element unlike diamond, is particularly suitable for iron group metal materials processing; Now, its machinery of the main focus utilization of the practicability of c-BN and mechanical property are widely used in the superhard coating of grinding tool, cutter, instrument, accurate window protective finish, lathe, space flight, fields such as military project.

C-BN has and now knows the wideest forbidden band (particle E _g≈ 6.4eV; Film E _g≈ 6.0eV), therefore very high light transmission rate can be arranged in very wide spectral region.It can realize that also n type and p type mix, so c-BN can prepare transparent under special environment, high temperature, high frequency, high-power, radioresistance short wavelength light electronic device.

The c-BN occurring in nature does not exist, and needs manually synthetic.Nineteen fifty-seven, the Wentorf of U.S. G.E company has synthesized the c-BN powder first with high temperature and high pressure method (HTHP).Yet, HTHP equipment requirements harshness, and can only prepare the c-BN particle, particle scale little (being up to the mm magnitude) and shape be malleable not, makes to use to be restricted.In 1979, the Sokolowski reported first used low pressure gas phase deposition to synthesize the c-BN film that has more application prospect.From then on, drawn back the prelude of intrinsic c-BN thin film study.

A kind of semi-conducting material realizes that the basis of device is p type and the n type conduction that realizes it, and will realize that device miniatureization must realize its filming.1987, people such as Osamu Mishima published an article on science, were reported in to adopt the HTHP method on the p type c-BN seed crystal, and in-situ doped extension has gone out n type c-BN particle.Yet nucleation, the growth conditions of low pressure gas phase deposition c-BN film are very harsh.If the employed in-situ doped method of directly transplanting HTHP method feeds original position impurity in its preparation process, can suppress the nucleation of BN cube of phase, be difficult to prepare simultaneously the BN film that contains cube phase.And, the activation energy of dopant in the c-BN film is 0.3～0.7eV (exceeding more than ten times than silicon), if adopt conventional semi-conducting material doping techniques, the impurity activation rate is very low, not obvious to the electric property improvement, promptly be difficult to realize the effective p type of c-BN film is mixed.

Summary of the invention

The problem that the present invention will overcome is: the c-BN film is difficult to realize that effective p type mixes.

In order to overcome the problems referred to above, the invention provides the specific technological process of a cover: comprise the vapor phase growth of c-BN intrinsic film, select of the ion implantation doping of metallic beryllium (Be) ion for use, at a slow speed with the quick hot activation technology that combines as p type dopant, can obtain p type c-BN film, its conductivity (～10 ^-5Ω ^-1Cm ^-1) than intrinsic film (～10 ^-11Ω ^-1Cm ^-1) increase 100,000 times.

Purpose of the present invention can realize by following techniqueflow:

(1) use low-pressure vapor phase film growth apparatus (for example rf magnetron sputtering, ion beam assisted depositing, electron cyclotron resonance chemical vapor deposition etc.) on substrate, to deposit one deck intrinsic c-BN film.

Described backing material can be monocrystalline polished silicon slice (Si), diamond thin, nickel sheet (Ni), titanium sheet (Ti), copper sheet (Cu), SiC, WC, TiN etc.

This layer intrinsic BN film: film thickness is 200～800nm; Cube phase content is 40～95%; Conductivity is 10 ^-11Ω ^-1Cm ^-1The order of magnitude on.

(2) the present invention selects for use metallic beryllium (Be) ion as p type dopant, and intrinsic c-BN film has been carried out ion implantation doping.Freely control two independent parameters: inject the energy and the dosage of beryllium ion, thus the degree of depth and the CONCENTRATION DISTRIBUTION of accurate controlled doping, and the good uniformity that mixes, repeatability is high, helps the large-scale production of thin film microelectronics and integrated circuit.

The energy range that the invention provides ion injection beryllium is 80～200 kilo electron volts (KeV).This parameter is determined by cube phase content and the thickness of film.

The dosage range that ion provided by the invention injects beryllium is 5 * 10 ¹⁵～1 * 10 ¹⁷Ion/cm ²

(3) the invention provides a kind of impurity activation technology of tube furnace slow annealing.Purpose is: make to be injected into Impurity Distribution homogenizing in the film; Make beryllium ion move to vacancy defect place in the lattice, and occupy by gap digit and to substitute the position, realize that the part of p type impurity activates; Repair implant damage, reduce fault of construction, improve the mobility of charge carrier rate; Improve crystallization degree, increase crystallite dimension, further improve film quality and electric property; Discharge membrane stress, increase the adhesiveness of film and substrate, help increasing thin-film device useful life.

Slow annealing temperature provided by the invention is 600～900 ℃; Constant temperature time is 40～60 minutes.

The slow annealing protective gas can use high purity inert gas (He, Ar etc.) (purity 99.999%) or high pure nitrogen (N2) (purity 99.999%).Annealing system vacuum degree is being extracted into below the 1Pa, is feeding protective gas, beginning to heat up, whole annealing process continues ventilation.

(4) will carry out laser irradiation secondary impurities activation technology again through the film of step (3).

Laser irradiation is risen film surface temperature rapidly.Annealing temperature is 1000～1050 ℃, and annealing time was 20～40 seconds.

Purpose is: further improved impurity activation efficient, significantly promoted film conductivity.

Compared with the prior art, the invention is characterized in: adopt the gas phase membrane growth technique to prepare intrinsic c-BN film earlier, the back is adopted ion to inject and is realized concentration and accurately controlled doping of the degree of depth; P type dopant adopts metallic beryllium; Two step process that adopted the quick irradiation secondary impurities of slow annealing and laser to activate make cube phase content increase nearly 100,000 times in the conductivity of the c-BN film more than 40%.

Embodiment

Further introduce the present invention with following example.

Example one

1. in radio frequency (13.56Hz) sputtering system, prepare intrinsic c-BN film.Sputtering system adopts high-purity h-BN (99.99%) hot pressing target of diameter 100mm.We are example with the most frequently used monocrystalline silicon piece of semicon industry, adopt n type polished silicon slice as substrate (resistivity 2～4 Ω cm, thickness is 0.3mm).Before deposition, substrate passes through toluene, acetone, ethanol respectively, 25% hydrofluoric acid solution and deionized water ultrasonic cleaning.System's forevacuum degree is 1.33 * 10 ^-3Below the Pa.The concrete growthing process parameter of this example film is listed in the table 1.

The parameter of table 1 radio frequency sputtering systems produce cubic boron nitride film

Prepared intrinsic c-BN film, its thickness is about 900nm, cube phase content 74%.Conductivity is 1.8 * 10 ^-11Ω ^-1Cm ^-1

2. the c-BN film for preparing is done ion and injected preceding conventional surface clean, put into ion implantor and do metallic beryllium injection doping.The injection energy is 200KeV, and implantation dosage is 1 * 10 ¹⁶Ion/cm ²

3. ion being injected the film sample finish puts into the tubular type annealing furnace and carries out nitrogen (N ₂) protection annealing.With mechanical pump tube furnace is extracted into below the 1Pa in vacuum, feeds high pure nitrogen (99.999%), begin to heat up, after 40 minutes, cool to room temperature in 800 ℃ of insulations of temperature naturally, whole process continues to lead in nitrogen.

4. make film temperature reach 1000 ℃ rapidly by laser irradiation, kept 30 seconds.

After adopting step 1,2,3,4, with vacuum vapour deposition at the film surface evaporation aluminium electrode of 2mm * 5mm, do 400 ℃ of alloyings (making aluminium electrode and c-BN film produce better ohmic contact) then.With the sheet resistance of KEITHLEY high resistant tester MEASUREMENTS OF THIN, the conductivity of having calculated film is 4.6 * 10 ^-5Ω ^-1Cm ^-1(resistivity than its intrinsic film has increased about 100,000 times).With n type silicon substrate tangible heterojunction rectification characteristic is arranged, successfully prepare p type c-BN film.

Example two

1. utilize vapour deposition to prepare intrinsic c-BN film, its thickness is about 450nm, cube phase content 40%.

Conductivity is 2 * 10 ^-11Ω ^-1Cm ^-1

2. after the c-BN film for preparing being done conventional surface clean, put into ion implantor and inject metallic beryllium.The injection energy is 100KeV, and implantation dosage is 5 * 10 ¹⁵Ion/cm ²

3. slow annealing.After 60 minutes, cool to room temperature in 900 ℃ of insulations of temperature naturally, omnidistance lasting logical high pure nitrogen protection.

4. make film temperature reach 1050 ℃ rapidly by laser irradiation, kept 20 seconds.Gained p type c-BN film conductivity is 1.2 * 10 ^-5Ω ^-1Cm ^-1

Example three

1. utilize vapour deposition to prepare intrinsic c-BN film, its thickness is about 200nm, cube phase content 95%.Conductivity is 1.3 * 10 ^-11Ω-1cm-1.

2. the injection energy that injects metallic beryllium is 80KeV, and implantation dosage is 1 * 10 ¹⁷Ion/cm ²

3. slow annealing.After 45 minutes, cool to room temperature in 600 ℃ of insulations of temperature naturally, omnidistance lasting logical protective gas high pure nitrogen.

4. make film temperature reach 1000 ℃ rapidly by laser irradiation, kept 40 seconds.Can obtain conductivity is 8.5 * 10 ^-5Ω ^-1Cm ^-1P type c-BN film.

Claims (1)

1, a kind of p type doping method of cubic boron nitride film is characterized in that, may further comprise the steps:

(1) use the low-pressure vapor phase film growth apparatus to deposit one deck intrinsic cubic boron nitride--c-BN film on substrate, this layer intrinsic c-BN film: film thickness is 200～800nm; Cube phase content is 40～95%; Conductivity is 10 ^-9～10 ^-11Ω ^-1Cm ^-1

(2) select for use the metallic beryllium ion as p type dopant, the energy range that ion injects beryllium is 80～200 kilo electron volts; The dosage range that ion injects beryllium is 5 * 10 ¹⁵～1 * 10 ¹⁷Ion/cm ²

(3 slow annealings: the slow annealing temperature is 600～900 ℃; Constant temperature time is 40～60 minutes;

(4) will carry out laser irradiation secondary impurities activation technology again through the film of step (3) annealing: annealing temperature is 1000～1050 ℃, and annealing time was 20～40 seconds.