CN101551324B - A semiconductor material property measurement device and method based on double probe beam - Google Patents
A semiconductor material property measurement device and method based on double probe beam Download PDFInfo
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- CN101551324B CN101551324B CN200910083565XA CN200910083565A CN101551324B CN 101551324 B CN101551324 B CN 101551324B CN 200910083565X A CN200910083565X A CN 200910083565XA CN 200910083565 A CN200910083565 A CN 200910083565A CN 101551324 B CN101551324 B CN 101551324B
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Abstract
The invention is a semiconductor material property measurement device and method based on double probe beam for measuring the characteristic parameters of semiconductor materials and monitoring the doping process. It obtains the free carrier absorption signal and the light-modulated reflecting signal simultaneously in the same set of test system based on the absorption of the exciting light of theperiodic intensity modulation by the semiconductor materials; it obtains the free carrier absorption signal and light-modulated reflecting signal of the frequency domain by changing the modulation fr equency of the exciting light; it obtains the free carrier absorption signal and light-modulated reflecting signal of the spatial domain by changing the spacing between the exciting light and the probe light; it may obtain the characteristic parameters of semiconductor materials and the process parameters as the doping concentration through the analysis and processing of the signals obtained or the comparison with the signal data of the calibration sample. The invention makes up for the shortcomings of the single technology and improves the measurement accuracy; it obtains two kinds of signalssimultaneously in one device and more important parameters of the semiconductor materials comparing with the single technology.
Description
Technical field
The invention belongs to the semiconductor material technical field of nondestructive testing, particularly unite free carrier absorption technique and optical modulation reflection technology, promptly the double probe beam Detection Techniques are determined semiconductor material property measurement device and measuring method.
Background technology
Semiconductor material is mixed, its structure and resistivity etc. are changed, semiconductor material just can become a kind of useful functional material.And the accurate monitoring of processing technologys such as the impurity concentration of mixing in the semiconductor material and annealing has been determined to a great extent the performance of semiconductor devices.In monitor procedure by to semiconductor material some characterisitic parameter measurements judge whether materials processing up to standard.Now semiconductor wafer sizes is increasing, if mix semi-conductive impurity concentration or relevant processing technology can not be up to standard, will cause decrease in yield.Therefore, the characterisitic parameter that can monitor doped semiconductor materials exactly is very important problem in the semiconductor fabrication.Along with dwindling of microelectronic component characteristic dimension, super shallow junction becomes inexorable trend.To super shallow junction, measure except needs the conventional parameters such as doping content, resistivity and carrier lifetime, the junction depth after also needing to measure it and mixing and the steepness of CONCENTRATION DISTRIBUTION, thereby need development to detect the measuring technique of its characteristic.
The classic method that is used for industrial measurement semiconductor material characteristic at present, as four-probe measurement, spreading resistance sonde method, ion microprobe and rutherford backscattering method etc., owing to there is certain shortcoming separately, its application is subjected to certain restriction: the four-probe measurement measuring accuracy is subjected to the restriction of probe size size, be mainly used in the monitoring of high-dopant concentration, can be used for measuring the material characteristics parameter in addition, but measure, have certain destructiveness for contact; The diffusion resistance law limitation is to need experienced operators, specimen preparation and test devastatingly; Ion microprobe is a kind of destructive measuring method in essence, and measurement needs the cost long time; Can only detection quality when rutherford backscattering is used to monitor doping content than the doping content of heavy ion.
Publication number is that the Chinese patent of CN1971868 is described the free carrier absorption measurement techniques, crosses the doping content that intensity takes place after the regions of carriers variation obtains sample by surveying transmittance.The charge carrier absorption signal is only relevant with the carrier density wave field in the free carrier absorption measurement techniques, and detection signal is with the doping content monotone variation.In addition, free carrier absorption technique also can be used for measuring semiconductor material electron transport characteristic parameter, has higher sensitivity when particularly measuring coefficient of diffusion.The optical modulation reflectometry technique then is by the absorption of sample to exciting light luminous energy, cause surveying the variation of luminous reflectivity, survey the intensity of reflected light that changes and to monitor the doping content of doped semiconductor (with reference to W.LeeSmith, Allan Rosencwaig, and David L.Willenborg, " Ion implant monitoring withthermal wave technology ", Appl.Phys.Lett.47,584-586 (1984)).The optical modulation reflectometry technique is the measuring accuracy height when to measure doping content be middle low dosage scope, but the optical modulation reflected signal is subjected to the double influence in temperature field and carrier density wave field in the semiconductor, and its signal amplitude value and doping content concern the right and wrong dullness when high-dopant concentration.Publication number is that the United States Patent (USP) of US7248367 has been described by the super shallow junction characteristic of optical modulation reflection technology sign, measures the junction depth and the steepness of super shallow junction.Sometimes on using, need simultaneously with these two kinds independently measuring method measure the characterisitic parameter of semiconductor material, measure if overlap independently measurement mechanism by two respectively, being difficult to guarantee to measure is to carry out on same position, and the cost of increase equipment.
Summary of the invention
Technology of the present invention is dealt with problems: overcome the deficiencies in the prior art, the semiconductor material property measurement device and the method for a kind of integrated free carrier absorption technique and optical modulation reflection technology are provided, to solve the problem that prior art exists, can in same measurement mechanism, obtain the free carrier absorption signal simultaneously and the optical modulation reflected signal is measured the semiconductor material doping content, remedy the optical modulation reflection technology and measure the nonmonotonic shortcoming of doping content; On the sample same point with two kinds independently method measure same parameter, improve to measure confidence level and precision.
Technical solution of the present invention: first aspect present invention relates to a kind of semiconductor material property measurement device based on double probe beam, comprises the exciting light source (1) that produces exciting light; Produce the optical modulation reflected signal and survey the probe source (2) of light; Produce the free carrier absorption signal and survey the probe source (3) of light; Be used to modulate the exciting light modulating system (4) of excitating light strength; Be used for automatic operation of control system and storage, processing signals data computing machine (5); Be used to reflect exciting light and make exciting light be radiated at sample surfaces and allow above-mentioned two first spectroscopes (7) of surveying transmittance to sample surfaces; Be used to change the position of first spectroscope (7) to change exciting light light beam and two precision displacement platforms (6) of surveying the light light beam in the spacing of sample surfaces; Be used to change two second spectroscope (8), the 3rd spectroscope (9) and the 4th spectroscopes (10) of surveying the light light path; The sample stage of fixed sample (11); Be used to survey the detector (12) of free carrier absorption signal and the detector (13) of detection optical modulation reflected signal; Be used for the digital storage oscilloscope of tracer signal or data collecting card (14), lock-in amplifier (15); Collect the condenser lens (16) of surveying free carrier absorption signal detecting light beam, the condenser lens (17) of collecting detection optical modulation reflected signal detecting light beam; Survey first optical filtering (18) and second optical filtering (19) of optical wavelength arrowband; Wherein the periodically variable exciting light of exciting light source (1) generation reflexes to the sample surfaces that places sample stage (11) through first spectroscope (7), sample causes sample to be energized the reflectivity generating period variation of rayed place because of the energy that absorbs exciting light produces periodically variable temperature field and carrier density wave field at illuminated place; The optical modulation reflected signal detection light that probe source (2) produces shines sample respectively and is energized on rayed place or the adjacent position behind the 4th spectroscope (10), the 3rd spectroscope (9), first spectroscope (7), the optical modulation reflected signal of reflection is surveyed light behind first spectroscope (7), the 3rd spectroscope (9), the 4th spectroscope (10), filter by second optical filtering (19) again, condenser lens (17) focuses on to be collected, and obtains the optical modulation reflected signal by detector (13) detection; In addition on the one hand, the free carrier absorption signal detection light that probe source (3) produces shines sample respectively and is energized on rayed place or the adjacent position behind second spectroscope (8), the 3rd spectroscope (9), first spectroscope (7), the excess carriers that free carrier absorption signal detection light is produced in the sample absorb the back and penetrate from the sample rear surface, filter through first optical filtering (18), condenser lens (16) focuses on to be collected, and obtains the free carrier absorption signal by detector (12) detection; The signal output port that is used to survey the detector (12) of free carrier absorption signal and surveys the detector (13) of optical modulation reflected signal is connected to the signal input port of lock-in amplifier (15) and the input port of digital storage oscilloscope or data collecting card (14), with the direct current amplitude of record free carrier absorption signal, exchange amplitude and optical modulation reflected signal the direct current amplitude, exchange amplitude; The signal output port of exciting light modulating system (4) is connected to the modulation input port of exciting light source (1), makes the excitation light intensity by periodic modulation; The synchronous signal output end mouth of exciting light modulating system (4) is connected to the reference signal input port of lock-in amplifier (15), to realize the collection of signal; Computing machine (5) is connected by PORT COM and digital storage oscilloscope or data collecting card (14), lock-in amplifier (15), automatically controlled precision displacement table (6), exciting light modulating system (4), realizes the automatic control of system and data acquisition and storage, processing.
Also can use two stand lock phase amplifiers (15) to write down the direct current amplitude of free carrier absorption signal, the direct current amplitude that exchanges amplitude and optical modulation reflected signal, interchange amplitude respectively in the described device.
The solid state laser of described exciting light source (1) employing continuous semiconductor laser instrument or diode pumping or gas laser are as light source; And the photon energy of the exciting light that described exciting light source (1) produces is greater than tested semi-conductive intrinsic semiconductor energy gap.
The excitation light intensity that described exciting light source (1) produces must be energized light modulation system (4) and periodically modulate, and produces modulated excitation light; The modulated excitation light intensity can pass through the drive current or the voltage of semiconductor laser modulation in modulating system (4) lining, or adopts acousto-optic modulator or electrooptic modulator or mechanical chopper modulation continuous laser beam to realize.
Described generation optical modulation reflected signal is surveyed the probe source (2) of light and is produced the free carrier absorption signal and surveys the probe source (3) of light and adopt the solid state laser of lower powered continuous semiconductor laser instrument or diode pumping or gas laser as light source, and the photon energy of probe source (3) light beam that wherein produces free carrier absorption signal detection light is less than tested semi-conductive intrinsic semiconductor energy gap.
The light beam of described exciting light source (1), free carrier absorption signal probe source (3) and optical modulation reflected signal probe source (2) outgoing adopts different lens focuss respectively or adopts diffusing lens of same colour killing or microcobjective to focus on testing sample surface or out-focus; Exciting light, free carrier absorption signal survey light and but the optical modulation reflected signal is surveyed light vertical incidence or the oblique sample surfaces that is mapped to; The free carrier absorption signal is surveyed light, optical modulation reflected signal detection light and exciting light in the sample surfaces coincidence or at a distance of in the scope of charge carrier diffusion length.
Described detector (13) employing photodiode detector or the photomultiplier tube detectors that is used to survey the detector (12) of free carrier absorption signal and surveys the optical modulation reflected signal.
At described detector (12) that is used to survey the free carrier absorption signal and detector (13) back, the preceding prime amplifier that adds of lock-in amplifier (15) of surveying the optical modulation reflected signal signal is amplified.
Described first spectroscope (7), second spectroscope (8), the 3rd spectroscope (9) and the 4th spectroscope (10) are placed with respect to incident light light 45 degree.
Described the 4th spectroscope (10) adopts the Transflective light splitting piece, or adopts polarization spectroscope; When adopting polarization spectroscope, need between the light path of the 3rd spectroscope (9) and the 4th spectroscope (10), add a quarter-wave plate of surveying optical wavelength corresponding to the optical modulation reflected signal.
In second aspect, provide a kind of semiconductor material characteristic measuring method of utilizing said apparatus based on double probe beam.This method may further comprise the steps:
(1) exciting light with free carrier absorption signal detection light, optical modulation reflected signal detection light and intensity periodic modulation shines the same or adjacent position of tested semiconductor samples simultaneously, sample produces periodically variable temperature field and carrier density wave field because of absorbing the exciting light energy at illuminated place, make the also generating period variation of illuminated place reflectivity; The optical modulation reflected signal is surveyed light and is gone back and form the optical modulation reflected signal through the periodically variable surface reflection of sample reflectivity; The free carrier absorption signal detection light of transmission forms the free carrier absorption signal because of the absorption of free carrier in the semiconductor material; Can record the interchange amplitude of two kinds of signals simultaneously by the lock-in amplifier demodulation; Can record the direct current amplitude of two kinds of signals simultaneously by digital storage oscilloscope or data collecting card;
(2) modulating frequency of change exciting light, the pairing output signal of each frequency when surveying the same spacing of light light beam that repeating step (1) obtains exciting light light beam and two, comprise the free carrier absorption signal the direct current amplitude, exchange amplitude and optical modulation reflected signal the direct current amplitude, exchange amplitude;
(3) change exciting light light beam and two spacings of surveying the light light beam that are radiated on the sample surfaces, pairing output signal when repeating step (1) obtains the different exciting lights of a certain fixed frequency and two detection light beam separations comprises the direct current amplitude of free carrier absorption signal, the direct current amplitude that exchanges amplitude and optical modulation reflected signal, interchange amplitude;
(4) measurement data that obtains of treatment step (2) and step (3), the data after utilizing data after the process of fitting treatment maybe will handle and the signal data of calibration sample relatively obtain a plurality of characterisitic parameters of testing sample, and detailed process is as follows:
A. when a certain semiconductor samples is measured, the frequency sweeping curve of its free carrier absorption signal and optical modulation reflected signal or position scanning curve all are unique, the signal curve that the sample of different qualities parameter, different processing conditionss is corresponding different, this character can be used for the measurement of material characteristic parameter and the monitoring of processing technology.The signal data of measuring gained signal and calibration sample is compared, can obtain parameters such as doping content, defect density, resistivity.
B. the free carrier absorption signal is relevant with the charge carrier field distribution of generation in the sample, charge carrier field distribution and different free carrier absorption signals that different carrier transport parameters is corresponding different.By the free carrier absorption signal frequency sweeping curve that measures or position scanning curve and correlation theory model are carried out match, the electron transport characteristic parameter of semiconductor material be can obtain, minority carrier lifetime, coefficient of diffusion, front and rear surfaces recombination velocity comprised.Wherein the position scanning result directly reflects the three-dimensional diffusion situation of charge carrier in semiconductor material, compares other metering system when it measures the charge carrier coefficient of diffusion and has higher degree of accuracy.
C. the optical modulation reflected signal except with sample in outside the Pass the charge carrier field that produces has, also relevant with the heat wave field, then by the frequency sweeping curve of optical modulation reflected signal or position scanning curve and correlation theory model are carried out match, except that can obtaining the carrier transport parameter, also can obtain the thermal parameters of sample, as thermal diffusion coefficient etc.But need the parameter of match many this moment, precise decreasing; The carrier transport parameter that b can be obtained is applied in the processing of optical modulation reflected signal as known quantity, and match obtains thermal parameters.
D. sample is annealed under different annealing conditions, the degree difference that its defective is repaired.Free carrier absorption signal and optical modulation reflected signal among the present invention are very sensitive to the concentration of defective, thereby the present invention can be used for monitoring the annealing grade of sample.Can characterize annealing grade by free carrier absorption signal and the optical modulation reflected signal of measuring testing sample.
E. apply the present invention to the detection of super shallow junction characteristic.The present invention measures the parameters such as the doping content of shallow junction or super shallow junction material, defect density, resistivity except utilizing described a, b, c, d scheme, also can measure two very important parameters of shallow junction or super shallow junction: junction depth and steepness.The optical modulation reflected signal is relatively more responsive to sample surfaces and inferior surface state, and then the optical modulation reflection technology is applicable to the sign of shallow junction or super shallow junction characterisitic parameter.Lock-in amplifier in device of the present invention (15) has four way of outputs, and promptly to exportable its in-phase component of same signal I, quadrature component Q, amplitude A mplitude and phase place Phase, the relation between them satisfies:
Phase＝arctan(Q/I)。The amplitude of optical modulation reflected signal is relatively more responsive to sample defects, if the most of defective in sample annealing back is repaired, measures sensitivity with amplitude signal and descends.And highly sensitive to the sample of anneal back and different junction depths, so characterize the junction depth that different ions is injected the sample of energy with Q component to the Q component of carrier density ripple sensitivity.Be specially the optical modulation reflected signal Q component value of measuring a certain sample, relatively can obtain the junction depth of sample again with the corresponding data of calibration sample.In addition, I and the Q component with the optical modulation reflected signal characterizes the steepness of mixing impurities concentration distribution.Measure exciting light and optical modulation reflection respectively and survey the light light beam is modulated reflected signal apart for the zero-sum certain distance time on sample I and Q component value, measured value is marked on 2 of the I-Q coordinate diagram, can utilize the steepness that characterizes the sample impurities concentration distribution by the slope of these 2 straight lines, because the corresponding different slope of different steepness.Be specially slope and the calibration sample signal corresponding data that to measure and compare, can obtain the steepness that the sample doping content distributes.
The semiconductor material property measurement device and the method for integrated free carrier absorption technique provided by the invention and optical modulation reflection technology have following advantage:
(1) the present invention's integrated free carrier absorption technique and optical modulation reflection technology in same set of measurement mechanism comes the doping content of measuring samples, compensation optical modulation reflection technology not high shortcoming of measuring accuracy when measuring low and higher-doped concentration range.
(2) the present invention obtains principle difference, non-interfering free carrier absorption signal and optical modulation reflected signal simultaneously and on the sample same position same (or same group) parameter (as doping content, resistivity etc.) is measured the confidence level and the precision that can improve measurement in same set of measurement mechanism.
(3) the present invention's integrated free carrier absorption technique and optical modulation reflection technology in same set of measurement mechanism can obtain how accurate semiconductor material characteristic parameter than monotechnics.
(4) the present invention carries out free carrier absorption signal and the optical modulation reflected signal that frequency or spatial domain are obtained in the scanning of frequency sweeping or position in same set of measuring system to sample.To different parameters to be measured, can select best scan mode or combination to obtain signal parameter is analyzed, improved measuring accuracy.
Description of drawings
Fig. 1 is the structured flowchart of measurement mechanism of the present invention;
Fig. 2 is the experiment detail drawing of the specific embodiment of the invention;
Among Fig. 1 and Fig. 2: exciting light source 1, probe source 2, probe source 3, exciting light modulating system 4, computing machine 5, automatically controlled precision displacement table 6, first spectroscope 7, second spectroscope 8, the 3rd spectroscope 9, the 4th spectroscope 10, specimen holder 11, survey the detector 12 of free carrier absorption signal, survey the detector 13 of optical modulation reflected signal, digital storage oscilloscope or data collecting card 14, lock-in amplifier 15, condenser lens 16, condenser lens 17, first optical filtering 18, second optical filtering 19, condenser lens 20, condenser lens 21, condenser lens 22, prime amplifier 23.
Fig. 3 is the graph of a relation of free carrier absorption signal among the present invention and dopant dose; Wherein the signal generator modulating frequency is 10KHz, and exciting light light beam and two detection light beam separations are zero; Horizontal ordinate is the dopant dose scope, and ordinate is the first harmonic amplitude of free carrier absorption signal and the ratio of direct current amplitude;
Fig. 4 is the graph of a relation of optical modulation reflected signal among the present invention and dopant dose; Wherein the signal generator modulating frequency is 10KHz, and exciting light light beam and two detection light beam separations are zero; Horizontal ordinate is the dopant dose scope, and ordinate is the first harmonic amplitude of optical modulation reflected signal and the ratio of direct current amplitude;
Fig. 5 is for recording the measurement result and the theoretical fitting result of the position scanning curve of free carrier absorption signal under different frequency of sample among the present invention, Fig. 5 a is an amplitude curve, and Fig. 5 b is a phase curve.
Embodiment
Can understand embodiment of the present invention more up hill and dale by following detailed, following description should be read in conjunction with the accompanying drawings.But, it should be noted that specific embodiment has only provided the measurement description of part semiconductor material characteristic parameter, but the present invention is not limited to this specific embodiment, can carry out various variations under the prerequisite that does not deviate from the spirit and scope of the present invention.
At first introduce a kind of semiconductor material property measurement device based on double probe beam provided by the invention, device comprises the exciting light source 1 that produces exciting light as shown in Figure 1; Produce the optical modulation reflected signal and survey the probe source 2 of light; Produce the free carrier absorption signal and survey the probe source 3 of light; Be used to modulate the exciting light modulating system 4 of excitating light strength; Be used for automatic operation of control system and storage, processing signals data computing machine 5; Be used to reflect exciting light and exciting light be radiated at sample surfaces and allow above-mentioned two first spectroscopes 7 of surveying transmittance to sample surfaces; Be used to change the position of first spectroscope 7 to change exciting light light beam and two automatically controlled precision displacement platforms 6 of surveying the light light beam in the spacing of sample surfaces; Be used to change two second spectroscope 8, the 3rd spectroscope 9, the 4th spectroscopes 10 of surveying the light light path; The specimen holder of fixed sample (or sample stage) 11; Survey the detector 12 of free carrier absorption signal and the detector 13 of detection optical modulation reflected signal; The digital storage oscilloscope of tracer signal or data collecting card 14 and lock-in amplifier 15; Collect the condenser lens 16 of surveying free carrier absorption signal detecting light beam, the condenser lens 17 of collecting detection optical modulation reflected signal detecting light beam; First optical filtering 18, second optical filtering 19.The 4th spectroscope 10 can adopt the Transflective light splitting piece in the device, or adopts polarization spectroscope; When adopting polarization spectroscope, need between the light path of the 3rd spectroscope 9 and the 4th spectroscope 10, add intensity and signal to noise ratio (S/N ratio) that a quarter-wave plate corresponding to optical modulation reflected signal detection optical wavelength increases the optical modulation reflected signal.The light beam of exciting light source 1, probe source 2 and probe source 3 outgoing adopts different lens focuss respectively or adopts diffusing lens of same colour killing or microcobjective to focus on testing sample surface or out-focus; Exciting light, free carrier absorption signal survey light and but the optical modulation reflected signal is surveyed light vertical incidence or the oblique sample surfaces that is mapped to.Adding prime amplifier before can and surveying detector 13 backs, lock-in amplifier 15 of optical modulation reflected signal at the detector 12 of surveying the free carrier absorption signal amplifies signal.Also can use two stand lock phase amplifiers to write down the amplitude that exchanges of free carrier absorption signal and optical modulation reflected signal respectively in the device.
Wherein the periodically variable exciting light of exciting light source 1 generation reflexes to the sample surfaces that places sample stage 11 through first spectroscope 7, sample causes sample to be energized the reflectivity generating period variation of rayed place because of the energy that absorbs exciting light produces periodically variable temperature field and carrier density wave field at illuminated place; The optical modulation reflected signal detection light that probe source 2 produces shines sample respectively and is energized on rayed place or the adjacent position behind the 4th spectroscope 10, the 3rd spectroscope 9, first spectroscope 7, the optical modulation reflected signal of reflection is surveyed light behind first spectroscope 7, the 3rd spectroscope 9, the 4th spectroscope 10, filter by second optical filtering 19 again, condenser lens 17 focuses on to be collected, and obtains the optical modulation reflected signal by detector 13 detections; In addition on the one hand, the free carrier absorption signal detection light that probe source 3 produces shines sample respectively and is energized on rayed place or the adjacent position behind second spectroscope 8, the 3rd spectroscope 9, first spectroscope 7, the excess carriers that free carrier absorption signal detection light is produced in the sample absorb the back and penetrate from the sample rear surface, filter through first optical filtering 18, condenser lens 16 focuses on to be collected, and obtains the free carrier absorption signal by detector 12 detections; The signal output port of detector 12 and detector 13 is connected to the signal input port of lock-in amplifier 15 and the input port of digital storage oscilloscope (or data collecting card) 14, exchanges amplitude and direct current amplitude with record free carrier absorption signal and optical modulation reflected signal; The signal output port of exciting light modulating system 4 is connected to the modulation input port of exciting light source 1, makes the excitation light intensity by periodic modulation; The synchronous signal output end mouth of exciting light modulating system 4 is connected to the reference signal input port of lock-in amplifier 15, to realize the collection of signal; Computing machine 5 is connected with digital storage oscilloscope (or data collecting card) 14, lock-in amplifier 15, automatically controlled precision displacement table 6, exciting light modulating system 4 by PORT COM, and utilizes relative program to realize the automatic control of system and data acquisition and storage, processing.
Introduce the experimental provision of the specific embodiment of the invention below in detail, device as shown in Figure 2.Exciting light source 1 employing wavelength is the semiconductor laser of 785nm (photon energy that this exciting light produces is 1.58eV, greater than the intrinsic energy gap 1.1eV of silicon) in the experiment, and its peak power output is 95mw; The function of exciting light modulating system 4 is realized that by function signal generator the driving voltage of the direct modulated laser of periodic square wave signal (or periodic signal of other waveform) that function signal generator 4 produces makes the exciting light of exciting light source 1 output intensity periodic modulation (periodic modulation of exciting light intensity also can drive acousto-optic modulator, electrooptic modulator or the continuous exciting light of mechanical chopper modulation by the cyclical signal of function signal generator output and realize); Probe source 2 and probe source 3 adopt continuous gas laser and semiconductor laser, and its wavelength is respectively 632.8nm, 1310nm, and its peak power output is respectively 15mw, 5mw; First spectroscope 7, second spectroscope 8, the 3rd spectroscope 9, the 4th spectroscope 10 relative incident ray 45 degree are placed in the experiment; The light reflectivity of 7 couples of 785nm of first spectroscope is 85%, and the light transmission of 1310nm and 632.8nm is respectively 70% and 80%; The light transmission of 9 couples of 1310nm of the 3rd spectroscope is 85%, is 80% to the light reflectivity of 632.8nm; Condenser lens 20 makes the exciting light light beam focus on the sample surfaces (but also out-focus); Condenser lens 21 and condenser lens 22 make the optical modulation reflected signal survey light and free carrier absorption signal respectively and survey the light light beam and focus on the sample surfaces (but also out-focus); The free carrier absorption signal is focused on by short focal length lens 16 and collects and surveyed by detector 12, and this detector is the InGaAs photodiode detector, and the detection wavelength coverage is 800-1700nm; The optical modulation reflected signal is focused on by short focus lens 17 and collects and surveyed by detector 13, and this detector is the Si photodiode detector, and the detection wavelength coverage is 200nm-1100nm; But prime amplifier 23 stopping direct currents and the interchange amplitude (if under the also very little situation of free carrier absorption signal, can be before detector 12 and detector 13 backs, lock-in amplifier 15 23 pairs of two signals of adding prime amplifier all amplify) of only amplifying the optical modulation reflected signal; Lock-in amplifier 15 maximum probe frequencies are 2MHz, only adopt a stand lock phase amplifier to write down the interchange amplitude (also can use two records respectively) of free carrier absorption signal and optical modulation reflected signal in this specific embodiment; First optical filtering 18 is the high pass optical filtering, less than 0.1%, is 76% to the light transmission rate of 1310nm to the light wave transmitance of wavelength 1000nm-1250nm, places before the detector 12; Second optical filtering 19 is the low pass filtered light microscopic, less than 0.1%, is 50% to the light transmission rate of 632.8nm to the light transmission rate of wavelength 780nm-1310nm, places before the detector 13.
Introducing the performing step based on the semiconductor material characteristic measuring method of the described measurement mechanism of specific embodiment below, is the using method of apparatus of the present invention simultaneously.Measurement mechanism of the present invention produces free carrier absorption signal and optical modulation reflected signal: with the free carrier absorption signal survey exciting light that light, optical modulation reflected signal surveys light and intensity periodic modulation simultaneously vertical irradiation to sample same or adjacent position (apart in the scope of charge carrier diffusion length), sample produces periodically variable temperature field and carrier density wave field because of absorbing the exciting light energy at illuminated place, make the also generating period variation of illuminated place reflectivity; The optical modulation reflected signal is surveyed light and is gone back and form the optical modulation reflected signal through the periodically variable surface reflection of sample reflectivity, and is detected device 13 and surveys; The free carrier absorption signal detection light of transmission forms the free carrier absorption signal because of the absorption of free carrier in the semiconductor material, and is detected device 12 detections; Can record the interchange amplitude of two kinds of signals simultaneously by lock-in amplifier 15 demodulation; Can record the direct current amplitude of two kinds of signals simultaneously by digital storage oscilloscope (or data collecting card) 14.Wherein the sample of choosing in the experiment here is a silicon chip, and its parameter hereinafter will be mentioned.
Measuring process:
1. sample is fixed on the specimen holder, successively opening signal generator 4, laser instrument 1,2 and 3, photodetector 12 and 13, prime amplifier 23, oscillograph 14, lock-in amplifier 15, and computing machine 5.
2. the position of condenser lens 17, the 4th spectroscope 10 and detector 13 is regulated in combination, makes the amplitude of the optical modulation reflected signal that detector 13 is exported reach maximum, and exciting light and optical modulation reflected signal are surveyed light and focused on the sample same point at this moment.
3. the position of condenser lens 18, second spectroscope 8 and detector 12 is regulated in combination, makes the amplitude of the free carrier absorption signal that detector 12 is exported reach maximum, and exciting light and free carrier absorption signal are surveyed light and focused on the sample same point at this moment.
4. constant excitation light and two survey light and are zero or are fixed as a certain separation delta d by after the moving of automatically controlled precision displacement table in spacing on the sample, repeatedly change the modulating frequency of exciting light by the exciting light modulating system, obtain the Δ d pairing free carrier absorption signal of each frequency S when constant
FCAWith optical modulation reflected signal S
MOR
5. change Δ d many times, repeating step 4 obtains the free carrier absorption signal S under the different spacing different modulating frequency
FCAWith optical modulation reflected signal S
MOR
Introduce measurement result of the present invention below:
(1) be the P type to parameter, crystal orientation＜100 〉, resistivity 15-25 Ω cm, thickness 550 μ m, the front surface polishing, surperficial autoxidation, the P ion doping is injected on the surface, and the injection energy is 100KeV, and the dopant dose scope is 1 * 10
10/ cm
2---1 * 10
16/ cm
2Silicon chip sample test; Obtain result as shown in Figures 2 and 3 respectively.
(2) be the P type to parameter, crystal orientation＜100 〉, resistivity 8-12 Ω cm, thickness 550 μ m, the front surface polishing, a sample of surperficial autoxidation is measured.Obtain the free carrier absorption signal S under the different frequency f different spacing Δ d this moment
FCA, signal is the function (is carrier lifetime, coefficient of diffusion, front surface recombination velocity for the carrier transport parameter at this) of f, Δ d and parameter to be measured.F and Δ d are known in measurement, can [correlation formula sees Zhang Xiren for details according to the correlation theory formula of signal, Li Bincheng, Liu Xianming. " modulation free carrier absorptiometry semiconductor carriers transports the cube theory of parameter ". Acta Physica Sinica, 57 (11), 7310 (2008)], the signal data that measures is carried out match, obtain parameter to be measured and (obtain diffusion coefficient D at this
*=15.1cm
2/ s, carrier lifetime τ=31.8 μ s and front surface recombination velocity s
1=3.51 * 10
3Cm/s).The theory signal data plot that Fig. 4 has provided the experimental signal data and calculated with fitting parameter, the figure mid point is an experimental result, solid line is a fitting result.
Outside the amplitude A mplitude and phase place Phase of the exportable signal of lock-in amplifier that is adopted in the specific embodiment of the invention, also the in-phase component I of exportable signal, quadrature component Q, the relation between them satisfies:
Phase＝arctan(Q/I)。If will realize disclosed by the invention when utilizing junction depth that the optical modulation reflection technology measures super shallow junction and steepness, can take following technical scheme: constant excitation light and two detection light separation delta d on sample are zero, change modulating frequency f, the I and the Q component value of optical modulation reflected signal under the different frequency when measuring Δ d and being zero; It is a certain distance (this distance is less than the diffusion length of charge carrier) that constant excitation light and two survey light separation delta d on sample, changes modulating frequency f, measurement Δ d be a certain apart from the time different frequency under the I and the Q component value of optical modulation reflected signal; Choose the Q component value of sample under f and Δ d best of breed, this value and the corresponding signal data of calibration sample relatively can be obtained the junction depth of sample.Under certain modulating frequency, I and Q component value when being recorded in Δ d respectively and being zero-sum another one value, and measured value is marked on 2 of the I-Q coordinate diagram, can utilize the steepness that characterizes the sample impurities concentration distribution by the slope of these 2 straight lines, because the corresponding different slope of different steepness.Be specially slope and the calibration sample signal corresponding data that to measure and compare, can obtain the steepness that the sample doping content distributes.
In this specific embodiment, only provide the technical scheme of measurement result, the super shallow junction junction depth of measurement and the steepness of carrier transport parameter and doping content; But for other parameters to be measured of energy measurement of the present invention, can be with reference to the method for operating of the foregoing description.There is any to it is to be noted, can selects best scan mode or combination to obtain signal parameter is analyzed, improve measuring accuracy different parameters to be measured.
The semiconductor material property measurement device of integrated free carrier absorption technique provided by the invention and optical modulation reflection technology and method are applicable to but are not limited to the monitoring of semiconductor epitaxial doping, ion injection, thermal treatment and pollution metal content.
Although only specify and described preferred embodiment here, be appreciated that, but under enlightenment of the present invention, can carry out multiple modification and distortion, and under the situation that does not break away from the spirit and scope of the present invention, it is all in the scope of claims of the present invention to the present invention.
Claims (11)
1. the semiconductor material property measurement device based on double probe beam is characterized in that comprising: the exciting light source (1) that produces exciting light; Produce the optical modulation reflected signal and survey the probe source (2) of light; Produce the free carrier absorption signal and survey the probe source (3) of light; Be used to modulate the exciting light modulating system (4) of excitating light strength; Be used for automatic operation of control system and storage, processing signals data computing machine (5); Be used to reflect exciting light and make exciting light be radiated at sample surfaces and allow above-mentioned two first spectroscopes (7) of surveying transmittance to sample surfaces; Be used to change the position of first spectroscope (7) to change exciting light light beam and two precision displacement platforms (6) of surveying the light light beam in the spacing of sample surfaces; Be used to change two second spectroscope (8), the 3rd spectroscope (9) and the 4th spectroscopes (10) of surveying the light light path; The sample stage of fixed sample (11); Be used to survey the detector (12) of free carrier absorption signal and the detector (13) of detection optical modulation reflected signal; Be used for the digital storage oscilloscope of tracer signal or data collecting card (14), lock-in amplifier (15); Collect the condenser lens (16) of surveying free carrier absorption signal detecting light beam, the condenser lens (17) of collecting detection optical modulation reflected signal detecting light beam; Survey first optical filtering (18) and second optical filtering (19) of optical wavelength arrowband;
Wherein the periodically variable exciting light of exciting light source (1) generation reflexes to the sample surfaces that places sample stage (11) through first spectroscope (7), sample causes sample to be energized the reflectivity generating period variation of rayed place because of the energy that absorbs exciting light produces periodically variable temperature field and carrier density wave field at illuminated place; The optical modulation reflected signal detection light that probe source (2) produces shines sample respectively and is energized on rayed place or the adjacent position behind the 4th spectroscope (10), the 3rd spectroscope (9), first spectroscope (7), the optical modulation reflected signal of reflection is surveyed light behind first spectroscope (7), the 3rd spectroscope (9), the 4th spectroscope (10), filter by second optical filtering (19) again, condenser lens (17) focuses on to be collected, and obtains the optical modulation reflected signal by detector (13) detection; In addition on the one hand, the free carrier absorption signal detection light that probe source (3) produces shines sample respectively and is energized on rayed place or the adjacent position behind second spectroscope (8), the 3rd spectroscope (9), first spectroscope (7), the excess carriers that free carrier absorption signal detection light is produced in the sample absorb the back and penetrate from the sample rear surface, filter through first optical filtering (18), condenser lens (16) focuses on to be collected, and obtains the free carrier absorption signal by detector (12) detection; The signal output port that is used to survey the detector (12) of free carrier absorption signal and surveys the detector (13) of optical modulation reflected signal is connected to the signal input port of lock-in amplifier (15) and the input port of digital storage oscilloscope or data collecting card (14), with the direct current amplitude of record free carrier absorption signal, exchange amplitude and optical modulation reflected signal the direct current amplitude, exchange amplitude; The signal output port of exciting light modulating system (4) is connected to the modulation input port of exciting light source (1), makes the excitation light intensity by periodic modulation; The synchronous signal output end mouth of exciting light modulating system (4) is connected to the reference signal input port of lock-in amplifier (15), to realize the collection of signal; Computing machine (5) is connected by PORT COM and digital storage oscilloscope or data collecting card (14), lock-in amplifier (15), automatically controlled precision displacement table (6), exciting light modulating system (4), realizes the automatic control of system and data acquisition and storage, processing.
2. the measurement mechanism of semiconductor material characteristic according to claim 1 is characterized in that: use two stand lock phase amplifiers (15) to write down the direct current amplitude of free carrier absorption signal, the direct current amplitude that exchanges amplitude and optical modulation reflected signal, interchange amplitude respectively in the described device.
3. the measurement mechanism of semiconductor material characteristic according to claim 1 and 2 is characterized in that: described exciting light source (1) adopts the solid state laser of continuous semiconductor laser instrument or diode pumping or gas laser as light source; And the photon energy of the exciting light that described exciting light source (1) produces is greater than tested semi-conductive intrinsic semiconductor energy gap.
4. the measurement mechanism of semiconductor material characteristic according to claim 1 and 2 is characterized in that: the excitation light intensity that described exciting light source (1) produces must be energized light modulation system (4) and periodically modulate, generation modulated excitation light; The modulated excitation light intensity can pass through the drive current or the voltage of semiconductor laser modulation in modulating system (4) lining, or adopts acousto-optic modulator or electrooptic modulator or mechanical chopper modulation continuous laser beam to realize.
5. the measurement mechanism of semiconductor material characteristic according to claim 1 and 2, it is characterized in that: described generation optical modulation reflected signal is surveyed the probe source (2) of light and is produced the free carrier absorption signal and surveys the probe source (3) of light and adopt the solid state laser of lower powered continuous semiconductor laser instrument or diode pumping or gas laser as light source, and the photon energy of probe source (3) light beam that wherein produces free carrier absorption signal detection light is less than tested semi-conductive intrinsic semiconductor energy gap.
6. the measurement mechanism of semiconductor material characteristic according to claim 1 and 2 is characterized in that: the light beam of described exciting light source (1), free carrier absorption signal probe source (3) and optical modulation reflected signal probe source (2) outgoing adopts different lens focuss respectively or adopts loose lens or microcobjective of same colour killing to focus on testing sample surface or out-focus; Exciting light, free carrier absorption signal survey light and but the optical modulation reflected signal is surveyed light vertical incidence or the oblique sample surfaces that is mapped to; The free carrier absorption signal is surveyed light, optical modulation reflected signal detection light and exciting light in the sample surfaces coincidence or at a distance of in the scope of charge carrier diffusion length.
7. the measurement mechanism of semiconductor material characteristic according to claim 1 and 2 is characterized in that: described detector (13) employing photodiode detector or the photomultiplier tube detectors that is used to survey the detector (12) of free carrier absorption signal and surveys the optical modulation reflected signal.
8. the measurement mechanism of semiconductor material characteristic according to claim 1 and 2 is characterized in that: at described detector (13) back, the preceding prime amplifier that adds of lock-in amplifier (15) that is used to survey the detector (12) of free carrier absorption signal and surveys the optical modulation reflected signal signal is amplified.
9. the measurement mechanism of semiconductor material characteristic according to claim 1 and 2 is characterized in that: described first spectroscope (7), second spectroscope (8), the 3rd spectroscope (9) and the 4th spectroscope (10) are placed with respect to incident light light 45 degree.
10. the measurement mechanism of semiconductor material characteristic according to claim 1 is characterized in that: described the 4th spectroscope (10) employing Transflective light splitting piece, or employing polarization spectroscope; When adopting polarization spectroscope, need between the light path of the 3rd spectroscope (9) and the 4th spectroscope (10), add a quarter-wave plate of surveying optical wavelength corresponding to the optical modulation reflected signal.
11. the semiconductor material characteristic measuring method based on double probe beam is characterized in that step is as follows:
(1) exciting light with free carrier absorption signal detection light, optical modulation reflected signal detection light and intensity periodic modulation shines the same or adjacent position of tested semiconductor samples simultaneously, sample produces periodically variable temperature field and carrier density wave field because of absorbing the exciting light energy at illuminated place, make the also generating period variation of illuminated place reflectivity; The optical modulation reflected signal is surveyed light and is gone back and form the optical modulation reflected signal through the periodically variable surface reflection of sample reflectivity; The free carrier absorption signal detection light of transmission forms the free carrier absorption signal because of the absorption of free carrier in the semiconductor material; Can record the interchange amplitude of two kinds of signals simultaneously by the lock-in amplifier demodulation; Can record the direct current amplitude of two kinds of signals simultaneously by digital storage oscilloscope or data collecting card;
(2) modulating frequency of change exciting light, the pairing output signal of each frequency when surveying the same spacing of light light beam that repeating step (1) obtains exciting light light beam and two, comprise the free carrier absorption signal the direct current amplitude, exchange amplitude and optical modulation reflected signal the direct current amplitude, exchange amplitude;
(3) change exciting light light beam and two spacings of surveying the light light beam that are radiated on the sample surfaces, pairing output signal when repeating step (1) obtains the different exciting lights of a certain fixed frequency and two detection light beam separations comprises the direct current amplitude of free carrier absorption signal, the direct current amplitude that exchanges amplitude and optical modulation reflected signal, interchange amplitude;
(4) measurement data that obtains of treatment step (2) and step (3); The data after utilizing data after the process of fitting treatment maybe will handle and the signal data of calibration sample relatively obtain a plurality of characterisitic parameters of testing sample, use lock-in amplifier to write down the amplitude that exchanges of free carrier absorption signal and optical modulation reflected signal respectively.
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| CN104697556B (en) * | 2015-02-28 | 2017-09-12 | 武汉联钧科技有限公司 | A kind of two waveband photoelectric sensor |
| CN105137125B (en) * | 2015-08-31 | 2018-11-13 | 电子科技大学 | A kind of double frequency multi-channel synchronous detection method for electricdomain imaging |
| US10712145B2 (en) * | 2016-10-20 | 2020-07-14 | Kla-Tencor Corporation | Hybrid metrology for patterned wafer characterization |
| CN108072613B (en) * | 2016-11-11 | 2020-09-08 | 台湾积体电路制造股份有限公司 | Optical detection device and detection method thereof |
| US10921369B2 (en) * | 2017-01-05 | 2021-02-16 | Xcalipr Corporation | High precision optical characterization of carrier transport properties in semiconductors |
| CN109239023B (en) * | 2018-08-28 | 2020-11-17 | 西安工业大学 | Semiconductor material characteristic measuring method based on free carrier absorption imaging |
| CN110646384B (en) * | 2019-09-24 | 2021-12-14 | 西安工业大学 | Semiconductor material resistivity optical measurement method |
| CN112799272B (en) * | 2019-11-13 | 2023-09-15 | 深圳光峰科技股份有限公司 | Display apparatus and control method thereof |
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