Method and system for broadband optical reflectance spectroscopy

Abstract

A photo-reflectance (PR) spectroscopy system and method are disclosed for independently accumulating "pump-on" and "pump-off" beams reflected from a sample. The system includes: (a) a probe source for generating a probe beam for measuring the spectral reflectance of the sample; (b) a pump source for generating a pump beam; (c) at least one spectrometer; (d) a first modulation device that allows the pump beam to alternately modulate the spectral reflectance of the sample such that the beams reflected from the sample are alternating "pump-on" and "pump-off" beams; (e) a second modulation device positioned in the path of the beams reflected from the sample to alternately direct the "pump-on" and "pump-off" beams to the at least one spectrometer; and (f) a computer.

Description

TECHNICAL FIELD

[0001] The present invention relates to semiconductor metrology techniques. More specifically, the present invention relates to semiconductor metrology techniques for measuring critical dimensions of semiconductor devices by optical instrumentation. BACKGROUND

[0002] The semiconductor manufacturing industry is continuously moving towards smaller device sizes in order to improve performance, energy efficiency and cost. Maintaining this trend requires more stringent and efficient process control, and thus metrology in terms of critical dimensions and material properties.

[0003] In this context, optical metrology methods stand out due to their non-destructive, non-contact mechanism, as well as high throughput and small measurement spot. In particular, spectroscopic methods such as Spectroscopic Reflectometry (SR) and Spectroscopic Ellipsometry (SE) are commonly used for dimensional metrology (OCD) and process control. By detecting the light reflected from the sample, information about the optical properties and thickness of thin films as well as dimensional parameters of complex patterned structures can be inferred. However, these methods are generally less sensitive to intrinsic material properties such as electrical parameters (e.g. carrier lifetime, mobility) and mechanical parameters (e.g. strain / stress). Other methods of measuring such properties tend to suffer from various drawbacks such as being destructive, requiring contact with the sample, long measurement times or too large measurement spots. It is therefore an object of the present invention to provide an apparatus and method for measuring light-induced changes in optical properties of a sample. A system and method that overcomes the above-mentioned drawbacks of existing systems and methods. SUMMARY

[0004] Modulated spectroscopy (MS) refers to a range of techniques in which a sample is perturbed from its nominal state in some way, and the change in the spectrum (rather than the spectrum itself) is measured as a response to this perturbation. Examples in this regard are thermal reflectometry, electrical / magnetic reflectometry with static electric / magnetic fields applied respectively, or photoreflectometry using a light field.

[0005] Since the spectral reflectivity of a material is closely related to electronic properties such as band structure, density of states, free carriers, etc., modulated spectroscopy (MS) is more sensitive to these properties than any other spectroscopic method. This can be of high value when electrical testing of semiconductor devices needs to be performed at an early stage of their manufacturing process, which is not possible with conventional electrical testing.

[0006] The present invention is directed to an apparatus and method for broadband photo-reflectance (PR) spectroscopy, i.e. for measuring light-induced changes in the optical properties of a sample. According to some embodiments of the present invention, the PR apparatus uses two light beams: a first probe beam for measuring the spectral reflectivity of the sample and a second pump beam for modulating the reflectivity. The PR measurement is AR / R, where R(ω) + AR(ω) and R(ω) are the spectral reflectivity with and without the pump beam, respectively.

[0007] In most cases, the value of AR / R is very small, on the order of 10 -5 -10 -4 The measurement of such a small change in reflectivity requires a signal-to-noise ratio (SNR) of ~10 -6 This is a challenge because of the presence of noise and spurious signal sources in standard spectroscopic systems.

[0008] The final performance and advantages of the PR apparatus and method of the present invention are described below.

[0009] According to the present invention, the main noise factors in the PR measurement are as follows:

[0010] • Shot noise: the shot noise in detecting N photons (or photoelectrons) is In PR, the signal of interest, AR, is the result of subtracting the two much stronger signals R and R + AR. The noise in each of these signals is uncorrelated and thus does not cancel out. Thus, if N photoelectrons are detected at the reflectivity R, the SNR becomes For example, to detect a PR signal where SNR = 10, a total of 2-10 12 photoelectrons (per pixel) need to be collected, amounting to μJ of visible light photoelectrons.

[0011] • "1 / f" noise, from the source, the detector, and the electronics. This type of noise is difficult to overcome because, as the name suggests, it is inversely proportional to the frequency, or linearly proportional to the acquisition time - which means that increasing the measurement time does not help to average it out (or, in other words, it contains long-term correlations).

[0012] A common mitigation for this is called lock-in detection (LID), i.e. modulating the pump beam at a sufficiently high frequency (typically on the order of hundreds of Hz) and passing the probe detector signal through a lock-in amplifier (LIA) that is locked to the pump modulation frequency, thus isolating frequencies close to the modulation frequency and rejecting the rest.

[0013] This works well, but the complex electronics make it suitable only for single-channel measurement systems. Acquiring a full spectrum in this way requires measuring each spectral component of the probe beam sequentially, typically by scanning a monochromator.

[0014] This approach greatly increases the measurement time compared to the multi-channel approach used in standard spectroscopic methods, e.g. by dispersing the collected probe beam onto a CCD or other multi-channel sensor and measuring all wavelengths in parallel.

[0015] • Quantization and readout noise are uncorrelated noise sources that occur with every CCD acquisition. If the modulation frequency is increased to better handle 1 / f noise, the amount of readout will increase proportionally, eventually making these noises dominate over shot noise.

[0016] As mentioned above, in order to overcome 1 / f noise, PR measurements require the use of modulated pumping with lock-in detection. Pump modulation can be achieved in one of several ways: by placing a modulation device (such as a mechanical chopper wheel, electro-optic or acousto-optic modulator) in the path of the pump laser beam, or by directly modulating the pump laser power.

[0017] If the probe is monochromatic (laser PR), it is relatively simple to use the available fast detectors and LIA electronics. However, optical reflectance (PR) spectroscopy is another matter - here the probe source is broadband, and the reflected light needs to be sampled at many different wavelengths to build up the PR spectrum. In general, there are two ways to do this:

[0018] - Use conventional lock-in detection (LID) as described above, the reflected probe beam must be passed through a monochromator and each wavelength measured sequentially. This means repeating the same measurement hundreds of times, making the throughput very low, unsuitable for industrial applications

[0019] - Use a spectrometer to disperse the probe beam onto a multi-channel detector (such as a CCD) and read out all wavelengths simultaneously, as is common in SE and SR. However, for optical reflectance (PR) spectroscopy, the small signal still requires some form of LID to overcome the noise, which is difficult to do on a pixel-by-pixel basis. The way this is achieved is to use a high-end CCD and electronics that can read out the spectrum at a high frame rate (synchronized to the pump modulation) and low noise. The data is then processed on a computer to mathematically achieve the same effect as the LIA, essentially applying a narrow bandpass filter around the pump modulation frequency to reject all other frequencies of noise. If the frames are perfectly aligned with the pump periods, this essentially amounts to accumulating all the "pump-off" frames and subtracting the result from the accumulated "pump-on" frames to obtain the PR signal δR(λ). However, the problem with this approach is that it requires complex and expensive sensors and electronics, which are likely to be custom-built. Accordingly, in accordance with some embodiments of the present invention, there is provided an improved apparatus and method for measuring light-induced changes in optical properties of a sample. More particularly, an apparatus and method that overcomes the above-mentioned limitations of existing devices and methods.

[0020] Thus, according to some embodiments of the application, there is provided a Photo-Reflectance (PR) spectroscopy apparatus for independently accumulating "on-pump" and "off-pump" beams reflected from a sample. The Photo-Reflectance (PR) spectroscopy apparatus comprises:

[0021] - a probe source for generating a probe beam for measuring the spectral reflectance of the sample;

[0022] - a pump source for generating a pump beam;

[0023] at least one spectrometer;

[0024] - a first modulation device for allowing the pump beam to alternately modulate the spectral reflectance of the sample so that the beams reflected from the sample are alternately "on-pump" and "off-pump" beams; and

[0025] - a second modulation device located in the path of the beams reflected from the sample for alternately directing the "on-pump" and "off-pump" beams to the at least one spectrometer;

[0026] wherein, if the Photo-Reflectance (PR) spectroscopy apparatus comprises a single spectrometer, the single spectrometer projects the "on-pump" beam onto at least one row on a CCD and the "off-pump" beam onto another row on the CCD so as to independently accumulate "on-pump" and "off-pump" signals, and wherein, if the Photo-Reflectance (PR) spectroscopy apparatus comprises a plurality of spectrometers, the second modulation device directs the "on-pump" beam to one spectrometer and the "off-pump" beam to another spectrometer so as to independently accumulate "on-pump" and "off-pump" signals.

[0027] Further, according to some embodiments of the application, the pump beam is attenuated via electronic, optical or electro-optical devices.

[0028] Further, according to some embodiments of the application, the first modulation device is either located in the path of the pump beam or directly modulates the pump source power.

[0029] Further, according to some embodiments of the application, the first modulation device and / or the second modulation device are selected from a mechanical chopper wheel, an electro-optical modulator or an acousto-optical modulator.

[0030] Further, according to some embodiments of the application, each of the first modulation device and the second modulation device is a synchronized chopper wheel controller or a deflection device.

[0031] Further, according to some embodiments of the application, if the second modulation device is a synchronous chopper wheel controller, the photo-reflectance (PR) spectroscopy apparatus further comprises a beamsplitter for splitting the light beam reflected from the sample into a "pump-on" light beam and a "pump-off" light beam.

[0032] Further, according to some embodiments of the application, the photo-reflectance (PR) spectroscopy apparatus further comprises an optical element for directing the "pump-on" light beam to the second modulation device.

[0033] Further, according to some embodiments of the application, the CCD of the single spectrometer is a multi-array sensor or a plurality of independent linear array sensors.

[0034] Further, according to some embodiments of the application, the multi-array sensor is a 2D sensor array.

[0035] Further, according to some embodiments of the application, the frame rate of the CCD is constrained by the full well capacity of the multi-array sensor or the plurality of independent linear array sensors.

[0036] Further, according to some embodiments of the application, there is provided a photo-reflectance (PR) spectroscopy system for measuring and calculating photo-induced changes in optical properties of a sample.

[0037] The photo-reflectance (PR) spectroscopy system comprises the photo-reflectance (PR) spectroscopy apparatus described above and a computer, wherein the photo-reflectance (PR) spectroscopy apparatus converts the "pump-on" light beam and the "pump-off" light beam into a "pump-on" signal and a "pump-off" signal and transmits the "pump-on" signal and the "pump-off" signal to the computer, which subtracts the "pump-on" signal corresponding to the spectrum (R) from the "pump-off" signal corresponding to the spectrum (R+AR) to obtain the PR signal AR.

[0038] Further, according to some embodiments of the application, there is provided a photo-reflectance (PR) spectroscopy method for measuring and calculating photo-induced changes in optical properties of a sample. The method comprises:

[0039] (a) providing the photo-reflectance (PR) spectroscopy system described above;

[0040] (b) converging the probe light beam and the pump light beam onto a single spot on the sample;

[0041] (c) alternatingly directing the pump light beam to the single spot on the sample using the first modulation device;

[0042] (d) continuously impinging the single spot by the probe light beam;

[0043] (e) the pump beam alternately impinges on the single spot to alternately modulate the reflectivity of the single spot on the sample, whereby the light beam reflected from the sample consists of "on" and "off" pump beams;

[0044] (f) using a second modulation device to direct the "on" and "off" pump beams to a single spectrometer or to multiple spectrometers;

[0045] (g) converting the "on" and "off" pump beams to "on" and "off" signals and transmitting the "on" and "off" signals to a computer; and

[0046] (h) subtracting the "on" signal corresponding to spectrum (R) from the "off" signal corresponding to spectrum (R+AR) to obtain the PR signal AR.

[0047] Further, according to some embodiments of the application, the method further comprises, in the case of a single spectrometer, projecting the "on" pump beam to at least one row on a CCD and projecting the "off" pump beam to another row on the CCD.

[0048] Further, according to some embodiments of the application, the method further comprises, in the case of multiple spectrometers, projecting the "on" pump beam to one spectrometer and projecting the "off" pump beam to another spectrometer, BRIEF DESCRIPTION OF DRAWINGS DETAILED DESCRIPTION

[0049] The present application provides new apparatuses and methods for broadband optical spectral reflectometry by utilizing high frequency lock-in detection readout by low frequency detectors.

[0050] Unlike the previous methods described above, which require complex and expensive sensors and electronics, likely custom-made, the apparatuses and methods of the present application allow PR measurements using off-the-shelf general-purpose hardware.

[0051] Figure 1 An optical reflectance (PR) spectroscopy apparatus 100 for measuring light-induced changes in optical properties of a sample, in accordance with some embodiments of the present application, is shown.

[0052] The optical reflectance (PR) spectroscopy apparatus 100 includes a probe source 102 and a pump source 104 for generating a probe beam 106 and a pump beam 108, respectively. The probe beam 106 is used for measuring the spectral reflectivity of a sample 110, while the pump beam 108 is used for modulating the reflectivity of the sample 110. The pump beam 108 can be attenuated electronically or via appropriate attenuating optical filters (e.g., can be mechanically moved in / out of the optical path of the pump beam) and / or based on electro-optical devices, etc.

[0053] The photo-reflectance (PR) spectroscopy apparatus 100 also includes two modulation devices, a first modulation device in the path of the pump beam 108 (or directly modulating the pump power), a second modulation device in the path of the probe beam 107 reflected from the sample 110; a beamsplitter 112; optical elements, such as mirrors 114, for directing the light beams 124 to the desired directions; and a spectrometer 116 consisting of a charge-coupled device (CCD) 126, which can include a 2D spectral resolution sensor array and readout circuitry.

[0054] According to some embodiments of the present application, when light enters the spectrometer 116, it is projected by the spectrometer optical elements onto a spectral resolution sensor array, for example onto the CCD 126, which converts the incident spectrum into an electrical signal.

[0055] According to some embodiments of the present application, the CCD 126 can be a single multi-dimensional sensor array or a plurality of one-dimensional sensor arrays.

[0056] According to some embodiments of the present application, the first and second modulation devices can be selected from a mechanical chopper wheel, an electro-optical modulator, an acousto-optical modulator, and the like. Here, as shown in the figure, the first and second modulation devices are a first synchronous chopper wheel controller 118 and a second synchronous chopper wheel controller 120.

[0057] The first synchronous chopper wheel controller 118 alternately directs (transmits) the pump beam 108 to the sample 110, for example, the pump beam 108 is alternately transmitted through a non-occluded channel, for example channel 122, so as to alternately reach the sample 110.

[0058] Thus, according to some embodiments of the present application, there are two measurement modes, one when the pump beam 108 reaches the sample 110 and the other when the pump beam 108 is blocked.

[0059] When the pump beam 108 reaches the sample 110, the light beam 107 reflected from the sample 110 is a "pump-on" beam, and when the pump beam 108 is blocked, the light beam 107 reflected from the sample 110 is a "pump-off" beam.

[0060] Due to the use of the "pump-on" beam and the "pump-off" beam, there is no need to synchronize the CCD readout with the pump, and it is possible to accumulate multiple modulation periods without any readout.

[0061] The second synchronous chopper wheel controller 120 switching element in the collection channel is used to alternately direct the light beam 107 collected from the sample 110, for example the "pump-on" beam and the "pump-off" beam, to the spectrometer 116.

[0062] According to some embodiments of the application, the light beam 107 collected from the sample 110 is split into a "pump off' output light beam 124A and a "pump on' output light beam 124B via a beamsplitter, such as a 50:50 beamsplitter 112, before reaching the second synchronous chopper wheel controller 120.

[0063] As shown, the mirror 114 redirects the "pump on' output light beam 124B to the spectrometer 116.

[0064] According to some embodiments of the application, the spectrometer 116 projects the "pump off' output light beam 124A and the "pump on' output light beam 124B onto different rows on the CCD 126, for example, row 126A and row 126B.

[0065] According to some embodiments of the application, since the spectrometer optical elements project the "pump off' output light beam 124A and the "pump on' output light beam 124B onto different rows on the CCD 126, the frame rate is not limited by the modulation frequency, for example, the frequency at which the "pump on' state becomes the "pump off' state, and vice versa. Instead, the frame rate is limited only by the full well capacity of the CCD 126, and thus, PR measurements can be made using off-the-shelf hardware.

[0066] Figure 2 An example of a CCD illumination 200 is shown, according to some embodiments of the application.

[0067] As shown, in a conventional spectroscopic measurement, the CCD line (line 202) is vertically integrated to produce a single spectrum 204, which is transmitted to a computer.

[0068] It should be noted that the spectrometer acquisition electronics typically integrate the CCD pixels by row into Figure 2 a single accumulated spectrum 204, as shown. However, a multi-region mode is a common feature in these systems, which allows for easy definition of multiple regions to perform this integration and readout. Once this is done, it is easy to subtract the two spectra to produce the PR signal, for example, the spectrum (R+AR) 125A produced via the first modulated output light beam 124A minus the spectrum (R) 125B produced via the second modulated output light beam 124B to produce AR.

[0069] It should be noted that, although the final signal read out from the CCD 126 is done at low frequency, any low frequency noise or drift that affects the measurement will be removed by this method. More specifically, since the switching of the "pump on' and "pump off' signals occurs at high frequency, this slow variation will have the same effect on both signals and will be cancelled out upon subtraction of the signals.

[0070] It should be noted that a disadvantage of this method is that at any given time, 50% of the light is lost in the shading channel (e.g., shading channel 121), however, no loss occurs when the beam is transmitted through the non-shading channel (e.g., non-shading channel 122).

[0071] To overcome this drawback, for example, to avoid a 50% loss of light, an alternative light reflection (PR) spectral device 300 is described below.

[0072] Figure 3 An alternative light reflectance (PR) spectroscopic apparatus 300 for measuring light-induced changes in the optical properties of a sample, according to some embodiments of the present invention, is shown.

[0073] As shown in the figure, the optical reflection (PR) spectral device 300 includes a detector source 302 and a pump source 304 for generating a detector beam 306 and a pump beam 308, respectively. The pump beam 308 can be attenuated electronically or by means of an appropriate attenuating optical filter (e.g., an optical path that can be moved in / out of the pump beam) and / or based on an electro-optic device.

[0074] The optical reflection (PR) spectrometer 300 also includes two modulation devices, a first modulation device located in the path of the pump beam 308 (or directly modulating the pump power), and a second modulation device located in the path of the probe beam 307 reflected from the sample 310; and a spectrometer 316.

[0075] The spectrometer 316 consists of a charge-coupled device (CCD) 326, which may include a 2D spectral resolution sensor array and readout circuitry.

[0076] Here, the modulation device may include a synchronous chopper controller 318 and a deflector 320.

[0077] Deflector 320 replacement Figure 1 The second synchronous chopper controller 120, beam splitter 112, and reflector 114 of the light reflection (PR) spectrometer 100 alternately guide the light collected from the sample 310 to the spectrometer 316.

[0078] According to some embodiments of the present invention, the function of the synchronous chopper controller 318 is similar to... Figure 1 The first synchronous chopper controller 118 has the same function because it alternately guides the pump beam 308 to the sample 310. For example, the pump beam 308 is transmitted alternately through an unshielded channel (such as channel 322), and thus arrives at the sample 310 alternately. Therefore, when the pump beam 308 arrives at the sample 310, the beam 107 reflected from the sample 110 is a "pump-on" beam, and when the pump beam 308 is blocked, the beam 107 reflected from the sample 110 is a "pump-off" beam.

[0079] Since "pump-on" and "pump-off" beams are used, there is no need to synchronize the CCD readout with the pump source 304 and multiple modulation cycles can be accumulated without any readout.

[0080] According to some embodiments of the application, the deflector 320 switches the element in the collection channel that alternately directs the "pump-on" beam 324B and the "pump-off" beam 324A to the spectrometer 316. The deflector 320 periodically deflects the beams to the desired position on the spectrometer entrance slit, for example, by an acousto-optic deflector (AOD), a MEMS mirror, etc.

[0081] As shown, the deflector 320 directs the "pump-off" output beam 324A and the "pump-on" output beam 324B to the desired position on the spectrometer entrance slit, and the spectrometer optical elements project the "pump-off" output beam 324A and the "pump-on" output beam 324B onto different rows on the CCD 326, for example, row 326A and row 326B.

[0082] Thus, like in the photo-reflectance (PR) spectroscopy apparatus 100 of Figure 1 In the alternative photo-reflectance (PR) spectroscopy apparatus 300, the frame rate is only constrained by the full well capacity of the CCD, and not by the modulation frequency, allowing for PR measurements using off-the-shelf hardware.

[0083] According to some embodiments of the application, the spectral acquisition can be implemented in several ways, for example, as described using multiple arrays such as 2D sensor arrays, but also using two independent linear sensor arrays. The high full well capacity and frame rate that are more easily achieved in linear sensor arrays are advantageous compared to 2D sensor arrays.

[0084] The 2D sensor array and readout circuit 326 can comprise multiple single array CCDs or one 2D CCD. Thus, the deflector 320 alternately directs the collected light to different areas of the multiple CCDs or the one 2D CCD, so that the "pump-on" and "pump-off" signals are independently accumulated. In this way, there is no need to synchronize the CCD readout with the pump, and multiple modulation cycles can be accumulated without any readout.

[0085] Figure 4 is a dual-spectrometer photo-reflectance (PR) spectroscopy apparatus 400 for measuring light-induced changes in the optical properties of a sample, according to some embodiments of the application.

[0086] The photo-reflectance (PR) spectroscopy apparatus 400 is basically the photo-reflectance (PR) spectroscopy apparatus 300 of Figure 3 with an additional spectrometer.

[0087] As shown, the photo-reflectance (PR) spectroscopy apparatus 400 includes a probe source 402 and a pump source 404 for generating a probe beam 406 and a pump beam 408, respectively. The pump beam 408 can be attenuated electronically or by a suitable attenuating optical filter (e.g., movable in / out of the optical path of the pump beam) and / or based on electro-optical devices.

[0088] The photo-reflectance (PR) spectroscopy apparatus 400 also includes two modulation devices, a first modulation device in the path of the pump beam 408 (or directly modulating the pump power) and a second modulation device in the path of the probe beam 407 reflected from the sample 410; and two spectrometers, a spectrometer 426A and a spectrometer 426B.

[0089] The modulation devices can be a synchronized chopper wheel controller 418 for modulating the pump beam 408 and a deflector 420 for alternately directing light collected from the sample 410 (e.g., a "pump-off" beam 424A and a "pump-on" beam 424B) to the spectrometer 426A and the spectrometer 426B (or different regions of a single 2D CCD), respectively.

[0090] According to some embodiments of the present application, each of the synchronized chopper wheel controller 418 and the deflector 420 can have multiple "intermediate" (or "continuous" transmission change) states / modes, e.g., fully opaque, partially opaque / reflective, and fully transparent. In this case, in addition to the "pump-on" and "pump-off" beams, an attenuated pump beam mode can also be performed within the same measurement phase.

[0091] Unlike the photo-reflectance (PR) spectroscopy apparatus of Figure 1 and Figure 3 , the photo-reflectance (PR) spectroscopy apparatus of Figure 1 and Figure 3 includes a single spectrometer, and thus, the "pump-on" and "pump-off" beams are alternately directed onto the single spectrometer and projected onto different rows of a single CCD via the spectrometer optical elements. Here, the "pump-off" output beam 424A and the "pump-on" output beam 424B are directed onto two different spectrometers, i.e., the spectrometer 426A and the spectrometer 426B. In this way, the apparatus is simpler and more convenient to use since there is no need to separate the "pump-off" signal and the "pump-on" signal onto different rows of a single CCD. Spectra can be retrieved from the two CCDs, e.g., a spectrum (R+AR) 430A generated via the "pump-off" output beam 424A can be retrieved from the CCD 428A and a spectrum (R) 430B generated via the "pump-on" output beam 424B can be retrieved from the CCD 428B. Once this is done, the spectrum (R) 430B can be subtracted from the spectrum (R+AR) 430A to generate the PR signal AR.

[0092] According to some embodiments, the photo-reflectance (PR) spectroscopy system can include the photo-reflectance (PR) spectroscopy device 100, the photo-reflectance (PR) spectroscopy device 300, or the photo-reflectance (PR) spectroscopy device 400 and a computer.

[0093] The photo-reflectance (PR) spectroscopy device 100, 300, 400 converts the "pump-on" light beam and the "pump-off" light beam into the "pump-on" signal and the "pump-off" signal, and transmits the "pump-on" signal and the "pump-off" signal to the computer, which subtracts the "pump-on" signal corresponding to the spectrum (R) from the "pump-off" signal corresponding to the spectrum (R+AR) to obtain the PR signal AR.

[0094] Figure 5 A method 500 for measuring photo-induced changes in optical properties of a sample according to some embodiments of the present application is shown.

[0095] The method 500 includes the following steps:

[0096] Step 502: providing the photo-reflectance (PR) spectroscopy system described above Figure 1 、 Figure 3 or Figure 4 a photo-reflectance (PR) spectroscopy system;

[0097] Step 504: converging the probe light beam 106, 306, 406 and the pump light beam 108, 308, 408 onto a single point on the sample 110, 310, 410;

[0098] Step 506: alternately directing the pump light beam 108, 308, 408 onto the single point on the sample 110, 310, 410 using the first modulation device;

[0099] Step 508: continuously impinging the single point on the sample 110, 310, 410 via the probe light beam 106, 306, 406;

[0100] Step 510: alternately impinging the single point on the sample 110, 310, 410 via the pump light beam 108, 308, 408 to alternately modulate the reflectivity of the single point on the sample 110, 310, 410 so that the light beam 107, 307, 407 reflected from the sample 110, 310, 410 is a "pump-on" light beam when the pump light beam 108, 308, 408 reaches the sample 110, 310, 410, and is a "pump-off" light beam when the pump light beam 108, 308, 408 is blocked.

[0101] Step 512: when using the system of Figure 3 or Figure 1When using a system of the type shown in FIG. 4, the "pump on" and "pump off" beams are directed to a single spectrometer 116, 316 using a second modulating device in the collection channel. In the single spectrometer, the "pump on" beam is projected onto at least one row on the CCD and the "pump off" beam is projected onto another row on the CCD.

[0102] Alternatively, when using a system of the type shown in FIG. 5, the "pump on" beam is directed to one spectrometer 426B and the "pump off" beam is directed to another spectrometer 426A. Figure 4

[0103] Step 514: converting the "pump on" and "pump off" beams into "pump on" and "pump off" signals and transmitting the "pump on" and "pump off" signals to a computer; and

[0104] Step 516: subtracting the "pump on" signal (e.g., the spectrum (R) generated via the "pump on" output beam) from the "pump off" signal (e.g., the spectrum (R+AR) generated via the "pump off" output beam) to obtain the PR signal AR.​

Claims

1. A light reflection (PR) spectral device for independently accumulating "pump-on" and "pump-off" beams reflected from a sample, comprising: (a) A detection source for generating a probe beam, the probe beam being used to measure the spectral reflectance of a sample; (b) A pump source used to generate a pump beam; (c) At least one spectrometer; (d) A first modulation device that allows the pump beam to alternately modulate the spectral reflectivity of the sample, such that the beam reflected from the sample alternately consists of a "pump-on" beam and a "pump-off" beam; and (e) A second modulation device, located in the path of the beam reflected from the sample, for alternately directing the "pump-on" beam and the "pump-off" beam to the at least one spectrometer; Where the light reflection (PR) spectral device includes a single spectrometer, the single spectrometer projects the "pump-on" beam onto at least one row of the CCD and the "pump-off" beam onto another row of the CCD, such that the "pump-on" signal and the "pump-off" signal are accumulated independently, and In the case where the light reflection (PR) spectral device includes multiple spectrometers, the second modulation device directs the "pump-on" beam to one spectrometer and the "pump-off" beam to another spectrometer, thereby independently accumulating the "pump-on" signal and the "pump-off" signal. Each of the first modulation device and the second modulation device is a synchronous chopper controller or a deflection device. In the case where the second modulation device is a synchronous chopper controller, the optical reflection (PR) spectral device further includes a beam splitter for splitting the light beam reflected from the sample into a "pump-through beam" and a "pump-off beam".

2. The optical reflection (PR) spectrometer according to claim 1, wherein, The pump beam is attenuated by electronic, optical, or electro-optical devices.

3. The optical reflection (PR) spectrometer according to claim 1, wherein, The first modulation device modulates the power of the pump source either in the path of the pump beam or directly.

4. The light reflection (PR) spectral device according to claim 1, further comprising optical elements for guiding the "pump-through" beam to the second modulation device.

5. The optical reflectance (PR) spectrometer according to claim 1, wherein, The CCD of the single spectrometer is a multi-array sensor or multiple independent linear array sensors.

6. The optical reflection (PR) spectrometer according to claim 5, wherein, The multi-array sensor is a 2D sensor array.

7. The optical reflection (PR) spectrometer according to claim 5, wherein, The frame rate of the CCD is limited by the full well capacity of the multi-array sensor or the multiple independent linear array sensors.

8. A light reflectance (PR) spectral system for measuring and calculating light-induced changes in the optical properties of a sample, comprising: According to any one of claims 1 to 7, the optical reflection (PR) spectral device and the computer, wherein the optical reflection (PR) spectral device converts the "pump-on" beam and the "pump-off" beam into a "pump-on" signal and a "pump-off" signal, and transmits the "pump-on" signal and the "pump-off" signal to the computer, and the computer subtracts the "pump-on" signal corresponding to the spectrum R from the "pump-off" signal corresponding to the spectrum R+ΔR to obtain the optical reflection PR signal ΔR.

9. A light reflectance (PR) spectral method for measuring and calculating light-induced changes in the optical properties of a sample, comprising: (i) Providing a light reflection (PR) spectral system according to claim 8; (j) Converging the probe beam and pump beam onto a single point on the sample; (k) Using a first modulation device, the pump beam is alternately directed to the individual point on the sample; (l) The single point is continuously struck by the probe beam; (m) The pump beam alternately strikes the individual point to alternately modulate the reflectivity of the individual point on the sample, such that the beam reflected from the sample includes a "pump-on" beam and a "pump-off" beam; (n) Using a second modulation device, the "pump-on" beam and the "pump-off" beam are directed to a single spectrometer or multiple spectrometers; (o) Converting the "pump-on" beam and the "pump-off" beam into "pump-on" signals and "pump-off" signals, and transmitting the "pump-on" signals and "pump-off" signals to a computer; and (p) Subtract the "pump on" signal corresponding to spectrum R from the "pump off" signal corresponding to spectrum R+ΔR to obtain the light reflection PR signal ΔR.

10. The optical reflectance (PR) spectroscopy method according to claim 9, wherein, In the case of a single spectrometer, the "pump-through" beam is projected onto at least one row of the CCD and the "pump-off" beam is projected onto another row of the CCD.

11. The optical reflectance (PR) spectroscopy method according to claim 9, wherein, In the case of multiple spectrometers, the "pump-on" beam is projected onto one spectrometer and the "pump-off" beam is projected onto another spectrometer.

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