Measurement device and measurement method

Abstract

To provide a measurement device capable of improving a strength of a detection signal of a weak secondary harmonic wave.SOLUTION: A measurement device 100 comprises: a light source 101 that injects a basic wave as a pulse laser of a predetermined wavelength; a secondary harmonic wave generator 103 that converts one part of the basic wave into a first secondary harmonic wave having an almost half of the predetermined wavelength; a birefringent crystal 105 that separates the first secondary harmonic wave to the basic wave in an angle; a wavelength selection element 108 that blocks a light of the basic wave, and transmits the first secondary harmonic wave and a second secondary harmonic wave generated by irradiating the basic wave to an objective front surface; a polarizer 111 that polarizes the first secondary harmonic wave and the second secondary harmonic wave as a same polarization; an image detector 112 that converts the first secondary harmonic wave and the second secondary harmonic wave that are entered at a different angle each other into an electric signal; and a processing device that calculates a strength of the second secondary harmonic wave from an amplitude of an interference pattern generated on the image detector.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a measuring device and a measuring method.

Background Art

[0002] In the field of semiconductor device manufacturing, until about 20 years ago, miniaturization of circuit patterns was the only axis of evolution, and in addition to improving drive speed and reducing power consumption, cost reduction could also be achieved simultaneously by miniaturization. However, the technical difficulty of miniaturization has increased, and in addition to the three-dimensional structuring of devices, the introduction of new materials such as High-K / Low-K, and the improvement of electron mobility by intentionally adding strain, the contribution of performance improvement by controlling physical properties has been particularly increasing in recent years. Due to these factors, high-precision and high-throughput physical property measurement has become indispensable in both process construction in research and development and yield improvement during mass production. For example, there are measurements such as the amount and spatial distribution of dopants in the ion implantation process, the reactivation state after annealing, and the amount of internal strain in the selective epitaxial growth process of SiGe.

[0003] However, these cannot be evaluated by physical measurement devices such as OCD (Optical Critical Dimension) or CD-SEM (Critical Dimension Scanning Electron Microscope). Also, although chemical measurement methods using fluorescent X-rays or mass spectrometry have a certain level of accuracy, they are difficult to handle in terms of throughput and often involve destructive testing. On the other hand, as an alternative approach, electrical property inspection includes the inspection of transistors with a MOS (Metal-Oxide-Silicon) structure, which is a basic component, and electrical property evaluation such as C-V characteristics is performed by electrically connecting probes. These are direct performance evaluations of semiconductor devices, and LADA (Laser-assisted device alteration) and OBIRCH (Optical Beam Induced Resistance CHange), etc., by irradiating light, can not only confirm defects but also identify the margin against defects and the location within a high-resistance device. However, since all of these are contact measurements, they are impossible to perform in semiconductor post-processes where wiring layers and pads are formed. If these electrical property evaluations can be non-contact confirmed in the semiconductor pre-process and the spread of depletion layers and inversion regions formed inside the semiconductor can be accurately analyzed from the results, it will be possible to quickly provide feedback to processes such as ion implantation and annealing, which is very effective in shortening the development period and manufacturing cycle time. However, there is still no established measurement technology that meets this need.

[0004] One of the possible non-contact electrical property measurement techniques is inspection using second harmonic generation due to the nonlinear optical properties of the object to be measured. Nonlinear optical properties are represented by the product of susceptibility and electric field. The susceptibility can be determined from the intensity of the second harmonic, and the band structure within the material can be obtained from each element of the susceptibility tensor. The main materials used as semiconductor substrates such as silicon have a crystal structure with inversion symmetry, and second harmonic generation does not usually occur in the bulk state. However, Bloembergen et al. conducted a theoretical study of second harmonic generation due to symmetry breaking at the material interface in Non-Patent Document 1, and with the subsequent development of pulsed lasers, it has become possible to evaluate it quantitatively and experimentally. Also, Guidotti et al. experimentally evaluated the generation of second harmonics on the silicon surface with an inversion symmetric structure in Non-Patent Document 2. In Patent Document 1, there is a proposal for a measurement method using second harmonics for the progress of the process in a semiconductor process apparatus. In Patent Document 2, there is a proposal for a method of evaluating the presence of contaminants on the semiconductor substrate surface by observing the second harmonics and sum frequencies generated under illumination of multiple wavelengths. Also, in Patent Document 3, a screening method using photoelectrons generated by illumination and charging, a process in which second harmonics change over time, and an analysis method for the band structure using the measurement results are proposed. In Patent Document 4, there is a proposal for a method of detecting defects that are insensitive to the fundamental wave by observing both the fundamental wave and the second harmonic in a semiconductor inspection apparatus.

[0005] In semiconductor manufacturing, there have been several important technological advancements. However, what has become more practical is that Viktor Koldiaev et al. invented a technique in Patent Document 5 to saturate screening and charging with UV illumination light different from the fundamental wave prior to measurement, and complete the measurement of the second harmonic in a short time. In Patent Document 6, it was further improved to enhance the resolution of the time variation measurement of the second harmonic with a delay mechanism, and a technique of mounting an electric field application function on a wafer holder to apply an external electric field to the wafer was proposed. In Patent Document 7, it was configured to illuminate with fundamental waves of multiple wavelengths and be able to measure third-order non-linear phenomena including four-wave mixing. In Patent Document 8, the polarization state of the second harmonic generated on the wafer was also analyzed, and a configuration was made to separately measure the effects of strain and crystallization state and the effects of electrical characteristics. In Patent Document 9, considering the actual semiconductor manufacturing process, a practical test pattern structure for measurement was proposed. Also, in Non-Patent Document 3, a method is used in which the second harmonic generated in the illumination system is illuminated on the wafer surface together with the fundamental wave and interfered with the second harmonic generated on the wafer surface. This configuration aims to measure the phase of the second harmonic generated on the wafer, and performs interference wave system analysis in the time domain using a delay mechanism.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

[0007] [Non-Patent Document 1] BLOEMBERGEN, N. et. al., Light Waves at the Boundary of Nonlinear Media, Phys. Rev. 128, 606 (1962) [Non-Patent Document 2] Guidotti, D. et.al, Second harmonic generation in centro-symmetric semiconductors, Solid state communications 46.4 (1983): 337-340 [Non-Patent Document 3] Terlinden, Nick M., et al. "Second-harmonic intensity and phase spectroscopy as a sensitive method to probe the space-charge field in Si (100) covered with charged dielectrics." Journal of Vacuum Science & Technology A 32.2 (2014). [Summary of the Invention] [Problems to be Solved by the Invention]

[0008] However, there is a problem that it is difficult to detect weak second harmonics with high sensitivity. [Means for Solving the Problems]

[0009] The measuring device according to one embodiment includes a light source that emits a fundamental wave which is a pulsed laser of a predetermined wavelength, a second harmonic generator that converts a part of the fundamental wave into a first second harmonic having a wavelength approximately half of the predetermined wavelength, a birefringent crystal that angularly separates the first second harmonic from the fundamental wave, a wavelength selection element that blocks the fundamental wave and transmits the first second harmonic and a second second harmonic generated by irradiating the surface of an object with the fundamental wave, a polarizer that makes the first second harmonic and the second second harmonic have substantially the same polarization, an image detector that converts the first second harmonic and the second second harmonic incident at different angles into electrical signals, and a processing device that obtains the intensity of the second second harmonic from the amplitude of the interference fringes generated on the image detector.

[0010] According to the measuring device of one embodiment, for one-point measurement, the measurement time of about 1 second to 10 seconds is shortened by about one digit to several digits, and more semiconductor wafers can be measured. Also, multiple-point measurement can be performed within about 100 full exposure shots at several points within the wafer.

[0011] The measuring device according to one embodiment includes, in the birefringent crystal, a wave plate that converts at least the angularly separated first second harmonic into circular polarization, and a beam splitter that separates the first second harmonic transmitted through the wavelength selection element and the second second harmonic transmitted through the wavelength selection element into two polarization components. The image detector includes a first image detector that converts one of the polarization components into an electrical signal and a second image detector that converts the other of the polarization components into an electrical signal.

[0012] According to the measuring device of one embodiment, by making the first second harmonic circularly polarized, measurement can be performed regardless of the polarization direction taken out by the polarization beam splitter.

[0013] The measuring device according to one embodiment includes a cylindrical lens that makes the fundamental wave emitted from the light source linear when viewed from a plane perpendicular to the optical axis, and the second harmonic generator converts a part of the fundamental wave into a first second harmonic having a wavelength half of the predetermined wavelength.

[0014] According to the measuring device of one embodiment, the second second harmonic can be independently measured within the line projected onto the object to be inspected, and the measurement time can be significantly shortened or the measurement area can be significantly enlarged.

[0015] In the measuring device of one embodiment, the fundamental wave and the first second harmonic have linearly polarized lights that are substantially orthogonal to each other within the illumination optical system, and the optical path lengths of the fundamental wave and the first second harmonic from the second harmonic generator to the surface of the object are substantially equal. The configuration of the birefringent crystal is determined so as to have such a configuration.

[0016] In the measuring device of one embodiment, the image detector and the birefringent crystal have an optically substantially conjugate positional relationship with each other.

[0017] In the measuring device of one embodiment, the image detector is arranged at a position optically substantially conjugate with the exit pupil of the objective optical system.

[0018] In the measuring device of one embodiment, the birefringent crystal is any one of a Wollaston prism, a Rochon prism, and a Nomarski prism.

[0019] In the measuring device of one embodiment, the processing device separates the AC component and the DC component of the interference fringes using Fourier transform, and obtains the intensity of the second second harmonic using both the AC component and the DC component.

[0020] In the measuring device of one embodiment, the object is a semiconductor element.

[0021] According to the measuring device of one embodiment, in the second harmonic measurement capable of measuring surface contamination and internal dopant amount of a semiconductor device during manufacturing, the intensity of the detection signal can be dramatically improved. Currently, the measurement time of about 1 second to 10 seconds per point measurement is shortened by one digit to several digits, and more semiconductor wafers can be measured. Also, if the speed increase is used for the distribution within the wafer surface, within the same measurement time as before, the measurement points, which were about several points within the wafer, can be measured at a plurality of points within about 100 full exposure shots within the wafer, and the feedback accuracy of the process is significantly improved.

[0022] The measuring device according to one embodiment is configured to obtain any one of the SiO2 film thickness on the semiconductor surface, the metal contamination of SiO2 on the semiconductor surface, the defect amount at the boundary between SiO2 and the semiconductor substrate, the impurity dopant amount in the semiconductor substrate, and the recrystallization of the semiconductor substrate from the obtained intensity information of the second second harmonic.

[0023] In one embodiment of the measuring method, the wavelength selection element has a dichroic filter.

[0024] In one embodiment of the measuring method, the wavelength selection element includes a prism arranged to change the traveling direction of light for each wavelength, and a relay lens aperture arranged to transmit at least the first second harmonic and the second second harmonic.

[0025] In one embodiment of the measuring method, the wavelength selection element includes a diffraction grating arranged to change the traveling direction of light for each wavelength, and a relay lens aperture arranged to transmit at least the first second harmonic and the second second harmonic.

[0026] In one embodiment of the measuring method, a second harmonic generator converts a part of the fundamental wave, which is a pulsed laser of a predetermined wavelength, into a first second harmonic having a wavelength approximately half of the predetermined wavelength. A birefringent crystal angularly separates the first second harmonic from the fundamental wave. The fundamental wave and the first second harmonic are reflected from the object surface at different positions. A wavelength selection element blocks the fundamental wave and transmits the first second harmonic. The second second harmonic generated by irradiating the object surface with the fundamental wave is transmitted through the wavelength selection element. A polarizer makes the first second harmonic and the second second harmonic have the same polarization, and the intensity of the second second harmonic is obtained from the amplitude of the interference fringes formed by the first second harmonic and the second second harmonic incident at different angles.

[0027] According to the measurement method of one embodiment, the measurement time of about 1 second to 10 seconds per point measurement is shortened by about one digit to several digits, and more semiconductor wafers can be measured. In addition, multiple-point measurements can be performed within about 100 full exposure shots at several points within the wafer.

Advantages of the Invention

[0028] According to the measurement apparatus and measurement method of the present disclosure, the intensity of the detection signal of a weak second harmonic can be improved.

Brief Description of the Drawings

[0029]

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Mode for Carrying Out the Invention

[0030] (Embodiment 1) Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of a semiconductor measuring device according to Embodiment 1. In FIG. 1, the semiconductor measuring device 100 includes a laser light source 101, a condenser lens 102, a nonlinear optical crystal 103, a collimator lens 104, a birefringent crystal 105, a beam splitter 106, an objective lens 107, a wavelength selection element 108, relay lenses 109 and 110, a relay lens aperture 121, a linear polarizing plate 111, and an image detector 112.

[0031] The laser light source 101 emits laser light of a predetermined wavelength to the condenser lens 102. For example, the laser light source 101 is preferably a femtosecond laser light source with a pulse width of 1 picosecond or less.

[0032] The condenser lens 102 is a lens that condenses the laser light emitted from the laser light source 101 at the position of the nonlinear optical crystal 103.

[0033] The nonlinear optical crystal 103 functions as a second harmonic generation element (second harmonic generator). Specifically, the nonlinear optical crystal 103 splits the laser light emitted from the laser light source 101 into the fundamental wave and the first second harmonic having approximately twice the frequency (having approximately half the wavelength). The nonlinear optical crystal 103 may split the laser light emitted from the laser light source 101 into the fundamental wave and the first second harmonic having twice the frequency (having half the wavelength). The nonlinear optical crystal 103 is preferably a nonlinear optical crystal that satisfies the type I phase matching condition. For example, the nonlinear optical crystal 103 that satisfies the type I phase matching condition includes LBO (lithium triborate), BBO (beta barium borate), and KTP (potassium titanyl phosphate).

[0034] The collimator lens 104 refracts the laser light of the fundamental wave and the first second harmonic from the nonlinear optical crystal 103 to make it parallel light. The optical axis of the fundamental wave and the optical axis of the laser light of the first second harmonic are the same.

[0035] The birefringent crystal 105 shifts the angle between the optical axes of the fundamental wave and the first second harmonic with orthogonal polarization directions from coaxial. Also, the birefringent crystal 105 corrects the phase shift between the fundamental wave and the first second harmonic due to wavelength dispersion that occurs between the nonlinear optical crystal 103 and the object to be inspected. By this correction of the birefringent crystal 105, the optical path lengths of the fundamental wave and the first second harmonic from the second harmonic generator to the surface of the object become substantially equal. Note that by this correction of the birefringent crystal 105, the optical path lengths of the fundamental wave and the first second harmonic from the second harmonic generator to the surface of the object may be made equal. The birefringent crystal 105 is preferably, for example, a Wollaston prism, a Rochon prism, or a Nomarski prism.

[0036] The beam splitter 106 reflects the laser light from the birefringent crystal 105 and makes it incident on the objective lens 107. Also, the beam splitter 106 transmits the light from the objective lens 107 and makes it incident on the wavelength selection element 108.

[0037] The objective lens 107 refracts the laser light from the beam splitter 106 so as to focus on the measurement point of the object 120. The fundamental wave laser light focuses on the measurement point of the object, and generates a second second harmonic wave with different intensities, polarizations, and phases depending on the substance, structure, and electric field state in the semiconductor device that is the object. Also, the first second harmonic wave similarly focuses on the object, but due to the angular difference caused by the birefringent crystal, it is at a slightly shifted position from the fundamental wave.

[0038] The wavelength selection element 108 cuts the fundamental wave of the laser light. For example, the wavelength selection element 108 is preferably a dichroic filter.

[0039] The relay lenses 109 and 110 are optical systems for imaging in the image detector 112. The relay lens 109 refracts the fundamental wave, the first second harmonic wave, and the second second harmonic wave at different angles according to the wavelength. Then, the fundamental wave of the laser light is cut by the diaphragm plate of the relay lens diaphragm 121. And at least the first second harmonic wave and the second second harmonic wave pass through the diaphragm hole of the relay lens diaphragm 121. For example, the relay lenses 109 and 110 are preferably prisms arranged to change the traveling direction of light for each wavelength, or diffraction gratings arranged to change the traveling direction of light for each wavelength. Note that only the first second harmonic wave and the second second harmonic wave may be arranged to pass through the diaphragm hole of the relay lens diaphragm 121.

[0040] Note that the cutting of the fundamental wave can be realized by having at least one of the wavelength selection element 108 and the relay lens diaphragm 121.

[0041] The linear polarizing plate (polarizer) 111 makes the polarization states of the laser light of the first second harmonic wave and the laser light of the second second harmonic wave substantially coincide. Note that the linear polarizing plate 111 may be made to coincide the polarization states of the laser light of the first second harmonic wave and the laser light of the second second harmonic wave.

[0042] The image detector 112 receives light at each of the two-dimensional coordinates and converts this light into electrical signals respectively. The image detector 112 is arranged at a position that is optically substantially conjugate to the birefringent crystal 105. That is, the position where the image detector 112 is arranged is a position where the first second harmonic wave and the second second harmonic wave that are angularly separated return to the same point again on the image detector 112. Note that the image detector 112 may be arranged at a position that is optically conjugate to the birefringent crystal 105.

[0043] With the above configuration, the semiconductor measurement device 100 measures the object to be measured. Next, the measurement principle of the semiconductor measurement device 100 will be described.

[0044] First, a laser beam (fundamental wave) with a pulse width of 1 picosecond or less is emitted from the laser light source 101.

[0045] The laser beam is refracted by the condenser lens 102 so as to be focused at the position of the nonlinear optical crystal 103.

[0046] Then, in the nonlinear optical crystal 103, a second harmonic wave having a frequency twice that of the fundamental wave is generated from the laser beam.

[0047] The laser beams of the fundamental wave and the first second harmonic wave both become parallel light by the collimator lens 104. Here, the polarization directions of the laser beam of the fundamental wave and the laser beam of the first second harmonic wave are orthogonal to each other. FIG. 2 is a diagram showing an example of the polarization state in the optical axis cross section in the semiconductor measurement device according to Embodiment 1. In FIG. 2, (a) shows the polarization of the laser beam of the fundamental wave traveling from the laser light source 101 toward the condenser lens 102. Further, (b) shows the polarization of the laser beam of the fundamental wave and the laser beam of the first second harmonic wave traveling from the collimator lens 104 toward the beam splitter 106. As shown in FIGS. 2(a) and 2(b), the polarization 201 of the laser beam of the fundamental wave is substantially orthogonal to the polarization 202 of the laser beam of the first second harmonic wave. Note that the polarization 201 of the laser beam of the fundamental wave may be orthogonal to the polarization 202 of the laser beam of the first second harmonic wave.

[0048] Then, the fundamental wave laser light and the laser light of the first second harmonic, which have become parallel light, enter the birefringent crystal 105.

[0049] Then, the optical axis of the fundamental wave laser light and the optical axis of the second harmonic laser light are slightly displaced from the optical axis in the birefringent crystal 105.

[0050] The fundamental wave laser light and the laser light of the first second harmonic are reflected in the direction of the objective lens 107 by the beam splitter 106.

[0051] Then, the fundamental wave laser light and the laser light of the first second harmonic are focused on the measurement point of the object to be inspected (target object) by the objective lens. Since the optical axes of the fundamental wave laser light and the laser light of the first second harmonic are displaced from each other by the birefringent crystal 105, the position where the fundamental wave laser light irradiates the object to be inspected and the position where the laser light of the first second harmonic irradiates the object to be inspected are also displaced from each other.

[0052] FIG. 3 is an enlarged view showing an example of the optical path near the object to be inspected in the semiconductor measuring apparatus according to Embodiment 1. As shown in FIG. 3, the fundamental wave laser light 301 is reflected at the measurement point 311, and the second second harmonic 312 is generated on the surface of the object to be inspected. Further, the first second harmonic 302 is reflected at a position 321 deviated from the measurement point.

[0053] The reflected fundamental wave, the first second harmonic, and the laser light of the second second harmonic enter the dichroic filter 108 through the objective lens 107 and the beam splitter 106. By this dichroic filter 108, the fundamental wave of the laser light is cut, and the laser light of the first second harmonic and the second second harmonic is transmitted.

[0054] Then, the laser light of the first second harmonic and the second second harmonic enter the linear polarizer 111 through the relay lens 109 and the relay lens 110. In the linear polarizer 111, the polarization states of the laser light of the first second harmonic and the laser light of the second second harmonic are aligned.

[0055] By correcting the phase difference for each wavelength using the nonlinear optical crystal 103 and matching the polarization states using the linear polarizer 111, the first second harmonic wave and the second second harmonic wave become mutually coherent and form interference fringes on the image detector 112.

[0056] FIG. 4 is a diagram showing an example of interference fringes on an image detector in the semiconductor measurement apparatus according to Embodiment 1. As shown in FIG. 4, interference fringes 401 appear at positions on the two-dimensional grid of the image detector 112 where the laser light of the first second harmonic wave and the second second harmonic wave is irradiated.

[0057] In this way, using the illuminating fundamental wave, the first second harmonic wave is generated at a location other than the object to be measured (for example, a semiconductor wafer), and the second second harmonic wave generated in the semiconductor wafer and the first second harmonic wave are made to enter the image detector at slightly different angles to form interference fringes.

[0058] Note that the interval 402 of the interference fringes corresponds to the separation angle in the birefringent crystal and is set to an angle favorable for measurement. Considering that the light source is a femtosecond laser, the coherence length is on the order of several μm to 100 μm. If the separation angle is increased too much, the contrast of the interference fringes decreases at the ends of the interference fringes, and the signal-to-noise ratio with respect to the amplitude of the interference fringes decreases. Therefore, when the λ and Δλ of the light source and the NA of the objective lens are determined, the upper limit d of the fundamental wave and the second harmonic wave is obtained by the following formula (1). d ≦ λ^2 / (2 · Δλ · ”NA”) (1)

[0059] Conversely, if the separation angle is decreased, a decrease in the contrast of the interference fringes can be avoided, but the positional resolution within the interference fringes decreases. Let λ1 be the fundamental wave wavelength and λ2 be the second harmonic wave wavelength, then the lower limit d is obtained by the following formula (2). d ≧ 0.66 / NA × (λ1 + λ2) (2)

[0060] The cross-section of the obtained interference fringe image is I in FIG. 5 S1+S2It corresponds to. FIG. 5 is a graph showing an example of a detection signal of the semiconductor measurement device according to Embodiment 1. In FIG. 5, the vertical axis represents the intensity of the detection signal. The horizontal axis represents time.

[0061] Here, assuming I S1 = 1 and I S2 = 0.02, in the conventional method, the detection signal is I S2 and is very small. When the present disclosure is applied, the detection signal becomes I S1+S2 and since the AC component is 0.28, it can be seen that a signal intensity more than 10 times that of the conventional method is obtained. The intensity of I S1 can be arbitrarily set, and by appropriately setting it according to the intensity of I S2 , a high intensity can be obtained for I S2 in any case.

[0062] I S1+S2 is derived as follows. Equation (3) and Equation (4) represent the electric field ES1 of the first second harmonic and the electric field ES2 of the second second harmonic, respectively. Equation (5) represents the intensity IS1 of the first second harmonic and the intensity IS2 of the second second harmonic. Note that the intensity is the square of the amplitude. The second second harmonic includes a term, φ(x), corresponding to the phase change, which is a function of the position (x) in the direction perpendicular to the interference fringes on the image detector. TIFF2025091192000002.tif12153··· (3) TIFF2025091192000003.tif12153TIFF2025091192000004.tif11153···(4) TIFF2025091192000005.tif12153···(5)

[0063] Equation (6) represents the intensity of the interference light of the first second harmonic and the second second harmonic. The first two terms are DC components, and the third term is an AC component that changes with time due to φ(x). The amplitude of the observed AC component is represented by 2·|E S1 ||E S2 |, and |E s2 | is among the DC components, where I S2 = |ES2 | 2 can be obtained because it is negligibly small. TIFF2025091192000006.tif12153···(6)

[0064] Here, in the conventional measurement technique, I S2 =|E S2 | 2 is observed, but this is very small because it is the square of the weak electric field E S2 . On the other hand, 2·|E S1 ||E S2 |cos(iφ(x)), which is the AC component of the interference light, can observe an appropriate amount of light by setting the electric field E S1 to be large.

[0065] Therefore, the AC component and the DC component of I are obtained by waveform analysis such as Fourier transform, and |E S1+S2 | can be obtained from Equation (6). The silicon wafer of the test object is fixed on the wafer holder by a vacuum chuck or the like as shown in FIG. 6, and the wafer holder on which the silicon wafer is mounted can move the measurement point by the wafer stage. FIG. 6 is a schematic diagram showing an example of the semiconductor measurement apparatus according to Embodiment 1. S2 | can be obtained. The silicon wafer of the test object is fixed on the wafer holder by a vacuum chuck or the like as shown in FIG. 6, and the wafer holder on which the silicon wafer is mounted can move the measurement point by the wafer stage. FIG. 6 is a schematic diagram showing an example of the semiconductor measurement apparatus according to Embodiment 1.

[0066] In FIG. 6, the semiconductor inspection apparatus 600 includes a semiconductor measurement apparatus 100, a frame grabber 601, a femtosecond laser controller 602, a stage controller 603, a wafer holder 604, a wafer stage 605, and a processing apparatus 606. In FIG. 6, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

[0067] The frame grabber 601 is an interface that reads a signal from the image detector 112.

[0068] The femtosecond laser controller 602 is a controller that controls the timing of the laser light source 101 and the like.

[0069] The stage controller 603 is a controller that controls the moving direction and amount of movement of the wafer stage 605.

[0070] The wafer holder 604 is a holder that fixes the semiconductor (wafer) to be measured.

[0071] The wafer stage 605 is a stage that moves the semiconductor (wafer) to be measured to the measurement position.

[0072] The processing device 606 applies the above formula to the signal from the image detector 112 to obtain the intensity. For example, the processing device 606 separates the AC component and the DC component of the interference fringes using Fourier transform, and obtains the intensity of the second second harmonic using both the AC component and the DC component. The processing device 606 is preferably a computer, for example.

[0073] Thus, according to the semiconductor measuring device of Embodiment 1, in the second harmonic measurement capable of measuring surface contamination and internal dopant amount of a semiconductor device during manufacturing, the intensity of the detection signal can be dramatically improved. Currently, the measurement time of about 1 second to 10 seconds per point measurement is shortened by one digit to several digits, and more semiconductor wafers can be measured. Also, if the speed increase is used for the distribution within the wafer surface, within the same measurement time as before, the number of measurement points, which was about several points within the wafer, can be measured at multiple points within about 100 full exposure shots, and the feedback accuracy of the process is greatly improved.

[0074] (Embodiment 2) In Embodiment 2, an example of converting the first second harmonic into circular polarization and applying it will be described. FIG. 7 is a cross-sectional view showing an example of a semiconductor measuring apparatus according to Embodiment 2. In FIG. 7, the semiconductor measuring apparatus 700 includes a laser light source 101, a condenser lens 102, a nonlinear optical crystal 103, a collimator lens 104, a birefringent crystal 105, a wave plate 701, a beam splitter 106, an objective lens 107, a dichroic filter 108, relay lenses 109 and 110, a relay lens aperture 121, a beam splitter 702, an image detector 112-1, and an image detector 112-2. In FIG. 7, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

[0075] The wave plate 701 converts the first second harmonic from linearly polarized light to circularly polarized light. The first second harmonic converted to circularly polarized light is incident on the beam splitter 106.

[0076] The beam splitter 702 emits two orthogonally polarized components, which are incident on the two image detectors 112-1 and 112-2, respectively. Specifically, the beam splitter 702 separates the first second harmonic and the second second harmonic that have passed through the wave plate 701 into two orthogonally polarized components.

[0077] The image detector 112-1 and the image detector 112-2 receive two orthogonally polarized components respectively and convert them into electrical signals. In this way, information on the second second harmonic corresponding to each polarization direction can be obtained, and information corresponding to the amplitude intensity ratio ψ and the phase difference Δ for each polarization can be obtained.

[0078] FIG. 8 is a diagram showing an example of the polarization state in the optical axis cross section of the semiconductor measuring apparatus according to Embodiment 2. In FIG. 8, (a) shows the polarization 801 of the fundamental wave laser light traveling from the laser light source 101 toward the condenser lens 102. Also, (b) shows the polarization 801 of the fundamental wave laser light and the polarization 802 of the laser light of the first second harmonic traveling from the collimator lens 104 toward the beam splitter 106. (c) shows the polarization 803 of the laser light of the first second harmonic converted into circular polarization by the wave plate 701.

[0079] FIG. 9 is a diagram showing an example of interference fringes on the detector in the semiconductor measuring apparatus according to Embodiment 2. As shown in FIG. 9, interference fringes 901 and 902 appear at positions on the two-dimensional grid of the image detector 112 where the laser light of the first second harmonic and the second second harmonic are irradiated.

[0080] As described above, according to the semiconductor measuring apparatus of Embodiment 2, by making the first second harmonic into circular polarization, measurement can be performed regardless of the polarization direction extracted by the polarization beam splitter.

[0081] Note that although the polarization state of the fundamental wave is assumed not to change before and after the wave plate in FIG. 7, it may be converted into circular polarization in the same manner as the first second harmonic. This is possible by appropriately selecting the thickness if the material of the wave plate is quartz, but it can be more easily realized by using a wave plate in which quartz and magnesium fluoride are bonded.

[0082] Also, depending on the installation orientation of the polarization beam splitter, the laser light of the first second harmonic and the second second harmonic can be measured even without a wave plate.

[0083] (Embodiment 3) In Embodiment 3, an example will be described in which the lens in front of the nonlinear optical crystal is a cylindrical lens, and the light irradiated onto the object to be inspected is linear (here, "linear" means a line as a figure). FIG. 10 is a cross-sectional view showing an example of a semiconductor measurement apparatus according to Embodiment 3. In FIG. 10, a semiconductor measurement apparatus 1000 includes a laser light source 101, a cylindrical lens 1001, a nonlinear optical crystal 103, a collimator lens 104, a birefringent crystal 105, a beam splitter 106, an objective lens 107, a dichroic filter 108, a relay lens 109, a relay lens 1002, a linear polarizer 111, and an image detector 112. In FIG. 10, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

[0084] The cylindrical lens 1001 makes the fundamental wave laser light and the first second harmonic laser light emitted from the laser light source 101 linear when viewed from a plane perpendicular to the optical axis.

[0085] The relay lens 1002 is a relay lens including a cylindrical lens.

[0086] The image detector 112 is optically substantially conjugate to the surface of the object to be inspected in a plane including the line projected on the object to be inspected and the optical axis of the relay lens, but is optically substantially conjugate to the exit pupil of the objective lens in a plane perpendicular thereto (in the plane of the paper of FIG. 10). Note that the image detector 112 may be optically conjugate to the exit pupil of the objective lens in a plane perpendicular thereto (in the plane of the paper of FIG. 10).

[0087] FIG. 11 is an enlarged view showing an example of an optical path near the object to be inspected in the semiconductor measurement apparatus according to Embodiment 3. Further, FIG. 12 is a diagram showing an example of the second harmonic generated in the illumination optical system in the semiconductor measurement apparatus according to Embodiment 3.

[0088] As shown in FIG. 11, the fundamental wave laser beam 2201 is reflected at the measurement point 1111, and the second second harmonic wave 1112 is generated on the surface of the object under test. Also, the first second harmonic wave 1102 is reflected at a position 1121 shifted from the measurement point.

[0089] On the other hand, as shown in FIG. 12, in a plane perpendicular to the optical axis, the fundamental wave 1201 and the first second harmonic wave 1202 generated by the illumination optical system are linear. In FIG. 12, the first second harmonic wave 1202 is shown by a broken line in the figure in order to distinguish it from the fundamental wave, but it is actually a continuous line.

[0090] FIG. 13 is a diagram showing an example of interference fringes on a detector in the semiconductor measurement apparatus according to Embodiment 3. As shown in FIG. 13, interference fringes 1301 are generated by the interference of two second harmonic waves.

[0091] Thus, according to the semiconductor measurement apparatus of Embodiment 3, it becomes possible to independently measure the second second harmonic wave within the line projected on the object under test, and it becomes possible to significantly shorten the measurement time or significantly expand the measurement area.

[0092] Note that the present invention is not limited to the above-described embodiments, and can be appropriately modified without departing from the gist. For example, in the above-described embodiments, the measurement target is a semiconductor, but the measurement target may be other substances. Further, the measurement apparatus of the above-described embodiments may obtain the SiO2 film thickness on the semiconductor surface, the metal contamination of SiO2 on the semiconductor surface, the defect amount at the boundary between SiO2 and the semiconductor substrate, the impurity dopant amount of the semiconductor substrate, and the recrystallization of the semiconductor substrate from the information on the intensity of the second second harmonic wave obtained by measurement.

Description of Reference Numerals

[0093] 100, 700, 1000 Semiconductor measurement apparatus 101 Laser light source 102 Condensing lens 103 Nonlinear optical crystal 104 Collimator lens 105 Birefringent crystal 106, 702 Beam splitter 107 Objective lens 108 Wavelength selection element 109, 110, 1002 Relay lens 111 Linear polarizer 112 Image detector 120 Object under test 121 Relay lens aperture 600 Semiconductor inspection device 601 Frame grabber 602 Femtosecond laser controller 603 Stage controller 604 Wafer holder 605 Wafer stage 606 Processing device 701 Waveplate 1001 Cylindrical lens

Claims

1. A light source that emits a fundamental wave which is a pulsed laser of a predetermined wavelength, A second harmonic generator that converts a part of the fundamental wave into a first second harmonic having a wavelength approximately half of the predetermined wavelength, A birefringent crystal that angularly separates the first second harmonic from the fundamental wave, A wavelength selection element that blocks the fundamental wave and transmits the first second harmonic and a second second harmonic generated by irradiating the surface of an object with the fundamental wave, A polarizer that makes the first second harmonic and the second second harmonic have substantially the same polarization, An image detector that converts the first second harmonic and the second second harmonic incident at different angles into electrical signals, A measurement apparatus comprising a processing device that obtains the intensity of the second second harmonic from the amplitude of the interference fringes generated on the image detector.

2. A wave plate that converts at least the angularly separated first second harmonic into circular polarization in the birefringent crystal, Comprising a beam splitter that separates the first second harmonic transmitted through the wavelength selection element and the second second harmonic transmitted through the wavelength selection element into two polarization components, The image detector has a first image detector that converts one of the polarization components into an electrical signal and a second image detector that converts the other one of the polarization components into an electrical signal, the measurement apparatus according to claim 1.

3. Comprising a cylindrical lens that makes the fundamental wave emitted from the light source linear when viewed from a plane perpendicular to the optical axis, The second harmonic generator converts a part of the fundamental wave into a first second harmonic having a wavelength half of the predetermined wavelength, the measurement apparatus according to claim 1.

4. The birefringent crystal is configured such that the fundamental wave and the first second harmonic have linearly polarized light that is substantially orthogonal to each other within the illumination optical system, and the optical path lengths of the fundamental wave and the first second harmonic from the second harmonic generator to the surface of the object are substantially equal, the measurement apparatus according to any one of claims 1 to 3.

5. The measuring device according to any one of claims 1 to 3, wherein the image detector and the birefringent crystal are optically in a substantially conjugate positional relationship with each other.

6. The measuring device according to any one of claims 1 to 3, wherein the image detector is disposed at a position optically substantially conjugate to the exit pupil of the objective optical system.

7. The measuring device according to any one of claims 1 to 3, wherein the birefringent crystal is any one of a Wollaston prism, a Rochon prism, and a Nomarski prism.

8. The measuring device according to any one of claims 1 to 3, wherein the processing device separates the AC component and the DC component of the interference fringes using Fourier transform, and obtains the intensity of the second second harmonic using both the AC component and the DC component.

9. The measuring device according to any one of claims 1 to 3, wherein the object is a semiconductor element.

10. From the information on the intensity of the obtained second second harmonic, any one of the SiO film thickness on the semiconductor surface, the metal contamination of SiO on the semiconductor surface, the defect amount at the boundary between SiO and the semiconductor substrate, the impurity dopant amount of the semiconductor substrate, and the recrystallization of the semiconductor substrate is obtained. The measuring device according to any one of claims 1 to 3. ２ film thickness, SiO on the semiconductor surface ２ of the metal contamination, SiO ２ and the defect amount at the boundary between the semiconductor substrate, the impurity dopant amount of the semiconductor substrate, the recrystallization of the semiconductor substrate. The measuring device according to any one of claims 1 to 3.

11. The wavelength selection element is having a dichroic filter, The measuring device according to any one of claims 1 to 3.

12. The wavelength selection element is a prism arranged to change the traveling direction of light for each wavelength, and having a relay lens aperture arranged to transmit at least the first second harmonic and the second second harmonic. The measuring device according to any one of claims 1 to 3.

13. The wavelength selection element is a diffraction grating arranged to change the traveling direction of light for each wavelength, The measuring device according to any one of claims 1 to 3, having a relay lens aperture arranged to transmit at least a first second harmonic and a second second harmonic.

14. A part of the fundamental wave, which is a pulsed laser of a predetermined wavelength, is converted into a first second harmonic having a wavelength approximately half of the predetermined wavelength by a second harmonic generator, The first second harmonic is angularly separated from the fundamental wave by a birefringent crystal, The fundamental wave and the first second harmonic are reflected from the surface of the object at different positions, The fundamental wave is blocked by the wavelength selection element, the first second harmonic is transmitted by the wavelength selection element, and the second second harmonic generated by irradiating the surface of the object with the fundamental wave is transmitted by the wavelength selection element, The first second harmonic and the second second harmonic are made into the same polarization by a polarizer, A measuring method for obtaining the intensity of the second second harmonic from the amplitude of interference fringes formed by the first second harmonic and the second second harmonic incident at different angles to each other.

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