JP2007333640A - Apparatus and method for measuring semiconductor electrical characteristic - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for measuring semiconductor electrical characteristics that not only computes the lifetime and diffusion length of carriers but also measures electrical characteristics of semiconductors, such as the mobility of carriers, directly without requiring high time resolution and advanced arithmetic functions. <P>SOLUTION: The apparatus for measuring semiconductor electrical characteristics comprises an excitation light irradiation means for exciting carriers with excitation light on the obverse of a semiconductor sample, an electric field application means for applying an electric field to a region including the entire area irradiated with the excitation light such that the electric field is oriented in one direction in the region, an observation light irradiation means for irradiating the region including the entire area irradiated with the excitation light or the reverse of the semiconductor corresponding to the region with observation light, a light receiving means for receiving reflected light or transmitted light of the observation light reflected by or transmitted through the semiconductor, and a control means for controlling each means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a semiconductor electrical property measurement apparatus and measurement method for non-contact evaluation of electrical properties of a semiconductor.

  In a semiconductor device using a semiconductor wafer, a semiconductor thin film, or the like, the electrical characteristics of the semiconductor such as mobility and conductivity greatly affect the characteristics of the device. In particular, a polycrystalline silicon film (poly-Si film) is usually formed by depositing an amorphous silicon film (amorphous-Si film) on a substrate such as quartz or glass, and then ELA (Excimer Laser Annealing) or SPC (SPC). Since it is created using a crystallization method such as Solid Phase Crystallization), there is a large variation in electrical characteristics within the surface, which greatly affects the quality of device characteristics such as TFTs (Thin Film Transistors). Recently, the silicon thickness of SOI (Silicon On Insulator) substrates has also been reduced to about several tens of nanometers, and management relating to film thickness has been made, but management relating to electrical characteristics of films other than electrical conductivity is generally used. Not done.

  Conventionally, the electrical characteristics of such a semiconductor have been evaluated by a contact method such as a four-probe method or a TEG (Test Element Group) measurement in which a probe measurement is performed using a test pattern portion after creating a TFT. It was. With regard to mobility evaluation in particular, it takes a long time to evaluate because TFTs are created and measured, and the substrate may be damaged or contaminated, resulting in a decrease in the yield of subsequent processes. It was.

  On the other hand, several methods for measuring such electrical characteristics of semiconductors in a non-contact manner have been developed. Main examples thereof include (1) μ-PCD (Photo Conductive Decay) method, (2) SPV (Surface Photo Voltage) method, and (3) Free carrier absorption analysis method.

  In the μ-PCD method of (1), a semiconductor is irradiated with excitation light, the lifetime of excess carriers generated by the excitation light is measured with respect to the time change of the reflection intensity due to microwave irradiation, and the lifetime is measured from the attenuation curve. Is the method. For example, for a Si epi-wafer having a thickness of several μm to several tens of μm, the carrier lifetime is measured using a differential method (Non-patent Document 1). However, since the recombination lifetime can be measured by this method, information on crystallinity and heavy metal contamination on the surface can be obtained, but it is not a method for directly evaluating electrical characteristics such as mobility.

  The SPV method of (2) is a method in which carriers are excited on the semiconductor surface using pulsed light of a plurality of wavelengths, the surface photoelectromotive force of the generated carriers is measured, and the diffusion length is obtained from the relationship between the wavelength and the electromotive force. . For example, there is a method in which monochromatic radiation beams having different photon energies are sequentially excited, a surface photovoltage of a semiconductor is measured, and a diffusion length is obtained (Patent Document 1). According to this method, the lifetime of the carrier can be obtained using the diffusion length. However, this method can also obtain information on crystallinity and heavy metal contamination on the surface, but is not a method for directly evaluating electrical characteristics such as mobility. Further, it is necessary to fix the potential of the substrate, and a semiconductor formed on an insulator such as glass cannot be measured.

  The free carrier absorption analysis method (3) is a method of irradiating a semiconductor while changing the wavelength of light in the infrared region, and evaluating electrical characteristics such as carrier density and mobility from the wavelength dependence of the reflectance. It is. For example, the carrier mobility of a doped poly-Si film having a thickness of 50 nm has been measured (Non-Patent Document 2). However, this method requires the computing power and time of the computer to measure the reflectance by changing the wavelength of light in the infrared region and to perform fitting with theoretical calculation. For this reason, time is required for evaluation, and it is difficult to use as an in-line inspection apparatus.

  In order to solve the problem of the method (3), as shown in FIG. 15, the visible light pulse from the femtosecond visible light pulse laser 21 is first branched in two directions by the semi-transmissive mirror 28. The visible light pulse 21a passes through the time delay movable mirror 24 and enters the terahertz pulse detector 26. The other visible light pulse 21b emits the terahertz pulse light 22a from the terahertz pulse light source 22, and the terahertz pulse light 22a is measured. An apparatus has been proposed in which the transmitted pulsed light 25a enters the terahertz pulse detector 26 through the semiconductor wafer 25 through the optical system 23a (Patent Document 2). This device discloses a method for obtaining electrical characteristics such as mobility by Fourier transforming time-series data using Drude's theory instead of changing the wavelength by free carrier absorption analysis. .

However, this device irradiates a semiconductor material with terahertz pulse light, calculates it from the time-series waveform of the electric field intensity using Drude's light absorption theory, and calculates values related to electrical characteristics such as carrier density and mobility. Since it is calculated, high-precision measurement is required with respect to the time axis. Therefore, a measurement device with high time resolution and a calculation function for performing Fourier transform are required.
Japanese Patent Laid-Open No. 02-119236 JP 2002-098634 A IEICE Technical Report ED97-30, p. 29-34 (1997) Jpn. J. et al. Appl. Phys. vol. 38 (1999) p. 1892-1897

  The present invention has been made in view of the current situation as described above, and its purpose is not to simply determine the lifetime or diffusion length of carriers, but to directly measure the electrical characteristics of semiconductors. Another object of the present invention is to provide a semiconductor electrical characteristic measuring apparatus and measuring method that do not require high time resolution and high calculation functions. In particular, a measurement apparatus and a measurement method suitable for measuring and confirming semiconductor electrical characteristics such as semiconductor carrier mobility and electrical characteristics related to carrier mobility are provided.

  The semiconductor electrical property measuring apparatus according to the present invention includes an excitation light irradiating means for exciting carriers with excitation light to the surface of a semiconductor as a sample, and a region including the entire range irradiated with the excitation light. An electric field applying means for applying an electric field so that the direction of the electric field in the region is one direction, and a region including the entire range irradiated with the excitation light, or a semiconductor back surface corresponding to the region. Observation light irradiating means for irradiating observation light, light receiving means for receiving reflected light or transmitted light reflected by the semiconductor, and control means for controlling the above means It is characterized by having.

  In addition, the semiconductor electrical property measuring apparatus has a distribution of reflected light intensity or transmitted light intensity of observation light after irradiation with excitation light when an electric field is applied by the electric field applying means and when it is not applied. The distribution changes, and the change in the distribution can be detected by the light receiving means.

  Further, the semiconductor electrical property measuring apparatus is characterized in that a change in reflected light intensity or transmitted light intensity due to observation light before and after excitation light irradiation is applied when an electric field is applied by the electric field applying means. The quantity distribution changes, and the change of the change quantity distribution can be detected by the light receiving means.

  Further, the light receiving means can be any one of a one-dimensional line sensor, a two-dimensional area sensor, or a point sensor.

  The semiconductor electrical property measuring apparatus may further include a calculation unit, and the calculation unit may be directly or indirectly connected to the light receiving unit. The semiconductor electrical property measuring apparatus may further include an oscillator, and the oscillator may be connected to the electric field applying means.

  The electric field applied by the electric field applying means can be a constant electric field or a high-frequency electric field (in the case of a high-frequency electric field, the frequency is in the range of 100 MHz to 10 GHz).

  The semiconductor electrical property measuring apparatus moves the semiconductor as a sample relative to a measurement system including the excitation light irradiation unit, the electric field application unit, the observation light irradiation unit, and the light reception unit. A means is further provided, and a plurality of locations on the surface of the semiconductor can be measured.

  Further, the semiconductor electrical property measuring apparatus is connected to the excitation light irradiating means and the light receiving means, and the excitation light irradiating means irradiates excitation light multiple times with periodicity, In addition, the light receiving means can receive light in synchronization with the period of the excitation light.

  Further, the semiconductor electrical property measurement method of the present invention corresponds to an observation light irradiation step for irradiating the surface of a semiconductor, which is a sample, with observation light, and a region irradiated with the observation light or the region thereof. Excitation light irradiation step for exciting a carrier by irradiating a specific range in the region of the backside of the semiconductor and receiving the reflected light or the transmitted transmitted light reflected by the semiconductor A first light receiving step for applying the electric field, an electric field applying step for applying an electric field in which the direction of the electric field is one direction to the region including the entire range irradiated with the excitation light, and A second light receiving step for receiving the reflected light reflected or transmitted by the semiconductor in the applied range, the first light receiving step, and the second light receiving step; Determined by calculating the change in the distribution range of the distribution range or transmitted light intensity of the reflected light intensity detected Oite, is characterized by comprising a calculating step for calculating the electrical characteristics based on the result, the.

  The electric field applied in the electric field applying step can be a constant electric field or a high frequency electric field.

  The measurement method omits the first light receiving step, uses a two-dimensional area sensor as the light receiving means in the second light receiving step, and reflects or transmits the reflected light or transmitted light obtained in the second light receiving step in the calculation step. A change in the distribution range of the two-dimensional intensity of light can be obtained by calculation.

  Also, the semiconductor electrical property confirmation method of the present invention is a method for confirming semiconductor electrical property using the semiconductor electrical property measurement apparatus described above, wherein a point sensor is used as the light receiving means, and a semiconductor as a sample is used. Confirming whether or not the distribution range of the reflected light intensity on the surface is in an appropriate range, or using a one-dimensional line sensor or a two-dimensional area sensor as the light receiving means, and a part of the surface of the semiconductor as a sample It is characterized by confirming whether or not the distribution range of the reflected light intensity is in an appropriate range.

  Furthermore, the semiconductor electrical property measurement method of the present invention is a method for measuring semiconductor electrical properties using the above-mentioned semiconductor electrical property measurement apparatus, wherein the observation light irradiation means irradiates the surface of the semiconductor with observation light. However, the variation distribution of the reflected light intensity or the transmitted light intensity of the observation light in the case where the excitation light is irradiated by the excitation light irradiation means and the case where the excitation light irradiation is not performed in a state where no electric field is applied by the electric field application means. And the reflected light intensity or transmitted light intensity of the observation light in the case where the excitation light is irradiated by the excitation light irradiation means in the state where the electric field is applied by the electric field application means and in the case where the excitation light is not irradiated. The step of detecting the variation distribution by the light receiving means and the threshold processing of these variation distributions to determine the respective variation distribution ranges. And Mel step is characterized by including the calculation steps for obtaining the semiconductor electrical characteristics (semiconductor carrier mobility) by determining a change in their variation distribution range.

  According to the semiconductor electrical property measurement apparatus and measurement method of the present invention, it is possible to directly measure electrical properties such as carrier mobility of a semiconductor, rather than simply obtaining the lifetime and diffusion length of carriers, Neither time resolution nor advanced calculation functions are required. For this reason, it is particularly suitable as an in-line inspection apparatus or an in-line inspection method in various semiconductor manufacturing processes.

  Hereinafter, the present invention will be described in more detail with reference to embodiments, but the present invention is not limited thereto. In the following description of the embodiments, the description is made with reference to the drawings. In the drawings of the present application, the same reference numerals and symbols denote the same parts (contents) or corresponding parts (contents). ing.

<Embodiment 1>
The semiconductor electrical property measuring apparatus of the present invention is basically composed of excitation light irradiation means, electric field application means, observation light irradiation means, light reception means and control means. The excitation light irradiating means, the electric field applying means, the observation light irradiating means, and the light receiving means are referred to as a measurement system for convenience. Hereinafter, a method for measuring the carrier mobility of a semiconductor as the electrical characteristics of the semiconductor using the semiconductor electrical characteristics measurement apparatus will be described with reference to FIGS.

  FIG. 1 shows a flowchart for executing a semiconductor mobility measurement method using the semiconductor electrical property measurement apparatus of the present invention. FIGS. 2 and 3 show the semiconductor electrical property measurement apparatus of the present invention. FIG. 4 is an image diagram of a distribution state of photoexcited carriers excited by irradiating the surface of a semiconductor, which is a sample, with excitation light in a perfect circle shape. The case where the electric field is not applied is shown, and (b) shows the case where the electric field is applied.

(Semiconductor as sample)
First, as a semiconductor to be a sample for measuring mobility which is an electrical property, a semiconductor thin film 2 having a film thickness of several tens of nanometers (for example, poly) is formed on a glass substrate or a substrate 1 on which a base layer such as SiO ₂ is formed on a glass substrate. -Si film) can be used. However, the semiconductor material to be measured is not limited to this, and it goes without saying that any semiconductor material can be targeted.

(Observation light irradiation means)
Next, the semiconductor as a sample is set in the semiconductor electrical property measuring apparatus of the present invention, and the observation light irradiation means 6 irradiates the surface of the semiconductor (on the side of the semiconductor thin film 2) with observation light (step S1). . As the light source included in the observation light irradiation means 6, a light source that generates light in a wavelength range that does not excite carriers is employed. The wavelength range varies depending on the type of semiconductor material to be a sample. For example, when the semiconductor material is Si, it is preferable to use a light source that emits light having a wavelength of 1.2 μm or more. This is because the wavelength region does not excite carriers as described above.

  Further, the beam diameter of such observation light irradiation is not particularly limited as long as it can irradiate a region including the entire range irradiated with excitation light described later.

  In addition, the installation direction of the observation light irradiation means 6 is a direction slightly deviated from the direction perpendicular to the surface of the semiconductor thin film 2 of the sample, that is, an angle of 30 ° or less with respect to the vertical line. It is preferable to install. This is because the reflected light reflected from the sample semiconductor is easily received by the light receiving means 7 described later. In addition, it can also install coaxially with the excitation light irradiation means mentioned later using optical elements, such as a prism.

  Note that, as will be described later, the observation light irradiation means 6 can also be installed so that the observation light can be irradiated to the back surface (substrate 1 side) of the semiconductor that is the sample.

(Excitation light irradiation means)
Subsequently, the excitation light is irradiated by the excitation light irradiation means 3 on the semiconductor surface irradiated with the observation light as described above (step S2). The excitation light serves as means for exciting carriers to the semiconductor thin film 2. Therefore, as a light source included in the excitation light irradiation means 3, when the semiconductor thin film 2 is a poly-Si film having a film thickness of several tens of nanometers, the energy of the excitation light is used to generate carriers in the thin film. It is preferable to employ one that generates light having a wavelength shorter than the wavelength corresponding to the energy gap and having a high absorptance (short penetration depth). Examples of this include an N ₂ laser (wavelength = 337 nm) that generates light having a wavelength of 400 nm or less, a third harmonic of a YAG laser (wavelength = 355 nm), and the like.

  The irradiation range 31a (FIG. 4) on the semiconductor thin film 2 by the excitation light irradiation means 3 constitutes an irradiation optical system so as to have a substantially circular shape with a diameter of about 10 μm to 100 μm, for example. Irradiate to form a perfect circle on the surface of 2. By this excitation light irradiation, carriers are excited in a circular region on the surface of the semiconductor thin film 2. Here, since the photoexcited carriers excited by the excitation light irradiation diffuse the surface of the semiconductor thin film 2 approximately two-dimensionally by natural diffusion after the excitation light irradiation, the region where the number of carriers changes by the excitation light irradiation is the excitation light. The range is wider than the irradiation range 31a by the amount of natural diffusion.

  In this embodiment, the portion irradiated with the observation light on the semiconductor thin film 2 is irradiated with the excitation light. However, this is for convenience and the excitation light is irradiated first. In addition, it is possible to continuously irradiate the observation light to the region including the irradiation range after a certain time within the lifetime of the photoexcited carrier.

(Light receiving means—first light receiving step)
Next, the reflected light reflected by the surface of the semiconductor thin film 2 is received by the light receiving means 7 (first light receiving step, step S3). Thereby, the distribution of reflected light intensity in a state where no electric field is applied is detected.

  The carrier density of the semiconductor thin film 2 is increased by the amount of photoexcited carriers by irradiation with excitation light. Since the dielectric constant of the semiconductor thin film 2 is dependent on carrier density, it changes according to the carrier density. And, as the dielectric constant ε of the semiconductor thin film 2 changes according to the carrier density in this way, the refractive index n of the semiconductor thin film 2 becomes

It depends on the relationship. As a result, the reflected light intensity of the observation light irradiated on the semiconductor thin film 2 also changes.

  Therefore, since the reflected light intensity of the observation light irradiated on the semiconductor thin film 2 changes according to the spatial distribution state of the carrier density, the reflected light intensity of the reflected light is received by receiving the reflected light of the observation light with the light receiving means. If the distribution is detected, after all, the carrier distribution of the semiconductor thin film 2, that is, the carrier density distribution state can be detected.

  As such a light receiving means 7, for example, a one-dimensional line sensor can be used. As such a one-dimensional line sensor, a light receiving element such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) sensor is used. Can be used.

  The light receiving means 7 is installed in a direction perpendicular to the surface of the semiconductor thin film 2 so that the reflected light reflected from the surface of the semiconductor thin film 2 can be received from the observation light irradiation means 6. It is preferable to install it so as to make an angle of 30 ° or less with respect to the vertical line in a direction slightly deviating from the direction in which the observation light irradiation means 6 oscillates. In addition, it can also install coaxially with the above-mentioned excitation light irradiation means using optical elements, such as a prism.

  The one-dimensional line sensor as the light receiving means 7 includes the center of the excitation light irradiation range 31a as shown in FIG. 4, and detects the reflected light intensity at each position in the electric field application direction described later. It is preferable to have a measurement region 71a so that the reflected light intensity distribution can be detected.

  Further, such detection may basically be performed once. It should be noted that step S3 may be detected a plurality of times in order to reduce noise, reduce errors, or to accumulate for easy reading of intensity changes.

  4A is an image diagram of the distribution state of excited carriers when the electric field E is not applied (first light receiving step, step S3), and shows a state captured as reflected light intensity. . A range 33a indicates a range where the distribution of reflected light intensity is equal to or greater than a certain threshold. The length of the range in the X-axis direction is X1, and the length in the Y-axis direction is Y1. In the present embodiment, the measurement is performed by a one-dimensional line sensor having the measurement region 71a from the position X0 to the position X3. Therefore, the reflected light intensity less than the above threshold is from the position X0 to the position X1L and from the position X1R to the position X3. Observed, a reflected light intensity equal to or greater than the above threshold is observed from position X1L to position X1R (the distance from position X1L to position X1R is X1).

(Electric field applying means)
Subsequently, with respect to the region of the surface of the semiconductor thin film 2 that includes the entire range in which photoexcited carriers are excited by the excitation light irradiation unit 3, the direction of the electric field in the region is changed using the electric field applying unit 5. A single frequency electric field is applied in a non-contact manner so as to be in one direction (step S4). The electric field is preferably a high-frequency electric field and can oscillate from the oscillator 4. The photoexcited carriers generated by irradiating the surface of the semiconductor thin film 2 with the excitation light by the excitation light irradiating means 3 diffuses the surface of the semiconductor thin film 2 approximately two-dimensionally by natural diffusion after the excitation light irradiation. The application of the electric field also causes carrier movement by electric field driving along the direction of the electric field.

The maximum amount of carrier movement by this electric field drive depends on mobility, electric field strength, and frequency. The frequency f of the high-frequency electric field needs to be higher than 1 / (2τ) where τ is the carrier lifetime. For example, when the carrier lifetime is about 10 ns and the electric field strength is 1E5 V / m, the frequency f is 100 MHz or more, preferably several hundred MHz or more. The upper limit of the frequency f is determined by the mobility. For example, when the mobility is 100 cm ² / V · s, the frequency f is 10 GHz or less, preferably 1 GHz or less. When electromagnetic waves with a frequency not in such a range are used, for example, when the frequency f is low, the change in the electric field is slow, the carrier lifetime of the photoexcited carrier is reached before the electric field becomes maximum, and most of the carriers disappear due to recombination. Therefore, it becomes impossible to distinguish from the amount that should be moved by the electric field, and the carrier mobility cannot be estimated. On the other hand, when the frequency f is high, the change in the electric field is fast, so that the maximum movement amount of the carrier is small, and it is difficult to obtain a difference in the movement amount unless the spatial resolution of the light receiving means can be increased. In addition, although it is preferable to employ | adopt the thing of a single frequency as such electromagnetic waves from a viewpoint of the ease of analysis, it is not restricted only to this.

  As a specific method for applying an electric field, it can be applied in a non-contact manner by an antenna such as a dipole antenna or a horn antenna. Since it is non-contact, it does not damage or destroy the semiconductor thin film. In the case of a dipole antenna, the antenna has a long axis direction that is the direction of the electric field. When the opening surface of the horn antenna is rectangular, the short axis direction of the rectangle is the direction of the electric field. Therefore, the direction in which the electric field is to be applied and the short axis direction of the rectangle are aligned. The distance between the semiconductor thin film 2 and the antenna is preferably as close as possible in order to apply an electric field in one direction.

  Since the application of such an electric field is oscillated by the oscillator 4 as described above, this oscillator 4 is usually connected to the electric field applying means 5. If necessary, a matching unit for impedance matching can be inserted between the oscillator 4 and the electric field applying means 5.

  In the above description, the high-frequency electric field is illustrated as an example of the electric field applied by the electric field applying unit. However, the applied electric field is not limited to the high-frequency electric field in this way, and a constant electric field is applied. Needless to say, you can.

(Light receiving means—second light receiving step and calculation step)
Subsequently, on the semiconductor surface (semiconductor thin film 2 side) to which the electric field is applied in this way, the reflected light obtained by reflecting the observation light is received by the light receiving means 7 (second light receiving step, step S5). Thereby, the distribution of the carrier density in a state where an electric field is applied is detected by detecting the distribution of the reflected light intensity on the surface (main surface) of the semiconductor thin film 2. Thus, based on the same idea as the first light receiving step (step S3) described above, it is possible to detect the spatial distribution state of the carrier density in a state where an electric field is applied.

  That is, the one-dimensional line sensor is used as the light receiving means 7, and the one-dimensional line sensor is installed in the same direction as that measured in the first light receiving step (step S3) and reflected from the semiconductor thin film 2. By receiving the reflected light, the distribution of the reflected light intensity is detected, and the spatial distribution of the carrier density is detected.

  FIG. 4B is an image diagram of a distribution state of excited carriers when the electric field E is applied (second light receiving step, step S5), and shows a state captured as reflected light intensity. . A range 33b indicates a range in which the reflected light intensity is equal to or greater than a certain threshold, and the length in the X-axis direction of the range is X2, and the length in the Y-axis direction is Y2. In the present embodiment, as described above, since the measurement is performed by the one-dimensional line sensor having the measurement region 71a from the position X0 to the position X3, the position X0 to the position X2L and the position X2R to the position X3 are less than the above threshold. The reflected light intensity is observed, and the reflected light intensity equal to or higher than the above threshold is observed from the position X2L to the position X2R (the distance from the position X2L to the position X2R is X2).

  Subsequently, after the series of measurements is completed as described above, the application of the electric field is stopped, the irradiation of the excitation light is stopped, and the irradiation of the observation light is also stopped (step S6). In order to continuously perform the next measurement, these stop operations may not be performed.

  Subsequently, with respect to the distribution of the reflected light intensity detected in the first light receiving step (step S3) and the second light receiving step (step S5), FIGS. 4 (a) and 4 (b) are merely represented as images. However, this is actually subjected to arithmetic processing such as threshold processing, and the range of reflected light intensity above a certain threshold is identified by changing the carrier density and applying an electric field (step S7). That is, when no electric field is applied (first light receiving step, step S3), the position of the boundary where the reflected light intensity reaches a certain threshold (positions represented by X1L and X1R in FIG. 4A), and the electric field When applied (second light receiving step, step S5), the positions of the boundaries (positions represented by X2L and X2R in FIG. 4B) where the reflected light intensity reaches a certain threshold are actually obtained by calculation. Thus, the range in which the reflected light intensity distribution is equal to or greater than a certain threshold (that is, the reflected light intensity distribution range) is, for example, as shown in FIGS. 4 (a) and 4 (b), X1L, X1R, X2L and X2R are obtained, and further, X1 and X2 are obtained as the length of this range in the X-axis direction. Therefore, it is preferable that the measuring apparatus of the present application includes the calculation means 9 so that such calculation can be easily performed, and the calculation means 9 is preferably connected directly or indirectly to the light receiving means 7. . For example, in FIG. 3, the calculating means 9 is indirectly connected to the light receiving means 7 via the control means 8 described later.

  Next, based on the distribution of each reflected light intensity obtained in step S7 (that is, the distribution range of the reflected light intensity subjected to the threshold processing), the change in the distribution of the reflected light intensity depending on whether or not the electric field is applied (the distribution range of the reflected light intensity) Change) ΔX (= X2−X1) is obtained (step S8). As a result, the light receiving means 7 (and the calculating means 9) can detect the range (reflected light intensity distribution range) in which the reflected light intensity due to the presence or absence of electric field application exceeds a certain threshold value. That is, when the frequency and the electric field are constant, the position of the boundary where the intensity of the reflected light when the electric field is applied becomes a threshold value changes mainly depending on the magnitude of the carrier mobility. Therefore, when the calculation means 9 is used to calculate the difference in the position of this boundary (that is, the change in the distribution range of the reflected light intensity) depending on whether or not an electric field is applied (calculation step), this difference corresponds to the carrier mobility due to the electric field. Therefore, as a result, carrier mobility (that is, electrical characteristics of the semiconductor) is required.

That is, when the carrier velocity is v, the carrier mobility is μ, and the electric field is E,
v = μE
It is expressed. If the electric field is a single-frequency high-frequency electric field and the carrier is an electron, the carrier has a negative charge, and therefore, it moves by receiving a force in the direction opposite to the electric field direction at the single frequency. A single-frequency electric field E has an electric field amplitude E ₀ , a frequency f, a time t, and an initial phase φ.
E = E ₀ sin (2πft + φ)
Using this, the carrier speed v is
v = μE ₀ sin (2πft + φ)
It is expressed.

  Since the carrier displacement may be obtained by integrating v with time, the integrated displacement is proportional to the product of the mobility and the electric field and inversely proportional to the frequency. Therefore, although the value of ΔX changes depending on the setting of the threshold value of the reflected light intensity, if the electric field, the frequency, and the threshold value are constant, measuring ΔX results in measuring the carrier mobility of the semiconductor thin film 2. Will be.

  As described above, the distribution of the reflected light (or transmitted light) intensity changes between when the electric field is applied by the electric field applying means and when it is not applied, and the change in the distribution (the amount of change in the distribution range). ) Is detected by the light receiving means (more specifically, calculation is performed by the arithmetic means connected to the light receiving means), and as a result, semiconductor electrical characteristics such as carrier mobility can be measured.

(Control means)
The timing of application of electric field, excitation light / observation light irradiation, stop, detection, and the amount and direction of application and irradiation in each step are controlled by the control unit 8 in a centralized manner. Therefore, the control means 8 controls each said means by being connected to each said means indirectly or directly.

  As such a control means 8, a switching circuit, a computer, etc. can be used, for example. It is also desirable to sequence the controls for efficient measurement. Furthermore, it is desirable to attach a database or memory for storing control conditions and recording measurement results.

(transportation)
A plurality of locations on the semiconductor surface are measured by providing a moving means for moving the semiconductor as a sample relative to the measurement system comprising the excitation light irradiation means, the electric field application means, the observation light irradiation means, and the light receiving means. Can be. As a result, the mobility distribution on the semiconductor surface can be measured more easily, and an amorphous-Si film, such as a poly-Si film prepared by the ELA method or the like, can be easily distributed in in-plane characteristics. It is possible to configure an electrical property measuring apparatus that measures semiconductor carrier mobility effective for evaluation. Therefore, the measurement apparatus may include a moving unit that moves the semiconductor as a sample relative to the measurement system as necessary.

  As described above, when the semiconductor electrical property measuring apparatus having the above-described configuration is used, the carrier mobility equivalent amount of the semiconductor thin film can be easily measured without contact. Further, if the threshold value related to ΔX is set to a desired value, it is possible to easily perform the pass / fail judgment process of the electrical characteristics of the semiconductor.

  In the above, the case where the reflected light intensity becomes higher as the carrier density is higher is described. Therefore, attention is paid to the case where the reflected light intensity exceeds a certain threshold, but depending on the wavelength of the observation light and the type of the semiconductor material. In some cases, the higher the carrier density, the lower the reflected light intensity. In such a case, the above-described magnitude relationship of the reflected light intensity is reversed, and the distribution range of the reflected light intensity within a range below a certain threshold is detected.

  In the above description, the carrier mobility has been described as an example of the semiconductor electrical characteristics. However, the semiconductor electrical characteristics referred to in the present invention are not limited to such carrier mobility, and various types related to the carrier mobility. And other electrical characteristics are included.

<Embodiment 2>
In the present embodiment, the measurement of the carrier mobility by the semiconductor carrier mobility measuring device when the light receiving means 7 is equipped with a two-dimensional area sensor instead of the one-dimensional line sensor in the first embodiment described above, This will be described with reference to FIG.

  In the present embodiment, in the case where the sample is a semiconductor having isotropicity in the sample surface, the second light receiving step (step S3) is directly performed without performing the operation of the first light receiving step (step S3) in the first embodiment. Two-dimensional measurement (calculation of change in distribution range of two-dimensional intensity) is performed by the operation of S5). That is, the distribution of the reflected light intensity in a direction perpendicular to the direction parallel to the electric field application direction is detected by the second light receiving step, and the change in the distribution range of the two-dimensional intensity is detected in the calculation step (step S8). It is obtained by calculation.

  An imaging element such as a CCD or CMOS can also be used as the two-dimensional area sensor.

  First, as shown in FIG. 5A, when the sample is an isotropic semiconductor, X1 = Y1 in the state of the first light receiving step (step S3) in which no electric field is applied. That is, FIG. 5A is an image diagram of a distribution state of excited carriers when the electric field E is not applied (first light receiving step, step S3), and shows a state captured as reflected light intensity. When the excitation light irradiation means irradiates the excitation light irradiation range 31a with the excitation light irradiation means, the range 33a indicates a range where the reflected light intensity is equal to or greater than a certain threshold, and the length of the range in the X-axis direction is X1, Y The length in the axial direction is Y1. In the present embodiment, since the measurement is performed by the two-dimensional area sensor having the measurement region 71a surrounded by the X-axis direction (from the position X0 to the position X3) and the Y-axis direction (from the position Y0 to the position Y3), From the position X1L to the position X3, and from the position Y0 to the position Y1L and from the position Y1R to the position Y3 (that is, the portion other than the range 33a), the reflected light intensity less than the above threshold is observed, and from the position X1L to the position X1R. And from the position Y1L to the position Y1R (that is, the portion of the range 33a), the reflected light intensity equal to or higher than the above threshold value is observed (the distance from the position X1L to the position X1R is X1, and the position Y1L to the position Y1R) To Y1).

  On the other hand, in the state of the second light receiving step (step S5) in which an electric field is applied as shown in FIG. 5B, the electric field is applied in one direction and no electric field is applied in the Y-axis direction, so that Y2 = Y1. Become. FIG. 5B is an image diagram of a distribution state of excited carriers when the electric field E is applied (second light receiving step, step S5), and shows a state captured as reflected light intensity. A range 33b indicates a range in which the reflected light intensity is equal to or greater than a certain threshold, and the length in the X-axis direction of the range is X2, and the length in the Y-axis direction is Y2. In the present embodiment, since the measurement is performed by the two-dimensional area sensor having the measurement area 71a as described above, the position X0 to the position X2L, the position X2R to the position X3, the position Y0 to the position Y2L, and the position Y2R to the position Y3. Up to (that is, the portion other than the range 33b), the reflected light intensity less than the above threshold value is observed, and from the position X2L to the position X2R and from the position Y2L to the position Y2R (that is, the portion of the range 33b), the reflected light having the above threshold value or more. Intensity will be observed (the distance from position X2L to position X2R is X2, and the distance from position Y2L to position Y2R is Y2).

  For this reason, if X2 and Y2 are compared by a two-dimensional area sensor, after all, X2 and X1 are compared. Therefore, in such a case, the displacement range of the carrier density before and after the electric field application can be obtained by performing only the second light receiving step (step S5) without performing the first light receiving step (step S3). Therefore, by using a semiconductor carrier mobility measuring device equipped with a two-dimensional area sensor as the light receiving means 7, compared to the first embodiment, when measuring the mobility of a semiconductor sample having isotropic properties in the sample plane. Step S3 can be omitted for measurement.

  On the other hand, if the sample is a semiconductor having anisotropy in a certain direction within the sample surface, a difference occurs in the direction of natural diffusion of the photoexcited carriers even if the excitation light spot is a perfect circle. Therefore, there is a case where X1 ≠ Y1 even in the state of the first light receiving step (step S3) where no electric field is applied. Therefore, in such a case, as in the first embodiment, the measurement results of the first light receiving step (step S3) and the second light receiving step (step S5) are compared, or compared with the reference sample. It is desirable to do it. In addition, it is desirable to match the direction of application of the electric field with the anisotropic direction or the direction perpendicular to the anisotropic direction. When the direction of anisotropy is unknown, the direction of the electric field is changed in the sample plane with respect to a certain measurement point, and the direction of anisotropy is determined by comparing each reflected light intensity within a certain threshold range or more. Can be detected.

  In the above, the case where the reflected light intensity becomes higher as the carrier density is higher is described. Therefore, attention is paid to the case where the reflected light intensity exceeds a certain threshold, but depending on the wavelength of the observation light and the type of the semiconductor material. In some cases, the higher the carrier density, the lower the reflected light intensity. In such a case, the above-described magnitude relationship of the reflected light intensity is reversed, and the reflected light intensity within a certain threshold value is detected.

<Embodiment 3>
In the first embodiment, the measurement is performed using values calculated from the reflected light intensity information at a plurality of positions at a certain timing. However, in the present embodiment, as a principle at a certain timing, A semiconductor electrical property confirmation method for confirming whether or not the distribution range of the reflected light intensity on the surface of the semiconductor is in an appropriate range using the information on the reflected light intensity at a single position will be described. Below, the case where the information of reflected light intensity is used is described as an example.

  That is, in this embodiment, as shown in FIGS. 6A to 6D, an electric field is applied from an irradiation point (center of the excitation light irradiation range 31a) where the excitation light is irradiated onto the surface of the semiconductor as a sample. The reflected light intensity r is measured with a point sensor having a measurement region 71a at the position xy0 after a predetermined time after the excitation light is applied and the electric field is applied at the position xy0 in the direction of It is characterized only by determining whether or not r is within an appropriate intensity range (range from Rmin (minimum intensity) to Rmax (maximum intensity)).

  Here, 36a and 36b represented by lengths Xl2 and Yl2 in FIGS. 6 (a) and 6 (b) indicate ranges where the reflected light intensity is equal to or higher than Rmin, and are the lengths in FIGS. 6 (c) and 6 (d). 36c and 36d represented by the lengths Xu2 and Yu2 indicate a range in which the reflected light intensity is Rmax or more. For example, if the measurement point (position xy0) corresponds to both FIGS. 6B and 6C, the reflected light intensity r at the measurement point (position xy0) is within an appropriate intensity range (from Rmin to Rmax). It can be evaluated that it has an appropriate reflected light intensity. As the point sensor, a light receiving element such as a semiconductor light receiving element or a photomultiplier tube can be used.

  Hereinafter, the steps of executing the above confirmation method will be described with reference to FIG. FIG. 7A shows a semiconductor sample (NG sample) whose reflected light intensity is not within an appropriate range, and FIG. 7B shows a semiconductor sample (Good sample) whose reflected light intensity is within an appropriate range.

  First, (i) while irradiating observation light by the observation light irradiation means and applying an electric field in one direction by the electric field application means, the excitation light is irradiated by the excitation light irradiation means to the irradiation point A on the surface of the semiconductor as a sample. Irradiate.

  Next, (ii) after a certain period of time, the reflected light intensity is measured by a point sensor as a light receiving means at a measurement point a at a certain distance from the irradiation point A of the excitation light.

  Subsequently, (iii) the sample is moved relative to the measurement system including the excitation light irradiation means and the light receiving means (not shown). Accordingly, (iv) the excitation light irradiating means can irradiate the irradiation point B different from the above with the excitation light.

  On the other hand, (v) it is inspected whether or not the reflected light intensity at the measurement point a is within a predetermined range 37 of appropriate reflected light intensity (not shown). (Vi) Then, the reflected light intensity is measured after a certain time in the same manner as described above at the measurement point b that is at a certain distance from the irradiation point B of the different excitation light. Thereafter, such operations of irradiation, measurement, movement, and inspection are repeated.

  By performing such an operation, it is possible to confirm whether or not the distribution range of the reflected light intensity at each measurement point on the surface of the semiconductor that is the sample is within an appropriate range. Note that the inspection (v) may be performed after the completion of (ii) to the start of the inspection corresponding to (vi).

  As a configuration of the apparatus suitable for such an operation, the excitation light irradiation means and the light receiving means are arranged on a straight line in the electric field direction, and further, the excitation light irradiation means, the electric field application means, the observation light irradiation means, and By synchronizing the measurement system composed of the light receiving means and scanning the sample semiconductor relatively, it is possible to continuously measure the sample semiconductor. Such an apparatus configuration is suitable for in-line inspection that requires quick evaluation.

  If the electric field applying means can apply a constant electric field within the region to be measured by scanning, it is not always necessary to perform relative movement with respect to the sample synchronized with the excitation light irradiating means, etc. Or may be intermittently synchronized with the excitation light irradiation means or the like.

  In such an in-line inspection, a two-dimensional area sensor or a one-dimensional line sensor can be used as a point sensor instead of a point sensor as a light receiving means. That is, using a two-dimensional area sensor or a one-dimensional line sensor, it is confirmed whether only a part of the reflected light intensity information (distribution range) captured by the sensor is within a predetermined appropriate range. You can also.

  For example, as shown in FIG. 8, a case where a one-dimensional line sensor having a measurement region 71a parallel to the locus 38 of the excitation light irradiation point is used will be described. In FIG. 8, (i) shows before excitation light irradiation, and (ii) shows after excitation light irradiation. Further, the ellipse indicates an appropriate reflected light intensity range 37.

  First, the excitation light irradiation means, the observation light irradiation means, and the electric field application means are synchronized, and these are moved relative to the sample synchronized with the one-dimensional line sensor. At the timing at which the measurement point a at a certain distance from the irradiation point A is to be measured, the reflected light intensity information corresponding to the measurement point a is used for confirmation in the one-dimensional line sensor, while At the timing at which the measurement point b at a certain distance is to be measured, the information on the reflected light intensity corresponding to the measurement point b is also used for confirmation in the one-dimensional line sensor.

  This eliminates the need for synchronous movement of the sensor. However, when the measurement area is wide, the angle and amount of light from the observation light irradiation means with respect to the sensor differ, which may cause an error in the reflected light intensity. For this reason, such a measuring method is suitable for a relatively small sample.

<Embodiment 4>
In the present embodiment, a case will be described in which the excitation light irradiation range in the first embodiment is a shape other than a perfect circle instead of a perfect circle.

  That is, in each of the above-described embodiments, the surface of the semiconductor that is the sample is irradiated with excitation light so as to form a perfect circle, but the shape of the irradiation range 31a of the excitation light on the semiconductor surface is, for example, It may be oval or an elongated rectangular shape as shown in FIG.

  9A shows the case where the electric field E is not applied, and FIG. 9B shows the case where the electric field E is applied. Reference numerals 33a and 33b each represent a distribution range of reflected light intensity exceeding a certain threshold value.

  On the other hand, when the irradiation range of the excitation light is elliptical, it is a case where X1 ≠ Y1 in FIG. 4, but each of the above-mentioned factors is considered by taking into account the aspect ratio (Y1 / X1) between the major axis direction and the minor axis direction of the ellipse. Measurement similar to the embodiment can be performed.

<Embodiment 5>
In the present embodiment, a case will be described in which each embodiment described above treats reflected light as a light reception target, whereas it treats transmitted light as a light reception target.

  That is, in each of the above-described embodiments, the target of light reception by the light receiving means is reflected light. However, depending on the type of semiconductor, the amount of change in transmitted light intensity is larger than the amount of change in reflected light intensity. There is a case. In such a case, as shown in FIG. 10, while the observation light irradiation means 6 is installed so that the observation light can be irradiated from the back surface of the semiconductor that is the sample (that is, the substrate 1 side), the surface of the semiconductor (that is, the surface) A semiconductor electrical property measuring apparatus capable of measuring semiconductor carrier mobility by installing excitation light irradiation means 3, oscillator 4, electric field application means 5, light receiving means 7 and control means 8 on the semiconductor thin film 2) side. Constitute. And by setting it as such an apparatus structure, the distribution of transmitted light intensity is received by the light receiving means, the distribution range of transmitted light intensity above a certain threshold is measured, and thereby the distribution range of transmitted light intensity above a certain threshold Thus, it is possible to measure the carrier mobility (ie, semiconductor electrical characteristics) of the semiconductor.

  In this case, as shown in FIG. 10, the observation light irradiating means 6 and the light receiving means 7 are installed in the vertical direction of the semiconductor surface, and the excitation light irradiating means 3 is at a certain angle from the vertical line, for example, 30 ° or less. It can be installed to make an angle. In addition, the configuration of the apparatus can be reduced in size by using a prism or the like so that the axes of the excitation light and the observation light are coaxial. The electric field applying means 5 can be provided with the same oscillator 4 as described above, and the light receiving means 7 can be provided with the same calculating means 9 as described above.

<Embodiment 6>
In the present embodiment, a case where a constant electric field is applied will be described, whereas a high frequency electric field having a single frequency is used for applying an electric field in each of the above embodiments.

  A dipole antenna was used for applying a high-frequency electric field. When a constant electric field was applied, a gap of several μm to several tens of μm was provided from the semiconductor thin film surface at two locations across the measurement point on the semiconductor thin film as a sample. Thus, an electrode is provided. Alternatively, a mercury probe or a metal electrode is provided in close contact with the semiconductor thin film. In this way, an electric field is applied by these electrodes.

When a constant electric field is applied, the carrier velocity v is calculated using the carrier mobility μ and the electric field E as described above.
v = μE
Can be expressed as

  For this reason, since the electric field E is constant, if the electric field is increased, the carrier velocity v increases in proportion to the electric field. Therefore, the moving distance after a certain period of time also increases in proportion to the electric field. However, since photoexcited carriers have a lifetime, the time during which they can move is limited by this carrier lifetime, and the distance that they can move is also limited.

  Since it is difficult to evaluate the carrier life by the method of the present embodiment, if the carrier life is measured by another method (for example, μ-PCD method) and the moving distance is obtained by the above method, the value corresponding to the mobility is obtained. Can be calculated, and mobility evaluation and pass / fail judgment can be made.

  In the case of a high frequency electric field, the direction of the electric field has two directions, a positive direction and a negative direction with respect to the reference point. Therefore, in the case of an isotropic sample, the change range of the light intensity is at the irradiation point of the excitation light. On the other hand, both sides are equal, but in the case of a constant electric field, since the direction of the electric field is one direction, the change range of the light intensity is not usually equal on both sides with respect to the irradiation point.

<Embodiment 7>
In the first embodiment, the light receiving step (both the first light receiving step and the second light receiving step) is performed in the excitation light irradiation state, whereas in the present embodiment, the excitation light irradiation state and the excitation light are This is a method of measuring semiconductor electrical characteristics (semiconductor carrier mobility) by performing a light receiving step in both non-irradiation states. The reflected light intensity or transmitted light intensity due to the observation light before and after the excitation light irradiation changes, and the change distribution of the reflected light intensity or transmitted light intensity (the change caused by the above change is a specific change width (ie, change amount)). The region to be changed further depends on the presence or absence of an electric field. The light receiving means detects the change in the variation distribution of the reflected light intensity or the transmitted light intensity.

  Such a measuring method is effective when the amount of change in reflected light intensity or the amount of transmitted light intensity of observation light is very small before and after irradiation with excitation light. That is, by continuously irradiating observation light and periodically irradiating excitation light, the reflected light intensity or transmitted light intensity of the observation light is synchronized with the excitation light period to lock the signal received by the light receiving means. By measuring with the in-amplifier, the component (DC component) that does not depend on the periodicity of the excitation light of reflected light intensity or transmitted light intensity is removed, and the component synchronized with the excitation light is amplified. The amount of change in reflected light intensity or transmitted light intensity can be detected. Therefore, the electrical characteristics of the semiconductor, such as carrier mobility, are measured from changes in the amount of change due to whether or not an electric field is applied. Hereinafter, the case of reflected light will be described as an example, but it goes without saying that it can also be used in transmitted light.

  FIG. 11 shows a flowchart for measuring the carrier mobility of a semiconductor by such a measuring method, and FIG. 12 is a schematic block diagram of a semiconductor electrical property measuring apparatus of the present invention suitable for such a measuring method. FIG. 13 and FIG. 14 are diagrams showing details of a range surrounded by a dotted line in FIG.

  FIG. 11 is a flowchart in the case of using the measuring apparatus shown in FIG. 13 so that the distinction between the light receiving steps can be easily understood. That is, the excitation light irradiating means and the light receiving means are connected, and the excitation light irradiating means 3 uses a pulse laser 301 that irradiates the excitation light multiple times with periodicity, and is synchronized with the period of the excitation light. A lock-in amplifier 701 and a light receiving sensor 702 are incorporated as the light receiving means 7 so that light can be received before the excitation light irradiation is turned on (excitation light non-irradiation state) and before the excitation light irradiation state (excitation light irradiation state) (that is, In the measuring apparatus of FIG. 13, the excitation light irradiation means 3 and the light receiving means 7 are connected, and a transmission frequency synchronization signal is sent from the pulse laser 301 to the lock-in amplifier 701.

  The pulse laser 301 used here is preferably a pulse laser having a frequency of about several tens of Hz to about 1 kHz, for example. The lock-in amplifier 701 is a kind of synchronous detector and belongs to a kind of voltmeter.

  On the other hand, while the pulsed light is irradiated by the excitation light irradiation means 3, that is, while the excitation light irradiation (ON) and non-irradiation (OFF) are periodically performed, the light reception means 7 may continue to receive light continuously. In such a case, information according to the period of the excitation light can be utilized in a post-process in the calculation step.

  Further, as shown in FIG. 14, as the excitation light irradiation means 3 that irradiates excitation light multiple times with periodicity, a device capable of irradiating continuous excitation light (CW (continuous oscillation) laser 302) and excitation light are used. By using the optical element (optical chopper 303) to be cut off and issuing a reference signal from the oscillator 304, the driving of the optical chopper 303 and the light reception of the light receiving means 7 (the lock-in amplifier 701 and the light receiving sensor 702) are synchronized (that is, It is also possible to measure (by receiving light in synchronization with the period of the excitation light). That is, an optical chopper 303 (rotating disk with slits) that rotates at a frequency of about several tens of Hz to 1 kHz in the optical path between the excitation light emitted by the CW laser 302 and the sample irradiated with the excitation light. By placing, the excitation light is chopped. Thereby, the excitation light irradiated to the sample is repeatedly irradiated (ON) and non-irradiated (OFF), and the amount of change in reflected light intensity can be measured by synchronizing the light receiving step with this.

  As described above, this measurement method irradiates the sample with excitation light periodically in a state where an electric field is applied and a state where no electric field is applied, and repeatedly receives reflected light from observation light in synchronization with the cycle. By receiving light at multiple locations by means, and processing the signal at each location with a lock-in amplifier, the amount of change in reflected light intensity due to the presence or absence of excitation light detection is detected at multiple locations, and the amount of change in reflected light intensity by threshold processing Obtain the distribution range. Next, electrical characteristics such as carrier mobility of the semiconductor are measured by calculating the amount of change in the distribution range of the amount of change in reflected light intensity depending on whether or not the electric field is applied. Hereinafter, a description will be given based on FIG.

  First, the observation light irradiation means 6 irradiates the surface of the semiconductor (semiconductor thin film 2), which is a sample, with observation light (step S11). The reflected light reflected from the surface of the semiconductor sample is received by the light receiving means 7 at a plurality of locations, and the reflected light intensity of the observation light from the semiconductor sample is received at the plurality of locations (step S12). . That is, by this step, reflected light intensity in a state where no electric field is applied and excitation light is not irradiated is received at a plurality of locations.

  Next, excitation light is irradiated by the excitation light irradiation means 3 on the surface of the semiconductor sample irradiated with the observation light as described above (step S13). In this state, the light receiving means 7 receives the reflected light intensity of the observation light from the semiconductor sample at a plurality of locations (step S14). That is, by this step, the reflected light intensity in a state where no electric field is applied and excitation light irradiation is received at a plurality of locations.

  Subsequently, the irradiation of excitation light is stopped (step S15). The operations in steps S12 to S15 are repeated. The number of repetitions is about 10 to 10000, and is selected according to the noise of the signal. By repeating these operations in this manner, the reflected light intensity of the observation light depending on the presence or absence of excitation light irradiation with no electric field applied is received at a plurality of locations (the distribution of changes in the reflected light intensity of the observation light is received by the light receiving means). Can be detected).

  During the above operation, for example, the light reception signal of the reflected light reflected from the semiconductor sample is input to the lock-in amplifier 701 built in the light receiving means 7 and the synchronization signal of the period of the excitation light irradiated to the semiconductor sample is obtained. Is also input to detect the change amount of the reflected light intensity by acquiring the output signal, and the change amount distribution range of the reflected light intensity is identified by the threshold processing (step S16).

  Subsequently, the electric field applying unit 5 applies a region on the surface of the semiconductor sample (semiconductor thin film 2) that includes at least the range irradiated with the excitation light by the excitation light irradiation unit 3. An electric field is applied so that the direction of the electric field is one direction (step S17). Next, the reflected light reflected by the surface of the semiconductor sample is received by the light receiving means 7, and the reflected light intensity of the observed light from the semiconductor sample is received at a plurality of locations (step S18). That is, the reflected light intensity in the electric field applied state and the excitation light non-irradiated state is received at a plurality of locations by this step.

  Next, excitation light is irradiated by the excitation light irradiation means 3 on the surface of the semiconductor sample irradiated with the observation light as described above (step S19). In this state, the light receiving means 7 receives the reflected light intensity of the observation light from the semiconductor sample at a plurality of locations (step S20). That is, by this step, the reflected light intensity in the electric field application state and the excitation light irradiation state is received at a plurality of locations.

  Subsequently, the irradiation of excitation light is stopped (step S21). The operations in steps S18 to S21 are repeated. The number of repetitions is about 10 to 10000 as described above, and is selected according to the noise of the signal, but it goes without saying that it is preferable to reduce the number of repetitions. By repeating these operations in this way, the reflected light intensity of the observation light depending on the presence or absence of excitation light irradiation in an electric field applied state is received at a plurality of locations (the distribution of changes in the reflected light intensity exceeding a certain threshold is received by the light receiving means. Detection).

  During the above operation, for example, the light reception signal of the reflected light reflected from the semiconductor sample is input to the lock-in amplifier 701 built in the light receiving means 7 and the synchronization signal of the period of the excitation light irradiated to the semiconductor sample is obtained. Is also input to detect the change amount of the reflected light intensity by acquiring the output signal, and the change amount distribution range of the reflected light intensity is identified by threshold processing (step S22).

  Subsequently, after the series of measurements is completed as described above, the application of the electric field is stopped and the irradiation of the observation light is also stopped (step S23).

  Next, the carrier mobility of the semiconductor sample can be obtained by performing an arithmetic process (calculation) on the change amount (difference) in the change amount distribution range of the reflected light intensity obtained in step S16 and step S22, respectively. Yes (step S24 (calculation step)).

  Thus, since the amount of change in the reflected light intensity of the observation light irradiated on the semiconductor sample changes according to the spatial distribution state of the carrier density, the reflected light is received by receiving the reflected light of the observation light with the light receiving means. If the amount of change in intensity is detected at a plurality of locations, the carrier distribution in the plane of the semiconductor sample, that is, the carrier density distribution state can be detected after all, and in the same manner as in the first embodiment. The carrier mobility can be measured.

  In short, the measurement method described above is a method for measuring semiconductor electrical characteristics using a semiconductor electrical property measurement device having a specific structure as described above, and irradiating the surface of the semiconductor with observation light by observation light irradiation means. However, the variation distribution of the reflected light intensity (or transmitted light intensity) of the observation light in the case where the excitation light irradiation means irradiates the excitation light and the case where the excitation light irradiation means does not irradiate in the state where no electric field is applied by the electric field application means. And the reflected light intensity (or transmitted light intensity) of the observation light in the case where the excitation light is irradiated by the excitation light irradiation means in the state where the electric field is applied by the electric field application means and in the case where the excitation light is not irradiated. Detecting the change distribution of the light by the light receiving means, and thresholding the change distributions to obtain respective change distribution ranges. A step, is intended to include a calculation step for obtaining a semiconductor electrical characteristics by determining the changes in their variation distribution range.

  Note that the above-described method for handling a minute signal is based on the fact that, for example, in the first embodiment, when the change in the variation distribution range of the reflected light intensity is small when the electric field is turned on and off, the electric field is turned on and off periodically. It is also possible to measure a minute variation distribution range of reflected light intensity by performing light reception, calculation, etc. by the light receiving means in synchronization with it.

  In the above first to seventh embodiments, a semiconductor thin film of about several tens of nanometers is targeted as a semiconductor sample for measurement, but the semiconductor electrical property measuring apparatus of this embodiment is a thick film of several μm order, The present invention can also be applied to a bulk semiconductor substrate or an SOI substrate. However, in that case, the wavelength of the light for exciting the carriers varies depending on the thickness of the semiconductor portion or the portion to be measured and the semiconductor material. Therefore, an excitation light irradiation means having an excitation light source according to the purpose is required. It is preferable to select. Further, in the electric field applying means, it is preferable to select the frequency and electric field strength of the electromagnetic wave for applying the electric field according to the carrier lifetime and the carrier mobility.

  The wavelength of the light source included in the observation light irradiation means is not particularly limited as long as appropriate reflection is possible in consideration of the thickness of the semiconductor thin film, the refractive index, the irradiation angle, the nearby layer configuration, and the like. It is preferable to select such that the change in reflected light intensity is large. Further, as the observation light, light having a single wavelength or a narrow wavelength band is desirable so that the refractive index does not vary greatly with the wavelength of the observation light. More specifically, it is preferable to use single wavelength light having a wavelength of 1.2 to 4.0 μm.

  The embodiments and examples disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a flowchart for performing the measuring method of a semiconductor electrical property (semiconductor carrier mobility) using the semiconductor electrical property measuring apparatus of this invention. It is a schematic block diagram of the measuring apparatus of semiconductor electrical characteristics. It is a schematic block diagram of the semiconductor electrical property measuring apparatus provided with a calculating means. It is an image figure of the distribution range of the carrier excited by irradiating the semiconductor surface with excitation light in a perfect circle shape, (a) shows the case where no electric field is applied, (b) shows the electric field. The case where is applied is shown. It is an image figure of the distribution range of the carrier in the case of using a two-dimensional area sensor as a light receiving means, (a) shows the case where an electric field is not applied, (b) shows the case where an electric field is applied. ing. It is an image diagram of a carrier distribution range when a point sensor is used as a light receiving means, where (a) is r <Rmin, (b) is Rmin ≦ r, (c) is r ≦ Rmax, d) shows the case where Rmax <r. It is the schematic of the method of confirming using the point sensor as a light-receiving means whether the reflected light intensity in the surface of a semiconductor exists in an appropriate range, Comprising: (a) is not in an appropriate range. A semiconductor sample is shown, (b) shows a semiconductor sample whose reflected light intensity is within an appropriate range. It is the schematic of the method of confirming whether the reflected light intensity in the surface of a semiconductor exists in an appropriate range using a one-dimensional line sensor as a light-receiving means. It is an image figure of the distribution range of the carrier excited by irradiating a semiconductor surface with excitation light in the shape of a long and narrow rectangle, (a) shows the case where an electric field is not applied, and (b) shows an electric field. The case where is applied is shown. It is a schematic block diagram of the measurement apparatus of the semiconductor electrical property in the case of receiving transmitted light. To perform a method for measuring semiconductor electrical characteristics (semiconductor carrier mobility) when the change in reflected light intensity of observation light is very small before and after irradiation with excitation light, using the semiconductor electrical property measurement apparatus of the present invention It is a flowchart. It is a schematic block diagram of a semiconductor electrical property measuring apparatus to which excitation light irradiation means and light receiving means are connected. It is the schematic block diagram which showed the detail of the excitation light irradiation means in the said apparatus, and the light-receiving means. It is another schematic block diagram which showed the detail of the excitation light irradiation means in the said apparatus, and the light-receiving means. It is a schematic block diagram of the conventional semiconductor electrical property measuring apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Substrate, 2 Semiconductor thin film, 3 Excitation light irradiation means, 31a Excitation light irradiation range, 33a, 33b range, 4 Oscillator, 5 Electric field application means, 6 Observation light irradiation means, 7 Light reception means, 71a Measurement area, 8 Control means, 9 arithmetic means, 301 pulse laser, 302 CW laser, 303 optical chopper, 304 oscillator, 701 lock-in amplifier, 702 light receiving sensor, 21 femtosecond visible light pulse laser, 21a, 21b visible light pulse, 22 terahertz pulse light source, 22a terahertz Pulse light, 23a Photometric optical system, 24-hour delay movable mirror, 25 semiconductor wafer, 26 terahertz pulse detector, 28 semi-transmission mirror.

Claims (14)

Excitation light irradiation means for exciting carriers with excitation light to the surface of a semiconductor that is a sample;
An electric field applying means for applying an electric field to a region including the entire range irradiated with the excitation light so that the direction of the electric field in the region is one direction;
Observation light irradiation means for irradiating observation light to a region including the entire range irradiated with the excitation light, or the back surface of the semiconductor corresponding to this region;
A light receiving means for receiving the reflected light transmitted by the semiconductor or the transmitted light transmitted by the semiconductor;
Control means for controlling each means;
A device for measuring semiconductor electrical characteristics, comprising:   In the case where an electric field is applied by the electric field applying means and in the case where an electric field is not applied, the reflected light intensity distribution or transmitted light intensity distribution by the observation light after excitation light irradiation changes, and the change in the distribution is 2. The semiconductor electrical property measuring apparatus according to claim 1, wherein the device is detected by a light receiving means.   In the case where an electric field is applied by the electric field applying means and in the case where the electric field is not applied, the variation distribution of the reflected light intensity or transmitted light intensity due to the observation light before and after the excitation light irradiation changes, and the variation distribution 2. The semiconductor electrical property measuring apparatus according to claim 1, wherein the change is detected by the light receiving means.   4. The semiconductor electrical property measuring apparatus according to claim 1, wherein the light receiving means is one of a one-dimensional line sensor, a two-dimensional area sensor, and a point sensor.   5. The semiconductor electrical property measuring apparatus further comprises a calculation means, and the calculation means is connected directly or indirectly to the light receiving means. The semiconductor electrical property measuring apparatus according to 1.   The semiconductor electrical property measuring apparatus according to claim 1, further comprising an oscillator, and the oscillator is connected to the electric field applying unit. measuring device.   7. The semiconductor electrical property measuring apparatus according to claim 1, wherein the electric field applied by the electric field applying means is a constant electric field or a high-frequency electric field.   The semiconductor electrical property measuring apparatus includes a moving unit that moves a semiconductor as a sample relative to a measurement system including the excitation light irradiation unit, the electric field application unit, the observation light irradiation unit, and the light receiving unit. The device for measuring semiconductor electrical characteristics according to claim 1, further comprising a plurality of locations on the surface of the semiconductor.   The excitation light irradiating means and the light receiving means are connected, the excitation light irradiating means irradiates excitation light multiple times with periodicity, and the light receiving means has a period of the excitation light. 4. The semiconductor electrical property measuring device according to claim 3, wherein the device receives light in synchronization with the signal. An observation light irradiation step for irradiating the surface of the semiconductor, which is a sample, with the observation light;
An excitation light irradiation step for exciting the carriers by irradiating excitation light to a specific area within the region irradiated with the observation light or the region of the back surface of the semiconductor corresponding to the region;
A first light receiving step for receiving the reflected light reflected by the semiconductor or the transmitted light transmitted by the semiconductor;
An electric field applying step for applying an electric field in which the direction of the electric field in the region is one direction to a region including the entire range irradiated with the excitation light;
A second light receiving step for receiving the reflected light reflected or transmitted by the semiconductor in the range where the electric field is applied;
A calculation step for obtaining a change in the distribution range of the reflected light intensity or the distribution range of the transmitted light intensity detected in the first light receiving step and the second light receiving step by calculation, and obtaining an electric characteristic based on the result;
A method for measuring semiconductor electrical characteristics, comprising:   11. The method for measuring semiconductor electrical characteristics according to claim 10, wherein the electric field applied in the electric field applying step is a constant electric field or a high-frequency electric field.   The first light receiving step is omitted, and a two-dimensional area sensor is used as the light receiving means in the second light receiving step, and the two-dimensional intensity distribution of reflected light or transmitted light obtained in the second light receiving step in the calculation step. 12. The method for measuring semiconductor electrical characteristics according to claim 10, wherein a change in the range is obtained by calculation. A method for confirming semiconductor electric characteristics using the semiconductor electric characteristic measuring apparatus according to claim 4, comprising:
A point sensor is used as the light receiving means, and it is confirmed whether or not the distribution range of reflected light intensity on the surface of the semiconductor as a sample is in an appropriate range, or a one-dimensional line sensor or a two-dimensional area as the light receiving means Using a sensor and confirming whether the distribution range of a part of the reflected light intensity on the surface of the sample semiconductor is within an appropriate range;
A method for confirming semiconductor electrical characteristics. A method for measuring semiconductor electrical characteristics using the semiconductor electrical characteristics measuring device according to claim 9, comprising:
The observation light in the case where the excitation light is irradiated by the excitation light irradiation means and the irradiation is not performed in the state where the electric field is not applied by the electric field application means while the observation light irradiation means irradiates the surface of the semiconductor with the observation light. Detecting a variation distribution of reflected light intensity or transmitted light intensity by the light receiving means;
A variation distribution of the reflected light intensity or transmitted light intensity of the observation light when the excitation light is irradiated by the excitation light irradiating means and when the excitation light is not irradiated in a state where an electric field is applied by the electric field applying means. Detecting with
A step of thresholding these variation distributions to obtain respective variation distribution ranges;
A calculation step for obtaining semiconductor electrical characteristics by obtaining changes in the variation distribution range thereof,
A method for measuring semiconductor electrical characteristics, comprising:

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