JP2008026496A - Apparatus for measuring electrostatic latent image, method for measuring electrostatic latent image, program, and apparatus for measuring latent image diameter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely measure an electrostatic latent image formed on a sample without eliminating the electrostatic latent image. <P>SOLUTION: The apparatus for measuring the electrostatic latent image includes: a charged particle beam generating means for applying charged particle beams; a first light source for applying an exposure light; a second light source for applying a destaticizing light; and a secondary charged particle detecting means for detecting secondary charged particles generated on the sample surface by applying the charged particle beams. The apparatus destaticizes the sample surface by applying the discharging light thereto using the second light source, electrostatically charges the sample surface by irradiating the sample surface with the charged particle beams in a prescribed current capacity using the charged particle beam generating means, thereafter scans the sample surface by applying the charged particle beams in which the current capacity is changed, starts recording the detected amount of the secondary charged particles detected by the secondary charged particle detecting means, irradiates the sample surface with the exposure light using the first light source to expose the sample surface, and finishes recording the detected amount of the secondary charged praticles detected by the secondary charged particle detecting means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrostatic latent image measuring device, an electrostatic latent image measuring method, a program, and a latent image diameter measuring device that measure an electrostatic latent image formed on a photosensitive photoreceptor.

In an electrophotographic image forming apparatus such as a copying machine or a laser printer, the following image forming process is usually performed when an image is output.
<a> Charging step for uniformly charging the photoconductive photoconductor <b> Exposure step for irradiating the photoconductor with light to form an electrostatic latent image by photoconductivity <c> Using charged toner particles Development process for forming a visible image on a photoconductor <d> Transfer process for transferring the developed visible image to a transfer material such as a piece of paper <e> Fixing process for fusing and fixing the transferred image on the transfer material <F> Cleaning step for cleaning residual toner on photoreceptor after transfer of visible image <g> Static elimination step for removing residual charge on photoconductor The process factor and process quality in each of the above steps are based on the final output image. Greatly affects quality. In recent years, in addition to high image quality, there has been a growing demand for environmentally friendly imaging processes such as high durability, high stability, and energy saving, and there is a strong demand for improving the process quality of each process.

  In the development (image formation) step <c>, the electrostatic latent image formed on the photoconductor by the charging and exposure in the previous step is a “factor that directly affects the behavior of the toner particles”. Evaluation of the quality of the electrostatic latent image is important. By observing the electrostatic latent image on the photoconductor and feeding back the result to the design, it is possible to improve the process quality of the charging process <a> and the exposure process <b>. Further improvement of stability, stability and energy saving can be expected.

  However, it is extremely difficult to measure an electrostatic latent image formed by charging and exposure on a photoconductive photoreceptor.

  As a method for measuring the potential distribution, the conventional method is to “close a sensor head such as a cantilever to a sample with a potential distribution, and measure the electrostatic attraction and induced current generated as an interaction at that time and convert it to a potential distribution. The electrostatic attraction type observation device is commercially available as SPM (Scanning Probe Microscope), and the induction current type is disclosed in Patent Documents 1 and 2 and the like.

In these methods, the sensor head needs to be close to the sample. For example, in order to obtain a spatial resolution of 10 μm, the distance between the sensor and the sample needs to be 10 μm or less.
Measurement under these conditions is
・ Absolute distance measurement is required.
・ Measurement takes time, and the latent image changes during that time.
-Discharge and adsorption occur between the sensor head and the sample.
・ The sensor itself disturbs the electric field.
In practice, proper measurement of the electrostatic latent image is extremely difficult.

  As a method other than the above method, the electrostatic latent image is developed to form a toner image, the obtained toner image is transferred to paper or tape, and the state (quality) of the electrostatic latent image is measured by the toner image. Although a method is conceivable, in this measuring method, the state of the electrostatic latent image is indirectly observed through the development / transfer process, and the electrostatic latent image itself is not measured.

  As a method other than the above method, Patent Document 3 discloses a method of measuring a charging characteristic, a photosensitive characteristic, and a dark attenuation characteristic with a surface potential meter as a method for measuring an electrostatic latent image. However, in the measurement method described in Patent Document 3, the spatial resolution obtained is only on the order of centimeters or millimeters, and the original image quality such as 600 dpi (1 dot: 42 μm) and 1200 dpi (1 dot: 21 μm) is required. Compared to the micron-order spatial resolution, it is many orders of magnitude worse and is not necessarily sufficient for evaluating the electrostatic latent image itself.

  Patent Documents 4 and 5 describe methods for measuring an electrostatic latent image by irradiating an electrostatic latent image or surface charge distribution with an electron beam. However, in the measurement technique described in Patent Document 5, what holds the charge distribution to be measured is a conductor sample such as an LSI chip, and the measurement technique described in Patent Document 4 stably holds charges. It can only be applied to a dielectric sample capable of being applied, and cannot be applied to a sample whose charge distribution attenuates with time due to dark decay, such as a photoconductive sample.

  That is, a normal dielectric can hold a charge semi-permanently, and thus the charge distribution can be measured over time. However, since a photoconductive sample has a finite resistance value, the surface charge can be measured. Cannot be maintained for a long time, and the surface potential decreases with time due to dark decay. The time for which the photoconductive sample can hold the surface charge is at most several tens of seconds even in a dark room. For this reason, even if an attempt is made to observe in an electron microscope (SEM) after charging and exposure, the electrostatic latent image disappears in the preparation stage.

Further, when an electrostatic latent image (surface charge distribution) is measured by an electron beam, there is a possibility that the electrostatic latent image itself may be lost by the electron beam irradiation.
Japanese Patent No. 3009179 JP-A-11-184188 JP 2002-82572 A Japanese Patent Laid-Open No. 3-49143 JP-A-3-29867

  The present invention has been made in view of the above circumstances, and a sample which is a photoconductive photosensitive member is irradiated with a charged particle beam (a charged particle beam affected by an electric field or a magnetic field) to be one-dimensional or two-dimensional. By detecting secondary charged particles generated in the sample by this scanning, the electrostatic latent image formed on the photoconductive photoreceptor through the charging process and the exposure process is lost, It is an object of the present invention to provide an electrostatic latent image measuring device, an electrostatic latent image measuring method, a program, and a latent image diameter measuring device that can accurately measure the electrostatic latent image.

  In order to achieve such an object, the invention described in claim 1 is a charged particle beam generating means for irradiating a sample, which is a photosensitive photoconductor, with a charged particle beam, and a first method for irradiating the sample with exposure light. A static light source including a first light source, a second light source that irradiates the sample with static elimination light, and secondary charged particle detection means that detects secondary charged particles generated on the surface of the sample by irradiation of the charged particle beam. An electrostatic latent image measuring device, wherein a second light source irradiates a sample surface with a neutralization light for a predetermined time to neutralize the sample surface, and a charged particle beam generating means applies a charged particle beam to the sample surface with a predetermined current. After the sample surface is charged with a predetermined amount to charge the sample surface, the current amount of the charged particle beam is changed, the sample surface is irradiated with the predetermined current amount for a predetermined time, the secondary charged particle detection means Description of detected amount of detected secondary charged particles , Irradiating the sample surface with exposure light for a predetermined time by the first light source, exposing the sample surface, forming an electrostatic latent image, and detecting the secondary charged particles detected by the charged particle detecting means The recording of the quantity is ended.

  The invention according to claim 2 is the invention according to claim 1, further comprising a grid arranged in the vicinity of the sample, and a voltage applying means for applying a voltage to the grid. After exposing the sample surface by irradiating exposure light for a predetermined time, the voltage applied to the grid is changed stepwise by the voltage applying means, and then the detected amount of secondary charged particles detected by the charged particle detecting means This is characterized in that the recording of is terminated.

  The invention described in claim 3 is characterized in that, in the invention described in claim 1 or 2, the frequency of recording the detection amount of the secondary charged particles is variable.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the irradiation current per unit area on the surface of the sample is changed even when the scanning range of the sample surface by the charged particle beam is changed. Current amount adjustment control is performed to adjust the amount so as to be constant.

  The invention according to claim 5 is the invention according to claim 4, further comprising irradiation current amount measuring means for measuring the irradiation current amount of the charged particle beam, and the irradiation current amount measuring means copes with a change in the scanning range of the sample surface. The refracting power of the electron lens that refracts the charged particle beam is changed, the irradiation current amount is measured in advance, and the current amount adjustment control is performed based on the irradiation current amount measured in advance.

  The invention according to claim 6 is the invention according to any one of claims 2 to 5, wherein the voltage change interval of the voltage applying means is longer than one screen recording time for recording the detected amount of the secondary charged particles. It is characterized by.

  A seventh aspect of the invention is characterized in that, in the sixth aspect of the invention, the voltage change of the voltage applying means is performed between the end of recording of one screen and the start of recording of the next screen. To do.

  According to an eighth aspect of the present invention, there is provided a charged particle beam generating means for irradiating a sample, which is a photosensitive photoreceptor, with a charged particle beam, a first light source for irradiating the sample with exposure light, and a sample. The electrostatic latent image measuring device includes a second light source that irradiates the neutralizing light and a secondary charged particle detection unit that detects secondary charged particles generated on the sample surface by irradiation of the charged particle beam. An electrostatic latent image measuring method, wherein the electrostatic latent image measuring device includes a charge removing step of irradiating the sample surface with a neutralizing light for a predetermined time by a second light source, and a charged particle beam generating unit. By irradiating the surface of the sample with a charged particle beam at a predetermined current amount for a predetermined time to charge the sample surface, the current amount of the charged particle beam is changed and irradiated at a predetermined current amount for a predetermined time. Charge / scan step to scan the surface and secondary A recording start step for starting recording of the detection amount of the secondary charged particles detected by the electroparticle detection means; and an exposure step for exposing the sample surface by irradiating the sample surface with exposure light for a predetermined time by the first light source. And a recording end step of ending the recording of the detection amount of the secondary charged particles detected by the charged particle detecting means.

  The invention according to claim 9 is the case where, in the invention according to claim 8, the electrostatic latent image measuring device further comprises a grid arranged in the vicinity of the sample and a voltage applying means for applying a voltage to the grid. The electrostatic latent image measuring apparatus executes an applied voltage changing step for stepwise changing a voltage applied to the grid by the voltage applying means after executing the exposure step, and after executing the applied voltage changing step, a recording end step. It is characterized by performing.

  The invention described in claim 10 is characterized in that, in the invention described in claim 8 or 9, the frequency of recording the detected amount of the secondary charged particles is variable.

  According to an eleventh aspect of the present invention, in the invention according to any one of the eighth to tenth aspects, the electrostatic latent image measuring device is configured to detect the sample even when the scanning range of the sample surface by the charged particle beam is changed. A current amount adjustment control step for adjusting the irradiation current amount per unit area on the surface to be constant is executed.

  According to a twelfth aspect of the present invention, in the eleventh aspect, when the electrostatic latent image measuring device includes an irradiation current amount measuring means for measuring the irradiation current amount of the charged particle beam, the electrostatic latent image measuring device The irradiation current amount measuring means performs the irradiation current amount measurement step of measuring the irradiation current amount in advance by changing the refractive power of the electron lens that refracts the charged particle beam by changing the scanning range of the sample surface by the irradiation current amount measuring means. The current amount adjustment control step is executed based on the irradiation current amount measured in the irradiation current measurement step.

  According to a thirteenth aspect of the present invention, in the invention according to any one of the ninth to twelfth aspects, the voltage change interval of the voltage applying means in the applied voltage changing step is one screen for recording the detected amount of the secondary charged particles. It is characterized by being longer than the recording time.

  According to a fourteenth aspect of the invention, in the thirteenth aspect of the invention, the voltage change of the voltage applying means in the applied voltage changing step is performed between the end of recording one screen and the start of recording the next screen. It is characterized by being.

  According to a fifteenth aspect of the present invention, there is provided a charged particle beam generating means for irradiating a sample, which is a photosensitive photoreceptor, with a charged particle beam, a first light source for irradiating the sample with exposure light, and a sample. And an electrostatic latent image measuring device comprising: a second light source that irradiates the neutralizing light; and secondary charged particle detection means that detects secondary charged particles generated on the sample surface by irradiation of the charged particle beam. For the electrostatic latent image measuring device, the second light source irradiates the surface of the sample with the neutralizing light for a predetermined time, and neutralizes the surface of the sample, and the charged particle beam generating means Irradiate the surface with a charged particle beam with a predetermined amount of current for a predetermined time to charge the sample surface, then change the amount of charged particle beam current and irradiate with a predetermined amount of current for a predetermined time to scan the sample surface Charging / scanning process and secondary charging A recording start process for starting recording of the detection amount of the secondary charged particles detected by the child detection means, and an exposure process for exposing the sample surface by irradiating the sample surface with exposure light for a predetermined time by the first light source; And a recording end process for ending the recording of the detected amount of the secondary charged particles detected by the charged particle detecting means.

  According to a sixteenth aspect of the present invention, in the electrostatic latent image measuring device according to the fifteenth aspect, the apparatus further comprises a grid disposed in the vicinity of the sample, and a voltage applying means for applying a voltage to the grid. Then, the electrostatic latent image measuring device is caused to execute an applied voltage changing process for changing the voltage applied to the grid stepwise by the voltage applying means after performing the exposure process, and after executing the applied voltage changing process, the recording end process is performed. Is executed.

  The invention described in claim 17 is characterized in that, in the invention described in claim 15 or 16, the frequency of recording the detected amount of the secondary charged particles is variable.

  According to an eighteenth aspect of the present invention, in the invention according to any one of the fifteenth to seventeenth aspects, even when the scanning range of the sample surface by the charged particle beam is changed in the electrostatic latent image measuring device, A current amount adjustment control process for adjusting the irradiation current amount per unit area on the surface to be constant is executed.

  According to a nineteenth aspect of the present invention, in the eighteenth aspect, when the electrostatic latent image measuring device includes an irradiation current amount measuring means for measuring the irradiation current amount of the charged particle beam, the electrostatic latent image measuring device In addition, the irradiation current amount measuring means executes the irradiation current amount measurement process in which the irradiation current amount is measured in advance by changing the refractive power of the electron lens that refracts the charged particle beam by changing the scanning range of the sample surface by the irradiation current amount measuring means. The current amount adjustment control process is executed based on the irradiation current amount measured in the irradiation current measurement process.

  According to a twentieth aspect of the present invention, in the invention according to any one of the sixteenth to nineteenth aspects, the voltage change interval of the voltage applying means in the applied voltage changing process is one screen for recording the detected amount of the secondary charged particles. It is characterized by being longer than the recording time.

  According to a twenty-first aspect of the invention, in the twentieth aspect of the invention, the voltage change of the voltage applying means in the applied voltage changing process is performed until one screen recording is completed and the next screen recording is started. It is characterized by being.

  A twenty-second aspect of the invention includes the electrostatic latent image measuring device according to any one of the first to seventh aspects.

  According to the present invention, the electrostatic latent image can be accurately measured without losing the electrostatic latent image formed on the photoconductive photoreceptor through the charging step and the exposure step. Therefore, by feeding back the measurement results obtained in the present invention to the design, it is possible to improve the process quality of the charging process and the exposure process in the image forming method by the electrophotographic process. -Further improvement in stability and energy saving can be expected.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings.

[First Embodiment]
FIG. 1 is a diagram showing a first embodiment of an electrostatic latent image measuring apparatus according to the present invention.
Reference numeral 11 is a charged particle gun, reference numerals 12 and 12A are apertures, reference numeral 13 is a condenser lens for charged particles, reference numeral 14 is a beam blanker, reference numeral 15 is a scanning lens which is a beam deflection means for charged particle beams, and reference numeral 16 is a charged particle beam. The objective lenses for are respectively shown. The “charged particle beam” refers to a beam of charged particles that is affected by an electric field or magnetic field, such as an electron beam or an ion beam.

  The charged particle gun 11, the apertures 12 and 12A, the condenser lens 13, the beam blanker 14, the scanning lens 15 and the objective lens 16 are driven by the charged particle beam driving unit 31 according to a command from the computer 40 which is a “computer”. It has become. Note that the computer 40 performs image processing by controlling each means (each part) of the electrostatic latent image measuring device and control software for controlling each means (each part) of the electrostatic latent image measuring device. The control operation described below is executed under the control of the image processing software.

  Reference numeral 17 denotes a semiconductor laser that is a “first light source”, reference numeral 18 denotes a collimating lens, reference numeral 19 denotes an aperture, and reference numerals 21, 22, and 23 denote lenses that form an “imaging lens”. These constitute the “light image irradiating part” and constitute the “exposure means” together with the semiconductor laser driving part 32.

  The semiconductor laser driving unit 32 causes the semiconductor laser 17 to emit light according to a command from the computer 40.

  Reference numeral 24 denotes a charged particle trap, reference numeral 25 denotes a secondary electron detector, and reference numeral 26 denotes a signal processor. The charged particle trap 24, the secondary electron detector 25, and the signal processor 26 constitute “observation means”.

  Reference numeral 28 denotes a sample mounting table, reference numeral SP denotes a sample, and reference numeral 29 denotes a “light emitting element for charge removal” which is a second light source. Sample SP is a “photoconductive photoreceptor”. In the present embodiment, the light-emitting element 29 for static elimination is an LED that emits light in a wavelength region in which the sample SP has sensitivity, and is driven by the LED driving unit 35 in accordance with a command from the computer 40. Of course, the semiconductor laser 17 emits laser light in a wavelength region in which the sample SP has sensitivity.

  The sample mounting table 28 is a grounded metal plate. The sample mounting table 28 is driven by the sample table driving unit 34 in accordance with a command from the computer 40 to place the sample SP at the “appropriate measurement position”.

  Each of the above parts is disposed in the casing 30 as shown in the figure, and the inside of the casing 30 can be highly decompressed by the suction means 33. That is, the casing 30 has a function as a “vacuum chamber”.

  The sample SP is held on the sample mounting table 28, is positioned at an appropriate measurement position by the sample table driving unit 34, and the inside of the casing 30 is highly depressurized by the suction means 33 such as a vacuum pump, thereby obtaining a “measurement state”. Become.

  Further, as shown in the figure, the entire apparatus is controlled by a computer 40 which is a “computer”. The charged particle beam control unit 31, the signal processing unit 26, the semiconductor laser drive unit 32, the LED control unit 35, etc. in FIG. 1 can be set as part of the function of the computer 40.

  In the state shown in FIG. 1, the sample SP whose surface is uniformly charged is placed on the sample placing table 28, and the inside of the casing 30 is highly decompressed. When the semiconductor laser 17 is turned on in this state, the emitted laser beams are collimated by the collimating lens 17, the beam diameter is regulated by the aperture 19, and the “uniformly charged sample” of the sample SP is formed by the imaging lenses 21, 22, and 23. Focused as a light spot "on the surface".

  The semiconductor laser 17 is driven by the semiconductor laser driving unit 32 in accordance with the light emission intensity and light emission time commands from the computer 40 and can irradiate with appropriate exposure time and exposure energy. That is, the “desired light beam” can be irradiated to the sample SP.

  It is also possible to add a “scanning mechanism using a galvanometer mirror or a polygon mirror” to the optical system of such an exposure means, so that a line pattern is exposed by optical scanning to form a line-shaped electrostatic latent image. .

  As described above, the sample SP is exposed to a light spot having a “desired spot diameter and beam profile”, and an electrostatic latent image, that is, a surface charge distribution corresponding to the light intensity distribution of the light spot is formed. The

  The sample surface on which the electrostatic latent image is thus formed is scanned two-dimensionally with a charged particle beam. That is, when a charged particle beam is emitted from the charged particle gun 11, the emitted charged particle beam passes through the aperture 12 and the beam diameter is regulated, and then is converged by the condenser lens 13 while being focused by the aperture 12 A and the beam blanker 14. Pass through.

  Finally, the charged particle beam is focused on the surface (sample surface) of the sample SP by the objective lens 16. At this time, the amount of current toward the sample SP can be changed by changing the refractive power of the condenser lens 13. For example, in FIG. 1, most of the charged particles emitted from the charged particle gun 11 reach the sample SP. However, by increasing the refractive power of the condenser lens 13 as shown in FIG. 3, the flow of charged particles is blocked by the aperture 12A. Current amount is reduced. If the refractive power of the condenser lens 13 is changed in multiple steps, the amount of current directed to the sample also changes in multiple steps.

  The relationship between the refractive power of the condenser lens 13 and the amount of current is measured by placing a jig for measuring the amount of current, such as a Faraday cup, at the position where the sample is to be placed, and changing the refractive power of the condenser lens 13 before the actual measurement. Then, it is desirable that the relationship is incorporated in the control software, and when the current amount is specified at the time of measurement, the computer 40 sends a command to the charged particle beam driving unit so that the current amount can be obtained, and is automatically adjusted.

  Further, by deflecting the direction of the charged particle beam by the scanning lens 15, the position where the charged particle beam is focused is displaced two-dimensionally (for example, the horizontal direction in the drawing and the direction orthogonal to the drawing) on the sample SP surface. be able to.

  In this way, the “sample surface on which the electrostatic latent image is formed” of the sample SP is two-dimensionally scanned by the charged particle beam. The area to be scanned can be changed in size by changing the magnification of the scanning lens. For example, the scanning area can be scanned at various magnifications such as a low magnification of about 5 mm × 5 mm and a high magnification of about 1 μm × 1 μm. can do.

  Here, if the size of the scanning region is changed, the amount of irradiation current per unit area of the sample differs even if the amount of current directed to the sample per unit time is the same. If there is a difference in the amount of current that reaches the sample, the effect on the sample also differs. For example, since the rate of increase in charge accumulation on the sample is different, the relationship between irradiation time and charge accumulation also changes.

  Therefore, if you want to measure under the same conditions while changing the magnification, the amount of current going to the sample is adjusted by the above method in conjunction with the magnification so that the amount of irradiation current per unit area of the sample is constant. It is desirable. It is further desirable that there is a mode in which the control software automatically adjusts so that the amount of current that reaches the sample becomes constant when the magnification is changed.

  When the above scanning is performed, a trapping voltage having a predetermined polarity is applied to the charged particle trap 24. Then, by the action of the trapping voltage, “charged particles that are electrically affected by the electrostatic latent image pattern” are captured by the charged particle trap 24, the intensity (number of trapped particles per unit time) is detected, and the electric signal is detected. Is converted to

  The “region to be scanned two-dimensionally by the charged particle beam: S” of the sample SP is represented by S (X, Y) using two-dimensional coordinates, for example, 0 mm ≦ X ≦ 1 mm, 0 mm ≦ Y ≦ 1 mm. It is. The electrostatic latent image pattern formed in this region: S (X, Y) is defined as its surface potential distribution: V (X, Y).

  Since the two-dimensional scanning of the region by the charged particle beam is performed under a predetermined condition, if the time from the start to the end of the two-dimensional scanning is T0 ≦ T ≦ TF, the scanning is performed. Time: T corresponds to each scanning position in the scanning area: S (X, Y) 1: 1. Accordingly, the distribution of the number of trapped particles in the scanning region can be measured. This information is converted into a video signal by the signal processing unit 26, and image processing, recording, and display are performed by the computer 40.

  Image signals are successively sent from the signal processing unit 26 to the computer 40. However, if all of these are recorded, a large amount of memory and a recording medium capacity are required, resulting in an increase in cost. Therefore, the recording interval can be varied so that most of the image signal is recorded in a scene where the state changes suddenly, such as immediately after exposure, and the image signal is thinned out and recorded in a scene where the state change such as dark decay that occurs thereafter is gradual. It is desirable to do.

  Since the charged particles captured by the charged particle trap 24 are electrically influenced by the surface potential distribution of the electrostatic latent image pattern: V (X, Y), the intensity of the charged particles captured at time: T: F (T) has a correspondence relationship with surface potential distribution: V {X (T), Y (T)} with time: T as a parameter. This correspondence can be known by observing the intensity of the charged particles affected by the reference potential: VN, and by calibrating the intensity of the charged particles: F based on the known correspondence. The electric potential: V corresponding to the intensity: F can be known.

  As described above, the charged particle beam is a particle beam that is affected by an electric field or a magnetic field such as an electron beam or an ion beam. An “electron gun” is used, and if an ion beam is used, a “liquid metal ion gun” or the like is used.

  In the present embodiment shown in FIG. 1, the charged particle gun 11 is an “electron gun”, and therefore, the case where an electron beam is used as a charged particle beam will be specifically described below. At this time, the “sample surface on which the electrostatic latent image is formed” of the sample SP is two-dimensionally scanned by the electron beam.

  In order to form an electrostatic latent image on the sample SP, it is necessary to uniformly charge the surface of the sample SP prior to exposure with a light image. Regarding the uniform charging of the sample SP, charging may be performed outside the observation apparatus, and the uniformly charged sample SP may be mounted on the sample mounting table 28. However, as described above, the inside of the casing 30 is highly advanced. If the sample SP is reduced from the set to the inside of the casing 30, the charged potential disappears due to dark decay until scanning by the electron beam becomes possible unless the suction by the suction means 33 is performed very strongly. In some cases, the electrostatic latent image cannot be observed. From this point of view, it is preferable that the uniform charging of the sample SP is performed in the casing 30 “after realizing a high degree of decompression”. When charging is performed under a high pressure reduction, charging by corona discharge, which is often performed in an electrophotographic apparatus, is difficult to implement, but charging by a so-called contact type charging means is possible.

  In the present embodiment shown in FIG. 1, charging by an electron beam is performed using a charged particle beam scanning unit (electron gun 11). When the sample SP is irradiated with the electron beam, “secondary electrons (including higher-order emitted electrons such as tertiary electrons as described above)” are generated from the sample SP due to the impact of the irradiated electrons. In the balance between the amount of electrons irradiated to the sample SP as an electron beam and the amount of secondary electrons generated, the amount of secondary electrons emitted: the amount of irradiated electrons with respect to R2: the ratio of R1: If R1 / R2 is 1 or more The amount of electrons irradiated by subtraction exceeds the amount of secondary electrons, and the difference between the two accumulates in the sample SP to charge the photoconductive sample SP.

  Therefore, the amount of electrons emitted from the electron gun 11 and the acceleration voltage thereof are adjusted, and the “ratio: the condition that R1 / R2 is greater than 1” is set, and the electron beam is scanned two-dimensionally. SP can be uniformly charged. Such adjustment of the amount of emitted electrons and the acceleration voltage is performed by the computer 40 performing calculations and sending commands to the charged particle beam driving unit 31. Also, on / off of the electron beam accompanying the scanning of the electron beam, the beam blanker 14 is driven by the charged particle beam driving unit 31 according to a command of the computer 40.

  FIG. 4 schematically shows a state in which the surface of the sample SP is charged by the electron beam as described above. The sample SP shown in FIG. 4 is a so-called “function-separated type photoreceptor”, in which a charge generation layer 2 is provided on a conductive layer 1 and a charge transport layer 3 is formed thereon.

  Electrons irradiated by the electron gun 11 are shot into the surface of the charge transport layer 3, captured in the electron orbits of charge transport layer material molecules on the surface of the charge transport layer 3, and charge transported in a state where the molecules are negatively ionized. It remains on the surface of layer 3. This state is a “state in which the sample SP is charged”.

  When the light LT is irradiated to the sample SP in such a charged state, the irradiated light LT passes through the charge transport layer 3 and reaches the charge generation layer 2, and the energy is positively or negatively generated in the charge generation layer 2. Generate negative charge carriers. Of the generated positive and negative charge carriers, the negative carriers move to the conductive layer 1 (at ground potential) due to the repulsive force of the negative charge on the surface of the charge transport layer 3, and the positive carriers are transferred to the charge transport layer 3. Are offset by the negative charges (captured electrons) on the surface portion of the same layer 3.

  In this manner, the charged charge is attenuated in the portion irradiated with the light LT in the sample SP, and a surface charge distribution according to the intensity distribution of the light LT is formed. This surface charge distribution is nothing but an electrostatic latent image. That is, in the present embodiment, the measurement target is an “electrostatic latent image”, but the electrostatic latent image appears as a surface potential or an electric field distribution in the vicinity of the surface. It can also be said that the charge distribution or the electric field distribution near the surface.

  The sample SP uniformly charged as described above is exposed by a light beam to form an electrostatic latent image. This exposure is performed by the aforementioned “exposure means”. That is, the semiconductor laser 17 is turned on, and the collimated light beam is condensed on the surface of the sample SP by the action of the imaging lenses 21, 22, and 23.

  Of course, a semiconductor laser 17 having a light emission wavelength in a wavelength region in which the sample SP is sensitive is used. Further, since the exposure energy is “time integration of optical power” on the surface of the sample SP, the sample SP can be exposed with the desired exposure energy by controlling the lighting time of the semiconductor laser 17.

  Returning to FIG. 1, in the state where the electrostatic latent image is formed on the sample SP as described above, the scanning region of the sample SP is two-dimensionally scanned by the electron beam. Secondary electrons generated by this scanning are detected by the charged particle trap 24. Since the target of detection is secondary electrons and negative polarity, the charged particle trap 24 applies a positive voltage (attraction voltage) for capturing secondary electrons, and positively generates secondary electrons generated by scanning of the electron beam. Capture by aspiration with voltage. The captured electrons are converted into scintillation luminance in the secondary electron detector 25 and further converted into an electric signal (detection signal).

  In the space between the surface of the sample SP and the charged particle trap 24, the charge on the surface of the sample SP (negative charge that forms an electrostatic latent image) and the positive trapping voltage applied to the charged particle trap 24. Thus, a “potential gradient” is formed. FIG. 5A illustrates the potential distribution in the space between the charged particle trap 24 and the sample SP in the form of contour lines. Since the surface of the sample SP is uniformly charged to a negative polarity except for the portion where the potential is attenuated due to light attenuation, and the charged particle trap 24 is given a positive potential, In the “potential contour line group”, the “potential becomes higher” as it approaches the charged particle trap 24 from the surface of the sample SP.

  Therefore, the secondary electrons el1 and el2 generated at the points Q1 and Q2 in the figure, which are “negatively uniformly charged portions” in the sample SP, are attracted to the positive potential of the charged particle trap 24, and the arrow G1. And is displaced as indicated by the arrow G2 and is captured by the charged particle trap 24.

  On the other hand, in FIG. 5A, the point Q3 is “a portion where the negative potential is attenuated by light irradiation”, and the arrangement of the potential contour lines is “as shown by the broken line” in the vicinity of the point Q3. “The closer to Q3 point, the higher the potential”. In other words, the secondary electron el3 generated in the vicinity of the point Q3 is subjected to an electric force restrained on the sample SP side as indicated by an arrow G3. For this reason, the secondary electron el3 is trapped in the “potential hole” indicated by the broken line potential contour and does not move toward the charged particle trap 24.

  FIG. 5B schematically shows the “potential hole”. That is, the intensity of secondary electrons (number of secondary electrons) detected by the charged particle trap 24 is such that the portion with the high intensity is “the ground portion of the electrostatic latent image (part of FIG. The portion having a small intensity corresponds to “the image portion of the electrostatic latent image (the portion irradiated with light: the point Q3 in FIG. 5A)”. Part) ”.

  Therefore, if the electrical signal obtained by the secondary charged particle detector 25 is sampled by the signal processor 26 at an appropriate sampling time, the surface potential distribution: V (X, Y) can be specified for each “small area corresponding to sampling”, and if the surface potential distribution (potential contrast image): V (X, Y) is configured as two-dimensional image data by the signal processing unit 26, static An electrostatic latent image is obtained as a visible image.

  For example, if the intensity of captured secondary electrons is expressed by “brightness and weakness”, the image portion of the electrostatic latent image is dark and the ground portion is bright and contrasted as shown in FIG. It can be expressed (output) as a corresponding bright and dark image. Of course, if the surface potential distribution is known, the surface charge distribution can also be known. The latent image diameter can be obtained by measuring the diameter of the dark part.

  In addition, when the surface of the sample SP set in the casing 30 is initially charged unevenly for some reason, such a charged state becomes a measurement noise, so that the charging process in the measurement is performed. Prior to this, it is preferable that the LED drive unit 35 causes the light-emitting element 29 for charge removal to emit light in accordance with an instruction from the computer 40 to perform light charge removal of the sample SP.

  As described above, the secondary particles generated by the electron beam applied to the image portion (light irradiated portion) of the electrostatic latent image formed on the sample SP are not captured by the charged particle trap 24. Therefore, in the image portion of the electrostatic latent image, the “equivalent amount of incident electrons” of the irradiated electron beam is accumulated as an external charge.

Therefore, if the amount of incident electrons of the electron beam is large, the charge distribution on the surface of the sample SP disappears due to scanning of the electron beam. In order to avoid this, it is desirable to reduce the “irradiation current”, which is the irradiation amount of the electron beam, by the above-described method compared with the charging.
The above is the configuration of the electrostatic latent image measuring apparatus according to the first embodiment of the present invention.

  Below, the sequence performed by the control software built in the computer 40 which is a computer is demonstrated. A flowchart of this sequence is shown in FIG.

  In (1) of FIG. 10, the lighting (light emission) time of the light-emitting element (LED) 29, which is the second light source, is calculated (step S1), and the LED 29 is caused to emit light based on the time (step S2). As a result, the sample SP which is a “photoconductive photosensitive member” becomes a conductor, and the charge on the sample SP escapes to the ground, and there is no charge on the sample SP (a state where the charge is removed). If the light emission time is too short, the charge cannot escape to the ground, and the charge remains on the sample SP, which impairs the accuracy of measurement. The light emission time required to completely remove the charge on the sample SP depends on the brightness of the LED, the sensitivity of the photoconductor, the charge transfer speed in the photoconductor, and the like. Therefore, the characteristics for each LED and photoconductor are stored in the control software as photoconductor characteristic information, and an optimal lighting time is calculated based on the photoconductor characteristic information. The result is sent from the computer 40 to the LED drive unit 35. It is desirable to be sent.

  In (2) of FIG. 10, the irradiation current amount for charging is calculated (step S3), and a charged particle beam having the first current amount is generated from the electron gun 11 based on the current amount (first current amount). (Step S4). Then, the sample SP is scanned with the charged particle beam having the first current amount for an arbitrary time. Thereby, the sample SP is charged. The charged potential of the photoconductor is determined by the amount of charge at this time. Here, if the amount of current applied to the sample is too small, the necessary charged potential cannot be obtained, and if it is too large, the sample may be damaged. Therefore, it is desirable that the characteristics of each photoconductor are stored in the control software as photoconductor characteristic information, and the optimum scanning time is sent from the computer 40 to the charged particle beam driving unit 31. Further, when the scanning range is changed by changing the magnification, if the amount of current directed to the sample does not change, the irradiation amount per unit area of the sample changes, and conditions other than the magnification also change. Therefore, it is desirable that there is a mode in which adjustment is automatically performed so that the amount of irradiation current per unit area of the sample becomes constant when the magnification is changed.

  In (3) of FIG. 10, scanning of the sample with the charged particle beam having the second current amount and recording of the detection amount detected by the charged particle detection method are started (step S7). In step (2), a large amount of charged particle beam is applied to charge the photosensitive member (sample SP). However, before step S7, an irradiation current amount for observation is calculated (step S5). Based on the current amount (second current amount), the irradiation amount of the charged particle beam is changed, the current amount is limited (step S6), and the charged particle beam having the second current amount is generated from the electron gun 11. This is because in a state exposed to a large amount of charged particle beam, even if a latent image is formed, it is immediately filled with charged particles and measurement is impossible. Further, when the scanning range is changed by changing the magnification, if the amount of current directed to the sample does not change, the irradiation amount per unit area of the sample changes, and conditions other than the magnification also change. Therefore, it is desirable that there is a mode in which adjustment is automatically performed so that the amount of irradiation current per unit area of the sample becomes constant when the magnification is changed.

  In (4) of FIG. 10, the lighting time of the semiconductor laser 17 as the first light source is calculated (step S8), and the semiconductor laser 17 is turned on based on the lighting time (step S9). That is, since the exposure energy is “time integration of optical power” on the surface of the sample SP, the lighting time for obtaining the desired exposure energy is calculated by the control software of the computer 40, and the control command is sent to the semiconductor laser driving unit 32. And the semiconductor laser 17 is turned on, whereby the sample SP can be exposed with a desired exposure energy.

  After step S9, it is determined whether or not the magnification has been changed (step S10). When the magnification has been changed (step S10 / YES), the irradiation current amount for observation is calculated again (step S11), and the charged particle beam irradiation amount is changed based on the current amount (step S12). It is determined whether or not to end the measurement (step S13). When there is no magnification change (step S10 / NO), it is determined whether or not the measurement is ended as it is (step S13). When the measurement is finished (step S13 / YES), the process proceeds to step S14, and when the measurement is continued (step S13 / NO), the process returns to step S10.

  In FIG. 10 (5), the recording of the detection amount detected by the charged particle detection method is terminated (step S14). This is the end of the measurement.

[Second Embodiment]
FIG. 2 is a diagram showing a second embodiment of the electrostatic latent image measuring apparatus of the present invention. In order to avoid complications, the same reference numerals as those in FIG. That is, the difference in the apparatus configuration from the first embodiment is that there are a grid 45 and a voltage applying means 44 for applying a voltage to the grid 45 as the electric field strength varying means.

  In the second embodiment shown in FIG. 2, in order to “change the detection signal amount”, there are electric field strength varying means 44 and 45 for changing the electric field strength generated on the sample surface. Of the electric field strength varying means 44 and 45, reference numeral 45 denotes a grid made of a conductive member, and a voltage can be applied from the voltage applying means 44.

  As shown in FIG. 2, the grid mesh 45 is arranged above the sample surface of the sample SP, and a voltage is applied by the voltage applying means 44. The power supply application means 44 is a power supply capable of generating a high voltage up to several tens of KVs, and can arbitrarily set a voltage value applied to the grid mesh 45.

  FIG. 8 schematically shows the vicinity of the sample SP. The grid 45 is formed in a mesh shape with a conductive material (Au, Cu, Ni, etc. are suitable) (see FIG. 7), and the electron beam sample SP is applied in accordance with the applied voltage value applied from the voltage applying means 44. The electric field distribution in the vicinity of the sample surface is “uniformly level-shifted in a biased manner” without blocking the irradiation on the surface. The pitch and shape of the grid mesh 45 can be appropriately set depending on the measurement area and measurement magnification of the sample.

  When a voltage is applied to the grid 45, the uniform electric field formed by the grid mesh 45 is superimposed on the electric field formed by the charge distribution on the sample surface and becomes a bias component of the electric field strength on the sample surface. Shift the field strength distribution.

For example, to shift the electric field strength of 2 × 10 6 V / m as “bias component”, a voltage of 2000 V may be applied 1 mm above the sample surface.
FIG. 9 shows a state in which a voltage is applied to the grid 45 and the bias component of the electric field strength on the sample surface is shifted by Eb, when the grid 45 in FIG. 6 is set to 0V. By this shift, the level of electric field strength: 0 is shifted upward from the state of FIG. That is, the electric field intensity: E = Eb in the state (a) becomes E = 0 due to the bias shift.

  In this way, if the applied voltage of the grid 45 is changed stepwise and the image is observed, the diameter of the latent image obtained by cutting the latent image into a plurality of potentials can be measured. The (potential) profile can be measured. The time interval for changing the applied voltage is longer than the one-screen recording time of the charged particle detection means signal, and the timing for changing the applied voltage is from the end of recording of one screen until the start of recording of the next screen. In this case, it is desirable to record an image in which the applied voltage is changed for each screen. If the applied voltage is changed in the middle of one screen, different states of the applied voltage overlap on one screen, and accurate measurement cannot be performed.

  Next, a sequence executed by control software built in the computer 40 which is a computer will be described. A flowchart of this sequence is shown in FIG.

  The control sequence of the present embodiment is a sequence in which “the applied voltage of the grid 45 is changed stepwise” in FIG. 11 (4) when there is no magnification change in the determination of step S10 (NO in step S10). “Save one screen” (step S11 ′) and “change applied voltage” (step S12 ′) are inserted. Other sequences in FIG. 11 are the same as the sequences in FIG. 10 described in the first embodiment, and a description thereof is omitted here.

As mentioned above, although Embodiment 1 and 2 of this invention were demonstrated, it is not limited to description of said each embodiment, A various deformation | transformation is possible in the range which does not deviate from the summary.
In addition, a latent image diameter measuring apparatus including the electrostatic latent image forming apparatus according to the first and second embodiments can be realized.

  The present invention can be applied to any apparatus capable of forming an electrostatic latent image.

1 is a block diagram showing a configuration according to a first embodiment of the present invention. It is a block diagram which shows the structure which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the operation example of the condenser lens which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating an example of the photoconductive photoreceptor which is an example of a sample. It is a figure for demonstrating a measurement principle. It is a figure for demonstrating the electric field strength distribution by an electrostatic latent image, and the binarized contrast image. It is a figure which shows the grid mesh which is an electroconductive member for applying a voltage as an electric field strength variable means. It is a figure which shows typically the mode of the sample vicinity in the 2nd Embodiment of this invention. It is a figure for demonstrating the effect | action of the electric field strength change by an electric field strength variable means. It is a flowchart which shows the operation | movement which concerns on the 1st Embodiment of this invention. It is a flowchart which shows the operation | movement which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductivity 2 Charge generation layer 3 Charge transport layer 11 Charged particle gun (electron gun, charged particle beam generating means)
12, 12A Aperture 13 Condenser lens 14 Beam blanker 15 Scan lens (beam deflection means)
16 Objective lens 17 Semiconductor laser (first light source)
DESCRIPTION OF SYMBOLS 18 Collimating lens 19 Aperture 21, 22, 23 Imaging lens 24 Charged particle trap 25 Secondary charged particle detection part 26 Signal processing part 28 Sample mounting base 29 Light-emitting element for static elimination (2nd light source)
DESCRIPTION OF SYMBOLS 30 Casing 31 Charged particle beam drive part 32 Semiconductor laser drive part 33 Aspiration means 34 Sample stand drive part 35 LED drive part 40 Computer (computer)
44 Voltage application means (field strength variable means)
45 grid (field strength variable means)
SP sample LT light

Claims (22)

Charged particle beam generating means for irradiating a charged particle beam to a sample which is a photosensitive photoreceptor;
A first light source for irradiating the sample with exposure light;
A second light source for irradiating the sample with static elimination light;
An electrostatic latent image measuring device comprising: secondary charged particle detecting means for detecting secondary charged particles generated on the sample surface by irradiation of the charged particle beam;
The second light source irradiates the surface of the sample with the charge removal light for a predetermined time to discharge the surface of the sample,
The charged particle beam generation means irradiates the sample surface with the charged particle beam with a predetermined current amount for a predetermined time to charge the sample surface, and then changes the current amount of the charged particle beam, Irradiating with a current amount of a predetermined time, scanning the sample surface,
Start recording the amount of detection of the secondary charged particles detected by the secondary charged particle detection means;
The first light source irradiates the sample surface with the exposure light for a predetermined time, exposes the sample surface, and forms an electrostatic latent image,
The electrostatic latent image measuring apparatus, wherein the recording of the detection amount of the secondary charged particles detected by the charged particle detecting means is terminated. A grid disposed in the vicinity of the sample;
Voltage application means for applying a voltage to the grid, and
After irradiating the sample surface with the exposure light for a predetermined time by the first light source and exposing the sample surface, the voltage application unit changes the voltage applied to the grid stepwise, 2. The electrostatic latent image measuring apparatus according to claim 1, wherein the recording of the detection amount of the secondary charged particles detected by the charged particle detecting means is terminated.   The electrostatic latent image measuring apparatus according to claim 1, wherein the frequency of recording the detection amount of the secondary charged particles is variable.   The current amount adjustment control is performed to adjust the irradiation current amount per unit area on the surface of the sample to be constant even when the scanning range of the sample surface by the charged particle beam is changed. Item 4. The electrostatic latent image measuring device according to any one of Items 1 to 3. An irradiation current amount measuring means for measuring the irradiation current amount of the charged particle beam;
The irradiation current amount measuring means changes the refractive power of the electron lens that refracts the charged particle beam, corresponding to the change in the scanning range of the sample surface, and measures the irradiation current amount in advance.
5. The electrostatic latent image measuring apparatus according to claim 4, wherein the current amount adjustment control is performed based on the irradiation current amount measured in advance.   6. The electrostatic latent image measurement according to claim 2, wherein a voltage change interval of the voltage application unit is longer than a one-screen recording time of recording of the detection amount of the secondary charged particles. apparatus.   7. The electrostatic latent image measuring device according to claim 6, wherein the voltage change of the voltage applying unit is performed between the end of the one-screen recording and the start of the next screen recording. Charged particle beam generating means for irradiating a charged particle beam to a sample which is a photosensitive photoreceptor;
A first light source for irradiating the sample with exposure light;
A second light source for irradiating the sample with static elimination light;
An electrostatic latent image measuring method performed by an electrostatic latent image measuring device comprising secondary charged particle detecting means for detecting secondary charged particles generated on the sample surface by irradiation of the charged particle beam,
The electrostatic latent image measuring device includes:
A neutralization step of neutralizing the sample surface by irradiating the sample surface with the neutralization light for a predetermined time by the second light source;
The charged particle beam generation means irradiates the sample surface with the charged particle beam with a predetermined current amount for a predetermined time to charge the sample surface, and then changes the current amount of the charged particle beam, Charging and scanning step of irradiating with a current amount of a predetermined time and scanning the sample surface;
A recording start step for starting recording of the detected amount of the secondary charged particles detected by the secondary charged particle detection means;
An exposure step of exposing the sample surface by irradiating the sample surface with the exposure light for a predetermined time by the first light source;
A recording end step for ending the recording of the detected amount of the secondary charged particles detected by the charged particle detecting means;
The method for measuring an electrostatic latent image, comprising: The electrostatic latent image measuring device is
A grid disposed in the vicinity of the sample;
When further comprising a voltage applying means for applying a voltage to the grid,
The electrostatic latent image measuring device includes:
After the exposure step, the voltage application means executes an applied voltage change step that changes the voltage applied to the grid stepwise, and after the applied voltage change step, the recording end step is executed. The method of measuring an electrostatic latent image according to claim 8.   10. The electrostatic latent image measuring method according to claim 8, wherein the frequency of recording the detected amount of the secondary charged particles is variable. The electrostatic latent image measuring device includes:
A current amount adjustment control step is performed for adjusting the irradiation current amount per unit area on the surface of the sample to be constant even when the scanning range of the sample surface by the charged particle beam is changed. The method of measuring an electrostatic latent image according to any one of claims 8 to 10. The electrostatic latent image measuring device is
When equipped with an irradiation current amount measuring means for measuring the irradiation current amount of the charged particle beam,
The electrostatic latent image measuring device includes:
An irradiation current amount measuring step of measuring the irradiation current amount in advance by changing the refractive power of the electron lens that refracts the charged particle beam by changing the scanning range of the sample surface by the irradiation current amount measuring means. Run,
12. The electrostatic latent image measuring method according to claim 11, wherein the current amount adjustment control step is executed based on the irradiation current amount measured in the irradiation current measurement step.   The voltage change interval of the voltage application means in the applied voltage change step is longer than one screen recording time for recording the detected amount of the secondary charged particles. Of measuring electrostatic latent image.   14. The electrostatic change according to claim 13, wherein the voltage change of the voltage applying means in the applied voltage changing step is performed between the end of the one-screen recording and the start of the recording of the next screen. Latent image measurement method. Charged particle beam generating means for irradiating a charged particle beam to a sample which is a photosensitive photoreceptor;
A first light source for irradiating the sample with exposure light;
A second light source for irradiating the sample with static elimination light;
A program for causing an electrostatic latent image measuring apparatus to include a secondary charged particle detecting unit that detects secondary charged particles generated on the sample surface by irradiation of the charged particle beam,
In the electrostatic latent image measuring device,
A neutralization treatment for neutralizing the sample surface by irradiating the sample surface with the static elimination light for a predetermined time by the second light source;
The charged particle beam generation means irradiates the sample surface with the charged particle beam with a predetermined current amount for a predetermined time to charge the sample surface, and then changes the current amount of the charged particle beam, Charging and scanning processing for irradiating with a current amount of a predetermined time and scanning the sample surface;
A recording start process for starting recording of the detected amount of the secondary charged particles detected by the secondary charged particle detector;
An exposure process for exposing the sample surface by irradiating the sample surface with the exposure light for a predetermined time by the first light source;
A recording end process for ending the recording of the detected amount of the secondary charged particles detected by the charged particle detection means;
A program characterized in that is executed. The electrostatic latent image measuring device is
A grid disposed in the vicinity of the sample;
When further comprising a voltage applying means for applying a voltage to the grid,
In the electrostatic latent image measuring device,
After executing the exposure process, the voltage applying unit causes the applied voltage change process to change the voltage applied to the grid in a stepwise manner, and the recording end process is executed after the applied voltage change process. The program according to claim 15.   The program according to claim 15 or 16, wherein the frequency of recording the detection amount of the secondary charged particles is variable. In the electrostatic latent image measuring device,
Even when the scanning range of the sample surface by the charged particle beam is changed, a current amount adjustment control process for adjusting the irradiation current amount per unit area on the surface of the sample to be constant is executed. The program according to any one of claims 15 to 17. The electrostatic latent image measuring device is
When equipped with an irradiation current amount measuring means for measuring the irradiation current amount of the charged particle beam,
In the electrostatic latent image measuring device,
Irradiation current amount measurement processing for measuring the irradiation current amount in advance by changing the refractive power of the electron lens that refracts the charged particle beam by changing the scanning range of the sample surface by the irradiation current amount measurement means. Let it run
The program according to claim 18, wherein the current amount adjustment control process is executed based on the irradiation current amount measured in the irradiation current measurement process.   20. The voltage change interval of the voltage application means in the applied voltage change process is longer than a one-screen recording time for recording the detected amount of the secondary charged particles. 20. Program.   21. The program according to claim 20, wherein the voltage change of the voltage application means in the applied voltage change process is performed between the end of the one-screen recording and the start of the recording of the next screen.   A latent image diameter measuring apparatus comprising the electrostatic latent image measuring apparatus according to claim 1.

Images