JP2004233261A - Electrostatic latent image observation method and system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for observing a charge distribution state of an electrostatic latent image pattern formed from charge and exposure of a light image on an optical conductive sample in μm order. <P>SOLUTION: A face forming the electrostatic latent image pattern of the optical conductive sample SP forming the electrostatic latent image pattern by the charge and exposure of the light image is two-dimensionally scanned with a charged particle beam. Charged particles receiving electric influence by the electrostatic latent image pattern are caught with a charged particle detector 24, the intensity corresponds the position on the face to be detected so as to observe the charge distribution state in the electrostatic latent image pattern. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrostatic latent image observation method and device.
[0002]
[Prior art]
2. Description of the Related Art In an electrophotographic image forming apparatus such as a copying machine or a laser printer, when an image is output, the following image forming process is usually performed.
[0003]
a. Charging process to uniformly charge photoconductive photoconductor
b. Exposure step of irradiating photoreceptor with light to form electrostatic latent image by photoconductivity
c. Developing process of forming a visible image on photoreceptor using charged toner particles
d. Transfer process of 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 process for cleaning residual toner on photoreceptor after visible image transfer
g. A charge removal process for removing charges remaining on the photoconductor;
[0004]
The process factor and process quality in each of these steps greatly affect the quality of the final output image. In recent years, in addition to high image quality, the demand for environmentally friendly imaging processes such as high durability, high stability, and energy saving has been increasing, and the improvement of process quality in each process has been strongly demanded. I have.
[0005]
In the image forming process, the electrostatic latent image formed on the photoconductor by charging / exposure is a "factor directly affecting the behavior of toner particles", and it is important to evaluate the quality of the electrostatic latent image on the photoconductor. Become. By observing the electrostatic latent image on the photoreceptor and feeding back the result to the design, the process quality of the charging step and the exposure step can be improved, resulting in image quality, durability, stability and saving. Further improvement in energy use can be expected.
[0006]
However, it is extremely difficult to observe the electrostatic latent image formed on the photoconductive photoconductor by charging and exposure.
[0007]
As a method of observing the potential distribution, a conventional method is to use a sensor head such as a cantilever that is close to the sample on which the potential distribution has been formed, and measure the electrostatic attraction or induced current generated as an interaction at that time to convert it into a potential distribution. The electrostatic attraction type observation device is commercially available as SPM (scanning probe microscope), and the induced current type is disclosed in Patent Documents 1 and 2.
[0008]
In these systems, it is necessary to bring the sensor head 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.
[0009]
Observation under these conditions is
・ Absolute distance measurement is required.
[0010]
-Measurement takes time, during which the latent image state changes.
[0011]
-Discharge and adsorption occur between the sensor head and the sample.
[0012]
・ The sensor itself disturbs the electric field.
It is extremely difficult to properly observe an electrostatic latent image in practical use.
[0013]
A method of developing the electrostatic latent image to form a toner image, transferring the obtained toner image to paper or tape, and observing the state (quality) of the electrostatic latent image with the toner image is considered. In the method, the state of the electrostatic latent image is indirectly observed via the development and transfer processes, and the electrostatic latent image itself is not observed.
[0014]
As a method of observing an electrostatic latent image, Patent Document 3 discloses a method of measuring a charging characteristic, a photosensitive characteristic, and a dark decay characteristic using a surface voltmeter or the like. However, in the observation method described in Patent Document 3, the obtained spatial resolution 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. It is orders of magnitude worse than the spatial resolution of the order of microns, and is not necessarily sufficient for evaluating the electrostatic latent image itself.
[0015]
Patent Documents 4 and 5 describe that an electrostatic latent image is observed by irradiating the electrostatic latent image with an electron beam. However, in the observation technique described in Patent Document 5, the one that holds an electrostatic latent image to be observed is a conductor sample such as an LSI chip, and in the observation technique described in Patent Document 4, the charge is stabilized. It can be applied only to a dielectric sample that can be held, and cannot be applied to a sample whose charge distribution attenuates with time due to dark decay, such as a photoconductive sample.
[0016]
[Patent Document 1]
Japanese Patent No. 309179
[Patent Document 1]
JP-A-11-184188
[Patent Document 3]
JP-A-2002-82572
[Patent Document 4]
JP-A-3-49143
[Patent Document 5]
JP-A-3-29867
[0017]
[Problems to be solved by the invention]
The present invention relates to an electrostatic latent image observing method capable of directly observing an electrostatic latent image formed on a photoconductive sample by charging and exposure of a light image with high spatial resolution, and an apparatus for realizing the method. The challenge is to realize
[0018]
[Means for Solving the Problems]
The method for observing an electrostatic latent image according to the present invention is based on a method in which a surface of a photoconductive sample, on which an electrostatic latent image pattern is formed by charging and exposure of a light image, on which the electrostatic latent image pattern is formed is charged with a charged particle beam. Scans two-dimensionally, captures charged particles that are electrically affected by the electrostatic latent image pattern, detects their intensities corresponding to the positions on the surface, and detects the charge distribution state in the electrostatic latent image pattern. "Observe" (claim 1).
[0019]
“Charged particle beam” refers to a charged particle beam that is affected by an electric or magnetic field, such as an electron beam or an ion beam.
The “charged particles that are electrically affected by the electrostatic latent image pattern” are the charged particles themselves that make up the scanned charged particle beam (for example, a charged charge that charges a photoconductive sample and a charged particle beam). Charged particles are of the same polarity, and the scanned charged particles are repelled and captured by the charged charge of the photoconductive sample), or charged particles generated in the photoconductive sample by the impact of the charged particle beam. There may be.
[0020]
2. The electrostatic latent image observation method according to claim 1, wherein an electron beam is used as the "charged particle beam for two-dimensionally scanning the surface on which the electrostatic latent image pattern is formed" of the photoconductive sample. "Secondary electrons generated in the photoconductive sample" can be captured as charged particles electrically affected by the latent image pattern (claim 2).
[0021]
The so-called “secondary electrons” refer to electrons generated in the photoconductive sample “attributed” to the scanned electron beam, and are necessarily literally “electrons generated secondary by the impact of the electron beam. Does not mean. That is, the secondary electrons actually include higher-order ones such as tertiary electrons.
[0022]
In the method for observing an electrostatic latent image according to claim 2, it is possible to "form the electrostatic latent image pattern by uniformly charging the photoconductive sample by two-dimensional scanning with an electron beam and then exposing the optical image". (Claim 3). That is, the electron beam can be used to uniformly charge the photoconductive sample. This eliminates the need for a dedicated charging means for charging the photoconductive sample.
[0023]
In the method for observing an electrostatic latent image according to any one of claims 1 to 3, it is possible to "project an image of a mask pattern for a resolution test to form an electrostatic latent image pattern" (claim 4). In this case, “the formed electrostatic latent image can be a negative latent image”. A "negative latent image" is a latent image in which the potential of a portion visualized as an image (the portion to which toner adheres) is lightly attenuated with respect to other portions. Be visualized.
[0024]
In recent years, in most image formation based on the electrophotographic principle, a latent image is formed by writing an image by optical scanning, and an electrostatic latent image formed by optical scanning is generally a negative latent image. It is preferable to form a negative latent image also as an electric latent image.
[0025]
In the method for observing an electrostatic latent image according to any one of claims 1 to 5, it is preferable that the exposure of the light image is performed by monochromatic light (claim 6). A semiconductor laser is suitable as the "light source" (claim 7).
By irradiating an optical image using monochromatic light, there is no need to consider the chromatic aberration of the optical system for irradiating the optical image, the design of the optical system is easy, and since there is no chromatic aberration, the resolution is high. A good light image can be emitted.
[0026]
An "electrostatic latent image observing apparatus" of the present invention is an apparatus for performing the electrostatic latent image observing method according to claim 1 and includes charged particle beam scanning means and observing means (claim 8). ).
[0027]
"Charged particle beam scanning means" is means for two-dimensionally scanning the surface of the photoconductive sample on which the electrostatic latent image pattern is formed, on which the electrostatic latent image pattern is formed, with a charged particle beam.
The "observation means" captures charged particles that are electrically affected by the electrostatic latent image pattern, detects their intensities corresponding to their positions on the surface, and observes the charge distribution state in the electrostatic latent image pattern It is a means to do.
[0028]
9. The electrostatic latent image observation device according to claim 8, wherein the charging unit uniformly charges the photoconductive sample and the exposing unit performs exposure by irradiating the uniformly charged photoconductive sample with a light image. (Claim 9). In this case, the exposing means may be “a mask pattern projected and exposed” (claim 10), and the mask pattern may be a “mask pattern for resolution inspection” (claim 11). An electrostatic latent image pattern based on a negative latent image can be formed on a photoconductive sample by using the mask pattern as a “negative pattern”.
[0029]
Exposure means in the electrostatic latent image observation apparatus according to any one of claims 9 to 12, wherein the exposure means sets an optical path for exposure outside a region through which a charged particle beam for performing two-dimensional scanning of the photoconductive sample passes. A "set" configuration (claim 13). With this configuration, the photoconductive sample can be two-dimensionally scanned with the charged particle beam without being blocked by the exposure unit.
[0030]
In the electrostatic latent image observation device according to the thirteenth aspect, the exposing means is “projecting and exposing a mask pattern” according to the tenth or eleventh aspect, and the optical path for exposure is “to expose a photoconductive sample. The mask pattern can be tilted with respect to the optical axis of the light path for exposure so that the mask pattern is tilted with respect to the "normal of the surface" and the image of the mask pattern is formed on the surface to be exposed.
[0031]
In the electrostatic latent image observation device according to any one of claims 9 to 14, the exposure means may include a semiconductor laser as a light source for exposure.
[0032]
Also, the electrostatic latent image observation device according to any one of claims 9 to 15 can control the exposure time of the exposure unit (claim 16). By controlling the exposure time, a desired light energy can be given to the photoconductive sample, and various electrostatic latent image patterns having different degrees of light attenuation can be formed. Observable. It goes without saying that the light emission intensity of the light source can be controlled instead of controlling the exposure time or together with the control of the exposure time.
[0033]
In the electrostatic latent image observation device according to any one of claims 8 to 16, the charged particle beam scanning means scans the electron beam two-dimensionally, and the observation means reads "generated on the photoconductive sample, A configuration that captures "secondary electrons that are electrically affected by the latent image pattern" can be adopted (claim 17). In this case, the charged particle beam scanning means can "uniformly charge the photoconductive sample with the electron beam scanned two-dimensionally and also serve as a charging means for the photoconductive sample".
[0034]
The photoconductive sample can be, for example, a part of the photoconductive photoconductor in a prototype stage. By observing the electrostatic latent image, it is possible to know what kind of electrostatic latent image pattern is formed on such a photoconductive sample. It is possible to evaluate whether or not the photoconductor has desired quality and performance, and to feed back the evaluation to the design, it is possible to improve the quality and performance of the photoconductor. It is also possible to evaluate whether the manufactured photoconductive photoconductor actually has the performance and quality as designed.
[0035]
Further, it is possible to know what the “conditions for forming an optimal electrostatic latent image” are on the produced photoconductive photoconductor.
[0036]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments will be described.
FIG. 1 is a diagram showing one embodiment of an electrostatic latent image observation device.
[0037]
Reference numeral 11 denotes a charged particle gun, reference numeral 12 denotes an aperture, reference numeral 13 denotes a condenser lens for charged particles, reference numeral 14 denotes a beam blanker, reference numeral 15 denotes a scanning lens for a charged particle beam, and reference numeral 16 denotes an objective lens for a charged particle beam.
[0038]
The charged particle gun 11, the aperture 12, the condenser lens 13, the beam blanker 14, the scanning lens 15, and the objective lens 16 constitute a charged particle beam irradiation unit 11A, and each component of the charged particle beam irradiation unit 11A is a charged particle beam irradiation unit. The beam is controlled by the beam controller 31.
[0039]
The charged particle beam irradiation unit 11A and the charged particle beam control unit 31 constitute "charged particle beam scanning means".
[0040]
Reference numeral 17 denotes a semiconductor laser as a light source, reference numeral 18 denotes a collimating lens, reference numeral 19 denotes an aperture, reference numeral 20 denotes a mask, and reference numerals 21, 22, and 23 denote lenses that form an “imaging lens”. These constitute an "optical image irradiating unit", and constitute "exposure means" together with a "semiconductor laser driving unit" and an "optical image irradiation control unit" (not shown).
[0041]
The light image irradiation control unit (not shown) controls the blinking of the light emission of the semiconductor laser 17 and the adjustment and setting of the light emission intensity, and also performs focusing and magnification conversion by adjusting the positional relationship between the imaging lenses 21, 22, and 23 and the mask 20. You can do it.
[0042]
Reference numeral 24 denotes a charged particle detector, reference numeral 25 denotes a signal processing unit, reference numeral 26 denotes a monitor, and reference numeral 27 denotes an output device such as a printer. The charged particle detector 24, the signal processing unit 25, the monitor 26, and the output device 27 constitute "observation means".
[0043]
Reference numeral 28 denotes a sample mounting table, reference numeral SP denotes a photoconductive sample, and reference numeral 29 denotes a light-emitting element for discharging electricity. The sample mounting table 28 is a grounded metal plate.
[0044]
The above components are disposed in a casing 30 as shown, and the inside of the casing can be highly depressurized by suction means 32. That is, the casing 30 has a function as a “vacuum chamber”.
[0045]
Further, the entire apparatus is controlled by a “control means such as a computer” (not shown). The above-described charged particle beam control unit 31, signal processing unit 25, and the like can be set as “part of the functions” in control means such as the computer.
[0046]
In the state shown in FIG. 1, the photoconductive sample SP whose surface is uniformly charged is mounted on the sample mounting table 28, and the inside of the casing 30 is highly depressurized.
In this state, the semiconductor laser 17 is turned on to form an optical image of the mask 20 on the uniformly charged surface of the photoconductive sample SP.
[0047]
By this exposure, an electrostatic latent image pattern corresponding to the irradiated light image is formed on the photoconductive sample SP. The surface on which the electrostatic latent image pattern is formed is two-dimensionally scanned by the charged particle beam. That is, when a beam of charged particles is emitted from the charged particle gun 11, the emitted charged particle beam passes through the aperture 12, the beam diameter is regulated, and then passes through the beam blanker 14 while being focused by the condenser lens 13. .
[0048]
The charged particle beam focused by the condenser lens 13 is focused on the surface of the photoconductive sample SP by the objective lens 16. At this time, by deflecting the direction of the charged particle beam by the scanning lens 15, the position at which the charged particle beam is focused is two-dimensionally positioned on the surface of the photoconductive sample SP (for example, perpendicular to the horizontal direction of the drawing and orthogonal to the drawing). Direction).
[0049]
Thus, the surface of the photoconductive sample SP on which the electrostatic latent image pattern is formed is two-dimensionally scanned by the charged particle beam. The size of the scanned area can be changed by setting the magnification of the scanning lens. For example, various magnifications such as a low magnification of about 5 mm × 5 mm and a high magnification of about 1 μm × 1 μm can be used. Is to observe.
[0050]
At this time, a capture voltage of a predetermined polarity is applied to the charged particle detector 24. By the action of the capture voltage, the “charged particles that have been electrically affected by the electrostatic latent image pattern” are captured by the charged particle detector 24, and the intensity (the number of captured particles per unit time) is detected. Converted to a signal.
[0051]
When the “region scanned two-dimensionally by the charged particle beam: S” of the photoconductive sample SP is represented by S (X, Y) using two-dimensional coordinates, for example, 0 mm ≦ X ≦ 1 mm, 0 mm ≦ Y ≦ 1 mm. The electrostatic latent image pattern formed in this area: S (X, Y) is defined as a surface potential distribution: V (X, Y).
[0052]
Since the two-dimensional scanning of the area by the charged particle beam is performed under predetermined conditions, the time from the start to the end of the two-dimensional scanning is T. ₀ ≤T≤T _F Then, the time during scanning: T corresponds to each scanning position in the scanning area: S (X, Y) 1: 1.
[0053]
Since the charged particles captured by the charged particle detector 24 are electrically affected by the surface potential distribution of the electrostatic latent image pattern: V (X, Y), the intensity of the charged particles captured at time T is as follows: F (T) has a correspondence with time: surface potential distribution using V as a parameter: V {X (T), Y (T)}.
[0054]
This correspondence is based on a reference potential: V _N Can be known by observing the intensity of the charged particles affected by the above. Based on such a known relationship, by calibrating the intensity: F of the charged particles, the potential corresponding to the intensity: F: V You can know.
[0055]
Therefore, by sampling the detection signal obtained from the charged particle detector 24 at appropriate intervals, the surface potential distribution: V (X, Y) can be specified for each “small region corresponding to sampling”.
[0056]
As described above, the charged particle beam is a beam of a particle 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. If an ion beam is used, a "liquid metal ion gun" or the like is used.
[0057]
Hereinafter, a case where an electron beam is used as a charged particle beam will be specifically described. At this time, the charged particle gun 11 is an “electron gun”, and the “surface on which the electrostatic latent image pattern is formed” of the photoconductive sample SP is two-dimensionally scanned by the electron beam.
[0058]
In order to form an electrostatic latent image pattern on the photoconductive sample SP, it is necessary to uniformly charge its surface prior to exposure with a light image. Regarding the uniform charging of the photoconductive sample SP, the charging may be performed outside the observation device, and the uniformly charged photoconductive sample SP may be mounted on the sample mounting table 28. The inside of the casing 30 needs to be highly decompressed. When the inside of the casing 30 is decompressed from the setting of the photoconductive sample SP, the charged potential is attenuated due to dark decay before scanning by the electron beam becomes possible. In some cases, the electrostatic latent image pattern cannot be observed.
[0059]
From this viewpoint, it is preferable that the uniform charging of the photoconductive sample SP is performed “after a high degree of reduced pressure is realized” in the casing 30. When charging is performed under a high degree of reduced pressure, charging by corona discharge, which is often performed in an electrophotographic apparatus, is difficult, but charging by a so-called contact-type charging means is possible.
[0060]
In the embodiment shown in FIG. 1, charging by an electron beam is performed using charged particle beam scanning means.
[0061]
When the photoconductive sample SP is irradiated with the electron beam, the impact of the irradiated electrons causes the photoconductive sample SP to generate “secondary electrons (including higher-order emitted electrons such as tertiary electrons as described above). Is generated. In the balance between the amount of electrons emitted to the photoconductive sample SP as an electron beam and the amount of secondary electrons generated, the ratio of the amount of secondary electrons emitted: the amount of irradiated electrons to R2: R1: R1 / R2 is 1 or more. If so, the amount of electrons irradiated by subtraction exceeds the amount of secondary electrons, and the difference between the two accumulates in the photoconductive sample SP to charge the photoconductive material SP.
[0062]
Therefore, by adjusting the amount of electrons emitted from the electron gun 11 and the accelerating voltage thereof, and setting the “ratio: a condition that R1 / R2 is greater than 1” and scanning the electron beam two-dimensionally, The conductive sample SP can be uniformly charged. Such adjustment of the amount of emitted electrons and the acceleration voltage is performed by the charged particle beam control unit 31. On / off of the electron beam accompanying the scanning of the electron beam is performed by controlling the beam blanker 14 by the charged particle beam control unit 31.
[0063]
FIG. 2 schematically shows a state where the surface of the photoconductive sample SP is charged by the electron beam as described above. FIG. 2 shows a photoconductive sample SP, which is a so-called “functionally separated photoconductor”, in which a charge generation layer 2 is provided on a conductive layer 1 and a charge transport layer 3 is formed thereon. It is.
[0064]
Electrons irradiated by the electron gun are bombarded on the surface of the charge transport layer 3, are captured by the electron orbits of the charge transport layer material molecules on the surface of the charge transport layer 3, and are negatively ionized in the charge transport layer 3. 3 remains on the surface. This state is a state where the photoconductive sample SP is charged.
[0065]
When light LT is irradiated on the photoconductive 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 of the light LT in the charge generation layer 2 To generate positive and negative charge carriers. Of the generated positive and negative charge carriers, the negative carriers move to the conductive layer 1 by the action of the repulsion due to the negative charges on the surface of the charge transport layer 3, and the positive carriers are transported through the charge transport layer 3 to form the same layer. 3 offset with the negative charge (captured electrons) on the surface.
[0066]
In this manner, in the portion of the photoconductive sample SP irradiated with the light LT, the charged charge is attenuated, and a charge distribution according to the intensity distribution of the light LT is formed. This charge distribution pattern is nothing but an electrostatic latent image pattern.
[0067]
The photoconductive sample SP uniformly charged as described above is exposed to a light image to form an electrostatic latent image pattern. This exposure is performed by the aforementioned “exposure means”. That is, the semiconductor laser 17 is turned on, and the image of the mask 20 is formed on the surface of the photoconductive sample SP by the operation of the imaging lenses 21, 22 and 23.
[0068]
As the semiconductor laser 17, of course, one having an emission wavelength in a wavelength region where the photoconductive sample SP has sensitivity is used. Since the exposure energy is the time integral of the optical power on the surface of the photoconductive sample SP, the photoconductive sample SP is exposed with the desired exposure energy by controlling the lighting time of the semiconductor laser 17. be able to.
[0069]
FIG. 3 schematically shows the “light image irradiating section” in the “exposure means”.
Reference numeral 17 denotes a semiconductor laser as a light source, reference numeral 18 denotes a collimating lens, reference numeral 19 denotes an aperture, and reference numeral 20 denotes a mask. Reference numeral 210 is a simplified drawing of the “imaging lens” composed of the three lenses 21, 22, and 23 in FIG. 1 and is drawn as one lens.
[0070]
The light beam emitted from the semiconductor laser 17 is converted into a parallel light beam by the collimator lens 18, and the light beam diameter is regulated by the aperture 19 to irradiate the mask 20. The light beam that has passed through the mask 20 forms an image of a mask pattern of the mask 20 on an image plane by the operation of the imaging lens 210. The “image surface” is a “uniformly charged surface” of the photoconductive sample SP mounted on the sample mounting table 28.
Thus, the photoconductive sample SP is exposed, and an electrostatic latent image pattern corresponding to the mask pattern is formed.
[0071]
As shown in FIG. 3, assuming that the object distance of the mask 20 in the imaging lens 210 is L1 and the image distance is L2, the imaging magnification of the imaging lens 210 in the “perpendicular direction to the optical axis”: β = L2 / L1 and a mask pattern image corresponding to the magnification is formed.
[0072]
The imaging lens 210 is arranged so that the mask 20 and the surface of the photoconductive sample are conjugate. Since the imaging magnification: β and the size of the mask pattern are known in advance, the size of the mask pattern image formed on the surface of the photoconductive sample can be calculated, and the desired electrostatic latent image pattern on the photoconductive sample can be calculated. Can form
Since the optical path for exposure in the exposure means is set to “out of the area through which the charged particle beam for performing the two-dimensional scanning of the photoconductive sample passes”, the optical axis of the imaging lens 210 is uniform in the photoconductive sample. It is inclined with respect to the normal line on the charged surface.
[0073]
Therefore, the mask 20 is also arranged at an angle to the optical axis of the imaging lens 210 as shown in FIG. 3 so that the “image of the mask pattern” by the imaging lens 20 matches the surface of the photoconductive sample. Have been. The “tilt angle of the imaging lens 210 with respect to the optical axis: α, θ” of the mask 20 and the surface of the photoconductive sample is α = θ = 45 degrees in the embodiment being described. This is because the magnification is equal (L1 = L2).
[0074]
For this reason, the image of the mask pattern formed on the surface of the photoconductive sample becomes √2 times larger in the plane parallel to the drawing than in the direction perpendicular to the drawing of FIG. To design a mask pattern.
[0075]
In a general case where the imaging magnification is other than the same magnification, assuming that the object distance is L1 and the image distance is L2, the relationship between these distances L1 and L2 and the inclination angles α and θ is as follows:
L1 · tanα = L2 · tanθ
Holds.
[0076]
The mask pattern in the mask 20 is a “mask pattern for resolution inspection”. In the embodiment being described, the mask pattern is also a negative pattern so that a negative latent image can be formed on the photoconductive material. The other parts are light-shielding.
[0077]
FIG. 4 shows an example of the mask pattern. In this mask pattern, a pattern for a resolution test is formed as a transmission portion on a light-shielding portion. As shown in the figure, the pattern for the resolution test is a “basic pattern in which three rectangular shapes are arranged in parallel at a predetermined pitch”. A plurality of basic pattern pairs P1 to P5 different from each other are arranged as shown in FIG.
[0078]
Returning to FIG. 1, in a state where the electrostatic latent image pattern is formed on the photoconductive sample SP as described above, the scanning region of the photoconductive sample SP is two-dimensionally scanned by the electron beam. Secondary electrons generated by this scanning are detected by the charged particle detector 24. Since the detection target is a secondary electron, which is a negative charge, the charged particle detector 24 applies a positive voltage (capture voltage) for capturing the secondary electron, and converts the secondary electron generated by the scanning of the electron beam into a positive charge. Suction and capture by voltage. The captured electrons are converted by a scintillator into scintillation brightness, which is further converted into an electric signal.
[0079]
In the space between the surface of the photoconductive sample SP and the charged particle detector 24, the charge (negative charge forming an electrostatic latent image) on the surface of the photoconductive sample SP and the charged particle detector 24 are applied. The “potential gradient” is formed by the positive capture voltage.
[0080]
FIG. 5 is an explanatory diagram showing a potential distribution in a space between the charged particle detector 24 and the photoconductive sample SP by contour lines. The surface of the photoconductive sample SP is in a state of being uniformly charged to a negative polarity except for a portion where the potential is attenuated due to light attenuation, and the charged particle detector 24 is given a positive potential. Therefore, in the group of potential contours indicated by solid lines, the potential increases from the surface of the photoconductive sample SP toward the charged particle detector 24.
[0081]
Accordingly, the secondary electrons el1 and el2 generated at the points Q1 and Q2 in the figure, which are the “parts that are negatively charged uniformly” in the photoconductive sample SP, are attracted to the positive potential of the charged particle detector 24. Then, it is displaced as shown by arrows G1 and G2 and is captured by the charged particle detector 24.
[0082]
On the other hand, in FIG. 5, point Q3 is "a portion where the negative potential is attenuated by light irradiation by the irradiation of the negative latent image". Near point Q3, the arrangement of the potential contours is as shown by a broken line. In the distribution, "the closer to Q3, the higher the potential". In other words, as shown by the arrow G3, an electric force constrained on the photoconductive sample SP acts on the secondary electrons el3 generated near the point Q3. Therefore, the secondary electron el3 is captured by the “potential hole” indicated by the dashed potential contour, and does not move toward the charged particle detector 24.
[0083]
In other words, the intensity of the secondary electrons (the number of secondary electrons) detected by the charged particle detector 24 is such that a portion having a large intensity is “a ground portion of the electrostatic latent image pattern (a portion that is uniformly negatively charged). Of the electrostatic latent image pattern (portion illuminated by light) (the portion typified by point Q3 in FIG. 5). Will respond.
[0084]
Therefore, if the electric signal obtained by the charged particle detector 24 is sampled by the signal processing unit 25 at an appropriate sampling time, the surface potential distribution: V (X, Y), using the sampling time: T as a parameter as described above. Can be specified for each “small region corresponding to sampling”, and the surface charge distribution (potential contrast image): V (X, Y) is configured as two-dimensional image data by the signal processing unit 25 and monitored. 26, or output by the output device 27, the electrostatic latent image pattern can be obtained as a visible image.
[0085]
Although the mask pattern actually projected on the photoconductive sample is minute, the image displayed on the monitor 25 and the image output from the output device 27 must be appropriately enlarged to a size suitable for observation. Can be.
[0086]
FIG. 6 shows a potential contrast image obtained as described above. Each of the two types of potential contrast images shown in FIG. 6 corresponds to an electrostatic latent image pattern formed by the mask pattern shown in FIG.
[0087]
The potential contrast image shown in FIG. 6B corresponds to the electrostatic latent image pattern formed on the “photoconductive sample having a relatively low resolution”, and the electrostatic latent image pattern spreads out. In the basic pattern pair P1, P2, portions corresponding to the originally separated rectangular shapes are connected to each other and are not separated. Therefore, the resolving power is at the level of the basic pattern pair P3 (see FIG. 4).
[0088]
On the other hand, the potential contrast image shown in FIG. 6A corresponds to the electrostatic latent image pattern formed on the “photoconductive sample with high resolution”, and has the smallest basic pattern pair P1 (FIG. 4). ), The images corresponding to the rectangles of each basic pattern pair are separated.
[0089]
In this way, by using a plurality of basic pattern pairs having different pitches and observing “how far these patterns are resolved” in the electrostatic latent image pattern, the resolution of the photoconductive sample can be identified and determined. By appropriately selecting the size, pattern pitch, shape, and the like of the mask pattern, it becomes possible to evaluate the characteristics of the electrostatic latent image formed on the photoconductive sample.
[0090]
If the surface of the photoconductive sample SP set in the casing 30 is initially non-uniformly charged for some reason, such a charged state becomes an observation noise. Prior to the charging step in (1), it is preferable to irradiate light with light from the light-emitting element 29 (semiconductor laser or light-emitting diode) for static elimination to perform photostatic elimination of the photoconductive material SP.
[0091]
In addition, in the case where a plurality of observations are performed on the same photoconductive sample SP by changing the conditions for forming the electrostatic latent image pattern, the light elimination by the light emitting element 29 is performed prior to each observation. The light emitting element 29 for light neutralization may be omitted in some cases.
[0092]
FIG. 7 shows another configuration example of the light image irradiation unit. In order to avoid complication, the same reference numerals as those in FIGS.
In this example, the “light image irradiating unit” includes a semiconductor laser 17 (driven by a semiconductor laser driving unit 17A) as a light source, a collimating lens 18, and an aperture 19, as in the examples described with reference to FIGS. , A mask 20, and an imaging lens 210, are provided on the side of the sample mounting table 28, and the optical path of the imaging light flux is bent by the mirrors M1 and M2 to convert the image of the mask pattern of the mask 20 into the photoconductive sample SP. An image is formed on the surface.
[0093]
In FIG. 7, reference numeral 30B schematically shows a casing that functions as a vacuum chamber.
[0094]
FIG. 8 shows another embodiment of the electrostatic latent image observation device. In FIG. 8, the same reference numerals as those in FIG.
[0095]
A charged particle gun 11, an aperture 12, a condenser lens 13, a beam blanker 14, a scanning lens 15, and an objective lens 16 constituting a charged particle beam irradiation unit 11A have the same configuration as that of FIG. 1, and the charged particle gun 11 is an electron gun. It is. The charged particle detector 24 and a signal processing unit (not shown) are the same as those described above with reference to FIG. Reference numeral 30A indicates a casing.
[0096]
The photoconductive sample SP1 is formed in a drum shape, which is a general form of a photoconductive photoconductor, and is rotated at a constant speed in a direction indicated by an arrow (counterclockwise) by a driving unit (not shown). After the photoconductive sample SP is set in the casing 30A, the inside of the casing 31A is highly depressurized by suction means (not shown).
[0097]
The charging unit denoted by reference numeral 41 is a contact-type charging unit such as a charging brush or a charging roller, and uniformly contacts and charges the photoconductive sample SP in a casing under reduced pressure. At this time, the photoconductive sample SP1 is rotated at a constant speed in the direction of the arrow. Of course, as in the example described with reference to FIG. 1, the photoconductive sample SP1 can be charged by charging using an electron beam.
[0098]
The “exposure section” indicated by reference numeral 40 performs exposure by irradiating a uniformly charged photoconductive sample SP1 with a light image. As the exposure unit 40, for example, an "optical scanning device" widely known in relation to an optical printer or the like is used, and "irradiation of an optical image" can be performed by optical writing. When the “irradiation of an optical image” is performed by optical writing, the form of the electrostatic latent image pattern formed by writing can be changed arbitrarily, and a desired electrostatic latent image pattern can be easily formed.
[0099]
In addition, when an optical scanning device is used as the exposure unit 40, when the optical scanning device is large and it is difficult to install the optical scanning device in the casing 31A, the optical scanning device is provided outside the casing 31A, and the casing 31A is provided. A transparent window may be provided, and the photoconductive sample SP1 may be externally irradiated with a light image through the window.
[0100]
The scanning of the electron beam by the charged particle beam irradiation unit 11A may be performed by two-dimensionally deflecting the electron beam as in the embodiment of FIG. 1, but the photoconductive sample SP1 is moved at a constant speed in the direction of the arrow. Since the scanning is performed while rotating, the electron beam can be one-dimensionally deflected in a direction orthogonal to the drawing, and two-dimensional scanning can be realized by combining this deflection with the rotation of the photoconductive sample SP1.
[0101]
The electrostatic latent image observation device described above with reference to FIGS. 1, 7 and 8 is an electrostatic latent image of the photoconductive samples SP and SP1 on which the electrostatic latent image pattern is formed. A charged particle beam scanning unit 11A for scanning a pattern-formed surface two-dimensionally with a charged particle beam, and capturing charged particles that are electrically affected by an electrostatic latent image pattern; An electrostatic latent image observing apparatus (claim 8) having observation means 24 for observing the charge distribution state in the electrostatic latent image pattern by detecting the charge corresponding to the upper position. There are charging means for charging, and exposure means for irradiating a uniformly charged photoconductive sample with a light image to perform exposure.
[0102]
In the electrostatic latent image observing apparatus according to the embodiment shown in FIGS. 1 and 7, the exposing means is for "projecting and exposing a mask pattern" (claim 10), and the mask pattern is used for resolving power inspection. This is a mask pattern (claim 11), and the pattern of the mask pattern is a negative pattern (claim 12).
[0103]
In the electrostatic latent image observation apparatus shown in FIGS. 1 and 7, the exposure means sets an optical path for exposure outside a region through which a charged particle beam for performing two-dimensional scanning of the photoconductive sample passes. Yes (claim 13), the exposure light path is inclined with respect to the normal to the surface of the photoconductive sample SP to be exposed, and the exposure is performed so that the mask pattern forms an image on the surface to be exposed. The optical path is inclined with respect to the optical axis of the optical path.
[0104]
1 and 7 has a semiconductor laser 17 as a light source for exposure (claim 15), and the exposure time of the exposure means can be controlled (claim 16). ), The charged particle beam scanning means scans the electron beam two-dimensionally, and the observation means 24 and the like detect "the secondary electrons generated in the photoconductive sample SP and electrically affected by the electrostatic latent image pattern". It is captured (claim 17).
[0105]
1 and 7, the charged particle beam scanning means uniformly charges the photoconductive sample SP with the electron beam to be scanned two-dimensionally, and charges the photoconductive sample SP. (Claim 18).
[0106]
In the electrostatic latent image observation device described in the above embodiment, the electrostatic latent image pattern is formed on the photoconductive samples SP and SP1 on which the electrostatic latent image pattern is formed by charging and exposing the optical image. The scanned surface is two-dimensionally scanned by the charged particle beam, the charged particles that have been electrically affected by the electrostatic latent image pattern are captured, and the intensity is detected in correspondence with the position on the surface, and the static electricity is detected. An electrostatic latent image observing method for observing a charge distribution state: V (X, Y) in an electrostatic latent image pattern is implemented.
[0107]
In the electrostatic latent image observing apparatus according to the embodiment shown in FIGS. 1, 7 and 8, the charged surface for two-dimensionally scanning the surface of the photoconductive samples SP and SP1 on which the electrostatic latent image pattern is formed. An electrostatic latent image observation method for capturing secondary electrons generated in photoconductive samples SP and SP2 as charged particles electrically affected by an electrostatic latent image pattern using an electron beam as a particle beam (claim 2) Is performed.
[0108]
In the electrostatic latent image observing method implemented by the electrostatic latent image observing apparatus shown in FIGS. 1 and 7, the photoconductive sample SP is uniformly charged by two-dimensional scanning with an electron beam and then exposed to a light image. To form an electrostatic latent image pattern (claim 3).
[0109]
In the observation method implemented by the electrostatic latent image observation device of FIGS. 1 and 7, the electrostatic latent image pattern is formed by projecting an image of a mask pattern for resolving power inspection (claim 4). The electrostatic latent image is a negative latent image (Claim 5), the exposure of the light image is performed by monochromatic light (Claim 6), and the semiconductor laser 17 is used as a light source for performing the exposure of the light image (Claim 5). Item 7).
[0110]
【The invention's effect】
As described above, according to the present invention, an electrostatic latent image observation method and apparatus can be realized. According to the observation method and apparatus of the present invention, it is possible to observe an electrostatic latent image pattern formed on a photoconductive sample by uniform charging and irradiation of a light image.
[0111]
In addition, by scanning the charged particle beam, the charged particles that are electrically affected by the electrostatic latent image pattern are captured, and the intensity is detected in accordance with the position on the photoconductive sample, and the electrostatic latent image pattern is detected. , The charge distribution state of the electrostatic latent image pattern can be observed on the order of μm.
[Brief description of the drawings]
FIG. 1 is a diagram showing only a main part of an embodiment of an electrostatic latent image observation means.
FIG. 2 is a diagram for explaining a state in which a photoconductive photoconductor is charged.
FIG. 3 is a diagram schematically showing a light image irradiation unit of the exposure unit of the embodiment shown in FIG.
FIG. 4 is a diagram for explaining an example of a mask pattern of the mask 20 in the embodiment shown in FIG.
FIG. 5 is a diagram for describing capture of secondary electrons by a charged particle detector.
FIG. 6 is a diagram illustrating two examples of observed electrostatic latent image patterns.
FIG. 7 is a diagram for explaining another embodiment of the electrostatic latent image observation device.
FIG. 8 is a diagram for explaining another embodiment of the electrostatic latent image observation device.
[Explanation of symbols]
10 Electrostatic latent image observation device
11A charged particle beam irradiation unit
17 Semiconductor laser
20 mask
21, 22, 23 Imaging lens
SP Photoconductive sample
24 charged particle detector

Claims (18)

The surface of the photoconductive sample, on which the electrostatic latent image pattern is formed by charging and exposure of the optical image, on which the electrostatic latent image pattern is formed is two-dimensionally scanned with a charged particle beam, and the electrostatic latent image is scanned. Capturing the charged particles electrically affected by the image pattern, detecting their intensities corresponding to the positions on the surface, and observing a charge distribution state in the electrostatic latent image pattern. Electrostatic latent image observation method. The method for observing an electrostatic latent image according to claim 1,
An electron beam is used as a charged particle beam for two-dimensionally scanning the surface of the photoconductive sample on which the electrostatic latent image pattern is formed, and the light beam is used as a charged particle electrically affected by the electrostatic latent image pattern. A method for observing an electrostatic latent image, comprising capturing secondary electrons generated in a conductive sample. The electrostatic latent image observation method according to claim 2,
A method for observing an electrostatic latent image, comprising: uniformly charging a photoconductive sample by two-dimensional scanning with an electron beam; and forming an electrostatic latent image pattern by exposing the optical image. The electrostatic latent image observation method according to any one of claims 1 to 3,
A method for observing an electrostatic latent image, comprising projecting an image of a mask pattern for a resolution test to form an electrostatic latent image pattern. The method for observing an electrostatic latent image according to claim 4,
An electrostatic latent image observation method, wherein the formed electrostatic latent image is a negative latent image. The electrostatic latent image observation method according to any one of claims 1 to 5,
A method for observing an electrostatic latent image, wherein exposure of a light image is performed by monochromatic light. The method for observing an electrostatic latent image according to claim 6,
A method for observing an electrostatic latent image, comprising using a semiconductor laser as a light source for exposing a light image. An apparatus for performing the electrostatic latent image observation method according to claim 1,
Charged particle beam scanning means for two-dimensionally scanning the surface of the photoconductive sample on which the electrostatic latent image pattern is formed, with the surface on which the electrostatic latent image pattern is formed, using a charged particle beam;
Observing means for capturing charged particles electrically affected by the electrostatic latent image pattern, detecting the intensity of the charged particles corresponding to the position on the surface, and observing a charge distribution state in the electrostatic latent image pattern. And an electrostatic latent image observation device comprising: The electrostatic latent image observation device according to claim 8,
Charging means for uniformly charging the photoconductive sample,
An electrostatic latent image observation apparatus, comprising: an exposure unit for irradiating a uniformly charged photoconductive sample with a light image to perform exposure. The electrostatic latent image observation device according to claim 9,
An electrostatic latent image observing apparatus, wherein the exposing means projects and exposes a mask pattern. The electrostatic latent image observation device according to claim 10,
An electrostatic latent image observation device, wherein the mask pattern is a mask pattern for a resolution test. The electrostatic latent image observation device according to claim 11,
An electrostatic latent image observation device, wherein the pattern of the mask pattern is a negative pattern. The electrostatic latent image observation device according to any one of claims 9 to 12,
An electrostatic latent image observation device, wherein an exposure unit sets an optical path for exposure outside a region through which a charged particle beam for performing two-dimensional scanning of a photoconductive sample passes. The electrostatic latent image observation device according to claim 13,
Exposure means projects and exposes the mask pattern according to claim 10 or 11 or 12,
The optical path for exposure is inclined with respect to the normal to the surface of the photoconductive sample to be exposed,
An electrostatic latent image observation apparatus, wherein the mask pattern is inclined with respect to the optical axis of an optical path for exposure so that an image is formed on the surface to be exposed. The electrostatic latent image observation device according to any one of claims 9 to 14, wherein the exposure means includes a semiconductor laser as a light source for exposure. The electrostatic latent image observation device according to any one of claims 9 to 15,
An electrostatic latent image observation device, wherein an exposure time of an exposure means can be controlled. The electrostatic latent image observation device according to any one of claims 8 to 16,
Charged particle beam scanning means scans the electron beam two-dimensionally,
An electrostatic latent image observation apparatus, wherein the observation means captures secondary electrons generated in the photoconductive sample and electrically affected by the electrostatic latent image pattern. The electrostatic latent image observation device according to claim 17,
An electrostatic latent image observation apparatus, wherein a charged particle beam scanning unit uniformly charges a photoconductive sample with an electron beam scanned two-dimensionally and also serves as a charging unit for the photoconductive sample.

Images