JP3765988B2 - Electron beam visual inspection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electron beam appearance inspection apparatus used in the manufacture of a sample having a fine circuit pattern such as a semiconductor device or a liquid crystal, and more particularly to a pattern inspection technique for a semiconductor device or a photomask. The present invention relates to the above pattern inspection technique and a technique of comparative inspection using an electron beam.
[0002]
[Prior art]
A conventional electron beam appearance inspection apparatus will be described by taking a semiconductor wafer inspection as an example.
A semiconductor device is manufactured by repeating a process of transferring a pattern formed on a photomask on a semiconductor wafer by lithography and etching. In the manufacturing process of a semiconductor device, the quality of lithography processing, etching processing, and other conditions, and the occurrence of foreign matter greatly affect the yield of the semiconductor device. Therefore, in order to detect abnormalities and defects early or in advance, the semiconductor in the manufacturing process A method for inspecting a pattern on a wafer has been conventionally performed.
[0003]
As a method for inspecting defects present in patterns on a semiconductor wafer, a defect inspection apparatus that irradiates a semiconductor wafer with white light and compares the same kind of circuit patterns of a plurality of LSIs using an optical image has been put into practical use. The outline of the inspection method is described in “Monthly Semiconductor World” August 1995, pp 96-99. In the inspection method using an optical image, as described in JP-A-3-167456, an optically illuminated region on a sample is imaged by a time delay integration sensor, and the image is input in advance. A method for detecting defects by comparing the design characteristics that are present, and monitoring the image deterioration during image acquisition and correcting it during image detection as described in Japanese Patent Publication No. 6-58220. A method for performing a comparative inspection with an optical image is disclosed. When a semiconductor wafer in the manufacturing process is inspected by such an optical inspection method, residues and defects of a pattern having a silicon oxide film or a photosensitive photoresist material on the surface through which light is transmitted cannot be detected. Moreover, the etching residue which is below the resolution of the optical system and the non-opening defect of the minute conduction hole could not be detected. Furthermore, a defect generated at the bottom of the step of the wiring pattern could not be detected.
[0004]
As described above, defect detection by optical images has become difficult due to miniaturization of circuit patterns, complicated circuit pattern shapes, and diversification of materials, so electron beam images with higher resolution than optical images are used. A method for comparing and inspecting circuit patterns has been proposed. When comparing circuit patterns with electron beam images, it is necessary to obtain images much faster than observation with a scanning electron microscope (hereinafter referred to as SEM) in order to obtain a practical inspection time. There is. It is necessary to ensure the resolution of the image acquired at high speed and the SN ratio of the image.
[0005]
As a pattern comparison inspection apparatus using an electron beam, a circuit pattern inspection apparatus using an electron beam has been put into practical use as a circuit pattern of a semiconductor wafer is miniaturized.
[0006]
For example, Japanese Unexamined Patent Publication Nos. 59-192943 and 5-258703, Sandland, et al., “An electron-beam inspection system for x-ray mask production”, J. Vac. Sci. Tech. B, Vol. 9, No. 6, pp. 3005-3009 (1991), literature Meisburger, et al., “Requirements and performance of an electron-beam column designed for x-ray mask inspection”, J. Vac. Sci. Tech. B, Vol. 9, No. 6, pp. 3010-3014 (1991), literature Meisburger, et al., “Low-voltage electron-optical system for the high-speed inspection of integrated circuits”, J Vac. Sci. Tech. B, Vol.10, No.6, pp.2804-2808 (1992), Hendricks, et al., “Characterization of a New Automated Electron-Beam Wafer Inspection System”, SPIE Vol. 2439, pp.174-183 (20-22 February, 1995) and the like are known.
[0007]
In order to perform high-throughput and high-precision inspection following the increase in wafer diameter and circuit pattern miniaturization, it is necessary to acquire a high SN image at a very high speed. Therefore, the number of electrons irradiated using a large current beam 100 times or more (10 nA or more) of a normal scanning electron microscope (SEM) is secured, and a high SN ratio is maintained. Furthermore, high-speed and highly efficient detection of secondary electrons and reflected electrons generated from the sample is essential.
[0008]
Conventionally, optical appearance inspection devices have been commercialized, but for measurement of the position of each printed unit of a predetermined printed figure, the array offset, rotation, and orthogonality are measured as an array of printing units, The amount of expansion / contraction between printing units is not considered. This is because the printing unit interval is actually measured using a wafer of the same type or the same process as the wafer to be inspected, and, in addition, even if an inspection position shift occurs, the adjacent comparison inspection areas are similarly cleaned. This is because comparative inspection is possible.
[0009]
However, an actual wafer expands and contracts for each wafer or lot depending on the printing accuracy of each exposure machine, the heat treatment process, and the like. Conventionally, the positional accuracy within the printing unit is not taken into consideration. For this reason, when a comparative inspection area within the wafer is selected, a misdetection occurs due to a positional shift, and the comparative inspection becomes impossible. Further, even if a comparison inspection area interval capable of comparison inspection is selected, the positional accuracy of the detected defect causes an error of several micrometers. Although this has not been regarded as a problem so far, it is impossible to compare the appearance inspection results between processes and to compare the element unit with the fail bit map which is the electrical characteristic test result after completion of the device, and to review and classify the inspection. In order to detect defects again using the result of the appearance inspection in the apparatus after the appearance inspection such as the above, it is necessary to detect a wide area, and it takes a long time.
[0010]
Further, a semiconductor sample with an insulating film such as a resist is irradiated with a low acceleration electron beam of 2 KeV or less so as not to be affected by charging. This technology is described in pages 622 to 623 of the “Electron / Ion Beam Handbook (2nd edition)” edited by the 132nd Committee of the Japan Society for the Promotion of Science (Nikkan Kogyo Shimbun, 1986). However, an electron beam with a large current and a low acceleration causes aberration due to the space charge effect, and high-resolution observation is difficult.
[0011]
As a method for solving this problem, there is known a method in which a high acceleration electron beam is decelerated immediately before a sample and irradiated on the sample as a substantially low acceleration electron beam. For example, there are techniques described in Japanese Patent Laid-Open Nos. 2-142045, 6-139985, 5-258703, and 6-188294.
[0012]
Japanese Patent Laid-Open No. 6-188294 detects an image signal from a repeated pattern to be inspected, generates a statistical image signal of the pattern to be tested repeated from the image signal, and uses the statistical image signal as a reference image signal. A technique for extracting a defect or a defect candidate existing in a pattern to be inspected by aligning and comparing with a detected image signal is disclosed.
[0013]
[Problems to be solved by the invention]
However, in these techniques, there is a problem that the primary electron beam is affected by the retarding electric field immediately before the sample is irradiated by applying a retarding voltage to the wafer.
[0014]
In general, the change in electric field is distributed symmetrically with respect to the central axis of the primary electron beam. Therefore, the primary electron beam is deflected to a desired region by adjusting the deflection sensitivity uniformly regardless of the wafer position. be able to. However, at the outer periphery of the wafer, there is a problem in that an asymmetrical retarding electric field is generated in the axis due to the cross-sectional shape of the wafer itself and the cross-sectional structure of the end of the sample stage on which the wafer is placed.
[0015]
Therefore, depending on whether or not the comparative inspection position on the wafer is near the outer periphery of the wafer, there is a problem that a non-negligible difference, so-called beam distortion, occurs in the sample irradiation region of the primary beam due to the same deflection signal. is there.
[0016]
As a result, even when trying to irradiate the edge of the wafer with the electron beam, the accuracy of the relationship between the electron beam irradiation position and the sample position is significantly reduced due to the fluctuation of the electric field. This part could not be processed, analyzed or inspected.
[0017]
The present invention has been made in view of the above points, and in the electron beam type visual inspection apparatus, the position of each printed figure is measured for each printing unit, the position within the printing unit is measured, and the periphery of the sample is measured. It is an object of the present invention to provide an appearance inspection apparatus capable of accurately specifying an inspection position by measuring the amount of positional deviation.
[0018]
Another object of the present invention is to provide an appearance inspection apparatus that has a high inspection speed, enables a wider inspection inside a sample, and can accurately determine the position of a detected defect.
[0019]
  The object is to provide an electron source for generating a primary electron beam, lens means for focusing the primary electron beam, a sample stage on which a sample is placed, and transport means for transporting the sample to a sample chamber including the sample stage. A primary electron beam scanning unit that scans the focused primary electron beam on the sample, a unit that detects secondary charged particles that are secondarily generated from the sample, and a signal from the detector. Storage means for storing the image signal of the first area on the sample, and the image of the area stored in the storage means for the image of the second area on which another identical sample pattern is formed on the sample And an SEM visual inspection apparatus that inspects a sample printed with the same repeated figure, and detects an image on the sample. Before detecting defects,Means for selecting an alignment graphic of three or more printing units not on a straight line on the sample, Means for detecting an alignment graphic using an image obtained by irradiating the sample with a primary electron beam, Detection The amount of deviation of the sample on the XY coordinate is obtained from the alignment pattern thus obtained.Stretching amount of printing unit, rotation,andMeasure the straightness,Calculation of the amount of expansion / contraction, rotation and straightnessBy statistically calculating the result ofeachCalculate alignment error of printing unitMeans to do,From arrangement errors for printing unitsCompensate defect inspection position specified in advanceMeans to do, Control the stage and the position to deflect the electron beamHaving meansIs achieved.
[0020]
  Other features of the present invention are: means for detecting a figure on the sample; means for storing the figure; means for moving the sample; means for measuring a shift amount between the stored figure and the detected figure; Means for storing the amount of displacement of the figure corresponding to the positions of a plurality of samples, and calculating the amount of expansion / contraction, rotation, and straightness by statistically calculating the amount of displacement of the figure corresponding to the positions of the plurality of samples stored Electron beam appearance inspection with means to calculateInspectionIn the device.
[0021]
  A feature of the present invention is that it is possible to measure a reference sample having reference values for the amount of expansion / contraction, rotation, and straightness of printing units determined in advance to unify the coordinate system of a plurality of inspection apparatuses. The electron beam type visual inspection apparatus which calculates the displacement amount from the result and the reference value, and stores or outputs the defect detection position of the separately inspected sample in the coordinate system of the reference sample and the displacement amount as the correction amount It is in.
[0022]
  The feature of the present invention is that the print distortion in the print unit is calculated by using the correction amount of the expansion / contraction amount, rotation, and straightness in the print unit separately obtained, and the defect inspection position designated in advance is calculated in consideration of the calculation result. The electron beam type visual inspection apparatus corrects and controls the stage and the position where the electron beam is deflected.
  Further, the present invention is characterized in that it is possible to input the amount of expansion / contraction of the printing unit, the amount of correction of the rotation and the straightness, and the electron beam type which corrects the defect detection position of the specimen to be separately inspected by the amount of correction and stores or outputs it It is in the appearance device.
[0023]
Another feature of the present invention is that means for calculating an error amount from a reference grid determined from the expansion / contraction amount, rotation, and straightness, and a region where the error amount is large from the error amount to the stage moving direction at the time of inspection. The SEM type visual inspection apparatus includes means for correcting the defect inspection position and controlling the stage and the position for deflecting the electron beam in consideration of being continuous in the adjacent region.
[0024]
According to the present invention, it is possible to inspect a wider inspection area and accurately determine the position of a detected defect in the appearance inspection apparatus. For example, since it is possible to estimate the process of creating a defect based on the defect distribution of the entire sample to be inspected, the inspection area of the sample to be inspected can be designated as a random print unit, and inspection can be performed in a short time Become.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Example 1)
FIG. 1 shows the configuration of an SEM visual inspection apparatus 1 according to the first embodiment of the present invention. The SEM visual inspection apparatus 1 includes an inspection chamber 2 in which the chamber is evacuated, and a spare chamber (not shown in the present embodiment) for transporting the sample 9 to be inspected into the inspection chamber 2. The spare room is configured to be evacuated independently of the examination room 2. Further, the SEM type visual inspection apparatus 1 includes a control unit 6 and an image processing unit 5 in addition to the inspection room 2 and the spare room.
[0026]
The inspection chamber 2 is roughly divided into an electron optical system 3, a secondary electron detection unit 7, a sample chamber 8, and an optical microscope unit 4. The electron optical system 3 includes an electron gun 10, an electron beam extraction electrode 11, a condenser lens 12, a blanking deflector 13, a scanning deflector 15, an aperture 14, an objective lens 16, a reflecting plate 17, and an ExB deflector 18. ing. Of the secondary electron detector 7, a secondary electron detector 20 is disposed above the objective lens 16 in the examination room 2. The output signal of the secondary electron detector 20 is amplified by a preamplifier 21 installed outside the examination room 2 and converted into digital data by the AD converter 22. The sample chamber 8 includes a sample stage 30, an X stage 31, a Y stage 32, a rotary stage 33, a position monitor length measuring device 34, and an inspected sample height measuring device 35. The optical microscope section 4 is installed in the vicinity of the electron optical system 3 in the room of the examination room 2 and at a position far away from each other so as not to affect each other, and the distance between the electron optical system 3 and the optical microscope section 4 Is known. Then, the X stage 31 or the Y stage 32 reciprocates a known distance between the electron optical system 3 and the optical microscope unit 4.
[0027]
The optical microscope unit 4 includes a light source 40, an optical lens 41, and a CCD camera. The image processing unit 5 includes a first image storage unit 46, a second image storage unit 47, a calculation unit 48, and a defect determination unit 49. The captured electron beam image or optical image is displayed on the monitor 50. Operation commands and operation conditions of each part of the apparatus are input / output from the control unit 6. In the control unit 6, conditions such as the acceleration voltage at the time of electron beam generation, the electron beam deflection width, the deflection speed, the signal acquisition timing of the secondary electron detector, the sample stage moving speed, etc. are arbitrarily or arbitrarily selected according to the purpose. It is input so that it can be set. The control unit 6 uses the correction control circuit 43 to monitor the position and height deviation from the signals from the position monitor length measuring device 34 and the sample height measuring device 35, and generates a correction signal from the result. Then, a correction signal is sent to the objective lens power supply 45 and the scanning deflector 44 so that the electron beam is always irradiated to the correct position.
[0028]
In order to obtain an image of the sample 9 to be inspected, the electron beam 19 narrowed down is irradiated to the sample 9 to be inspected, and secondary electrons 51 are generated, which are scanned by the electron beam 19 and the stages 31 and 32. By detecting in synchronization with the movement, an image of the surface of the sample 9 to be inspected is obtained.
[0029]
As described in the subject of the present invention, one object of the present invention is to provide an automatic inspection apparatus having a high inspection speed. Therefore, unlike an ordinary SEM, an electron beam having an electron beam current of the pA order is scanned at a low speed, and multiple scans and superposition of each image are not performed. Further, in order to suppress charging of the insulating material, it is necessary to scan the electron beam once or several times at a high speed. In this embodiment, therefore, an image is formed by scanning only a large current electron beam of, for example, 100 nA, which is about 100 times or more that of a normal SEM, only once. The scan width was 100 μm, one pixel was 0.1 μm, and one scan was performed in 10 μs.
[0030]
The electron gun 10 uses a diffusion supply type thermal field emission electron source. By using this electron gun 10, a stable electron beam current can be ensured as compared with a conventional tungsten (W) filament electron source or a cold field emission electron source. An image is obtained. Further, since the electron beam current can be set large by the electron gun 10, high-speed inspection as described later can be realized. The electron beam 19 is extracted from the electron gun 10 by applying a voltage between the electron gun 10 and the extraction electrode 11. The electron beam 19 is accelerated by applying a high negative potential to the electron gun 10. As a result, the electron beam 19 travels in the direction of the sample stage 30 with energy corresponding to the potential, is converged by the condenser lens 12, and is further narrowed down by the objective lens 16 to be XY stages 31, 32 on the sample stage 30. The sample 9 to be inspected (a sample having a fine circuit pattern such as a semiconductor wafer, a chip or a liquid crystal, a mask) mounted on the substrate is irradiated.
[0031]
The blanking deflector 13 is connected to a signal generator 44 for generating a scanning signal and a blanking signal, and the condenser lens 12 and the objective lens 16 are connected to a lens power source 45, respectively. A negative voltage can be applied to the sample 9 to be inspected by a high voltage power source 36. By adjusting the voltage of the high voltage power source 36, the primary electron beam is decelerated, and the electron beam irradiation energy to the sample 9 to be inspected can be adjusted to an optimum value without changing the potential of the electron gun 10.
[0032]
Secondary electrons 51 generated by irradiating the specimen 9 with the electron beam 19 are accelerated by a negative voltage applied to the specimen 9. An ExB deflector 18 is disposed above the sample 9 to be inspected, and the secondary electrons 51 accelerated thereby are deflected in a predetermined direction. The amount of deflection can be adjusted by the voltage applied to the ExB deflector 18 and the strength of the magnetic field. The electromagnetic field can be varied in conjunction with a negative voltage applied to the sample. The secondary electrons 51 deflected by the ExB deflector 18 collide with the reflecting plate 17 under a predetermined condition. The reflecting plate 17 has a conical shape integrally with a shield pipe of a deflector of an electron beam (hereinafter referred to as a primary electron beam) irradiated on a sample. When the accelerated secondary electrons 51 collide with the reflecting plate 17, second reflecting electrons 52 having energy of several V to 50 eV are generated from the reflecting plate 17.
[0033]
The secondary electron detector 7 has a secondary electron detector 20 inside the evacuated inspection chamber 2, and a preamplifier 21, an AD converter 22, an optical conversion means 23, a transmission means 24 outside the inspection room 2, It comprises an electric conversion means 25, a high voltage power supply 26, a preamplifier drive power supply 27, an AD converter drive power supply 28, and a reverse bias power supply 29. As already described, the secondary electron detector 20 of the secondary electron detector 7 is disposed above the objective lens 16 in the examination room 2. The secondary electron detector 20, the preamplifier 21, the AD converter 22, the optical conversion means 23, the preamplifier drive power supply 27, and the AD converter drive power supply 28 are floated to a positive potential by the high voltage power supply 26. The second secondary electrons 52 generated by colliding with the reflecting plate 17 are guided to the detector 20 by this attractive electric field. The secondary electron detector 20 includes second secondary electrons 52 generated when the secondary electrons 51 generated while the electron beam 19 is irradiated on the sample 9 to be inspected are then accelerated and collide with the reflector 17. Is detected in conjunction with the scanning timing of the electron beam 19.
[0034]
The output signal of the secondary electron detector 20 is amplified by a preamplifier 21 installed outside the examination room 2 and converted into digital data by the AD converter 22. The AD converter 22 is configured to immediately convert an analog signal detected by the semiconductor detector 20 into a digital signal after being amplified by the preamplifier 21 and transmit the digital signal to the image processing unit 5. Since the detected analog signal is digitized and transmitted immediately after detection, a signal having a higher speed and a higher SN ratio can be obtained.
[0035]
A specimen 9 to be inspected is mounted on the XY stages 31 and 32, and the X-Y stages 31 and 32 are stationary when the inspection is performed, and the electron beam 19 is scanned two-dimensionally. A method of scanning the electron beam 19 in a straight line in the X direction by continuously moving the Y stages 31 and 32 in the Y direction at a constant speed can be selected. When inspecting a specific relatively small area, the former stage is inspected with the stationary stage, and when inspecting a relatively large area, the stage is continuously moved at a constant speed and inspected. It is. When the electron beam 19 needs to be blanked, it can be controlled so that the electron beam 19 is deflected by the blanking deflector 13 so that the electron beam does not pass through the diaphragm 14.
[0036]
As the position monitor length measuring device 34, a length measuring device based on laser interference is used in this embodiment. The positions of the X stage 31 and the Y stage 32 can be monitored in real time and transferred to the control unit 6. Similarly, data such as the number of rotations of the motors of the X stage 31, the Y stage 32, and the rotary stage 33 is also transferred from each driver to the control unit 6, and the control unit 6 receives these data. It is possible to accurately grasp the area and position where the electron beam 19 is irradiated based on the correction, and the correction control circuit 43 corrects the displacement of the irradiation position of the electron beam 19 in real time as necessary. It has become. In addition, the region irradiated with the electron beam can be stored for each sample to be inspected.
[0037]
The optical height measuring device 35 uses an optical measuring device that is a measuring method other than an electron beam, such as a laser interference measuring device or a reflected light measuring device that measures changes at the position of reflected light. The height of the sample 9 to be inspected mounted on the Y stage 31 and 32 is measured in real time. In this embodiment, the inspected sample 9 is irradiated with the elongated white light that has passed through the slit through the transparent window, the position of the reflected light is detected by the position detection monitor, and the amount of change in height is calculated from the change in position. The calculation method was used. Based on the measurement data of the optical height measuring device 35, the focal length of the objective lens 16 for narrowing down the electron beam 19 is dynamically corrected, and the electron beam 19 always focused on the non-inspection area can be irradiated. It is like that. In addition, the warpage and height distortion of the specimen 9 to be inspected are measured in advance before electron beam irradiation, and it is possible to configure the correction conditions for each inspection area of the objective lens 16 based on the data. It is.
[0038]
The image processing unit 5 includes a first image storage unit 46, a second image storage unit 47, a calculation unit 48, a defect determination unit 49, and a monitor 50. The image signal of the sample 9 to be inspected detected by the secondary electron detector 20 is amplified by a preamplifier 21, digitized by an AD converter 22, converted into an optical signal by an optical converter 23, and an optical fiber 24. And converted into an electric signal again by the electric converter 25 and stored in the first image storage unit 46 or the second storage unit 47. The arithmetic unit 48 performs alignment of the stored image signal with the image signal of the other storage unit, normalization of the signal level, various image processing for removing the noise signal, and compares both image signals. Calculate. The defect determination unit 49 compares the absolute value of the difference image signal calculated by the calculation unit 48 with a predetermined threshold value. If the difference image signal level is larger than the predetermined threshold value, the defect determination unit 49 determines that the pixel is defective. The candidate is determined, and the position, the number of defects, and the like are displayed on the monitor 50.
[0039]
So far, the overall configuration of the SEM type visual inspection apparatus 1 has been described.
When actually inspecting, the area to be compared and inspected is determined in advance. However, the exposure accuracy of the exposure equipment that repeatedly prints figures on the sample, deformation due to heat treatment during the production of the sample, and transport of the appearance inspection device For accuracy, it is necessary to perform an operation called alignment for recognizing the position of the repeated figure on the sample and re-determining the inspection area.
[0040]
Next, the alignment operation in the embodiment of FIG. 1 will be described with reference to FIGS.
FIG. 2 is a diagram showing an alignment coordinate system. In the present invention, in order to accurately recognize the printed figure on the sample, the alignment coordinate system of the apparatus is managed by a stage coordinate system 100, a wafer coordinate system 101, and a shot coordinate system 102 as shown in FIG.
[0041]
  The stage coordinate system 100 is a coordinate system indicating the position of the sample stage. The wafer coordinate system 101 indicates the position on the inspection sample 9 in the array 103 of printing units. Further, the position on the sample 9 to be inspected is the center of the deflection visual field where the electron beam 19 irradiates the sample 9 to be examined without being deflected by the scanning deflector 15. The printing unit 104 has one or more dies 106 as structural units therein.2Shows the case where there are three dies 106. In the printing unit 104, at least one alignment graphic 105 exists. In the actual alignment operation, first, two alignment figures 105 of the printing unit 104 are selected from the sample 9 to be inspected, and the optical microscope unit 4 having a wide detection field of view is used. First, using the reference arrangement position set in advance, the specimen 9 is moved to the alignment figure 105 position of the first printing unit so as to be the center of the visual field of the optical microscope section 4, and the deviation amount is obtained by image processing. taking measurement. NextOn the secondThe same measurement is performed on the alignment graphic 105 of the second printing unit. The rotation 110 and offset of the printing unit array can be calculated from the first and second deviation amounts.
[0042]
  Subsequently, the alignment figure 105 of three or more printing units 104 that are not on a straight line is selected, and the alignment figure 105 is detected using the image by the electron beam 19.Coordinate axesMeasure the deviation amount,From deviations of 3 or more pointsRotation 110, offset, and expansion / contraction amount 122 of the printing unit array shown in FIGS.andStraightness 130CalculationAnd thatCalculationBy statistically calculating the resultsEach on the sample to be inspectedPrinting unitAbout the amount of expansion, contraction and rotation on the XY coordinateArrangement error is calculated and the inspection position for each printing unit is corrected. Figure 3On XY coordinatesRotate printing unit array110FIG. 4 shows the expansion and contraction of the printing unit array.That is, the reference array 120 of print units, the enlarged print unit array 121, the expansion / contraction amount 122 of the print unit array, andFIG.On XY coordinatesStraightness of print unit array130FIG.
[0043]
As a result, even if the exposure accuracy of the exposure apparatus that repeatedly prints the figure on the sample 9 to be inspected or deformation due to heat treatment during the production of the sample, the inspection position can be accurately recognized and inspected.
[0044]
(Example 2)
  As a second embodiment of the present invention, using the alignment function of the first embodiment, the expansion / contraction amount and rotation of a printing unit determined in advance.andA reference sample having a reference value for the straightness is measured, the result of measurement of the reference sample and the amount of displacement are obtained from the reference value, and the defect detection position of the separately inspected sample is set in the coordinate system of the reference sample.By correcting by the amount of displacementAlso memorize or output.
  Thereby, it becomes possible to match the coordinate position of the detected defect among a plurality of apparatuses.
[0045]
【The invention's effect】
A typical effect obtained by the present invention will be briefly described below.
The fact that an accurate inspection position can be obtained according to the present invention enables comparison of distant print units in a sample to be inspected. For example, in the inspection of a semiconductor, a process of creating defects by the defect distribution of the entire sample to be inspected. Since it can be estimated, according to the present invention, the inspection area of the sample to be inspected can be designated as a random printing unit, and the inspection can be performed in a short time.
[0046]
In addition, according to the present invention, it is possible to accurately create a database of defect detection positions between a plurality of devices, which is effective for analysis of the cause of the defect, and inspecting defects on the same sample with other inspection and analysis devices, It is also possible to reduce the time for detecting the same defect when analyzing.
[0047]
In addition, according to the present invention, it is possible to correct the displacement caused by the apparatus depending on the position of the sample to be inspected, such as deflection distortion generated in the outer periphery of the sample to be inspected, and the outer periphery of the sample to be inspected can be inspected. The area can be expanded.
[Brief description of the drawings]
FIG. 1 is a diagram showing a device configuration of an SEM visual inspection apparatus according to a first embodiment of the present invention.
FIG. 2 is a diagram showing an alignment coordinate system in the embodiment of FIG.
FIG. 3 is a diagram showing rotation of a printing unit array in the embodiment of FIG.
4 is a diagram showing expansion and contraction of a printing unit array in the embodiment of FIG.
FIG. 5 is a diagram illustrating the degree of orthogonality of the print unit array in the embodiment of FIG. 1;
[Explanation of symbols]
1 ... SEM visual inspection equipment
2 ... Inspection room
3 ... Electronic optical system
4 ... Optical microscope
5 Image processing unit
6 ... Control unit
7 ... Secondary electron detector
8 ... Sample chamber
9 ... Inspected sample
10 ... electron gun
11 ... Extraction electrode
12… Condenser lens
13 ... Blanking deflector
14 ... Aperture
15 ... Scanning deflector
16 ... Objective lens
17 ... Reflector
18 ... ExB deflector
19 ... electron beam
20 ... Secondary electron detector
21 ... Preamplifier
22 AD converter
23 ... Light conversion means
24: Optical transmission means
25 ... Electric conversion means
26 ... High voltage power supply
27… Preamplifier drive power supply
28… AD converter drive power supply
29… Reverse bias power supply
30 ... Sample stage
31 ... X stage
32 ... Y stage
33 ... Rotation stage
34… Position monitor length measuring device
35 ... Inspected sample height measuring instrument
36 ... retarding power supply
40 ... White light source
41 ... Optical lens
42 ... CCD camera
43 ... Correction control circuit
44 ... Scanning signal generator
45 ... Lens power supply
46… First memory
47 ... Second memory part
48 ... Calculation unit
49 ... Defect judgment section
50 ... Monitor
51 ... Secondary electrons
52… Secondary secondary electrons
100 ... Stage coordinate system
101 ... Wafer coordinate system
102 ... Shot coordinate system
103 ... Print unit array
104 ... printing unit
105… Alignment figure
106 ... Die
110… Rotation of printing unit array
120 ... Print unit reference array
121… Enlarged print unit array
122 ... Expansion / contraction amount of printing unit array
130: Straightness of print unit array

Claims (2)

An electron source that generates a primary electron beam, a lens unit that focuses the primary electron beam, a sample stage on which a sample is placed, a transport unit that transports the sample to a sample chamber including the sample stage, and the focused A primary electron beam scanning means for scanning the sample with a primary electron beam; means for detecting secondary charged particles generated secondarily from the sample; and a first electron beam scanning means on the sample based on a signal from the detector. Storage means for storing an image signal of one area, and means for comparing an image of the area stored in the storage means with an image of a second area on which another same sample pattern is formed on the sample In the SEM type visual inspection apparatus that has a means for discriminating defects on the sample pattern from the comparison result and inspects the sample on which the same repeated graphic is printed,
Prior to detecting an image on the sample and detecting defects, means for selecting an alignment figure of three or more printing units not on a straight line on the sample, obtained by irradiating the sample with a primary electron beam Means for detecting an alignment figure using an image, obtaining a displacement amount on the XY coordinate of the sample from the detected alignment figure, measuring an expansion amount, rotation, and straightness of a printing unit, and Means for calculating the arrangement error of each printing unit by statistically calculating the calculation results for the quantity, rotation and straightness, means for correcting the defect inspection position designated in advance from the arrangement error for the printing unit, stage, and electronic An electron beam type visual inspection apparatus comprising means for controlling a position for deflecting a line.   The inspection apparatus according to claim 1, wherein a reference sample having a predetermined reference value for the amount of expansion / contraction, rotation, and straightness of a printing unit can be measured, and the printing accuracy or the reference value is obtained from the measurement result of the reference sample and the reference value. The amount of displacement due to the expansion and contraction of the sample in the heat treatment problem is obtained, and the defect detection position of a sample to be separately inspected is corrected by the displacement amount, and stored or output in accordance with the coordinate system of the reference sample. Electron beam type visual inspection equipment.

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