JP2011129624A - Method of diagnosing fault of charged particle beam lithography system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of diagnosing a fault of a charged particle beam lithography system using a defect inspection device, the method correctly sensing the fault caused in the charged particle beam lithography system in an initial stage. <P>SOLUTION: A substrate is lithographed under three conditions including a normal condition, a safe condition hardly causing a defect, and an acceleration condition easily causing a defect and, after forming a resist pattern, the number of defects is counted with respect to each area using the defect inspection device. An average relation between the inspection sensitivity and the number of defects is obtained with respect to each condition to see if there is any value outside the relation (the number of defects). For example, if there is a defect increasing in the same manner from an average value in both of the area lithographed under the safe condition and the area lithographed under the acceleration condition, it is assumed that the defect depends on the process. On the other hand, defects varying in the number of defects between these areas can be assumed to be caused by the electron beam lithography system. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a failure diagnosis method for a charged particle beam drawing apparatus.

  In recent years, the circuit line width required for a semiconductor element has become increasingly narrower as the large scale integrated circuit (LSI) is highly integrated and has a large capacity. A semiconductor element uses an original pattern (a mask or a reticle, which may be collectively referred to as a mask hereinafter) on which a circuit pattern is formed, and the pattern is exposed and transferred onto a wafer by a reduction projection exposure apparatus called a stepper. It is manufactured by forming a circuit. For manufacturing a mask for transferring such a fine circuit pattern onto a wafer, an electron beam drawing apparatus capable of drawing the fine pattern is used. Attempts have also been made to develop a laser beam drawing apparatus for drawing using a laser beam. The electron beam drawing apparatus is also used when drawing a pattern circuit directly on a wafer.

  Yield improvement is indispensable for the manufacture of LSIs that are costly. On the other hand, as represented by a 1 gigabit class DRAM (Random Access Memory), the pattern constituting the LSI is going to be on the order of submicron to nanometer, and the manufacturing cost tends to increase more and more. For this reason, there is an urgent need to take measures to eliminate factors that reduce yield.

  One of the causes of a decrease in yield is a failure of the electron beam drawing apparatus. Until now, during the maintenance period, a pattern was drawn with an electron beam on a QC (Quality Check) mask, and the dimensions and position of the obtained pattern were measured with a measuring instrument. However, this measurement was not performed on the entire mask surface. Since the measurement is performed partially, even if there is a pattern with variations in dimensions and positions, measurement may not be performed at the variation locations. In particular, if there is a slight variation in the pattern at the initial stage of failure, it is difficult to detect the variation, and even if a failure has occurred in the apparatus, it may not be recognized as a failure. In addition, when the number of detected defects exceeds a predetermined value, the device is stopped and the cause of the failure is investigated, so an urgent response is required and it is a factor that reduces the operating rate of the device. It was. For these reasons, there is a need for a method that can correctly detect a failure in an apparatus at an early stage.

  By the way, a defect inspection apparatus is used for defect detection of a transfer mask used in LSI manufacturing. There are a die-to-die inspection method and a die-to-database inspection method as defect detection methods performed by this inspection apparatus.

  In the die-to-die inspection method, when a plurality of chips having the same pattern configuration are arranged in a part or the whole of the same mask, the same pattern in different chip transfer regions of the mask is obtained. This is an inspection method to be compared. According to this method, since the mask patterns are directly compared, a highly accurate inspection can be performed. On the other hand, the die-to-database inspection method is an inspection method in which layout data or data artificially generated from layout data is compared with an actual pattern on a mask. This method is often adopted mainly when there is only one chip transfer area in one mask.

  In die-to-database inspection, light emitted from a light source is irradiated onto a mask to be inspected via an optical system. The mask is placed on a table, and light irradiated as the table moves scans the mask. The light transmitted or reflected through the mask forms an image on the image sensor via the lens, and the optical image captured by the image sensor is sent to the comparison unit as measurement data. In the comparison unit, the measurement data and the reference data are compared according to an appropriate algorithm. If these data do not match, it is determined that there is a defect (see, for example, Patent Document 1).

  The inspection using the defect inspection apparatus is performed on all patterns formed on one mask. Therefore, if the defect inspection apparatus is used, it is possible to detect a slight variation occurring in the pattern. However, a conventional defect inspection apparatus has been used to inspect whether a mask or a resist film is manufactured according to a standard. For example, Patent Document 2 discloses a method for performing such an inspection in a short time.

JP 2008-112178 A JP-A-9-21840

  The present invention has been made in view of these points. That is, an object of the present invention is a charged particle beam drawing apparatus failure diagnosis method using a defect inspection apparatus, and when a defect occurs in a charged particle beam drawing apparatus, it can be correctly detected at an initial stage. It is to provide a method.

  Other objects and advantages of the present invention will become apparent from the following description.

The present invention provides a step of preparing a substrate having a resist film on the surface;
Irradiating a resist film with a charged particle beam under a plurality of drawing conditions to form a predetermined resist pattern;
Inspecting the resist pattern with an inspection device, and determining the number of defects with a predetermined inspection sensitivity for each drawing condition;
In the obtained number of defects, there is a step of examining whether or not there is a deviation from the average relationship according to the drawing condition between the inspection sensitivity and the number of defects, and if there is a deviation, there is a step of checking whether there is a difference due to the drawing condition ,
The present invention relates to a failure diagnosis method for a charged particle beam drawing apparatus, wherein the drawing conditions are at least two conditions that are different in the probability of occurrence of defects.

  If there is a number of defects that deviate from the average relationship, obtain the number of defects again with the same inspection sensitivity, or obtain at least one of inspection sensitivity and drawing conditions to obtain the number of defects. It is preferable to further include a step of examining whether or not there is a deviation from the average relationship in the same manner as the previous number of defects.

  The plurality of drawing conditions are preferably determined by combining two or more of settling time, multiplicity, stage operation, and dose, and changing each combined value.

  When one of the components of the drawing condition is the settling time, it is preferable that the longest settling time that can be set by the charged particle beam drawing apparatus to be diagnosed is set as a condition in which a defect is hardly generated.

  When one of the components of the drawing condition is multiplicity, it is preferable that the maximum multiplicity that can be set by the charged particle beam drawing apparatus to be diagnosed is set as a condition that hardly causes a defect.

  According to the present invention, there is provided a failure diagnosis method for a charged particle beam drawing apparatus using a defect inspection apparatus, which can correctly detect a defect in the charged particle beam drawing apparatus at an initial stage. Provided.

It is a block diagram of the electron beam drawing apparatus in this Embodiment. It is explanatory drawing of the drawing method by an electron beam. It is the figure which showed typically the relationship between drawing conditions and the ease of generating a defect. It is a block diagram of the inspection apparatus in this Embodiment. It is a conceptual diagram which shows the flow of the data in this Embodiment. It is a flowchart which shows an inspection process. It is a figure for demonstrating the acquisition procedure of an optical image. It is a figure explaining a filter process. It is an example showing the relationship between inspection sensitivity and the number of defects for each drawing condition. This is an example in which a circuit pattern and a failure diagnosis pattern are arranged on a mask substrate.

  FIG. 1 is a configuration diagram of an electron beam drawing apparatus according to the present embodiment.

  In FIG. 1, a stage 3 on which a mask substrate 2 is installed is provided in a sample chamber 1 of an electron beam drawing apparatus. The stage 3 is driven by the stage drive circuit 4 in the X direction (left and right direction on the paper surface) and the Y direction (vertical direction on the paper surface). The moving position of the stage 3 is measured by a position circuit 5 using a laser length meter or the like.

  An electron beam optical system 10 is installed above the sample chamber 1. The optical system 10 includes an electron gun 6, various lenses 7, 8, 9, 11, 12, a blanking deflector 13, a shaping deflector 14, a beam scanning main deflector 15, and a beam scanning sub deflector. 16 and two beam shaping apertures 17, 18 and the like.

  FIG. 2 is an explanatory diagram of a drawing method using an electron beam. As shown in this figure, the pattern 51 drawn on the mask substrate 2 is divided into strip-shaped frame regions 52. Drawing with the electron beam 54 is performed for each frame region 52 while the stage 3 continuously moves in one direction (for example, the X direction). The frame area 52 is further divided into sub-deflection areas 53, and the electron beam 54 draws only necessary portions in the sub-deflection areas 53. The frame area 52 is a strip-shaped drawing area determined by the deflection width of the main deflector 15, and the sub-deflection area 53 is a unit drawing area determined by the deflection width of the sub-deflector 16.

  The positioning of the electron beam 54 in the sub deflection region 53 is performed by the sub deflector 16. The position of the sub deflection region 53 is controlled by the main deflector 15. That is, the main deflector 15 positions the sub deflection region 53, and the sub deflector 16 determines the beam position in the sub deflection region 53. Further, the shape and size of the electron beam 54 are determined by the shaping deflector 14 and the beam shaping apertures 17 and 18. Then, the sub-deflection area 53 is drawn while continuously moving the stage 3 in one direction. When drawing of one sub-deflection area 53 is completed, the next sub-deflection area 53 is drawn. When drawing of all the sub-deflection areas 53 in the frame area 52 is completed, the stage 3 is stepped in a direction orthogonal to the direction in which the stage 3 is continuously moved (for example, the Y direction). Thereafter, the same processing is repeated, and the frame area 52 is sequentially drawn.

  CAD data created by a designer (user) is converted into design intermediate data in a hierarchical format such as OASIS. In the design intermediate data, pattern data created for each layer and formed on the mask substrate 2 is stored. Here, generally, the electron beam drawing apparatus is not configured to directly read OASIS data. That is, different format data is used for each manufacturer of the electron beam drawing apparatus. For this reason, the OASIS data is input to the electron beam drawing apparatus after being converted into format data unique to each electron beam drawing apparatus for each layer. In the case of the electron beam drawing apparatus of FIG. 1, this data is recorded in the input unit 21 which is a storage medium. The recorded data is read by the control computer 20 and temporarily stored in the pattern memory 22 for each frame area 52. The pattern data for each frame area 52 stored in the pattern memory 22, that is, the frame information composed of the drawing position, the drawing graphic data, and the like is sent to the pattern data decoder 23 and the drawing data decoder 24 which are data analysis units. Subsequently, the information is sent to the sub deflection region deflection amount calculation unit 30, the blanking circuit 25, the beam shaper driver 26, the main deflector driver 27, and the sub deflector driver 28 via these.

  In addition, a deflection control unit 32 is connected to the control computer 20. The deflection control unit 32 is connected to the settling time determination unit 31, the settling time determination unit 31 is connected to the sub deflection region deflection amount calculation unit 30, and the sub deflection region deflection amount calculation unit 30 is connected to the pattern data decoder 23. is doing. The deflection control unit 32 is connected to the blanking circuit 25, the beam shaper driver 26, the main deflector driver 27, and the sub deflector driver 28.

  Information from the pattern data decoder 23 is sent to a blanking circuit 25 and a beam shaper driver 26. Specifically, blanking data is created based on the drawing data by the pattern data decoder 23 and sent to the blanking circuit 25. Further, desired beam size data is also created based on the drawing data, and is sent to the sub deflection area deflection amount calculation unit 30 and the beam shaper driver 26. Then, a predetermined deflection signal is applied from the beam shaper driver 26 to the shaping deflector 14 of the optical system 10 to control the shape and size of the electron beam 54.

  The sub deflection region deflection amount calculation unit 30 calculates the deflection amount (movement distance) of the electron beam for each shot in the sub deflection region 53 from the beam shape data created by the pattern data decoder 23. The calculated information is sent to the settling time determination unit 31, and the settling time corresponding to the moving distance by the sub deflection is determined.

  The settling time determined by the settling time determination unit 31 is sent to the deflection control unit 32, and then the blanking circuit 25, the beam shaper driver 26, It is appropriately sent to either the deflector driver 27 or the sub deflector driver 28.

  The drawing data decoder 24 creates positioning data for the sub deflection region 53 based on the drawing data, and sends this data to the main deflector driver 27 and the sub deflector driver 28. Then, a predetermined deflection signal is applied from the main deflector driver 27 to the main deflector 15 of the optical system 10, and the electron beam 54 is deflected and scanned to a predetermined main deflection position. Further, a predetermined sub deflection signal is applied from the sub deflector driver 28 to the sub deflector 16, and drawing in the sub deflection area 53 is performed. Specifically, this drawing is performed by repeatedly irradiating the electron beam 54 after the settling time has elapsed.

  Next, a failure diagnosis method for the charged particle beam drawing apparatus according to the present embodiment will be described with reference to the drawings. This diagnostic method is periodically performed on the charged particle beam drawing apparatus at a frequency of about once every 1 to 2 weeks, for example.

  In the method for diagnosing a charged particle beam according to this embodiment, first, a mask substrate having a resist film provided on the surface is prepared, and drawing is performed on the mask substrate while changing drawing conditions. Specifically, the pattern is drawn under a plurality of conditions with different susceptibility to defects, in this embodiment, a plurality of conditions with different settling time and multiplicity (number of electron beam irradiations). These conditions are roughly classified into standard drawing conditions (hereinafter referred to as standard conditions), drawing conditions in which defects are difficult to occur (hereinafter referred to as safety conditions), and drawing conditions (hereinafter referred to as safety conditions) in which defects are likely to occur. It can be divided into three types. Table 1 shows an example of each condition. The drawing conditions may be any two or more of the standard conditions, the safety conditions, and the acceleration conditions.

  In Table 1, the settling time and multiplicity under each condition are fixed to predetermined values, but the settling time and multiplicity may be changed within a predetermined range for each condition.

  In Table 1, the settling time is changed for each condition for each of the main deflector, the sub deflector, and the shaping deflector, but the settling time of at least one of these deflectors may be changed. . For example, drawing is performed by changing the settling time and multiplicity of any one deflector. Then, when a failure of the electron beam drawing apparatus is suspected through the inspection results described later, the drawing is performed in the same manner by changing the settling time and multiplicity of the other one or two deflectors, and the reproducibility of the inspection results. You may make it see.

  Each value of the settling time can be set as appropriate, but the safety condition is preferably the longest time that can be set by the electron beam drawing apparatus.

  The multiplicity can also be set as appropriate, but the minimum value is 1. The maximum value is preferably the maximum value possible with an electron beam drawing apparatus, and is generally 8. Furthermore, it is preferable to set it as 2-4 about standard conditions.

  Since drawing may be performed by changing factors that affect the probability of occurrence of defects, factors other than settling time and multiplicity can be changed. For example, the drawing may be performed by changing the stage operation or the dose amount. Further, two or more of the settling time, the multiplicity, the stage operation, and the dose amount may be combined, and each value may be changed for rendering.

  FIG. 3 is a diagram schematically showing the relationship between the drawing conditions and the likelihood of defects. In FIG. 3, the parts denoted by the same reference numerals as those in FIGS. 1 and 2 are the same.

  In FIG. 3, the stripe region 55 is drawn by an electron beam while moving a stage (not shown) in the X direction. Subsequently, the stage is stepped in the Y direction to draw the next adjacent stripe region 55. By repeating this, drawing is performed on the entire surface of the mask substrate 2.

  In the example of FIG. 3, the settling time and the multiplicity are changed within a predetermined range for each of the safety condition, the standard condition, and the acceleration condition. Specifically, patterns having different settling times are arranged in the X direction, and patterns having different multiplicity are arranged in the Y direction. In this case, the condition where the settling time is slow and the multiplicity is large is the safety condition B in which defects are hardly generated. On the other hand, the condition where the settling time is fast and the multiplicity is small is the acceleration condition C where defects are likely to occur. And there is a standard condition A between them. In the figure, the lines surrounding the conditions (A to C) roughly indicate the positions of the pattern areas corresponding to the conditions, and do not strictly divide the pattern areas.

  After the drawing is performed with the drawing conditions changed as described above, development processing is performed to pattern the resist film. Thereafter, a defect inspection apparatus (hereinafter, also simply referred to as an inspection apparatus) is used to change the inspection sensitivity and obtain the number of defects for each region.

  FIG. 4 is a configuration diagram of the inspection apparatus according to the present embodiment. As shown in this figure, the inspection apparatus 100 includes an optical image acquisition unit A and a control unit B.

  The optical image acquisition unit A includes a light source 103, an XYθ table 102 that can move in the horizontal direction (X direction, Y direction) and the rotation direction (θ direction), an illumination optical system 170 that constitutes a transmission illumination system, and magnification optics. A system 104, a photodiode array 105, a sensor circuit 106, a laser length measurement system 122, and an autoloader 130 are included.

  In the control unit B, the control computer 110 that controls the entire inspection apparatus 100 has a position circuit 107, a comparison circuit 108, a reference circuit 112, a development circuit 111, an autoloader control unit 113, a bus 120 serving as a data transmission path, The table control circuit 114 is connected to a magnetic disk device 109, a magnetic tape device 115, a flexible disk device 116, a CRT 117, a pattern monitor 118, and a printer 119 as an example of a storage device. The XYθ table 102 is driven by an X-axis motor, a Y-axis motor, and a θ-axis motor controlled by the table control circuit 114. As these motors, for example, step motors can be used.

  Design pattern data serving as database-based reference data is stored in the magnetic disk device 109, read out as the inspection progresses, and sent to the development circuit 111. In the development circuit 111, the design pattern data is converted into image data (design pixel data). Thereafter, this image data is sent to the reference circuit 112 to be used for generating reference data.

  In FIG. 4, the constituent elements necessary for the present embodiment are shown, but other known elements necessary for the inspection may be included.

  FIG. 5 is a conceptual diagram showing a data flow in the present embodiment.

  As shown in FIG. 5, CAD data 201 corresponding to the drawing conditions of the present embodiment is converted into design intermediate data 202 in a hierarchical format such as OASIS. The design intermediate data 202 stores pattern data created for each layer and formed on the substrate. As described above, since the electron beam drawing apparatus 300 is not configured to directly read OASIS data, the OASIS data is converted into the format data 203 unique to each electron beam drawing apparatus for each layer and then converted into the electronic data. Input to the beam drawing apparatus 300. Similarly, the inspection apparatus 100 is not configured to directly read OASIS data, but is input after being converted into format data 203 compatible with the electron beam drawing apparatus 300. In some cases, data is input after being converted into format data unique to the inspection apparatus 100.

  By the way, the format data for drawing or inspection, or the OASIS data before conversion into these, maintains the auxiliary pattern for increasing the resolution of the pattern drawn on the mask, and the accuracy of the line width and the gap of the pattern. For this purpose, a figure for processing the pattern shape in a complicated manner is added. Therefore, the capacity of the pattern data is enlarged, and the electron beam drawing apparatus and the inspection apparatus are devised to prevent the stagnation of the drawing time and the inspection time. Specifically, a parallel processing computer capable of high-capacity and high-speed processing and a hard disk device designed to sufficiently cope with the read speed necessary for processing are combined with a mechanism portion that reads pattern data and develops data. Etc.

  FIG. 6 is a flowchart showing the inspection process.

  As shown in FIG. 6, the inspection process includes an optical image acquisition process (S202), a design pattern data storage process (S212), a development process (S214) as an example of a design image data generation process, and a filtering process ( S216) and a comparison step (S226).

  In the optical image acquisition process of S202, the optical image acquisition unit A of FIG. 4 acquires an optical image (measurement data) of the mask substrate 2. Here, the optical image is an image of a mask on which a graphic based on graphic data included in the design pattern is drawn. A specific method for acquiring an optical image is as follows, for example.

  A mask substrate 2 serving as an inspection sample is placed on an XYθ table 102 provided so as to be movable in a horizontal direction and a rotation direction by motors of XYθ axes. Then, the pattern formed on the mask substrate 2 is irradiated with light from the light source 103 disposed above the XYθ table 102. More specifically, the light beam emitted from the light source 103 is applied to the mask substrate 2 via the illumination optical system 170. Below the mask substrate 2, an magnifying optical system 104, a photodiode array 105, and a sensor circuit 106 are arranged. The light transmitted through the mask substrate 2 is formed as an optical image on the photodiode array 105 via the magnifying optical system 104. Here, the magnifying optical system 104 may be configured such that the focus is automatically adjusted by an automatic focusing mechanism (not shown).

  FIG. 7 is a diagram for explaining an optical image acquisition procedure.

  As shown in FIG. 7, the inspection area is virtually divided into a plurality of strip-shaped inspection stripes 140 having a scanning width W in the Y direction, and each of the divided inspection stripes 140 is continuously scanned. Thus, the operation of the XYθ table 102 is controlled, and an optical image is acquired while moving in the X direction. In the photodiode array 105, images having a scan width W as shown in FIG. 7 are continuously input. Then, after acquiring the image on the first inspection stripe 140, the image on the second inspection stripe 140 is continuously input in the same manner while moving the image on the second inspection stripe 140 in the opposite direction. When an image in the third inspection stripe 140 is acquired, the image is moved in the direction opposite to the direction in which the image in the second inspection stripe 140 is acquired, that is, in the direction in which the image in the first inspection stripe 140 is acquired. While getting the image. In this way, it is possible to shorten a useless processing time by continuously acquiring images.

  The pattern image formed on the photodiode array 105 is photoelectrically converted by the photodiode array 105 and further A / D (analog-digital) converted by the sensor circuit 106. Sensors are arranged in the photodiode array 105. An example of this sensor is a TDI (Time Delay Integrator) sensor. The pattern of the mask substrate 2 is imaged by the TDI sensor while the XYθ table 102 continuously moves in the X-axis direction. Here, the light source 103, the magnifying optical system 104, the photodiode array 105, and the sensor circuit 106 constitute a high-magnification inspection optical system.

  The XYθ table 102 is driven by a table control circuit 114 under the control of the control computer 110, and can be moved by a drive system such as a three-axis (XY-θ) motor that drives in the X, Y, and θ directions. It has become. As these X-axis motor, Y-axis motor, and θ-axis motor, for example, step motors can be used. The movement position of the XYθ table 102 is measured by the laser length measurement system 122 and sent to the position circuit 107. The mask substrate 2 on the XYθ table 102 is automatically conveyed from the autoloader 130 driven by the autoloader control circuit 113, and is automatically discharged after the inspection is completed.

  Measurement data (optical image) output from the sensor circuit 106 is sent to the comparison circuit 108 together with data indicating the position of the mask substrate 2 on the XYθ table 102 output from the position circuit 107. The measurement data is, for example, 8-bit unsigned data, and represents the brightness gradation of each pixel.

  S212 in FIG. 6 is a storage step, and the design pattern data used when forming the pattern of the mask substrate 2 is stored in the magnetic disk device 109, which is an example of a storage device (storage unit).

  The figure included in the design pattern is a basic figure of a rectangle or a triangle. In the magnetic disk device 109, for example, information such as coordinates at a reference position of a figure, a side length, a figure code serving as an identifier for distinguishing a figure type such as a rectangle or a triangle, and the shape and size of each pattern figure The graphic data defining the position and the like are stored.

  Furthermore, a set of figures existing in a range of about several tens of μm is generally called a cluster or a cell, and data is hierarchized using this. In the cluster or cell, arrangement coordinates and repeated description when various figures are arranged alone or repeatedly at a certain interval are also defined. The cluster or cell data is further arranged in a strip-shaped region called a frame or stripe having a width of several hundreds μm and a length of about 100 mm corresponding to the total length of the photomask in the X direction or Y direction. .

  S214 in FIG. 6 is a development process. In this step, the development circuit 111 of FIG. 4 reads design pattern data from the magnetic disk device 109 through the control computer 110, and the read design pattern data of the mask substrate 2 is converted into binary or multivalued image data (design). Image data). Then, this image data is sent to the reference circuit 112.

  When design pattern data as graphic data is input to the expansion circuit 111, the expansion circuit 111 expands the design pattern data to data for each graphic, and displays a graphic code, a graphic dimension, and the like indicating the graphic shape of the graphic data. Interpret. Then, binary or multivalued design image data is developed as a pattern arranged in a grid having a grid with a predetermined quantization size as a unit. The developed design image data calculates the occupancy ratio of the figure in the design pattern for each area (square) corresponding to the sensor pixel. And the figure occupation rate in each pixel becomes a pixel value.

  S216 in FIG. 6 is a filtering process. In this step, the reference circuit 112 performs an appropriate filtering process on the design image data that is the image data of the sent graphic.

  FIG. 8 is a diagram for explaining the filter processing.

  The measurement data as an optical image obtained from the sensor circuit 106 is in a state in which the filter is activated by the resolution characteristic of the magnifying optical system 104, the aperture effect of the photodiode array 105, or the like, in other words, in an analog state that changes continuously. . Therefore, it is possible to match the measurement data by applying the filter process to the design image data which is the image data on the design side where the image intensity (the gray value) is a digital value. In this way, a reference image (optical data) to be compared with the optical image is created.

  The measurement data is sent to the comparison circuit 108 as described above. The design pattern data is converted into reference image data by the development circuit 111 and the reference circuit 112 and sent to the comparison circuit 108.

  The comparison circuit 108 compares the optical image obtained from the sensor circuit 106 with the reference image generated by the reference circuit 112 using an appropriate comparison / determination algorithm, and if the error exceeds a predetermined value, that portion is regarded as a defect. to decide. If it is determined as a defect, the coordinates, the sensor image (optical image) and the reference image that are the basis for the defect determination are stored as inspection results.

  In the present embodiment, the number of defects is obtained by changing the inspection sensitivity for each drawing condition of the standard condition, the safety condition, and the acceleration condition. Then, an average relationship between the inspection sensitivity and the number of defects is obtained, and it is checked whether there is a value (number of defects) that deviates from this relationship. For example, a value outside the range of ± 3σ around the average value can be out of the above relationship. If the defect is caused by the electron beam lithography system, the number of the defects decreases in the order of acceleration conditions, standard conditions, and safety conditions. If the number of defects is increased uniformly under each condition, it is determined that the defect is not caused by the electron beam drawing apparatus, and it is understood that there is no need to investigate the failure location for the drawing apparatus. In other words, by measuring the number of defects with different inspection sensitivities, it is initially determined whether the increase in the number of defects is due to the electron beam lithography system or due to other processes or particles. It becomes possible to do.

  FIG. 9 is an example showing the relationship between the inspection sensitivity and the number of defects for each drawing condition of the standard condition, the safety condition, and the acceleration condition. In the present embodiment, the inspection sensitivity is roughly divided into three stages: low, medium, and high. The level of inspection sensitivity can be changed by changing a predetermined value in the comparison circuit.

In FIG. 9, region S ₁ corresponds to inspection sensitivity: low, region S ₂ corresponds to inspection sensitivity: medium, and region S ₃ corresponds to inspection sensitivity: high. Here, the inspection sensitivity: medium can be set to a level defined by normal defect inspection, that is, inspection of whether or not a mask or a resist film is manufactured according to the standard. Note that the areas S ₁ , S ₂ , and S ₃ are merely provided for convenience of explanation, and do not strictly divide the inspection sensitivity level.

  In FIG. 9, each straight line corresponding to each drawing condition represents the average value of the number of defects depending on the inspection sensitivity. As the inspection sensitivity increases, the number of defects naturally increases. After obtaining such an average value of the number of defects for each drawing condition in advance, drawing is performed while changing the drawing conditions on a mask substrate having a resist film on the surface. Then, with respect to the obtained resist pattern, for example, the inspection sensitivity is set high, and the number of defects for each drawing condition is obtained.

In FIG. 9, C1 is _one of the defect number data when the pattern drawn under the acceleration condition is inspected sensitivity: high, but this data deviates from the straight line indicating the average value. A ₁ is the number of defects in the inspection sensitivity of the pattern which is a part of the same resist pattern as C ₁ and drawn under the standard conditions. A _{1 is} also deviated from the straight line indicating the average value, similarly to C ₁ . Further, B ₁ is defect number data when inspection sensitivity is low for a pattern which is a part of the same resist pattern as C ₁ and A ₁ and is drawn under safe conditions. B _{1 is} also deviated from the straight line indicating the average value, like C ₁ and A ₁ . When C ₁ , A ₁ , B ₁ are compared, they show a similar rate of increase compared to the average value. That is, the number of defects similarly increases regardless of the drawing conditions. Therefore, it is estimated that the cause of the defect increase is not the electron beam drawing apparatus but the pattern forming process such as development.

In Figure 9, C _2, the inspection sensitivity of the drawn pattern accelerated conditions: which is one of the number of defects data at high. This data also deviates from the straight line indicating the average value. A ₂ is the defect number data in the inspection sensitivity: medium of a part of the resist pattern formed by the same process as C ₂ and drawn under the standard conditions. A ₂ is different from C _2, are located on a straight line indicating the average values. Further, B ₂ is defect number data at a low inspection sensitivity: low, which is a part of a resist pattern formed by the same process as C ₂ and A ₂ and drawn under safe conditions. B _{2 is} also located on the straight line indicating the average value as in A ₂ . That is, C ₂ increases from the average value, but A ₂ and B ₂ indicate the average value. In this case, the number of defects varies depending on the drawing conditions. That is, it is estimated that the cause of the increase in the number of defects is not the pattern formation process but the electron beam lithography apparatus.

When a difference in the number of defects such as C ₂ , A ₂ , and B ₂ is observed, the number of defects is again obtained with inspection sensitivity: high, and the reproducibility is observed. Alternatively, depending on the case, the number of defects is obtained by changing the inspection sensitivity and the drawing conditions, and it is examined whether or not each obtained value is increased from the average value. For example, the number of defects is examined for each drawing condition with a medium inspection sensitivity. Further, the number of defects may be examined in the same manner for inspection sensitivity: low. Alternatively, when the settling time of only the main deflector is changed, the settling time of the sub-deflector or the shaping deflector may be changed and checked. Further, it is also possible to draw by changing drawing conditions other than settling time and multiplicity, for example, changing the stage operation and dose, and changing the inspection sensitivity to check the number of defects. If there is a difference in the drawing conditions with respect to the number of newly obtained defects, it is determined that a failure has occurred in the electron beam drawing apparatus, the apparatus is stopped, and the failure location is investigated and maintained.

  As described above, drawing is performed on one mask substrate while changing the drawing conditions, and the obtained pattern is inspected by an inspection apparatus to check the number of defects at a predetermined inspection sensitivity. By comparing with the average value of the number of defects at the inspection sensitivity, it is possible to diagnose whether or not a failure has occurred in the electron beam drawing apparatus. According to this method, since the inspection apparatus is used for detecting the number of defects, the detection accuracy of defects can be remarkably improved as compared with the method of detecting defects by measuring the dimension and position of the pattern at a predetermined location. Therefore, slight fluctuations in the pattern in the initial stage of failure of the electron beam lithography apparatus can be captured. Therefore, it is possible to take a planned response before the failure progresses, for example, to stop the device systematically and investigate the failure location.

  The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

  For example, in the above-described embodiment, the act of changing the drawing conditions for one mask and drawing a fault and diagnosing the failure of the electron beam drawing apparatus is performed periodically, for example, once every 1 to 2 weeks. To implement. On the other hand, in the present invention, a pattern is drawn around a product mask, that is, around a region where a circuit pattern to be a product is drawn, and the pattern is drawn, and this pattern is diagnosed for failure of the electron beam drawing apparatus. You may use it.

FIG. 10 shows an example in which a circuit pattern and a failure diagnosis pattern are arranged on the mask substrate 2 ′. In this figure, P ₁ is a region where the circuit pattern serving as the product is drawn. Further, P ₂ is a region where patterns for fault diagnosis is drawn, the pattern is drawn by changing the settling time and multiplicity are arranged. Specifically, patterns with different settling times are arranged in the X direction, and patterns with different multiplicity are arranged in the Y direction. In this case, the pattern drawn under the condition that the settling time is slow and the multiplicity is large (the pattern located in the upper right in FIG. 10) is a pattern in which defects are relatively difficult to occur. On the other hand, the pattern drawn under the condition of fast settling time and low multiplicity (pattern located in the lower left in FIG. 10) is a pattern in which defects are relatively likely to occur.

  As shown in FIG. 10, by disposing a pattern for failure diagnosis around the product mask, it becomes possible to simultaneously perform failure diagnosis while manufacturing the mask. That is, failure diagnosis can be performed in accordance with a normal manufacturing process without performing drawing only for failure diagnosis every predetermined period. According to this method, the number of samples can be easily obtained as compared with the method described in the above embodiment, and for example, it is easy to reach the number of samples necessary for obtaining the average value of the number of defects.

  In the above embodiment, the electron beam is used in the above embodiment. However, the present invention is not limited to this, and the present invention can also be applied to the case where another charged particle beam such as an ion beam is used. .

DESCRIPTION OF SYMBOLS 1 Sample chamber 2, 2 'Mask substrate 3 Stage 4 Stage drive circuit 5, 107 Position circuit 6 Electron gun 7, 8, 9, 11, 12 Various lenses 10 Optical system 13 Blanking deflector 14 Molding deflector 15 Main deflection 16 Sub-deflector 17, 18 Beam shaping aperture 20, 110 Control computer 21 Input unit 22 Pattern memory 23 Pattern data decoder 24 Drawing data decoder 25 Blanking circuit 26 Beam shaper driver 27 Main deflector driver 28 Sub deflector driver 30 Sub deflection region deflection amount calculation unit 31 Settling time determination unit 32 Deflection control unit 51 Pattern to be drawn 52 Frame region 53 Sub deflection region 54 Electron beam 55 Stripe region 100 Inspection device 102 XYθ table 103 Light source 104 Enlarging optical system 105 Photo die Doarei 106 sensor circuit 108 comparator circuit 109 the magnetic disk device 111 expand circuit 112 the reference circuit 113 autoloader control circuit 114 table control circuit 115 the magnetic tape device 116 a flexible disk unit 117 CRT
118 Pattern Monitor 119 Printer 120 Bus 122 Laser Length Measurement System 130 Autoloader 140 Inspection Strip 170 Illumination Optical System 201 CAD Data 202 Design Intermediate Data 203 Format Data 300 Electron Beam Drawing Device

Claims (5)

Preparing a substrate having a resist film on the surface;
Irradiating the resist film with a charged particle beam under a plurality of drawing conditions to form a predetermined resist pattern;
Inspecting the resist pattern with an inspection apparatus, and determining the number of defects with a predetermined inspection sensitivity for each drawing condition;
A step of examining whether or not there is a deviation from an average relationship between the inspection sensitivity and the number of defects in the number of defects according to the drawing condition and whether there is a difference due to the drawing condition when there is the deviation. And
The drawing conditions are at least two conditions that are different in the probability of occurrence of defects, and a failure diagnosis method for a charged particle beam drawing apparatus.   If there is a number of defects that deviate from the average relationship, obtain the number of defects again with the same inspection sensitivity, or obtain the number of defects by changing at least one of the inspection sensitivity and the drawing conditions. 2. The charged particle beam drawing apparatus failure diagnosis method according to claim 1, further comprising a step of examining whether or not there is a deviation from the average relationship in the same manner as the number of defects.   The plurality of drawing conditions are determined by combining two or more of settling time, multiplicity, stage operation, and dose, and changing each combined value. The charged particle beam drawing apparatus failure diagnosis method according to claim.   2. When one of the components of the drawing condition is settling time, the longest settling time that can be set by the charged particle beam drawing apparatus to be diagnosed is set as a condition in which a defect is hardly generated. The failure diagnostic method for a charged particle beam drawing apparatus according to any one of claims 1 to 3.   2. When one of the components of the drawing condition is multiplicity, the maximum multiplicity that can be set by the charged particle beam drawing apparatus to be diagnosed is set as a condition in which a defect is hardly generated. The failure diagnostic method for a charged particle beam drawing apparatus according to any one of claims 1 to 4.