JP2008311311A - Charged particle beam exposure method and charged particle beam exposure system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charged particle beam exposure method and a charged particle beam exposure system which remedy the irregularity of pattern line widths (CD) caused by fogging in an exposure area. <P>SOLUTION: According to the charged particle beam exposure method, charged particle beams are emitted on a sample substrate to expose a desired pattern to the beams. An area affected by fogging caused by exposure to charged particle beams is determined in advance (step 1). An exposure area of the pattern on the sample substrate is divided into subareas smaller than the area affected by fogging, and the amount of fogging irradiation on the sample substrate resulting from fogging in each small area is calculated (step 4 and 5). In beam exposure to the pattern extending from the outermost periphery of the sample substrate into the area affected by fogging, the amount of irradiation of charged particle beams is corrected for each small area in corresponding to the calculated amount of fogging irradiation (step 9). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a charged particle beam exposure technique for forming a semiconductor integrated circuit or other fine element pattern on a sample such as a semiconductor wafer or a pattern transfer mask, for example, fogging by reflected charged particles from a sample substrate. The present invention relates to a charged particle beam exposure method and a charged particle beam exposure apparatus that can be corrected.

  In recent years, miniaturization of device patterns has progressed, and lithography with a wiring pitch (HP) of 100 nm or less has become necessary. Under the influence of such miniaturization, an increase in mask cost has become an increasingly serious problem in system on chip (SoC) device production characterized by high-mix low-volume production. Maskless lithography using an electron beam exposure apparatus has been put to practical use as a solution for realizing the increasing mask cost and shortening of the turn-around time (TAT).

  Electron beam exposure is highly accurate but has a drawback of low throughput, and various techniques have been developed to improve throughput. In the past, drawing was performed by raster scanning of a point beam, but since the throughput is extremely low, the exposure method of the variable shaping method is currently the mainstream. This method is a method in which a beam is formed into a rectangle having a desired size and drawn using two forming apertures (AP). Recently, a graphic part batch exposure method called cell projection, character projection, or block exposure has been put into practical use. In the figure partial batch exposure method, repetitive transfer exposure is performed using a repetitive circuit small pattern (about 5 μm square on a wafer (sensitive substrate)) using a reticle on which a plurality of similar small patterns are formed. A pattern that cannot be drawn with the character opening on the reticle is drawn with a variable shaped beam using the variable shaped beam opening on the reticle. By using this character projection method, it is possible to greatly improve the turnaround time compared to the variable molding method.

  However, in an exposure apparatus using an electron beam, when a pattern is exposed on the wafer surface, backscattered electrons of the irradiated electron beam and reflected electrons from the wafer surface are generated. The reflected electrons collide with a member on the lower surface of the lens of the projection optical system at a position facing the wafer surface, and a part of the reflected electrons are reflected again on the same surface. This reflected electron is then irradiated over a wide range including the non-exposed surface on the wafer surface. Such an exposure phenomenon caused by electrons other than the pattern beam is called fogging.

  Many techniques for fog correction have been proposed so far. For example, an area density map showing the density of the drawing pattern is created to correct the exposure amount, a pre-exposure method or a ghost method in which multiple exposure is performed to compensate for the exposure amount correction portion, and a lower surface of the lens of the projection optical system. Devices that can reduce the amount of fogging by changing the structure and material have been developed (see, for example, Patent Documents 1 and 2).

  However, each of the above methods has the following problems.

(1) The method of correcting the exposure amount by creating an area density map is to correct the exposure amount by calculating only one chip of the device pattern to be drawn. Therefore, when the influence of the fog covers a wide range of several mm square, the influence cannot be taken in completely, resulting in incomplete exposure amount correction.

(2) When multiple drawing is performed, the throughput is greatly reduced.

(3) Even if the material of the lower surface of the lens of the projection optical system is made of a low reflection material with respect to electrons, or an antireflection plate having a honeycomb structure is installed, it is difficult to completely suppress the influence of fogging.

  Further, in order to attempt to correct the drawing design data in order to solve the above-described problem, a correction operation in consideration of the design data and the chip layout on the wafer is required as in the problem (1). However, since the correction calculation considering the chip layout on the wafer is very complicated and enormous, the fog correction performed by correcting the pattern shape of the design data is very difficult from the viewpoint of throughput.

When the pattern is exposed on the entire surface of the wafer, the fog is generated more in the region near the center of the wafer and less as it is closer to the periphery. When such a resist on the wafer is developed, the exposure dose is large near the center of the wafer, and the exposure dose is small as it is closer to the periphery. In the vicinity of the center of the wafer, the line width of the pattern of the beam irradiation portion becomes large. As a result, the critical dimension (CD) within the wafer surface, that is, the uniformity of the dimension of the pattern transferred to the resist deteriorates, leading to deterioration in device accuracy and yield.
Japanese Patent No. 3466900 Japanese Patent No. 3671152

  An object of the present invention is to provide a charged particle beam exposure method and a charged particle beam exposure apparatus that can improve non-uniformity of a pattern line width (CD) generated in an exposure region by fogging.

  A charged particle beam exposure method according to an embodiment of the present invention is a charged particle beam exposure method in which a desired pattern is exposed on a sample substrate by controlling an irradiation amount of a charged particle beam according to a pattern arrangement. A step of obtaining an area affected by the fog caused by exposure by the particle beam, and dividing the exposure area of the pattern of the sample substrate into smaller areas smaller than the area affected by the fog; Calculating the amount of fog irradiation given to the sample substrate by the above, and the fog irradiation obtained by the calculation for the pattern included in the region affected by the fog from the outermost periphery of the sample substrate And a step of correcting the irradiation amount of the charged particle beam for each of the small regions according to the amount.

  A charged particle beam exposure apparatus according to another embodiment of the present invention provides a charged particle beam exposure apparatus that exposes a desired pattern on a sample substrate by controlling an irradiation amount of a charged particle beam according to a pattern arrangement. Storage means for storing information on an area affected by fog caused by exposure with a charged particle beam, and dividing an exposure area of the pattern of the sample substrate into smaller areas smaller than the area affected by fog, First calculation means for calculating the amount of fog irradiation given to the sample substrate by the fog in a small area, and the pattern included in the area affected by the fog from the outermost periphery of the sample substrate, A second calculation for correcting the irradiation amount of the charged particle beam for each of the small regions in accordance with the fog irradiation amount obtained by the first calculation means. Characterized by comprising a stage.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide the charged particle beam exposure method and charged particle beam exposure apparatus which can improve the nonuniformity of the pattern line width (CD) which arises in an exposure area | region by fogging.

  Embodiments of the present invention will be described below with reference to the drawings. As the charged particle beam exposure apparatus and the charged particle beam exposure method, an electron beam exposure apparatus and an electron beam exposure method using electrons as charged particles are taken as an example. In the description, common parts are denoted by common reference symbols throughout the drawings.

[First Embodiment]
FIG. 1 is a schematic diagram showing the configuration of an electron beam exposure apparatus according to the first embodiment of the present invention.

  An electron gun 10 is installed in the electron optical column 8. A blanking electrode 11, a blanking aperture 12, a beam scanning sub deflector 13, and a beam scanning main deflector 14 are disposed in the lens barrel 8 along the path of the electron beam 28 irradiated from the electron gun 10. is set up. A sample stage 16 that moves in a plane is installed in a sample chamber 9 connected to the lens barrel 8, and a sample substrate 15 is placed on the sample stage 16. The electron beam 28 emitted from the electron gun 10 controls the irradiation position on the blanking aperture 12 by the blanking electrode 11, thereby irradiating the sample substrate 15 with the electron beam 28 on or off, that is, the electron beam. Whether to shut off or not is controlled. The irradiation amount of the electron beam 28 is changed by controlling the on or off time of the electron beam 28. The adjustment of the irradiation amount is performed by converting the irradiation amount calculated in the drawing control circuit 3 into the irradiation time by the irradiation amount control unit 6 and controlling the blanking time by the blanking electrode 11 via the blanking amplifier 7. Do by.

  Note that an electro-optic lens, a deflector, and an aperture (not shown) are installed in the electron-optical column 8 of the actual exposure apparatus (drawing apparatus). Adjustment for irradiating a desired position on the sample substrate with the electron beam 28 is performed using the electron optical lens, the deflector, and the aperture.

  Further, the drawing design data 29 and the chip layout 30 to the sample substrate 15 are input to the control computer 1. Then, correction calculation and drawing setting are performed by the calculation module 31 of the control computer 1, and drawing data of a predetermined small area unit is divided and transferred to the data development circuit 2. The drawing data is transferred to the drawing control circuit 3 to perform detailed correction and control of the drawing position, and further, a voltage signal for deflecting the electron beam 28 to a desired drawing position by the main deflection amplifier 5 and the sub deflection amplifier 4. Is converted to The main deflector 14 and the sub deflector 13 are controlled by the voltage signals output from the main deflecting amplifier 5 and the sub deflecting amplifier 4.

  The position of the sample stage 16 is constantly monitored by a laser interferometer 18 provided in the stage control unit 17 and fed back to the main deflection amplifier 5 via the reception unit 19 and the calculation unit 23, thereby drawing the sample substrate 15. The position is corrected. At this time, the calculation unit 23 uses the monitor output from the laser interferometer 18 to perform a calculation for correcting the drawing position in real time. The sub deflection amplifier 4 and the main deflection amplifier 5 are composed of digital circuit portions 24 and 26 and analog circuit portions 25 and 27, respectively, and digital input signals from the drawing control circuit 3 are converted into analog voltage signals inside these amplifiers. It has been converted.

  The electron beam 28 that has passed through the blanking aperture 12 is shaped into a rectangular beam by a beam shaping deflector and a shaping aperture (not shown), and the size of the rectangle is controlled. The shaped electron beam 28 is deflected and scanned on the sample substrate 15 by the beam scanning deflectors 13 and 14, and a desired pattern is drawn on the sample substrate 15.

  The beam scanning main deflector 14 deflects a large distance of about 1 mm, and the beam scanning sub deflector 13 deflects in a region called a subfield of about 50 μm at high speed. When the drawing in the subfield is completed, the main deflector 14 deflects the electron beam to the next subfield, and the next subfield is drawn.

  Further, the calculation module 31 of the control computer 1 executes the calculation for correcting the fog using the input drawing design data 29 and the chip layout 30, and as a result, the generated dose correction file is generated by the drawing control circuit 3. Store in the internal memory 20. Further, the irradiation unit for the deflection area is determined by the calculation unit 22 in the drawing control circuit 3, and the irradiation amount is transferred to the irradiation amount control unit 6. At the same time, the correction value of the irradiation amount is transmitted to the calculation unit 23 to control the staying time at the deflection position.

  Next, the electron beam exposure method according to the first embodiment of the present invention will be described.

  In the present embodiment, a drawing method for simply correcting fog (exposure) that occurs in drawing using an electron beam exposure apparatus and affects a wide range of drawing patterns on a sample substrate will be described.

  First, fogging in the electron beam exposure apparatus will be described with reference to FIG. When the irradiation position A on the sample substrate 15 is irradiated with the electron beam 28, a part of the electron beam 28 is reflected from the sample substrate, collides with the pole piece 34 on the lower surface of the objective lens 33, and is reflected again. Re-enters the irradiation position B. This phenomenon is called fogging. Although devices have been proposed in which the pole piece 34 is coated with a low-reflectance material and devices that reduce the fog by making the pole piece 34 part a honeycomb structure, it is impossible to completely prevent fogging. Could not perform highly accurate drawing over the entire surface of the sample substrate 15.

  In order to solve this problem, a method of correcting an exposure amount by creating an area density map indicating the density of a drawing pattern has been proposed. With this method, high-precision drawing can be achieved, but fogging is a phenomenon that covers a wide area such as several mm to several tens of mm on the sample substrate, so global exposure correction calculation across chips is performed. Enormous calculation time is required. For this reason, the time required for drawing increases, and the throughput is extremely impaired.

  Therefore, by using the electron beam exposure method according to the first embodiment, it is possible to realize drawing that does not impair the dimensional accuracy over the sample surface while realizing a significant reduction in throughput.

  Details of the electron beam exposure method (drawing method) of the first embodiment will be described below. First, prior to drawing, “fogging spread” will be described using an electron beam exposure apparatus. The “fogging spread” refers to a region in which the final dimension of the resist pattern varies due to electrons re-incident on the sample substrate due to the fogging. That is, in the positive resist line pattern drawing, the finished dimension is an area formed thicker than a predetermined dimension. In this embodiment, the spread of the fog is obtained by experiment.

  FIG. 3 is a diagram showing a layout on the sample substrate of a drawing pattern for confirming the spread of the fog. On the sample substrate 15, the isolated pattern 35 and the filled pattern 36 are arranged as shown in FIG. Then, the boundary portion of the upper end portion of the filled pattern 36 is set to 0, and the upward direction of the sample substrate 15 is defined as the positive direction of the coordinate axis. Here, the isolated pattern 35 is an isolated line pattern of 100 nm, for example. The filled pattern 36 is a solid pattern in which one surface is filled with, for example, a variable shaped beam.

  The drawing pattern shown in FIG. 3 is drawn by the exposure apparatus of the present embodiment, and the result of measuring a plurality of central isolated patterns 35 in the coordinate axis direction shown in FIG. 3 with a scanning electron microscope (CD-SEM) is shown. 4 shows. The vertical axis represents the dimension value of the central isolated pattern 35, and the horizontal axis represents the position in the coordinate axis direction shown in FIG. Plotted with a triangular mark 37 shown in FIG. 4 is a drawing result on a substrate in which a resist film is laminated on a metal film. Plotted with a circle mark 38 is a drawing result on a substrate in which a resist film is applied on a silicon (Si) substrate. Abrupt dimensional variations occur at each coordinate 0, and the slope of the variation affects several millimeters. From the experimental results shown in FIG. 4, the spread of the fog can be estimated to be about 10 mm. The reference dimensions (design values) 39 and 40 in the isolated line are different between the triangular mark 37 and the round mark 38. When the metal film is laminated, the amount of reflection of the electron beam due to the back scattering from the base metal film is different. It is thought that it is large.

However, in order to calculate the spread of the fog more accurately, in the first embodiment, the influence of the fog is represented by the second term of the equation (1).

Here, the function F (x, y, σ) is

It is.

  The first term of equation (1) mainly represents the contribution due to the proximity effect, and the second term represents the contribution due to fogging. W in Formula (1) is represented by the fitting curve 44 shown in FIG. The first term of Expression (1) is represented by a fitting curve 45, and the second term, that is, the contribution of fogging is represented by a fitting curve 46. In the graph shown in FIG. 5, the vertical axis represents the contribution rate, and the horizontal axis represents the distance from the electron beam shot position. Since the contribution of the fog covers a wide range, the fitting curve 46 shows a very wide graph.

W ₁ and W _{2 in} equation (1) represent weights for the respective contributions. σ is a standard deviation, and when σ ₁ << σ ₂ , σ ₂ is defined as a range affected by fogging, that is, the spread of fogging. The experimental data shown in FIG. 4 is fitted with the equation (1) to obtain σ ₂ and set as the fog spread. Here, 3 × σ ₂ may be defined as the extent of the cover, and the intersection of the extrapolated straight line of the round mark (experiment data) 38 and the reference dimension 40 is defined as the extent of the cover, regardless of the fitting by the above formula. It may be defined.

  Next, a drawing method for performing fog correction in the first embodiment will be described with reference to the flowchart shown in FIG.

  First, as described above, a range in which the influence of fogging, which varies depending on the difference in substrate structure, is obtained in advance by experiments (step 1). The obtained value is stored in a predetermined location of the control computer 1. Then, pattern data to be drawn and a weighting file are input (steps 2 and 3). The input of the pattern data indicates that the drawing design data 29 is transferred from a data conversion machine (not shown in FIG. 1), a predetermined drawing recipe is set, and a chip to be drawn on the sample substrate 15 is laid out. On the other hand, the weighting file is a parameter file for weighting the contribution ratio of the fog according to the distance from the shot position of the electron beam. For this, the above-described equation for the spread of the fog can be used. Even if the above equation is not used, the ratio of the dimensional variation according to the distance from the shot position of the beam may be used as a map by experiment, and this may be used as the weighting file.

  When the input of necessary data is completed, area density calculation is performed in step 4 next. FIGS. 7A and 7B are views for explaining a method of creating an area density map. Data to be drawn is divided into small area data. Here, the entire drawing data is divided in units of sub-deflection areas (for example, 50 μm square). This is shown in FIG. The sum of the areas of the patterns to be drawn is obtained for the divided sub deflection areas, and the number divided by the sub deflection area size indicates the area density of the sub deflection areas. Then, a file describing the area density of each sub deflection region is created as an area density map. Normally, the area density map needs to be created over the entire surface of the wafer. In this embodiment, however, only the fogging distance 43 shown in FIG. Only the sub deflection region included in the correction calculation target region 48 shown in FIG. As shown in FIG. 9, the correction calculation target area 48 in FIG. 8 is an area corresponding to a width twice as large as the fog spreading distance 47 from the outermost periphery of the wafer.

Next, using the area density map in each sub deflection region obtained in step 4, the optimum electron beam irradiation amount in each sub deflection region is obtained (step 5). The correction calculation of the irradiation amount in each sub deflection region is performed using the following general relational expression. The optimal dose D (x, y) is determined when considering the effects of proximity effect and fogging caused by backscattered electrons.

Meet. Here, E denotes an integration region, η is a backscattering coefficient for forward scattering, f (x′−x, y′−y) is an exposure distribution function due to backscattered electrons, and θ is a contribution due to fogging to an incident electron irradiation amount. G (x′−x, y′−y) is a fog distribution function. If D (x′−x, y′−y) is substantially constant in the integration region, it can be out of the integration symbol. Thereby, if the distribution function of the proximity effect and the distribution function of the fogging are known, the optimal dose D (x, y) at the coordinates (x, y) can be calculated by performing the convolution integral calculation. In the present embodiment, the local dimensional variation including the proximity effect correction is not performed because the drawing design data is corrected by applying a predetermined data correction calculation to the design data. That is, the second term of Equation (2) is not necessary. Further, the influence of the fog on the rightmost pattern shown in FIG. 7B is that the fog data from the data arranged next to it is the largest, and the farther it is within the distance of the spread of the fog, the more the fog contributes. Decrease. This effect is expressed by the function g (x′−x, y′−y), which means the weighting of the fog. Here, the fitting Gaussian function used when the “fogging spread” is obtained by experiment in step 1 is used. Of course, instead of using the obtained Gaussian function, a fogging weight map file prepared separately may be used. Note that the coefficient W ₂ of the fitting Gaussian function is used as θ in the equation (2).

  The dose correction calculation is performed by setting as described above, and the dose correction file is created. The dose correction file holds a correction coefficient M (x, y) obtained by dividing the dose D (x, y) obtained for each sub deflection region by the set dose D0 before correction in units of sub deflection regions. Then, the drawing method setting is read (step 6), and the calculated correction coefficient M (x, y) is rearranged into sub-deflection area units in the drawing order (step 7). The dose correction file is created in units of stripes. When the drawing method is the drawing of the stage continuous movement method, the stripe indicates the range in which the main deflection area size can be drawn by continuously moving the stage in one direction. FIG. 10 illustrates this stripe. When drawing is performed by the stage continuous movement method from the drawing chip 49 on the substrate 15 toward the drawing chip 50, the band portion indicated by the oblique lines in the figure is the stripe 51, and the size of the short side of the stripe is the main size. Represents the deflection area size. The dose correction file is created for all the sub-deflection areas to be drawn, and 1 is input to the correction coefficient M (x, y) of the sub-deflection area that was not subjected to the correction calculation when the dose correction file was created.

  Finally, the dose correction file is transferred to the memory 20 in stripe units (step 8), and continuous moving drawing in stripe units is executed (step 9). In the drawing procedure, drawing data in units of stripes is transferred to the drawing control circuit 3 via the data development circuit 2, and the data is developed into deflection position data and irradiation time data by the calculation unit 21, and the data is transferred to the subsequent circuit. Is transferred. Then, the position of the sample substrate 15 is monitored by the laser interferometer 18 while continuously moving the stage 16, and when the numerical value of the laser interferometer 18 reaches a predetermined pattern drawing position, the arithmetic unit 22 reads the predetermined sub-volume from the memory 20. The deflection irradiation amount correction data is read to correct the irradiation time. When data is read for each sub deflection area, an internal counter is incremented. The correction method is an operation of multiplying the transferred irradiation time by the dose correction data. The sub-deflection amplifier 4 and the main deflection amplifier 5 are controlled with the calculated irradiation time, and a voltage is applied to the blanking amplifier 7 through the irradiation amount control unit 6 for a predetermined time, whereby the sample substrate is corrected with the corrected irradiation amount. Drawing is carried out at 15. The drawing position of the next sub deflection area is detected by the numerical value of the laser interferometer 18, the correction coefficient M (x, y) of the next sub deflection area is read from the memory 20, and the internal counter is incremented. Further, after the drawing of one stripe is completed, the stage is moved to the next stripe, and at the same time, the drawing data of the next stripe and the dose correction file are transferred to the drawing control circuit 3. At this time, the counter inside the calculation unit 22 is reset to zero. By repeating this, it is possible to perform drawing over the entire surface of the sample substrate 15.

  As described above, by changing the shot time in accordance with the position of the sub-deflection area, it is possible to give a substantially uniform dose to all the sub-deflection areas on the wafer in consideration of the influence of fogging by the reflected electrons. For this reason, the reproducibility of the pattern line width (CD) on the wafer can be made substantially uniform, and the irradiation amount correction calculation is performed only for the sub-deflection region located at the fog spreading distance from the outermost periphery of the sample. As a result, the calculation time can be greatly shortened, and the fog correction can be easily realized.

  As described above, according to the first embodiment, the amount of exposure with respect to the wafer central portion is corrected in order to correct the backscattered electrons due to the proximity effect in the electron beam drawing and the fog exposure due to the reflected electrons from the wafer irradiated with the electron beam. On the other hand, the influence of the fog exposure over a wide range can be corrected relatively easily by increasing the exposure amount at the peripheral portion of the wafer, which is the fog correction area, and the pattern line width (CD) within the wafer surface. Can improve the uniformity.

  Next, a modification of the first embodiment will be described.

  As a modification of the first embodiment of the present invention, the fog correction calculation is performed in advance using the drawing design data 29 and the chip layout 30 using another computer not shown in FIG.

  By calculating in advance steps 1 to 5 or 7 shown in FIG. 6 using a computer different from the control computer 1 provided in the exposure apparatus, it is possible to save time required for correction calculation before drawing. For this reason, the substantial drawing time can be further shortened compared to the first embodiment.

[Second Embodiment]
Next explained is the second embodiment of the invention. The same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the second embodiment of the present invention, the correction of fogging can be more simply performed by performing the correction calculation performed in wafer units in the first embodiment in chip units.

  FIG. 11 shows a flowchart of a drawing method according to the second embodiment of the present invention.

  First, in the same manner as in the first embodiment, the “fogging spread”, which is the distance that the influence of the fogging, is obtained in advance by experiments (step 11). At the same time, in this embodiment, a pattern as shown in FIG. 12A, FIG. 12B, and FIG. One chip is composed of, for example, a 100 nm line and space pattern, and all the chips have the same pattern. The amount of fog correction is calculated using this pattern (step 12). The fog correction amount calculated in step 12 is obtained by the following procedure.

(1) Each of the patterns shown in FIGS. 12A to 12C is drawn and developed under a plurality of dose conditions.

(2) Of the patterns shown in FIGS. 12A to 12C, the dimension of the line and space pattern in each evaluation chip 52, 54, 56 is measured for each irradiation condition.

(3) Evaluation chip pattern size 52 determines the dose _{D B} which has finished in the target dimension (100 nm), the test chip 54, 56 of the pattern dimension dose D _Tateyoko which has finished in the target dimension (100 nm), D _naname is determined at the same time.

(4) _Let (D _tateyoko -D _B ) / 4 be the fog contribution amount for one chip 55 in the vertical and horizontal arrangement shown in FIG.

(5) _Let (D _naname −D _B ) / 4 be the fogging contribution amount for one chip 57 in the oblique arrangement shown in FIG. In step 12, for each chip in which at least one part is included in the area affected by the fogging, the fogging dose is calculated according to the arrangement of the chips adjacent to the chip.

  Next, a correction calculation of the irradiation amount on the entire wafer surface is performed (step 13). The correction calculation in step 13 will be described with reference to FIG. The fog correction area 59 from the outermost periphery of the wafer is set using the fog spread distance obtained in advance in step 11. The chip layout 30 on the sample substrate 15 is read, and chips partially included in the fog correction area 59 are extracted. In FIG. 13, for example, the drawing chip 60 is one of the chips partially included in the fog correction region 59. Then, an irradiation amount correction calculation is performed on the extracted drawing chip 60 and stored in the irradiation amount map in the sample substrate 15 (step 14). As an example, correction calculation for the drawing chip 60 will be described.

Since the drawing chip 60 has a smaller number of adjacent chips than the drawing chip 61, for example, it is considered that the influence of fogging is small. Here, since the chip 62 and the chip 63 do not exist, the irradiation amount is small by the fogging contribution of these chips. Therefore, in order to correct to the irradiation amount of the drawing chip 61,
An irradiation amount of ((D _tateyoko -D _B ) / 4) × 2 + (D _naname -D _B ) / 4 is added as a correction amount to the reference irradiation amount. This is stored in the irradiation amount map of the drawing chip 60. Here, the irradiation amount map describes one irradiation amount for one chip, and is stored in the control computer 1 as a map file corresponding to the layout on the sample substrate 15.

  As described above, the created dose map is transferred to the memory 20 shown in FIG. 1 immediately before drawing (step 15), and the calculation unit 22 reads the dose of the corresponding chip in the dose map of the memory 20. Then, the set irradiation time is calculated, and a desired pattern is drawn (step 16).

  By using the fog correction method according to the second embodiment described above, the fog correction can be performed more easily and at high speed. Furthermore, since the dose map can be transferred to the drawing control circuit 3 in a batch before starting drawing, and the dose can be corrected, transfer of the dose correction file from the control computer 1 can be eliminated. In addition, since the calculation of the drawing circuit can be made more redundant, the drawing time can be further shortened.

  According to the embodiment of the present invention, the fog correction region is the exposure amount with respect to the exposure amount with respect to the center of the wafer in order to correct the fog exposure by the backscattered electrons due to the proximity effect in electron beam writing and the reflected electrons from the irradiation substrate. By drawing with the exposure amount at the periphery of the wafer being increased, the influence of fog exposure over a wide range can be corrected relatively easily, and the uniformity of the pattern line width (CD) within the wafer surface can be improved.

  In the embodiment of the present invention, when a desired pattern is exposed to the sample substrate by the electron beam, the irradiation amount is obtained so that the actual irradiation amount given to the sample substrate becomes a predetermined irradiation amount at the irradiation position of the electron beam. It is possible to provide an electron beam exposure method for irradiating an electron beam based on the obtained irradiation amount.

  In addition, each of the above-described embodiments can be implemented not only independently but also in an appropriate combination. Furthermore, the above-described embodiments include inventions at various stages, and the inventions at various stages can be extracted by appropriately combining a plurality of constituent elements disclosed in the embodiments.

It is the schematic which shows the structure of the electron beam exposure apparatus in 1st Embodiment of this invention. It is a figure for demonstrating the fog in 1st Embodiment. It is a figure which shows the layout on the sample substrate of the drawing pattern for confirming the breadth of the fog in 1st Embodiment. It is a figure which shows the result of having measured the isolated pattern 35 when drawing the drawing pattern shown in FIG. 3 with the exposure apparatus of 1st Embodiment in the coordinate-axis direction several places. It is the figure which made the vertical axis | shaft the contribution rate and showed the horizontal axis | shaft as the distance from the shot position of an electron beam. It is a flowchart which shows the drawing method which performs the fog correction in 1st Embodiment of this application. It is a figure for demonstrating the creation method of the area density map in the drawing method of 1st Embodiment. It is a figure which shows the calculation area of the area density for the fog correction in the drawing method of 1st Embodiment. It is a figure which shows the correction area | region of the irradiation amount in the drawing method of 1st Embodiment. It is a figure which shows the stripe in the case of the continuous movement drawing in the drawing method of 1st Embodiment. It is a flowchart which shows the drawing method in 2nd Embodiment of this invention. It is a figure which shows the experimental pattern for calculating | requiring the correction of the irradiation amount on a sample board | substrate. It is a figure for demonstrating the correction method of the irradiation amount in the drawing method of 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Control computer, 2 ... Data expansion circuit, 3 ... Drawing control circuit, 4 ... Sub deflection amplifier, 5 ... Main deflection amplifier, 6 ... Irradiation amount control part, 7 ... Blanking amplifier, 8 ... Electro-optic lens barrel, 9 DESCRIPTION OF SYMBOLS ... Sample chamber, 10 ... Electron gun, 11 ... Blanking electrode, 12 ... Blanking aperture, 13 ... Sub-deflector for beam scanning, 14 ... Main deflector for beam scanning, 15 ... Sample substrate, 16 ... Sample stage, DESCRIPTION OF SYMBOLS 17 ... Stage control part, 18 ... Laser interferometer, 19 ... Reception part, 20 ... Memory, 21, 22, 23 ... Calculation part, 24, 26 ... Digital circuit part, 25, 27 ... Analog circuit part, 28 ... Electron beam 29 ... Drawing design data, 30 ... Chip layout, 31 ... Arithmetic module, 32 ... Objective deflector, 33 ... Objective lens, 34 ... Pole piece, 35 ... Isolated pattern, 36 ... Filled pattern, 7 ... Triangle mark, 38 ... Circle mark, 39, 40 ... Reference dimension (design value), 41, 42 ... Drawing chip, 43, 59 ... Fog correction area, 44, 45, 46 ... Fitting curve, 47, 58 ... Fog 48 ... Correction calculation target area, 49, 50 ... Drawing chip, 51 ... Stripe, 52, 54, 56 ... Evaluation chip, 53, 55, 57 ... Chip, 60, 61 ... Drawing chip, 62, 63 ... Chip.

Claims (5)

In the charged particle beam exposure method of exposing a desired pattern on a sample substrate by controlling the irradiation amount of the charged particle beam according to the pattern arrangement,
A step of previously obtaining a region that is affected by fogging caused by exposure with a charged particle beam;
Dividing the exposure area of the pattern of the sample substrate into smaller areas smaller than the area affected by the fog, and calculating a fog irradiation amount given to the sample substrate by the fog in the small area;
Irradiation of the charged particle beam for each of the small regions according to the amount of fog irradiation obtained by the calculation on the pattern included in the region affected by the fog from the outermost periphery of the sample substrate Correcting the amount;
A charged particle beam exposure method comprising:   The small region is a chip region disposed on the sample substrate, and the step of calculating the fogging irradiation amount is performed for each chip region including at least one part in the region affected by the fogging in the sample substrate. 2. The charged particle beam exposure method according to claim 1, wherein the fogging dose is calculated in accordance with an arrangement of a chip area adjacent to the chip area.   3. The charged particle beam exposure method according to claim 1, wherein the step of correcting the irradiation amount of the charged particle beam is a step of correcting the irradiation amount by changing an irradiation time of the charged particle beam. . In a charged particle beam exposure apparatus that exposes a desired pattern on a sample substrate by controlling the irradiation amount of a charged particle beam according to the pattern arrangement,
Storage means for storing information on a region that is affected by fogging caused by exposure with the charged particle beam;
A first calculation for dividing the exposure area of the pattern of the sample substrate into smaller areas smaller than the area affected by the fog, and calculating the fog irradiation amount given to the sample substrate by the fog in the small area Means,
The charged particles for each of the small regions according to the fogging dose obtained by the first calculation means for the pattern included in the region affected by the fogging from the outermost periphery of the sample substrate. A second calculating means for correcting the irradiation amount of the beam;
A charged particle beam exposure apparatus comprising:   The small area is a chip area arranged on the sample substrate, and the first calculation means for calculating the fogging irradiation amount includes, for each chip area including at least one part in the area affected by the fogging, 5. The charged particle beam exposure apparatus according to claim 4, wherein the fogging dose is calculated in accordance with an arrangement of a chip area adjacent to the chip area.

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