JP2007173499A - Charged particle beam exposure device and computing method for target corrected value database - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charged particle beam exposure device capable of accurately carrying out the measurement of the resolution, the position, the shape correction value of the adjusting sub-field formed on a reticle, and the optimization of an electron beam optical system. <P>SOLUTION: First, the rough measurement of the blurring in the 0° direction is carried out, and successively the high precision measurement thereof is carried out. Then, the rough measurement of the blurring is carried out in the normal direction, and successively the high precision measurement thereof is carried out. However, either of the measurement of the blurring in the normal direction and the measurement of the blurring in the normal direction may be carried out first. Successively, the rough measurement of the blurring in the 45° direction is carried out, and then the high precision measurement of the blurring in the 45° direction and the high precision measurement of the blurring in the 135° direction are carried out. Also in this case, either of the high precision measurement of the blurring in the 45° direction and the high precision measurement of the blurring in the 135° direction may be carried out first. Further, the rough measurement of the blurring in the 135° direction may be carried out instead of the rough measurement of the blurring in the 45° direction. Successively, the rough measurement of the position of the sub-field is carried out, and then the high precision measurement of the position of the sub-field and the high precision measurement of the shape of the sub-field are carried out. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a charged particle beam exposure apparatus and a target correction value database calculation method.

  In an electron beam exposure apparatus, in order to ensure exposure transfer accuracy, a mark (reticle fiducial mark) provided on a reticle stage is projected onto an electron beam sensor provided on a wafer stage or an electron column. Then, from the projected position, each subfield in the main field is exposed and transferred in any state (a parameter indicating the focal position, astigmatism, subfield shape, and subfield position is called an EO parameter). The electron beam optical system is adjusted so that exposure transfer is performed at a normal focal position, astigmatism, subfield shape, and subfield position.

  However, in the past, it has not been known in what order to perform measurement and adjustment in order to perform measurement and adjustment. In addition, although the actual reticle fiducial mark has a processing error, since the information has not been taken in, accurate correction of the electron optical system may not be performed.

  The present invention has been made in view of such circumstances, and the resolution and position of the adjustment subfield formed on the reticle, the measurement of the shape correction value, and the electron beam optical system can be accurately optimized. It is an object of the present invention to provide a charged particle beam exposure apparatus that can be used and a method for calculating a target correction value database that is used to correct a processing error of a reticle fiducial mark.

  A first means for solving the problem includes an adjustment reticle mark and an adjustment detector, and is formed on the reticle by detecting a projected image of the adjustment reticle mark with the adjustment detector. A charged particle beam exposure apparatus having a function of measuring the resolution (focal position, astigmatism), position, and shape correction value of the adjustment subfield and optimizing the electron beam optical system based on the measured value. A charged particle beam exposure apparatus having a function of measuring and optimizing the position and shape correction value after measuring and optimizing the resolution.

  There is an interference between the resolution, the position, and the shape correction value, and there is a relationship that changing one changes the other. On the other hand, when the accuracy required for resolution is compared with the accuracy required for the position and shape correction values, there is no problem even if the former is coarser. Therefore, in this means, resolution measurement and optimization are performed first, and then position and shape correction values are measured and optimized.

  A second means for solving the above-described problem has an adjustment reticle mark and an adjustment detector, and is formed on the reticle by detecting a projected image of the adjustment reticle mark with the adjustment detector. A charged particle beam exposure apparatus having a function of obtaining an astigmatism correction value in the 45 ° -135 ° direction of the adjustment subfield, and an astigmatism correction value that minimizes blur in the 45 ° direction, and a 135 ° direction A charged particle beam exposure apparatus having a function of setting an average value of an astigmatism correction value that minimizes blurring to an astigmatism correction value in a 45 ° -135 ° direction.

  The astigmatism correction value that minimizes the blur in the 45 ° direction and the astigmatism correction value that minimizes the blur in the 135 ° direction should be essentially the same value, but actually differ depending on the measurement error, etc. In many cases. Therefore, in this means, an error is reduced by using these average values as astigmatism correction values.

  A third means for solving the above-described problem has an adjustment reticle mark and an adjustment detector, and is formed on the reticle by detecting a projected image of the adjustment reticle mark with the adjustment detector. A charged particle beam exposure apparatus having a function of measuring and optimizing the resolution (focal position, astigmatism), position and shape correction values of the adjustment subfield, and correcting the error of the adjustment reticle mark The charged particle beam exposure apparatus has a function of measuring and optimizing the resolution, the position, and the shape correction value in consideration of a target correction value database.

  As described above, the reticle fiducial mark which is an adjustment reticle mark has a processing error. This means uses the target correction value database to correct this processing error, and has the function of measuring and optimizing the resolution, position, and shape correction value in consideration of this, so it can be used for adjustment. Even when the reticle mark has a processing error, it is possible to accurately optimize the resolution, position, and shape correction value.

  A fourth means for solving the above problem is a method for obtaining a target correction value database used in the third means, wherein the resolution, position, and shape correction value are determined assuming that the adjustment reticle mark is correct. After measuring and optimizing, the subfield actually formed on the reticle is exposed and transferred to the wafer and developed, and the resolution, position, and shape of the subfield formed on the wafer are measured to obtain the target value. The target correction value database calculation method is characterized in that a target correction value database for correcting an error of the adjustment reticle mark is determined based on the shift.

  After measuring and optimizing the resolution, position, and shape correction value assuming that the adjustment reticle mark is correct, the subfield actually formed on the reticle is exposed and transferred to the wafer and developed, and the subfield formed on the wafer is developed. If the position and shape of the field are measured and the deviation from the target value is calculated, the deviation is based on the error of the adjustment reticle mark. In this way, in this way, the error can be calculated without actually measuring the error of the adjustment reticle mark.

  According to the present invention, a charged particle beam exposure apparatus that can accurately perform resolution and position of a subfield for adjustment formed on a reticle, measurement of a shape correction value, and optimization of an electron beam optical system, and a reticle film It is possible to provide a method of calculating a target correction value database used for correcting a processing error of a dual mark.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of a charged particle beam exposure apparatus of a divided exposure transfer system which is an example of an embodiment of the present invention. In FIG. 1, reference numeral 100 denotes a reticle, 100a denotes a subfield on the reticle 100, 100b denotes a boundary region between the subfields 100a, 110 denotes a sensitive substrate such as a wafer coated with a resist, and 110a denotes an area for one chip of the sensitive substrate 110. , 110b is a transfer area of the sensitive substrate 110 corresponding to each subfield 100a, AX is an optical axis (system axis) of the charged particle beam optical system, EB is a charged particle beam, and CO is a crossover point of the charged particle optical system. is there.

  On the reticle 100, there are a large number of subfields 100a each having a pattern to be transferred to the sensitive substrate 110 on the membrane, separated by a boundary region 100b where no pattern exists. A grid-like column (crosspiece) is provided at a portion corresponding to the boundary region 100b to protect the membrane in terms of heat and strength.

  Each subfield 100a includes a partial pattern obtained by dividing a pattern to be transferred onto the area 110a for one chip of the sensitive substrate 110, and each divided partial pattern is transferred to the sensitive substrate 110.

  The appearance shape of the sensitive substrate 110 is as shown in FIG. 1B, and in FIG. 1A, a part of the sensitive substrate 110 (Va portion in FIG. 1B) is shown enlarged. .

  In FIG. 1, a z-axis is taken in parallel with the optical axis AX of the charged particle beam optical system, and an x-axis and a y-axis are taken in parallel with the arrangement direction of the subfields 100a. Then, as indicated by arrows Fm and Fw, the charged particle beam is scanned stepwise in the y-axis direction while continuously moving the reticle 100 and the sensitive substrate 110 in the opposite directions in the x-axis direction to form a row of subfields 100a. After the pattern transfer of the row is completed, the next subfield 100a row adjacent in the x-axis direction is scanned with a charged particle beam, and thereafter the transfer is performed for each subfield 100a (divided). The pattern for one chip is transferred by repeating (exposure transfer). The x-axis direction indicated by the arrows Fm and Fw is called the stage scanning direction.

  The scanning order of the subfield 100a and the transfer order to the sensitive substrate 110 at this time are as indicated by arrows Am and Aw, respectively. Note that the continuous movement direction of the reticle 100 and the sensitive substrate 110 is opposite because the x axis and the y axis are reversed between the reticle 100 and the sensitive substrate 110 by the pair of projection lenses.

  When performing transfer (divided transfer) in such a procedure, simply projecting the pattern of the subfield 100a in a row in the y-axis direction onto the sensitive substrate 110 with a pair of projection lenses as it is is a sensitive substrate corresponding to each subfield 100a. A gap corresponding to the boundary region 100b is generated between each of the 110 transferred regions 110b. As a countermeasure against this, the pattern transfer position is corrected by deflecting the charged particle beam EB that has passed through each subfield 100a in the y-axis direction by an amount corresponding to the width Ly of the boundary region 100b.

  Also in the x-axis direction, not only the scattering transmission reticle 100 and the sensitive substrate 110 are moved at a constant speed considering the pattern reduction ratio and the subfield interval Lx, but also the relative speed between the image of the subfield 100a and the sensitive substrate 110 is Exposure is performed while deflecting to zero, and the pattern transfer position is corrected so that there is no gap in the x-axis direction between the transferred regions 110b.

  As described above, in the divided exposure transfer method, a pattern corresponding to one chip on the reticle 100 is divided into a large number of subfields 100a, and lattice-like pillars are formed in the boundary region 100b formed between the subfields 100a. Since the (strut) is provided, deflection and thermal distortion of the reticle substrate due to charged particle beam irradiation can be suppressed, and accurate exposure transfer can be performed.

  In addition, since exposure is performed by such a method, compared to a conventional charged particle beam exposure apparatus, the subfield region is exposed all at once, and all the patterns to be exposed are formed on the reticle. Throughput can be improved.

  An example of the optical system of such a charged particle beam exposure apparatus is shown in FIG. FIG. 2 is a schematic diagram of an optical system of the charged particle beam exposure apparatus. In FIG. 2, 11 is a charged particle beam source, 12A to 12C are illumination lenses, 13 is a beam shaping aperture, 14 is an aperture stop, 15 is a reticle, 16A and 16B are projection lenses, 17 is a scattering aperture, and 18 is a wafer. It is.

  The charged particle beam emitted from the charged particle beam source 11 uniformly illuminates the opening surface of the beam shaping aperture 13 by the illumination lens 12A, and images of the opening surface of the beam shaping aperture 13 are obtained on the reticle 15 by the lenses 12B and 12C. To form. This image area is an illumination area. The pattern image formed on the reticle 15 is formed on the wafer 18 by the projection lenses 16A and 16B, and the resist on the wafer 18 is exposed. An aperture stop 14 is provided to limit the aperture angle of the illuminating charged particle beam, and a scattering aperture 17 is provided to cut the scattered radiation scattered by the reticle 15.

  In addition, focus coils (dynamic focus coils) 19A, 19B, and 19C are provided to quickly adjust the magnification, rotation, and focal position in small amounts, and astigmatism, orthogonality, and anisotropic magnification can be adjusted. For this purpose, two stigmeters 20A and 20B are provided. In order to adjust the position of the pattern image, deflectors 21A to 21D are provided.

  FIG. 3 is a flowchart showing the order of measuring blur, subfield position, and subfield shape. First, coarse measurement of 0 ° direction blur is performed, and then high-precision measurement is performed. Next, rough measurement of 90 ° direction blur is performed, and then high-precision measurement is performed. However, either 0 ° direction blur or 90 ° direction blur may be measured first.

  Subsequently, rough measurement of 45 ° direction blur is performed, and then high-precision measurement of 45 ° direction blur and 135 ° direction blur are performed. Also in this case, either high-precision measurement of 45 ° direction blur or 135 ° direction blur may be performed first. Further, instead of the rough measurement of the 45 ° direction blur, the 135 ° direction blur may be roughly measured.

  Subsequently, rough measurement of the position of the subfield is performed, and then high-precision measurement of the subfield position and high-precision measurement of the subfield shape are performed.

FIG. 4 is a diagram illustrating a method for obtaining the focal position F and astigmatism S1 from blur in the x direction (0 ° direction) and blur in the y direction (90 ° direction). In FIG. 2, the horizontal axis represents the position in the optical axis direction, and the vertical axis represents the amount of blur. If the optical axis direction position where the blur in the x direction is minimum is Fx, and the optical axis direction position where the blur in the y direction is minimum is Fy,
F = (Fx + Fy) / 2
S1 = (Fy−Fx) / 2
Can be obtained as

  FIG. 5 is a diagram illustrating a method of actually measuring the amount of blur. In FIG. 5, the horizontal axis represents the position in the optical axis direction or 45 ° -135 ° astigmatism correction value S2, and the vertical axis represents the amount of blur. Taking measurement points of a predetermined number of steps with a predetermined step width, the value of the blur amount between them is obtained by complementation.

  FIG. 6 is a diagram showing an automatic adjustment sequence using the target correction value database. In the automatic adjustment sequence, the adjustment detector detects the projected image of the adjustment reticle mark, and the resolution (focal position, astigmatism), position, and shape correction value of the adjustment subfield formed on the reticle are detected. It has a function of measuring and optimizing the electron beam optical system based on the measurement. As described above, since the adjustment reticle mark has a processing error, this error (distortion) is measured in advance and used as a target correction value database. Since the measurement value obtained using the automatic adjustment sequence includes a mark error, the target correction value database is taken into consideration and the error is subtracted to obtain a new correction value.

  FIG. 7 shows another method of using the target correction database. In this method, an accurate subfield shape formed on a reticle is exposed on a wafer without using an adjustment reticle mark, and the electron beam optical system is corrected based on the shape error. That is, distortion and focus / astigmatism deviation of the shot actually exposed on the wafer are measured by a coordinate measuring device, SEM, etc., and the measured error is used as a target correction value database. In other words, the target value database is originally a database that stores the processing error of the adjustment reticle mark, but here, instead of the processing error of the adjustment reticle mark, the solution when the wafer having the correct shape subfield is exposed to the wafer is used. The error of the image, position, and shape correction value is stored.

  After that, when the automatic correction sequence is executed using the target correction value database as a dummy (execution is performed but the measurement operation is not actually performed and an error from the target value is input as 0), the target correction value database is Since it is reflected as it is as a correction value and the result that the error from the ideal of the electron optical system is 0 is output, ideal correction is performed and the new correction value becomes accurate.

  That is, in the present embodiment, the electron beam optical system that actually has an error does not have an error. Instead, the error of the electron beam optical system is entered in the target correction value database, and the adjustment reticle mark corresponds. The error of the electron beam optical system is corrected as having an error. Even in this case, the error of the electron beam optical system can be corrected.

  FIG. 8 shows a method for obtaining the target correction value database by calculation without actually measuring the processing error of the reticle mark for adjustment. An automatic adjustment sequence is performed assuming that there is no processing error of the adjustment reticle mark, and a new correction value is obtained. Then, the electron beam optical system is adjusted with the new correction value, and then the reticle subfield is actually exposed on the wafer, and distortion (error) of the exposure pattern is measured. Since the electron beam optical system is optimally adjusted, this error can be considered to be caused by a processing error of the adjustment reticle mark. Therefore, a target correction value database is calculated based on this error.

It is a figure which shows the outline | summary of the charged particle beam exposure apparatus of the division | segmentation exposure transfer system which is an example of embodiment of this invention. It is a figure which shows an example of the optical system of a charged particle beam exposure apparatus. It is a flowchart which shows the order which measures a blur, a subfield position, and the shape of a subfield. It is a figure which shows the method of calculating | requiring the focus position F and astigmatism S1 from the blur of x direction, and the blur of ay direction. It is a figure which shows the method of actually measuring the amount of blurs. It is a figure which shows the automatic adjustment sequence using a target correction value database. It is a figure which shows another usage method of a target correction | amendment database. It is a figure which shows the method of calculating | requiring a target correction value database by calculation, without actually measuring the processing error of the reticle mark for adjustment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Charged particle beam source, 12A-12C ... Illumination lens, 13 ... Beam shaping aperture, 14 ... Aperture stop, 15 ... Reticle, 16A, 16B ... Projection lens, 17 ... Scattering aperture, 18 ... Wafer, 19A-19C ... Focus coil, 20A, 20B ... Stigmeter, 21A-21D ... Deflector, 100 ... Reticle, 100a ... Subfield, 100b ... Boundary region 110 ... Sensing substrate, AX ... Optical axis, EB ... Charged particle beam, CO ... Cross Over point

Claims (4)

An adjustment reticle mark and an adjustment detector are provided, and the adjustment detector detects a projected image of the adjustment reticle mark, thereby resolving an adjustment subfield formed on the reticle (focal position, non-focus position). A charged particle beam exposure apparatus having a function of measuring a point aberration), a position, and a shape correction value and optimizing an electron beam optical system based on the measured value, and after performing the measurement and optimization of the resolution, A charged particle beam exposure apparatus having a function of measuring and optimizing the position and shape correction value. An adjustment reticle mark and an adjustment detector are provided, and a projection image of the adjustment reticle mark is detected by the adjustment detector, whereby an adjustment subfield formed on the reticle in a 45 ° -135 ° direction. An charged particle beam exposure apparatus having a function for obtaining an astigmatism correction value, and an average value of an astigmatism correction value that minimizes blur in the 45 ° direction and an astigmatism correction value that minimizes blur in the 135 ° direction Has a function of making astigmatism correction values in the 45 ° -135 ° direction. An adjustment reticle mark and an adjustment detector are provided, and the adjustment detector detects a projected image of the adjustment reticle mark, thereby resolving an adjustment subfield formed on the reticle (focal position, non-focus position). A charged particle beam exposure apparatus having a function of measuring and optimizing (point aberration), position, and shape correction value, in consideration of a target correction value database for correcting an error of the adjustment reticle mark, A charged particle beam exposure apparatus having a function of measuring and optimizing resolution, position, and shape correction value. A method for obtaining a target correction value database used in the charged particle beam exposure apparatus according to claim 3, wherein the resolution, position, and shape correction values are measured and optimized on the assumption that the reticle mark for adjustment is correct. The subfield actually formed on the reticle is transferred onto a wafer, developed, and the resolution, position, and shape of the subfield formed on the wafer are measured to calculate the deviation from the target value. A target correction value database calculation method, wherein a target correction value database for correcting an error of the adjustment reticle mark is determined based on a deviation.

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