JP2006303361A - Method and apparatus for correcting shot amount of electronic beam drawing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for correcting a shot amount of an electronic beam drawing apparatus capable of correcting a change in a CD ray width due to a delay during exposure. <P>SOLUTION: The method and the apparatus for correcting the shot amount of the electronic beam drawing apparatus is configured such that a state of a pattern width in a test mode is recorded up to an image drawing end; a shot amount correction value in an actual image drawing is obtained on the basis of the pattern width; a resist sensitivity ratio, and an image drawing prediction time in an image drawing start in the test mode; and the image drawing accuracy is corrected by adding the shot amount correction value to the image drawing data when no correction is applied. As a result, the change in the CD ray width due to a delay during exposure can be corrected. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a shot amount correction method and apparatus for an electron beam lithography apparatus.

  An electron beam drawing apparatus is used to design an IC circuit by drawing a fine pattern (several μm or less) on a wafer. Pattern data to be drawn is input by a magnetic tape or the like and temporarily stored in a magnetic disk memory. Thereafter, the drawing data stored in the magnetic disk is read by the computer 10 and sent to the beam deflection control unit 12 and the blanking control unit 11 for turning on / off the beam via a high-speed data processing circuit.

  On the other hand, the electron beam 4 emitted from the electron gun 1 is focused on the wafer 7 by the electron lens 3 to form a very small spot. The beam is turned on / off by a blanking control unit 11 and a beam deflection control unit 12 to draw a pattern, and is deflected to a predetermined position. In this way, a designed pattern is drawn.

  Reference numeral 13 denotes a stage movement position measurement control unit for controlling the position of the stage 8, and 5 denotes a material exchange chamber for exchanging materials. 9 is a vacuum chamber. Reference numeral 6 denotes a deflection electrode deflected by the beam deflection control unit 12. The wafer 7 is usually coated with a resist, and a target pattern is drawn by being deflected by an electron beam.

As a conventional device of this type, there is known a technique for improving the reliability of the control circuit by increasing the time resolution without using a high-frequency clock in the electron beam irradiation time control and further reducing the occurrence of crosstalk. (See, for example, Patent Document 1).
Japanese Patent Laid-Open No. 11-135057 (paragraph 0010, FIG. 1)

  In general, a chemically amplified resist generates protonic acid at an exposed portion. The generated proton acid causes polarity conversion of the resin by PEB (post-exposure baking), and the resin becomes soluble in the developer. In the unexposed area, no proton acid is generated, so that it remains insoluble in the developer and remains as a pattern.

  Protonic acid generated by exposure is unstable, so if it comes into contact with basic substances in the air (ammonia, organic amine, etc.), it will be neutralized, and the resist pattern will be exposed and the exposed area will not be developed. End up. Here, eaves means that a pattern contact occurs between adjacent patterns. For this reason, the time from exposure to PEB (PED time) and the basic substance concentration at the boundary are carefully controlled.

  On the other hand, the delay during exposure (the time from the first beam shot to the last beam shot) was not captured as a delay because the inside of the electron beam drawing apparatus was vacuum. Although it is in a vacuum, the production exposure takes ten and several hours. Recently, it has been reported that this delay during exposure affects the line width, and there is concern about the adverse effect on CD (line width) accuracy.

  The present invention has been made in view of such a problem, and an object thereof is to provide a shot amount correction method and apparatus for an electron beam lithography apparatus capable of correcting a change in CD line width due to a delay during exposure. Yes.

(1) According to the first aspect of the present invention, the pattern width state is recorded up to the drawing end in the test mode, and in actual drawing, the pattern width at the start of drawing in the test mode, the resist sensitivity ratio, and the estimated drawing time A shot amount correction value is obtained from the above, and the drawing accuracy is corrected by adding the shot amount correction value to the drawing data when there is no correction.

Here, the resist sensitivity ratio indicates how much the line width changes when the dose amount changes by, for example, 1%.
(2) The invention described in claim 2 is a recording means for recording the pattern width state to the drawing end in the test mode, and in actual drawing, the pattern width at the start of drawing in the test mode, the resist sensitivity ratio, and the drawing. Computation means for obtaining a shot amount correction value from the predicted time, and correction means for correcting the drawing accuracy by adding the shot amount correction value to the drawing data when there is no correction.

(1) According to the first aspect of the present invention, the change in the CD line width due to the delay during exposure can be corrected.
(2) According to the second aspect of the present invention, it is possible to correct a change in the CD line width due to a delay during exposure.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing an example of the operation of the present invention. The following processing is performed by the computer 10 built in FIG. In the present invention, the apparatus is first calibrated (S1). Here, as contents of the apparatus calibration, current density measurement and beam position deviation measurement are performed. When the apparatus calibration is completed, actual drawing is performed (S2). When drawing is completed, the process returns to step S1 again to calibrate the apparatus. That is, the drawing apparatus repeats such device calibration and drawing in a cycle of several minutes.

In the conventional technique, the shot time is expressed by the following equation from the dose amount and the current density.
Shot time = Dose amount / Current density (1)
As is clear from the equation (1), in the conventional technique, the current density which changes every moment is measured, and the shot value corresponding to the dose is calculated by using the measured value. In this equation (1), line width correction by delay is not taken into consideration.

On the other hand, in the present invention, the delay is obtained as Delay (t) as a function of the elapsed drawing time, and the shot time is obtained by the following equation.
Shot time = (Dose amount / current density) × Delay (t) (2)
In the present invention, the shot amount is corrected by drawing elapsed time. In the shot amount correction according to the present invention, the shot time calculated every time the apparatus is calibrated is multiplied by Delay (t). As a result, the CD line width change due to the delay during exposure is corrected. Delay (t) corrects a difference that appears when beam exposure is performed under the same conditions. This Delay (t) can be obtained from the shift line width and the resist sensitivity ratio. The resist sensitivity ratio is a coefficient of the change amount of the line width and the change amount of the dose amount, and is used for obtaining a variable of how much the shot amount should be shifted from the actual shot amount. /% · Dose]. For example, it shows how many nm the line width changes when the dose changes by 1%.

  FIG. 2 is a diagram showing an example of creating Delay (t). The upper characteristic f1 indicates the delay (t) characteristic, and the lower characteristic f2 indicates the line width deviation [nm] in the test mode. The horizontal axis for f1 represents the elapsed drawing time, the vertical axis represents Delay (t), the horizontal axis for f2 represents the drawing time, and the vertical axis represents the line width deviation.

The drawing result f1 is calculated using the resist sensitivity ratio and the predicted drawing time. As a result, Delay (t) is calculated using the resist sensitivity ratio and the estimated drawing time.
In this case, specifically, Delay (t) is obtained based on the drawing result in the test mode. f1 indicates a correction at the time of actual drawing, and f3 indicates a drawing characteristic when the correction is not performed. By adding the correction f1 to the characteristic of f3, it is possible to keep the change in the line width at a constant reference value. Expression (2) means that a shot amount correction value is obtained from the pattern width at the start of drawing, the resist sensitivity ratio, and the drawing prediction time.

  In this way, the blanking control unit 11 controls the beam shot time under the control of the computer 10. In response to an instruction from the computer 10, the beam deflection control unit 12 controls the deflection electrode 6 to draw a pattern.

  As described above in detail, according to the present invention, it is possible to provide a shot amount correcting method and apparatus for an electron beam lithography apparatus capable of correcting a change in CD line width due to a delay during exposure. Changes in CD line width due to delay can be corrected.

It is a figure which shows an example of operation | movement of this invention. It is a figure which shows the creation example of Delay (t). It is a figure which shows the structural example of an electron beam drawing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electron gun 2 Blanking electrode 3 Electron lens 4 Electron beam 5 Material exchange chamber 6 Deflection electrode 7 Wafer 8 Stage 9 Vacuum chamber 10 Computer 11 Blanking control part 12 Beam deflection control part 13 Stage movement position measurement control part

Claims (2)

Record the pattern width status in the test mode until the drawing end.
In actual drawing, the shot amount correction value is obtained from the pattern width at the start of drawing in the test mode, the resist sensitivity ratio, and the drawing prediction time.
A shot amount correction method for an electron beam drawing apparatus, wherein the drawing accuracy is corrected by adding the shot amount correction value to the drawing data when there is no correction. A recording means for recording the pattern width state to the drawing end in the test mode;
In actual drawing, calculation means for obtaining a shot amount correction value from the pattern width at the start of drawing in the test mode, the resist sensitivity ratio, and the drawing prediction time;
Correction means for correcting the drawing accuracy by adding the shot amount correction value to the drawing data when there is no correction;
An apparatus for correcting a shot amount of an electron beam lithography apparatus.

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