JPH02215120A - Distortion correction in charged particle beam lithography - Google Patents

Abstract

PURPOSE:To remove the effect of drift from the amount of distortion by a method wherein the amount of drift is worked out from the amount of distortion at the same position of the two measurements, the amount of drift at each position is worked out from the amount of drift obtained as above, and the amount of distortion at each position is corrected in accordance with the above-mentioned amount of drift. CONSTITUTION:A stage driving device 14 is driven by the instruction sent from a computer 8, and a cross-shaped mask provided on a material 4 is arranged at the first position O1. Then, an ion beam is scanned on the position P1 by controlling a scanner 4. A signal detected by a detector 7 is outputted to a computer 8, and the actually measured position is found. The amount of distortion is worked out from the difference between the actually measured position and the target position, and the amount of distortion of measurement positions P1 to Pn are stored in a distortion memory 19. Subsequently, the amount of distortion at position P1 is worked out again, a drift amount is worked out from the amount of distortion at the same position of the two measurements, the amount of distortion at position P1 to Pn is corrected in accordance with the amount of drift, and the result is stored in the distortion memory 19. Through these procedures, the effect of drift is removed, and a highly precise pattern can be drawn.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a distortion correction method in a charged particle beam drawing method in which a desired pattern is drawn by irradiating an electron beam or an ion beam onto a material to be drawn.

(Prior Art) In electron beam lithography apparatuses and ion beam lithography apparatuses, distortion correction is performed to remove field distortion such as pincushion distortion and field shape correction during oblique ion beam irradiation. The procedure for measuring the amount of distortion for performing this distortion correction will be explained using an ion beam lithography apparatus as an example with reference to the flowchart of FIG. 3.

■ Move the stage and place the fiducial mark on the material at the target location in the field. FIG. 4 shows the target position P of the mark in the field F, where Pl is the initial target position and 0 is the optical axis.

(2) The ion beam is deflected to this first reference position 21, and the vicinity of the mark is scanned by the ion beam. For example, secondary electrons generated when the mark portion is irradiated with an ion beam are detected, and the center position of the mark is measured based on this detection signal.

(2) Find the difference between the actual value of the measured mark position and a predetermined target position, and find the amount of distortion at that position P1.

(2) Perform steps (1) to (2) above for each position P1 to P7, and obtain the amount of distortion at each position.

(2) From the distortion amounts at positions P and -P7, the distortion amount at each point between the actually measured target positions is determined by interpolation or the like and stored in the distortion correction memory.

(Problems to be Solved by the Invention) In the field distortion correction procedure as described above, in order to perform distortion correction with high precision, the number of positions P at which the amount of distortion is to be measured must be increased. If the number of measurement positions increases, the measurement time will inevitably increase, and the influence of drift cannot be ignored.

The present invention has been made in view of these points, and its purpose is to make it possible to extremely minimize the influence of drift even when the number of measurement points is increased in order to perform highly accurate strain measurements. The object of the present invention is to realize a distortion correction method in a charged particle beam writing method.

(Means for Solving the Problems) The distortion correction method based on the present invention focuses a charged particle beam on a material and deflects the charged particle beam to move a charged particle beam irradiation point on the material to obtain a desired target particle beam. In a charged particle beam drawing method that draws a pattern on a material, a stage is moved to sequentially move marks on the material to predetermined positions, and at each predetermined position, the charged particle beam is moved to the mark position. irradiation, detect the position, and calculate the amount of distortion at that position from the difference between the actual measured position of the detected mark and the target position of the mark. After calculating the amount of distortion at each determined position, the first step is to Move the stage so that the mark is located at the position, calculate the distortion amount again at the initial position, calculate the drift amount from the distortion amount at the same position twice, and calculate the drift amount at each position from the calculated drift amount. The method is characterized by the steps of determining the amount of drift and correcting the amount of distortion at each position according to the amount of drift.

(Function) After detecting the mark at many positions in the field and measuring the amount of strain at each position, measure the amount of strain again at the first position, and calculate the amount of strain determined at the same position twice. The amount of drift is determined based on the amount of drift, and the amount of distortion at each position is corrected by the amount of drift thus determined.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an example of an ion beam lithography apparatus for implementing the distortion correction method based on the present invention. In the figure, 1 is an ion source, and an ion beam from the ion source 1 is narrowly focused onto a material 4 by a focusing lens 2.3. The ion beam irradiation position on the material 4 is changed according to signals supplied to the electrostatic deflection plates 5 and 6. The secondary electrons generated from the material 4 upon irradiation with the ion beam are 2
It is detected by the secondary electron detector 7.

The deflection signal to the deflector 5.6 is generated from a scanner 9 controlled by instructions from a computer 8;
This deflection signal is sent to the deflector 5.6 via the DA converter 1-0.
is applied to The signal detected by the secondary electron detector 7 is amplified by the amplifier 11 and then sent to the AD converter 1.
2 into a digital signal and sent to the computer 8.
is supplied to The computer 8 further controls a driving means for driving the stage 13 on which the material 4 is placed,
It also receives a movement amount signal from a laser length measurement system 15 that monitors the movement amount of the stage.

The computer 8 obtains various data, and this data is supplied to the distortion memory 19 via the data memory 17 and the addition/subtraction section 18 via the interface 16. 20 is a correction calculation section.

The operation of the above-described configuration will be explained with reference to the flowchart shown in FIG.

■ The stage driving means 14 is driven by a command from the computer 8, and the cross mark provided on the material 4 is moved to the first position.
(see Fig. 4). At this time, when the stage is moved to the first position, the amount of movement of the stage is constantly monitored by the laser length measurement system 15, and the position of the mark after movement is accurately confirmed by the computer 8.

(2) After the mark position has been moved, the computer 8 controls the scanner 9 and sends a signal to the deflector 5.6 to deflect the ion beam to the first reference position 27 and scan the vicinity of the mark with the ion beam. The secondary electrons generated when the mark part is irradiated with the ion beam are sent to the detector 7.
The detected signal is detected by the amplifier 11°AD
The signal is supplied to the computer 8 via the converter 12, and the actual measured value of the center position of the mark based on the ion beam irradiation is determined in the computer 8.

(2) In the computer 8, the difference between the actual value of the mark position measured based on the secondary electron detection signal and a predetermined target position is determined, and the amount of distortion at that position P is determined. At the same time, the measurement time until this distortion amount measurement is measured. This measured amount of strain is stored in a position corresponding to position P of the strain memory 19.

(2) Determine whether the obtained distortion amount is due to the first position or the second or later position, and if it is the distortion amount due to the first position P1, hold the value in the memory inside the computer 8. In addition, when measuring the strain amount 0 times from P1 to P, judge whether the measurement is the nth time, and if it is not the nth time, repeat steps 1 to 3 to measure the strain amount at each position. measurement and storage of the amount of distortion in the memory 19.

(2) After completing all measurements of the amount of strain at positions p and -p, measure again at position P and find the amount of strain at that time.

■ First distortion measurement obtained in step ■, and step ■
Find the difference between the amount of distortion D m + at the same position P, found in . This difference is a drift due to the passage of measurement time, and this drift measurement. is stored in the data memory 17.

■ If this drift amount is not zero, the correction calculation unit 2
0, the drift amount at each n1 fixed position (m position) is calculated based on a predetermined calculation formula. This calculation formula is, for example, the following formula.

D, - (T, /”ro)xp.

Here, Tl11 is the time elapsed until measurement at each position, and To is the total strain measurement time.

■ The calculated drift amount at each position is sent to the distortion memory addition/subtraction unit 18, and is added or subtracted from the distortion amount H1 at each position stored in the distortion memory 19 to the drift amount calculated by the correction calculation unit 20. It will be done. The calculated results are stored again at each location in the distortion memory 19. At this stage, the distortion amount data stored in the distortion memory 19 has been corrected for the influence of drift. Furthermore, the computer 8 calculates the amount of distortion at fine positions between the n1 fixed positions from the distortion amount data of each measurement position P1 to P, in which the influence of drift has been corrected, by interpolation or the like, and calculates the amount of distortion at a predetermined value in the distortion memory. Store in position.

After measuring the distortion at each position in the field of the ion beam through these steps, the computer 8 controls the scanner 9 based on data from a memory (not shown) in which drawing data (not shown) is stored. Draw a pattern on the material. As a result, the pattern drawn on the material has distortions such as pincushion distortion removed, as well as the effects of drift, making it possible to draw the desired pattern with extremely high precision. can.

Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment. For example, although an ion beam lithography apparatus has been described as an example, the present invention can also be applied to an electron beam lithography apparatus. Furthermore, the shape of the mark may be L-shaped instead of cross-shaped, and although secondary electrons are detected for mark detection, secondary ions, reflected electrons, etc. may also be detected. Furthermore, the calculation formula for determining the amount of drift at each position is not limited to the above-mentioned formula. If the measurement time at each n1 fixed point is constant, the drift amount at the m-th n1 fixed point can also be determined by the following equation.

D # −D o / m (Effect of the invention) As explained in detail above, in the present invention, the amount of strain is measured twice at a specific measurement point, the amount of drift is determined from the results of these two measurements, and other Since the amount of drift at each n1 fixed point is determined from the relationship between the amount of drift at this specific point and the measurement time, and the amount of distortion is corrected based on each amount of drift, the influence of drift can be removed from the amount of distortion.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of an ion beam lithography apparatus for implementing a drift correction method that is an embodiment of the present invention;
FIG. 2 is a flowchart for explaining an embodiment of the present invention, and FIG. 3 is a flowchart for conventional strain measurement.
FIG. 4 is a diagram for explaining the movement of the mark position on the material.

Claims (1)

[Claims] Charged particles that focus a charged particle beam on a material and deflect the charged particle beam to move a charged particle beam irradiation point on the material to draw a desired pattern on the material. In the beam writing method, a stage is moved to sequentially move marks on the material to predetermined positions, and at each predetermined position, a charged particle beam is irradiated onto the mark position to detect the position, and this detected Step of calculating the amount of distortion at each position from the difference between the measured position of the mark and the target position of the mark. After calculating the amount of distortion at each predetermined position, move the stage to position the mark at the initial position. step, calculate the amount of distortion at the first position again, calculate the amount of drift from the amount of strain at the same position twice, calculate the amount of drift at each position from the amount of drift found, and adjust each position according to this amount of drift. A distortion correction method in a charged particle beam writing method comprising a step of correcting the amount of distortion at a position.