JP3296807B2 - Electron beam drawing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam lithography system having a plurality of deflectors having different deflection areas and deflection sensitivities for performing high-speed drawing. The present invention relates to an electron beam lithography apparatus capable of simultaneously having a high-precision drawing mode for performing an alignment mark and detecting a position of a registration mark with high accuracy.

[0002]

2. Description of the Related Art As semiconductor devices are miniaturized, semiconductor manufacturing apparatuses for forming fine patterns, particularly lithography apparatuses, are shifting from i-line steppers to excimer laser steppers or scanning steppers thereof. These lithography systems have advantages such as high device throughput and process technology that is an extension of the conventional technology.However, peripheral technologies such as process and mask manufacturing, which are approaching the fundamental resolution limit, are becoming complicated. However, there is a problem that the yield and the overall throughput are reduced.

Therefore, a so-called direct-drawing electron beam lithography apparatus that directly forms a pattern on a wafer with an electron beam having a high resolution without using a mask has attracted attention.

[0004] However, since the apparatus throughput is lower than that of the stepper, in recent years, the use of the stepper and the electron beam lithography apparatus, that is, device manufacturing by so-called mix-and-match has become mainstream. Under such circumstances, the electron beam lithography apparatus is required to further improve the throughput, resolution, and alignment accuracy. Conventionally, various countermeasures have been devised to meet these requirements. For example, a multi-stage deflection electron beam lithography system that has multiple stages of deflectors for deflecting an electron beam and deflects a beam over a wide area at high speed, or a pattern that is repeatedly exposed, is extracted, and a beam formed in this pattern shape is used. Various measures such as improving the throughput by using the batch transfer exposure method for batch exposure, etc., and improving the resolution by increasing the acceleration voltage and current density of the electron gun that generates the electron source, etc. We are responding elaborately.

[0005] However, as the miniaturization of semiconductor devices progresses and the accuracy of a minimum line width of 0.2 micrometers or less is required today, the influence of beam fluctuation due to noise has become a very serious problem. I have. Factors causing the beam fluctuation are roughly classified into mechanical vibration, influence of external disturbance (magnetic field or the like), and electric noise superimposed on the deflector itself. Mechanical vibration is suppressed by vibration isolation stand and reinforcement of housing strength, etc., and the influence of external disturbance is eliminated by mounting a magnetic field shield and equipment in a shield chamber.Furthermore, beam fluctuation is fed back to deflection data. Although some measures have been taken such as canceling out, there is no way to eliminate the influence of noise superimposed on the deflector itself. In addition, various filter functions and detection algorithms have been devised in order to increase the detection accuracy of the alignment mark detection in order to improve the alignment accuracy. However, these methods cannot avoid deterioration of the detection accuracy due to beam fluctuation. . Currently, multi-stage deflection electron beam lithography systems with multiple stages of deflectors are the mainstream, but the noise components and amounts differ for each deflector and the analog element that drives it, and the largest one is the device. Final performance.

[0006]

As described above, in an electron beam lithography system which draws a wide area at high speed while changing a deflection area and a plurality of deflectors having different deflection sensitivities, a deflector and the same are used. The noise components and amounts differ for each driving amplifier and control circuit, and the largest one among them determines the final performance of the device. Also, in mark detection that does not need to deflect a wide area, beam deflection is performed using the same plurality of deflectors, so that detection accuracy is inevitably degraded due to beam fluctuation.

An object of the present invention is to provide an electron beam lithography apparatus having a plurality of stages of deflectors, having both a high-speed drawing mode for performing high-speed drawing and a high-precision drawing mode for performing high-precision drawing. An object of the present invention is to provide an electron beam lithography apparatus suitable for realizing high-accuracy mark detection by eliminating harmful noise to be superimposed.

[0008]

In order to achieve the above object, the fluctuation of a beam caused by noise superimposed on each of the plurality of stages of deflectors is measured and evaluated, and an arbitrary deflector on which harmful noise is superimposed is measured. The deflection data may be forcibly invalidated and separated, and writing and mark detection may be performed while reducing the beam fluctuation due to noise.

In an electron beam lithography system having a plurality of deflectors having different deflection ranges and deflection sensitivities, beam fluctuation due to noise superimposed on each of the plurality of deflectors is measured and evaluated, and a relatively high accuracy is obtained. For the drawing of layers that are not required, all deflectors are used to perform high-speed drawing by deflecting a wide area at high speed with an electron beam.For the drawing of critical layers that require precision, deflection with harmful noise is used. High-speed writing and high-accuracy writing can be realized by a single apparatus by forcibly separating the deflection data of the image forming apparatus, invalidating the data, and reducing the fluctuation of the beam caused by noise. Furthermore, in mark detection that does not need to deflect a beam over a wide area, if the decoupling mark detection is performed by forcibly invalidating the deflection data of the deflector that does not need to be deflected, the accuracy degradation due to beam deflection noise is eliminated. Accurate mark detection can be realized.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic view showing an example of an electron beam lithography apparatus most suitable for realizing the present invention.

An electron beam 10 emitted from an electron beam source 101
2 is transmitted through the first shaping aperture 103, is imaged by the shaping lens 104 on the second shaping aperture 106 at the lower stage, and the beam irradiation position on the second shaping aperture is controlled by the shaping deflector 105. The shaping beam formed by the two-stage shaping aperture is reduced by the reduction lens 107 and is imaged on the sample surface by the objective lens 109. The rotation of the exposure shot is corrected by a rotation correction lens 108, and the beam irradiation position on the sample surface is adjusted by an electromagnetic deflector 110 having a deflection range of about 5 mm, a large-angle electrostatic deflector 111 having a deflection range of about 500 μm, and an about 80 μm Are deflected by the three-stage beam irradiation positioning deflector of the high-speed electrostatic deflector 112 having the deflection range of Electron optical means including these deflectors are controlled by a drawing control means 117, and a control computer 121 scans the drawing control means 117 and a mark on a wafer or a sample table via a data bus 122 with an electron beam. The reflected electrons generated at this time are detected by the reflected electron detector 113, and the signal processing means 116 for detecting the mark position based on the detection signal and the stage control means 115 for moving the sample stage 114 to the beam irradiation position are collectively controlled.

The drawing control means 117 includes an alignment correction unit 11
8, including a deflection control unit 119 and an absolute calibration unit 120, the position of the standard mark on the stage 114 and the position of the alignment mark on the wafer are detected by the signal processing means 116, and the result is transmitted from the control computer 121 to the data bus 122 via the data bus 122. The reading, the deflection distortion of each deflector, the beam shape and the distortion of the pattern of the previous layer exposed on the wafer are calculated, and the correction coefficient is calculated and passed to the alignment correction unit 118 and the absolute calibration unit 120.
The alignment correction unit 118 receives alignment correction to the wafer shape in shot figure units, and the deflection control unit 119 converts it into a deflection amount.
Finally, after the deflection amount is calibrated by the absolute calibrating unit 120, analog conversion is performed to control the electron beam mirror to expose a desired pattern on the wafer.

Here, the deflector selection circuit 123 which is a feature of the present invention is a means for forcibly invalidating the deflection data of an arbitrary deflector and disconnecting the deflector from the electron beam. Can be switched between the deflector and a dummy load outside the electron beam mirror by a switch or the like, so that the influence of noise due to the amplifier and the control circuit for driving the deflector can be completely completely separated from the deflector. .

FIG. 2 is a schematic diagram showing a simple circuit example of the deflector selection circuit 123. In this figure, the flow of the deflector selection control process will be described by taking the electromagnetic deflector 110 in the above-described three-stage positioning deflector of the electron beam drawing apparatus as an example. The deflection data of each deflector is converted from the figure pattern data to be exposed into a deflection amount to be given to each deflector by the deflection control unit 119 and is absolutely calibrated by the absolute calibrating unit 120 before being given to each deflector. . In normal drawing, the electromagnetic deflection data 20
1 is passed to a D / A converter 206 and is converted into analog data corresponding to the deflection amount, and then converted to analog data.
The electron beam 102 is input to the electromagnetic deflector 110 via the control unit 5 to control the deflection of the electron beam 102. When the deflection data of the electromagnetic deflector is forcibly invalidated, since the electromagnetic deflector is a deflector that deflects the widest area in the three-stage deflection described above, the deflection control unit 119 controls each deflector. When the deflection amount of the electromagnetic deflector is calculated, the deflection area of the electromagnetic deflector is set to 0 μm.
01 is passed to the D / A converter 206 as 0 μm.

However, even if the deflection data is 0 .mu.m, the electron beam 102 is minutely deflected by noise superimposed on the control circuit for controlling the deflection data of the electromagnetic deflection and the electromagnetic deflection amplifier 205, causing deterioration in accuracy. I will.

Therefore, the deflector selection switch 202
By completely electrically disconnecting the output of the electromagnetic deflection amplifier 205 from the electromagnetic deflector 110, the beam fluctuation due to this noise is eliminated. At this time, the electromagnetic deflection amplifier 20
5 is connected to the dummy load 203, and the deflection amplifier 20
5 protects. The large-angle electrostatic deflector 111 and the high-speed electrostatic deflector 112 are also electrically separated from the amplifier and the control circuit for driving the deflector by the same means to eliminate the beam fluctuation caused by noise superimposed on each deflector. Accuracy can be improved. According to another aspect of the present invention, deflection data to be given to a deflector that forcibly invalidates deflection data is supplied to a deflection controller 11.
When the deflection amount of each deflector is calculated in step 9, instead of calculating the deflection area of the deflector as 0 μm, for example, when only the large-angle electrostatic deflector 111 is separated, the deflection is performed in the same manner as in normal drawing. Large angle electrostatic deflection data 208 by the control unit 119
Is calculated, and the deflection data input to the D / A converter 209 is passed as non-deflection data by the deflection data selection switch. After the D / A converter, the above-described electromagnetic deflector 1
As in the case of 10, the deflector and the deflection amplifier for driving the deflector are completely electrically disconnected by the deflector selection switch.
At this time, the large-angle electrostatic deflection data 208 converted into a deflection amount to be given to the large-angle electrostatic deflector 111 is added to the electromagnetic deflection data 201 by an adder 210 via a deflection data addition switch 208. Then, the deflection amount of the large-angle electrostatic deflector 111 in which the deflection data is forcibly invalidated is deflected by the electromagnetic deflector 110. There is also provided means for automatically adding the deflection data of the deflector for which the deflection data has been forcibly invalidated to the deflection data of the deflector having a wider deflection area to perform drawing.

As described above, there is provided a means for forcibly invalidating the deflection data of an arbitrary deflector, which is a feature of the present invention, and for electrically disconnecting the deflector from the amplifier and the control circuit for driving the deflector. The processing flow of the present invention in the electron beam lithography apparatus described above will be described below.

In an electron beam lithography system having a plurality of deflectors, means for automatically measuring and evaluating beam fluctuation due to noise superimposed on an amplifier for driving the deflectors and a control circuit for each deflector is conventionally used. However, it does not have to measure and evaluate the overall noise of all deflectors. According to an aspect of the present invention, there is provided a means for automatically measuring and evaluating a beam noise amount for each deflector in a multi-stage deflection electron beam writing apparatus.

FIG. 3 is a flowchart showing the flow of processing at the time of superposition drawing in the electron beam drawing apparatus of the present invention. According to the present invention, in a multi-stage deflection electron beam lithography system having a plurality of deflectors, one electron beam lithography system has both a high-speed lithography mode for performing high-speed lithography and a high-precision lithography mode for performing higher-precision lithography. Step 30
In step 1, whether or not to perform high-precision drawing is selected.

The processing when the high-precision drawing mode is selected will be described below.

In order to perform high-precision writing, first, it is necessary to measure and evaluate beam fluctuation caused by noise superimposed on each deflector. In step 302, the reference mark prepared on the stage is detected, and the position of the edge of the mark is calculated. Next, in step 303, any one of the plurality of deflectors is selected, and the other deflectors are separated by the deflector selection circuit 123. Then, in step 304, in step 302 The stage is moved to the measured edge position of the reference mark, and the mark edge is irradiated with a beam. At step 305, the fluctuation of the beam by the deflector selected at step 303 is measured from the reflected electron signal generated at this time. The fluctuation of the beam is calculated by calculating the beam size when the reference mark is detected in step 302, and the signal intensity of the reflected electrons at the position where the beam completely deviates from the mark and the position where the beam is completely irradiated on the mark. If this is done, it can be easily calculated from the signal intensity change of the reflected electrons when the mark edge is irradiated with the beam in step 304. Similarly, the processing of steps 303 to 305 is repeated until the measurement of all the deflectors is completed in step 306. In this way, the fluctuation of each beam of the plurality of deflectors is measured, and the result is displayed on the CRT screen in step 307.

Step 308 is a step of selecting a deflector that forcibly invalidates the deflection data among the plurality of stages of deflectors from the above-described noise measurement results. Calculate the minimum value,
The noise of each deflector in the noise measurement result screen 315 displayed on the CRT screen in Steps 309 and 307 in which the deflector on which noise equal to or higher than the threshold is superimposed is automatically cut off as compared with an arbitrarily set threshold. From information 316, C
There are provided two selection means in step 310 for arbitrarily selecting a deflector for which the deflection data is invalidated by the deflector selection switch 317 on the RT screen. After selecting a deflector that forcibly invalidates the deflection data in step 308, superimposition writing is performed. In order to perform superimposition writing in accordance with the pattern shape exposed on the previous layer, It is necessary to detect the overlay mark exposed around the chip of the preceding layer and measure the shape of the preceding layer pattern. Here, the size of the alignment mark is about several μm, and the alignment mark detection is performed by so-called step-and-repeat detection in which the stage is moved to the mark position and then beam scanning is repeated for detection. Therefore, the beam deflection at the time of detecting the mark is only required to be able to deflect in a range of about 10 to 30 μm. Therefore, in step 311, only the lowest deflector capable of deflecting the narrow range at the highest speed is selected, and the other deflectors forcibly invalidate the deflection data and eliminate the influence of unnecessary deflector noises. At 312, the registration mark is detected. Thereafter, in step 313, switching to the deflector arbitrarily selected in step 308 is performed, and in step 314, overlay drawing on the previous layer is performed, whereby drawing in the high-precision drawing mode can be performed.

When the high-speed drawing mode is selected in step 301, if the processing after step 311 is performed without performing noise measurement for each deflector, high-speed drawing is performed while performing highly accurate mark detection. I can do it.

As described above, in a multi-stage deflection electron beam lithography system having a plurality of stages of deflectors, deflection data of an arbitrary deflector is forcibly invalidated, and a deflector and an amplifier and a control circuit for driving the deflector are driven. Is provided with means for completely electrically disconnecting each other, and if drawing is performed by selecting an appropriate deflector arbitrarily for each required accuracy of the drawing and mark detection or drawing device, one electron beam drawing apparatus can be used. It has both a high-speed drawing mode for high-speed drawing and a high-accuracy drawing mode for high-precision drawing, and can perform high-precision mark detection while eliminating the effects of beam fluctuations due to noise superimposed on the deflector. .

The present invention further includes the following configuration.

(1) In the electron beam lithography apparatus according to the first aspect, deflection data to be given to the deflector whose deflection data has been forcibly invalidated is added to deflection data of another deflector having a wider deflection area. An electron beam drawing apparatus characterized by having a function.

(2) In the electron beam lithography apparatus according to the first aspect, the deflection data of an arbitrary deflector is forcibly invalidated and separated, and the electron beam due to a noise component superimposed on an amplifier for driving the deflector and a control circuit is separated. Eliminate fluctuations,
An electron beam drawing apparatus having a high-precision drawing mode for performing drawing with high precision.

(3) In the electron beam lithography apparatus according to the first aspect, when performing mark detection for detecting the mark position by scanning the mark with an electron beam, the deflection data of an arbitrary deflector is forcibly invalidated. An electron beam writing apparatus characterized in that a high-precision mark detection is performed by eliminating a fluctuation of an electron beam due to a noise component superimposed on an amplifier and a control circuit for driving the deflector.

(4) In the electron beam lithography apparatus according to claim 1, the lowermost deflector deflects a narrow area at the highest speed when detecting a mark by scanning the mark with an electron beam. The deflection data of all the deflectors other than the above is forcibly invalidated and separated, and the fluctuation of the electron beam due to the noise component superimposed on the amplifier and the control circuit for driving the deflector is eliminated, thereby performing highly accurate mark detection. Characteristic electron beam lithography system.

(5) In the electron beam lithography apparatus according to the first aspect, deflection data other than any one of the deflectors is forcibly invalidated and separated, and fluctuation of the electron beam caused by the arbitrary deflector is measured. An electron beam lithography apparatus having a function of evaluating beam noise by each deflector.

(6) In the electron beam lithography apparatus according to claim 1, the fluctuation of the electron beam caused by each of the plurality of deflectors is measured, and an arbitrarily set threshold value and the fluctuation of the electron beam fluctuation are measured. An electron beam lithography apparatus comprising means for automatically selecting a deflector for forcibly invalidating and separating deflection data from measurement results.

(7) In the electron beam lithography apparatus according to claim 1, the fluctuation of the electron beam caused by each of the plurality of deflectors is measured, and the measurement result is displayed on a CRT screen. An electron beam lithography apparatus having a function of arbitrarily selecting, on a CRT screen, a deflector that forcibly invalidates and separates data.

[0034]

According to the present invention, a high-precision drawing mode for performing high-precision drawing and a high-precision drawing mode for performing high-speed drawing, which eliminates beam fluctuation caused by noise superimposed on the deflector, are provided. The present invention provides a multi-stage deflection electron beam writing apparatus suitable for performing high-accuracy mark detection while eliminating beam fluctuations due to noise superimposed on the electron beam.

[Brief description of the drawings]

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

FIG. 2 is a schematic configuration diagram of a deflector selection circuit.

FIG. 3 is an explanatory diagram of a process of the present invention.

[Explanation of symbols]

101: electron beam source, 102: electron beam, 103: first shaping aperture, 104: shaping lens, 105: shaping deflector, 106: second shaping aperture, 107: reduction lens, 108: rotation correction lens, 109: objective Lens, 1
10 electromagnetic deflector, 111 large-angle electrostatic deflector, 112
High-speed electrostatic deflector, 113 ... backscattered electron detector, 114 ... stage, 115 ... stage control means, 116 ... signal processing means, 117 ... drawing control means, 118 ... alignment correction unit, 1
19: deflection control unit, 120: absolute calibration unit, 121: control computer, 122: data bus, 123: deflector selection circuit, 201: electromagnetic deflection data, 202: deflector selection switch, 203: pseudo load, 204: deflection Data selection switch, 205: deflection amplifier, 206: D / A converter, 207: deflection data addition switch, 208: large-angle electrostatic deflection data, 209: D / A converter, 210: adder, 315: noise measurement result screen, 316: deflector noise information, 317: deflector selection switch.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-9-237747 (JP, A) JP-A-61-95520 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/027 G03F 7/20 504

Claims (1)

(57) [Claims] 1. An electron beam source for generating an electron beam, electron optical means for projecting an electron beam from the electron beam source onto a sample surface of a sample to draw a pattern, and applying the electron beam to the sample surface. A deflection area when scanning, and a plurality of deflectors having different deflection sensitivities, electron beam deflection control means for controlling the deflector, and reflected electrons generated when the electron beam is projected onto the sample surface or A detector for detecting secondary electrons, signal processing means for performing arithmetic processing on a detection signal from the detector, and stage control means for controlling a stage on which the sample is placed and moved with respect to the electron optical means, A data control means for performing drawing control based on pattern data of a pattern to be drawn on the sample surface; and a collective control of the electron optical means, deflection control means, signal processing means, stage control means, and data control means. High-speed drawing mode for high-speed drawing and high-precision drawing
Combined with high-precision drawing mode, each of the multiple stages
Measurement and evaluation of beam fluctuation due to noise superimposed on the detector
An electron beam lithography system having means for forcibly invalidating deflection data of an arbitrary deflector on which harmful noise is superimposed and electrically disconnecting the deflector from an amplifier and a control circuit for driving the deflector. apparatus.