JPH04123418A - Electron beam lithography equipment and lithography process - Google Patents

Abstract

PURPOSE:To prevent deterioration in positional accuracy due to variable electromagnetic fields by providing a lithography equipment with an electron gun for measuring variable electromagnetic fields. CONSTITUTION:This invention is an electron beam lithography equipment comprising an electron gun 11 for measuring variable electromagnetic fields and an electron-position detector 13 in addition to a lithography electron gun 1: for example, the electron gun is a field emission type electron gun whose electron source is TiW. When electrons for measuring variable electromagnetic fields are kept detected by the detector 13, electromagnetic fields, if generated, other than those for deflection appear in the form of a positional deviation of an electron beam and can be sensed immediately. The intensity of electromagnetic fields can be estimated from the amount of positional deviation, and the distribution of intensity can be realized with a plurality of electron beams. Therefore, processing by estimation and correction of influences of these variable electromagnetic fields on lithography electron orbits allow high-accuracy electron beam lithography.

Description

[Detailed description of the invention]

[Industrial Application Field 1] The present invention relates to an electron beam lithography device and a lithography method using the same, and particularly to a lithography device suitable for highly accurate lithography. 2. Description of the Related Art An electron beam lithography system is a device that irradiates an electron beam onto a predetermined position on a wafer according to given data. The accuracy of the position is determined by the accuracy of the deflection, and the accuracy is improved by performing periodic calibration. However, since the deflection accuracy is measured only by drawing electrons, it is not possible to calibrate the deflection accuracy during drawing. Therefore, “Journal
Obvacuum Science Ant Technology (
Journal of Vcuumm 5science
and Technology) B7 (6), Nov.
,/Dec, 1989 P, 1532-P, 1535
J, etc., if an electromagnetic field different from the control electromagnetic field is generated during drawing, the accuracy of deflection decreases, causing a decrease in the positional accuracy of drawing.

Problem 1 to be Solved by the Invention An object of the present invention is to prevent the deterioration of position accuracy due to the above-mentioned fluctuating electromagnetic field. [Means for solving the problem 1] The above problem can be solved by providing the drawing apparatus with an electron gun for measuring a fluctuating electromagnetic field. [Operation] If electrons for measuring a fluctuating electromagnetic field are detected by a detector capable of position detection, if an electromagnetic field other than the deflection electromagnetic field is generated, it will appear as a shift in the position of the electron beam and can be detected immediately. Furthermore, it is possible to estimate the strength of the electromagnetic field from the amount of positional shift, and by using a plurality of electron beams, the strength distribution can be determined. Therefore, if the influence of this fluctuating electromagnetic field on the drawn electron trajectory is estimated and corrected before drawing, accurate electron beam drawing becomes possible. In particular, if the accelerating voltage of the measuring electrons is low, they will be affected by the fluctuating electromagnetic field more than the drawing electrons, so highly sensitive detection is possible. Furthermore, since electrons are affected by any electromagnetic field, it is possible to deal with not only the fluctuating electromagnetic fields generated within the device such as eddy currents and charge-up, but also the influence of leakage magnetic fields from outside the device.

【Example】

Example 1 FIG. 1 shows an example of the present invention. This is an electron beam drawing apparatus that includes an electron gun 1 for drawing, an electron gun 11 for measuring a fluctuating electromagnetic field, and an electron position detector 13. For example, the electron gun is a field emission (FE) type electron gun using TiW as an electron source. The accelerating voltage of the electron gun for drawing was 50 KV, and the accelerating voltage of the electron gun for I'l determination was 2 KV. A semiconductor device detector was used as a position detector. The measurement electrons are deflected by the leakage magnetic field of the objective lens, but since this is a constant magnetic field, it does not pose a problem in the measurement. First, use this device to perform step-and-repeat drawing. The material of the stage 12 is phosphor bronze. The stage moves at a maximum speed of 100 mm/see, and an eddy current is generated by a leakage magnetic field from an objective lens with an aperture diameter of 30 mm. Since the measuring electrons move horizontally at a distance of 1 mm above the wafer 11, if an eddy current is generated, the resulting magnetic field is felt and the trajectory is bent. A detector is installed at a location 200 mm away from the center of the lens to measure this trajectory change. At the above movement speed, the electrons showed a maximum position change of 2 mm on the detector. The magnetic field at this time is estimated to be about 0.5 G on average, and the 50 kV drawing electrons cause a positional shift of about 4 μm on the wafer. Since the positional resolution of the detector is 1 μm, it is possible to monitor positional deviations up to 1 nm on the wafer. In step-and-repeat drawing, drawing is not performed during movement, but it is necessary to wait until the eddy current subsides and the influence of the magnetic field on drawing can be ignored. FIG. 2 shows the detection positions of measurement electrons before and after the wafer is stopped. Oμsec is the time when the wafer stopped. It can be seen that in order to reduce the drawing position error on the wafer to 0.02 μm or less, a writing time of about 50 μsec is required even after the wafer stops. Example 2 When performing continuous movement writing using a similar stage, the measured magnetic field must be fed back to the deflector. For this purpose, six electron guns 14 and two detectors 16a and 16b were provided for measuring the rough distribution of the magnetic field on the stage shown in FIG. As a result, the electron beam is 2 m
It is possible to cover an m square field 15. In addition, in this example, in order to suppress the generation of eddy current, T
i is used as the stage material. FIG. 4 shows an example of the results of measuring the magnetic field generated during the movement of the stage. Although the amount of eddy current varies depending on the moving speed of the stage and the material of the substrate, in this example, since a T1 stage was used, the strength of the magnetic field is small, around 0.02G. Since the influence on the drawn electrons can be calculated from this magnetic field distribution, the amount of deflection can be controlled to cancel it. Figure 5 shows the case where the influence of eddy current is fed back (b)
This is the result of comparing the drawing position accuracy in the case (a) without the above. When no feedback was performed, a positional deviation of 0.25 μm occurred, but with feedback, it was possible to reduce it to 0.08 μm. Furthermore, in the case of constant velocity movement, the distribution of the magnetic field itself does not change, so it is possible to measure the intensity using only one electron gun and feed it back to drawing. Example 3 A 0.4 μm resist was applied to a Si wafer having a resistivity of 10 Ωam, and drawing was performed. At this time, contact resistance occurred between the wafer and the ground pin, so the wafer was slightly charged up. The measurement electrons are deflected by the electric field due to charge-up, and during writing, a positional shift of Q, Q3 mm occurs on the detection surface, and an electric field of 3000 (V/m) is generated at 1 mm above the wafer. I understand. Although the amount of positional deviation is small, sensitivity can be improved by moving the detector further apart or moving the electron trajectory closer to the wafer. This electric field disappears quickly as the electrons escape from the wafer, and
It is not observed after that. With this device, the exposure is 200nse.
Since the printing was performed with a gap between C, there was no effect on the actual drawing, and the drawing results were good. After 20 images were written using this drawing device, a defect occurred in the ground pin, the electric field due to charge-up increased, and the speed at which it disappeared slowed. This device is 200nse
If an electric field of 300 (V/m) remains even after C or more has elapsed, the next drawing waits until the electric field disappears, so the drawing time for the 20th wafer was doubled. but,
The drawing accuracy was good. On the 21st wafer, the ground pin contact became even worse, and the writing time was 500n.
sec was exceeded, so drawing was stopped midway. These things can prevent a drop in drawing accuracy due to charge-up. Example 4 As in Example 2, six electron guns were used. The remaining electric fields are measured by six electron guns and fed back to the drawing process. An example of the measured electric field is shown in FIG. The electric field is expanding around the location drawn just before. The electric field is very small, and the correction amount may be 0.02 μm. Example 5 The present invention is also effective against leakage magnetic fields from the outside. FIG. 7 shows the results of recording the detection positions of measurement electrons over time. Around 11 o'clock, the position suddenly changed dramatically. This is thought to be due to a magnetic field entering the device for some reason. Drawing was stopped when the positional shift of electrons exceeded 3 μm, and resumed 1 minute after the positional shift of electrons returned to within 3 μm. Example 6 As shown in FIG. 8, an electron beam (not shown) was passed from an electron gun 11 1 mm above the objective aperture 7. This makes it possible to measure the eddy currents on the aperture generated by the electromagnetic deflector. By detecting the positional shift on the detection surface 13, it was found that the time from the start of electromagnetic deflection until the magnetic field was no longer observed was approximately 200 μsec. Therefore, the settling time of this electromagnetic deflector is 250 μsec.
It was set as C. Effect of the Invention 1 As described above, by providing the electron gun for measuring a fluctuating electromagnetic field according to the present invention, it becomes possible to detect eddy currents and charge-ups that degrade the accuracy of electron beam lithography. By feeding that influence back to drawing, drawing accuracy can be greatly improved. This greatly contributes to improving the reliability and throughput of products manufactured using electron beam lithography equipment.

[Brief explanation of the drawing]

Fig. 1 is an apparatus configuration diagram for explaining Embodiment 1 of the present invention, Fig. 2 is a measurement diagram of the time dependence of the magnetic field of eddy current generated by stage movement, and Fig. 3 is illustrating Embodiment 2. Figure 4 is a diagram of the magnetic field distribution of eddy currents generated by stage movement; Figures 5 (a) and (b) are diagrams showing the improvement in position accuracy due to feedback of the fluctuating electromagnetic field, respectively; FIG. 6 is a distribution diagram of an electric field generated by charge-up, FIG. 7 is a diagram showing an example of It measurement of a leakage magnetic field from the outside, and FIG. 8 is an apparatus configuration diagram for explaining the sixth embodiment. Explanation of symbols 1... Electron gun for drawing, 2. First aperture, 3...
・Lens for molding transfer, 4... Deflector for molding transfer, 5...
2nd aperture, 6... Reduction lens, 7... Objective aperture, 8... Deflector for drawing, 9... Objective lens, 1
0... Wafer, 11... Measurement electron gun, 12...
Stage, 13...Electronic position checker, 14...Electron gun for measuring electromagnetic field distribution, 15...Drawing field, 16
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Claims (1)

[Claims] 1. An electron beam lithography apparatus having at least one electron gun for measuring the electromagnetic field in the orbit of the lithography electrons in addition to the lithography electron gun. 2. At least one electron gun provided in addition to the drawing electron gun for measuring the electromagnetic field in the trajectory of the drawing electrons measures an electromagnetic field other than the electromagnetic field that controls the drawing electrons, and controls drawing. An electron beam lithography method characterized by the following. 3. The electron beam drawing apparatus according to claim 1, wherein the acceleration voltage of the electron gun for measurement is lower than the acceleration voltage of the electron gun for drawing. 4. The electron beam lithography apparatus according to claim 1 or 3, wherein the electron beam emitted from the measurement electron gun passes between the wafer and an objective lens. 5. The electron beam drawing apparatus according to claim 1, wherein the electromagnetic field other than the electromagnetic field for controlling the drawn electrons is an electromagnetic field caused by charging. 6. The electron beam drawing apparatus according to claim 1, wherein the electromagnetic field other than the electromagnetic field for controlling the drawn electrons is an electromagnetic field generated by an eddy current caused by a deflection or dynamic correction electromagnetic coil. 7. The electron beam drawing apparatus according to claim 1, wherein the electromagnetic field other than the electromagnetic field for controlling the drawing electrons is an electromagnetic field caused by an eddy current generated as the stage moves. 8. Claim 1, wherein the electromagnetic field other than the electromagnetic field that controls the drawn electrons is a leakage magnetic field from outside the apparatus.
The electron beam lithography device described above. 9. The electron beam drawing apparatus according to claim 1, further comprising means for controlling the amount of deflection as the means for controlling the drawing electrons. 10. The electron beam lithography method according to claim 2, wherein the lithography control is control of the duration of lithography. 11. The electron beam drawing method according to claim 2, wherein the drawing control is to stop drawing. 12. The electron beam lithography according to any one of claims 1 or 3 to 8, characterized in that the electron beam lithography comprises a plurality of electron guns having different acceleration voltages as the electron guns for measuring the electromagnetic field in the trajectory of the lithography electrons. Device. 13. The electron beam lithography according to any one of claims 1, 3 to 8, and 12, characterized in that the electron gun for measuring the electromagnetic field in the trajectory of electrons for lithography includes an electron gun that does not expose the resist to light. Device.