JPS5866330A - Position correction method for electron beam drawing system - Google Patents

Abstract

PURPOSE:To contrive the improvement of the position accuracy of a lithographic pattern by a method wherein marks are provided at the reflector body structure of a laser measuring system mounted on a movable pedestral and a lithographed substrate and the marks are detected by electron beams at fixed time intervals for measurement and a variation in position is fed back to a control system for correction. CONSTITUTION:The position of a mark A1 on the face perpendicular to the face of a reflecting mirror 19 and that of a mark B1 on a lithographed substrate 12 are measured by the sum of the integral value of the doppler shift of a laser beam caused by moving pedestral to position C and the conversion value of the position of a beam deflection voltage. The mark A1 is provided with variation amounts delta1, deltac, epsilon caused by an optical axis position and electrical factor for the reflecting surface of the mirror and the B1 is provided with variations deltac and epsilon, and delta2 for the reflecting surface of the mirror. Each variation amount of variation factors can not be separated in each measurement and a plurality of variation amounts during measurement is mostly controlled by an independent factor. Now, when the partition wall of the device is strictly controlled at about 1/100 deg.C to measure the variation amount between B1 and A1 and the substrate position is corrected for the A1 at fixed intervals of 10-30min, variation to the lithographic position is controlled by only the variation amount deltac+epsilon of an electron optics system and pattern position accuracy of 0.2mum or less is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electron beam lithography, and its first purpose is to provide a reflector for a laser length measurement system attached to a movable stage that supports a substrate to be lithographically mounted. Marks are provided on the structure, and marks are also provided on the substrate to be drawn, and the positions of these two marks are detected at arbitrary intervals with an electron beam, and the positional fluctuations measured by a laser length measurement system are detected. The present invention provides a method for improving the positional accuracy of a drawn pattern by feeding back and correcting it to a control system. Furthermore, in the first and second steps, the positional fluctuation near the bottom end of the electron beam optical lens barrel is measured by another laser length measurement system, and the positional fluctuation values measured from the two mark positions are corrected. It also provides a method for dramatically improving the positional accuracy of patterns.

The method of the present invention will be explained below with reference to the drawings.

FIG. 1 is a side sectional view conceptually showing all the main parts of an electron beam lithography apparatus used in the present invention. 1 is the outer wall of the electron optical lens barrel, 2 is the upper wall of the drawing chamber, 3 is the drawing chamber base grate, 4 is an electron gun consisting of a filament and Wehnelt, 5 is a blanking electrode that controls the transmission and blocking of the beam to the electron optical system, 6 is con 7 / f L / 7 X', 7
C M small projection lens, 8 and 9 are deflection electrodes supported by the tube 1o, and 11 is a backscattered electron detector, which is supported by the tube 1o. Reference numeral 12 denotes a substrate to be drawn, such as a semiconductor substrate or a substrate serving as a photomask for a semiconductor, and 13 a metal cassette for holding all the substrates, which is held on a metal movable stage 14. The stage 14 is driven by a motor 15 and a feed screw 16, and the amount of movement thereof is measured by a well-known length measurement system such as a two-wavelength laser beam 17, an interferometer 18, a reflecting mirror 1951, etc. A change in the position of the mechanical optical axis of the electron optical system is detected by another laser interferometer 21 and a reflecting mirror 22 fixed to the cabinet 1o.

Figure 2 is a plan view conceptually explaining the position measurement system.
Laser beams 23, 25 and laser interferometers 24, 28, which have an increased dimension, are added compared to FIG. 1. The electron beam lithography system shown in FIG. 1 is capable of measuring two-dimensional positional movement. In the electron beam writing system, the main parts of the electron optical system, stage movement, and its length measurement system mentioned above are all controlled by a computer system, and the stage movement and electron beam blanking/deflection are performed according to pattern data prepared in advance. It is used to draw by combining.

However, in an actual device, there are usually mechanical positional changes due to temperature changes in the main parts shown in FIG. 1, and positional changes of the beam optical axis due to electrical changes in the electron optical system. The present invention provides a novel method for detecting these fluctuations and correcting errors associated with the fluctuations.

In FIG. 2, 1j is an electron beam detection mark formed on a surface that makes an angle of 90 degrees with the reflecting surface of the laser beam reflecting mirror 190, and B1 is an electron beam detection mark formed on the surface of the substrate 12 to be drawn. It is.

The zero point is the position where the optical axis of the electron beam optical system (when the deflection electrode voltages are zero in both two-dimensional directions) intersects the surface of the substrate 12 to be imaged. That is, the position of M1°B1 is
The sum of the integral value of the Doppler shift of the laser beam when those marks are moved near C by the stage movement operation, and the position displacement value of the deflection voltage detected when the mark is scanned by the changing electron beam. (or difference).

Regarding the irregularity mark, the fluctuation factor δ1 of the mark with respect to the reflecting surface of the reflecting mirror and the position of the optical axis of the electron optical system are factors contributing to the fluctuation of the fillet over time, which is the value measured in this way. The amount of variation δ due to mechanical causes. and a variation amount ε based on electrical causes. Regarding B1 mark,
It consists of an amount δ2 that varies with respect to the light reflecting surface of the electron optical system.

Further, regarding the distance between the marks A1 and 81, therefore, both the fluctuation amounts of δ1 and B2 are related to each other.

The problem when attempting to correct the drawing pattern position by measuring these fluctuation amounts is that it is difficult to separate each fluctuation amount among the above fluctuation factors in each measurement, and that multiple fluctuations included in one measurement are difficult to separate. The reason is that the amount of variation in is controlled by almost independent factors. Therefore, in order to perform higher-precision correction, one measure is to extremely shorten the measurement time interval, but this is not practical as it would reduce the production capacity of the drawing equipment. , and it doesn't make much sense.

The present invention suppresses related conditions so that each of the above-mentioned fluctuation factors is as small as possible, and performs highly accurate correction without practically reducing the production capacity of the drawing apparatus.

The walls of the electron beam lithography equipment must be kept strictly at
If the temperature is controlled (to a certain degree), the upper wall 2 of the drawing chamber of the first illustration device
It can be expected that the variation δC of the markum 1 that occurs during a normal drawing operation period, that is, a period of about 10 to 30 minutes, can be suppressed to about 0.1 μm. Also, within this period,
It can be expected that the amount of variation ε can also be suppressed to about 0.1 μm.

It is almost impossible to control fluctuations due to temperature factors of the stage 14 due to the movement of the metal stage and fluctuations due to temperature factors of the metal cassette 13 from outside the drawing room.
Furthermore, it must be assumed that the fulcrum at which the cassette 13 is held on the stage 14 changes each time the cassette is replaced. Therefore, the variation amount δ2 of the mark B1 is normally
It can be about 0.1 μm or more. Regarding the amount of variation δ in the position of markum 1 attached to the reflecting mirror structure, the amount of variation δ1 is so small that it can be ignored since the reflecting mirror is usually made of hard glass.

To summarize the above, in the present invention, the electron beam detection Markum 1f! :Attach mark B1 on the substrate to be drawn, and measure the distance between M1 above M1.
The substrate position relative to i within about 10 to 30 minutes is corrected at fixed time intervals, so by strictly controlling the temperature of the outer wall of the electron beam lithography system as described above, fluctuations in the lithography position can be reduced. , it is only controlled by the amount of variation (δC+ε) of the electron optical system. Therefore, according to the method of the present invention, a pattern position accuracy of 0.2 μI11 or less can be obtained.

On the other hand, as conventionally practiced, a Faraday tube with a wire number mark for electron beam detection is installed near the position above the stage 13 in FIG. 2, for example, to detect the position D.・With a method of correcting the position of the drawn pattern only by correction, it is possible to ignore fluctuations of 0.1 μm or more in the interval between the position on the stage 13 and the reflecting surface of the reflecting mirror over a time interval of 10 to 30 minutes. Also, the amount of substrate 12 relative to the position on the stage is
Since the variation in position is a non-negligible amount of 91 μm or more, the pattern position accuracy in this method is 10.

was over 0.2 μm. Therefore, in order to improve accuracy, it is necessary to shorten the measurement time interval, take measures to control the chamber wall temperature, take measures to stabilize the stage temperature, and take strict measures from other aspects. Measures are required.

On the other hand, a separate 10-minute to 3-minute
There is also a method of detecting and correcting only the positional fluctuation of mark B1 at time intervals of about 0 minutes, but even with this method, the above-mentioned inseparable fluctuation amounts of δC1ε and δ2 as well as δ1. B
Since we are dealing with an inseparable variation amount of 2, the actual situation is that within the above time range, it is inevitable that an error exceeding at least 0.2 .mu.iaf will be involved, which cannot be ignored.

Therefore, it is clear that the method of the present invention is superior to the conventional method described above.

The second method of the present invention is to provide, in addition to the stage length measurement system, a length measurement system for detecting positional fluctuations near the bottom end of the electron beam column, as shown in FIGS. 1 and 2. be.

A reflecting mirror 22 attached to the tube 1o at the bottom end of the lens barrel. Interferometer 2
1.26, this is done, and the variable element δC or the amount correlated thereto is detected. What remains of the amount of variation in system 1 is δ1, which is negligibly small, and ε, which is normally impossible to measure.

Therefore, 1. Only in this way can ε be clearly measured and corrected. The measurement and correction of the B1 position with respect to the B1 position are as described above.Therefore, according to the second method of the present invention, the outer wall temperature of the drawing device is loosely controlled to about 0.1°C to 0.2°C. However, the drawing pattern position accuracy is 0.
．． It can be kept at about 1 μm or less.

In the above explanation, errors due to quantum noise in the measurement system, the production/failing of detection marks, etc. have been omitted as common problems. Further, the present invention is not applicable to the case where drawing is performed based on a large number of marks arranged at regular intervals on the substrate to be drawn, that is, the case of so-called direct drawing of a semiconductor crystal substrate.

However, in order to perform such a drawing method, the above-mentioned large number of marks cannot be made on the substrate.

In applying the present invention, instead of forming the mark 1 to be added to the reflecting mirror directly on a surface that makes a 90 degree angle with the reflecting surface of the reflecting mirror, for example, the mark 1 is formed by vacuum deposition and photoetching on another thin glass plate. A cross-shaped or L-shaped mark is entirely formed using a gold double film, and this mark substrate is attached to the side surface of the reflector. is the most practical. In addition, the darning mark substrate is made by photo-etching a plate with a low expansion coefficient such as silicon into a cross shape or L shape with a depth of about 1 μm.
You can also form a letter-shaped mark and paste it on the side of the reflector in the same way. Further, as shown in FIG. 2, the mark substrate 27t may be extended to cover a part of the surface of the stage 14, and the mark 2 may be provided on this extended portion. In this way, the amount of movement of the stage 14 for detecting the markum 1 is small, and as a result, the distance between the laser interferometers 18 and 21 and the distance between 24 and 26 can be widened. Convenience will be provided. It goes without saying that the mark substrate requires conduction a as shown in FIG. 28 in order to allow current to flow out.

In Fig. 2, the reflecting mirror 19, which is an element of the laser length measurement system, is 2
Although it has an L-shape so that only one piece is required in the dimensional direction, the groove may be divided into two pieces. In that case, a mark must be added to each reflector. Two or more marks corresponding to M1 or M2 may be added in any case. In this case, it is also possible to measure the inclination of the reflecting mirror in the horizontal plane over time by measuring two or more marks, and to correct errors in position measurement due to this inclination. This is usually a secondary correction and should be taken into account when its amount is large.

When the substrate 12 is a so-called hard mask substrate in which a thin film of chromium or chromium and chromium oxide is deposited on a glass plate, a cross-shaped or L-shaped mark is formed in advance by photo-etching or other method. It has been confirmed that if the mask substrate is provided directly on the mask substrate, it is possible to detect the mark using backward scattered electrons, and there is no need to form another heavy metal film mark. Furthermore, as described above with respect to Markum 2, the mark substrate piece 29 provided with another mark B2 y2 can be temporarily pressed against the substrate 12 and used in place of B1.

If the substrate to be drawn is a semiconductor wafer, the marks Ihf may be formed directly on the substrate in advance by photoetching or other methods.

Two or more Bli or B2'i may also be provided.

Furthermore, by detecting these relative fluctuation amounts, the rotational fluctuation amount of the substrate can also be found, and thereby it is also possible to recognize instability in the holding between the substrate and the cassette or between the cassette and the stage.

The horizontal plane of the electron beam detection mark described above may be designed to be within the focal depth of the electron beam and within the same plane as the substrate to be drawn, but only the surface of a specific mark can be specified from the surface of the substrate to be drawn. If the focus is automatically adjusted even if the focus is shifted within a distance of

In the above explanation, the shape of the electron beam was not mentioned, but the shape of the electron beam is a spot beam, a fixed rectangle 16, etc.

Since the shape and dimensions of the beam are controlled in the system, whether it is a shaped beam or a variable area beam, there is no problem in applying the method of the present invention to either beam shape.

As explained in detail above, the present invention provides a new method for uniformly improving the writing position accuracy in an electron beam lithography system, and it is clear that the present invention has certain industrial significance. it is obvious.

[Brief explanation of the drawing]

FIG. 1 is a conceptual cross-sectional view showing the main parts of an electron beam lithography system used in a method according to an embodiment of the present invention, and FIG. 2 is a conceptual plan view showing a position measuring system of the same system. 1.2.3...Electron beam lithography device wall, 12
...Drawing substrate, 13...Metal cassette, 14...Metal stage, 16...
...Feed screw, 17゜20.23.26...2
Wavelength laser beam, 18°21.24.26...
・Interferometer, 19.22...Reflector, 27.29
・・・・・・Small board for mark, 1. M2゜Bl, B2
・・・・・・Electron beam detection mark, 0・・・・・・
Electron optical system optical axis position, D...- Faraday cup position. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure, 2 FigurezzIθ

Claims (1)

[Claims] (1) In order to measure the position of a movable stage that supports a substrate to be drawn, at least one electron beam is applied to a reflecting mirror structure for a two-dimensional laser length measurement system attached to the stage. a detection mark, and at least one mark for electron beam detection is provided on the substrate to be drawn, and the positions of these marks are detected by the electron beam at arbitrary approximately constant time intervals; A method for correcting the position of an electron beam writing system, characterized in that positional fluctuations measured by a laser length measurement system are corrected by being fed back to a substrate position control system. ? ) A small substrate with a low expansion coefficient for marks provided with at least one electron beam detection mark is fixed to the two-dimensional laser length measurement system reflecting mirror structure mounted on the stage. 2. A position correction method for a 2-1° electron beam drawing system according to claim 1, characterized in that a mark is used. (3) A small substrate with a low expansion coefficient for marks provided with at least one electron beam detection mark is temporarily fixed to the substrate adjacent to the substrate to be drawn, and the mark is used. A method for correcting the position of an electron beam writing system according to claim 1. (Two marks for electron beam detection are provided on the reflector for the 42-dimensional laser length measurement light, and two marks for electron beam detection are provided on the substrate to be drawn, and the former allows the detection of the two-dimensional laser length measurement system. 2. A position correction method for an electron beam lithography system according to claim 1, characterized in that variations in the surface angle are corrected, and the mechanical stability of the substrate to be drawn and the cassette holding the same is completely monitored by the latter. (6) At least one electron beam detection unit is installed in the first two-dimensional laser length measurement system reflector structure mounted on the movable stage that supports the substrate to be drawn. At least one mark for detecting the electron beam is provided on the substrate to be drawn, and a reflecting mirror is attached to the tube for the electron optical optical axis of the electron beam. A second two-dimensional laser length measurement system for measuring the position of the cylinder part is provided, and each mark position is detected by an electron beam at arbitrary approximately constant time intervals, and the first and second laser length measurement systems A position correction method for an electron beam lithography system, characterized in that position fluctuations measured by the above are corrected by feeding them back to an all-substrate position control system.