JPH0328049B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron beam exposure method, and more particularly to an electron beam exposure method in which exposure is performed using alignment marks formed on a wafer.

In conventional electron beam exposure methods, an object to be irradiated, such as a wafer, is generally exposed by using an electron beam emitted from an electron gun through a focusing and deflecting lens system.

To explain in detail about FIG. 1, the electron beam 2 emitted from the electron gun 1 is transmitted to the beam blanking coil 3.
After passing through the first, second, and third condenser lenses 4, 5, and 6 for focusing, and passing through the aperture of the final lens 7, the electron beam 2 is deflected by a deflection lens system 8 such as a deflection coil. An object 9 is irradiated with an electron beam.

Furthermore, the input signal 12 of the teletype etc. is input to the computer 1.
3, and the control signal from the scan control unit 14 controlled by the computer is sent to the blanking circuit 15.
In addition, a blanking pulse from the blanking circuit is applied to the beam blanking coil 3. Further, a sawtooth wave is applied to the deflection amplifier 16 in the deflection coil 8 to deflect the electron beam 2.

Furthermore, the output from the computer 13 is sent to the motor drive circuit 1.
7, a motor such as a pulse motor 18 is driven to move the mounting table on which the object 9 to be irradiated is placed.

When the object 9 to be irradiated is a wafer, there is a limit to the area that can be exposed when a resist coated on the wafer is exposed to an electron beam, so marks 20 are usually attached to each chip 19 as shown in FIG. By detecting these chip marks, signals regarding the chip position and rotation were fed back to the electron beam scanning system.

In this way, the positional and rotational deviations of the chips on the wafer 9 have been corrected. However, with this configuration, it is necessary to mark each chip, which not only makes it impossible to achieve high integration, but also makes it difficult to Since the position is detected, the detection time is long.

The present invention provides an electron beam lightning method that eliminates the above-mentioned drawbacks, and its purpose is to add alignment marks at five locations on a wafer without performing alignment processing for each chip. The purpose of this invention is to provide an electron beam exposure method in which alignment is performed using .

An embodiment of the present invention will be described in detail below with reference to FIGS. 3 to 6.

FIG. 3 shows the object 9 to be irradiated according to the present invention, in which marks 21a, 21b, 21 are placed at five locations on each chip 19 on the wafer so that the center 22 can be detected.
Add c, 21d, and 21e. That is, as shown in FIG. 4, X-shaped marks 21a to 21e composed of two diagonal lines are formed on the five chips 19 selected in a cross shape on the wafer.
As shown in FIG. 5 of the cross-sectional view taken along the line A-A, a groove 23 of, for example, width 10μ×depth 1μ is carved, and the intersections 22 of two diagonal lines are marked 21a, 21b, 21c,
21d and 21e.

Mark 21a on the five chips 19 as described above.
The operation of placing the wafer 9, ie, the object to be irradiated with the wafers 9 to 21e on it, on a mounting table for exposure and deflecting the electron beam will be described with reference to FIG.

FIG. 6 shows one embodiment of an electron beam exposure apparatus according to the present invention, and the same parts as in FIG. 1 are given the same reference numerals and redundant explanation will be omitted. Marks 2 placed on five chips on the wafer 9 of the irradiation object
The electron beam 2 irradiated onto 1a to 21e generates secondary electrons and the like. The secondary electrons were detected by a backscattered electron detector 24 such as a scintillator, and in order to convert the secondary electrons into light, a signal passed through a photomultiplier 25 was digitally converted by a signal processing circuit 26 such as an analog-to-digital conversion circuit. It is later sent to computer 13. The computer 13 determines the rotation angle θ of the wafer 9 with respect to the mounting table 30 system using marks 21a and 21b on the wafer in the X-axis direction. Next, the marks 21a and 21 inputted as the input signal 12 to the computer 13
Find the elongation ΔL _X of the wafer with respect to the design value L _X between b. Furthermore, a mark 21c in the Y-axis direction of the wafer,
Distance between marks 21c and 21d by 21d
Find L _Y and find the elongation ΔL _Y of the wafer 9 in the Y-axis direction. In this manner, the orthogonality Δθ of the chips in the Y-axis direction and the X-axis direction can be determined. The detection signal components having these factors are compared with the output from the deflection amplification circuit 16 by the computer 13 to calculate the amount of positional deviation and rotation angle θ of the scanning position, and the results are sent to the deflection control correction circuit 29 to calculate the deviation amount and the rotation angle θ. In addition to the coil, the wafer 9 is exposed by irradiating the corrected deflected beam.

Assuming that the deflection field is exposed with a 2mm aperture, the pulse motor 18 is used to expose the next field.
The mounting table 30 is moved in the XY-axis directions and the amount of movement of the mounting table 30 is measured via a measuring device 27 such as a laser interferometer and a detection circuit 28.
Move 0. At this stage, in order to match the deflection system and the movement system _{of the} mounting table, _ΔL
Of course, both systems can be corrected by taking into account the values of L _Y , θ, etc.

Also, when exposing, for example, the offset amount is determined centering on the chip with mark 21e, and each chip 1 is exposed.
9 is exposed, and the degree of orthogonality Δθ is taken into account in the movement in the Y-axis direction between the chips. Furthermore, in order to solve the problem of drift of the electron beam, etc., it is sufficient to calculate the offset amount using the mark 21e of the center chip 19 at regular intervals and perform correction.

As explained in detail above, the electron beam exposure method according to the present invention does not require benchmarking all chips except for five chips in a wafer as alignment marks, which not only increases the degree of integration but also improves accuracy. It has the feature that the exposure speed during mark detection can be increased while maintaining the above characteristics.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram for explaining the alignment method of the conventional electron beam exposure method, Fig. 2 is a plan view of the wafer showing the alignment marks of the conventional irradiated object (wafer), and Fig. 3 is the book. An explanatory diagram of the wafer alignment mark of the invention, FIG. 4 is an enlarged view of the wafer mark in FIG. 3, FIG. 5 is a cross-sectional view taken along line A-A in FIG. FIG. 2 is a system diagram for explaining an exposure method. 1... Electron gun, 2... Electron beam, 3... Beam blanking coil, 4, 5, 6... Condenser lens, 8... Deflection lens, 9... Irradiated object (wafer), 13... Computer , 14... Scanning control unit, 18... Pulse motor, 25... Backscattered electron detector, 26... Signal processing circuit, 28... Detection circuit, 29... Correction circuit.

Claims (1)

[Claims] 1. In an exposure method in which an object to be irradiated, such as a wafer, is exposed to an electron beam emitted from an electron gun, a first mark is formed on a chip located at the center of the wafer; forming second and third marks on chips located in the vertical direction from the center of the wafer; forming fourth and fifth marks on chips located in the horizontal direction from the center of the wafer; The vertical elongation of the wafer is measured by scanning the second and third marks with an electron beam, and the horizontal elongation of the wafer is measured by scanning the fourth and fifth marks with an electron beam. Measure and determine the rotation angle of the wafer and/or the orthogonality of the chip from the coordinate positions of the second to fifth marks, and determine the amount of offset with respect to the first mark from the obtained information. An electron beam exposure method characterized in that exposure is performed by controlling the movement of an electron beam deflection system and an irradiated object mounting table.