JPS6335095B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron beam exposure method using a continuous stage movement type that enables direct exposure of a wafer.

Various types of electron beam exposure have already been proposed, and an electron beam exposure method using a continuously moving stage is also known. When directly exposing a wafer using this continuous stage moving electron beam exposure method, the wafer has undergone various pattern formation processes, so unlike mask formation, it is necessary to match the pattern that has already been formed. It is necessary and the correction must be made. In other words, whether the pattern already formed on the wafer is created by an optical process or by direct electron beam exposure, when drawing is performed next by direct electron beam exposure, for example, position correction is required for each chip. , it is necessary to perform rotation correction and size correction. This inevitably causes positional deviation, rotational error, and size error because the conditions of the drawing system are not the same as those of the previous pattern.
Of course. This correction can be performed by detecting marks pre-formed on the wafer, but scanning and detecting marks with a size of about 15 μm with an electron beam requires a scanning time of about 20 mS. , since it is necessary to detect at least three marks in order to correct the three items above,
This means that high-speed exposure will not be possible.

In addition, the continuous stage movement speed must be at least 20 mm/S due to economical considerations compared to other exposure methods, and when the stage is continuously moved at such a movement speed, alignment Unless the time required for detection is approximately the time required to detect one mark, direct exposure of a predetermined pattern within the chip will not be possible. That is, in the conventional electron beam exposure method in which the stage is continuously moved, high-speed exposure is not possible when direct exposure is performed after correction for alignment with an existing pattern on the wafer.

The present invention improves the above-mentioned conventional drawbacks, and aims to enable direct wafer exposure to be performed at high speed. Examples will be described in detail below.

FIG. 1 is a block diagram of an embodiment of the present invention, in which 1 is a housing with a high vacuum inside, 2 is an electron beam generating section, 3 is a planking section, 4 is a slit,
5 is a deflection unit, 6 is a detection unit that detects reflected electrons, and 7
is a stage, 8 is a wafer, 9 is a laser interferometer for detecting the position of stage 7, 10 is a servo motor for moving stage 7, 11 is an amplifier, 12 is a DA converter, 13 is a pattern correction circuit, 14 is a pattern generation circuit, 15 is a mark position detection circuit, 16 is a storage device for storing mark positions, 17 is a drive circuit for the servo motor 10, and 18 is an electronic computer.

The stage 7 is continuously moved, for example, in the Y direction at a speed of 20 mm/s or more by a servo motor 10 based on a command from an electronic computer 18,
Next, after being moved in the X direction by several millimeters, the direction of movement is reversed. The position of this stage 7 is detected with high accuracy by a laser interferometer 9 and is applied to a pattern correction circuit 13. As is well known, the position detection accuracy by a laser interferometer is about 0.02 μm, so even if the stage 7 is continuously moved, the amount of movement can be detected with virtually no error. This detection result is added to the feed pack system (not shown) for driving the stage, and the stage is moved in accordance with the command value from the electronic computer 18 with high accuracy, and the slight offset that cannot be compensated for by the feed pack system is eliminated. If the amount is generated, this is added as correction information to the pattern correction circuit 13 and correction to the beam deflection system is performed, and the electronic computer 18
The stage is moved according to the specified values from . The stage movement amount data may be applied to the electronic computer 18 in the conventional manner for checking for malfunctions. Such a high-precision stage movement system is known, for example, from Japanese Patent Application Laid-Open No.
It is equivalent to the known one described in Japanese Patent No. 145865. Further, data to be exposed in the chip by the computer 18, such as the X, Y coordinate data of the starting point of the pattern and the X, Y coordinate data of the ending point, is transferred to the pattern generating circuit 14 by the direct memory access (DMA) mode or the like. The pattern data from the pattern generation circuit 14 is corrected by the pattern correction circuit 13, applied to the DA converter 12, converted into an analog deflection signal, amplified by the amplifier 11, and applied to the deflection section 5, and then the pattern data is The electron beam from the generator 2 is deflected.

The electron beam passes through a blanking section 3 controlled by a control signal from a pattern generation circuit 14, is focused by a condenser lens shown in a simplified manner, is deflected by the deflection section 5, and is irradiated onto a wafer 8. This wafer 8 is coated with an electron beam resist. Further, the reflected electrons from the wafer 8 are detected by the detector 6, and the mark is identified by the mark position detection circuit 15. This mark position data is stored in the storage device 16.

Figures 2 and 3 are explanatory diagrams of marks on the wafer. The marks are formed at the intersections of scribe lines SL for separating chips CP, and the wafer 8 is moved in the first direction by the stage. Then, depending on the deflection range of the electron beam, it is moved, for example, to the left by 5 mm, and then it is continuously moved in the direction of . At this time, when the mark is continuously moved in the first direction, only the position of the mark is detected and stored in the storage device 16. When continuously moving in the next direction, one mark is detected and the two marks previously stored in the storage device 16 are detected.
The pattern correction is performed by determining the position correction amount, rotation correction amount, and size correction amount necessary for drawing on the chip CP based on the mark positions.

In other words, by knowing the positions of at least three of the marks provided around the chip area CP, it is possible to determine the difference between the expected position (in the X and Y directions) of the chip area to be exposed. Since the difference from the expected rotation and the expected chip area size can be known, pattern correction is performed for these differences.

Specifically, the computer 18 reads three necessary mark positions from the storage device 16 and provides correction information to the pattern correction circuit 13. Since the rotation and size of the chip area are fixed within one chip area, they can be corrected in the pattern correction circuit 13 for each chip area. Further, the position of the chip area is corrected by combining the amount of correction from the mark position and the amount of correction from the laser interferometer.

For example, in FIG. 3, if the exposure of the vertical column to which the chip CP1 belongs has been completed and the positions of the marks Ma and Mb have already been stored in the storage device 16, then the next vertical column to which the chip CP2 belongs will be exposed from above. In the case of downward exposure, one mark Mc is newly identified by the mark position detection circuit 15 before chip CP2 is exposed during continuous movement, and the marks Ma and Mc, and the marks Ma and Mb are used to detect the chip CP2. position error,
Since the rotation error and the size error are determined, correction information is given from the electronic computer 18 to the pattern correction circuit 13 to correct the pattern data, and the position of the mark Mc is stored in the storage device 16 and stored in the chip CP2. A pattern is drawn using an electron beam. The amount of movement during continuous movement is always corrected with virtually no error by a correction system using a laser interferometer.

When the continuous movement progresses and the exposure of the chip CP2 by the electron beam is completed, the mark Md for exposure of the next chip (the chip located below the chip CP2) is detected. For chip CP3, the vertical rows belonging to chip CP3 are exposed from bottom to top, but the marks Mc,
The position of Md is stored in the storage device 16, and the amount of stage movement can be determined accurately using a laser interferometer.
For example, detect mark Mf, mark Mc, Md,
The position error, rotation error, and size error of the chip CP3 are determined from the positional relationship of Mf, and when the exposure is completed, the mark Me for exposure of the next chip (the chip located above the chip CP3) is detected.

Due to the warping of the wafer 8, the chip positions for the same amount of electron beam deflection will shift, but since the shifts between adjacent chips are extremely small, one mark is detected based on the previously detected mark position. This makes it possible to accurately correct the positional deviation of the chip. Note that the storage device 16 does not need to have a capacity sufficient to store all mark positions on the wafer 8, and may have a capacity sufficient to store mark positions detected by at least one continuous movement. is possible.

As explained above, the present invention detects the mark formed on the wafer 8, stores the mark position in the storage device 16, and uses the stored mark position and the newly detected mark position to generate an electron beam. The scanning position is determined by an electronic computer and pattern correction circuit 1.
It is corrected by three correction means,
Even if the stage 7 is moved continuously, the two mark positions of the chip to be exposed next are already stored, so the chip position can be determined just by obtaining one new mark position, and the necessary correction can be made. Therefore, only one new mark is required to be detected, so stage 7
Even by continuously moving at high speed, a given pattern can be accurately exposed to the electron beam.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG.
3 and 3 are explanatory diagrams of marks on a wafer. 1 is a housing, 2 is an electron beam generation section, 3 is a blanking section, 4 is a slit, 5 is a deflection section, 6 is a detector, 7 is a stage, 8 is a wafer, 9 is a laser interferometer, and 10 is a servo motor. , 11 is an amplifier, 12
is a DA converter, 13 is a pattern correction circuit, 14 is a pattern generation circuit, 15 is a mark position detection circuit,
16 is a storage device, 17 is a drive circuit, 18 is an electronic computer, Ma to Mf are marks, and CP1 to CP3 are chips.

Claims (1)

[Claims] 1. In an electron beam exposure method in which a stage on which a wafer is placed is continuously moved to expose the wafer directly to an electron beam, marks formed around each chip area within the wafer are detected and the mark positions are memorized. and a correction means for correcting the electron beam scanning position, detecting marks around the chip area located on the first row in the wafer and storing the mark positions in the storage device. Then, before exposing the chip area located on the second column adjacent to the first column, the position of the mark corresponding to each chip area is newly detected, and the previously memorized mark position is and correcting the scanning position of the electron beam based on the newly detected mark position and exposing the chip area,
An electron beam exposure method characterized in that the operation of storing the newly detected mark position in the storage device is repeated as the stage continuously moves.