JPS5847005B2 - Position detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a position detection method using marks on a substrate that serve as rotational references in electron beam exposure.

Conventionally, when electron beam exposure is performed on a substrate, such as a weber, the exposure pattern is usually arranged on the webr according to a predetermined coordinate system.

At that time, it is necessary to rotate the weber or the electron beam deflection section.

In this case, the rotation angle is usually determined by detecting alignment marks provided on the weber.

In other words, two alignment marks separated by a certain distance are detected and the angle is calculated from the distance between them and the amount of deviation from the perpendicular direction, but in this case, the two marks must be searched first. Therefore, the work is doubled.

Furthermore, since an electron beam scanning line is used for mark detection, there is a drawback that unnecessary areas are also exposed to the electron beam.

SUMMARY OF THE INVENTION An object of the present invention is to provide a position detection method that detects a rotation angle relative to an exposure position using a single mark or a combination of marks with fewer electron beam scans.

In order to achieve the above object, the position detection method of the present invention detects the rotation of the substrate by scanning a mark on the substrate with an electron beam. Form two linear marks,
The present invention is characterized in that rotation of the substrate is detected by comparing signal intervals obtained by scanning the mark with an electron beam.

FIG. 1 is an explanatory diagram of an embodiment of the position detection method of the present invention.

In the figure, a combination mark 20 consisting of three linear marks 1, 2, and 3 is formed by etching a silicon substrate or a silicon dioxide (Si02) film 10 formed on a silicon substrate.

This shape allows the mark 2 to be placed in a predetermined reference direction, for example, in the second direction.
It is aligned in the direction of the cut plane (OF plane) 11 of the weber 10 shown in the figure or in the direction perpendicular to a predetermined crystal direction 110.

The other marks 1 and 3 are linear patterns arranged symmetrically and inclined at a certain angle with respect to the mark 2.

Therefore, if ■ and ■ of the electron beam scanning line now come to three positions and intersect marks 1 and 2.3, the respective intersections are A1 * Ble C1m A2 * B2 e
If C2 * A3 + B3 e C3, then comparing the lengths of the line segments to be cut, we can see that the scanning line has stone 1.
, <B1C1, and in scanning line ■ A3B-B3C
.

It can be seen that the scanning lines are all inclined at a certain angle with respect to the mark.

On the other hand, in the case of scanning line ■ perpendicular to mark 2, A
It can be seen that 2B2=B2C2 and the scanning line ■ matches the reference line.

If the exposure position is determined using this scanning line (2) as a reference, it becomes possible to detect the rotation angle.

FIG. 2 is an explanatory diagram of an embodiment of a position detection circuit for realizing the position detection method explained in FIG.

The weber 10 on which the combination mark 20 described above has been formed is scanned by an electron beam 12, the reflected electrons or secondary electrons are received by a detector 13 consisting of a Pn junction, and the detection signal is passed through an amplifier 14 and a waveform shaping circuit 15. ,
Pulses corresponding to intersection points A, B, and C where the scanning line intersects the mark 1°2.3 are generated.

This pulse is input to the control circuit 16 to perform comparative detection of line segments AB and BC as explained in FIG.

In other words, the pulse generated at the intersection A with mark 1 sets the counter 7□ and resets the counter 17□, then the clock is applied and the counter 17□ counts, and the pulse generated at the intersection B resets the counter 7. Set 1□, count, and find the intersection C.
The counter 72 is reset by the pulse generated at .

The contents of these counters 171 and 172 are compared by a coincidence circuit 18, and if they match, a coincidence signal 19 is sent out and the scanning line in question is adopted as a reference line.

If they do not match, the control circuit 16 and counters 7□, 1
Return 7□ to its original state.

Next, rotate the Weber and scan the mark again so that the count value of counter 71.17□ matches 0
The direction of rotation is determined by which of the counters 171 and 172 has a larger count.

That is, if the weber is rotating counterclockwise, the mark will be scanned by one of the scan lines.

In this state, the intersection A1. From the interval between pulses generated at B1, the intersection B1. The interval between pulses generated in C1 is long.

Therefore, in this case, the count value of the counter 17□ is larger than the count value of the counter 171.

When the weber is rotating clockwise, the mark is a scanning line■
The pulse interval is reversed to that described above.

Therefore, the count value of the counter 17□ is larger than that of the counter 172.

As explained above, according to the present invention, a combination mark consisting of three linear marks is formed on a substrate, and an electron beam scanning line is intersected with this combination mark, and line segments cut by the marks are compared. When the lengths are equal, the scanning line coincides with the reference line.

In this way, since the reference line can be determined using one set of marks, there is no need to spend time searching for the mark, and searching for the reference line only requires a few scanning lines, so an effective and simple position detection method can be obtained. .

Although the mark 2 is provided in a direction perpendicular to the cut surface, it may be provided at an angle.

In this case, if the pulse interval ratio is a constant value, it is determined that alignment is accurate.

Furthermore, it is possible to detect not only the rotation of the weber but also the rotation of the weber holder.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the position detection method of the present invention, and FIG. 2 is an explanatory diagram of an embodiment of a position detection circuit realizing the present invention.
In the figure, 1.2.3 is Yark, 10 is Weber, 11 is a cutting surface, 12 is an electron beam, 13 is a detector, 14 is an amplifier, 15 is a waveform shaping circuit, 16 is a control circuit, 170.17
□ is a counter, 18 is a coincidence circuit, and 19 is a coincidence signal.

Claims (1)

[Claims] 1.' In a position detection method in which a mark on a substrate is scanned by an electron beam to detect the rotation of the substrate, two linear marks are formed on the substrate at an axis-symmetrical angle with respect to the center mark; A position detection method characterized in that rotation of the substrate is detected by comparing signal intervals obtained by scanning the mark with an electron beam.