JPS62208628A - Mark position detector - Google Patents

Abstract

PURPOSE:To enable the stable mark position to be detected constantly regardless of the level of mark signals by a method wherein, when the changing ratio in amplification degree of an amplifier is decreased exceeding the specified lower limit, the position signals detected and held so far are erased. CONSTITUTION:A little changes in signal levels are increased in the scannings 11, 12 as shown in the section A while the threshold value 17 is set up as, e.g., 1/2 of the maximum value of signals so that a mark detecting circuit may detect any mistaken mark positions to be held as they are in the section A. However, in the scannings 13, 14 containing a true mark 10 on the way of scanning, the signal levels are rapidly increased decreasing the amplification degree Y of an amplifier to make the true mark signals coincide with the target value 16 as shown in the section B. On the other hand, the mark detecting circuit is actuated to erase the so far held mistaken mark position data holding the true mark positions to be successively detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a mark position detection device, and more particularly to a mark position detection mounting suitable for detecting mark positions of an electron beam exposure device in a short time.

[Conventional technology]

The method of determining the electron beam position at the time when the mark waveform signal generated from the mark crosses a threshold value by scanning the electron beam is generally called mark detection.

In order to detect marks using IE, it is essential that the threshold value be set within the amplitude range of the mark waveform signal.

However, since the actual amplitude of the mark waveform signal varies greatly depending on the mark type, electron beam intensity, etc., it is necessary to set the amplification degree of the amplifier so that the amplitude becomes a predetermined value. . Conventionally, for example, Japanese Patent Application Laid-Open No. 55-85028
As shown in No. 2, the electron beam scans the location where the fault mark is present, and the amplification degree and offset of the amplifier are determined from the amplitude of the obtained mark waveform, and the After setting, mark detection was performed. Due to this logic+l+, extra time is required before detecting marks.

If the setting of the amplification degree of the amplifier and the mark detection can be performed at the same time, it will be possible to significantly shorten the time.

In order to solve this problem, it is considered that the signal is considered valid only when the amplification level of the signal amplifier falls below a certain level, but it is said that if the amplitude of the original mark signal is small, it becomes impossible to detect the mark. There was a problem.

[Problem that the invention seeks to solve]

Since the above technology considers the signal to be valid only when the amplification level of No. 46 amplifier is below a certain level of 1 novel,
If the amplification degree of the amplifier always exceeds the specified value,
That is, if the amplitude of the original mark signal is small, the mark detection operation is prohibited, making it impossible to detect the mark.

An object of the present invention is to provide a mark position detecting device that always enables stable mark detection regardless of the size of the mark signal.

[Means for solving problems]

The above purpose is to detect 11! when the rate of change in the amplification degree of the amplifier, which is controlled according to the strength of the mark signal, decreases beyond a predetermined range. This is achieved by providing means for erasing the held position signal and holding the position signal based on the subsequent mark signal.

[Effect]

With the above configuration, when a true mark signal is detected, the signal that was erroneously detected as a mark signal is erased, and the true mark signal is maintained, so that a stable mark is always maintained. Can be detected.

〔Example〕

FIG. 1 is a diagram illustrating an embodiment of the present invention. FIG. 5A is a plan view of the mark, and in order to detect the mark 10, the electronic beam 13 is scanned at 1.1, 12°, 13.14. The signal obtained when the electron beam scans the mark 10 has a waveform 15 shown in FIG.

Figures (c) and (d) show the amplification degree and detection signal of the amplifier of the mark detection circuit, with the number of scans plotted on the horizontal axis. In scans 11 and 1.2, since areas other than the marks are scanned, the amount of signal obtained is small, and therefore the degree of amplification is set large so that the maximum value of the detection signal matches the target output level 16. Here, the amplification degree is set to the maximum at the start of scanning. It has a function of decreasing the degree of amplification so that when the signal increases, the amplitude of the amplified signal reaches a desired level. Further, the set amplification degree continues to be maintained unless the signal increases further. Therefore, in scan it, 12, small changes in signal amount are amplified, for example as shown in section A of FIG. 1(d).

On the other hand, the threshold value 17 is, for example, 172
is set to be.

Therefore, in part A, a threshold value is set for detecting a noise signal that is not a mark as a mark position. As a result, the mark detection circuit detects and holds the erroneously recognized mark position.

As the beam scan progresses and reaches scans 13 and 14, there is a true mark in the middle of the scan, so the signal amount increases rapidly, and as a result, the amplification degree of the amplifier decreases as shown in Figure (c). Become. Therefore, as shown in section B in FIG. 1(d), the true mark signal comes to match the target value 16 in scans 13 and 14.

On the other hand, when the amplification degree of the amplifier changes, the mark detection circuit erases the previously held erroneously recognized mark potential temperature data at the timing of the change, and maintains the true mark position that is subsequently detected. Operate. These operations completely eliminate misidentification of mark positions due to noise, making it possible to detect only true mark positions.

Next, an embodiment of the mark position detection device of the present invention will be described with reference to FIG. The beam scanning controller 21 controls the beam 2
When 0 scans the target 22 having a mark, the mark signal generated from the target 22 passes through the detector 23 and the offset level adjustment amplifier 24, and appears as a voltage change on the output line 40.

The output of the A/D converter 30 is applied to a maximum value detection circuit 31 having a maximum value holding register.

The output of the maximum value detection circuit 31 is outputted by the amplification degree setting circuit 32 to a coefficient K such that Eo = KIEl = constant, where the voltage level of the output line 40 is set to E and the voltage level of the output line 41 is set to Eo. and controls the amplification degree of the amplifier 25.

On the other hand, the output of the amplification degree setting circuit 32 is also applied to the amplification degree change detection circuit 33. When a predetermined change occurs in the signal K of the signal line 42, the amplification change detection circuit 33 detects the output line 4.
3, a reset signal appears.

The mark signal of the output line 41-H whose amplification degree is controlled is A/
The signal is encoded by the D converter 26 and supplied to the mark position detection circuit 29 at the next stage.

The mark position detection circuit 29 performs 1. The beam position is determined each time the mark signal crosses the threshold value based on the threshold value shown in - corresponding to 2E o and the mark signal output of the A/D converter 26, and the results are sequentially held.

As the above operation progresses and the electron beam reaches scanning 13 shown in FIG. 1(a), since a true mark exists in the middle of scanning, the output line 41
K of 2 changes. As a result, a reset signal is generated on the output line 43, and all erroneous mark position data detected and held by the mark position detection circuit 29 is erased.

As the scan progresses, after scan 14 (FIG. 1(a)), there is no change in the magnitude of the mark signal, so it remains constant on the output line. Therefore, the mark position detection circuit 29 continues to detect and hold the true mark position until a predetermined number of electron beam scans are completed.

The retained mark position data is processed and used by a computer (not shown) as necessary.

FIG. 3 shows another embodiment of the present invention. In this example,
It is configured so that the threshold level can also be optimized.

FIG. 4(a) shows how the threshold value 17 is set for the mark signal, and FIG. 2(b) shows a configuration diagram. The operation will be explained below.

The maximum value detection circuit 27 detects the maximum value of the mark signal,
It has the function of holding. The threshold value setting section 28 reduces the output of the maximum value detection circuit 27 to approximately 1/2 and provides a threshold value to the mark position detection circuit 29 at the primary stage. Therefore, the mark position detection circuit 29 can perform a mark detection operation based on the mark signal output from the A/l) converter 26.

On the other hand, the maximum value detection circuit 27 has a function of being reset to the minimum value when a reset signal is generated on the output line 43. Therefore, in the amplification degree setting circuit 32, the threshold value is re-qualified every time a change occurs in the amplification degree K. That is, as shown in FIG.
7 will always be set to 1/2 of the mark signal.

Although the embodiment has been described using the maximum value detection circuits 27, 3 as an example, a minimum value detection circuit or a combination of maximum value and minimum value may be used.

〔Effect of the invention〕

According to the present invention, the mark position can be reliably detected while searching for the mark and setting the conditions for mark detection, that is, setting the amplification degree and threshold value to optimize the amplitude of the mark waveform. Moreover, since they can be performed simultaneously, it is possible to shorten the mark detection time.

Although the present invention has been described using an electron beam exposure apparatus as an example, it is also applicable to an electron beam length measuring apparatus or similar apparatus, and further to an apparatus using an ion beam or the like.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the operation of an embodiment of the present invention, FIG. 2 is a circuit diagram showing a mark position detection device according to an embodiment of the invention, and FIG. 3 is a diagram illustrating another embodiment. be. 10... Mark, 26.23...Al1) converter, 27.31 Maximum value detection circuit, :l : Heat amplification degree setting circuit, 3:N ・Amplification degree change detection circuit, 28...
[Threshold value setting section, 29... mark (I/h" detection circuit).

Claims (1)

[Claims] 1. Scanning a mark formed on a substrate with a charged particle beam,
In a mark position detection device that detects the position of the mark based on changes in the intensity of reflected electrons etc. emitted from the mark, the amplification degree of the signal amplifier is adjusted according to the intensity of the mark signal emitted from the mark. means for controlling the
means for detecting and holding the mark position at the time when the mark signal crosses the threshold; and when the rate of change in the amplification degree decreases beyond a predetermined range, the mark position data already held 1. A mark position detection device comprising: means for erasing mark position data and holding mark position data detected based on subsequent mark signals. 2. The threshold value in the mark position detection device is provided with means for resetting when the rate of change in the amplification degree of the amplifier decreases beyond a predetermined range. The mark position detection device according to item 1.