JPS5927379A - Pattern video signal processing system - Google Patents

Abstract

PURPOSE:To obtain a two-dimensional pattern video signal with high precision, by controlling the amplitude gain of a pattern video signal so as to be in inverse proportion to the measured value of a start signal interval, in a two- dimensional pattern inspecting device. CONSTITUTION:That which converts pattern video information accumulated in each interval of an impressed start signal to a pattern video signal successively in accordance with a prescribed clock at the following interval and sends it out is used as a linear image sensor 18 for scanning and inspecting a circuit pattern of a manufacturing mask MSK loaded on an XY table 11. With respect to an A/D converter 21 whose quantization gain is controlled so as to be in inverse proportion to reference voltage Vref, an exposure time T is detected by a start signal interval detector 20 and is provided as reference voltage Vref=J.T (J is a proportional constant), so that an output pattern video signal VO of the sensor 18 is quantized. Accordingly, a photodetecting sensitivity variation is corrected by a real time, and a pattern video signal which is stable and has high accuracy is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for performing defect inspection, dimension measurement, etc. of circuit patterns of IC manufacturing masks, IC wafers, thick film modules, etc.
The present invention relates to a pattern video signal processing method for obtaining a two-dimensional pattern video signal with high precision in a dimensional pattern inspection device.

First, the conventional method will be explained according to the drawings.

FIG. 1 is a system configuration diagram of an example of a conventional pattern video signal processing system, and is for a mask inspection apparatus for IC manufacturing.

In this conventional method, an IC manufacturing mask 2 to be inspected mounted on an XY table 1 is irradiated with a light source 5, and linear image sensors 3 and 4 are used to detect the ICM manufacturing mask 2 according to the transmitted light.
Detects the upper pattern and moves the XY table 1 to the Y axis drive unit 8
．． In some cases, the X-axis driving section 9 drives and scans, and the defect determining section 6 inspects the entire surface of the IC manufacturing mask 2 by a two-pattern comparison method.

The scanning method of the XY table 1 is, for example, that it is driven in the (+)
After moving one step in the (+) Y direction, (-)
The operation of turning back and driving in the X direction is repeated. In this case, based on the position information from the position sensor 10, the microprocessor 7 recognizes the scan start point, end point, and turning point in the X direction, and performs a constant speed reciprocating motion in the X direction.

In such a conventional method, the linear image sensor 3
, 4 is directly affected by, for example, speed fluctuations and vibrations in the X direction of the XY table 1, so expansion and contraction distortion occurs in the It was difficult to

The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to
An object of the present invention is to provide a pattern video signal processing method that can obtain a dimensional pattern video signal with high precision.

The configuration of the pattern video signal processing system according to the present invention has a function of scanning a two-dimensional pattern using a linear image sensor and comparing and determining the resulting video signal with design data of the two-dimensional pattern. In a dimensional pattern inspection device, the linear image sensor sequentially converts pattern video information accumulated during each interval of a start signal applied thereto into a pattern video signal according to a predetermined clock signal at each next interval. The start signal is generated every predetermined scanning movement amount in synchronization with the two-dimensional pattern scanning position, and the amplitude gain of the pattern video signal is controlled in inverse proportion to the measured value of the signal interval. It is processed in such a way as to encourage

In short, by including the influence of speed fluctuations, vibrations, etc. of two-dimensional pattern scanning in the start signal interval, the influence can be corrected according to the measured values of the same interval.
The purpose is to obtain a stable pattern video signal.

Embodiments of the present invention will be described below based on the drawings.

FIG. 2 is a system configuration diagram of an embodiment of the multi-turn video signal processing method according to the present invention, and FIGS. 3 and 4 are a block diagram and a time chart of a start signal interval detector thereof.

Here, 11 is an XY tapered tape, 12 is its X-axis position sensor, 13 is its Y-axis position sensor, 1
4 is the same X-axis driver, 15 is the same X-axis driver, 16 is
17 is an objective lens, 18 is a linear image sensor, 19 is a timing generator, 20 is a start signal interval detector, 20a is a monostable multi-novel generator (MM), and 20b is a flip-flop (F)
F), 20C is the same oscillator (osc), 20d is the same counter, 20e is the latch, 20f is the same D/A converter, 21 is the A/D converter, 22 is the two-dimensional pattern a magnetic tape storage device (MT) for storing design data;
23 is a pit no-turn generator, 24 is a defect determiner, and 25 is a processor.

In this embodiment, the circuit turns of the IC manufacturing mask MSK mounted on the XY table 11 are transferred to the linear image sensor 1.
8 to scan and detect the turn video signal Vo.
The value quantized by the D converter 21 and this mask to be inspected MS
A defect determiner 24 compares and determines the pattern data created by the pit notter/generator 23 based on the design data (stored in the magnetic tape storage device 22) used when manufacturing K. This is to execute the inspection of the mask MSK.

Here, if the pattern video signal Vo detected by the linear image sensor 18 has an expansion/contraction distortion as seen in the conventional method, it may cause a misjudgment (inspection error) when comparing and judging with the above design data. The above problem arises.

In order to eliminate this influence, in this embodiment, when the X-axis driver 14 drives and scans the XY table 11 at a constant speed in the X direction based on the control signal of the processor 25,
In synchronization with the distance detection value (pattern scanning position) of the axis position sensor 12, the timing generator 19 generates a start signal φX and a specified number of clock signals φ at every fixed scanning distance.
T is generated and supplied to the linear image sensor 18.

As a result, even if there is a speed fluctuation in the XY table 11, an accurate pattern video signal V without expansion/contraction distortion can be obtained. The aim is to obtain the following.

However, if this continues, the light receiving sensitivity of the linear image sensor 18 will fluctuate in proportion to the interval of the start signal φX, that is, the exposure time T, as described above, so the pattern video signal VO obtained from the linear image sensor 18
A new problem arises in that fluctuations occur in the loss width direction, making it impossible to obtain a stable pattern image.

Therefore, in this embodiment, the reference voltage Vr*
For the A/D converter 21 whose quantization gain is controlled in inverse proportion to f, the start signal interval detector 20 detects the exposure time (start signal interval) T and calculates the reference voltage Vr, f=J-T. (J is a proportionality constant), the output turn video signal V of the linear image sensor 18 is given. I am trying to quantize it.

Therefore, a stable and highly accurate pattern video signal can be obtained by correcting fluctuations in light receiving sensitivity in real time.

Next, a specific example of the start signal interval detector 20 will be described based on FIGS. 3 and 4.

Every time the start signal φX is input, a pulse signal A is sent out from the monostable multivibrator 20a, the counter 20d is cleared to zero, and the flip-flop 20b is set.

In accordance with this output B, the oscillator 20C starts sending out the clock signal C, the counter 20d starts counting, and the period T continues.

Continue in this state.

Next, when the start signal φX is input again, the flip-flop 20b is reset, the oscillator 20C stops sending out the clock, and the count value X0 of the counter 20d is held in the latch 20e, and the value is used for D/A conversion. The reference voltage Vra of the analog signal is set by the device 20f.
It is output as t ” K ” Xo.

Thereafter, the oscillator 20C starts transmitting the clock again, and the counter 20d starts counting, but the reference voltage VgaI remains at a value of - during the period T+++1 until the next start signal φX is input. It is held at xゎ.

Therefore, the output return video signal Vo of the linear image sensor 18 obtained during the previous accumulation period T is also output during the accumulation period Tゎ+l, and in complete synchronization with this, the reference image signal Vo is sent to the A/D converter 21. Voltage Vraf = -X, (=J-
T) is given, and the light-receiving sensitivity due to fluctuations in the accumulation time T can be corrected in real time.

Finally, the above-mentioned linear image sensor 18 will be explained based on the block diagram and time chart of representative examples of the linear image sensor in FIGS. 5 and 6.

This linear image sensor 18 includes a photoelectric conversion element 18a that receives an image pattern Q by a plurality of pixels 18C and converts it into an electrical signal, and a photoelectric conversion element 18a that temporarily stores the output signal from this and outputs an image according to the input of a clock signal φT. It is composed of a CCD shift register 18b for obtaining signals.

This is done in synchronization with the clock signal φT after inputting the start signal φX and transferring the charges accumulated in each pixel 18c of the photoelectric conversion element 18a to the CCD shift register 18b in accordance with the amount of light of the received light image pattern Q. and the video signal Vo
This outputs the following.

Therefore, the input interval T(T,,T
□I+Tn+24...) This is the exposure time of the photoelectric conversion section of the image sensing pattern, so as mentioned above, the light receiving sensitivity is determined in proportion to the input interval T.

As described above in detail, according to the present invention, I'C
Since it is possible to realize an inspection device that can stably obtain accurate video signals of minute patterns such as manufacturing masks, IC wafers, and M-thick modules, it is possible to perform comparative inspections with design data,
A remarkable effect can be obtained in improving the reliability and efficiency of high-precision dimension measurement of patterns and other pattern inspection processes.

[Brief explanation of drawings]

FIG. 1 is a system configuration diagram of an example of a conventional pattern image signal processing system, FIG. 2 is a system configuration diagram of an example of a pattern video signal processing system according to the present invention, and FIGS. The diagram is
A block diagram of one embodiment of the start signal interval detector,
5 and 6 are block diagrams and time charts of typical examples of linear image sensors. 11...XY table, 12.13...X@, Y-axis position sensor, 14.15...X-axis, Y-axis drive u
, 16... Irradiation light source, 17... Objective lens, 18.
... Linear image sensor, 19... Timing generator, 20... Start signal interval detector, 20a...
Monostable multivibrator, 20b... flip-flop, 20C... oscillator, 20d... counter, 2
0e...Latch, 20f...D/A converter, 21.
... A/D converter, 22 ... magnetic tape storage device, 2
3... Pit pattern generator, 24... Defect determiner, 25... Processor. 3rd eye $4! 45 eyes, 6 eyes

Claims (1)

[Claims] 1. A two-dimensional pattern inspection device having a function of comparing and determining a video signal obtained by scanning a two-dimensional pattern with a linear image sensor and design data of the two-dimensional pattern. , the linear image sensor uses one that sequentially converts the pattern video information accumulated during each interval of the start signal applied to it into a pattern video signal according to a predetermined clock signal at the next interval and sends it out. , the start signal is generated every predetermined movement amount in synchronization with the two-pattern scan position, and the amplitude gain of the pattern video signal is controlled in inverse proportion to the measured value of the signal interval. A pattern video signal processing method characterized by: 2. In the device described in claim 1, the amplitude gain of the pattern video signal is controlled by generating a predetermined reference voltage proportional to the count value of the clock signal during the same interval immediately before the start signal interval; A pattern video signal processing method that performs processing in inverse proportion to this.