JPH0467740B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a material inspection device that achieves shortening of inspection time and improvement of inspection accuracy.

[Prior Art] As is well known, a mask is an original plate for printing a pattern onto a wafer, and the quality of this mask has a great effect on the yield and performance of the electrical devices that are finally produced. Therefore, inspection of the mask on which the pattern to be printed is drawn has become indispensable.

In this type of mask inspection, a beam scans a mask on which a pattern has been drawn, and the information obtained from the material (actual measurement data) through the scanning is compared with the ideal material information (design data) to determine the pattern. Defects (for example, partial missing portions of patterns, protrusions of patterns, bridges formed between adjacent patterns), dust, etc. are inspected.

After such an inspection, such defects are repaired by a mask repairer or the like based on the inspection data.

Incidentally, such an inspection apparatus employs either a beam scanning mechanism using electrostatic deflection or a beam scanning mechanism using electromagnetic deflection.

[Problems to be solved by the invention] Now, when a beam scanning mechanism using electrostatic deflection is adopted, high-speed and highly linear scanning is possible, making it possible to perform highly accurate inspection, but since the deflection width is small, Testing takes a lot of time. If the electrostatic deflection voltage is increased in an attempt to increase the deflection width, the distributed capacitance in the circuit will increase and high-speed scanning will not be possible, and the deflection distortion will exceed the allowable range. On the other hand, if a beam scanning mechanism using electromagnetic deflection is used, the deflection width can be increased, so
Although the inspection time is not so long, the scanning speed and linearity are poorer than the former, and the deflection distortion is also large, so that highly accurate inspection cannot be performed.

The object of the present invention is to solve the problem of an inspection apparatus employing either a beam scanning mechanism using electrostatic deflection or a beam scanning mechanism using electromagnetic deflection.

[Means for Solving the Problems] Therefore, the material inspection apparatus of the present invention includes an electromagnetic deflection beam scanning means, an electrostatic deflection beam scanning means, and
An electromagnetic deflector is used to perform beam scanning with a scanning pitch such that at least one part of the defective area can be scanned for each pattern defective area, and the beam is scanned in a specific area on the material using a scanning pitch smaller than the scanning pitch. A control mechanism is provided that uses an electrostatic deflector.

[Operation] In general, pattern defects (for example, partial missing parts of patterns, protrusions of patterns, bridges formed between adjacent patterns) and dust are of a size that can be ignored compared to the size of the pattern. It is not small, but has a certain size. Also, 1
There are not many patterns for one pattern. Therefore, first, when a pattern defect exists, the material is scanned once by an electromagnetic deflection beam scanning means at a scanning pitch coarse enough to scan at least some part of the defective part for each pattern defective part. The position of any part of the pattern defect is detected by scanning. Next, a predetermined range including the position is scanned by an electrostatic deflection beam scanning means at a scan pitch finer than the scan pitch, and the detailed position where the pattern defect exists is measured by the scan. In this way, by combining coarse scanning by the electromagnetic deflection beam means and fine scanning in a specific area by the electrostatic deflection beam scanning means, highly accurate material inspection can be performed at high speed.

[Embodiment] FIG. 1 is a schematic diagram of a material inspection apparatus shown as an embodiment of the present invention.

In the figure, 1 is an electron gun, 2 is a focusing lens, 3 is a stage, 4X and 4Y are electrostatic deflection electrodes in the X direction and Y direction, respectively, 5X and 5Y are electromagnetic deflection coils in the X direction and Y direction, respectively, and 6 and 7 are respectively A step scan voltage signal generation circuit, a step scan current signal generation circuit, 8 a control device, 9 a backscattered electron detector, 10 and 11 DA converters, and 12 an AD converter.

The operation of such an apparatus will be described below when a material 13 on which a pattern P as shown in FIG. 2 is drawn is placed on a predetermined position on the stage 3 and the material is inspected.

First, the step scanning current signal generating circuit 7 is activated by a command from the control device 8 which stores data (design data) such as the drawing position of the pattern.
X and Y direction electromagnetic deflection coils 5X and 5Y, respectively,
A Y-direction scanning current signal is supplied. Now, assuming that the size of the pattern defect is 1 μm or more in diameter, the scanning step pitch of the X-direction and Y-direction step scanning current signals are both set to 1 μm (see Fig. 3a,
b), so that the former frequency is, for example, 3 KHz, and the latter frequency is about 11.7×10 ^-3 KHz. With a scan step pitch of this size, it is possible to traverse any portion of normal pattern defects or dust. At this time, the electron beam focused on the material 13 by the focusing lens 2 is transmitted over the entire surface of the material 13 in the X and Y directions at a scanning step pitch of 1 μm by the X and Y direction electromagnetic deflection coils 5X and 5Y. Scan coarsely. Due to the scanning, reflected electrons generated from the material are detected by the detector 9 and sent to the control device 8 via the AD converter 12. The control device calculates a difference between pattern data on the material from the detector and pre-stored design data;
Measure defects. At this time, if a missing part K exists in the pattern P, if the electron beam crosses one position (X ₀ , Y ₀ ) in the defective part, that position is measured as the missing position. . The control device controls a region R having _a width of D/ ₂ (X ₁
~X ₂ and Y ₁ ~The area created by _{Y 2} ) As the length is scanned,
Sends a command to the step scan voltage signal generation circuit 6,
Activate the circuit. The step scanning voltage signal generation circuit 6 generates a step scanning voltage signal (a third signal) which scans the material in the X direction from X ₁ to _{X 2} and in the Y direction from Y ₁ to _{Y 2} in response to a command from the control device. (thick solid line portions of the waveforms shown in FIGS. c and d) are supplied to the X-direction and Y-direction electrostatic deflection electrodes 4X and 4Y, respectively. The X direction, Y
The scanning step pitch of the directional step scanning voltage signal is set to 0.1 μm, and the frequency of the former is set to, for example, 300 KHz, and the frequency of the latter is set to about 1.17 KHz.
The frequency is set to about 100 times the frequency of the X-direction and Y-direction step scanning current signals supplied to the X-direction and Y-direction electromagnetic deflection coils 5X and 5Y. At this time, the electron beam focused on the material 13 by the focusing lens 2 is transmitted through the X and Y direction electrostatic deflection electrodes 4X and 4Y.
Accordingly, the partial length of region R on material 13 in X and Y directions
Finely scan with a scanning step pitch of 0.1 μm.
Due to the scanning, reflected electrons generated from the material are detected by the detector 9 and sent to the control device 8 via the AD converter 12. The control device measures defects by taking the difference between pattern data on the material from the detector and pre-stored design data. Since the design data is originally pattern drawing position data with a fineness corresponding to the fineness of scanning by the electrostatic deflection electrode, the detailed position where the defect K exists is measured.

In the above embodiment, an inspection apparatus using electron beam scanning is shown, but it can also be applied to a scanning apparatus using ion beam scanning. Further, in the above embodiment, reflected electrons are detected, but secondary electrons may be detected instead.

[Effects of the Invention] The present invention allows an electromagnetic deflector to perform scanning with a scanning pitch such that at least some part of the defective portion of one pattern can be scanned,
Since the electrostatic deflector is configured to scan a specific region on the material using a scanning pitch smaller than the scanning pitch, highly accurate material inspection can be performed at high speed.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a material inspection device shown as an embodiment of the present invention, Fig. 2 shows materials,
FIG. 3 is a scanning signal waveform diagram. 1: Electron gun, 2: Focusing lens, 3: Stage,
4X, 4Y: X direction, Y direction electrostatic deflection electrode, 5
X, 5Y: X direction, Y direction electromagnetic deflection coil, 6:
Step scan voltage signal generation circuit, 7: Step scan current generation circuit, 8: Control device, 9: Backscattered electron detector, 10, 11: DA converter, 12: AD converter.

Claims (1)

[Claims] 1 In an apparatus configured to inspect a pattern for defects based on information obtained from the material by scanning a material on which a pattern is drawn with a beam, an electromagnetic deflection beam scanning means, an electrostatic deflection beam a scanning means, and an electromagnetic deflector to perform beam scanning with a scanning pitch such that at least one part of the defective part can be scanned for each pattern defective part, and to scan a specific area on the material with a scanning pitch smaller than the scanning pitch. A material inspection device comprising: a control mechanism for causing beam scanning to be performed by an electrostatic deflector.