JPH0523501B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a material inspection method that reduces inspection time.

[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.

Now, in the conventional mask inspection method, a beam on which a pattern has been drawn is scanned by a beam at an appropriate constant scanning pitch, and the information obtained from the material (actual measurement data) and the ideal material information ( design data) and detect pattern defects (e.g. missing parts of the pattern), pattern protrusions,
Bridges formed between adjacent patterns) and dust are inspected.

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

[Problems to be Solved by the Invention] Recently, as patterns have become finer, it is necessary to make the scanning pitch of the beam for inspection finer accordingly.

However, if the scanning pitch of the beam is made finer in accordance with the miniaturization of patterns, the mask inspection time increases. Therefore, if such mask inspection is incorporated into one process of semiconductor manufacturing, the time required for the entire semiconductor manufacturing will increase.

The present invention aims to solve these problems and shorten the inspection time for materials on which patterns have been drawn.

[Means for Solving the Problems] Therefore, in the present invention, the region on the material where the pattern is drawn is scanned closely, and the other regions are roughly scanned.

[Operation] The area on the material where the pattern is drawn is scanned closely, and the other areas are roughly scanned. The reason why the area where no pattern exists is coarsely scanned is because it is sufficient to check for the presence of dust in the area where no pattern exists, and such dust can be found by coarse scanning. If you scan in this way, compared to scanning the entire surface of the material densely,
Scanning time for material inspection becomes extremely short.

[Example] FIG. 1 shows a specific example of an apparatus for carrying out the material inspection method of the present invention.

In the figure, 1 is an electron gun, 2 is a focusing lens for focusing the electron beam from the electron gun onto a material 3, and 4 is a stage on which the material is placed. 5X and 5Y are X and Y direction deflectors for scanning the material with an electron beam. 6 is a clock generator, and 7 is a clock signal from the clock generator whose frequency is 1/N.
(N is a positive integer). 8X,
8Y is a counter for counting the clock signals from the clock generator 6 and frequency divider 7, respectively.
9X and 9Y are DA converters that convert the outputs from the counters 8X and 8Y, respectively, into analog signals. The output of each DA converter 9X, 9Y is outputted by an amplifier 10X,
10Y to the X and Y direction deflectors 5X and 5Y.
is supplied to Gain control circuits 11X and 11Y control the gains of the amplifiers 10X and 10Y according to commands from the control device 12. 13 is a detector for detecting reflected electrons generated from the material. The output of the detector is amplifier 1
4, sent to the control device 12 via the AD converter 15. Design data on the material 3 placed on the stage 4 (data on whether there is a pattern at each position with each X, Y coordinate) is stored in advance in the control device, and the control device Defects are identified by taking the difference between the design data and the actual measurement data from the detector 13.

Now, for example, as shown in Figure 2, x ₁ ~
A material inspection method when a pattern is drawn in the area length of x ₂ and y ₁ to _{y 2} will be described below.

As described above, data (design data) indicating that a pattern is drawn in the region heights x ₁ to x ₂ and y ₁ to y ₂ on the material is stored in advance in the control device 12. The control device sends a command to the gain control circuits 11X and 11Y based on the position data of the area where the pattern is drawn, and controls the gains of the amplifiers 10X and 10Y. That is, the clock signal from the clock signal generator 6 is sent to the amplifier 1 via the counter 8X and the DA converter 9X.
0X, frequency divider 7, counter 8Y, DA converter 9
The signals are respectively input to the amplifier 10Y via Y. At this time, the area where the above pattern is drawn (x ₁ ~ x ₂
In the area other than the area formed by y ₁ and _{y 2} ), one pattern is set so that the beam scans steps in the X direction by ΔX _a in the time Δt, and in the Y direction by Δy _a in the time NΔt. In the area where is drawn (the area formed by x ₁ - x ₂ and y ₁ - y ₂ ), the beam scans steps in the X direction by Δx _b (Δx _b < Δx _a ) in the time Δt, and PNΔt ( Δy _b at the time P>1)
The control device 12 controls the gains of the amplifiers 10X and 10Y so that step scanning is performed in the Y direction by (Δy _b <Δy _a ). Note that the degree of density and coarseness can be controlled by arbitrarily controlling Δx _b , Δx _a , Δy _b , and Δy _a . By this control, the X direction scanning signal and the Y direction scanning signal supplied from the amplifiers 10X and 10Y to the X and Y direction deflectors 5X and 5Y, respectively, have the waveforms shown in FIGS. 3a and 3b, respectively. According to each of the X-direction scanning signals and Y-direction scanning signals, the beam changes Δx at a time of Δt in areas other than the area where the pattern is drawn (the area formed by x ₁ to x ₂ and y ₁ to y ₂ ). _A rough step scan is performed in the X direction by a step, and a coarse step scan is performed in the Y direction by Δy _a at a time of NΔt. Then, in the area where the pattern is drawn (the area formed by x ₁ to x ₂ and y ₁ to y ₂ ), step scanning is performed in the X direction densely by Δx _b (Δx _b < Δx _a ) at a time of Δt. , PNΔt (P>1), dense step scanning is performed in the Y direction by Δy _b (Δy _b <Δy _a ).

By scanning the material 3 with the beam in this manner, reflected electrons generated from the material are detected by the detector 13 and sent to the control device 12 via the amplifier 14 and AD converter 15. The control device calculates the difference between pattern data on the material from the detector and design data stored in advance to measure defects.

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

[Effects of the Invention] In the present invention, the area on the material where the pattern is drawn is scanned densely, and the other areas are scanned coarsely, so compared to the case where the entire material is scanned densely. , the scanning time for material inspection becomes extremely short. Therefore, when such mask inspection is incorporated into one process of semiconductor manufacturing, the time required for the entire semiconductor manufacturing is shortened.

[Brief explanation of the drawing]

FIG. 1 shows a specific example of an apparatus for carrying out the material inspection method of the present invention, FIG. 2 shows a certain area on the material used to explain the operation of the present invention, and FIG. FIG. 3 shows a signal waveform diagram used to explain the operation of the present invention. 1... Electron gun, 2... Focusing lens, 3... Material, 4... Stage, 5X, 5Y... X and Y direction deflector, 6... Clock generator, 7... Frequency divider,
8X, 8Y...Counter, 9X, 9Y...DA converter, 10X, 10Y...Amplifier, 11X, 11
Y... Gain control circuit, 12... Control device, 13... Detector.

Claims (1)

[Claims] 1 A method of inspecting a pattern for defects based on information obtained from the material by scanning a material with a beam over the material on which the pattern is drawn, which involves closely scanning the area on the material on which the pattern is drawn. A material inspection method characterized by roughly scanning other areas.