JPS6222264B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for inspecting dust in a resist film.

When drawing is performed using an electron beam, most of the pattern defects that occur are due to dust that adheres during each mask manufacturing process.

In particular, dust that adheres during the process from resist coating to electron beam exposure accounts for almost all mask defects. If pattern inspection is performed after pattern formation is completed, patterns with many defects will be wasted in the mask manufacturing process, and countermeasures for recovery tend to be delayed.

The present invention eliminates these drawbacks, detects pattern defects early, eliminates unnecessary mask manufacturing, enables early countermeasures for recovery, and provides a method for shortening pattern inspection time. This was done for the purpose of providing a method.

As mentioned above, the present invention focuses on the fact that almost all pattern defects are caused by dust that adheres during the writing process, and achieves the above object by performing pattern inspection at the same time as pattern writing. It is something to do.

Hereinafter, the inspection method of the present invention will be explained in detail based on one embodiment.

FIG. 1 is a schematic drawing when a negative type resist is used, and the principle of the present invention will be explained first using this diagram.

In the figure, reference numeral 1 denotes a substrate on which a negative resist film 2 is applied. Pattern drawing is performed by irradiating the pattern portion with an electron beam 3 and performing polymer crosslinking in the irradiated negative resist 2.

However, if dust exists in the film or on the surface of the negative resist 2, this portion cannot be sufficiently irradiated with the electron beam 3, resulting in pattern defects. In other words, if there is dust 4a and 4b outside the irradiation area of the electron beam 3, the dust will not cause pattern defects, but the dust 4c and 4d existing in the irradiation area of the electron beam 3 will be pinned. This becomes a hole defect, and dust that straddles the electron beam irradiation part as shown in 4e results in a pattern chipping.

On the other hand, particle beams and electromagnetic waves such as reflected electrons, secondary electrons, absorbed electrons, characteristic X-rays, and cathodoluminescence are emitted from the part irradiated with the electron beam 3, but the amount of these emissions is different from that of negative resists. The case where there is only the film 2 and the case where there is dust 4 are different.

Therefore, by simultaneously detecting these amounts during pattern drawing and comparing the emitted amounts, it is possible to know whether there is dust 4, that is, a pattern defect, and where it exists.

FIG. 2 shows a case where an embodiment of the present invention is applied to an electron beam lithography apparatus. In the figure, reference numeral 5 denotes a sample moving stage, on which a sample 6 to be drawn is placed. The pattern is drawn by scanning the sample 6 to be drawn with the electron beam 3 controlled by the deflection and blanking control circuit 8 in response to a pattern signal from the pattern data generation circuit 7, or by moving the sample moving table 5. It is done by moving.

The backscattered electrons 9 emitted from the sample portion irradiated with the electron beam 3 are detected by the backscattered electron detector 10 and converted into an electrical signal B. This electrical signal output is input to the comparison circuit 11, and the pattern signal A is output from the pattern data generation circuit 7.
compared to

For example, if we consider the case where patterns as shown in 12a and 12b in FIG. 3 are drawn using a raster method, the pattern signals are This results in a time-series electric signal corresponding to the pattern position as shown in FIG. 4c, which is synchronized with the electron beam scanning signal in the direction.

On the other hand, the backscattered electrons 9 detected by the backscattered electron detector 10 are similarly converted into time-series electrical signals corresponding to the pattern positions. - If there is dust 4 shown as 4g and 4f in FIG. 3 in Y2, the amount of reflected electrons 9 in this part changes to be larger or smaller than the amount of reflected electrons in the part without dust 4,
Electrical signal output B from reflection detector 10 is at position X6
In the portions corresponding to -Y2 and X3 -Y3, fluctuations as shown in FIG. 4d occur. In figure 4d,
P and Q indicate areas where dust exists.

Therefore, by comparing the pattern signal A and the backscattered electron detection signal B in the comparison circuit 11, a signal c relating to the pattern defect (dust presence) position as shown in FIG. 4e can be obtained. In the same figure, R and S are X6-Y2 and X3-Y, respectively.
This signal corresponds to defect No. 3. The defect position is determined by inputting this defect position signal c, information regarding the electron beam position from the pattern data generation circuit, and information regarding the movable table position from the movable table position control/detection circuit 14 to the position detection circuit 15. The output signal is displayed on the display 16.

Although the present embodiment has been described assuming that dust is the main cause of pattern defects, according to the present invention, it is also possible to detect pattern defects caused by resist peeling or disturbance. Further, in this embodiment, the case of the raster method has been described, but the same applies to the vector method.

Note that this example shows application to a circular or rectangular beam, but when the size of the electron beam changes, such as a variable rectangular beam, the backscattered electron detection signal is used to detect the electrons incident on the sample to be drawn. The signal normalized by the beam diameter may be input to the comparison circuit. Such normalization can also be applied when the scanning speed of the electron beam or the amount of the electron beam is changed depending on the pattern. Furthermore, although reflected electrons were used as signals in this embodiment, any information obtained as a result of the interaction between the electron beam and the sample, such as secondary electrons and characteristic X-rays, can be used.

Note that the present invention is applicable to all devices that draw patterns using light other than electron beams or stimulation beams such as X-rays. Furthermore, if there is no need to detect unnecessarily small defects, defects can be repaired efficiently by detecting the position using only pulses with a certain pulse width or more as defect position signals.

As described above, by using the means of one embodiment of the present invention, it is possible to perform an early defect inspection in the drawing stage, and it is possible to take early measures when a defect occurs and shorten the defect inspection time.

[Brief explanation of the drawing]

Fig. 1 is a drawing mechanism diagram for explaining the operating principle of an embodiment of the present invention, Fig. 2 is a mechanical diagram of a drawing apparatus according to an embodiment of the invention, Fig. 3 is a plan view of a pattern, and Fig. 4a 4e to 4e are various signal waveform diagrams when the pattern drawing of FIG. 3 is executed by the drawing apparatus of FIG. 2. DESCRIPTION OF SYMBOLS 1...Substrate, 2...Resist film, 3...Electron beam, 4...Dust, 7...Pattern data generation circuit, 8...Deflection and blanking control circuit, 9...
... Backscattered electrons, 10... Backscattered electron detection and electrical signal conversion circuit, 11... Comparison circuit, 12... Pattern, 14... Moving table position control detection circuit, 15...
Position detection circuit, 16...indicator.

Claims (1)

[Claims] 1. When drawing a pattern by irradiating a sample with a resist on the surface of a substrate with an electron beam or X-rays, there may be dust present in the resist film of the sample, based on the irradiation of the electron beam or X-rays. A method for inspecting dust in a resist film, characterized in that the presence or absence of dust in the resist film is inspected by detecting changes in particle beams or electromagnetic waves generated from the sample surface as changes in electrical signals. .