Pattern estimating method and pattern forming method

Radiation imagery chemistry: process – composition – or product th – Including control feature responsive to a test or measurement

Reexamination Certificate

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C430S311000

Type

Reexamination Certificate

Status

active

Patent number

06187488

Description

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-074046, filed Mar. 18, 1999; and No. 11-273212, filed Sep. 27, 1999, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
This invention relates to a pattern estimation method for measuring the size of a resist pattern during optical lithography employed in the manufacture of a semiconductor device. It also relates to a pattern forming method for determining a development interrupting period for forming the resist pattern.
In optical lithography employed in the manufacture of a semiconductor device, it is important to form an accurate resist pattern. To this end, the prior art employs a method for executing developing period control and size measurement by providing a monitor pattern different from a device pattern and monitoring the intensity of light reflected from the monitor pattern during development or after development.
Japanese Patent Application KOKAI Publication No. 10-300428, for example, discloses a method using a monitor pattern whose element pattern is different from that of a device pattern. In this method, however, a pattern that shows a greater change in size with lapse of development time than the device pattern is used as the monitor pattern, and only this monitor pattern is monitored. Accordingly, when defocusing occurs in an optical system for exposure, a characteristic difference will occur between the device pattern and the monitor pattern. This interrupts accurate developing period control and size measurement.
Further, there is a case where variations will occur in the intensity of reflected light during development, or where lots of time is required until a development interrupting liquid is supplied after the termination of monitoring. If in such a case, a control method for monitoring variations in the intensity of reflected light during development, and stopping development when the measured intensity reaches a threshold value is employed, it is difficult to accurately determine the actual development time period.
With the advance of techniques for refining the size of LSIs, more and more accurate size measurement is required during developing a resist. As afore-mentioned, the method for using a monitor pattern whose element pattern is different from that of a device pattern to measure the size of a resist pattern is disadvantageous in that accurate measurement cannot be realized when defocusing has occurred in an exposure optical system.
BRIEF SUMMARY OF THE INVENTION
The present invention has been developed in light of the above, and aims to provide a pattern estimation method for realizing accurate measurement of the size of a resist pattern even when defocusing has occurred in an exposure optical system.
It is another object of the invention to provide a pattern forming method for accurately determining a development interruption period of a resist to enhance the pattern accuracy.
To attain the first-mentioned object, there is provided a pattern estimating method of exposing a resist film on a to-be-processed substrate, thereby developing a device pattern, and estimating the size of the device pattern, comprising the steps of:
cutting part of the device pattern, using the cut part as an element area or designing an element area by partially changing the size of the cut part, and repeatedly arranging the element area into a monitor pattern;
exposing the device pattern and the monitor pattern when exposing the resist film;
developing the resist film, then applying light of a predetermined wavelength to the monitor pattern, and detecting the intensity of diffracted light reflected from the monitor pattern; and
estimating the size of the device pattern corresponding to the intensity of the detected diffracted light on the basis of a relationship between a predetermined diffracted light intensity and a device pattern size.
To attain the second-mentioned object, there is provided a pattern forming method of exposing a resist film on a to-be-processed substrate, thereby developing the exposed resist film for a predetermined period, and forming a device pattern, comprising the steps of:
cutting part of the device pattern, using the cut part as an element area or designing an element area by partially changing the size of the cut part, and repeatedly arranging the element area into a monitor pattern;
exposing both the device pattern and the monitor pattern when exposing the resist film;
developing the resist film, then applying light of a predetermined wavelength to the monitor pattern, and detecting the intensity of diffracted light reflected from the monitor pattern;
estimating the size of the device pattern corresponding to the intensity of the detected diffracted light on the basis of a relationship between a predetermined diffracted light intensity and a device pattern size; and
stopping development when the estimated size of the device pattern has reached a desired value.
In the present invention constructed as above, the measurement accuracy is significantly enhanced by monitoring (in particular, monitoring zero-order light under the conditions for preventing generation of diffracted light of one-order or more) diffracted light reflected from a pattern which shows a greater reflected light intensity change with respect to a change in its size than the device pattern, or diffracted light reflected from the device pattern itself. Further, even where defocusing has occurred in the exposure optical system, the size of the device pattern can be determined from the intensity of diffracted light by selecting that one of monitor patterns showing a great reflected light intensity change, which corresponds to the type of the device pattern (i.e. selecting a line-type monitor pattern for a line-type device pattern, or a hole-type monitor pattern for a hole-type device pattern).
In addition, simpler measurement can be executed than in the conventional SEM by optically monitoring a monitor pattern as above in a coater/developer unit. As a result, the throughput can be enhanced. Moreover, monitoring a monitor pattern during developing a resist film can enhance the processing accuracy and hence the yield of the products.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.


REFERENCES:
patent: 2-30112 (1990-01-01), None
patent: 9-152716 (1997-06-01), None

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