Radiation imagery chemistry: process – composition – or product th – Registration or layout process other than color proofing
Reexamination Certificate
2000-12-14
2003-02-18
Young, Christopher G. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Registration or layout process other than color proofing
C430S030000, C250S491100, C250S492200, C250S492220, C356S400000
Reexamination Certificate
active
06521385
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a position detecting method, a position detecting apparatus, an exposure method, an exposure apparatus, a computer readable recording medium and a device manufacturing method. More particularly, the present invention relates to the position detecting method and the position detecting unit for detecting positions of plural divided areas formed on an object; the exposure method and the apparatus for using the position detecting method; the computer readable recording medium in which the programs to be executed are stored; and a device manufacturing method for using the exposure method.
DESCRIPTION OF THE RELATED ART
Conventionally, in a lithographic process for manufacturing a semiconductor device, liquid crystal display device and so forth, an exposure apparatus has been used. In such an exposure apparatus, patterns formed on a mask or reticle (to be genetically referred to as a “reticle” hereinafter) are transferred through a projection optical system onto a substrate such as a wafer or a glass plate (to be referred to as a “substrate or wafer” herein after, as needed) coated with a resist or the like. As the exposure apparatus, a static exposure type projection exposure apparatus such as a so-called stepper, or a scanning exposure type one such as a so-called scanning stepper is generally used.
In these exposure apparatus, prior to exposure, the positioning of the reticle and the wafer (alignment) must be precisely performed. In order to perform the alignment, position detection marks formed in the above-mentioned lithographic process, i.e., alignment marks formed by exposure transfer, are associates to each shot area. Therefore, the position of the wafer or the circuit pattern on the wafer might be detected by detecting the alignment mark. Then, the alignment is performed by using the detection result of the position of the wafer or the circuit pattern on the wafer.
At present, several methods for position detecting of the alignment mark on the wafer is practically used. Recently, the position detecting method depends on the image detection became major. In this method, optical images of the alignment marks are picked-up by using the image pick-up unit, and the signal of the picked-up image, that is, the distribution of light intensity of the image is then analyzed to detect the positions of the alignment marks. As procedures for such waveform analysis, there is a pattern matching procedure (a template matching). In this method, the position of the alignment of which image is picked-up is set to a parameter, and the correlation between the parameter and the template waveform previously prepared is investigated in the image pick-up range for the alignment mark. Signal waveforms are analyzed by the pattern matching procedure, and the parameter value with the highest correlation between the template waveform is obtained. By using the parameter value, the position of the alignment marks is precisely detected.
The method, which is based on the template matching of the above-mentioned mark image pick-up signal (to be referred to as a “raw waveform” hereinafter, as needed) and used in the conventional method, has high tolerance to the noise having enough smaller period than the arrangement pitch of the line pattern (to be referred to as a “high frequency noise”, hereinafter). For example, when the mark is structured as the line and space mark, the position detection of the mark is precisely performed by using the template matching of the raw waveform, even though the high frequency noise is superposed on the image pick-up signal. The line and space mark is composed of plural line pattern arranged in the predetermined intervals and direction. This derives from that the template matching has a averaging effect of the noise, and the effect caused by the high frequency noise is effectively deleted by the averaging effect of such noises.
However, the noise superposed on the image pick-up signal is not limited to the high frequency noise. For example, in the line and space mark, the noise which has the same degree of the arrangement frequency of the line mark or higher one (to be referred to as a “low frequency noise”, hereinafter) sometimes superposed on the image pick-up signal. In this case, the effect of the noise caused by the averaging effect from the template matching of the raw waveform can not be efficiently removed. Accordingly, the position detection of the mark can not be precisely performed by using the raw waveform template matching, when the low frequency noise is superposed on the image pick-up signal.
SUMMARY OF THE INVENTION
The purpose of the present invention is to provide the position detecting methods and the apparatuses thereof for detecting the positional information of the mark formed on the object.
The another purpose of the present invention is to provide the exposure method and the exposure apparatus for transferring the predetermined pattern to the object accurately.
The yet another purpose of the present invention is to provide the computer readable recording medium in which a program for precisely detecting the positional information of the mark formed on the object is stored.
The still another purpose of the present invention is to provide the device manufacturing method for manufacturing the highly integrated device with fine patterns.
The present inventors have been studied the detection for the position detection mark consisting of line patterns and line spaces formed on the substance and used for positioning. In light of this, the following knowledge is obtained: it is important to detect the border between the line part and the space part (to be referred to as the “edge”, hereinafter), at which the signal level of the imaging signal (i.e., signal intensity) is drastically changed in the position detection of the mark; and it is possible to detect the edge position by detecting the position, at which the absolute value of the rate of change in the signal waveform of the imaging signal is maximum, or the point of inflection in the signal waveform of the imaging signal. The other knowledge is also obtained: that is, the width of the edge portion is very narrow comparing to the line or space width, and the waveform of the edge portion is effected when the high frequency noises are superposed, but not affected when the low frequency noises are superposed. The present invention is completed based on the above mentioned knowledge.
In the first aspect of the present invention, the present invention is a position detecting method for detecting a positional information of a mark formed on an object comprising the steps of: performing an image pick-up of the mark; obtaining a predetermined order differential waveform of a signal waveform, which is obtained in the image pick-up; and detecting said positional information of the mark, based on a correlation between said differential waveform and a predetermined template waveform.
According to this, the imaging signal of the mark obtained is differentiated, and the predetermined order differentiated waveform of the imaging signal is obtained. The differentiated waveform is obtained by focusing on the edge, which is less effected by the low frequency noises derived from the drastically changed signal level of the imaging signal. For example, the rate of change for the signal level of the image pick-up signal (imaging signal) depending on the position is obtained as a waveform, when the predetermined differential waveform is the first order waveform. Since the waveform with the drastic change of the signal level of the imaging signal is obtained, and the waveform showing the characteristics of the edge portion is obtained. Furthermore, the rate of change for the signal level of the image pick-up signal depending on the position is obtained as a waveform, when the predetermined differential waveform is the second order waveform. Therefore, the waveform showing the characteristics of the edge portion is obtained. Still further, the wave
Kokumai Yuuji
Yoshida Kouji
Nikon Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Young Christopher G.
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