JPH01187409A - Method and device for electron beam length measurement - Google Patents

Abstract

PURPOSE:To find a specific pattern among high-density patterns formed on a wafer and to measure its length by aligning chips, one by one. CONSTITUTION:Two global alignment marks 103 are formed on the wafer 101 at both ends in addition to three rows and three columns, i.e. nine chips 102 in total. On each chip 102, alignment marks 104 and patterns 105-107 as objects of length measurement are formed. When this wafer 101 is measured, the two marks 103 are scanned with an electron beam to adjust alignment roughly. Then a stage is moved and the chip 102 to be measured first is scanned with an electron beam to calculate the position of the mark 104 from the signal waveform of a secondary electron emitted by the reflecting surface. Then, the accurate positions of the patterns 105-107 on the chip 102 are calculated from the position of the mark 104 and then those are moved to right below the beam to scan the pattern 105-107 with the electron beam, thereby measuring the line width from the signal waveform of a reflected secondary electron. Thus, the chips 102 are measured repeatedly, one by one.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for measuring the width of a pattern on a wafer using an electron beam.

[Conventional technology]

In the LSI manufacturing process, when measuring the line width of a pattern formed on a wafer using an electron beam, the following steps are performed. That is, the measurement position on the wafer is moved to just below the beam.

Thereafter, the line width of the pattern is determined by scanning the pattern with an electron beam and processing the signal waveform of the secondary electrons emitted from the reflecting surface.

Conventionally, when moving a pattern on a wafer directly under the beam, the alignment mark position is determined by scanning the electron beam over one or two alignment marks formed on the wafer, and then determining the alignment mark position. The line width was measured by moving the stage by the distance from to the measurement pattern position.

[Problem to be solved by the invention]

However, according to the conventional method, since alignment is performed at only one or two locations on the wafer, the accuracy of movement to the desired position is only a few degrees. therefore,
If patterns exist on the wafer at high density on the order of submicrons, portions other than the predetermined patterns will be measured.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems, and to provide a method and apparatus for searching and measuring a predetermined pattern with high precision from among high-density patterns formed on a wafer.

[Means for Solving the Problems] The present invention scans alignment marks formed for each chip on a wafer with an electron beam, and performs alignment from the signal waveform of secondary electrons emitted from the alignment mark from a reflective surface. The process of determining the position of the mark, the process of calculating the position of the pattern in the chip from the position of the alignment mark and moving the pattern directly under the electron beam, and the process of scanning the pattern with the electron beam and detecting the reflection from the pattern. An electron beam length measurement method characterized by repeating the step of measuring the line width of a pattern from a signal waveform of secondary electrons for each chip; and an electron beam measuring method for measuring alignment marks formed on each chip on a wafer. A function to scan and find the position of the alignment mark from the signal waveform of secondary electrons reflected from the alignment mark.
There is a function that calculates the pattern position in the chip from the determined position of the alignment mark and moves the pattern directly under the electron beam, and a function that scans the pattern with the electron beam and calculates the pattern from the signal waveform of the secondary electrons reflected from the pattern. This is an electron beam length measuring device characterized by having a function of measuring the line width of a chip, and a function of repeatedly performing each of the above functions for each chip.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an example of a wafer for carrying out the method of the present invention, and FIG. 2 is a flowchart showing a length measurement sequence when using the apparatus of the present invention.

In FIG. 1, a total of nine chips 102 are formed in three rows and three columns on a wafer 101, and two global alignment marks 103 are formed on both ends thereof. Chip alignment mark 104 inside each chip
and patterns 105, 106, 10 as length measurement targets
7 is formed. When measurement on this wafer 101 is started, as shown in FIG. 2, first, two global alignment marks 103 are scanned with an electron beam to roughly adjust the alignment. As a result, each chip position from the global alignment mark 103 is corrected. Next, the stage is moved to scan the chip alignment mark 104 with an electron beam on the first chip to be measured, and the position of the chip alignment mark 104 is calculated from the signal waveform of the secondary electrons emitted from the reflecting surface.

After calculating the exact positions of the patterns 105, 106 and 107 to be measured within the chip from the obtained chip alignment mark positions, each pattern is moved directly under the beam, and the pattern is scanned with an electron beam to detect the reflected secondary The line width of each pattern is measured from the electron signal waveform. When the measurement for a predetermined pattern within the chip is completed, the chip moves to the next chip and repeats the measurement using the same method.

〔Effect of the invention〕

As described above, according to the present invention, since alignment is performed for each chip, it is possible to accurately determine the position of the pattern to be measured.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an example of a wafer for carrying out the method of the present invention, and FIG. 2 is a flowchart showing a length measurement sequence by the apparatus of the present invention.

Claims (1)

[Claims] 1. An alignment mark formed for each chip on a wafer is scanned with an electron beam, and the position of the alignment mark is determined from the signal waveform of secondary electrons emitted from the alignment mark from a reflective surface. The process of calculating the position of the pattern in the chip from the position of the alignment mark and moving the pattern directly under the electron beam, and the process of scanning the pattern with the electron beam and measuring the secondary electrons reflected from the pattern. An electron beam length measurement method characterized by repeating the step of measuring the line width of a pattern from a signal waveform for each chip. 2. A function that scans the alignment mark formed on each chip on the wafer with an electron beam and determines the position of the alignment mark from the signal waveform of secondary electrons reflected from the alignment mark. A function that calculates the pattern position in the chip from the position and moves the pattern directly under the electron beam, and a function that scans the pattern with the electron beam and measures the line width of the pattern from the signal waveform of the secondary electrons reflected from the pattern. What is claimed is: 1. An electron beam length measuring device characterized by having the following functions: and a function of repeatedly performing each of the above functions on a chip-by-chip basis.