JPH032508A - Microscopic dimension measurement method using a scanning electron microscope - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] <Industrial Field of Application> The present invention relates to a minute dimension measurement method using a scanning electron microscope used in the semiconductor industry, etc. 6. <Prior Art> As the degree of integration of semiconductor integrated circuits increases When the width of a pattern formed on a substrate to be inspected is on the order of 1 μm or less, it is no longer appropriate to measure it using an optical method, and more accurate measurements can be made using a scanning electron microscope. I try to do it. That is, as shown in FIG. 4, by scanning and irradiating the substrate 30 with negative electrons a at a predetermined energy, the energy level of the secondary electrons emitted from the substrate 3o is detected by a scintillator. Furthermore, after the detection data of the scintillator is converted in a predetermined manner, it is captured into an image memory, and the captured image data is sequentially read out from the image memory to project an image of the substrate 3o on the cathode ray tube. Furthermore, by utilizing the fact that the energy level of the emitted secondary electrons is different between the edge portion and the flat portion of the pattern 31 on the substrate 3o, the spacing between the edge portions of the pattern 31 is determined based on the corresponding image data. This is calculated and outputted to the outside as the pattern 310 width dimension.

<Problems to be Solved by the Invention> However, before performing the pattern width dimension measurement described above, it is necessary to perform image adjustments such as focus and brightness. This has the drawback that accurate measurement results cannot be obtained due to the so-called charge-up phenomenon (see FIG. 4). The measurement error based on this charge-up phenomenon is −
Although it depends on the voltage and current of the next muntin a or the conditions of electron beam irradiation time, the order of magnitude is 0.1 to 0.2 μm.
This has led to a degree of measurement error. Conventionally, next kumiko a
Efforts have been made to reduce the effect of the charge-up phenomenon by reducing the energy of This is a very serious obstacle in the development of integrated circuit amplifiers.

The present invention was devised in view of the above circumstances, and aims to improve measurement accuracy by -1- by eliminating the influence of the charge-up phenomenon as much as possible.
The purpose of this study is to provide a microscopic measurement method using a scanning electron microscope.

<Means for Solving the Problems> In the micro-dimensional measurement method using a scanning electron microscope according to the present invention, after measuring the dimensions of the object with an electron beam irradiation time T, Measured value correction data corresponding to the electron beam irradiation time T is obtained from a charge-up characteristic data table consisting of a data pair of beam irradiation time and measured value correction data, and the dimensions of the object to be measured are measured based on the measured value correction data. The results have been corrected.

<Example> Hereinafter, an example of a method for measuring minute dimensions using a scanning electron microscope according to the present invention will be described with reference to the drawings. 1st
The figure is a simplified configuration diagram of a scanning electron microscope, Figure 2 is a graph showing the relationship between electron beam irradiation time and measured dimensions to explain measurement errors due to charge-up phenomenon, and Figure 3 is a cross-section of the object to be measured. It is the mouth.

The scanning electron microscope shown in FIG.
This device measures the width dimension of the pattern 31 formed on the screen and outputs the measured data for display on the cathode ray tube 10. A filament 25, a magnetic lens 21.21, a deflection coil 22, a magnetic lens 23, and a scintillator 24 are arranged at predetermined locations in the vacuum chamber 20, respectively.
The magnetic lenses 21 and 21 give energy to the primary electrons a generated in the filament 25, and the deflection coil 22 and the magnetic lens 23 irradiate the substrate 10 with the energized primary electrons a while scanning them. It looks like this.

Furthermore, the scintillator 24 detects the energy level of secondary electrons emitted from the substrate 30 by irradiating the -order muntin a, and after converting this detected data in a predetermined manner, the main component of the microcomputer is The data are sequentially guided to an arithmetic circuit 40 where In addition, CRT 1
Synchronized deflection voltages supplied to the zero deflection coil 11 and the above-mentioned deflection coil 22 are generated by an arithmetic circuit 40.

Since the measurement principle of a scanning electron microscope having such a basic configuration is well known, the explanation thereof will be omitted, and the operation of the arithmetic circuit 40 related to the Himuro method will be explained below.

A predetermined memory in the arithmetic circuit 40 includes programs related to the Himuro method and a charge-up characteristic data table in addition to programs necessary for operating the scanning electron microscope, that is, calculating the width dimension of the pattern 31 on the substrate 30. 41 is stored in advance.

First, the charge-up characteristic data table 41 will be explained. This is a ROM table consisting of a data pair of electron beam irradiation time and measured value correction data, and is prepared in advance for each measurement target. Here, the electron beam irradiation time is the time during which the -th muntin a is irradiated onto the substrate 30, and the measured value correction data is the time when the -th muntin a is irradiated onto the substrate for the electron beam irradiation time. This is measurement error data based on the influence of the charge-up phenomenon.

By the way, when the inside of the vacuum chamber 20 is in a vacuum state, in order to obtain stable operation, the filanone 1-25 is usually in an operating state. Then, in the arithmetic circuit 40, 1. The built-in timer is started at the timing when the supination blanking mechanism that shields the primary electrons a emitted from Filanon I.25 in front of the substrate 30 is opened, and then the timing when the blanking mechanism is closed. In other words, at the timing when the adjustments necessary for measurement are completed, the above-mentioned timer is stopped, and the electronic year 1 hour T of the primary electrons a irradiated to the substrate 30 is calculated. There is. Furthermore, in step 1-, the arithmetic circuit 40 reads measured value correction data corresponding to the calculated electronic beam J and irradiation time T from the charge-up characteristic data table 41, and creates a pattern based on the read measured value correction data. The calculation result of the width dimension of 3I is corrected. The corrected calculation result is then output to the outside onto the cathode ray tube 10.

Next, a process of obtaining the width dimension of the pattern 31 on the substrate 30 using the scanning electron microscope configured as described above will be described.

First, after the substrate 30 is set in the vacuum chamber 20, the chamber 20 is brought to a predetermined vacuum state and the filament 25 is energized. When the blanking mechanism is opened, the filament 25 generates a magnetic lens 21.
The primary electrons a given energy by 21 are irradiated onto the substrate 30 while being scanned.

Then, secondary electrons are emitted from the substrate 30 and this energy level is detected by the scintillator 24, and the detected data is sequentially taken into the image memory of the arithmetic circuit 40. Then, the edge portion of the pattern 31 is picked up among the images related to the substrate 30, and the edge interval of the pattern 31 is calculated (this calculation result is used as calculation data). Thereafter, the electron beam irradiation time T is read from the count value of the timer built in the arithmetic circuit 40, and measured value correction data corresponding to the read electron beam irradiation time T is searched from the old charge-up characteristic data table. The measured value correction data read from the charge-up characteristic data table 41 provides measurement error data when the electron beam irradiation time is 1゛.
If the calculated data is corrected using this, the measurement error due to the charge-up phenomenon caused by the time required for image adjustment before pattern width measurement can be eliminated, and the accurate width dimension of pattern 31 can be obtained. .

Incidentally, FIG. 3 shows a typical example of a patterned substrate. That is, a pattern 31 consisting of two layers of tungsten silicide 311 and phosphorus-doped polysilicon 312 is formed on a substrate 30 on which a silicon oxide film 32 is deposited on the upper surface of silicon.
is formed. When attempting to measure a measurement object consisting of such a two-layer pattern 31 using the conventional method, if an attempt is made to reduce the influence of the charge-up phenomenon,
-It is necessary to adjust the voltage of the secondary electron a and the electron irradiation time as appropriate, but in the Himuro method, information on measurement errors based on the charge-up phenomenon is pre-implanted for each measurement target, so such Highly accurate measurement results can be obtained for any object to be measured without making any troublesome adjustments. Therefore, it is of great significance in manufacturing and developing highly integrated semiconductor integrated circuits.

It should be noted that the minute dimension measurement method using a scanning electron microscope according to the present invention is not limited to the above embodiment, and for example, it is also possible to use a hardware configuration using an analog electronic circuit in which the charge-up characteristic data table is approximated by a polygonal line. be.

<Effects of the Invention> As described above, the method for measuring minute dimensions using a scanning electron microscope according to the present invention can cancel measurement errors due to the charge-up phenomenon based on the time required for image adjustment performed before pattern width measurement.

In other words, the influence of the charge amplifier phenomenon is eliminated as much as possible, and measurement accuracy can be improved. Therefore, it is not necessary to do troublesome things such as reducing the energy of negative electrons or shortening the electron beam irradiation time, which is of great significance in manufacturing and developing highly integrated semiconductor integrated circuits. .

[Brief explanation of the drawing]

1 to 3 are diagrams for explaining an embodiment of the method for measuring minute dimensions using a scanning electron microscope according to the present invention, and FIG. 1 is a simplified diagram of the scanning electron microscope. FIG. 2 is a graph showing the relationship between electron beam irradiation time and measured dimensions to explain measurement errors due to the charge-up phenomenon, and FIG. 3 is a cross-sectional view of the object to be measured. Fourth
The figure is a schematic diagram mainly used to explain the charge amplifier phenomenon. 30・ 31・ 41 ・ ・Substrate/pattern charge-up characteristic data table ・-Primary electrons/Secondary electrons

Claims (1)

[Claims] (1) A micro-dimensional measurement method using a scanning electron microscope that measures the dimensions of an object to be measured by scanning and irradiating the object with electrons, which After measuring the dimensions of the object to be measured, the measured value correction data corresponding to the electron beam irradiation time T is obtained from a charge-up characteristic data table consisting of data pairs of the electron beam irradiation time and measured value correction data prepared in advance. A method for measuring minute dimensions using a scanning electron microscope, characterized in that the result of dimension measurement of the object to be measured is corrected based on the measurement value correction data.