JPS61124810A - Pattern shape inspecting apparatus - Google Patents

Abstract

PURPOSE:To make evaluation at high accuracy on the shape of a microscopical hole pattern, by binary starting per image luminances of two-dimensional images obtained by scanning of electron beams and calculating the hole area of the hole pattern from the stored content. CONSTITUTION:Electron beams 10 are scanned to a specimen 13 with a hole pattern and the secondary electron 14 is detected by a secondary electron detector 15 for starting the luminances of the pattern memory 16 stored two-dimensional electron images. The luminances of the two-dimensional electron images stored in this pattern memory 16 are compared per each image by a binarizing circuit 17 with a threshold value for binarization. This binarized output is stored in the memory 18 per image as white and black color information. And, an area of a portion corresponding to the hole of the hole pattern is calculated by a calculating unit 19 by taking in the stored content of the memory 18 and the magnifying ratio of the image at the time of electron scanning.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a pattern shape inspection device, and more particularly to a pattern shape inspection device suitable for evaluating the shape of a microhole pattern in a semiconductor integrated circuit.

[Background technology]

Conventionally, when examining the pattern shape in detail, especially during pattern processing in the LSI manufacturing process, the shape of a hole 3 formed in, for example, an insulating film (pattern material) 2 on a semiconductor substrate 1 is considered in detail, as shown in FIG. 3(b). If necessary, use an optical microscope to set a scan line 4 for dimension measurement at approximately the center of the hole pattern as shown in FIG. Ta.

However, due to limitations in the positioning performance of the dimension measuring optical system, it is difficult to correctly determine the position of the scanning line 4, and sometimes the dimension is measured at the position of the scanning line 5, resulting in an error.

It becomes difficult to accurately evaluate dimensions and therefore shape.

Also, as LSIs become smaller, patterns become smaller.
When the size of contact holes, through holes, etc. becomes 1 μm or less, even if the mask shape is square, it collapses into a circular hole 6 on the wafer as shown in FIG. 4.

In this case it becomes extremely difficult to center the scan line 7 correctly.

As described above, with the conventional method using an optical microscope, it is extremely difficult to measure the dimensions of a microhole pattern, and the shape of the microhole pattern cannot be evaluated correctly. Even if the dimensions are measured by electron beam scanning using a scanning electron microscope that can obtain
The inventor has revealed that the optical method has similar problems when it comes to measuring the dimensions of holes as described below.

A known example of a distance measuring device for a scanning electron microscope is JP-A-56-61604.

[Purpose of the invention]

An object of the present invention is to provide a pattern shape inspection device that can evaluate the shape of hole patterns, particularly the shape of fine and large patterns, with high precision.

The above and other objects and novel features of the present invention include:
It will become clear from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

That is, by scanning a sample with a hole pattern with an electron beam and comparing the brightness of a two-dimensional image based on the information signal obtained thereby with a threshold value, a binary Cal 1 is calculated for each pixel.
19, #O#), divide each pixel into a white part and a black part, calculate the area of the white part and black part of the part corresponding to the hole part of the hole pattern, and calculate the high resolution of this electron beam method (optical method). 0.2 to 0.3 μm in case.

It is 0.01 μm. ) Based on the highly accurate calculated area, it is possible to evaluate the shape of hole patterns, especially micro hole patterns, with high accuracy.

〔Example〕

FIG. 1 shows an embodiment of a pattern shape inspection apparatus according to the present invention.

The present invention will be described below with application to the case of evaluating the shape of a fine hole pattern on a wafer in an LSI manufacturing process.

A device with an electron optical system that scans a sample (a wafer with a fine hole pattern formed on it) with an electron beam and forms a two-dimensional image of the sample based on the information signals obtained. , for example a scanning electron microscope can be applied. Then, the electron beam 10 from the electron gun 9 is passed through the electron lens (convergent lens) 11 to the sample stage.
The electron beam is focused on a sample 13 (a wafer with a fine hole pattern formed thereon) on the sample 2, and is two-dimensionally scanned on the sample 13 by an electron beam deflection circuit (not shown).

At this time, 14 secondary electrons are generated from the sample 13 and collected by the secondary electron detector 15. When the electron beam is scanned one after another at the same pitch on the microhole pattern, the secondary electron detector 1
5, signal waveforms as shown in FIG. 2 are successively obtained. In FIG. 2, the positions where the pulses rise correspond to the edges of the holes in the minute pattern. Therefore, the peak value (or threshold value) of the rising pulse-like portion in Figure 2
If you take the envelope at the position corresponding to , the inside corresponds to the area of the hole in the hole pattern.

The configuration of the latter stage after the secondary electron detector 15 is particularly added in the present invention, and a two-dimensional image of a fine and large pattern is stored in the pattern memory 16 based on the output of the secondary electron detector 15. . This pattern memory 16 is usually 8
Since it has a bit gradation, images with different brightness and darkness are obtained on the pattern memory 16. Then, bright and dark areas corresponding to the hole shape are displayed. The brightness and darkness of the two-dimensional electronic image stored in the pattern memory 16 is compared with a threshold value for each pixel in the subsequent binarization circuit 17, and if it is equal to or higher than the threshold value, it is 1''(white); If it is smaller than the threshold value, it is output as 110 #1 (black).The output of this binarization circuit 17 (“1” or as Ot
o), each pixel is displayed in white or black in the pattern memory 18. As a result, a two-dimensional image of the hole pattern expressed in black and white is drawn in the pattern memory 18.

On the other hand, the area per pixel of the pattern memory 18 can be determined separately by the magnification of the image during electron beam scanning, so the area corresponding to the holes of the hole pattern is
It can be determined by counting the number of pixels in the portion corresponding to the hole in the two-dimensional image of the hole pattern stored in 8, and multiplying this count by the area per pixel. Therefore, the calculation unit 19 that calculates the area corresponding to the hole in the hole pattern includes a counting circuit that counts the number of pixels in the white part and black part of the part corresponding to the hole in the hole pattern image stored in the memory 18; It consists of a multiplication circuit that calculates the area of the portion corresponding to the hole by multiplying the output count value of the counting circuit by the separately determined area of the pixel. Next, the area calculated by the calculation unit 19 is displayed on the display unit 20, so that the shape of the fine and large patterns on the wafer can be evaluated. Furthermore, since an electron beam scanning method is used that provides high resolution (for example, 0.01 μm), a highly accurate two-dimensional electron image of the hole pattern can be obtained. Then, by measuring the area of the part corresponding to the hole in this hole pattern image, the area of the hole in the hole pattern can be calculated with high accuracy. It is possible to evaluate the shape of a microhole pattern with high precision.

The output of the calculation unit 19 can also be used to determine and select the quality of the shape of the microhole pattern.

In the above embodiment, the pattern memory 16 is interposed, but the output of the secondary electron detector 15 is directly input to the pattern memory 18 via the binarization circuit 17, and the output is input to the pattern memory 18. It is also possible to obtain a black and white two-dimensional electronic image of the hole pattern. In this case, in order to remove the influence of noise etc., the position where the first pulse-like part of each signal waveform as shown in FIG. 2, which is the output of the secondary electron detector 15, exceeds a predetermined threshold value is For example, “
Each pixel in the part corresponding to the hole is are all “1” (white), pattern memory 1
8, the hole can also be displayed as a white two-dimensional image.

Then, by adding all the white parts of each pixel as II 179, the total number of pixels in the hole can be obtained.

[Effects] (1) When evaluating the shape of the hole pattern, by using the electron beam scanning method, which has higher resolution than the optical scanning method, the portion corresponding to the hole in the two-dimensional image of the hole pattern obtained with high accuracy. Since we decided to use the area calculated for the area of , it is possible to evaluate the shape of the hole pattern with high accuracy.

(2) Therefore, it is suitable for highly accurate evaluation of the shape of a fine hole pattern on a wafer in the LSI manufacturing process.6 Furthermore, it is suitable for highly accurate evaluation of pattern shapes that generally have submicron dimensions regardless of LSI manufacturing.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the above Examples and can be modified in various ways without departing from the gist thereof. Nor.

[Application field]

In the above description, the invention made by the present inventor was mainly applied to the evaluation of the shape of a fine hole pattern on a wafer in the LSI manufacturing process, which is the field of application in which the invention is based.

The present invention is not limited thereto, and can be applied to the evaluation of hole pattern shapes in the manufacturing process of semiconductor devices in general, and can also be applied to the evaluation of a wide range of general pattern shapes, such as pattern shapes having submicron dimensions, for example.

[Brief explanation of the drawing]

The first part is a block diagram showing an embodiment of the pattern shape inspection apparatus according to the present invention, and the second part is a diagram obtained one after another in accordance with electron beam scanning. 2 is an operation explanatory diagram showing an example of an output waveform of the secondary electron detector of FIG. 1. FIG. FIGS. 3(a) and 3(b) are diagrams for explaining the conventional pattern shape inspection method, in which FIG. 3(a) is a plan view of the hole pattern, and FIG. 3(b) is a cross section of the hole pattern. It is a diagram. FIG. 4 is an explanatory diagram of the same conventional pattern shape inspection method. 9... Electron gun, 10... Electron beam, 11... Focusing lens. 12... Sample stand, 13... Sample, 14... Secondary electron. 15... Secondary electron detector, 16.18... Pattern memory, 17... Binarization circuit, 19... Arithmetic unit, 2
0...Display section. Figure 1 Figure 3

Claims (1)

[Claims] 1. Scanning a sample having a hole pattern with an electron beam,
In an apparatus having an electron optical system that forms a two-dimensional image of a sample based on an information signal obtained thereby, a binarization circuit that binarizes the brightness of the two-dimensional image for each pixel; a memory that stores each pixel by dividing it into one of two color parts according to the output of the color part, and a calculation part that calculates the area of the part corresponding to the hole of the hole pattern stored in this memory. A pattern shape inspection device characterized by: 2. The arithmetic unit includes a counting circuit that counts the number of pixels in a portion corresponding to a hole in the hole pattern stored in the memory, and a counting circuit that multiplies the output count value of this counting circuit by the area of the pixel and calculates the number of pixels in the hole in the hole pattern stored in the memory. 2. The pattern shape inspection device according to claim 1, further comprising a multiplication circuit for calculating the area of the corresponding portion.