JPS61148312A - Inspection - Google Patents

Abstract

PURPOSE:To achieve a higher measuring accuracy, by varying the magnification of orthogonal two axes in a measuring view composed of electron beam scans over an object to be inspected at a display section. CONSTITUTION:A sample 2 to be measured is placed on an XY table 1 and then, the table 1 is moved to hold a specified portion of the sample 2 within the irradiation range of electron beams 7 from an electron beam source 6. Then, the specified portion of the sample 2 is scanned by the electron beams 7 to compose a measuring view range. In this case, the magnitude of x and y in the longitudinal and laterial way of the measuring view are made unequal in sides as shown by x>y with an electron beam source control section 11 and the values thereof are held at a main control section 16. On the other hand, secondary electrons 8 released from the sample 2 with the scanning of the electron beams 7 are trapped with secondary electron detectors 9 and 10 and the number of the electrons trapped at the secondary electron detectors 9 and 10 are converted into electronical signals respectively with signal conversion section 12 and 13. Then, the signals are synthesized with a image processing section 14 into an image and an image equal in sides is outputted to a display section 15 from the measuring view unequal in sides based on the values of x and y held at the main control section 16.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an inspection technique, and particularly to a technique that is effective when applied to inspecting the cross-sectional shape of a wafer in the manufacture of semiconductor devices.

[Background Art] In recent years, in the manufacture of semiconductor devices, integrated circuit patterns formed on semiconductor substrates, ie, wafers made of silicon, etc., are becoming increasingly denser and more integrated due to demands for higher density and higher integration of integrated circuit elements. There is a growing trend towards further miniaturization and complexity.

For this reason, in the manufacturing technology of semiconductor devices, especially in the lithography technology directly related to the processing of fine patterns,
There is a need to measure the dimensions of fine patterns, distances between patterns, and defects with a higher precision than the manufacturing accuracy of circuit elements, and a scanning electron microscope, for example, is sometimes used as an inspection device to measure fine patterns. .

That is, the surface of the sample to be measured is scanned with an electron beam of a predetermined intensity emitted from an electron beam source with an axis perpendicular to the sample surface fixed on a sample stage, and at this time the electron beam emitted from the wafer surface is scanned. Detecting the secondary electrons by a plurality of secondary electron detectors placed at different positions near the wafer surface,
This system converts the difference in the number of secondary electrons observed by each secondary electron detector into an electrical signal, and displays the fine structure of the sample surface on a similarly enlarged screen, such as on a CR7 screen. be.

For example, when measuring changes in the thickness of a resist coated on a wafer in the evaporator plane direction, that is, waviness, a predetermined part of the wafer coated with the resist is cut in the thickness direction, and the wafer is embedded in, for example, resin. The cross section is polished and used as a measurement sample.

It is conceivable to measure the waviness of the resist coated on the wafer plane by observing this sample using the method described above.

In this case, if the wafer plane is taken as the horizontal axis of the observation field, the resist thickness will be measured in the vertical axis direction perpendicular to this horizontal axis, but if the waviness of the resist is minute,
If the observation field where the electron beam is scanned is simply enlarged onto a CRT, the wafer plane direction will extend outside the CR7 screen as the resist expands in the thickness direction, and the coating will not be applied to the wafer surface. The inventors have discovered that there is a problem in that it is not possible to accurately observe the waviness of the resist.

In addition, documents describing inspection techniques using a scanning electron microscope include "Electronic Materials" September 1983 issue, published by Kogyo Research Association Co., Ltd., September 1, 1983, P52-
There is a P57.

[Object of the Invention] An object of the present invention is to provide an inspection technique that allows observation of an object to be measured by changing the magnification of each axis of a measurement field of view.

The above and other objects and novel features of the present invention will become apparent 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 making variable the magnification ratio in the display section of the two orthogonal axes of the inspection field formed by the electron beam scanned over the inspection object, dimensional changes in a predetermined axial direction within the inspection field of view are emphasized. to make it possible to measure
This improves the inspection accuracy □ of the inspected object.

[Example] Figure 1 is a perspective view showing an inspection method using a scanning electron microscope, which is an example of a zero source, Figure (b) is its block diagram, and Figure (c) is an observed image. FIG.

A measurement sample 2 is fixed on an XY table l that is movable within a predetermined plane.

The measurement sample 2 is constructed by, for example, cutting a wafer 4 coated with a resist 3 in the thickness direction, embedding and holding a section in a resin 5, and polishing the measurement cross section.

Furthermore, an electron beam source 6 is provided above the XY table l, and secondary electrons 8 emitted from the surface of the measurement sample 2 by the electron beam 7 irradiated onto the measurement sample 2 from the electron beam source 6 are It is configured to be captured by a pair of secondary electron detectors 9 and 10 that are provided obliquely near the XY table 1.

In this case, the electron beam 7 irradiated from the electron beam source 6 to the measurement sample 2 has the width X in the horizontal direction and the width y in the vertical direction of the scanned measurement field of view adjusted by the electron beam source control unit 11, for example. , when observing with emphasis on the vertical direction, the measurement field of view is determined so that x>y.

Further, the secondary electrons 8 emitted from the measurement sample 2 within the measurement field of view are captured by the secondary electron detectors 9 and 10,
The detected number of secondary electrons is converted into an electrical signal by the signal conversion units 12 and 13, and an image signal is formed in the image processing unit 14, and the image signal is displayed on the display unit 15 as shown in FIG. 1(c), for example. It will be displayed on the CR7 screen like this.

Further, the electron beam source control section 11 and the image processing section 14 are configured to be controlled by a main control section 16.

Next, the operation of this embodiment will be explained.

First, a measurement sample 2 is placed on an XY table 1, and by appropriately moving the XY table 1, a predetermined portion of the measurement sample 2 is brought within the irradiation range of the electron beam 7 from the electron beam source 6.

Next, an electron beam 7 is scanned from the electron beam source 6 to a predetermined portion of the measurement sample to form a measurement field of view.

In this case, the vertical and horizontal size y of the measurement field of view and/or the electron beam source control unit 11 is configured such that X>y (scalene side), and the value is held in the main control unit 16.

On the other hand, by scanning the electron beam 7, the measurement sample 2
The secondary electrons 8 emitted from the secondary electron detectors 9 and 1
The number of captured electrons in each secondary electron detector is converted into an electrical signal in signal conversion units 12 and 13, and then combined into an image signal in an image processing unit 14.

At this time, the image processing unit 14 determines the magnification m and n of each axis based on the vertical and horizontal sizes y and X of the measurement field of view held in the main control unit 16. Then, an equilateral image is outputted to the display unit 15 from the scalene measuring field of view as m x −ny.

As a result, an enlarged image of the measurement field of view in which the vertical direction is emphasized compared to the horizontal direction is displayed on the isotonic CRT screen of FIG. 1(c), which is the display section 15.

As a result, in the measurement sample 2 of this embodiment in which the horizontal axis direction is the plane direction of the wafer 4 and the vertical axis direction is the thickness direction of the wafer 4, the resist 3 applied to the wafer 4 is
The thickness of the resist 3 is displayed with emphasis, and minute changes in the waviness of the resist 3 can be measured with high accuracy.

[Effects] (1) Since the magnification ratio of the two orthogonal axes of the inspection visual field formed by the electron beam scanned over the object to be inspected is variable on the display section, measurement is performed with emphasis on a predetermined axis direction. This makes it possible to improve the measurement accuracy of the object to be inspected.

(2) As a result of the above (1), it becomes possible to accurately inspect the waviness of the resist applied to the wafer, and the yield in the manufacturing process of semiconductor devices is improved.

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 Examples and can be modified in various ways without departing from the gist thereof. Nor.

For example, it is also possible to make the measurement field of view longer in the vertical axis direction than in the horizontal axis direction.

[Field of Application] In the above explanation, the invention made by the present inventor has been mainly applied to the field of application which is its background, a scanning electron microscope used for wafer measurement technology, but the present invention is not limited thereto. Rather, it can be widely applied to technologies that require highly accurate measurement of the dimensions of minute parts.

[Brief explanation of the drawing]

FIG. 1(a) is a perspective view showing an inspection method using a scanning electron microscope which is an embodiment of the present invention, FIG. 1(b) is a block diagram illustrating the operation of the inspection method, and FIG. 1(c) 1 is a diagram showing a CRT screen which is a display section. DESCRIPTION OF SYMBOLS 1...XY table, 2...Measurement sample, 3...Resist, 4...Wafer, 5...Resin, 6..., Thunder Rod Bee LJ-700, Thunder Shrimp-1-Q・...Secondary electron, 9
．． lO...Secondary electron detector, 11...Electron beam source control unit, 12.13...Signal conversion unit, 14...Image processing unit, 15...Display unit, 16...Main control section.

Claims (1)

[Scope of Claims] 1. An inspection method for inspecting an object to be inspected by detecting secondary electrons generated by an electron beam irradiated onto the object, which is scanned over the object to be inspected. An inspection method characterized in that the magnification ratio of two orthogonal axes of an inspection field formed by an electron beam is variable in a display section. 2. The inspection method according to claim 1, wherein the object to be inspected is a wafer.