JPS61168853A - Testing device - Google Patents

Abstract

PURPOSE:To enable to test rapidly, by furnishing an optical system whose axis is parallel to that of an electronic optical system and the distance between the axes is variable, and observing an object to be tested thereover. CONSTITUTION:A wafer 4 is placed on a turn table 2 over an XY table 1. The distance between the axis of an electron beam source 5 and the axis of an optical microscope 10, both axes being parallel each other, is adjusted to be times of integral numbers of the pitch of the element pattern formed on the wafer 4, by an axis-to-axis distance adjusting mechanism 13. the image of the wafer 4 by the microscope 10 is displayed on the display 15, and it is adjusted by moving the table 1, to display at the same position of the testing point of the element pattern. In this case, the axis of the beam source 5 is placed on the position of the objective to be tested. Then the testing position of the object is scanned by the electron beams from the beam source 5. By detecting the secondary electrons generated from the testing position, a high magnification of image is observed in the display 15, and the desired testing is performed.

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 patterns formed on the surface of a wafer in the manufacture of semiconductor devices.

In recent years, in the manufacture of semiconductor devices, integrated circuit patterns formed on semiconductor substrates, or wafers, made of silicon, for example, have been increasing 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 semiconductor device manufacturing technology, especially in phosphorography technology that is 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 plane of the wafer to be inspected is scanned with an electron beam of a predetermined intensity emitted from an electron beam source installed above the wafer placed on a sample stage, and the electron beam is emitted from the part of the wafer that is irradiated with the electron beam. The secondary electrons are detected by a secondary electron detector installed near the wafer, and an image of the pattern formed on the wafer is obtained from the scanning position of the electron beam and the intensity of the secondary electrons detected at that time. is displayed at high magnification on a display device such as a plumber tube.

In this case, it is convenient to inspect a predetermined portion of a pattern formed on a wafer at high magnification, but it is also convenient to identify a predetermined portion of an individual semiconductor element to be inspected from the entire wafer prior to inspection. The disadvantage is that it takes a long time.

For this reason, the sample stage on which the wafer is fixed is configured with an XY table that is movable within the plane on which the wafer is positioned.
The wafer is always fixed at a predetermined position on the sample stage using a positioning jig provided on the sample stage, and the wafer is inspected based on the outer circumferential shape of the wafer and the positional relationship of the individual semiconductor elements formed within the wafer. It is conceivable to specify a predetermined portion of the wafer.

However, the accuracy of the outer circumferential shape of a wafer is generally not as good as the inspection accuracy of a scanning electron microscope, as the wafer is slightly damaged during transportation, and therefore The inventors have found that this method has the disadvantage that it is not sufficient to quickly identify a predetermined inspection site on a wafer.

An example of a patent related to wafer inspection using a scanning electron microscope is Japanese Patent Laid-Open No. 56-61604.

C. Object of the Invention] An object of the present invention is to provide an inspection technique that allows rapid and highly accurate inspection.

The above and other objects and novel features of the present invention will become apparent from the description herein and the accompanying drawings.

[Summary of the Invention] A brief overview of typical inventions disclosed in this application is as follows.

In other words, it is parallel to the axis of an electron optical system that obtains an image of the object by detecting secondary electrons generated by an electron beam scanned over the object, and the distance from the axis of this electron optical system is variable. By providing at least one optical system that has a fixed axis and observes the object to be measured, the object to be inspected can be observed with a wider field of view at low magnification prior to high-precision inspection using the high-magnification electron optical system. A predetermined inspection part of the test object can be quickly identified using an optical system that can be used to quickly identify the predetermined test part of the test object, reducing the time required to specify the predetermined test part of the test object, and ensuring that the optical system and the predetermined positional relationship are the same. This makes it possible to quickly inspect a highly accurate inspection object using a certain electron optical system.

〔Example〕

FIG. 1 is a perspective view showing the main parts of an inspection device that is an embodiment of the present invention.

On the XY table 1, which is movable in a horizontal plane,
A turntable 2 is rotatably provided, and the amount of rotation is controlled by a turntable drive mechanism 3.

A wafer 4 (object to be inspected) on which patterns of a plurality of semiconductor elements are regularly formed at a predetermined pitch is placed on the turntable 2 so as to have a predetermined positional relationship with respect to the XY table 1. has been done.

Further, above the turntable 2, there is a beam source 5 with a shaft attached to the wafer 4.
(electron optical system) is provided, and is configured to irradiate a predetermined portion of the wafer 4 placed on the turntable 2 with an electron/electron beam.

In this case, the electron beam irradiated onto the wafer 4 is configured to scan a predetermined portion of the wafer 4 by a deflection lens 6 provided inside the electron beam source 5.

The secondary electrons generated from the wafer 4 scanned by the electron beam are captured by the secondary electron detector 7 (electron optical system), and then amplified by the secondary electron amplification section 8. Based on the scanning position at and the intensity of the secondary electrons detected by the secondary electron detector 7 at that time, an image of the part of the wafer 4 scanned by the electron beam is stored in the electron optical system image memory 9. It is composed of

Furthermore, an optical microscope 10 (optical system) whose axis is parallel to the axis of the electron beam source 5 is provided above the turntable 2, and the surface of the wafer 4 is detected by the electron beam source 5 and the secondary electron detector 7. It is said that it has a structure that can be clearly observed on the L1 sleep page of the electronic light reception "FIR^h," which is composed of electronic light reception "FIR^h,""Subaru Postal Service hf," and "Sasao Hiroshi."

In this case, the image of the surface of the wafer 4 obtained by the optical microscope 10 is configured to be held in the optical system image memory 11.

Further, the distance between the axis of the optical microscope IO and the axis of the electron beam source 5 is made variable by an inter-axis distance adjustment mechanism 13 controlled by a pitch control section 12.

This inter-axis distance control mechanism 13 is composed of, for example, a numerical control mechanism equipped with a laser interferometer, and is capable of precisely controlling the distance between the axis of the electron beam source 5 and the axis of the optical microscope 10.

The distance between the axis of the electron beam source 5 and the axis of the optical microscope 10 is controlled to be, for example, an integral multiple of the pitch of the pattern of semiconductor elements regularly arranged at predetermined intervals on the wafer 1. , the field of view of the optical microscope 10 and the field of view obtained by the electron optical system composed of the electron beam source 5 and the secondary electron detector 7 provide images of the same part of different semiconductor elements having mutually congruent patterns. Furthermore, the images held in the electron optical system image memory 9 and the optical system image memory 11 as described above are alternately displayed on a display section 15 constituted by, for example, a cathode ray tube via an image switching section 14. shall be visibly displayed at or at the same time.

As a result, by specifying a predetermined part of the semiconductor element pattern formed on the wafer 4 based on the image of the optical microscope 10 that can obtain a clear image with a low magnification, that is, a wide field of view, The field of view of the electron optical system that performs a high-precision predetermined inspection can be quickly set to the target area of the semiconductor element pattern formed on the wafer 4. This reduces the time required to set up the settings, making it possible to quickly perform high-precision inspection using the electron optical system.

The operation of this embodiment will be explained below.

First, the wafer 4 is placed on the turntable 2.

At this time, the turntable is driven so that the arrangement direction of the semiconductor element patterns regularly formed on the wafer 4 at a predetermined pitch is parallel to a predetermined movement axis of the XY table 1 that moves the turntable 2 in a horizontal plane. The rotation angle of the turntable 2 is adjusted by the mechanism 3.

Then, the pitch controller 12 controls the distance between the axis of the electron beam source 5 and the axis of the optical microscope 10 to be an integral multiple of the pitch of the semiconductor element pattern regularly formed on the wafer 4. It is set by the controlled center distance adjustment mechanism 13.

Next, the image of the wafer 4 taken by the optical microscope 10 is displayed on the display section 1.
5, the image of the optical microscope 10 displayed on the display section 15 is displayed on the wafer 4 by moving the XY table 1 in a predetermined direction as appropriate. Adjusted to display the same part as the part.

At this time, the axis of the optical microscope 10 and the axis of the electron beam source 5, which is located at a distance that is an integral multiple of the pitch of the pattern of semiconductor elements regularly formed on the wafer 4, are congruent to each other and are separated by a predetermined distance. They are set simultaneously at the same portion of the pattern of the semiconductor device, that is, the target portion to be inspected.

Next, the electron beam emitted from the electron beam source 5 scans the target inspection area of the wafer 4 set as described above, and detects secondary electrons generated from the inspection area. A magnified image is displayed on the display unit 15, and a predetermined inspection is performed precisely.

In this way, the wafer 4 is imaged based on the image of the optical microscope 10 that can obtain a clear image with low magnification, that is, a wide field of view.
By specifying a predetermined portion of the semiconductor device pattern formed on the wafer 4, the field of view of the electron optical system that performs a high-precision, predetermined inspection with high magnification, that is, a narrow field of view, can be determined by specifying a predetermined portion of the semiconductor device pattern formed on the wafer 4. It can be quickly set to the target area, the time required to set the field of view of the electron optical system to the target area of the semiconductor element pattern is shortened, and high-precision inspection using the electron optical system can be performed quickly. Become.

Furthermore, since the operation of identifying the target portion of the wafer 4 to be inspected is performed using the image of the optical microscope 10, the time during which the wafer 4 is irradiated with the electron beam is shortened, and the Damage is reduced.

Then, by appropriately moving the XY table 1, which moves the turntable 2 on which the wafer 4 is placed, within a predetermined plane, by a predetermined distance, a pattern of a plurality of semiconductor elements regularly formed on the wafer 4 is formed. Desired areas can be inspected quickly and with high precision.

[Effects] (1) Parallel to the axis of an electron optical system that obtains an image of the object by detecting secondary electrons generated by an electron beam scanned over the object; It has an axis whose distance from the
Since both are equipped with a single optical system, the object to be inspected is inspected using a low-magnification optical system that allows the object to be observed in a wider field of view, prior to high-precision inspection using a high-magnification electron optical system. As a result, the time required to identify the predetermined inspection part of the object to be inspected is shortened, and as a result, high-precision Inspection of the object to be inspected can be carried out quickly.

(2) As a result of the above (1), the time during which the object to be inspected is irradiated with the electron beam is shortened, and damage to the object to be inspected due to irradiation with the electron beam is reduced.

(3) As a result of (1) and (2) above, productivity in inspection is improved.

Although the invention made by the present inventor has been specifically explained based on Examples above, the present invention is not limited to the Examples (although it is possible to make various changes without departing from the gist of the invention). Not even.

For example, it is also possible to adopt a structure in which a plurality of optical microscopes are arranged around an electron beam source.

[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 inspection 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 drawings]

FIG. 1 is a perspective view showing the main parts of an inspection device that is an embodiment of the present invention. 1...XY table, 2...turntable, 3...
... Turntable drive mechanism, 4... Wafer (object to be inspected), 5... Electron beam source (electron optical system), 6...
Polarizing lens, 7... Secondary electron detector (electron optical system),
8... Secondary electron amplification unit, 9... Electron optical system image memory, 10... Optical microscope (optical system), 11... Optical system image memory, 12... Pitch control unit, 13. ... Inter-axis distance adjustment mechanism, 14... Image switching section, 15... Display section.

Claims (1)

[Scope of Claims] 1. An inspection device equipped with an electron optical system that obtains an image of an object to be inspected by detecting secondary electrons generated by an electron beam scanned over the object, the inspection device comprising: An inspection device comprising at least one optical system that is parallel to an axis of an optical system and whose distance from the axis of the electron optical system is variable, and that observes an object to be inspected. 2. The inspection device according to claim 1, wherein the optical system is an optical microscope. 3. The inspection apparatus according to claim 1, wherein the object to be inspected is a wafer.