JPS61241614A - Displacement detecting mechanism - Google Patents

Abstract

PURPOSE:To enable detection at high accuracy by constituting the nozzle multiply to constitute pressure wall of fluid jetted from outside nozzle around fluid jetted from inside nozzle. CONSTITUTION:A nozzle 5 is constituted doubly of an inner tube 6 and an outer tube 7. Accordingly, flow of air jetted from the opening end of the inner tube 6 is sorrounded by a pressure wall constituted by flow of air jetted from the opening end of the outer tube 7. When a space between the opening end of the nozzle 5 and the plane of a wafer 2 becomes more than a specified value, outflow of air to outside starts from a space A in the inner tube 6 through the pressure wall. Consequently, when a safety space to prevent damage of the wafer 2 is provided between the opening of the nozzle 5 and the plane of the wafer 2 caused by contact of the two, variation of pressure in the space A detected by an air pressure detecting section 12 for specified displacement of the plane of the wafer 2 in the direction of optic axis of a microscope section 3 becomes large. Thus, sensitivity of detection of displacement in the direction of optic axis of the microscope section 3 can be increased.

Description

[Detailed Description of the Invention] [Technical Field] The present invention is applied to displacement detection technology, particularly to technology for detecting displacement of a wafer surface in the optical axis direction of an inspection optical system in wafer appearance inspection in the manufacture of semiconductor devices. related to effective techniques.

[Background Art] In general, in the manufacturing of semiconductor devices, in the process of forming a large number of semiconductor elements on a substrate, ie, a wafer, made of silicon or the like, the wafer is A visual inspection will be conducted.

As such an inspection device, the following can be considered.

That is, an image obtained by optically magnifying a predetermined part of the wafer using a microscope section located above the wafer to be inspected is converted into an electrical signal, and compared with a predetermined reference pattern. This is used to judge whether the patterns formed on each part of the wafer are good or bad.

In this case, due to variations in the thickness of each part of the wafer, it is necessary to adjust the focal position of the microscope section for each measurement part of the wafer.

For this reason, for example, a nozzle is provided concentrically with the lens barrel so that the lens barrel of the microscope section is housed inside, and a gas such as air at a constant pressure is injected from this nozzle onto the wafer located below. Configure.

The axial displacement between the wafer plane and the lens barrel is detected by detecting the change in the gap between the wafer plane and the nozzle tip, that is, the pressure of the gas inside the nozzle, which changes due to the axial displacement of the microscope lens barrel. The wafer plane is detected and the wafer plane is displaced relative to the lens barrel so as to correct this displacement, so that the measurement part of the wafer plane is always located at the focal position of the microscope section. be.

On the other hand, the smaller the gap between the nozzle tip and the wafer plane, the larger the pressure change inside the nozzle per unit displacement, and the better the sensitivity for detecting displacement in the nozzle axis direction. To prevent damage to the wafer due to contact, a so-called safety gap is established so that a certain gap is formed between the nozzle tip and the wafer plane when the wafer plane is at the best focus position. It is being

Therefore, in the structure in which displacement is detected using a single nozzle as described above, the position of the wafer plane relative to the focal position of the microscope section is determined when the nozzle tip and the wafer plane are at a safe distance, that is, when the sensitivity to displacement is low. The inventor has found that the position of the wafer plane tends to fluctuate from the best focal position due to changes in external conditions, and the wafer inspection accuracy may be reduced. .

In addition, documents explaining wafer inspection technology include Kogyo Kenkyukai Co., Ltd., November 15, 1983 [Electronic Materials J, 1983 special volume, P2O4-P2O
There are 9.

[Object of the Invention] An object of the present invention is to provide a displacement detection technique that can detect displacement with high accuracy.

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, the relative displacement in the axial direction of a nozzle positioned opposite to the object to be measured with respect to the object to be measured is detected based on the pressure change of the fluid injected from the nozzle toward the object to be measured. By configuring the nozzles of the displacement detection mechanism in multiple layers, a pressure wall of the fluid injected from the outer nozzle is formed around the fluid ejected from the inner nozzle, and the nozzle and the object to be measured are The fluid inside the inner nozzle starts to flow out to the outside at a position where the The sensitivity for detecting displacement is maximized at a position where the nozzle is a predetermined distance from the object to be measured, thereby improving the accuracy of displacement detection.

[Embodiment] FIG. 1 is a schematic cross-sectional view of a wafer visual inspection apparatus equipped with a displacement detection mechanism according to an embodiment of the present invention.

A wafer 2 (object to be measured) is removably placed on a stage 1 provided horizontally.

Further, above the stage 1, a microscope section 3 housing a predetermined lens group is provided with its optical axis perpendicular, at a predetermined distance from the wafer 2 placed on the stage l. , an image of a predetermined part of the wafer 2 is connected to an imaging section 4, which is made of, for example, a charge-coupled device, arranged above the microscope section 3 in a plane perpendicular to the optical axis of the microscope section 3, and is converted into an electrical signal. The converted pattern shape formed at a predetermined portion of the wafer 2 is recognized, and the appearance of the wafer 2 is inspected.

Further, around the microscope section 3, a nozzle 5 (displacement detection mechanism) is provided concentrically with the microscope section 3 as the center, and the opening end of the nozzle 5 is connected to the wafer 2 positioned below with a predetermined gap. The plane of the wafer 2 is positioned at the optimal focal position of the microscope section 3.

In this case, the nozzle 5 is configured to have a double structure with an inner cylindrical part 6 and an outer cylindrical part 7, and each internal space A and space B are independently connected to a throttle valve 8 and a throttle valve 9 (displacement detection mechanism). It is connected to the regulator 10 (displacement detection mechanism) via the regulator 10 (displacement detection mechanism), and is configured so that air at a predetermined pressure flows into the space A and the space B.

Further, the regulator IO is connected to a predetermined air pressure source 11 (
(displacement detection mechanism), and clean air at a predetermined pressure from which moisture and dust have been removed is supplied to each of the inner cylinder part 6 and outer cylinder part 7 of the nozzle 5 via the regulator 10 and the throttle valves 8 and 9. It is supplied to the internal space.

Then, around the flow of air that is injected from the open end of the inner cylinder part 6 toward the plane of the wafer 2 below, air is injected from the open end of the outer cylinder part 7 that surrounds the open end of the inner cylinder part 6. The structure is such that a pressure wall is formed by the flow of air.

Further, on the downstream side of the throttle valve 8 provided in the piping path communicating with the space A inside the inner cylinder section 6, an air pressure detection section 12 is provided.
(Displacement detection mechanism) is connected to the space A that changes due to the change in the gap between the opening end of the nozzle 5 and the plane of the wafer 2, that is, the displacement of the plane of the wafer 2 in the optical axis direction of the microscope section 3. The air pressure is converted into a predetermined electrical signal and detected.

Then, by comparing the electrical signal from the air pressure detection unit 12 with a predetermined reference value, the control unit 13 (displacement detection mechanism) appropriately drives the servo motor 14 (displacement detection mechanism) that raises and lowers the stage 1. The gap between the opening end of the nozzle 5 and the plane of the wafer 2 placed on the stage 1 is always controlled to a predetermined value, so that the position of the plane of the wafer 2 in the optical axis direction of the microscope section 3 is It is configured to be located at the optimum focal position of the section 3.

As described above, since the nozzle 5 has a double structure including the inner cylinder part 6 and the outer cylinder part 7, the air flow injected from the open end of the inner cylinder part 6 is injected from the open end of the outer cylinder part 7. When the gap between the open end of the nozzle 5 and the plane of the wafer 2 exceeds a predetermined value, the air is surrounded by a pressure wall formed by the flow of air. Air passes through the pressure wall and begins to flow outside.

As a result, if a safety distance is provided between the opening of the nozzle 5 and the flat surface of the wafer 2 for the purpose of preventing damage to the wafer 2 due to contact between the flat surface of the wafer 2 and the open end of the nozzle 5. , the air pressure detection unit 1 detects a relative displacement of the plane of the wafer 2 in the axial direction of the nozzle 5, that is, a predetermined displacement of the plane of the wafer 2 in the optical axis direction of the microscope unit 3.
2, a characteristic is obtained in which the pressure fluctuation in the space A detected by
Control to always position the microscope section 3 at the focal position is performed stably.

FIG. 2 is a diagram showing the relative spacing Z of the nozzle 5 in the axial direction with respect to the plane of the wafer 2 in this case, and the change in the air pressure P detected in the space A inside the inner cylinder part 6 of the nozzle 5 at that time. It is.

In the figure, the curve shown as a solid line is the case of this embodiment, and the curve shown as a broken line is the case of a possible single nozzle.

As shown in the figure, when the distance Z is within the safe distance, in the case of the considered nozzle, the change in pressure P with respect to a unit change in the distance Z becomes slower as the distance Z increases, but the solid line In the case of this embodiment shown in FIG.
Due to the action of the pressure wall formed by
is a safe distance apart from the wafer 2 by a predetermined distance,
In other words, since it is made to coincide with the focal point position in the optical axis direction of the microscope section 3, changes in the distance Z controlled based on changes in the pressure P can be detected with high sensitivity, and the plane of the wafer 2 can be stabilized and The microscope section 3 is accurately positioned at the optimum focal point position, and the accuracy of the visual inspection of the wafer 2 is improved.

The operation of this embodiment will be explained below.

First, the wafer 2 is placed on the stage 1.

Next, by adjusting the throttle valves 8 and 9, air at a predetermined pressure is flowed into the space A and the space B respectively constituted by the inner cylindrical part 6 and the outer cylindrical part 7 of the nozzle 5. Air is injected from the open end toward the plane of the wafer 2 placed on the stage 1 through the nozzle 5.
The liquid flows out from the gap between the open end of the wafer 2 and the flat surface of the wafer 2.

At this time, the gap between the opening end of the nozzle 5 and the plane of the wafer 2 changes, that is, the wafer 2 in the optical axis direction of the microscope section 3.
The space A inside the nozzle 5 depends on the relative displacement of the plane of
The pressure inside is changed, and this pressure change is detected by the air pressure detection section 12 connected to the downstream side of the throttle valve 8 connected to the space A.

Then, the control unit 13 compares the pressure value detected by the air pressure detection unit 12 with a predetermined reference value, and takes steps to correct the difference between the pressure value detected by the air pressure detection unit 12 and the predetermined reference value. The servo motor 14 is driven, and the surface of the wafer 2 is positioned so that the gap between the surface of the wafer 2 and the opening end of the nozzle 5 becomes a predetermined value, that is, the optimal focal position in the optical axis direction of the microscope section 3. The stage 1 is raised and lowered as appropriate so that the

In this case, in order to prevent the opening end of the nozzle 5 from coming into contact with the surface of the wafer 2 placed on the stage 1 and damaging the wafer 2, the surface of the wafer 2 is placed at the focal position of the microscope section 3. When the nozzle 5 is positioned, a reference value is set in the control unit 13 so that a predetermined safety distance is maintained between the open end of the nozzle 5 and the surface of the wafer 2. In this embodiment, the nozzle 5 is is formed double, so that the inner cylinder part 6
By appropriately selecting the air pressures flowing into the space A of Air begins to flow out of the nozzle 5 from A, and as shown in FIG. It can be adjusted to be optimal near where the plane of the wafer 2 is located.

As a result, for example, the stage 1 is placed on a predetermined XY table (not shown), and the wafers 2 placed on the stage 1 are moved in the horizontal direction with respect to the optical axis of the microscope section 3, and the wafers 2 are sequentially placed on the stage 1. When different parts of the plane of the wafer 2 are inspected successively, changes in the gap between the nozzle 5 and the plane of the wafer 2 due to variations in thickness in each part of the wafer 2, that is, changes in the gap from the focal position of the microscope section 3, When a plane shift of the wafer 2 occurs, the shift of the inspection area of the wafer 2 from the focus position of the microscope unit 3 is corrected accurately and stably, so that defects in the visual inspection of the wafer 2 by the microscope unit 3 are corrected. Detection accuracy is improved.

[Effects] (1) Relative displacement in the axial direction of a nozzle positioned opposite to the object to be measured causes a change in the pressure of the fluid injected from the nozzle toward the object to be measured. Because the nozzles of the displacement detection mechanism that is detected based on The fluid inside the inner nozzle starts to flow out to the outside at the position where the distance between the object and the object increases by a predetermined value, and the flow is performed in the axial direction of the nozzle based on the pressure change inside the inner nozzle. The sensitivity for detecting displacement with respect to the object to be measured can be adjusted so that it is best at a position where the nozzle is a predetermined distance from the object to be measured, and the accuracy of displacement detection is improved.

(2) As a result of (11) above, in the displacement detection mechanism that detects the displacement of the wafer in the optical axis direction of the microscope section of the wafer visual inspection device, when the wafer is positioned at the optimal focal position of the microscope section, the displacement is detected. The sensitivity of the mechanism is maximized, and the alignment of the wafer to the optimal focal position of the microscope section is performed stably and with high precision.

(3) As a result of (2) above, the wafer defect detection accuracy of the wafer visual inspection apparatus is improved, and the productivity in the inspection process 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, the structure of the nozzle may be multiple, and is not limited to the double nozzle of the above embodiment, but can also be three or more.

[Field of Application] In the above explanation, the invention made by the present inventor was mainly applied to wafer visual inspection technology, which is the field of application that formed the background of the invention, but the invention is not limited thereto. It can be widely applied to technologies that require detection.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a wafer visual inspection apparatus equipped with a displacement detection mechanism that is an embodiment of the present invention, and FIG. 2 is a diagram illustrating the characteristics of the displacement detection mechanism that is an embodiment of the present invention. It is a line diagram. 1... Stage, 2... Wafer (object to be measured), 3...
... Microscope section, 4... Imaging section, 5... Nozzle (displacement detection mechanism), 6... Inner cylinder part (nozzle), 7... Outer cylinder part (nozzle), 8.9... - Throttle valve (displacement detection mechanism),
10...Regulator (displacement detection mechanism), 11...
Air pressure source (displacement detection mechanism), 12...Air pressure detection section (
displacement detection mechanism), 13...control unit, 14...servo motor, A, B...space. Figure 1

Claims (1)

[Claims] 1. A relative displacement in the axial direction of a nozzle positioned opposite to the object to be measured with respect to the object to be measured is a change in the pressure of the fluid injected from the nozzle toward the object to be measured. What is claimed is: 1. A displacement detection mechanism that detects displacement based on the above-mentioned displacement detection mechanism, characterized in that the nozzle is configured in multiple ways. 2. The displacement detection mechanism according to claim 1, wherein the displacement detection mechanism is a displacement detection mechanism that detects displacement of the wafer in the optical axis direction of a microscope section of a wafer visual inspection apparatus. 3. The displacement detection mechanism according to claim 1, wherein the fluid is air.