JPS61241659A - Inspecting device - Google Patents

Abstract

PURPOSE:To detect defect in an object to be inspected surely and quickly by making an oscillating section and a receiving section scan the object and detecting the defect by ultrasonic wave arriving from the oscillating section to the receiving section through the object of inspection. CONSTITUTION:Ultrasonic wave radiated from a cable transmitter 6 toward the photomask substrate 3 passes the substrate 3 from the lower face to the upper face, and defect of the substrate 3 is detected by a receiver 6. Every time an XY table 1 moves in left and right direction by specified distance, it is sent by specified pitch in the direction perpendicular to the surface of the paper, and the transmitter 6 and receiver 7 scan the whole face of the substrate fixed to the table 1 at specified speed. After inspecting the whole face of the substrate 3, the table 1 is stopped, and fixing of the substrate 3 by a positioning pin 4 is released, and the substrate 3 is removed from the table 1. By repeating this series of operations, inspection of defect of many substrates 3 can be made quickly at high accuracy.

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 the inspection of photomask substrates used in the manufacture of semiconductor devices.

[Background Art] Generally, in the manufacture of semiconductor devices, a photomask is used as an original plate for transferring a pattern such as a wiring structure of a semiconductor element formed on a semiconductor substrate or wafer made of silicon or the like.

This photomask is made by depositing a light-shielding film such as chrome over the entire surface of the photomask substrate, which is usually made of a transparent glass plate, and then removing a portion of the light-shielding film by etching. It is manufactured by forming a transparent part.

In this case, if there are defects such as bubbles, scratches, or foreign matter formed during the manufacturing of the photomask substrate in the light-transmitting part of the photomask substrate, which should be transparent, the shadows of these defects may appear during pattern transfer. is transferred together with the original pattern, causing pattern defects.

In addition, as semiconductor devices become smaller, pattern shapes tend to become finer and denser, and there is a need to inspect defects such as bubbles, scratches, and foreign objects on photomask substrates with higher precision. It is being done.

For this reason, before forming a light-shielding film on a photomask substrate, it is conceivable to visually inspect the presence or absence of the above-mentioned bubbles, scratches, foreign objects, etc. In addition, to improve inspection accuracy, the inspection work must take a long time, and it is inevitable that some defects will be missed. The present inventor has discovered that this causes a decrease in work efficiency.

Furthermore, in visual inspection, inspection is usually performed by irradiating the photomask substrate with a light beam from a projector and observing the transmitted light, so inspection cannot be performed after the light-shielding film is formed on the photomask substrate. There is also the problem that restrictions are placed on the inspection process.

In addition, documents explaining photomask inspection techniques include Kogyo Kenkyukai Co., Ltd., published November 10, 1981, "Electronic Materials" 1981 special edition, P214~
There is P220.

[Object of the Invention] An object of the present invention is to provide a test wave that allows rapid and highly accurate testing.

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, an oscillating section and a vibration receiving section are provided that are movable relative to the object to be inspected, and the oscillating section and the receiving section are made to scan the object to be inspected, and the vibrations emitted from the oscillating section are received via the object to be inspected. By adopting a structure in which the inspection of the object to be inspected is performed using ultrasonic waves that reach the area, any defects present in the object to be inspected can be detected reliably and quickly without omission. This improves accuracy and productivity.

[Example 1] FIG. 1 is a cross-sectional view of an inspection device that is an example of the present invention.

XY that can move freely in the horizontal direction of the diagram and in the direction perpendicular to the paper surface
A window 2 is formed in the center of the table 1 so as to vertically penetrate the XY table 1.

A photomask substrate 3 (object to be inspected) is placed at the center of the upper part of the XY table 1 so as to cover the window 2.
It is placed horizontally so as to be exposed below the Y table 1,
A plurality of positioning pins 4 arranged around the window portion 2
It is removably fixed by.

In addition, the photomask substrate 3 placed on the XY table l
A transmitter 6 (oscillating section) connected to an ultrasonic pulse oscillator 5 (oscillating section) is provided on the lower surface side of the photomask, and ultrasonic waves of a predetermined frequency are placed above the transmitter 6. It is configured to radiate toward the lower surface of the substrate 3.

Furthermore, a wave receiver 7 (wave receiving section) is provided on the upper surface side of the photomask substrate 3 so as to face the wave transmitter 6 via the photomask substrate 3, and a wave receiver 7 (wave receiving section) is provided so as to face the wave transmitter 6 through the photomask substrate 3. The structure is such that ultrasonic waves emitted from the photomask substrate 3 and passing through the photomask substrate 3 from the bottom surface toward the top surface are detected.

In this case, the transmitter 6 and the receiver 7 are configured to be independently fixed to the XY table 1 by a predetermined support arm (not shown) or the like, and the XY table 1 is moved horizontally in the figure. By driving the wave transmitter 6 and the wave receiver 7 so as to move the photomask substrate 3 fixed to the XY table 1 by a predetermined pitch in a direction perpendicular to the plane of the paper each time it is moved by a predetermined distance, The entire surface is relatively scanned at a predetermined speed.

In the wave receiver 7, the ultrasonic vibrations emitted from the wave transmitter 6 and incident through the photomask substrate 3 are converted into a predetermined electric signal, and a signal processing section 8 (wave receiving section)
The structure is such that, for example, the waveform of the ultrasonic vibration is observed on a display section 9 (vibration receiving section) consisting of a television screen or the like.

On the other hand, in a normal part of the photomask substrate 3, physical properties such as density are almost uniform, but if there are various defects caused by bubbles, scratches such as cracks, foreign matter, etc.
Physical properties such as density become discontinuous at this defective part.

Then, it is radiated from the transmitter 6 to the photomask substrate 3,
In the photomask substrate 3, ultrasonic waves that pass through areas with defects such as those described above cause disturbances in waveforms, transmission speeds, etc. due to scattering and attenuation in areas with discontinuous density, and these disturbances are By observing changes and disturbances in the waveform on the display section 9 via the receiver 7 and the signal processing section 8, it is possible to determine the size of defects present in the photomask substrate 3 and the thickness direction of the photomask substrate 3. depth,
The position of the photomask substrate 3 on the plane is detected from the position of the XY table 1 at that time.

In addition, by appropriately selecting the wavelength of the ultrasonic waves emitted from the transmitter 6 to the photomask substrate 3, it is possible to easily improve the accuracy of detecting defects present in the photomask substrate 3. can be performed with high precision.

In this way, a wave transmitter 6 and a wave receiver 7 are provided which face each other with the photomask substrate 3 in between and scan the plane of the photomask substrate 3. Since the inspection is performed using the ultrasonic waves that pass through and reach the receiver 7, any defects present in the photomask substrate 3 can be detected reliably and quickly.

The operation of this embodiment will be explained below.

First, the photomask substrate 3 is placed horizontally on the XY table 1, and is positioned between the wave transmitter 6 and the wave receiver 7, which are vertically opposed to each other, and is fixed by the positioning pins 4. .

Next, the movement of the XY table 1 is started, and the transmitter 6 and receiver 7, which are vertically opposed to each other via the photomask substrate 3 and are fixed and stationary independently of the XY table 1, are Photomask substrate 3 placed on table l
is relatively scanned along a predetermined path over the entire surface of the area.

At this time, an ultrasonic wave of a predetermined frequency is emitted upward from the transmitter 6 located below the photomask substrate 3 placed on the XY table 1, that is, toward the bottom surface of the photomask substrate 3. Ru.

A part of the ultrasonic waves emitted from the transmitter 6 to the lower surface of the photomask substrate 3 passes through the photomask substrate 3 and is incident on the transfer device 7 provided on the upper surface side of the photomask substrate 3, and a signal is generated. After passing through the processing section 8, the signal is displayed on the display section 9 as a predetermined waveform, for example.

If defects such as bubbles, scratches, and foreign objects exist in the part of the photomask substrate 3 through which the ultrasonic wave passes, discontinuity in physical properties such as density between the normal part other than the defect part and the defect part may occur. This causes scattering and attenuation of the ultrasonic waves, which causes changes in the waveform and transmission speed observed on the display section 9. Based on these changes, the size of the defect and the thickness of the photomask substrate 3 can be determined. The depth in the horizontal direction is detected, and at this time, from the position of the XY table 1 that is being moved to scan the transmitter 6 and receiver 7 relative to the photomask substrate 3, Defect locations in the planar direction of the photomask substrate 3 placed on the XY table 1 are grasped.

In this way, defects present in the photomask substrate 3 can be detected without fail, reliably, and quickly, and it can be accurately determined whether the photomask substrate 3 is suitable for later manufacturing of a photomask.

As a result, it is possible to avoid using the photomask substrate 3 which has defective parts and is not suitable for photomask production due to omission of inspection for defects existing in the photomask substrate 3, and to produce photomasks. Pattern defects are prevented from occurring in the process and in the pattern transfer operation to the wafer performed using this photomask, and the yield and productivity in the semiconductor device manufacturing process are improved.

After the above inspection is performed over the entire surface of the photomask substrate 3, the XY table 1 is stopped, the fixation of the photomask substrate 3 by the positioning pins 4 is released, and the photomask substrate 3 is removed from the top of the XY table 1. be removed.

By repeating the above series of operations, a large number of photomask substrates 3 can be inspected with high precision and quickly.

Furthermore, in the above explanation, the inspection of the photomask substrate 3 made of a single material such as glass was explained.
This can also be applied to inspecting the presence or absence of defects in mask blanks in which a light-shielding film such as chromium is uniformly formed on the surface of the photomask substrate 3, reducing restrictions on when to inspect materials in photomask production. The scope of inspection will be expanded.

[Embodiment 2] FIG. 2 is a cross-sectional view of an inspection device that is another embodiment of the present invention.

The second embodiment differs from the first embodiment in that the ultrasonic transmitter 6 and receiver 7 are provided on the same side of the photomask substrate 3 to be inspected.

That is, on the upper surface side of the photomask substrate 3 placed horizontally on the XY table 1, a wave transmitter 6 and a wave receiver 7 are provided with their axes inclined at a predetermined angle with respect to the plane of the photomask substrate 3. The ultrasonic wave emitted from the transmitter 6 is incident on the upper surface of the photomask substrate 3 at a predetermined angle, and the reflected wave reflected on the lower surface of the photomask substrate 3 is captured by the receiver 7. It is composed of

Then, on the photomask substrate 3 which is fixed to the XY table 1 driven along a predetermined path and is being moved relative to the wave transmitter 6 and the wave receiver 7, the radiation is emitted from the wave transmitter 6 and is received. The display section 9 is caused by scattering or attenuation of reflected waves generated due to defects existing in the reflecting section of the photomask substrate 3 where the ultrasonic waves reaching the wave transmitter 7 are reflected.
A defect is detected as a change in the waveform observed in the waveform.

[Embodiment 3] FIG. 3 is a cross-sectional view of an inspection device that is still another embodiment of the present invention.

In the third embodiment, a part of the wave transmitter 6, the wave receiver 7, and the photomask substrate 3 are immersed in a liquid such as water or oil stored in a fluid tank 10 with an open top. This embodiment differs from the previous two embodiments in that the inspection is carried out in the current state.

That is, in the liquid 11 stored inside the fluid tank 10, the wave transmitter 6 and the wave receiver 7 are positioned so as to face each other in the horizontal direction with a predetermined distance apart, and are placed above the fluid tank 10. The photomask substrate 3 is held in a suspended state with its uniform end facing upward, and is held by a holding jig 12 that is provided vertically and is movable in the vertical direction of the figure and in the direction perpendicular to the plane of the paper. The liquid 1 stored in the fluid tank 10
The part to be immersed in the liquid 11 and inspected is located between a wave transmitter 6 and a wave receiver 7, which are horizontally opposed to each other in the liquid 11.

The photomask substrate 3 held in a suspended state by the holding jig 12 is moved by a predetermined pitch in a direction perpendicular to the plane of the paper every time it is moved by a predetermined distance in the vertical direction. A transmitter 6 fixedly provided within the
Then, the wave receiver 7 is scanned relative to the photomask substrate 3, and the inspection is performed with the wave transmitter 6, the wave receiver 7, and the inspection portion of the photomask substrate 3 constantly immersed in the liquid 11. It is configured to take place.

In this case, a liquid 11 is provided between the transmitter 6 and the receiver 7 and the photomask substrate 3, which has a higher density than a gas such as air, and therefore has a lower attenuation rate of the ultrasonic waves transmitted inside.
is interposed, the ultrasonic waves emitted from the transmitter 6 toward the surface of the photomask substrate 3 and the ultrasonic waves that pass through the photomask substrate 3 and reach the receiver 7 are efficiently transmitted. Due to the scattering and attenuation of reflected waves generated due to defects present in the inspection area of the photomask substrate 3, changes in the waveform observed on the display section 9 can be observed more clearly, and defects can be inspected. Accuracy is further improved.

[Effects] (1) Consisting of an oscillating part and a vibration receiving part that are movable relative to the object to be inspected, the oscillating part and the vibration receiving part are scanned with respect to the object to be inspected, and the oscillating part emits radiation from the oscillating part to the object. Since the structure is such that the object to be inspected is inspected by ultrasonic waves that reach the vibration receiver through the object, it is possible to detect any defects in the object to be inspected reliably and quickly. The accuracy and productivity of inspecting objects to be inspected are improved.

(2) Since the inspection is performed with the oscillating part, the receiving part, and at least part of the object to be inspected immersed in the fluid, the density between the oscillating part, the receiving part, and the object to be inspected is relatively low. large, and therefore the attenuation rate of the transmitted ultrasound waves is low,
Due to the presence of fluid, ultrasonic waves are efficiently transmitted between the oscillating section and the receiving section and the object to be inspected, thereby improving inspection accuracy.

(3) As a result of (1) above, it is avoided that a photomask substrate that has defective parts and is not suitable for photomask production is used for the production of photomasks, etc. due to omission of inspection for defects existing on the photomask substrate. This prevents wasteful processing in the photomask manufacturing process and pattern defects in the pattern transfer work to the wafer performed using a photomask with such defects, and improves yield in the semiconductor device manufacturing process. and productivity 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, in Example 1 and Example 2, the transmitter,
It is also possible to adopt a structure in which the delivery device and the photomask substrate are immersed in liquid for inspection.

[Field of Application] In the above description, the invention made by the present inventor was mainly applied to the field of application for photomask substrates, which is the background of the invention, but the invention is not limited to this, for example. It can also be applied to internal defect inspection of wafers.

Furthermore, it can be applied to ingot inspection before cutting out photomask substrates, silicon single crystal ingot inspection before cutting out wafers, etc.

[Brief explanation of the drawing]

1 is a cross-sectional view of an inspection device according to a first embodiment of the present invention, FIG. 2 is a cross-sectional view of an inspection device according to a second embodiment of the present invention, and FIG. 3 is a cross-sectional view of an inspection device according to a third embodiment of the present invention. It is a sectional view of a certain inspection device. DESCRIPTION OF SYMBOLS 1... XY table, 2... Window part, 3... Photomask board (object to be inspected), 4... Positioning pin, 5...
... Ultrasonic pulse oscillator (oscillation part), 6... Transmitter (
oscillation part), 7... delivery device (vibration receiving part), 8... signal processing part (vibration receiving part), 9... display part (vibration receiving part), 1o...
-Fluid tank, 11...liquid, 12...holding jig. Figure 1 Figure 3 δ

Claims (1)

[Claims] 1. The oscillator and the receiver are movable relative to the object to be inspected, and the oscillator and the receiver are moved relative to the object to be inspected. An inspection apparatus characterized in that the object to be inspected is inspected using ultrasonic waves emitted from the section and reaching the vibration receiving section via the object to be inspected. 2. The inspection apparatus according to claim 1, wherein the oscillating section and the vibration receiving section are disposed at positions facing each other with the object to be measured interposed therebetween. 3. The inspection device according to claim 1, wherein the oscillating section and the vibration receiving section are disposed on the same side of the object to be measured. 4. The inspection apparatus according to claim 1, wherein the inspection is performed with the oscillating section, the vibration receiving section, and at least a portion of the object to be inspected being immersed in a liquid. 5. The inspection apparatus according to claim 1, wherein the object to be inspected is a photomask substrate.