JP2008064665A - Optical length measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical length measuring apparatus which has a simple structure and is stable, by reducing temperature influences on a laser optical path of a laser interferometer. <P>SOLUTION: The optical length measuring system comprises: an optical length measuring machine which has a heating section; a chamber in which the optical length measuring machine is disposed; a device for supplying descending current of air in the chamber; a cover containing the heating section and having a lower end with an aperture which opens downward, and an upper end with an aperture smaller than that of the lower end; and an exhaust means which is connected to the aperture of the upper end and discharges air in the cover to the outside of the chamber. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to an optical length measuring device used in an inspection process of a semiconductor or a liquid crystal display device, and more specifically, a thermostatic chamber in which clean air of a predetermined temperature is blown out from above to below. The present invention relates to an optical length measuring device having a heat generating part such as a CCD camera, which is installed inside.

The measurement accuracy of the optical length measuring device used in the inspection process of semiconductors and liquid crystal display devices is required to be on the order of sub-μm. Therefore, the optical length measuring device body always has a predetermined temperature from the top to the bottom. It is installed in a thermostatic bath in which clean air is blown out, and the temperature difference in the thermostatic bath is maintained at ± 0.1 ° C., for example.
However, since this optical length measuring instrument has a heat generating part such as a CCD camera or illumination means, temperature unevenness is likely to occur in the thermostat, and the temperature of the object to be measured becomes non-uniform due to this temperature unevenness. In addition, there is a problem that an error occurs in the measurement due to a change in the air temperature of the laser optical path of the laser displacement meter used as the measuring means of the optical length measuring device.

  Therefore, conventionally, the heat generation portion is dispersed so as not to cause temperature unevenness in the thermostat (for example, Patent Document 1), or the object to be measured and the laser displacement meter of the optical length measuring instrument in the thermostat. A method (for example, Patent Document 2) is disclosed in which the portion is further covered with a cover and the inside of the cover is maintained at a constant temperature.

However, even if the heat generating portion is dispersed as in the conventional example (the former), a part of the air heated by the heat generating portion is blown from the upper side of the thermostatic chamber downward (hereinafter referred to as “down”). The air flow is blown down to the laser optical path of the laser interferometer, causing fluctuations in the air temperature of the laser optical path, and the laser interferometer has a problem that the measured value is not stable.
In addition, in the method of covering the object to be measured and the laser displacement meter with a cover as in the conventional example (the latter), the entire apparatus becomes complicated, and the object to be measured must be moved in two dimensions. There was a problem such as the area becoming large.
JP 2004-205441 A JP 2003-151892 A

Therefore, the present invention has been made in view of the above circumstances, and provides a stable optical length measuring device having a simple structure by reducing the temperature influence on the laser optical path of the laser interferometer. is there.

The present invention is characterized by the following points in order to solve the above problems.
That is, the optical length measuring device according to claim 1 is installed in a thermostatic chamber (hereinafter referred to as “thermal clean chamber”) in which clean air of a predetermined temperature is blown out from above to below. An optical length measuring device having a heat generating portion, which houses the heat generating portion of the optical length measuring device and has a lower end opened, and an exhaust for discharging the air in the cover from the upper portion of the cover Means.

  An optical length measuring device according to claim 2 is the optical length measuring device according to claim 1, wherein cooling air is supplied from the vicinity of the lower side of the heat generating portion in the cover toward the heat generating portion. A cooling nozzle for spraying and an air supply means for supplying cooling air to the cooling nozzle are provided.

  An optical length measuring device according to claim 3 is the optical length measuring device according to claim 2, wherein a cooling air flow rate supplied to the cooling nozzle is discharged from the cover by the exhaust means. It is characterized by a flow rate less than the air flow rate.

The present invention has the following excellent effects.
According to the first aspect of the present invention, the air in the cover is discharged from the cover by the discharge means from the upper end of the cover that houses the heat generating portion. Part of the air in the thermal clean chamber flows into the cover from the inside of the cover, and an air flow is formed in the cover, and the flow of air in the thermal clean chamber that has flowed in is formed. Thus, the heat generating part is cooled.
Then, the air heated by the heat generating part is discharged out of the cover without affecting the air temperature of the laser light path by the discharge means, so that the air temperature of the laser light path is set to a predetermined temperature. Can be maintained.

According to the invention of claim 2, since the cooling air is blown from the cooling nozzle toward the heat generating part from the lower side of the heat generating part in the cover, the heat generating part can be effectively cooled, The cooling air flow causes an air flow from the outside of the cover to the inside of the cover, so that the air can be easily discharged from the cover by the discharging means.
In addition, when the cooling air is ejected from the cooling nozzle, a temperature drop of the cooling air is caused by adiabatic expansion, so that the heat generating portion can be cooled more effectively.

  According to the third aspect of the present invention, the flow rate of air blown from the cooling nozzle to the heat generating portion in the cover is substantially equal to the flow rate of air exhausted from the upper part of the cover to the outside by the exhaust means. The cooling air does not flow back into the thermal clean chamber from the opening at the lower end of the cover, and the descending air flow in the thermal clean chamber is not disturbed. It can be maintained stably.

Hereinafter, an optical length measuring device according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1 to FIG. 3, the optical length measuring device 1 includes a base 2, a pair of Y-axis guides 3 and 3 arranged in parallel on the base 2, and the guides 3 and 3. The Y-axis table 4 moving in the Y-axis direction, a pair of support columns 5 and 5 erected on the base 2, and the Y-axis guide 4 supported by the support columns 5 and 5 with respect to the Y-axis guide 3 The X-axis moving along the X-axis direction along the X-axis guides 7 and 7 and the pair of X-axis guides 7 and 7 arranged parallel to the side surface of the beam body 6. A table 8, a pair of Z-axis guides 9, 9 arranged in parallel on the side surface of the X-axis table 8, and a Z-axis table 10 that moves in the Z-axis direction along the Z-axis guides 9, 9. And installed in a thermal clean chamber (not shown).
In the thermal clean chamber, a descending air flow is blown downward from the optical length measuring device 1 toward the optical length measuring device 1.

On the Z-axis table 10, a microscope 12, a CCD camera (heating unit) 13 optically connected to the microscope 12, a microscope 12, and a CCD camera 13 are opposed to a glass substrate (inspection object) P. The cover 11 having a lower end opened downward, the exhaust means 17 connected to the upper portion of the cover 11 via the exhaust tube 16, and penetrated through the cover 11 to be cooled by the CCD camera (heat generating part) 13. The cooling nozzles 14 and 15 for blowing the working air are integrally attached.
The CCD camera 13 is electrically connected to an image processing unit 34 that processes an image signal and an image display unit 35 that displays the image processed image.

The cooling nozzles 14 and 15 are arranged in two stages, upper and lower (in the X-axis direction), shifted in the Y-axis direction, and each supply cooling air to the cooling nozzles 14 and 15 via the air supply tube 18. An air supply device 19 serving as an air supply means is connected.
The air nozzles of the cooling nozzles 14 and 15 have a small diameter so that when the cooling air is ejected from the air nozzles, the air is adiabatically expanded so that the cooling air itself has a low temperature. It has become.
Further, the upper end opening of the cover 11 is connected via an exhaust tube 16 to an exhaust device 17 as exhaust means for exhausting the air in the cover 11 out of the thermal clean chamber.
Further, the amount of air discharged by the exhaust device 17 through the exhaust tube 16 is larger than the amount of air ejected from the cooling nozzles 14 and 15 into the cover 11.
Specifically, based on the amount of heat released from the CCD camera 13, the flow rate and temperature of the cooling air, the diameter of the air injection ports of the cooling nozzles 14 and 15, and the cooling air supplied to the cooling nozzles 14 and 15. The pressure and temperature are set so that the aperture of the upper opening of the cover 11 (portion connected to the exhaust tube 16) is optimized.

  The Y-axis table 4, the X-axis table 8, and the Z-axis table 10 are respectively driven by driving means (for example, ball screw and ball nut, servo motor and motor driver) not shown.

Further, as shown in FIGS. 1 and 4, the base 2 has a laser interference length measuring device 20 used for measuring the position of the Y-axis table 4 in the Y-axis direction and the position of the X-axis table 8 in the X-axis direction. Is provided.
The laser interference length measuring apparatus 20 includes a laser head 22 disposed on a support base 21 provided on a side surface of the base 2, and a beam splitter that branches laser light from the laser head 22 in the X-axis direction and the Y-axis direction. 23, a beam bender 26 provided on a support base 25 provided on a side surface of the base 2, an interference unit 28X provided on a support base 27X provided on a side surface of the column 5, and the base 2 The interference unit 28Y is provided on the upper support 27Y, the mirror 29X is provided on the X-axis table 8, and the mirror 29Y is provided on the Y-axis table 4.

The laser head 22 includes a laser oscillation unit 22A that oscillates a two-frequency He—Ne laser beam, a laser splitter 22B that separates the laser beam into a length measuring laser L1 and a reference laser L2, and a reference laser L2. And a photodetector 22C for detecting the frequency.
The interference units 28X and 28Y have a beam splitter 28A for separating the reference laser L3 from the length measuring laser L1 branched in the X-axis direction and the Y-axis direction, and the separated reference laser L3 is reflected to the beam splitter 28A. A reference prism 28B, and a photodetector 28C that detects the frequency of the interference light between the reflected laser and the reference laser L3.

A signal corresponding to the degree of the interference is transmitted from the photodetector 28C to an arithmetic processing unit 32 including a pulse converter 30 and a counter 31, and the arithmetic processing unit 32 uses the Y-axis direction moving distance of the Y-axis table 4 and X The movement distance in the X-axis direction of the axis table 8 can be detected.
Then, as shown in FIG. 5, the conversion processor 32 is connected to the control device 33. Further, the control device 33 is connected to a drive means for the Y-axis table 4 and the X-axis table 8, a drive means for the Z-axis table 10, an air supply device 19, an exhaust device 17, a CCD camera 13, and image processing via an interface (not shown). The unit 34 and the image display unit 35 are connected.

When measuring the glass substrate P in the optical length measuring device 1 having the above configuration, first, as shown in FIG. 1, after holding the glass substrate P on the table 4, the exhaust device 17 is operated, The air supply device 19 is activated. As a result, cooling air (cooling air that has fallen in temperature due to adiabatic expansion at the time of jetting) is blown upward from the jet nozzles of the cooling nozzles 14 and 15 toward the CCD camera 13 to cool the CCD camera 13. At the same time, while the cooling air that has been used for cooling the CCD camera 13 and has risen in temperature is exhausted out of the thermal clean chamber by the exhaust device 9, the air temperature of the descending air flow in the thermal clean chamber is locally determined. A plurality of measurement points provided on the glass substrate P are measured without being raised.
The control device 33 receives design dimension values of each measurement point on the glass substrate P, and performs positioning control of the Y-axis table 4 and the X-axis table 8 based on the design dimension values.

  The control device 33 outputs drive signals to the drive means of the Y-axis table 4 and the X-axis table 8 and the drive means of the Z-axis table 10, and drives each drive means to connect the microscope 12 and the CCD camera 13 to the first measurement point. Is moved while measuring in units of μm using the laser interference length measuring device 20 above the design arrangement position.

  As shown in FIG. 6, when the microscope 12 and the CCD camera 13 are moved above the design arrangement position of the first measurement point, the first measurement point enters the field of view of the CCD camera 13 and the first measurement point is enlarged by the microscope 12. The image is taken into the CCD camera 13. The distance (x1, y1) from the center of the captured image (that is, the center of the in-view coordinate system) to the center of the first measurement point is obtained in units of μm by counting the number of CCD pixels. At the same time, the positions of the Y-axis table 4 and the X-axis table 8 (that is, the position of the in-field coordinate system center in the table coordinate system) (X1, Y1) are measured in μm units using the laser interference length measuring device 20. .

  Next, a driving signal is output from the control device 33, the driving means for the Y-axis table 4 and the X-axis table 8, and the Z-axis table 10 are driven so that the microscope 12 and the CCD camera 13 are placed at the design position of the second measurement point. Move upward. When moving, as described above, the information detected by the laser interference length measuring apparatus 20 is fed back to control the position.

  When the microscope 12 and the CCD camera 13 move above the design arrangement position of the second measurement point, the distance from the center of the visual field coordinate system to the center of the second measurement point (x2,. y2) and the position (X2, Y2) of the in-field coordinate system center in the table coordinate system at that time are measured in μm units.

If the positional relationship between the measured in-field coordinate system and the first and second measurement points is the positional relationship shown in FIG. 6, for example, the position of the first measurement point in the table coordinate system is (X1 + x1, Y1 + y1). ), And the position of the second measurement point in the table coordinate system is (X2-x2, Y2-y2).
Therefore, the relative position between the first measurement point and the second measurement point can be expressed as ((X2−x2) − (X1 + x1), (Y2−y2) − (Y1 + y1)) in the XY coordinate system.

The laser interference length measuring apparatus 20 used in this embodiment is called a two-frequency heterodyne laser interferometer, and the case of measuring the moving distance of the Y-axis table 4 will be described with reference to FIG. To do.
The He—Ne laser having two frequencies (F1 and F2) oscillated in the laser oscillator 22A is branched into a length measuring laser L1 and a reference laser L2 in the beam splitter 22B. The reference laser L2 enters the photodetector 22C, and the frequency difference (L1-L2) is output to the pulse converter 30 as a reference signal.

The length measurement laser L1 is separated from the reference laser L3 (frequency F2) by the laser splitter 28A and directed to the reference prism 28B, and the remaining length measurement laser L1 (frequency F1) is directed to the mirror 29Y. Since the mirror 29Y moves in the Y-axis direction as the Y-axis table 4 moves, the frequency of the length measuring laser L1 reflected by the mirror 29Y changes by ΔD (F1 ± ΔD) due to the Doppler effect.
The reflected length measuring laser L1 and reference laser L2 interfere with each other in the laser splitter 28A and enter the photodetector 28C, and the frequency difference (F1-F2 ± ΔD) is output to the pulse converter 30 as an interference signal. The

  In the pulse converter 30, the reference signal (F1-F2) and the interference signal (F1-F2 ± ΔD) are processed, and the frequency signal difference (± ΔD) due to the Doppler effect is counted in the counter 31. Is output to the control device 33 as position information to measure an accurate position.

As described above, the cooling nozzles 14 and 15 are arranged in two stages (up and down (X-axis direction)) and shifted in the Y-axis direction, so that the air flow in the cover 11 is less uneven and the cover 11 Air is less likely to stay in the local area.
Furthermore, a part of the outer surface of the cover 11 is caused by the fact that the air is less likely to stay in the inner part of the cover 11 and the temperature of the cooling air itself is low due to the adiabatic expansion of the cooling air as described above. Of the thermal clean chamber around the outer surface of the cover 11 is less likely to be heated.
As a result, the temperature fluctuation of the air around the laser optical path of the laser interferometer is small, and the accuracy of the laser interferometer can be kept constant.
In the above embodiment, the air in the cover 11 is exhausted to the outside of the thermal clean chamber by the exhaust device 17. You may circulate to i.

According to the above configuration, since the laser interferometer is used for measurement, the positions of the Y axis table 4 and the X axis table 8 in units of μm, that is, the position of the center of the in-field coordinate system in the table coordinate system are measured. be able to. As a result, the position of the measurement point can be measured with high accuracy, and the relative positional relationship between the measurement points can be obtained with high accuracy.
Furthermore, since the temperature in the thermal clean chamber is less likely to be uneven, errors due to thermal expansion are unlikely to occur even when a glass scale or the like is used in addition to the laser interferometer, and the relative positional relationship of each measurement point is highly accurate. Can be obtained.

The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
In particular, the above embodiment shows a case where there is one CCD camera 13 which is a heat generating portion. However, the present invention is not limited to this, and a plurality of CCD cameras may be built in the cover 11.
In that case, a plurality of cooling nozzles are arranged in the vicinity of each CCD camera in accordance with the number of CCD cameras, and the cooling nozzles are arranged apart from each other in the vertical direction and the Y-axis direction. Since the air flow is maintained throughout the cover 11, the air is less likely to stay in the cover 11, so that the temperature of a part of the outer surface of the cover 11 is less likely to increase, and the descending air around the outer surface of the cover 11 The stream is prevented from being heated.
The technical scope of the present invention is applicable to driving means using a linear motor in addition to the ball screw mechanism for driving the Y-axis table 4 and the X-axis table 8 in the above embodiment.

It is a top view which shows one Embodiment of the optical length measuring apparatus by this invention. It is a conceptual diagram of the cover part in FIG. 1, (a) is a front view (alpha arrow directional view of FIG. 1), (b) is a side view (beta arrow directional view of FIG. 1). It is sectional drawing of a cover part, (a) is a conceptual diagram showing the AA cross section of FIG. 2, (b) is a conceptual diagram which shows the BB cross section of FIG. It is a conceptual diagram which shows the structure of a laser length measuring apparatus. It is a control block diagram in one Embodiment of the optical length measuring apparatus by this invention. It is explanatory drawing which shows the relationship between the table coordinate system and the coordinate system in a visual field in one Embodiment of the optical length measuring apparatus by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical length measuring device 2 Base 4 Table 5 Beam body 12 Microscope 13 CCD camera 14, 15 Cooling nozzle 20 Laser interference length measuring device
P glass substrate (inspected object)

Claims (3)

An optical length measuring device having a heat generating part installed in a thermostatic chamber in which clean air of a predetermined temperature is blown out from above to below,
An optical length measuring device comprising: a cover that houses a heat generating portion of the optical length measuring device and having a lower end opened; and an exhaust unit that discharges air in the cover from an upper portion of the cover.   A cooling nozzle that injects cooling air from the vicinity of the lower side of the heat generating portion in the cover toward the heat generating portion, and an air supply unit that supplies the cooling air to the cooling nozzle. The optical length measuring device according to claim 1. 3. The optical length measuring device according to claim 2, wherein a cooling air flow rate supplied to the cooling nozzle is a flow rate equal to or lower than an air flow rate discharged from the cover by the exhaust means.