JPH03220407A - Inclination detector - Google Patents

Abstract

PURPOSE:To enable measurement of the inclination of the face of a substance to be measured, without necessitating virtually any special space on the substance side, by applying a laser light along a reference axis from a remote place and by measuring a reflected light at a position being apart from the substance to be measured. CONSTITUTION:A laser light is emitted from a laser head 11, so as to form a laser light spot on a reflecting plane 7 on a substance 5 to be measured, and a reflected light is bent downward by a beam bender 12 and detected by a position-sensitive detecting element 14. The position of the laser light detected by the element 14 when the reflecting plane 7 is disposed vertically to the laser light is made to be a reference position, and how much the detected position is shifted on the element 14 when the reflecting plane 7 is inclined is detected. The shift of the position detected on the element 14 when the normal line of the reflecting plane 7 is inclined at an angle thetafrom the optical axis of the laser light can be expressed as r.sin(2theta) when a distance between the reflecting plane 7 and the element 14 is denoted by (r). As the result, a minute inclination can be detected with ease. Accordingly, no measuring device other than the reflecting plane needs to be set in the vicinity of a face to be measured, and therefore the degree of freedom of design is increased.

Description

[Detailed Description of the Invention] Two Industrial Application Fields] The present invention is a tilt detection device! Regarding SOR exposure equipment, especially the normal to the surface of the object to be measured such as a mask or wafer,
The present invention relates to a tilt detection device for detecting a tilt relative to a reference axis such as an optical axis.

It is thought that the positioning accuracy of the precision stage for next-generation VLSI exposure equipment needs to be improved by about one order of magnitude or more from the current 0.1 μm order to be in the range of 0.01 μm or less. For example, an X-ray exposure device using SOR light has been developed as one of the next-generation VLSI exposure devices, but this exposure device requires mask and wafer positioning on the order of submicrons. The positioning accuracy of the stage on which these are placed is desired to be one order of magnitude higher than o, oi μm.

[Prior art] In conventional optical exposure devices such as optical steppers, the light source, mask stage, and exposure stage are formed in the same horizontal body, so the inclination of the stage surface with respect to the optical axis must be adjusted during assembly and adjustment. That's enough.

However, in exposure equipment that uses SOR light, the light source and the stage are placed at least several meters apart, often about 10 meters apart4.Therefore, it is necessary to place the light source and stage on a common base with sufficient rigidity. The SOR optical axis is not constant and changes with respect to the exposure device. Therefore, s.

It becomes necessary to constantly measure a reference axis such as the R optical axis.

Further, the SOR, i-light mask usually has an addendum as shown in FIG. 2(A). That is, the mask 20 includes an 81 wafer 21 having a thickness of, for example, about 2n1 with a hollowed out center portion, and a membrane 22 formed on the 81 wafer 21 having a thickness of about several μm and having high transmittance for SOR light, such as an SiN film.
SOR light absorption pattern 2 formed on top of this is made of an absorbing material such as U or Ta that has a high absorption coefficient for SOR light.
It has 3.

However, it is extremely difficult to make the combined thickness of the Si wafer 21 and the SOR light transmitting membrane 22 uniform over the entire surface of the mask with high precision, and it is difficult to prevent variations on the order of several μm from occurring during processing.

For example, as shown in FIG.
gradually decreases from one end to the other,
As shown in FIG. 2(C), a thickness distribution occurs in which the thickness increases once and then decreases again.

Such thickness distribution varies from mask to mask.

In an exposure process for semiconductor devices, masks are exchanged depending on a desired exposure pattern. Then, the thickness distribution changes for each mask. Depending on this shape change for each mask, it is required to align the mask surface with the optical axis. To do this, it is necessary to measure the mask surface for each mask and adjust the mask surface according to the measurement results.

There are air micro sensors, capacitive sensors, and other methods for detecting the inclination of a surface relative to a reference axis that can fluctuate, but each requires space to install and has problems with response speed. .

[Invention or problem to be solved U] As explained above, an attempt is made to measure the angle formed between the reference axis whose position can be changed relatively and the surface of the object to be measured without requiring much mounting space. Then, there was no conventional technology that could be applied.

SUMMARY OF THE INVENTION An object of the present invention is to provide an inclination measuring device that can measure the inclination of a surface of an object to be measured with respect to a reference axis without requiring almost any special space on the side of the object.

'LMeans to solve the problem A reflective surface is formed on the surface of the object to be measured.

Laser light is irradiated onto a reflective surface from a distance along a reference axis, and the reflected light is measured at a position away from the object to be measured.

; Effect] When the reflected light is measured at a distant position, when the surface is tilted, the reflected light moves significantly due to the principle of light leverage. Therefore, minute inclinations of surfaces can be detected with high precision.

Third Embodiment FIG. 1 is a schematic diagram showing the configuration of a tilt detection device according to an embodiment of the present invention. The SOR ring 1 contains orbits of electrons accelerated to almost the speed of light, and SORs the orbital synchrotron radiation in the horizontal direction.
Focus on optical axis 2 and fire.

The SOR light emitted from the SOR ring l travels straight along the SOR optical axis 2. An exposure device 3 is arranged on the SOR optical axis 2. The exposure apparatus 3 has a stage 4, on which a measured object '#R5 such as a mask or a wafer is placed.

In exposure equipment, the surface of the target object, such as a wafer or mask, is placed perpendicular to the incident light! In the case of the system shown in FIG. 1, it is preferable that the SOR optical axis 2 be perpendicular to the surface of the object to be measured 5.

A reflective surface 7 such as an aluminum layer is formed on the measurement surface of the mask or wafer that is the object to be measured.

Assuming that the direction in which the SOR light travels is the X direction, and the upward direction in the figure is the Y direction, the inclination of the normal to the reflective surface 7 from the X-axis direction is measured and adjusted. The stage 4 is provided with at least three level actuators 8 for adjusting the height in the X direction, so that the surface normal of the stage can be illuminated. Note that the stage 4 is also provided with adjustment devices for other degrees of freedom, but their explanation and illustration are omitted.

A laser head 11 is fixed near the SOR light extraction port of the SOR ring 1. Also, Konoshi-zahe/do 1
A beam bender 12 is placed on the optical axis of the laser beam emitted from 1.
A position sensitive detector 14 for detecting the reflected light bent by the beam bender 12 is placed on the same structure as the SOR ring 1. The laser head 11 is SO
It is arranged in a predetermined positional relationship with respect to the R optical axis 2, and is initially adjusted to emit laser light parallel to the SOR optical axis.

Prior to the exposure process, a laser beam is emitted from the sheave head 11, a laser beam spot is formed on the reflective surface 7 on the object to be measured 5, and the reflected beam that is reflected and sweeps on the same optical axis is sent to the beam bender 12. The 6-position sensitive detection element 14, which is bent downward in the figure and detected by the position-sensitive detection element 14, is, for example, a PSD (position 5-ensi
tive device) -CCD(charge
(coupled device) + photodiode array configuration and has sufficient resolution for detecting the position of light irradiation within the plane 1 When the reflecting surface 7 is arranged perpendicular to the laser beam, it is a position-sensitive detection element. The position of the laser beam detected in step 14 is used as a reference position, and when the reflecting surface 7 is tilted, how far the detection position moves on the position sensitive detection element 14 is detected. The movement of the position detected on the position-sensitive detection element 14 when tilted at an angle θ from the optical axis of ) can be expressed as By measuring the reflected light, the angle of inclination θ is doubled, and by further increasing the distance from the reflecting surface, the measured value is multiplied by r. The zero position sensitive detection element 14, which can easily detect minute inclinations due to such tip plate action, can easily have a resolution of several microns or less, so it can measure the inclination of a surface in seconds. Things are also easy. Furthermore, by detecting in which direction the receiving beam point moves on the position sensitive detection element 14, it is possible to know in which direction the reflecting surface 7 of the object is tilted, and this signal can be controlled. The surface of the object to be measured 5 can always be kept perpendicular to the SOR optical axis 2 by feeding the mask through the port 15 and feeding it to the actuator 8 for correcting the mask inclination. Note that a beam splinter may be provided in the optical path of the reflected light, and a coarse position detection system may also be provided. According to this configuration, there is no need to install any measuring device other than the reflective surface near the surface to be measured, which increases the degree of freedom in design. Measurement is possible even if the surface is not specially formed, as long as it has some kind of surface with a certain degree of reflectance.

By making the optical path length sufficiently long, it is easy to increase the height of l! You can get the ability.

It should be noted that although the present invention has been described along with the embodiment of the SOR light exposure apparatus, the technology of the same device can be used in other than the SOR light exposure apparatus. In place of the SOR optical axis 2, by using a reference axis of a beam that has the property of traveling in a straight line, and by irradiating the object with a laser beam parallel to this, the measured object can be similarly aligned with respect to the reference axis. Can measure the slope of an object's surface.

Although the present invention has been described above in accordance with the examples, it will be obvious to those skilled in the art that the present invention is not limited to these examples, and that, for example, the seeds can be changed, improved, and combined.

Effects of the Invention As described above, according to the present invention, when the normal to the surface of the object to be measured, such as a wafer or mask, is inclined with respect to a reference axis such as the SOR optical axis, the inclination can be increased. It can be detected with precision.

Furthermore, by feeding back the detected inclination, the target surface of the object to be measured can always be calibrated in a predetermined direction.

Transfer errors in SOR exposure equipment and the like can be reduced.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram of a tilt detection device according to an embodiment of the present invention. In the figure, SOR ring SOR optical axis SOR exposure device stage object to be measured reflective surface leveling actuator laser head beam bender position 1 sensitive detection element control circuit

Claims (1)

[Claims] (1) A measured object having a predetermined reference axis, a surface whose inclination of the surface normal to the reference axis is to be detected, and a reflective surface on the surface, and a laser beam parallel to the reference axis. a laser optical system that emits a laser beam and hits the reflective surface; a laser optical system that receives the laser beam reflected by the reflective surface on a plane substantially perpendicular to the traveling direction of the laser beam at a position away from the object to be measured; A tilt detection device having a detection system for detecting a light irradiation position.