JPS59168445A - Method and apparatus for optically aligning mask for manufacturing ic and patterns on two members arranged on separate parallel planes away therefrom - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mask for integrated circuit manufacturing, and a method and apparatus for optically aligning nosoturns on two members disposed in separate parallel planes a full distance apart.

When manufacturing integrated circuits, it is important to align the mask and wafer within very tight tolerances. When circuits are stacked in layers on a wafer,
Each new layer is produced by exposing the wafer to Noreen on a mask. The new pattern on the mask needs to be coated onto the pattern of the previous layer on the wafer with a recording precision that is in some cases on the order of 0.1 microns. . Achieving such coverage accuracy requires highly advanced mask-to-wafer alignment techniques.

In addition, alignment techniques have also increased in complexity as a necessary condition for achieving smaller minimum characteristics and higher coating accuracy. Two techniques that are precursors to mask and wafer alignment are described in US Pat. No. 4,037,969 and US Pat. No. 4,311,389. These two alignment devices use zone plates formed on the mask.

No. 4,037,969 describes an alignment device in which circular zone plates are formed as alignment marks on both the mask and the wafer. The monochromatic light beam that is transmitted through the mask is reflected by the mask and the zone plate of the wafer, forming image points in a predetermined plane. The coincidence of these two points indicates mask and wafer alignment.

U.S. Pat. No. 4,311,389 discloses an alignment apparatus that uses a linear 7 Renel zone plate formed on a mask and a reflective grating on the wafer. The distance between this mask and the wafer is the focal length of the zone plate (
The monochromatic light beams emitted via the zone plate are therefore imaged as original straight lines on the plane of the wafer. The coincidence of the linear grating with a linear focus on the wafer, determined by detecting the reflectance from the wafer, indicates the alignment of the mask and the wafer.

The two alignment devices are extremely inefficient in their use of light flux.

In particular, the device described in US Pat. No. 4,311,389 suffers from poor diffraction efficiency, poor signal-to-noise ratio, large fourth-order reflections, and/or VC difficulties in the turn formation process.

The present invention aims to overcome all these drawbacks and in particular to obtain a significant improvement over the device described in US Pat. No. 4,311,389.

The present invention provides two
The present invention relates to a method and apparatus for aligning two members. More particularly, the present invention relates to an apparatus for aligning patterns on a mask with compensatory grooves on a wafer for use in manufacturing integrated circuits. When implementing the invention,
A linear fully transparent phase reversal zone plate is formed on the mask and a reflective linear pattern is formed on the wafer. The ξ parameter is selected such that the monochromatic light beam that is transmitted through the area of the phase-inverted zone plate forms a line at the surface of the wafer. The reflected intensity of the beam from the wafer surface is maximum when the linear focal point is located directly above the wafer's linear par, and this therefore means that the mask and wafer, and therefore the circuit nozzles thereon, are aligned in a given direction. Display what has been done. Hawk straight line/? - may be slightly less reflective than its surroundings, in which case the reflected light is at a minimum when the straight focus and straight par are aligned.

Fully transparent phase-reversing zone plates provide imaging of the beam without the opacity required by Fresnel zone plates, thus using the beam in a highly efficient manner and eliminating most of the zero-order beam. Remove.

The use of fully transparent phase-shifting zone plates in the device according to the invention increases the overall first-order diffraction power of the light beam by a factor of about 16 over the device disclosed in U.S. Pat. No. 43/11389. and significantly increase signal strength and signal-to-noise ratio. At the same time, the substantial elimination of zero-dimensional flux allows one to replace the low-efficiency grating grooves needed to prevent zero-dimensional flux when aligning marks and solid patterns on the wafer. do.

Furthermore, the device of the invention is reflected by the wave 7.
A device is required for detecting the light flux transmitted through the zone plate in the opposite direction and obtaining a signal representation of this reflected light flux. This signal is processed and feed-punctured to move the wafer support table in a direction that aligns the imaging straight line of the light beam with the solid line notches on the wafer, thus aligning the mask and wafer in a predetermined direction.

In the following, the invention will be explained in detail with reference to drawing examples.

FIG. 1 shows a portion of a mask 11 in which a phase inversion type zone plate 10 is formed. This mask 11 is typically transparent to radiation and x-ray radiation and can be made of polyimide, sic%BN or other suitable material. The phase reversal zone plate is formed of alternating zones 12 of a material transparent to the wavelength of the monochromatic light source used, for example a photoresist such as AZ 1470 for wavelength 63281e. These zones 12 have relative heights to the plane of the mask 11 and differ only in their optical paths;
It can also be formed by etching the adjacent zone 13 with a PD difference.

In order to satisfy 0PD=- which is the condition of λ zone 12,
The height H of the zone 12 on the surface of the mask 11 is determined by the formula: [where λ=wavelength of the monochromatic source.

[Delta]n=refractive index, difference, of a transparent material, eg photoresist, and air, and N=any odd integer, eg 1, 3.5...].

If the zone plates are manufactured by etching these zones into gold masks, then Δn in the above formula is n-1 if the refractive height of the transparent portion of the mask space is n.

The phase reversal type zone plate has the following formula: [However, λ = wavelength of monochromatic source f = zone plate focal length Xm = zone boundary measured from axis of symmetry X = O m = 1, 2, 3... Designed by.

The above equation limits the width of zones 12 and 13 and the distance between them, forming a zone plate that images monochromatic light of wavelength λ to a distance equal to f.

FIG. 2 shows a phase inversion type zone plate on a wafer 15.
is shown in relation to a reflective solid line par 14 formed on the surface of the surface. This pattern of straight lines has different reflectances or has a height or depth that satisfies the following formula: n = refractive index of the medium, e.g. photoresist covering the pattern area It is formed by two surfaces. In the latter two cases, the maximum phase difference is obtained for the laser beam by reflection.

Zone or zone straight line 12 is parallel to straight line A-14. As shown in FIGS. 2 and 3, the distance between mask 11 and wafer 15 is equal to the focal length f for the selected monochromatic or laser beam to be used. Therefore, as shown in FIG.
The light beam that can pass through the wafer 15 forms an image on the surface of the wafer 15 as a straight line. Furthermore, the width W of the straight line grooves 14 is 2.411. X
λ×f/l [where λ is the wavelength and f/flri
F-nannos of the zone plate are selected to be equal to the focal line width of the phase-reversing zone plate, which is limited by the F-nannos of the zone plate. The amount of light emitted is maximum.

Therefore, detection of the maximum value of light reflectance indicates perfect alignment of the alignment marks.

The zone plate lO and the linear mark 14 are oriented as in FIG. 2, ie the orientation of the zone 12 and the linear par 14 adjusts the alignment in the direction perpendicular to the zone, ie in the X direction. Alignment in the Y direction is obtained by alignment marks oriented perpendicular to the X direction.

The first-order diffraction efficiency of the completely transparent phase-inverting zone plate io of the present invention is approximately 1 (1.1%) of that of the 7-Renel zone plate.
It was calculated to be about 40.5%.

Therefore, the original energy that is greater than those orders that cause the noise base enters the signal carrying orders.

The signal from the diffracted beam that is reflected and transmitted in the opposite direction through the phase-shifting zone plate is 16 times greater than the signal from the beam transmitted through the 7-Renel zone plate. This fully transparent phase-shifting zone plate does not actually shoulder the zero-order transmitted beam, which can be measured by summing the power of all diffraction orders, which is The result was that there was no remaining power difference (to zero order) equal to the power entering the plate.

What is noteworthy is that the polarization of the phase-inverted zone plate is reversed. In this case, zone 13 has zone 12 and, conversely, zone 13 faces the covering of the material as if zone 12 were formed by engraving anchorage. Also, the straight pars 14 may be non-reflective instead of light reflective, which will result in a minimum as opposed to a maximum reflected light upon alignment. In addition, the phase reversal type zone plate has an adjacent zone (
The length can be such that the phase relationship of the light beams transmitted through the plurality of light beams is maintained.

The formation of phase-inverted zone plates by depositing or etching 7-otoresist on mask 11 can be carried out very economically. moreover,
The dimensional stability of the mask is better than with Fresnel zone plates due to the less induced stresses.

FIG. 3 shows the operation of a mask 11 having a phase inversion type zone laser 10 on a straight line pattern 1 formed on a wafer 15.
4.

The distance Dil-j between the mask 11 and the wafer 15 is equal to the primary focal length f of the zone plate 100.

This distance Dfl is selected to satisfy the requirements of the device. Therefore, for a given monochromatic light source, e.g.
For a H e Ne laser with 8 angstroms, the boundaries of the phase-shifted zone plates are completely constrained by equation (2) if appropriate zone play) F nanos are given and given. be done. A typical phase-inversion type zone plate has a mask-wafer gap of 50 microns, an f/l lens, and a no.
The dimensions are such that the diameter is approximately 50 microns.

FIG. 3 shows a laser beam 16 directed perpendicular to the plane of the mask 11 and wafer 15.

This laser beam is imaged onto the surface of the wafer 15 as an original straight line. As shown in the diagram, this original straight line is a straight line par 14
, thus displaying the exact alignment of these nodes. During the actual alignment operation, the straight par 14 is generally moved from its alignment position. During alignment, the laser beam 16 is angularly scanned across the phase-inverted zone plate in a direction perpendicular to the length of the straight nozzle 14, as indicated by the arrow 17 in FIG. The reflected light from wafer 15 is detected and processed to provide a signal representative of the distance of linear nozzle 14 from its aligned position. This signal is then used to drive a motor that moves the table on which the wafer 15 is placed until the straight pars 14 are aligned.

Further elaborating this in the context of the apparatus of FIG. 4, said actuation aligns these marks in one direction, e.g. It is clear that at least one more zone plate and a straight par must be arranged having a zone longitudinal dimension in the direction and a straight par.

Using at least one set of zone plates and straight grooves located at opposite ends of the two planes to be aligned, in-plane rotational errors are corrected through lateral alignment performed at these locations. Sanru.

Also, at the three alignment positions, the reflected signals are simultaneously maximized by adjusting the gaps to remove the two tilt errors and set the parallelism and optimal gap between these planes.

Further, FIG. 4 details an optical alignment device for carrying out the alignment operation according to the present invention.

The apparatus contains a laser light source 18 that produces a highly stable continuous waveform linearly polarized monochromatic laser source. This laser beam is directed to a scanning mirror 19 and from there through a polarizing beam splinter prism 20 to a mask 110 surface.

As mentioned above, this laser beam 16 is imaged as a straight line onto the surface of the wafer by using a phase-inverted zone plate lo formed on or in the transparent portion of the mask 11.

The laser polarization direction is determined by the polarization beam splinter prism 20.
They are arranged so that the amount of light that passes through them is maximized, and the minimum amount of light is reflected.

A lens system consisting of lenses L1 and L2 arranged between the laser light source 18 and the scanning mirror 19 is used for collimation and reduction of the original east diameter in order to obtain a suitable filling according to the design parameters of the phase-reversing zone plate 10. It is a converging lens.

The scanning mirror 19 angularly scans the scanning light beam 16 in a direction perpendicular to the longitudinal direction of the zones 12 and 13 in the phase inversion type zone play 1-10 or in a direction parallel to the direction of alignment correction. Driven by. The center point of symmetry of this laser angle scan is the reference position for alignment.

Before reaching the mask 11, the laser beam 16 passes through an l=1 telesending link imaging system L3 and L4, which directs the beam spot from the axis of the scanning mirror onto the phase-inverting zone plate lO of the mask 11. bring together.

The quarter wavelength plate 22 is the lens L4 and the mask 1.
1 to ensure that the reflected beam is properly polarized such that the intensity of the beam reflected by the beam splinter 20 to the photodetector device 24 is maximum. For reasons described later, the slit-shaped spatial filter 23
It may be placed between the beam splinter 21 and the photodetector 24 in order to pass only the reflected light beam of a required order from the wafer 14.

The output voltage from the photodetector 24 is transmitted to the cryophase amplifier 25.
is supplied as input to A scanner driver 21 provides an input voltage representative of the scan position to a phase amplifier 25 . The output of phase amplifier 25, which is an error signal representative of the deviation of linear par 14 from alignment, is provided as an input to power supply 26, where it is amplified and provided as an input voltage to positioner 27.

The positioner 27 is mechanically connected to the table 28 and moves the table 28 until the error signal voltage is reduced to zero when the mask 11 and wafer 15 are aligned in one direction, for example the X direction. Alignment in the orthogonal direction, for example the Y direction, requires similar equipment.

In operation, the laser beam 16 is angularly scanned across a phase-shifting zone plate on the mask 11. This scan sweeps the linear focus of the zone plate across the plane of the wafer 15. Zone plate I O, half wavelength plate 2
2 and L4 in opposite directions is reflected to the photodetector 24 via the beam sinter 20.

This reflection source signal itself contains deviation information of the straight line ζ from the alignment position. This bias information is combined with information from the scanner drive 20 that provides the reference position to produce an error signal that is used to drive the tape A/D until alignment is obtained.
Move 28.

Quarter wave plate 22 ensures that the reflected beam signal is properly polarized to provide maximum intensity reflected by beam splinter 20 to photodetector 24.

Since the phase reversal zone plate 10 eliminates the zero diffraction order beam, solid lines 14 can be used.

However, if the phase reversal zone plate is imperfectly manufactured, some amount of zero-dimensional flux will be reflected by the zone plate and collected by lens 22. In this case, dashed nodes or gratings are used as opposed to solid nodes in order to cause the orders to be reflected at predictable angles, thus transmitting the desired orders, e.g. And a spatial filter 23 is allowed which filters out unfavorable orders, for example high orders and zero orders. however,
The use of linear gratings and spatial filters has been described to complete the invention; one of the novel advantages of using a phase reversal zone plate over a Fresnel zone plate is that all zeros of the original signal are eliminated. It is clear that the next component is substantially removed.

It is clear that the above description does not limit the invention, and further variations are possible within the scope of the invention.

[Brief explanation of the drawing]

1 is a partial sectional view of an embodiment of a mask according to the invention; FIG. 2 is a perspective view of the structure of the mask of FIG. 1 in relation to a wafer; and FIG. FIG. 2 is a light path diagram outlining an alignment method according to the invention using a mask according to the invention, and FIG. 4 is a system diagram outlining a practical example of an alignment apparatus according to the invention.

Claims (1)

[Claims] 1. In a mask having at least one transparent part used in manufacturing integrated circuits, in order to image a monochromatic light beam as a straight line on a predetermined focal plane, a straight line is formed in the transparent part. A mask for manufacturing integrated circuits, which is a device consisting of a completely transparent phase-inverted zone plate. 2. A mask for the production of integrated circuits according to claim 1, characterized in that the device comprises alternating zones of transparent material having an optical path difference of half a wavelength relative to adjacent zones. 3. A mask 4 for manufacturing an integrated circuit according to claim 2, wherein the intersection difference is formed by a layered zone of a transparent material.The optical path difference is etched into the surface of the mask. 3. A mask for manufacturing an integrated circuit according to claim 2, characterized in that the mask is formed of zones with a ridge. 5. A patent characterized in that the height difference between adjacent zones is obtained by equation 2, where λ = wavelength, Δn = difference in refractive index between the transparent material and air, and N = any odd integer. A mask for manufacturing an integrated circuit according to claim 3. 6. The height difference between adjacent zones is obtained by the equation: [where λ = wavelength, Δn = difference in refractive wealth between the material and air in the transparent part of the mask, N = any odd integer] A mask for manufacturing a dyed circuit according to claim 4, characterized in that: 7. A method for optically arranging patterns on two members disposed in separate parallel planes at a distance, including the following steps: In one of the members, a linear fully transparent phase-inverting pattern is formed. A zone plate is formed, a straight line par is formed on the surface of the other member, a monochromatic light beam is transmitted through the zone plate to form an image of the original straight line on the surface of the other member, and a straight line is formed on the surface of the other member. detecting light reflections passing through the zone plate in the opposite direction; and moving the members relative to each other until the detected reflected light indicates that the light line is imaged onto the straight line par. A method of optically aligning patterns on two members placed in separate parallel planes at a distance, the method comprising: moving the patterns optically. 8. In the step of forming a linear fully transparent phase reversal type zone plate, forming alternating zones of the zone plate having an optical path difference, relative to adjacent zones, equal to a half wavelength of the monochromatic light. A method for optically aligning patterns on two members arranged in separate parallel planes separated by a distance according to claim 7. 9. Furthermore, in the step of forming a linear fully transparent phase inversion type zone plate, a transparent material is placed on the surface of the one member at a height such that an optical path difference equal to a half wavelength of monochromatic light is generated. A method for optically aligning chisel turns on two members disposed on separate parallel planes separated by a distance according to claim 8, characterized in that the alternating zones are formed by attaching 10. Furthermore, in the step of forming a linear fully transparent phase inversion type zone plate, a depth is provided in the transparent portion of the one member such that the optical path difference is equal to a half wavelength of the monochromatic light. Claim 8, characterized in that the alternating zone is formed by etching a recess in the
A method for optically aligning patterns on two members placed on separate parallel planes separated by a distance as described in Section 1. 11. In the step of forming a straight line par, a straight line par with a reflectivity different from that of its surroundings in the direction of alignment correction is formed. A method of optically aligning chisel turns on two members arranged in a plane. 12. In the step of forming a straight line, the formula: %
Forming a straight line par with a height or depth equal to the formula % [where λ = wavelength, n = reflectance of the medium covering the reflective mark, N - any odd integer] A method for optically aligning patterns on two members arranged on separate parallel planes separated by a distance according to scope 7. 13. For optically aligning chisel turns on two members disposed in separate parallel planes at a distance, the following steps are carried out: In one of said members, a linear fully transparent phase-reversing shape is placed. A zone plate is formed, a straight line par is formed on the surface of the other member, a monochromatic light beam is transmitted through the zone plate to form an image of the original straight line on the surface of the other member, and a straight line is formed on the surface of the other member. The members are moved relative to each other until a light reflection passing through the zone plate in the opposite direction is detected and the detected reflected light indicates that the original straight line is imaged onto the straight line. An apparatus for carrying out a method comprising relative movement, which comprises: a completely transparent phase-inversion type zone plate formed on the one member, a linear par formed on the surface of the other member, and a luminous flux of monochromatic light. A first device that transmits through the zone plate and forms an image on the surface of the other member, and a second device that transmits the zone plate from the surface of the other member in the opposite direction and detects the reflected light beam. and a third device for moving the two members relative to each other until the detected reflected light indicates alignment of the two members, located in separate parallel planes at a distance. A device that optically aligns the two parts on one member. 14. The fully transparent phase-inversion zone plate comprises alternating zones having an optical path difference, relative to adjacent zones, equal to a half wavelength of the monochromatic light. A device for optically aligning the turrets on two members placed in separate parallel planes with a distance of . 15. Further, the fully transparent phase-inverting zone plate has a height at which the alternating zones of the transparent portion of the one member have an optical path difference equal to a half wavelength of the monochromatic light relative to the adjacent zone. 15. A device for optically aligning turrets on two members disposed in separate parallel planes at a distance as claimed in claim 14, characterized in that the device comprises a transparent material formed in a transparent material formed in a transparent material. 16. The fully transparent phase-inversion type zone plate has alternating zones in which the surface of the one member is etched to a depth having an optical path difference equal to a half wavelength of the monochromatic light relative to the adjacent zone. 15. A device for optically aligning patterns on two members placed on separate parallel planes separated by a distance, as set forth in claim 14. 17. An apparatus for optically aligning patterns on two members disposed in separate parallel planes separated by a distance as claimed in claim 15, wherein the transparent material is a 7-otoresist. 18. The straight line par is a solid line of light reflectivity limited by the difference in reflectivity between the nocturne and its surroundings. A device for optically aligning patterns on two members arranged in parallel planes. 15, wherein the linear par is a solid line of light reflectivity limited by a difference in reflectivity between the no-shaped pattern and its surroundings. A device for optically aligning the turrets on two members arranged in parallel planes. 20. The straight line is a solid line of light reflectivity limited by a par shape, an O-turn, and a difference in reflectivity between its surroundings. on two members placed in separate parallel planes,
A device that optically aligns J-turns. 21. The M-line node is a solid line of light reflectivity limited by a difference in reflectivity between the node shape/gutter and its surroundings. A device for optically aligning turrets on two members placed in separate parallel planes at a distance. 22. The distance set forth in claim 17, wherein the straight line is a solid line of light reflection limited by the difference in reflection power between the no-shaped pattern and its surroundings. A device for optically aligning turrets on two members placed in separate parallel planes. 23. The linear pattern on two members arranged on separate parallel planes separated by a distance according to claim 13, characterized in that the straight line is a light-reflective maximum phase difference solid line. A device for optical alignment. 24. A nozzle on two members disposed on separate parallel planes separated by a full distance according to claim 14, wherein the straight line is a solid line with maximum phase difference that reflects light. A device that optically aligns turns. 25. The linear pattern on two members arranged on separate parallel planes separated by a distance according to claim 15, characterized in that the straight line is a light-reflective maximum phase difference solid line. A device for optical alignment. 26. The linear pattern on two members arranged on separate parallel planes separated by a distance according to claim 16, characterized in that the straight line is a light-reflective solid line with maximum phase difference. A device for optical alignment. 27. The pattern on two members arranged on separate parallel planes separated by a distance according to claim 17, wherein the straight line notches are light reflective solid lines with maximum phase difference. A device that optically aligns the 28. Claim 1, wherein the straight lines are light-reflective, periodically interrupted lines.
2 placed on separate parallel planes with a distance of 2 as described in item 3.
A device that optically aligns the grooves on two members. 29. Claim 1, characterized in that the straight line grooves are light-reflective, periodically interrupted grooves.
2 placed on separate parallel planes separated by the distance described in item 4
A device for optically aligning R-turns on two members. 30. Claim 1, wherein the straight lines are light-reflective, periodically interrupted lines.
2 placed on separate parallel planes separated by the distance described in item 5.
No' on one member? A device that optically aligns turns. 31. Claim 1, wherein the straight lines are light-reflective, periodically interrupted lines.
2 placed on separate parallel planes separated by the distance described in item 6
A device that optically aligns patterns on two members. 32. Claim 17, characterized in that the straight lines are light-reflective, periodically interrupted bars.
A device for aligning patterns on two members placed in separate parallel planes separated by a distance as described in Section 1.