GB2129124A - Aligning mask with body - Google Patents
Aligning mask with body Download PDFInfo
- Publication number
- GB2129124A GB2129124A GB08229616A GB8229616A GB2129124A GB 2129124 A GB2129124 A GB 2129124A GB 08229616 A GB08229616 A GB 08229616A GB 8229616 A GB8229616 A GB 8229616A GB 2129124 A GB2129124 A GB 2129124A
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- Prior art keywords
- mask
- radiation
- pattern
- machine
- interference pattern
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F9/00—Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically
- G03F9/70—Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically for microlithography
- G03F9/7065—Production of alignment light, e.g. light source, control of coherence, polarization, pulse length, wavelength
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F9/00—Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically
- G03F9/70—Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically for microlithography
- G03F9/7049—Technique, e.g. interferometric
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)
Abstract
In a machine, in which is mounted a body, for example, comprising a semiconductor substrate 10 having a photoresist layer, over passivating material on the substrate, the passivating layer, and the photoresist layer, both with a relief pattern therein, monochromatic radiation is reflected at both surfaces of the part of the photoresist layer with the relief pattern, without affecting the photoresist, to form a corresponding interference pattern, capable of being aligned with a related portion of the mask 12. The detection of the interference pattern is facilitated by providing means to vary the wavelength of the monochromatic radiation, for example, by providing a tunable laser source, or, when a multicoloured source 16 is provided, by providing a variable passband filter 18 to be used in combination therewith. <IMAGE>
Description
SPECIFICATION
Aligning a mask with a body
This invention relates to aligning a mask with a body, both mounted in a machine, and in particular, although not exclusively, to the alignment of a mask through which a photoresist layer of the body is exposed in a subsequent photolithographic process, but in any such alignment procedure, to which the present invention relates, a pattern is provided within the body, monochromatic radiation, or radiation of a narrow range of wavelengths and capable of being considered as monochromatic radiation, is incident upon the body, and is reflected, thereby to form an interference pattern corresponding with the pattern provided within the body, the interference pattern is transmitted through the mask to be received by a detector of the machine, when the interference pattern, and hence also the pattern provided within the body, are aligned with a related portion of the mask in a predetermined way, as indicated by the detector, the mask being aligned in a required manner with the body.
Forms of machines each, in use, employing such an alignment procedure, for a mask and a body including a semiconductor substrate, are known, for example, kinds of so-called Direct Step on Wafer machines.
For convenience, in this specification and the accompanying claims, machines employing alignment procedures of any form as referred to above, are referred to as machines of the type referred to.
The detection of the interference pattern, when transmitted through the related portion of the mask, may be by any form of detector responsive to such radiation, for example, the detector including a TV camera. Possibly, the radiation is caused to scan along a raster pattern of lines on the body, coincident with a raster pattern of scan lines on the body associated with the TV camera, and the radiation is incident upon the body by scanning in synchronism with the action of the TV camera.
When there is any misalignment between the mask and the body, the corresponding superimposition of the interference pattern upon the mask is recognised as not providing a predetermined configuration associated with the alignment of the mask and the body. There is an output of the detector corresponding to the misalignment, and such an output either is recognised by an operator, for example, when the detector includes a TV camera, by the detector output comprising a display on the screen of a visual display unit connected to the TV camera, or the output is detected automatically within the machine. Usually, the machine also includes means whereby the operator, or the machine automatically, adjusts the position of the body relative to the mask within the machine, until the desired degree of alignment therebetween is obtained.
The interference pattern is formed by the monochromatic radiation incident upon the body being reflected at two planes provided by the body, although at least one of the planes may be only generally planar in form, and the two planes extend at least generally parallel to each other, there being a constituent layer, or layers, of the body between the two planes. Such a layer may comprise the body; or a substrate, or be provided on a substrate, or on another constituent layer, of a composite body. The radiation reflected at the two planes interferes.The radiation,partially providing the interference pattern is considered to be reflected at one of the reflecting planes, at portions of the body providing the pattern therein, and radiation partially providing the background of the interference pattern is considered to be reflected at said one reflecting plane, at portions of the body contiguous with the portions providing the pattern within the body.The pattern is formed in the constituent layer, or layers, of the body between the two reflecting planes, either by the interfering pattern forming portions of each such layer having a thickness different from the uniform thickness of the other, contiguous portions of the layer, and/or the interfering pattern forming portions of each such layer having a refractive index different from the refractive index of the other, contiguous portions of the layer. In any such construction for the body there is introduced an optical path length, between the two reflecting planes, at the portions of the body providing the pattern therein, which optical path length differs from the optical path length, between the two reflecting planes, at the portions of the body contiguous with the portions providing the pattern within the body.
When the different optical path lengths, between the two reflecting planes, are provided solely by having portions of the body with different refractive indices, both reflecting planes are precisely planar in form.
However, when the different optical path lengths, between the two reflecting planes, are provided, at least partially, by having a relief pattern formed in a constituent layer, or layers, of the body between the two reflecting planes, one of the reflecting planes is planar in form, and the other reflecting plane is generally planar in form, having a part with the relief pattern formed therein. Hence, radiation reflected at said other reflecting plane, and interfering with radiation reflected at said one reflecting plane, provides, partially, the interference pattern when reflected at portions of the layer of a thickness different from the otherwise uniform thickness of the other, contiguous portions of the layer; and provides, partially, the background of the interference pattern when reflected at said other, uniformly thick, contiguous portions of the layer.
For any construction of a body, ideally, the optical path length, between the two reflecting planes, of the interfering radiation partially providing the background of the interference pattern, is equal to one of the two following possibilities, the optical path length being an integral number of wavelengths of the incident monochromatic radiation, or an odd integral number of half wavelengths, and the optical path length, between the two reflecting planes, of the interfering radiation partially providing the interference pattern, is equal to the other of the two possibilities. Thus, there is obtained the maximum possible contrast for the interference pattern. However, it may be difficult, if not impracticable, to obtain this condition in a reproducible way, for example, it being difficult to control the height, or depth, of a relief pattern provided within the body.Further, it may not be practicable to provide an optical path length, between the two reflecting planes, at the portions of the body providing the pattern therein, which optical path length differs from the optical path length, between the two reflecting planes, at the portions of the body contiguous with the portions providing the pattern within the body, by the minimum required to obtain the maximum possible contrast associated with the interference pattern, namely, one-half of the wavelength of the incident monochromatic radiation. For example, this may be because it is not practicable to provide a relief pattern within the body with the required minimum height or depth.Hence, the arrangement of a machine of the type referred to, usually, is required to be such that the interference pattern is capable of detecting when the contrast associated with the interference pattern is significantly less than the maximum possible referred to above.
The optical system employed in a machine of the type referred to is designed to be substantially free from introducing chromatic aberration at only one wavelength, or over only a narrow range of wavelengths, for example, between the 405 and 436 nanometre lines of the mercury emissive spectrum.
When the alignment procedure is to precede a photolithographic process, as is usual, a monochromatic source of the design wavelength of the optical system, such as a mercury arc lamp, used in combination with a filter to pass, say, only the 405 or 436 nanometres lines, is employed in exposing the photoresist in the subsequent photolithographic process. A separate lowemissive power source is used in aligning the mask with the body, in order not to affect the photoresist. Conveniently, but not essentially, such a low power source is multicoloured, and is used in combination with a filter having a narrow passband centered on the design wavelength, or design mean wavelength, of the optical system of the machine, as stated above, the radiation transmitted by the filter being considered to be monochromatic radiation.Hence, when the alignment of the mask with the body is performed with radiation of a low intensity, for example, at a lower intensity than is employed in the subsequent exposure of a constituent photoresist layer of the body in a photolithographic process, the alignment may be difficult, especially when the maximum possible contrast associated with the interference pattern cannot be obtained, at least in a readily reproducible manner, for example, because the required minimum height or depth of a relief pattern is not obtainable, as referred to above.
There may be reasons other than those stated above why, in a machine of the type referred to, detection of the interference pattern, and the alignment of the interference pattern with the related portion of the mask, is difficult.
It is an object of the present invention to provide a machine of the type referred to, and arranged to facilitate the detection of the interference pattern, and the alignment of the interference pattern with the related portion of the mask.
According to the present invention, in a machine of the type referred to, in which is to be mounted a mask and a body, a pattern being provided within the body, the machine including a source of radiation to be incident upon, and reflected by, the body, thereby to form an interference pattern corresponding with the pattern provided by the body, the interference pattern being transmitted through the mask to be received by a detector of the machine, the machine also including means to cause displacement of the mask relative to the body, the detector being arranged to be capable of indicating when the interference pattern, and hence the corresponding pattern provided within the body, is aligned with a related portion of the mask in a predetermined way, representative of the mask being aligned in the required manner with the body, and there is provided means to vary either the wavelength of radiation from the source when comprising a monochromatic source, or the mean wavelength of a passband of wavelengths associated with a filter arrangement employed in combination with a multicoloured source.
The wavelength, or the mean of a passband of wavelengths, of radiation employed in aligning the mask with the body, cannot vary so as to be sufficiently different from the design wavelength, or the design mean wavelength, of the optical system of the machine, that significant chromatic aberration is introduced.
However, the maximum possible change in the wavelength of the radiation incident upon the body may be such that the maximum possible contrast associated with the interference pattern is obtained, or, at least, the contrast is enhanced significantly, without introducing an undesired amount of chromatic aberration, thereby facilitating the detection of the interference pattern, and the alignment of the interference pattern with the related portion of the mask.
Further, for a particular contrast associated with the provided interference pattern, less than the maximum possible contrast, if the detected background of the interference pattern, provided partially by radiation reflected at the portions of the body contiguous with the portions providing the pattern, either is as light, or as dark, as possible, respectively, because the interfering radiation providing the background either is in phase, or is out of phase, the provided interference pattern is as readily detectable as possible.The lightest possible background is obtained for the interference pattern when the optical path length between the two reflecting planes provided by the body, and for the interfering radiation providing the background, is equal to an integral number of wavelengths of the incident radiation, and the darkest possible background is obtained when such an optical path length is equal to an odd integral number of half wavelengths.Again, the maximum possible change in the wavelength of the radiation incident upon the body, in accordance with the present invention, may be such that, in relation to the background of the provided interference pattern, the darkest, or the lightest, background is obtained, or at least there is a significant darkening or lightening thereof, without introducing an undesired amount of chromatic aberration, thereby facilitating the detection of the provided interference pattern, and the alignment of the provided interference pattern with the related portion of the mask.
If the wavelength, or the mean of the passband of wavelengths, of the radiation employed in aligning the mask with the body can be varied within a range equal to, at most, one quarter of the mean wavelength in the range, it is possible to select a wavelength, or the mean of a passband of wavelengths, at which the interference pattern is most detectable because of the radiation intensity obtainable for the background of the interference pattern.
It may not be possible simultaneously, by varying the incident radiation wavelength, both to improve the contrast, and to increase, or decrease, where appropriate, the background radiation intensity, for the interference pattern, but an optimum compromise condition for the detection of the interference pattern is obtainable, and thereby this detection, and the alignment of the interference pattern with the related portion of the mask, is facilitated. An improvement in the ability to detect the interference pattern may be obtainable if the wavelength, or the mean of the passband of wavelengths, of the incident radiation can be varied within a range less than one quarter of the mean wavelength in the range.
In accordance with the present invention, the incident radiation wavelength may be variable only by an amount sufficient to be able to obtain some such improvement in the ability to detect the interference pattern.
Conveniently, the wavelength, or the mean of a narrow passband of wavelengths, of the incident radiation employed in aligning the mask with the body, is continuously variable.
The means to vary the wavelength of the radiation from a monochromatic source may be provided by including within the machine a tunable laser as the radiation source.
Alternatively, the means to vary the mean wavelength of a passband of wavelengths of radiation incident upon the body may be provided by including within the machine a variable bandpass filter, of a known form, and employed in combination with a multicoloured source of radiation.
The present invention will now be described
by way of example with reference to the accompanying drawing, comprising a diagrammatic representation of a so-called Direct
Step of Wafer machine, in the form of one embodiment of a machine of the type referred to, in accordance with the present invention.
In the illustrated machine of the type referred to, comprising a Direct Step on Wafer machine, it is required to align a mask with a body including a semiconductor substrate of silicon, through which mask a constituent photoresist layer of the body, and provided on the semiconductor substrate, is exposed in a subsequent photolithographic process. The photoresist layer is over a layer of passivating material, such as silicon oxide, the passivating layer also being a constituent layer of the body. Both the mask and the body are mounted in the machine in any convenient manner. The body is not shown, except for the semiconductor substrate, in the form of a wafer, and indicated at 10. The mask is indicated generally at 12.For convenience, the opaque regions of the mask are not shown; and the photoresist layer, and the passivating layer, on the semiconductor substrate, are not shown, except for the complement of a required relief pattern, which complement of the required relief pattern is provided within the passivating layer, and is indicated generally at 1 4, details of the complement of the relief pattern not being shown.
The surface of the passivating layer remote from the semiconductor substrate is planar, except for the part having the complement of the relief pattern protruding therefrom. The photoresist layer, provided on the passivating layer, has a planar surface remote from the passivating layer, although covering the complement of the relief pattern provided within the passivating layer, and the required relief pattern is reproduced in the layer of photoresist.
The arrangement is such that, during the alignment of the mask 12 with the semiconductor substrate 10, radiation from a multicoloured source 16 is incident upon the photoresist layer on the semiconductor substrate, after passing through a filter indicated generally at 18, the radiation also being reflected at mirrors 20 and 22, and being transmitted by a magnifying lens system indicated generally at 24. The radiation reflected at the photoresist layer is transmitted by the lens system 24 in the reverse direction, is reflected by the mirror 22, but is transmitted by the mirror 20, which is half-silvered, to be received by a detector 26 including a conventional
TV camera.The radiation incident upon the photoresist layer is caused to scan along a raster pattern of lines, coincident with a raster pattern of scan lines associated with the TV camera 26, and in synchronism with the action of the TV camera.
The incident radiation is, at least partially, reflected by the body. The intensity of radiation incident upon the photoresist layer, during the alignment of the mask 12 with the semiconductor substrate 10, is such that the photoresist is not affected thereby. Thus, a low powered source 16 is employed in the alignment of the mask 12 with the semiconductor substrate 10.
The lens system indicated generally at 24 may be part of a larger optical system included in the machine, for example, a microscope, not shown, also being included in the illustrated radiation path.
The optical system is designed to be substantially free from introducing chromatic aberration at only one wavelength, or over only a narrow range of wavelengths, and consequently the filter 18 is required to have only a narrow passband of wavelengths, for example, between the 405 and 436 nanometre lines of the mercury emissive spectrum. For convenience, radiation of such a narrow passband of wavelengths can be considered to be monochromatic radiation.
When the monochromatic radiation is incident upon the photoresist portions providing the relief pattern, partially, it is reflected at the generally planar interface between the passivating layer and the photoresist layer, and partially at the planar surface of the photoresist layer remote from the passivating layer. Hence, there is formed an interference pattern corresponding with the relief pattern.If the height, or depth, of the relief pattern at the interface is such that the radiation reflected, at the interface, at the portions of the photoresist layer providing the relief pattern is in phase with, and the radiation reflected, at the interface, at the portions of the photoresist layer contiguous with the relief pattern is out of phase with, the radiation reflected at the surface of the photoresist layer remote from the passivating layer, or vice versa, the greatest contrast is associated with the corresponding interference pattern.
The interference pattern produced in the way described above is received by the TV camera 26 after it has been transmitted through the mask 12.
When the semiconductor substrate 10 is aligned in the required manner with the mask 12, the interference pattern is transmitted by a related portion of the mask, this related portion being indicated generally at 28. The pattern of the related portion of the mask is thus superimposed upon the interference pattern in the field of view of the TV camera 26, and on the display provided on the screen of a visual display unit, not shown, coupled to the TV camera. Further, when the mask is aligned in the required manner with the semiconductor substrate, the relief pattern provided within the photoresist layer, and the corresponding interference pattern, are aligned with the related portion 28 of the mask in a predetermined way, as detected by the TV camera, and displayed by the visual display unit.
Conveniently, the pattern of the related portion of the mask, the relief pattern provided within the photoresist layer, and the corresponding interference pattern, each has a reticular form. The superimposition of the interference pattern upon the related portion of the mask has a predetermined configuration, and any
misalignment between the mask and the semiconductor substrate is capable of being
recognised, the recognition being in response to the output of the TV camera corresponding to the misalignment.
The information received by the TV camera may be digitised in any known way, and compared with stored digitised information, in order to determine whether, or not, the mask is aligned with the semiconductor substrate. In such a manner the machine is capable of determining automatically whether the semiconductor substrate is aligned with the mask, and, if not, a signal may be produced which causes adjusting means, not shown, provided within the machine, automatically to displace the semiconductor substrate relative to the mask, until it is detected by the TV camera that the semiconductor substrate is aligned with the mask.
Alternatively, an operator inspects the display provided by the visual display unit, and in response to detecting any misalignment between the semiconductor substrate and the mask, the operator employs manually operable adjusting means to correct the location of the semiconductor substrate relative to the mask.
Because only a low emissive power, multicoloured source, such as a lamp having a 15 watt tungsten filament, is employed in aligning the mask with the semiconductor substrate, in order to avoid affecting the photoresist in this process step, difficulty may be experienced in detecting when the semiconductor substrate is aligned with the mask, and possibly in detecting the interference pattern corresponding with the relief pattern. Hence, it is required that the interference pattern is made as readily detectable as possible.
It may not be practicable to provide a relief pattern within the layer of photoresist with a predetermined height or depth, and/or to provide a photoresist layer with a predetermined mean thickness, in order to provide the maximum possible contrast for the interference pattern, in the way described above. Thus, the arrangement of the machine is required to be such that the interference pattern is capable of detection when the contrast associated therewith is significantly less than the maximum possible.
Irrespective of the contrast associated with the interference pattern, and when the contrast is less than the maximum possible, as referred to above, if the detected background of the interference pattern, provided by radiation reflected at the surface of the photoresist layer remote from the passivating layer interfering with radiation reflected at the interface between the photoresist layer and the passivating layer, at the portions of the photoresist layer contiguous with the relief pattern, either is as light, or as dark, as is possible, the interference pattern is as readily detectable as possible.Hence, radiation reflected, at the interface, at the portions of the photoresist layer contiguous with the relief pattern, respectively, and desirable, is in phase, or out of phase, with radiation reflected at the surface of the photoresist layer remote from the passivating layer.
In accordance with the present invention the illustrated machine is modified so that the detection of the interference pattern, and the alignment of the mask with the semiconductor substrate, are facilitated. In particular, means is provided in the machine to ensure that the radiation incident upon the photoresist layer is of a desired wavelength, empirically determined whilst the mask is being aligned with the substrate.
Thus, means for varying the wavelength of the radiation incident upon the photoresist layer is provided within the machine. In the illustrated embodiment such means is to vary the mean wavelength of the narrow passband of wavelengths transmitted by the filter 18, by the filter comprising a variable bandpass filter of a known form. Such a variable bandpass filter may comprise two elements, one comprising a long wavelength pass filter element, and the other comprising a short wavelength pass filter element, there being a narrow bandpass between the cutoff wavelengths associated with both elements.
Further, each constituent element of the variable bandpass filter has an associated cut-off wavelength which is variable by rotating the element in the radiation path, and the bandpass is varied by varying the angle of incidence on the filter of radiation to be transmitted by the filter. In one particular embodiment of such a filter, when both constituent elements of the filter are normal to the incident radiation, and the angle of incidence on the filter of the radiation is zero, the mean wavelength of the passband is 475 nanometres. However, when both constituent elements of the filter are inclined at 450 to the incident radiation, and the angle of incidence on the filter of the radiation is 450, the mean wavelength of the passband is 425 nanometres.
Between these limits, the mean wavelength of the passband is continuously variable; and the filter may be provided with a substantially constant bandpass width.
In one particular construction of a body including a silicon semiconductor substrate, the layer of silicon oxide passivating material has an overall thickness of 300 nanometres, upon which is superimposed a relief pattern having a height of 20 nanometres. The layer of photoresist has a refractive index of 1.6; and an overall thickness of 1 micrometre.
The optical system of the machine is free from introducing chromatic aberration for monochromatic radiation of a wavelength of 436 nanometres.
The machine is capable of aligning a mask with the semiconductor substrate to an accuracy greater than 0.3 micrometre.
The machine is capable of site-by-site alignment of a mask with a regular array of sites within the body, the mask alignment procedure described above being performed at each constituent site within the body.
In the subsequent photolithographic process, the photoresist layer is exposed, through the mask, to monochromatic radiation of a wavelength from a high emissive power mercury arc lamp, used in combination with an appropriate filter.
It is not essential that the wavelength of the monochromatic radiation, or the mean wavelength of a narrow passband of wavelengths of radiation, incident upon the body, is continuously variable.
Conveniently, stepped variations are provided.
Thus, for example, a variable passband filter arrangement may comprise a plurality of narrow bandpass filters, with different constituent filters having different mean wavelengths for the radiation which they are capable of transmitting, the arrangement being such that each constituent filter, individually, can be selected and placed in the radiation path.
In an alternative arrangement for a machine in accordance with the present invention, the illustrated multicoloured source 16, and filter 18, are replaced by a source of monochromatic radiation, with means to vary the wavelength of the radiation emitted by the source. For example, the source may comprise a tunable laser, such as a Helium-Neon laser, or a Helium-Cadmium laser.
Any form of detector responsive to radiation from the source may be employed.
The machine may have any convenient arrangement by which a mask is aligned to a body having a pattern provided therein, the alignment being by monochromatic radiation, or radiation of a narrow range of wavelengths, and capable of being considered as monochromatic radiation, incident upon the body, and reflected, thereby to form an interference pattern corresponding with the pattern provided within the body, the interference pattern being transmitted through the mask to be received by a detector, when the interference pattern, and hence also the pattern provided within the body, are aligned with a related portion of the mask in a predetermined way, as indicated by the detector, the mask being aligned in a required manner with the body.
The two reflecting planes may be provided within a body in several different ways. The reflecting planes may be provided by any constituent layer, or layers, of a composite body, for example, by an epitaxially deposited layer comprising part of a semiconductor substrate.
The relief pattern can be formed in the layer of photoresist in any convenient way. For example, the pattern may have been provided in a preceding photolithographic process; or be caused by enhanced oxide growth over heavily Phosphorus doped surface regions in the silicon semiconductor substrate, a corresponding pattern of heavily Phosphorous doped surface regions having been formed in a preceding diffusion process step, before the layer of silicon oxide passivating material is grown upon the silicon semiconductor substrate; or the surface of the semiconductor substrate is formed with the required relief pattern, in any convenient way, before a layer of passivating material, of a uniform thickness, is provided thereon.
The pattern formed within the body may have any convenient form.
The body may have any convenient construction with a pattern provided therein. The interference pattern is formed by the monochromatic radiation incident upon the body being reflected at two planes provided by the body, although at least one of the planes may be only generally planar in form, and the two planes extend at least generally parallel to each other, and there being a constituent layer, or layers, of the body between the two planes. Such a layer may comprise the body, or a substrate of a composite body. There is required to be an optical path length, between the two reflecting planes, at the portions of the body providing the pattern therein, which optical path length differs from the optical path length, between the two reflecting planes, at the portions of the body contiguous with the portions providing the pattern within the body.
The required difference in optical path lengths may be provided by the interfering pattern forming portions of each such layer having a refractive index different from the refractive index of the other, contiguous portions of the layer. Thus, the pattern may be provided within the body by exposing a constituent photoresist layer, the exposed and unexposed portions of the photoresist having different refractive indices. The two refracting planes provided by the body are both planar.
The pattern provided in the body may be partially a relief pattern, and be caused partially by different portions of the body having different refractive indices.
It is not essential that the body includes a semiconductor substrate, and/or a photoresist layer, nor that a photolithographic process be performed upon the body after the aligning of the mask with the body.
Claims (5)
1. A machine of the type referred to, in which is to be mounted a mask and a body, a pattern being provided within the body, the machine including a source of radiation to be incident upon, and reflected by, the body, thereby to form an interference pattern corresponding with the pattern provided by the body, the interference pattern being transmitted through the mask to be received by a detector of the machine, the machine also including means to cause displacement of the mask relative to the body, the detector being arranged to be capable of indicating when the interference pattern, and hence the corresponding pattern provided within the body, is aligned with a related portion of the mask in a predetermined way, representative of the mask being aligned in the required manner with the body, and there is provided means to vary either the wavelength of radiation from the source when comprising a monochromatic source, or the mean wavelength of a passband of wavelengths associated with a filter arrangement employed in combination with a multicoloured source.
2. A machine as claimed in Claim 1 arranged so that the wavelength, or the mean of a passband of wavelengths, of the incident radiation employed in aligning the mask with the body, is continuously variable.
3. A machine as claimed in Claim 1 or Claim 2, in which there is provided means to vary the wavelength of the radiation from a monochromatic source, by providing a radiation source comprising a tunable laser.
4. A machine as claimed in Claim 1 or Claim 2, in which there is provided means to vary the mean wavelength of a passband of wavelengths of radiation incident upon the body, by providing a variable bandpass filter, employed in combination with a multicoloured source of radiation.
5. A machine of the type referred to, in which is to be mounted a mask and a body, the mask to be aligned in a required manner with the body, the machine being substantially as described herein, with reference to the accompanying drawing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08229616A GB2129124B (en) | 1982-10-16 | 1982-10-16 | Aligning mask with body |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08229616A GB2129124B (en) | 1982-10-16 | 1982-10-16 | Aligning mask with body |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2129124A true GB2129124A (en) | 1984-05-10 |
| GB2129124B GB2129124B (en) | 1985-12-11 |
Family
ID=10533651
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08229616A Expired GB2129124B (en) | 1982-10-16 | 1982-10-16 | Aligning mask with body |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2129124B (en) |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1168971A (en) * | 1966-07-08 | 1969-10-29 | Melvin Seymour Cook | Improvements in or relating to Optical Measurement of Length |
| GB1308957A (en) * | 1969-03-25 | 1973-03-07 | Philips Electronic Associated | Methods and apparatus for determining the distance of an object |
| GB1531909A (en) * | 1975-09-03 | 1978-11-15 | Siemens Ag | Automatic adjustment of a mask with respect to the surface of a substrate body |
| GB2086572A (en) * | 1980-10-27 | 1982-05-12 | Rosemount Eng Co Ltd | Differential pressure measuring apparatus |
-
1982
- 1982-10-16 GB GB08229616A patent/GB2129124B/en not_active Expired
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1168971A (en) * | 1966-07-08 | 1969-10-29 | Melvin Seymour Cook | Improvements in or relating to Optical Measurement of Length |
| GB1308957A (en) * | 1969-03-25 | 1973-03-07 | Philips Electronic Associated | Methods and apparatus for determining the distance of an object |
| GB1531909A (en) * | 1975-09-03 | 1978-11-15 | Siemens Ag | Automatic adjustment of a mask with respect to the surface of a substrate body |
| GB2086572A (en) * | 1980-10-27 | 1982-05-12 | Rosemount Eng Co Ltd | Differential pressure measuring apparatus |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2129124B (en) | 1985-12-11 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 732 | Registration of transactions, instruments or events in the register (sect. 32/1977) | ||
| 732 | Registration of transactions, instruments or events in the register (sect. 32/1977) | ||
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19941016 |