GB1560778A - Methods of aligning articles - Google Patents
Methods of aligning articles Download PDFInfo
- Publication number
- GB1560778A GB1560778A GB1104978A GB1104978A GB1560778A GB 1560778 A GB1560778 A GB 1560778A GB 1104978 A GB1104978 A GB 1104978A GB 1104978 A GB1104978 A GB 1104978A GB 1560778 A GB1560778 A GB 1560778A
- Authority
- GB
- United Kingdom
- Prior art keywords
- light
- wafer
- groove
- article
- beams
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000000034 method Methods 0.000 title claims description 36
- 235000012431 wafers Nutrition 0.000 claims description 59
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 15
- 229910052710 silicon Inorganic materials 0.000 claims description 15
- 239000010703 silicon Substances 0.000 claims description 15
- 239000004065 semiconductor Substances 0.000 claims description 7
- 239000013078 crystal Substances 0.000 claims description 5
- 238000005530 etching Methods 0.000 claims description 4
- 239000000463 material Substances 0.000 claims description 3
- 230000000873 masking effect Effects 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000008021 deposition Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/26—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes
- G01B11/27—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes for testing the alignment of axes
- G01B11/272—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes for testing the alignment of axes using photoelectric detection means
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Container, Conveyance, Adherence, Positioning, Of Wafer (AREA)
- Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)
Description
(54) IMPROVEMENTS IN OR RELATING TO METHODS OF
ALIGNING ARTICLES
(71) We, INTERNATIONAL COM
PUTERS LIMITED, a British Company, of
ICL House, Putney, London S.W. 15, hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to methods of aligning articles and in particular to a method of aligning a semi-conductor wafer in a predetermined position during the manufacture of an integrated circuit structure.
Such integrated circuit structures are produced by selectively acting on a face of the wafer and by forming circuit interconnections by successive deposition and etching operations. In order to facilitate these operations photo-resists are utilised and these photo-resists are required to be selectively irradiated with light to form patterns thereon corresponding to required circuit features.
It has previously been proposed to pass the light through masks or stencils superimposed on the face of the wafer. In order to accurately position each of these masks on the face of the wafer alignment marks have previously been provided on the face. One arrangement of such alignment marks is a sequence of progressively smaller squares placed one inside another. A disadvantage of providing alignment marks on the same face of the wafer as the circuit features, however, is that the alignment marks take up space that could otherwise be utilised for additional circuit features.
Furthermore, during such an alignment process which is carried out manually, it is necessary to illuminate the face of the wafer with visible light in order that the alignment marks can be seen. Thus, this use of visible light restricts the type of photo-resist used in forming the circuit features to one which is insensitive to visible light. Photo-resists which are sensitive to ultra-violet light but relatively insensitive to visible light are commonly used in this application.
According to the present invention a method of aligning an article in a predetermined position includes the steps of providing in the article at a predetermined location a first groove of V-section. the first groove having reflective surfaces; providing a light source to produce first beams of light; moving the article to a position in which the first beams of light from the light source are incident on each of the surfaces of a first region of the first groove; detecting the light reflected from each of the surfaces and adjusting the position of the article until the detected light reflected from each surface of the first groove is of substantially equal value, the light source being positioned so that when the reflected light from each surface is of equal value the article is aligned in said predetermined position.
In a preferred arrangement the groove will be elongate and by directing beams of light at spaced apart regions of the groove
and moving the article both linearly and rotationally until the amount of light reflected from each of the surfaces at both regions of the groove attains a substantially equal value, the article will be aligned in a predetermined angular orientation in said predetermined position.
In a further arrangement an additional groove may be provided orthogonally disposed with respect to the first groove, so that by moving the article until the reflected light from each surface of the additional groove also attains substantially equal values, the article is aligned with respect to said predetermined position in two dimensions perpendicular to one another..
The invention will now be described, by way of example, with reference to the accompanying drawing, in which,
Figure 1 is a plan view of a back face of a silicon wafer showing a V-section groove formed therein. and
Figure 2 is a schematic diagram showing an arrangement for aligning the V-section groove in a predetermined position.
Referring to Figure 1 of the drawing, a circular wafer 1 which is used in the manufacture of integrated circuit chips is shown. The wafer is of silicon and is formed by cutting a slide from a silicon rod. On the underside, or front face, of the wafer 1 (not shown), a number of discrete areas containing circuits will be formed and the wafer will subsequently be cut to separate the areas to so produce a number of individual integrate circuit chips. On the back face of the wafer 1 an L-shaped groove 2 of V-section is formed. The sides of the groove 2 have surfaces capable of reflecting light.
The groove 2 is formed in the silicon wafer by etching and in order to accomplish this the wafer must be cut in the so called (100) orientation. In practice this is not a limitation as most wafers are cut in this orientation for other reasons. Cutting the silicon this way ensures that two orthogonally disposed preferred crystal planes are aligned with the plane of the wafer. The significance of the preferred crystal planes is that selective etchants are available which, when utilised to etch along these preferred planes, produce V-section grooves in the silicon. The depths of the grooves are determined solely by their width irrespective of the time that the etchant is in contact with the silicon and the angle between the sides of the grooves is determined by the physical properties of the silicon.Thus, it is only necessary to define the required outline of the groove in a mask or in a layer of photo-resist material on the surface of the silicon, for example, and upon application of the etchant the depth and section of the groove is automatically produced. In the present application of this technique the two arms 3 and 4 of the
L-shaped groove are aligned one with each of the preferred crystal planes. For further details of forming V-section grooves in silicon wafers reference may be made to a paper entitled "Dielectric Isolation:
Comprehensive, Current and Future" by K.
E. Bean and W. R. Dunyan in the "Journal of the Electrochemical Society" of January
1977. When grooves are etched in silicon
using this technique the sides of the grooves
have a highly polished appearance, thus providing surfaces ideal for the reflection of light.
Light reflected from the sides of the
V-section groove in the back face of the
wafer is utilised in the present invention to
precisely position the wafer relative to a
pattern of light representing circuit features
which is optically projected on to the front
face of the wafer.
A method of achieving this will now be
described with reference to Figure 2. A pair
of light sources 5 and 6 are arranged to
produce respective beams 7 and 8 of collimated light, the beams being directed to cross over one another and to impinge one on each side of the V-section groove 2.
As the sides of the groove 2 have highly reflective surfaces the beams will be reflected from these surfaces as shown in
Figure 2. It will be realised that each light beam will always be reflected from its respective surface at an angle, equal to the angle between the incident beam and the respective surface. Thus, it is possible to position a pair of detectors 9 and 10 such that when both of the reflected beams 7a and 8a fall on their respective detectors the
V-section groove 2 is in a known predetermined position. In practice this is achieved when the quantities of reflected light, as measured by the detectors 9 and 10 are of substantially equal values. To align the wafer 1 in a known position therefore, it is only necessary to move the wafer until both the detectors 9 and 10 are indicating equal intensities of light.
It will be appreciated that the operation described, using a single pair of detectors, will align the wafer in one dimension only.
In order to precisely position the wafer it is necessary to orientate it and to align it in two orthogonally disposed dimensions. A method of positioning the wafer using the same principles as previously set out will now be described with reference to Figure 1. In this case the light sources 5 and 6 project their light through respective elongate slots, in a mask for example. The slots are arranged parallel to one another and are effective to produce a pair of flat beams of light having parallel planes and being as great or greater in width than the length of the arm 3 of the L-shaped groove 2. An additional pair of detectors 13, 14 are employed in this case so that sensing of light reflected from spaced apart regions of the long arm 3 of the L-shaped groove 2 as indicated by the broken lines linking the pairs 9, 10 and 13, 14 can be effected. Thus, when the intensity of light is of equal value at all four of the detectors 9, 10 and 13, 14 the arm 3 of the L-shaped groove 2 is angularly aligned with the planes of the beams of light.
The orientation of the parallel slots is, of course, arranged such that when the long arm.3 of the L-shaped slot 2 is lying parallel with them the orientation of the wafer is as required.
A further pair of light sources (not shown), but similar to the light sources 5 and 6 are arranged to project beams of light on to the arm 4 of the L-shaped slot 2 and a further pair of detectors 15 and 16 are positioned to receive the light reflected from the arm 4 at a region indicated by the broken line linking the detectors 15 and 16.
The wafer is now moved in a direction parallel to the long arm 3 of the L-shaped groove 2, while maintaining the equal readings on the detectors 9, 10, 13 and 14, until equal light intensity is indicated on the detectors 15 and 16. When equal light intensity is indicated on all of the six detectors the wafer is precisely aligned in the predetermined position.
Being able to precisely position a wafer in this way enables it to be aligned with the previously mentioned pattern of light representing circuit elements. The pattern
11 is optically projected on to a layer of photo-resist material (not shown) on the opposite side or front face of the wafer by a projector 12 mounted on the same frame structure as that which supports the light sources 5 and 6 and the detectors 9 and 10.
Using this method of alignment a plurality of wafers can be brought successively into alignment for the projection thereon of a pattern of light. It will be understood that in processing a wafer, the wafer needs to be subjected to a plurality of masking operations and the above method of alignment permits the wafer to be repeatedly aligned in the required predetermined position so that different patterns of light projected thereon at different times are correctly and precisely aligned on the wafer.
It will be realised that, although the means for providing each pair of light beams has been described as including two separate sources of light, this arrangement could be modified. For example, a single source of light contained with an enclosure and arranged to project two beams of light could replace the separate light sources such as 5 and 6.
It will be appreciated that the provision of alignment means on the back face of the wafer avoids any conflict such as can exist between conventional alignment marks and circuit features on the front face of the wafer and thus all types of wafer can be aligned in an identical manner by this method.
It will also be appreciated that this method of alignment is easily adapted to automation in that signals produced by the reflected light can be utilised to operate positioning mechanism effective to move the wafer.
WHAT WE CLAIM IS:
1. A method of aligning an article in a predetermined position including the steps of providing in the article at a predetermined location a first groove of
V-section, the first groove having reflective surfaces; providing a light source to produce first beams of light; moving the article to a position in which the first beams of light from the light source are incident on each of the surfaces of a first region of the first groove; detecting the light reflected from each of the surfaces and adjusting the position of the article until the detected light reflected from each surface of the first groove is of substantially equal value, the light source being positioned so that when the reflected light from each surface is of equal value the article is aligned in said predetermined position.
2. A method as claimed in Claim 1, including the steps of providing said first groove in elongate form; providing second beams of light incident on to each of the surfaces of the groove at a second region spaced apart from said first region and detecting the light reflected from each of the surfaces at said second region; and adjusting the position of the article both linearly and rotationally until the amount of light reflected from each of the surfaces at said first and at said second regions of the groove is of substantially equal value to thereby align the article in a predetermined angular orientation in said predetermined position.
3. A method as claimed in Claim 2, including the steps of providing a second groove of V-section having reflective surfaces, the second groove being orthogonally disposed with respect to the first groove providing third beams of light, moving the article until the third beams are incident on to each of the surfaces of the second groove and detecting the light reflected from each of the surfaces thereof; and further adjusting the position of the article until the reflected light from each surface of the second groove is also of substantially equal value to thereby align the article with respect to said predetermined position in two dimensions perpendicular to one another.
4. A method as claimed in any of Claims 1 to 3, in which the beams of light are collimated.
5. A method as claimed in any of Claims 1 to 4, in which each of the first, second and third beams of light are respectively produced from a single light source.
6. A method as claimed in any preceding claim, in which the article is a semi-conductor wafer.
7. A method as claimed in Claim 6, in which the semi-conductor wafer is formed from silicon cut in the (100) orientation and in which the grooves are formed by selectively etching along orthogonally disposed preferred crystal planes in the silicon.
8. A method as claimed in Claim 6 or 7, including the step of optically projecting a light image such that when the semi-conductor wafer is aligned in said predetermined position the image is displayed in a predetermined position on a face of the wafer.
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (9)
- **WARNING** start of CLMS field may overlap end of DESC **.groove 2, while maintaining the equal readings on the detectors 9, 10, 13 and 14, until equal light intensity is indicated on the detectors 15 and 16. When equal light intensity is indicated on all of the six detectors the wafer is precisely aligned in the predetermined position.Being able to precisely position a wafer in this way enables it to be aligned with the previously mentioned pattern of light representing circuit elements. The pattern11 is optically projected on to a layer of photo-resist material (not shown) on the opposite side or front face of the wafer by a projector 12 mounted on the same frame structure as that which supports the light sources 5 and 6 and the detectors 9 and 10.Using this method of alignment a plurality of wafers can be brought successively into alignment for the projection thereon of a pattern of light. It will be understood that in processing a wafer, the wafer needs to be subjected to a plurality of masking operations and the above method of alignment permits the wafer to be repeatedly aligned in the required predetermined position so that different patterns of light projected thereon at different times are correctly and precisely aligned on the wafer.It will be realised that, although the means for providing each pair of light beams has been described as including two separate sources of light, this arrangement could be modified. For example, a single source of light contained with an enclosure and arranged to project two beams of light could replace the separate light sources such as 5 and 6.It will be appreciated that the provision of alignment means on the back face of the wafer avoids any conflict such as can exist between conventional alignment marks and circuit features on the front face of the wafer and thus all types of wafer can be aligned in an identical manner by this method.It will also be appreciated that this method of alignment is easily adapted to automation in that signals produced by the reflected light can be utilised to operate positioning mechanism effective to move the wafer.WHAT WE CLAIM IS: 1. A method of aligning an article in a predetermined position including the steps of providing in the article at a predetermined location a first groove of V-section, the first groove having reflective surfaces; providing a light source to produce first beams of light; moving the article to a position in which the first beams of light from the light source are incident on each of the surfaces of a first region of the first groove; detecting the light reflected from each of the surfaces and adjusting the position of the article until the detected light reflected from each surface of the first groove is of substantially equal value, the light source being positioned so that when the reflected light from each surface is of equal value the article is aligned in said predetermined position.
- 2. A method as claimed in Claim 1, including the steps of providing said first groove in elongate form; providing second beams of light incident on to each of the surfaces of the groove at a second region spaced apart from said first region and detecting the light reflected from each of the surfaces at said second region; and adjusting the position of the article both linearly and rotationally until the amount of light reflected from each of the surfaces at said first and at said second regions of the groove is of substantially equal value to thereby align the article in a predetermined angular orientation in said predetermined position.
- 3. A method as claimed in Claim 2, including the steps of providing a second groove of V-section having reflective surfaces, the second groove being orthogonally disposed with respect to the first groove providing third beams of light, moving the article until the third beams are incident on to each of the surfaces of the second groove and detecting the light reflected from each of the surfaces thereof; and further adjusting the position of the article until the reflected light from each surface of the second groove is also of substantially equal value to thereby align the article with respect to said predetermined position in two dimensions perpendicular to one another.
- 4. A method as claimed in any of Claims 1 to 3, in which the beams of light are collimated.
- 5. A method as claimed in any of Claims 1 to 4, in which each of the first, second and third beams of light are respectively produced from a single light source.
- 6. A method as claimed in any preceding claim, in which the article is a semi-conductor wafer.
- 7. A method as claimed in Claim 6, in which the semi-conductor wafer is formed from silicon cut in the (100) orientation and in which the grooves are formed by selectively etching along orthogonally disposed preferred crystal planes in the silicon.
- 8. A method as claimed in Claim 6 or 7, including the step of optically projecting a light image such that when the semi-conductor wafer is aligned in said predetermined position the image is displayed in a predetermined position on a face of the wafer.
- 9. A method of aligning an article in a predetermined position substantially as described herein with reference to the accompanying drawing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB1104978A GB1560778A (en) | 1978-03-21 | 1978-03-21 | Methods of aligning articles |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB1104978A GB1560778A (en) | 1978-03-21 | 1978-03-21 | Methods of aligning articles |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB1560778A true GB1560778A (en) | 1980-02-06 |
Family
ID=9979071
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB1104978A Expired GB1560778A (en) | 1978-03-21 | 1978-03-21 | Methods of aligning articles |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB1560778A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3211928A1 (en) * | 1981-04-03 | 1983-01-20 | N.V. Philips' Gloeilampenfabrieken, 5621 Eindhoven | ARRANGEMENT FOR DETECTING THE POSITION OF AN OBJECT |
| GB2159939A (en) * | 1984-03-02 | 1985-12-11 | Hewlett Packard Co | Detector apparatus |
| US6342735B1 (en) | 1999-09-01 | 2002-01-29 | International Business Machines Corporation | Dual use alignment aid |
-
1978
- 1978-03-21 GB GB1104978A patent/GB1560778A/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3211928A1 (en) * | 1981-04-03 | 1983-01-20 | N.V. Philips' Gloeilampenfabrieken, 5621 Eindhoven | ARRANGEMENT FOR DETECTING THE POSITION OF AN OBJECT |
| GB2159939A (en) * | 1984-03-02 | 1985-12-11 | Hewlett Packard Co | Detector apparatus |
| US6342735B1 (en) | 1999-09-01 | 2002-01-29 | International Business Machines Corporation | Dual use alignment aid |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PS | Patent sealed | ||
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19950321 |