GB2439529A

GB2439529A - Positioning device for laser micro-machining

Info

Publication number: GB2439529A
Application number: GB0611546A
Authority: GB
Inventors: Mark Harman
Original assignee: Exitech Ltd
Current assignee: Exitech Ltd
Priority date: 2006-06-12
Filing date: 2006-06-12
Publication date: 2008-01-02
Also published as: GB0611546D0; TW200819241A; WO2007144566A1; KR20090037994A; JP2010500173A; CN101605627A; EP2032302A1

Abstract

A laser optics unit including: an optics head with an imaging or focussing lens and lens control means adapted to provide a laser beam giving an image of a mask or a focus of a beam 14 along an axis of the beam at a datum point in the unit; a work station adapted to position a substrate work piece relative to the datum point so as to provide for the positioning of the mask image or beam focus along the axis of the beam perpendicular to a substrate work piece positioned by the work station; the work station being further adapted to displace the work place in a given direction transverse the beam axis; a puck 11 and means for providing for the puck to be fluid supported over a puck region on a substrate work piece at the work station; and link means linking the puck to the optics head to enable the puck to displace the optics head relative to the axis direction; characterised by off-setting means whereby the puck, and so the puck region, at least when the puck 11 is fluid supported, is offset from the axis of the laser beam in a direction perpendicular to the beam axis.

Description

I

POSITIONING DEVICE FOR LASER MICRO-MACHINING

TEcHNIcAl. FIELD

This invention relates to a positioning device that accurately maintains the distance of a laser projection or focussing lens from the surface of a large flat substrate in order to keep the image of a mask or the focal spot exactly focussed on the substrate surface at all times during processing and allows the laser beams to machine right up to the edge of the substrate

BACKGROUND ART

in our previous GB Patent 2400063 and co-pending GB Application 0525111.1 (the Prior Applications') there is described a Positioning method and apparatus and a : , : :* product thereof. In its broadest method and aspect the Prior Applications provide a I..

method of micro-machining, by means of a laser, a work piece comprising the steps of: locating the work piece on a carrier forming a part of a transport system whereby the S...

carrier can be displaced along a path parallel to an X-axis of the work piece, a Y-axis lying transverse the path, and a Z-axis lying transverse the path; causing an output :.: * beam from the laser to establish a datum position relative to the X, Y and Z axis of a * : : work piece and displacing the work piece along the path by way of the transport system so as to enable the work-piece to be subject to micro-machining process by way of the laser characterised by the steps of: maintaining distance between the datum position and a location on a surface of the work piece in the vicinity of the datum position; and accommodating loca. l variations in thickness of the work piece so that the datum position is maintained at a fixed distance relative to a surface of the work piece.

The Prior Applications go on to formulate that the step of accommodating local variations in thickness in the work piece is by displacing the datum position to follow the surface of the work piece. it goes on to envisage that the step of maintaining distance is undertaken by means of a distance sensing device comprising a body member riding on a fluid cushion on a first surface of the work piece, the fluid cushion being established by a flow of fluid fed from the body member so as to maintain the body member at a predetermined distance from first surface; and in the event the body member is displaced from a current position of the body member due to a variation in thickness of the work piece any change in position of the body member perpendicular to the first surface is used to move the focussing or imaging lens to cause a corresponding change in the current datum position so as to restore the working datum position to its predetermined distance relative to the first surface of the work piece. Preferably the body member is located relative to a first side of the work piece and a further body member is provided located relative to a second side of the work piece on the opposite side of the work piece to the first side and the further body member serves to urge the work piece towards the body member when a local : : :* thickness of the work piece is reduced. * .

: .15 This concept of a distance sensing device comprising a body member riding over a a...

*:. surface of a work piece to be micro machined has now been developed further.

Hereafter such a distance sensing device is referred to as a puck'. The puck can be : * one of several types but in all cases a fluid layer which is generally air or other gas but * in some cases can be a liquid separates the lower side of the puck from the substrate surface. The puck can have the supporting fluid entering the gap between the puck and the substrate over a region distributed towards the outside of the puck. In this case the force between the puck and the substrate surface is always trying to force them apart. Alternatively the fluid entering the gap between the puck and the substrate can be injected at the centre of the puck. In this case the fluid expands radially outwards from the injection point creating a venturi effect that causes a low pressure to form below the outer region of the puck. This vacuum causes the puck to be forced towards the substrate surface. The high pressure at the puck centre and the low pressure at the puck edges balance each other and cause the puck to maintain its height above the substrate. Such a type of puck is called a "Bernoulli puck". It is also possible to use a puck where the fluid is injected around the outside and a vacuum is applied to the centre region. Such a puck is known as "vacuum preloaded" and also has the advantage that the vacuum and pressure counterbalance each other to stabilize the puck to substrate separation.

DISCLOSURE OF INVENTION

According to the present invention there is provided a laser optics unit including: an optics head with an imaging or focussing lens and lens control means adapted to provide a laser beam giving an image of a mask or a focus of a beam along an axis of the beam at a datum point in the unit; a work station adapted to position a substrate work piece relative to the datum point so as to provide for the positioning of the mask image or beam focus along the axis of the beam perpendicular to a substrate work piece positioned by the work : * : : station; the work station being further adapted to displace the work place in a given I...

direction transverse the beam axis; : .L5 a puck and means for providin.g for the puck to be fluid supported over a puck S...

* region on a substrate work piece at the work station; and S..

link means linking the puck to the optics head to enable the puck to displace * : the optics head relative to the axis direction; * : ": characterised by off-setting means whereby the puck, and so the puck region, at least when the puck is fluid supported, is offset from the axis of the laser beam in a direction perpendicular to the beam axis.

According to a first preferred version of the present invention the laser optics unit is characterised by off-setting means providing for the puck region to be capable of location so that the axis lies between the puck region and an edge, or a corner, of a work piece at the work station so allowing the laser beam to be located stably by means of the puck at least up to an edge or a corner of the work piece.

According to a second preferred version of the present invention or of the first preferred version thereof the link means provides for a small degree of rotation of the puck around one or two axes perpendicular to the beam to allow the puck to automatically pivot so as to provide for an underside of the puck to be positioned parallel to the substrate surface.

According to a third preferred version of the present invention or of any preceding preferred version thereof the laser optic unit is characterised by the puck being adapted for movement with respect to the optics head in a plane parallel to the surface of the substrate and in a direction parallel to a direction in which a substrate is being moved during laser processing involving the puck.

According to a fourth preferred version of the present invention or of any preceding preferred version thereof the laser optic unit is characterised by the puck being : * : :* adapted for movement with respect to the optics head in a plane parallel to the surface I...

of the substrate and in a circular direction about an axis perpendicular to the plane of the substrate surface. S... S..

According to a fifth preferred version of the present invention or of any preceding * : preferred version thereof the laser optic unit is characterised in that the puck is linked * : : to more than one optics head by a separate link means for each optics head to enable the puck to displace all such optics head relative to the axis direction.

The present invention is broadly characterised by a puck adapted to float relative to a surface of a work piece with a predetermined clearance between puck and work piece and in the event the clearance is changed, such as by dimensional variation in the work piece, then the puck functions to cause the restoration of the predetermined clearance. The rigid attachment of the puck to the lens in the direction perpendicular to the substrate surface ensures that a datum position for the laser beam functioning as the micro machining means is niaintained by means of the puck at the pre..

determined distance. Typically the control can either: involve any movement of the puck arising from a variation in work-piece causing a corresponding displacement of an associated imaging or focussing lens so that the datum position is maintained constant; or the puck, and so the datum position being fixed and the work-piece being displaced relative to the puck to provide for maintenance of the pre-determined clearance.

A number of exemplary embodiments of the body member are described in detail in GB 0525111.1 with reference to accompanying figures 1 to 13 which show diagrammatically a range of types of puck. In most examples there is shown a puck which has an openwork central region through which a beam from the machining laser is directed. * .. * * I a...

*: :: :* In many situations it is necessary to perform laser machining operations right up to : the very edge of flat substrates. In this case a puck that surrounds the laser beam fails **..

to operate satisfactorily as parts of the puck pass off the edge of the substrate and the integrity of the fluid cushion is destroyed causing the distance between the substrate * : surface and the datum position to change. a I

In the present application we describe new puck arrangements to overcome this problem. The proposed ideas differ significantly from those discussed in GB 0525111.1 and are characterised by the fact that that the laser beam does not pass though the centre of the puck but is displaced to the side of it.

In the present invention the fluid supported pucks are attached to the imaging or focussing lens via a linkage that positions the puck at some distance from the laser beam and displaced in one direction from the beam in the plane parallel to the surface of the substrate. This means that the substrate can move with respect to the laser beam so that the laser beam can machine the surface of the substrate right up to one edge of the substrate, that edge being the one that is on the opposite side of the beam to the puck.

By this method it is also possible to machine right up to two adjacent edges and right into the corner between the edges of a square or rectangular substrate if the puck is positioned with respect to the laser beam so that the substrate corner is on the opposite side of the beam to the puck.

For large flat substrates multiple parallel optical projection and focussing systems are often used to speed process rate. In this case it is possible to arrange for the pucks to be displaced in different directions with respect to the laser beams so that different optics units can be used to approach the different edges of the substrate. * .. * a S a...

*: : : :* A convenient number of optics units in four are arranged in a 2x2 array where each : .5 optics unit is used to process a quarter of the area of a square or rectangular substrate. *

In this case the pucks on all four optics heads are displaced diagonally inwards towards the centre line or centre point of the substrate at 45 degrees to the edges so : .: that all four edges of the substrate can be machined by the laser beam without any "S...

* . puck approaching the substrate edge.

Displacing the pucks at 45 degrees to the substrate edges is a convenient angle for dealing with square or rectangular substrates as it allows the possibility to minimize the lateral displacement of the puck from the beam. This is important as variations in substrate height between the beam position and the puck are not compensated for so the offset distance should be kept as small as possible. Angles other than 45 degrees are also possible if more convenient so long as the puck lower surface remains fully on the top surface of the substrate when the laser beam processes right up to the substrate edges. If the substrates to be processed are not square or rectangular and do not have right angle corners the angles other than 45 degrees are used. In general for an optics unit to machine effectively into the corner of a substrate means that the optimum displacement direction of the puck from the laser beam is close to that which bi-sects the angle between the two side edges of the substrate that join at the substrate corner.

When more than four optics heads are needed for processing a substrate it is also possible to arrange the pucks with respect to each laser beam to avoid edge issues. For example if six or eight heads are used in an array of 3 x 2 or 4 x 2 then the four corner most optics units have their associated pucks displaced diagonally inwards towards the centre or centre line of the substrate and the other two or four centre optics units have their associated pucks displaced laterally inwards on a line perpendicular to the substrate edge towards the centre of the substrate.

: * : :* For the case where only two optics units or a single line of multiple optics units are *: :: :* used to process a substrate then the pucks can be arranged to fit between pairs of : .5 optics units so that the processing datum point of both heads is controlled in position Sb..

with respect to the surface by a single puck. In this case the substrate can be processed * right up to the two edges that are perpendicular to the line joining the pucks and the :.: . laser beam..

S I

However, the two substrate edges that are parallel to the line joining the pucks and laser beams cannot be approached too closely as the pucks will overlap the edges. This problem is solved in the present invention by arranging for the pucks to be mounted on a suitable slide mechanism that causes the pucks to move with respect to the beams in the direction away from and perpendicular to the substrate edge as the row of optics units approaches any substrate edge that is parallel to the line of optics units.

The mechanism that links the pucks to the optics units must be such that it only allows motion of the puck with respect to the beams in a plane that is exactly parallel to the substrate surface. Clearly any movement in the direction perpendicular to this plane must be avoided as this will lead to change in the beam datum point position with respect to the substrate surface.

One simple example of the use of a moving puck is the case where two optics units are used and a single puck is used to support both of the imaging or focussing lenses at the correct distance from the substrate surface. In this case the puck is caused to move by a suitable control system in a direction perpendicular to the line joining the two laser beams in the direction away from the substrate edge that is to be processed. This movement is caused to happen automatically as the substrate or optics units are moved to cause the laser beams to approach a substrate edge that is parallel to the line between the beams. When the substrate or optics heads are moved to approach the opposite edge of the substrate the puck moves on its slide in the opposite direction. In * : all cases the movement direction of the puck is away from the approaching edge to * avoid failure of the fluid support. In this way the two beams can cover the full area of * ,j5 a square or rectangular substrate without the pucks approaching any edge. Is

If more than two beams are needed in a line to process a large area substrate then * : * pucks are placed between pairs of adjacent sets of optics units. For example if a row of * eight optics units are required to process a substrate then four moving pucks are used.

One puck is between optics heads I and 2. The second puck is between optics heads 3 and 4, the third between heads 5 and 6 and the fourth between heads 7 and 8. In all cases the puck supports only the two optic heads in each side of it so that there is independent movement of the four pucks in the direction perpendicular to the substrate surface in order to allow the pucks to compensate for changes in the substrate surface height during processing.

BRIEF DEscRIPTIoN OF DRAWINGS

Embodiments of the present invention will now be described with reference to the accompanying diagrams of laser optics units which: Figure us a perspective view of a first embodiment incorporating a single laser unit; Figure 2 shows a second embodiment in which four laser units are each supported by an independent puck; Figure 3 is a plan view of a third embodiment involving eight laser units; Figure 4 shows a fourth embodiment involving a single puck supports two laser units; and Figure 5 shows a fifth embodiment where eight laser units are in line with pairs of the units supported by a single puck.

DESCRIPTION OF DRAWINGS

Figure 1 shows an arrangement where a single puck 11 supports a single optics unit 12 containing a focussing or imaging lens and maintains the focal point or image plane 13 of the laser beam 14 exactly on the surface of the substrate 15 and where the : puck is displaced from the laser beam in the direction diagonally away from the corner 16 of the substrate. The substrate is able to move in 2 axes X and Y as shown 1,5 and the puck and optics unit are able to move in an orthogonal axis Z to compensate for changes in the substrate height. By this arrangement the beam can approach right S..

up to the edges of the substrate 17 and 17' without the puck approaching either edge.

* Figure 2 shows the top down view of an arrangement of 4 parallel laser optics units 21, 22, 23, 24 used to process the full area of a rectangular substrate 25 able to move in 2 axes X and Y as shown where the puck 26 associated with each optics unit is displaced with respect to each laser beam 27 diagonally inwards towards the centre of the substrate so that a line joining each puck to its corresponding laser beam is at 45 degrees to the substrate edges. In this case all 4 optics units are attached to a support frame that is not shown but which causes the optics units to maintain constant spacing in the X and Y directions during full area substrate processing but are allowed to move independently in the direction perpendicular to the substrate surface Z to compensate for changes in the substrate surface height.

Figure 3 shows the layout of an arrangement where 8 parallel laser optics units each with its own supporting puck 31 and associated focussing or imaging lens 32 are used to process a large flat substrate 33 able to move in 2 axes X and Y as shown. In this case the four corner optics units 34, 35, 36, 37 have pucks that are displaced at 45 degrees to the substrate edges whereas the four innermost optics units 38, 39, 40, 41 have pucks that are displaced at 90 degrees to the substrate edges. In this case all eight optics units are attached to a support frame that is not shown but which causes the optics units to maintain constant spacing in the X and Y directions during full area substrate processing but are allowed to move independently in the direction perpendicular to the substrate surface Z to compensate for the changes in the substrate surface height.

Figure 4 shows an arrangement where a single puck 41 supports two optics units 42, * : : s 42' containing lenses situated in each side of the puck and the lenses focus or image a...

a a. .T5 the laser beams 43, 43' at a point 44, 44'on the surface of a flat substrate 45. The puck : a**S is attached to a slide mechanism 46 that allows it to move in the plane parallel to the a...

a. substrate surface in a direction Y which is perpendicular to the line joining the 2 laser beams. The substrate is able to move in two axes X and Y as shown. The mechanism * a : a: , that attaches the puck to the carriage on the slide unit can also be made to allow a a, a.,.

* 20 small degree of rotation of the puck around both the X and Y axes to compensate for local tilting of the substrate surface and to allow the puck to automatically adjust itself so the lower surface is always parallel to the substrate surface. The whole assembly consisting of the puck together with the 2 lens units is able to move in the direction Z perpendicular to the substrate surface to compensate for changes in substrate height as the substrate is moved Figure 5 shows the top down view of an arrangement where 8 laser beams in a line are used to scribe parallel lines on the surface of a flat substrate 51. Alternate pairs of optics units 52, 52' are supported by single pucks 53 so that there are 4 separate assemblies consisting of a single puck and 2 optics units. All 4 optics assemblies are ii attached to a frame 54 to maintain constant spacing of the units in the X direction but allow independent movement in the direction Z perpendicular to the substrate surface. The substrate is able to move in two axes X and Y as shown. Lines are scribed parallel to the Y direction by moving the substrate over its full length in Y, stepping the substrate by an appropriate distance in X and then moving again in Y. This operation is repeated a sufficient number of times to scribe lines over the full surface of the substrate.

The figures shows how a row of pucks is positioned with respect to the line of the optics heads when the centre region of the substrate is being processed. In this case the pucks are positioned on the line joining the optics heads as shown. As the substrate moves in the Y direction so that the edges that are parallel at the line of optics heads approach the line of laser beams the pucks are moved with respect to the * : : :* line of optics heads. As the substrate moves in the Y direction so that the line of a...

* 15 optics heads approaches the right hand side of the substrate the pucks are displaced : * . away from the right edge as shown 55. When the substrate moves in the opposite Y **.* *:. direction so that the line of optics heads approaches the left hand side of the substrate : : the pucks are displaced away from the left edge as shown 56.

*.*..* 21J With multiple optics units the mechanisms that attach the pucks to the carriages on the slide units can also be made to allow a small degree of rotation of each puck around both the X and Y axes to compensate for local tilting of the substrate surface and to allow the pucks to automatically adjust themselves so their lower surface is always parallel to the substrate surface.

All these drawings show the substrate moving in 2 axes and optics units that are stationary in the plane of the substrate motion. Other arrangements are also possible.

The substrate can remain stationary and the optics units can be attached to a carriage on a moving gantry above the substrate so allowing optics units to move in 2 axes.

Alternatively the substrate can move in one direction the optics units attached to a moving carriage on a gantry over the substrate move in the other.

All the drawings show the case where the substrate is held in the horizontal plane and the laser beams are directed vertically downwards from above. It is also possible to use the present invention when the substrate is horizontal and is transparent to the laser beam with the beams being directed vertically upwards from below, the beams passing through the transparent substrate before interacting with the material to be machined on the top surface of the substrate.

All the drawings show the case where the substrate is held in the horizontal plane and the laser beams are directed vertically downwards from above. It is also possible to use the inventions discussed here when the substrate is held at some orientation other * ** :.. than horizontal. In particular one can readily envisage an arrangement where the *: : : l5 substrate is held in the vertical plane and the laser beams are directed at its surface : * . horizontally. In this case the substrate moves in 2 axes, vertically and horizontally S...

*:. with stationary optics units. In a preferably arrangement the substrate remains * stationary and the optics units are attached to a carriage on a moving gantry or robot beside the substrate so allowing the optics units to move in 2 axes, vertically and *.e...

* 2J horizontally. Alternatively the substrate moves in the horizontal direction and the optics units attached to a moving carriage on a gantry beside the substrate move in the vertical direction.

In the above embodiments reference is made to a laser beam being focussed on a point X on the surface of a work piece. The invention is not limited to surface working. The point X can be positioned within the work piece when a work operation requires it.

Claims

CLAIMS

1) A laser optics unit including: an optics head with an imaging or focussing lens and lens control means adapted to provide a laser beam giving an image of a mask or a focus of a beam along an axis of the beam at a datum point in the unit; a work station adapted to position a substrate work piece relative to the datum point so as to provide for the positioning of the mask image or beam focus along the axis of the beam perpendicular to a substrate work piece positioned by the work station; the work station being further adapted to displace the work place in a given direction transverse the beam axis; a puck and means for providing for the puck to be fluid supported over * a puck region on a substrate work piece at the work station; and : : : link means linking the puck to the optics head to enable the puck to * 15 displace the optics head relative to the axis direction; * : characterised by off-setting means whereby the puck, and so the puck :. region, at least when the puck is fluid supported, is offset from the axis of the * : laser beam in a direction perpendicular to the beam axis.

S.....

* 20 2) A laser optics unit as claimed in Claim 1 characterised by off-setting means providing for the puck region to be capable of location so that the axis lies between the puck region and an edge, or a corner, of a work piece at the work station so allowing the laser beam to be located stably by means of the puck at least up to an edge or a corner of the work piece.

3) A laser optics unit as claimed in Claim 1 or Claim 2 characterised by the link means providing for a small degree of rotation of the puck around one or two axes perpendicular to the beam to allow the puck to automatically pivot so as to provide for an underside of the puck to be positioned parallel to the substrate surface.

4) A laser optics unit as claimed in arty preceding claim characterised by the puck being adapted for movement with respect to the optics head in a plane parallel to the surface of the substrate and in a direction parallel to a direction in which a substrate is being moved during laser processing involving the puck.

5) A laser optic unit as claimed in any preceding claim characterised by the puck being adapted for movement with respect to the optics head in a plane parallel to the surface of the substrate and in a circular direction about an axis perpendicular to the plane of the substrate surface.

6) A laser optics unit as claimed in any preceding claim characterised in that the puck is linked to more than one optics head by a separate link means for each * optics head to enable the puck to displace all such optics head relative to the :::: axis direction. * S *

: *. 7) An optics unit as hereinbefore described with reference to the accompanying S...

drawings. * S * S S S.. S

S

S.....

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