TEMPORARY BOND ING OF THE SUBSTRATES TO CARRIERS

TECHNICAL FIELD

The present invention is related to a method for processing fragile, e.g. (ultra- ) thin and/or large, substrates, such as glass or semiconductor wafers. In particular, the present invention is directed to employing temporary bonding of the substrates to carriers , and further includes applying one or more vacuum treatment processes to a surface of the substrates . Furthermore , the present invention pertains to a method for manufacturing vacuum coated substrates using the proposed method for processing substrates .

BACKGROUND OF THE INVENTION

For manuf cturing high-quality, high-performance optical, optoelectronic and semiconductor devices for advanced applications such as in the field of photonics,

optoelectronics, microelectromechanical systems (MEMS ) and wireless communications there is a trend towards processing increasingly thinner and larger substrates . Such

substrates are extremely fragile and prone to be damaged when being handled directly, e.g. when being prepared for processing and transported within a system for processing substrates comprising several modules for different manufacturing steps. Furthermore, considerable stress and strain is imposed on the substrates when they undergo vacuum treatment processes . In the state of the art such fragile substrates are therefore typically mechanically clamped between two ring-shaped frames along the

circumference of the substrates for handling during the entire processing of the substrates . However, this has the disadvantage that a large part of the peripheral area of the substrates is sacrificed, i.e. is usable for providing end products, in the area of the mechanical clamping.

Furthermore, such clamping is labour intensive and

difficult to automate . The surface of the clamping frames is prone to particle formation. Therefore, the clapping frames need to be cleaned frequently. Hence, there exists a need for improved methods for handling and processing fragile substrates.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved method for handling and processing fragile, e.g.

(ultra-) thin, large substrates . This object is reached by the method according to claim 1. Specific embodiments of the method according to the present invention are given in the dependent claims . Moreover, it is a further goal of the present invention to provide an improved method for manufacturing a vacuum coated substrate for providing high-quality, high- performance optical, optoelectronic and semiconductor devices. This aim is achieved by the method according to claim 20.

The present invention provides a method for processing a substrate having a front side surface and a back side surface, the method comprising the steps of:

a) bonding the back side surface of the substrate to a

first carrier at one or more first bonding areas;

b) applying one or more first vacuum treatment processes to the front side surface of the substrate; and

c) debonding the first carrier from the back side surface of the substrate,

wherein the one or more first bonding areas comprise only a fraction of the back side surface, the fraction being less than 50% of the back side surface .

According to the proposed method only a portion, i.e. less than 50%, of the back side surface of the substrate is temporarily bonded to the first carrier at one or more separate (i.e. individual) first bonding areas. Temporary bonding of a large, thin substrate to a sturdy first carrier is performed in order to enable easy handling of the substrate, which is subsequently subjected to one or more first vacuum treatment processes, including physical or chemical coating processes, such as physical vapour deposition (PVD) , chemical vapour deposition (CVD) and atomic layer deposition (ALD) , or plasma etching processes (in particular thin film, surface processing) , which impose considerable stress and strain on the substrate usually leading to substantial warping/distorting/bending of the substrate surface. However, such deformation of the substrate is avoided (or at least considerably reduced) by having securely bonded the substrate to the resilient first carrier. Once vacuum treatment processing of the front side surface of the substrate has been completed the temporary bond can be released by an appropriate means of debonding. By selectively bonding only part of the back side surface of the substrate to the first carrier at the one or more first bonding areas, i.e. by minimising as far as possible the first bonding area (s) to achieve the required bonding strength, it is ensured that a large portion of the overall area of the substrate (e.g. 90%) remains usable for providing end products (such as

identified in claim 20), in case the first bonding area (s) is rendered unusable, in particular damaged, e.g. by residues of the first bonding/debonding procedure .

In an embodiment the method further comprises the steps of: d) after the step b) of applying the one or more first

vacuum treatment processes and before or essentially simultaneously (e.g. together) with the step c) of debonding the first carrier, bonding the front side surface of the substrate to a second carrier at one or more second bonding areas (whilst maintaining the bonding to the first carrier) ;

e) after the step c) of debonding the first carrier,

applying one or more second vacuum treatment processes to the back side surface of the substrate; and

f) debonding the second carrier from the front side surface of the substrate,

wherein the one or more second bonding areas comprise only a fraction of the front side surface, the fraction being less than 50% of the front side surface .

According to the proposed method a portion, e.g. up to 50%, of the front side surface of the substrate is temporarily bonded to the second carrier at one or more separate (i.e. individual) second bonding areas . Temporary bonding of a large, thin substrate to a sturdy second carrier, whilst still being temporarily bonded to a sturdy first carrier is performed in order to prevent severe warping/distorting/ bending of the thin substrate (which would occur after debonding from the first carrier before bonding to the second carrier) and to maintain easy handling of the substrate once the first carrier has been debonded from the substrate, which is subsequently subjected to one or more second vacuum treatment processes, including physical or chemical coating processes, such as physical vapour deposition (PVD) , chemical vapour deposition (CVD) and atomic layer deposition (ALD) , or plasma etching processes (in particular thin film, surface processing) , which again impose considerable stress and strain on the substrate usually leading to substantial warping/distorting/bending of the substrate surface . However, such deformation of the substrate is again avoided (or at least considerably reduced) by having securely bonded the substrate to the resilient second carrier . Once vacuum treatment processing of the back side surface of the substrate has been

completed the temporary bond can be released by appropriate means of debonding. By selectively bonding only part of the front side surface of the substrate to the second carrier at the one or more second bonding areas, i.e. by minimising as far as possible the second bonding area (s) to achieve the required bonding strength, it is ensured that a large portion of the overall area of the substrate (e.g. 90%) remains usable for providing end products (such as identified in claim 20), in case the second bonding area (s) is rendered unusable (in particular damaged) by the second bonding/debonding procedure . Maintaining the bonding to the first carrier also makes it easier and quicker to bond the substrate to the second carrier.

In a further embodiment the method further comprises the step of turning over the substrate from a front side processing position to a back side processing position after the step of applying the one or more first vacuum treatment processes and before the step of applying the one or more second vacuum treatment processes. To apply the one or more second vacuum treatment processes to the back side surface of the substrate typically requires turning over (by 180°) the substrate from a front side processing position to a back side processing position, This movement is especially delicate for large, thin substrates and is made less strain- and stressful by the substrate being bonding to either the first or second carrier, or

simultaneously to both the first and second carrier, which provides increased support compared to the substrate only being bonded to one of the two carriers whilst being reversed. The step of turning over the substrate can thus be performed before bonding the substrate to the second carrier whilst the substrate is still bonded to the first carrier, after bonding the substrate to the second carrier whilst the substrate is also bonded to the first carrier, or after debonding the substrate from the first carrier whilst the substrate is bonded to the second carrier.

In a further embodiment of the method a total area of the one or more first bonding areas is less than 10%, in particular less than 5%, more particularly less than 2%, of a total area of the back side surface of the substrate .

In a further embodiment of the method a total area of the one or more second bonding areas is less than 10%, in particular less than 5%, more particularly less than 2%, of a total area of the front side surface of the substrate.

In a further embodiment of the method the one or more first and/or second bonding areas are spot or (straight or curved) line shaped. In a further embodiment of the method three or more first bonding areas are employed.

In a further embodiment of the method three or more second bonding areas are employed.

In a further embodiment of the method one or more of the first bonding areas are located at a periphery of the back side surface of the substrate, and in particular at least one of the first bonding areas is located at a central area of the back side surface of the substrate.

In a further embodiment of the method one or more of the second bonding areas are located at a periphery of the front side surface of the substrate, and in particular at least one of the second bonding areas is located at a central area of the front side surface of the substrate.

In a further embodiment of the method the one or more second bonding areas are located opposite to the one or more first bonding areas, in particular the one or more second bonding areas are aligned with the one or more first bonding areas.

In a further embodiment of the one or more first and/or second bonding areas are rendered unusable by bonding and/or debonding for providing products resulting from applying the one or more first and/or second vacuum treatment processes, for instance due to residue of bonding material or strain/stress associated with the bonding and/or debonding.

In a further embodiment of the method bonding to the first and/or second carrier is achieved by at least one of van der Waals force (intermolecular force) , electrostatic force, and applying a polymer bonding material, in

particular in form of bonding pads and/or stripes. The bonding areas are dimensioned such that the total bonding force provided at the bonding areas to achieve bonding of the substrate to either the first or the second carrier is sufficient to hold the weight of the substrate (when hanging on the first or second carrier facing the ground) . This means that the bonding force per unit area will increase when the total bonding area is decreased in order to hold the weight of the substrate . Maintaining the bonding force per unit area below a certain level/threshold is important with respect to facilitating debonding of the substrate from the first/second carrier. However, the goal is to minimise the total bonding area as far as possible because this increases/maximises the area of the substrate usable for providing end products.

In a particular embodiment employing an electrostatic bonding force, debonding of the first carrier from the back side surface of the substrate is achieved simultaneously with bonding the front side surface of the substrate to a second carrier by inverting the charge applied to generate the electrostatic bonding force. Hence, debonding of the back side surface of the substrate from the first carrier and bonding of the front side surface of the substrate to the second carrier is carried out together (i.e.

essentially simultaneously when the charge is inverted in order to reverse the direction of the electrostatic holding/bonding force) . Here too, it is pointed out that the bonding area (s) is/are minimised in order to maximise the area of the substrate usable for providing end

products .

Bonding can be performed either under normal atmospheric conditions or in a vacuum (in particular under a pressure below atmospheric pressure) . Likewise, debonding can be performed either under normal atmospheric conditions or in a vacuum (in particular under a pressure below atmospheric pressure) . Bonding and debonding do not both need to take place under the same conditions, e.g. in terms of pressure and/or temperature.

In a further embodiment of the method the polymer bonding material comprises at least one of an organic material, silicone, polyamide, a material comprising a carboxylic end group, a multi-component material, in particular a two- component material, comprising a photo-active substance, in particular a primer. In a further embodiment of the method bonding to the first and/or second carrier is achieved by a directional bonding/ adhesive structure having direction-dependent bonding/ adhesive properties, in particular providing a greater bonding force in a direction perpendicular to the front or back side surface of the substrate than in a direction parallel to the front or back side surface of the substrate when applied at the one or more first or second bonding areas .

In a further embodiment of the method debonding the first and/or second carrier is achieved by at least one of applying a (external) mechanical separating force or a chemical solvent to the first and/or second bonding areas, and exposing the first and/or second bonding areas to light, in particular laser light, more particularly UV light of an excimer laser, and/or to heat, Debonding can in particular be performed at room temperature .

In a further embodiment of the method for debonding the first carrier the laser light is applied towards the back side surface of the substrate, in particular through the first carrier, and/or for debonding the second carrier the laser light is applied towards the front side surface of the substrate, in particular through the second carrier.

In a further embodiment of the method the front side surface of the substrate is coated with an optical filter layer, in particular a near infra-red, NIR (bandpass) filter layer, in particular the optical filter layer is a result of applying the one or more first vacuum treatment processes .

In a further embodiment of the method at least one of the one or more first and/or second vacuum treatment processes comprises at least one of (plasma) etching, plasma cleaning and vacuum coating, in particular physical vapour

deposition (PVD) , chemical vapour deposition (CVD) , plasma- enhanced chemical vapour deposition (PECVD) and atomic layer deposition (ALD) , more particularly at least one of depositing an optical filter layer, depositing a

metallisation layer and depositing a dielectric layer onto the front and/or back side surface of the substrate .

In a further embodiment of the method the substrate has a thickness of less than 500 mm, in particular less than 250 mm.

In a further embodiment of the method the first and/or second carrier has a thickness of more than 500 mm, in particular more than 1 mm.

In a further embodiment of the method the substrate has a lateral extension of at least 100 mm, in particular of at least 200 mm. In a further embodiment of the method the first and/or second carrier has a lateral extension of at least 100 mm, in particular of at least 200 mm.

In a further embodiment of the method the first and/or second carrier is adapted to act as a stabilising body or support/fixation structure, in particular is rigid.

In a further embodiment of the method the first and/or second carrier has a flat or curved surface.

In a further embodiment of the method a coefficient of thermal expansion of the substrate is essentially the same as a coefficient of thermal expansion of the first and/or second carrier, and in particular the substrate is made of the same material as the first and/or second carrier.

In a further embodiment of the method the substrate is a glass or semiconductor wafer.

In a further embodiment of the method the first and/or second carrier is made of glass, a ceramic material, metal or a metallised material (e.g. having a metal surface such as a metal surface coating) . In a further embodiment of the method the steps a) -c) and d)-f) are repeated consecutively one or more times.

Thereby, additional (third, fourth, etc.) vacuum treatment processes are applied to the front and back side surface of the substrate . The first and second carrier may be reused for this purpose or may be replaced by additional (third, fourth, etc.) other carriers. Generally, the carriers may be designed and adapted as single-use (disposable) or (many-times) reusable carrier, where in the latter case the carrier may need to undergo a cleaning step periodically, i.e. after a certain number of uses (bonding/debonding cycles) .

In a further embodiment of the method bonding is achieved by means of a thermally activated adhesive, a pressure activated adhesive, a solvent activated adhesive, a UV (ultraviolet) activated adhesive, a (low-temperature) plasma activated adhesive, a high-voltage electric

discharge activated adhesive, or any combination thereof. As part of the bonding process the bonding material can be activated by applying heat, pressure, a solvent, UV light (at a chosen wavelength, e.g. 300 nm) , a high-voltage electric discharge, a ( low-temperature) plasma, or any combination thereof. Upon contact with the activated bonding material or adhesive, the substrate adheres or attaches to the carrier, thus bonding (the back side or front side surface of) the substrate to the (first or second) carrier. The present invention further provides a method for manufacturing a vacuum coated substrate for providing high- quality, high-performance optical, optoelectronic and semiconductor devices, displays, micro-displays, device carrier systems for advanced packaging technology, such as fanout substrates, the method comprising the previously specified method for processing a substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is further explained below by means of non-limiting specific embodiments and with reference to the accompanying drawings, which show the following:

Fig. 1 a) a top view of an exemplary carrier according to the present invention with an exemplary arrangement of four spot-shaped bonding pads,

b) a top view of an exemplary carrier according to the present invention with an exemplary arrangement of three stripe-shaped bonding pads, and

c) a top view of an exemplary carrier according to the present invention with an exemplary arrangement of a central spot-shaped bonding pad and three peripherally arranged arc-shaped bonding pads;

Fig. 2 a) a series of side views of an exemplary substrate bonded to carriers at the front and back side surfaces during three exemplary phases of the method according to the present invention, and b) an exemplary sequence of steps of the method according to the present invention;

Fig. 3 a) a series of top views of an exemplary system for processing substrates illustrating how the substrates and carriers are moved through the system modules during four exemplary phases according to the method of the present invention, and

b) a corresponding series of side views of the substrate bonded to the carrier (s) along with a corresponding sequence of steps of the method according to the present invention; and

Fig. 4 a) a series of top views of an alternative

exemplary system for processing substrates illustrating how the substrates and carriers are moved through the system modules during four exemplary phases according to the method of the present invention, and

b) a corresponding series of side views of the substrate bonded to the carrier (s) along with a corresponding sequence of steps of the method according to the present invention. In the figures, like reference signs refer to like parts .

DETAILED DESCRIPTION OF THE INVENTION

In the following we exemplify and provide details of the method according to the present invention by means of an exemplary substrate in the form of a large round ultra-thin glass wafer, e.g. having a diameter of 200 mm and a thickness of 200 mm. However, the proposed method is equally applicable to fragile substrates of other sizes, thicknesses and materials.

In order to stabilise the fragile substrate, it is bonded to a carrier for subsequent handling. Examples of suitable carriers with different bonding patterns/areas are

illustrated in Fig. la) -c) . These exemplary carriers 2 have the same round shape, size and flatness as the substrate which is mounted onto the carrier 2. The carrier 2 is for instance also made of the same glass material as the substrate, thus having the same coefficient of thermal expansion as the substrate, but is considerably thicker, e.g. 1 mm thick. Consequently, the carrier 2 is much sturdier than the fragile substrate and can therefore act as a stabilising body or support structure for the

substrate. Fig. la) shows a top view of a first (or likewise/similarly a second) carrier 2 with an exemplary arrangement of four small spot-shaped/circular bonding pads 3, 3 ' , 3 ' ' , 3 ' ' , three of which are located at the periphery of the carrier 2 (i.e. close to its outer edge), and the fourth one of which is at the centre of the carrier 2. The total bonding area of the pads 3, 3', 3 ' ' , 3 ' ' is approximately 2% of the total area of the back (or front) side surface of the substrate. Fig. lb) shows a top view of a carrier 2 with an alternative exemplary arrangement of three stripe-shaped bonding pads 3, 3 ' , 3 ' ' radially extending from the centre of the substrate . The total bonding area of the pads 3, 3', 3 ' ' in this case is about 10% of the total area of the back (or front) side surface of the substrate. Finally, Fig. lc) shows a top view of a carrier 2 with yet another exemplary arrangement of a central spot-shaped bonding pad 3 ' ' ' and three peripherally arranged circumferential arc-shaped bonding pads 3, 3 ' , 3 '' . Here, the total bonding area of the pads 3, 3 ' , 3 '' ,

3' ' ' is roughly 6% of the total area of the back (or front) side surface of the substrate. Other shapes and sizes of the bonding pads/areas are conceivable according to the present invention for bonding a portion of up to 50% of the back (or front) side surface of the substrate to the carrier 2.

According to the example illustrated in Fig. 2, the substrate 1 is initially mounted and bonded onto a first carrier 2 (cf . step 101 in Fig. 2b) ) . The back side surface of the substrate 1 is temporarily bonded onto the carrier 2 for example by means of polymer bonding using four small circular (spot-shaped) bonding pads 3, 3 ' , , ' '

3''' , the first three 3, 3 ' , 3' ' of which are for instance arranged at equal distances apart from one another along the periphery of the carrier 2 and the fourth one 3 V V I is located at the centre of the carrier 2 (cf. Fig. la) & Fig.

2a) i) ) . These bonding pads 3, 3', 3 '' , 3' ' ' only take up very little space on the back side surface of the substrate 1 (~2% thereof) , and therefore in case the back side surface of the substrate 1 is damaged or contaminated by the (de-) bonding at the (first) bonding areas this will result in only a minor loss of the area usable for

providing end products, i.e. only a small portion of the substrate 1 area is sacrificed due to bonding, On the other hand, these bonding areas are enough to fixate the substrate 1 during subsequent vacuum treatment processing and avoid warping/distorting/bending of the substrate surface due to the stress and strain imposed upon the substrate 1 (now fixated by the carrier 1) by the vacuum treatment processing.

Subsequently, one or more first vacuum treatment processes are applied to the front side surface of the substrate 1, e.g. an optical coating 6 such as an optical filter layer is deposited onto the front side surface (cf . step 102) . After this, whilst the back side surface of the substrate 1 is still bonded to the carrier 2 the front side coated surface of the substrate 1 is bonded, e.g. again by polymer bonding, onto a second carrier 4 at the second bonding areas (cf . step 103 & Fig. 2a) ii) ) . The second carrier 4 is identical to the first carrier 2, i.e. the shape, size and material as well as the shape, size and location of the bonding pads 5, 5 ' , 5 ' ' , 5 T V T are the same. The first and second bonding areas are thereby aligned opposite to each other . After bonding of the front side surface of the substrate 1 onto the second carrier 4, the back side surface of the substrate 1 is detached, i.e. debonded from the first carrier 2 (cf. step 104) . This debonding is for instance achieved by means of exposing the polymer bonding to UV light of an excimer laser. The UV light passes through the first carrier 2 and interacts with the first polymer bonding on the back side surface of the substrate 1 at the first bonding areas, but does not interact with the second polymer bonding on the front side surface of the substrate 1 at the second bonding areas, thus leaving the second bonding intact, because it is blocked by the optical filter (e.g. an NIR bandpass filter) layer/coating 6 previously deposited onto the front side surface of the substrate 1. If bonding/debonding is for instance

alternatively achieved by means of electrostatic force, the debonding from the first carrier 2 and the bonding onto the second carrier 4 is performed simultaneously by inverting the electrostatic bonding/holding charge . It is pointed out that the substrate 1 should always be bonded to at least one of the first and second carriers 2, 4 during this phase of the process/method in order to ensure that the stress imposed onto the substrate 1 during the one or more first vacuum treatment processes does not cause the substrate surface to warp/distort/bend, as would happen if the substrate 1 were to be released from the first carrier

2 while not yet bonded to the second carrier 4 (i.e. when temporarily not bonded to a carrier und thus not affixed to a stabilising body or support structure capable of

withstanding the stress and strain imposed by the preceding first vacuum treatment processes) .

After being separated from the first carrier 2, the substrate 1 bonded to the second carrier 4 is flipped over (i.e. turned by 180° onto its other side; cf. step 105 & Fig. 2a) iii) ) . One or more second vacuum treatment processes are then applied to the back/bottom side surface of the substrate 1 which is now facing upward (cf. step 106) , and a further coating 7 is deposited onto to the back/bottom side surface of the substrate 1. These second vacuum treatment processes may be different than the first vacuum treatment processes applied to the front/top side surface of the substrate 1. Finally, the substrate 1 is debonded from the second carrier 4, e.g. again by means of exposing the polymer bonding to UV light of an excimer laser.

It should be pointed out that flipping/turning over the substrate 1 onto its other side can also be performed before debonding/detaching the substrate 1 from the first carrier 2 (i.e. between steps 103 & 104) . This has the advantage that the substrate is bonded to both the first and second carrier 2, 4, which provides extra stability whilst being flipped/turned over onto the other side . It should be noted that by using only a few (i.e. three to four) small spot-shaped bonding pads debonding is

simplified and achieved more rapidly, and furthermore, the sacrificed total bonding area is minimised, so that very little of the total surface area of the substrate 1 is potentially rendered unusable for providing products by the destructive bonding/debonding, which is an important benefit of the proposed method according to the present invention.

Fig. 3a) depicts a series of top views of an exemplary system for processing substrates illustrating how the substrates and carriers are moved through the individual system modules during various phases of processing of the substrates according to the method of the present

invention. The system comprises a cassette station 8, in which a plurality of substrates and (first and second) carriers are stored prior to and after completing

processing. Three different system modules are arranged around and adjacent to the cassette station 8, namely an assembly station 9, a flip station 10 and a load lock 11, each of which is accessible from the cassette station 8.

In the assembly station 9 the substrates are bonded onto and debonded from the ( first and second) carriers . In the flip station the substrates are turned over by 180° from their front/top side processing position to their back/ bottom side processing position. The cassette station 8, the assembly station 9 and the flip station 10 are

operating at normal/ambient atmosphere. However, for applying vacuum treatment processes the substrates need to be moved to the process module 13, which is operating under vacuum. For this the substrates to be processed are passed into a load lock 11 where the air is pumped out in order to achieve a vacuum. The substrates then pass through a vacuum handler 12 which includes transport/conveying means, such as a robot (arm) or a conveyer, and is entered into a process module 13 where the one or more (first and second) vacuum treatment processes are applied to the substrate. The process module 13 may be comprised of several modules each adapted to apply a certain one of the vacuum treatment processes, such as etching, plasma cleaning and vacuum coating, in particular physical vapour deposition (PVD) , chemical vapour deposition (CVD) , plasma-enhanced chemical vapour deposition (PECVD) and atomic layer deposition

(ALD) . Fig. 3b) shows a corresponding series of side views of the substrate bonded to the carrier (s) along with a corresponding sequence of steps of the method according to the present invention.

Initially, a substrate and a first carrier are loaded from the cassette station 8 into the assembly station 9 (cf. the two downward pointing arrows in Fig. 3a) i) ) where the back side surface of the substrate is bonded onto the first carrier (cf. step 201 & Fig. 3b) i) ) . Then the substrate affixed to the first carrier is passed through the load lock 11 and conveyed by the vacuum handler 12 into the process module 13 (cf. the leftward pointing arrow in Fig. 3a) i)) where a top coating is deposited onto the front/top side surface of the substrate (cf . step 202) . After this the one-sided coated substrate is returned to the assembly station 9 (cf. the rightward pointing arrow in Fig.

3a) ii) ) . A second carrier is loaded into the assembly station 9 from the cassette station 8 (cf. the downward pointing arrow in Fig. 3a) ii) & step 203 first action).

Now the front side surface of the substrate is bonded onto the second carrier (cf. step 203 second action & Fig.

3b) ii) ) , after which the back side surface of the substrate is debonded from the first carrier (cf. step 203 third action & Fig. 3b) iii) ) . Next the first carrier is returned to the cassette station 8 (cf. the short upward pointing arrow in Fig. 3a) iii) ) , and the substrate affixed to the second carrier is passed to the flip station 10 (cf. the longer upward pointing arrow in Fig. 3a) iii) ) where the substrate is turned from its back side onto its front side, i.e. flipped over by 180° (cf. step 204 & Fig. 3b) iv) ) . After this the substrate affixed to the second carrier is passed through the load lock 11 and conveyed by the vacuum handler 12 into the process module 13 (cf. the leftward pointing arrow in Fig. 3a) iii) ) where a back coating is deposited onto the back/bottom side surface of the

substrate (cf . step 205) . Then the both-sided coated substrate is returned to the assembly station 9 (cf. the rightward pointing arrow in Fig. 3a) iv) ) where the front side surface of the substrate is debonded from the second carrier (cf . step 206 first action & Fig. 3b) v) ) . Finally, the second carrier and the both-sided coated substrate are returned to the cassette station 8 (cf. the two upward pointing arrows in Fig. 3a) iv) & step 206 second and third actions) .

Fig. 3b) depicts a series of top views of an alternative exemplary system for processing substrates illustrating how the substrates and carriers are moved through the

individual system modules during various phases of

processing of the substrates according to the method of the present invention. The alternative system comprises the same modules but interconnected in a different manner.

Here the cassette station 8 is attached only to the load lock 11, and the load lock 11, the assembly station 9, the flip station 10 and the process module 13 are all arranged around and adjacent to the vacuum handler 12. The

functions of the individual modules remain the same.

However, bonding and debonding as well as flipping/turning over the substrates onto their other side are performed under vacuum. Fig. 4b) shows the same corresponding series of side views of the substrate bonded to the carrier (s) along with a corresponding sequence of steps of the method according to the present invention as presented in Fig.

3b) .

Initially, a substrate and a first carrier are loaded from the cassette station 8 through the load lock 11 and conveyed by the vacuum handler 12 into the assembly station 9 (cf. the two long leftward pointing arrows in Fig. 4a) i) ) where the back side surface of the substrate is bonded onto the first carrier (cf. step 201 & Fig. 4b) i) ) . Then the substrate affixed to the first carrier is conveyed by the vacuum handler 12 into the process module 13 (cf. the short leftward pointing arrow in Fig. 4a) i) ) where a top coating is deposited onto the front/top side surface of the substrate (cf . step 202) . Then the one-sided coated substrate is returned to the assembly station 9 (cf. the rightward pointing arrow in Fig. 4a) ii) ) . A second carrier is conveyed into the assembly station 9 by the vacuum handler 12 (cf. the downward pointing arrow in Fig. 4a) ii) & step 203 first action) . Now the front side surface of the substrate is bonded onto the second carrier (cf. step 203 second action & Fig. 4b) ii)), after which the back side surface of the substrate is debonded from the first carrier (cf. step 203 third action & Fig. 4b) iii) ) . Next the first carrier is conveyed into the vacuum handler (cf. the short upward pointing arrow in Fig. 4a) iii)), and the substrate affixed to the second carrier is conveyed by the vacuum handler 12 into the flip station 10 (cf. the longer upward pointing arrow in Fig. 4a) iii) ) where the substrate is turned from its back side onto its front side, i.e. flipped over by 180° (cf. step 204 & Fig. 4b) iv) ) . After this the substrate affixed to the second carrier is conveyed by the vacuum handler 12 into the process module 13 (cf. the leftward pointing arrow in Fig. 4a) iii) ) where a bottom coating is deposited onto the back/bottom side surface of the substrate (cf . step 205) . After this the both-sided coated substrate is returned to the assembly station 9 (cf. the short rightward pointing arrow in Fig. 4a) iv) ) where the front side surface of the substrate is debonded from the second carrier (cf. step 206 first action & Fig. 4b) v) ) . Finally, the second carrier and the both-sided coated substrate are returned to the cassette station 8 through the load lock 11 (cf. the two long rightward pointing arrows in Fig. 4a) iv) & step 206 second and third actions) .

Once again it is pointed out that in the sequences

described in conjunction with Fig. 3 & 4 the step of flipping/turning over the substrates can alternatively be performed whilst the substrates are bonded to both the first and second carrier in order to achieve increased support compared to the substrates only being bonded to one of the two carriers whilst being reversed, As a further alternative the substrate bonded to the first carrier can be fl i pped/turni ng over before bonding the substrate onto the second carrier and debonding the substrate from the first carrier.

LIST OF REFERENCE SYMBOLS

1 substrate

2 first carrier, carrier 1

3, 3', 3 '' , 3' ' ' bonding pads (temporary bond) on carrier 1 4 second carrier, carrier 2

5, 5', 5 ' ' , 5' ' ' bonding pads (temporary bond) on carrier 2 6 front/top side coating

7 back/bottom side coating

8 cassette station

9 assembly station

10 flip station

11 load lock

12 vacuum handler

13 process module