# Patent

## Title
Device for detaching a product substrate off a carrier substrate

## Abstract

Device for stripping a product substrate off a carrier substrate connected to the product substrate by an bonding layer by means of a film frame, a flexible film which is connected to the film frame and which has an adhesive layer for holding the product substrate in a contacting surface section of the film, the film being connected to the film frame in an attachment section of the film which surrounds the contacting surface section, as well as a solvent reservoir formed by the film frame and the film, especially of variable volume, for holding the solvent for detaching the bonding layer, and the product substrate and the bonding layer can be accommodated in the solvent reservoir, and by delivery means for delivering the solvent into the solvent reservoir and by stripping means for stripping the product substrate off the carrier substrate.

## Background
FIELD OF THE INVENTION
The invention relates to a device and a method for stripping a product substrate off a carrier.
BACKGROUND OF THE INVENTION
The back-grinding of product substrates is often necessary in the semiconductor industry and can take place mechanically and/or chemically, For purposes of back-grinding in general the product substrates are temporarily fixed on a carrier, there being various methods for the fixing. The carrier material can be for example films, glass substrates or silicon wafers.
Depending on the carrier materials used and the bonding layer used between the carrier and the product substrate, different methods for dissolving or destroying the bonding layer are known, such as for example the use of UV light, laser beams, the action of temperature, or solvents.
Stripping increasingly constitutes one of the most critical process steps since thin substrates with substrate thicknesses of a few microns easily break during stripping/peeling or are damaged by the forces which are necessary for the stripping process.
Moreover thin substrates have hardly any stability of shape or none at all and typically curl without support material. During handling of back-ground wafers therefore fixing and support of the wafers are essentially indispensable.
Therefore the object of this invention is to devise a device and a method to detach a product substrate from a carrier as nondestructively and easily as possible.
This object is achieved with the features of the claims. Advantageous developments of the invention are given in the dependent claims. The framework of the invention also encompasses all combinations of at least two of the features given in the specification, the claims, and/or the figures. In the specified value ranges, values which lie within the indicated limits will also be disclosed as boundary values and they are to be claimed in any combination.
SUMMARY OF THE INVENTION
The invention is based on the idea of developing a generic device and a generic method by solvent being delivered to a solvent reservoir which is formed by the film frame and the film attached to it. Due to the elasticity or flexibility of the film which is mounted on the film frame it is at the same time possible to make the solvent tank of variable volume and the elasticity or flexibility of a film is moreover used to carefully strip the product substrate starting from the edge of the product substrate. In this way the product substrate is immediately available for other process steps directly after separation and is protected by the film and the film frame. Many process steps can be carried out directly on the product substrate mounted on the film frame.
A product substrate is defined as a product substrate, for example a semiconductor wafer, which is conventionally thinned to a thickness between 0.5 μm and 250 μm, the trend being toward thinner and thinner product substrates. This invention works especially effectively with product substrates which themselves have a flexibility similar to the film mounted on the film frame. The product substrate in the device as claimed in the invention and the method as claimed in the invention is peeled off the carrier substrate, especially proceeding concentrically from the periphery of the product substrate.
The carrier is for example a carrier substrate with a thickness between 50 μm and 5000 μm, especially between 500 μm and 1000 μm.
The bonding layer can be an adhesive, for example a soluble adhesive, especially a thermoplastic, which is applied for example selectively in the edge region of the carrier-product substrate combination, especially in an edge zone from 0.1 to 20 mm. Alternatively the adhesive can be applied over the entire surface, and the adhesive force can be reduced in the center by an adhesion-reducing layer, for example a fluoropolymer, preferably teflon.
A chuck is especially well suited as the holding means, especially a spinner chuck for holding the carrier substrate, especially by means of negative pressure, for example on suction paths, holes or suction cups. Alternatively, mechanical holding, for example by lateral clamps, is conceivable. Holding takes place electrostatically in another alternative configuration.
The stripping means encompass the film mounted on the film frame and a film frame holder which applies a force and which holds the film frame.
In one advantageous embodiment of the invention it is provided that the solvent is made to work essentially without heating. The solvent is preferably used at ambient temperature. In this way it is possible to omit any heating means.
By the solvent being intended for at least partially detaching the connection between the carrier substrate and the product substrate caused by the bonding layer, stripping by the stripping means is advantageously clearly facilitated.
Because the solvent comprises especially a fluid agent which selectively dissolves the bonding layer for at least partial detachment of the bonding layer, for bonding layers encompassing different adhesives it becomes possible to dissolve a certain bonding layer in a controlled manner or in defined regions. Chemical dissolution of the bonding layer is especially protective of the product substrate and with the corresponding material choice, dissolution can also take place very quickly, especially when only edge regions of the product substrate are provided with an bonding layer, so that the solvent can act very quickly from the side. In this way perforations in the carrier substrate and/or product substrate can be omitted.
To the extent the solvent reservoir is made such that the solvent acts at least at the start of detachment of the bonding layer, especially solely in the region of the periphery of the product substrate, action on the product substrate and/or carrier substrate from the top and/or bottom, especially the inner region of the product substrate which lies within the side edge, can be omitted.
In another configuration of the invention it is provided that the stripping means are made to cause a force Fs which acts on the carrier substrate and a force Ff which acts on the film frame and which is directed against the force Fs. In this way stripping is effected in a manner which is simple and especially protective by the film. The force FF acts on the periphery of the film frame, especially at at least two locations on the film frame which are distributed over the periphery, and the forces Ff1 and Ff2 can be controlled differently in one advantageous embodiment in order to strip the product substrate from the side with the greater force Ff.
Here it is especially advantageous if the film can be clamped, especially by the force Fs and force Ff in a stripping section which lies between the contacting surface section and the attachment section. In this way stripping is carefully effected on the periphery of the product substrate. Detachment by the solvent and stripping by the forces Fs and Ff mutually support one another.
According to one advantageous embodiment of the invention it is provided that there is a vibration generator which acts on the solvent and/or the bonding layer, which adjoins especially the film, and/or which can be placed in the solvent in the solvent reservoir. “Can be placed” comprises both surface contact and also at least partial immersion. This supports detachment by the solvent and accelerates the detachment process at least by a factor of 2, with an optimized configuration by a factor of 5, even more preferably by a factor of 10 to 50. Preferably the vibration generator acts by ultrasonic waves, especially in the region of the contacting surface section.
In another advantageous embodiment the solvent reservoir is made trough-shaped, by which stripping of the product substrate can be achieved with a minimum solvent consumption.
Other advantages, features and details of the invention will become apparent from the following description of preferred exemplary embodiments and using the drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1a shows a schematic top view of a substrate combination consisting of the product substrate, the carrier substrate and the bonding layer on a film frame,
FIG. 1b shows a schematic side view to FIG. 1a with a detailed view,
FIG. 2 shows a schematic according to FIG. 2 when the solvent is being delivered,
FIG. 3 shows a schematic of the method step of detaching the bonding layer,
FIG. 4 shows a schematic of the method step of stripping of the product substrate off the carrier substrate as claimed in the invention, and
FIG. 5 shows a schematic of one alternative method step of stripping the product substrate off the carrier substrate as claimed in the invention.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the figures the same components and components with the same function are identified with the same reference number.
FIG. 1a shows a film frame 1 which is round in this embodiment at least on the inner periphery 1i, on whose bottom according to the sectional view shown in FIG. 1b a film 3 is cemented with its adhesive layer 3s concentrically to the film frame 1. With a radial distance A to the inner periphery 1i of the film frame 1, within the film frame 1 the product substrate-carrier substrate combination is cemented on a adhesive layer 3s of the film 3 concentrically to the film frame 1. The product substrate-carrier substrate combination consists of a product substrate 4 which adheres to the film 3, a carrier substrate 2 and a bonding layer 6 which connects the product substrate 4 and the carrier substrate 2, The diameters of the product substrate 4 and of the carrier substrate 2 are essentially identical, while the thickness of the product substrate 4 is less than the thickness of the carrier substrate 2.
The film 3 consists of an attachment section 3b which has the shape of a circular ring in this case and in which the film 3 is fixed to the film frame 1. Furthermore, the film 3 consists of a contacting surface section 3k in which the product substrate 4 can be fixed on the adhesive layer 3s of the film 3. Between the attachment section 3b and the contacting surface section 3k there is a stripping section 3a which is located especially concentrically to the attachment section 3b and the contacting surface section 3k, and which need not have a cementing function, to which however a function which is critical as claimed in the invention is attached. The stripping section 3a thus extends from the periphery 4u of the product substrate 4 to the inner periphery 1i of the film frame 1, here labeled the radial distance A. The ratio between the thickness D of the film frame 1 and the distance A is advantageously at least 1:2 to 1:50, especially 1:5 to 1:25.
In the initial position shown in FIG. 1b, the side of the product substrate 4 which makes contact with the film 3 and the side of the film frame 1 which makes contact with the film 3 are arranged flush and in one plane E. The parts shown in FIGS. 1a and 1b are assembled on a known film frame mounter.
The film 3 and the inner periphery 1i of the film frame 1 form a trough-shaped solvent reservoir 20 in which the product substrate-carrier substrate can be arranged as described above.
According to the method step shown in FIG. 2 the solvent 22 can be delivered into the solvent reservoir 20 by delivery means 23. The delivery means 23 here consists of a line 24 and a solvent storage 25 which can be triggered from a central unit in order to deliver the solvent 22 into the solvent reservoir 20.
As FIG. 2 shows, the solvent reservoir 20 is of variable volume due to the film 3 which is elastic at least in the stripping section 3a by a force Fs acting on the carrier substrate 2 downwardly and a force Ff acting on the film frame 1 upwardly. Application of the force is likewise controlled by a central unit.
Increasing the volume of the storage means reservoir prevents the solvent 22 running over the edge of the film frame 1 and at the same time prompt distribution or delivery of the solvent 22 is enabled.
The force Fs as shown in FIG. 3 is transferred by way of the carrier substrate holder 7 for holding the carrier substrate 2, fixing of the carrier substrate 2 on the carrier substrate holder 7 taking place by vacuum paths 8 which have been machined into the surface of the carrier substrate holder 7 and via a vacuum means which is connected to them and which is not shown.
On the opposite side of the film 3 to the product substrate 4 there can be an acoustic wave generator 10, especially for producing ultrasonic waves, by which ultrasonic waves can be transmitted onto the product substrate 4, but especially onto the bonding layer 6 and the solvent 22, since in this way the process of detachment is greatly accelerated, especially by a factor of 2, preferably by a factor of 5, even more preferably by a factor of 10 to 50.
According to one alternative embodiment shown in FIG. 5, the acoustic wave generator 10′ is in contact at least with the surface of the fluid solvent 22, but preferably is at least partially immersed in it. In this way the acoustic waves can be transmitted directly onto the solvent 22 and from the solvent 22 onto the bonding layer 6.
The force Ff acting on the film frame 1, as shown in FIG. 3, can act uniformly distributed as a superficial force on the film frame 1 so that a change in the volume of the solvent reservoir 20 can be caused by way of deformation of the film 3 in the stripping section 3a. 
As shown in FIG. 4, stripping of the product substrate 2 from the carrier substrate 4 takes place in reverse, by the forces Fs and Ff or Fs1 and Fs2 being pointed in the opposite direction, the force Ff1 in the embodiment shown here being set to be greater than the force Ff2 in order to have the stripping of the product substrate 4 start carefully first from the edge side according to the enlargement shown in FIG. 4.
The force Ff1or several forces Ff1, Ff2 to Ffn can be delivered in spots distributed on the periphery of the film frame 1 or can be delivered distributed by a film frame holder.
To the extent the forces Ff1, Ff2 and/or Ffn are made differently, the holding means for applying the force to the film frame 1 must be made to allow tilting of the film frame 1.
Between the process step of detachment by the solvent 22 shown in FIG. 3 and the method step of stripping by opposing forces Fs, Ff1, Ff2, Ffn shown in FIG. 4 there can be one method step by which the solvent 22 is removed from the solvent reservoir 20, especially by suction,.
DESCRIPTION OF THE REFERENCE NUMERALS


    1 film frame
    2 carrier substrate
    3 film
    3a stripping section
    3b attachment section
    3k contacting surface section
    3s adhesive layer
    4 product substrate
    4u periphery
    6 bonding layer
    7 carrier substrate holder
    8 vacuum paths
    10, 10′ acoustic wave generator
    20 solvent reservoir
    22 solvent
    23 delivery means
    24 line
    25 solvent storage
    Fs, Ff1, Ff2 . . . Fn force
    Fs force

## Claims

1. System for stripping a product substrate off a carrier substrate connected to the product substrate by a bonding layer, said bonding layer fixing the product substrate to the carrier substrate, wherein said system comprises:
a flexible film including:
a contacting surface section having an adhesive layer for mounting the product substrate to the flexible film,
an attachment surface section disposed at the outer periphery of the contacting surface section, and
a stripping section disposed between the contacting surface section and the attachment surface section, wherein the flexible film is elastic at least in the stripping section;

a film frame fixed to the flexible film at the attachment surface section, wherein surfaces of the film frame and the flexible film define a recess that serves as a solvent reservoir for receiving (i) the bonding layer and (ii) a solvent for dissolving the bonding layer;
a delivery device for delivering the solvent to the solvent reservoir;
a carrier substrate holder for holding the carrier substrate, said carrier substrate holder engages with the carrier substrate (i) to apply a force to the carrier substrate in a generally downward direction and (ii) to apply a force to the carrier substrate in a generally upward direction;
a film frame holder that engages with the film frame to apply to the film frame (i) at least one force in a generally upward direction and (ii) at least one force in a generally downward direction; and
a control unit for:
(i) controlling operation of the carrier substrate holder to engage with the carrier substrate and thereby selectively control application to the carrier substrate of (i) the force in the generally downward direction and (ii) the force in the generally upward direction, wherein the forces applied to the carrier substrate are transferred to the flexible film through connection of the carrier substrate to a product substrate mounted to the flexible film, and/or
(ii) controlling operation of the film frame holder to engage with the film frame and thereby selectively control application to the film frame of (i) the at least one force in the generally upward direction and (ii) the at least one force in the generally downward direction,

wherein the at least one force applied to the film frame in the generally upward direction by the film frame holder is directed against the downward force applied to the carrier substrate by the carrier substrate holder to deform at least the stripping section of the flexible film, and the at least one force applied to the film frame in the generally downward direction by the film frame holder is directed against the upward force applied to the carrier substrate by the carrier substrate holder to deform at least the stripping section of the flexible film.

2. System as claimed in claim 1, wherein said carrier substrate holder includes at least one of the following to attach the carrier substrate holder to the carrier substrate: a chuck, an apparatus for applying a negative pressure, vacuum paths, suction paths, suction holes, suction cups, a mechanical holding device, lateral clamps, and an electrostatic holding apparatus.

3. System as claimed in claim 2, wherein said system further comprises:
vacuum means connected with vacuum paths, suction paths or suction holes of the carrier substrate holder.

4. System as claimed in claim 1, wherein said control unit controls operation of the carrier substrate holder and/or controls operation of the film frame holder to vary the volume of said solvent reservoir by controlling application of said force to the carrier substrate and/or controlling application of said at least one force to the film frame.

5. System as claimed in claim 1, wherein the flexible film is clamped in the stripping section by application of said force to the carrier substrate and application of said at least one force to the film frame.

6. System as claimed in claim 1, wherein the system further comprises:
a vibration generator for producing acoustic waves that are transmitted to at least one of:
(i) solvent received in the solvent reservoir, and (ii) the bonding layer.

7. System as claimed in claim 6, wherein said vibration generator is located adjacent to the flexible film.

8. System as claimed in claim 6, wherein said vibration generator is located in contact with the solvent in the solvent reservoir.

9. System as claimed in claim 1, wherein said control unit controls operation of the carrier substrate holder and the film frame holder to make the solvent reservoir trough-shaped.

10. System as claimed in claim 1, wherein solvent received in the solvent reservoir starts dissolving the bonding layer from a periphery of the product substrate.

11. System as claimed in claim 1, wherein said control unit controls operation of the carrier substrate holder and/or controls operation of the film frame holder such that the contacting surface section of the flexible film is moved to a different plane than the attachment section of the flexible film.

12. System as claimed in claim 1, wherein said control unit controls operation of the film frame holder such that said at least one force acting on the film frame is uniformly distributed on the film frame.

13. System as claimed in claim 1, wherein said control unit controls operation of the film frame holder to engage with the film frame and thereby control application of first and second forces to the film frame, wherein the first force is applied at a first location of the film frame and the second force is applied at a second location of the film frame, the first force being greater than the second force to strip the product substrate from the carrier substrate starting at a peripheral edge of the product substrate.

14. System as claimed in claim 1, wherein said control unit controls operation of the film frame holder to engage with the film frame and thereby control application of a plurality of different forces to the film frame, wherein each of said plurality of different forces is applied at different locations of the film frame to strip the product substrate from carrier substrate concentrically from the periphery of the product substrate to a center of the product substrate.

15. System as claimed in claim 1, wherein said control unit controls operation of the carrier substrate holder and the film frame holder (i) in a first mode to increase a volume of the solvent reservoir and (ii) in a second mode to strip the product substrate from the carrier substrate.

16. System as claimed in claim 15, wherein in the first mode the force applied to the carrier substrate and the at least one force applied to the film frame moves the contacting surface section of the flexible film in a first direction, and in the second mode the force applied to the carrier substrate and the at least one force applied to the film frame moves the contacting surface section of the flexible film in a second direction that is opposite of the first direction.

17. System as claimed in claim 1, wherein said control unit controls operation of the carrier substrate holder and the film frame holder to move the flexible film between (i) an initial position, wherein the contacting surface section and the attachment surface section are in the same plane, (ii) a detachment position, wherein the contacting surface section is located below the attachment surface section, and (iii) a stripping position, wherein the contacting surface section is located above the attachment surface section.

18. System as claimed in claim 1, wherein said carrier substrate is nonporous.

19. System as claimed in claim 1, wherein said film frame has a circular inner periphery and said stripping section of the flexible film is ring-shaped, wherein a ratio between (i) a thickness D of the film frame and (ii) a radial width A of the stripping section is in a range of 1:2 to 1:50.

20. System for stripping a product substrate off a carrier substrate connected to the product substrate by a bonding layer, said bonding layer fixing the product substrate to the carrier substrate, wherein said system comprises:
a flexible film including:
a contacting surface section having an adhesive layer for mounting the product substrate to the flexible film,
an attachment surface section disposed at the outer periphery of the contacting surface section, and
a stripping section disposed between the contacting surface section and the attachment surface section, wherein the flexible film is elastic at least in the stripping section;

a film frame fixed to the flexible film at the attachment surface section, wherein surfaces of the film frame and the flexible film define a recess that serves as a solvent reservoir for receiving (i) the bonding layer and (ii) a solvent for dissolving the bonding layer;
a delivery device for delivering the solvent to the solvent reservoir;
a carrier substrate holder for holding the carrier substrate, said carrier substrate holder engages with the carrier substrate to apply a force to the carrier substrate;
a film frame holder that engages with the film frame to apply at least one force to the film frame; and
a control unit for:
(i) controlling operation of the carrier substrate holder to engage with the carrier substrate and thereby control application of the force to the carrier substrate, wherein the force applied to the carrier substrate is transferred to the flexible film through connection of the carrier substrate to a product substrate mounted to the flexible film, and/or
(ii) controlling operation of the film frame holder to engage with the film frame and thereby control application of the at least one force to the film frame,

wherein the at least one force applied to the film frame by the film frame holder is directed against the force applied to the carrier substrate by the carrier substrate holder to deform at least the stripping section of the flexible film, and
wherein the control unit controls operation of the film frame holder to tilt the film frame.