Patent Application
20150251404
The invention relates to a device and a method for stripping a product substrate off a carrier.
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.
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.
a 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,
b shows a schematic side view to
In the figures the same components and components with the same function are identified with the same reference number.
a 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
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 li 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
The film 3 and the inner periphery li 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
As
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
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
The force Ff acting on the film frame 1, as shown in
As shown in
The force Ff1 or 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
| Number | Date | Country | Kind |
|---|---|---|---|
| 10004313.2 | Apr 2010 | EP | regional |
The present application is a divisional of U.S. application Ser. No. 13/641,479, filed Oct. 16, 2012, which is a U.S. National Stage Application of International Application No. PCT/EP11/01556, filed Mar. 29, 2011, which claims priority from European Patent Application No. 10004313.2, filed Apr. 23, 2010, said patent applications hereby fully incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13641479 | Oct 2012 | US |
| Child | 14715691 | US |
