TWI685915B - Carrier for temporary bonded wafers - Google Patents

Abstract

A carrier is disclosed onto which a wafer can be temporarily bonded. The carrier comprises a plate shaped laminate. The plate shaped laminate comprises a first layer. The first layer comprises a foil, a sheet or a plate. The plate shaped laminate comprises a second layer comprising a porous metal medium with three-dimensional open pores. The porous metal medium comprises metal fibers. The first layer is permanently bonded to the porous metal medium thereby closing the pores of the porous metal medium at the side where the first layer is located. The porous metal medium comprises a first porous layer and a second porous layer. The first porous layer is provided between the first layer and the second porous layer. The porosity of the first porous layer is higher than the porosity of the second porous layer.

Description

Carrier for temporarily bonding wafers

The invention relates to the field of carriers for wafers. The carriers can be used for temporary bonding of wafers during their processing (for example in wafer thinning).

The use of temporarily bonding wafers to carriers to allow wafer processing is well known. The subsequent debonding of the wafer from the carrier is a challenge. Different vehicles that allow degumming by solvents have been documented. In these processes, the adhesive used for temporary bonding is chemically soluble.

US2009/197070A describes a support plate which is bonded to a substrate to support the substrate. In this supporting plate, a plurality of openings penetrate from the bonding surface to the non-bonding surface. The bonding surface faces the substrate, and the non-bonding surface faces the bonding surface. A porous region including a first region and a second region surrounding the first region is formed on the bonding surface, and the first region has an opening ratio greater than that of the second region. In this way, it is possible to realize a support plate that can be easily peeled from a semiconductor wafer using a solvent However, it is not easy to peel from the substrate during the process operation on the semiconductor wafer.

US2005/0173064A1 provides a supporting plate having a structure that can supply a solvent to the adhesive layer between the supporting plate and the substrate (for example, a semiconductor wafer) within a short time after the substrate is thinned. The document also revealed the method used to peel off the support plate. The supporting plate may have a diameter larger than that of the semiconductor wafer, and penetrating holes are formed in the supporting plate. The outer peripheral portion of the support plate is a flat portion where no penetration holes are formed. When alcohol is injected from the above support plate, the alcohol passes through the permeation hole to reach the adhesive layer, dissolves and removes the adhesive layer.

US8882096B2 discloses a perforated support plate used to support the surface of the wafer by inserting an adhesive layer. The perforated support plate has penetration holes. The perforated support plate is bonded to the wafer using an adhesive, and the solution is used to dissolve the adhesive that penetrates through the perforation of the support plate. The perforated support plate includes reinforcement members to prevent deflection.

US2004/0231793A1 discloses a use of porous sintered metal as a temporary carrier for wafers. To dissolve the adhesive used to bond the wafer to the temporary carrier, the carrier can be released by passing the solvent through the thickness of the temporary carrier through its thickness.

US2009325467A describes a process in which the wafer can be thinned without generating dimples. The support plate has some perforations. The circuit formation surface of the wafer is bonded to one surface of the supporting plate by an adhesive member, and the corrugation preventing member having a thickness of 100 μm or more and having an adhesive layer on one surface is bonded to the other surface. So wearing The openings at both ends of the hole are blocked. The support plate is vacuum-absorbed to the support table via the ripple prevention member, and the wafer is ground/polished to thin the wafer. The corrugation prevents the member from being peeled off, and the solvent penetrates into the adhesive member through the perforation to peel the wafer from the support plate.

US2001005043A discloses a technology that implements wafer thinning and wafer separation from a support substrate in a short time at a high yield rate. The non-porous support substrate is bonded to the second surface of the support substrate, which has holes and an adhesive layer that is melted by heating to block the holes. The wafer is bonded to the first surface of the support substrate, which has holes and an adhesive layer melted by the solvent. The wafer is thinned by grinding and etching. The adhesive layer is melted by heating and the supporting substrate with holes slides relative to the non-porous supporting substrate, thereby separating the supporting substrate with holes from the non-porous supporting substrate. The adhesive layer is then dissolved by passing the solvent through the holes defined in the supporting substrate with holes. Thereby, the wafer and the supporting substrate with holes are separated. When no load is applied to the wafer, damage to the wafer is prevented.

The object of the present invention is to provide a carrier for temporary wafer bonding. The object of the present invention is to provide such a vehicle with improved characteristics. The object of the present invention is to provide a carrier that makes the wafer easily degummed by using a solvent to penetrate through the holes of the carrier to dissolve the adhesive. The object of the present invention is to provide a carrier that can thin the wafer to obtain the required quality specifications.

The first aspect of the present invention is a carrier capable of temporarily bonding a wafer thereon, for example, to thin the wafer. Carrier including flat laminate board. The flat laminate includes a first layer. The first layer includes a foil, sheet or plate. The flat laminate includes a second layer including a porous metal medium with three-dimensional openings. The porous metal medium includes or consists of metal fibers. The first layer is permanently bonded to the porous metal medium, thereby closing the pores of the porous metal medium on the side where the first layer is located. The porous metal medium includes a first porous layer and a second porous layer. The first porous layer is provided between the first layer and the second porous layer. The porosity of the first porous layer is higher than the porosity of the second porous layer.

The first layer is permanently bonded to the porous metal medium so that the first layer remains bonded to the porous metal medium during the period after the wafer temporarily bonded to the carrier is degummed or degummed.

Preferably, the carrier has a disc shape, possibly where the disc deviates from the outer periphery of the circle with a straight side. The straight side exists to match the shape of the wafer to be bonded to the work carrier. The diameter of the circular portion of the disc is preferably suitable for 6-inch, 8-inch, or 12-inch wafers. This means that the disk diameter is equal to or slightly larger than the wafer diameter.

The carrier has the following advantages: the degumming solvent can flow through the three-dimensional openings of the porous metal medium, and pass through the entire volume of the porous metal medium from the side edge of the carrier adhesively bonded to the wafer. The presentation of the first porous layer with higher porosity ensures that the degumming liquid quickly penetrates through the first porous layer and then through the thickness of the second porous layer, thereby achieving rapid degumming. As a result, the degumming solvent can quickly reach the adhesive layer that bonds the wafer to the carrier. The carrier is rigid enough to transport the bonded wafers through different process steps without bending or other mechanical deformation or pressure. The vehicle also has the following advantages Point: It has sufficient mechanical properties, such as rigidity, to achieve the dimensional properties required to thin the wafer, such as total thickness variation (TTV), bowing or warping. Another advantage of the present invention is that the vehicle can be reused multiple times. The carrier of the present invention has the additional advantage that due to the low porosity level of the second porous layer, the adhesive penetrates less and penetrates into the porous metal medium shallower, so it is used to temporarily join the wafer to the carrier The binder consumes less. In addition, when the adhesive penetrates less into the second porous layer, the thickness of the adhesive layer is reduced and the time required for degumming is reduced.

In a preferred embodiment, the first porous layer is directly bonded to the first layer. In other preferred embodiments, the second porous layer is directly bonded to the first porous layer. In other preferred embodiments, the second porous layer is configured to be bonded to the wafer.

Preferably, the porosity of the first porous layer is higher than 50%; and preferably lower than 80%.

Preferably, the porosity of the second porous layer is below 60%; and preferably above 30%.

Preferably, the first layer includes or consists of metal, glass, silicon or ceramic. In a preferred embodiment, the first layer is composed of metal, or glass, or silicon, or ceramic.

Specific examples of porous metal media include sintered or welded metal fiber nonwovens.

Preferably, the first layer covers at least one plane of the second layer More preferably, the first layer covers the entire surface of at least one planar side of the second layer.

In a preferred embodiment, the first layer covers the entire surface of one plane side of the second layer.

Preferably, the first layer includes or consists of metal. Preferably, the first layer includes or consists of a metal foil, a metal flat plate or a metal foil. Preferably, the first layer includes the same metal or alloy as the porous metal medium.

Preferably, the porous metal medium comprises stainless steel, titanium, palladium or tungsten or consists of stainless steel, titanium, palladium or tungsten, or the porous metal medium comprises an alloy or consists of an alloy which comprises more than 50% by weight Of titanium, palladium or tungsten. More preferably, in an embodiment where the first layer includes or consists of metal foil, metal flat plate or metal foil, the first layer includes the same metal or alloy as the porous metal medium .

In a preferred embodiment, where the first layer comprises or consists of metal, the first layer is formed by metal bonding (eg sintering) or welding (and preferably by using no additional filler material in the welding process Welding) and permanently bonded to the porous metal medium. An example of a welding process that can be used is capacitance discharge welding (CDW).

In a preferred embodiment, the first layer is permanently bonded to the porous metal medium with an adhesive. The adhesive can be selected from a wide range of adhesives that will not be affected by the degumming liquid used to debond the temporarily bonded wafer from the carrier. Examples of suitable adhesives are based on epoxy Adhesive.

Preferably, the carrier has a thickness between 650 μm and 750 μm.

Preferably, the first layer has a thickness between 20 μm and 650 μm, more preferably between 150 μm and 650 μm.

Preferably, the porous metal medium has a thickness between 50 μm and 150 μm, more preferably between 50 μm and 150 μm.

Preferably, the diameter of the metal fiber is between 2 μm and 50 μm, more preferably between 2 μm and 40 μm, and even more preferably between 2 μm and 25 μm. Even more preferably between 10 μm and 25 μm.

In a preferred embodiment, the first porous layer includes or consists of metal fibers with a first equivalent diameter, and the second porous layer includes metal fibers with a second equivalent diameter or It is composed of metal fibers of the second equivalent diameter. In a more preferred embodiment, the first equivalent diameter is greater than the second equivalent diameter. Having an equivalent diameter means that the diameter of the circle and the cross-section of the fiber whose cross-sectional shape deviates from the circular shape have the same area.

Preferably, the porous metal medium has a surface for bonding to the wafer, wherein the surface is parallel to the first layer. The surface is polished so that the carrier has a total thickness variation (TTV) of less than 10 μm. The total thickness variation (TTV) is measured by randomly selecting 5 points on the surface of the material by drop gauge measurement. In terms of the test method, the diameter of the drop gauge is 5.99. TTV is determined by the difference between the measured maximum thickness and the measured minimum thickness Righteousness.

Preferably, the second layer includes a contact layer for bonding to the wafer. The contact layer includes a mixture of metal fibers and metal powder. The metal fiber and the metal powder are permanently joined to each other at their contact points. In this preferred embodiment, the porous metal medium has a porosity higher than 20% and preferably higher than 30%, more preferably higher than 40%, even more preferably higher than 50%, still more preferably higher than 60%. Furthermore, the porosity is preferably less than 80%, and more preferably less than 60%.

In this preferred embodiment, the porosity of the contact layer is higher than 20% and preferably higher than 30%. Moreover, the porosity of the contact layer is preferably less than 50%, and more preferably less than 40%. In a more preferred embodiment, the porous metal medium includes an additional porous layer disposed between the first layer and the contact layer. The additional porous layer may include metal fibers, metal powder, or metal foam. Specific examples of the additional porous layer include sintered or welded metal fiber nonwoven fabric, sintered metal powder, and metal foam.

Preferably, the metal powder in the contact layer has a diameter ranging from 2 to 30 μm, preferably ranging from 2 to 20 μm, and more preferably ranging from 2 to 10 μm.

In a preferred embodiment, the side edges of the porous metal medium are permanently sealed so that there are no openings in the side edges of the porous metal medium. Preferably, the sealing of the side edges is entirely provided by metal.

The size and shape of the porous metal medium can be cut by welding the edges, or by laser cutting, or by laser cutting after welding the edges or after joining the first layer and the second layer. The combined size and shape of the layer and the second layer are cut to seal the side edges.

An alternative method of manufacturing a sealed edge is by machining the flat plate to produce an upright edge, and the porous metal medium is inserted into a cup produced by the machining, and the porous metal medium is subsequently joined to the first layer on.

When it is desired to use a permanent bonding edge to debond the temporarily bonded wafer from the carrier, wicking without debonding liquid is initially generated in the porous metal medium. The initial debonding occurs on the thin layer of adhesive between the carrier and the wafer. When this thin layer decomposes, the degumming speed is increased by having a capillary structure that increases through the degumming liquid in the porous metal medium through the opening created by the glue layer dissolved at the edge.

Preferably, the vehicle is arranged such that when a pressure of 4 bar is applied on it, the permanent deformation of the vehicle before applying the pressure is less than 5% of its original thickness. This can be tested by measuring the thickness of the vehicle between 20 seconds before and after applying a pressure of 4 bar. The carrier according to this embodiment can limit future permanent deformation by pre-compressing the carrier or the porous metal layer or multiple porous metal layers therein. These embodiments surprisingly synergistically improve the characteristics of the wafer after it is temporarily bonded to the carrier after its manufacturing process (for example, thinning).

The second aspect of the present invention is an assembly (or stack) of a wafer and the carrier as in the first aspect of the present invention. The wafer is bonded to the second porous layer with an adhesive. Preferably, the adhesive is an adhesive that can be removed by contacting a suitable degumming liquid with the adhesive.

The third aspect of the invention is a method of processing wafers. The method includes the steps of temporarily bonding the wafer to the first solution of the present invention by means of an adhesive Carrier; processing wafers temporarily bonded to the carrier, such as thinned wafers; using a degumming liquid to break the temporary adhesive bond between the wafer and the carrier, and debonding the wafer from the carrier; where the degumming liquid Infiltrate into the porous metal medium from the side edge of the wafer assembly bonded to the carrier by the adhesive.

During degumming and degumming of the wafer temporarily bonded to the carrier, the first layer remains bonded to the porous metal medium.

In a preferred method, the degummed carrier is reused one or more times to temporarily bond other wafers thereto. Preferably, the vehicle can be used at least 5 times, more preferably at least 10 times.

100‧‧‧vehicle

102‧‧‧straight side

200‧‧‧vehicle

210‧‧‧First floor

222‧‧‧Metal fiber mesh

224‧‧‧Metal fiber mesh

301‧‧‧Assembly or stack

370‧‧‧adhesive layer

380‧‧‧ Wafer

D‧‧‧Diameter

Figure 1 shows a top view of an exemplary carrier according to the invention.

2 shows a cross-sectional view of an exemplary carrier according to the invention.

FIG. 3 shows an example of a wafer assembly temporarily bonded to the carrier of the present invention.

Figure 1 shows a top view of a carrier 100 according to the invention. The carrier 100 has a disk shape and deviates from the circular periphery (diameter D) with the straight side 102. The straight side 102 exists to match the shape of the wafer to be bonded to the work carrier.

2 shows a cross-section of an exemplary carrier 200 according to the invention Face map. The carrier 200 includes a first layer 210. The first layer is a metal foil or metal foil. The carrier 200 also includes a first porous layer (eg, sintered nonwoven metal fiber mesh 222) and a second porous layer (eg, another sintered nonwoven metal fiber mesh 224), which is welded (eg, capacitor discharge welding) Sintered or bonded). The porosity of the first porous layer is higher than the porosity of the second porous layer.

Preferably, the fibers of the metal foil or metal foil and the non-woven metal fiber web are made of the same metal or alloy.

The non-woven metal fiber webs 222, 224 are permanently bonded to each other and to the first layer 210 by an adhesive (eg, epoxy adhesive) or sintering or welding (eg, capacitor discharge welding).

As an alternative to one or two nonwoven metal fiber webs, a sintered porous metal powder layer and/or a metal foam layer can be used for the first porous layer and/or the second porous layer.

As an alternative to metal foils or metal foils, glass, ceramic or silicon foils or flat plates can be used as the first layer. The first and second porous layers are bonded to each other by metal bonding (for example, sintering), and the bonding with the first layer can then be completed by an adhesive (for example, epoxy resin).

FIG. 3 shows an example of a wafer assembly or stack 301 temporarily bonded to a carrier of the present invention, such as the carrier 200 of the example of FIG. 2. The same reference numerals in FIG. 3 and the same reference numerals described in FIG. 2 have the same meaning. The temporary adhesive layer 370 is applied on the porous metal layer of the carrier 200, and the wafer 380 is temporarily bonded on the carrier 200 through the adhesive layer 370.

The exemplary carrier was fabricated with a total thickness of 700 μm and used for 8-inch wafers. The carrier has a titanium foil with a thickness of 250 μm as the first layer. A nonwoven titanium fiber web (which has titanium fibers with an equivalent diameter of 22 μm) was applied thereon and a sintering operation was performed to sinter the first porous layer to the titanium foil. In the final carrier, the first porous layer has a specific weight of 500 g/m ² and a porosity of 56%. On top of the first porous layer, a second porous layer with a thickness of 200 μm is applied, which is composed of a nonwoven titanium fiber web of titanium fibers with an equivalent diameter of 14 μm. The second porous layer has a density of 500 g/m ² and a porosity of 45% in the final carrier. The second porous layer is bonded into the carrier by separate sintering operations. The surface of the carrier to be bonded to the wafer can be polished to a total carrier thickness variation (TTV) of less than 10 μm.

By spin coating, a silicon-based adhesive is applied to the second porous layer of the carrier. The device wafer was bonded at 25°C and 0.8 bar for 10 minutes. By having lower porosity in the second porous layer, the cross-sectional view shows that the adhesive does not additionally penetrate into the porous layer compared to the second porous layer. The wafer can be thinned to 50 μm when bonded to the carrier. In the degumming step, the immersion bonded stack (the stack is a combination of wafers temporarily bonded to the carrier) immersed in Daeclean 300 (a commercially available solvent system for curing silicone adhesives) at 25° C. The circle completely degummed in 4 minutes and 50 seconds.

200‧‧‧vehicle

210‧‧‧First floor

222‧‧‧Metal fiber mesh

224‧‧‧Metal fiber mesh

Claims (14)

A carrier for temporarily bonding wafers, wherein the carrier includes a flat laminate, the flat laminate includes: a first layer, wherein the first layer includes a foil, a sheet, or a flat plate; and a second layer, It includes a porous metal medium with three-dimensional openings, wherein the porous metal medium includes metal fibers; wherein the first layer is permanently bonded to the porous metal medium, thereby closing the porous metal medium on the side where the first layer is located The pore; wherein the porous metal medium includes a first porous layer and a second porous layer, wherein the first porous layer is disposed between the first layer and the second porous layer; and wherein the first The porosity of a porous layer is higher than the porosity of the second porous layer. The carrier as described in item 1 of the patent application scope, wherein the porosity of the first porous layer is higher than 50%. The carrier according to item 1 of the patent application scope, wherein the porosity of the second porous layer is less than 60%. The carrier as described in item 1 of the patent application scope, wherein the first layer comprises metal, glass, silicon or ceramic. The carrier as described in item 1 of the patent application scope, wherein the first layer includes a metal; and wherein the first layer includes the same metal or alloy as the porous metal medium. The carrier as described in item 1 of the patent application scope, wherein the porous metal medium includes stainless steel, titanium, palladium or tungsten; or the porous metal medium includes an alloy including titanium, palladium or tungsten more than 50% by weight . The carrier as described in item 1 of the patent application scope, wherein the first layer includes metal; and wherein the first layer is permanently bonded to the porous metal medium by a metal bond. The carrier as described in item 1 of the patent application scope, wherein the first layer is permanently bonded to the porous metal medium by an adhesive. The carrier as described in item 1 of the patent application scope, wherein the equivalent diameter of the metal fiber is between 2 μm and 50 μm. The carrier as described in item 1 of the patent application scope, wherein the porous metal medium has a surface for bonding to a wafer, wherein the surface is parallel to the first layer; and wherein the surface is polished so that the The carrier has a total thickness variation (TTV) of less than 10 μm. The carrier according to item 1 of the patent application scope, wherein the second layer includes a contact layer for bonding to the wafer, wherein the contact layer includes a mixture of metal fibers and metal powder, wherein the metal fibers and the metal The powders are permanently joined to each other at their points of contact. The carrier as described in item 1 of the patent application scope, wherein the side edge of the porous metal medium is permanently sealed so that there is no opening in the side edge of the porous metal medium. A kind of wafer and such as the first to twelfth items in the patent application scope The carrier assembly according to any one of the claims, wherein the wafer is bonded to the second porous layer by an adhesive. A method of processing a wafer, comprising the steps of: temporarily bonding the wafer to the carrier as described in any one of claims 1 to 12 by means of an adhesive; processing temporarily bonding to the carrier The wafer; the temporary adhesive bond between the wafer and the carrier is broken by the degumming liquid, and the wafer is degummed from the carrier; wherein the degumming liquid is bonded to the carrier by the adhesive The side edge of the wafer assembly penetrates into the porous metal medium.

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