阅读说明：本技术 用于3d ic应用的可激光释放粘结材料 (Laser releasable adhesive material for 3D IC applications ) 是由 R·普利吉达 吴起 刘晓 白东顺 B·黄 于 2018-12-21 设计创作，主要内容包括：提供了新型的基于热塑性聚羟基醚的组合物,其用作用于暂时性粘结和激光脱粘工艺的可激光释放的组合物。本发明组合物可以使用各种UV激光脱粘,几乎不留残渣。由这些组合物形成的层具有良好的热稳定性,并且可溶于通常使用的有机溶剂(例如环戊酮)中。该组合物还可以用作RDL形成的堆积层。(Novel thermoplastic polyhydroxy ether-based compositions are provided for use as laser-releasable compositions for temporary bonding and laser debinding processes. The composition of the present invention can be debonded using various UV lasers with little residue left. The layers formed from these compositions have good thermal stability and are soluble in commonly used organic solvents (e.g., cyclopentanone). The composition may also be used as a build-up layer formed from RDL.)

1. A temporary bonding method, comprising:

providing a stack comprising:

a first substrate having a back surface and a front surface;

a tie layer adjacent to the front surface and comprising a polyhydroxy ether; and

a second substrate having a first surface adjacent to the bonding layer; and

the bonding layer is exposed to laser energy to facilitate separation of the first substrate and the second substrate.

2. The method of claim 1, wherein the polyhydroxy ether comprises a copolymer of a diglycidyl ether and a dihydroxy dye.

3. The method of claim 2, wherein the diglycidyl ether is selected from the group consisting of: bisphenol a diglycidyl ether, bisphenol F diglycidyl ether, 1, 4-cyclohexanedimethanol diglycidyl ether, resorcinol diglycidyl ether, bisphenol a propoxylated diglycidyl ether, ethylene glycol diglycidyl ether, 1, 4-cyclohexanedimethanol diglycidyl ether, glycerol diglycidyl ether, 1, 4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, 1, 3-butanediol diglycidyl ether, 1, 3-bis (3-glycidoxypropyl) tetramethyldisiloxane, and combinations thereof.

4. The method of claim 2, wherein the dihydroxy dye is selected from the group consisting of: 4,4 '-dihydroxybenzophenone, dihydroxychalcone dyes, 4- [ (2-phenylhydrazono) methyl ] resorcinol, dihydroxyazobenzene, dihydroxyanthraquinone, 2' -methylenebis [6- (benzotriazol-2-yl) -4-tert-octylphenol ], curcumin derivatives, and combinations thereof.

5. The method of claim 1, wherein the tie layer is a thermoplastic layer.

6. The method of claim 1, wherein the exposing is at about 200mJ/cm²To about 400mJ/cm²The dosage of (a).

7. The method of claim 1, wherein the providing the stack comprises forming the bonding layer on the front surface.

8. The method of claim 7, wherein forming the bonding layer on the front surface comprises applying a flowable bonding composition to the front surface, the flowable composition containing a polyhydroxy ether dispersed or dissolved in a solvent system.

9. The method of claim 8, further comprising: heating the composition at a temperature of about 120 ℃ to 250 ℃ for a time of about 60 seconds to about 10 minutes to form the tie layer.

10. The method of claim 7, wherein forming the bonding layer on the front surface comprises applying a free-standing film comprising a polyhydroxy ether to the front surface to form the bonding layer.

11. The method of claim 10, wherein applying a free-standing film comprising a polyhydroxy ether to the front surface to form the tie layer comprises adhering the free-standing film to the front surface.

12. The method of claim 1, wherein one of the front surface and the first surface is selected from the group consisting of:

(1) a device surface comprising an array of devices selected from the group consisting of: an integrated circuit; MEMS; a micro-sensor; a power semiconductor; a light emitting diode; a photonic circuit; an inserter; embedded passive devices and micro-devices fabricated on or from silicon, silicon-germanium, gallium arsenide and gallium nitride.

(2) A device surface comprising at least one structure selected from the group consisting of: welding a bump; a metal rod-shaped member; a metal post; and structures formed from materials selected from the group consisting of silicon, polysilicon, silicon dioxide, (oxy) silicon nitride, metals, low-k dielectrics, polymer dielectrics, metal nitrides, and metal silicides.

13. The method of claim 1, wherein one of the first and second substrates comprises glass or other transparent material.

14. The method of claim 1, further comprising: prior to separating the first and second substrates, subjecting the stack to a process selected from the group consisting of: back grinding, chemical-mechanical polishing, etching, metallization, dielectric deposition, patterning, passivation, annealing, redistribution layer formation, and combinations thereof.

15. The method of claim 1, wherein the bonding layer is the only layer between the first substrate and the second substrate.

16. The method of claim 1, the bonding layer having a first bond strength, and the stack further comprising a second bonding layer between the first and second substrates, the second bonding layer having a bond strength greater than the first bond strength.

17. A microelectronic structure, comprising:

a first substrate having a back surface and a front surface;

a tie layer adjacent to the front surface, the tie layer comprising a polyhydroxy ether; and

a second substrate having a first surface adjacent to the bonding layer, at least one of the front surface and the first surface being a device surface.

18. The microelectronic structure of claim 17, wherein the polyhydroxy ether comprises a copolymer of a diglycidyl ether and a dihydroxy dye.

19. The microelectronic structure of claim 18, wherein the diglycidyl ether is selected from the group consisting of: bisphenol a diglycidyl ether, bisphenol F diglycidyl ether, 1, 4-cyclohexanedimethanol diglycidyl ether, resorcinol diglycidyl ether, bisphenol a propoxylated diglycidyl ether, ethylene glycol diglycidyl ether, 1, 4-cyclohexanedimethanol diglycidyl ether, glycerol diglycidyl ether, 1, 4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, 1, 3-butanediol diglycidyl ether, 1, 3-bis (3-glycidoxypropyl) tetramethyldisiloxane, and combinations thereof.

20. The microelectronic structure of claim 18, wherein the dihydroxy dye is selected from the group consisting of: 4,4 '-dihydroxybenzophenone, dihydroxychalcone dyes, 4- [ (2-phenylhydrazono) methyl ] resorcinol, dihydroxyazobenzene, dihydroxyanthraquinone, 2' -methylenebis [6- (benzotriazol-2-yl) -4-tert-octylphenol ], curcumin derivatives, and combinations thereof.

21. The microelectronic structure of claim 17, wherein the bonding layer is a thermoplastic layer.

22. The microelectronic structure of claim 17, wherein the bonding layer has an average thickness of about 1 μ ι η to about 100 μ ι η.

23. The microelectronic structure of claim 17, wherein one of the front surface and the first surface is selected from the group consisting of:

(1) a device surface comprising an array of devices selected from the group consisting of: an integrated circuit; MEMS; a micro-sensor; a power semiconductor; a light emitting diode; a photonic circuit; an inserter; embedded passive devices and micro-devices fabricated on or from silicon, silicon-germanium, gallium arsenide and gallium nitride.

(2) A device surface comprising at least one structure selected from the group consisting of: welding a bump; a metal rod-shaped member; a metal post; and structures formed from materials selected from the group consisting of silicon, polysilicon, silicon dioxide, (oxy) silicon nitride, metals, low-k dielectrics, polymer dielectrics, metal nitrides, and metal silicides.

24. The microelectronic structure of claim 17, wherein one of the first and second substrates comprises glass or other transparent material.

25. The microelectronic structure of claim 17, wherein the bonding layer is the only layer between the first and second substrates.

26. The microelectronic structure of claim 17, the bonding layer having a first bonding strength, and further comprising a second bonding layer between the first and second substrates, the second bonding layer having a bonding strength greater than the first bonding strength.

27. A method of forming a microelectronic structure, the method comprising:

(I) forming a build-up layer on a surface of a substrate, the build-up layer comprising a polyhydroxy ether and having an upper surface remote from the surface of the substrate;

(II) forming a first redistribution layer on the upper surface; and

(III) optionally forming one or more additional redistribution layers on the first redistribution layer.

28. The method of claim 27, the method further comprising:

(IV) attaching solder balls to the final redistribution layer of the forming step (II) and optionally the forming step (III);

(V) attaching a chip to the solder balls; and

(VI) optionally repeating the attaching step (IV) and the attaching step (V) one or more times.

29. The method of claim 28, further comprising forming an epoxy layer on the die and solder balls to form a fan-out wafer level package structure on the substrate.

30. The method of claim 29, the method further comprising: and separating the substrate and the fan-out wafer level packaging structure.

31. The method of claim 30, wherein the separating comprises: exposing the build-up layer to laser energy to facilitate separation of the substrate and the fan-out wafer level package structure.

32. The method of claim 31, wherein the exposing is at about 200mJ/cm²To about 400mJ/cm²The dosage of (a).

33. The method of claim 27, wherein the polyhydroxy ether comprises a copolymer of a diglycidyl ether and a dihydroxy dye.

34. The method of claim 33, wherein the diglycidyl ether is selected from the group consisting of: bisphenol a diglycidyl ether, bisphenol F diglycidyl ether, 1, 4-cyclohexanedimethanol diglycidyl ether, resorcinol diglycidyl ether, bisphenol a propoxylated diglycidyl ether, ethylene glycol diglycidyl ether, 1, 4-cyclohexanedimethanol diglycidyl ether, glycerol diglycidyl ether, 1, 4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, 1, 3-butanediol diglycidyl ether, 1, 3-bis (3-glycidoxypropyl) tetramethyldisiloxane, and combinations thereof.

35. The method of claim 33, wherein the dihydroxy dye is selected from the group consisting of: 4,4 '-dihydroxybenzophenone, dihydroxychalcone dyes, 4- [ (2-phenylhydrazono) methyl ] resorcinol, dihydroxyazobenzene, dihydroxyanthraquinone, 2' -methylenebis [6- (benzotriazol-2-yl) -4-tert-octylphenol ], curcumin derivatives, and combinations thereof.

36. The method of claim 27, wherein the forming step (I) comprises applying a flowable composition to the surface of the substrate, the flowable composition containing the polyhydroxy ether dispersed or dissolved in a solvent system.

37. The method of claim 36, further comprising: heating the composition at a temperature of about 120 ℃ to 250 ℃ for a time of about 60 seconds to about 10 minutes to form the build-up layer.

38. The method of claim 27, wherein the forming step (I) comprises applying a free-standing film comprising the polyhydroxy ether to a surface of the substrate to form the build-up layer.

39. The method of claim 38, wherein applying a free-standing film comprising the polyhydroxy ether to the surface of the substrate to form the build-up layer comprises adhering the free-standing film to the surface of the substrate.

40. The method of claim 27, wherein the substrate comprises glass or other transparent material.

41. The method of claim 27, the method further comprising:

attaching a plurality of solder balls to the final redistribution layer of the forming step (II) and optionally the forming step (III); and

attaching a chip to at least two of the plurality of solder balls.

42. A microelectronic structure, comprising:

a substrate having a surface;

a build-up layer on the surface of the substrate, the build-up layer comprising a polyhydroxy ether and having an upper surface remote from the surface of the substrate; and

a first redistribution layer on the upper surface.

43. The structure of claim 42, further comprising one or more additional redistribution layers on the first redistribution layer.

44. The structure of claim 42, further comprising at least one solder ball on the first redistribution layer and a chip attached to the at least one solder ball.

45. The structure of claim 44 further comprising an epoxy coating on the solder balls and chips.

46. The structure of claim 42, wherein the polyhydroxy ether comprises a copolymer of a diglycidyl ether and a dihydroxy dye.

47. The structure of claim 46, wherein the diglycidyl ether is selected from the group consisting of: bisphenol a diglycidyl ether, bisphenol F diglycidyl ether, 1, 4-cyclohexanedimethanol diglycidyl ether, resorcinol diglycidyl ether, bisphenol a propoxylated diglycidyl ether, ethylene glycol diglycidyl ether, 1, 4-cyclohexanedimethanol diglycidyl ether, glycerol diglycidyl ether, 1, 4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, 1, 3-butanediol diglycidyl ether, 1, 3-bis (3-glycidoxypropyl) tetramethyldisiloxane, and combinations thereof.

48. The structure of claim 46, wherein the dihydroxy dye is selected from the group consisting of: 4,4 '-dihydroxybenzophenone, dihydroxychalcone dyes, 4- [ (2-phenylhydrazono) methyl ] resorcinol, dihydroxyazobenzene, dihydroxyanthraquinone, 2' -methylenebis [6- (benzotriazol-2-yl) -4-tert-octylphenol ], curcumin derivatives, and combinations thereof.

49. The structure of claim 42, wherein one of the first and second substrates comprises glass or other transparent material.

Technical Field

The present invention relates to a laser releasable composition for use as an adhesive composition in a temporary wafer bonding process or as a build-up layer during redistribution layer formation.

Background

RELATED APPLICATIONS

The present application claims priority from U.S. provisional patent application serial No. 62/609,426 entitled LASER-recoverable BONDING material FOR 3D IC APPLICATIONS, filed 2017, 12, month 22, the entire contents of which are incorporated herein by reference.

Summary of The Invention

The present invention relates broadly to temporary bonding methods, redistribution layer forming methods, and structures formed by these methods. In one embodiment, a temporary bonding method comprises: a stack is provided that includes a first substrate, a bonding layer, and a second substrate. The first substrate has a back surface and a front surface. The tie layer is adjacent the front surface and includes a polyhydroxy ether. The second substrate has a first surface adjacent to the bonding layer. The bonding layer is exposed to laser energy to facilitate separation of the first substrate and the second substrate.

In other embodiments, the present invention provides a microelectronic structure comprising a first substrate having a back surface and a front surface. A tie layer is adjacent the front surface, and the tie layer includes a polyhydroxy ether. A second substrate having a first surface is adjacent the bonding layer, and at least one of the front surface and the first surface is a device surface.

In another embodiment, the method of the present invention comprises forming a build-up layer on a surface of a substrate. The build-up layer includes a polyhydroxy ether and has an upper surface remote from the substrate surface. A first redistribution layer is formed on the upper surface, and one or more additional redistribution layers are optionally formed on the first redistribution layer.

In another embodiment, a microelectronic structure includes a substrate having a surface. The build-up layer is on the surface of the substrate, and the build-up layer includes a polyhydroxy ether and has an upper surface remote from the surface of the substrate. A first redistribution layer is on the upper surface.

Brief description of the drawings

FIG. 1 is a schematic cross-sectional view showing a preferred temporary bonding method of the present invention;

FIG. 2 is a schematic cross-sectional view showing a variation of the embodiment of FIG. 1;

FIG. 3 is a schematic view showing the formation of a redistribution layer according to the present invention;

FIG. 4 is a graph depicting the TGA (in air) of Polymer 1 tested in example 2;

FIG. 5 is a graph depicting the TGA (in nitrogen) of Polymer 1 tested in example 2;

FIG. 6 is a SUSS Chroclail plot of bond lines produced by formulation 1 tested in example 4; and

figure 7 is a blank device debonded at 308nm as described in example 6.

Detailed Description

The present invention relates to novel compositions or bulk compositions useful as temporary binders, and methods of using these compositions.

Temporary binding or stacking polymers and compositions

1. Polyhydroxy ethers

The composition used in the present invention includes polyhydroxy ether. Preferred polyhydroxy ethers may be polymeric or oligomeric, and preferred recycle units include: containing a dihydroxy dye and a diglycidyl ether.

Preferred dihydroxy-containing dyes include one or more aromatic moieties with two hydroxyl groups (-OH) present on the dye. The dye or chromophore should absorb light at a wavelength of about 300nm to about 400nm, thereby imparting light absorbance properties to the polyhydroxy ether. Preferred such dyes include those selected from the group consisting of: 4,4 '-dihydroxybenzophenone, dihydroxychalcone dyes, 4- [ (2-phenylhydrazono) methyl ] resorcinol, dihydroxyazobenzene, dihydroxyanthraquinone, 2' -methylenebis [6- (benzotriazol-2-yl) -4-tert-octylphenol ], curcumin derivatives, and combinations thereof.

Preferred diglycidyl ethers contain a ring family having two epoxide rings (preferably C)₃To C₈) Aromatic (preferably C)₆To C₁₂) Or aliphatic (preferably C)₂To C₁₀) In part, these epoxides are typically attached to an oxygen atom that is bonded to a cyclic or aromatic moiety. Preferred diglycidyl ethers include those selected from the group consisting of: bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, 1, 4-cyclohexanedimethanol diglycidyl ether, resorcinol diglycidyl ether, bisphenol A propyleneAn alkoxylated diglycidyl ether, ethylene glycol diglycidyl ether, 1, 4-cyclohexanedimethanol diglycidyl ether, glycerol diglycidyl ether, 1, 4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, 1, 3-butanediol diglycidyl ether, 1, 3-bis (3-glycidoxypropyl) tetramethyldisiloxane, and combinations thereof.

Polyhydroxy ethers are synthesized by reacting a dihydroxy-containing dye and a diglycidyl ether in a solvent system and in the presence of a catalyst at elevated temperatures. The monomers are preferably provided at a level such that the molar ratio of dihydroxy-containing dye to diglycidyl ether is from about 10:90 to 90:10, more preferably from about 30:70 to about 70:30, and even more preferably from 40:60 to about 60: 40.

Suitable catalysts for use during the polymerization include those selected from the group consisting of: ethyltriphenylphosphonium bromide and tetramethylammonium hydroxide. The catalyst is generally present in an amount of from about 1 to about 5 weight percent catalyst, preferably from about 2 to about 3 weight percent catalyst, based on the total weight of monomer solids taken as 100 weight percent.

Suitable solvents for use in the polymerization system include those selected from the group consisting of: cyclopentanone, cyclohexanone, gamma-butyrolactone (GBL), tetrahydrofurfuryl alcohol, benzyl alcohol, dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), and mixtures thereof. The solvent is typically present during polymerization at a level of from about 40% to about 90% by weight solvent, and preferably from about 50% to about 80% by weight solvent, based on the total weight of the composition taken as 100% by weight, with the balance being solids.

The polymerization is carried out at a temperature of from about 70 ℃ to about 150 ℃, more preferably from about 130 ℃ to about 150 ℃ for a period of from about 3 hours to about 24 hours, more preferably from about 6 hours to about 15 hours, more preferably about 12 hours. The crude product was precipitated in alcohol and dried under vacuum. The resulting polyhydroxy ether preferably has a weight average molecular weight of from about 1,000 daltons to about 100,000 daltons, preferably from about 10,000 daltons to about 50,000 daltons, more preferably from about 20,000 daltons to 40,000 daltons.

2. Polyhydroxy ether compositions

The cohesive or bulk composition used in the present invention is formed by simply dissolving the polyhydroxy ether in a solvent system. Suitable solvents include those selected from the group consisting of: cyclopentanone, cyclohexanone, gamma-butyrolactone (GBL), tetrahydrofurfuryl alcohol, benzyl alcohol, dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), and mixtures thereof. Preferably, the dissolution is allowed to proceed during about 24 hours while stirring, resulting in a homogeneous solution. The solution is preferably filtered before use.

The final laser releasable bonding or build-up composition preferably contains from about 5% to about 50% by weight solids, more preferably from about 10% to about 40% by weight solids, more preferably from about 20% to about 30% by weight solids, based on the total weight of the composition taken as 100% by weight. These solids are typically 100 wt% polyhydroxy ether based on the total weight of solids in the composition taken as 100 wt%, however, in some examples, it may be from about 95 wt% to about 100 wt% polyhydroxy ether, more preferably from about 98 wt% to about 100 wt% polyhydroxy ether.

In one embodiment, the composition is substantially free of a crosslinking agent. That is, the composition comprises less than 3 wt%, preferably less than 1 wt%, more preferably about 0 wt% of the crosslinking agent, based on the total weight of the composition taken as 100 wt%.

In one embodiment, the composition may comprise a surfactant. In another embodiment, no other ingredients are included. That is, the composition consists essentially of, or even consists of, the polyhydroxy ether in the solvent system. In another embodiment, the composition consists essentially of, or even consists of, the polyhydroxy ether and the surfactant in the solvent system.

Regardless of the exact formulation, the laser-releasable composition may be used as an adhesive composition in a temporary bonding process to bond a device substrate to a carrier substrate using the methods described below. Additionally, the laser-releasable composition may be used as a build-up composition in a redistribution layer forming process, as also described below.

Methods of using temporary bonding or stacking polymers

1. Temporary bonding embodiments

Referring to fig. 1(a) (not to scale), a precursor structure 10 is shown in schematic and cross-sectional views. The structure 10 includes a first substrate 12. The substrate 12 has a front or device surface 14, a back surface 16, and an outermost edge 18. Although the substrate 12 may be any shape, it is generally circular. Preferred first substrates 12 include device wafers, such as those whose device surfaces include an array of devices (not shown) selected from the group consisting of: integrated circuits, MEMS, microsensors, power semiconductors, light emitting diodes, photonic circuits, interposers (interposers), embedded passive devices, and other microdevices fabricated on or from silicon and other semiconductor materials such as silicon-germanium, gallium arsenide, gallium nitride, aluminum gallium arsenide, aluminum indium gallium phosphide, and indium gallium phosphide. The surfaces of these devices typically include structures (also not shown) formed from one or more of the following materials: silicon, polysilicon, silicon dioxide, (oxy) silicon nitride, metals (e.g., copper, aluminum, gold, tungsten, tantalum), low-k dielectrics, polymer dielectrics, and various metal nitrides and silicides. The device surface 14 may also include at least one structure selected from the group consisting of: welding a bump; a metal rod-shaped member; a metal post; and structures formed from materials selected from the group consisting of silicon, polysilicon, silicon dioxide, (oxy) silicon nitride, metals, low-k dielectrics, polymer dielectrics, metal nitrides, and metal silicides.

As shown in fig. 1(a), a laser releasable adhesive composition according to the present invention is applied to a first substrate 12 to form a laser releasable adhesive layer 20 on the device surface 14. The bonding layer 20 has an upper surface 21 remote from the first substrate 12, and preferably, the bonding layer 20 is formed directly on the device surface 14 (i.e., without any intermediate layer between the bonding layer 20 and the substrate 12). The bonding composition may be applied by any known application method. One preferred method comprises: the composition is spin coated at a speed of about 500rpm to about 3,000rpm (preferably about 1,000rpm to about 2,000rpm) for a time period of about 10 seconds to about 120 seconds (preferably about 30 to about 90 seconds).

After the composition is applied, it is preferably heated to a temperature of from about 120 ℃ to about 250 ℃, more preferably from about 150 ℃ to about 200 ℃ for a time of from about 60 seconds to about 10 minutes (preferably from about 120 seconds to about 5 minutes). Importantly, little or no crosslinking occurs during this heating. In other words, the resulting tie layer 20 is preferably thermoplastic.

In some embodiments, depending on the composition used, it is preferred to subject the tie layer 20 to a multi-stage baking process. Also, in some examples, the above-described application and baking processes may be repeated on another aliquot of the composition to "build" the first bonding layer 20 on the first substrate 12 in multiple steps.

In another embodiment, the laser releasable bonding composition of the present invention may be formed as a preformed dry film, rather than being applied as a flowable composition. In this example, the composition is formed into an unsupported self-sustaining film that does not collapse or change properties (no force or energy applied) even when unsupported and then the film is adhered to a first substrate 12 to form a laser releasable adhesive composition 20, as shown in fig. 1 (a).

Regardless of how the tie layer 20 is formed, its average thickness (measured at five locations) should be from about 1 μm to about 200 μm, more preferably from about 5 μm to about 50 μm, and even more preferably from about 1 μm to about 30 μm. Any film thickness measurement tool can be used to measure the thickness used herein, and one preferred tool is an infrared interferometer, such as those sold by SUSS Microtec or Foothill.

The tie layer 20 should also have a low total thickness variation ("TTV"), meaning that the thickest and thinnest points of the layer 20 do not differ significantly from one another. TVV is preferably calculated by measuring the thickness at a plurality of points or locations on the film, preferably at least about 50 points or at about 50 points, more preferably at least about 100 points or at 100 points, even more preferably at least about 1,000 points or at about 1,000 points. The difference between the highest thickness measurement and the lowest thickness measurement obtained at these points is referred to as the TTV measurement for that particular layer. In some TTV measurement examples, edge culling or outliers may be removed from the calculations. In these cases, the number of measurements involved is expressed as a percentage, i.e., if TTV is given at an inclusion rate of 97%, the highest and lowest measurements of 3% will be rejected, and 3% will be divided equally between the highest and lowest measurements (i.e., 1.5% each). Preferably, the above-described TTV range is achieved using a measurement of about 95% to about 100%, more preferably a measurement of about 97% to about 100%, and even more preferably a measurement of about 100%.

In addition to having a low TTV in absolute numbers (e.g., 5 μm), the TTV should also be low relative to the average film thickness of the tie layer 20. Thus, the TTV of the tie layer 20 on the blank substrate should be less than about 25% of the average thickness of the tie layer 20, preferably less than about 10% of the average thickness of the tie layer 20, and more preferably less than about 5% of the average thickness of the tie layer 20. For example, if the tie layer 20 has an average thickness of 50 μm, the maximum acceptable TTV will be about 12.5 μm or less (less than about 25% of 50 μm), preferably about 5 μm or less (less than about 10% of 50 μm), more preferably about 2.5 μm or less (less than about 5% of 50 μm).

In addition, the laser releasable bonding layer 20 will form a strong bond with the desired substrate. Any material having a bond strength greater than about 50psig, preferably about 80-250psig, more preferably about 100-150psig, as measured by astm D4541/D7234, is suitable for use as the bond layer 20.

The k-value of the bonding layer 20 will be at least about 0.008, preferably at least about 0.05, more preferably at least about 0.1, and even more preferably from about 0.1 to about 0.4.

The cross-sectional schematic in fig. 1(a) also depicts a second precursor structure 22. The second precursor structure 22 includes a second substrate 24. In this embodiment, the second substrate 24 is a carrier wafer. That is, the second substrate 24 has a front or carrier surface 26, a back surface 28, and an outermost edge 30. While the second substrate 24 can be any shape, it is generally circular and similar in size to the first substrate 12. The preferred second substrate 24 comprises a transparent substrateA glass wafer or any other (laser energy) transparent substrate that allows laser energy to pass through the carrier substrate. A particularly preferred glass carrier wafer is corningEAGLEA glass wafer.

The structures 10 and 22 are then pressed together in a face-to-face relationship such that the upper surface 21 of the adhesive layer 20 is in contact with the front or carrier surface 26 of the second substrate 24 (fig. 1 (b)). Upon pressing, sufficient pressure and heat are applied for a sufficient time to bond the two structures 10 and 22 together to form a bonded stack 34. Depending on the composition of which the tie layer 20 is formed, the bonding parameters will vary, but typical temperatures in this step are from about 150 ℃ to about 250 ℃, preferably from about 180 ℃ to about 220 ℃, typical pressures are from about 1000N to about 25,000N, preferably from about 3,000N to about 20,000N, and durations of from about 30 seconds to about 20 minutes, preferably from about 3 minutes to 10 minutes.

The TTV of the bonded stack 34 should be less than about 10% of the total average thickness, preferably less than about 5% of the total average thickness (measured at five locations throughout the stack 43), and more preferably less than about 3% of the total average thickness of the bonded stack 34. That is, if the average thickness of the bonded stack 34 is 100 μm, then less than about 10% of the TTV is about 10 μm or less.

The first substrate 12 can now be safely handled and further processed, which may damage the first substrate 12 if the first substrate 12 is not bonded to the second substrate 24. Thus, the structure can be safely backside processed, such as back grinding, chemical-mechanical polishing ("CMP"), etching, metal deposition (i.e., metallization), dielectric deposition, patterning (e.g., photolithography, via etching), passivation, annealing, redistribution layer formation, and combinations thereof, without separation of the substrates 12 and 24 and without infiltration of any chemicals encountered in these subsequent processing steps. The bonding layer 20 can withstand not only these processes, but also processing temperatures up to about 300 ℃, preferably about 150 ℃ to about 280 ℃, and more preferably about 180 ℃ to about 250 ℃.

Once processed, the substrates 12 and 24 may be separated by breaking or ablating all or part of the laser releasable adhesive layer 20 using a laser, suitable lasers including UV lasers, preferably having a wavelength of about 200nm to about 400nm, most preferably having a wavelength of about 300nm to about 360nm scanning lasers in a serpentine pattern across the surface of the carrier wafer to expose the entire wafer exemplary laser debonding tools include SUSS MicroTec Lambda STEEL 2000 laser debonder, EVG850 DB automated debonding system, and Kingyou LD-automated 200/300 laser debonder the wafer is preferably scanned with a laser spot having a field size of about 40 × 40 μm to about 12.5 × 4mm a suitable energy density (fluence) for debonding the substrate is about 100mJ/cm²To about 400mJ/cm²Preferably about 150mJ/cm²To about 350mJ/cm². Suitable power for debonding the substrate is from about 2W to 6W, preferably from about 3W to about 4W.

After laser exposure, the substrates 12 and 24 will readily separate. After detachment, any remaining adhesive layer 20 may be removed by plasma etching or a solvent capable of dissolving adhesive layer 20.

In the above embodiments, the laser releasable bonding layer 20 is shown on the first substrate 12 of the device wafer. It is understood that these substrate/layer schemes may be reversed. That is, the bonding layer 20 may be formed on the second substrate 24 (i.e., carrier wafer). The same composition and processing conditions as those of the above embodiment apply to this embodiment.

In a particularly preferred embodiment, the tie layer 20 is the only layer between the substrates 12 and 24. However, it should be understood that in alternative embodiments, the bonding layer 20 may be used with other bonding materials, structural support layers, lamination aids, coupling layers (for adhesion to the initial substrate), pollution control layers, and cleaning layers. The preferred structure and application technique will be determined by the application and process flow.

An example of this alternative multi-layer embodiment is shown in fig. 2, where like reference numerals refer to like parts from fig. 1. In the embodiment of fig. 2, the bonding composition of the present invention is applied to a second substrate 24 to form a bonding layer 20 on a carrier surface 26, forming a structure 22', as shown in fig. 2 (a). Alternatively, the structure 22' may be provided in a formed form. A second composition different from that used to form the laser releasable bonding layer 20 is applied to the device surface 14 of the first substrate 12 to form the layer 32. Layer 32 has an upper surface 34 remote from first substrate 12 and a lower surface 36 adjacent to first substrate 12. In one embodiment, layer 32 is a second adhesive layer, for example where a multi-layer adhesive scheme is desired. In this example, it is preferred that the bond strength of the second adhesive layer 32 be greater (stronger) than the bond strength of the laser releasable adhesive layer 20. In particular, the bonding strength of the second adhesive layer 32 is at least about 1.2 times, preferably at least about 1.5 times, and more preferably from about 1.7 to about 4 times the bonding strength of the laser releasable adhesive layer 20. The separation of the first and second substrates 12, 24 may be performed as previously described.

Alternatively, in a multi-layer approach, the substrate/layer approach may be reversed. That is, the layer 32 may be formed on the second substrate 24 (carrier wafer) while the laser releasable bonding layer 20 of the present invention is formed on the first substrate 12 (device wafer). In this example, layer 32 (whether it is an adhesive layer or not) is selected such that laser energy passes through layer 32 after passing through second substrate 24, thereby allowing the laser energy to contact laser-bondable layer 20 and cause decomposition, as previously described.

2. Stacked layer embodiments

In another embodiment, the laser-releasable composition of the present invention may be used as a buildup layer for regeneration layer ("RDL") formation, especially in RDL-first/chip post-packaging in wafer-level or panel-level processes, which is advantageous for minimizing or even avoiding known good-die loss during packaging. One version of this process is shown in figure 3.

As shown in fig. 3(a), a laser releasable bonding or build-up composition as previously described is applied to the upper surface 38 of the carrier substrate 40 to form a laser releasable bonding layer 42 on the carrier surface 38. Build-up layer 42 is formed in any of the ways described above with respect to the temporary bonding embodiments, including processing conditions and resulting properties. The build-up layer 42 has an upper surface 44 remote from the carrier substrate 40, and preferably, the build-up layer 42 is formed directly on the upper surface 38 of the carrier substrate 40 (i.e., without any intervening layers between the build-up layer 42 and the substrate 40).

A seed layer 46 is then conventionally disposed on the upper surface 44. The seed layer 46 may then be coated with photoresist, patterned and electroplated, again in a known manner, to form the structure shown in fig. 3 (c). Referring to fig. 3(d), the photoresist is stripped and the metal is etched followed by coating, patterning and curing of the dielectric layer. This results in the formation of a first RDL48, as shown in fig. 3 (e). The steps of fig. 3(b) to 3(e) may be repeated as many times as necessary to produce a plurality of RDLs (45(a) - (d), i.e., four RDLs in the embodiment shown in fig. 3 (f)).

Referring to fig. 3(g), after the desired number of RDLs are formed, solder balls 50 are attached to the uppermost (last formed) RDL, again in a conventional manner. Die 52 is bonded to solder balls 50, and a conventional epoxy molding layer 54 is then applied and ground to form a fan-out wafer level package structure 56. Finally, laser energy is applied to the carrier substrate 40 under laser separation conditions as described above to decompose or ablate all or a portion of the laser releasable build-up layer 42. After laser application, the carrier substrate 40 will release and separate from the fan-out wafer level package structure 56 (fig. 3(h)), and any remaining build-up layer 42 is removed by the solvent.

It should be noted that the above process for forming fan-out wafer level package structures is only one example of the type of process that can be performed using the composition of the present invention as a build-up layer, and that the process can be varied according to the needs of the user. For example, the number of RDL layers and the number and location of chips and solder balls may vary as desired. Those skilled in the art will understand and customize these settings.

Other advantages of various embodiments of the present invention will be apparent to those of ordinary skill in the art upon reading the invention described herein and the working examples below. Unless otherwise stated, it is to be understood that the various embodiments described herein are not necessarily mutually exclusive. For example, features illustrated or described in one embodiment can be, but are not necessarily, included in other embodiments. Thus, the invention is susceptible to variations on the combination and/or integration of the specific embodiments described herein.

As used herein, the word "and/or" when used in a list of two or more items means that any one of the listed items can be used alone, or any combination of two or more of the listed items can be used. For example, if a composition is described as containing or excluding components A, B and/C, then the composition contains or excludes component a alone; a separate component B; a separate component C; a combination of A and B; a combination of A and C; a combination of B and C; or a combination of A, B and C.

The present invention also uses a range of values to quantify certain parameters relating to various embodiments of the invention. It should be understood that when numerical ranges are provided, such ranges are to be construed as providing literal support for claim limitations that only describe the lower value of the range and claims that only describe the upper value of the range. For example, a disclosed numerical range of about 10 to about 100 provides literal support for a claim reciting "greater than about 10" (without an upper bound) and a claim reciting "less than about 100" (without a lower bound).

Examples

The following examples describe the process according to the invention. It is to be understood, however, that these examples are provided by way of illustration and nothing contained therein should be taken as a limitation on the overall scope of the invention.