Patent Application
20240010892
This application claims priority under 35 U.S.C. § 119 to Taiwanese Patent Application No. 111125507, filed Jul. 7, 2022, the entirety of which is incorporated by reference herein.
The present invention relates to a laser-releasable composition for forming a sacrificial layer used in a temporary bonding process or in a redistribution layer formation process.
Temporary wafer bonding (TWB) generally refers to a process of attaching a component wafer or a microelectronic substrate to a carrier wafer or substrate by polymeric bonding materials. In order to make the wafer more heat-dissipating during use, prolong its life and facilitate later system packaging, it is usually necessary to thin the component wafer to less than 50 μm. Generally speaking, the component wafer is temporarily bonded to a thicker carrier glass, and then etching, grinding or other process for thinning is performed to the back of the wafer. Also, through-silicon vias (TSV), redistribution layers, bonding pads and other circuit features can be formed. During backside processing (need to withstand repeated cycles between ambient temperature and extremely high temperature (greater than 250° C.), mechanical shocks generated from wafer processing and transfer steps, and strong mechanical forces (such as the force applied during the wafer backside grinding process used to thin the component wafer)), the carrier wafer supports the fragile component wafer. After all the processing is completed, the adhesive layer is deactivated by external light, electricity and heat to separate (i.e., peel off) the component wafer from the carrier, and further operation is performed for cleaning.
In the conventional technology, the temporary bonding layer mainly includes UV debonding glue, thermal debonding glue, solvent debonding glue and laser debonding glue. However, the UV debonding glue and the thermal debonding glue have a heat resistance temperature of about 120-150° C. and cannot withstand the temperature up to 260° C., and are easily affected by the ambient environment, causing the debonding reaction to occur early. The disadvantage of solvent debonding glue is that it has poor solvent resistance and has limitations in the manufacturing processes. Laser debonding has better heat resistance and chemical resistance, but it is easy to produce residual glue during the debonding process, which needs to be removed with a high-polarity solvent, causing other materials on the component to be corroded, so it also has limitations in use.
In view of the technical problems described above, an object of the present invention is to provide a novel temporary bonding method, which can use an alkaline aqueous solution to remove the residual glue that may be produced during the debonding process, thereby greatly reducing the possibility of components being corroded.
Another object of the present invention is to provide a novel method of forming a microelectronic structure, which can use an alkaline aqueous solution to remove the residual glue that may be produced during the debonding process, thereby greatly reducing the possibility of components being corroded.
To achieve the above objects, the present invention provides a temporary bonding method, which comprises: providing a stack comprising: a first substrate having an upper surface and a lower surface; an adhesive layer in contact with the lower surface; a second substrate having a first surface; and a sacrificial layer disposed between the first surface and the adhesive layer; and applying laser energy to the sacrificial layer to facilitate separation of the first substrate from the second substrate, wherein the sacrificial layer is formed by a composition comprising an alkali-soluble polymer; and a solvent for dispersing or dissolving the alkali-soluble polymer, wherein the alkali-soluble polymer contains a divalent residue of a diamine having a carboxyl group, and the alkali-soluble polymer comprises polyamic acid, polyimide or polyamideimide.
Preferably, the method further comprises washing the adhesive layer with an alkaline aqueous solution to remove the sacrificial layer remaining on a surface of the adhesive layer after the step of applying laser energy to the sacrificial layer.
Preferably, the alkaline aqueous solution is 3% to 5% by weight of an aqueous alkali metal hydroxide solution or an aqueous alkali metal carbonate solution.
Preferably, the divalent residue of the diamine having the carboxyl group comprises the following group:
wherein * indicates a connection point.
Preferably, the sacrificial layer has a thermal expansion coefficient of less than 50 ppm/° C.
The present invention further provides a method of forming a microelectronic structure, which comprises: forming a sacrificial layer on a surface of a substrate; and forming a redistribution layer on the sacrificial layer, wherein the sacrificial layer is formed by a composition comprising an alkali-soluble polymer; and a solvent for dispersing or dissolving the alkali-soluble polymer, wherein the alkali-soluble polymer contains a divalent residue of a diamine having a carboxyl group, and the alkali-soluble polymer comprises polyamic acid, polyimide or polyamideimide.
Preferably, the method further comprises forming one or more additional redistribution layers on the redistribution layer.
Preferably, the method further comprises applying laser energy to the sacrificial layer to separate the redistribution layer from the substrate after forming the redistribution layer.
Preferably, the method further comprises washing the redistribution layer with an alkaline aqueous solution to remove the sacrificial layer remaining on a surface of the redistribution layer after applying laser energy to the sacrificial layer.
Preferably, the alkaline aqueous solution is 3 to 5% by weight of an aqueous alkali metal hydroxide solution or an aqueous alkali metal carbonate solution.
Preferably, the divalent residue of the diamine having the carboxyl group comprises the following group:
wherein * indicates a connection point.
According to the present invention, a temporary bonding method and a method of forming a microelectronic structure can be obtained that can easily remove the residual glue produced in the debonding process with an alkaline aqueous solution.
The present invention provides a temporary bonding method, which comprises: providing a stack comprising: a first substrate having an upper surface and a lower surface; an adhesive layer in contact with the lower surface; a second substrate having a first surface; and a sacrificial layer disposed between the first surface and the adhesive layer; and applying laser energy to the sacrificial layer to facilitate separation of the first substrate from the second substrate, wherein the sacrificial layer is formed by a composition comprising an alkali-soluble polymer; and a solvent for dispersing or dissolving the alkali-soluble polymer, wherein the alkali-soluble polymer contains a divalent residue of a diamine having a carboxyl group, and the alkali-soluble polymer comprises polyamic acid, polyimide or polyamideimide.
As described above, in the present invention, the composition for forming the sacrificial layer (or referred to as a laser releasable composition) comprises an alkali-soluble polymer; and a solvent for dispersing or dissolving the alkali-soluble polymer, wherein the alkali-soluble polymer contains a divalent residue of a diamine having a carboxyl group, and the alkali-soluble polymer comprises polyamic acid, polyimide or polyamideimide.
The polyamic acid is preferably synthesized by condensation polymerization by mixing dianhydride and diamine monomers in a specific solvent to form a polyamic acid precursor solution. Next, a capping agent is preferably added to eliminate terminal functional groups in order to prevent possible subsequent aging. The specific solvent includes, but is not limited to: cyclohexanone, cyclopentanone, propylene glycol monomethyl ether, N-methyl-2-pyrrolidone, N,N-dimethylacetamide, γ-butyrolactone, ethyl 3-ethoxy propionate, propylene glycol methyl ether acetate, ethyl lactate or a combination of two or more of the aforementioned solvents.
In a preferred embodiment, the polyimide is mainly formed by polymerizing dianhydride monomers and diamine monomers, and at least one diamine monomer has a carboxyl functional group.
In a preferred embodiment, the polyamideimide is mainly formed by polymerizing dianhydride monomers, diamine monomers and aromatic dicarbonyl monomers, at least one diamine monomer has a carboxyl functional group, and the mole number of the aromatic dicarbonyl monomer account for 10%-50% of the total mole number of the dianhydride monomer and the aromatic dicarbonyl monomer. In a preferred embodiment, the thermal expansion coefficient of the sacrificial layer is less than 50 ppm/° C.
In the present invention, the divalent residue of the diamine having the carboxyl group comprises the following group:
wherein * indicates a connection point.
Other diamine monomers applicable to the present invention include but are not limited to: 2-(trifluoromethyl)-1,4-phenylenediamine, bis(trifluoromethyl)benzidine (TFDB), 4,4′-Oxydianiline (ODA), para-Methylene Dianiline (pMDA), meta-Methylene Dianiline (mMDA), 1,3-bis(3-aminophenoxy)benzene (133APB), 1,3-bis(4-aminophenoxy)benzene (134APB), 2,2′-bis[4(4-aminophenoxy)phenyl]hexafluoropropane (4BDAF), 2,2′-bis(3-aminophenyl)hexafluoropropane (33-6F), 2,2′-bis(4-aminophenyl)hexafluoropropane (44-6F), bis(4-aminophenyl)sulfone (4DDS), 3-aminophenyl)sulfone (3DDS), 2,2-Bis[4-(4-aminophenoxy)-phenyl]propane (6HMDA), 2,2-Bis(3-amino-4-hydroxy-phenyl)-hexafluoropropane (DBOH), 4,4′-Bis(3-amino phenoxy)diphenyl sulfone (DBSDA), 9,9-Bis(4-aminophenyl)fluorine (FDA), 9,9-Bis(3-fluoro-4-aminophenyl)fluorine (FFDA) or a combination of two or more of the aforementioned diamine monomers.
The dianhydride monomers applicable to the present invention include but are not limited to: 4,4′-(4,4′-isopropyldiene diphenoxy) bis(phthalic anhydride), 4,4′-(hexafluoroisopropylidene)diphthalic anhydride, 3,3′,4,4′-diphenyl ketone tetracarboxylic dianhydride, 3,3′,4,4′-biphenyl tetracarboxylic dianhydride, 2,3,3′,4′-biphenyltetracarboxylic dianhydride, 4,4′-oxydiphthalic anhydride, 3,3′,4,4′-diphenylsulfone tetracarboxylic dianhydride, biscarboxyphenyldimethylsilane dianhydride, bisdicarboxyphenoxydiphenyl sulfide dianhydride, sulfonyl diphthalic anhydride, 1,2,3,4-cyclobutane tetracarboxylic dianhydride, cyclohexane-1,2,4,5-tetracarboxylic dianhydride, 1,1′-bi(cyclohexyl)-3,3′,4,4′-tetracarboxylic dianhydride, 1,1′-bi(cyclohexane)-2,3,3′,4′-tetracarboxylic dianhydride, 1,1′-bi(cyclohexane)-2,2′,3,3′-tetracarboxylic dianhydride, 4,4′-methylene bis(cyclohexane-1,2-dicarboxylic anhydride), 4,4′-(propane-2,2-diyl) bis(cyclohexane-1,2-dicarboxylic anhydride), 4,4′-oxybis(cyclohexane-1,2-dicarboxylic anhydride), 4,4′-thiobis(cyclohexane-1,2-dicarboxylic anhydride), 4,4′-sulfonylbis(cyclohexane-1,2-dicarboxylic anhydride), 4,4′-(dimethylsilanediyl)bis(cyclohexane-1,2-dicarboxylic anhydride), 4,4′-(tetrafluoropropane-2,2-diyl)bis(cyclohexane-1,2-dicarboxylic anhydride), octahydropentalene-1,3,4,6-tetracarboxylic dianhydride, bicyclo[2.2.1]heptane-2,3,5,6-tetracarboxylic dianhydride, (8aS)-hexahydro-3H-4,9-methylfuran[3,4-g]isoamylene-1,3,5,7(3aH)-tetraketone, bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic dianhydride, bicyclo[2.2.2] oct-5-ene-2,3,7,8-tetracarboxylic dianhydride, tricyclo[4.2.2.02,5]decane-3,4,7,8-tetracarboxylic dianhydride, tricyclo[4.2.2.02,5]dec-7-ene-3,4,9,10-tetracarboxylic dianhydride or a combination of two or more of the aforementioned dianhydride monomers.
The aromatic dicarbonyl monomers applicable to the present invention include but are not limited to: 4,4′-biphenyldicarbonyl chloride (BPC), isophthaloyl chloride (IPC), terephthaloyl chloride (TPC) or a combination of two or more of the aforementioned aromatic dicarbonyl monomers.
As described above, it is preferable to use a capping agent to improve the stability of the final product by capping the terminal amine and consuming excess diamine in the reaction solution. It is preferable to use aromatic monoanhydrides as the capping agent. A particularly preferred capping agent is phthalic anhydride. The molar supply ratio of the dianhydride monomer, the diamine monomer and the capping agent is preferably about 0.7:1:0.3 to about 0.98:1:0.02, more preferably about 0.85:1:0.15 to about 0.95:1:0.05.
The solvent for dispersing or dissolving the alkali-soluble polymer includes but is not limited to cyclohexanone, cyclopentanone, propylene glycol monomethyl ether, N-methyl-2-pyrrolidone, N,N-dimethyl acetamide, γ-butyrolactone, ethyl 3-ethoxypropionate, propylene glycol methyl ether acetate, ethyl lactate or a mixture of two or more of the aforementioned solvents.
In the present invention, the sacrificial layer formed by the composition can be removed by an alkaline aqueous solution. The alkaline aqueous solution is preferably 3 to 5% by weight of an aqueous alkali metal hydroxide solution or an aqueous alkali metal carbonate solution. In some embodiments, the heat-resistant temperature of the sacrificial layer is 350-450° C.
With reference to
In the present invention, the first substrate can be a component wafer, including but not limited to micro-electromechanical systems (MEMS), micro-sensors, integrated circuits and power semiconductors. The lower surface 14 of the first substrate may have structures such as solder bumps, metal posts, and metal pillars.
The composition used to form the adhesive layer 20 is not particularly limited, and can be selected from commercially available adhesive compositions, as long as it can form a layer with the above-mentioned adhesive properties, and at the same time, the solvent can be removed by heating. These compositions are typically organic and comprise polymers or oligomers dissolved or dispersed in the solvent system. The polymer or oligomer can generally be selected from: cycloolefins, epoxy resins, acrylics, silicones, styrenes, vinyl halides, vinyl esters, polyamides, polyimides, polysulfones, polyethersulfones, cycloolefins, polyolefin rubbers, polyurethanes, ethylene-propylene rubbers, polyamide esters, polyimide esters, polyacetals, polyvinyl butyral or a mixture thereof. Typical solvent systems depend on the choice of polymers or oligomers.
The adhesive layer 20 can be applied to the lower surface 14 of the first substrate 10 by any known coating process, including but not limited to: dip coating, roll coating, slot coating, die coating, screen printing or spraying etc. In addition, before the coating is applied to the surface of the first substrate or the second substrate, it can be formed as a free-standing film, and the adhesive layer 20 can be applied to the lower surface 14 of the first substrate 10 by means of transfer attaching.
After the adhesive layer 20 is coated on the lower surface 14 of the first substrate 10, the solvent is removed by heating at about 50° C. to 150° C. for about 60 seconds to about 10 minutes. Afterwards, the adhesive layer 20 is bonded to the sacrificial layer 30 on the second substrate 40 by applying pressure, and then the adhesive layer 20 is cured after baking, so that the stack 100 shown in
In this embodiment, the second substrate 40 is a carrier wafer as a carrier substrate. The substrate 40 has a first surface 42 (upper surface) and a second surface 44 (lower surface) opposite to the first surface 42. The second substrate 40 preferably comprises a transparent wafer or any other transparent (to the laser energy) substrate that allows the laser energy to pass through the carrier substrate. Examples of the second substrate 40 include, but are not limited to: glass, Corning Gorilla glass, sapphire.
As shown in
Optionally, the stack 100 can be processed. After other processing procedures, all or part of the sacrificial layer 30 can be debonded by laser decomposition or ablation, so as to separate the first substrate 10 and the second substrate 40. Suitable laser wavelengths are from about 200 nm to about 400 nm, preferably from about 300 nm to about 360 nm. After the separation, the sacrificial layer substance remaining on the adhesive layer 20 can be removed with an alkaline aqueous solution. In this embodiment, as shown in the direction of the arrow in
The compositions for forming the sacrificial layer described herein can also be used as the laser release sacrificial layer during the formation of the redistribution layer (“RDL”), especially in the RDL-first/chip-last packaging of wafer or panel-level processes, in which it is very useful for minimizing or even avoiding known-good die loss during packaging.
Therefore, the present invention further provides a method of forming a microelectronic structure. The method comprises: forming a sacrificial layer on a surface of a substrate; and forming a redistribution layer on the sacrificial layer, wherein the sacrificial layer is formed of a composition comprising an alkali-soluble polymer; and a solvent for dispersing or dissolving the alkali-soluble polymer, wherein the alkali-soluble polymer contains a divalent residue of a diamine having a carboxyl group, and the alkali-soluble polymer comprises polyamic acid, polyimide or polyamideimide.
Please refer to
Next, as shown in
Referring to
The above-mentioned process for forming the fan-out wafer-level package structure is only one example of such a process that can be performed using the composition of the present invention as a build-up layer, and can be modified according to user needs. For example, the number of RDL layers and the number and location of solder balls and dies can be varied as desired. Such configurations will be understood and customized by people having ordinary skill in the art to which this invention pertains.
In order to highlight the effect of the present invention, the inventor completes the examples and comparative examples in the manner set forth below. The following examples and comparative examples will further illustrate the present invention, but are not intended to limit the scope of the present invention. All the changes and modifications made by those skilled in the technical field of the present invention without departing from the spirit of the present invention fall within the scope of the present invention.
In this example, 7.61 g of 3,5-diaminobenzoic acid was dissolved in 113.16 g of γ-butyrolactone (GBL) in a 250 mL three-neck round bottom flask. Subsequently, 11.11 g of 2,2′-bis-(dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 6.2 g of bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride was added to the reaction mixture as a solid. The reaction was carried out with stirring at room temperature for 24 hours.
In this example, 7.61 g of 3,5-diaminobenzoic acid was dissolved in 113.16 g of γ-butyrolactone (GBL) in a 250 mL three-neck round bottom flask. Subsequently, 11.11 g of 2,2′-bis-(dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 7.36 g of 3,3′,4,4′-biphenyl tetracarboxylic dianhydride (BPDA) was added to the reaction mixture as a solid. The reaction was carried out with stirring at room temperature for 24 hours.
In this example, 14.31 g of 6,6′-bisamino-3,3′-methylene dibenzoic acid was dissolved in 113.16 g of γ-butyrolactone (GBL) in a 250 mL three-neck round bottom flask. Subsequently, 11.11 g of 2,2′-bis-(dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 8.06 g of 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA) was added to the reaction mixture as a solid. The reaction was carried out with stirring at room temperature for 24 hours.
In this example, 14.31 g of 6,6′-bisamino-3,3′-methylene dibenzoic acid was dissolved in 113.16 g of γ-butyrolactone (GBL) in a 250 mL three-neck round bottom flask. Subsequently, 12.41 g of bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride was added to the reaction mixture as a solid. After adding 1.67 g of isoquinoline, the temperature was raised to 180° C. for dehydration reaction, and the reaction lasted for 4 hours.
In the reaction vessel, 10 mmol of 6,6′-bisamino-3,3′-methylene dibenzoic acid was added and dissolved in dimethylacetamide. Stirring under nitrogen atmosphere, the solvent amount was equivalent to the total solid weight component concentration of 15% by weight. After complete dissolution, 2 mmol of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) and 3 mmol of 6FDA were added and stirred for 4 hours to dissolve and react, and then the temperature of the solution was maintained at 15° C. while 5 mmol of terephthaloyl chloride (TPC) was added, followed by reaction with stirring for 12 hours. Next, 15 mmol of pyridine and 30 mmol of acetic anhydride were added and stirred for 30 minutes, and then the temperature was raised to 70° C., followed by stirring for 1 hour and then cooling to normal temperature. Finally, a large amount of methanol was used for precipitation, and the precipitated solid was pulverized by a pulverizer, followed by drying into powder through vacuum drying.
In the reaction vessel, 10 mmol of 6,6′-bisamino-3,3′-methylene dibenzoic acid was added and dissolved in dimethylacetamide. Stirring under nitrogen atmosphere, the solvent amount was equivalent to the total solid weight component concentration of 15% by weight. After complete dissolution, 4 mmol of CBDA and 5 mmol of 6FDA were added and stirred for 4 hours to dissolve and react, and then the temperature of the solution was maintained at 15° C. while 1 mmol of TPC was added, followed by reaction with stirring for 12 hours. Next, 15 mmol of pyridine and 30 mmol of acetic anhydride were added and stirred for 30 minutes, and then the temperature was raised to 70° C., followed by stirring for 1 hour and then cooling to normal temperature. Finally, a large amount of methanol was used for precipitation, and the precipitated solid was pulverized by a pulverizer, followed by drying into powder through vacuum drying.
The alkali-soluble polymers of Examples 1 to 6 were dispersed or dissolved in dimethylacetamide, coated on a glass of 700 μm with a thickness of about 1 μm, and then placed in an oven and backed at 150° C. for 2 minutes to dry the surface, followed by being baked at 300° C. for half an hour to obtain a temporary bonding composition film (A) temporarily placed on the glass surface. After being removed from the glass, a temporary bonding composition film (B) of the present invention with a thickness of about 1 μm could be obtained.
Titanium Copper Plated Test
For the film (A) made in Examples 1 to 6, a Ti/Cu layer (the thickness of Ti/Cu were respectively 100 nm/500 nm) was set on the film (A). With respect to the titanium copper plated test, if there is no crack on the copper film-plated surface after 2 hours of high-temperature aging at a temperature of 230° C., it is passed (V), and if there are cracks, it is failed (X).
Thermal Cracking Temperature
For the film (B) made in Examples 1 to 6, the surrounding temperature was raised to 700° C. from 25° C. with a rate of 10° C./min in air environment, and the temperature at which 5% by weight of the film (B) was lost was measured by thermogravimetric analyzer (TGA), which was the Td5 thermal cracking temperature.
Coefficient of Thermal Expansion (CTE)
The CTE value and glass transition temperature were measured from 50° C. to 200° C. with a thermomechanical analyzer (TA Instrument TMA Q400EM). Before the thermal analysis, all the temporary bonding composition films (B) were thermally treated at 220° C. for 1 hour, and then the glass transition temperature was measured by TMA. The measurement was carried out in the film mode, in which the heating rate was 10° C./min and the load was applied constantly at 30 mN. Similarly, the linear thermal expansion coefficient was measured by TMA at a temperature of 50-200° C., the load strain was 30 mN, and the heating rate was 10° C./min.
Adhesion
For the films (A) made in Examples 1 to 6, the evaluation method of adhesion adopted the cross-cut adhesion test, and the test method used a hundred knife to draw 10×10 (100) 1 mm×1 mm small grids on the surface of the test sample (glass material), with each drawn line as deep as the bottom layer. Afterwards, a brush was used to clean up the fragments in the test area, and then the small grids to be tested were firmly stuck with the adhesive tape, which was then wiped vigorously with an eraser to increase the contact area and strength between the tape and the tested area. Next, one end of the tape was grabbed with hand and the tape was quickly torn off in a vertical direction. The evaluation results are shown in Table 5 below, in which a test result of 5B indicates good adhesion.
Debonding Test
The films (A) made in Examples 1 to 6 were debonded by irradiation with laser light having energy of 230 mJ/cm2 and a wavelength of 308 nm. If the film can be peeled off successfully after debonding, it is passed (V), and if it cannot be peeled off, it is failed (X).
Chemical Resistance Test
The films (A) made in Example 1 to Example 6 were soaked in different chemicals listed in Table 1 below for 10 minutes, and then measured with a tension meter. When the measured result was higher than 300 g/cm, it represented good chemical resistance.
From the above, it can be seen that the sacrificial layer of the present invention not only has good heat resistance, chemical resistance and debonding property, but also has a low coefficient of thermal expansion, and can be easily removed with the alkaline aqueous solution. Therefore, it is very suitable for temporary bonding process and redistribution layer process.
However, the above describes preferred embodiments of the present invention only and cannot be used to limit the scope of the present invention, which means that all the simple and equivalent changes and modifications made according to the claims and the description of the present invention still fall within the scope covered by the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 111125507 | Jul 2022 | TW | national |
