Adhesive transfer

An adhesive transfer method includes depositing an adhesive on a first substrate, transferring a layer of the adhesive from the first substrate to an intermediate substrate, and transferring adhesive from the layer of the adhesive to at least one area of a second substrate.

BACKGROUND

Semiconductor die, wafers, and/or substrates may be joined to other semiconductor die, wafers, and/or substrates with an adhesive. Application of adhesive to the semiconductor die, wafers, and/or substrates to be joined, however, may be complicated by topography of the semiconductor die, wafers, and/or substrates. In addition, establishing a uniform layer of adhesive on the areas of the semiconductor die, wafers, and/or substrates to be joined may be challenging.

DETAILED DESCRIPTION

FIG. 1schematically illustrates one example of an adhesive transfer and bonding process100. At102, process100includes reducing viscosity (i.e., increasing flowability) of an adhesive used in process100. An example of an adhesive used in process100includes a dual-cure adhesive such as EMS 405-57 from Engineered Materials Systems Inc.

Reducing viscosity of the adhesive helps facilitate dispensing and depositing of the adhesive during subsequent processing. In one example, viscosity of the adhesive is reduced by diluting or thinning the adhesive with a solvent. An example of a solvent used for diluting or thinning the adhesive in process100includes cyclopentanone.

At104, process100includes depositing the diluted adhesive on a dummy wafer or donor substrate10. More specifically, a layer of diluted adhesive12is deposited on a surface11of donor substrate10. In one example, adhesive12is deposited on surface11of donor substrate10by spin coating.

Next, at106, process100includes transferring adhesive12from donor substrate10to an intermediate or carrier substrate13. An example of a material used for intermediate or carrier substrate13includes a flexible film including a polyester film such as Mylar.

In one example, transferring adhesive12from donor substrate10to intermediate or carrier substrate13includes contacting or pressing a surface14of intermediate or carrier substrate13against adhesive12deposited on donor substrate10. As such, adhesive12is transferred to surface14of intermediate or carrier substrate13such that a layer15of adhesive12is formed on intermediate or carrier substrate13and remains on intermediate or carrier substrate13when intermediate or carrier substrate13is separated, peeled, or removed from donor substrate10.

In one example, layer15of adhesive12is a substantially uniform layer, and has a thickness less than a total thickness of adhesive12deposited on donor substrate10such that a layer of adhesive12remains on donor substrate10after transferring adhesive12to intermediate or carrier substrate13.

After transferring adhesive12to carrier substrate13, at108, process100includes removing the solvent from adhesive12of layer15. In one example, removing the solvent from adhesive12includes heating layer15of adhesive12and carrier substrate13at a predetermined temperature for a predetermined time so as to evaporate the solvent from adhesive12.

In one example, at110, process100includes partially cross-linking or “B-staging” adhesive12as provided on carrier substrate13. In one example, partially cross-linking or “B-staging” adhesive12includes semi-curing adhesive12by exposing layer15of adhesive12to ultra-violet (UV) light. Partially cross-linking or “B-staging” adhesive12essentially “freezes” adhesive12in position to reduce wicking of adhesive12, and reduces a tack of adhesive12such that carrier substrate13with layer15of adhesive12may be “staged” or held for a period of time, and/or may be more easily handled during subsequent processing.

At112, process100includes transferring adhesive12of layer15from carrier substrate13to a device wafer or substrate16. In one example, device wafer or substrate16includes a patterned substrate having a topography of raised portions or areas17. As such, transferring adhesive12of layer15from carrier substrate13to substrate16includes transferring adhesive12to raised portions or areas17of substrate16.

In one example, transferring adhesive12from carrier substrate13to substrate16includes pressing layer15of adhesive12against substrate16and contacting raised portions or areas17of substrate16with layer15of adhesive12. As such, adhesive12from layer15is transferred to raised portions or areas17of substrate16and remains on raised portions or areas17of substrate16when carrier substrate13is separated, peeled, or removed from substrate16. Thus, a pattern of adhesive12transferred to substrate16follows and is aligned with a pattern of substrate16such that adhesive12transferred to substrate16is self-patterned and self-aligned.

Partially cross-linking or “B-staging” adhesive12(as described, for example, at110) reduces wicking of adhesive12so that adhesive12, after transfer at112, remains on raised portions or areas17of substrate16instead of wicking into recessed areas or regions among raised portions or areas17of substrate16.

At114of process100, substrate16with self-patterned and self-aligned adhesive12is aligned with another substrate18for bonding with substrate18such that at116of process100, substrate16and substrate18are bonded together by adhesive12. In one example, substrate16and substrate18are bonded together by placing substrate16and substrate18in a thermal bonding machine at a predetermined temperature for a predetermined time. Thereafter, at118of process100, adhesive12is cured by heating substrates16and18at a predetermined temperature for a predetermined time.

FIG. 2schematically illustrates another example of an adhesive transfer and bonding process200. At202, process200, similar to process100, includes reducing viscosity of an adhesive used in process200. Similar to102of process100, viscosity of the adhesive is reduced by diluting or thinning the adhesive with a solvent.

At204, process200includes depositing the diluted adhesive on a dummy wafer or donor substrate20. More specifically, a layer of diluted adhesive22is deposited on a surface21of donor substrate20. In one example, similar to104of process100, adhesive22is deposited on surface21of donor substrate20by spin coating.

Next, at206, process200includes transferring adhesive22from donor substrate20to an intermediate or carrier substrate23. An example of a material used for intermediate or carrier substrate23includes a flexible film including a polyester film such a Mylar.

In one example, similar to106of process100, transferring adhesive22from donor substrate20to intermediate or carrier substrate23includes contacting or pressing a surface24of intermediate or carrier substrate23against adhesive22deposited on donor substrate20. As such, adhesive22is transferred to surface24of intermediate or carrier substrate23such that a layer25of adhesive22is formed on intermediate or carrier substrate23and remains on intermediate or carrier substrate23when intermediate or carrier substrate23is separated, peeled, or removed from donor substrate20.

In one example, similar to layer15of adhesive12, layer25of adhesive22is a substantially uniform layer, and has a thickness less than a total thickness of adhesive22deposited on donor substrate20such that a layer of adhesive22remains on donor substrate20after transferring adhesive22to intermediate or carrier substrate23.

After transferring adhesive22to carrier substrate23, at208, process200includes removing the solvent from adhesive22of layer25. In one example, similar to108of process100, removing the solvent from adhesive22includes heating layer25of adhesive22and carrier substrate23at a predetermined temperature for a predetermined time so as to evaporate the solvent from adhesive22.

At210, process200includes transferring adhesive22of layer25from carrier substrate23to a semiconductor die or substrate26. In one example, semiconductor die or substrate26includes a patterned substrate formed by a singulated wafer resulting in a topography of raised portions or areas27on a backing member (e.g., saw tape)28. As such, transferring adhesive22from carrier substrate23to substrate26includes transferring adhesive22to raised portions or areas27of substrate26.

In one example, similar to112of process100, transferring adhesive22from carrier substrate23to substrate26includes pressing layer25of adhesive22against substrate26and contacting raised portions or areas27of substrate26with layer25of adhesive22. As such, adhesive22from layer25is transferred to raised portions or areas27of substrate26and remains on raised portions or areas27of substrate26when carrier substrate24is separated, peeled, or removed from substrate26. Thus, a pattern of adhesive22transferred to substrate26follows and is aligned with a pattern of substrate26such that adhesive22transferred to substrate26is self-patterned and self-aligned.

In one example, at212, process200includes partially cross-linking or “B-staging” adhesive22as provided on substrate26. In one example, partially cross-linking or “B-staging” adhesive22includes semi-curing adhesive22by exposing adhesive22to ultra-violet (UV) light. Partially cross-linking or “B-staging” adhesive22essentially “freezes” adhesive22in position to reduce wicking of adhesive22, and reduces a tack of adhesive22such that substrate26with self-patterned and self-aligned adhesive22may be “staged” or held for a period of time, and/or may be more easily handled during subsequent processing. Partially cross-linking or “B-staging” adhesive22also reduces wicking of adhesive12into areas or regions between raised portions or areas27of substrate26or along edges of substrate26after transfer at210.

At214of process200, substrate26with self-patterned and self-aligned adhesive22is stacked with another silicon or semiconductor die or substrate29for bonding to silicon or semiconductor die or substrate29with adhesive22.

FIG. 3illustrates one example of application of an adhesive transfer and bonding process as described herein. In one example, adhesive transfer and bonding process100and/or adhesive transfer and bonding process200is used in fabrication of a fluid ejection device300.

Schematically illustrated in cross-section inFIG. 3, one example of fluid ejection device300includes an electronics wafer or substrate310, a piezeoelectric wafer or substrate320attached to electronics wafer310, a piezoelectric element330supported by piezoelectric wafer320, a cap wafer or substrate340attached to piezoelectric wafer320, and a nozzle plate350attached to cap wafer340.

In one example, piezoelectric wafer320is attached to electronics wafer310with an adhesive layer360formed using adhesive transfer and bonding process100and/or adhesive transfer and bonding process200. In addition, in one example, cap wafer340is attached to piezoelectric wafer320with an adhesive layer370formed using adhesive transfer and bonding process100and/or adhesive transfer and bonding process200, and nozzle plate350is attached to cap wafer340with an adhesive layer380also formed using adhesive transfer and bonding process100and/or adhesive transfer and bonding process200.

In one example, electronics wafer310includes a fluid (or ink) feed hole312communicated with a supply of fluid (or ink), and piezoelectric wafer320includes fluidic routing communicated with fluid feed hole312of electronics wafer310such that application of an electrical signal to piezoelectric element330deflects piezoelectric element330and ejects fluid (or ink) through cap wafer340and out a nozzle352of nozzle plate350.

In one example, as illustrated inFIG. 4, fluidic routing of piezoelectric wafer320includes fluid channels322separated and formed by spaced ribs324, and includes pinch points326communicated with fluid channels322and formed by spaced posts328. Using adhesive transfer and bonding process100and/or adhesive transfer and bonding process200, adhesive is applied to ribs324and posts328for bonding of piezoelectric wafer320to electronics wafer310. By using adhesive transfer and bonding process100and/or adhesive transfer and bonding process200, a layer of self-patterned and self-aligned adhesive is applied to ribs324and posts328without blocking fluid channels322or spilling over the edges of ribs324to adjacent fluid channels322, and without blocking pinch points326or spilling over the edges of posts328.

By using adhesive transfer and bonding process100and/or adhesive transfer and bonding process200, as described herein, a self-aligned and self-patterned adhesive layer may be formed on a semiconductor die, wafer, and/or substrate while minimizing wicking or flow of adhesive beyond edges of an intended application area for the adhesive. In addition, with adhesive transfer and bonding process100and/or adhesive transfer and bonding process200, a thin layer of adhesive of substantially uniform thickness providing for a thin bond line may be selectively applied to a semiconductor die, wafer, and/or substrate having a topography of small or narrow features.