Release layer for subsequent manufacture of flexible substrates in microelectronic applications

Abstract

Compositions and methods are described for a release layer that is affixed directly onto a carrier or with the use of an interfacial adhesive layer to fabricate a flexible work product, and upon completion, the release layer is removed by an external applied force of a given value that overcomes the adhesive force without harm to the work product. The release layer serves as a permanent support for the manufacture of flexible electronic devices and upon completion offers a simple means to achieve a wide range of thin and ergonomically pleasing options for the consumer. The invention provides benefits of flexibility in choosing a host of materials to meet the needs of a specific manufacturing objective and rapidly moving towards the next step in the manufacture of semiconductors and flat panel displays.

Claims

1. A release layer comprising a binder material that is affixed to a rigid carrier substrate, and subsequently, with the aid of an external force, is removed from the rigid substrate without harm to the release layer and without the need for a subsequent cleaning process, wherein the release layer serves as a permanent substrate onto which is fabricated a flexible work product, wherein both release layer and work product are removed as one unit from the rigid carrier substrate, and wherein the binder is affixed directly to the carrier substrate without the aid of external adhesive and comprises organic and inorganic chemical families.

2. The release layer of claim 1, wherein the binder is affixed to the carrier substrate and comprises organic and inorganic chemical families which do not substantially outgas after curing.

3. The release layer of claim 1, wherein the binder comprises one or more chemical resins.

4. The release layer of claim 3, wherein the chemical resins of the binder comprise one or more from the group of epoxy, acrylate, silicone, urethane, rubber, and engineering polymers.

5. The release layer of claim 4, wherein the engineering polymers comprise one or more from the group of polyimide, polyamide, polyamideimide, polybenzimidazole, polybenzoxazole, polysulfone, polyethersulfone, polyphenylsulfone, polyarylether, polyetheretherketone, polyvinyidenedifluoride, cyclic olefin copolymer, polyethylene terephthalate, polybutylene terephthalate, polyacrylonitrile, polyaryletherketone, polyketoneketone, styrene-acrylonitrile, polycarbonate, polystyrene, polyvinylchloride, polyphenylene sulfide, polytrimethylene terephthalate, polyvinylidene chloride, acrylonitrile butadiene styrene, and liquid crystal polymer.

6. The release layer of claim 4, wherein the binder further comprises one or more polymer reaction initiators.

7. The release layer of claim 6, wherein the initiators comprise one or more from the group of organic acid, photoacid generator, photo base generator, organic amine, thermal free radical, and photo free radical initiators.

8. The release layer of claim 1, wherein the binder comprises one or more conjugated salts.

9. The release layer of claim 8, wherein the one or more conjugated salts comprise anions and cations.

10. The release layer of claim 9, wherein the anions comprise one or more of acetate, borate, bromate, carbonate, chlorate, chlorite, chromate, cyanamide, cyanide, dichromates, ferricyanide, ferrocyanide, phosphate, sulfate, nitrate, sulfite, oxide, oxalate, nitride, nitrite, hydroxide, hypochlorite, permanganate, silicate, stannate, stannite, tartrate, thiocyanate, and additionally halogen, hydrogen, oxygen, nitrogen, phosphorous and sulfur is represented as Y.sup.x , where Y is Br, Cl, F, H, I, O, N, P, and S, and x varies from 1-3.

11. The release layer of claim 9, wherein the cations comprise one or more of ammonium (NH4+), hydronium (H30+), and metal represented as M.sup.+n, where M includes Al, Sb, As, Ba, Be, Bi, Cd, Ca, Cr, Co, Cu, Fe, Pb, Li, Mg, Mn, Hg, Ni, K, Sc, Ag, Na, Sr, Sn, and Zn, and n varies from 1 to 5.

12. The release layer of claim 1, wherein the binder further comprises a filler.

13. The release layer of claim 12, wherein the filler comprises one or more from the group of nanoparticle, nanofiber, nanometal, fiber, glass bead, glass sphere, ceramic, and cellulose.

14. The release layer of claim 1 wherein the binder comprises one or more from the group of metal, ceramic, glass, and organic polymer.

15. The release layer of claim 1 wherein the binder is produced from evaporation and comprises one or more from the group of metal, ceramic, glass, and organic polymer.

16. The release layer of claim 1 wherein the binder is produced from plasma deposition and comprises one or more from the group of metal, ceramic, glass, and organic polymer.

17. The release layer of claim 1 wherein the binder is produced from electrolytic deposition and comprises one or more from the group metal, ceramic, glass, and organic polymer.

18. A manufacturing process using the release layer of claim 1, where the process is used in an electronics process.

19. The manufacturing process of claim 18 where the electronics process is used in a semiconductor process.

20. The manufacturing process of claim 19 where the electronics process is used in a display process.

21. The release layer of claim 1, where the release layer is exposed to elevated temperatures of 350 C. and outgassing is less than 0.5%.

Description

EXAMPLES

(1) The compositions of the invention and the method of making of the examples are described. It is understood, however, that the invention is not meant to be limited to the details described therein. In the examples, the percentages provided are percent (%) by weight unless otherwise stated. The invention is further illustrated, without limitation, by the following examples. The measurement of performance and selectivity of the invention is conducted using practices readily accepted by the industry.

(2) Coatings are produced on a Brewer Science, Inc. CB-100 spin-coater, while spray and encapsulation uses custom tooling designed at Daetec. Metrology data is generated by a XP-1 stylus profiler, AFP-200 atomic force profiler, and a Xi-100 optical profiler (www.kla-tencor.com), using equipment settings 5 mg stylus load, minimum 4 mm distance, and a speed of 0.5 mm/sec. Modified thermogravimetric test methodology for outgas is conducted by typical laboratory scales (+/0.1 mg). Furnace support uses box type #ST-1200C-121216 with microprocessor programming, nitrogen purge, and dispersion fan for chamber uniformity (www.sentrotech.com). Force gage M5-series with 90 degree configuration as tape peel with moving sled and stand ESM301, fixtures, and software (www.mark-10.com).

(3) Silicon wafers and glass plates (0.5 mm thick) are used as the inorganic substrate (carrier substrate) procured as display quality substrates (www.fitekcorp.com.tw). Onto these substrates, the material representing the release layer is applied, cured, and processed in a manner consistent with affixing of the solid work unit material (material make-up of the electronic device).

(4) The materials listed here form the basis for the survey, which the invention is demonstrated. Multiple materials are tested and described for each example. Where organic polymers are used, these resins are commonly dissolved into n,n-dimethylacetamide (DMAC), may exist as their monomer within n-methylpyrrolidone (NMP), or may exist as their monomer in a 100% solids system (no casting solvent) as a silicone. Polyimide samples include UBE u-varnish (UBE Industries, LTD, www.ube.com.jp) and U-imide series (Unitika Trading Company, LTD, www.unitika.co.jp). Silicone monomers exist as Silres series of flake resins 603, 805 (Wacker Chemical Corporation, www.wacker.com).

(5) Inorganic candidate release layers are prepared from various aqueous solutions containing nanoparticle fillers and having specific binder/filler ratios. Binder systems include lithium and potassium silicate (PQ Corporation, www.pqcorp.com). Fillers are present as fumed silica as Aerosil 200 nanoparticle and dispersions thereof, including Aerodisp W-series silica with various chemical pH additives (Evonik Deguss GmbH, www.aerosil.com). Polymer fixing agent is polyvinylpyrollidone (PVP), an aqueous dissolvable polymer used to maintain dispersion during cure (International Scientific Products Corporation, www.ispcorp.com).

(6) The following experiments demonstrate the thermal and mechanical properties of materials used as release coatings to form the substrate upon which fabrication of the microelectronic device proceeds.

Example #1

(7) The organic materials are chosen for their thermal resistance and tested by measuring outgassing as % weight loss when subjected to certain temperatures, commonly referred to a thermogravimetric analysis (TGA). Polymers are prepared in respective casting solvents and cured to 350C in oxygen atmosphere before testing. Results for TGA are shown in Table 1. Results suggest polyimide and POSS nanoparticle addition result in lowest outgas values over the thermal exposure.

(8) TABLE-US-00001 TABLE 1 TGA results of organic polymers for release layers. Outgas measurement as % wt loss for each exposure temperature (30 min). Preferred outgas levels are low and non-substantial. Release Layer 350 C. 400 C. 450 C. 500 C. PI - UBE U-Varnish -0- 8.56 9.81 10.80 PI - U Imide AR -0- 7.89 8.36 9.46 PI - U Imide C + POSS -0- 1.07 1.59 2.14 Veradel A301 -0- 2.07 3.80 14.36 (polyethersulfone) Silicone 805:603 blend -0- 9.70 25.08 35.55

Example #2

(9) Release layer candidates are applied to glass plates and cured to 350C. In the case of polyimide and silicone release layers, an interfacial silicone coating is applied to effect adhesive interaction with the substrate. Coating samples are subjected to thin film vacuum deposition of silicon dioxide at 400C. The single layer of thin film deposit is applied and subsequent temperature exposure is held at 400C for 30 min. Adhesion testing is performed before and after the deposition utilizing standard tape peel measurement with a force gage and using sample preparations with tape adhesion to the release layer. The adhesion test results are shown in Table 2.

(10) TABLE-US-00002 TABLE 2 Adhesion test performed as 90 degree manual pull, force as grams/cm. All materials which exhibited removal and quantified as adhesion force data are intact and free of residue, no cleaning is necessary. Before After Deposition Deposition Interfacial Peel Force Peel Force Release Layer adhesive (gF/cm) (gF/cm) PI - UBE U-Varnish Yes 19.4 38.9 PI - U Imide AR Yes 73.1 207.6 PI - U Imide C + POSS Yes 64.9 105 Silicone 805:603 blend None No Removal* No Removal* Veradel A301 None 5.7 15.1 (polyethersulfone) *No removal: release layer exhibited damage upon removal. Material is not intact.

Example #3

(11) Inorganic candidates for release layers are studied for their thermal resistance by thermogravametric analysis (TGA) using % wt loss by outgas. The baseline used is Veradel A301, polyethersulfone blend from examples #1 and #2. Inorganic polymers are blended with inorganic nanoparticles at various loading and cured to 350C to remove excessive water in the system. Inorganic systems are represented in normalized wt % content as follows: filler:PVP:silicate ratio, silicate described as lithium or potassium based product. For example, 60:30:10 Li is 60%/30%/10% as fumed silica/PVP/lithium silicate. The results are provided in Table 3.

(12) TABLE-US-00003 TABLE 3 TGA results of release layer candidates. Outgas measurement as % wt loss for each exposure temperature (30 min). Preferred outgas levels are low and non-substantial. Release 200 250 350 450 500 550 600 Layer C. C. C. C. C. C. C. 60:30:10 Li 0 0 0 0 0.21 0.2 0.52 60:30:10 K 0 0 0 0 0 0 0 25:1:74 Li 0 0 0 0.32 0.44 0.49 0.59 25:1:74 K 0 0 0 0.33 0.53 0.41 0.58 Veradel A301 0 0 0 2.08 10.68 40.28 58.46

Example #4

(13) Release layer coatings are prepared and applied to glass plates, coated and cured on to 350C. Cured release layers are subjected to thin film vacuum deposition of silicon dioxide at 400C. The single layer of thin film deposit is applied and subsequent temperature exposure is held at 400C for 30 min. An adhesion test is performed before and after the deposition. Inorganic systems are represented in normalized wt % content as follows: filler:PVP:silicate ratio, silicate described as lithium or potassium based product. For example, 60:30:10 Li is 60%/30%/10% would be fumed silica/PVP/lithium silicate. The adhesion test results on release layers with silicon dioxide deposition are shown in Table 4.

(14) TABLE-US-00004 TABLE 4 Peel test as 90 degree manual pull, results as pass/fail. All materials which exhibited removal as a pass by overcoming the respective adhesion force are intact and free of residue, no cleaning is necessary. Peel Force Peel Force (gF/cm) (gF/cm) Before After Release Layer Adhesive Deposition Deposition 60:30:10 Li Inorganic Blend Removal No Removal* 60:30:10 K Inorganic Blend Removal Removal 25:1:74 Li Inorganic Blend Removal Removal 25:1:74 K Inorganic Blend Removal No Removal* Veradel A301 No Adhesive Removal No Removal* *No removal: release layer exhibited damage upon removal. Material is not intact.