(12) Patent Application Publication (10) Pub. No.: US 2003/ A1

Transcription

1 US 2003O183916A1 (19) United Sttes (12) Ptent Appliction Publiction (10) Pub. No.: US 2003/ A1 Heck et l. (43) Pub. Dte: Oct. 2, 2003 (54) PACKAGING (22) Filed: Mr. 27, 2002 MICROELECTROMECHANICAL SYSTEMS Publiction Clssifiction (76) Inventors: John Heck, Mountin View, CA (US); Michele J. Berry, Chndler, AZ (US); (51) Int. Cl."... H01L 23/06 Dniel Wong, Fremont, CA (US); (52) U.S. Cl /684 Vlluri Ro, Srtog, CA (US) (57) ABSTRACT Correspondence Address: Timothy N. Trop A pckged microelectromechnicl System my be formed TROP, PRUNER & HU, PC. in hermetic cvity by forming the System on Semicon STE 100 ductor Structure nd covering the System with thermlly 8554 KATY FWY decomposing film. Tht film my then be covered by HOUSTON, TX (US) Seling cover. Subsequently, the thermlly decomposing mteril my be decomposed, forming cvity, which cn (21) Appl. No.: 10/107,624 then be Seled to hermeticlly enclose the System. 2Z, 2 2 ZZZZZZZZZZZYZZYZZYZZYZ h h....

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7 US 2003/ A1 Oct. 2, 2003 PACKAGING MICROELECTROMECHANICAL SYSTEMS BACKGROUND This invention reltes generlly to microelectrome chnicl Systems (MEMS) nd prticulrly to pckging for Such systems AMEMS device is generlly delicte mechnicl Structure formed by n etching technique tht llows the device to move freely. As result, there is need to encpsulte MEMS devices for controlling the pressure nd composition of the environment in which those devices operte. The devices lso need to be protected from destruc tive processes involved in Stndrd pckging including dicing nd clening. In ddition, there is need to reduce the cost of pckging MEMS devices by reducing the mount of die Spce used by the pckging. Generlly the more die Spce tht is utilized the more expensive the resulting MEMS Thus, there is need for better wys to pckge MEMS devices. BRIEF DESCRIPTION OF THE DRAWINGS 0004 FIG. 1 is n enlrged crosssectionl view of pckged MEMS device in ccordnce with one embodi ment of the present invention; 0005 FIG. 2 is n enlrged crosssectionl view t n erly stge of mnufcturing of the device shown in FIG. 1 in ccordnce with one embodiment of the present inven tion; 0006 FIG. 3 is n enlrged crosssectionl view of Subsequent Stge of mnufcturing in ccordnce with one embodiment of the present invention FIG. 4 is n enlrged crosssectionl view t Subsequent Stge of mnufcturing in ccordnce with one of the present invention; 0008 FIG. 5 is n enlrged crosssectionl view t Subsequent Stge of mnufcturing in ccordnce with one embodiment of the present invention; 0009 FIG. 6 is n enlrged crosssectionl view t Subsequent Stge of mnufcturing in ccordnce with one embodiment of the present invention; FIG. 7 is n enlrged crosssectionl view t Subsequent Stge of mnufcturing in ccordnce with one embodiment of the present invention; FIG. 8 is n enlrged crosssectionl view t Subsequent Stge of mnufcturing in ccordnce with one embodiment of the present invention; nd 0012 FIG. 9 is n enlrged crosssectionl view of nother embodiment of the present invention. DETAILED DESCRIPTION 0013 Referring to FIG. 1, pckge 10 my include microelectromechnicl system (MEMS) device 18 within cvity 22 defined between cover 20 nd semiconductor Structure 12. Openings 32 in the cover 20 my be plugged with the ptch 24 in one embodiment of the present inven tion Electricl connections from the outside world my be mde to the MEMS device 18 through n interconnection lyer 16 which is buried within the semiconductor structure 12. In prticulr, the interconnection lyer 16 my be bove lyer 14 nd below lyer 13 tht my be formed of ny dielectric mteril. In one embodiment, the lyer 13 is n oxide. As result, electricl connections cn be mde to the MEMS device 18, bypssing the cover 20 nd voiding the need to penetrte the cover 20. Penetrting the cover 20 my compromise the environment within the cvity 22, nd if the cover 20 is electriclly conductive, the electricl connec tions 16 would be electriclly shorted. In some embodi ments, the cvity 22 my be vcuum cvity but in generl, it my be desirble in mny embodiments to mintin hermetic Sel in the cvity Referring to FIG. 2, the fbriction of the pckge 10 shown in FIG. 1 begins by depositing scrificil lyer 15 on the semiconductor structure 12. The scrificil lyer 15 my include thermlly decomposing film tht my be formed for exmple by spinon process. The film my be one tht decomposes to form gs t tempertures bove 350 C. in one embodiment. In one embodiment the film my be polynorbornene tht decomposes t temperture of 425 C. The preprtion of polynorbornene is described in Bhusri et l., Fbriction of AirChnnel Structures for Microfluidic, Microelectromechnicl, nd Microelectronic Applictions, Journl of Microelectromechnicl Systems, Vol. 10, No. 3, September 2001 t pge 400. Polynorbornene functionlized with triethoxysilyl (TES) dheres to oxides so the lyer 13 my be n oxide in one embodiment Referring to FIG. 3, the film 15 my be ptterned using conventionl techniques to form n perture through the film 26. As shown in FIG. 4, the MEMS device 18 my be formed, for exmple, by depositing nd ptterning tech niques Referring to FIG. 5, second lyer 25 of the thermlly decomposing film my then be formed s shown in FIG. 5. As result of the imposition of the ptterned lyer 15 nd the MEMS device 18, humped configurtion my result in some embodiments. As shown in FIG. 6, the lyer 25 my be ptterned to form edges ) As shown in FIG. 7, cover 20 my be formed, for exmple, by deposition, encpsulting the MEMS device 18 nd the lyers 15 nd 25. Openings 32 my be formed in the cover using ptterning techniques in one embodiment of the present invention. The cover 20 my be formed of vriety of mterils including metl or dielectric or combintion of metls nd dielectrics tht cn form hermetic brrier. The openings 32 my be ptterned So tht the scrificil lyers 25 nd 15 my be removed by therml decomposition Referring to FIG. 8, the structure shown in FIG. 7 my be exposed to elevted tempertures tht cuse the lyers 15 nd 25 to thermlly decompose relesing the MEMS device 18 nd creting cvity 22 beneth the cover 20. In one embodiment the thermlly decomposed mteril Sublimtes in response to heting nd psses s gs through the openings 32. Any technique for heting the lyers 15 nd 25 cn be used including bking or exposure to infrred or other energy Sources Referring to FIG. 1, ptch 24 my simply be deposited or printed directly onto the holes 32 to sel the

8 US 2003/ A1 Oct. 2, 2003 cvity 22. In one embodiment the Seling process my be done in controlled environment So tht the cvity 22 contins the desired mbient gs t the desired pressure. The holes my be positioned fr enough wy from the device 18 tht the device 18 is not ffected by tht deposition process. The ptch 24 my be formed of epoxy, Solder, or frit glss s three exmples Referring next to FIG. 9, in ccordnce with nother embodiment of the present invention Seling mteril 34 my be formed over the entire cover 20, seling the holes 32 t the sme time. Seling the entire cover 20 my improve the cover's bility to mintin the hermetic cvity 22. In one embodiment, the cover 20 my be formed without openings 32 by mking the cover 20 sufficiently porous to pss the decomposed lyers 15 nd 25. In Such n embodiment, the Seling mteril 34 therefter provides the brrier needed to sel the cvity Some embodiments of the present invention my hve vrious dvntges. For exmple, Some embodiments my be dvntgeous becuse the relese process is done t the wfer level, eliminting the need for expensive dielevel processing. Prticulrly, the embodiments shown in FIGS. 19 my be wfers tht hve not yet been severed into dice. AS result, ll the processing shown in those figures, in Some embodiments, my be done t the wfer level. This elimintes the need for expensive dielevel processing in Some embodiments In ccordnce with some embodiments of the present invention, reltively smller mount of re on die is dedicted to encpsulting the MEMS devices 18. Agin, reducing the mount of die re devoted to the encpsultion technique reduces the cost of the resulting pckged product In some embodiments, the relese process uses therml decomposition film, eliminting ny Stiction prob lem. Stiction occurs in processes where liquid etchnt is used to relese MEMS structure. The liquidvpor menis cus forces delicte mechnicl elements into contct, where Solid bridging, Vn der Wls forces nd/or hydrogen bond ing my result in permnent bonding of the Structures In Some embodiments, the pckging process my be performed using Stndrd deposition nd etch processes. Such processes my be redily integrted into existing process flows In ddition, in some embodiments, once the device 18 is Seled, conventionl integrted circuit pckging tech niques my be utilized. Therefore, expensive Specilty pro cesses for MEMS pckging Such s wfer bonding my not be necessry While the present invention hs been described with respect to limited number of embodiments, those skilled in the rt will pprecite numerous modifictions nd vritions therefrom. It is intended tht the ppended clims cover ll Such modifictions nd vritions s fll within the true Spirit nd Scope of this present invention. Wht is climed is: 1. A method comprising: forming microelectromechnicl System on Semicon ductor Structure; covering Sid System with thermlly decomposing lyer; forming cover over Sid thermlly decomposing lyer; nd thermlly decomposing the thermlly decomposing lyer underneth Sid cover. 2. The method of clim 1 wherein thermlly decomposing includes cusing the thermlly decomposing lyer to Subli mte. 3. The method of clim 2 including forming openings in Sid cover to llow the relese of Sid Sublimted lyer. 4. The method of clim 3 including closing Sid openings fter Sid film hs been thermlly decomposed. 5. The method of clim 4 including coting Sid cover to close Sid openings. 6. The method of clim 4 including depositing Seling mteril over Sid openings without covering the entire COVC. 7. The method of clim 1 including llowing the thermlly decomposing mteril to escpe through Sid cover nd therefter Seling Sid cover. 8. The method of clim 1 including removing the ther mlly decomposing lyer nd forming hermetic cvity between Sid cover nd Sid structure round Sid micro electromechnicl System. 9. The method of clim 1 including providing n electricl connection to Sid microelectromechnicl System through Sid Semiconductor Structure. 10. The method of clim 1 including forming n electricl connection to Sid System without penetrting Sid cover. 11. A microelectromechnicl structure comprising: Semiconductor lyer; microelectromechnicl System formed on Sid lyer; thermlly decomposing lyer formed over Sid System; nd cover over Sid thermlly decomposing lyer. 12. The structure of clim 11 wherein sid structure is Semiconductor wfer. 13. The structure of clim 11 wherein sid thermlly decomposing lyer is formed of mteril tht decomposes t temperture bove 350 C. 14. The structure of clim 13 wherein sid mteril includes polynorbornene. 15. The structure of clim 11 wherein sid thermlly decomposing lyer is formed of mteril tht Sublimtes to form gs when heted. 16. The structure of clim 11 wherein sid cover is Sufficiently nonporous to define hermetic cvity. 17. The structure of clim 11 wherein sid cover includes plurlity of pertures through sid cover. 18. The structure of clim 11 including buried intercon nection lyer extending through sid Semiconductor lyer nd electriclly coupling Sid System. 19. The structure of clim 11 including first sublyer of thermlly decomposing mteril formed t lest prtilly beneth Sid System nd Second Sublyer of thermlly decomposing mteril formed over Sid System. 20. A pckged microelectromechnicl Structure com prising: Semiconductor lyer; microelectromechnicl System formed on Sid lyer;

9 US 2003/ A1 Oct. 2, 2003 cover over Sid System defining hermetic cvity between Sid cover nd Sid lyer nd Surrounding Sid System; nd Seling mteril over Sid cover to mintin Sid her metic cvity. 21. The structure of clim 20 wherein sid structure is Semiconductor die. 22. The structure of clim 20 wherein sid cover includes n perture through Sid cover. 23. The Structure of clim 22 including Seling ptch over Sid perture. 24. The structure of clim 20 wherein sid mteril extends over Sid entire cover. 25. The structure of clim 20 including buried intercon nection lyer coupled to Sid System nd extending out wrdly of sid cover.