US8558330 (Раздаточный материал)

US008558330B2(12) Ulllted States Patent(10) Patent N0.:Yu et al.(54)(45) Date of Patent:DEEP WELL PROCESS FOR MEMSPRESSURE SENSOR10/1977 Marshall ..................... .. 205/6564,618,397 A * 10/1986 ShimiZu et al.438/535,002,901 A * 3/1991 KurtZ et al.438/51*Shim-Chi“, Hsinchv 0W);Hollg-sellg Shue,HS1I1Ch11CO11I1Iy(TW)(73)Assignee: Taiwan Semiconductor Manufacturing.23533333?2 4 51332‘ $551“; Z‘1.a1.1..1:-5,511,428 A * 4/1996 Goldberg etal.Cm’Ltd” Hsin_chu (TW)patentSubjectistoextendedany disclaimer,or adjustedthe termunderof this35U.S.C.

154(1)) by 0 days.5/19965,643,803 A *7/ 1997 Fulfada et ?1~ ~5,869,876 A *2/1999 Ish10_et al.257/4196,020,618 A *2/2000257/419632183866 B1Q1 *4.6,293,149 B1*6,472,244.Appl' NO" 13/541’918(22)Flledi.B1 *.4/2001 gigilzteillétfwPoplevine etal. .9/2001 Yoshida et al.10/2002Ferrari et al.......326/10373/514.01. . . ..438/53257/419257/780B2*B2 *7,192,819 B1 *May 2,2013Sakai ........ ..7/2004 Wagenaar et al. .7,514,285US 2013/0105923 A1438/506/2004 Yoshihara et al.6,875,673 B2*Prior Publication Data257/4176,765,300 B1 *7,091,057(65)Hartauer ...... ..6,747,329 B2*6,826,320Jul- 5’ 2012111-233???73/7775,514,898 A **(21)Oct. 15, 20134,054,497 A *<75)( * ) Notice:US 8,558,330 B2B2 *7,514,287 B2 *11/2004DeliWala..

... .... . . ..4/2005 Ishio ......... ..8/2006Gan et al.. ... ... .... ... .. . . ..3/2007 Padmanabhan et al.4/2009Brown et al.385/14438/462.. .... ... .438/48438/197. . . ..438/504/2009 Huang et al. .................. .. 438/53(Continued)Related US. Application Data___Przmary Exammer * N DreW Rlchards(60)Provisional application No. 61/553,475, ?led on Oct.31’ 2011'Assistant Examiner i Ankush singal(74) Attorney, Agent, or Firm * EschWeiler & Associates,LLC(51)Int. Cl.G01L 9/00(2006.01)(52) US‘ Cl‘USPC ..........

.. 257/419, 257/E21.219, 257/E29.324,(57)ABSTRACTA micromechanical systems (MEMs) pressure sensorincludes a Semiconductor Substrate having a deep well257/E21'21/6’ 2_57/E/21'5_59’ 2/57/_E21'/599’located Within a ?rst surface and a cavity located Within aFleld of Classl?catlon SearchUSPC ......... .. 257/419, 1321.219, B29324, 1321.216,257/E21~559> B21599; 43863, 462> 622’?rst doping type. The deep Well has a second doping type,With a gradient doping pro?le’ thereby forming a PNjunCtiOnWithin the substrate. The cavity forms a diaphragm, Which is_(58)__(56)4_38 53’ 438 462’ 438 62’ 438 977__438/977See apphcanon ?le for Complete Search hlstory'R fCt de erences1 eU.S. PATENT DOCUMENTS3,893,228 A *7/1975George et al. .................

.. 438/534,033,787 A *7/1977Marshall ....................... .. 438/53second, opposing surface. The semiconductor substrate has aa substrate section that is thinner than the surrounding substrate sections, that comprises the deep Well. One or morepiZeoresistor elements are located Within the deep Well. ThepieZoresistors are sensitive to deformations, such as bending,in the diaphragm caused by changes in the pressure of thecavity.20 Claims, 7 Drawing Sheets100-3‘122L,CDUS 8,558,330 B2Page 2(56)References CitedU.S. PATENT DOCUMENTS7,527,997 B2 *8,330,224 B2 *2004/0253760 A1*2006/0141659 A1*5/2009Xu et a1........................ .. 438/5212/2012Kwa......

..12/2004Zhang et a1. .................. .. 438/53. 257/3516/2006Gan etal. ...................... .. 438/512007/01643792008/00613742008/02782792010/03045182012/00129492012/0081171A1* 7/2007 Brown et a1. ............... .. 257/417A1* 3/2008 Chiang et a1.257/371A1* 11/2008 Chiang et a1. ...............

.. 338/311A1* 12/2010 Suminto et a1. ............... .. 43 8/51A1* 1/2012 Winkler et a1. .257/415A1* 4/2012 Tan et a1. .................... .. 327/427* cited by examinerUS. Patent1000a. 15, 2013Sheet 1 of7N122FIG. 2US 8,558,330 B2US. Patent0a. 15, 2013Sheet 2 of73001‘DLogofno-ptiynpgeUS 8,558,330 B2[-306(conme’tr\a-i3)Q\iz‘zéiééfééfo?fzDepth from wafer surface (um)FIG. 3404“~104104i106FIG. 4R192US. Patent0a. 15, 2013Sheet 3 of7US 8,558,330 B2Provide semiconductor substratePerform deep well implant[-506Drive in deep4' well implant[-508lForm MEMs pressure sensor within substrate having deep well— — — — — — — — ——I———————~-—-.L Form protective layer(s) on backside of substrate516[I - - - ~ - - - ~ --I- - — - ~ - - ~ -—-,Ll —Form metallization layer(s)———~———--—I—~———518(r~———~—-1520L Forming passivation layer above metallization layer fl—Selectively remove protectivelagler fronTbacksideof-qlf' 522lI -substrate~~---m--~I--|---~_----1L_Perform electrochemically controlled etching process I524F510US.

Patent0a. 15, 2013Sheet 4 of7US 8,558,330 B2FIG.6jwmmiwi;FIG.7$$$$$$$5$5$5$$5W122.FIG. 8US. Patent0a. 15, 2013Sheet 5 of7US 8,558,330 B290o-\4llllllllHQ“I@HLgL£332K106F|G.91000-N7'[1102US. Patent0a. 15, 2013Sheet 6 of7US 8,558,330 B2122XI1__2_K1102FIG. 121soo-\41102FIG. 13US. Patent14000a. 15, 2013Sheet 7 of7US 8,558,330 B2[1404\Potentiostatr124 1406eRlfctronde122/eCloucntred104 &1102FIG.

14r116r114/-1o4AW102Ar1102124Kj110FIG. 15US 8,558,330 B212DEEP WELL PROCESS FOR MEMSPRESSURE SENSORdeep Well abuts the cavity. The cavity forms a pliable diaphragm Within the substrate having a thickness that is de?nedby the depth of the deep Well.In yet another embodiment, the present disclosure relatesBACKGROUNDto a MEMs pressure sensor. The MEMs pressure sensor comprises a p-type non-epitaxial silicon substrate. A diaphragm isPieZoresistive micromechanical system (MEM) pressuresensors are con?gured to translate a pressure into an electricallocated Within a top side of the non-epitaxial silicon substrate.signal corresponding to the pressure.

Normally, a pieZoresisAn n-type deep Well having a gradient doping pro?le istive MEMs pressure sensor comprises a pliable diaphragmlocated Within the diaphragm. One or more p-type shalloWWells that operate as piezoelectric resistors are located Withinhaving one or more resistive elements diffused into it. Thediaphragm is con?gured to measure a pressure Within anthe n-type deep Well. A cavity is located Within the backsideof the non-epitaxial silicon substrate and abuts the diaphragm. A pressure Within the cavity is con?gured to generatea force that acts upon the diaphragm to change the pieZoelecadjacent cavity based upon resistive changes caused by aforce that the pressure exerts on the diaphragm.

For example,a high pressure Within an adjacent cavity causes the diaphragm to bend in a ?rst direction that compresses the resistric resistors’ resistance as a function of pressure Within thecavity.tive element, thereby decreasing the resistance. Alternatively,The folloWing description and annexed draWings set forthin detail certain illustrative aspects and implementations ofa loW pressure in the cavity causes the diaphragm to bend ina second direction that expands the resistive elements,thereby increasing the resistance.the disclosure. These are indicative of but a feW of the various20The diaphragm is formed Within a silicon substrate usingan electrochemically controlled etching (ECE) process.

TheWays in Which the principles of the disclosure may beemployed.ECE process utiliZes a Wafer comprising a p-type substrateBRIEF DESCRIPTION OF THE DRAWINGSWith an n-type epitaxial layer formed thereupon. During etching, the Wafer is immersed in an etchant (e.g., a KOH bath),and a controlled bias is applied betWeen the n-type epitaxiallayer and the etchant. A PN junction, formed at the border ofthe n-type epitaxial layer and the p-type substrate, acts as a25comprising a deep Well.FIG.

2 illustrates an exemplary embodiment of a diaphragm of a MEMs pressure sensor in various stages ofreverse-biased diode preventing the etchant from beingexposed to any current, so that the etchant performs a normalanisotropic etch through the substrate until it reaches thejunction. Then, because the diode has been etched aWay, theetchant is exposed to the applied bias, and a reaction forms athin layer of silicon dioxide on the substrate, Which stops theetch.SUMMARYThe folloWing presents a simpli?ed summary in order toFIG. 1 illustrates a cross sectional vieW of an embodimentof a MEMs pressure sensor having a pieZoresistive element30operation.FIG.

3 illustrates a graph shoWing a simulation of thedoping pro?le of a MEMs pressure sensor deep n-Well, inaccordance With an embodiment.FIG. 4 illustrates a cross sectional vieW of an embodiment35 of a monolithic MEMs pressure sensor.FIG. 5 is a How diagram of an exemplary embodiment of amethod for forming a MEMs pressure sensor.FIGS.

6-15 are cross-sectional vieWs of some embodiments of an example semiconductor substrate upon Which a40provide a basic understanding of one or more aspects of thedisclosure. This summary is not an extensive overvieW of themethod of forming a MEMs pressure sensor is performed.DETAILED DESCRIPTIONdisclosure, and is neither intended to identify key or criticalelements of the disclosure, nor to delineate the scope thereof.Rather, the primary purpose of the summary is to present45The description herein is made With reference to the draWings, Wherein like reference numerals are generally utiliZed,prelude to the more detailed description that is presented later.to refer to like elements throughout, and Wherein the variousstructures are not necessarily draWn to scale. In the folloWingIn an embodiment, the present disclosure relates to adescription, for purposes of explanation, numerous speci?csome concepts of the disclosure in a simpli?ed form as amethod of MEMs processing.

The method comprises providing a semiconductor substrate having a ?rst doping type. Adeep Well having a second doping type is formed Within the50semiconductor substrate. One or more shalloW Wells havingdetails are set forth in order to facilitate understanding. It Willbe appreciated that the details of the ?gures are not intendedto limit the disclosure, but rather are non-limiting embodiments.

For example, it may be evident, hoWever, to one ofthe ?rst doping type are formed Within the deep Well, Whereinordinary skill in the art, that one or more aspects describedthe one or more shalloW Wells operate as resistive elementsherein may be practiced With a lesser degree of these speci?cWithin the deep Well. A backside of the semiconductor substrate is selectively etched by performing an electrochemically controlled etching (ECE) process to form a cavity abut55details. In other instances, knoWn structures and devices are60shoWn in block diagram form to facilitate understanding.Some aspects of the present disclosure provide for a micromechanical system (MEMs) pressure sensor comprising asemiconductor substrate having a ?rst doping type (e.g.,p-type).