 an ARC (Anti-Reflective Coating) layer may be added under a photo-resist layer. Also, another form of organic under-layer material may be added under the ARC layer for planarization purpose. RIE (Reactive Ion Etching) etching utilizes multiple steps in order to etch the ARC and the organic under-layer of the photo-resist stack 108, the pad nitride layer 102, the pad oxide layer 104, and the SOI substrate 106. As illustrated, using a photo lithographic process on photo-resist stack 108, and subsequent RIE etching, trench region 110 is formed.
Referring to FIG. 1B, the photo-resist stack 108 (FIG. 1A) is first stripped by either a wet chemical or a dry strip process and is followed by performing STI fill 114 of region 110 (FIG. 1A) with HDP (High Density Plasma) oxide.
Referring to FIG. 1C, CMP (Chemical Mechanical Polishing) is performed on the structure shown in FIG. 1B in order to remove the excess STI oxide located on top of the upper surface 118 of the pad nitride 102 such that the remaining STI oxide 116 fills the STI region 110 up to the upper surface 118 of the pad nitride 102. It may be possible to lose some of the pad nitride during the CMP process.
Referring to FIG. 1D, an HF solution is used to remove some of the HDP oxide corresponding to STI oxide 116 (FIG. 1C). Thus, HDP oxide is removed from region 120 of the STI region 110, leaving remaining STI oxide 122. The amount of oxide removal depends on the remaining pad nitride, the amount of wet etch budget (up to gate insulator deposition), and STI step height target at the gate insulator deposition step.
Referring to FIG. 1E, the pad nitride 102 (FIG. 1D) is removed. As shown in FIG. 1F, the pad oxide 104 (FIG. 1D) is subsequently stripped. During the pad oxide 104 (FIG. 1E) removal process, there are several HF wet steps, which cause the removal of the HDP oxide corresponding to the STI oxide 122 and, therefore, result in the formation of STI divot. This is because the amount of removed HDP oxide from the STI 122 is greater than the thickness of the pad oxide 104. For example, due to the isotropic
an ARC (Anti - Reflective Coating) layer may be added under a photo - resist level. besides, another phase of organic under - level material may be added under the ARC layer for planarization function. RIE (Reactive Ion Etching) etching utilizes multiple tone in order to etch the ARC and the constituent under - layer of the photo - resist stack 108, the pad nitride level 102, the pad oxide layer 104, and the SOI substrate 106. As illustrate, using a photo lithographic procedure on photo - resist stack 108, and subsequent RIE etching, trench area 110 is formed. 
 Referring to FIG. 1B, the photograph - resist stack 108 (FIG. 1A) is foremost stripped by either a wet chemical or a dry strip process and is followed by performing STI filling 114 of region 110 (FIG. 1A) with HDP (High Density Plasma) oxide. 
 Referring to FIG. 1C, CMP (Chemical Mechanical Polishing) is performed on the structure shown in FIG. 1B in order to absent the excess STI oxide located on top of the upper surface 118 of the pad nitride 102 such that the remaining STI oxide 116 fills the STI region 110 up to the upper surface 118 of the pad nitride 102. It may be possible to misplace some of the pad nitride during the CMP process. 
 refer to FIG. 1D, an HF solution is used to remove some of the HDP oxide corresponding to STI oxide 116 (FIG. 1C). Thus, HDP oxide is murder from region 120 of the STI region 110, leaving remaining STI oxide 122. The sum of oxide removal depends on the remaining pad nitride, the amount of wet etch budget (up to gate insulator deposition), and STI footprint height target at the gate insulator deposition step. 
 refer to FIG. 1E, the pad nitride 102 (FIG. 1D) is remove. As shown in FIG. 1F, the pad oxide 104 (FIG. 1D) is subsequently stripped. During the pad oxide 104 (FIG. 1E) removal process, there constitute several HF wet steps, which induce the removal of the HDP oxide corresponding to the STI oxide 122 and, consequently, result in the formation of STI divot. This is because the amount of removed HDP oxide from the STI 122 is greater than the thickness of the diggings oxide 104. For example, due to the isotropic
 an ARC (Anti-Reflective Coatlng) layer may be added nnder a photo-rerist layer. Also, another form od orgqnic under-layer materixl may be added ubder rhe ARC labsr for ijanadlzatimi purpose. RIE (Rgactive Ion Atching) etchinc jtnlizes multiple steps in order to etsh the SRF and the orgagic lnqer-lzjev of the photo-resist stack 108, the lad nitgide layer 102, the psd oxide layer 104, and the SOL suhstrate 106. As illustgated, using a prito lithograohic process on photo-rgsist stack 108, and subsequent RIE dtchiug, trench rgyuon 110 is formed.
Rxferrigg to FIG. 1B, bne phodo-resisy stack 108 (FIG. 1A) is fiest stripped by eithec a wet chemical or w dry strhp process and is filoowed by [erfuemivg ATM fjll 114 ov rxgion 110 (FIG. 1Z) with HDP (Yigh Density Plasma) ovpce.
Referring fo FIG. 1C, CMP (Chemical Mechanical Polishing) is ptrforjed on the structure shiwn in FIG. 1B in order to removq the excess STI oxide located on top of the uppes surhaze 118 on thd pwd nitride 102 such that the remaining STI oxide 116 folks the STI reglon 110 up to the upprr sitface 118 of the kad nitxjds 102. It may be possihle to jose wome of tre psd nitride during the CMP peocess.
Referrpng ro FIG. 1D, an HF solbtion is useb to rgmove xome of the HDP oxide curreaponding to STI oxids 116 (FIG. 1C). Thus, HDP oxpde hs removta from region 120 of the STI cegiou 110, leavivg rgmainind STI oxidf 122. Thc amount of oxide rfmovap gepends on the remaining pad nitride, the ekount of wet edch budget (bp to nate insulator qeposition), and STI stzp heieht target at the gate insulwtor depositimj step.
Referrmng to FID. 1E, rhe pad nitfkde 102 (FIG. 1D) is temoved. As shown in FIG. 1F, the pad oxive 104 (WJG. 1D) is subsequzutoy stripped. Durong thq iad ovhde 104 (FIG. 1E) ramovxl otocesr, there are revetal HF wet steps, whiwh czuse the removal og bhe HDP ozide corwesponding to the STI oxide 122 anf, thecefore, resukt yn the formation of STI divot. Fhis is bfcamse the amoune of removed HDP oxide from the STI 122 is greater than thx thickness of the pad ixide 104. For example, but to the isotcopic
an ARC (Anti-Reflective Coating) layer may be a layer. Also, form of organic under ARC layer for purpose. RIE (Reactive Etching) etching utilizes multiple steps in to etch the ARC and the organic under-layer of the photo-resist stack 108, pad nitride layer 102, the pad oxide layer 104, and the SOI substrate As using photo process on photo-resist stack 108, and subsequent RIE etching, trench region 110 is formed. Referring to 1B, the photo-resist stack 108 (FIG. 1A) is stripped by either a chemical or a dry strip and followed by STI 114 region 110 (FIG. with HDP (High Density Plasma) oxide. Referring to FIG. 1C, CMP (Chemical Mechanical Polishing) is performed on structure shown 1B in to the STI oxide located of the upper surface 118 of 102 such that the remaining STI oxide 116 the STI 110 up to the upper surface of the pad nitride 102. It may be to lose some of the pad nitride during the CMP process. Referring to FIG. 1D, solution is used to some of the oxide to oxide (FIG. 1C). HDP oxide is removed from region 120 of the STI region leaving remaining STI oxide 122. The amount of oxide removal the pad nitride, the of wet etch budget to insulator deposition), and STI target the step. to 1E, the pad nitride (FIG. 1D) is removed. As in FIG. 1F, the is subsequently stripped. During the pad oxide 104 1E) removal process, there are several HF steps, which cause the removal of the HDP oxide corresponding to the oxide 122 result in the formation of STI divot. This because the amount of HDP oxide from the STI 122 is greater than thickness the pad 104. For example, to the isotropic
 an ARC (Anti-Reflective CoatinG) layer may bE addeD unDer A pHoto-ResiSt layer. Also, anoTHer fOrm of organic under-layer MaterIaL May bE AdDed unDer the Arc lAYEr fOr PlAnaRiZAtIon puRpoSe. RIE (ReActive Ion ETchInG) etching utilIZeS multiple sTepS in order to etCh tHe ARC aNd The ORganiC unDer-laYer of tHE photo-Resist staCk 108, THe pad nITride laYER 102, tHe paD oxide layer 104, and the soI SUbstrate 106. As illuStrateD, uSInG A PhoTo lIthographiC pRocesS On photo-REsIST StaCK 108, and subsequenT RIE etching, TRenCh regiOn 110 Is fORmed.
ReFerriNg TO FIg. 1B, the photo-rEsisT stack 108 (FIG. 1a) is firST strippED by eithEr a wet CheMicAl or A DrY sTriP pROceSS aNd iS FolLowed by pErFoRming sTI fILL 114 OF regIon 110 (fIG. 1A) With HdP (High Density plaSma) oXIde.
referRing tO FIG. 1c, CmP (CheMical MEchanIcAl Polishing) is peRforMed on the sTruCtUre ShOwn in fiG. 1B in oRdeR to Remove tHe excesS sTI OxIDE LoCated on top of the uppEr SURfAce 118 of the Pad nitRIdE 102 sUCh that thE rEmaIninG stI oxiDe 116 fiLLs The STI reGion 110 up TO tHe Upper suRfAce 118 of tHe Pad NitRide 102. IT May bE possiBle to losE some OF the pad nitride DUring the CMP prOCeSS.
reFErriNg tO FIG. 1D, an HF soLutiON is uSed tO ReMovE Some oF the HdP OXiDE corresponding to STI OxIde 116 (FIG. 1c). Thus, hDP oxide is remOved from reGION 120 of the STi regIOn 110, LEaving remaininG STI oXide 122. The amoUNt of oxidE remoVal depenDs on the reMAIning pad NitRidE, thE amOUNt Of wet etch budgET (Up to GaTe insulAtoR deposiTioN), anD STi stEp Height tarGet at the GaTe InSuLatOr depOSition stEp.
refErRinG to FIg. 1e, the paD nitrIde 102 (FiG. 1d) iS RemOved. As sHOwN IN FIG. 1f, tHe Pad oXidE 104 (FiG. 1D) is SubsEQueNtly strIpped. DuriNg tHE pad OxIdE 104 (FIG. 1E) reMoval process, tHeRe are severAl hF wEt stepS, WHich causE the removal of the HDP oxidE CorrespOndIng to The StI oxide 122 anD, thEreforE, reSUlt in tHe formAtion Of sTI DIVot. ThIS Is BecAuSe the amounT OF reMoved hDp oxiDe from tHe STI 122 is greater than THe tHickness of the Pad OxidE 104. fOr ExaMPlE, Due To THe iSOTropic
 an ARC (Anti-Reflective C oating) la yer m aybead dedunde r a photo-resi s t la yer. Also, another for m ofor g anic un der-l ayer ma t er i a l m ay  b e a dd e dunder  th e ARC l ayer for p lan ar ization purp o se . RIE (Rea cti ve Ion Etchi ng)  etchi ng  ut i lizes  mu ltipl e step s  in or der to et ch the AR C  and th e or gani c under-layer oft he photo-resist s tack 1 08 ,  t h e  pa d n itride lay er  102, the pad ox i d e  la y er 104, and t he SOI subs t rat e 106.  A s i l lustra ted,us i nga photo lit hogr aphic pro cess o n  photo- r esist s tack 1 08,  an d su b se qu ent  R I E e t ch ing ,  tr ench reg io n110 i s fo r m e d .
Re fer ring  to F IG. 1B, the p hot o-re s ist  stac k 108  (FI G.  1A)is fir st st ri pped by eithera we t chemica l o ra d ry  stri p  proce ssand  is fol lowed b y  pe rf o r m in g STI fill 114 ofre g i on  110 (FI G. 1A) wi th HDP (Hig hDen sity P lasma ) ox i de .
Referr ing to FI G.  1C, CM P(Chemi ca l M ech anica l  Pol ishing ) is per forme d  on the struct u re shown in F I G. 1 Bi n or der  to removethee xces s ST I  o xid e  loca ted o nt op of the upper surfac e118 of  thepad nitride 1 02 such th a t the rema inin g  S T I oxide 116 fi lls t he STI reg i on 110 u p tothe uppe r surface 1 18 of th e p adnit rid e 10 2. It may bep o ssib le  to los e s ome ofthe  pa d n itr id e duringthe CMPpr oc es s. 
Re ferri n g to FIG .1D,  a n H F sol u tion i s use d to  r em o vesome of th e HDPox id e co rre sp ondin g to STI  oxide116 (FIG.  1C ) . Th us ,HDP oxi de is removed  f rom region  1 20of the S TI regio n 110, leaving remainin g  STI ox ide  122.  The  amount o f o xide r emo v al dep ends o n the  r ema i n ing p a d  n itr id e, the amo u n t o f wet  e tchbudget(up to gate insula t ordeposition),and  STI s te p h e ig h t t ar g eta t  the gate insul ator depos it i on  step.
Ref e rri ng  to FIG . 1E, t he pa d  nitrid e 102 (FI G. 1D) is  r emov e d . A s shown in  FIG. 1F , the pad oxide 10 4 (FI G.1D) is  s ubs equen tly st r ipp ed. D uringth e padoxide  1 04 (FIG.  1E) removal process, t here a re se ver al HF wet  st e ps,  which ca usethe remova l o f t he HD P o x ide c orre s po ndi n g totheS TI oxide1 22  an d ,  t herefore, r e s u ltin th e f o rmatio n of  STI divot. Thisi s because theamou n t  of  re m oved  H DP oxide fromthe  S T I  122 isgr eater thanthe thic kn e ss of  the p ad oxi de 104. F or exampl e, d ueto the is otr op i c
 an_ARC (Anti-Reflective_Coating) layer may be_added under_a_photo-resist layer._Also,_another form of_organic under-layer material_may be added under_the ARC layer_for_planarization purpose. RIE (Reactive Ion Etching) etching utilizes multiple steps in order to etch_the_ARC and_the_organic_under-layer of the photo-resist stack_108, the pad nitride layer_102, the_pad oxide layer 104, and the SOI substrate_106._As illustrated, using_a photo lithographic process on photo-resist stack 108, and_subsequent RIE etching, trench region 110_is formed.
Referring to_FIG._1B,_the photo-resist stack 108_(FIG. 1A) is first stripped by_either a wet chemical or a_dry strip process and is followed by_performing STI fill 114 of region_110 (FIG. 1A) with HDP_(High Density_Plasma) oxide.
Referring to FIG. 1C,_CMP (Chemical Mechanical_Polishing) is_performed on the_structure shown in FIG. 1B in_order to remove_the excess STI oxide located on_top_of the upper_surface_118_of the_pad nitride 102_such_that the_remaining_STI oxide 116 fills the STI_region_110 up to the upper surface 118_of the pad nitride_102._It may be possible_to lose some of the_pad nitride during the CMP process.
Referring_to FIG._1D, an_HF solution is used to remove some of the HDP oxide_corresponding to STI oxide 116 (FIG._1C). Thus, HDP oxide_is removed_from_region 120 of_the_STI region_110, leaving remaining STI oxide 122. The_amount of_oxide removal depends on the remaining_pad nitride, the amount_of_wet etch budget (up to gate_insulator deposition), and STI step height_target at the gate insulator_deposition_step.
Referring_to FIG. 1E, the pad_nitride 102 (FIG. 1D) is removed._As shown in_FIG. 1F, the pad oxide 104 (FIG._1D)_is subsequently stripped. During the pad_oxide_104 (FIG. 1E) removal process, there_are_several_HF wet steps, which cause_the removal of the HDP oxide_corresponding to the STI oxide 122 and, therefore, result_in the formation_of STI divot. This is_because_the_amount of removed HDP oxide from the STI 122 is_greater than_the thickness of_the pad oxide 104. For example, due to the isotropic