摩擦化學(xué)反應(yīng)活化能對(duì)CMP的影響

卜小峰

摘要：

根據(jù)質(zhì)量作用定律，測定了銅膜在靜態(tài)腐蝕和化學(xué)機(jī)械拋光（Chemical Mechanical Polishing，CMP）兩種反應(yīng)條件下的化學(xué)反應(yīng)速率常數(shù)；通過Arrhenius方程，測定了銅膜在兩種反應(yīng)條件下的化學(xué)反應(yīng)活化能.結(jié)果表明：當(dāng)拋光液溫度為298.15 K，工作壓力為13 780 Pa時(shí)，靜態(tài)腐蝕條件下體系化學(xué)反應(yīng)速率常數(shù)是114.80 s-1，而CMP條件下體系的化學(xué)反應(yīng)速率常數(shù)是412.11 s-1，同時(shí)，CMP條件下的反應(yīng)活化能為4 849.80 J，靜態(tài)腐蝕條件下的反應(yīng)活化能為31 870.30 J，由此得出，反應(yīng)活化能的降低是CMP過程中的機(jī)械摩擦作用所致.因此，根據(jù)CMP過程中銅膜和拋光墊各自克服滑動(dòng)摩擦力所作的系統(tǒng)功，推導(dǎo)出CMP過程中活化能降低值的系統(tǒng)功表達(dá)式，并通過改變工作壓力和轉(zhuǎn)速來驗(yàn)證該表達(dá)式的適用性.

關(guān)鍵詞：

質(zhì)量作用定律； Arrhenius方程； 化學(xué)反應(yīng)； 活化能； 機(jī)械摩擦作用

中圖分類號(hào)： O 647； TN 43文獻(xiàn)標(biāo)志碼： A

Abstract：

According to the law of mass action，the reaction rate constants of copper film chemical reaction are measured under static corrosion and dynamic chemical mechanical polishing （CMP） process.The activation energy of copper film chemical reaction is acquired under the two kinds of reaction conditions above mentioned based on the Arrhenius equation.The results show that：as the slurry temperature is 298.15 K with working pressure 13 780 Pa during the CMP process，and the chemicalreaction rate constant of the system under the static corrosion condition is 114.80 s-1，and the reaction activation energy is 31 870.30 J，while the reaction rate constant increases to 412.11 s-1 and reaction activation energy decreases to 4 849.80 J under the CMP condition.Thus，the mechanical friction effect in the CMP process causes the decline of activation energy as a result. Therefore，according to the system power produced by the sliding friction between the copper film and the polishing pad in the CMP process，system power expression used for describing the decline of activation energy in the CMP process is calculated. And also the applicability of the expression has been verified by changing the work pressure and speed of the CMP process.

Keywords：

law of mass action； Arrhenius equation； chemical reaction； activation energy； mechanical friction effect

化學(xué)機(jī)械拋光（Chemical Mechanical Polishing，CMP）技術(shù)是目前半導(dǎo)體行業(yè)的重要加工手段，是當(dāng)前能夠?qū)崿F(xiàn)全局拋光的唯一實(shí)用技術(shù).探索更加溫和且更容易實(shí)現(xiàn)銅膜凹凸速率差的CMP工藝成為影響微電子產(chǎn)業(yè)發(fā)展的關(guān)鍵因素.大量文獻(xiàn)證實(shí)，CMP過程中材料去除速率并非化學(xué)和機(jī)械作用的簡單線性相加，而是遠(yuǎn)遠(yuǎn)大于兩者單獨(dú)作用之和.若再考慮到凹處和凸處不同材料的去除環(huán)境，問題將會(huì)更加復(fù)雜[1-3].部分文獻(xiàn)[4-5]認(rèn)為只要加入了BTA等一些腐蝕抑制劑，就能從根本上解決凹處速率快的問題，但并未考慮到由于機(jī)械摩擦作用而導(dǎo)致的鈍化膜脫落現(xiàn)象.也有部分文獻(xiàn)[6-7]認(rèn)為，溫和的反應(yīng)條件即大幅度削弱機(jī)械摩擦作用，有利于實(shí)現(xiàn)表面的拋光.因?yàn)樵诘蜋C(jī)械強(qiáng)度下，凹處所形成的鈍化膜難以脫落，而凸處的材料卻不斷被去除，由此循環(huán)往復(fù)，通過延長反應(yīng)時(shí)間來最終實(shí)現(xiàn)銅布線表面的拋光.但其并未考慮到拋光效率等因素，無法滿足工業(yè)生產(chǎn)的需要[7].基于此現(xiàn)象，本文以摩擦化學(xué)反應(yīng)活化能為切入點(diǎn)，通過質(zhì)量作用定律探究了CMP過程和靜態(tài)腐蝕過程的化學(xué)反應(yīng)活化能的差值，并通過Preston方程和Arrhenius方程分別對(duì)銅膜的凸處和凹處的材料去除機(jī)理進(jìn)行研究.

4 結(jié)論

通過靜態(tài)腐蝕和CMP過程中銅離子的絡(luò)合反應(yīng)，闡述了CMP過程中機(jī)械作用對(duì)化學(xué)反應(yīng)的影響.揭示了CMP過程中機(jī)械摩擦與化學(xué)反應(yīng)的協(xié)同作用機(jī)理，即CMP條件下速率提升的原因正是因?yàn)榛瘜W(xué)反應(yīng)活化能的降低，降低的數(shù)值被系統(tǒng)機(jī)械摩擦所產(chǎn)生的內(nèi)能所彌補(bǔ)，機(jī)械作用所帶來的最主要的效果是降低了化學(xué)反應(yīng)的活化能，即提高了活化分子的數(shù)量.

參考文獻(xiàn)：

[1]OH S，SEOK J.An integrated material removal model for silicon dioxide layers in chemical mechanical polishing processes[J].Wear，2009，266（7/8）：839-849.

[2]TSAI T C，TSAO W C，LIN W，et al.CMP process development for the viamiddle 3D TSV applications at 28 nm technology node[J].Microeletronic Engineering，2012，92（3）：29-33.

[3]ZHENG J P，ROY D.Electrochemical examination of surface films formed during chemical mechanical planarization of copper in acetic acid and dodecyl sulfate solutions[J].Thin Solid Films，2009，517（16）：4587-4592.

[4]NG D，KULKARNI M，JOHNSON J.Oxidation and removal mechanisms during chemicalmechanical planarization[J].Wear，2007，263：1477-1483.

[5]PANDIJA S，ROY D，BABU S V.Achievement of high planarization efficiency in CMP of copper at a reduced down pressure[J].Microelectronic Engineering，2009，86：367-373.

[6]YANG J C，OH D W，LEE G W.Step height removal mechanism of chemical mechanical planarization（CMP） for subnanosurface finish[J].Wear，2010，268（3/4）：505-510.

[7]KRISTIN G，SHATTUC K，JENG Y L，et al.Characterization of phosphate electrolytes for use in Cu electrochemical mechanical planarization[J].Electrochemical Acta，2008，53：8211-8216.

[8]王同慶，韓桂全，趙德文，等.拋光墊特性及其對(duì)300 mm晶圓銅化學(xué)機(jī)械拋光效果的影響研究[J].摩擦學(xué)學(xué)報(bào)，2013，33（4）：394-399.

[9]NOH K，SAKA N，CHUN J H.Effect of slurry selectivity on dielectric erosion and copper dishing in copper chemicalmechanical polishing[J].CIRP AnnalsManufacturing Technology，2004，53（1）：463-466.

（編輯：丁紅藝）