摘要(yao)：硅(gui)(gui)片(pian)(pian)背(bei)面(mian)磨(mo)削減薄工藝中，機械磨(mo)削使硅(gui)(gui)片(pian)(pian)背(bei)面(mian)產生(sheng)損傷(shang)，導(dao)致表(biao)(biao)面(mian)粗(cu)(cu)(cu)糙，且發生(sheng)翹(qiao)曲(qu)(qu)變形。分別采(cai)用(yong)粗(cu)(cu)(cu)磨(mo)、精磨(mo)、精磨(mo)后(hou)(hou)拋(pao)光(guang)和(he)(he)(he)精磨(mo)后(hou)(hou)濕法(fa)腐蝕等四種不同背(bei)面(mian)減薄方(fang)法(fa)對15．24cm（6英(ying)寸）硅(gui)(gui)片(pian)(pian)進(jin)行了(le)(le)(le)背(bei)面(mian)減薄，采(cai)用(yong)掃(sao)描電(dian)子顯(xian)(xian)微鏡(jing)對減薄后(hou)(hou)的(de)硅(gui)(gui)片(pian)(pian)表(biao)(biao)面(mian)和(he)(he)(he)截面(mian)形貌(mao)進(jin)行了(le)(le)(le)表(biao)(biao)征，用(yong)原子力顯(xian)(xian)微鏡(jing)測(ce)(ce)試了(le)(le)(le)硅(gui)(gui)片(pian)(pian)表(biao)(biao)面(mian)的(de)粗(cu)(cu)(cu)糙度(du)(du)，用(yong)翹(qiao)曲(qu)(qu)度(du)(du)測(ce)(ce)試儀測(ce)(ce)試了(le)(le)(le)硅(gui)(gui)片(pian)(pian)的(de)翹(qiao)曲(qu)(qu)度(du)(du)。結果表(biao)(biao)明，經過粗(cu)(cu)(cu)磨(mo)與精磨(mo)后(hou)(hou)的(de)硅(gui)(gui)片(pian)(pian)存在機械損傷(shang)，表(biao)(biao)面(mian)粗(cu)(cu)(cu)糙且翹(qiao)曲(qu)(qu)度(du)(du)大，粗(cu)(cu)(cu)糙度(du)(du)分別為0．15和(he)(he)(he)0．016μm，翹(qiao)曲(qu)(qu)度(du)(du)分別為147和(he)(he)(he)109μm；經過拋(pao)光(guang)和(he)(he)(he)濕法(fa)腐蝕后(hou)(hou)的(de)樣(yang)品無(wu)表(biao)(biao)面(mian)損傷(shang)，粗(cu)(cu)(cu)糙度(du)(du)均小于0．01μm，硅(gui)(gui)片(pian)(pian)翹(qiao)曲(qu)(qu)度(du)(du)低于60μm。
硅片(pian)(pian)(pian)背面(mian)減(jian)(jian)薄(bo)是一(yi)步重(zhong)要的(de)(de)硅片(pian)(pian)(pian)制造(zao)工藝(yi)(yi)，目(mu)的(de)(de)是去除(chu)硅片(pian)(pian)(pian)背面(mian)多(duo)余(yu)材料(liao)，以有(you)效減(jian)(jian)小硅片(pian)(pian)(pian)封裝(zhuang)體積，降低(di)熱(re)阻，提高(gao)(gao)器件(jian)(jian)的(de)(de)散熱(re)性(xing)能(neng)，降低(di)封裝(zhuang)后芯(xin)片(pian)(pian)(pian)因(yin)受(shou)熱(re)不均而(er)開裂(lie)的(de)(de)風險，提高(gao)(gao)產品可(ke)靠性(xing)；同(tong)時，減(jian)(jian)薄(bo)后的(de)(de)芯(xin)片(pian)(pian)(pian)機械(xie)性(xing)能(neng)與(yu)電(dian)氣性(xing)能(neng)也得到顯(xian)著提高(gao)(gao)。硅片(pian)(pian)(pian)背面(mian)減(jian)(jian)薄(bo)技(ji)(ji)術(shu)(shu)有(you)很(hen)多(duo)種，如(ru)磨(mo)削、拋(pao)(pao)光(guang)(guang)、干式拋(pao)(pao)光(guang)(guang)、電(dian)化(hua)(hua)(hua)學(xue)(xue)腐(fu)(fu)蝕(shi)、濕法腐(fu)(fu)蝕(shi)、等離(li)子輔助化(hua)(hua)(hua)學(xue)(xue)腐(fu)(fu)蝕(shi)和(he)常壓(ya)等離(li)子腐(fu)(fu)蝕(shi)等。其中硅片(pian)(pian)(pian)磨(mo)削減(jian)(jian)薄(bo)技(ji)(ji)術(shu)(shu)是一(yi)種效率高(gao)(gao)、成本較低(di)的(de)(de)減(jian)(jian)薄(bo)技(ji)(ji)術(shu)(shu)，已得到廣泛應用。該技(ji)(ji)術(shu)(shu)通過(guo)砂輪在(zai)(zai)硅片(pian)(pian)(pian)表面(mian)旋轉施壓(ya)、損傷、破裂(lie)、移除(chu)而(er)實現(xian)硅片(pian)(pian)(pian)減(jian)(jian)薄(bo)。工藝(yi)(yi)中不可(ke)避免(mian)引入損傷，降低(di)器件(jian)(jian)可(ke)靠性(xing)和(he)穩定性(xing)。拋(pao)(pao)光(guang)(guang)工藝(yi)(yi)采用硅片(pian)(pian)(pian)與(yu)拋(pao)(pao)光(guang)(guang)頭之(zhi)間相對運動來(lai)平坦化(hua)(hua)(hua)硅片(pian)(pian)(pian)表面(mian)，在(zai)(zai)硅片(pian)(pian)(pian)和(he)拋(pao)(pao)光(guang)(guang)頭之(zhi)間有(you)磨(mo)料(liao)；濕法化(hua)(hua)(hua)學(xue)(xue)腐(fu)(fu)蝕(shi)是一(yi)種通過(guo)腐(fu)(fu)蝕(shi)液(ye)(ye)與(yu)硅片(pian)(pian)(pian)發生化(hua)(hua)(hua)學(xue)(xue)反應實現(xian)硅片(pian)(pian)(pian)減(jian)(jian)薄(bo)的(de)(de)工藝(yi)(yi)技(ji)(ji)術(shu)(shu)，常用的(de)(de)腐(fu)(fu)蝕(shi)液(ye)(ye)有(you)酸(suan)性(xing)腐(fu)(fu)蝕(shi)液(ye)(ye)（如(ru)硝(xiao)酸(suan)、冰乙酸(suan)與(yu)氫氟酸(suan)）和(he)堿(jian)性(xing)腐(fu)(fu)蝕(shi)（如(ru)KOH溶(rong)液(ye)(ye)［1］）。
本(ben)文以15．24cm（6英寸）硅(gui)片背(bei)面減(jian)薄(bo)為例，通過對經(jing)過磨(mo)削(xue)(xue)、磨(mo)削(xue)(xue)后拋光與(yu)磨(mo)削(xue)(xue)后濕法腐蝕工(gong)藝后硅(gui)片的損傷(shang)、表面粗糙度與(yu)翹曲度的分析(xi)，優化(hua)硅(gui)片背(bei)面減(jian)薄(bo)技術。
取(qu)4片(pian)6英寸單(dan)(dan)晶硅片(pian)，硅片(pian)厚(hou)度(du)為(wei)(wei)675μm，正面(mian)(mian)貼保(bao)護膜，保(bao)護膜厚(hou)度(du)為(wei)(wei)140μm；采(cai)用方達(da)(da)科(ke)技(ji)單(dan)(dan)片(pian)研磨(mo)(mo)機對(dui)硅片(pian)進行(xing)(xing)磨(mo)(mo)削(xue)(xue)減薄(bo)加(jia)工(gong)，加(jia)工(gong)選用325＃－DISCO砂(sha)(sha)輪(lun)，砂(sha)(sha)輪(lun)粒度(du)為(wei)(wei)40～60μm，將4片(pian)6英寸硅片(pian)減薄(bo)140μm至(zhi)535μm，取(qu)出其中1個(ge)樣(yang)品，編號(hao)為(wei)(wei)1＃；接著采(cai)用方達(da)(da)單(dan)(dan)面(mian)(mian)研磨(mo)(mo)機對(dui)余下3個(ge)樣(yang)品進行(xing)(xing)精磨(mo)(mo)削(xue)(xue)加(jia)工(gong)，加(jia)工(gong)選用2000＃－DISCO砂(sha)(sha)輪(lun)，砂(sha)(sha)輪(lun)粒度(du)為(wei)(wei)4～6μm，去除硅片(pian)厚(hou)度(du)為(wei)(wei)30μm，取(qu)出其中1個(ge)樣(yang)品，編號(hao)為(wei)(wei)2＃；對(dui)余下的兩個(ge)樣(yang)品，一(yi)個(ge)采(cai)用方達(da)(da)科(ke)技(ji)單(dan)(dan)面(mian)(mian)拋光機進行(xing)(xing)化學(xue)機械拋光40min，編號(hao)為(wei)(wei)3＃，另一(yi)個(ge)用濕法(fa)化學(xue)腐蝕(shi)方式減薄(bo)，腐蝕(shi)時間5min，編號(hao)為(wei)(wei)4＃。濕法(fa)腐蝕(shi)采(cai)用硝酸、冰乙(yi)酸和氫氟(fu)酸混(hun)合液腐蝕(shi)液，體積比為(wei)(wei)硝酸∶冰乙(yi)酸∶氫氟(fu)酸＝5∶4∶1，反(fan)應原(yuan)理如下［2］：
完(wan)成上述減薄工藝(yi)后，去除樣(yang)品(pin)(pin)(pin)正面(mian)保護膜，清洗，然后采用Mitotuyo厚度(du)(du)測試儀測試樣(yang)品(pin)(pin)(pin)厚度(du)(du)，用翹曲(qu)度(du)(du)測試儀測試樣(yang)品(pin)(pin)(pin)翹曲(qu)度(du)(du)，采用FEG450掃描(miao)電子顯微(wei)(wei)鏡(jing)(jing)觀察樣(yang)品(pin)(pin)(pin)表面(mian)和截面(mian)形貌，用原子力顯微(wei)(wei)鏡(jing)(jing)測試樣(yang)品(pin)(pin)(pin)粗糙度(du)(du)。
2．1表面形貌分析
圖2是減(jian)薄后樣(yang)品(pin)(pin)表(biao)(biao)面(mian)掃描電子(zi)形貌圖（SEM）。由圖可見，1＃樣(yang)品(pin)(pin)表(biao)(biao)面(mian)粗(cu)糙、起伏大，存在凸起與凹坑；2＃樣(yang)品(pin)(pin)表(biao)(biao)面(mian)存在大量(liang)細小劃痕。原子(zi)力顯微鏡測試得出(chu)1＃樣(yang)品(pin)(pin)與2＃表(biao)(biao)面(mian)粗(cu)糙度Ra分(fen)別為0．15和(he)0．016μm。
單晶硅材料的原子在晶體內部按照金剛石結構周期性排列，硅片背面磨削減薄是一種物理損傷工藝，砂輪的磨削會破壞硅原子內部的周期性排列順序，在硅片表面產生機械損傷。對比圖2（a）與圖2（b）可知，樣品表面形貌和表面粗糙度與研磨所用砂輪有關，砂輪粒度越小，硅片表面越平整，粗糙度越小。
圖(tu)2（c）和圖(tu)2（d）分別(bie)為(wei)3＃與4＃樣(yang)品(pin)表(biao)面(mian)(mian)(mian)形貌(mao)圖(tu)，對比兩圖(tu)可見，化學(xue)機械(xie)(xie)拋(pao)光后樣(yang)品(pin)表(biao)面(mian)(mian)(mian)平整，沒(mei)有磨(mo)削(xue)劃(hua)痕，濕(shi)(shi)(shi)法(fa)腐(fu)(fu)蝕(shi)后樣(yang)品(pin)表(biao)面(mian)(mian)(mian)依然可見砂輪磨(mo)削(xue)留下的(de)劃(hua)痕。3＃與4＃樣(yang)品(pin)表(biao)面(mian)(mian)(mian)粗(cu)糙(cao)(cao)度Ra分別(bie)為(wei)0．001和0．008μm。化學(xue)機械(xie)(xie)拋(pao)光工(gong)藝(yi)(yi)是一種全局性(xing)平坦(tan)化工(gong)藝(yi)(yi)，由(you)上述結(jie)果可知，拋(pao)光工(gong)藝(yi)(yi)有效地改善(shan)了硅片表(biao)面(mian)(mian)(mian)形貌(mao)；腐(fu)(fu)蝕(shi)工(gong)藝(yi)(yi)后樣(yang)品(pin)表(biao)面(mian)(mian)(mian)粗(cu)糙(cao)(cao)度降低，結(jie)合酸性(xing)濕(shi)(shi)(shi)法(fa)腐(fu)(fu)蝕(shi)工(gong)藝(yi)(yi)是一種各向同性(xing)腐(fu)(fu)蝕(shi)工(gong)藝(yi)(yi)［3］，樣(yang)品(pin)表(biao)面(mian)(mian)(mian)損傷與凸起部分被優先腐(fu)(fu)蝕(shi)，可見濕(shi)(shi)(shi)法(fa)腐(fu)(fu)蝕(shi)可改善(shan)硅片表(biao)面(mian)(mian)(mian)形貌(mao)。4個樣(yang)品(pin)表(biao)面(mian)(mian)(mian)粗(cu)糙(cao)(cao)度Ra見表(biao)2所示。
2．2截面形貌分析
圖(tu)3為樣(yang)(yang)品截(jie)(jie)面(mian)形貌圖(tu)（SEM），可(ke)見(jian)1＃樣(yang)(yang)品截(jie)(jie)面(mian)粗糙，截(jie)(jie)面(mian)存在裂紋，2＃樣(yang)(yang)品截(jie)(jie)面(mian)平直，有微(wei)裂紋。由(you)圖(tu)可(ke)知(zhi)，樣(yang)(yang)品截(jie)(jie)面(mian)損傷層厚度分別為5．382與(yu)1．115μm。
硅片磨削減薄是一種物理性損傷工藝，根據Hadamovsky提出的損傷層模型［4］，機械研磨減薄工藝后，基體硅之上存在著損傷層，損傷層自上而下分為多層結構。結合上述實驗可知，損傷層厚度與研磨硅片砂輪粒度有關，砂輪粒度越大，磨削產生的損傷層越大，硅片表面越粗糙。3＃與4＃樣品截面圖如圖3（c）與圖3（d）所示，樣品截面無損傷層，結合上文可知，拋光工藝和濕法腐蝕工藝去除了樣品表面的機械損傷，減薄后樣品厚度以及表面損傷層厚度如表3所示。表3中還列出了樣品的翹曲度，由表中可知，樣品翹曲度與表面損傷層厚度相關，如圖4所示，損傷層厚度越大，翹曲度也越大。硅片表面的機械損傷破壞了硅片晶體結構，降低硅片強度，增大硅片在傳遞過程中碎片率，影響后續工藝的可靠性與穩定性，降低了產品成品率。拋光工藝和濕法腐蝕不僅可以去除硅片表面損傷層，還降低了硅片翹曲度，有效提高減薄后硅片質量，這對提高生產線成品率，拓寬元器件使用條件，提高元器件使用性能，延長使用壽命等都具有極其重要的意義。
硅(gui)(gui)(gui)片(pian)(pian)(pian)(pian)背面(mian)(mian)(mian)(mian)(mian)機(ji)械研(yan)磨減(jian)(jian)薄(bo)是一種物(wu)理損(sun)傷(shang)(shang)工藝(yi)，減(jian)(jian)薄(bo)會在硅(gui)(gui)(gui)片(pian)(pian)(pian)(pian)表(biao)(biao)(biao)面(mian)(mian)(mian)(mian)(mian)引(yin)入(ru)機(ji)械損(sun)傷(shang)(shang)。文中對比分析了(le)粗(cu)(cu)磨、精磨、拋(pao)(pao)光和濕法(fa)腐蝕(shi)工藝(yi)后硅(gui)(gui)(gui)片(pian)(pian)(pian)(pian)表(biao)(biao)(biao)面(mian)(mian)(mian)(mian)(mian)與(yu)截面(mian)(mian)(mian)(mian)(mian)形(xing)貌(mao)(mao)，并且測試了(le)硅(gui)(gui)(gui)片(pian)(pian)(pian)(pian)厚(hou)度(du)(du)(du)、粗(cu)(cu)糙(cao)度(du)(du)(du)和翹(qiao)曲(qu)(qu)度(du)(du)(du)，結(jie)合(he)理論分析，得(de)到(dao)結(jie)論如下(xia)：機(ji)械研(yan)磨減(jian)(jian)薄(bo)工藝(yi)中硅(gui)(gui)(gui)片(pian)(pian)(pian)(pian)表(biao)(biao)(biao)面(mian)(mian)(mian)(mian)(mian)形(xing)貌(mao)(mao)和損(sun)傷(shang)(shang)層(ceng)厚(hou)度(du)(du)(du)和研(yan)磨減(jian)(jian)薄(bo)砂輪粒度(du)(du)(du)有(you)關，砂輪粒度(du)(du)(du)越(yue)(yue)大(da)，硅(gui)(gui)(gui)片(pian)(pian)(pian)(pian)表(biao)(biao)(biao)面(mian)(mian)(mian)(mian)(mian)越(yue)(yue)不平整，粗(cu)(cu)糙(cao)度(du)(du)(du)也(ye)越(yue)(yue)大(da)，損(sun)傷(shang)(shang)層(ceng)厚(hou)度(du)(du)(du)越(yue)(yue)大(da)。采用(yong)粗(cu)(cu)磨與(yu)精磨結(jie)合(he)減(jian)(jian)薄(bo)的(de)(de)方法(fa)，可(ke)(ke)以改善(shan)硅(gui)(gui)(gui)片(pian)(pian)(pian)(pian)表(biao)(biao)(biao)面(mian)(mian)(mian)(mian)(mian)形(xing)貌(mao)(mao)，降低(di)硅(gui)(gui)(gui)片(pian)(pian)(pian)(pian)表(biao)(biao)(biao)面(mian)(mian)(mian)(mian)(mian)損(sun)傷(shang)(shang)層(ceng)厚(hou)度(du)(du)(du)；濕法(fa)腐蝕(shi)與(yu)拋(pao)(pao)光工藝(yi)可(ke)(ke)以改善(shan)硅(gui)(gui)(gui)片(pian)(pian)(pian)(pian)表(biao)(biao)(biao)面(mian)(mian)(mian)(mian)(mian)形(xing)貌(mao)(mao)，去除硅(gui)(gui)(gui)片(pian)(pian)(pian)(pian)減(jian)(jian)薄(bo)中產生(sheng)的(de)(de)機(ji)械損(sun)傷(shang)(shang)，拋(pao)(pao)光工藝(yi)可(ke)(ke)以得(de)到(dao)粗(cu)(cu)糙(cao)度(du)(du)(du)更低(di)的(de)(de)硅(gui)(gui)(gui)片(pian)(pian)(pian)(pian)表(biao)(biao)(biao)面(mian)(mian)(mian)(mian)(mian)，速率(lv)較慢(man)，濕法(fa)腐蝕(shi)工藝(yi)效率(lv)高，表(biao)(biao)(biao)面(mian)(mian)(mian)(mian)(mian)較粗(cu)(cu)糙(cao)；減(jian)(jian)薄(bo)硅(gui)(gui)(gui)片(pian)(pian)(pian)(pian)的(de)(de)翹(qiao)曲(qu)(qu)度(du)(du)(du)與(yu)損(sun)傷(shang)(shang)層(ceng)厚(hou)度(du)(du)(du)有(you)關，損(sun)傷(shang)(shang)層(ceng)厚(hou)度(du)(du)(du)越(yue)(yue)大(da)，硅(gui)(gui)(gui)片(pian)(pian)(pian)(pian)翹(qiao)曲(qu)(qu)度(du)(du)(du)越(yue)(yue)大(da)。實(shi)際工藝(yi)中，結(jie)合(he)器件需求，可(ke)(ke)以采用(yong)先分段研(yan)磨，再拋(pao)(pao)光或濕法(fa)腐蝕(shi)的(de)(de)方法(fa)，得(de)到(dao)高質(zhi)量(liang)的(de)(de)減(jian)(jian)薄(bo)硅(gui)(gui)(gui)片(pian)(pian)(pian)(pian)。