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      基于穩(wěn)定pH值的硅襯底晶圓拋光液成分優(yōu)化

      2023-01-09 12:06:12許寧徽李薇薇錢佳孫運(yùn)乾
      表面技術(shù) 2022年12期
      關(guān)鍵詞:緩沖劑拋光液二氧化硅

      許寧徽,李薇薇,錢佳,孫運(yùn)乾

      基于穩(wěn)定pH值的硅襯底晶圓拋光液成分優(yōu)化

      許寧徽,李薇薇,錢佳,孫運(yùn)乾

      (河北工業(yè)大學(xué) 電子信息工程學(xué)院,天津 300401)

      目的 探究不同配比方案配制pH值相同的拋光液對(duì)拋光去除速率、拋光液壽命和表面粗糙度的影響,優(yōu)化硅襯底晶圓拋光液,使其滿足半導(dǎo)體產(chǎn)業(yè)的發(fā)展要求。方法 以二氧化硅水溶膠為磨料,通過(guò)設(shè)置有機(jī)堿、pH緩沖劑、pH穩(wěn)定劑的不同配比來(lái)調(diào)節(jié)和穩(wěn)定拋光液的初始pH值(11.0~12.0),在最佳工藝參數(shù)下循環(huán)使用拋光液對(duì)2英寸(1英寸≈2.54 cm)硅襯底晶圓進(jìn)行拋光實(shí)驗(yàn)。研究不同配比下拋光液pH值、拋光去除速率隨拋光液循環(huán)使用時(shí)間的變化情況。對(duì)比實(shí)驗(yàn)結(jié)果,分析各種成分在拋光過(guò)程中的作用,以及對(duì)拋光效果產(chǎn)生的影響,得出最佳配比方案,優(yōu)化拋光液方案。結(jié)果 通過(guò)優(yōu)化硅襯底晶圓的拋光液方案,使拋光去除速率達(dá)到0.804 μm/min,拋光液的壽命延長(zhǎng)了約114.29%,拋光后硅襯底晶圓的表面粗糙度最低為0.156 nm。結(jié)論 得到了拋光液的最佳配比方案,有機(jī)堿的質(zhì)量分?jǐn)?shù)為1.0%,pH緩沖劑的質(zhì)量分?jǐn)?shù)為1.1%,并加入pH穩(wěn)定劑調(diào)節(jié)pH,使其拋光去除速率、拋光液壽命、表面粗糙度都得到很大提升。

      拋光液;二氧化硅水溶膠;有機(jī)堿;pH緩沖劑;pH穩(wěn)定劑;拋光去除速率;拋光液壽命;表面粗糙度

      隨著半導(dǎo)體產(chǎn)業(yè)的發(fā)展,半導(dǎo)體工藝向著更精細(xì)、更便捷、更高效的方向發(fā)展,化學(xué)機(jī)械拋光作為可以實(shí)現(xiàn)半導(dǎo)體晶圓全局平坦化的唯一方法[1-3],其精度要求已經(jīng)達(dá)到納米級(jí),甚至更低。作為化學(xué)機(jī)械拋光的核心組成部分,拋光液是整個(gè)半導(dǎo)體集成電路制造過(guò)程中的主要材料之一,它直接影響加工精度和電性能。目前,用于硅襯底晶圓的拋光液主要由二氧化硅水溶膠磨料、pH調(diào)節(jié)劑、絡(luò)合劑、拋光促進(jìn)劑等成分構(gòu)成[4-5],在拋光時(shí)采用循環(huán)使用的方式[6]。拋光液能夠循環(huán)使用的有效時(shí)間稱為拋光液壽命,它是衡量拋光液質(zhì)量的重要參數(shù)之一。在一般情況下,拋光去除速率會(huì)隨著拋光液循環(huán)使用時(shí)間的增加而衰減,拋光效率和拋光效果也相應(yīng)降低。拋光液的pH值、二氧化硅水溶膠磨料的濃度和粒徑,拋光過(guò)程中的壓力、溫度,以及拋光機(jī)的上下轉(zhuǎn)盤(pán)相對(duì)轉(zhuǎn)速等,都會(huì)對(duì)拋光液壽命和拋光去除速率產(chǎn)生影響[7-8]。其中,拋光液的pH值作為化學(xué)作用的主導(dǎo),是直接對(duì)拋光液壽命和拋光效果產(chǎn)生影響的重要因素[9]。

      目前,國(guó)際上廣泛采用的硅襯底晶圓拋光液都存在隨著使用時(shí)間的延長(zhǎng)pH值緩慢下降、緩沖能力欠佳的問(wèn)題[10],且國(guó)產(chǎn)納米二氧化硅水溶膠與國(guó)際水平有較大差距,需要對(duì)其拋光液配方進(jìn)行優(yōu)化,達(dá)到半導(dǎo)體產(chǎn)業(yè)對(duì)拋光去除速率、拋光液壽命、表面質(zhì)量的要求。楊金波等[11]研究了有機(jī)和無(wú)機(jī)pH值調(diào)節(jié)劑對(duì)Si片拋光速率的影響,結(jié)果表明,隨著pH值的升高,Si片與拋光液的反應(yīng)產(chǎn)物在拋光液中的溶解度越大,拋光液的pH值在10~11.5之間時(shí),拋光去除速率較高。索開(kāi)南等[4]研究分析了不同拋光液對(duì)拋光片表面質(zhì)量的影響,確定了不同拋光階段對(duì)拋光液的要求,研究表明,拋光過(guò)程先是以化學(xué)腐蝕為主導(dǎo)的化學(xué)機(jī)械平衡過(guò)程,與pH值的聯(lián)系較緊密。LI等[12]研究了各種添加劑對(duì)二氧化硅氧化膜去除率的影響機(jī)理,發(fā)現(xiàn)拋光液的pH值過(guò)高,受到OH—靜電斥力的影響,會(huì)阻礙膠體二氧化硅磨料與二氧化硅氧化膜間的接觸,導(dǎo)致機(jī)械作用下降,拋光去除速率下降。李鳳英等[13]通過(guò)研究FA/O Ⅱ型螯合劑和KOH調(diào)節(jié)劑對(duì)硅晶圓拋光速率的影響,提出一種新型堿性拋光液,延緩了拋光液pH值的下降,提高了拋光液的循環(huán)使用次數(shù)。汪海波、蔣先偉[14]研究了在硅拋光中加入不同濃度有機(jī)堿乙二胺(EDA)對(duì)拋光速率的影響,解釋了硅在含有EDA堿性拋光液中的拋光動(dòng)力學(xué)過(guò)程。KANG等[15]通過(guò)分析pH值、固體含量、Na+濃度和SiO2粒徑的變化情況,研究了以二氧化硅水溶膠作為磨料的拋光液的循環(huán)特性,表明剛配制的拋光液體系狀態(tài)不穩(wěn)定,會(huì)不斷發(fā)生化學(xué)反應(yīng),拋光液的pH值會(huì)隨著反應(yīng)的進(jìn)行而緩慢下降,直至達(dá)到穩(wěn)態(tài)。

      以上研究多為定性分析,缺乏深入的定量配比研究。由于在拋光過(guò)程中化學(xué)作用會(huì)不斷消耗OH—,拋光液的pH值會(huì)持續(xù)下降,因此提高拋光液對(duì)pH值的緩沖能力是提升拋光液使用壽命的一個(gè)重要手段。文中從拋光液的pH值穩(wěn)定性著手,通過(guò)多種方法來(lái)減緩pH值在拋光過(guò)程中的變化,提升以國(guó)產(chǎn)納米二氧化硅水溶膠為磨料的拋光液的壽命和效果。同時(shí),通過(guò)大量實(shí)驗(yàn)進(jìn)行定量分析,找到最優(yōu)的拋光參數(shù),并對(duì)整個(gè)拋光過(guò)程進(jìn)行系統(tǒng)分析。

      1 拋光實(shí)驗(yàn)

      1.1 原料

      主要原料:二氧化硅水溶膠(廣東惠爾特納米科技有限公司)、無(wú)機(jī)堿(NaOH)、有機(jī)堿(哌嗪)、pH緩沖劑(四硼酸鈉)、pH穩(wěn)定劑(碳酸氫鈉)、純水。

      1.2 步驟

      1.2.1 拋光液的制備及表征

      稱取二氧化硅水溶膠,用磁力攪拌器攪拌10 min,在攪拌同時(shí)加入用純水溶解的有機(jī)堿,再加入pH緩沖劑和pH穩(wěn)定劑后充分?jǐn)嚢?0 min。滴加濃度(用質(zhì)量分?jǐn)?shù)計(jì))為10%的無(wú)機(jī)堿調(diào)節(jié)pH值至10.5~11.0,控制滴加速度,避免二氧化硅水溶膠出現(xiàn)凝膠現(xiàn)象,繼續(xù)攪拌30 min。最終將配制好的拋光液的pH值控制在11.0~11.5之間,相對(duì)密度為1.295~1.305,黏度小于10 mPa·s,二氧化硅水溶膠的質(zhì)量分?jǐn)?shù)為40%左右即可。

      測(cè)定所配制拋光液的pH值,將其稀釋15倍后再測(cè)其pH值。通過(guò)拋光機(jī)對(duì)2英寸(1英寸≈2.54 cm)硅襯底晶圓進(jìn)行拋光實(shí)驗(yàn),硅襯底晶圓的初始表面粗糙度約為1.2 μm,實(shí)時(shí)記錄每次實(shí)驗(yàn)值,觀察拋光液pH值和晶圓拋光去除量的變化情況,測(cè)試并記錄其拋光去除速率和拋光液壽命。

      1.2.2 拋光工藝過(guò)程與參數(shù)設(shè)置

      實(shí)驗(yàn)采用沈陽(yáng)科晶UNIPOL?1200S單面拋光機(jī)拋光2英寸硅襯底晶圓。在每次實(shí)驗(yàn)時(shí),用蠟將3片硅襯底晶圓均勻地粘貼在拋光盤(pán)上,并與其邊緣相切。為了保證拋光過(guò)程中化學(xué)作用與機(jī)械作用的協(xié)同配合,設(shè)置拋光硅襯底晶圓的最佳工藝參數(shù):上盤(pán)轉(zhuǎn)速40 r/min、下盤(pán)轉(zhuǎn)速100 r/min、拋光壓力0.5 MPa、拋光溫度25~26 ℃、拋光液流量50 mL/min。在拋光完成后,通過(guò)加熱將硅襯底晶圓取下,使用大量去離子水和無(wú)水乙醇將硅襯底晶圓洗凈,并用壓縮空氣將其吹干。

      1.2.3 拋光效果檢測(cè)方法

      使用pH測(cè)量?jī)x每隔30 min檢測(cè)一次拋光液的pH值。使用測(cè)厚儀測(cè)量每次實(shí)驗(yàn)硅襯底晶圓中心點(diǎn)、軸線上邊緣兩點(diǎn)、與軸線垂直的邊緣兩點(diǎn)等共計(jì)15個(gè)采樣點(diǎn)的初始厚度和拋光后的厚度,按式(1)計(jì)算各點(diǎn)的拋光去除速率()[16]。

      式中:0為初始硅襯底晶圓采樣點(diǎn)的厚度;1為CMP拋光后硅襯底晶圓采樣點(diǎn)的厚度;為拋光時(shí)間。

      在每次拋光實(shí)驗(yàn)后,將測(cè)得的硅襯底晶圓上15個(gè)點(diǎn)的拋光去除速率的最大值記為拋光最大速率,平均值記為拋光平均速率。得到不同配比條件下拋光液pH值與拋光去除速率隨拋光液循環(huán)使用時(shí)間的變化關(guān)系,以此作為衡量拋光液壽命的依據(jù)。最后,通過(guò)Bruker Dimension 3100型原子力顯微鏡對(duì)拋光后的硅襯底晶圓進(jìn)行表面粗糙度檢測(cè),確定拋光效果。

      2 結(jié)果與討論

      2.1 不同pH值調(diào)節(jié)方法對(duì)硅襯底晶圓拋光去除速率的影響

      拋光液中的磨料為納米二氧化硅水溶膠,為了保證膠體磨料在拋光液中穩(wěn)定分散,最佳的pH值范圍為10.0~12.0[11]。在硅襯底晶圓拋光實(shí)驗(yàn)中,為了滿足較高的拋光去除速率,保持化學(xué)作用與機(jī)械作用的平衡,pH值一般選擇11.0~12.0。由此,文中通過(guò)有機(jī)堿、無(wú)機(jī)堿、pH緩沖劑、pH穩(wěn)定劑等成分,利用不同的配比和添加量將拋光液初期pH值調(diào)節(jié)在11.0~12.0內(nèi)。通過(guò)不同的pH值調(diào)節(jié)方法,研究隨著拋光的進(jìn)行,拋光液能夠保持pH值穩(wěn)定,拋光去除速率滿足要求的持續(xù)能力。

      2.1.1 不同比例的有機(jī)堿和pH緩沖劑對(duì)拋光去除速率的影響

      表1 不同比例的有機(jī)堿和pH緩沖劑對(duì)拋光液的影響

      2.1.2 有機(jī)堿與pH緩沖劑的量對(duì)拋光去除速率的影響

      調(diào)整有機(jī)堿和pH緩沖劑的量,按照2.1.1所述方法調(diào)節(jié)拋光液的初始pH值,并觀察拋光前后拋光液pH值的變化情況,并測(cè)定拋光去除速率。通過(guò)比較(表2)可知,拋光液的拋光去除速率隨著有機(jī)堿和pH緩沖劑加入量的增多而加快,且拋光前后拋光液的pH差值變小。這主要是因?yàn)殡S著有機(jī)堿含量的增加,其電離平衡向正反應(yīng)方向移動(dòng),能夠源源不斷地為體系供給OH–,化學(xué)作用速率得到提高[21],且有機(jī)堿分子量大,與硅襯底晶圓表面反應(yīng)的產(chǎn)物為大分子,在壓力和拋光墊的摩擦作用下很容易脫離反應(yīng)表面,從而加速了機(jī)械去除過(guò)程,其綜合作用提高了拋光去除速率[22]。上述配比中,在有機(jī)堿的質(zhì)量分?jǐn)?shù)為1.98%、pH緩沖劑的質(zhì)量分?jǐn)?shù)為0.66%時(shí)拋光去除速率最大,但相對(duì)于有機(jī)堿質(zhì)量分?jǐn)?shù)為1%的拋光液,其拋光去除速率提升不明顯。這是由于在二氧化硅水溶膠保持完好的最佳工藝生產(chǎn)時(shí)間內(nèi),質(zhì)量分?jǐn)?shù)為1%的有機(jī)堿足以將OH–濃度維持在較高水平。在考慮生產(chǎn)成本和工藝要求的基礎(chǔ)上,確定有機(jī)堿質(zhì)量分?jǐn)?shù)為1%、pH緩沖劑質(zhì)量分?jǐn)?shù)為1.1%的拋光液最為適合工業(yè)生產(chǎn)。

      2.1.3 pH穩(wěn)定劑對(duì)拋光去除速率的影響

      在2.1.2節(jié)的基礎(chǔ)上,研究在有機(jī)堿質(zhì)量分?jǐn)?shù)為1%、pH緩沖劑質(zhì)量分?jǐn)?shù)為1.1%的拋光液中加入一定量pH穩(wěn)定劑后對(duì)拋光去除速率的影響,如表3所示。

      表2 有機(jī)堿和pH緩沖劑的含量對(duì)拋光液的影響

      表3 pH穩(wěn)定劑對(duì)拋光液的影響

      2.2 不同pH值調(diào)節(jié)方法對(duì)硅襯底晶圓拋光液壽命的影響

      結(jié)合2.1節(jié)的實(shí)驗(yàn),設(shè)置6種實(shí)驗(yàn)方案(見(jiàn)表4),研究在不同pH值調(diào)節(jié)方法下拋光液壽命和pH值的變化情況,并進(jìn)行比較。

      表4 拋光液配比

      6種方案對(duì)拋光液pH值與拋光去除速率的影響如圖1—2所示。如圖1所示,方案1、方案2、方案3、方案4、方案5的pH值下降幅度較大,拋光液壽命較短。經(jīng)比較可知,增加有機(jī)堿的量,提高其在體系中的比例,能夠從整體上提高拋光過(guò)程中的pH值,拋光液壽命也能得到提升,但對(duì)pH值下降幅度的作用不大。這是由于有機(jī)堿是弱堿,在膠體體系中不能直接提供OH–,只能通過(guò)促進(jìn)水的電離實(shí)現(xiàn),故不能有效抑制pH值的下降。通過(guò)比較圖1a、b可知,pH穩(wěn)定劑的加入能使拋光液壽命得到明顯提升,且方案3的提升幅度相對(duì)最大。這是由于在拋光初期以pH緩沖劑的緩沖作用為主,而在拋光后期pH緩沖劑的緩沖作用趨于飽和,以pH穩(wěn)定劑的穩(wěn)定作用為主,將pH值變化的范圍縮小,保證pH值的穩(wěn)定性[26-27],使有機(jī)堿能夠充分補(bǔ)充體系中被消耗的OH–,pH值回升,進(jìn)而提高拋光液壽命。

      圖1 拋光過(guò)程pH值隨時(shí)間的變化情況

      圖2 拋光過(guò)程中拋光去除速率隨時(shí)間的變化情況

      如圖2所示,方案1、方案4的拋光去除速率的衰減相對(duì)較快,拋光液壽命較短。比較方案1和方案2,由于有機(jī)堿在體系中比例的增加,拋光液的pH值升高,拋光液中的OH—能夠源源不斷地得到補(bǔ)充,拋光去除速率得到明顯提高。在加入pH穩(wěn)定劑后(方案6),拋光去除速率的降幅較小,且穩(wěn)定性好,可以大大提高拋光液的循環(huán)使用壽命。

      比較圖1—2可知,方案6的拋光液質(zhì)量相較于其他方案有了很大的提升,拋光液壽命達(dá)到15 h左右,且保持較好的拋光去除速率。原因是pH緩沖劑起到了緩沖作用,使pH值的降幅明顯減小,pH穩(wěn)定劑保證了pH值的穩(wěn)定,使有機(jī)堿提供的OH–能夠與硅襯底晶圓表面的化學(xué)反應(yīng)充分進(jìn)行。另外,由于拋光液可循環(huán)使用,隨著拋光的進(jìn)行,表面反應(yīng)產(chǎn)物、碎屑等會(huì)在拋光液中逐漸積累,增加了體系中發(fā)生碰撞的概率,使磨料與硅襯底晶圓脫離接觸狀態(tài),降低了其機(jī)械作用的有效長(zhǎng)度,體系中電解質(zhì)的增加會(huì)降低二氧化硅膠體磨料的分散穩(wěn)定性,容易發(fā)生團(tuán)聚、絮凝等現(xiàn)象,造成拋光液壽命的下降[28]。pH穩(wěn)定劑的加入在一定程度上可以增加拋光液的pH穩(wěn)定性,維持二氧化硅膠體磨料的穩(wěn)定分散,保證二氧化硅水溶膠磨料與硅襯底晶圓表面的機(jī)械研磨作用充分進(jìn)行,進(jìn)而提高拋光去除速率和拋光液壽命。

      2.3 不同pH值調(diào)節(jié)方法對(duì)硅襯底晶圓表面粗糙度的影響

      硅襯底晶圓的表面粗糙度會(huì)影響半導(dǎo)體器件或集成電路的性能,其表面粗糙度越小,生長(zhǎng)的外延層缺陷越少,器件性能越好。另外,也有助于光刻和刻蝕工藝的進(jìn)行,降低后期線寬控制的難度[29]。為了研究不同pH值調(diào)節(jié)方法對(duì)拋光效果的影響,對(duì)2.2節(jié)中的方案1、方案2、方案3、方案6進(jìn)行了6組平行實(shí)驗(yàn),并對(duì)拋光后的每片硅襯底晶圓選取3個(gè)采樣點(diǎn)進(jìn)行表面粗糙度的檢測(cè),取其平均值,檢測(cè)結(jié)果如圖3所示。

      經(jīng)4種方案拋光后,每種方案表面粗糙度最小位置的原子力顯微圖如圖4所示,對(duì)其使用Gwyddion軟件進(jìn)行表面平整度分析,如圖5所示。

      圖3 硅襯底晶圓表面粗糙度曲線

      Fig.3Roughness curve of silicon substrate wafer surface

      圖4 硅襯底晶圓表面原子力顯微圖

      圖5 硅襯底晶圓表面平整度分析

      如圖3所示,在拋光后方案1、方案2、方案3、方案6的硅襯底晶圓表面粗糙度平均值逐漸下降,且方案6的表面粗糙度曲線最平緩,方差最小,比方案3的方差降低了約30.3%,即平整度提升了約30.3%。如圖5所示,方案6的高度分布最集中,說(shuō)明其表面平整度最高,均一性最好。原因是有機(jī)堿和pH緩沖劑量的增加能夠起到緩沖作用,pH值雖有波動(dòng)但不會(huì)迅速降低,能有效避免二氧化硅水溶膠在低pH值環(huán)境下運(yùn)動(dòng)時(shí)產(chǎn)生犁溝結(jié)構(gòu)[30]。在硅襯底晶圓表面凹陷處,有機(jī)堿氧化性較弱,浸潤(rùn)后的化學(xué)腐蝕作用較小,并能夠?qū)ζ湫纬杀Wo(hù),降低了二氧化硅水溶膠磨料的機(jī)械劃擦作用,使凹陷處的拋光去除速率下降。在硅襯底晶圓表面凸起處,有機(jī)堿能夠持續(xù)提供OH—,促進(jìn)了化學(xué)反應(yīng)的進(jìn)行,并生成了容易脫離反應(yīng)表面的大分子,而pH穩(wěn)定劑則會(huì)抑制pH值的波動(dòng),維持膠體體系的穩(wěn)定,保證了二氧化硅水溶膠磨料與凸起處機(jī)械作用的充分進(jìn)行,化學(xué)作用與機(jī)械作用達(dá)到平衡,使凸起處的拋光去除速率上升,降低了硅襯底晶圓的表面粗糙度,提升了表面均一性。

      3 結(jié)論

      拋光去除速率和拋光液壽命是衡量拋光液質(zhì)量的重要指標(biāo),文中主要從pH值的調(diào)節(jié)方式入手,通過(guò)改變有機(jī)堿與pH緩沖劑的比例和用量,以及在拋光液中加入pH穩(wěn)定劑來(lái)調(diào)節(jié)和穩(wěn)定拋光液的pH值。對(duì)于堿性拋光液,無(wú)機(jī)堿將pH值粗調(diào)節(jié)在11.40~ 11.45內(nèi)時(shí),有機(jī)堿與pH緩沖劑的質(zhì)量比為3∶1時(shí)的拋光去除速率最大,達(dá)到了0.891 μm/min??紤]生產(chǎn)成本和工藝要求,確定拋光液中有機(jī)堿的質(zhì)量分?jǐn)?shù)為1.0%、pH緩沖劑的質(zhì)量分?jǐn)?shù)為1.1%。pH穩(wěn)定劑的加入能明顯提高拋光液的拋光去除速率和拋光液壽命,其拋光液壽命能延長(zhǎng)5 h,達(dá)到15 h,且拋光后硅襯底晶圓的表面粗糙度較低,平整度提升了約30.3%。在追求拋光去除速率和拋光液壽命的同時(shí),保證了拋光質(zhì)量,得到了優(yōu)化拋光液的最佳配比方案:有機(jī)堿的質(zhì)量分?jǐn)?shù)為1.0%,pH緩沖劑的質(zhì)量分?jǐn)?shù)為1.1%,并加入pH穩(wěn)定劑以調(diào)節(jié)pH值。

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      Component Optimization of Polishing Slurry for Silicon Substrate Wafer Based on Stable pH Value

      ,,,

      (College of Electronic Information Engineering, Hebei University of Technology, Tianjin 300401, China)

      In order to solve the problem that the pH value of polishing slurry on silicon substrate wafer is slowly decreasing with the increase of service time and poor buffering ability, and that the domestic nano-silica hydrosol has a large gap with the international level, the work aims to explore the effects of different proportioning formulas on polishing rate, service life of polishing slurry and surface roughness under the same pH value and optimize the polishing slurry for silicon wafer to meet the development requirements of semiconductor industry.

      From the point of stabilizing the pH value of the polishing slurry, the pH value of the polishing slurry was adjusted and stabilized in the range of 11.0-12.0 by setting different proportions of organic base, pH buffer and pH stabilizer with the domestic nano-silica hydrosol as the abrasive. The polishing experiments of 2 inch silicon substrate wafer were carried out under the optimum polishing parameters. The changes of pH value and polishing rate of polishing slurry with the circulating time of polishing slurry at different proportions were studied. By comparing the experimental results, the effects of various components in the polishing process and their effects on the polishing effect were analyzed, and the best proportioning formula was obtained to optimize the polishing slurry.

      By setting up comparative experiments, the effects of mass fraction of organic base and pH buffer, usage and pH stabilizer on polishing rate and service life of polishing slurry were investigated. The surface roughness of the polished silicon substrate wafer was measured. The results showed that: The function of the pH buffer was to generate an equal amount of conjugated acid and base to stabilize the pH of the polishing slurry system to a certain range. However, a large number of pH buffers could destroy the original chemical stability of the colloid system, such as coagulation and crystallization. A large number of organic base could continuously provide OH—for the system, the rate of chemical reaction was increased, and the products of organic base reacting with the surface of silicon substrate wafer were macromolecules, which were easy to detach from the reaction surface and accelerate the mechanical removal process. In addition, the chemical etching effect after organic base infiltration was weak, which could protect the crystal circle depression of the silicon substrate wafer. The combination of organic base and pH buffer could ensure that the pH value of polishing slurry did not decrease rapidly and effectively avoid the formation of plough groove structure. The hydrolysis of pH stabilizer was weakly alkaline, which could work together with the pH buffer to ensure the pH stability, and its hydrolysis by-product was H2CO3. It could overcome the disadvantage of excessive pH buffer to cause the agglutination of silica hydrosol and ensure the full mechanical action of silica hydrosol abrasives and the raised surface of silicon substrate wafer.

      For the polishing slurry optimized for silicon substrate wafer, the polishing rate reached 0.804 μm/min, the service life was prolonged by 114.29%, and the surface roughness of the polished silicon substrate wafer was as low as 0.156 nm. The optimum proportion of polishing slurry is: organic base 1.0wt.% and pH buffer 1.1wt.%. pH stabilizer can be added to adjust and stabilize the pH value. The polishing rate, service life of polishing slurry and surface roughness are all improved greatly.

      polishing slurry; silica hydrosol; organic base; pH buffer; pH stabilizer; polishing rate; service life of polishing slurry; surface roughness

      TN405

      A

      1001-3660(2022)12-0277-08

      10.16490/j.cnki.issn.1001-3660.2022.12.028

      2021?12?15;

      2022?04?11

      2021-12-15;

      2022-04-11

      光電信息控制和安全技術(shù)重點(diǎn)實(shí)驗(yàn)室基金(614210701041705)

      Key Laboratory of Optoelectronic Information Control and Security Technology (614210701041705)

      許寧徽(1998—),男,碩士生,主要研究方向?yàn)槲㈦娮庸に嚺c材料。

      XU Ning-hui (1998-), Male, Postgraduate, Research foucs: microelectronics technology and materials.

      李薇薇(1978—),女,博士,副教授,主要研究方向?yàn)槲㈦娮庸に嚺c材料

      LI Wei-wei (1978-), Female, Doctor, Associate professor, Research foucs: microelectronics technology and materials.

      許寧徽, 李薇薇, 錢佳, 等.基于穩(wěn)定pH值的硅襯底晶圓拋光液成分優(yōu)化[J]. 表面技術(shù), 2022, 51(12): 277-284.

      XU Ning-hui, LI Wei-wei, QIAN Jia, et al. Component Optimization of Polishing Slurry for Silicon Substrate Wafer Based on Stable pH Value[J]. Surface Technology, 2022, 51(12): 277-284.

      責(zé)任編輯:彭颋

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