新型CVD鑽石碟開發及修整CMP拋光墊特性之研究

Abstract

化學機械拋光是目前所有平坦化方法應用在半導體製程中最有效的技術，也是製程中不可或缺的重要步驟。為了維持化學機械拋光製程穩定、產量連續及晶圓品質，必須使用鑽石碟適時修整拋光墊，恢復其表面形貌與特性，因此鑽石碟的切削特性直接影響拋光墊的表面形貌與特性。本研究利用CVD鑽石表面呈現微小多晶體突出多樣性形貌特徵，期以獲得切削及犁削(切)之縮小化精密複合切削機制，另為改善鑽石高度差及避免熱分解導致掉鑽產生並降低製作成本，提出以基準板控制CVD鑽石膜突出高度，並於室溫下以環氧樹脂結合固定於金屬圓板上新製程，成功製成新型CVD鑽石碟。透過實驗的方式，探討CVD鑽石碟對拋光墊進行修整之切削機制、切削速率、表面粗糙度及表面形貌等，進一步分析CVD鑽石使用數量之影響，並同時與傳統鑽石碟進行比較。結果顯示，新型MPCVD鑽石碟高度差小於15μm，除有助更平均分擔鑽石承受壓力，可提高鑽石參與修整拋光墊之工作粒數，修整拋光墊速率約高於為傳統硬銲鑽石碟6倍。修整後再生拋光墊之孔洞數形貌接近原始新的拋光墊形貌，修整後之表面粗糙度(Sa、Rpk及Rvk)均優於傳統硬銲鑽石碟並經SEM觀察可產生細密切削溝紋，有助拋光墊更能涵養拋光液及磨粒。另就成本效益考量HFCVD鑽石碟雖於修整時部分鑽石產生破裂脫落現象，若能精進HFCVD產製品質，HFCVD鑽石碟也是一個可以考慮選用方向。

Chemical Mechanical Polishing (CMP) is the most effective method of all kinds of semiconductor global planarization processes nowadays, and also is indispensable procedure in manufacturing process. In order to maintain CMP dressing process stable, production continuous and wafer quality, the surface morphology and characteristics of pad needs to be recovered by means of dressing the pad with diamond conditioner timely. Therefore the surface morphology and characteristics of pad are affected by cutting characteristics of diamond conditioner directly. In the study, a new CVD diamond disk is developed by utilizing the CVD diamonds with tiny polycrystal protrusion on surface in order to obtain minified complex Cutting and Plowing. In addition to diamond leveling control, thermal degradation (weak bonding of diamond) prevention and cost reduction, a brand new process can be done in room temperature as follow: CVD diamonds to be leveled by adhering to a base disk in advance. After the other side of CVD diamonds has been adhered to substrate metal disk by epoxy, remove the base disk at the end. The study discussed cutting phenomenon, dressing rate, surface roughness and surface morphology of CVD diamonds to pad, and also analyzed the influence by utilizing quantity of CVD diamonds compare to traditional diamond disk. The experimental result reveals that new MPCVD diamond disk is leveled to less than 15μm which helps to separate pressure on diamonds. Consequently, the leveled CVD diamond disk improves density of working diamond grits, and PDR is 6 times faster than traditional diamond disk. The dressed pad is unchanged from the initial morphology and pores, and has outstanding Sa, Rpk and Rvk compare to traditional diamond disk; in addition, under observation of SEM, many tiny grooves on the surface are also produced through the process that helps slurry filling torn pores. In addition to cost consideration, even though the film of HFCVD diamond disk might collapse partially during dressing process, this still could be the good selection if HFCVD diamond can be improved.