改善硬式罩幕轉印金屬膜的精準度

Abstract

本論文內容主要是以高密度電漿源蝕刻技術中的感應式偶合電漿技術將矽晶圓蝕刻吃穿(蝕刻深度約400um)形成一硬式罩幕(Shadow mask)以應用於微機電光通訊產品(Optical MEMS)後期結構層已懸浮後的鍍膜需求，而主要研究特點是在原先的硬式罩幕上以第二階段乾式蝕刻方式製作出高約50um的凸塊(Post)，用以固定當光學產品與硬式罩幕結合後不會出現滑動而影響後續鍍膜的準度。 本實驗需進行兩階段的乾式蝕刻，於是在阻擋層的部份則須分兩種材料近兩階段的阻擋作用，在此是以乾式氧化層為主要阻擋層，並在欲定義為凸塊的氧化層區域上加多晶矽層形成雙層結構，第一階段先以氧化層當阻擋層進行矽晶圓深蝕刻，接著運用對氧化層與多晶矽層高選擇比的反應性離子蝕刻技術將除了由多晶矽保護之外的氧化層全數移除，接著再進行第二階段矽晶圓蝕刻而形成凸塊。 經此實驗所製作出的硬式罩幕業已使用於產線，已大幅降低工廠端人員操作所需花費的時間，並且在產品端的鍍膜準確度亦獲得相當大的改善，結果對於產能的調節與成本的控管皆有相當大的助益。

In this thesis, shadow mask with post structure was fabricated by utilizing the inductively coupled plasma (ICP) etching technique (one of the high density plasma etching techniques). The mask was used for metal deposition on release device layer in an optical MEMS product. The characteristic of this mask is that it contains 50um-thick post after 2-step deep dry etching. The post structure can fix device wafer and shadow mask’s positions so that there is no alignment shift after the two objects are in contact. As a result, the precise alignment of subsequent metal deposition was not worsened.

In this experiment, two materials were chosen as etch hard masks for the 2-step dry etching process. PEOX was the jard mask for the 1st step etching, while poly-Si was deposited and patterned on PEOX areas where post structure was formed subsequently. In the 1st step etching, deep Si etching was performed with PEOX as hard mask. Then, reactive ion etching (RIE) was utilized to remove the PEOX areas without poly-Si protection. Another deep Si etching was the carried out to etch Si areas where PEOX was removed. Post structure was defined as the result of these process steps.

The shadow mask with post made during this experiment has been used in manufacturing line, and the usage of this mask has greatly reduced manufacturing staffs’ operation time. The precision of film deposition on products was also significantly improved. Thus, the usage of the mask helps in cost control and manufacture capacity adjustment.