以離子佈植於複晶矽中形成淺接面之技術研究

Abstract

當元件的尺寸日益縮小，淺接面的製造和控制就變得更加困難，因而有一 些特殊構造被發展出來。其中〞以離子佈植於複晶矽中〞 (ITP)是一種有 效的方式。複晶矽被用來作為墊層以降低離子佈植入矽基板的能量，將離 子佈植產生的缺陷侷限其中，並提供金屬矽化物生成時的矽原子來源。本 論文對非金屬矽化及鈷矽化接觸的 ITP結構作有系統的探討，顯示 ITP 結構是一種可行的方式。對於非金屬矽化的p+/n接面來說，較低的能量使 缺陷留在複晶矽中，再加上足夠的雜質推入是較好的方式。高能的佈植在 矽基板上留下了嚴重的缺陷，以致經過攝氏1000度的退火仍舊無法降低漏 電流。矽化鈷的形成促進了缺陷的消除，因此以125keV的佈植能量仍能得 到優良的接面特性。更進一步的，鈷矽化p+/n接面中，鈷的厚度須在〞促 進缺陷消除程度〞及〞雜質被限制於矽化物中〞兩因素間作適當的選擇。 然而，對於以磷佈植的n+/p接面來說，無論是非金屬矽化或鈷矽化結構經 攝氏 800度以上高溫的退火，能量已不再顯如此顯著的效應。它被猜測為 磷佈植形成非晶矽所致。然而為求接面深度和電性兼顧，因此製程條件的 選擇彈性較小。另外，由於鈷原子在形成矽化物時可能經由佈植留下的缺 陷穿入矽基板，也使得製程的決定變得更加複雜。 As the device geometries are continuously scaling down,the abrication and control of shallow junctions become increas- ingly difficult. Implantation through polysilicon (ITP) is onethe effective approaches to fabricate shallow junctions. Theysilicon serves as the buffer layer to reduce the ion energ- mplanted into substrate, confines most of the implantations in it,and provides silicon atoms to react with theayer during the silicidation process. In this thesis, shallow junctions with nonsilicided andobalt silicided contacts formed by ITP method have been systemtically investigated. For the nonsilicided p+/n samples, highantation energies introduces severe damages in the Sirate and thus causes very leaky junction characteristics.ast, cobalt silicided samples provide the enhancementannihilation during the silicidation. For theanted n+/p samples,the compromise between theand the electrical characteristics results inindow.For the cobalt silicided n+/p samples,ano- ration into substrate along the implant-inducedsilicidation was observed.