矽化鈷在含鍺介電質形成奈米點並構成非揮發性記憶體之研究

Abstract

近年來，數位生活在台灣電子工業市場扮演了舉足輕重的角色，數位電子產品的應用已經受到廣大的青睞，像是數位相機、筆記型攜帶式、攜帶隨身聽MP3或CD、信用卡晶片，攜帶型USB記憶體或記憶卡和日常生活會用到的PDA、GPS 等等。這些個人式電子產品的發展則基於非揮發性記憶體元件的低功率消耗和可攜式。傳統的非揮發性記憶體是利用複晶矽浮停閘(floating gate)作為載子儲存的單元，而在元件尺寸持續微縮下，該結構將面臨一些瓶頸。當電子從通道注入浮停閘儲存層，記憶體元件將會受到儲存載子影響它本身存在電場的影響，造成起始電壓的漂移。我們可將受浮停閘改變的起始電壓定義為1與O。然而，因為這種浮停閘結構為整層的半導體薄膜，在電子反覆的從穿遂氧化層進出這層浮停閘，會使得穿遂氧化層劣化以至於出現缺陷，當缺陷一旦產生之後，所有儲存的電子將會隨這層缺陷而產生局部漏電路徑，導致所寫入的儲存載子全部流失掉，無法達到原本應有之記憶的效果。 矽化鈷是一種金屬矽化合物現今已經因為它本身的低電阻( 10-20 ~μΩcm)和熱穩定性而被廣大的應用在接觸面上。在本論文中我們使用共同濺鍍和快速退火系統分別進行薄膜沉積和進行退火。我們會使用快速退火系統是因為溫度控制的方便性和利用減少熱預算來降低擴散程度。 在本篇論文，我們透過濺鍍系統共打的方式沉積鈷、矽、鍺的混合性薄膜，再利用快速退火的方式製作一種新穎之矽化鈷物奈米點於含鍺介電層，並研究該結構金氧絕氧半(MOIOS)結構之儲存效益。除了此金氧半電容結構之C-V、J-V量測外，並透過一些材料分析如二次離子能譜(SIMS)、X光光電子能譜儀(XPS)釐清各元素扮演儲存機制之角色。此外，我們亦研究透過共同濺鍍金屬鈷和介電質材料如氧化矽，氮化矽及氧化鋁作為儲存層，透過電性量測，該結構亦展示不錯之載子儲存效果，除電性量測外亦透過相關之材料分析X光光電子能譜儀(XPS) 探討在不同介電質材料之間的形成機制。

In recent years, digital life has attracted great importance for Taiwan，s electronics market. Then he portable electronic products have been applied widely, such as digital cameras, notebooks, hand-carry USB memories, a chip on credit card , PDA, GPS, memory card, MP3 audio players and so on. However, these portable electronic products are based on the nonvolatile memory (NVM) due to the need of low working power and portability. In a conventional nonvolatile memory (NVM), charge is stored in a ploy-silicon floating-gate (FG). However, it suffers some limitations for continual scaling down of the device structure. In FG memory, the electrons which injected from channel to the poly-silicon trapping layer influence the shift of threshold voltage in the memory. Then it can be defined through the difference of threshold voltages as logic “0” & “1”. Nevertheless, the definition fails if the tunneling oxide provides a leakage path after repeatedly performing write/erase cycling. On other hand, the oxide will produce some defect after repeat impact during electrons the write/erase cycle because the whole structure of FG is semiconductor. All of the charge stored in FG will be trapped into trapping layer or be lost from trapping layer with leak path which was formed with defects. FG structure will have reliability problem when device scale down to nano-meter level. Among the Metal Silicide, cobalt-silicide (CoSi2) has been widely used as a contact source due to the lowest resistivity value ( 10-20 ~μΩcm) and good thermal stability. In this thesis, CoSi2 films were sputtered and we choose rapid thermal annealing (RTA) and sputter system in order to reduce process cost because of temperature controlling and reduce thermal budget because of diffusion reducing. Co-sputtering approach was used to deposit the mixed cobalt, silicon and germanium film. After rapid temperature oxidation (RTO), Novel cobalt silicide nanocrystals embedded in the dielectrics which are doped with Ge have been formed. The charge storage effect of this novel trapping layer have also been investigated by capacitance-voltage (C-V), current density-voltage (J-V) measurement. Transmission Electron Microscopy (TEM), Secondary Ion Mass Spectrometer (SIMS) and X-ray photoelectron spectroscopy (XPS) have been used to analyze formation of the cobalt-silicide nanocrystals. In addition, the structure formed by co-sputtering the Co target with SiO2, Si3N4 target and Al2O3 target have also been demonstrated in this work. The approach also shows good charge storage ability. The charge storage mechanism of various dielectrics has also been revealed by related material analysis.