針對半導體製程金屬層良率提昇研究

Abstract

矽晶圓成熟的技術與低廉的價格，造就了蓬勃的消費性電子產業，但隨著元件線寬不斷縮小下，半導體製程技術越趨困難，已無法用一致化的程式來面對多元化的產品，因此需要更多的儀器分析與實驗，來為每個產品進行微調！ 本公司的產品便深受其害，良率無法達到量產的標準，於是便利用了SEM與SIMS分析，找出下列的問題： 1. 接觸窗與下方的金屬對準不良 2. 鈷金屬矽化物出現缺陷與阻值過高 3. 接觸窗蝕刻程式無法共用，有些產品蝕刻不足導致短路，有些蝕刻過頭導致電化學效應，讓金屬層下方的接觸窗遭到侵蝕 針對上述的問題我們進行了一連串的實驗與分析，亦找到一些方法來改善這個現象，下列是我們採取的方法： 1. 使用曝光較為精準的Scanner 機台來取代Stepper。 2. 使用新的錐狀金屬蝕刻程式，將金屬層蝕刻為錐狀，可以完整覆蓋下方的接觸窗 3. 使用PE SiH4機台來取代LPTEOS機台，讓鈷金屬矽化物不會有缺陷的產生。 4. 改變鈷金屬矽化物的回火溫度，讓其阻值更低。 5. 改變金屬窗蝕刻程式，讓不同厚度的產品都可使用，不致於讓厚度較厚的產品沒有蝕刻開來，而造成短路，也不會讓厚度較薄的產品蝕刻過頭，導致金屬層下方的接觸窗掏空。 針對不同的產品設計與特性，便會有不同的改善良率的方法，讓我們不斷的努力研究，讓電子產品更加進步與便宜。

The mature technology and inexpensive price of Silicon wafer makes electrical consumer industrial become popular. But the technology of semiconductor process becomes more difficult with the device width becomes smaller. Therefore, we can’t use the same recipe on various products. We need more instruments for analysis and experiments. And use the results to optimize the recipe for each product. Our company’s product has suffered this issue and yield can’t meet the criteria of production. Hence, we used SEM and SIMS to analyze and found below issues. 1. Metal via and under layer metal line un-landing 2. Defect occurred and resistance too high on cobalt silicide 3. We can’t use the same metal via etching recipe for all products. Some products may encounter short issue due to etch not enough. Some products may induce electrochemistry effect with over etch. And this caused the metal via under metal be damaged. We did a series of experiments and analysis for above issues and found some methods to improve them. The methods are listed as below: 1. Use scanner which has more accurate exposure ability instead stepper. 2. Use taper metal etching recipe and this can fully cover the metal via under metal layer. 3. Use PE SiH4 tool to replace LPTEOS tool and this can make defect not occur of cobalt silicide. 4. Change anneal temperature of cobalt silicide to reduce resistance. 5. Change metal etching recipe to let the products with different metal thickness can use the same recipe. And it won’t cause short issue when metal is thicker. When metal is thinner, it won’t cause metal via under metal layer be damaged. For diverse product designs and characteristics, it will have different methods to improve yield. Let us keep putting efforts on research and make electrical products more progress and cheaper.