- 學位論文
尖峰式快速熱處理系統之熱預算與溫度均勻性控制策略
Control Strategy for Thermal Budget and Temperature Uniformity in Spike Rapid Thermal Processing Systems
摘要
單一晶圓的快速熱處理(rapid thermal processing, RTP)在半導體製程中有相當廣泛的應用，例如快速升溫退火、氧化、氮化、化學器相沈積等，是半導體製程中最重要的關鍵技術之一。在RTP中，晶圓的溫度控制相當重要，其目的是為了要給予晶圓適當的熱預算(thermal budget)，隨著半導體線寬逐漸收縮，唯有利用尖峰式的溫度設定才能給予精確的熱預算，然而，這使得傳統的伺服控制設計變的非常困難且複雜。 為了克服此一困難，本研究首先假設RTP系統可用線性模式表示，發展出一個新穎的控制策略來提供準確的熱積存控制，作法為不針對溫度做伺服控制，而是直接來控制熱預算指標。然而真實RTP程序具有高度非線性，故以簡單的線性模式來代表RTP系統似乎較不符合實際應用。因此，本研究進一步將RTP系統識別成非線性Wiener模式，據以發展尖峰式RTP系統熱預算之非線性控制策略，Cho 於 2008年提出一個簡單RTP物理模式，本研究使用其所識別得到的物理模式藉以驗證可行性，由模擬結果可知我們所提出之非線性控制策略確實能達到精準的熱預算控制。另一方面，晶圓上溫度分布的均勻性亦是RTP系統必須考量的重要指標，要維持晶圓溫度分布之均勻性，則必須運用多變數控制策略與燈圈配置方法，因此本研究推展到多變數控制。由於提出的方法已經經由簡單物理模式確定其可行性，所以將其應用於真實的RTP物理模式，並且探討燈圈的配置方法對於熱預算控制目標精準程度與晶圓上溫度分布均勻性的影響，由結果可知，在真實物理模式中，我們所提出的控制策略不僅能精準控制熱預算的控制目標，對於晶圓上溫度的分布亦能維持其均勻性，此結果更加確定此法的可行性。在半導體產業線寬窄化的趨勢中，精準的控制熱預算無非是其中一個重大議題，期望本研究能對於RTP製程方面能有所幫助。
並列摘要
The spike-shaped temperature profile in thermal treatments is widely used in IC industry for providing a precise thermal budget. This thermal budget control issue gets more crucial as the technology node progressively shrinks. Therefore, rapid thermal processing (RTP), such as spike annealing, has the ability to yields ultra-shallow junctions. With its exceptionally stringent performance requirements (for example, high temperature uniformity and high temperature ramp-up/down rate), temperature control in RTP systems is a challenging task. This study first presents a novel methodology of control system design for providing precise thermal budget based on a linearized RTP model. By tuning controller parameters and designing the set-point profile, the method targets thermal budget indices instead of temperature servo control. However, the actual RTP system is highly nonlinear, and thus the linear model cannot describe its dynamic behavior well over a wide operating range. This study uses a nonlinear Wiener model to represent the RTP system and then proposes a nonlinear control strategy for thermal budget control. In practice, the wafer temperature uniformity is also a very important specification. The RTP equipment has many lamps, and these lamps are clustered into several adjusting zones for simplicity. Therefore, this study extends the proposed method to multivariable control system to achieve good temperature uniformity within wafer. Moreover, how to group these lamps for achieving better temperature uniformity is also discussed. Simulation results confirm that the proposed method not only provide the desired thermal budget, but also maintain good wafer temperature uniformity in spike-RTP system.