- 學位論文
扇出型晶圓級構裝於模壓成型之晶片偏移探討
Die Shift Assessment During Compression Molding in Fan-out Wafer-Level Packaging Process
摘要
由於電子產品有微型化、多功能、高性能及可攜性之迫切需求，且微影製程技術正面臨瓶頸，因而促使先進構裝技術之蓬勃發展。扇出型晶圓級構裝已成為目前發展最迅速的半導體構裝技術之一，其雖有成本低、體積小、I/O數高、電熱性能優良及多功能整合能力佳等優點。但仍有許多技術待解決，其中如晶片偏移之問題即頗為重要，將導致製程之對位不佳，致影響良率與後續製程之執行。 造成晶片偏移之原因可概分為流場效應與熱機械效應兩大類。流場效應乃源自於高溫模壓製程中，液態模封材料因受擠壓往晶圓外側流動，晶片承受模流拖曳力而產生偏移。熱機械效應則係由於製程中之升降溫造成構裝元件之熱膨脹與收縮、模封材料之固化收縮及構裝元件之翹曲，而造成晶片偏移。本論文主要目標，即在針對流場與熱機械效應所導致之晶片偏移進行探討，並尋求可能改善方案。 對於流場效應產生之晶片偏移，本論文首先進行熱示差掃描分析(Differential Scanning Calorimetry, DSC)實驗，找出模封材料溫度與時間相依之固化程度，配合數學模型建構其固化反應動力特性。再結合黏度量測得到溫度與固化度相依之黏度，並藉Moldex3D®模流分析軟體計算晶片承受之模流拖曳力。根據此計算求得之模流拖曳力，本論文接著利用ABAQUS®有限元素套裝軟體計算流場效應引發之晶片偏移量。 對於熱機械效應產生之晶片偏移，本論文進行動態熱機械分析(Dynamic Mechanical Analysis, DMA)與熱機械分析(Thermal-Mechanical Analysis, TMA)實驗，分別量測模封材料之溫度相依楊氏模數與熱膨脹係數。並藉ANSYS®有限元素套裝軟體計算經多段製程後由熱機械效應引發之晶片偏移量。 經由本論文分析流體與熱機械效應所導致之晶片偏移量，本論文最後進行各影響參數之分析。結果顯示，降低壓縮速度、晶片數量、晶片間距與厚度或增加模封材料之厚度與初始直徑，或選用與模封材料室溫CTE相近之載板，或使用高體積收縮率之模封材料等，皆可降低晶片偏移量。本論文之成果將對降低扇出型晶圓級構裝於模壓成型之晶片偏移量提供一可參考之設計方向。
並列摘要
Due to the urgent need for miniaturization, multi-function, high performance and portability of electronic products, and the bottlenecks of lithography process technology, the advanced packaging technology is booming. The fan-out wafer level assembly has become one of the fastest growing semiconductor assembly technologies, which has the advantages of low cost, small size, high I/O count, excellent electrothermal performance and excellent multi-functional integration capability. However, there are still many problems to be solved, such as die shift, which will lead to poor alignment of the subsequent process, hence impacting the yield and subsequent process execution. The causes of die shift can be broadly divided into two categories: fluid flow effect and thermal-mechanical effect. The fluid flow effect is derived from the compression molding process at high temperature. The liquid molding compound flows to the periphery of the wafer and the dies are subjected to the drag force of the mold flow to cause the die shift. The thermal-mechanical effect is due to the thermal expansion and contraction of the packaging components during the processes, the curing shrinkage of the molding compound and the warpage due to the mismatch of the coefficient of thermal expansion between the packaging components, which causes the die shift. The main goal of this paper is to explore the die shift caused by fluid flow and thermo-mechanical effects, and to seek possible improvement. For the die shift generated by the fluid flow effect, the paper firstly conducted a Differential Scanning Calorimetry (DSC) experiment to find out the time- and temperature-dependent degree of cure of the molding compound, and constructed the cure kinetic characteristics with the mathematical model. The temperature- and cure-dependent viscosity is determined by combining the time- and temperature-dependent viscosity and the developed cure kinetics model. The mold flow analysis is conducted using Moldex3D® to calculate the flow drag force acting on the dies. Based on the calculated drag force, this paper then uses the finite element software ABAQUS® to calculate the die shift caused by the fluid flow effect. For the die shift caused by the thermal-mechanical effect, this thesis conducts dynamic mechanical analysis (DMA) and thermal-mechanical analysis (TMA) experiments to measure the temperature-dependent Young’s Modulus and coefficient of thermal expansion of the molding compound. The finite element software ANSYS® is used to calculate the die shift caused by the thermal-mechanical effect after the multi-stage process. Through the paper, the die shift caused by fluid and thermal-mechanical effects is analyzed. At the end of this paper, the analysis of each parameter is carried out. The results show that reducing the compression speed, the number of dies, the die pitch and thickness, or increasing the thickness and initial diameter of the molding compound, or using a carrier plate with a CTE similar to the molding compound at room temperature, or using a molding compound with high volume shrinkage, etc., can reduce the die shift. The results of this paper will provide a reference design direction for reducing the die shift of the fan-out wafer level packaging in compression molding process.