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晶圆越做越薄背后
半导体行业观察· 2025-03-21 01:08
Core Viewpoint - The demand for ultra-thin wafers is increasing due to the transition from planar SoC to 3D-IC and advanced packaging, which enhances performance and reduces power consumption [1][18]. Group 1: Thin Wafer Processing - The total thickness of HBM modules, which include 12 DRAM chips and basic logic chips, is still less than that of high-quality silicon wafers [1]. - Thin wafers play a crucial role in fan-out wafer-level packaging and advanced 2.5D and 3D packaging for AI applications, which are growing faster than mainstream ICs [1]. - The processing of ultra-thin wafers requires careful decisions regarding temporary bonding adhesives, carrier wafers, and debonding processes [1][3]. Group 2: Challenges in Wafer Thinning - Engineers face challenges in preventing defects or micro-cracks, especially at the wafer edges, which can significantly impact yield [10]. - The thinning process involves a balance of grinding, chemical mechanical polishing (CMP), and etching to meet strict total thickness variation (TTV) specifications [8]. - The most common TSV architecture in silicon features a diameter of 11 micrometers and a depth of 110 micrometers, with a barrier metal and oxide insulation layer occupying 1 micrometer of that diameter [9]. Group 3: Temporary Bonding and Debonding - The industry is refining thinning steps, adhesives, and debonding chemicals, with temporary bonding typically performed under vacuum thermal compression or UV exposure [3][7]. - Glass and silicon carrier wafers are both used, with glass being popular due to its thermal expansion coefficient (CTE) compatibility with silicon [5]. - Mechanical debonding methods are preferred for thinner wafers, as they allow for lower stress levels and better thermal budgets [15]. Group 4: Adhesive Properties and Requirements - Ideal adhesives should bond at low temperatures and withstand high-temperature processing without degrading performance [7]. - The adhesive's uniformity in thickness is critical, as any inconsistency can lead to uneven back grinding and processing challenges [7][8]. - The choice of adhesive is influenced by temperature stability, with some materials capable of withstanding temperatures up to 350°C [7]. Group 5: Yield and Reliability - Chip manufacturers are seeking customized solutions for specific device types, emphasizing the need for tool reliability and process repeatability [2]. - The industry is focused on achieving high yield and reliability in producing ultra-thin devices with thicknesses below 50 micrometers [18]. - The management of back and edge defects is essential for maintaining yield, with selective plasma etching and CVD being employed to mitigate edge defects [10][11].