晶圓在經過封裝廠的研磨薄化及切割後，形成晶粒；晶粒的強度在不同面向會受到相對製程的影響。具體來說：非金屬面(矽晶圓的矽面)，會受到研磨薄化的影響，若研磨輪在晶粒上留下的齒痕越深，晶粒強度就越弱；相反，若研磨輪留下的齒痕淺或經過拋光處理，表面無明顯磨痕，則晶粒強度較強。金屬面(球面/凸塊面/接點面)，會受到切割影響。晶圓切割方法多樣，如鑽石刀切割、雷射開槽切割、隱形雷射切割、雷射全切穿切割等。在雷射開槽切割道中，奈秒（長脈衝）雷射和皮秒（短脈衝）雷射各有不同。短脈衝及高峰值功率特性減少對加工物的熱影響，減少燒融現象及微裂紋的產生，降低熱融物再結晶及相變，形成光滑的開槽表面及低粗糙度，減少應力集中點，增強晶粒抗裂能力及整體強度。了解皮秒雷射開槽切割中各參數因子對加工物切割道的開槽表現，如寬度、深度、形狀。通過一次一因子分析找出最佳參數搭配，並挑選三組雷射開槽參數在切割道上加工，而後對晶粒做三點應力強度分析。結果顯示皮秒雷射開槽參數因子的加工次數及功率對晶粒有些微影響，但整體應力強度608Mpa相較於奈秒雷射238Mpa提升2~3倍。皮秒雷射減少了晶粒表面的微裂紋和熱融物再結晶，形成更光滑表面，減少應力集中點，期望藉由提高晶粒強度，而能提升產品的封裝良率。

After being thinned and cut by the packaging plant, the wafer forms into individual die. The strength of these die is affected by different aspects of the process. Specifically, the non-metallic side (the silicon side of the wafer) is influenced by the grinding process. If the grinding wheel leaves deep grooves on the die, the strength of the die will be weaker. Conversely, if the grinding wheel leaves shallow grooves or if the surface undergoes polishing with no visible grinding marks, the die strength will be stronger. The metallic side (ball surface/bump surface/contact surface) is affected by the cutting process. Various wafer cutting methods exist, such as diamond blade cutting, laser scribing, stealth dicing, and full laser cutting.
In the laser scribing process, nanosecond (long pulse) lasers and picosecond (short pulse) lasers behave differently. The short pulse and high peak power characteristics of picosecond lasers reduce the thermal impact on the material being processed, minimizing melting phenomena and the formation of microcracks. This reduces recrystallization of molten material and phase changes, resulting in a smooth scribed surface with low roughness, reducing stress concentration points, and enhancing the die's crack resistance and overall strength.
Understanding the effect of various parameters in picosecond laser scribing on the scribed groove, such as width, depth, and shape, is crucial. Through a one-factor-at-a-time analysis, the optimal parameter combinations were identified, and three sets of laser scribing parameters were selected for processing the scribe lines. Subsequently, a three-point bending strength test was performed on the die. The results showed that while the number of passes and power settings of the picosecond laser had a slight impact on the die, the overall stress strength reached 608 MPa, which is 2-3 times higher than the 238 MPa achieved with nanosecond lasers. Picosecond laser scribing reduces microcracks and recrystallization on the die surface, forming a smoother surface, reducing stress concentration points, and ultimately improving the packaging yield by enhancing the die strength.

[1] DISCO Corporation, "ZH05 series," from https://www.disco.co.jp/eg/products/blade/zh05.html
[2] Te-Jen Su, Yi-Feng Chen, Jui-Chuan Cheng, and Chien-Liang Chiu, "Optimizing the dicing saw parameters of 60 μm wafer dicing street," Microsyst Technol, vol. 24, pp. 3965–3971, October (2018).
[3] Accretech CORPORATION , " Perfect wafers for perfect microchips," from https://www.accretech.eu/en/applications/semiconductor/
[4] Olga Varlamova, Mourad Bounhalli and Juergen Reif, "Influence of irradiation dose on laser-induced surface nanostructures on silicon," Applied Surface Science, vol. 278, pp. 62-66, June (2013).
[5] Esther Rebollar, Javier R. Vázquez de Aldana, José A. Pérez-Hernández, Tiberio A. Ezquerra, Pablo Moreno and , Marta Castillejo, "Ultraviolet and infrared femtosecond laser induced periodic surface structures on thin polymer films," Applied Physics Letters, vol. 100, 041106, January (2012).
[6] B. N. Chichkov, C. Momma and S. Nolte and F. von Alvensleben and A.Tünnermann "Femtosecond, picosecond and nanosecond laser ablation of solids," Indian Journal of Forensic Medicine & Toxicology, vol. 63, pp. 109–115 (1996).
[7] Mingying Sun, Urs Eppelt, Claudia Hartmann, Wolfgang Schulz, Jianqiang Zhu, and Zunqi Lin, "Damage morphology and mechanism in ablation cutting of thin glass sheets with picosecond pulsed lasers," Optics & Laser Technology, vol. 80,pp. 227-336, June (2016).
[8] Daragh S. Finn, Zhibin Lin, Jan Kleinert, Michael J. Darwin and Haibin Zhang " Study of die break strength and heat-affected zone for laser processing of thin silicon wafers," Journal of Laser Applications, vol. 27, No. 3, August, 032004 (2015).
[9] Matthias Domke, Bernadette Egle, Sandra Stroj, Marius Bodea, Elisabeth Schwarz and Gernot Fasching " Ultrafast-laser dicing of thin silicon wafers: strategies to improve front- and backside breaking strength," Applied Physics A, vol. 123, article number 746, (2017).
[10] C. Moutin, B. Bouillard, C. Cowache, O. Robin, M. Porto and , E. Noraz, "Laser grooving process modifications to avoid recast growth during reliability stresses," Applied Physics Letters, vol. 100, 041106, Jun (2022).
[11] N. Semmar, A. Talbi, M. Mikikian, A. Stolz, A. Melhem and D. de Sousa Meneses, "Micro-spikes formed on mesoporous silicon by UV picosecond laser irradiation," Applied Surface Science, vol. 509,144820, April (2020).
[12] P. Laurent, O. Robin and B. Bouillard, "LowK wafer dicing robustness considerations and laser grooving process selection," IEEE 8th Electronics System-Integration Technology Conference (ESTC), Oct (2020).
[13] Natsuki Suzuki, Takayuki Ohba, Yuta Kondo, Takeshi Sakamoto, Naoki Uchiyama and Kazuhiro Atsumi, "High Throughput and Improved Edge Straightness for Memory Applications Using Stealth Dicing," 2018 IEEE 68th Electronic Components and Technology Conference (ECTC), Aug (2018).
[14]　 James Weber and Shogo Okita, "Plasma Dicing of Wafers for Reduced Total Cost of Ownership and Increased Quality," 2020 IEEE 8th Electronics System-Integration Technology Conference (ESTC), Sep (2020).
[15]　 Canwen Wang, Jingyang Su, Siyuan Lu, Wenhui Zhu and Liancheng Wang, "Study on Picosecond Pulsed Laser Grooving Technology for Low-k Silicon Wafer," 2023 24th International Conference on Electronic Packaging Technology (ICEPT), Apr (2024).
[16]　 Ru Zhang, Chuanzhen Huang, Jun Wang, Dongkai Chu, Dun Liu and Shaochuan Feng, "Experimental investigation and optimization of femtosecond laser processing parameters of silicon carbide–based on response surface methodology," Sciencedirect, vol. 48, pp. 14507-14517, May (2022).
[17]　 Ru Zhang, Chuanzhen Huang, Jun Wang, Hongtao Zhu, Peng Yao and Shaochuan Feng, "Micromachining of 4H-SiC using femtosecond laser," Sciencedirect, vol. 44, pp. 17775-17783, Oct (2018).
[18]　 Quanjing Wang, Ru Zhang, Qingkui Chen and Ran Duan, "A Review of Femtosecond Laser Processing of Silicon Carbide," Micromachines, vol. 15, May (2024).
[19]　 Michael Raj Marks, Kuan Yew Cheong and Zainuriah Hassan, "A review of laser ablation and dicing of Si wafers," 2020 IEEE 8th Electronics System-Integration Technology Conference (ESTC), vol. 79, pp. 377-408, Jan (2022).
[20]　 A. Podpodent, F. Inoue, I. De Wolf, M. Gonzalez, M. K. Rebibis, R. A. Miller and E. Beyne, "Investigation of Advanced Dicing Technologies for Ultra Low-k and 3D Integration," 2016 IEEE 66th Electronic Components and Technology Conference (ECTC), Aug (2016).
[21]　 Wang ZhiJie, Sonder Wang, J.H. Wang, Stephen Lee, Yao SuYing, Richard Han and Y.Q. Su, "300mm Low K Wafer Dicing Saw Study," Proc.IEEE 6th International Conf. on Electronic Packaging Technology, Aug (2005).
[22]　 C. Chen, M. Li and K. Cao, "Laser Grooving Technology Study at Dicing Process in Wafer Level Package," 2018 19th International Conference on Electronic Packaging Technology (ICEPT), Oct (2018).
[23]　 E. Gourvest, I. Raid, O. Robin, C. Trouiller, S. Gallois-Garregnot and J-E. Luan, "Experimental and Numerical Study on Silicon Die Strength and its Impact on Package Reliability," 2018 20th Electronics Packaging Technology Conference, Feb (2019).
[24]　 M. Fuegl, G. Mackh, E. Meissner and L. Frey, "Assessment of dicing induced damage and residual stress on the mechanical and electrical behavior of chips," 2015 IEEE 65th Electronic Components and Technology Conference (ECTC), Jul (2015).
[25] "Pansci.", from https://pansci.asia/archives/143163
[26] Ankita Sinha, Susant Mohanty and Sonu Acharya, "Lasers in Pediatric Dentistry: A Review Article," Indian Journal of Forensic Medicine & Toxicology, vol 14, Issue 4, pp. 8990-8997 (2020).
[27] Keyence CORPORATION, "Laser theory." from https://www.keyence.com.tw/ss/products/marking/lasermarker/knowledge/principle.jsp
[28] Keyence CORPORATION, "Fiber vs. CO2 vs. UV: Which Laser Marker Should I Choose?." Apr 23, 2023 from https://www.keyence.com/products/marker/laser-marker/resources/laser-marking-resources/fiber-vs-co2-vs-uv-which-laser-marker-should-i-choose.jsp
[29] Ganesh Dongre, Ramesh Gondil and Avadhoot U Rajurkar, "High aspects ratio micro-drilling of super-alloys using ultra short pulsed laser."International Journal of Precision Technology, vol 8, pp. 124-141 (2019).
[30] Wikipedia, "Three-point_flexural_test." ,from https://en.wikipedia.org/wiki/Three-point_flexural_test
[31] Geoff Shannon and Steven Hypsh, "Femtosecond laser processing of metal and plastics in the medical device industry." (2014).
[32] "Hi-Top." ,from https://www.hi-top.com.tw/OLYMPUS/keyence%20sem%20ra%20VK-X100-200-1.pdf
[33] MTS Systems, "3-Point Bend Fixtures," ,from https://www.mts.com/en/products/materials/fixtures/3-point-bend-fixtures