标题: | 应用于毫微米波段高电子迁移率电晶体之覆晶封装研究 Flip-chip Packaging Structure of HEMTs Devices for Millimeter-wave Applications |
作者: | 王景德 Wang, Chin-Te 张翼 Chang, Edward Yi 材料科学与工程学系所 |
关键字: | 覆晶封装;高电子迁移率电晶体;毫微米波;底胶填充;可靠度;Flip-Chip Package;HEMTs;Millimeter-wave;Underfill;Reliability |
公开日期: | 2013 |
摘要: | 近年来,无线通讯与成像技术的快速发展,推动其频率源朝向毫微米与次毫微米波段,较大的传输频宽、高传输速度与高解析度为这些频率波段良好的特性,为了实现这些应用,封装技术扮演了非常重要的角色,不仅提供了晶片与基板的传输途径,还提供了散热与保护的功能。在毫米波段的晶片层级封装上,覆晶封装为受到注目的技术,与传统的打线接合比较,覆晶封装的优点包含了较短的转接路径来减少寄生效应、较高的生产效率以及更小的封装尺寸。 本论文探讨应用于毫微米波段之覆晶封装。首先,砷化镓铟高电子迁移率电晶体封装于氧化铝基板上,在60GHz量测结果,藉由最佳化的覆晶转接,覆晶封装前后的元件特性几乎相同。此外,利用微波积体电路概念设计并制作60GHz 两阶增益器,来验证覆晶封装元件设计V-band电路的可行性,将高电子迁移率电晶体封装于设计有匹配电路的氧化铝基板上,在60GHz时此增益器呈现9dB的小讯号增益,从结果显示此微波积体电路的概念于毫微米波段的可行性。此外,由于晶片与基板的热膨胀系数的不匹配会产生热应力,而导致封装结构的损坏,利用BCB当做底胶填充的材料来增加覆晶结构的机械强度与可靠度,从100GHz量测结果中,拥有较好的介电特性的BCB表现出优于传统环氧树脂底胶填充的高频特性,从热循环测试与剪切力测试的结果,BCB的填充可以有效的提升覆晶封装结构的可靠度。 利用直接覆晶封装(FCOB)于第二层的基板而省略晶片层级的封装,在未来毫微米波应用达成兼顾成本效应与良好特性,商用的RO3210高分子基板因为有与氧化铝基板相近的介电特性为有潜力的基板材料,封装在高分子基板上的元件搭配经过最佳化的覆晶转接直到W-band呈现良好的特性,利用最佳化的封装结构,封装元件仍拥有低杂讯且良好的增益特性,同时环氧树脂底胶填充有效增加高分子覆晶结构的可靠度且没有明显的特性损耗。此外,也探讨覆晶封装制程中的温度对封装元件特性的影响,从实验中可以发现较高的接合温度会产生高频特性的损耗,主要的原因是覆晶结构中砷化镓晶片与高分子基板的热膨胀系数不同所产生的热应力,且利用有效电路模型,从S参数中萃取出的寄生电阻电容数值中可以发现,较高的接合温度有较高的数值,因此,合理的覆晶接合条件可以减少热应力并保持良好特性。 In recent years, the rapid development for wireless communication and imaging system has pushed the operational frequency for wireless communication to millimeter-wave or sub millimeter-wave bands. These frequency bands have several advantages, including wide transmission bandwidth, high transmission speed, and high signal resolution. In order to realize the targeted applications, the packaging technology plays an important role to provide the transmission path from chip to substrate, the heat dissipation, environment protection. In the chip-level packaging, the flip-chip is the more promising approach for millimeter-wave applications in comparison with conventional wire bonding. The advantages of the flip-chip interconnection are short path to reduce the parasitic effect and compact product size. This dissertation presents the study on the flip-chip packaging structure of HEMT devices for millimeter-wave applications. The flip-chip packaged In0.7Ga0.3As MHEMT device was firstly demonstrated on Al2O3 substrate. By adopting the optimized design for the flip-chip transition, the packaged device shows almost similar RF performance as the bare die up to 60 GHz. In addition, a two-stage gain block at 60 GHz was designed and fabricated using the microwave integrated circuit (MIC) approach to demonstrate the applicability for V-band applications. The MHEMT device was flip-chip packaged on Al2O3 substrate with the matching circuit. The gain block exhibited a small signal gain of 9 dB at 60 GHz, indicating the feasibility of MIC approach for millimeter-wave applications. The thermal stress induced by the coefficient of thermal expansion (CTE) mismatch between the chip and the substrate can distort the flip-chip structure. BCB material was used as the underfill to improve the reliability and mechanical property of the flip-chip structure. The good dielectric property of BCB exhibited better RF characteristics up to 100 GHz as compared to the conventional epoxy-based underfill. From the results of thermal cycling test and shear force test, BCB underfill can effectively improve the reliability of the flip-chip structure. The flip-chip on board (FCOB) technology bypassed the chip-level package to achieve cost-effective millimeter-wave package. The RO 3210 polymer substrate was the promising substrate because its dielectric property is similar to Al2O3 substrate. The packaged device with the optimal flip-chip structure exhibited good RF results up to W-band. An exopy-based underfill was applied to improve the reliability without the characteristic degradation of the device. Analytical results revealed that the proposed packaging structure maintained a low minimum noise figure of 3 dB with 6 dB of associated gain at 62 GHz. In addition, the impact of bonding temperature on the device performance was also investigated. The degradation in RF performance was observed at higher bonding temperature. The reason of the degradation was mainly due to the mismatch in the CTE between the GaAs chip and the polymer substrate. From the equivalent circuit extraction from S-parameter measurements, the higher parasitic values occurred during the higher bonding temperature. The applicable bonding condition could reduce the thermal stress without degrading the RF performance. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#GT079518522 http://hdl.handle.net/11536/74216 |
显示于类别: | Thesis |
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