Si-H bond breaking induced retention degradation during packaging process of 256 mbit DRAMs with negative wordline bias
Si-H bond breaking induced retention degradation during packaging process of 256 mbit DRAMs with negative wordline bias
复制标题
在具有负字线偏置的 256 mb DRAM 封装过程中，Si-H 键断裂导致保持力下降
DOI：
10.1109/ted.2005.844743
复制
发表时间：
2005
影响因子：
3.1
通讯作者：
P.
中科院分区：
文献类型：
--
作者：
Minchen Chang;Jengping Lin;Chao;Ruey;S. Shih;Mao;P.
本文研究了 256-Mbit DRAM 在封装过程中的数据保留退化。电气测量和设备模拟表明，即使在约 250/spl deg/C 的封装过程中，陷阱辅助泄漏也会降低保留时间。退化芯片的保留时间强烈依赖于负字线电压和工作温度，但对衬底偏压不太敏感。陷阱辅助栅极引起的漏极泄漏被认为是退化芯片中保留损失的机制。退化的芯片通常可以通过另一种热烘烤工艺来修复。根据后端钝化氧化物和氮化物层的 Si-H 键密度与具有负字线偏置的 DRAM 芯片的保留性能密切相关的事实，我们提出 Si-H 键断裂以及随后在栅极和漏极重叠区域产生陷阱作为保留退化的根本原因。此外，封装芯片在 250/spl deg/C 的热烘烤过程中表现出可变的保持行为。理论计算表明，陷阱的产生或移动到栅极下方的高电场区域可以使陷阱辅助栅极引起的漏极泄漏增加大约一个数量级。
Data retention degradation of a 256-Mbit DRAM during the packaging process is investigated in this paper. Electrical measurement and device simulation show that a trap-assisted leakage degrades the retention time even in packaging process at about 250/spl deg/C. Retention time of the degraded chip is strongly dependent on the negative wordline voltage and operation temperature, but less sensitive to the substrate bias. Trap-assisted gate induced drain leakage is proposed as the mechanism of retention loss in the degraded chip. The degraded chips usually can be repaired by another thermal baking process. We propose Si-H bond breaking and the subsequent trap generation at the gate and drain overlap region as the root cause of retention degradation according to the fact that the Si-H bond density of backend passivation oxide and nitride layers correlate well with the retention performance of DRAM chips with negative wordline bias. Moreover, the packaged chip shows variable retention behavior during a thermal baking of 250/spl deg/C. Theoretical calculation indicates that the trap generation or movement to the high electrical field region beneath the gate can increase the trap-assisted gate induced drain leakage by about an order of magnitude.