变温LPCVD沉积氮化硅薄膜的均匀性优化

以低压化学气相沉积(LPCVD)热壁立式炉为实验平台,由二氯硅烷和氨通过LPCVD工艺合成氮化硅薄膜,利用降温成膜提高氮化硅薄膜的膜厚均匀度。基于气体碰撞理论建立了氮化硅薄膜沉积速率与反应气体浓度的关系式。分析比较了LPCVD炉内不同升温速率沉积氮化硅薄膜的表面性能。发现在变温沉积阶段,选择合适的降温速率是实现薄膜沉积过程中预设温度变化的关键。在保证各温度区平均膜厚和晶圆片之间膜厚均匀度基本不变的前提下,通过实验找到沉积阶段的最佳变温速率,将晶圆片内(WIW)均匀度优化到1%以下,比恒温沉积薄膜的均匀度提高了约70%。这将有助于设备工艺能力的提升,更好地适应IC芯片工艺关键尺寸的缩小趋势。

Uniformity Optimization of the Silicon Nitride Film Deposited by Variable Temperature LPCVD

A low pressure chemical vapor deposition(LPCVD)hot wall vertical furnace was used as an experimental platform to synthesize the silicon nitride film by dichlorosilane and ammonia via the LPCVD process,the thickness uniformity of the silicon nitride film was improved by cooling film formation.Based on the gas collision theory,the relationship between the deposition rate of the silicon nitride film and the concentration of the reaction gas was established.The surface properties of the silicon nitride films deposited at different heating rates in the LPCVD furnace were analyzed and compared.It is found that in the variable temperature deposition stage,the selection of the appropriate cooling rate is the key to realize the preset temperature changes during the film deposition process.On the premise that the average film thickness in each temperature zone and the film thickness uniformity between wafers are basically unchanged,the optimal temperature change rate in the deposition stage is found through experi-ments,and the within wafer(WIW)uniformity is optimized to less than 1%,which is about 70%higher than that of the film deposited at constant temperature.It will be conducive to improve the equipment process capacity and adapt to the trend of the scaling of the IC chip process critical dimension.