THE RELATIONSHIP BETWEEN DEPOSITION CONDITIONS, THE BETA TO ALPHA PHASE-TRANSFORMATION, AND STRESS-RELAXATION IN TANTALUM THIN-FILMS
THE RELATIONSHIP BETWEEN DEPOSITION CONDITIONS, THE BETA TO ALPHA PHASE-TRANSFORMATION, AND STRESS-RELAXATION IN TANTALUM THIN-FILMS
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DOI：
10.1063/1.352059
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发表时间：
1992-11-15
影响因子：
3.2
通讯作者：
BARMAK, K
中科院分区：
文献类型：
--
作者：
CLEVENGER, LA;MUTSCHELLER, A;BARMAK, K
我们证明了高温多晶钽相从四方β相到立方α相的转变导致薄膜电阻的大幅降低，并且在本质上是压缩应力的薄膜中完全应力松弛。通过蒸发或直流磁控溅射，在热氧化（100）硅片上沉积了100 nm的β钽薄膜，其固有应力为2.0 X 10(10) dynes/cm2（拉伸）至-2.3 X 10(10) dynes/cm2（压缩）。在纯化的氦气中，在10℃/min至850℃的温度下测量原位应力和电阻。加热后的主要应力机制为低温弹性变形、中温塑性变形和高温β - α相变导致的应力消除。随着沉积压力和衬底偏置的不同，发生弹塑性变形和β - α相变的温度范围也不同。如果薄膜最初沉积在α相，或者由于沉积过程中衬底偏置导致β相在800℃下未完全转变为α相，则在高温下观察到不完全压应力松弛。结果表明，具有本征压应力的钽薄膜完全解除应力的主要机制是β - α相变，而对于具有本征拉应力的薄膜，这种转变对应力的影响要小得多。
We demonstrate that the high temperature polymorphic tantalum phase transition from the tetragonal beta phase to the cubic alpha phase causes a large decrease in the resistance of thin films and a complete stress relaxation in films that were intrinsically compressively stressed. 100 nm beta tantalum thin films with intrinsic stresses of 2.0 X 10(10) dynes/cm2 (tensile) to -2.3 X 10(10) dynes/cm2 (compressive) were deposited onto thermally oxidized (100) silicon wafers by evaporation or dc magnetron sputtering with argon. In situ stress and resistance at temperature were measured at 10-degrees-C/min up to 850-degrees-C in purified helium. Upon heating, the main stress mechanisms were elastic deformation at low temperature, plastic deformation at moderate temperatures and stress relief because of the beta-to-alpha phase transition at high temperatures. The temperature ranges over which the elastic and plastic deformation and the beta-to-alpha phase transition occurred varied with deposition pressure and substrate biasing. Incomplete compressive stress relaxation at high temperatures was observed if the film was initially deposited in the alpha phase or if the beta phase did not completely transform into alpha by 800-degrees-C due to substrate biasing during the deposition. We conclude that the main stress relief mechanism for tantalum films with intrinsic compressive stresses to completely relax their stress is the beta-to-alpha phase transition, while for intrinsically tensile films, this transformation has a much smaller effect on the stress.