Internal Stress and Atomic Transportation in Thin Film and Line Structure

Research Project

Project/Area Number	10650092
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Single-year Grants
Section	一般
Research Field	Materials/Mechanics of materials
Research Institution	The University of Tokushima
Principal Investigator	HANABUSA Takao Faculty of Engineering, The University of Tokushima, Professor, 工学部, 教授 (20035637)
Co-Investigator(Kenkyū-buntansha)	KUSAKA Kazuya Faculty of Engineering, The University of Tokushima, Research Assistant, 工学部, 助手 (70274256)
Project Period (FY)	1998 – 1999
Project Status	Completed (Fiscal Year 1999)
Budget Amount *help	¥3,500,000 (Direct Cost: ¥3,500,000) Fiscal Year 1999: ¥1,500,000 (Direct Cost: ¥1,500,000) Fiscal Year 1998: ¥2,000,000 (Direct Cost: ¥2,000,000)
Keywords	Thin film / Internal stress / Thermal stress / In-situ observation / Surface morphology / Stress migration / Preferred orientation / X-ray stress measurement / Cu膜 / 熱サイクル / ストレスマグレーション
Research Abstract	In order to investigate the property of atomic migration in high temperature region of aluminum and copper for the materials used in LSI technology, in-situ X-ray thermal stress measurement and optical as well as electronic observations of surface morphology of Al and Cu films. Al and Cu films deposited on a glass or a Si substrate by RF sputtering had strong < 111 > preferred orientation. Residual stress in an as-deposited state was tensile in all the case regardless of the RF power, Ar gas pressure and sputtering time. An in-situ thermal stress measurement was made by X-ray diffraction technique on the specimens under the heating and cooling cycles between RT and 200℃, 300℃, and 400℃. The tensile stress in the films almost diminished to zero level by increasing temperature to 100℃ and after that there was no significant change in the stress level up to the maximum temperature in each thermal cycle. In the cooling stage, the stress in the film changed to tensile but the increasing rate was small in the initial stage and became large in the final stage of low temperature range. It is due to the ability of grain boundary diffusion, surface diffusion and body diffusion. On the other hand, the variation of the thermal stress in films covered by thin AlN or TiN film was large during the thermal cycles because of the constraining of the atomic transportation by the protective film deposited on the surface of Al or Cu film. From SEM and AFM observations, it was cleared that hillocks and voids develop in the heating stage and cooling stage, respectively. Furthermore, the change in surface roughness and the appearance of recrystallization were observed in the heating stage by the in-situ laser microscopic investigation.