Patent ID: 8852385

Claim:
A plasma etching apparatus comprising: a process container configured to be vacuum-exhausted; a first electrode disposed inside the process container and serving as an upper electrode; a second electrode disposed inside the process container and opposite to the first electrode and serving as a lower electrode configured to support a target object thereon; a first RF power supply unit connected to the first electrode or the second electrode and configured to apply a first RF power for plasma generation to the first electrode or the second electrode, the first RF power having a frequency of 27 to 100 MHz; a second RF power supply unit connected to the second electrode and configured to apply a second RF power for providing a bias for ion attraction to the second electrode, the second RF power having a frequency of 400 kHz to 13.56 MHz; a process gas supply unit configured to supply a process gas into the process container; a bias controller configured to control the second RF power supply unit; and a control section configured to control an operation of the apparatus and including a non-transitory storage medium storing a control program, the control program being programmed to control the apparatus by the control section to conduct a plasma etching sequence for processing as the target object a target substrate having a layer structure including an underlying film and an etching target film formed thereon, the plasma etching sequence including etching at least part of the etching target film down to an upper surface of the underlying film by first performing a main etching process and then switching to a sub etching process on the layer structure while generating plasma above the etching target film, wherein the main etching process includes operating the second RF power supply unit in a continuous mode that executes continuous supply of the second RF power at a constant power level, while operating the first RF power supply unit to apply the first RF power, the sub etching process includes operating the second RF power supply unit in a power modulation mode that repeats power modulation on levels of the second RF power between a first power of 10 to 500 W and a second power of 100 to 5,000 W and larger than the first power, while operating the first RF power supply unit to apply the first RF power, such that the first power is used during a first period to deposit polymers on the layer structure and the second power is used during a second period to promote etching of the layer structure, and a thickness of the polymers obtained by the first period on the upper surface of the underlying film is larger than an ion penetration depth obtained by the second period, the continuous mode is switched to the power modulation mode immediately before the etching target film is penetrated by the main etching process and the underlying film is thereby eroded, and the first RF power applied by the first RF power supply unit for plasma generation remains the same in the main etching process and the sub etching process.