Study on processing step uniformity tuning during FET fabrication and sensor wafer response as a function of chuck temperature adjustment

Abstract

The effect of chuck temperature adjustment on critical dimension uniformity was studied for the shallow trench isolation etch process by introducing a temperature gradient in a multi-temperature-zone electrostatic chuck. It is shown that the initial radial critical dimension non-uniformity can be improved by a gradual temperature adjustment of the electrostatic chuck and results in the target specification values of uniformity, 3σ ≤ 1.5 nm, for a critical dimension of about 35 nm. Both temperature and RF sensor wafers were used to analyze the impact of an electrostatic chuck temperature gradient on process uniformity by utilizing their unique in situ spatial and temporal mapping capabilities. Thus, the across-wafer thermal sensitivity of the critical dimension was estimated for dense structures: a temperature change of 1 °C leads to a critical dimension change of ∼0.7 nm. The RF sensor wafer was also shown to have a clear response of RF current uniformity to the electrostatic chuck temperature gradient that suggests there could be other phenomena affecting critical dimension uniformity besides temperature itself. The pure temperature contribution to critical dimension change was found to be less than 0.3 nm/°C for the temperature range studied. Finally, a possible mechanism of critical dimension tuning is discussed and an assessment of each separate etch step’s sensitivity to the electrostatic chuck temperature gradient is performed.

Planar heating chuck to improve temperature uniformity of plasma processing equipment

“…Reducing the temperature gradient across the wafer has become more important than ever. [1][2][3] As three-dimensional technologies such as 3D-NAND flash and FinFET are introduced 4) and continue to develop, semiconductor manufacturing productivity benefits from the ability to rapidly and cyclically ramp temperature up and down for the deposition of multi-layer thin films. Since the temperature characteristics of the chuck directly affect the uniformity of deposition and etch on the wafer, the temperature control capability of the wafer chuck cannot be overemphasized.…”

Assessment of STI dry etch process variability by means of dynamic time warping technique

“…In our case, the active litho stack consists of 150 nm spin-on carbon (SoC)/28 nm spin-on glass (SoG)/90 nm Resist layers, though a combination of advanced patterning film (APF) and SiOC could also be used in place of SoC/SoG layers. 12) The stack to pattern consists of 50 nm SiN, 5 nm pad SiO 2 , and the Si. The latter should be etched down to the depth of 270 nm in shallowest region.…”

Progress in nanoscale dry processes for fabrication of high-aspect-ratio features: How can we control critical dimension uniformity at the bottom?

“…41) Milenin et al reported that the electrostatic chuck temperature affected the CD uniformity. 42) A multiple temperature-zone chuck enabled the control of CD drift and shift. 42) Uniformity across the wafer scale is dominated by the spatial distribution of the plasma density.…”

“…42) A multiple temperature-zone chuck enabled the control of CD drift and shift. 42) Uniformity across the wafer scale is dominated by the spatial distribution of the plasma density. Maeda et al reported that the plasma density uniformity was controlled by the magnetic field in an ECR plasma etcher.…”