Abstract
This is the first demonstration of sidewall slope control of InP via holes with an etch depth of more than 10 μm for 3D integration. The process for the InP via holes utilizes a common SiO2 layer as an InP etch mask and conventional inductively coupled plasma (ICP) etcher operated at room temperature and simple gas mixtures of Cl2/Ar for InP dry etch. Sidewall slope of InP via holes is controlled within the range of 80 to 90 degrees by changing the ICP power in the ICP etcher and adopting a dry-etched SiO2 layer with a sidewall slope of 70 degrees. Furthermore, the sidewall slope control of the InP via holes in a wide range of 36 to 69 degrees is possible by changing the RF power in the etcher and introducing a wet-etched SiO2 layer with a small sidewall slope of 2 degrees; this wide slope control is due to the change of InP-to-SiO2 selectivity with RF power.
Highlights
The operation pressure, the temperature, and the type of the gas mixture are important input parameters of the inductively coupled plasma (ICP) etcher for the InP dry etching process that determine the etch morphology of the InP via holes
Process methodology for sidewall slope control of InP via holes with an etch depth of more than 10 μm for 3D integration was proposed for the first time
InP via holes was controlled within the range of 80 to 90 degrees by changing the ICP power in the ICP etcher and utilizing a dry-etched SiO2 layer with a sidewall slope of 70 degrees
Summary
Because sputter equipment has better step coverage than that of evaporator equipment, seed metals in the EP-based InP TSV process have mainly been deposited mainly by sputtering. Sputter-based seed metal deposition is known to suffer from shadowing effects when the aspect ratio (AR) of via holes, defined as the ratio of the height to the width of the structures, is more than one, leading to poor step coverage on via hole sidewalls [9]. TSV for integration hasofbeen decreased to about μm, corto the width of the structures, more than one, leading to poor step for coverage via hole responds to the limit value of is the CMP processes [6,7].
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