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Centura® Avatar™ Etch

Brad Howard outlines the challenges in etching 3D NAND Flash memory structures and the Avatar system’s breakthrough solutions.

Conventional planar flash memory technology is approaching critical scaling limitations that are driving the transition to 3D solutions. This creates significant challenges for dielectric etching, especially of high aspect ratio (HAR) features. Furthermore, emerging 3D NAND architecture involves stacks of alternating dielectric layers that intensifies demands placed on the etch system. It must be capable of exacting profile control across the entire wafer for feature aspect ratios up to 80:1, high throughput, and exceptionally high tungsten selectivity for 3D NAND’s signature staircase contact.

The Applied Avatar system combines step-to-step temperature tuning and control, which ensures the correct temperature set point and stability for each portion of the etch sequence, with triple-frequency power and multi-zone gas injection to attain aggressive etch depths with benchmark profile control. Customers can manufacture high performance, robust, next-generation devices at high throughput with 97% bottom-to-top CD ratios across the wafer and no sidewall bowing. Moreover, high-selectivity etch produces negligible loss of the underlying contact material.

These capabilities are essential for the complex 3D NAND staircase contact application. It demands highly sophisticated control of ion energy, wafer temperature, and passivation to achieve the multi-level contact etch in one pass without eroding the tungsten (or future contact material) at the bottom of the shallowest contact holes.

Maintaining adequate mask selectivity and integrity are vital yet highly challenging for HAR etch. For these applications, tuning the very high frequency top source creates higher plasma densities that make possible higher mask etch rates and throughput without jeopardizing profile and selectivity.