Ted Ming-Lang Guo

Wet Etch Rate Behavior of Poly-Si in TMAH Solution at Various Ambient Gas Conditions

As the demand for greater speed in semiconductor devices continues, a typical method of increasing charge mobility is to maximise the silicon strain at the depletion region in p-type transistors through the implementation of “Sigma Cavity” structures in the bulk silicon on either side of the gate structure. These structures, when filled, exhibit a uniaxial strain in the depletion region thus, increasing the charge transport speed [1]. The shape of the Sigma Cavity structure is important in maximising the strain in this region, thus strict control of the shape dimensions is imperative to the electrical performance of the device.

Single Wafer Selective Silicon Nitride Removal with Phosphoric Acid and Steam

A single wafer silicon nitride (SiN) selective etch process with an etch rate greater than 80A/min of low-pressure chemical vapor deposited (LPCVD) SiN has been developed. Previous work with a similar single wafer system utilized a mixture of sulfuric acid, phosphoric acid and steam to achieve a high SiN etch rate [1]. The process in this work relies on phosphoric acid and steam for a high SiN etch rate. In both of these applications, addition of steam doubles the SiN etch rate. The single wafer system utilizes a closed chamber design with integrated spray bar to uniformly dispense hot phosphoric acid and steam onto the wafer surface achieving within wafer non-uniformities of less than 3%. Rinsing and drying of the phosphoric acid from the wafer surface occurs in the same chamber (dry in/dry out) providing a stable, haze free wafer. Figure 1 contains a schematic of the phosphoric acid delivery and single wafer system.

Static Charge Induced Damage during Lightly Doped Drain (LDD) by Single Wafer Cleaning Process

The present work reports some approaches to reduce the static charge defects induced during single wafer cleaning process. Increase conductivity of DIW with CO2, adding backside rinse and IPA drying sequence optimization were evidenced to be effective by surface potential difference with Quantox tool. TEM and EELS were also used for analysis of volcano-like discharge defects.

Clean Process Mechanism of HKMG during N-PMOS Patterning

Chemical and physical modifications of photoresist and BARC during plasma patterning process on HKMG structure can cause residual defects and yield loss that challenges the subsequent wet cleaning process to resolve this issue. The chemical behavior of materials post dry etching and wet clean was systematically studied by various surface analytical techniques including STEM-EELS, XPS and AES. With a greater understanding of the etching and clean mechanisms, a combined aqueous/solvent cleaning method was developed and tested on a spin clean tool to effectively clean etching by-products. A significant improvement of yield with the application of the new cleaning approach has been observed.