Methods and devices to reduce defects in dielectric stack structures
A variety of techniques may be employed alone or in combination to reduce the incidence of defects arising in dielectric stack structures formed by chemical vapor deposition (CVD). Incidence of a first defect type attributable to reaction between an unreacted species of a prior CVD step and reactants of a subsequent CVD step, is reduced by exposing a freshly-deposited dielectric layer to a plasma before any additional layers are deposited. Incidence of a second defect type attributable to the presence of incompletely vaporized CVD liquid precursor material, is reduced by exposing the freshly-deposited dielectric layer to a plasma, and/or by continuing the flow of carrier gas through an injection valve for a period beyond the conclusion of the CVD step.
1. A method of reducing incidences of defects in a stack of dielectric layers formed by chemical vapor deposition, the method comprising:
flowing a liquid silicon-and-oxygen-containing precursor material to an injection valve;
vaporizing the liquid silicon-and-oxygen-containing precursor material in a carrier gas flowed through the injection valve;
causing a reaction involving the vaporized liquid silicon-and-oxygen-containing precursor material to deposit a first dielectric layer;
halting the flow of liquid silicon-and-oxygen-containing precursor material to the injection valve at a first time while maintaining a flow of the carrier gas to the injection valve; and
halting the flow of carrier gas to the injection valve at a second time after the first time,
wherein a delay between halting of the flow of liquid silicon-and-oxygen-containing precursor material to the injection valve and halting the flow of carrier gas to the injection valve vaporizes the liquid silicon-and-oxygen-containing precursor material remaining in the injection valve and reduces incidences of defects in the stack of dielectric layers caused by subsequent deposition of liquid silicon-and-oxygen-containing precursor material.
2. The method of claim 1 wherein the flow of liquid silicon-and-oxygen-containing precursor material to the injection valve is halted between about 1-10 seconds before the flow of carrier gas to the injection valve is halted.
3. The method of claim 1 wherein a delay between the first time and the second time is a result of a software instruction.
4. The method of claim 1 wherein a delay between the first time and the second time is a result of physical operation of at least one of a valve and a mass flow controller.
5. The method of claim 1 wherein flowing the liquid silicon-and-oxygen-containing precursor material comprises flowing a liquid precursor material selected from the group consisting of tetraethyl orthosilicate (TEOS), tetramethylcyclotetrasiloxane (TOMCATS), octamethylcyclotetrasiloxane (OMCTS), and dimethyldimethoxysilane (Z2DM).
6. The method of claim 1 wherein flowing the carrier gas comprises flowing a carrier gas selected from the group consisting of nitrogen, helium, argon, N2O, and combinations thereof.