Paper TF+AP-TuM3
Improved Control of Atomic Scale Processing: Characterization and Optimization of Precursor Mass Delivery Utilizing a Novel Thermal Sensor

Tuesday, October 22, 2019, 8:40 am, Room A124-125

For Area Selective Deposition (ASD), control of precursor mass delivery is even more critical to process viability. Here, excessive precursor material can initiate growth on "Non-growth” surfaces, leading to a need for intermittent etch steps.

More process control may make problematic processes viable for semiconductor manufacturing. Recently RASIRC introduced a novel dry hydrogen peroxide (H₂O₂) precursor. A novel H₂O₂ mass flow sensor was developed to aid in product characterization. This thermal sensor accurately measures heat of decomposition for minute amounts of H₂O₂:

H₂O₂ --> ½ O₂ + H₂O + heat

Our work uses this device to characterize H₂O₂ delivery parameters to:

• Minimize total precursor mass required
• Maximize precursor mass delivered in shortest time
• Limit purge time for increased throughput
• Minimize nucleation of “Non-growth" surfaces

Quantitative experimental methods are used to understand the effects of:

• Ampoule headspace pressure
• Carrier gas flow rate
• Liquid precursor temperature
• Precursor pulse time
• Saturation efficiency of carrier gas with precursor vapor
• Binary interactions for multicomponent liquids
• System heat transfer
• Ampoule design

An ALD simulation manifold was built to re-create typical ALD conditions. An automated test program controls valves and sensors to simulate process recipes. Initial results indicate highly variable mass delivery w.r.t. pressure. An ampoule outlet pressure of 20 torr results in 33.22 mg/min H₂O₂ mass delivery, vs 15.11 mg/min at 70 torr and 1.22 mg/min at 760 torr. Results are less affected by flow rate, where 0.5 slm at 22 torr leads to 33mg/min H₂O₂ vs 1.0 slm at 34 torr leads to 42 mg/min, and 2.0 slm at 57 torr leads to 44 mg/min. Here, increased mass delivery from higher flow rate is offset by a corresponding increase in pressure. In addition, while increased flow rate does not result in significant mass delivery increase for 2 slm, there is a significant decrease in precursor concentration, where the molar ratio of H₂O₂/N₂ is decreased by 70% vs 0.5 slm. Concentration effects are significant to film uniformity in ALD and have ramifications in ASD.

Mass delivery vs pulse time was also examined. Data will be presented for 3s, 1s, 0.3 sec, and 0.1s pulses. Application to process optimization will also be discussed.