ALD_QA 8_4_21.pdf

Questions:

1.A. specifies a steel reactor versus an aluminum hot wall reactor. Please describe what is driving this requirement?

1.C. specifies a requirement for insitu ellipsometry… with ALD being a very repetitive process, please advise what is driving the requirement for insitu ellipsometry?

1.D. specifies a need to achieve hot wall operation… why not go with a hot wall reactor?

1.E. specifies a top down flow versus a cross flow. Please advise what is driving this requirement?

The specifications are quite broad… we are typically specified for Al2O3 in the < 1% range.

The introduction of precursors in a vertical, top down flow has been demonstrated to have better performance with respect to uniformity of not only thickness, but resistance, and optical properties, as well. This is due to better distribution, concentration, and thermal decomposition of precursor, precurosor impurities and by‐products over the substrate.

Depending on the material being deposited and the precursors used, it has been found that precursor impurities and by‐products can significantly impact the resulting film unifomity. In a cross‐flow design you would see a greater impact of these uniformity issues across the reactor space in the direction of flow.

The system will be a research based tool and needs to be able to demonstrate the deposition of more than just Al2O3. Therefore, we have specifications for not only Al2O3, but for HfO2 and AlN as well.

Section 1

Section 3

Atomic Layer Deposition (ALD) with an integrated glovebox transfer system

Responses:

Stainless steel is the preferred material for vacuum based systems. Stainless steel is made up of iron, chromium, nickel, manganese and copper. The chromium is added as an agent to provide corrosion resistance. Also, because stainless steel is non‐ porous the resistance to corrosion is increased.

When aluminum is oxidized, its surface will turn white and will sometimes pit. In some extreme acidic or base environments, Aluminum may corrode rapidly with catastrophic results. Furthermore, stainless steel has higher resistance to wear and abrasion, which is important during regular maintaenance of the reactor.

In‐situ ellipsometry allows for the monitoring of process development and material quality in real time, as well as, allow for end‐point process control once a particular value of interest is reached. As processes can sometimes drift or material properties need to be tuned during processing having the real time feed back is paramount without having to take samples in and out of a chamber.

The system should operate as a hot wall reactor with temperature control separate from that of the substrate heater. Unlike furnace based hot wall reactors, the ability to independently heat various zones of the reactor will create a thermal gradient‐ thereby, avoiding cold sposts within the system that could be potential cause for condensation and contamination. Futhermore, the ability to control the substrate temperature independent from the reactor heating provides better control of the deposited films' material properties.