Gas Flow Control Showerhead with Integrated Restrictors
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Solution Overview
Problem
Conventional semiconductor fabrication tools face challenges in rapidly transitioning between gas species and mixtures due to slow mass flow controller (MFC) transitions, leading to uncertainty in process conditions near the wafer and consumption of error budgets, especially at low flow rates.
Innovation Solution
A gas flow control showerhead with integrated flow restriction, featuring a stack of plenum disks and restriction disks with characterized flow paths, uses electronically commandable pressure regulators to control mass flow rates, reducing transition times and improving control over gas delivery by locating flow measurement and control closer to the wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional remote MFCs are used for gas flow control, then flow measurement and control is provided, but transition time between gas species is slow and error budgets are consumed
Solution Approach 1:
The gas delivery system is segmented into multiple independent flow control zones, each with its own integrated flow restrictor and control mechanism. This allows individual zones to transition between gas species independently and rapidly, eliminating the slow system-wide transitions of conventional remote MFCs while maintaining precise control through localized measurement and adjustment.
Solution Approach 2:
Integrated flow restrictors serve as intermediary elements between the gas distribution plenum and the wafer surface. These restrictors create controlled flow paths that enable rapid gas species transitions by limiting the volume of gas that must be displaced, while simultaneously providing flow measurement capability to maintain control precision during transitions.
2Device complexity
If flow control is located remote from the wafer, then system complexity is reduced, but transport time and unknown resistances increase
Solution Approach 1:
The flow measurement, control, and restriction functions are merged into integrated flow restrictor assemblies located at the wafer interface. This consolidation eliminates separate remote MFC components and long transport conduits, reducing both system complexity through integration and transport time by positioning control directly at the point of gas delivery to the wafer.
3Ease of manufacture
If conventional showerhead design is used, then manufacturing is simplified, but flow control precision and transition speed are insufficient
Solution Approach 1:
The showerhead incorporates locally optimized flow control zones with integrated restrictors positioned at specific locations where precise flow management is critical. Each local zone can be manufactured with standard techniques while the integrated restrictor geometry is optimized for precise flow control and rapid transitions, achieving local precision without requiring complete redesign of the entire showerhead structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables faster and more precise control of gas flow transitions, conserving error budgets and ensuring repeatable and uniform chemistry on the wafer surface, enhancing the efficiency of semiconductor processing and other applications like Solar and MEMs devices.
Implementation Method 1
a characteristic dimension (e.g., effective hydraulic diameter) of the restriction channel is small relative to a characteristic dimension of an inlet and a characteristic dimension of an outlet of the restriction channel, a ratio between the restriction channel characteristic dimension and those of the inlet and outlet generating an impedance causing a pressure drop used to control the mass flow rate of the process gas
Data Source
AI summary
A gas flow control showerhead with integrated characterized restrictions for a gas delivery system. An input distribution disk with a plurality of inputs is fluidly coupled to a plurality of conduits each conduit exhausting a process gas to the input distribution disk from a controllable pressure regulator in a gas box. A plurality of restriction flow paths is formed by one or more stacked triples of plenum disks, restriction disks, and outlet diffuser disks that are grouped with each group providing a pressure drop used in control of a mass flow rate of a process gas. Each outlet diffuser disk having a plurality of outputs distributed around different locations of the outlet diffuser disks exhausting the process gases for application to a wafer being processed within a process chamber at designated mass flow rates.