Distance Measuring Device Laminar Flow Channel Wafer Thinning
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Solution Overview
Problem
Existing optical distance measuring devices are unsuitable or of limited suitability for monitoring the thickness of semiconductor wafers during thinning due to interference from grinding particles and reliability issues, particularly with liquid-tight light-emitting regions prone to failure.
Innovation Solution
A distance measuring device with a measuring head featuring a liquid guide and flow element with a laminar flow channel, where the measuring light beam passes through, maintaining a homogeneous optical medium and suppressing turbulence to enhance measurement accuracy and reliability, and a liquid outlet designed to coaxially direct a rinsing jet perpendicular to the measurement surface to remove impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a liquid-tight light-emitting region with liquid nozzle is used to rinse away impurities, then the light path is protected from grinding particles, but the device becomes prone to failure and reliability deteriorates
Solution Approach 1:
The patent extracts the light-emitting region from the liquid-tight enclosure, allowing the light source to be positioned outside the liquid environment. This eliminates the need for complex liquid-tight seals while still protecting the light path through strategic positioning of the light source relative to the liquid flow direction, thus maintaining particle protection while improving reliability
Solution Approach 2:
The patent introduces an intermediary air gap or protective window between the light-emitting region and the liquid environment. This intermediary element allows light to pass through while preventing direct contact between the light source and liquid, eliminating seal failure risks while maintaining optical path protection from particles
2Object-affected harmful factors
If a jet of liquid is directed at the measurement object to remove impurities, then the light path is kept clear, but liquid turbulence impairs measurement accuracy
Solution Approach 1:
The patent applies different flow characteristics to different regions: a laminar flow regime is maintained in the region where the light beam passes through the liquid, while turbulent or higher-velocity flow can exist in other regions for effective particle removal. This is achieved through carefully designed nozzle geometry that creates a controlled laminar jet along the optical path
Solution Approach 2:
The patent employs dynamic flow control where the liquid flow characteristics can be adjusted or vary over time. The flow rate, velocity profile, or flow pattern can be dynamically modified to maintain laminar conditions during measurement while still achieving effective particle removal, balancing measurement precision with cleaning effectiveness
3Productivity
If the flow rate of the liquid jet is increased to improve particle removal, then rinsing effectiveness increases, but the liquid jet breaks up into droplets creating air-liquid transitions that impair measurements
Solution Approach 1:
The patent utilizes hydraulic principles to maintain a continuous liquid jet at high flow rates by optimizing nozzle design, liquid pressure, and jet velocity. The nozzle geometry is specifically designed to prevent jet breakup and air entrainment even at high flow rates, ensuring the liquid remains in a continuous phase along the measurement path while effectively removing particles
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
The solution effectively increases measurement accuracy and reliability by maintaining a clear light path through the use of a laminar flow channel and rinsing mechanism, allowing for high flow rates without breaking the liquid jet and impairing the optical properties, suitable for monitoring semiconductor wafer thinning processes.
Implementation Method 1
the at least one measuring light beam is able to reach the measurement object by passing through the laminar flow channel
Implementation Method 2
making it possible to increase both measurement accuracy and measurement reliability
Implementation Method 3
the flow element being designed such that the at least one measuring light beam is able to reach the measurement object by passing through the laminar flow channel
Implementation Method 4
the jet of liquid can thus be de-swirled or laminarized such that it continues to act to largely as a homogenous optical medium
Data Source
AI summary
A distance measuring device comprises a measuring head, the measuring head having an optical measuring system for carrying out an optical measurement process on a measurement object by means of at least one measuring light beam formed from a broad-band measuring light. The measuring head further has a liquid guide with a liquid inlet and a liquid outlet for producing a jet of liquid directed at the measurement object, the liquid guide being designed such that in certain sections at least the measuring light beam runs essentially along the jet of liquid. The measuring head further has a flow element with a laminar flow channel, the flow element being designed such that the at least one measuring light beam is able to reach the measurement object by passing through the laminar flow channel.