Wafer Inspection Vacuum Control for Probe Card Protection
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Solution Overview
Problem
Existing wafer inspection apparatuses face challenges in quickly and stably generating a desired vacuum attractive force during the inspection process, leading to potential damage from excessive vacuum pressure to the contactors and electrode pads.
Innovation Solution
A wafer inspection apparatus equipped with a vacuum mechanism featuring a proportional control valve, pressure sensor, and valve control unit, which allows for exponential pressure decrease from atmospheric pressure to a set pressure, and subsequent stepwise pressure maintenance, preventing excessive vacuum force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the surrounding space is depressurized to a set pressure at a high speed, then the vacuum attractive force is generated quickly and productivity is improved, but the pressure shows an undershoot waveform and exceeds the absolute value of the set pressure, causing damage to contactors or electrode pads
Solution Approach 1:
A pressure sensor detects the actual pressure in the surrounding space and feeds this information back to a valve control unit. The valve control unit adjusts the proportional control valve based on the feedback signal to maintain pressure at the set point, preventing undershoot and excessive vacuum force while enabling rapid vacuum generation.
Solution Approach 2:
The system dynamically changes the opening degree of the proportional control valve based on real-time pressure conditions. By adjusting the valve parameter (opening degree) in response to pressure changes, the system achieves rapid vacuum generation without exceeding the safe pressure threshold, thus preventing damage to contactors and electrode pads.
2Reliability
If a proportional control valve with pressure feedback is used to maintain precise pressure control, then damage to contactors is prevented, but the vacuum generation time increases and productivity decreases
Solution Approach 1:
The pressure sensor continuously monitors the surrounding space pressure and provides feedback to the valve control unit. This feedback mechanism enables precise pressure control by automatically adjusting the proportional control valve to maintain the set pressure, preventing both excessive vacuum and pressure oscillations while achieving rapid vacuum generation.
Solution Approach 2:
The proportional control valve operates dynamically by continuously adjusting its opening degree based on real-time pressure feedback. This dynamic control allows the system to rapidly respond to pressure changes, achieving fast vacuum generation while maintaining precise pressure control to prevent contactor damage.
3Reliability
If the vacuum attractive force is increased to ensure stable pressure-contact between probe card and wafer, then measurement reliability is improved, but the risk of damaging contactors or electrode pads increases
Solution Approach 1:
The system maintains pressure-contact stability by dynamically adjusting the proportional control valve opening degree to hold the pressure at the optimal set point. This parameter adjustment ensures sufficient vacuum attractive force for stable contact while preventing excessive force that could damage contactors or electrode pads.
Solution Approach 2:
The pressure sensor provides continuous feedback on the actual pressure in the surrounding space, enabling the valve control unit to maintain the set pressure. This feedback control ensures stable pressure-contact between the probe card and wafer while preventing excessive vacuum force that could cause damage.
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
Enables quick and stable generation of a desired vacuum attractive force, preventing damage to the contactors and electrode pads by maintaining a consistent pressure level during the inspection process.
Implementation Method 1
a vacuum source; an electropneumatic regulator having a proportional control valve having a first port connected to the vacuum source and a second port connected to the surrounding space
Implementation Method 2
an upward force is generated by a pressure difference between a pressure (negative pressure) in the surrounding space and an ambient pressure (atmospheric pressure) and applied to the chuck top
Implementation Method 3
a valve control unit configured to control the proportional control valve such that a pressure measured by the pressure sensor becomes close to or equal to the set pressure
Implementation Method 4
a pressure sensor configured to measure a pressure in a predetermined gas channel or a space which is sealed and connected to the second port
Data Source
AI summary
A wafer inspection apparatus includes a probe card, a chuck top, and a vacuum mechanism for evacuating a surrounding space surrounded by the chuck top and the probe card to a set pressure. The vacuum mechanism includes an electropneumatic regulator having a proportional control valve, a pressure sensor, and a valve control unit to control the proportional control valve such that a pressure measured by the pressure sensor becomes close to or equal to a set pressure; and a gas channel network switched between first mode in which a second port of the proportional control valve is connected to the surrounding space via the pressure sensor and second mode in which the second port of the proportional control valve is connected to the surrounding space and the pressure sensor is connected to the surrounding space in parallel with the proportional control valve.