Wafer Inspection Pressure Control for Probe Overdrive
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Solution Overview
Problem
In wafer inspection apparatuses, the precise determination of negative pressure for maintaining a desired overdrive amount between a probe card and a wafer is challenging due to design and manufacturing errors in probe cards, leading to potential damage or abnormal inspection results.
Innovation Solution
A method involving a vacuum mechanism that measures a reference pressure and height position to set an optimal negative pressure for maintaining a predetermined overdrive amount by controlling the pressure in the surrounding space between the probe card and the wafer, ensuring consistent and safe press-contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed set value of negative pressure is applied to the surrounding space, then the wafer inspection can be performed with a simple configuration, but the overdrive amount cannot be maintained properly due to design and manufacturing errors in probe cards
Solution Approach 1:
The patent applies dynamics by making the set value of negative pressure adjustable rather than fixed. The control unit dynamically changes the negative pressure set value based on actual measurements of the overdrive amount, allowing the system to adapt to variations in probe card characteristics while maintaining a relatively simple overall configuration.
Solution Approach 2:
The patent implements feedback by measuring the actual overdrive amount and using this information to adjust the negative pressure set value. The measurement unit measures the overdrive amount, and the control unit uses this feedback to optimize the negative pressure, ensuring consistent press-contact force despite manufacturing variations.
2Reliability
If the vacuum attractive force is increased to ensure stable press-contact, then the contactors can maintain press-contact reliably, but the overdrive amount increases causing damage to contactors or electrodes
Solution Approach 1:
The patent applies parameter changes by adjusting the negative pressure set value within an optimal range rather than using a fixed high value. By dynamically changing the pressure parameter based on measured overdrive amounts, the system maintains reliable press-contact while preventing excessive force that could cause damage.
Solution Approach 2:
The measurement and control mechanism provides feedback to prevent harmful effects. By continuously monitoring the overdrive amount and adjusting the negative pressure accordingly, the system avoids both insufficient press-contact and excessive force that could damage contactors or electrodes.
3Object-affected harmful factors
If the vacuum attractive force is decreased to reduce overdrive amount, then damage to contactors or electrodes is prevented, but the press-contact becomes unstable and wafer inspection is performed abnormally
Solution Approach 1:
The system optimizes the negative pressure parameter to achieve the lowest value that still ensures stable press-contact. By dynamically adjusting the pressure set value based on measurements, the system prevents damage while maintaining inspection reliability.
Solution Approach 2:
The feedback mechanism ensures that the negative pressure is never reduced below the level needed for stable press-contact. The measurement unit monitors the overdrive amount, and the control unit adjusts the pressure to maintain reliability while preventing damage.
4Productivity
If a predetermined set value of negative pressure is used based on theoretical calculation, then the inspection process is simple and fast, but the set value cannot guarantee the predetermined overdrive amount due to probe card variations
Solution Approach 1:
The patent applies preliminary action by performing a measurement of the overdrive amount before actual wafer inspection. This preliminary measurement allows the system to determine the optimal negative pressure set value in advance, ensuring both efficiency and precision during the inspection process.
Solution Approach 2:
The system optimizes parameters by adjusting the negative pressure set value based on preliminary measurements. This allows the inspection process to proceed efficiently with pre-determined optimal parameters while ensuring accurate overdrive amounts.
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 method ensures stable and reliable press-contact between the probe card and the wafer, maintaining the desired overdrive amount and preventing damage, even with variations in probe card design or manufacturing.
Implementation Method 1
a vacuum mechanism configured to control a pressure in a surrounding space sealable between the chuck top and the probe card to a predetermined set value of a negative pressure for inspection in order to generate or maintain a press-contact state between the probe card and the wafer by a predetermined pressing force
Data Source
AI summary
In a method for determining a set value of a pressure for inspection in a wafer inspection apparatus, a surrounding space sealable between a chuck top and a probe card by a vacuum mechanism is evacuated and a highest negative pressure in the surrounding space is measured as a reference pressure when the chuck top has floated by the evacuation. Then as a reference height position, a height position of the chuck top corresponding to the reference pressure is obtained. Further, a pressure in the surrounding space is decreased to a level lower than the reference pressure, the pressure in the surrounding space, when the chuck top reaches a target height position obtained by adding a preset overdrive amount for a press-contact state between the probe card and the wafer to the reference height position, is measured and the measured pressure is set as the set value of the pressure.