I/O Capacitance Measurement by Transition-Time Sensing
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Solution Overview
Problem
Existing methods for measuring input/output capacitance of semiconductor devices, particularly those with small I/O interfaces like high-bandwidth memory (HBM) devices, face challenges such as difficulty in direct contact due to small micro bump interfaces, requiring small current drivers and high-speed clocks, which are unreliable and difficult to implement.
Innovation Solution
A method to measure I/O capacitance without direct contact using a circuit with a current source and comparator to generate a constant current through the I/O node, comparing the voltage to a reference voltage, and calculating capacitance based on transition time, allowing for accurate measurements without the need for small current drivers or high-speed clocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct contact measurement methods are used for small micro bump interfaces, then measurement precision can be achieved, but difficulty in direct contact and reliability deteriorate due to small interface size
Solution Approach 1:
The patent introduces an intermediary measurement approach by using a current source and comparator circuit that measures capacitance through voltage transition timing rather than direct electrical contact. The current source charges the I/O node and the comparator detects voltage transitions, serving as intermediaries that eliminate the need for direct probe contact with the micro bump interface, thereby maintaining measurement precision while improving reliability.
Solution Approach 2:
The patent replaces the mechanical contact-based measurement system with an electrical field-based measurement system. Instead of using physical probes that must mechanically contact the small micro bump interfaces, the invention uses a current source to charge the node and a comparator to detect voltage transitions, substituting mechanical interaction with electrical field interaction, thus eliminating contact difficulties and improving reliability.
2Measurement precision
If small current drivers and high-speed clocks are used for measurement, then measurement precision can be maintained, but device complexity and ease of implementation worsen
Solution Approach 1:
The patent changes the measurement parameters from requiring small current drivers and high-speed clocks to using a standard current source and normal clock speeds. By measuring the transition time of the voltage signal rather than using high-frequency signals, the invention maintains capacitance measurement precision while significantly reducing device complexity and making the measurement easier to implement with standard components.
3Measurement precision
If small current drivers are used for measurement, then measurement precision can be achieved, but ease of manufacture and reliability worsen due to difficulty in implementation
Solution Approach 1:
The patent replaces the need for specialized, difficult-to-manufacture small current drivers with a standard current source that can be easily manufactured. The measurement is performed by charging the node and measuring the transition time, which can be done with readily available components, thus improving ease of manufacture while maintaining measurement precision through the timing-based measurement approach.
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 accurate measurement of I/O capacitance without direct contact, compensating for process, voltage, and temperature variations, and is applicable to devices with small I/O interfaces like HBM, improving measurement reliability and ease of implementation.
Implementation Method 1
measuring an input/output capacitance of a device
Implementation Method 2
comparing the voltage to a reference voltage
Data Source
AI summary
A device may include a current source configured to couple a charged node to a ground voltage to generate a current. The device may include a second circuit coupled to the node and configured to compare, beginning during a first clock cycle of a clock signal and for each clock cycle of a number of clock cycles of the clock signal, the voltage at the node to a reference voltage to generate a result. The device may further include a control unit configured to: detect, upon completion of a subsequent clock cycle of the clock signal, a change in the result; determine, in response to the change in the result, a transition time based on a number of elapsed clock cycles from the first clock cycle to completion of the subsequent clock cycle; and determine a capacitance of the node based on the transition time. Related systems and methods are also described.