Capacitor Test Structure for Non-Destructive Metal Recess Measurement
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Solution Overview
Problem
The semiconductor industry faces challenges in non-destructively and efficiently measuring metal recess depths, such as copper recesses, which affect product performance due to processes like etching and Chemical-Mechanical Polishing, as existing methods like spectroscopy are time-consuming and expensive.
Innovation Solution
A system and method using a test structure with probe pads and capacitors to measure metal recess depths by calculating capacitance values, allowing for non-destructive, in-situ, and cost-effective determination of recess depths through a capacitance measurement device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If spectroscopy methods are used to measure metal recess depths, then measurement accuracy can be achieved, but the process becomes time-consuming and expensive
Solution Approach 1:
The patent creates test structures with metal layers and dielectric layers in advance, forming capacitors that are ready for measurement. The metal recesses are prepared beforehand with known geometries, allowing rapid capacitance-based depth measurement without time-consuming spectroscopy procedures during actual measurement
Solution Approach 2:
The patent replaces the complex spectroscopy measurement system with a simpler electrical capacitance measurement system. By substituting optical/spectroscopic methods with electrical field-based capacitance measurements through probe pads, the system achieves fast, inexpensive measurements while maintaining accuracy
2Measurement precision
If spectroscopy methods are used to measure metal recess depths, then measurement accuracy can be achieved, but the cost increases
Solution Approach 1:
The patent uses simple, inexpensive probe pads and standard capacitor structures instead of expensive spectroscopy equipment. The test structures are designed to be simple and cost-effective to manufacture, using常规 semiconductor fabrication processes that are already in place, thereby reducing measurement costs while maintaining accuracy
Solution Approach 2:
The patent replaces expensive spectroscopy instrumentation with affordable electrical capacitance measurement systems. The substitution of complex optical measurement equipment with simple electrical measurement circuits significantly reduces the cost of metal recess depth measurement while preserving measurement precision
3Measurement precision
If existing measurement techniques are used, then metal recess depths can be measured, but the process is destructive or not in-situ
Solution Approach 1:
The test structures are designed to be self-contained within the semiconductor device, with metal layers, dielectric layers, and probe pads that work together autonomously. The in-situ capacitance measurement capability allows the structure to measure its own metal recess depths without requiring external destructive analysis, enabling non-destructive evaluation during normal device operation or testing
Solution Approach 2:
The patent introduces dielectric layers and probe pads as intermediary elements that enable non-destructive measurement. These intermediaries allow electrical field penetration and capacitance measurement without physically damaging the metal recesses, facilitating in-situ depth measurement while preserving the integrity of the measured features
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 and efficient measurement of metal recess depths, improving product performance by providing a non-destructive and time-saving solution.
Implementation Method 1
measuring capacitance values of the first, the second, the third, and the fourth capacitors by a capacitance measuring device coupled to the probe pads; and calculating a recess depth of the first metal pad from the top surface of the dielectric layer as a function of the capacitance values
Data Source
AI summary
A system for testing metal recess depths into a wafer includes a test structure formed in the wafer, and probe pads positioned vertically over the test structure. The test structure includes a first region and a second region laterally adjacent to each other. The first region includes a dielectric layer having a top surface and a metal layer formed under the top surface. The second region includes the dielectric layer, the metal layer, and a first metal pad and a second metal pad laterally separated, vertically extend into the dielectric layer from the top surface, and in contact with the metal layer. The probe pads include a first and a second probe pads configured to be vertically over the first region, and a third and a fourth probe pads configured to be vertically over the second region and to align with the first and the second metal pads, respectively.