DRAM Landing Pad Test Structure for Early Quality Detection
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Solution Overview
Problem
Current DRAM manufacturing processes lack an effective method to early detect the quality of landing pads, which are crucial for reliable electrical connections between MOS transistors and cell capacitors, leading to potential structural issues and performance problems.
Innovation Solution
A test structure for DRAM that includes a semiconductor substrate, gate structures, source/drain regions, bit lines, dielectric layers, landing pads, and conductive layers, allowing for the detection of landing pad quality through wafer acceptance tests, ensuring reliable electrical connections and identifying potential structural issues like necking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional DRAM manufacturing processes are used without dedicated test structures, then the manufacturing process remains simple, but the quality of landing pads cannot be early detected
Solution Approach 1:
The test structure is formed concurrently with the DRAM manufacturing process at an early stage, allowing landing pad quality to be detected before final assembly. The conductive layer is deposited and planarized in advance to create testable landing pads that can be evaluated for structural integrity and electrical properties during wafer acceptance testing
Solution Approach 2:
The test structure creates a simplified copy of the actual DRAM cell structure with identical landing pads, contact plugs, and conductive layers. This copy allows quality detection of landing pads without requiring complete functional DRAM cells, reducing test complexity while maintaining measurement accuracy
2Reliability
If landing pad quality is not detected early, then the manufacturing process remains fast, but structural issues like necking are not identified until later stages
Solution Approach 1:
The test structure enables wafer acceptance testing to be performed at an intermediate manufacturing stage rather than at the end. By forming the conductive layer and planarizing it to create flat landing pad surfaces early in the process, quality issues such as necking can be detected before subsequent manufacturing steps, preventing defective devices from proceeding further
Solution Approach 2:
The patent replaces late-stage functional testing with early-stage electrical property measurement. By using the test structure to measure electrical characteristics of landing pads and contact plugs during manufacturing, the system substitutes comprehensive end-of-line testing with targeted intermediate measurements, reducing total detection time
3Ease of manufacture
If no test structure is formed, then the manufacturing process has fewer steps, but electrical properties of structures cannot be verified
Solution Approach 1:
The test structure serves multiple functions within the manufacturing process: it provides landing pads for electrical connection verification, contact plugs for inter-layer connectivity testing, and a platform for measuring electrical properties. These test elements are formed using the same deposition and planarization processes as the actual DRAM devices, making the test structure universal to the manufacturing flow
Solution Approach 2:
The test structure acts as an intermediary between the manufacturing process and quality measurement systems. By creating dedicated test landing pads and contact plugs that are electrically connected through the same processes as functional devices, the test structure provides accessible measurement points that simplify electrical property verification without requiring complete device assembly
Data Source
AI summary
A test structure for use in a dynamic random access memory is provided. A first gate structure is disposed in a semiconductor substrate. First and second source/drain regions are disposed in the semiconductor substrate and at two sides of the first gate structure. A bit line structure is disposed on the first source/drain region. A dielectric layer is disposed on the semiconductor substrate and the bit line structure. A first landing pad is disposed on the dielectric layer. A first contact plug is disposed in the dielectric layer and electrically connects the second source/drain region and the first landing pad. A conductive layer is disposed on and electrically connected to the first landing pad, in which a first upper surface of the first landing pad is entirely covered by the conductive layer, and the conductive layer has a substantially planar upper surface.