Sidewall Spacer Test Structure for MOL Reliability Evaluation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current manufacturing processes lack a suitable test structure to evaluate the integrity of sidewall spacers in semiconductor transistors, which are critical for determining transistor performance and reliability.
Innovation Solution
A test structure is developed that includes a scribe line area on a semiconductor substrate with an under-test region, conductive regions, and dielectric material, featuring silicon fins and epitaxial regions, sidewall spacers, and metal contacts, allowing for the measurement of leakage current, breakdown voltage, and breakdown time of the sidewall spacers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional test structures are used, then manufacturing process is simple, but sidewall spacer integrity cannot be evaluated
Solution Approach 1:
The test structure is segmented into distinct functional regions: an under-test region containing the sidewall spacer, conductive regions for electrical contact, and isolation dielectric regions. This segmentation allows the sidewall spacer to be tested in isolation from other device components, enabling reliable integrity evaluation without requiring a complete transistor structure.
Solution Approach 2:
Isolation dielectric material is introduced as an intermediary element between the under-test region and the substrate, and between adjacent conductive regions. This intermediary prevents electrical interference and current leakage paths, enabling accurate measurement of sidewall spacer integrity while maintaining a relatively simple overall structure.
2Reliability
If sidewall spacer integrity is not tested, then manufacturing process is faster, but device reliability cannot be ensured
Solution Approach 1:
The test structure is fabricated using the same manufacturing process steps as production devices, with sidewall spacers formed during normal device fabrication. This preliminary formation of the test structure allows sidewall spacer integrity to be evaluated before final device assembly, enabling early detection of process defects without adding post-manufacturing testing steps.
Solution Approach 2:
The test structure utilizes self-aligned fabrication steps where conductive regions and isolation dielectric are automatically positioned relative to the sidewall spacer through standard lithography and deposition processes. This self-service approach eliminates the need for additional alignment and positioning steps, maintaining manufacturing cycle time while enabling reliability testing.
3Measurement precision
If conventional test methods are used, then measurement is simple, but leakage current and breakdown voltage cannot be measured
Solution Approach 1:
The sidewall spacer is extracted from the complete transistor structure and placed in a dedicated under-test region where it can be measured independently. Conductive regions are positioned to make direct contact with the sidewall spacer, allowing leakage current and breakdown voltage measurements to be performed on the spacer alone without interference from gate, source, or drain structures.
Solution Approach 2:
Isolation dielectric material serves as an intermediary that blocks parasitic current paths between the substrate and conductive regions, and between adjacent test structures. This intermediary enables precise measurement of sidewall spacer electrical properties by eliminating leakage currents through alternative paths, while the measurement setup remains relatively simple.
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 test structure enables effective evaluation of sidewall spacer integrity, enhancing the reliability assessment of semiconductor transistors and identifying potential failure points, thereby improving device performance and manufacturing yield.
Implementation Method 1
a layer of dielectric material underneath the under-test region, insulating the under-test region from the semiconductor substrate
Implementation Method 2
a leakage current, a breakdown voltage, or a breakdown time of the first sidewall spacer is measured by applying a voltage between the first conductive region and the gate
Data Source
AI summary
Embodiments of present invention provide a test structure. The test structure includes a scribe line area in a semiconductor substrate; a first fin and a second fin in the scribe line area and an insulating region between the first fin and the second fin; a first epitaxial region directly on top of the first fin and a second epitaxial region directly on top of the second fin; and an under-test region on top of the insulating region in the scribe line area and between the first epitaxial region and the second epitaxial region. In one aspect, the under-test region includes a gate and a first and a second sidewall spacer formed at a first and a second sidewall of the gate, the first epitaxial region being in contact with the first sidewall spacer and the second epitaxial region being in contact with the second sidewall spacer.