HDP Oxide Deep Trench Isolation Yield Improvement
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Solution Overview
Problem
Conventional deep trench cap oxidation processes in semiconductor fabrication lead to structural deformation, volume displacement stress, and the formation of deep trench nodules, which complicate defect inspection and can cause cracking and high leakage currents due to thermal and mechanical stresses.
Innovation Solution
The method involves forming a high density plasma (HDP) oxide layer over the filler material in the deep trench, which is planarized using chemical-mechanical polishing to eliminate thermal oxide growth, thereby preventing volume expansion and deformation, and eliminating the need for a deep trench cap oxidation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deep trench cap oxidation process is performed to provide electrical isolation, then electrical isolation is achieved, but structural deformation and volume displacement stress occur in the semiconductor substrate
Solution Approach 1:
The patent removes the deep trench cap oxidation process from the fabrication sequence, extracting the harmful thermal oxidation step that causes volume expansion. Electrical isolation is achieved through alternative means (trench filling and planarization) that do not induce structural deformation or displacement stress in the semiconductor substrate.
Solution Approach 2:
The patent changes the physical and chemical parameters of the trench filling process by using HDP oxide deposition instead of thermal oxidation. This parameter change eliminates the volume expansion effect while maintaining the electrical isolation function, as the deposited oxide layer does not undergo the same volumetric transformation as thermally oxidized materials.
2Reliability
If deep trench cap oxidation process is performed, then electrical isolation is provided, but deep trench nodules are formed making defect inspection difficult
Solution Approach 1:
The patent extracts and eliminates the deep trench cap oxidation process that generates nodules. By removing this process step, the harmful nodule formation is prevented, allowing subsequent optical inspection tools to effectively detect trench defects without interference from nodule-related artifacts.
Solution Approach 2:
The patent performs preliminary planarization of the HDP oxide layer before subsequent processing steps. This preliminary action creates a flat surface that prevents nodule formation and enables effective optical inspection, addressing the inspection difficulty before it becomes a problem in later fabrication stages.
3Reliability
If deep trench cap oxidation process is performed, then thermal oxide is formed, but thermal and mechanical stresses cause cracking of the semiconductor substrate
Solution Approach 1:
The patent extracts and eliminates the thermal oxidation process that generates harmful thermal and mechanical stresses. By removing this process, the substrate is protected from stress-induced cracking while electrical isolation is achieved through alternative HDP oxide deposition and planarization methods that do not induce such stresses.
Solution Approach 2:
The patent replaces the thermal-mechanical oxidation process with a chemical vapor deposition process (HDP oxide). This substitution eliminates the thermal field and associated mechanical stresses that cause substrate cracking, using instead a low-stress deposition mechanism that achieves the same electrical isolation function without compromising substrate integrity.
4Manufacturing precision
If conventional deep trench fabrication process is used, then deep trenches are formed and filled, but volume expansion during oxidation pushes and lifts up additional layers causing displacement stress
Solution Approach 1:
The patent changes the material deposition parameters by using HDP oxide deposition instead of thermal oxidation. This parameter change eliminates volume expansion during the filling process, preventing the pushing and lifting of additional layers and the associated displacement stresses, while maintaining precise trench formation and filling.
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 approach effectively eliminates deep trench nodules and thermal/mechanical stresses, improving product yield by preventing substrate cracking and reducing fabrication costs and time.
Implementation Method 1
forming a high density plasma (HDP) oxide layer over the filler material in the deep trench
Implementation Method 2
which is planarized using chemical-mechanical polishing to eliminate thermal oxide growth
Data Source
AI summary
A semiconductor structure having a deep trench isolation structure for improved product yield is disclosed. The semiconductor structure includes a deep trench having a filler material therein. The deep trench is adjacent to field oxide regions in a semiconductor substrate. A high density plasma (HDP) oxide layer, substantially free of thermal oxide, is situated over the filler material in the deep trench. The HDP oxide layer has a substantially co-planar top surface with at least one of the field oxide regions. According to the present disclosure, formation of nodules in the deep trench is prevented.