DRAM Buried Contact Pad Structure for Larger Active-Region Contact
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Solution Overview
Problem
The increasing difficulty in manufacturing processes for high-integration integrated circuit devices due to reduced design rules and the challenge of enhancing the contact area between conductive patterns and active regions, particularly in dynamic random access memory (DRAM) semiconductor devices with buried cell array transistors, where the contact area is insufficient with traditional recess spaces.
Innovation Solution
The introduction of an additional pad formed in a self-aligning manner on the active region with a greater horizontal width than the active region, which increases the contact area between the buried contact and the active region, utilizing a stacked structure of doped polysilicon and metal, and optionally including a metal silicide film, to enhance electrical connection without adding complexity to the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If traditional recess spaces are used to connect buried contacts to active regions, then the manufacturing process remains simple, but the contact area is insufficient
Solution Approach 1:
The pad structure extends the contact area horizontally beyond the active region boundaries, utilizing the lateral dimension to increase contact area without increasing vertical complexity. The pad protrudes from the active region in the horizontal plane, providing additional contact surface for buried contacts while maintaining a planar manufacturing approach.
Solution Approach 2:
The self-aligning process allows the pad to automatically position itself relative to the active region through the etching sequence, where the pad's first sidewall is formed by etching along the active region's sidewall. This self-alignment mechanism eliminates the need for additional photolithography alignment steps, maintaining manufacturing simplicity while achieving the desired geometric configuration.
2Productivity
If design rules are reduced to increase integration, then device density increases, but the difficulty of manufacturing processes increases
Solution Approach 1:
The self-aligning pad formation process eliminates the need for separate photolithography alignment steps. The pad automatically positions itself relative to the active region through the etching sequence, where the pad's first sidewall is formed by etching along the active region's sidewall. This self-alignment mechanism maintains manufacturing ease despite reduced design rules by eliminating complex alignment procedures.
Solution Approach 2:
The pad structure merges multiple functions into a single geometric feature: it serves as both a contact area expansion element and a self-aligning reference structure. The same pad geometry that increases contact area also provides the sidewall reference for automatic alignment, combining structural and process control functions.
3Manufacturing precision
If photolithography is used to form the pad, then precise positioning is achieved, but the manufacturing process becomes more complex
Solution Approach 1:
The self-aligning process allows the pad to automatically position itself relative to the active region through the etching sequence, where the pad's first sidewall is formed by etching along the active region's sidewall. This self-alignment mechanism eliminates the need for additional photolithography alignment steps, maintaining manufacturing simplicity while achieving the desired geometric configuration.
Solution Approach 2:
The patent replaces the photolithography-based positioning system with an etching-based self-aligning system. Instead of using light patterns and photoresist to define the pad position, the process uses the active region's physical sidewall as a mechanical reference for the etching process, substituting optical alignment with mechanical self-alignment through the etching sequence.
Data Source
AI summary
Provided is an integrated circuit device including a substrate that includes an active region defined by a trench isolation, a word line that extends in a first horizontal direction inside the substrate across the active region, a bit line that extends on the word line in a second horizontal direction orthogonal to the first horizontal direction, a direct contact that electrically connects the bit line to the active region, a pad that is on the active region and has a horizontal width that is greater than that of the active region, a buried contact that contacts a sidewall of the pad, and a conductive landing pad that extends on the buried contact in a vertical direction and faces the bit line in the first horizontal direction.