Backside Source/Drain Contact Formation for Small-Pitch Alignment
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Solution Overview
Problem
Forming backside contacts in semiconductor devices is challenging due to process variations and patterning issues, particularly at small pitches, leading to voids and misalignment with adjacent structures, which affect power delivery efficiency.
Innovation Solution
A method involving a non-SASI scheme is used to form a conductive spacer and a placeholder backside source/drain contact, with controlled height through chamfering, reducing height variations and improving process margin, and using a barrier metal to minimize contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional patterning methods are used to form backside contacts, then manufacturing process is simpler, but manufacturing precision deteriorates due to voids and misalignment at small pitches
Solution Approach 1:
The method performs preliminary actions by forming a placeholder contact and conductive spacer before final contact formation. The placeholder contact is formed first, then a conductive spacer is deposited on its sidewall, and finally the placeholder is replaced with the actual contact material. This sequence of preliminary actions enables precise alignment control at small pitches by establishing reference structures beforehand, resolving the technical contradiction between manufacturing precision and process complexity.
Solution Approach 2:
The conductive spacer acts as an intermediary element between the placeholder contact and the final contact structure. It provides a bridging structure that facilitates precise material deposition and alignment during the contact formation process. The spacer serves as a temporary mediator that enables controlled material placement, then is replaced by the final contact material, thus resolving the precision-complexity contradiction.
2Manufacturing precision
If placeholder contact height is not controlled, then process margin is larger, but manufacturing precision deteriorates due to height variations
Solution Approach 1:
The method changes the height parameter of the placeholder contact through controlled deposition processes. By precisely controlling the deposition thickness and using chamfering techniques, the placeholder contact height is optimized to provide adequate process margin while ensuring precise alignment. This parameter optimization resolves the contradiction between manufacturing precision and ease of manufacture.
Solution Approach 2:
The method uses partial action by forming the conductive spacer only on the exposed sidewall portion of the placeholder contact after chamfering. This selective deposition on the chamfered surface provides precise height control without requiring excessive processing steps, thus resolving the contradiction between precision and manufacturing ease.
3Reliability
If barrier metal is not used, then device complexity is lower, but power delivery performance deteriorates due to increased contact resistance
Solution Approach 1:
The method applies local quality by inserting a barrier metal layer specifically at the contact interface where it is most needed for performance. The barrier metal is placed locally between the contact material and the semiconductor substrate to minimize contact resistance and improve power delivery, while the rest of the contact structure maintains simplicity. This localized enhancement resolves the contradiction between reliability and device complexity.
Data Source
AI summary
Methods of forming semiconductor devices are provided. A method of forming a semiconductor device includes forming a preliminary backside (BS) source/drain (S/D) contact that includes a barrier metal. In some embodiments, forming the preliminary BS S/D contact includes depositing the barrier metal, such as depositing the barrier metal as a sidewall spacer. Moreover, the method includes forming a BS S/D contact on the barrier metal.