Backside Compressive Nitride Film for Thermally Stable Wafer Bow Compensation
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Solution Overview
Problem
Semiconductor manufacturing processes face challenges in managing wafer bow due to changes in stress caused by deposition and etching operations, particularly in 3D-NAND fabrication, which can lead to frontside lithographic overlay mismatch and exceed the chucking limit of electrostatic chucks.
Innovation Solution
A method involving the deposition of a compressive nitride film on the backside of a bowed semiconductor substrate using plasma-enhanced chemical vapor deposition (PECVD), where the film has a compressive film stress equal to or greater than 400 MPa and a stress shift of 40% or less when exposed to temperatures greater than the deposition temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional PECVD is used to deposit nitride film, then deposition can be performed, but the film exhibits large stress shift (>50%) when exposed to high temperatures
Solution Approach 1:
The patent changes the deposition temperature parameter from conventional high temperatures to low temperature (room temperature to 200°C range), which fundamentally alters the film stress characteristics. This parameter change results in films with compressive stress and minimal stress shift (<40%) when exposed to subsequent high-temperature processing, directly resolving the contradiction between stress stability and wafer bow mitigation reliability
Solution Approach 2:
The patent deposits composite structures consisting of multiple nitride film layers with different stress characteristics. By combining low-stress-shift films deposited at low temperature with other functional layers, the composite structure achieves both wafer bow compensation and thermal stability, resolving the contradiction between stress control and processing reliability
2Device complexity
If thick high stress carbon-based hard masks are used in 3D-NAND fabrication, then manufacturing complexity is reduced, but significant wafer warpage occurs exceeding chucking limits
Solution Approach 1:
The patent applies preliminary anti-action by depositing nitride films with controlled compressive stress on the backside of the wafer before subsequent processing steps. This pre-applied stress counteracts the tensile stress that will be induced by thick carbon-based hard masks, preventing wafer bow from exceeding chucking limits while maintaining the simplified fabrication process
Solution Approach 2:
The patent moves the stress compensation action to another dimension by depositing films on the backside of the wafer rather than on the frontside where the device structures are located. This dimensional approach allows stress management without interfering with the primary fabrication operations, resolving the contradiction between process simplicity and wafer shape control
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
The method effectively mitigates wafer bow by achieving high compressive stress values in the nitride film that are thermally stable, reducing the stress shift and maintaining the compressive stress even at elevated temperatures, thus addressing the challenges of wafer warpage in semiconductor fabrication.
Implementation Method 1
depositing, by plasma-enhanced chemical vapor deposition (PECVD) at a deposition temperature, a compressive nitride film on a backside of the bowed semiconductor substrate
Implementation Method 2
exposing the backside of the bowed semiconductor substrate to plasma to drive a reaction between the silicon-containing precursor and the nitrogen-containing reactant to deposit the compressive nitride film
Data Source
AI summary
A high-stress, thermally-stable compressive nitride film is deposited on a semiconductor substrate. The compressive nitride film may be deposited by plasma-enhanced chemical vapor deposition (PECVD) under conditions that produce a compressive nitride film with high compressive film stress and with a minimal stress shift when exposed to a temperature greater than a deposition temperature of the compressive nitride film. In some implementations, the compressive nitride film is a silicon nitride film. The PECVD conditions may reduce a number of Si—H bonds in the silicon nitride to obtain improved thermal stability. In some implementations, the high-stress, thermally-stable nitride film is deposited on a backside of the semiconductor substrate for wafer bow compensation.