Low-Stress Silicon Nitride Film via PECVD Parameter Optimization
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Solution Overview
Problem
Existing methods for producing silicon nitride thin films using PECVD face challenges in achieving low mechanical stress, particularly at low temperatures below 350°C, as adjusting the power ratio of high-frequency to low-frequency sources is insufficient to meet specific stress requirements, especially on machines like the NOVELLUS C1, where traditional stress reduction techniques fail to deliver the necessary low-stress films.
Innovation Solution
A method involving plasma-enhanced chemical vapor deposition (PECVD) with specific parameters: charging silane at 300-350 sccm, ammonia gas at 1000 sccm, high frequency power of 0.15-0.30 KW, low frequency power of 0.15-0.30 KW, reaction pressure of 2.3-2.6 Torr, and reaction duration of 4-6 seconds, using nitrogen gas as a diluent, to produce silicon nitride thin films with stress within ±50 MPa at low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If PECVD is used to produce SIN thin film, then the stress is lower than LPCVD, but the stress cannot be reduced to the required level (0±50 MPa) by simply adjusting power ratio
Solution Approach 1:
The patent changes multiple process parameters simultaneously including gas flow rates (silane 300-350 sccm, ammonia 1000 sccm), reaction pressure (2.3-2.6 Torr), temperature (200-350°C), and dual-frequency power settings to achieve the target stress range of 0±50 MPa, which cannot be achieved by power ratio adjustment alone
Solution Approach 2:
The patent employs dynamic control of dual-frequency plasma sources (13.56 MHz and 27.12 MHz) with independently adjustable powers, allowing real-time optimization of plasma chemistry and ion bombardment energy to control film stress during deposition
2Temperature
If temperature is reduced below 350°C for low stress film, then thermal damage is reduced, but stress control becomes more difficult
Solution Approach 1:
The patent operates at reduced temperatures (200-350°C) and compensates for the reduced thermal stress relaxation by optimizing gas flow rates (particularly ammonia at 1000 sccm) and dual-frequency power settings to maintain film stress within 0±50 MPa
Solution Approach 2:
The patent uses diluent gases (nitrogen or nitrogen oxide) as intermediaries to modulate plasma chemistry and reaction kinetics, enabling stress control at low temperatures by adjusting the gas composition rather than relying solely on thermal effects
3Length of stationary object
If film thickness is increased beyond 300 nm, then better coverage is achieved, but film fracture and drop-off occur due to high stress
Solution Approach 1:
The patent applies preliminary stress control during the deposition process itself by optimizing process parameters from the beginning, preventing stress accumulation that would lead to fracture, rather than attempting stress relief after deposition
Solution Approach 2:
The patent uses optimized parameter combinations including silane flow rate (300-350 sccm), ammonia flow rate (1000 sccm), and dual-frequency power settings to deposit thick films (>300 nm) with low stress, enabling films to achieve both thickness and mechanical integrity
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 method effectively produces silicon nitride thin films with low stress levels, meeting the requirement of ±50 MPa at low temperatures, improving the mechanical stability and reliability of the films, even on machines where traditional methods fail.
Implementation Method 1
A method for manufacturing a silicon nitride thin film using plasma-enhanced chemical vapor deposition
Implementation Method 2
a process of chemical vapor deposition (CVD)
Implementation Method 3
Since low-frequency plasma generates compressive stress, and high-frequency plasma generates tensile stress
Data Source
AI summary
A method for manufacturing a silicon nitride thin film comprises a step of charging silane, ammonia gas and nitrogen gas at an environment temperature below 350° C. to produce and deposit a silicon nitride thin film, wherein a rate of charging silane is 300-350 sccm, a rate of charging ammonia gas is 1000 sccm, a rate of charging nitrogen gas is 1000 sccm; a power of a high frequency source is 0.15˜0.30 KW, a power of a low frequency source is 0.15˜0.30 KW; a reaction pressure is 2.3˜2.6 Torr; a reaction duration is 4˜6 s. The above method for manufacturing a silicon nitride thin film provides a preferable parameter range and preferred parameters for generating a low-stress SIN thin film at low temperatures, achieves manufacture of a low-stress SIN thin film at low temperatures, and thus, better satisfies the situation requiring a low-stress SIN thin film.