Thin Film Deposition via Re-sputtering for Step Coverage
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Solution Overview
Problem
Current methods for forming thin films on substrates with trenches or via holes of 3 μm or less and an aspect ratio of 1 or more face challenges such as insufficient void reduction, film flatness, and difficulty in achieving desired thickness on sidewalls, particularly on larger substrates like 300 mm wafers, with existing techniques often requiring multiple steps and leading to defects and limited gas options.
Innovation Solution
A thin film forming method involving a plasma processing device with a first and second electrode, where different powers are applied from high-frequency sources, and a magnetic field is generated to create plasma, allowing for one-time film deposition on the bottom and re-sputtering to form a film on the sidewall, with lower chamber pressure and increased anode power in the second step to achieve desired thickness and step coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional reflow technique is used to fill trenches or via holes, then void occurrence is prevented, but film flatness is insufficient and CMP process is required
Solution Approach 1:
The invention changes the deposition parameters by controlling the ratio of substrate power to target power within a specific range (0.01 to 10) and adjusting process gas flow rates to achieve simultaneous void prevention and film flatness improvement, eliminating the need for CMP process
2Reliability
If barrier film is formed on sidewall and bottom of trench by reactive ionization sputtering, then void occurrence is prevented, but sufficient thickness coating on sidewall is difficult especially on large substrates
Solution Approach 1:
The invention changes the sputtering parameters by optimizing the substrate power to target power ratio and process gas conditions to achieve uniform film thickness distribution across the entire substrate including peripheral areas, ensuring sufficient barrier film thickness on sidewalls without requiring multiple coating passes
3Manufacturing precision
If ECR plasma CVD is used to form insulating film, then plasma reforming and film homogenization are achieved, but raw material gas options are limited and inner stress differences occur
Solution Approach 1:
The invention replaces ECR plasma CVD with a different plasma generation mechanism that uses magnetic field confinement and radio frequency power coupling to achieve plasma reforming and film homogenization, thereby expanding raw material gas options while maintaining film quality and reducing inner stress differences
4Manufacturing precision
If film formation step and sputter step are repeated multiple times, then shape defects are suppressed, but process time increases and productivity decreases
Solution Approach 1:
The invention changes the deposition parameters by setting the substrate power to target power ratio within a specific range (0.01 to 10) and optimizing process gas conditions to achieve both excellent film shape quality and uniform thickness distribution in a single deposition step, thereby eliminating the need for repeated film formation and sputter steps and significantly improving productivity
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 enables the formation of a thin film with desired thickness on the inner sidewall of trenches or via holes with excellent step coverage in a single film formation and etching step, eliminating the need for multiple steps and improving film quality by controlling power ratios and pressure, thus avoiding defects and voids.
Implementation Method 1
a plasma processing device with a first and second electrode, where different powers are applied from high-frequency sources, and a magnetic field is generated to create plasma
Implementation Method 2
different powers are applied from high-frequency sources, and a magnetic field is generated to create plasma
Implementation Method 3
a first step of depositing a thin film on a bottom of the step; and a second step of forming a film on an inner sidewall of the step by re-sputtering the thin film deposited on the bottom of the step
Data Source
AI summary
According to the present invention, a thin film having a desired thickness is formed on an inner sidewall of a step with excellent step coverage in a film forming step and an etching step at least once, respectively. In an embodiment of the present invention, a target material is deposited on a substrate (17) having a concave step (31, 32) having an opening width or opening diameter of 3 μm or less and an aspect ratio of 1 or more. At this time, a film forming method according to the present invention has a first step of depositing a thin film onto a bottom (33) of the step (31, 32) and a second step of forming a film on an inner sidewall (34) of the step (31, 32) by re-sputtering the thin film deposited on the bottom (33) and the pressure in a process chamber in the second step is set lower than that in the process chamber in the first step and the ratio of anode power to cathode power in the second step is set greater than the power ratio in the first step.