Dual-Target Vacuum Processing for Stable MRAM Resistance
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Solution Overview
Problem
Existing methods for forming metal oxide films in MRAM manufacturing suffer from instability in resistance values due to surface oxidation of metal targets and residual oxygen, leading to inconsistent film characteristics and reduced yield rates.
Innovation Solution
A vacuum-processing apparatus and method utilizing a first target with oxygen adsorption properties and a second metal target, where the first target is used to getter oxygen within the vacuum container, and the second target forms a metal film on the substrate, which is then oxidized with controlled oxygen supply to stabilize the metal oxide film's resistance value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a metal-made target is used for sputtering to form a metal oxide film, then the film formation process can be simplified, but the target surface oxidizes during sputtering causing unstable resistance values
Solution Approach 1:
The patent divides the target into two separate entities: a metal target for sputtering and a separate oxygen supply system. This segmentation allows the metal target to remain pure during sputtering while oxygen is introduced separately to form the oxide film, preventing target surface oxidation and ensuring stable resistance values.
Solution Approach 2:
The patent performs preliminary sputtering of the metal target to form a clean metal film on the substrate before introducing oxygen. This preliminary action ensures that the metal film is formed without target oxidation, and subsequent oxygen introduction occurs under controlled conditions to achieve precise oxide film properties.
2Productivity
If oxygen is introduced into the sputtering chamber during film formation, then a metal oxide film can be formed in one chamber, but residual oxygen causes resistance value variation between substrates
Solution Approach 1:
The patent performs preliminary sputtering of the metal film before introducing oxygen. This preliminary action establishes a clean metal film foundation, and oxygen is then introduced in a controlled manner to form the oxide film with precise stoichiometry, ensuring consistent resistance values across substrates while maintaining high throughput.
Solution Approach 2:
The patent precisely controls oxygen partial pressure and flow rate parameters during the oxide film formation process. By optimizing these parameters, the patent achieves complete oxygen utilization for film formation without residual oxygen remaining in the chamber, ensuring consistent resistance values while maintaining high productivity.
3Ease of manufacture
If a metal oxide target is used for reactive sputtering, then a metal oxide film can be formed directly, but the target surface gradually oxidizes reducing process stability
Solution Approach 1:
The patent separates the metal target from the oxygen supply system. The metal target remains pure and does not oxidize during sputtering, while oxygen is introduced separately to form the oxide film. This segmentation maintains target integrity and process stability throughout production.
Solution Approach 2:
The patent maintains an inert or low-oxygen environment during the metal film sputtering process, preventing target surface oxidation. Oxygen is then introduced in a controlled manner only when needed for oxide film formation, ensuring target longevity and process reliability.
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 approach ensures stable resistance values across substrates by reducing residual oxygen in the vacuum container and allowing precise control of oxygen content in the metal oxide film, enhancing the yield rate and quality of MRAM memory devices.
Implementation Method 1
a first target composed of a material having a property of adsorbing oxygen
Implementation Method 2
forming a metal film on a substrate by sputtering a target with ions of plasma
Implementation Method 3
oxidizing the metal film
Data Source
AI summary
The present disclosure provides a vacuum-processing apparatus for forming a metal film on a substrate by sputtering targets with ions of plasma, and then oxidizing the metal film, the apparatus including: a first target composed of a material having a property of adsorbing oxygen; a second target composed of a metal; a power supply unit configured to apply a voltage to the targets; a shutter configured to prevent particles generated from one of the targets from adhering to the other of the targets; a shielding member; an oxygen supply unit configured to supply an oxygen-containing gas to the substrate mounted on the mounting unit; and a control unit configured to perform supplying a plasma-generating voltage to the targets and sputtering the targets and supplying the oxygen-containing gas from the oxygen supply unit to the substrate.