Low Temperature GST CVD Process for Conformal Amorphous Films
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Solution Overview
Problem
Conventional CVD techniques cannot deposit amorphous or partially amorphous GST films with high Te content at temperatures below 300 degrees C, resulting in non-conformal crystallization due to the difficulty in activating Te precursors, which limits the Ge:Sb:Te composition to below 45% Te.
Innovation Solution
A deposition process involving an activation region with a heat source to activate precursors before depositing them onto a substrate at a lower temperature, using a combination of heating sources to maintain the substrate at 110-250 degrees C, allowing for the formation of conformal GST films with up to 50% Te content by incorporating dopants like N, C, In, and Se.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional CVD techniques are used to deposit GST films, then Te precursors can be activated, but the substrate temperature must be above 300 degrees C which causes crystallization and non-conformal deposition
Solution Approach 1:
The heating system is segmented into two independent zones: a substrate heater that maintains low substrate temperature (110-250°C) and a precursor activation heater that activates Te precursors at higher temperature. This spatial segmentation allows simultaneous precursor activation and amorphous film deposition, resolving the contradiction between Te activation and film conformality.
Solution Approach 2:
Different regions of the deposition system are assigned different thermal characteristics: the substrate region maintains low temperature to prevent crystallization and ensure conformal deposition, while the precursor activation region operates at high temperature to activate Te precursors. This local quality differentiation enables both requirements to be satisfied simultaneously.
2Stability of the object's composition
If substrate temperature is kept below 300 degrees C to maintain amorphous GST films, then conformal deposition is achieved, but Te precursors cannot be activated
Solution Approach 1:
The heating function is segmented between substrate heater and activation heater, allowing precursor activation to occur independently of substrate temperature. Te precursors are activated in the hot activation zone before reaching the cold substrate, enabling amorphous film deposition with high Te content.
Solution Approach 2:
Te precursors are activated in advance in the activation region before being deposited onto the substrate. This preliminary activation at high temperature enables subsequent low-temperature amorphous deposition, as the precursors are already reactive when they reach the substrate.
3Quantity of substance
If high Te content (above 45%) is incorporated in GST films, then desired composition is achieved, but conventional CVD causes film crystallization and non-conformal deposition
Solution Approach 1:
The deposition system segments the heating function to allow high Te content deposition at low substrate temperature. The activation heater enables Te precursor activation without heating the substrate above crystallization temperature, achieving conformal amorphous GST films with up to 50% Te content.
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
Enables the deposition of conformal phase change material films with high Te content at lower temperatures, achieving amorphous or partially amorphous states suitable for memory devices with improved conformality and reduced crystallization, overcoming the limitations of conventional CVD techniques.
Implementation Method 1
use of an activation region through which precursors pass before the deposit thereof onto the substrate surface. The activation region, with sufficient interaction of the precursors passing therethrough in the presence of heat, causes the activation of one or more of the precursors
Implementation Method 2
The deposition is often effected using CVD (chemical vapor deposition) or other processes
Implementation Method 3
the substrate process temperature is preferred to be below the GST crystallization temperature
Data Source
AI summary
A deposition process to form a conformal phase change material film on the surface of a substrate to produce a memory device wafer comprises providing a substrate to a chamber of a deposition system; providing an activation region; introducing one or more precursors into the chamber upstream of the substrate; optionally introducing one or more co-reactants upstream of the substrate; activating the one or more precursors; heating the substrate; and depositing the phase change material film on the substrate from the one or more precursors by chemical vapor deposition. The deposited phase change material film comprises GexSbyTezAm in which A is a dopant selected from the group of N, C, In, Sn, and Se. In one implementation, the process is carried out to form GST films doped with carbon and nitrogen, to impart beneficial film growth and performance properties to the film.