Patent Application
20150140213
Processes and apparatus for producing glancing angle deposited thin films.
Glancing angle deposited (GLAD) thin films are known from U.S. Pat. Nos. 6,248,422, 6,206,065 and 5,866,204. The GLAD patents focus on the possible structures and methods for controlling them, as does the scientific work which followed. There are a few patents which describe fabrication methods, but to the inventors' knowledge, all use multiple wafers in a single chamber. This approach limits the number of substrates that can be processed, adversely impacting the commercialization of the GLAD process.
In an embodiment, there is disclosed an apparatus for producing glancing angle deposited thin films, the apparatus comprising a source of collimated vapour flux, the source of collimated vapour flux having a deposition field; and a travelling substrate disposed within the deposition field of the source of collimated vapour flux, the collimated vapor flux being collimated at a defined non-zero angle to a normal to the travelling substrate. In an embodiment, there is disclosed a method of producing glancing angle deposited thin films, the method comprising collimating a vapour flux; and exposing a travelling substrate to the collimated vapour flux, the vapor flux being collimated at a non-zero angle to a normal to the substrate. The source of collimated vapour flux may comprise a material having angled channels, for example a louvre. The travelling substrate may comprise an endless conveyor or a discrete substrate on an endless conveyor. Collimating the vapour flux may comprise selecting a defined angle of vapour flux by passing the vapour flux through a material having angled channels.
Embodiments of the production method and apparatus will now be described with reference to the figures, by way of example, in which like reference characters denote like elements, and in which:
Immaterial modifications may be made to the embodiments described here without departing from what is covered by the claims. In the claims, the word “comprising” is used in its inclusive sense and does not exclude other elements being present. The indefinite articles “a” and “an” before a claim feature do not exclude more than one of the feature being present. Each one of the individual features described here may be used in one or more embodiments and is not, by virtue only of being described here, to be construed as essential to all embodiments as defined by the claims.
There is disclosed a roll-to-roll approach modified for GLAD films, which has been the basis for commercial scale thin film processes such as potato chip bags, magnetic tape, film production, and others. To produce precise nanostructured films 12, the GLAD process dynamically controls substrate 10 orientation in time. As shown in
The travelling substrate 10 is positioned so that in operation it is exposed to the vapour flux 16 to allow the vapour 16 to be deposited on the substrate 10. The region in which the vapour flux 16 remains collimated so that it may be deposited on the substrate 10 is referred to here as the deposition field of the vapour source. For any given strength of vapour generation and type of vapour source, the deposition field can be easily calculated by an operator of the apparatus. In all the figures shown here, the travelling substrate 10 is within the deposition field of the vapour sources. The apparatus will normally be confined within a low pressure chamber, with pressures suitable to prevent or reduce undesirable scattering of the vapour 16. The effect of scattering is to reduce the definition of the structures grown on the substrate 10. The amount of permitted scattering is therefore dependent on the required definition in the structures. The operator may adjust the pressure of the pressure chamber accordingly. Thus, processes described here should be carried out in conditions in which the vapour flux 16 arrives at the substrate 10 in approximately a straight line. For this reason, it is preferred that the process be carried out under conditions approximating a vacuum, for example at less than 0.13N/m2 (10−3 torr), for example at 1.3×10−4N/m2 (10−6 torr).
The substrate 10 may be any solid material on which a vapour 16 may be deposited, and will depend on the application. The substrates 10 include, but are not limited to, flexible sheets of metal or plastic, or discrete rigid substrates such as silicon or glass substrates. The material to be deposited may be any material for which conditions are achievable to support vapor generation and deposition of the vaporized material on the substrate 10. In some cases, this may require cooling or heating of the substrate 10. To assist in bonding one vaporized material to another, an intervening layer may be first deposited, as for example using a chromium intermediate layer to bond gold to amorphous silicon dioxide (glass). In addition, the material used should have a sticking co-efficient of at least about 0.9 to enable the formation of distinct structures.
The travelling substrate 10 may travel by moving linearly or in an arc, such as when on the surface of a rotating element or spirally moving element.
A GLAD film's growth geometry can be described by a trajectory through a three dimensional space defined by height, the altitude of the vapour flux 16 (typically referred to as a in the GLAD literature), and the azimuth of the vapour flux 16 (typically referred to as Φ in GLAD literature). In addition to the geometry, a parameter which identifies the growth material is defined. The geometric parameters are shown in
Height: h, units of nm
Vapour Flux Altitude: α, units of degrees
Vapour Flux Azimuth: φ, units of degrees
Material: M, unitless
Each growth phase of a GLAD film can be described by a single set of these four numbers. The resolution required depends on the particular desired geometry. For simple films, such as slanted posts, a single set. More complex films, such as a phi-sweep slow corner square spiral can be made up with hundreds of sets, making up a deposition algorithm. Any possible GLAD film can be described by a deposition algorithm, and a R2R system will be required to achieve algorithms to deposit any GLAD film.
A R2R web or endless conveyor moves at a constant speed powered by a motor on one or both rolls. Therefore, to accommodate the full control needed for a GLAD film deposition in a R2R system, it is necessary to relate the growth rate on the travelling web to GLAD geometry and the conditions imposed by a 2D louvre. For one point on the surface of and physical vapour deposition source, the rate at the substrate 10 is given by
where Rsubstrate is the deposition rate at the substrate 10, Rsource is the physical vapour emission rate at the source, R is the distance between the infinitesimal point on the substrate 10 and the infinitesimal point on the travelling web, a is the altitude of the infinitesimal point on the substrate 10 measured from the travelling web, and n is a parameter describing the shape of the physical vapour emission plume.
The height for a growth phase of a GLAD film is defined by
where Tphase is the time required for a given phase, Lphase is the length required for a given phase, and Vweb is the speed of the travelling substrate(s) 10. For a single growth phase, the distance required for a single phase is then given by
For any given growth phase, the 2D louvres 14 will impose the correct altitude and azimuth. Details of this process and worked examples are given in the next section. A final important aspect is that the travelling substrate 10 can travel without impinging vapour flux 16 for arbitrary periods, as necessary to achieve the necessary changes in vapour flux direction in the 2D louvre 14.
This section introduces the 2D louvres 14, and the configurations required to produce GLAD structures.
The film deposit can be built up to any desired height by extending the length of the 2D louvre 14, or by performing multiple passes under the same 2D louvre 14, or by moving the travelling substrate 10 in a spiral under multiple 2D louvres.
Films of multiple materials can be produced by changing composition of the physical vapour source material, using multiple sources with different source material composition or by replacing source material and depositing additional material.
To adjust the pitch of the chevron, the length of each section should be adjusted according to the equations outlined above. As the distance Lphase is decreased (or Vweb is increased), serial bi-deposition films will be produced.
Slightly more complicated than the chevron, the square spiral can also be produced using the 2D louvre shown in
To reduce figure complexity, going forward the individual growth phases will be denoted using an arrow for the helical, vertical post, and supersets of the canonical GLAD films shown here. This approach is shown in
Advanced GLAD deposition algorithms, such as Phi-sweep, are possible using this invention.
This technology can be used with any of the following source types: E-beam evaporation, Ion-beam assisted deposition, Sputtering, Thermal evaporation, Molecular beams.
A linear source can be synthesized by arranging any of these source types, or any combination thereof, into a line to produce vapour flux 16. Multiple materials can be deposited in a single deposition by using different sources or source material.
The 2D louvres 14 can be used in any configuration relative to the source, including above, below and to the side. Any substrate type can be used in this technology, including conventional roll-to-roll webs and discrete substrates. A discrete substrate may be carried by a conveyor such as a travelling conveyor. The conveyor could be any conventional conveyor used in industrial processing and could be an endless conveyor.
The 2D louvre technology can be used with any material compatible with any of the evaporation technologies listed here: E-beam evaporation, Ion-beam assisted deposition, Sputtering, Thermal evaporation, Molecular beams, including, but not limited to those listed here:
This application claims the benefit under 35 USC 119(e) of U.S. provisional application No. 61/881,815 filed Sep. 24, 2013.
| Number | Date | Country | |
|---|---|---|---|
| 61881815 | Sep 2013 | US |
