Etching a substrate: processes – Forming or treating optical article
Reexamination Certificate
1998-06-16
2001-05-29
Bareford, Katherine A. (Department: 1762)
Etching a substrate: processes
Forming or treating optical article
C427S164000, C427S162000, C427S165000
Reexamination Certificate
active
06238583
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention concerns a process for the production of a structure of colour filter layer system regions where:
a coating layer structure with coated surface regions and coating-free regions is produced on a substrate;
a colour filter layer system is deposited on the coating layer structure;
the coated surface regions with the overlying colour filter layer system regions are removed.
Such a production system is known as the lift-off process. It is used for example to produce red-green-blue colour filter layer system structures, in particular for LCD or CCD production. The colour filter layer systems can structured by pixel structuring or strip structuring.
Often in such systems, between the colour filter layer system regions is applied an opaque layer of material, usually chromium, which covers the filter layer system transitions and is usually known as the black matrix structure.
In general the said lift-off technology is advantageous from the point of view of commercial production as relatively few process stages are necessary in a vacuum. In relation to this technology, reference is made to US-A-3 914 464 or DE-30 13 142. It is also known to produce metallic layer structures using the lift-off technique in semiconductor production for example. Such metallic layer structures, for example approximately 1 &mgr;m thick, can be removed like a foil during lift-off without disintegrating. In this latter technique it is therefore necessary to produce the lift-off coating structure such that its side surfaces overhang. This ensures that the metal coating regions deposited on the coating-free regions are not also removed during the lift-off process. Overhanging coating structures can however only remain as such if the subsequent coating with the said metal coating is applied almost vertically to the base or substrate surface. When the coating structure is then dissolved during the lift-off process, the metal layer to be removed remains as a cohesive structure and during removal very few particles are produced which can be deposited on the remaining layer structures applied to the coating-free regions.
In this respect the lift-off process behaves totally differently on dielectric or generally brittle filter layer systems: on the one hand the overhanging coating layer structures can be omitted as the said filter layer systems are brittle and cannot be removed as a skin. They crumble into multiple small flakes during the lift-off process. At the structure edges, automatic layer system break points occur. The flakes can be deposited on the remaining structure where they frequently land, i.e. due to molecular forces they become attached to the surface of the remaining structure and are very difficult to remove, which can often cause damage to the filter layer system structure, for example the red-green-blue filter structure (RGB).
SUMMARY OF THE INVENTION
The problem of the present invention is to propose a process of the type described initially which prevents such defects on the end product. This is to be achieved with minimum cost and maximum simplicity.
The problem is solved in the said process by its formation according to the characterising part of claim
1
.
Accordingly, on each coating with one of the dielectric colour filter layer systems, for example in each case an R or G or B layer system, in addition a sacrificial layer is applied. The sacrificial layer material is firstly a material which withstands the lift-off or removal step of the coating regions with the colour filter layer system lying on this, and secondly the material for the sacrificial layer is selected such that it can be removed again from the colour filter layer system regions without damaging them. The application of the sacrificial layer according to the invention before the lift-off stage primarily has the effect that flakes are not deposited on the remaining filter layer system regions but on their sacrificial layer. A corresponding bonding only occurs with the latter and the flakes are removed in the removal stage of the sacrificial layer from the remaining filter layer system regions.
At the same time, the provision of the sacrificial layer according to the invention achieves a further important advantage:
The sacrificial layer on a filter layer system region can be used directly as a lift-off layer as, without providing a further coating layer structure, a subsequent colour filter layer system to be applied is applied directly onto the preceding sacrificial layer. This is dissolved in the lift-off stage as the material of the sacrificial layer must be removable without damaging the filter layer system materials. Thus in the production of structured multicolour filter layer systems, one process sequence consisting of mask coating/alignment, exposure/development can be omitted, which leads to a substantial increase in the yield of structured multicolour filter layer systems per time unit and in particular contributes to their low cost production. Thus in the production of a RGB pixel structure for example there are two coating lift-off processes and one sacrificial layer lift-off process.
The sacrificial layer preferably consists of a metal or dielectric, preferably Cr, Al or Y
2
O
3
.
If it is necessary to measure spectrally the colour filter layer system regions already deposited under the sacrificial layer, it is proposed that the sacrificial layer be structured partially transparent to allow this control, where preferably in production of the sacrificial layer from a metal, such as in particular Cr, this is formed maximum 10 nm thick. From this aspect the provision of the sacrificial layer of Y
2
O
3
is also extremely advantageous as this dielectric layer is totally transparent. If however a spectral control of the deposited colour filter layer systems is not required, an opaque sacrificial layer can be provided, for example by depositing a chromium layer more than 10 nm, e.g. 90 nm, thick.
As initially stated, often a black matrix layer is provided in a structured fashion both between remote colour filter layer system regions and at regions abutting in their peripheral areas. From this aspect there is a further advantage of the process according to the invention:
If namely a sacrificial layer is applied to the last colour filter layer system applied, advantageously its material is suitable as a black matrix layer material e.g. in particular chromium. Then the sacrificial layer as a black matrix layer is not removed completely but in structured fashion such as by etching. Otherwise, when namely no sacrificial layer is to be applied on the last colour filter layer system after which no lift-off process follows, and sacrificial-layer regions remain only on the colour filter layer system regions previously applied, an additional black matrix layer for example of Cr is applied and the latter removed in structured fashion together. with the regions of the remaining sacrificial layer.
REFERENCES:
patent: 3981568 (1976-09-01), Bartolomei
patent: 3013142 (1981-10-01), None
USPTO Translation of German patent 3013142, Oct. 8, 1981.
Edlinger Johannes
Schoch Helmut
Sperger Reinhard
Balzers Hochvakuum AG
Bareford Katherine A.
Cleveland Michael
Notaro & Michalos P.C.
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