Radiation imagery chemistry: process – composition – or product th – Registration or layout process other than color proofing
Reexamination Certificate
2000-01-14
2001-06-26
Young, Christopher G. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Registration or layout process other than color proofing
C430S030000
Reexamination Certificate
active
06251551
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention concerns a method and a device for treating and processing flat substrates, in particular silicon wafers, for the production of microelectronic components.
Substrates for microelectronic components e.g. silicon wafers require extremely clean surfaces necessitating repeated cleaning processes (treatments) during manufacture of a chip. The substrate must thereby be cleaned on both sides and at all surface locations. Among physical cleaning processes, wetting procedures are primarily used for single substrate cleaning comprising e.g. brushing, ultrasound, megasound, high-pressure and the like. The substrate must thereby be transported within the cleaning installation to the individual cleaning stations substantially in a wet condition. For single substrate processing, this is normally carried out in a horizontal substrate position using processing robots which e.g. hold the substrate at its lower side using vacuum or sideward clamping or through suitable bearing on transport belts, rollers and the like to facilitate transport. Contact with the surface during handling (both the front side as well as the back side) leads to contamination due to soiling (particles). In addition, the handling systems utilized in these extremely clean rooms are very complicated from a technical point of view and are expensive. The cleaning systems primarily used for the horizontal positioning of the substrate also require, for ever increasing substrate sizes, very large amounts of floor space in the clean rooms, which are consequently very expensive. In addition, collection of particles on the horizontal surfaces of the substrate also occurs in such clean rooms. The incidence of laminar guided clean room air containing residual particles on the large substrate surface leads to substantial contamination of the silicon wafers.
These processes also occur when cleaning rigid discs (metal substrates) or when producing microelectronic components generally referred to as chips on e.g. round silicon wafers using photolithographic processing, wherein the structures are exposed through masks on a photosensitive coating disposed on the surface of the substrate. The photosensitive coating (photo-resist) is thereby spun onto the substrate in a horizontal position, wherein subsequent processing, such as drying of the coating, exposure, development, etching and the like as well as the introduction of bonding agents prior to adding the coating are likewise all carried out in the horizontal substrate position. Handling between individual processing steps is effected using expensive handling robots capable of operation under clean room conditions.
Also known in the art is to spin dry individual wafers in the horizontal position following a wetting treatment. Very high rates of revolution are thereby required (in excess of 1000 to 5000 1/min), since the drops of water located on the wafer following the wetting processes are intrinsically very stable due to their surface tension and bond to the surface in the middle of the substrate. Only low centrifugal forces are active at the center of the substrate so that drying is only possible using very high rates of revolution to achieve sufficient forces in the middle of the substrate. This creates turbulence. Although such turbulence enhances drying, it also stirs-up particles causing contamination of the cleaned surface.
Other drying techniques, e.g. blowing nitrogen onto the middle of the substrate, also produce turbulence having the same effects. Additional warming of the surface (using infrared or laser techniques) can support the drying process. However, evaporation processes thereby occur which result in rinsing water residues in the form of drying spots on the surface of the substrate. These types of drying spots also constitute particles and are undesirable during production of the chips.
SUMMARY OF THE INVENTION
It is the underlying purpose of the invention to present a method and/or a device with which substrates of this type can be processed in an improved fashion and, in particular, less expensively.
This purpose is achieved in accordance with the invention with a method of the above mentioned kind, wherein the flat substrates, in particular silicon wafers, are aligned in such a fashion that the plane of the wafer is substantially vertical, with the wafers passing through at least one processing station in this (vertical) alignment. They thereby pass in vertical alignment into the processing station, are processed therein in vertical alignment, and also leave in vertical alignment. Although the wafers can be borne vertically in a transverse direction, they nevertheless maintain their vertical alignment.
The vertical alignment of the substrates or wafers leads to a substantial reduction in the relatively expensive clean room floor space and has the additional advantage that a substantially less amount of soiling particle deposit are incident on the surface of the wafers so that contamination in the clean room is accordingly reduced. In addition, installations of this type are substantially simpler and can be retrofitted to different wafer sizes.
The silicon wafers can be transported using handling robots. The wafers are thereby gripped on their edges using e.g. conical recesses on the robots.
For circular wafers, simple transport can be effected by passing the wafers pass through tilted processing stations under the force of gravity, in particular, by rolling. In this fashion, no separate transport device (handling robot) is required as a result of which the installation is relatively inexpensive. In particular, the wafers pass through a plurality of processing stations which are disposed one behind the other.
It is however also possible to effect substrate transport using guiding and/or transport rollers or transport elements which are disposed on a transport belt. Towards this end, the separation between the transport rollers or elements as well as the number and size thereof can be adjusted to the dimensions of the substrate to be processed or to the silicon wafers in such a fashion that as low as possible a bearing surface in the edge region of the substrate is effected on the transport rollers or elements.
The sideward guiding and thereby stabilization of the vertically aligned silicon wafers can be done without contact or in contact with the substrate surface, depending on requirements and processing techniques. For example, guiding without contact is possible during wetting processes effected by spray nozzles disposed on both sides of the substrate or guide rollers or guide strips wet with water or another liquid so that the substrate has surface contact only with the film of liquid or the liquid spray. Guiding using air or N
2
jets can be used for guiding without contact in drying processes. It is also possible to guide the substrate using air cushions generated between the substrate and the guide rollers or strips.
A contacted guiding can be effected using rollers or guide strips to guide the substrate in the edge region or at the sides.
The substrate must normally be turned for processing or handling procedures. This can be effected by lifting the substrate off the transport belt, wherein the substrate is pushed against drive rollers configured as rotational drive elements and engaging on one or two opposite sides of the silicon wafers to clamp same between themselves or between themselves and the transport roller or the roller of the lifting-off mechanism. Regulation of the clamping pressure can be effected using springs, resilient elements, pressure sensors or electronic means to which the drive rollers and/or the lift-off mechanisms are coupled. The transport roller itself can also be configured as a drive roller. The substrate can also be borne on the rotational drive by its intrinsic weight alone and held in vertical alignment using e.g. holding devices.
In order to achieve optimal handling processing results, the wafers are stopped and/or rotated during processing. They remain in the individual processing s
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