Electric lamp or space discharge component or device manufacturi – Process – With assembly or disassembly
Reexamination Certificate
2000-05-12
2001-11-20
Ramsey, Kenneth J. (Department: 2879)
Electric lamp or space discharge component or device manufacturi
Process
With assembly or disassembly
Reexamination Certificate
active
06319083
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to techniques for forming semiconductor devices such as field emission displays and particularly, in one embodiment, to techniques for sharpening the emitters of field emission displays.
There is currently considerable interest in field emission displays as an alternative to liquid crystal displays for use in electronic devices, such as laptop computers. Field emission displays offer many advantages. However, large displays must be formed on large supporting structures. Conventional silicon wafers have some drawbacks as the supporting structure for large field emission displays. The drawbacks include the fact that current wafer sizes may not be sufficiently large to accommodate these applications. Moreover, a wafer, of the size necessary to form a large field emission display on a single wafer, would be relatively expensive.
Therefore, there is some interest in developing field emission displays formed on structures called baseplates other than silicon wafers. One highly advantageous structure uses an amorphous silicon layer atop a glass supporting structure. These baseplates have a number of advantages including the ability to form large displays at reasonable cost. On the other hand, these structures are not amenable to high temperature processing normally associated with silicon wafer processing. By high temperature processing, it is intended to refer to the normal diffusion processes which take place temperatures on the order of 700° C. and higher.
For example, one problem that arises in using non-silicon wafer based support structures is that conventionally, the emitters are formed using high temperature oxide steps. One example would be that conventionally high temperatures may be utilized to sharpen the emitter tips so as to increase the emission efficiency of those devices. However, oxidizing processes conventionally require temperatures on the order of 900° C. and thus, are not suitable for some silicon-glass supporting structures.
One advantageous material for forming baseplates is soda-lime glass. However, soda-lime glass includes alkaline constituents, which may diffuse into and contaminate a silicon layer deposited on the glass baseplate. A number of techniques have been developed to attempt to isolate the silicon layer from the underlying soda-lime glass to prevent contamination from the alkaline constituents. One such technique is to use an intermediate barrier layer.
Thus, there is a need for a way of making structures such as glass structures that may be adversely affected by contaminants in the glass structures.
SUMMARY OF THE INVENTION
In accordance with one aspect, a method of forming an emitter for a field emission display includes the step of forming an upstanding silicon feature on a semiconductor layer. A porous silicon layer is formed in the surface of the upstanding feature. At least a portion of the porous silicon layer is then removed.
In accordance with another aspect of the present invention, a method of forming a field emission display includes the step of forming an emitter structure from a semiconductor layer. The tip of the emitter structure is sharpened without using high temperatures.
In accordance with still another aspect of the present invention, a process for making a semiconductor device includes the step of forming a silicon structure. A porous silicon layer is created on the structure. The structure is oxidized at a temperature lower than is typical for solid, non-porous silicon and the oxidized porous silicon is selectively removed.
In accordance with still another aspect, a method of forming a field emission display includes the step of forming a silicon structure having a silicon layer on a glass substrate. A layer of porous silicon is created in the surface of the silicon layer. The porous silicon is oxidized at a temperature below 700° C. The oxidized porous silicon layer is then selectively removed.
In accordance with another aspect, a method of making a semiconductor device using a soda-lime glass support layer includes the step of depositing a silicon layer directly on the soda-lime glass structure at a temperature below the temperature at which alkaline constituents in the soda-lime glass diffuse appreciably into the silicon layer. Features are defined in the silicon layer without using temperatures in excess of the temperature at which there is deleterious diffusion of alkaline constituents in the soda-lime glass into the silicon layer.
In accordance with yet another aspect of the present invention, a method for oxidizing and removing the oxidized layer from a silicon structure includes the step of oxidizing a silicon structure at a temperature below 700° C. The oxidized silicon structure is then removed. An oxide layer is formed on the structure at a temperature below 700° C. This oxide layer is then removed, as well.
In accordance with still another aspect of the present invention, a method of sharpening a tip formed in a silicon structure includes the step of forming a surface layer in the silicon structure which has micropassages which allow oxygen to penetrate the interior of the structure without bulk diffusion. The surface layer is selectively removed.
In accordance with yet another aspect of the present invention, a method of sharpening the tip of a silicon emitter includes the step of forming a layer of silicon on a silicon structure having a diffusivity to oxygen significantly greater than that of crystalline silicon. The layer is etched without applying a high oxidation temperature.
In accordance with another aspect of the present invention, a method for oxidizing silicon at low temperature includes the step of surface oxidizing a silicon layer without high temperature. When the silicon surface oxidation is substantially prevented by the overlying oxide growth, the overlying oxide growth is removed and the newly exposed silicon surface is surface oxidized without high temperature.
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Micro)n Technology, Inc.
Ramsey Kenneth J.
Trop Pruner & Hu P.C.
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