Substrate electrode plasma generator and substance/material processing method

The present invention relates to a new plasma generating apparatus and matter and materials processing methods using that apparatus, such as thin film formation, surface processing of substrates or matter, and chemical reactions.

Materials processing techniques using plasma generating apparatuses are widely used in advanced materials preparation, as currently represented by electronic devices and ULSI. However, the problems with these apparatuses include high costs, large size, high power consumption, difficult processes, and inefficiency in the creation of new matter and materials. In particular, there are no means for generating plasma in arbitrarily small regions and for processing using plasma.

In view of such circumstances, it is an object of the present invention to provide a plasma generating apparatus that is inexpensive, small in size, has low power consumption, allows for simple processing, and makes the creation and development of new matter and materials very efficient. Furthermore it is an object of the present invention to provide methods for processing matter and materials using the plasma generating apparatus, including thin film formation, surface processing, and chemical reactions in a plurality of arbitrarily small regions of a substrate.

In order to achieve these objects, the substrate electrode plasma generating apparatus relating to the present invention has at least one pair of electrodes arranged on a single substrate, generates plasma between the electrode pairs, and generates plasma in an arbitrary gas atmosphere.

In the abovementioned substrate electrode plasma generating apparatus of another embodiment of the present invention, the plasma generated between the abovementioned electrode pairs is direct current plasma or alternating current plasma. Also, in the abovementioned substrate electrode plasma generating apparatus, the abovementioned arbitrary atmosphere is vacuum, gas, or liquid. In the abovementioned substrate electrode plasma generating apparatus, the abovementioned electrode pairs are electrode pairs comprising thin films disposed on a substrate. Also, in the abovementioned substrate electrode plasma generating apparatus, a plurality of electrode pairs disposed on the same substrate, but each of the electrode pairs is controlled independently of the others.

With these substrate electrode plasma generating apparatuses, plasma generated between conventional upper and lower electrodes can form a plurality of small quantities of plasma at any location on the surface of a single substrate.

In order to achieve the abovementioned objects, the matter and materials processing method uses the abovementioned substrate electrode plasma generating apparatus to form thin films comprising any material at any location on a separate substrate or matter. The matter and materials processing method relating to another embodiment of the present invention uses the abovementioned substrate electrode plasma generating apparatus to form thin films comprising arbitrary materials at any position on the same substrate. Furthermore, in the method relating to another embodiment, the source material for said thin films is gas or liquid. Yet another embodiment uses the abovementioned substrate electrode plasma generating apparatus to perform surface processing such as ashing, etching, washing, and reforming of another substrate surface.

Another embodiment uses the abovementioned substrate electrode plasma generating apparatus to cause chemical reactions using arbitrary materials at any position on another substrate. Another embodiment causes chemical reactions using arbitrary materials at any position on the same substrate.

The matter and materials processing methods as discussed above make possible the formation of thin films comprising arbitrary materials on a plurality of arbitrarily small regions of a surface, or make it possible to perform surface processing such as ashing, etching, washing, and reforming, and chemical reactions, on the same or a different substrate. Furthermore, another embodiment uses an inkjet method as the method for supplying arbitrary liquid materials used in the processes.

In yet another embodiment of the matter and materials processing method, said inkjet method uses a plurality of nozzles and supplies one or more types of liquid material.

Particularly with the matter and materials processing method using such an inkjet method, one or a plurality of liquid materials, in the desired quantities, can be supplied easily to a plurality of small plasma formation regions.

FIG. 1 is a diagram showing the overall constitution of the substrate electrode plasma generating apparatus;

FIG. 2 is a view from above, using a scanning electron microscope, of a pair of substrate electrodes;

FIGS. 3 (A)- 3 (B) are views using a scanning electron microscope of a substrate electrode; 3 (A) is a view from above the substrate electrode array; and 3 (B) is a side view of the vicinity of the plasma generation area;

FIGS. 4 (A)- 4 (B) are diagrams showing the situation of plasma generation with the substrate electrodes shown in FIG. 2; 4 (A) shows before plasma generation; 4 (B) shows during plasma generation;

FIGS. 5 (A)- 5 (B) shows the process for forming various thin films at arbitrary locations on the same or a different substrate using the substrate electrode plasma generating apparatus;

FIGS. 6 (A)- 6 (B) shown a substrate surface processing method using the substrate electrode plasma generating apparatus;

FIGS. 7 (A)- 7 (B) show a process for forming micro-optical thin films with a combination of the substrate electrode plasma generating apparatus and an inject printing apparatus; and

FIG. 8 shows silicon etching using the substrate electrode plasma generating apparatus.

The preferred embodiments are explained below using the drawings.

First Embodiment

FIG. 1 shows an overall view of the substrate electrode plasma generating apparatus. Tungsten is sputtered and deposited on a silicon substrate 5 with an oxidized surface and small gap thin film electrode pairs 1 - 4 are formed with dry etching. A plasma array apparatus, comprising four pairs of plasma generating electrodes in a two by two arrangement, is shown here, but an arrangement of any number at any location, according to the desired plasma processing, is acceptable. Each of electrode is wired together in a matrix form so that plasma can be generated between any pair of electrodes. Also, plasma generation may be controlled by the application of voltage between any pair of electrodes by active elements such as transistors. Voltage is supplied through element 50 .

FIG. 2 is a micrograph of a pair of substrate electrodes taken with a scanning electron microscope. Tungsten electrodes 7 and 8 are formed with a 5 μm gap 9 between the electrodes. The size of the substrate electrodes may be on the order of μm to cm.

Table 1 shows the relationship between pressure and break-down voltage in an argon atmosphere.

Also, plasma generation in air or hydrogen at one atm was observed at an applied voltage of 400 V with both tungsten and platinum electrodes having gaps of 5 μm to 10 μm therebetween.

FIG. 3 (A) shows a micrograph from above the substrate electrode array. FIG. 3 (B) shows a micrograph of the vicinity of the plasma generation area 9 seen from the side.

FIG. 4 is a diagram showing the situation of plasma generation with the substrate electrodes; (A) shows before plasma generation; (B) shows during plasma generation.

Before now, there were no examples of plasma being generated in micro-regions using electrodes on a substrate; this first became possible with the present invention. The substrate electrode plasma generating apparatus makes possible micro-fine plasma generation at a plurality of arbitrary locations on a single substrate surface.

Second Embodiment

FIG. 5 is a diagram showing the process for forming various thin films at arbitrary locations on the same or separate substrates using the substrate electrode plasma generating apparatus 10 . As shown in FIG. 5 ( a ), the silicon substrate 12 is positioned opposite to the substrate electrode plasma generating apparatus 10 ; an SiO 2 thin film 13 can be formed at any desired position by generating plasma 11 at that position while triethoxysilane (TEOS) gas is introduced into an air or oxygen gas atmosphere. In FIG. 5 ( b ), an aluminum thin film 15 is formed when plasma 14 is generated at another electrode pair while trimethoxyaluminum (TMA) is introduced into vacuum. Next, FIG. 5 ( c ) shows the formation of a silicon thin film 16 at a separate location as monosilane (SiH 4 ) is introduced into vacuum. In this way, it becomes possible to use the substrate electrode plasma generating apparatus 10 to form and pattern thin films comprising arbitrary materials at arbitrary locations by varying the reaction gas. Furthermore, it becomes possible to form various elements such as TFT's at arbitrary positions by introducing apparatuses for laser abrasion and ion doping.

FIG. 5 ( d ) shows the formation of an SiO 2 insulating film 17 on the same substrate as the substrate electrode plasma generating apparatus 10 with the introduction of triethoxysilane (TEOS). Controlling the type of reaction gas and the plasma generation region makes it possible to form thin films, semiconductor films, and so forth on the same substrate at any location.

Also, it is possible to form acrylic on the substrate by plasma polymerization through generating plasma while a reaction material that is not gas, but rather a liquid such as acrylic monomer, is introduced. Micro-optical elements with differing refractive indexes can also be formed on the same substrate by controlling the type of monomer and plasma conditions.

Third Embodiment

FIG. 6 shows the process for surface processing of a substrate using the substrate electrode plasma generating apparatus 10 . A substrate comprising a polyimide film 18 formed on a glass substrate 19 undergoes plasma 20 processing in an oxygen atmosphere. This may be done in air or as oxygen gas is introduced. As shown in FIG. 6 ( b ), arbitrary locations 21 of the surface may be made hydrophilic. This oxygen plasma processing also has ashing effects on the polyimide residue. Next, a hydrophobic surface 23 can be formed by shifting the substrate or the substrate electrode plasma generating apparatus and performing plasma 22 processing for the unprocessed polyimide surface while CF 4 gas is introduced. The reaction gas may also be another fluorine gas such as SiF 4 . Accordingly, it becomes possible to reform any location 23 of the surface on the same substrate to have hydrophilic or hydrophobic properties, as shown in FIG. 6 ( d ).

Fourth Embodiment

FIG. 7 shows the process for forming micro-optical thin films with a combination of the substrate electrode plasma generating apparatus and an inkjet printing apparatus. From an inkjet printing apparatus 26 , having inkjet heads 27 , 28 , 29 , 30 , SiO 2 precursor ink 31 is sprayed and patterned from inkjet heads 27 , 28 , and 29 onto a desired glass surface on a glass substrate 25 having partitions 24 formed of polyimide. For example, liquid including polysilazane is preferred as the SiO 2 precursor ink. Plasma 37 is generated with substrate electrode pairs 33 and 34 and an SiO 2 thin film 38 is formed using the substrate electrode plasma generating apparatus 32 comprising substrate electrode pairs 33 , 34 , 35 , and 36 . Furthermore, as shown in FIG. 7 ( c ), TiO 2 precursor ink 39 is sprayed from inkjet heads 28 , 29 , and 30 . A liquid 40 including a metal alkoxide such as titanium tetraisopropoxide is used as the TiO 2 precursor ink. Finally, plasma 41 is generated with substrate electrode pairs 34 , 35 , and 36 and a TiO 2 film 42 and (Si, Ti)O 2 mixed film 43 are formed. Consequently, combining the substrate electrode plasma generating apparatus and inkjet printing apparatus as shown in FIG. 7 ( d ) makes it possible and simple to form four types of thin films, TiO 2 , SiO 2 , SiO 2 /TiO 2 layered film, and (Si, Ti)O 2 mixed film, on a single substrate. Optical thin films with different refractive indexes can be formed on the same substrate through the formation of thin films comprising materials with different refractive indexes such as TiO 2 , SiO 2 , and (Si, Ti)O 2 . The formation of a DBR mirror is also made possible by layering thin films with different refractive indexes.

Fifth Embodiment

FIG. 8 shows local etching of a silicon substrate 46 using the substrate electrode plasma generating apparatus 32 . Etching of silicon at any position, defined between polyimide partitions 45 , is possible. A fluorine gas such as CF 4 is effective as the atmospheric gas.

As discussed above, the substrate electrode plasma generating apparatus relating to the present invention is smaller, more inexpensive, and consumes less power than a conventional plasma apparatus, and furthermore, makes possible simple and highly efficient matter and materials processing methods such as the formation of functional thin films at a plurality of tiny regions anywhere on a substrate, surface processing, and chemical reactions. Combining the plasma generating apparatus with an inkjet printing apparatus makes possible simple functional thin film formation and matter and materials processing for a wide range of the abovementioned functional thin films and matter and materials.