Patent Application
20120329203
The present invention relates generally to methods of a silicon sheet fabrication, and more specifically to a roll press method of creating a silicon thin film for electric elements.
Mainly un-satisfied quality silicon for semiconductor use has been previously utilized as the silicon for the solar cells or semiconductor devices. From these, so-called metal melting process, where the reaction between molten zinc and silicon tetra-chloride is performed, is known for the independent supply of silicon, but has the problems of products having powdery and complicated treatment, difficulty of impurity treatments and also the difficulty of casting, which will result high cost, so the process has not been utilized.
To dissolve the problems, silicon production process by gas phase zinc reducing process was proposed, but together with the silicon produce, about ten times of amount of zinc chloride (ZnCl2) is co-produced and the disposal of it must be troublesome, so the commercial application of this process is very limited. From the point of view of reuse of zinc chloride, the objective has been established, but actually produced silicon is mixture of molten zinc and silicon itself became fine powders, so formed silicon particle having big surface area, then purification became difficult, which was big problem.
To obtain single crystal silicon from poly-crystalline or powdered silicon obtained under these processes, it must have less problem when those silicon poly-crystalline materials having rather big particle size and relatively small surface area are used, because those materials have less absorption of impurities and oxygen, but in the case of silicon being fine powder and having high surface area, removal of surface absorbed materials is required before installing to the crystal growing processes though such silicone bulk is very pure because the absorbed materials must be caused of impurity, which gives complicated procedure and requires treatment of abolishes. Then the producing cost must become high. And according to the normal process, complicated processes of high temperature treatment being applied at first to produce silicon powder or fine crystalline, then cooling and then heating to melt are required, and which requires repeating heating/cooling, which gives also troublesome from the energy consumption.
As shown in the above, previous technologies are all mainly aimed silicon to grown as solid or crystalline, so the formed crystal blocks or powder is considered to be exposed in air where once formed silicon is re-refined according to the requirement, then re-melt or crystallization is performed, when in grown single crystals or grown poly-crystalline, where at least excess energy is required for re-melting. And when in producing silicon blocks or powders, as the materials, is premised to expose in air, block silicon is preferred to minimize the impurity absorption when in producing silicon raw material, then reducing process of silicon tetra-chloride by zinc, which is the simplest way of producing silicon, could not be applied in the commercial process, which has also big problem. Recently, some trials of direct taking out of molten silicon from the reaction furnace is performed, but several problems such as corrosion by co-product hydrochloric acid and reaction between furnace wall and silicon, which gives shortening of furnace life, due to high operation temperature, have been arisen.
Based-on the above description, the present invention provides a method of creating a silicon thin film roll that can simultaneously highly reduce production cost and manufacturing cost.
One objective of the present invention is to provide a method of creating a PIN or PN semiconductor thin film roll with three type molten semiconductor materials. These PIN or PN semiconductor thin films are suitable for electric elements.
In order to achieve the objectives, the present invention is to provide a method of creating a PIN semiconductor thin film. The method comprises the steps of providing a molten P-type semiconductor material, a molten Intrinsic semiconductor material and a molten N-type semiconductor material. Next, it is performing a down draw process or a casting process of the molten P-type semiconductor material, the molten intrinsic semiconductor material and the molten N-type semiconductor material. Then, it is selectively performing a dual-side rolling process to the molten P-type semiconductor material, the molten Intrinsic semiconductor material and the molten N-type semiconductor material to create a P-type semiconductor ribbon, a Intrinsic semiconductor ribbon and a N-type semiconductor ribbon. Subsequently, it is performing a step of joining the P-type semiconductor ribbon, the Intrinsic semiconductor ribbon and the N-type semiconductor ribbon to form a PIN semiconductor ribbon. It is performing a step of roll press process to the PIN semiconductor ribbon to create the PIN semiconductor thin film.
The down draw process is made by selectively injecting the molten P-type semiconductor material, the molten Intrinsic semiconductor material and the molten N-type semiconductor material into their corresponding collection troughs and downward flowing out along their corresponding orifices, respectively. The dual-side rolling process is performed by dual-side rollers. The joining step may be performed by a set of alignment module established by XYθ stage and vision technology.
The method further comprising a step of performing a winging process of the PIN semiconductor thin film such that the PIN semiconductor thin film roll is created thereby.
According to an aspect of the present invention, a method of creating a semiconductor thin film, comprising the steps of providing a molten semiconductor material. Next, it is performing a down draw process or a casting process of the molten semiconductor material to create a semiconductor ribbon. Then, it is performing a roll press process or a pressing process to the semiconductor ribbon to create a semiconductor thin film. Subsequently, it is performing an ion implanting process of the semiconductor thin film to form a N or P type semiconductor thin film as traditional silicon fab process.
According to another aspect of the present invention, a method of creating a PN semiconductor thin film is provided which may referred to the method of creating the PIN semiconductor thin film.
The present invention and embodiments are now described in detail. In the diagrams and descriptions below, the same symbols are utilized to represent the same or similar elements. The possible embodiments of the present invention are described in illustrations. Additionally, all elements of the drawings are not depicted in proportional sizes but in relative sizes.
In accordance with embodiments of the present invention, systems and methods for determining the shape of silicon sheets during and/or after the forming process are described. As used herein, the term “silicon sheet” is intended to include silicon during or after its formation, without limitation. Thus, as one example, the term “silicon sheet” can include a silicon ribbon downstream from the root of an isopipe in its various states (e.g., visco-elastic, elastic, etc.), as well as the final silicon sheet that may be cut from the silicon ribbon.
While described herein with reference to the fusion down draw process, it is contemplated that the systems and methods described herein can be used to determine the shape of silicon ribbons or sheets formed using any of various known silicon forming processes, including float processes, slot draw processes, up draw processes, and single-sided overflow down draw processes.
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Silicon ribbon passes through several physical states during the forming process. The molten silicon overflows the sides of the isopipe 102 in a viscous state. The separate flows then fuse to form a silicon ribbon at the bottom of the isopipe 102, after which the silicon of the ribbon transitions from a visco-elastic state, to an elastic state. After the silicon has transformed into an elastic material, the silicon ribbon 106 can be scored and separated, such as illustrated by dash line 107, to form the final silicon sheet or silicon panel 108.
In some embodiments, the shape of the silicon may be determined for a moving ribbon of silicon, such as across the width of the ribbon. For example, the shape of a moving silicon ribbon being drawn from an isopipe in a fusion downdraw process can be determined across a width of the sheet at a given location, such as in the elastic region of the silicon. In a typical manufacturing environment, the fusion draw machine is an enclosed space that may reach a high temperature (e.g. 800.degree. C.), and access to the space is limited to preserve the delicate temperature balance necessary within the confines of the space surrounding the silicon ribbon. Thus, it may be necessary to direct the light source through a window into the space to irradiate the silicon ribbon. In such instances, a one-dimensional scan across the width of the ribbon may be the only practical option. In other embodiments, where access is less limited, a two dimensional measurement can be made, where the ribbon is scanned by the light source both across a plurality of points over the width of the ribbon and down the length of the ribbon in order to acquire a two dimensional shape and/or tilt. In a further aspect, the system can also scan a cut silicon sheet in two dimensions to determine its overall shape and ensure that it meets any required specifications.
Advantageously, the present invention may be used to measure the shape of a silicon having a temperature anywhere below a temperature at which the silicon ceases to have a defined shape (e.g. molten). For example, testing has shown the present invention to be applicable to shape measurement of silicon having a temperature in excess of 800.degree. C. On the other hand, shape measurement of silicon sheets at temperatures at or below room temperature may easily be made. Thus, there are a broad range of possible temperatures for the article being measured, based on the physical limitations of the material itself.
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The PN or PIN semiconductor thin film of the present invention may be applied for a solar cell device, for example silicon solar cells, amorphous silicon solar cells, Copper Indium Gallium Diselenide solar cells, Cadmium Telluride thin film photovoltaics, thin film silicon solar cells, or Dye-Sensitized solar cells.
In further embodiment, the PN or PIN semiconductor thin film may be stacked with at least one second PN or at least one PIN semiconductor thin film for further providing a wider energy hand to absorb solar rays.
Referring to
In a typical manufacturing environment of the present invention, the down draw process and the roll press process are performed under a high temperature (e.g. Transition Point temperature, or 800.degree. C.) and a vacuum situation to keep a stable physical state of the silicon ribbon.
Moreover, the PIN silicon sheet may be often produced by casting. In the casting technique, molten silicon in a crucible is gradually cooled from the bottom of the crucible for solidification of silicon, to obtain an ingot having long grains grown from the bottom of the crucible as its main body. This ingot is sliced into thin plates to obtain wafers available for the solar cells or the semiconductor devices.
As will be understood by persons skilled in the art, the foregoing preferred embodiment of the present invention illustrates the present invention rather than limiting the present invention. Having described the invention in connection with a preferred embodiment, modifications will be suggested to those skilled in the art. Thus, the invention is not to be limited to this embodiment, but rather the invention is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims, the scope of which should be accorded the broadest interpretation, thereby encompassing all such modifications and similar structures. While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made without departing from the spirit and scope of the invention.
