Claims:WE CLAIM:

1. Carrier to hold Silicon wafer during etching/texturing process for uniform process in liquid medium comprising a hollow container (100) having substantially trapezoidal section in top view and a detachable handle (200), wherein the container (100) includes opposite upper (101A, 101B) and lower side members (102A, 102B) with multiple slots (S) side by side on so as to accommodate wafers, wherein a side member (103) having substantially rectilinear shape with an opening (O) at the center thereof and another side member (104) having substantially H-section are positioned opposite to each other and interposed between said upper (101A, 101B) and lower side members (102A, 102B).

2. The carrier to hold Silicon wafer as claimed in claim 1, wherein the rectilinear side member (103) with an opening (O) at the center thereof and the side member (104) having substantially H-section are mounted on the lower side members (102A, 102B) and connected to the top side members (101A, 101B).

3. The carrier to hold Silicon wafer as claimed in claim 1 or 2, wherein the adjustable screws (W) are provided above and below the opening (O) of the side member (103) and on side member (104) so as to facilitate adjustment of the wafers of varying size.

4. The carrier to hold Silicon wafer as claimed in claims 1-3, wherein the handle (200) having substantially rectilinear shape is attached on the top of the container (100) of the carrier.

5. The carrier to hold Silicon wafer as claimed in claims 1-4, wherein the handle (200) has top arm (201) for holding the carrier filled with wafers, below the top arm (201), a middle arm (202) is placed so as to restrict movement of hand beyond the middle arm (202) while dipping into the chemical bath for the chemical treatment.

6. The carrier to hold Silicon wafer as claimed in claim 5, wherein the handle has a lower arm (203) which ensures that wafers are kept intact while the chemical process is going on and are not displaced because of the vigorous chemical reactions, in which said handle (200) is placed on base (204) forming a single piece, in which the lower arm (203) is detachable.

7. The carrier to hold Silicon wafer as claimed in claims 1-6, wherein the carrier device comprises of frame assembly made up of nonreactive material like Polytetrafluoroethylene (PTFE) commonly known as Teflon.
, Description:
“Carrier to hold Silicon wafer during etching/texturing process for uniform process in liquid medium”

FIELD OF INVENTION:
[001] This invention relates to Carrier to hold Silicon wafer during etching/texturing process for uniform process in liquid medium. The carrier keeps the wafers safe as well.

BACKGROUND OF INVENTION/PRIOR ART:
[002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[003] Silicon wafers need to undergo lot of chemical treatment during cleaning, texturization, etching etc. before they finally get converted into solar cells. The saw marks of the wafers are cleaned by dipping them in alkaline solution. After that, to increase the surface area and sunlight absorption, pyramids are made on the surface. This again requires dipping the wafers into chemical. Thereafter diffusion process is carried out to make a pn junction. This pn junction needs to be etched out from rear side which also requires wafers to be chemically treated. Commercially available wafers carrier are good for carrying out these processes but they hold the wafer from all sides and therefore lead to non uniform chemical treatment at the edges.

[004] Also the wafers size is rapidly changing these days and the commercially available carriers are fixed in size with no scope of modification.

PRIOR ART:
[005] Reference may be made to the following patents:
[006] US5074736A: The invention relates to a carrier-susceptor for use in a continuous chemical vapor deposition reactor system that serves as a carrier, cover and heat susceptor for a semiconductor wafer being processed through the reactor system. This is different from present invention as chemical treatment of the wafers is taking place in this case.

[007] EP0692817A1: The invention is a dimensionally stable and static dissipative carrier for semiconductor wafers or magnetic storage disks that has exceptionally low particle generation characteristics. The sidewalls, ribs, and end walls are all integral and formed of injection molded polybutyl terephthalate (PBT) with 12 percent to 25 percent carbon fiber filler by weight. This is provided only for keeping the wafers safe after any process step. It is again different from present invention because the carrier device developed here is used to keep wafers safe as well as undergo chemical treatment.

[008] US6068137A: It reduces adhesion of resin in a resin-made carrier used when washing, conveying and transporting semiconductor wafers, and the carrier is made from PBN having an elongation rate of 100% or less, whereby adhesion of resin is reduced. This also does not talk about the chemical treatment of the wafers using this carrier.

[009] None of the above can serve the purpose and fulfill the requirements for which the present invention has been devised.

OBJECTS OF THE INVENTION:

[0010] An object of the present invention is to propose a carrier device to safely hold multiple wafers but at minimum points so that it is exposed maximum to the etchant medium for carrying out uniform chemical treatment in batch processing during solar cell fabrication.

[0011] Another object of the invention is to provide a carrier device, which obviates drawbacks of the prior art(s).

[0012] Yet another object of the invention is to provide a carrier device wherein the width of the carrier can be modified slightly to incorporate a larger size of wafers also.

[0013] Still another object of the invention is to provide a carrier device, which is simple in construction and efficient.

[0014] These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.

SUMMARY OF THE INVENTION:
[0015] One or more drawbacks of conventional systems and process are overcome, and additional advantages are provided through the apparatus/composition and a method as claimed in the present disclosure. Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered to be part of the claimed disclosure.

[0016] The present invention deals with a carrier to hold wafers in specially designed grooves. It can hold upto 25 wafers at a time. The carrier supports the wafer at very few locations which ensures that there is minimum shadowing effect and maximum exposure to the etchant medium. Thus, this invention holds the wafers at minimum points and is a compromise between covered area of the wafer and proper gripping of the wafers. This ensures uniform etching throughout the wafer with minimum contamination. A “rectilinear” handle is also attached to the top of the carrier. The top arm helps in holding the carrier filled with wafers and dipping it into the etchant bath. The lower arm helps in keeping the wafers intact at their place so that they do not get displaced due the vigorous chemical reaction taking place in the bath. It is also equipped with adjustment screws on both sides which can be used to accommodate varying size of wafers. Thus, the width of the carrier can be modified slightly to incorporate larger size of wafers also.

[0017] New wafer carrier device has been developed and used successfully to carry out chemical processes with requisite uniformity and fabricate high efficiency solar cells.

[0018] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

[0019] It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.

[0020] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
[0021] The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and processes that are consistent with the subject matter as claimed herein, wherein:-

Figure 1 shows: Carrier to hold Silicon wafer during etching/texturing process for uniform process in liquid medium in accordance with the present invention.
Figure 2 shows: Side view of the carrier device of the present invention.
Figure 3 shows: Top view of the carrier device of the present invention.
Figure 4(a) shows: Non uniformly textured wafer.
Figure 4(b) shows: Uniformly textured wafer.

[0022] The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAIL DESCRIPTION OF THE PRESENT INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS OF PREFERRED EMBODIMENTS:

[0023] While the embodiments of the disclosure are subject to various modifications and alternative forms, specific embodiment thereof have been shown by way of example in the figures and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.
[0024] The invention is directed to an invention pertinent to Carrier to hold Silicon wafer during etching/texturing process for uniform process in liquid medium.

[0025] Now reference may be made to Fig.1-3, wherein the carrier device of invention comprises of frame assembly made up of nonreactive material like Polytetrafluoroethylene (PTFE) commonly known as Teflon without restricting scope of the invention to the same. Thus, other materials readily apparent to a person skilled in the art are understood to be within scope of the invention.

[0026] The carrier device can be divided into two parts. The first part constitutes a hollow container (100) having substantially trapezoidal section in top view and second part is detachable handle (200).

[0027] There are a number of slots (S) side by side on opposite upper (101A, 101B) and lower side members (102A, 102B) so as to accommodate wafers which prevent any slippage and hold the wafers effectively. A rectilinear side member (103) with an opening (O) at the center thereof is mounted on the lower side members (102A, 102B) and connected to the top side members (101A, 101B).Thus the rectilinear side member (103) is interposed between said upper (101A, 101B) and lower side members (102A, 102B). Another side member (104) having substantially H-section is similarly mounted on the lower side members (102A, 102B) and connected to the top side members (101A, 101B).Thus the side member (104) is interposed between said upper (101A, 101B) and lower side members (102A, 102B). The side member (103) and another side member (104) are positioned opposite to each other as illustrated in Figure 2.

[0028] A plurality of adjustable screws (W) are provided on both side members (103, 104). The adjustable screws (W) are provided above and below the opening (O) of the side member (103). Also there is provision of adjustable screws (W) on side member (104).The adjustable screws (W) help in adjustment of the wafers of varying size.

[0029] A substantially rectilinear shaped handle (200) is attached on the top of the container (100) of the carrier, in which the handle (200) is detachable. The top arm (201) of the handle helps in holding the carrier filled with wafers while dipping it into chemical bath for the chemical treatment. Below the top arm (201), a middle arm (202) is placed so as to restrict movement of hand beyond that while dipping into the chemical bath. Further, the handle has a lower arm (203) which ensures that wafers are kept intact while the chemical process is going on and are not displaced because of the vigorous chemical reactions. Said handle (200) is placed on base (204) forming a single piece, in which the lower arm (203) is detachable.

[0030] The side view and top view of the carrier device with detached handle is shown in Fig. 2 and Fig. 3 respectively. The adjustment screws (W) are best seen in Fig 2 which can be adjusted and width of the carrier device can be modified to incorporate bigger wafers. After placing the wafers in proper slots (S) the handle is attached on the top of the carrier as shown in Fig 1.

[0031] Referring to Fig. 3, the wafer touches the carrier at the minimum points so that contamination is reduced and maximum area of the wafers is exposed to the chemicals. This ensures uniformity of the chemical process on the wafers. The carrier serves the multiple purposes of holding the wafers intact, reducing contamination and enhancing uniformity of etching/texturing across the wafers.

[0032] Silicon wafers need to undergo lot of chemical treatment during cleaning, texturing, and etching before they finally get converted into solar cells. The saw marks of the wafers are formed while cutting the wafers from ingot. They need to be cleaned by dipping them in alkaline solution. After that, the surface is chemically etched resulting in the formation of microscopic pyramids to increase the surface area of the wafer and thereby enhancing absorption of sunlight. The current produced by a solar cell is directly proportional to the sunlight it absorbs. Then diffusion process is then carried out to make a pn junction. This pn junction needs to be etched out from rear side which again requires dipping the wafers into chemical solution. This carrier device is suitable to hold the wafers and carry out uniform process in all these stages.

[0033] Commercially available wafers carrier can be employed for carrying out these processes but they hold the wafer from all sides and therefore lead to non uniform chemical treatment at the edges. In contrast, the invention holds the wafers at minimum points yet ensuring proper gripping of the wafers during chemical treatment. On the one hand, the wafers need to be held loosely in the carrier so that the chemicals reach all the surfaces uniformly and on the other hand the wafers have to be held sufficiently firmly so that they do not get displaced during the chemical reaction due to gases generated which stick to silicon wafers. The specific shape of the carrier takes care of both the requirements. Also the wafers size is rapidly changing these days and the commercially available carriers are fixed in size with no scope of modification. The present invention is equipped with adjusting screws on both sides which can be adjusted to accommodate minor variations of wafers with different sizes.

[0034] New wafer carrier device has been developed and used successfully to carry out chemical processes with requisite uniformity and fabricate high efficiency solar cells.

ADVANTAGEOUS FEATURES:

• It is made of non reactive material that prevents contamination of silicon wafers during chemical treatment.
• It ensures minimum contact area between wafer and carrier itself so as to ensure maximum exposed area of the wafer to the chemicals during chemical treatment.
• Makes it possible to carry out uniform process across the wafer while providing it adequate support in the carrier.
• Helps in holding the carrier from one side and making firm grip on wafers from other side.
• Wafers with increased width can be accommodated.
WORKING OF INVENTION:
[0035] The wafers are inserted into the designated slots in the carrier device. The handle is tightened on the top of the device so that wafers are not misplaced during the chemical treatment. The whole assembly of wafers, carrier and handle is then picked up from the top and dipped into the chemical bath. It can be pulled up and down for rigorous and uniform reaction. After treating for pre-designated time it is removed and cleaned in the other tank containing water/ cleansing agent. Wafers are then picked out and dried for further processing.

TEST RESULT:

The uniformity of chemical process enhanced after using this carrier device for texturization. The quality of solar cell fabricated on any wafer depends on how much light it absorbs and how much less light it reflects back. The more is the absorption, better is the solar cells. Using this carrier for texturization has helped in increasing the absorption to a large extent. Reference may be made to Figure 4(a) and 4(b) illustrating Non uniformly textured wafer and Uniformly textured wafer respectively.
[0036] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the “invention” may in some cases refer to certain specific embodiments only. In other cases, it will be recognized that references to the “invention” will refer to subject matter recited in one or more, but not necessarily all, of the claims.

[0037] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.

[0038] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particulars claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogues to “at least one of A, B and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B”.

[0039] The above description does not provide specific details of manufacture or design of the various components. Those of skill in the art are familiar with such details, and unless departures from those techniques are set out, techniques, known, related art or later developed designs and materials should be employed. Those in the art are capable of choosing suitable manufacturing and design details.
[0040] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.

[0041] The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.

[0042] While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.