Claims:WE CLAIM:
1. A bowl-shaped jig (204) for measuring minority carrier lifetime of a semiconductor (402), the semiconductor (402) being placed in the bowl-shaped jig (204), the bowl-shaped jig (204) comprising:
a first ring A having a first inner diameter (ID1), a first outer diameter (OD2), and a first thickness (T1);
a second ring B having a second inner diameter (ID2) greater than the first inner diameter (ID1), a second outer diameter (OD2) greater than the first outer diameter (OD1), and a second thickness (T2), the second ring B being configured to be disposed concentrically with the first ring A and define a gap there between; and
a sheet (202) having dimensions greater than the first outer diameter (OD1) and the second outer diameter (OD2), the sheet (202) is configured to be disposed between the first ring A and the second ring B, such that first ring A and the second ring B are concentric to each other, wherein the second ring B is pressed towards the first ring A to accommodate a thickness (T3) of the sheet (202) in the gap and stretch the sheet (202) between the first thickness (T1) of the first ring A and the second thickness (T2) of the second ring B for providing a bowl-shape to the sheet (202).
2. The bowl-shaped jig (204) as claimed in claim 1, wherein the first ring A and the second ring B are made from one of wood, plastic, metal, fiber.
3. The bowl-shaped jig (204) as claimed in claim 1, wherein the sheet (202) is made from ethyl vinyl acetate (EVA).
4. The bowl-shaped jig (204) as claimed in claim 1, wherein the semiconductor (402) is a silicon wafer.
5. The bowl-shaped jig (204) as claimed in claim 1, wherein the bowl-shaped jig (204) is provided with an iodine solution (404) for passivating the semiconductor (402).
6. The bowl-shaped jig (204) as claimed in claim 1, wherein the first thickness (T1) of the first ring A protrudes beyond the second thickness (T2) of the second ring B after the second ring B is pressed towards the first ring A to stretch the sheet (202) therebetween, so as to create a resting base (206) for the bowl-shaped jig (204).
7. A method (300) for making a bowl-shaped jig (204) for measuring minority carrier lifetime of a semiconductor (402), the method (300) comprising:
placing a first ring A having a first inner diameter (ID1), a first outer diameter (OD1), and a first thickness (T1);
positioning a sheet (202) over the first ring A;
disposing a second ring B over the sheet (202), such that first ring A and the second ring B are concentric to each other, the second ring B having a second inner diameter (ID2) greater than the first inner diameter (ID1), a second outer diameter (OD2) greater than the first outer diameter (OD1), and a second thickness (T2), such that a gap is defined between the second ring B and the first ring A; and
pressing the second ring B towards the first ring A to accommodate a thickness (T3) of the sheet (202) in the gap and stretch the sheet (202) between the first thickness (T1) of the first ring A and the second thickness (T2) of the second ring B for providing a bowl-shape to the sheet (202), wherein dimensions of the sheet (202) are greater than the first outer diameter (OD1) and the second outer diameter (OD2).
8. A system (400) for measuring minority carrier lifetime of a semiconductor (402), the system (400) comprising:
a bowl-shaped jig (204) configured to receive the semiconductor (402), the bowl-shaped jig (204) having iodine solution (404) for passivating the semiconductor (402), the bowl-shaped jig having:
a first ring A having a first inner diameter (ID1), a first outer diameter (OD1), and a first thickness (T1),
a second ring B having a second inner diameter (ID2) greater than the first inner diameter (ID1), a second outer diameter (OD2) greater than the first outer diameter (OD1), and a second thickness (T2), the second ring B being configured to be disposed concentrically with the first ring A, such that a gap is defined between the second ring B and the first ring A, and
a sheet (202) having dimensions greater than the first outer diameter (OD1) and the second outer diameter (OD2), the sheet (202) is configured to be disposed between the first ring A and the second ring B, such that first ring A and the second ring B are concentric to each other, wherein the second ring B is pressed towards the first ring A to accommodate a thickness (T3) of the sheet (202) in the gap and stretch the sheet (202) between the first thickness (T1) of the first ring A and the second thickness (T2) of the second ring B for providing a bowl-shape to the sheet (202);
a microwave source (406) for receiving the bowl-shaped jig (204) and providing microwaves to the semiconductor (402); and
a flash lamp (408) positioned proximal to the microwave source (406), the flash lamp (408) being configured to illuminate the semiconductor (402) with light without any obstruction in the path of light.
9. The system (400) as claimed in claim 8, wherein the first thickness (T1) of the first ring A protrudes beyond the second thickness (T2) of the second ring B after the second ring B is pressed towards the first ring A to stretch the sheet (202) therebetween, so as to create a resting base (206) for the bowl-shaped jig (204), such that the resting base (206) of the bowl-shaped jig (204) makes a firm contact with microwave source (406), as the bowl-shaped jig (204) is placed on the microwave source (406).
10. The bowl-shaped jig (204) as claimed in the preceding claims, wherein the iodine solution (404) fully passivates the semiconductor (402) without any risk of spillage.
, Description:A bowl-shaped jig for measuring minority carrier lifetime of a semiconductor
FIELD OF INVENTION
[001] The present disclosure relates to solar photovoltaics, more particularly, the present disclosure relates to a jig for silicon wafers.

BACKGROUND OF THE INVENTION

[002] One of the important parameter to define quality of a silicon wafer is its Minority Carrier Lifetime (MCL). The solar cell efficiency is directly proportional to the MCL, as MCL is the measure of how long the photo generated carriers remain alive before recombining. It is very essential to know the wafer characteristics before beginning of fabrication process such that corrective actions can be taken in the production to enhance yield. The MCL of silicon (Si) wafer is very small and is measured in µs (micro second) or ms (millisecond) and is generally in the range of a few to 100s of µs. The testing instrument used for this purpose requires Si wafers where the surface is reasonably passivated.

[003] Si wafer surface can be passivated by depositing thin films of SiN, a-Si or Al2O3 by using expensive deposition setups. The passivation is required for reducing the noise. Further, passivation of the Si wafer may also be achieved by dipping in it iodine solution. During conventional testing, the dipping of Si wafer in iodine solution is carried out in a zip lock polythene bag which is placed over the microwave source, however the polythene bag restricts the light coming from an illuminating source, and there are great chances that the zip lock will malfunction and iodine solution will spoil the measurement setup.

[004] In order to overcome the deficiencies of the conventional setups, an innovative receptacle is required for receiving the Si wafer and the iodine solution for testing, that does not restrict the light from the illuminating source, and is also capable of non-spillage of the iodine solution.

PRIOR ART:

[005] Now, reference may be made to the following prior arts discussing state of the art techniques.

[006] WO2010130013A1 provides method and apparatus for characterizing a semiconductor material. The method involves a non-homogeneous illumination (1) to a semiconductor material (2). The material can be a block or wafer of semiconductor material such as silicone, a partially or fully processed solar cell with or without an emitter layer (11). The non- homogeneous illumination (1) provides a first portion subjected to a first predetermined illumination level and a second portion subjected to a second predetermined illumination level less than the first illumination level. The first predetermined illumination level is sufficient to produce a response, eg photoluminescent response in at least the first portion. The method involves acquiring an image of that response and processing the image to determine one or more spatially resolved characteristics of the material. The method is useful in solar cell manufacturing for quality control, process control and process monitoring.

[007] US20100178718A1 provides a method for optimizing a solar cell manufacturing process. The method includes determining a reference finger spacing value and a reference bulk lifetime for the solar cell manufacturing process. The method also includes measuring an actual bulk lifetime of a wafer with an in-line measurement tool. The method further includes calculating an optimal finger spacing value with a computer coupled to the in-line measurement tool, the optimal finger spacing value being the product of the reference finger spacing value and a square root of the actual bulk lifetime divided by the square root of the reference bulk lifetime. The method further includes forming a junction on the wafer, and depositing a set of busbars and a set of fingers on the wafer with a metal deposition device, wherein a distance between a first finger and a second finger of the set of fingers is about the optimal finger spacing value.

[008] However, the aforementioned references do not discuss or provide a direct or indirect solution to the problems, deficiencies, and inaccuracies faced during measuring MCL of a semiconductor.

OBJECTS OF THE INVENTION

[009] An object of the invention is to provide a measurement setup for measuring MCL of Si wafers by overcoming the deficiencies and disadvantages of the prior art.

[0010] In the present invention, a jig has been fabricated which will hold the passivated sample as per requirement of testing equipment for precise and accurate measurements without the risk of spillage of iodine solution on the highly sensitive sensors and interference with microwave source.

[0011] The object of the invention is to design a jig used for accurate measurements of MCL of a Si wafer by passivating it in Iodine solution in a microwave based testing tool.

SUMMARY OF THE INVENTION

[0012] A bowl-shaped jig (204) for measuring minority carrier lifetime of a semiconductor (402), the semiconductor (402) being placed in the bowl-shaped jig (204).The bowl-shaped jig (204) includes a first ring A having a first inner diameter (ID1), a first outer diameter (OD2), and a first thickness (T1);a second ring B having a second inner diameter (ID2) greater than the first inner diameter (ID1), a second outer diameter (OD2) greater than the first outer diameter (OD1), and a second thickness (T2), the second ring B being configured to be disposed concentrically with the first ring A and define a gap there between; and a sheet (202) having dimensions greater than the first outer diameter (OD1) and the second outer diameter (OD2), the sheet (202) is configured to be disposed between the first ring A and the second ring B, such that first ring A and the second ring B are concentric to each other, wherein the second ring B is pressed towards the first ring A to accommodate a thickness (T3) of the sheet (202) in the gap and stretch the sheet (202) between the first thickness (T1) of the first ring A and the second thickness (T2) of the second ring B for providing a bowl-shape to the sheet (202).

[0013] A method (300) for making a bowl-shaped jig (204) for measuring minority carrier lifetime of a semiconductor (402). The method (300) includes placing a first ring A having a first inner diameter (ID1), a first outer diameter (OD1), and a first thickness (T1);positioning a sheet (202) over the first ring A; disposing a second ring B over the sheet (202), such that first ring A and the second ring B are concentric to each other, the second ring B having a second inner diameter (ID2) greater than the first inner diameter (ID1), a second outer diameter (OD2) greater than the first outer diameter (OD1), and a second thickness (T2), such that a gap is defined between the second ring B and the first ring A; and pressing the second ring B towards the first ring A to accommodate a thickness (T3) of the sheet (202) and stretch the sheet (202) between the first thickness (T1) of the first ring A and the second thickness (T2) of the second ring B for providing a bowl-shape to the sheet (202), wherein dimensions of the sheet (202) are greater than the first outer diameter (OD1) and the second outer diameter (OD2).

[0014] A system (400) for measuring minority carrier lifetime of a semiconductor (402).The system (400) includes a bowl-shaped jig (204) configured to receive the semiconductor (402), the bowl-shaped jig (204) having iodine solution (404) for passivating the semiconductor (402).The bowl-shaped jig having a first ring A having a first inner diameter (ID1), a first outer diameter (OD1), and a first thickness (T1) a second ring B having a second inner diameter (ID2) greater than the first inner diameter (ID1), a second outer diameter (OD2) greater than the first outer diameter (OD1), and a second thickness (T2), the second ring B being configured to be disposed concentrically with the first ring A, such that a gap is defined between the second ring B and the first ring A, and a sheet (202) having dimensions greater than the first outer diameter (OD1) and the second outer diameter (OD2), the sheet (202) is configured to be disposed between the first ring A and the second ring B, such that first ring A and the second ring B are concentric to each other, wherein the second ring B is pressed towards the first ring A to accommodate a thickness (T3) of the sheet (202) in the gap and stretch the sheet (202) between the first thickness (T1) of the first ring A and the second thickness (T2) of the second ring B for providing a bowl-shape to the sheet (202). The system (400) further includes a microwave source (406) for receiving the bowl-shaped jig (204) and providing microwaves to the semiconductor (402); and a flash lamp (408) positioned proximal to the microwave source (406), the flash lamp (408) being configured to illuminate the semiconductor (402) with light without any obstruction in the path of light.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0015] Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings of the exemplary embodiments and wherein:
Figure 1ashows: First ring A and second ring B.
Figure 1bshows: The second ring B disposed concentrically with the first ring A.
Figure 2ashows: A sheet (202) configured to be received between the first ring A and the second ring B.
Figure 2bshows: A bowl-shaped jig (204) in accordance with an embodiment of the present disclosure.
Figure 3shows: A method (300) for making the bowl-shaped jig (204) of Fig. 2b in accordance with an embodiment of the present disclosure.
Figure 4 shows: A system (400) for measuring minority carrier lifetime (MCL) of a semiconductor (402).

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

[0016] The present invention, now be described more specifically with reference to the following specification.

[0017] Fig. 1a shows two rings, a first ring A and a second ring B. The first ring A includes a first inner diameter (ID1), a first outer diameter (OD1), and a first thickness (T1). The second ring B includes a second inner diameter (ID2) greater than the first inner diameter (ID1), a second outer diameter (OD2) greater than the first outer diameter (OD1), and a second thickness (T2). In an embodiment as shown in Fig. 1b, the second ring Bis being configured to be disposed concentrically with the first ring A, and define a gap between the first outside diameter (OD1) of the first ring A and the second inside diameter (ID2) of the second ring B, when the second ring B is concentrically disposed over the first ring A. In an example, the first inner diameter (ID1) of the first ring A may be 10”, and the gap may be 0.3mm. In an embodiment, the first ring A and the second ring B are made of wood, plastic, metal, fiber or the like materials.

[0018] Fig. 2a shows a sheet (202) configured to be received between the first ring A and the second ring B. In an embodiment, the sheet (202) have dimensions greater than the first outer diameter (OD1) and the second outer diameter (OD2). The sheet (202) defines a thickness (T3) substantially comparable to the gap defined between the concentric first ring A and the second ring B. In an example, the sheet (202) may be a 12” X 12” square sheet having the thickness (T3) of 0.5mm so that the sheet is tightly and firmly fixed between the first ring A and the second ring B.

[0019] In an embodiment as shown in Fig. 2b, the sheet (202) is configured to be disposed between the first ring A and the second ring B, such that first ring A and the second ring B are concentric to each other. Further, the second ring B is pressed towards the first ring A to accommodate the thickness (T3) of the sheet (202) in the gap defined between the concentric first ring A and the second ring B, and further stretch the sheet (202) between the first thickness (T1) of the first ring A and the second thickness (T2) of the second ring B for providing a bowl-shape to the sheet (202). The sheet (202) being disposed between the first ring A and the second ring B and having the bowl-shape is defined as a bowl-shaped jig (204). In an embodiment, the sheet (202) is made from ethyl vinyl acetate (EVA).

[0020] Further in an embodiment as shown in Fig. 2b depicting the bowl-shaped jig (204), the first thickness (T1) of the first ring A protrudes beyond the second thickness (T2) of the second ring B after the second ring B is pressed towards the first ring A to accommodate and stretch the sheet (202) there between, so as to create a resting base (206) for the bowl-shaped jig (204). In an example, the protrusion may be greater than 5 mm.

[0021] Fig. 3 illustrates a method (300) for making the bowl-shaped jig (204) in accordance with an embodiment of the present disclosure. The bowl-shaped jig (204) is configured for measuring minority carrier lifetime (MCL) of a semiconductor such as a silicon (Si) wafer. At step 302, the method (300) includes placing the first ring A having the first inner diameter (ID1), the first outer diameter (OD1), and the first thickness (T1). At step 304, the method (300) includes positioning the sheet (202) over the first ring A.

[0022] At step 306, the method (300) includes disposing the second ring B over the sheet (202), such that first ring A and the second ring B are concentric to each other, the second ring B having the second inner diameter (ID2) greater than the first inner diameter (ID1), the second outer diameter (OD2) greater than the first outer diameter (OD1), and the second thickness (T2), such that the gap is defined between the second ring B and the first ring A. The sheet (202) defines the thickness (T3) substantially comparable to the gap defined between the concentric first ring A and the second ring B.

[0023] At step 308, the method (300) includes pressing the second ring B towards the first ring A to accommodate the thickness (T3) of the sheet (202) in the gap, and stretch the sheet (202) between the first thickness (T1) of the first ring A and the second thickness (T2) of the second ring B for providing the bowl-shape to the sheet (202) and form the bowl-shaped jig (204).

[0024] Fig. 4 illustrates a system (400) for measuring minority carrier lifetime (MCL) of a semiconductor (402), for example silicon (Si) wafer (402) in accordance with an embodiment of the present disclosure. The system (400) includes the bowl-shaped jig (204) configured to receive the silicon wafer (402). In an example, size of the silicon wafer (402) may be 6” X 6”. In an embodiment, the bowl-shaped jig (204) receives an iodine solution (404), and the silicon wafer (402) is configured to be dipped in the iodine solution (404) for its passivation. Due the bowl-shape, the bowl-shaped jig (204) provides non-spillage or reduced risk of spillage of the iodine solution (404).

[0025] The system (400) further includes a microwave source (406) configured to receive the bowl-shaped jig (204), wherein the resting base (206) is placed over and is in firm contact with the microwave source (406). In an embodiment, the microwave source (406) provides microwaves to the silicon wafer (402). The microwaves reach the silicon wafer (402) due to non-interfering characteristics of the EVA sheet (202) of the bowl-shaped jig (204).

[0026] The system (400) further includes a flash lamp (408) positioned proximal to the microwave source (406). The flash lamp (408) is configured to illuminate the silicon wafer (402) placed in the bowl-shaped jig (204). The light from the flash lamp (408) reach the silicon wafer (402) directly as there is no obstruction in the path of light between the flash lamp (408) and the silicon wafer (402). The flash lamp (408) may be provided with a light sensor (not shown) configured to adjust an intensity of light from the flash lamp (408) based on requirement. The system (400) further includes a computing device (410) communicably coupled to the bowl-shaped jig (204), the microwave source (406), and the flash lamp (408). In an embodiment, the computing device (410) is configured to measure the minority carrier lifetime (MCL) of the silicon wafer (402).

[0027] In operation, the silicon wafer (402) dipped in the iodine solution (404) received by the bowl-shaped jig (204) is placed just over the microwave source (406). The flash lamp (408) illuminates the top surface of the silicon wafer (402) momentarily, and the minority carriers are generated. The intensity of the light is adjusted automatically as per the requirement with the help of feedback from the light sensor installed with the flash lamp (408). The origin and decay of these minority carriers is sensed by microwaves of the microwave source (406) and a result corresponding to the minority carrier lifetime (MCL) associated with the silicon wafer (402) is evaluated and displayed on the computing device (410).

[0028] It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims.