WO2010071609A2

WO2010071609A2 - System and processing of a substrate

Info

Publication number: WO2010071609A2
Application number: PCT/SG2009/000484
Authority: WO
Inventors: Hae Choon Yang
Original assignee: Rokko Ventures Pte Ltd
Priority date: 2008-12-17
Filing date: 2009-12-17
Publication date: 2010-06-24
Also published as: WO2010071609A3; SG162631A1; CN102439707A; TW201033600A

Abstract

A system for processing a substrate comprising a loading station for receiving the substrate; a bottom surface inspection station for inspecting the bottom surface of the substrate; a top surface inspection station for inspecting the top surface of the substrate and; a sorting station for sorting the substrate into a predetermined category based upon the bottom surface inspection and top surface inspection.

Description

SYSTEM AND PROCESSING OF A SUBSTRATE

FIELD OF THE INVENTION

The invention relates to the processing of substrates used in the semiconductor industry for a variety of purposes including unfeatured wafers, arrays of integrated circuits and the photovoltaic cell industry.

In particular, the invention relates to a means of processing such a substrate in the case where the substrate is fragile.

BACKGROUND OF THE INVENTION

The different processing techniques of substrates used in the semiconductor industry vary widely depending upon the end use of the substrate. In particular, the fragility of the substrates during processing can vary greatly, subject to a number of factors including material thickness, end use and whether external reinforcement has been applied to strengthen the substrate.

Wafers, for instance, maybe as thin as 0.18mm, and be made from materials that are of low flexural strength, such as mono-crystalline silicon. Handling of such cells requires a specialist operation to avoid damage. For instance, the robust handling of substrates normally associated substrates of integrated circuit arrays, as disclosed in PCT/SG2006/000015 the contents of which are incorporated, herein would be inappropriate and lead to an unacceptable level of damage to the cells. SUMMARY OF INVENTION

It is therefore an object of the present invention to provide a means of handling fragile substrates in a manner that is better suited to such elements.

In a first aspect, the invention provides a system for processing a substrate comprising a loading station for receiving the substrate; a bottom surface inspection station for inspecting the bottom surface of the substrate; a top surface inspection station for inspecting the top surface of the substrate and; a sorting station for sorting the substrate into a predetermined category based upon the bottom surface inspection and top surface inspection.

In a second aspect, the invention provides a substrate engagement device comprising a housing having a vacuum source for vacuum engagement of said substrate; a spacing device for contacting said substrate while in vacuum engagement with the device, said spacing device arrange to maintain a gap between the vacuum source and the substrate.

In a third aspect, the invention provides a method of engaging a substrate, the method comprising the steps of providing a vacuum source for vacuum engagement of said substrate; contacting said substrate with a spacing device while in vacuum engagement with the device, said spacing device arrange to maintain a gap between the vacuum source and the substrate. Accordingly, the invention provides for a means of engaging and supporting said cells whereby the engagement and support achieved by different functions. Particularly, it relates to a means for separating the substrate from the vacuum source during engagement.

BRIEF DESCRIPTION OF DRAWINGS

It will be convenient to further describe the invention, with respect to the accompanying drawings, that illustrate possible arrangements of the invention. Other arrangements of the invention are possible, and consequently the particularity of the accompanying drawings is not to be understood as superceding the generality of the preceding description of the invention.

Figure 1 is a plan view of a system according to one embodiment of the present invention;

Figure 2 is a detail plan view of a loading conveyor according to Figure 1;

Figure 3 is an isometric view of a bottom surface inspection station according to a further embodiment of the present invention;

Figure 4 is an isometric view of a top surface inspection station according to a further embodiment of the present invention;

Figure 5 is an isometric view of a peripheral inspection station according to a further embodiment of the present invention;

Figure 6 is an isometric view of a thickness measurement station according to a further embodiment of the present invention; Figure 7 is an isometric view of sorting bins according to a further embodiment of the present invention, and;

Figure 8, 8A, 8B and 8C are various views of a picker according to a further embodiment of the present invention.

DETAIL DESCRIPTION

Figure 1 shows an overview of the system for processing a substrate or wafer. The system 5 is positioned downstream from the singulation area, whereby the substrates are diced from a larger source of the material. Following singulation the substrates pass into a cleaning station 10 and a drying 15 station, before exiting the drying station 15 through a conveyor 17. The substrates then enter a laser marking head 20 before entering an inspection and sorting area 6.

The inspection and sorting area 6 includes a carrier 25 which acts as a buffer for substrates. This may be useful any differential in processing speed between the upstream cleaning/drying areas and the inspection and sorting area 6. In this embodiment, the substrates are delivered to a bottom surface inspection station 30, followed by a top surface inspection station 35. To handle bottleneck issues this embodiment also includes two thickness measurement stations 40, 45 before entering to a dual carriage carrier 50 to transport the substrates to respective bins 60 based upon the results of the previous inspection stations. When the respective bins are full, they are transported to the packaging area 80 and placed in the respective zones 85. Various aspects of the invention will be described in more detail in the subsequent figures.

Figure 2 shows the entry of the substrate 100 into the inspection and sorting area 6. Here a conveyor 17 transports the substrate 100 to a carrier 25. In this embodiment, the carrier has the capacity of 3 substrates 105. However, other embodiments may include carriers having capacities of 3, 4 or 5 substrates. Still further embodiments may carry many more substrates subject to the size of the substrate and the requirement for having a buffer of substrates to manage the process flow through the system. The carrier 25 is arranged to move 110 in direction at right angles to the conveyer 17 and so move the carrier 25 such that a vacant slot within the carrier corresponds to a substrate 100 being delivered from the carrier 17.

As shown in Figure 1, a linear rail 27 is present, having a picker arrangement whereby a picker 115 engages individual substrates 120 for delivery along in the linear rail 27. In this embodiment, the first station is a bottom surface inspection station 30 whereby the picker 115 engages the substrates 120 and moves them over a camera 130. The bottom surface inspection station 30 further includes a light 125 to enhance the image and allow more accurate inspection of the substrate 120. The bottom surface inspection station 130 maybe arranged to inspect various aspects of the substrate including adequate and accurate marking, macro cracks, micro cracks and any departure of the substrate from the allowable tolerance. The substrates are then delivered to a conveyer 150 for passing under a top surface inspection station 35. Figure 4 shows the motion of the substrates 145 on the conveyor 150 as they pass underneath a camera 140 again having lighting 135. The conveyer may include brackets or lights or other means to hold the substrate 145 in a precise position for more accurate and rapid inspection by the top surface inspection station 35. Further the conveyer 150 may be a lighting block which shines light towards the camera 140. This has the advantage of projecting light through any cracks or micro cracks that may be present in the substrate 145. Accordingly, having light shining through said cracks will make the inspection process more accurate particularly for micro cracks having a very narrow gap which may not be detected under normal circumstances.

A further top surface inspection station 155 may be included to specifically identify micro cracks. As shown in Figure 5, such a station may include a camera 160 projecting on a very specific field of view. Unlike previous inspection stations, which may have cameras which view large portions of, or the entire substrate, the micro crack inspection camera 160 may have a very detailed view. In one embodiment the field of view 170 having dimensions x and y maybe a square field of view of dimension 2.5mm by 2.5mm. As micro cracks have a greater likelihood of occurring during singulation, the substrate 145 may undergo micro crack inspection along the peripheral edges of the substrate.

The next station within the system according to this embodiment is inspection of the thickness of the substrate. There are a number of proprietary systems used for inspecting the thickness of the substrate. One such system may matter be resistivity of the wafer and determine thickness as a function of the resistivity of the material. Alternatively, and as shown in figure 6, the system 180 may measure an optical path and the shortening of the optical path as the wafer enters within the optical field.

In any event the skilled person will appreciate the available methods of measuring such thicknesses and the use of any one of said proprietary systems. Whichever method is chosen there are different measurement path maybe selected in order to determine with statistical reliability the thickness of the wafer 179. For instance, a boundary wl, w2 defined by a peripheral path 175 maybe chosen to ensure consistent measurement around the substrate. This together with, or instead of could also include center line 177, 178 or an internal path 176 within the face of the substrate 179.

It follows that the greater the number and/or length of path chosen to measure thickness will both increase the sensitivity for thickness inspection as well as slow the process. Accordingly, the thickness inspection station may prove to be a bottleneck to the system subject to the upstream and downstream processes. In the embodiment shown in Figure 1, two such thickness measurement stations 40, 45 are provided so as alleviate the bottleneck.

Following the various inspection station the substrates are delivered from a dual carrier 50 to a series of category bin 60 whereby each substrate is ranked according to compliance with any of the previous inspection. In this embodiment, there are 13 categories of substrate into which the substrate maybe classified. In further embodiments several of the bins maybe of the same category, for instance, bins 1 to 7 may for "passing" substrates with bins 8 to 11 being for "rework" and bins 12 to 13 being "reject" bins.

Further shown in Figure 7 are the actual bin arrangements 55 having upright brackets 195 placed on a table 185 into which the substrate 190 fit. Each of the bins will receive substrates until full whereby a gripper picker, arrangement located on linear slide 65, 70, deliver the bins to the packing station 70 whereby the bin are package within their respective categories before finally moving along a conveyer 90 to the unpacking the stacking zone 95 ready for delivery.

Such a gripper may be adapted to engage the entire bin. Further, the linear slide may include both a picker and gripper on the same slide so as to give a dual function to the linear slide, being substrate deposition, and bin removal. In the same fashion, the gripper and picker may be mounted together, to further save on infrastructure.

Figures 8A to 8D show a substrate engagement device according to a further embodiment of the present invention. In this case, the engagement device is a picker 200. The picker 200 includes a housing 205 to which is mounted several vacuum sources 215. At the edges of the housing 205 is a spacer device which, in this case, includes a series of separation blocks 210.

The vacuum sources 215 are shown here as a plurality of discrete vacuum sources. The vacuum source in am alternative embodiment may include a vacuum plate having a plurality of vacuum orifices. In a still further embodiment, the vacuum sources 215 maybe discrete vacuum nozzles providing a high negative pressure in order to engage the substrate 220.

In a still further embodiment the vacuum sources 215 maybe cyclone pads. The pads may receive a positive airflow, which is directed in a cyclonic direction around the circular periphery of the device. The circular flow air causes a low pressure region 245 at the center cyclone pad 255. In application where the substrate 220 is very light the cylone pad generating below pressure will draw the substrate upwards. The broad base of the cyclone pad 255 and low concentration of negative pressure is compared to conventional vacuum sources which allow the vacuum 255 to provide a more gentle engagement of the substrate.

The separation block 210 is intended to separate the substrate 220 from the vacuum source 215 and so provide a gap 236. This has the benefit of avoiding the localized stress concentration of the substrate against a conventional vacuum source having heavily concentrated negative pressure. In the case where the vacuum source is, in fact, a cyclone pad 255 the separation 236 provides a further benefit in vast allowing air to escape 240 between the cyclone pad 255 and substrate 220 is required for the operation of said cyclone pad.

With regard to the separation block 210, a step arrangement is used in this embodiment. The separation of the substrate 220 from the vacuum source 215 is achieved by contact between the substrate and a step face 230. On engagement of the substrate, said substrate is drawn upwards towards the vacuum source, but prevented from making actual contact.

Further, side projections 235 are used to encircle the substrate, to prevent lateral movement of the substrate. Thus, when manufactured to a close tolerance, the substrate fits to a high tolerance within the confines of the separation block 210, thus preventing further potential of damage to the substrate through excessive flexural strength or shifting through a misalignment with the engagement device 200. Further still, in this embodiment, the separation block 210 is made from a softer material, such as a polymer, for instances polypropylene, so as to further limit damage to the substrate during engagement.

Claims

CLAIMS:

1. A system for processing a substrate comprising a loading station for receiving the substrate; a bottom surface inspection station for inspecting the bottom surface of the substrate; a top surface inspection station for inspecting the top surface of the substrate and; a sorting station for sorting the substrate into a predetermined category based upon the bottom surface inspection and top surface inspection.

2. The system according to claim 1 further including a vacuum engagement device for engaging the substrate so as to expose the bottom surface of the substrate to the bottom surface inspection station.

3. The system according to claim 1 or 2, further including a conveyer for supporting and moving said substrate through the top surface inspection station.

4. The system according to claim 3 wherein said conveyer further includes a light source for projecting light from beneath the substrate so as to highlight cracks within the substrate while in the top surface inspection station.

5. The system according to any one of the preceding claims, further including a thickness measurement station for measuring the thickness of the substrate.

6. The system according to any one of the preceding claims wherein the loading station further includes a carrier for holding a plurality of substrate prior to movement to the inspection station.

7. A substrate engagement device comprising a housing having a vacuum source for vacuum engagement of said substrate; a spacing device for contacting said substrate while in vacuum engagement with the device, said spacing device arrange to maintain a gap between the vacuum source and the substrate.

8. The device according to claim 7 wherein said vacuum source is any one or a combination of vacuum plate with a plurality of vacuum orifices, a plurality of vacuum nozzles or a plurality of cyclone pads.

9. The device according to claim 7 or 8 wherein said spacing device includes a plurality of blocks, each block having a substrate engagement face, said engagement face offset from the vacuum source so as to maintain a gap between said substrate and vacuum source.

10. The device according to claim 9, wherein said blocks further include side projections, defining an engagement space into which the substrate fits, said side projections positioned so as to prevent horizontal movement of the substrate while engaged by said device.

11. A method of engaging a substrate, the method comprising the steps of: providing a vacuum source for vacuum engagement of said substrate; contacting said substrate with a spacing device while in vacuum engagement with the device, said spacing device arrange to maintain a gap between the vacuum source and the substrate.