HK1115096B - Device for the separation of substrates from a stack - Google Patents

Description

Device for separating a substrate from a stack

Technical Field

The invention relates to a device for separating substrates from a stack, in particular for separating wet silicon wafers from a wafer stack.

Background

Wafers made of silicon for producing optoelectronic components are cut out of a block, for example in microelectronic devices, by means of a wire saw. Such a block is previously glued to the glass plate in order to obtain the retention force required for complete separation. The individual units therefore only adhere to the adhesive layer, since the wire saw is also embedded in the glass substrate. The sawing process is carried out with continuous flushing of a special medium, which is mixed with the sawing particles. The wafers are firmly bonded to one another in clusters by the pasty mixture and are difficult to separate for further processing. It is difficult to keep the wafer wet all the time until the process. Until now, the wafers were separated from the adhesive layer in clusters by hand in a known manner and between the thumb and middle finger by removing the uppermost wafer. However, the simultaneous mass production in the manufacture of photovoltaic cells requires automated methods. In addition, the wafer size is getting larger. Currently, wafer sizes reach 156 × 156mm and the trend is to reach 210 × 210 mm. Consequently, it is no longer possible to separate the wafers by hand for ergonomic reasons in the end.

In the device of the type described above, which is known from DE 19904834 a1, the wafer stack is held in immersion liquid on a support arm of a lifting mechanism, the individual silicon wafers being arranged horizontally and bonded to a support glass plate. Each uppermost silicon wafer is detached from the glass plate by means of a tool and transported to the cassette by means of a liquid flow serving as a transport device. The required separation of each individual silicon wafer from the carrier glass plate takes time and carries the risk of damaging the edge of the associated silicon wafer. Furthermore, the trapping of detached silicon wafers by the liquid flow creates problems, since the individual silicon wafers are inclined from their horizontal position about the adhesive connection with the support glass plate, so that their outer edge sides will adhere to the next underlying silicon wafer. The larger the silicon wafer specification, the greater this problem.

Disclosure of Invention

It is therefore the object of the present invention to provide a device which reliably and rapidly separates and separates thin, easily breakable wet wafers, even large-format wafers, which are held in a stack.

In order to accomplish this task, the features described below are provided in an apparatus of the type described for separating substrates from a stack, in particular wet silicon wafers from a wafer stack.

The invention provides a device for separating wet silicon wafers from a wafer stack, wherein the wet wafers can be removed individually from the stack and can be transferred to a subsequent transport device, wherein the device has a separating roller on which the wafer stack is placed, by rotating the separating roller, the lowermost wafer is moved under a scraper through a gap of the wafer thickness between the roller plane and the scraper, and the wafers are pulled out of the wafer stack by the elastic pressure of pulling rollers which are stacked one above the other and driven at the same rotational speed, characterized in that the transport device is formed by one or more transport elements, and the transport elements behind the separating roller have a higher transport speed than the separating roller, which is provided with preferably rectangular grooves between preferably rectangular raised pieces, the grooves of the roller and the raised pieces being moved relative to the roller by a pitch, and the grooves and the projecting pieces of the adjacent rollers are fitted to each other.

By means of the measures according to the invention, it is achieved that the individual wet silicon wafers which have been detached from the carrier glass plate and are layered on top of one another can be pulled out of the stack from the underside of the stack in a simpler and faster manner. Damage to the wafer edge can thereby be avoided. The method of removing the silicon wafers from the wafer stack is independent of the wafer specifications.

With the above-described features it is achieved that a more reliable further transport is ensured and the spacing between the separated wafers required for further processing is formed.

With the above-described features it is achieved that the desired liquid film is maintained in the groove region of the separating roller and that excess moisture can be drained off.

With the above-described features, it is achieved that the roller spacing can be kept narrower in order to be able to also support thin, fragile wafers.

With the above-described features, it is achieved that the gap between the scraper and the flexible roller plane, i.e. the wafer thickness, can be kept constant by keeping the bearing force on the resilient separating roller constant despite the reduction of the wafer stack.

Drawings

Further details of the invention can be taken from the following description, in which the invention is explained and illustrated in more detail with reference to the embodiments shown in the drawings. Wherein:

fig. 1 shows in a schematic front view a stack of wafers resting on separating rollers, which stack is pressed by a press head, with a scraper, a pair of pulling rollers with exactly half of the pulled-off wafer in it, and a subsequent transport element, and

fig. 2 shows in a schematic top view the segmented rollers, which cooperate with the position of the stack of wafers, the guide plates which can be adjusted laterally before and after the separation, and the doctor blade and the upper pulling roller.

Detailed Description

In fig. 1, a wafer stack 1 of silicon wafers 2 can be seen, which is formed by cutting a silicon block into a plurality of silicon wafers 2 by means of a wire saw, wherein the silicon block is bonded to a carrier glass plate by means of an adhesive bond, and the silicon wafers 2 are separated or detached from the bottom of the carrier glass plate on a bonding layer or adhesive layer after the wire saw. A wafer stack 1 consisting of wet silicon wafers 2 stacked in layers is placed on a separating roller 4, which is constantly rotated during unstacking. The wafers 2 are kept wet at all times by the sprinkling apparatus 10 to facilitate unstacking and subsequent handling. A pressure head (Stempel)3 with adjustable pressing force keeps the supporting force of the separation roller constant regardless of the wafer stack height, wherein the separation roller is elastic and thus flexible at the outer circumferential side. It is achieved thereby that the gap between the separating roller plane I and the scraper (abstereifleist) 5 is constantly kept slightly larger than the wafer thickness, so that only one thin wafer 2 can be moved or pulled out and the remaining wafers of the stack 1 remain.

The pair of upper and lower traction rollers 6.1 and 6.2 assists the separation process as soon as the lowermost wafer 2.1 is moved out of the way by the friction fit separation roller 4. The pulling rolls 6.1, 6.2 are driven at the same rotational speed and apply an elastic pressure to the respective silicon wafer 2.1, wherein a friction-fit connection is likewise formed between the pulling rolls 6.1, 6.2 and the silicon wafer 2.1. The elastic pressure is achieved, for example, by an elastically pretensioned mounting of the upper drawing roller 6.1. The pulling rollers 6.1, 6.2 thus transfer the wafer 2.1 to a subsequent transport element 7, which can be configured not only as a roller track or a small wheel track but also as a conveyor belt or in some other suitable manner.

Fig. 2 shows in particular the mutual engagement of the segmented rollers 4, 6.1 and 6.2, which are formed by preferably rectangular grooves and projections (stem) aligned with one another, and, if appropriate, the mutual engagement of the positions of the roller 7 and the wafer stack 1. The device is supplemented by guide plates 8.1, 8.2 and 9.1, 9.2 and uses them to position the wafer stack 1 laterally in relation to the wafer format and to guide the separated silicon wafers 2.

Claims (3)

1. An apparatus for separating wet silicon wafers (2) from a wafer stack (1), wherein the wet silicon wafers (2) can be individually removed from the wafer stack (1) and can be transferred onto a subsequent transport device (7), wherein the apparatus has a separating roller (4) on which the wafer stack (1) is placed, wherein by rotating the separating roller (4) the lowermost wafer (2.1) is moved under a scraper (5) through a gap of the wafer thickness between a roller plane (I) and the scraper (5), and wherein the wafer (2.1) is pulled out of the wafer stack (1) by the elastic pressure of pulling rollers (6.1, 6.2) which are stacked one above the other and are driven at the same rotational speed, characterized in that the transport device is formed by one or more transport elements (7), and the transport elements (7) behind the separating roller (4) have a higher transport speed than the separating roller (4), the separating rollers (4), the drawing rollers (6.1, 6.2) and the rollers designed as the conveying elements (7) are provided with rectangular grooves between rectangular raised pieces, and the grooves and raised pieces of adjacent separating rollers (4) cooperate with one another.

2. The apparatus according to claim 1, characterized in that the stack (1) of wafers is pressed against the separating roller (4) by a press head (3).

3. The device according to claim 2, characterized in that the pressing force of the press head (3) is adjusted such that the sum of the weight of the stack (1) of wafers and the pressing force remains constant as the height of the stack (1) of wafers decreases.