Interlocking nest wafer protector

An interlocking ring wafer separator for reducing particles during shipment of integrated circuit wafers has a wafer shelf, an interlocking tab which prevents the edge of the wafer from coming into contact with the inner wall of the wafer shipping container, and an interlocking slot into which the interlocking tab of a second interlocking ring wafer separator may be inserted locking the two interlocking ring wafer separators together in the coin stacked wafers.

FIELD OF THE INVENTION

This invention generally relates to wafer carriers or packages used for shipping semiconductor wafers. More particularly, this invention relates to a protective ring separator for use between coin-stacked wafers during the shipping of wafers in a wafer shipping container.

BACKGROUND

Some manufacturers of integrated circuits produce semiconductor wafers at one location and ship the wafers for dicing and packaging at a different location. In such cases, the wafers are typically shipped in a container referred to as a coin-stack shipping container in which the wafers are stacked one on top of another. To prevent damage during shipment, a protective ring separator is placed between each wafer. The protective ring separators prevent one wafer from rubbing against another during shipment. The protective ring separator100(FIG. 1A) is a ring that is open in the center.

Such a coin-stack shipping container200is illustrated inFIG. 2A. The wafers204are stacked in the coin-stack shipping container200with a protective ring separator100between each wafer204.

A plan view of a typical protective ring separator100is illustrated inFIG. 1A. The circumference of the protective ring separator100is slightly smaller than the inside circumference of the wafer shipping container200(FIG. 2A) so that it fits comfortably inside the shipping container while providing little room for movement during shipping.

A magnified cross sectional view108of the protective ring separator100is shown inFIG. 1B. This magnified view108is taken along cut line106of the inset104inFIG. 1A. The protective ring separator108is typically L-shaped wherein the spine of the L faces the inner surface of the wafer shipping container200and the foot111of the L extends inward toward the center of the wafer shipping container200. The wafer sits face down on the top of the L (also called a wafer shelf112). The wafer shelf112is sufficiently higher than the foot111on the protective ring separator100to enable the wafers204and the ring separators108to be loaded and unloaded automatically from the wafer shipping container200.

As shown inFIG. 2Awafers204are coin-stacked in the wafer shipping container200with a ring separator108between each wafer204.

As shown inFIG. 2B, each wafer204is loaded face down on the wafer shelf112of the ring separator108and coin-stacked on the wafer204below it. The ring separators108prevent the front surface of one wafer204which contains the integrated circuits from rubbing against the backside of the wafer204below it in the coin-stack causing damage to the integrated circuits during shipment.

SUMMARY

An interlocking ring wafer separator for reducing particles during shipment of integrated circuit wafers has a wafer shelf, an interlocking tab which prevents the edge of the wafer from coming into contact with the inner wall of the wafer shipping container, and an interlocking slot into which the interlocking tab of a second interlocking ring wafer separator may be inserted locking the two interlocking ring wafer separators together in the coin stacked wafers.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

An interlocking ring separator300is illustrated in a plan view inFIG. 3Aand cross sectional views inFIGS. 3B and 3C. The interlocking ring separator300features an interlocking tab314(FIG. 3B) that extends around the outside circumference of the upper outer edge of the interlocking ring separator300and an interlocking slot310that extends around the outside circumference of the lower outer edge of the interlocking ring separator300. Surface tension release slots302are formed at various locations around the interlocking ring separator300to prevent the interlocking ring separator from sticking to a wafer400when it is removed from the shipping container.

As shown inFIG. 3B, the interlocking tab314surrounds the wafer shelf312and lies between the edge of the wafer404(FIG. 4A) and the inner wall of the wafer shipping container400. The inner diameter of the interlocking tab314is slightly larger than the diameter of a wafer404. The interlocking tab314has an angled/slanted top surface that extends from the outermost edge of the interlocking ring separator300and forms an acute angle with the outermost edge. The wafer404is placed face down on the wafer shelf312during shipment (FIG. 4B). The interlocking tab314prevents the edge of the wafer404from coming into contact with the walls of the shipping container400and generating particles by abrading the walls. The interlocking tab314extends above the wafer shelf312a sufficient height to be inserted into an interlocking slot310on an overlying interlocking ring separator300when a wafer is present on the wafer shelf312. This locks the two interlocking ring separators together further reducing the relative motion of wafers during shipment and additionally reducing particle formation.

The interlocking slot310extends around the lower outer circumference of the ring separator300and lies directly below the interlocking tab314. As shown inFIG. 3B, the interlocking slot310has an angled or slanted surface that extends from the outermost edge of the interlocking ring separator300. The width of the interlocking slot310is slightly larger than the width of the interlocking tab314so that the interlocking tab314fits into the interlocking slot310without binding. The interlocking tab314from a lower interlocking ring separator308, fits into the interlocking slot310of an upper interlocking ring separator309. As shown in the inset418inFIG. 4B, this locks the coin stack of wafers404together preventing independent motion of one wafer404with respect to another wafer404. The reduction of independent motion of the wafers404and the prevention of the wafer404edges from coming into contact with the inside walls of the wafer box400significantly reduces particle generation during the shipping of the wafers404. The wafer404lies face down on a wafer shelf312. The width of the wafer shelf312typically is about the size of the outer exclusion zone of processed wafers404so it does not come into contact with and damage active die. Typically this width is about 3 mm or less.

The foot311extends around the bottom inner circumference of the interlocking ring separator300. The foot enables automatic loading and unloading of the wafers404and the automatic loading and unloading of the interlocking ring wafer separators300from the wafer shipping container400. The width of the foot may depend upon the requirements of the automatic pick-and-place loader and unloader.

The wafer shelf312(FIG. 3B) is formed a sufficient height above the foot311to enable a pick-and-place machine to automatically load and unload wafers and to automatically load and unload the interlocking ring separators300from the wafer shipping container400. The height of the wafer shelf312above the foot311is also sufficient to prevent structures such as ball bonds which may be formed on the top side of the upper wafer404from coming into contact with the backside of the underlying wafer404. The height of the wafer shelf312above the foot311may depend upon the height features on the surface of the wafer and may depend upon requirements of the pick-and-place machine.

FIG. 3Cshows a cross section of one of the surface tension release slots302in the interlocking ring separator300. The surface tension release slots allow air to enter between the wafer404(FIG. 4B) and the wafer shelf312when the wafer is being removed from the wafer shipping container400. This prevents other wafers404with air trapped below them in the wafer shipping container400from moving when the top wafer404is removed. In the surface tension release slot302depicted in the cross section304inFIG. 3Ca notch is formed in the interlocking tab314and also formed in the wafer shelf312at various points around the circumference of the interlocking ring separator300. Typically between 4 and 8 surface tension release slots302are formed in the interlocking ring separator300. The dimension of the surface tension release slot is typically between about 1 to 3 mm but may be wider. The surface tension release slot302design inFIG. 3Cillustrates an example implementation. Other surface tension release slot302designs are also possible.

The interlocking ring separator300may have a variety of designs. The design inFIGS. 3 and 4illustrate the concept and are not intended to be limiting in any way. As may be appreciated by those skilled in the art other interlocking tab and slot designs are possible for locking the wafer coin stack together in a way that prevents independent motion of the wafers, prevents the edge of wafers from abrading the inside walls of the wafer shipping container400, and also enables automatic pick-and-place loading and unloading of wafers and the interlocking ring separators into and out of the wafer shipping container400.

An alternative design for an interlocking ring separator608formed according to embodiments is illustrated inFIG. 5. Wafers604are supported in a coin-stack by interlocking ring separators608and placed in a wafer shipping container600. This interlocking ring separator608is similar to the interlocking ring separator308inFIG. 4Bbut designed without a foot311. This interlocking ring separator608may require a vacuum ring pick-and-place machine to accommodate the design without a foot311.