JPH0722360A - Storing method of semiconductor wafer in cassette - Google Patents

Abstract

PURPOSE:To enhance end products in yield by a method wherein the upsides of all semiconductor wafers stored as stacked in a cassette provided to a grind ing machine which works the semiconductor wafers are prevented from being dried up so as to be protected against clouding or stain. CONSTITUTION:Water so specified in amount is poured as to keep a water layer 1 formed by surface tension on all the surface of a semiconductor wafer W placed uppermost in a cassette and to drip in drops on the upside of a semiconductor wafer W located next below the uppermost wafer W, whereby a water layer 1 is successively formed by surface tension on each surface of all semiconductor wafers W stored in a cassette.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface of a semiconductor wafer housed in a cassette after a grinding / polishing process such as a surface grinder that vacuum-sucks a semiconductor wafer onto the upper surface of a chuck to grind and polish the surface of the semiconductor wafer. The present invention relates to a method of storing without leaving traces of water drops.

[0002]

BACKGROUND OF THE INVENTION An automatic surface grinder for grinding and polishing semiconductor wafers of this type stores a large number of semiconductor wafers individually in a cassette on a delivery side, and the cassette on the delivery side can be raised and lowered. Is placed on the surface of the pre-position device by being inverted by the vertical rotation of the delivery side transfer mechanism, and is transferred by the delivery side transfer mechanism disposed in front of the elevator base. Accurate positioning and cleaning with a position device is performed by a jet of liquid, and an accurate trajectory of a horizontally-rotatable delivery-side transfer arm equipped with a vacuum suction pad at the tip,
It is accurately guided to the chuck formed on the grinding table of the automatic surface grinder, and is accurately vacuum-adsorbed, moved to the next processing position by the grinding table, fixed on the lower end with a cup wheel type diamond grindstone and rotated by a motor. The spindle shaft is automatically lowered and the first grinding is started.

Next, the semiconductor wafer is transferred to the next processing position together with the chuck by the grinding table, subjected to a predetermined processing by the next chuck, and is then provided with a suction pad at its tip and can be rotated in the horizontal direction. The storage side transfer mechanism equipped with a vacuum suction pad after being sucked by the transfer arm and transferred to the cleaning and drying device and then cleaned and dried is moved up and down by the storage-side elevator table on which the storage-side cassette is placed. The individual pieces are sequentially stored in the crosspiece of the storage-side cassette from the opening surface.

The above description is for the process of processing one semiconductor wafer, but when the semiconductor wafer is transferred from the cassette on the sending side to the preposition device via the sending mechanism on the sending side, the next semiconductor wafer is It has an automatic delivery mechanism that is held by the delivery-side transfer mechanism from the delivery-side cassette and waits for the previous semiconductor wafer to be transferred to the chuck position on the grinding table. At each chuck position of the chucks provided on the grinding table, the work is simultaneously and continuously performed.

[0005]

2. Description of the Related Art These automatic surface grinders grind and polish semiconductor wafers by the above-mentioned steps, and most of the steps are usually carried out in the atmosphere. Liquid is used for positioning, grinding liquid during grinding, cleaning after grinding, etc.
Immediately before storing, the liquid is removed with a drying device such as a centrifuge, but water drops are often attached.

[0006]

Therefore, the semiconductor wafers required these days have high-precision flatness and high-quality mirror finish, and can be processed to high-precision flatness with an automatic surface grinder or the like. However, after the water droplets that had adhered have evaporated, stains or cloudiness that cannot be seen by the human eye occur in the traces of the water droplets, which is an obstacle to improving the yield of the final product.

Therefore, the present applicant has filed Japanese Patent Application No. 4-7581.
In No. 4, a water tank portion is provided so as to surround at least the cassette on an automatic surface grinding machine, etc., the liquid is stored in the water tank portion, the cassette is put in and out in a substantially submerged state, and after grinding and polishing, the semiconductor wafer is placed in the cassette. An attempt was made to solve the above-mentioned problems by providing a mechanism for sealing with a liquid and its method.

However, the above-mentioned mechanism always fills the water tank portion with the liquid, and normally the liquid filling the water tank portion is pure water, resulting in high cost, and it is desired to reduce the cost. Is the reality.

[0009]

In view of the above-mentioned problems, the method of storing a semiconductor wafer in a cassette according to the present invention is, as a result of diligent research, integrated and stored in a cassette such as a grinding machine for processing a semiconductor wafer. The water layer that can be maintained by surface tension is formed on the entire upper surface of the semiconductor wafer.

[0010]

The operation of the present invention is such that the water layer formed on the entire upper surface of the semiconductor wafer placed on the uppermost layer in the cassette can be maintained by the surface tension and the upper surface of the semiconductor wafer located immediately below. By injecting a liquid to the extent that it drops in a drip state, a water layer is formed by dropping a drip state from the water layer formed on the entire upper surface of the uppermost layer to the upper surface of the semiconductor wafer located immediately below. With the lapse of time, a water layer that can be maintained by surface tension is sequentially formed on the upper surfaces of all the semiconductor wafers stored in the cassette.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for storing a semiconductor wafer according to the present invention which achieves the above object will be described with reference to the drawings of the following embodiments.

FIG. 1 is a side view for explaining the concept of the present invention.

According to the present invention, a trace of water droplets such as stains or fog is formed on the processed surface of a semiconductor wafer housed in a cassette after grinding and polishing such as a surface grinder that vacuum-sucks a semiconductor wafer onto the upper surface of a chuck to grind and polish it. The present invention relates to a method of storing without leaving a semiconductor wafer processed by a surface grinder or the like, which has an opening surface on one side for accommodating and storing the semiconductor wafer and has a plurality of crosspieces partitioning the inside into a horizontal shelf shape. A liquid that is capable of maintaining a water layer formed on the entire upper surface of the semiconductor wafer placed on the uppermost layer in the cassette by surface tension and that drops in a drip state on the upper surface of the semiconductor wafer located immediately below Water is poured, and a water layer that can be maintained by surface tension is sequentially formed on the upper surfaces of all the semiconductor wafers stored in the cassette.

That is, the cassette of the present invention is used before and after semiconductor wafers are stored in an integrated manner and ground and polished by a grinder or the like, and further, after processing, the cassette is transferred to the next step.

In a general cassette, an opening surface is formed on one side surface and a semiconductor wafer is inserted and removed from the opening surface. Inside the cassette, a plurality of crosspieces are arranged at equal intervals and in a horizontal shelf shape. The outer peripheral edges of at least two facing portions of the substantially disk-shaped semiconductor wafer except the orientation flat portion are supported from below.

As shown in FIG. 1, water drops are dropped on the upper surface of the uppermost semiconductor wafer placed horizontally on each of the crosspieces in the cassette, and once dropped, the upper surface of the semiconductor wafer is removed. A water layer is formed on the entire surface.

When the dropping is further continued, the water layer is subjected to surface tension, which is a property of a liquid, the middle surface of the upper surface of the semiconductor wafer becomes flat, and the outer peripheral edge is in a rounded state. When the amount of water in the water layer increases and exceeds the limit of the surface tension, water drops drop downward from the corners of the outer peripheral edge of the semiconductor wafer having a rectangular cross section. Acts to flow to the outer peripheral edge of the lower surface while adhering to the side surface of the outer peripheral edge of the semiconductor wafer, and beyond the corners of the outer peripheral edge of the lower end to be adhered to move to the lower surface of the semiconductor wafer to cause surface tension. When the surface tension exceeds the interfacial tension, it drops as water drops.

Therefore, even if a plurality of semiconductor wafers having the same outer diameter are stacked at intervals, the semiconductor wafers are surely dropped onto the upper surface of the semiconductor wafer immediately below in order to drop inside from the outer periphery of the semiconductor wafer. A water layer can be surely formed on the semiconductor wafer located in the lower layer.

[0019]

As described above, according to the present invention, the liquid is poured over the entire upper surface of the semiconductor wafer to the extent that it can be maintained by surface tension and drops onto the upper surface of the semiconductor wafer located immediately below it in a dripping state. As a result, the semiconductor wafer can be stored without being dried and the quality can be maintained in a stable state, and the yield of the final product is dramatically improved, which is epoch-making and its contribution is immeasurable. There is a very significant effect.

[0026]

[Brief description of drawings]

FIG. 1 is a side view for explaining the concept of the present invention.

[Explanation of symbols]

 W Semiconductor wafer 1 Water layer

Claims (1)

[Claims] 1. A cassette having an opening on one side for accommodating and storing semiconductor wafers processed by a surface grinder and partitioning the interior into a horizontal shelf shape by a plurality of crosspieces, the uppermost layer in the cassette. The water layer that is formed on the entire upper surface of the semiconductor wafer placed on the surface of the semiconductor wafer can be maintained by surface tension, and a liquid that falls in a drip state onto the upper surface of the semiconductor wafer immediately below is poured into the cassette. A method for storing semiconductor wafers in a cassette, wherein a water layer that can be maintained by surface tension is sequentially formed on the upper surfaces of all semiconductor wafers to be stored. [0001]