Material or article handling – Chamber of a type utilized for a heating function and... – Including driven device and/or inclined flow path to carry...
Reexamination Certificate
2002-10-21
2004-11-16
Dillon, Jr., Joe (Department: 3651)
Material or article handling
Chamber of a type utilized for a heating function and...
Including driven device and/or inclined flow path to carry...
C414S211000, C414S331170, C414S938000
Reexamination Certificate
active
06817821
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to a reflow tool used in a manufacture process for dies formed on a semiconductor wafer. The reflow tool performs a wafer bumping process (also known as solder bumping) to facilitate electrical connections between a die and a circuit board. Specifically, the handling of wafers within the reflow tool is improved to more precisely position wafers within a pass-through wafer carrier and to protect partially processed wafers in an oven in the event of a loss of power.
BACKGROUND OF THE INVENTION
Integrated circuits may be formed on one or more dies constructed from a semiconductor wafer. Dies are generally mounted on circuit boards that provide electrical pathways between the integrated circuits contained in the various dies. Traditionally, wires have been bonded to portions of the die to facilitate electrical connections between the die and the circuit board. The bonded wires allow the die to be easily connected to the circuit board through the use of a socket mounted on a circuit board or by soldering the bonded wires directly to electrical pathways on the circuit board. However the bonded wires, and possible addition of a socket, increase the size of the connection area of the die to the circuit board.
In order to reduce the size of the connection area between the die and the circuit board, the bonded wires may be replaced with solder bumps. The solder bumps typically line the edges of the dies and may be used to physically and electrically connect the dies to circuit boards. The solder bumps are created by placing a small amount of solder at the desired solder bump locations and performing a wafer bumping process on a wafer in a reflow tool. The wafer bumping process firmly adheres the solder to the die, thus creating solder bumps, and prepares the solder bumps for physical and electrical connection to a circuit board.
A solder bumping process typically involves sequentially removing wafers from an input carrier with a first robot and placing the wafers in an entrance to an oven. The oven may have a belt that the wafers are placed on that transports the wafers from the entrance to the exit of the oven. To improve the throughput of the reflow tool, a plurality of wafers may be on the belt at the same time. The temperature of the oven is sufficient to cause the solder to flow and form the desired solder bumps on the dies as each wafer moves from the entrance to the exit of the oven. As each wafer appears at the exit of the oven, the wafer is moved to a temporary storage area. A second robot may then be used to transport the wafer from the temporary storage area to an output carrier.
However, at least two problems may occur with the wafer handling of the above described conventional reflow tool. The first problem is that wafers are not consistently placed in the temporary storage area as they come off the belt. Small positional changes of a wafer in the temporary storage area may cause the second robot to position the wafer to far forward, or to far back, on the arm of the robot. If the wafer is too far back on the arm of the robot, the wafer may not be fully loaded into the output carrier causing the wafer to fall out of the output carrier and thereby possibly damaging the wafer. If the wafer is too far forward on the arm of the robot, the wafer may be rammed into the back of the output carrier as the robot attempts to load the wafer into the output carrier thereby also possibly damaging the wafer.
The second problem is that wafers in the oven will be damaged if electrical power is lost during the reflow process. Loss of electrical power will cause the belt to stop moving and the delicate integrated circuits on the wafers will be damaged by the extended cooking time in the oven. The wafers have gone through many manufacturing steps by the time they make it to the reflow process step and are thus very valuable.
What is needed is a reflow tool that precisely positions every wafer in the temporary storage area during the reflow process and that prevents wafers in the oven from being damaged in the event of loss of electrical power to the reflow tool.
SUMMARY OF THE INVENTION
The different embodiments of the invention may include one or more of the following objectives. One objective is to provide a storage carrier that consistently positions wafers in a desired location as the wafers exit an oven in a reflow tool. Another objective is to provide a reflow tool that does not damage wafers that happen to be in the reflow tool's oven in the event of a power loss from the main power supply.
The present invention provides a reflow tool for performing a reflow process on a semiconductor. The reflow tool includes an input wafer carrier for loading a new batch of wafers to be processed on the reflow tool. An input robot may be used to transport wafers from the input carrier to an entrance of an oven. The oven preferably has means for reaching a temperature sufficient to allow solder to flow and means for moving wafers through the oven, such as by a belt. A storage carrier may be positioned to receive wafers as the wafers exit from the oven. In a preferred embodiment, the storage carrier has mechanical means, such as chamfer tabs at the front face of the storage carrier to guide the wafer into the storage carrier and centering tabs towards the back face of the storage carrier to precisely align the wafer in the storage carrier. The storage carrier may be part of a buffer indexer that also includes an actuator for vertically positioning the storage carrier. An output robot may be used to sequentially remove the wafers from the storage carrier and place them in an output carrier.
In another embodiment of the invention, the electrical power from a main power supply is monitored during the reflow process. If power is lost, an uninterruptible power supply supplies power to the oven and buffer indexer to allow the oven and buffer indexer to move all the wafers in the oven to the storage carrier of the buffer indexer to prevent the wafers from being damaged by excessive exposure to the heat in the oven.
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Henderson Robert D.
Henderson Xan D.
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