Semiconductor device manufacturing: process – Including control responsive to sensed condition
Reexamination Certificate
2002-07-22
2004-09-14
Karlsen, Ernest (Department: 2829)
Semiconductor device manufacturing: process
Including control responsive to sensed condition
C156S378000
Reexamination Certificate
active
06790682
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to die bonders for die-bonding a semiconductor chip formed in a wafer to a lead frame and methods of producing a semiconductor device using the die bonder, and particularly to die bonders allowing increased yields of semiconductor devices and methods of producing a semiconductor device using the die bonder.
2. Description of the Background Art
FIG. 10
shows an appearance of a wafer marked with a bad mark. Conventionally, semiconductor chips formed in wafers are all tested by a tester apparatus wafer by wafer. Then, as shown in
FIG. 10
, any defective semiconductor chips are marked with a bad mark
34
. Then a die bonder used to die-bond a semiconductor chip for example to a lead frame recognizes bad mark
34
on a wafer to determine whether the chip passes or fails. Only conforming semiconductor chips are thus selected and die-bonded to the lead frame.
Whether a semiconductor chip passes or fails is determined from a value of a characteristic of the chip and the appearance of the chip. This decision is made by a tester conducting an electrical test and a tester conducting an appearance test and if the chip is defective it is marked by bad mark
34
. Rather than using the appearance tester, a visual inspection may alternatively be conducted in another step and products thus found to be defective in appearance may be marked by bad mark
34
manually.
While semiconductor chips have different sizes, such as 1 mm square, 2 mm square, 3 mm square and 4 mm square, bad mark
34
has a size for example of approximately 0.5 to 0.6 mm &phgr; to consider the tester's performance. If bad mark
34
is manually provided the mark would vary in size.
When a die bonder is used to detect bad mark
34
provided on a wafer, the wafer's surface condition, the size of bad mark
34
on the wafer, a reflection of light from the wafer, and the like vary for each lot of wafers. Accordingly to recognize a bad mark on a wafer a device included in the die bonder to recognize the bad mark needs to be adjusted for each lot of wafers, which is inefficient. Furthermore, the die bonder that has been adjusted still can be affected by a condition of a surface of a wafer and erroneously recognize a bad mark during production and a recognition error can thus be made.
Among semiconductor devices there are those called high rank products having a superior characteristic and those called ordinary products having a characteristic inferior to the high rank products. To produce a high rank product, a costly wafer corresponding to the high rank product needs to be used or a less costly wafer corresponding to an ordinary product having a characteristic wider in range than the high rank product is used to produce semiconductor devices and after the devices are completed only those having the characteristic corresponding to the high rank product need to be selected. The process using the costly wafer requires increased production cost and the process including screening semiconductor devices to select high rank products from provides reduced yields.
SUMMARY OF THE INVENTION
The present invention has been made to resolve the above disadvantages.
One object of the present invention is to provide a die bonder which can eliminate the necessity of marking a wafer with a bad mark and still provide increased yields of semiconductor devices having a superior characteristic (high rank products).
Another object of the present invention is to provide a semiconductor device production method which can eliminate the necessity of marking a wafer with a bad mark and still provide increased yields of semiconductor devices having a superior characteristic.
To achieve the above objects the present invention in one aspect provides a die bonder including: a storage storing inspection data of each of a plurality of semiconductor chips formed in a wafer and a position of each of the plurality of semiconductor chips as seen in the wafer, the inspection data being correlated with the position; a wafer screening portion referring to the inspection data of the semiconductor chips in the storage to screen a plurality of wafers to select a wafer; and a die-bonding portion die-bonding to a frame of a semiconductor device having a characteristic of a first level a semiconductor chip formed in a wafer selected by the wafer screening portion.
In accordance with the present invention semiconductor chip inspection data stored in the storage can be referred to to screen wafers and a semiconductor chip formed in a wafer thus selected can be die-bonded to a lead frame of a semiconductor device. This can eliminate the necessity of marking a wafer with a bad mark at the inspection step and requiring the die bonder to recognize the bad mark. Furthermore since a wafer selected in accordance with the semiconductor chip inspection data can be used to die-bond a semiconductor chip to a lead frame of a semiconductor device the die bonder can provide increased yields of semiconductor devices.
Preferably the wafer screening portion selects a wafer including no less than a prescribed number of semiconductor chips having the inspection data falling within a range of a first predetermined reference value.
In accordance with the present invention a wafer is selected when it includes no less than a prescribed number of chips having inspection data falling within the range of a first predetermined reference value. As a semiconductor device has a characteristic affected by a semiconductor chip to be mounted, selecting a wafer having no less than the prescribed number of chips having inspection data falling within the range of the first predetermined reference value allows the die bonder to produce from a single wafer at least a prescribed number of semiconductor devices having a characteristic having a value exceeding a predetermined value.
The present invention in another aspect provides a die bonder including: a storage storing inspection data of each of a plurality of semiconductor chips formed in a wafer and a position of each of the plurality of semiconductor chips as seen in the wafer, the inspection data being correlated with the position; a semiconductor chip screening portion referring to the inspection data of the semiconductor chips in the storage to screen a plurality of semiconductor chips to select a semiconductor chip; and a die-bonding portion die-bonding to a frame of a semiconductor device a semiconductor chip selected by the semiconductor chip screening portion.
In accordance with the present invention a semiconductor chip selected in accordance with inspection data can be die-bonded to a lead frame of a semiconductor device. As a semiconductor device has a characteristic affected by a semiconductor chip to be mounted, die-bonding a semiconductor chip selected in accordance with inspection data to a lead frame of a semiconductor device allows the die bonder to provide increased yields of semiconductor devices.
Preferably the semiconductor chip screening portion selects a semiconductor chip having the inspection data falling within a first range and the die-bonding portion die-bonds the selected semiconductor chip to a frame of a semiconductor device having a characteristic of a first level.
In accordance with the present invention a chip having inspection data falling within the first range can be selected and die-bonded to a frame of a semiconductor device having a characteristic of a first level. The die bonder can thus provide increased yields of semiconductor devices having the characteristic of the first level.
The present invention in still another aspect provides a method of producing a semiconductor device, including the steps of: inspecting each of a plurality of semiconductor chips formed in a wafer; correlating and storing inspection data obtained at the step of inspecting and a position of each of the semiconductor chips as seen on the wafer; screening the semiconductor chips in accordance with the stored inspection data of the semiconductor
Geyer Scott B.
Karlsen Ernest
Sharp Kabushiki Kaisha
LandOfFree
Die bonder for die-bonding a semiconductor chip to lead... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Die bonder for die-bonding a semiconductor chip to lead..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Die bonder for die-bonding a semiconductor chip to lead... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3246003