Patent Application
20060199283
This invention relates generally to semiconductor fabrication, and more particularly to a semiconductor device having voltage output function trim circuitry and a method for the same.
Semiconductor devices are often produced in families that share a common parent design but differ in terms of a selected output parameter, such as output voltage. In devices such as these, different output voltages are typically produced by coupling the main circuitry of the device with an appropriate resistor value, selected from a bank of resistors that is common to the entire family, to produce the desired output voltage. Although the entire family includes the common resistor bank, each design is produced from its own wafer utilizing a separate metal layer mask that provides an interconnect to the proper resistor value to produce the desired output voltage for that particular design. Despite the flexibility offered by the common parent design, the use of individual wafers for each of the voltage ranges wastes circuit space on the wafer and increases the process cycle time during wafer production. Furthermore, having to shift between the individual child designs during production may add to the production costs of the devices.
In accordance with the teachings of the present invention, a semiconductor device having voltage output function trim circuitry and a method for the same are provided. In a particular embodiment, the method comprises electrically coupling to a main circuit of a semiconductor device a plurality of resistances each operable to determine a different output voltage range of the main circuit, electrically coupling each of the plurality of resistances to a respective one of a plurality of fuses, electrically coupling each of a plurality of fuses to a respective one of a plurality of function trim pads, and electrically decoupling all but one of the plurality of resistances by applying a respective current between the respective function trim pads and an output node sufficient to open the respective fuses.
A technical advantage of some embodiments of the present invention includes the ability to produce a variety of output voltage ranges from a single wafer. This not only decreases the process complexity, but allows each wafer to serve multiple purposes depending on the quantity of each voltage range desired.
Another technical advantage of some embodiments of the present invention includes a decrease in overall cycle time. By allowing the output voltage of the wafer to be changed “on the fly,” particular embodiments of the present invention nullify the need to start new wafer lots to produce other desired output voltages.
Other technical advantages of the present invention may be readily apparent to one skilled in the art from the following figures, descriptions, and claims. Moreover, while specific advantages have been enumerated above, various embodiments may include all, some, or none of the enumerated advantages.
For a more complete understanding of the present invention and features and advantages thereof, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:
In accordance with the teachings of the present invention, a semiconductor having voltage output function trim circuitry and a method for the same are provided. Generally, the semiconductor comprises a bank of resistors used to determine the output voltage of the semiconductor. Each of these resistors is coupled to an output node with a corresponding fuse. By selectively opening the fuses, the appropriate resistive load may be applied to the semiconductor to produce the desired output voltage. In particular embodiments, this allows several semiconductor devices having different output voltages to be produced from a single wafer, resulting in lower process complexity and reduced production cycle time.
However, while the present disclosure describes the use of function trim circuitry in regard to output voltages, the teachings of the present invention are not limited to selecting an output voltage range for a semiconductor device. Instead, the teaching of the present invention may be applied to select other output parameters of a semiconductor device from a range of options. With the benefit of this disclosure, it should be within the ability of one skilled in the art to utilize function trim circuitry to select other such output parameters.
With that understanding,
A better understanding of the function trim circuitry of the present invention may be had by making reference to
To facilitate this selection, each resistor 208a-d in circuit 200 is coupled to a corresponding fuse 204a-d. In particular embodiments of the present invention, each fuse 204 may have a different fuse value. Often, these different fuse values are stepped so that each consecutive fuse 204 requires a higher measure of current to open. By opening a particular fuse 204, the corresponding resistor 208 may be unselected, and effectively removed from the circuit. For example, by opening fuse 204b, resistor 208b may be removed from circuit 200 such that it does not affect the output voltage at output 202. Thus, each fuse 204 corresponding to the undesired resistors 208 may be opened until only the desired resistor 208 remains active in function trim circuit 200. This remaining resistor 208 thus determines the output voltage range of the semiconductor device.
To facilitate the opening of the appropriate fuses, circuit 200 also includes function trim pads 206a-d, corresponding to fuses 204a-d, respectively. Function trim pads 206 provide a location to contact a probe to supply the current necessary to open the selected fuses 204. For example, by placing a probe tip in contact with output 202 and function trim pad 206a and applying a sufficient current, fuse 204a may be opened, removing resistor 208a from the circuit.
Once the desired output voltage range has been selected by opening the appropriate fuses 204, particular embodiments of the present invention may use traditional trim circuitry 210 to precision tune the final output voltage of the semiconductor after the output voltage range had been selected using the function trim circuitry.
An illustration of how the above-described function trim circuitry may appear on a die is shown in
As shown in
Wafer 300 also includes function trim pads 306a-d, which provide a location to contact a probe to supply the current necessary to open the corresponding fuses 304a-d. In this particular embodiment, function trim pads 306 are located on a scribe street 312. By utilizing the scribe street 312 to place the function trim pads 306, the size of the die may not need to be increased to accommodate their addition. This helps overcome one of the major stumbling blocks to past attempts to provide all output voltage options on a single die. By using the scribe street 312 to place the trim pads 306, the final die dimensions of the semiconductor wafer 300 may be the same as those for wafers employing traditional resistor bank designs. It should be recognized, however, that the presence of metal structures, such as the function trim pads 306, in the scribe street 312 may be problematic due to the propensity of the metal to clog the saw blade used to remove the scribe street and separate the chips on the wafer. In particular embodiments of the present invention, this problem may be overcome by adding a process step that etches away the function trim pads 310 once the desired fuses 304 have been opened. Particular embodiments of the present invention may also locate the function trim pads at other locations on the die, all within the teachings of the present invention. Such a placement, however, may require increasing the final die dimensions.
Once the function trim circuitry and function trim pads have been constructed, the desired output voltage range is selected by opening the appropriate fuses of the function trim circuitry in block 406. This may be accomplished by applying a current to the appropriate fuses sufficient to open the fuses between the appropriate function trim pads and the output of the device. In particular embodiments of the present invention, other trim processes may also be performed during this step, such as tempco trim and precision trim.
After the desired trim processes have been performed, a decision is made in block 408 regarding whether to remove the function trim pads prior to performing a saw operation on the wafer. As mentioned above, this may help reduce the wear on the saw used to separate the scribe street and reduce saw maintenance costs. If the function trim pads are to be removed prior to the saw operation, an etch resist is applied over the entire surface of the semiconductor wafer, except for the scribe street and function trim pads, in block 410. The function trim pads are then etched away in block 412. Once the function trim pads have been removed, the etch resist is then removed from the surface of the wafer in block 414, and a saw operation may be performed on the wafer in block 416.
If the function trim pads are not be removed prior to the saw operation, the process simply proceeds to the saw operation in block 416, where the scribe street is removed and the chips on the wafer are separated. After the saw operation has been completed, the fabrication process terminates in block 418.
By incorporating function trim circuitry into a semiconductor wafer, particular embodiments of the present invention offer the ability to produce an entire family of semiconductor devices from a single parent wafer design. Rather than having to produce multiple wafer designs, a single wafer design may be used to meet all of a users requirements for the different members of the device family. This helps reduce process complexity and may reduce overall cycle times.
Furthermore, particular embodiments of the present invention may be implemented by making only mask level changes. In such embodiments, no expensive hardware or costly retooling is needed to add the function trim circuitry to existing semiconductor wafer designs.
Finally, by reducing the number of wafer designs necessary to produce the family of semiconductor devices, particular embodiments of the present invention require less maintenance than tradition wafers employing resistor banks or other similar structures.
Although particular embodiments of the method and apparatus of the present invention have been illustrated in the accompanying drawings and described in the foregoing detailed description, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications, and substitutions without departing from the spirit of the invention as set forth and defined by the following claims.
