The present invention relates to electronic device workpieces, methods of semiconductor processing and methods of sensing temperature of an electronic device workpiece.
It is preferred in the semiconductor and related arts to utilize large wafers for fabrication of integrated circuits and other devices. Large wafers are preferred inasmuch as an increased number of chips can be fabricated from larger workpieces. As the size of the wafers continues to increase as processing techniques are improved, additional processing obstacles are presented.
For example, it is typically preferred to provide a substantially constant temperature across the surface of the wafers being processed because changes in temperature can influence device fabrication. Wafers of increased diameters and surface areas experience increased temperature fluctuations at various locations on the workpiece. In particular, a partial vacuum is typically used to pull small diameter wafers into direct thermal contact with a hot plate. Such processing methods facilitate substrate temperature control because the substrate temperature is closely associated to the temperature of the hot plate. Fabrication of small sub-micron devices upon larger diameter semiconductor wafers or workpieces requires minimal backside contamination. As such, contact of the workpiece with a hot plate is not typically not possible. Such workpieces are processed in conventional operations upon spacers or pins that position the workpiece approximately 0.1 millimeters above the hot plate heating surface. Such spacing intermediate a chuck or hot plate and the workpiece results in substrate temperatures which can be influenced by the environment above the substrate. Inconsistencies in temperature across the surface of the workpiece often result.
Absolute temperature and temperature uniformity of a workpiece are parameters which are closely monitored during wafer and workpiece fabrication to provide critical dimension (CD) control. Chemically amplified resists are utilized in deep ultraviolet (DUV) lithography in small micron geometries (eg., 0.25 microns and below). Chemically amplified resists are particularly temperature dependent further increasing the importance of temperature control and monitoring. Some thermal resist processing steps require process windows ranging from 1-2 degrees centigrade down to a few tenths of a degree centigrade. Meteorology that is four to ten times more precise than conventional process equipment may be required to provide thermal performance measurements to 0.1 degrees centigrade.
One approach has disclosed the use of temperature sensors across a surface of the wafer to provide temperature mapping of the workpiece during processing. Platinum foil leads and copper leads are utilized to electrically connect the temperature sensors. With the use of numerous temperatures sensors across an entire workpiece surface, numerous wires are required for coupling and monitoring. Such numerous wired connections can break and/or adversely impact processing of the workpiece or the temperature measurements taken of the surface of the workpiece. Some temperature sensors require four leads per sensor further impacting the processing and temperature monitoring of the workpieces.
Therefore, there exists a need to provide improved temperature monitoring of workpieces which overcomes the problems experienced in the prior art.
The present invention includes electronic device workpieces, methods of semiconductor processing and methods of sensing temperature of an electronic device workpiece. Exemplary electronic device workpieces include semiconductor wafers.
One electronic device workpiece includes a substrate having an upper surface and a temperature sensing device borne by the substrate. The temperature sensing device can comprise a preexisting device. Alternatively, the temperature sensing device can be formed upon a surface of the electronic device workpiece. The temperature sensing device comprises a resistance temperature device (RTD) in one embodiment. A plurality of temperature sensing devices are provided in temperature sensing relation with the electronic device workpiece in an exemplary embodiment.
An electrical interconnect is preferably provided upon the surface of the substrate. The electrical interconnect comprises a conductive trace in a preferred embodiment. The electrical interconnect is electrically coupled with the temperature sensing device. The electrical interconnect can be wire bonded to or physically coupled with the temperature sensing device. The electrical interconnect can be configured to couple the temperature sensing device with an edge of the electronic device workpiece. An interface can be provided to couple the electrical interconnects with external circuitry. Exemplary electrical circuitry includes a data gathering device, such as a digital computer.
An isolator is formed intermediate the temperature sensing device and electrical interconnect, and the substrate of the electronic device workpiece in one embodiment. The isolator provides electrical isolation. An exemplary isolator comprises silicon dioxide.
Temperature sensing devices are provided within a cavity formed within the substrate of the electronic device workpieces according to another embodiment. The cavity is preferably formed by an anisotropic etch forming sidewalls at an approximate angle of fifty-four degrees with respect to the surface of the substrate. Alternatively, temperature sensing devices are formed or positioned upon a surface of the electronic device workpiece.
The electronic device workpiece comprises a calibration workpiece in one embodiment. In another embodiment, the electronic device workpiece comprises a workpiece which undergoes processing from which subsequent devices are formed, such as a silicon wafer.