Thermal measuring and testing – Temperature measurement – By electrical or magnetic heat sensor
Reexamination Certificate
1999-06-08
2001-06-26
Gutierrez, Diego (Department: 2859)
Thermal measuring and testing
Temperature measurement
By electrical or magnetic heat sensor
C374S185000
Reexamination Certificate
active
06250803
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to measurement of temperature of rapid thermal processes and, more particularly, to a method using dopant segregation into titanium silicide.
BACKGROUND OF THE INVENTION
The production of semiconductor devices typically consists of forming or depositing a material on a substrate such as doped silicon. Typically, the processing requires annealing. The annealing can be performed as an equilibrium process in which an oven reaches the same temperature throughout, or a non-equilibrium process where the oven chamber is not itself heated. One example of a non-equilibrium process is a rapid thermal anneal (RTA), which can use high intensity lamps directed at a semiconductor wafer. With an equilibrium process, temperature measurement can be straight forward as the chamber temperature can be directly controlled, and is equal to the wafer temperature. With a non-equilibrium process it is generally necessary to use an indirect method of temperature control.
In order for such manufacturing processes to operate successfully, it is necessary to ensure that the annealing is performed at proper temperature. This is traditionally done through calibration of the annealing process. Various calibration methods have been used. However, no acceptable monitor has existed for measuring the temperature anneals such as the momentary titanium silicide transformation anneal, which ramps up to approximately 900° C., then immediately ramps back down. This anneal is important for controlling silicide resistance and certain device parameters such as P-FET polysilicon depletion. Currently, a rough attempt to match tools can be made using boron implanted wafers. This method, however, lacks the resolution required to carefully match RTA tools or monitor the process for shifts over time.
The present invention is directed to overcoming the problems discussed above in a novel and simple manner.
SUMMARY OF THE INVENTION
In accordance with the invention there is described a method of measuring temperature of momentary anneals using dopant segregation into titanium silicide.
Broadly, there is disclosed herein a method of measuring temperature of momentary anneals in a temperature range around 900° C. The method comprises the steps of providing a substrate of doped polysilicon or single crystal silicon, applying a blocking layer on a portion of the substrate, forming a silicide selectively on the unblocked regions of the substrate adjacent opposite ends of the blocking layer to define a resistor, subjecting the resistor to a momentary anneal in the temperature range around 900° C., and measuring interfacial resistance between the silicide and the substrate after the annealing step, the resistance being correlated to the anneal temperature.
It is a feature of the invention that the blocking layer step comprises applying a layer of silicon nitride, or other suitable dielectric material.
It is another feature of the invention that the substrate is doped with boron.
It is a further feature of the invention that the measuring step comprises measuring resistance between the silicide and the substrate. This measurement neglects resistance of the silicide and substrate per se.
It is still a further feature of the invention that the measuring step comprises measuring resistance using scaling resistors.
There is disclosed in accordance with another aspect of the invention a method of measuring temperature of RTA anneals in the temperature range around 900° C. The method comprises the steps of providing a substrate of doped polysilicon or single crystal silicon, applying a blocking layer on the substrate, forming silicide selectively on the substrate adjacent opposite ends of the blocking layer to define a resistor, subjecting the resistor to a momentary anneal in the temperature range around 900° C., securing electrical conductors on the silicide, and measuring interfacial resistance between the silicide and the substrate after the annealing step, the resistance being correlated to the anneal temperature.
Additionally, the use of the present invention can be extended beyond the calibration of RTA processors which operate at approximately 900° C. State of the art equipment used to conduct RTA processing is usually calibrated at only one temperature using a monitor. The operation of the system over its full range of capability, typically 400° C. to 1200° C., is based on the accuracy of that one calibration point. When the present invention utilized to conduct a single-point calibration of very high accuracy at a temperature near 900° C., the quality of the calibration of the system over the entire operating range is significantly improved. Thus, while the present invention operates near the temperature of 900° C., its effectiveness extends throughout the operating range of rapid thermal annealing systems.
Further, semiconductor manufacturing also requires processes such as oxidations, nitridization, or chemical vapor depositions. When these processes are conducted in a rapid thermal mode, with high ramp-up rates, short durations at processing temperature, and high ramp-down rates, they are considered rapid thermal processes (RTP). Temperature calibration of these systems is important because the reaction rates of these oxidation, nitridization, and chemical vapor deposition processes are often strong functions of temperature. Flowing of the reaction gases used in these processes would generally interfere with the operation of the invention described herein. However, using the present invention to calibrate temperature in an RTP system which is flowing only inert gases, such as argon and nitrogen, will allow the temperature of that system to be accurately calibrated. Then, subsequent processing with reaction gases flowing would be conducted in a system with well calibrated temperature. Thus, the performance of the RTP system would be improved.
Further features and advantages of the invention will be readily apparent from the specification and from the drawings.
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Ballantine Arne W.
Miles Glen L.
Gonzalez Madeline
Gutierrez Diego
International Business Machines - Corporation
Wood Phillips VanSanten Clark & Mortimer
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