Critical Dimension measurements for process control in semiconductor lithography are routinely made using Scanning Electron Microscopy (CD SEM). In many situations, organic contamination of the CD SEM chamber cannot be prevented due to the outgassing of hydrocarbons present in the photoresist films used to define device structures. In other cases advantageous hydrocarbons are deposited from the room air before the wafer is brought into the machine, or there are residual deposits left over from manufacturing of the tool. The interaction of the primary beam with these hydrocarbons, resident in the SEM chamber, results in a deposition of a hydrocarbon film, whose thickness is dependant upon the total dose provided to the structure of interest. This deposited film not only reduces the available image contrast but also physically changes the size of the measured feature. In extreme cases, such changes have been reported to be as large as several nanometers 1 2 during a typical measurement sequence. Such a value approaches the entire metrology error budget for the most advanced processes.

No abstract

No abstract

A preponderance of critical levels for the 90-nanometer (nm) process technology node utilize 193 nm lithography. The resist systems used in this processing show a much higher sensitivity to line width slimming at the traditional electron beam energies encountered in Critical Dimension Scanning Electron Microscope (CD SEM) metrology than do previous generations of chemically amplified resists. The uncertainty that results from this undesirable interaction can consume more than the entire process control budget for advanced devices.This paper reports measurements of resist CD uniformity taken with a new CD SEM metrology technology based on ultra low voltage, that significantly reduces the impact of the electron beam on 193 nm resist systems. Over the past several months this technology has been used for 193 nm resist development studies at ARCH Chemicals. Several examples, demonstrating the effectiveness of this new technology using the Yosemite Ultra Low voltage CD SEM will be presented and contrasted against results obtained at higher voltages.