Articles you may be interested inDeep in situ dry-etch monitoring of III-V multilayer structures using laser reflectometry and reflectivity modeling J. Vac. Sci. Technol. A 20, 748 (2002); 10.1116/1.1468652 In situ measurement of aspect ratio dependent etch rates of polysilicon in an inductively coupled fluorine plasma Real time monitoring and control of wet etching of GaAs/Al 0.3 Ga 0.7 As using real time spectroscopic ellipsometry J.In this article we present a low-cost, high-speed, high-accuracy in situ thin film measurement system for real-time process monitoring and industrial process control. This sensor, the two-channel spectroscopic reflectometer ͑2CSR͒, is a hybrid of spectroscopic ellipsometry and spectroscopic reflectometry. In 2CSR a polarized beam of white light is directed at the sample. The reflected light is resolved into its two orthogonal components, s and p, using a Wollaston prism. These data, ͉R s ͉ 2 and ͉R p ͉ 2 , are recorded simultaneously as a function of wavelength using a two-channel spectrometer with linear array detectors. The fact that 2CSR has no moving parts, coupled with the use of the two-channel linear array detectors, enables high-accuracy data acquisition across the sensor's spectral range in 6 ms. This makes the 2CSR ideal for real-time high-speed process monitoring and control in an industrial setting. We have used the 2CSR to make accurate in situ, high speed film thickness measurements during the plasma etching of both silicon dioxide and polycrystalline silicon samples. We show that, in addition to our ability to measure blanket film thicknesses and etch rates, the accuracy of the 2CSR makes this a viable technique for patterned wafer analysis.

The effect of ion production through ionizing collisions in a magnetically insulated crossed-field gap is studied by using one-dimensional particle-in-cell software. These results are compared with the predictions from previous efforts that assumed immobile sheets of positive charge at different positions within the gap. Our results with mobile ions created via collisions indicate that the diode can lose magnetic insulation of the electron flow at ion densities lower than that predicted from the immobile ion case. Furthermore, we observe that electron scattering plays a significant role in this gap closure. This loss of insulation depends on the background pressure and leads to time-dependent migration of charge across the gap. We characterize both the time-scale and the degree of current transport for cases relevant to the high-power microwave community.Index Terms-Crossed-field diode, high-power microwave devices, magnetic insulation, particle-in-cell simulation, plasma.

The industrial semiconductor community widely accepts that new process development is both costly and time consuming. In particular for plasma etch processing, multiple plasma input parameters such as gas flow, pressure, and radio frequency (rf) forward power directly affect desired wafer output parameters such as etch rate, uniformity, and material selectivity. Therefore, a high number of etch experiments must be performed to accurately quantify these input and output (I/O) relationships for each process. Moreover, in situ wafer monitoring in general is not currently widely pursued in the industry. 1 Therefore, the typical characterization procedure can only obtain data for a single given set point per process run, where a process set point refers to the nominal input parameters used for a particular plasma condition. Thus, money and time are spent etching only one wafer for each set point required to build the input/output response surface models for a typical design of experiments (DOE). With increasing process demands and the increasing cost of larger and larger individual wafers, these test wafer costs for model design continue to become more and more acute.This project leverages expertise from four primary research fields to achieve our results. Semiconductor process knowledge is needed to formulate the problem of new process characterization. Optical metrology background is used to obtain accurate material refractive index properties and to measure film thickness changes during processing. The thin-film properties help determine accurate film thickness and etch-rate information, which are used as inputs to the empirical process models. Nonlinear systems theory techniques are used to filter real-time optical data and estimate high speed thickness and etch-rate information. The high-speed filtering allows multiple set points to be explored per process run. Finally, response surface modeling is employed to generate empirical I/O predictions using plasma generation parameters as the model inputs, and film thickness, etch rate, and wafer uniformity as model outputs.The goal of this research is to maximize the number of set points one can observe during a single run of the etching process by monitoring output data in real-time. This decreases the number of runs required for a complete response surface mapping, effectively reducing the number of wafers and development time required to model a new process. We show accurate and instantaneous etch-rate information (on the order of tens to hundreds of milliseconds time scales) requiring less than 100 Å of etched material; 2 therefore, we obtain empirical I/O relationships at multiple set points in a short amount of time and on a single test wafer.In this paper, we demonstrate this in situ characterization mapping concept on two reactive ion etch (RIE) test-beds to show the versatility of the concept. One is an RIE chamber designed for flat panel display processing, where large area etch uniformity of an amorphous silicon (a-Si) film on metal and glass is the chosen m...

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