Current approaches to control critical dimensions (CD) uniformity during lithography is primarily based on run-to-
run (R2R) methods where the CD is measured at the end of the process and correction is done on the next
wafer (or batch of wafers) by adjusting the parameter set-points. In this work, we proposed a method to monitor the various photoresist parameters (e.g. photoresist thickness, photoactive compound) and CD in-situ and in real-time. Through modeling and real-time identification, we develop new in-situ measurement techniques for the various parameters of interest in the lithography sequence using existing available data in the manufacturing process.
A method for compensation of nonlinearities, mainly hysteresis, using augmented linear control for a piezoelectric stack actuator is presented in this paper, with its application in intra-cytoplasmic
sperm injection (ICSI). The linear control, realized via a PID control, is enhanced by a regulated chatter signal with variation of duty cycle as well as direction (sign), with constant magnitude and period. The main idea is to augment the PID control signal, which does most of the feedback control, in a low hassle manner by increasing or decreasing the signal via the regulated chatter signal, which does most of the nonlinearities compensation. The variation of duty cycle and direction
is updated via an iterative learning technique, taking into consideration the repetitive motion required in
the ICSI application. This device is used for assisting oocyte (egg cell) penetration during ICSI process,
where the actuator is required to drive a needle, containing a sperm cell, to penetrate an oocyte and
then inject the sperm into the oocyte. This technique is able to satisfy the requirements of the process, where
a highly-precise motion is mandatory.
Among the electric motor drives, the piezoelectric actuator (PA) is one drive which is becoming very popular in high precision biomedical applications, such as intracytoplasmic sperm injection. The main benefits of a PA include low thermal losses and, most importantly, the high precision and accuracy achievable consequent of the driect drive principle. One major source of uncertainties in PA control design is the hysteresis behavior which yields a rate-independent lag and residual displacement near zero input, reducing the precision of the actuators. Due to the typical precision positioning requirements and low offset tolerance of PA applications, the design and control of these systems, under the influence of these uncertainties, is particularly challenging since conventional PID control usually does not suffice in these application domains to meet the stringent performance requirements.
In this paper, we consider the design and realization of a piezo stack actuator which is capable of linear motion and non-full rotation to fulfill the stringent requirements associated with sperm injection applications. A complementary precise control system is developed employing a robust adaptive control algorithm to reject the hysteresis phenomenon associated with general PAs and to achieve rapid and highly precise positioning. The controller comprises of a PID feedback component and an adaptive component for hysteresis compensation. The adaptive component is continuously refined based on just prevailing input and output signals. In the paper, it will be proven that the tracking error can asymptotically converge to zero. In addition, analytical quantification is given to illustrate the improvement of the system's transient performance. Real-time experimental results verify the effectiveness of the proposed micro actuator for high precision motion trajectory tracking in intracytoplasmic sperm injection using mice eggs.
In this paper, the design of a partially-rotating piezoelectric motor/actuator based on a cylindrical piezoelectric material is presented. A prototype of the motor is developed and its performance, with respect to yielding a controllable partial rotation, is evaluated. The details of the design, development and tests will be duly provided in the paper.