With the miniaturization of CMOS, the gate insulator has extremely become thin until reaching the EOT (equivalent oxide thickness) of less than 1nm in order to keep maintaining high-speed performances of devices and low electric energy consumption. Since the gate insulator is so thin, leakage current increases and the gate dielectric breakdown can easily occur. This affects the reliability of semiconductor devices. To make good devices, it is necessary to use technologies for the evaluation of the gate insulator reliability.
TDDB (Time Dependent Dielectric Breakdown) lifetime has been one of the main factors for this evaluation. In this case, a wafer is destroyed in order to be evaluated, which reduces the semiconductor yield. To solve this problem, we propose a new technique for the evaluation of the gate insulator which is a non-destructive and contactless measurement method, and thus an appropriate method for inline processes.
A voltage is applied on a Si/SiO2 specimen. A voltage source electrode and the specimen are not in contact (10micron gap). After it is charged, the specimen is irradiated by a xenon-flash-lamp. Since the energy of this pulsed light is beyond 4eV, electrons are emitted and move from Si to SiO2. It is possible to estimate the condition (the electrical conductivity) of the insulator using this phenomenon. A multi-electrode system was developed for mass production. With this system, one is able to evaluate 10 thousand points over a 12-inch wafer in 1 minute.
In the manufacturing field of semiconductor devices, improvement of yield and increase of throughput is very important issue. Therefore, in the evaluation of semiconductor devices, a method using a light source is frequently used for in-line measurement. In our laboratory, we propose Pulsed Photo Conductivity Method (PPCM) as a device evaluation method for non-destructive and non-contact measurement. To inspect the whole wafer in one minute using PPCM evaluation equipment, high repetition frequency lamp is required .In general, laser is used as light source in device evaluation using light. Laser has a high repetition frequency, but the cost is very high compared with other light sources. Therefore, in this study, we developed a multi-flash system to be used for PPCM evaluation equipment. This system is a high repetition frequency and cheaper. In this study, the maximum repetition frequency of an L11035 Hamamatsu xenon flash lamp used is 530Hz which is not high. Therefore, we developed a light source with high repetition frequency by using several xenon flash lamps in this system.
This paper is focused on piezoelectric actuator for precision stage system which has nano-scale resolution. Nanometer
order positioning techniques are necessary for semiconductor manufacturing and its inspection. For these demands, we
propose the nonresonant-ultrasonic motor(NRUSM) as driving source of positioning stage. One can use as the stage
driving device in a SEM chamber, because NRUSM is non-magnetic device. In addition NRUSM is able to be made
compact, can be equipped at various miniature tools, for instance, manipulation, pumping, probing systems, having nano
scale resolution. NRUSM is also adopted to Reticle Free Exposure system which can make the flexible patterning by fine
displacing of mask patterns. NRUSM's weak point is the occurrence of a wear because of friction caused by the
ultrasonic motor. However this wear can be cut down by reducing the slipping. A previously proven effective solution,
by which the driving keeps in the range of static friction without the slipping, results in long life time, high-durability
and decrease of particles. We propose two solutions to reduce the slipping: driving method and change of structure. The
former is control method using variable frequency instead of constant frequency. The latter is increase of friction tips
because static frictional force is proportional to number of the tips.