A characteristic of a surface is measured by illuminating the surface with optical radiation over a wide angle and receiving radiation reflected from the surface over an angle that depends on the extend of the illumination angle. An emissivity measurement is made for the surface, and, alternatively, if a reflectivity measurement is made, it becomes more accurate. One application is to measure the thickness of a layer or layers, either a layer made of transparent material or a metal layer. A one or multiple wavelength technique allow very precise measurements of layer thickness. Noise from ambient radiation is minimized by modulating the radiation source at a frequency where such noise is a minimum or non-existent. The measurements may be made during processing of the surface in order to allow precise control of processing semiconductor wafers, flat panel displays, or other articles. A principal application is in situ monitoring of film thickness reduction by chemical-mechanical-polishing (CMP).

Optical techniques for measuring layer thicknesses and other surface characteristics of objects such as semiconductor wafers

An infrared obstruction detection system apparatus (100) is used to detect the presence of ambient light and initiate compensation to minimize the effects of the ambient light on the performance of the system in detetecting an obstacle (101). The magnitude of the ambient light is measured and an offset (112) proportional to that magnitude is fed to the obstruction detection system such that the data indicative of an obstacle from an evaluating detector (116) are not obscured. The apparatus continually monitors the effect of ambient light and adjusts the obstacle detection information during the changing state of the ambient light detected.

Infrared obstacle detection in the presence of sunlight

An apparatus for controlling the position of a screen pointer for an electronic device having a display screen, includes a light source for illuminating an imaging surface with a plurality of light pulses, thereby generating reflected light pulses. A detection circuit is configured to sense light, distinguish between the reflected pulses and ambient light, and generate a low signal indication if the magnitude of the reflected pulses falls below a threshold value. An optical motion sensor generates digital images based on the reflected pulses. The motion sensor is configured to generate movement data based on the digital images. The movement data is indicative of relative motion between the imaging surface and the apparatus.

Apparatus for controlling a screen pointer that distinguishes between ambient light and light from its light source

An object detection system (100) employs a photo-emitter (102) and photo-detector (104) for synchronously detecting and processing an optical signal (105) reflected from an object in a pinch zone of a window or door opening (101). A photo-emitter light signal (103) is modulated by a modulation signal (109) having an active phase and an inactive phase. The optical detector (104) provides an optical detector signal (107) that is a function of the intensity of the received light (105). The detected light (107) signal is synchronously detected using a switching amplifier (108) that multiplies the reflected modulated light signal by a first gain during the active phase and by a second gain during the inactive phase. The duration of the active and inactive phases and the first and second gains are selected such that the system gain will average to zero for ambient light when integrated over a predetermined measurement period. The synchronously detected signal is substracted (118) from a predetermined offset voltage, and this difference is then integrated over the measurement period. The output of the integrator (114) in then compared to a predetermined threshold value.

Obstacle detection sensor using synchronous detection

In a semiconductor process which utilizes a plasma within a process tool chamber, a method of using optical emission spectroscopy (OES) to monitor a particular parameter of the process is disclosed. A first wavelength present in the plasma is determined which varies highly in intensity depending on the particular parameter by observing a statistically significant sample representing variations of the particular parameter. A second wavelength of chemical significance to the process is also determined which is relatively stable in intensity over time irrespective of variations of the particular parameter, also by observing a statistically significant sample representing variations of the particular parameter. These two wavelengths may be determined from test wafers and off-line physical measurements. Then, the intensity of the first and second wavelengths present in the plasma is measured on-line during normal processing within the process tool chamber, and the ratio between the first and second wavelength's respective intensities generates a numeric value which is correlated to the particular parameter. As an example, such a method may be used to generate a reliable alarm signal indicating the presence of etch stop conditions within a plasma oxide etcher, as well as to indicate the oxide etch rate.

Methodology for improved semiconductor process monitoring using optical emission spectroscopy

A sensor board for use with an endpoint controller which monitors light intensity is provided. The sensor board can provide a dynamic range of up to five million because a constant current driver and phase sensitive detector help eliminate noise from the detected signal. The sensor board can also subtract a DC voltage offset from the detected signal and amplify the difference to provide increased resolution of small changes in the detected signal.

Sing-wing Hui

Papers

Apparatus and method for monitoring radiant energy signals with variable signal gain and resolution enhancement