As the critical dimensions of integrated circuits continue to grow smaller, overlay error is becoming increasingly important. Overlay error is mainly determined by the telecentricity of the exposure system in a photolithography tool. Existing telecentricity-measuring methods—which are photoresist-based—are complex and cannot obtain the telecentricity in real time. Moreover, the obtained result is influenced by the photoresist performance. We propose a light-cone-central-line method that measures telecentricity without the need of photoresist. Compared with photoresist-based methods, the light-cone-central-line method can be used in real time, accelerating the setup and tuning of the exposure system and thus significantly reducing the complexities and expenses of the existing measurement methods. The proposed method was applied in a lithography tool with a 90-nm resolution, and the results for five field positions (the center position and four corner-field positions) are presented. This method is found to provide sufficient measurement repeatability, and it satisfies the telecentricity measurement requirements of the tool.
Pupil parameters are important parameters to evaluate the quality of lithography illumination system. In this paper, a cloud based full-featured pupil processing application is implemented. A web browser is used for the UI (User Interface), the websocket protocol and JSON format are used for the communication between the client and the server, and the computing part is implemented in the server side, where the application integrated a variety of high quality professional libraries, such as image processing libraries libvips and ImageMagic, automatic reporting system latex, etc., to support the program. The cloud based framework takes advantage of server’s superior computing power and rich software collections, and the program could run anywhere there is a modern browser due to its web UI design. Compared to the traditional way of software operation model: purchased, licensed, shipped, downloaded, installed, maintained, and upgraded, the new cloud based approach, which is no installation, easy to use and maintenance, opens up a new way. Cloud based application probably is the future of the software development.
Illumination uniformity of the illuminator is significant for achieving stringent critical dimension (CD) control for lithography machine. In order to achieve high uniform illuminating, there is an urgent demand of accurate measurement for illumination uniformity. The difficulty for accurate measurement of illumination uniformity for the illuminator mainly lies in two aspects: the illumination plane is large; excimer laser pulse energy is variable from pulse to pulse. In this work, a spot sensor based 2-dimension scanning method for illumination uniformity measurement is proposed, where the spot sensor in combination with a 2-dimension moveable stage is located in the illumination plane of the illuminator is used to scan the illumination plane point-by-point so as to obtain the whole irradiation distribution. To improve measurement accuracy, the energy sensor of the illuminator serves as the reference and monitors each pulse in real-time showing benefit of excimer laser pulse energy fluctuation eliminating. Secondly, the used spot sensor is modified for strict synchronization control of the spot sensor and the energy sensor so that the measurement precision can be improved. Measurement results show that X direction transient non-uniformity, Y direction transient non-uniformity and X direction integral non-uniformity of the illuminator are 5.14%, 5.55% and 2.16% respectively with a measurement uncertainty of 0.31% (k=2). It is proved that the proposed method is effective and helpful for further system optimizing and alignment.
Gold labeled immunochromatography assay is widely used in many fields. Quantitative test can be realized by using a
reflectance photometer. However, theoretical analysis of the strip and the photometer has seldom been reported. In this
paper, the microstructure of immunochromatographic strip labeled by nanogold particles is analyzed with scanning
electron microscope (SEM). Based on the SEM images of the strip, Mie's scattering theory is used to investigate the
scattering behaviors of particles in the strip, and Lambert cosine law is applied to analyze the diffuse reflection of porous
strip. Besides, a reflectance photometer for gold labeled test strip has been developed for fast quantification of
immunochromatography assay in our group. Theoretical model is achieved by introducing the parameter of the
developed reflectance photometer. The calculated scattering signal distribution is well consistent with that measured by
the reflectance photometer.
A novel biosensor based on up-converting phosphor technology (UPT) was developed several years ago. It is a kind
of optical biosensor using up-converting phosphor (UCP) particles as the biological marker. From then on, some
improvements have been made for this UPT-based biosensor.
The primary aspects of the improvement lie in the control system. On one hand, the hardware of the control system
has been optimized, including replacing two single chip microcomputers (SCM) with only one, the optimal design of the
keyboard interface circuit and the liquid crystal module (LCM) control circuit et al.. These result in lower power
consumption and higher reliability. On the other hand, a novel signal processing algorithm is proposed in this paper,
which can improve the automation and operating simplicity of the UPT-based biosensor.
It has proved to have high sensitivity (~ng/ml), high stability and good repeatability (CV<5%), which is better than
the former system. It can meet the need of some various applications such as rapid immunoassay, chemical and
biological detection and so on.