Yinhua Cui

Measurement of adhesion and bonding strength studies in 3D interconnect structures using atomic force microscopy

The wafer bonding process has become a flexible approach to material and device integration. The bonding strength in 3-dimensional processes is a crucial factor in various interface bonding processes such as silicon to silicon, silicon to metal, and oxide to adhesive intermediates. A method for measurement of bonding strength is proposed utilizing an ‘atomic force microscopy (AFM) applied carbon nanotube (CNT) probe tip’ which requires relatively simple preparation of sample and is able to measure bond strength regardless of film type. The bonding strength of the SiO2-Si surfaces cleaned with SPFM was 0.089 J/m2, while the bonding strength of surfaces cleaned with RCA 1 (NH4OH:H2O:H2O2) was 0.044 J/m2. This work verified the possibility that the new method is capable of accurately measuring bonding strength. It was also confirmed that more effective bonding is possible after cleaning with SPFM.

Effect of pre-cleaning treatment and contact wetting angle in the interface between P-doped Si surfaces and selective solar cell electrodes

Prior to electroless plating of the solar cell electrode, the sample was cleaned with a mixture of a sulfuric acid and peroxide solution and a H2NCH2CH2CH2Si(OC2H5) solution. We measured the de-wetting and contact angles of the solar cell thin film electrode. After SPM and APTES treatments, an excellent hydrophilic contact angle was observed. Our results show that it is more effective to remove oxidizer with SiO2 than HF mixed solutions. When comparing the efficiency, pre-treatment with a NH4F:HF mixed solution was more efficient than pre-treatment with a diluted HF solution. After NH4F:HF mixed solution cleaning, when the electrode was formed, the contact resistance that most directly affected the cleaning effect was 0.8194 ohm/sq, which had three times more improvement effect. It is expected that if an optimum cleaning time and process conditions for each cleaning chemical is developed, more improved contact resistance will be secured when each cleaning chemical is applied.

Effect of the Graphene Oxide Reduction Temperature on Supercapacitor Performance

In this study, we investigated the influence of the reduction temperature on graphene oxide. After performing the thermal reduction at specific temperatures (200, 600, and 1000 °C), the morphological and crystallographic changes were investigated by several analysis methods. The reduced graphene oxides were used as supercapacitor electrodes and analyzed with various electrochemical techniques. The capacitance exhibited an increase up to 600 °C before decreasing abruptly at 1000 °C. This behavior was ascribed to the limited ionic accessibility into the compact graphene layer.

Effect of chemical mechanical treatment on the optoelectronic properties in CMOS image sensor

This paper presents the effect focal length variation by controlling chemical mechanical polishing (CMP) processes on the CIS optical performance. White sensitivity was drastically increased, and saturation signal variation and dead zone deviation were reduced. These experimental results showed that controlled focal length was able to increase CIS optoelectronic performance.

Radiofrequency characteristics of ionized sputtered tantalum nitride thin-film resistor in CMOS device

We report the analysis of the radiofrequency (RF) characteristics according to the size, area, and shape of TaN thin-film resistor (TFR) layers. As the TFR size increased, its characteristics were degraded with increasing frequency owing to the increased capacitive parasitic components. As the frequency increased from 1 MHz to 10 GHz, the effective resistance decreased by approximately 12.5%, 16.4%, and 37.8% when the resistor widths and lengths were 0.5 × 20, 1 × 40, and 2 × 80 μm, respectively. To optimize the performance of the high-frequency TFR, ensuring RF isolation via sufficient separation from the silicon substrates was crucial. To realize this RF isolation, methods for minimizing the effect of lossy Si substrates by using TFRs with a smaller area or by forming a patterned ground shield should be introduced.

Chemical Analysis of Patterned Mask Cleaning in Organic Light Emitting Diode Fabrication with Raman Spectroscopy

Abstract Despite the continually improving efficiency of the fabrication process used to manufacture the organic light emitting diode (OLED) emitter layer, which uses a shadow mask, a method for the cleaning and recycling of the shadow mask is still lacking. One of the main reasons for this is the absence of a quantitative/qualitative method to analyze the cleaning solution using simple in situ measurements. Recently, Raman analysis has become popular because of its convenience, ease of use, and suitability for in situ measurements. Thus, Raman spectroscopy has the capacity to analyze the solution used for cleaning shadow masks. A particular advantage of this approach is that it can detect organic contaminants in the cleaning solution, which are caused by the residue that remains on the shadow mask after the OLED emitter layer fabrication process. Raman spectroscopy has an advantage for analyzing solution condition and contaminant detection between the cleaning solution and organic chemical by using the Raman peak and fluorescence integration method.

Interface modification in solar cell contact electrode using pre-cleaning treatment chemistries.

Promoting and employing photovoltaic power as an alternative energy source, the solar cell industry has made rapid strides. However, improving the efficiency of these solar cells using low-cost fabrication processes is still needed. The interface between the Si surface and the electrode plays a very important role in the process of electrode formation of the solar cell. In this study, the electrode interface underwent four different pre-treatments in order to enhance the efficiency of Si-based solar cells. We analyzed the adhesion properties at the interface between the Si wafer and the electrode and conducted an analysis of the variation in contact resistance between the two contact surfaces. To reduce the cost of the entire experiment, we replaced the existing Ag screen printing-based electrode fabrication method with a low-temperature, low-cost Ni/Cu electroless plating method. The test cells exhibited improved adhesion and therefore improved efficiency as compared to cells treated with the currently used diluted HF.