Yu Ling Liu

Study on the Stability of Alkaline Silica Sol

The stability of slurry has a great effect upon the stability of polishing quality. At present the slurry of CMP includes SiO2 is applied in different fields respectively. But silicon sol is not enough to meet the requirement of CMP because of its instability. So the stability of silica sol is studied in this paper. It is known that the rate of coagulation depends mainly on the stability of the colloidal particles and that the solution pH and potential are the main factors affecting the colloidal stability. The stability of dispersion (the ability of the dispersion to resist coagulation) may be related to its kinetic stability, which in turn depends on the force barrier preventing collision between the particles and thus preventing their coagulation. The addition of surfactant can change the pH and the potential of silica sol. So o-20、JFC and PEG are selected to improve the stability of silica sol. The results presented here show that surfactant, PEG with low molecular weight, has a strong consequence on the stability of silica dispersion.

A Study of a New Cleaning Agent for Post-CMP Pattern Wafer

In this paper, it studies a new cleaning agent for post CMP pattern wafers. The polyamine chelating agent R(NH2)n complexing agent is used in pattern post-CMP cleaning, and the inhibitor BTA can effectively protect the wafer. The surfactant should be appropriate, and the concentration should be 1.5 ‰.

The Study of Specific Materials Used by the Copper Wiring CMP of GLSI

In this paper, the multi-hydroxyl polyamines researched by ourselves are used in the slurry of the copper wiring CMP of GLSI, which makes the slurry alkalization. It also has the using as a pH adjusting agent, complexion agent of copper ion, multi- metal chelating agents, aminating agent of acidic oxides, pH buffer, stainless steel corrosion inhibitor, the active agent and pro-oxidant. It improves the property of slurry and solves many different of acidity slurry. The alkalinity slurry contained the multi-hydroxyl polyamines is environmental, inexpensive and composition- simplified. Without the toxic BTA which is must be used in the international and has side effect, the slurry can achieve the high speed and high flat. In the same time the low pressure and the little abrasive can be realized, which provide the new material for the removal of TSV copper film.

Effects of Alkaline Nano-SiO2 Abrasive on Planarization of 300mm Copper Patterned Wafer

Silica abrasive plays an important role in chemical mechanical planarization (CMP) of copper. In this paper, effect of different silica abrasive concentrations on copper removal rate and planarization performance of copper was investigated. The results show that the copper removal rate was increased as the concentration of silica abrasive increase. However, excessive abrasive will lead to a decreased copper removal rate. The initial step height values of the multilayer copper wafers were all about 2500Å, and after being polished for 30s, the remaining values of step height of slurry A, B, C and D were 717 Å, 906 Å, 1222 Å and 1493 Å. It indicates that alkaline copper slurries with different abrasive concentrations all had a good planarization performance on copper patterned wafer CMP. As the abrasive concentration increased, the planarization capability was enhanced.

The Application of New Reagent in the Copper Wiring CMP

At present there are many challenges in the acidity slurry used widely. And the toxic BTA with side effect must be used in the international. So the component of slurry must be improved. The new reagent is studied. It makes the slurry alkalization. It also has the using as a pH adjusting agent, complexion agent of copper ion, multi- metal chelating agents, aminating agent of acidic oxides, pH buffer, stainless steel corrosion inhibitor, the active agent and pro-oxidant. It improves the property of slurry and solves many different of acidity slurry. The alkalinity slurry contained the multi-hydroxyl polyamines is environmental、inexpensive and composition- simplified. The slurry with it can achieve the high speed and high flat. In the same time the low pressure and the little abrasive can be realized, which provide the new material for the removal of copper film.

Study on CMP Test Technology of 65 nm and below Node Wafers with Copper Interconnects

It is of significance to research high-removal efficiency and low-cost CMP process for the 65 nm and below node. Chemical mechanical polishing (CMP) can realize the planarization of the wafer with free defects, free contamination and below nanometer level roughness. Test project of CMP slurry is main contain of these detections such as pH value, chelating agent content, SiO2 gel particle size, ζ-potential detection and the observation by Transmission electron microscopy (TEM). End point detection method of pattern wafer CMP usually includes the non destructive optical measurement, motor current feedback measurement and polishing pad temperature test. The main problems of the measurement for pattern wafer CMP are critical dimension (CD), section, film thickness, defects and particles measurement. Some of the new type of testing technology, such as atomic force profiler (AFP), can be used to compare CMP effect, such as dishing, erosion, tungsten plugs, the height of steps and flatness of the wafer, which is significant for wafer CMP research.

Effect of Complex Agent on Copper Dissolution in Alkaline Slurry for Chemical Mechanical Planarization

With the microelectronic technology node moves down to 45 nm and beyond, and to reduce the RC delay time, low-k dielectric materials have been used to replace regular dielectric materials. Therefore, the down force of chemical mechanical planarization (CMP) needs to decrease based on the characteristics of low-k materials: low mechanical strength. In this study, the effect of new complex agent on copper dissolution in alkaline slurry for CMP was investigated. Based on the reaction mechanism analysis of Cu in alkaline slurry in CMP, the performance of Cu removal rate and surface roughness condition were discussed. It has been confirmed that Cu1 slurry demonstrates a relatively high removal rate with low down force. And also, by utilizing the Cu1 slurry, good result of Cu surface roughness were obtained.

Effect of Colloidal Silica as Abrasive on Low-k Dielectric Materials in Chemical Mechanical Planarization

With low-k dielectric materials taking the place of oxide dielectrics as the primary dielectric materials, the low-k dielectric materials and interconnection Cu metals during Chemical Mechanical Planarization (CMP) is becoming a critical surface quality issue as well. In this study, experiments are carefully designed and conducted to investigate the effects of colloidal silica under compared acidic slurry and self-prepared alkaline slurry on k value of low-k dielectric materials, and in both of the slurry, colloidal silica (20~30nm) was used as polishing abrasive. The results showed that k value of low-k dielectric materials both increased within a similar range (self-prepared alkaline slurry, 3.27~3.33; commercial acidic slurry, 3.26~3.32), however, the results showed a obviously different result from reference’s report.

Removal Characteristics of Hillock Defects on Silicon Substrate by Chemical Uniformity Etching Enhanced Polishing Slurry

The thermally generated defects will lower the life time in bulk silicon and cause increasing in the leakage current of individual diodes in integrated circuits, that will finally cause the malfunction with advanced devices and IC chips. The removal characteristics of hillock defects on the single bare silicon wafer generated by the thermal process were experimentally analysed with respect to the chemical additives enhanced uniform chemical etching and mechanical abrasion of high pure nano sphere colloidal silica interplaying with the alkali based polishing slurry. During the polishing, it was found that the silicon surface contacted with high speed of rotated polishing pad under the down force pressure is chemically dissolved by the slurry containing FA/O organic polyamine(R(NH2)n) agent with adding proper proportional FA/O I non ions surfactant, which effectively lowered the surface strain of slurry contacted to the reactive surface of the wafer and slurry enhanced uniform chemical etch leading to the hillock region and no hillock region. However, by the process of chemical mechanical polishing，the results show it can eliminate the hillock defects on the surface of silicon wafer thoroughly with high removal rate, and achieve lower surface roughness than before process of polishing.

Surface Measurement of GLSI Wafer with Copper Interconnects after CMP

Chemical mechanical polishing (CMP) is the best global planarization technology of GLSI process. After CMP process, there may appear large roughness, micro scratch, dishing pit, erosion pit, with-in-wafer-non-uniformity (WIWNU), organic contamination, particles and metal ions pollution on wafer with copper interconnects. Surface measurement of CMP process on the wafer mainly involves the test of roughness, defects and the contaminations. Atomic force profiler (AFP) combined with the resolution of the AFM and long-range-scan ability of the steps instrument (100 mm), is suitable for CMP process which needs to measure both the planarization of long-range scanning and tungsten plug and copper interconnects with high resolution imaging. Optical detection technology combined with the advantages of dark and bright view detection is suitable for detection of particles, crystal originated pits (COP), defects, etc. The time-of-flight static secondary ion mass spectrometry (TOF-SIMS) and total reflection X-ray fluorescence (TXRF) are applicable to detect metal ions. The selection and use of advanced data analysis theory and method can help to improve the speed of analysis and to find the main factors of influence surface quality. Pareto diagram analysis is very beneficial for study polishing effects and the main reason of the surface state for Cu-CMP wafer. Nine sampling method and five sampling method fit to analysis the uniform surface distribution, on the contrast isometric sampling can reflect the distribution of the surface state along the radius difference.