Xin Huan Niu

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 ‰.

High Precision Finishing Technique of Sapphire Substrate Surface for Photoconducting Device

Sapphire (α-Al2O3) single crystal, as an important photoconducting device substrate material, stringent surface quality requirements, i.e. surface finish and flatness, are required. The use of chemical mechanical polishing (CMP) technique can produce high quality surface finishes at low cost and with fast material removal rates. The polishing mechanism was studied in this paper, and it was pointed that there were chemical and mechanical kinetics process respectively. The chosen polishing temperature was 40 oC. SiO2 sol was chosen as abrasive and the particle size is 40nm. The pH value was determined at 11.5~12. During CMP process C6382I-W/YJ single side polisher and SUBA 600 pad were used. After polishing and cleaning of sapphire surface, the measured removal rate was above 183.3nm /min and the surface roughness by using AFM was lower than Ra 0.3 nm. From the results, it was found that using such method, the optimal sapphire surface can be gotten, which is advantaged for epitaxial growth and device making-up.

The Important Role of Oxidant in Copper Interconnection Chemical Mechanical Polishing for GLSI

Chemical mechanical planarization (CMP) of copper interconnection in hydrogen peroxide (H2O2) as oxidizer based alkaline slurry was investigated. The new model is put forward, which is based on the characteristic of H2O2, chemical kinetics and mechanical removal. This properties of H2O2 can be effectively compensated the defect of surface topology during the process of polishing. Researcher previous study has shown that the surface is largely copper metal with Cu2O at low H2O2 concentrations and largely CuO at high H2O2 concentrations. Cu2O is more easily removed by both chemical and mechanical processes than CuO. During the CMP process, as the oxidizer concentration increases, the removal rate goes up initially followed by a gradual decay. This characteristic of oxidizer is used to achieve copper surface global planarity. The surface planarity was achieved by removing high area on the surface more quickly relative to the low area, because the concentration of Cu2O in the low area as the passivation film is more than the high area. Meanwhile the passivation film of the low area is thicker than the high area. In order to achieve polishing process optimization, the influence of pH adjustment and pressure, are also taken into consideration. Combining both RR and PE, the optimal H2O2 concentration and pressures are in range 1.0 ~1.5 vol% and 0.04 ~0.07 mpa, respectively. The roughness of surface which is measured by AFM is 0.49 after CMP.

The Study of Stability of Tungsten Plug CMP Slurry for IC Multilevel Interconnect

With the developing of integrated circuit(IC) technique, improving of integration level, reducing of feature size and increasing the wafer size, the stringent requirements for global planarization during IC fabrication are raised. During chemical mechanical polishing(CMP) of multilevel interconnect for IC, there are obvious influence of the polishing quality on performances of the device．CMP slurry is one of the important factors of influencing the polishing quality. In this work, the stability of tungsten plug CMP slurry for IC multilevel interconnect was studied. Through experiment, interaction between the components in the CMP slurry was analyzed, and stable slurry with optimized polishing parameters to achieve higher removal rate were defined．

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.

Defectivity Reduction in the Silicon Tough Polishing with Polyamine and Nonions Surfactant Additives

The effects of the polyamine chelating agent and nonions surfactant additive on the surface defectivity reduction in the final polishing of the mono silicon wafers were investigated using high-purity nano colloidal silica based organic alkaline slurry. Experimental results reveal that the chemical enhanced silicon final polishing slurry containing FA/O polyamine chelating agent and FA/O nonions surfactant changed the chemistry character of silicon surface, can realize the chemical uniform etch the surface areas with defects and defect-free area, deeply lower the surface microroughness of silicon polished wafer, achieving defect-free with perfect quality of flat mirror-surface.

Ultra Precision Machining Technique of InSb Substrate Material for Detector Devices

Indium antimony(InSb) is one of the important materials which can be used to make semiconductor devices such as infrared detection device. Due to the low hardness and great brittleness, the surface scratching always appears and surface roughness is hard to lower during surface preparation. So it should be increasing the InSb surface quality during ultra precision machining. In this paper the InSb surface adsorption-control technology was introduced. Through controlling surface roughness during chemical mechanical polishing(CMP) and using preferential adsorption during cleaning, the adsorptions of InSb surface were controlled. Through experiments, the CMP optimal process parameters under the alkaline conditions were gotten. Under such conditions, the preferable surface state was realized. According to the preferential adsorption model, through using FA/O non-ionic surfactant the polished wafer surface can be kept in physical adsorption and easy cleaning state, so the wafer surface adsorption can be controlled effectively and the clean surface was obtained.

Chemical Mechanical Planarization of Cu Pattern Wafer Based Alkaline Slurry in GLSI with R(NH2)n as Complexing Agent

Chemical mechanical planarization (CMP) of Cu pattern wafer based alkaline Cu slurry in GLSI was investigated. The performance of Cu removal rate and dishing condition were discussed in this paper. Different formation of alkali CMP slurry (Cu1 and Cu2 slurry) were observed by removal rate experiments and showed that alkaline slurry provided a robust polishing performance on initial removal rate, which Cu1 and Cu2 slurry were higher than that of commercial acidity slurry, and in addition, alkaline slurry also have good ending removal rate both in Cu1 and Cu2 slurry and favorable dishing in Cu2 slurry. Furthermore, the result indicated that Cu alkaline slurry with a complexing agent of R(NH2)n, compared with commercial acidity slurry with a inhibitor of Benzotriazol (BTA), have better application foreground for 45nm nod and more advanced nodes.

Effect of FA/O Chelating Agent on Copper Ion Removing on Silicon Surface

Along with the feature size reducing and the increase of integration level rapidly in ULSI，the request for metal impurities contamination on silicon substrate surface appears specially rigorous. In this paper the chelating agent was added in cleaning solution in order to removing copper ion. FA/O, a new kind of chelating agent was studied in RCA cleaning solutions, which has 13 chelating rings and is free of sodium, stable and easily soluble. The XPS and GFAAS measured results indicate that FA/O is more efficient than NH4OH as a ligand. Cu contaminations on silicon wafer can be removed remarkably when adding a little FA/O to the cleaning solution or polishing slurry. When the chelating agent concentration of cleaning solution is 0.1% the removal rate of Cu atom reaches 83 percent. The FA/O chelating agent substituting NH4OH in SC-1 may simplify cleaning steps, and one cleaning step can remove Cu pollution on silicon wafer surface and meet the requirements of microelectronics technology.