Browsing by Author "Fang, KL"

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A novel wafer reclaim method for amorphous SiC and carbon doped oxide films
(2005-11-01)
Tsui, BY
;
Fang, KL
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Amorphous SiC (a-SiC) films are the most promising dielectric diffusion barriers to replace silicon nitride in Cu-interconnect technology. However, reclaim of wafers with a-SiC films is a challenge issue for mass production. In this paper, a novel wafer reclaim method is proposed. It is observed that a-SiC can be oxidized to SiO2 in both dry O-2 and steam ambients at temperatures as low as 550 degrees C. The oxidation mechanism can be described by the Deal-Grove model that is traditionally used to describe oxidation of Si. Experiments prove that the oxidation process is clean and uniform. It is also observed that carbon doped oxide (CDO) films can be oxidized easily, too. Therefore, oxidation followed by HF etching could be a universal process to reclaim wafers deposited with a-SiC or CDO films. Since the oxidation rate of Si substrates at medium temperatures is much lower than that of a-SiC and CDO films, the oxidation process is virtually self-limiting. Compared with a traditional reclaim method based on wafer polishing, this universal oxidation-etching method exhibits great benefits in terms of low cost, high throughput, and the ability to perform nearly unlimited numbers of reclaim cycles.
A novel wafer reclaim method for silicon carbide film
(2003)
Tsui, BY
;
Fang, KL
;
Wu, CH
;
Li, YH
;
電子工程學系及電子研究所
As feature size keeps shrinking down, it is expected that amorphous SiC will replace Si3N4 in the Cu dual-damascene structure soon. SiC is chemically inert and is hard to be etched by wet processing. This property become adverse effect from the wafer reclaiming point of view. In this work, a novel wafer reclaiming method of oxidation followed by HF etching is proposed. Comparing with traditional reclaim method of wafer polish, this novel method exhibits great benefits of low cost, high throughput, and almost unlimited reclaim times.
Anisotropic thermal conductivity of nano-porous silica film
(2003)
Tsui, BY
;
Yang, CC
;
Fang, KL
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this work thermal conductivity of porous silica film was studied comprehensively. Silica films with porosity from 21% to 64% were spin coated. It is observed for the first time that the porous silica material has strong anisotropic characteristic. The pores in the higher porosity silica film tend to distribute horizontally. This distribution of the pores in the dielectric film is the main factor that induces the anisotropic characteristic. We proposed a Serial-Parallel Hybrid model to explain the correlation between porosity and thermal conductivity in both in-plane and cross-plane components. The anisotropic characteristic of the thermal conductivity may be accompanied by the anisotropic dielectric constant, which will greatly complicate the RC delay simulation of the circuits.
Anisotropic thermal conductivity of nanoporous silica film
(2004-01-01)
Tsui, BY
;
Yang, CC
;
Fang, KL
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this paper, thermal conductivity of porous silica film with porosity from 21 to 64 % was studied comprehensively. The corresponded dielectric constant is from 2.5 to 1.5. It is observed that the porous silica material has strong anisotropic characteristic. A serial-parallel hybrid model is proposed to explain the correlation between porosity and thermal conductivity in both in-plane and cross-plane components. The pores in the higher porosity silica film tend to distribute horizontally. This distribution of the pores in the dielectric film is the main factor that induces the anisotropic characteristic. The nonuniform distribution of pores also makes the conventional two-dimensional model of 36 method inappropriate for extracting the in-plane thermal conductivity. A new method based on the hybrid model was proposed to extract the in-plane thermal conductivity successfully. The anisotropic characteristic of the thermal conductivity may be accompanied by the anisotropic dielectric constant, which will greatly complicate the thermal management and resistance-capacitance delay simulation of the circuits and should be avoided. The proposed model would be helpful on evaluation of new porous low dielectric constant materials.
Electrical and material stability of Orion(TM) CVD ultra low-k dielectric film for copper interconnection
(2002)
Fang, KL
;
Tsui, BY
;
Yang, CC
;
Chen, MC
;
Lee, SD
The electrical and material stability of a newly developed CVD ultra low-k dielectric material called Orion, is explored. It has a dielectric constant of less than 2.2 with excellent thermal stability up to 600degreesC. It shows very low leakage current of only 1nA/cM(2) at 2.5MV/cm. Although both Al and Cu ions can be driven into Orion easily, no metal ions are observed in the Orion with a TAN gate. The Orion material also shows very good adhesion with TaN and oxide hardmask. The current transport mechanism and electrical reliability were investigated. Although weak dielectric polarization occurs under bias-temperature stress, Orion is a very promising material for next generation Cu-interconnect technology.
Electrical reliability issues of integrating low-K dielectrics with Cu metallization
(2000)
Wu, ZC
;
Shiung, ZW
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Wang, CC
;
Fang, KL
;
Wu, RG
Electrical reliability issues of two organic aromatic low-K materials (K = 2.6 similar to 2.8) were investigated. Both materials show acceptable thermal stability and good dielectric barrier property against Cu penetration. C-V curve instability was observed under bias-temperature stress (BTS) for the first time. It can be explained by the model of stress induced dielectric polarization charges. This instability may be an issue of long term stability of circuits.
Electrical reliability of low dielectric constant diffusion barrier (a-SiC : H) for copper interconnect
(2001)
Fang, KL
;
Tsui, BY
;
Yang, CC
;
Lee, SD
;
電子工程學系及電子研究所
The electrical stability and reliability of the Trimethylsilane (3MS) based a-SiC:H (SIC) film was investigated for the first time. Capacitance-Voltage (C-V) characteristic instability was observed due to polarization at high electrical filed and electron injection at Low electrical field. By adding nitrogen content in the film, the dielectric constant and leakage current are reduced but the time dependent dielectric breakdown (TDDB) lifetime becomes worse at high nitrogen content. It is suggested that the SiC deposition can be optimized at moderate nitrogen content to compromise all film properties.
Electrical stability and reliability of ultralow dielectric constant porous carbon-doped oxide film for copper interconnect
(2005)
Fang, KL
;
Tsui, BY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Nanoporous carbon-doped oxide (CDO) is a promising low dielectric constant (low-k) intermetal dielectric (IMD) for Cu interconnect. The electrical stability and reliability of CDO strongly depend on the contacted metal. An electrical instability model considering metal ion diffusion, dielectric polarization, and carrier injection is proposed for CDO under electrical stress. Both Al and Cu are not suitable for contact with CDO because they can be driven easily into CDO. Fortunately, TaN shows no mobile ion issues when in contact with CDO. The electron transport mechanism is identified to be Schottky emission at low electric field and low temperature. As metal ions are injected into CDO film, the electron transport mechanism changes to Frenkel-Pool emission at high temperature and high electric field. The injection of metal ions into CDO also degrades the time-dependent dielectric breakdown (TDDB) lifetime of CDO. Fortunately, the commonly used diffusion barrier TaN is an excellent contact metal with CDO. The 1-year-long TDDB lifetime allows an electric field stronger than 2 MV/cm, and the TDDB lifetime at 0.5 MV/cm becomes longer than 10 years by several orders of magnitude. It is concluded that the nanoporous CDO is a very promising IMD for next-generation interconnect systems. (c) 2005 The Electrochemical Society.
Metal drift induced electrical instability of porous low dielectric constant film
(2003-05-01)
Fang, KL
;
Tsui, BY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Nano-porous carbon doped oxide (CDO) is one of the potential low dielectric constant (low-k) materials that can achieve a dielectric constant as low as 2.2 and is expected to be suitable for the next generation multilevel interconnection. However, the electrical stability of CDO in contact with metal has not been addressed. In this work, metal ions' drift into nano-porous CDO is investigated. It is observed that both the Al and Cu ions can be driven into porous CDO film easily by applying electric field or thermal treatment. This results in a severe flat band voltage shift of the metal/CDO/Si capacitor structure. It is hypothesized that the lacking formation of self-limited aluminum oxide between Al and CDO film make Al ions drift into CDO. The adhesion of Al and Cu to CDO is also very poor. A physical model, combining weak dielectric polarization and metal ions drift, was proposed to explain the observed electrical instability. The inconsistent results regarding the Al/porous low-k/Si structure reported in the previous literatures can also be explained with this proposed model. Fortunately, TaN, as a common diffusion barrier material for Cu interconnect structure, is proved to have good adhesion to CDO. Negligible metal ions would drift in CDO during electrical stress. It is concluded that with a suitable diffusion barrier, such as TaN, CDO is still a very promising material for next generation Cu-interconnect technology. (C) 2003 American Institute of Physics.
Surface-processing-enhanced copper diffusion into fluorosilicate glass
(2001-11-01)
Tsui, BY
;
Fang, KL
;
Lee, SD
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This study investigated copper diffusion into processed fluorosilicate glass (FSG). It is observed that the surface process enhances the flatband voltage shift of the Cu/FSG/Si capacitor structure under bias-temperature stress. Secondary-ion mass spectroscopy analysis confirmed that the flatband voltage shift was due to Cu diffusion into the FSG film. Thermal desorption spectrometer analysis indicated that the surface damage layer took up more moisture. A surface-damage-layer-enhanced Cu ionization model was then proposed to explain the observation. The investigation concludes that the diffusion of Cu into FSG is strongly dependent on the surface condition of the FSG film. The proposed model also provides explanation for the inconsistent results reported in previous literature. (C) 2001 The Electrochemical Society.