Browsing by Author "Jang, SM"

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A physical model for hole direct tunneling current in P+ poly-gate PMOSFETs with ultrathin gate oxides
(2000-11-01)
Yang, KN
;
Huang, HT
;
Chang, MC
;
Chu, CM
;
Chen, YS
A model of the hole direct tunneling gate current accounting for heavy and light hole's subbands in the quantized inversion layer is built explicitly. This model comprises four key physical parameters: inversion layer charge density, hole impact frequency on SiO2/Si interface, WKB transmission probability, and reflection correction factor. With the effective hole mass m(oxh) = 0.5m(o) for parabolic dispersion relationship in the oxide, experimental reproduction without any parameter adjustment is consistently achieved in p(+) poly-gate pMOSFETs with 1.23, 1.85, and 2.16 nm gate oxide thicknesses. The proposed model can thereby serve as a promising characterization means of direct tunnel oxides. In particular, it is calculated that the secondary subbands and beyond, although occupying few holes, indeed contribute substantially to the direct tunneling conduction due to effective lo,vcr barrier heights, and are prevailing over the first subbands for reducing oxide field down below 1 MV/cm.
Barrier characteristics of PECVD alpha-SiC : H dielectrics
(2001)
Chiang, CC
;
Wu, ZC
;
Wu, WH
;
Chen, MC
;
Ko, CC
This work investigates the thermal stability and barrier characteristics of three species of PECVD alpha-SiC:H dielectric films with dielectric constants between 3.5 and 5.4. It is found that the dielectric constant decreases with increasing content of carbon in the alpha-SiC:H film. All of the three specie's of alpha-SiC:H films are thermally stable at temperatures of up to 500degreesC. However, degraded barrier capability and moisture resistance were observed for the alpha-SiC:H film with a k value around 3.5, which has a C/Si atomic ratio of 0.875. This is presumably attributed to poorly crosslinked molecular structure and porosity enhancement by the abundant amount of carbon in the alpha-SiC:H film.
Characterization and modeling of edge direct tunneling (EDT) leakage in ultrathin gate oxide MOSFETs
(2001-06-01)
Yang, KN
;
Huang, HT
;
Chen, MJ
;
Lin, YM
;
Yu, MC
This paper examines the edge direct tunneling (EDT) of electron from n(+) polysilicon to underlying n-type drain extension in off-state n-channel MOSFET's having ultrathin gate oxide thicknesses (1.4-2.4 mm), It is found that for thinner oxide thicknesses, electron EDT is more pronounced over the conventional gate-induced-drain-leakage (GIDL), bulk band-to-band tunneling (BTBT), and gate-to-substrate tunneling, and as a result, the induced gate and drain leakage is better measured per unit gate width. A physical model is for the first time derived for the oxide field fox at the gate edge by accounting for electron subband in the quantized accumulation polysilicon surface. This model relates fox to the gate-to-drain voltage, oxide thickness, and doping concentration of drain extension, Once fox is known, an existing DT model readily reproduces EDT I-V consistently and the tunneling path size extracted falls adequately within the gate-to-drain overlap region. The ultimate oxide thickness limit due to EDT is projected as well.
Comparative study of physical and electrical characteristics of F- and C-doped low-K CVD oxides
(2001)
Wu, ZC
;
Shiung, ZW
;
Chiang, CC
;
Wu, WH
;
Chen, MC
This work makes a comparative study of physical and electrical properties between two species of inorganic low-K CVD oxides, namely F-doped FSG (fluorinated silicate glass, K=3.5) and C-doped OSG (organosilicate glass, K=2.9). It is found that FSG has a higher thermal stability (>600degreesC) than OSG (500degreesC) based on the results of 30 min thermal anneal in N-2 ambient. The degradation of the low-K property in OSG is predominately due to the thermal decomposition of methyl (CH3) groups at temperatures above 500degreesC, which are incorporated to reduce the density and polarizability of OSG. For the Cu-gated oxide-sandwiched low-K dielectric MIS capacitors, Cu permeation was observed in both FSG and OSG after the MIS capacitors were subjected to bias-temperature stressing (BTS) at 250 and 150degreesC, respectively, with an effective applied field of 0.8 MV/cm. It appeared that Cu drifted more readily in OSG than in FSG presumably because OSG has a more porous and less dense structure than FSG. The Cu penetration can be efficiently mitigated by a thin nitride dielectric barrier layer.
Dielectric and barrier properties of spin-on organic aromatic low dielectric constant polymers FLARE and SiLK
(2001-06-01)
Wu, ZC
;
Shiung, ZW
;
Wu, RG
;
Liu, YL
;
Wu, WH
This work investigates the dielectric and barrier properties of two species of organic aromatic low dielectric constant (low-k) polymers, namely, FLARE and SiLK. Experimental results indicate that both of the low-k polymers exhibit acceptable thermal stability with respect to a thermal annealing at 400 degreesC for 8 h in an N-2 ambient. Moreover, they show a good dielectric barrier property against Cu penetration under bias-temperature stressing (BTS) at 150 degreesC with an applied effective field of 0.8 MV/cm. Nevertheless, an anomalous instability of the capacitance-voltage curve was observed for the first time under BTS. This finding is explained by the proposed model of stress induced dielectric polarization charges within these organic aromatic polymers. The polarization instability may seriously degrade the long term reliability of circuit operations. (C) 2001 The Electrochemical Society.
Edge hole direct tunneling in off-state ultrathin gate oxide p-channel MOSFETs
(2000)
Yang, KN
;
Huang, HT
;
Chen, MJ
;
Lin, YM
;
Yu, MC
This paper examines the edge direct tunneling (EDT) of hole from p(+) polysilicon to underlying p-type drain extension in off-state p-channel MOSFETs having ultrathin gate oxide thicknesses (1.2 - 2.2 nm). It is found that for thinner oxide thicknesses, hole EDT is more pronounced over the conventional GIDL and gate-to-channel tunneling, and as a result, the induced gate and drain leakage is better measured per unit gate width. A physical model accounting for heavy and light hole's subbands in the quantized accumulation polysilicon surface is built explicitly. This model consistently reproduces EDT I-V and the tunneling path size extracted falls adequately within the gate-to-drain overlap region. The ultimate oxide thickness limit due to EDT is projected as well.
Effects of O-2- and N-2-plasma treatments on copper surface
(2004-11-01)
Chiang, CC
;
Chen, MC
;
Li, LJ
;
Wu, ZC
;
Jang, SM
In this work, we investigate the effects of oxygen (O-2) and nitrogen (N-2) plasma treatments on the copper surface of aluminum/amorphous silicon-nitricarbide/copper (Al/alpha-SiCN/Cu) metal-insulator-metal (MIM) capacitors with respect to their leakage current and breakdown field. It is found that both the O-2- and N-2-plasma treatments have an adverse effect on the leakage current and breakdown field of MIM capacitors. The MIM capacitors with their Cu surfaces subjected to O-2- or N-2-plasma treatment exhibit a room-temperature leakage current density several orders of magnitude larger than that of the sample without plasma treatment at the same applied electric field. The room-temperature breakdown fields of the MIM capacitors with O-2- and N-2-plasma-treated Cu surfaces are 3.8 and 3.2 MV/cm, respectively, while that of the control sample without plasma treatment is 7.8MV/cm. The increased leakage currents and degraded breakdown fields of the O-2- and N-2-plasma-treated samples are attributed, respectively, to the presence of metastable Cu-O oxide and Cu-N azide at the Cu surfaces.
Electrical reliability issues of integrating low-K dielectrics with Cu metallization
(2000)
Wu, ZC
;
Shiung, ZW
;
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.
Improvement in leakage current and breakdown field of Cu-comb capacitor using a silicon oxycarbide dielectric barrier
(2004)
Chiang, CC
;
Ko, IH
;
Chen, MC
;
Wu, ZC
;
Lu, YC
This work investigates in the first place, the improvement in leakage current and breakdown field of the copper metal-insulator-semiconductor (Cu-MIS) capacitor with a plasma-enhanced chemical vapor deposited (PECVD) amorphous silicon oxycarbide (alpha-SiCO, k = 3.7) dielectric barrier. This is followed by investigating the improvement in leakage current and breakdown field of the Cu-comb capacitor with a carbon-doped low-k PECVD organosilicate glass (k = 3) as the intermetal dielectric and an alpha-SiCO dielectric film as the Cu cap barrier. The leakage current and breakdown field of Cu-MIS and Cu-comb capacitors are dependent on the species of the dielectric barrier. The Cu-MIS and Cu-comb capacitors with an alpha-SiCO dielectric barrier exhibit a leakage current at least three orders of magnitude smaller than those with an amorphous silicon carbide (alpha-SiC, k = 4.4) dielectric barrier at an applied electric field of 1.6 MV/cm between 25 and 250 degreesC. Moreover, the breakdown field of the Cu-MIS and Cu-comb capacitors with an alpha-SiCO dielectric barrier, measured at 200 degreesC, are 60 and 25%, respectively, higher than that of the capacitors with an alpha-SiC barrier. The decreased leakage current and increased breakdown field of the Cu-MIS and Cu-comb capacitors with an alpha-SiCO dielectric barrier are attributed to the higher density, oxygen-improved film property, nonsemiconductor behavior, and lower fringe- or surface-electric field of the alpha-SiCO dielectric film. (C) 2004 The Electrochemical Society.
Improvement of water-related hot-carrier reliability by optimizing the plasma-enhanced tetra-ethoxysilane deposition process
(1997-08-01)
Lin, YM
;
Jang, SM
;
Yu, CH
;
Lei, TF
;
電子工程學系及電子研究所
As-deposited, steam-exposed O-3-tetra-ethoxysilane (TEOS)-based intermetallic dielectric were characterized according to the LR-absorption spectra. The plasma-enhanced-TEOS films investigated here were formed by mixed-frequency plasma processes and differentiated by reaction oxidizers and/or plasma powers. Increasing stress and nitrogen or oxygen concentrations improved the moisture resistance of PE-TEOS oxide films. In addition to the moisture resistance of PE-TEOS films, another factor affecting hot-carrier robustness is the maximum thickness of the underlayer for O-3-TEOS films, which is limited by their conformity The integrated intermetallic dielectrics were evaluated by constant-current and hot-carrier stressing. In obtaining the best device reliability, a trade-off exists between moisture resistance, gapfilling capacity of the PE-TEOS underlayer, and plasma damage. Our results indicate that an O-2-rich, PE-TEOS film with a mechanical stress of 3 x 10(9) dyn/cm(2) is the optimum.
Improvement of water-related hot-carrier reliability by optimizing the plasma-enhanced tetra-ethoxysilane deposition process
(1997-08-01)
Lin, YM
;
Jang, SM
;
Yu, CH
;
Lei, TF
;
電子工程學系及電子研究所
As-deposited, steam-exposed O-3-tetra-ethoxysilane (TEOS)-based intermetallic dielectric were characterized according to the LR-absorption spectra. The plasma-enhanced-TEOS films investigated here were formed by mixed-frequency plasma processes and differentiated by reaction oxidizers and/or plasma powers. Increasing stress and nitrogen or oxygen concentrations improved the moisture resistance of PE-TEOS oxide films. In addition to the moisture resistance of PE-TEOS films, another factor affecting hot-carrier robustness is the maximum thickness of the underlayer for O-3-TEOS films, which is limited by their conformity The integrated intermetallic dielectrics were evaluated by constant-current and hot-carrier stressing. In obtaining the best device reliability, a trade-off exists between moisture resistance, gapfilling capacity of the PE-TEOS underlayer, and plasma damage. Our results indicate that an O-2-rich, PE-TEOS film with a mechanical stress of 3 x 10(9) dyn/cm(2) is the optimum.
Leakage and breakdown mechanisms in cu damascene with a bilayer-structured a-SiCN/a-SiC dielectric barrier
(2003)
Chiang, CC
;
Ko, IH
;
Chen, MC
;
Wu, ZC
;
Lu, YC
This work investigates the leakage and breakdown mechanisms in the Cu damascene structure with a carbon-doped low-k PECVD organosilicate glass (OSG, k=3) as the intermetal dielectric (IMD) and an alpha-SiCN(k=5)/alpha-SiC(k=4) bilayer-structured dielectric film as the Cu-cap barrier. It is found that the leakage mechanism between Cu lines is dependent on the thickness ratio of the alpha-SiCN/alpha-SiC bilayer barrier in the Cu damascene structure. In the Cu damascene using an alpha-SiCN/alpha-SiC bilayer barrier of 40nm/10nm or 30nm/20nm bilayer thickness, the large leakage current (Frenkel-Poole emission) between Cu lines is attributed to the plenty of interfacial defects, such as cracks, voids, traps or dangling bonds at the alpha-SiC/OSG interface, which are generated by the larger tensile force of the thicker alpha-SiC film. On the other hand, the breakdown field and TDDB (time-dependent-dielectric-breakdown) lifetime of the Cu damascene reveal little dependence on the thickness ratio of the alpha-SiCN/alpha-SiC bilayer barrier, and the observed breakdown of the Cu damascene structure is presumably due to dielectric breakdown of the bulk OSG layer.
Leakage and breakdown mechanisms of Cu comb capacitors with bilayer-structured alpha-SiCN/alpha-SiC Cu-cap barriers
(2004-02-01)
Chiang, CC
;
Ko, IH
;
Chen, MC
;
Wu, ZC
;
Lu, YC
This work investigates the leakage and breakdown mechanisms in copper (Cu) comb capacitors with carbon-doped low-k plasma-enhanced chemical vapor deposited organosilicate glass (OSG; k = 3) as the intermetal dielectric and an alpha-SiCN (k = 5)/ alpha-SiC (k = 4) bilayer-structured dielectric film as the Cu-cap barrier. The leakage mechanism between Cu lines is dependent on the thickness ratio of the alpha-SiCN/alpha-SiC bilayer barrier. Using an alpha-SiCN/alpha-SiC bilayer barrier of 40 nm/10 nm or 30 nm/20 nm bilayer thickness, the increased leakage current (Frenkel-Poole emission) between Cu lines is attributed to the large number of interfacial defects, such as cracks, voids, traps or dangling bonds at the alpha-SiC/OSG interface, which are generated by the larger tensile force of the thicker alpha-SiC film. The Cu comb capacitor with an alpha-SiCN (50 nm)/alpha-SiC (2 nm) bilayer barrier exhibits a much smaller leakage current. The breakdown field and time-dependent dielectric breakdown lifetime of the Cu comb capacitor reveal little dependence on the thickness ratio of the alpha-SiCN/alpha-SiC bilayer barrier, and the observed breakdown of the Cu comb capacitor is presumably due to dielectric breakdown of the bulk OSG layer. (C) 2004 The Electrochemical Society.
Leakage mechanism in Cu damascene structure with methylsilane-doped low-K CVD oxide as intermetal dielectric
(2001-06-01)
Wu, ZC
;
Chiang, CC
;
Wu, WH
;
Chen, MC
;
Jeng, SM
This letter investigates the leakage mechanism in the Cu damascene structure with methylsilane-doped low-k CVD organosilicate glass (OSG) as the intermetal dielectric (IMD), The leakage between Cu lines was found to be dominated by the Frenkel-Poole (F-P) emission in OSG for the structure using a 50-nm SiC etching stop layer (ESL), In the structure using a 50-nm SiN ESL, the leakage component through SiN also made a considerable contribution to the total leakage in addition to the bulk leakage from trapped electrons in OSG, An appropriate ESL of sufficient thickness is essential to reduce the leakage through the ESL if an ESL is used in the Cu damascene integration scheme.
Physical and barrier properties of amorphous silicon-oxycarbide deposited by PECVD from octamethylcyclotetrasiloxane
(2004)
Chiang, CC
;
Chen, CC
;
Li, LJ
;
Wu, ZC
;
Jang, SM
This work investigates the thermal stability and physical and barrier properties for three species of amorphous silicon-oxycarbide (alpha-SiCO) dielectric barrier films, deposited by plasma-enhanced chemical vapor deposition (PECVD), to copper (Cu) diffusion using octamethylcyclotetrasiloxane precursor and helium (He) carrier gas with and without oxygen (O-2) reaction gas. The alpha-SiCO dielectric barrier film deposited by PECVD without O-2 reaction gas exhibits a low k-value of 2.8, thermally stable at temperatures up to 550 degreesC, excellent moisture resistance, and superb Cu barrier property until 400 degreesC. With the addition of O-2 reaction gas during the dielectric deposition process, the dielectric constant of the alpha-SiCO dielectric barrier films increases with increasing flow rate of O-2 reaction gas. Increasing flow rate of O-2 reaction gas during the deposition of the alpha-SiCO dielectric barrier films also degrades the thermal stability and moisture resistance of the dielectric barrier films. Moreover, the addition of O-2 reaction gas also results in a degraded Cu barrier property of dielectric films. (C) 2004 The Electrochemical Society.
Physical and barrier properties of PECVD amorphous silicon-oxycarbide from trimethylsilane and CO2
(2004)
Chiang, CC
;
Ko, IH
;
Chen, MC
;
Wu, ZC
;
Lu, YC
This work investigates the thermal stability and physical and barrier properties of amorphous silicon-carbide (alpha-SiC) and amorphous silicon-oxycarbide (alpha-SiCO) dielectric barriers deposited by plasma-enhanced chemical vapor deposition (PECVD) using trimethylsilane (3MS) precursor and He carrier gas. Films were deposited without and with various CO2 flow rates. The dielectric constant of the alpha-SiCO films decreased with increasing CO2 flow rate. Increasing CO2 flow rate also promotes better thermal stability, higher breakdown field, lower leakage current, and superior resistance to Cu diffusion through the films. The improved barrier property is attributed to the denser and less porous structure of the alpha-SiCO dielectric barrier upon CO2 addition. The alpha-SiCO barrier films deposited with the large (1200 Seem) CO2 flow rate exhibit the low k value of 3.7, thermal stability up to 550degreesC, room-temperature breakdown field of 8 MV/cm and leakage current densities of 10(-7) to 10(-6) A/cm(2) at 3 MV/cm, and a superb Cu barrier property. (C) 2004 The Electrochemical Society.
Physical and barrier properties of plasma enhanced chemical vapor deposition alpha-SiC : N : H films
(2003-07-01)
Chiang, CC
;
Wu, ZC
;
Wu, WH
;
Chen, MC
;
Ko, CC
In this work, we investigate the thermal stability and physical and barrier properties of three species of plasma enhanced chemical vapor deposition (PECVD) alpha-SiC:N:H silicon carbide films with different carbon and nitrogen contents and dielectric constants less than a value of 5.5. For comparison, one species of alpha-SiN:H film with a k value of 7.2 is also studied. It is found that the dielectric constant decreases with increasing content of carbon and decreasing content of nitrogen in the alpha-SiC:N:H film. All of the three species of alpha-SiC:N:H and the one species of alpha-SiN:H films are thermally stable at temperatures up to 500degreesC. However, degraded barrier capability and moisture resistance were observed for the alpha-SiC:N:H film with a k value of 3.5, which has a C/Si atomic ratio of 0.875. This is presumably due to the poorly crosslinked molecular structure and porosity enhancement caused by the abundant amount of carbon in the alphaSiC:N:H film.
Physical and barrier properties of plasma-enhanced chemical vapor deposited alpha-SiC : H films from trimethylsilane and tetramethylsilane
(2003-07-01)
Chiang, CC
;
Chen, MC
;
Ko, CC
;
Wu, ZC
;
Jang, SM
This work investigates the thermal stability and physical and barrier properties of two species of plasma-enhanced chemical vapor deposited (PECVD) alpha-SiC:H silicon carbide films (with k-values less than 5) deposited using trimethylsilane, (CH3)(3)SiH (3MS) and tetramethylsilane, (CH3)(4)Si (4MS) organosilicate gases. It is found that the 4MS alpha-SiC:H film contains a higher content of carbon and has a lower dielectric constant. Both of the 3MS and 4MS alpha-SiC:H films are thermally stable at temperatures up to 500degreesC. However, degraded barrier property and moisture resistance were observed for the 4MS alpha-SiC:H film; this is attributed to the porosity enrichment caused by the film's high carbon content. The 3MS alpha-SiC:H film, which exhibits a superior Cu-barrier property, is a potential candidate for replacing the higher dielectric constant Si3N4 film as a Cu-cap barrier and etching stop layer in the Cu damascene structure.
Physical and barrier properties of plasma-enhanced chemical vapor deposited alpha-SiCN : H films with different hydrogen contents
(2003-08-01)
Chiang, CC
;
Chen, MC
;
Ko, CC
;
Jang, SM
;
Yu, CH
This work investigates the thermal stability and physical and barrier properties of two species of plasma-enhanced chemical-vapor-deposited (PECVD) amorphous silicon-nitrocarbide (alpha-SiCN:H) films with different hydrogen contents and dielectric constants of less than 5. It is found that the alpha-SiCN:H film with a higher hydrogen content has a lower dielectric constant. Both species of alpha-SiCN:H films are thermally stable at temperatures up to 500degreesC. However, a degraded dielectric strength was observed for the alpha-SiCN:H film with a lower k-value of 4, which has a much higher hydrogen content. This may be attributed to hydrogen-related defects, such as Si-H+-Si hydrogen bridges, and numerous Si-H weak bonds produced by the high hydrogen content in the alpha-SiCN:H film.
Physical and electrical characteristics of F- and C-doped low dielectric constant chemical vapor deposited oxides
(2001-06-01)
Wu, ZC
;
Shiung, ZW
;
Chiang, CC
;
Wu, WH
;
Chen, MC
This work compares the physical and electrical properties of two species of inorganic low dielectric constant (low-k) chemical vapor deposited (CVD) oxides, F-doped fluorinated silicate glass (FSG, k = 3.5) and C-doped organosilicate glass (OSG, k = 2.9). Experimental results indicate that FSG has a higher thermal stability >600 degreesC! than OSG (500 degreesC), based on the results of thermal annealing for 30 min in an N-2 ambient. The degradation of the low-k property in OSG is mainly due to the thermal decomposition of methyl (-CH3) groups at temperatures above 500 degreesC. For the Cu gated oxide-sandwiched low-k dielectric metal-insulator-semiconductor (MIS) capacitors, Cu penetration was observed in both FSG and OSG after the MIS capacitors were bias-temperature stressed at 250 and 150 degreesC, respectively, with an effective applied field of 0.8 MV/cm. Specifically, Cu appeared to drift more readily in OSG than in FSG, presumably because OSG has a more porous and less dense structure than FSG. The Cu permeation can be impeded by a thin nitride (SiN) barrier layer. (C) 2001 The Electrochemical Society.