Browsing by Author "Wu, ZC"

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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.
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.
Effects of BF2+ implantation on the oxidation resistance of copper films
(1999-06-01)
Wu, ZC
;
Liu, YL
;
Chen, MC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This work investigates the effects of BF2+ implantation on the oxidation resistance of copper films. The BF2+ ions were implanted into Cu films through a 1000 Angstrom thick screen SiO2 layer. We found that the oxidation resistance of Cu films can be significantly improved by BF2+ implantation at appropriate conditions. In particular, BF2+ implantation at 35 to 40 keV to a dose of 1 - 8 x 10(14) cm(-2) made the Cu films capable of resisting oxidation at temperatures up to 250 degrees C. At these BF2+ implantation energies, boron atoms of peak concentration were projected near the Cu surface; thus the diffusion paths of oxidizing species were efficiently blocked. Implantation at too high energy would result in greater depth of projection, thus a lower concentration of boron at the Cu surface; moreover, it generally leads to increased implantation defects that might serve as diffusion paths for the oxidation species. On the other hand, too high dosage implantation would also have an adverse effect on the capability of oxidation resistance for Cu films owing to the higher density of implantation damage as well as the formation of reactive fluorine compound (CuF2) near the Cu surface. (C) 1999 Elsevier Science S.A. All rights reserved.
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.
Electrical reliability issues of integrating thin Ta and TaN barriers with Cu and low-K dielectric
(1999-11-01)
Wu, ZC
;
Wang, CC
;
Wu, RG
;
Liu, YL
;
Chen, PS
This work investigates the integration of very thin sputtered Ta and reactively sputtered TaN barriers with Cu and a low-dielectric-constant (low-K) layer of poly(arylene ether) (PAE-2). It is found that Cu readily penetrates into PAE-2 and degrades its dielectric strength in metal-insulator semiconductor capacitors of Cu/PAE-2/Si structure at temperatures as low as 200 degrees C. Very thin Ta and TaN films of 25 nm thickness sandwiched between Cu and the low-K dielectric served as effective barriers during a 30 min thermal annealing at temperatures up to 400 and 450 degrees C, respectively. We propose a failure mechanism of outgassing induced gaseous stress of PAE-2 under the Ta film to explain its premature barrier degradation. The TaN barrier did not suffer from this gaseous stress problem because of its stronger adhesion to PAE-2 than that of Ta to PAE-2, leading to a better long-term reliability. (C) 1999 The Electrochemical Society. S0013-4651(99)04-046-X. All rights reserved.
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.
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.
Passivation of copper films with magnesium doping using recoil ion implantation
(2000-01-10)
Wu, ZC
;
Liu, YL
;
Chen, MC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This work investigates the effects of Ar+ ion implantation through a multilayer structure of SiO2(100 nm)/Mg(20 nm)/Cu/SiO2/Si on the oxidation resistance of Cu films. Experimental results indicate that implantation at 130 keV to a dose of 5 X 10(15) cm(-2) significantly enhances the oxidation resistance at temperatures up to 375 degrees C. At this energy, a small number of Mg atoms are knocked out, leading to formation of an impervious MgO barrier layer on the Cu surface, which effectively suppresses the oxidizing diffusion paths. (C) 2000 Elsevier Science S.A. All rights reserved.
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 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.
Physical and electrical characteristics of methylsilane- and trimethylsilane-doped low dielectric constant chemical vapor deposited oxides
(2001-06-01)
Wu, ZC
;
Shiung, ZW
;
Chiang, CC
;
Wu, WH
;
Chen, MC
This work investigates the physical and electrical properties of two species of inorganic C-doped low dielectric constant (low-k) chemical vapor deposited (CVD) organosilicate glasses (OSGs, alpha -SiCO:H). They are both deposited by plasma-enhanced CVD (PECVD) processes using methylsilane [(CH3)SiH3, 1 MS]- and trimethylsilane [(CH3)(3)SiH, 3 MS]-based gases as the reagents, and are designated as OSG1 and OSG2, respectively. Experimental results indicate that the thermal stability temperature of OSG1 is 500 degreesC, while that of OSG2 is 600 degreesC, based on the results of thermal annealing for 30 min in an N-2 ambient. The deterioration of the low-k property in OSG1 is predominately due to the thermal decomposition at temperatures above 500 degreesC of methyl (-CH3) groups, which are introduced to lower the density and polarizability of OSGs. For the Cu-gated oxide-sandwiched low-k dielectric metal-insulator-semiconductor (MIS) capacitors, Cu permeation was observed in both OSG1 and OSG2 after the MIS capacitors were bias-temperature stressed at 150 degreesC with an effective applied field of 0.8 MV/cm. Moreover, Cu appeared to drift more readily in OSG1 than in OSG2, presumably because OSG1 has a more porous and less cross-linked structure than OSG2. The Cu penetration can be mitigated by a thin nitride dielectric barrier. (C) 2001 The Electrochemical Society.
TDDB reliability improvement in Cu damascene by using a bilayer-structured PECVD SiC dielectric barrier
(2002)
Chiang, CC
;
Chen, MC
;
Wu, ZC
;
Li, LJ
;
Jang, SM
This work investigates the thermal stability and barrier characteristics of two species of silicon carbide dielectric films, alpha-SiCN with a dielectric constant of 4.9 and alpha-SiC with a dielectric constant of 3.8. The TDDB lifetime of Cu damascene metallization structure is greatly improved by using a alpha-SiCN/alpha-SiC bilayer dielectric stack as the etching stop layer (ESL). This improvement is presumably due to the alpha-SiC dielectric's lower leakage current, absence of nitridation on Cu surface, and better adhesion on Cu as well as OSG intermetal dielectric (IMD), though the alpha-SiC film has a very slow deposition rate. We believe that the alpha-SiCN/alpha-SiC bilayer dielectric is a favorable combination for the ESL because alpha-SiCN can protect alpha-SiC from plasma attack during the photoresist stripping.
TDDB reliability improvement of Cu damascene with a bilayer-structured alpha-SiC : H dielectric barrier
(2004-02-01)
Chiang, CC
;
Chen, MC
;
Wu, ZC
;
Li, LJ
;
Jang, SM
This work investigates the thermal stability and physical and barrier characteristics of two species of amorphous silicon carbide dielectric films: the nitrogen-containing alpha-SiCN film with a dielectric constant of 4.9 and the nitrogen-free alpha-SiC film with a dielectric constant of 3.8. The time-dependent-dielectric-breakdown (TDDB) lifetime of the Cu damascene metallization structure is greatly improved by using an alpha-SiCN/alpha-SiC bilayer dielectric stack as the barrier layer. This improvement is attributed to the lower leakage current of alpha-SiC, absence of nitridation on the Cu surface, and better adhesion of alpha-SiC on Cu and organosilicate glass intermetal dielectric. Although the alpha-SiC film has a very low deposition rate, the alpha-SiCN/alpha-SiC bilayer dielectric is a favorable combination for the barrier layer because alpha-SiCN can protect alpha-SiC from plasma attack, such as O-2 plasma attack during photoresist stripping and organosilicate plasma attack during organosilicate glass deposition. (C) 2004 The Electrochemical Society.