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Ambient pressure dried SiO2 aerogel film on GaAs for application to interlayer dielectrics
Thin Solid Films 420 – 421 (2002) 461–464
Ambient pressure dried SiO2 aerogel film on GaAs for application to interlayer dielectrics Sung-woo Parka, Sang-bae Junga, Jun-kyu Yanga, Hyung-ho Parka,*, Hae-cheon Kimb a Department of Ceramic Engineering, Yonsei University, 134 Shinchon-Dong, Seodaemun-Ku, Seoul 120-749, South Korea Semiconductor Technology Division, Electronics and Telecommunications Research Institute, 161 Kajong-Dong, Yusong-Ku, Taejon 305-350, South Korea
b
Abstract The interfacial layer between ambient pressure dried SiO2 aerogel film and GaAs has been examined with emphasis on varying the concentration of aerogel modification agent, trimethylchlorosilane (TMCS) in n-hexane solution. Through surface modification of aerogel, HCl was formed from the reaction between TMCS and –OH bonds of silica aerogel surface, and the GaAs surface could be influenced according to the TMCS concentration in surface modifying solution. When mol concentration of TMCS is 0.066%, the GaAs interface with aerogel was roughly etched from the reflection of surface microstructure of aerogel. However, when the aerogel was modified with 0.05 mol.% of TMCS, uniform shape of the GaAs interface could be obtained and the resultant electrical property, especially leakage current density, showed almost the same behavior when the aerogel was applied to Si system. 䊚 2002 Elsevier Science B.V. All rights reserved. Keywords: SiO2 aerogel; GaAs; Trimethylchlorosilane; Ambient pressure drying
1. Introduction In the technology for ultra large-scale integration technology devices, it is now no longer sufficient to adapt processing methods for known materials to the requirements of ever decreasing structure. As the devices become smaller and smaller, the distance of the electrically conducting interconnect lines also decreases. Thus, it has become dominant for higher device speed to guarantee the reduction of interconnection delay caused by parasitic capacitance between interlayer over the basic gate delay w1x. Therefore a lower dielectric constant material substituting for conventional interlayer dielectric (ILD) has become imperative. Now benzocyclobutene (BCB) polymer is used as an ILD due to its good properties, such as electrical behavior, gap filling, planarization, and etching process w2x. However, BCB is challenged by today’s thermal requirements of greater than 400 8C for CVD-W viayplug and post devicey contact anneal w3x. One of the various low-k candidate *Corresponding author. Tel.: q82-2-2123-2853; fax: q82-2-3655882. E-mail address: [email protected] (H.-h. Park).
materials in GaAs-based devices, SiO2 aerogel film has drawn an attention due to its adequate properties for ILD w4x. Supercritical drying or ambient pressure drying with surface modification can be applied to fabricate SiO2 aerogel film. In case of ambient pressure drying, through the surface modification, non-reactive Si–(CH3)3 group replaces the hydrogen of residual Si–OH group, which may cause irreversible shrinkage. This could maintain 3-dimensional structure with the aid of spring back effect even after ambient pressure drying. Meanwhile, in GaAs-based devices, instability of GaAs surface has been a major concern. For many years, high density of states on GaAs surface and nonuniform GaAs-oxides have been the obstacles for widening the usage of GaAs. Currently silicon nitride (Si3N4) is used to passivate GaAs surface w5,6x. Without Si3N4 GaAs surface is easily oxidized in atmosphere, resulting in the degradation of device properties. However, the surface treatment and deposition conditions for Si3N4 layer should be carefully controlled w7x. Thus, it is considered fabrication process is easier were it not for depositing passivation layer.
0040-6090/02/$ - see front matter 䊚 2002 Elsevier Science B.V. All rights reserved. PII: S 0 0 4 0 - 6 0 9 0 Ž 0 2 . 0 0 8 1 8 - 0
462
S.-w. Park et al. / Thin Solid Films 420 – 421 (2002) 461–464
In our previous study, SiO2 aerogel film deposited on GaAs was not properly formed with higher concentration of 6 vol.% trimethylchlorosilane (TMCS) in n-hexane due to sporadic etching w8x. However, Kim et al. reported that the properties of SiO2 aerogel film were hardly changed by slight variation in TMCS concentration from 6 vol.% if aging process was sufficiently conducted w9x. So, it can be estimated that slightly lower concentration of TMCS in hexane satisfied the formation of porous SiO2 aerogel film without severe modification of GaAs surface. Thus, this study intends to improve the properties of GaAs surface and interface without degradation of aerogel properties. 2. Experimental procedure The substrate used in this study was (1 0 0) oriented and n-doped GaAs with Si to a donor level of (0.6– 1)=1017 cmy3. Schottky diodes were fabricated as follows: first, low resistance-ohmic contact was formed on the back side of the wafers by e-beam evaporation of AuyGeyNiyAu followed by anneal at 350 8C. Prior to metal deposition, the wafers were HCl cleaned. Wafers were then degreased using a standard cleaning process with acetone, methanol, and de-ionized water. Sulfur passivated sample was prepared by immersing the HCl-cleaned sample in (NH4 )2 S solution for 10 min w10x. For preparing SiO2 aerogel film on GaAs, stock solution on GaAs was synthesized from tetraethoxysilane dissolved in ethanol using a two-step acidybase catalyzed procedure w11x. SiO2 stock solution was spindeposited on HCl-cleaned GaAs at 3000 rpm for 20 s. The wet-gel films were aged in ethanol for 12 h at 70 8C and then modified using n-hexane solution containing 0.05 (4.6 vol.%) or 0.066 mol.% (6 vol.%) of TMCS for 12 h at room temperature. The planar and crosssectional images of SiO2 aerogel film were observed using scanning electron microscopy (SEM, Hitachi S 4200). The X-ray photoelectron spectroscopy (XPS, VG Scientific, ESCALAB 220i-XL) measurement was carried out to characterize the chemical bonding state of the surface of substrate GaAs. The excitation source was monochromatic Al Ka radiation and narrow scan spectra of all region of interest were recorded with 20 eV of pass energy. Atomic force microscopy (AFM, Park Scientific Instrument) was employed to investigate the change on the morphology of substrate GaAs after the deposition of aerogel. Electrical characteristics of Schottky diode were evaluated from current–voltage (I– V) relation using HP4145B semiconductor parameter analyzer. 3. Results and discussion Fig. 1 is XPS spectra representing the interfacial bonding state of (a) HCl-cleaned and (c) sulfur-passi-
Fig. 1. The interfacial bonding state of (a) HCl-cleaned and (c) sulfurpassivated GaAs; (b) and (d) are those after removing SiO2 aerogel film aged for 12 h in EtOH.
vated GaAs surface, (b) and (d) are those after removing the upper SiO2 aerogel films aged for 12 h in EtOH. In Ga 3d peaks, three kinds of bonding state were found: Ga–As at 19.0 eV, Ga–S at 19.8 eV, and Ga–O at 20.3 eV. Meanwhile, with As 3d peaks, four different bonding states such as As–Ga at 41.3 eV, As–As (elemental As) at 42.0 eV, As–S at 42.9 eV, and As–O at 44.2 eV were observed. In Fig. 1a and b, it is found that the HClcleaned GaAs was oxidized after 12 h aging in EtOH. In case of S-passivated GaAs, even though GaAs surface was protected from air-oxidation due to stable Ga(or As)–S bonds, however, the surface was oxidized just the same as the HCl-cleaned GaAs and no more Ga(or As)–S bonds were found after 12 h aging in EtOH. Although sulfur passivation is effective in protecting GaAs surface from oxidation in many ways, however, through the aging, sulfur bonds can be desorbed from the GaAs surface w12,13x. For the preparation of SiO2 aerogel film, 12 h aging in EtOH is inevitable and this means that even with S-passivated GaAs, it seems to be impossible to protect GaAs surface during the formation of aerogel film. For ambient pressure drying of SiO2 aerogel, surface modification should be done for maintaining 3-dimensional microstructure of aerogel using modifying agent, as TMCS. However, in our previous study, 6 vol.% of
S.-w. Park et al. / Thin Solid Films 420 – 421 (2002) 461–464
463
Fig. 2. AFM images of GaAs surface after removing SiO2 aerogel film modified with (a) 0.05 and (b) 0.066 mol.% TMCS.
TMCS was found to damage GaAs surface, and with the SiO2 aerogelyGaAs system, it was impossible to obtain electrical properties due to severe modification of its interface. The substrate GaAs was roughly etched from the reflection of interfacial microstructure of aerogel w8x. Thus, in this study, the formation of SiO2 aerogel film on the HCl-cleaned GaAs using low TMCS concentration in n-hexane solution was tried. AFM images were taken from the GaAs surface after removal of SiO2 aerogel and given in Fig. 2. Two different mol concentrations of TMCS were used for modifying surface of aerogel; 0.05 and 0.066 mol.%. The roughness of GaAs interface after removing the aerogel modified with 0.05 mol.% was 0.36 nm, almost the same as that of HCl-treated GaAs w14x. Meanwhile, the roughness with 0.066 mol.% TMCS was 1.56 nm. As one can expect, the surface modification of SiO2 aerogel using 0.066 mol.% TMCS was too concentrate, but with 0.05 mol.% TMCS, the GaAs surface was almost unaffected from the TMCS. Furthermore, as shown in Fig. 3, with 0.05 mol.% TMCS, a typical SiO2 aerogel film was successfully formed on GaAs. The microstructure of aerogel shows a well-developed three-dimensional-network. Comparing with the case of 0.066 mol.% TMCS as surface modifying agent where the substrate GaAs was severely etched with the reflec-
tion of surface microstructure of aerogel, a lowering of TMCS mol concentration in modifying solution was revealed to form a well-developed interface with GaAs and fractal structure. Fig. 4 shows forwardyreverse of the I–V curves and characteristics of AuyGaAs Schottky diode. The GaAs was obtained after removal of upper SiO2 aerogel film prepared using 0.05 mol.% TMCS. In this figure, it is found that the leakage current density of GaAs interface is similar to that of HCl-cleaned GaAs surface. It could be considered that during the modification using TMCS of low concentration, the GaAs oxides were removed chemically and smoothly. Fig. 5 shows the leakage current behavior of ambient pressure dried SiO2 aerogel film on HCl-cleaned GaAs. It shows proper leakage current behavior, because in case of hexamethyldisilazane (another surface modifying agent of aerogel)-modified SiO2 aerogel film on GaAs, the leakage current density was measured as 10y5 A cmy2 with 5 V of applied voltage w8x. This was found to be higher than that observed with Si system because of interfacial GaAs-oxides which formed during the surface modification of aerogel. However, from the instability of GaAs surface, the leakage current behavior of 0.05 mol.% TMCS modified aerogel and GaAs system was found to be excellent one. From these
Fig. 3. (a) Planar and (b) cross-sectional SEM images of SiO2 aerogel film modified with 0.05 mol.% TMCS in n-hexane.
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S.-w. Park et al. / Thin Solid Films 420 – 421 (2002) 461–464
4. Conclusions Two different mol concentrations of TMCS in nhexane solution were used for the surface modification of SiO2 aerogel film on GaAs. With 0.066 mol.% of TMCS, the interfacial GaAs was roughly etched from the reflection of surface microstructure of aerogel, however, with 0.05 mol.%, the GaAs showed uniform interface and the aerogel film was formed with good characteristics. The interface of the GaAs with 0.05 mol.% TMCS modified aerogel showed leakage current behavior as that of the HCl-cleaned GaAs, and the SiO2 aerogelyGaAs MOS structure showed leakage current behavior as the same as Si based MOS using SiO2 aerogel. Acknowledgments Fig. 4. I–V characteristics of AuyGaAs Schottky diode; the contact was formed after the removal of 0.05 mol.% TMCS modified aerogel.
results, it was revealed that our actual SiO2 aerogely GaAs metal-oxide-semiconductor (MOS) showed its leakage behavior was mainly dependent on the SiO2 aerogel film itself rather than the interfacial GaAs.
Fig. 5. Leakage current behavior of SiO2 aerogel film on HCl-cleaned GaAs with 0.05 mol.% TMCS.
This work was supported by Electronics and Telecommunications Research Institute (ETRI) and Brain Korea 21 project. References w1x C.B. Case, A. Kornbit, K.S.Y Lau, N.H. Hendricks, Proc. ISMIC Conf. 104 (1995) 116. w2x G. Maier, Prog. Poym. Sci. 26 (2001) 3. w3x M.E. Mills, P. Townsend, D. Casillo, S. Martin, A. Achen, Microelectronic Eng. 33 (1997) 327. w4x H.S. Nalwa, Handbook of Low and High Dielectric Constant Materials and their Applications, first ed., Academic Press, Japan, 1999. w5x S. Pal, D.N. Bose, Appl. Sur. Sci. 181 (2001) 179. w6x K.L. Seaward, Appl. Phys. Lett. 61 (25) (1992) 21. w7x R. Soares, GaAs MESFET Circuit Design, first ed., Artech House, America, 1988. w8x S.W. Park, S.B. Jung, H.S. Jung, M.G. Kang, H.H. Park, H.C. Kim, Vacuum 67 (2002) 155. w9x J.H. Kim, S.B. Jung, H.H. Park, S.H. Hyun, Thin Solid Films 377–378 (2000) 467. w10x M.G. Kang, H.H. Park, J. Vac. Sci. Technol. A 17 (1999) 88. w11x C.J. Brinker, K.D. Keefer, K.W. Schaefer, C.S. Ashley, J. NonCryst. Solids 190 (1995) 264. w12x F. Barariu, H. Chiriac, F. Vinai, I. Murgulescu, E. Ferrarra, NanoStruct. Mater. 12 (1999) 1011. w13x P. Gorria, J.S. Gariataonandia, J.M. Barandiaran, J. Phys. Condens. Matt. 8 (1996) 5925. w14x M.G. Kang, H.H. Park, Thin Solid Films 332 (1998) 437.
Ambient pressure dried SiO2 aerogel film on GaAs for application to interlayer dielectrics Sung-woo Parka, Sang-bae Junga, Jun-kyu Yanga, Hyung-ho Parka,*, Hae-cheon Kimb a Department of Ceramic Engineering, Yonsei University, 134 Shinchon-Dong, Seodaemun-Ku, Seoul 120-749, South Korea Semiconductor Technology Division, Electronics and Telecommunications Research Institute, 161 Kajong-Dong, Yusong-Ku, Taejon 305-350, South Korea
b
Abstract The interfacial layer between ambient pressure dried SiO2 aerogel film and GaAs has been examined with emphasis on varying the concentration of aerogel modification agent, trimethylchlorosilane (TMCS) in n-hexane solution. Through surface modification of aerogel, HCl was formed from the reaction between TMCS and –OH bonds of silica aerogel surface, and the GaAs surface could be influenced according to the TMCS concentration in surface modifying solution. When mol concentration of TMCS is 0.066%, the GaAs interface with aerogel was roughly etched from the reflection of surface microstructure of aerogel. However, when the aerogel was modified with 0.05 mol.% of TMCS, uniform shape of the GaAs interface could be obtained and the resultant electrical property, especially leakage current density, showed almost the same behavior when the aerogel was applied to Si system. 䊚 2002 Elsevier Science B.V. All rights reserved. Keywords: SiO2 aerogel; GaAs; Trimethylchlorosilane; Ambient pressure drying
1. Introduction In the technology for ultra large-scale integration technology devices, it is now no longer sufficient to adapt processing methods for known materials to the requirements of ever decreasing structure. As the devices become smaller and smaller, the distance of the electrically conducting interconnect lines also decreases. Thus, it has become dominant for higher device speed to guarantee the reduction of interconnection delay caused by parasitic capacitance between interlayer over the basic gate delay w1x. Therefore a lower dielectric constant material substituting for conventional interlayer dielectric (ILD) has become imperative. Now benzocyclobutene (BCB) polymer is used as an ILD due to its good properties, such as electrical behavior, gap filling, planarization, and etching process w2x. However, BCB is challenged by today’s thermal requirements of greater than 400 8C for CVD-W viayplug and post devicey contact anneal w3x. One of the various low-k candidate *Corresponding author. Tel.: q82-2-2123-2853; fax: q82-2-3655882. E-mail address: [email protected] (H.-h. Park).
materials in GaAs-based devices, SiO2 aerogel film has drawn an attention due to its adequate properties for ILD w4x. Supercritical drying or ambient pressure drying with surface modification can be applied to fabricate SiO2 aerogel film. In case of ambient pressure drying, through the surface modification, non-reactive Si–(CH3)3 group replaces the hydrogen of residual Si–OH group, which may cause irreversible shrinkage. This could maintain 3-dimensional structure with the aid of spring back effect even after ambient pressure drying. Meanwhile, in GaAs-based devices, instability of GaAs surface has been a major concern. For many years, high density of states on GaAs surface and nonuniform GaAs-oxides have been the obstacles for widening the usage of GaAs. Currently silicon nitride (Si3N4) is used to passivate GaAs surface w5,6x. Without Si3N4 GaAs surface is easily oxidized in atmosphere, resulting in the degradation of device properties. However, the surface treatment and deposition conditions for Si3N4 layer should be carefully controlled w7x. Thus, it is considered fabrication process is easier were it not for depositing passivation layer.
0040-6090/02/$ - see front matter 䊚 2002 Elsevier Science B.V. All rights reserved. PII: S 0 0 4 0 - 6 0 9 0 Ž 0 2 . 0 0 8 1 8 - 0
462
S.-w. Park et al. / Thin Solid Films 420 – 421 (2002) 461–464
In our previous study, SiO2 aerogel film deposited on GaAs was not properly formed with higher concentration of 6 vol.% trimethylchlorosilane (TMCS) in n-hexane due to sporadic etching w8x. However, Kim et al. reported that the properties of SiO2 aerogel film were hardly changed by slight variation in TMCS concentration from 6 vol.% if aging process was sufficiently conducted w9x. So, it can be estimated that slightly lower concentration of TMCS in hexane satisfied the formation of porous SiO2 aerogel film without severe modification of GaAs surface. Thus, this study intends to improve the properties of GaAs surface and interface without degradation of aerogel properties. 2. Experimental procedure The substrate used in this study was (1 0 0) oriented and n-doped GaAs with Si to a donor level of (0.6– 1)=1017 cmy3. Schottky diodes were fabricated as follows: first, low resistance-ohmic contact was formed on the back side of the wafers by e-beam evaporation of AuyGeyNiyAu followed by anneal at 350 8C. Prior to metal deposition, the wafers were HCl cleaned. Wafers were then degreased using a standard cleaning process with acetone, methanol, and de-ionized water. Sulfur passivated sample was prepared by immersing the HCl-cleaned sample in (NH4 )2 S solution for 10 min w10x. For preparing SiO2 aerogel film on GaAs, stock solution on GaAs was synthesized from tetraethoxysilane dissolved in ethanol using a two-step acidybase catalyzed procedure w11x. SiO2 stock solution was spindeposited on HCl-cleaned GaAs at 3000 rpm for 20 s. The wet-gel films were aged in ethanol for 12 h at 70 8C and then modified using n-hexane solution containing 0.05 (4.6 vol.%) or 0.066 mol.% (6 vol.%) of TMCS for 12 h at room temperature. The planar and crosssectional images of SiO2 aerogel film were observed using scanning electron microscopy (SEM, Hitachi S 4200). The X-ray photoelectron spectroscopy (XPS, VG Scientific, ESCALAB 220i-XL) measurement was carried out to characterize the chemical bonding state of the surface of substrate GaAs. The excitation source was monochromatic Al Ka radiation and narrow scan spectra of all region of interest were recorded with 20 eV of pass energy. Atomic force microscopy (AFM, Park Scientific Instrument) was employed to investigate the change on the morphology of substrate GaAs after the deposition of aerogel. Electrical characteristics of Schottky diode were evaluated from current–voltage (I– V) relation using HP4145B semiconductor parameter analyzer. 3. Results and discussion Fig. 1 is XPS spectra representing the interfacial bonding state of (a) HCl-cleaned and (c) sulfur-passi-
Fig. 1. The interfacial bonding state of (a) HCl-cleaned and (c) sulfurpassivated GaAs; (b) and (d) are those after removing SiO2 aerogel film aged for 12 h in EtOH.
vated GaAs surface, (b) and (d) are those after removing the upper SiO2 aerogel films aged for 12 h in EtOH. In Ga 3d peaks, three kinds of bonding state were found: Ga–As at 19.0 eV, Ga–S at 19.8 eV, and Ga–O at 20.3 eV. Meanwhile, with As 3d peaks, four different bonding states such as As–Ga at 41.3 eV, As–As (elemental As) at 42.0 eV, As–S at 42.9 eV, and As–O at 44.2 eV were observed. In Fig. 1a and b, it is found that the HClcleaned GaAs was oxidized after 12 h aging in EtOH. In case of S-passivated GaAs, even though GaAs surface was protected from air-oxidation due to stable Ga(or As)–S bonds, however, the surface was oxidized just the same as the HCl-cleaned GaAs and no more Ga(or As)–S bonds were found after 12 h aging in EtOH. Although sulfur passivation is effective in protecting GaAs surface from oxidation in many ways, however, through the aging, sulfur bonds can be desorbed from the GaAs surface w12,13x. For the preparation of SiO2 aerogel film, 12 h aging in EtOH is inevitable and this means that even with S-passivated GaAs, it seems to be impossible to protect GaAs surface during the formation of aerogel film. For ambient pressure drying of SiO2 aerogel, surface modification should be done for maintaining 3-dimensional microstructure of aerogel using modifying agent, as TMCS. However, in our previous study, 6 vol.% of
S.-w. Park et al. / Thin Solid Films 420 – 421 (2002) 461–464
463
Fig. 2. AFM images of GaAs surface after removing SiO2 aerogel film modified with (a) 0.05 and (b) 0.066 mol.% TMCS.
TMCS was found to damage GaAs surface, and with the SiO2 aerogelyGaAs system, it was impossible to obtain electrical properties due to severe modification of its interface. The substrate GaAs was roughly etched from the reflection of interfacial microstructure of aerogel w8x. Thus, in this study, the formation of SiO2 aerogel film on the HCl-cleaned GaAs using low TMCS concentration in n-hexane solution was tried. AFM images were taken from the GaAs surface after removal of SiO2 aerogel and given in Fig. 2. Two different mol concentrations of TMCS were used for modifying surface of aerogel; 0.05 and 0.066 mol.%. The roughness of GaAs interface after removing the aerogel modified with 0.05 mol.% was 0.36 nm, almost the same as that of HCl-treated GaAs w14x. Meanwhile, the roughness with 0.066 mol.% TMCS was 1.56 nm. As one can expect, the surface modification of SiO2 aerogel using 0.066 mol.% TMCS was too concentrate, but with 0.05 mol.% TMCS, the GaAs surface was almost unaffected from the TMCS. Furthermore, as shown in Fig. 3, with 0.05 mol.% TMCS, a typical SiO2 aerogel film was successfully formed on GaAs. The microstructure of aerogel shows a well-developed three-dimensional-network. Comparing with the case of 0.066 mol.% TMCS as surface modifying agent where the substrate GaAs was severely etched with the reflec-
tion of surface microstructure of aerogel, a lowering of TMCS mol concentration in modifying solution was revealed to form a well-developed interface with GaAs and fractal structure. Fig. 4 shows forwardyreverse of the I–V curves and characteristics of AuyGaAs Schottky diode. The GaAs was obtained after removal of upper SiO2 aerogel film prepared using 0.05 mol.% TMCS. In this figure, it is found that the leakage current density of GaAs interface is similar to that of HCl-cleaned GaAs surface. It could be considered that during the modification using TMCS of low concentration, the GaAs oxides were removed chemically and smoothly. Fig. 5 shows the leakage current behavior of ambient pressure dried SiO2 aerogel film on HCl-cleaned GaAs. It shows proper leakage current behavior, because in case of hexamethyldisilazane (another surface modifying agent of aerogel)-modified SiO2 aerogel film on GaAs, the leakage current density was measured as 10y5 A cmy2 with 5 V of applied voltage w8x. This was found to be higher than that observed with Si system because of interfacial GaAs-oxides which formed during the surface modification of aerogel. However, from the instability of GaAs surface, the leakage current behavior of 0.05 mol.% TMCS modified aerogel and GaAs system was found to be excellent one. From these
Fig. 3. (a) Planar and (b) cross-sectional SEM images of SiO2 aerogel film modified with 0.05 mol.% TMCS in n-hexane.
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S.-w. Park et al. / Thin Solid Films 420 – 421 (2002) 461–464
4. Conclusions Two different mol concentrations of TMCS in nhexane solution were used for the surface modification of SiO2 aerogel film on GaAs. With 0.066 mol.% of TMCS, the interfacial GaAs was roughly etched from the reflection of surface microstructure of aerogel, however, with 0.05 mol.%, the GaAs showed uniform interface and the aerogel film was formed with good characteristics. The interface of the GaAs with 0.05 mol.% TMCS modified aerogel showed leakage current behavior as that of the HCl-cleaned GaAs, and the SiO2 aerogelyGaAs MOS structure showed leakage current behavior as the same as Si based MOS using SiO2 aerogel. Acknowledgments Fig. 4. I–V characteristics of AuyGaAs Schottky diode; the contact was formed after the removal of 0.05 mol.% TMCS modified aerogel.
results, it was revealed that our actual SiO2 aerogely GaAs metal-oxide-semiconductor (MOS) showed its leakage behavior was mainly dependent on the SiO2 aerogel film itself rather than the interfacial GaAs.
Fig. 5. Leakage current behavior of SiO2 aerogel film on HCl-cleaned GaAs with 0.05 mol.% TMCS.
This work was supported by Electronics and Telecommunications Research Institute (ETRI) and Brain Korea 21 project. References w1x C.B. Case, A. Kornbit, K.S.Y Lau, N.H. Hendricks, Proc. ISMIC Conf. 104 (1995) 116. w2x G. Maier, Prog. Poym. Sci. 26 (2001) 3. w3x M.E. Mills, P. Townsend, D. Casillo, S. Martin, A. Achen, Microelectronic Eng. 33 (1997) 327. w4x H.S. Nalwa, Handbook of Low and High Dielectric Constant Materials and their Applications, first ed., Academic Press, Japan, 1999. w5x S. Pal, D.N. Bose, Appl. Sur. Sci. 181 (2001) 179. w6x K.L. Seaward, Appl. Phys. Lett. 61 (25) (1992) 21. w7x R. Soares, GaAs MESFET Circuit Design, first ed., Artech House, America, 1988. w8x S.W. Park, S.B. Jung, H.S. Jung, M.G. Kang, H.H. Park, H.C. Kim, Vacuum 67 (2002) 155. w9x J.H. Kim, S.B. Jung, H.H. Park, S.H. Hyun, Thin Solid Films 377–378 (2000) 467. w10x M.G. Kang, H.H. Park, J. Vac. Sci. Technol. A 17 (1999) 88. w11x C.J. Brinker, K.D. Keefer, K.W. Schaefer, C.S. Ashley, J. NonCryst. Solids 190 (1995) 264. w12x F. Barariu, H. Chiriac, F. Vinai, I. Murgulescu, E. Ferrarra, NanoStruct. Mater. 12 (1999) 1011. w13x P. Gorria, J.S. Gariataonandia, J.M. Barandiaran, J. Phys. Condens. Matt. 8 (1996) 5925. w14x M.G. Kang, H.H. Park, Thin Solid Films 332 (1998) 437.