to accomplish deposition of sio 2 layers on semiconductor structures through use of the invention , tetramethylsilane ( tms ) is used as the precursor for its quality and its ability to enable low temperature oxide growth . tms is known to be non - toxic and non - pyrophoric and its high vapor pressure ˜ 580 torr allows for conventional mfc use at room temperature . thus , tms avoids the health and safety issues associated with silane and the manufacturing complexities inherent with teos . further , each parent tms molecule ( si ( ch 3 ) 4 )) contains half as much carbon and 3 / 5ths as much hydrogen as a teos molecule ( si ( oc 2 h 5 ) 4 ), and it is hypothesized that carbon and hydrogen free films will be obtainable at lower temperatures . also , s greater dissociation is possible at lower temperatures with tms because its si -- c bond has a lower bond energy than the si -- h bond in silane and si -- o bond in teos . applicants have found that all of these features of tms are indeed valid and most importantly have shown , for the first time , that thin - film transistor ( tft ) gate quality oxides can be deposited at as low as 130 ° c . using tetramethylsilane in a plasma reaction . tms oxide deposition conditions have been found to mimic very closely , the conditions found to produce high quality pecvd teos oxides in the semiconductor industry . in particular , a relatively high pressure of about 3 torr is used to decrease the plasma potential , increase the atomic - oxygen concentration and lessen the effect of residual chamber gases . helium can be added to the precursor gases . when added , it is done so for several important reasons : it improves deposition uniformity ; it aids in tms fragmentation by the penning effect , he ion bombardment or both ; it does not participate in chemical bonds ; its small size prevents its inclusion in the film from disrupting the growing film ; and it causes negligible ion damage to the growing film . sixty sio 2 400 - 850 å thin films were deposited on 6 &# 34 ; 10 - 25 ω - cm p - type & lt ; 100 & gt ; c - si wafers using tms ( alfa aesar 99 . 9 %) and uhp o 2 . the depositions were performed in a capacitively coupled rf ( 13 . 56 mhz ) pecvd reactor , schematically shown in fig1 . a 1 cm separation was used between the 6 &# 34 ; wafer , teos showerhead top electrode and the heated sample stage . the tms vapor was delivered under its own vapor pressure , without heating . the vapor was metered using a standard mfc with an assumed calibration factor of 0 . 18 relative to n 2 . each wafer sample was initially cleaned in acetone , isopropyl alcohol , and deionized water before the native oxide was stripped in 10 : 1 buffered hf ( boe ). the base pressure was & lt ; 1 × 10 - 6 torr and processing pressures ranged from 0 . 5 torr to 8 torr . for all samples , a predeposition o 2 plasma ( no tms ) surface treatment was performed prior to the bulk oxide deposition to remove any residual carbonaceous matter and to define the si wafer surface . following the predeposition , a similar o 2 plasma without tms was struck at the same pressure , rf power , and gas flow rates as desired for the bulk oxide deposition . the bulk petms - ox film deposition then took place with injection of a small tms flow into the stabilized plasma . to stop the deposition , the tms flow was halted , but the plasma remained on to remove any residual tms byproducts . the rf power , deposition temperature , and o 2 and tms flow rates were varied between 40 - 70 w , 40 - 250 ° c ., 31 . 2 - 660 sccm and 0 . 43 - 1 . 2 sccm , respectively . uhp he dilution was also investigated in some predepositions and bulk depositions to mimic published accounts of teos and silane based pecvd oxide deposition conditions . following the petms - ox growth , the wafer samples were halved . on one - half wafer , mos - capacitance structures were fabricated by high vacuum thermal evaporation of al through a shadow mask , forming 1 mm 2 gate electrodes on the oxide and a blanket al deposition on the boe - etched wafer &# 39 ; s backside . on the mos - capacitors , both quasi - static and high - frequency c - v , and i - v dynamic sweeps ( 1 v / s ) were performed with a keithly ki - 82 system . on the second half wafer , film thicknesses were measured with elipsometry and ftir , boe etch rate , and p - etch ( hf : hno 3 : h 2 o = 1 . 5 : 1 : 30 ) rate measurements were performed . one very sensitive measure of a deposited oxide &# 39 ; s quality is its current - voltage ( i - v ) dynamic sweep behavior . a quality oxide will display very low leakage currents of & lt ; 10 - 8 a / cm 2 at electric fields below that required for the onset of fowler - norheim ( f - n ) tunneling ( typically 5 - 6 mv / cm ). the i - v dynamic sweeps for petms - ox films deposited at temperatures between 40 ° c . and 250 ° c . at 40 w and 8 torr with he : o 2 : tms flows of 200 : 31 . 2 : 1 . 18 sccms are shown in fig2 . fig2 shows that a 250 ° c . oxide , produced under the above deposition conditions , has a leakage current of & lt ; 10 - 9 a / cm 2 at electric fields below 3 mv / cm , but , the leakage current for the lower temperature films becomes progressively higher , with reduced deposition temperature . also , the leakage current density for the 40 - 170 ° c . films rises quickly and then becomes saturated ( shows a &# 34 ; ledge &# 34 ;) this behavior has been studied previously in deposited oxides and it results from localized electric field reductions due to electron trapping in the oxides . although these current ledges can occur in deposited oxides which are silicon rich , the ledges observed in fig2 correlate to the presence of si -- oh in the lower temperature films . fig3 shows this . it gives the ir spectra for the same deposition conditions presented in fig2 along with the spectrum for a thermally grown oxide for reference . these data show that while the thermal oxide and the petms oxides have similar si -- o bending , and rocking peaks present at wavenumbers of ˜ 808 , and ˜ 457 cm - 1 , respectively , there is a si -- oh peak at ˜ 933 cm - 1 , which is not present in the thermal oxide or the 250 ° c . oxide . this peak becomes increasingly apparent in the petms oxides as the deposited temperature is reduced . furthermore , the si -- o stretching peak for petms oxides appears at 1062 cm - 1 for the 250 ° c . film and shifts to higher wavenumbers as the deposition temperature is reduced . in fact , the si -- o stretching peak for the 40 ° c . oxide is found to be the same as that for the thermal oxide , 1073 cm - 1 . it has been shown that the location of the si -- o -- si stretching peak increases in thermal oxides as their density decreases . however , the viscoelastic relaxation induced density decrease which results from increasing the growth temperature between 700 ° c . and 1100 ° c . in thermal oxides cannot occur in the petms oxides because the deposition temperature is too low . alternatively , it is likely that stress relaxation occurs due to the increased incorporation of non - bridging si -- oh bonds in these oxides . it is noted that the measured film thicknesses were found to be 694 , 856 , 739 , 709 , and 622 å for the 250 , 170 , 130 , 90 , and 40 ° c . films , respectively . therefore , the larger concentrations of si -- oh found with reduced deposition temperatures are not the result of thicker films at the reduced temperatures . also , no carbon by - products were detected by ftir for any of the films deposited in this work . to further study the influence of the si -- oh incorporation on the properties of the sio 2 films , the deposition and etch rates were examined . fig4 shows that deposition rate increased from 231 å / min to 356 å / min , while the boe relative etch rate increased from 4 . 0 to 7 . 5 , between the 250 ° c . and 40 ° c . films , respectively . correspondingly , the p - relative etch rate increased from 3 . 7 to 15 . 8 . these results show that under conditions which are favorable for si -- oh incorporation , a stress reduction indicated by the si -- o stretching peak location accompanies a reduction in the film &# 39 ; s density , leading to higher etch rates and a degradation of the film &# 39 ; s dielectric properties . note that a higher etch rate implies a lower quality film . in an attempt to remove the si -- oh from the lower temperature films , both the deposition pressure and the tms flow rate were investigated . the as - deposited petms - ox film deposition rate and boe and p - etch rates relative to thermally grown oxide for films deposited at 250 ° c . and 40 w with o 2 : tms 660 : 1 . 2 sccm are shown in fig5 . fig5 shows that as the deposition pressure is reduced from 8 torr to 1 . 4 torr , the deposition rate is seen to decrease from 178 . 7 å / min to 140 . 53 å / min , while the relative etch rate decreased from 3 . 26 to 2 . 04 in a boe , and 5 . 22 to 2 . 46 for a p - etch . this reduction in deposition raze at the lower deposition pressures is likely due to the reduced tms concentration in the reactor . the lower p - and boe relative etch rates at these lower deposition pressures suggests that higher density films , with possibly less by - products , are formed due to the higher degree of ion bombardment at lower deposition pressures . based solely on fig5 one might expect higher quality oxides at lower temperatures , if a 1 . 4 torr deposition pressure is used . however , as the deposition pressure is decreased in the reactor , a flow - field non - uniformity effect arose due to non - symmetric exhaust pumping . this flow field effect was detected by wafer mapping of current spikes in the dynamic i - v sweeps ( wafer maps not shown ). the number and severity of the spikes was found to become progressively worse as the deposition pressure was reduced . it was therefore found that careful consideration had to be given to flow design to assure uniformity thereof . as an example , fig6 shows the i - v dynamic sweeps for 12 mos - capacitors on a single petms oxide , deposited at 1 . 4 torr , 250 ° c ., and 40 w with 660 : 1 . 2 sccm of o 2 and tms , respectively . here , non - symmetric exhaust pumping was present . to determine the physical mechanism behind these current spikes , successive dynamic sweeps were performed on a 1 . 4 torr oxide mos - capacitor . these tests showed that the spikes were filamentary electron conduction paths which burn - out to a greater degree with each successive sweep . therefore , despite the fact that these spikes could be eliminated by voltage cycling , the unwanted current spikes became more prevalent and pronounced at reduced deposition pressures . the petms oxide deposition rate as a function of tms flow rate is shown in fig7 for films deposited at 130 ° c . and 8 torr ( with he dilution ) compared to films deposited at 250 ° c . and 3 torr . for the 250 ° c . films , fig7 shows that the oxide deposition rate increases in direct proportion to the tms flow rate at 154 å / min - sccm . also , the 130 ° c . oxides deposited at tms flow rates up to 0 . 5 sccm , appear to follow a similar deposition rate behavior . however , it is clear from fig7 that 130 ° c . films , deposited at tms flow rates above 0 . 5 sccm , deposit at an increasingly faster rate with increasing tms flows than do the 250 ° c . oxides . in looking at the ftir for these films , the 250 ° c . oxides showed no obvious signs of si -- oh while the 130 ° c . films deposited at 0 . 79 and 1 . 2 sccm displayed clear si -- oh absorption peeks at 933 cm - 1 ( implying less dense oxides ). similarly , the i - v dynamic sweeps for the 250 ° c . oxides did not show si -- oh electron trapping ledges , but i - v spikes were present due to the reduced deposition pressure , while the 130 ° c . films deposited at tms flow rates above 0 . 62 sccm did have trapping ledges . the results discussed above and fig7 therefore , show that at reduced temperatures , si -- oh incorporation in the petms - ox can be reduced by reducing the tms flow feed rate . the i - v dynamic sweeps and high - frequency c - v characteristics for as - grown thermal oxides ( see fig8 ) are shown in fig9 and 10 , along with the typical characteristics for gate quality tms films deposited at 250 ° c . and 130 ° c . here , the tms deposition conditions used are centered around the 8 torr deposition pressure to reduce the flow field non - uniformity effects and low tms flow rates for the 130 ° c . film , since these were found to reduce si -- oh related electron trapping . specifically , the 250 ° c . deposition conditions are 8 torr , 40 w and 660 : 1 . 2 o 2 : tms sccms , and the 130 ° c . oxide deposition conditions are 8 torr , 45 w , 200 : 31 : 0 . 43 sccms of he : o 2 : tms . it is noted that he was found to be very advantageous for low temperature oxide films ( e . g ., 130 ° c .). the 130 ° c . oxide films , for example , were found to have reduced trapping ledge levels when deposition was performed with a high degree of helium dilution . in fig9 it can be seen that i - v characteristics of both the 130 ° c . and 250 ° c . tms oxides are similar to the as - grown thermal oxide in that they all have leakage currents below 10 - 9 a / cm 2 at electric fields & lt ; 4 . 5 mv / cm . the petms oxides also exhibit breakdown fields of & gt ; 8 mv / cm whereas the thermal oxide has a breakdown field of & gt ; 10 mv / cm . the petms oxides do , however , show a slight trapping ledge in both 130 ° c . and 250 ° c . oxides which indicates small amounts of deep electron traps to be present . this fact is further evidenced by the c - v characteristics for the oxides . the results shown in fig9 indicate that by controlling the feed rate of tms , that sio 2 films produced by the invention at relatively low temperatures ( e . g ., 130 ° c .) are substantially equivalent in characteristics to sio 2 films produced at 250 ° c . in fig1 , it can be seen that while the thermal oxide has a flat band voltage of vfb =- 1 . 82 , hysteresis of h = 0 , effective oxide charge of qeff = 7 × 10 - 9 / cm 2 , and interface state density of dit = 0 . 7 × 10 12 cm - 2 ev - 1 , the 250 ° c . petms oxide has vfb =- 2 . 55 , h = 0 . 1 , q eff = 111 × 10 - 9 coul / cm 2 , and d it = 0 . 5 × 10 12 cm - 2 ev - 1 while the 130 ° c . oxide has vfb =- 2 . 88 , h = 0 . 5 , q eff = 120 × 10 - 9 coul / cm 2 , and d it = 4 . 8 × 10 12 cm - 2 ev - 1 . in summary , high quality silicon dioxide films have been deposited at temperatures of 130 ° c . and 250 ° c ., using tetramethylsilane in a capacitively coupled pecvd system . under the best conditions , the unannealed al / petms - ox / c - si capacitor structures displayed flat band voltages of v fb .=- 2 . 9 v and breakdown fields ( v bd ) in excess of 8 mv / cm . those petms - ox films also showed low leakage current densities & lt ; 10 - 9 a / cm 2 which could be maintained up to fields in excess of 4 . 5 mv / cm . it was found for the first time that tms oxide deposition rates could be increased by lowering deposition temperatures . it was also found that he dilution could be used to reduce trapping in low temperature deposition temperature films . also , by carefully metering the tms flow rates into the reactor , the presence of oh inclusions in the sio 2 films could be substantially reduced , leading to high quality films at temperatures substantially below any reported by others . importantly , there appears to be no reason why such high quality films cannot be produced at even lower temperatures , by adjusting the tms flow rate downward to prevent an excess of oh ions from being incorporated into the sio 2 layer . of course , such lower tms flow rates imply longer processing times -- however they allow film depositions on polymeric substrates -- an important commercial application . it should be understood that the foregoing description is only illustrative of the invention . various alternatives and modifications can be devised by those skilled in the art without departing from the invention . for example , while a capacitively coupled plasma reactor was utilized in producing the sio 2 films , other plasma reactors can also be used . further , instead of mixing the gases in the reaction chamber , they can be mixed in an upstream chamber and then fed into the reaction chamber . accordingly , the present invention is intended to embrace all such alternatives , modifications and variances which fall within the scope of the appended claims .