Yuko Nishimoto

Silicon Dioxide Deposition by Atmospheric Pressure and Low‐Temperature CVD Using TEOS and Ozone

We report characteristics of the film deposited by an atmospheric pressure and low‐temperature CVD process using TEOS and ozone. Nondoped silicon oxide was deposited on thermally grown oxide, silicon, and aluminum steps. The film surface was very smooth even on aluminum lines and step coverage of the films changed from isotropic to flow shape with ozone concentration increase. This is one of the largest advantages of this CVD technology and is promising for advanced VLSI device fabrication. The film has tensile stress of less than , typically , low enough to fabricate VLSI devices. Film shrinkage was 5% in the film deposited at the higher ozone concentration when annealed at 950°C, which was comparable to that of the conventionally deposited films. The largest thickness without any cracks varied depending on deposition conditions. A thickness of 2 μm without cracks was obtained at 400°C and 0.1 μm/min deposition rate with an ozone concentration of 4.8%. Particle generation was very low and the number of particles of more than 0.3 μm were less than 20 on a 6 in. diam wafer.

Dependence of Deposition Characteristics on Base Materials in TEOS and Ozone CVD at Atmospheric Pressure

TEOS and O 3 atmospheric pressure chemical vapor deposition has excellent conformality, film quality, and low particle generation; however, deposition rate obtained on thermal oxide is lower than that on silicon and the films have rough surface and higher etching rates if deposited with high ozone concentrations. When deposited on silicon with a higher ozone concentration, films of sufficiently high quality are obtained. This drawback of the low film quality has been removed by double-layer deposition with two different ozone concentrations on thermal oxide, depositing the thin films at first with a low ozone concentration on thermal oxide and next with a high ozone concentration to the desired thickness. The film quality, namely, etch rate, depends on the thickness and ozone concentration for the first layer. The thicker the first film and the higher the ozone concentration, the better the film quality. By adjusting the first layers thickness and ozone concentration, films can be obtained with quality that is sufficiently high for VLSI device applications

Surface Modification of Base Materials for TEOS / O 3 Atmospheric Pressure Chemical Vapor Deposition

Atmospheric pressure tetraethyloxysilicane (TEOS)/O 3 chemically vapor deposited provides excellent step coverage for submicron device structures ; however, the proeprties of the deposited films depend on the surface characteristics of the base materials being used. To illustrate this dependence, the deposition rate of nondped silicon dioxide obtained on a thermal oxide surface is significantly lower than the deposition rate obtained on a abre silicon surface. A new method to eliminate this base material dependence involving plasma treatment has been investigated. The optimum treatment consists of exposing the base materials to a nitrogen plasma for 1 min while maintaining the base materials at 250°C. Films deposited on thermal oxide base materials which have first been treated by this new method were found to have the same deposition rate, aqueous HF etch rate, and surface morphology as those films deposited on untreated bare silicon

Thermal desorption spectra of SiO2 films deposited on Si and on thermal SiO2 by tetraethylorthosilicate/O3 atmospheric-pressure chemical vapor deposition

SiO2 films deposited on Si and on thermal SiO2 by tetraethylorthosilicate [TEOS,u200aSi(OC2H5)4]/O3 atmospheric-pressure chemical vapor deposition (APCVD) were analyzed by thermal desorption spectra (TDS). The TDS results show that more silanols were incorporated during deposition and more water was absorbed during and after deposition in films deposited on Si substrates than on thermal oxide substrates. The latter result indicates that the elimination of water by-products is not the limiting step in TEOS/O3 APCVD. Based on the former result, a silanol model was proposed for the surface processes. On surfaces with a uniform and high density of silanol sites, or on which silanols readily form under TEOS/O3 APCVD conditions, the active silanol groups in the gas phase contribute to film formation and replenish silanol sites, resulting in continuous, high growth rates. On surfaces with few silanol sites, it is difficult to form silanol sites and the nonsilanol-containing polysiloxanes contribute to film formation...

TEOS and Ozone Atmospheric Pressure CVD of Borophosphosilicate Glass Films Using Triethylborate and Trimethylphosphate

Borophosphosilicate glass (BPSG) films were deposited using tetraethoxysilane (TEOS), triethylborate (TEB), trimethylphosphate (TMOP), and ozone at atmospheric pressure. A uniform distribution of borate was obtained throughout the thickness of the film using TEB instead of trimethylborate (TMB). The deposition rates were characterized as functions of dopant gas flow rates, deposition temperature, and ozone concentration. Both dopants enhanced the deposition rates. The deposition rates did not show ozone concentration dependence. The typical deposition rate was as high as 0.2 [mu]m/min. The borate and phosphate contents were characterized as functions of dopant gas flow rates, and deposition temperature. They ranged from 8 to 15 mole percent (m/o) for borate and from 3 to 8 m/o for phosphate. The film stress was as low as 1 [times] 10[sup 9] dyn/cm[sup 2] (tensile) when deposited at 400 C with 4% ozone and relaxed to [minus]0.7 [times] 10[sup 9] dyn/cm[sup 2] a week after deposition. The film shrinkage was minimum (5%) at 400 C, and decreased with increasing ozone concentration. The step-coverage of an as-deposited film was superior, hence, the film reflowed smoothly even after the low temperature (850 C) annealing.

Low temperature, atmospheric pressure CVD using hexamethyldisiloxane and ozone

Hexamethyldisiloxane (HMDSO), a new organic silicon source, was studied for use in depositing high quality non-doped silicon dioxide for very large scale integrated device fabrication. The high vapor pressure, 20 mm Hg at 13 o C, makes it easier to use than other conventional sources, such as tetraethyorthosilicate (TEOS). A deposition rate of 0.1 μm/min at 400 o C with 2-6% ozone was obtained making it suitable for production oxide applications. Step coverage was found to be excellent and varied from conformal to «flow»-shaped with a 40 degree step angle

Low Temperature Chemical Vapor Deposition of High Quality SiO2 Film Using Helicon Plasma Source

Helicon plasma, a new compact high density plasma source, was investigated for chemical vapor deposition (CVD) of dielectric oxide. High quality films having low compressive stress of 1-2 × 10 9 dyne/cm 2 , lower SiOH content with water-blocking capability and a wet HF etch rate comparable to that of thermal oxide were obtained. Sub-half-micron gaps with high aspect ratio were successfully filled by applying a substrate bias. A combination of biased helicon plasma CVD and atmospheric pressure (AP) tetraethyl orthosilicate [TEOS]-O 3 nondoped silicate glass (NSG) which has self-planarizing characteristics is proposed for planarization without chemical-mechanical polish (CMP)

Copper Barrier Properties of Low Dielectric Constant SiOCNH Film Deposited by Plasma-Enhanced CVD

We have developed a silicon oxi-carbide and nitride (SiOCNH) barrier film to protect against copper (Cu) thermal diffusion by plasma-enhanced chemical vapor deposition (PECVD) using hexamethyldisiloxane, nitrous oxide (N 2 O), and ammonia (NH 3 ) gases. We tried to enhance the Cu barrier property and etching selectivity for low dielectric constant (low-k) film by adding nitrogen (N) into the barrier silicon oxicarbide (SiOCH) film. The film protects against Cu thermal diffusion at 450°C for 4 h in N 2 . The k value is lower than that for PECVD silicon nitride (SiN) and silicon carbide (SiC) films, but is slightly larger than that of PECVD SiOCH film; it is in the range of 4.17 to 5.21. The leakage current is as low as the value of PECVD SiN film; it is in the range of 10 -9 to 10 -10 A/cm 2 at I MV/cm. This value decreases with increasing NH 3 flow rate. However, Cu thermal diffusion increased with increasing NH 3 flow rate. The diffusion depth is less than 20 nm. The diffusion behavior can be explained by the result that diffusion is controlled by the small pore size, high density, and small compressive stress in SiOCNH film. The average pore size is smaller than 0.49 nm, which is generally smaller than that of SiOCH film deposited using N 2 O gas. The film density is greater than 2.14 g/cm 3 , which is larger than that of SiOCH film. The etching selectivity to silicon oxide deposited by PECVD using tetraethoxysilane (PECVD tetraethylorthosiloxane, TEOS SiO 2 ) film is ∼15. The dynamic hardness is almost the same as the value of quartz and is 2.0 to 2.5 times larger than the value of PECVD TEOS SiO 2 film. The Youngs modulus was ∼2.0 and 2.5 times larger than the values of quartz and PECVD TEOS SiO 2 film, respectively. The adhesion strength on Cu is the same as that of PECVD SiOCH film and slightly smaller than that of PECVD SiN film. The desorption of ammonium (NH + 3) ions from SiOCNH film, which is known as the cause of poisoned via-holes, is very low.

Low Temperature Chemical Vapor Deposition of Dielectric Films using Ozone and Organosilane

The silicon dioxide film was chemically vapor deposited at low temperature below 450C using ozone and silicon alkoxide r a source. The conventional pyrolytic decomposition of TEoS (Tetraethylorthosilicate) has required temperature above 650c to form this film, The doped oxide film such as PSG, BSG, or BPSG was also formed by adding alkoxide of phosphorus or boron as a dopant. This doped oxide film is ,rr] useful as the interlayer dielectric film for high aensity devices. The step coverage on the. fine pattern can be enhanced because thi; CVD method enables isotropic deposition and self-planarization. This paper outlines the study of each parameter to control this CVD reaction, orrrideration of the reaction mechanisms and evaluation results of film properties.

Low-Temperature Atmospheric-Pressure Chemical Vapor Deposition Using 2, 4, 6, 8-Tetramethylcyclotetrasiloxane and Ozone

Tetramethylcyclotetrasiloxane (TMCTS) was studied as a possible silicon source for atmospheric-pressure chemical vapor deposition (CVD) using ozone chemistry. High-quality silicon dioxide films were produced at 400° C with a typical deposition rate of 100 nm/min. During the study, TMCTS was observed to have base material dependent characteristics which varied as a function of both deposition temperature and ozone concentration. The deposition rate vs deposition temperature relationship indicated that the film structure varies slightly as a function of the deposition temperature. Data collected for film shrinkage after annealing supported these structural changes. The typical as-deposited film stress was 2×109 dyn/cm2 (tensile). The step coverage varied from conformal to flow-shaped depending on the deposition temperature and ozone concentration. The results of this study show that TMCTS is a promising precursor for use in intermetal dielectric applications for ultra large-scale integration (ULSI) devices.