PSG Films Research Articles

Study of PSG Thickness Uniformity Influencing Factors in LPCVD

In the fabrication of SiC high-temperature sensors, the phosphosilicate glass film (PSG) is deposited on the SiC wafer as the intermediate layer, achieving the bonding of two SiC wafers. The ease of bonding is affected by the PSG film thickness uniformity. In this paper, the flow field distribution in the LPCVD tube is simulated under different deposition conditions,obtaining the wafer surface uniformity of gas flow distribution, which was verified by the experiment, The aim of this work is to study the impact of several deposition conditions such as the location of SiC wafers, wafer inclination and wafer spacing on the thickness uniformity of PSG film. Experimental results show that SiC wafer position in the tube and its own inclination and wafer spacing affect gas flow field on the SiC wafer surface,leading to uneven distribution of gas flow, thus affect the thickness uniformity of PSG.

Deposition of borophosphosilicate glass films using the TEOS–dimethylphosphite–trimethylborate system

Modernization of horizontal low pressure deposition system has been performed. The liquid source delivery system using the bubblers has been developed. The PSG and BPSG film deposition processes and film properties using TEOS-Dimethylphosphite-TEB system have been studied. It is shown that the use of dimethylphosphite allows varying the phosphorus concentration in the wide range. It is found that the optimal range of the total boron and phosphorus concentration ensuring the acceptable topology planarity and resistance to defect formation during storage is 8.7±0.3 wt% when the phosphorus concentration is 3.0—3.8 wt%. It is found that at use of the TEOS-DMP-TEB system the depletion of the phosphorus concentration along reaction zone does not occur, and the total dopant concentration is practically constant. At the same time the deposition rate of BPSG films is 9.0—10.0 nm/min and the good film thickness uniformity are ensured. The as-deposited films have “mirror-like surface” that is proof of minimal surface roughness. The BPSG films with optimal composition are characterized by the reduced reaction capability against atmospheric moisture.

High Doping HDP PSG Process Development

In this study, we report a 9wt% PSG film for increasing the etch selectivity to poly gate by changing the sputtering gas from Argon to Helium to avoid the film haze and other issues. Due to the change of new sputtering gas, a new recipe has been developed to fine tune key film properties, including within wafer thickness non-uniformity (WIW NU%) and phosphor concentration uniform-ity in three dimensions. In order to get desired profile after etch process, it is very crucial to control the profile of initial layer and bulk PSG film phosphor doping concentration. Therefore, a new concept which is called "PH3 flow ramp up" has been developed and implemented. Other key concern of integration, i.e., how to control "flower pattern" shape is also discussed in this paper.

Flexible Poly(amic acid) Conducting Polymers: Effect of Chemical Composition on Structural, Electrochemical, and Mechanical Properties

A new approach for creating flexible, mechanically strong poly(amic acid) (PAA) hybrid copolymers is described. The reduction of gold salts to gold nanoparticles by PAA coupled with its copolymerization in the presence of various silanes (e.g., N-[3-(trimethoxysilyl)-propyl] aniline (TMOSPA), 3-aminopropyl-trimethoxysilane (APTMOS), dichlorodimethylsilane (DCMS), and tetramethoxysilane (TMOS)) has enabled the design of a series of polymeric films. The resulting poly(amic acid), silane, and gold (PSG) solutions were employed for the fabrication of flexible, ternary polymers with a minimum bend ratio of 3 mm using thermal desolvation and/or wet-phase inversion techniques. By controlling the composition and synthesis conditions, porous PSG films were produced that are flexible or rigid, transparent or opaque, and/or mechanically strong. (1)H NMR, (13)C NMR, and Fourier transform infrared spectroscopy (FTIR) characterization results showed that the carboxylic acid moieties were retained in the PSG copolymer. Thermal stabilities with degradation characteristics of the polymers were determined using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Although structurally and morphologically different from the parent PAA, copolymerization with silanes had significantly improved the mechanical and interfacial property of the PSG class of films.

Development of P-Doped SiO[sub 2] as Proton Exchange Membrane for Microfuel Cells

Phosphorus-doped silicon dioxide PSG thin films with improved ionic conductivity were deposited via plasma-enhanced chemical vapor deposition for application as a thin-film proton exchange membrane PEM in microfabricated fuel cells. More than three orders of magnitude improvement in the ionic conductivity is obtained by P doping of low-temperature deposited SiO2. The area resistance of 3 m thick film of PSG is comparable to a 200 m thick film of Nafion. Application of these PSG films as PEM in microfuel cells yielded more than one order of magnitude improvement in power density compared to low-temperature, undoped SiO2 membranes. © 2005 The Electrochemical Society. DOI: 10.1149/1.2050587 All rights reserved.

Novel Common Cell Via and Etch Stopper Technology for 0.25 μM 1T1C 32 MBIT FRAM

In the 0.25 μm FRAM technology generation, it is extremely difficult to define the hole-type cell via on very small top electrode area, because there is no process margin for the hole type cell via. Therefore, a runner via technology based on line-type cell via with Ir etch stopper is developed for 0.25 μm FRAM technology generation. However, it was found that the severe charge degradation occurred during the runner cell via process. It was found that the stress of Ir film plays a dominant role in degrading the capacitor value. Since the Ir film shows severe severe stress variation from compressive to tensile during heating and cooling, the ferroelectric capacitors using the Ir etch stopper show the charge degradation during integration. Therefore, we developed a common cell via scheme and stable PE-SiN etch stopper which possess compressive stress and high etching selectivity against PSG film for replacing Ir etch stopper. The polarization value of ferrolectric capacitor was not degraded after etch-stopper process. The 0.25 μm ferroelectric capacitors exhibited excellent P r value of 15 μC/cm2 after completing whole process integration, which guarantees a reliable high yield.

Charge instability in mis structures with dielectric silicon dioxide-phosphoro-silicate glass layers under conditions of high-field tunnel injection

The processes of charge degradation in MIS structures with dielectric silicon dioxide-phosphoro-silicate glass (PSG) layers are investigated for high-field tunnel electron injection from silicon. A model for their description is proposed. It is shown that in a PSG film the interband shock ionization intensity significantly decreases compared toSiO 2. This phenomenon is quantitatively described within the framework of the model examined. It has been found that in structures with polysilicon gate doped with phosphorus the PSG film can be formed at the gatesemiconductor interface, which results in the formation of electronic traps in the dielectric and in a decreased thickness of theSiO 2 layer in which the interband shock ionization proceeds.

Chemical mechanical polishing of PSG and BPSG dielectric films: the effect of phosphorus and boron concentration

Chemical-mechanical polishing of blanket and patterned oxide films doped with phosphorus and boron has been studied. FTIR was used to characterize the film microstructure. Experimental results show that an increase of phosphorus level promoted the polish rate of PSG film. We also found that increasing the boron content enhanced the polish rate of BPSG films although phosphorus contents is decreased. This implies that boron is more effective than phosphorus in enhancing the polishing rate of BPSG films. However, the hardness of these doped films is slightly affected by doping level. Excellent planarity achieved by CMP is demonstrated for patterned wafers. Here, we also identify inversion patterns for the composite dielectric formed by a thin hard film on the top of a thick soft film. Such inversion phenomenon can be used for monitoring CMP process as a means of end point detection.

Electron and hole trapping in doped oxides

An electron paramagnetic resonance, thermally stimulated current, and capacitance-voltage study has been carried out on phosphorus (PSG), boron (BSG), and boron and phosphorus (BPSG) co-doped oxide films on Si. The principal spin-active defects are the phosphorus-oxygen-bole-center (POHC) and the boron-oxygen-hole-center (BOHC), which are unpaired electrons on oxygen atoms with P or B in the near vicinity. The centers are activated by hole capture. We find that holes are trapped in the PSG, BSG, and BPSG dielectrics; however, hole trapping is most effective in the PSG and BPSG dielectrics. We find that electrons are trapped to differing extents in the doped films. The BPSG films are the most efficient in trapping electrons the PSG films are the least efficient. The electrical data can be explained by assuming that the precursor to the BOHC is negatively charged and the precursor to the POHC is electrically neutral. Last, the charge trapping properties of PSG, BSG, and BPSG dielectrics are compared and contrasted with those observed in thermally grown oxides.

An Analysis by Scanning Acoustic Microscopy of the Mechanical Stability of PSG and Si3N4 Passivation Films

ABSTRACTTwo types of mechanical tests associated with acoustic microscopy characterizations were performed to investigate the mechanical stability of PSG and Si3N4 passivation films. An in situ tensile test micro-device was installed under a scanning acoustic microscope to study the damage development in the passivation films deposited on A1,1%Si substrates. The analysis of the attenuation of the acoustic signature of the film/substrate systems and the variations of the leaky surface acoustic wave velocity permitted detection of the cracking and decohesion of the passivation films. The four-point bending test was used to submit passivated aluminum multilayers deposited on silicon substrates to cyclic compression. Then subsurface acoustic images revealed decohered zones in the passivation.

Surface Stability and Flow Characteristics of BPSG Film by N2O Plasma Treatment

ABSTRACTBPSG films show good flow characteristics with the increase of boron and phosphorus concentration. As–deposited BPSG films with high boron and phosphorus concentration, however, have a dopant instability which results in film bursts, cracks, and precipitates, due to water absorption. Elimination of dopant instabilities of BPSG films by N2O plasma treatment is investigated. Film structure, composition and flow properties are evaluated by FT-IR, SIMS, and SEM, respectively. Dopant stability is examined after H2SO4 boiling. After H2SO4 boiling without N2O plasma treatment, BPSG films with high boron and phosphorus concentration show poor flow characteristics. Boron and phosphorus are leached out of the BPSG films by reaction with absorbed water during the H2SO4 boil. N2O plasma treatment results in a thin surface layer composed of Si-O-B bonds. These bonds do not dissolve in water. It is proposed that the thin layer consisting of Si-O-B bonds prevents the penetration of water into BPSG film during H2SO4 boiling.

The APCVD Growth of PSG and BPSG Films Using Tertiarybutylphosphine as a Phorphorus Dopant

The use of a less hazardous alternative to phosphine gas, tertiarybutylphosphine (TBP), has been investigated for the growth of phosphosilicate and borophosphosilicate films in an atmospheric pressure chemical vapor deposition reactor (APCVD). Data on film growth rate, composition, stress properties, and refractive index are reported. The results indicate that TBP serves as a viable alternative to phosphine gas in the APCVD growth of doped silicate glasses.

A composite process for eprom and eeprom and its reliability

AbstractA process to form an IC with an EPROM (erasable programmable ROM) and EEPROM (electrically erasable PROM) was a developed and a module was tested. Fabricating a floating‐gate type EEPROM and the process to achieve high reliability in write/erase performance and the high data‐retention characteristic were investigated. The write/erase endurance is higher when the tunnel oxidation is carried out by wet oxidation than when carried out by dry oxidation.As the temperature for forming the inter‐polyoxide increases, the leakage current decreases but the write/erase endurance decreases. As the tunnel oxide film becomes thinner, the write/erase endurance decreases. The passivation layer has a great influence on the Vth window and data‐retention characteristics. When the passivation layer is a P‐SiN, the foregoing characteristics are poorer than when a PSG film is used. However, if PSG and P‐SiO films are formed under the P‐SiN film, the degradation of the forementioned characteristics decreases.

Rapid Thermal Flow of PSG Films in Vacuum Using a Graphite Heater

Rapid thermal flow (RTF) of 7 and 9 mole percent phosphosilicate glass films deposited by atmospheric pressure CVD on steep polysilicon steps has been studied. The films were treated in vacuum at temperatures ranging from 1000° to 1200°C and for exposure times ranging from 5 to 420s. The isothermal flow was characterized by means of the maximum tangential angle and then analyzed according to the flow model proposed by Mullins (12). Our results of flow performed in vacuum are compared with the results reported by Hara for similar films flowed by rapid thermal processing (RTP) at atmospheric pressure. From this comparison, an enhanced viscous flow mechanism was observed for thermal treatments at atmospheric pressure. This means that pressure has a beneficial effect on viscous flow of PSG films. However, for short RTF processing times, an enhanced flow process is observed for thermal treatments in vacuum, where at least two mass transport mechanisms take place.

D.c. dielectric breakdown in phosphosilicate glass films prepared by low temperature chemical vapour deposition

The aim of this work is to study the influence of phosphorus concentration, annealing temperature and medium on the d.c. dielectric breakdown of CVD PSG films deposited in the SiH 4 -PH 3 -O 2 -N 2 system at atmospheric pressure and low temperature

Electron-beam evaporated phosphosilicate glass encapsulant for post-implant annealing of GaAs

Electron-beam deposited films of phosphosilicate (PSG) have been investigated as dielectrics for the encapsulation of Si-implanted GaAs for the purpose of post-implant annealing. The processing parameters that were optimized included the thickness of PSG film, the substrate temperature, and the annealing time and temperature. PSG films deposited at temperatures ≥300 °C showed no signs of deterioration up to temperatures in excess of 900 °C for 30-min anneals carried out in a forming gas and/or nitrogen ambient. Depth profiles in excellent agreement with the Lindhard–Scharff–Schiott curves were obtained with 1000-Å-thick films when annealed at 850 °C for 30 min. The diffusion coefficient of implanted silicon was found to be an order of magnitude smaller for the PSG films than that for the conventional plasma assisted chemical vapor deposited SiO2 films at 850 °C.

Wet-chemical etching of SiO 2 and PSG films, and an etching-induced defect in glass-passivated integrated circuits : Werner Kern. RCA Rev.47, 186 (June 1986)

Rapid changes in photoluminescence (PL) intensity and blue shifts of typically 100 nm have been measured for porous silicon wetted by hydrofluoric acid. The differences between continuous and interrupted PL excitation show that the process is not solely limited by photo-activation. In contrast, the effect of potassium hydroxide, a second silicon etchant, is to reduce PL intensity without any significant blue shift. These experiments show the importance of surface chemistry in PL of wet porous silicon and are interpreted in terms of surface termination by different species.

P2O5–SiO2 film deposition by reactive sputtering in phosphorus vapor

P2O5–SiO2 (PSG) films were deposited from a nondoped silicon target by reactive sputtering in an oxygen–argon mixture added to phosphorus vapor. The phosphorus vapor was generated by heating a crucible containing solid red phosphorus in the sputtering system. PSG films with phosphorus concentration of up to 3×1021 cm−3 were successfully deposited at low substrate temperature. Phosphorus concentration in the films could be controlled by not only the crucible temperature but also the sputtering gas pressure.

Plasma‐Activated Deposition and Properties of Phosphosilicate Glass Film

Phosphosilicate glass film deposited by a plasma‐activated reaction system (P‐PSG) was studied. Fundamental characteristics of the P‐PSG were investigated by systematically varying deposition parameters. In this plasma deposition method, the P‐PSG having a high deposition rate (130 nm/min) and a high doped phosphorus concentration [about 10 weight percent (w/o) P] was deposited using the reaction gases , , and . The P‐PSG deposited by this method showed properties such as a strong film crack resistance during heat‐treatments, a conformai step coverage, and a controllable compressive stress, compared with those of conventional PSG film deposited under atmospheric pressure (AP‐PSG).

Void Formation in Phosphosilicate Glass Film with Heat‐Treatment in H 2 Atmosphere

The void formation process and phosphorus behavior in phosphosilicate glass film deposited by chemical vapor deposition techniques were investigated. The films were heat‐treated three times, first in atmosphere for densification, then in or atmosphere, and after that in atmosphere. It was found that (i) void formation takes place with the third heat‐treatment in atmosphere, (ii) with the second heat‐treatment in atmosphere, absorbance of P=O band at 1330 cm−1decreases and absorbance of band at 1250 cm−1 increases, but further absorbance change does not take place with the third heat‐treatment. The gain in absorbance of the band at 1250 cm−1 is proportional to the loss in absorbance of the P=O band at 1330 cm−1. The quantity of phosphorus products formed with heat‐treatment in atmosphere was estimated from the absorbance change of the P=O band at 1330 cm−1. Comparing the quantity of the phosphorus products with the void size and number, it was proposed that the phosphorus products are gaseous species at high temperature, and the quantity of the gaseous species determines the product of the void number in the PSG film and square of the void size.