High-density Plasma Deposition Research Articles

Mechanism Analysis of Plasma Charging Damage on Gate Oxide for HDP FSG Process

For its stability and relatively lower K value, FSG (fluorine silica glass) is widely used in 0.18μm and below VLSI process. In this paper, the plasma charging damage on 30Aå gate oxide from the high-density-plasma deposition (HDP) of FSG is investigated. Positive and negative nondestructive JTDDB stress is applied to fresh transistors to simulate the plasma charging current. According to the results comparison, positive plasma stress at the end of the HDP-CVD FSG deposition is found to be the major cause of damage. The damage is located near the Gate/SiO2 interface. By increasing the FSG thickness, the damage is effectively suppressed.

Silane injection in a high-density low-pressure plasma system and its influence on the deposition kinetics and material properties of SiO2

High-rate, low temperature deposition is an essential requirement for industrial fabrication technology to be suitable for the deposition of optical and protective coatings. High-density, low-pressure plasmas have received significant attention for such applications due to their ability to create large and controllable ion fluxes onto the substrate. In this study, the high-rate deposition of silica films from a silane and oxygen gas mixture in a high-density plasma system based on a matrix distributed electron cyclotron resonance (MDECR) plasma source is investigated using directional jet injection of undiluted silane. The influence of process parameters such as the microwave power, radio frequency biasing of the substrate holder, and gas flows on the OH content of the oxide films is studied using phase-modulated spectroscopic ellipsometry (SE), Fourier transform infrared (FTIR) spectroscopy, and transmission measurements. The results of the measurements, taken at various points across the wafer, show a decrease in the thickness-normalized OH concentration in the areas of higher deposition rates. The corresponding gas phase composition is investigated using optical emission spectroscopy and compared to the FTIR, transmission and SE measurement results in order to validate our findings and ultimately optimize the deposition process. It is found that the primary silane flux onto the surface, which depends on the positioning of the jet injection point and gas flow rate, plays an important role not only on the deposition rate but also on the OH content of the films. The authors conclude that high-density plasma deposition systems such as the MDECR plasma enhanced chemical vapor deposition system cannot be considered as well mixed for gases with dissociation products that have high sticking coefficients, contrary to the accepted paradigm.

Prevention of plasma-induced damage during HDP–CVD deposition

The high-density plasma (HDP)–chemical vapor deposition (CVD) process consists of a simultaneous sputter etch and chemical vapor deposition. As the CMOS process continues to scale down to sub-quarter micron technology, the HDP process has been widely used for the gap-fill of small geometry metal spacing in the inter-metal dielectric (IMD) process. However, the HDP–CVD system has some potential problems including plasma-induced damage. Plasma-induced gate oxide damage has become an increasingly important issue for integrated circuit process technology. In this paper, the thin gate oxide charge damage caused by the HDP deposition of IMD layer was studied. As an experimental result, the multiple step of HDP deposition process was prevented the plasma-induced damage by introducing an in situ top SiH 4 unbiased liner deposition before conventional deposition.

Reduction of Plasma Process Induced Damage during HDP IMD Deposition

The HDP (High Density Plasma) CVD process consists of a simultaneous sputter etch and chemical vapor deposition. As CMOS process continues to scale down to sub- quarter micron technology, HDP process has been widely used fur the gap-fill of small geometry metal spacing in inter-metal dielectric process. However, HBP CVD system has some potential problems including plasma-induced damage. Plasma-induced gate oxide damage has been an increasingly important issue for integrated circuit process technology. In this paper, thin gate oxide charge damage caused by HDP deposition of inter-metal dielectric was studied. Multiple step HDP deposition process was demonstrated in this work to prevent plasma-induced damage by introducing an in-situ top SiH unbiased liner deposition before conventional deposition.

Fixed Abrasive Technology for STI CMP on a Web Format Tool

ABSTRACTShallow trench isolation (STI) requires a high quality oxide with superior fill capability provided by High Density Plasma (HDP) oxide. Unfortunately, the HDP deposition process can create large within die topographies that are difficult to polish directly using conventional silica slurries. As a result, etch back integration schemes have traditionally been incorporated for STI polish. A more revolutionary approach is the use of Fixed Abrasive (FA) CMP [1]. FA CMP allows direct STI polish with good planarization/process stability, eliminating the need for prior etch back. The planarization efficiency is strongly dependent on the shape of the pad composites that hold the CeO2 mineral. Fixed abrasive pads with pyramid and pole shapes are available. In this work, three different fixed abrasive pads supplied by 3M corporation were evaluated for STI CMP polish performance using the Obsidian 8200C web format CMP tool. Basic polish characteristics such as planarity (dependence on sub-pad/pattern density), selectivity to topography, oxide dishing and nitride erosion are presented. The FA pads discussed here have been classified as “slow”, “medium” or “fast” depending on blanket oxide removal rate.The slow rate pad had a very high selectivity to topography and very low dishing of the down area oxide. The removal rate of blanket oxide was less than 100 Å/min. The pad was best suited to the polish of isolation trench structures with small, controlled overfill (> 200 Å) across the wafer. A large process window was demonstrated. The removal rate of the “medium” pad also decreased significantly at the onset of planarization with a blanket oxide removal rate of ca. 200 Å/min. Unlike the slow rate pad, the medium rate pad did not provide a suitable overpolish process window required for a manufacturable STI process. It is believed this pad would be a good choice for BPSG polish. In contrast to the slow and medium rate pads, the blanket oxide removal rate of the fast pad was ca. 2000 Å/min with no self-stopping capability at the onset of planarization. The removal rate was extremely center fast, such that it could not be compensated by adjustment of tool parameters. Use of a modified process developed within the DRAM development alliance (DDA) at East Fishkill (IBM/ Infineon) enabled the fast pad to polish deep STI structures that would otherwise be impossible using the slow or medium rate pads.

Modeling of SiO2 deposition in high density plasma reactors and comparisons of model predictions with experimental measurements

High-density-plasma deposition of SiO2 is an important process in integrated circuit manufacturing. A list of gas-phase and surface reactions has been compiled for modeling plasma-enhanced chemical vapor deposition of SiO2 from SiH4, O2, and Ar gas mixtures in high-density-plasma reactors. The gas-phase reactions include electron impact, neutral–neutral, ion–ion, and ion–neutral reactions. The surface reactions and deposition mechanism is based on insights gained from attenuated total reflection Fourier transform infrared spectroscopy experiments and includes radical adsorption onto the SiO2 surface, ion-enhanced desorption from the surface layer, radical abstractions, as well as direct ion-energy-dependent sputtering of the oxide film. A well-mixed reactor model that consists of mass and energy conservation equations averaged across the reactor volume was used to model three different kinds of high-density plasma deposition chambers. Experimental measurements of total ion densities, relative radical densities, and net deposition rate, as functions of plasma operating conditions, have been compared to model predictions. The results show good quantitative agreement between model predictions and experimental measurements. The compiled reaction set and surface reaction network description was thus validated and can be employed in more sophisticated two- or three-dimensional plasma simulations.

Hard boron–suboxide-based films deposited in a sputter-sourced, high-density plasma deposition system

Boron–suboxide-based thin films have been deposited on Si in an electron cyclotron resonance microwave plasma using a radio frequency (rf) magnetron as a source of boron. Variations of the oxygen fraction in the deposition ambient and of the rf bias applied to the substrate were related to film tribology. The best films have hardnesses of ∼28 GPa and moduli of ∼240 GPa and were deposited in oxygen fractions <1% at substrate temperatures <350 °C. The films contain 4%–15% O and ∼15% C, with carbon originating from the sputter target. They are amorphous and have surface roughnesses of ∼0.2 nm. Boron–oxide films may form a self-generating lubricating layer of B(OH)3 in ambient atmosphere. Compositional depth profiling of these films reveals an oxygen-enriched surface of ∼10 nm thickness. Initial nanoscratch test results indicate that these films fail at high critical loads and have low friction coefficients relative to other hard coatings.

New and possible future trends in inductively coupled plasmas (ICPs) for semiconductor processing

ICPs have become one of the dominant high-density plasma sources for etching. More variations of ICP etch sources are currently being developed and inductive systems for high-density plasma deposition are also being developed. In addition, helicon inductive sources are being developed in single loop and spiral antenna configurations. In the future these two fields may merge to combine the optimum features of both systems. The physics of low-pressure ICP systems will be discussed. Experimental effects of multipole magnetic fields near the rf coil will be described as they relate to low pressure and electronegative gases.

Characterization of an argon magnetron plasma by a cylindrical Langmuir probe

Magnetic fields enhance the synthesis of high-quality thin films in plasma chemical vapour deposition (CVD) at low pressures. To understand this phenomenon, it is first required that we closely examine the role of the magnetic field in the generation of a highdensity plasma. For this purpose, the present study has been performed on the dependences of the plasma parameters such as the electron temperature, electron density and ionization current of the plasma on the magnetic field strength. It was found that the generation of high-density plasma in low-pressure CVD strongly depends on the magnetic field strength. High-density plasma CVD was reported to be appropriate for the synthesis of high-quality thin films [1]. However, the plasma CVD technique is usually used for a low-density plasma. In view of this, a magnetic field has been applied for the generation of high-density plasma since it can effectively raise the confinement of the secondary electrons [2]. So far, major parts of the investigation on high-density plasma deposition have been performed using a sputtering technique and only rarely using CVD [3, 4]. In 1988, Ohnishi et al. [5] reported the influence of a magnetic field on the CVD of hydrogenated amorphous Si films using silane gas. They found that the magnetic field can markedly improve the optical emission intensity of the plasma by the motion of the secondary electrons. This implies that the magnetic field plays a significant role in the generation of high-density plasma even in low-pressure CVD. In spite of such an important role of the magnetic field, however, it is still not clear how the lowpressure CVD process enables the synthesis of highquality thin films by a magnetron plasma. To solve this problem, it is first required to understand the generation mechanism of the high-density plasma in low-pressure magnetron plasma CVD. Therefore, we investigated the dependences of the plasma parameters such as the electron temperature, Te, electron density, ne, and saturation ion current, Isat i0 , of the plasma on the magnetic field strength. The generation mechanism of the high-density plasma was also discussed in terms of the plasma parameters. A schematic diagram of the radio-frequency (RF) planar magnetron plasma CVD system is shown in Fig. 1. In the figure, permanent magnets are attached perpendicular to the cathode. Fig. 2 shows the magnetic field lines formed by the magnetron of this study. Te, ne and Isat i0 were determined by a Langmuir probe measurement [6]. The single cylindrical probe, in which the copper wire core is insulated with a Pyrex glass tube [7] and stainless steel tube, was positioned 47 mm above the cathode surface. The schematic diagram for the cylindrical probe used is shown in Fig. 3. The system was then evacuated to 1:33 3 10y4 Pa before the generation of plasma. The plasma source was supplied by a 13.56 MHz RF generator with 100 W and low-pressure argon gas of 0.6 Pa. The magnetic field strength at the probe position was varied to 45, 74 and 82 G by the arbitrary configuration of the magnets in the chamber. Under these magnetic field strengths, the probe current was measured by applying the direct current probe potential in the range between y100 and ‡250 V. The electrical equivalent circuit for a Langmuir probe measurement is shown in Fig. 4.