KR20020046232A - Deposited Thin Film Void-Column Network Materials - Google Patents

Abstract

The present invention provides a novel porous film (3) comprising a network of silicon columns in a continuous void that can be made using a high density plasma deposition at a low temperature, i.e. below about 250 ° C. This silicon film is a two-dimensional nano-sized array of bar columns. This void-column morphology can be controlled according to the deposition conditions, and the porosity can be changed to less than 90%. In the plasma process used, a unique opportunity to simultaneously obtain low-temperature deposition and corrosion, with columnar structures, continuous voids and polycrystalline column composition is allowed. A unique device can be made using this porous continuous film by plasma depositing the film on a glass, metal foil, insulator or plastic substrate (5).

Description

[0001] Deposited Thin Film Void-Column Network Materials [0002]

The interest in porous silicon structures is considerable. There are two reasons for this. First, these porous films can be used in a variety of applications including MEMS (microelectro-mechanical devices), interconnected dielectrics, micro-sensors, cell and molecular immobilization, Can be used in the field. Second, these materials are well suited for Si microelectronics. There are a variety of methods for making porous silicon materials. Today's most interesting technology for fabricating porous silicon is based on the use of wet chemical solutions and electrochemical techniques of anodic oxidation (RC Anderson, RC Muller, and CW Tobias, Journal of Microelectromechanical Systems, vol. 3, (1994), 10). So far, this technique has provided the best level of porosity among known methods. The starting material for such wet etched materials is conventional silicon wafers or thin film Si produced by several deposition methods such as low pressure chemical vapor deposition (LPCVD) or plasma enhanced chemical vapor deposition (PECVD). In an electrochemical wet etching process, the sample is exposed to a wet solution and through a contact to the corrosion sample, through a corrosion sample, through a solution (e.g., a mixture of hydrofluoric acid, water, and ethanol) And the current is passed through the electrode (cathode: for example, platinum). This current causes " pitting " or corrosion of Si that creates a porous network structure.

In electrochemical (bipolar) corrosion methods, the structure (e.g., pore size and spacing) and the porosity-Si layer thickness are determined by the resistivity (size and type) of the silicon itself, the current density, the applied potential, Temperature and exposure time. In the case of sufficiently long exposures and sufficiently thick starting materials, this electrochemical erosion process can continue to the point where nanoscale structures (i.e., features of the order of nanometers) are obtained. The silicon feature is a continuous single crystal when the sample is corroded from a single crystal wafer or a large grain polycrystalline silicon if the sample is corroded from the deposited film. These conventional (electrochemically corroded) porous silicon materials are all the result of (1) wet electrochemical corrosion methods, (2) contact with the sample during such wet corrosion is required, (3) (4) is the result of a continuous process requiring subsequent wet corrosion after first requiring the formation of silicon.

An intensive research activity in porous semiconductors has been made in 1990 by the discovery of room temperature visible light emissions from porous Si produced electrochemically by Kantham (LT Canham, Appl. Phys. Lett. 57, 1046 (1990) It has been much more encouraging for more than a decade. Additional interesting properties of porous semiconductor materials such as gas sensitivity, biocompatibility and ease of micromachining have also been realized shortly after the discovery of Kamhan (I. Schecter et al., Anal. Chem. 67, P. Steiner et al., Thin Solid Films 255, 52 (1995); J. Wei et al., Nature 399, 243 (1999); LT Canham et al., Thin Solid Films, 297, (1995)). All of the proven applications to date have been based on porous silicon materials produced by electrochemically etching silicon wafers or deposited films.

The approach to porous silicon in the present invention is to use a deposition method to grow a deposited porous film, specifically porous silicon, in which the voids thereof are deposited as voids between the columns and the clusters of the columns It is a columnar material. In the present invention, the void region is ideally uniform through the thickness of the film and across the film. The method of the present invention is unique because it is performed at low temperatures and we are able to control the void size and void fraction using the present invention and that the void-column network morphology does not change over the desired thickness, Material and demonstrate that plasma methods can be used to control the interaction between deposition and corrosion during growth. The process of the present invention provides highly porous (less than about 90%) pore size regulated material without any back contact and anodization-based wet processing. Unlike other deposition methods, the method of the present invention is based on high-density plasma deposition-corrosion interaction and therefore requires highly regulatable porosity (90% or less), morphological and doped or undoped polycrystalline A sex column can be provided. In addition, a feature of the present invention is its ability to assemble the porous silicon on various types of substrates including glass, metal foil, insulators, plastics and semiconductor-containing materials.

The high density plasma (HDP) deposition tool used in the present invention was an electron cyclotron resonance plasma machine. In particular, the porous silicon of the present invention can be used in high density plasma tools (e.g., electron cyclotron resonance plasma enhanced chemical vapor deposition (CVD)) using hydrogen diluted silane (H ₂ : SiH ₄ ) as a precursor gas at substrate deposition temperatures below about 250 ° C (ECR-PECVD) tool (PlasmaTherm SLR-770). This tool influences silicon corrosion and deposition to create a two-dimensional silicon array, the silicon column size can be adjusted by analysis, the spacing between the columns is adjustable, and the morphology does not vary with thickness . Unlike other deposited columnar silicon materials, the column spacing can be maintained as the thickness of the film grows, and the columnar composition can be controllably varied from polycrystalline to amorphous. The resulting void-column network structure has a nanoscale minimum feature size and is fully formed after film thicknesses in the 10-20 nm range have been set. This enables the direct deposition of high porosity crystalline or amorphous silicon to any thickness between about 10 nm and greater, preferably between 10 and 20 nm, on any substrate. The porous semiconductor film produced by the present invention can be converted to an insulator or a metallic compound through an in situ process or an ex situ process.

The prior art involves two approaches to porous silicon: (1) producing porous silicon with a "coral-like" morphology of polycrystalline or single-crystal silicon "fingers" Wet electrochemical corrosion of deposited silicon or silicon wafers, or (2) deposition of silicon to produce porous materials composed of tapered amorphous silicon rods with morphology varying with thickness. The former has the advantage of highly regulatable morphology and porosity and is the subject of numerous research and development activities. However, this requires wet chemical corrosion for its formation. The latter materials have disadvantages that they are only available in amorphous form and have porosity which requires subsequent wet corrosion for morphology and control which varies with thickness. The porous silicon of the present invention does not require a wet process. It has fully adjustable morphology and porosity, and can be present in polycrystalline or amorphous form, if desired.

The present invention describes the deposition of porous materials at low temperatures. These materials are particularly suitable for depositing on glass or plastic or other substrates requiring low process temperatures, such as pre-formed sensors, electronic or opto-electronic devices, and substrates including circuitry. Due to the extensively proven porosity range for the materials of the present invention they can be used for sensing, airgap (optical mixing, microfluidics, molecular sorting, low dielectric constant structures, etc.) Molecular < / RTI > and cell, and mass desorption fields. The present invention is demonstrated using deposited porous silicon.

This application claims the benefit of U.S. Provisional Patent Application No. 60 / 137,385, filed June 3, 1999, U.S. Provisional Patent Application Serial No. 60 / 139,608, filed June 17, 1999, On October 27, the United States claims priority 60 / 161,848.

The present invention relates to the production of high porosity semiconductor thin films through a plasma-enhanced chemical vapor deposition system. More specifically, the present invention relates to a unique high-density plasma method of obtaining a high-porosity semiconductor thin film using simultaneous plasma deposition and etching.

Figure 1 is a cross-sectional TEM micrograph of a void-column network silicon thin film on glass.

Figure 2 is a graph of the XRD pattern of a void-columned film deposited at 100 < 0 > C and various pressures of 6, 8 and 10 mTorr.

Figure 3 is a graph showing the correlation between process pressure and absorbed microwave power for hydrogen and silane flow rates of 40 sccm and 2 sccm, respectively.

Figure 4 is a graph of reflectance for a barium sulphate reflector in the case of films deposited at various process pressures of 100 < 0 > C and 5-12 mTorr. The degree of embedding represents the calculated porosity.

5A is an AFM surface image of a void-columnar film deposited at 100 < 0 > C and 6 mTorr.

Figure 5b is an AFM surface image of a void-columnar film deposited at 100 < 0 > C and 8 mTorr.

5C is an AFM surface image of a void-columnar film deposited at 100 < 0 > C and 10 mTorr.

6 is a photoluminescence spectrum of a void-column silicon film deposited at 100 < 0 > C and 6, 8 and 10 mTorr.

Figure 7 shows the effect on the structure caused by the magnetic field in the vicinity of the substrate. These SEM micrographs show (a) application of a 100 G magnetic field perpendicular to the substrate, or (b) deposition of two films deposited at 100 < 0 > C and 10 mTorr on ITO (indium tin oxide) It is about. The calculated porosity results based on reflectance data are 0.62 and 0.22, respectively.

8 is a graph showing the increase in the conductivity (the current passed at a fixed voltage of 10 V) of the void-column silicon film in response to increasing relative humidity (RH). The film was deposited at a temperature of 100 DEG C and a pressure of 8 mTorr. This film was subjected to Pd-stabilization treatment before use. The measurement was carried out after depositing a 100 Å thick Pd layer and then annealing at 600 ° C. for 1 hour to improve reproducibility. The applied voltage is 10 V.

Figure 9 is a graph showing the conductivity behavior of voided-column silicon films of different porosity in response to changes in relative humidity (RH). The films were deposited at three different pressures of 6, 8 and 10 mTorr. The applied voltage is 50 V. Measurements were performed after Lewis acid treatment. These films were subjected to Lewis acid exposure prior to use.

Figure 10 is a graph of various current versus relative humidity measurements taken with an applied voltage of 50 V using a void-column film deposited at 100 캜 and 10 mTorr, showing repeatability and stability. This film was subjected to Lewis acid exposure prior to use.

11 is a graph of the enhancement of the porosity of voided-column silicon films by a 5-and 15-minute post-deposition hydrogen plasma exposure, respectively, as can be seen from the reflectance spectra.

Figure 12a illustrates a basic arrangement useful for creating isolation or confinement sites defined by removal of a porous material. This basic arrangement includes a capping layer, a nanostructured " on-column " film, a base layer and a substrate.

Figure 12b is a top plan view of the isolation region created from the material of Figure 12a.

12C is a cross-sectional view taken along the line C-C in FIG. 12A.

Figure 13 shows several layers of a basic arrangement useful for creating isolation or confinement sites using porous materials. There are two porous layers, a capping layer, a base layer and a substrate.

14 shows a tube or " air gap " created by removal of a voided-column network of deposited porous silicon.

Figure 15 is a laser desorption spectrum, in which a sample drop was applied directly to the porous silicon film and dried prior to laser impingement. Identification of the molecules in the sample is done.

DETAILED DESCRIPTION OF THE INVENTION [

The present invention describes a unique high density plasma process that utilizes simultaneous plasma deposition and corrosion to obtain a high porosity crystalline or amorphous semiconductor thin film. All drying processes are used for film formation, and it is not necessary to include a wet process. By appropriate conditioning of the process chamber, proper preparation of the substrate, and appropriate selection of deposition parameters, these films are always aligned with an adjustable, adjustable void having an interconnected void (void) and an untapered column perpendicular to the substrate - Has a column network morphology. Unlike conventional porous silicon produced by wet etching, this interconnected continuous void network appears for any film thickness of about 10-20 nm or more. Unlike conventional porous silicon, the films of the present invention may be doped or undoped. Further, unlike conventional porous silicon, the continuous void-column network material of the present invention can be produced on a variety of substrates such as glass, metal foil and plastic as well as more conventional substrates such as silicon wafers. For example, silicon and ECR high density plasma (HDP) tools were used for demonstration. The experiment also established visible luminescence, gas sensitivity, air gap structure formation, desorption mass spectrometry, and the like. The obvious continuous void arrangement, oriented column and uniform nanostructures, low temperature processes and unique methods of the present invention are relatively thick < RTI ID = 0.0 > necessary < / RTI > in the conventional method of obtaining small minimum wiring widths by wet processes, wet corrosion, Taking advantage of plasma deposition techniques that provide a number of new possibilities that are not hampered by the need for starting materials. The present invention also has a number of technical and economical advantages over conventional porous silicon fabrication techniques.

Unlike other structured deposited silicon films and columnar deposited silicon films, the method of the present invention is not a sputter deposition technique with the potential for sputter damage. It can be deposited at very low temperatures, have morphology that can have amorphous or polycrystalline columns, have high density levels of porosity (up to 90%), can have doped or undoped columns, And is a plasma corrosion / deposition technique that produces a film that is very well adjustable to have a void (i.e., void) size suitable for the application. Because the process temperature during film deposition is very low (i.e., from room temperature to about 250 ° C), this technique has no limitations on the substrate.

A high density plasma source was used to produce the continuous void / vertical non-tapered column morphology of the present invention. Particularly, in the experiment, ECR (Electron Cyclotron Resonance) high density plasma (HDP) PECVD system was used. In an HDP approach to high porosity films, an electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD) tool (Plasma Therm SLR-770) was used to deposit hydrogen diluted silane (H ₂ : SiH ₄ ). The deposition apparatus consists of two coaxially connected plasma chambers, an ECR chamber and a deposition chamber, 14.9 and 35.6 cm in diameter and 13.3 and 29.2 cm in height, respectively. To ignite the plasma, microwave power having an excitation frequency of 2.45 GHz is introduced into the ECR plasma chamber through a rectangular waveguide and a fused quartz window. The reflected microwave power is sent to the dummy load by a directional coupler and a 3-stub tuner is used to minimize the reflected power. The substrate bias, independently adjustable by the 13.56 MHz RF power supply to independently adjust the substrate impact, was discontinued to reduce impact energy. The DC-electromagnets coaxially disposed around the ECR chamber to meet the electron cyclotron resonance conditions generated an upper magnetic field with a sperm density of 875 Gauss (G) in the ECR chamber. H ₂ is introduced into the ECR chamber through the gas distribution ring proximate the quartz window. SiH ₄ is introduced into the deposition chamber through the gas inlet in the upper ring of about 1.3 ㎝ (27.9 ㎝ lower the ECR chamber) of the substrate position. Although hydrogen gas and silane were used in the experiments, other hydrogen and silicon-containing precursors may be used in the case of void-column network Si films. H ₂ (99.999%) was fed through the gas dispersion ring in the ECR chamber to ignite the ECR plasma, while SiH ₄ (99.999%) was introduced through the gas distribution ring around the substrate-mounting facility. In this study, hydrogen was fed into the ECR chamber to initiate ECR plasma for the silicon film. The second DC-electromagnet is positioned directly below the substrate level to set an adjustable magnetic flux density that can vary from about +800 to -600 Gauss. This magnetic flux exists around the substrate. A vacuum chamber for holding a substrate, a turbo molecular pump has been pumped by the Circular (turbomolecular pump), a base pressure of less than 4 × 10 ^-7 Torr, as vacuum base pressure of 2 × 10 ^-7 Torr. Table I lists the range of irradiated plasma deposition parameters. The film was deposited on a Corning 1737 glass substrate coated with a 80 nm thick silicon nitride barrier layer (unless otherwise noted). The film thickness was measured with a profilometer with a Tencor-500 profile. The nanostructures were tested with cross section TEM (Hitachi HF-2000 cold filed emission) and AFM (Digital Instruments Multimode AFM system with NanoScope IIIa Controller). The AFM was used in an Olympus cantilever and a tapping mode with a tip angle of ~ 35 ° C and a corroded silicon tetrahedron probe with a radius of 5-10 nm. The crystallinity was investigated using an X-ray diffractometer (Phillips X'pert) with glancing incidence optics. The UV reflectance of the film was obtained using a Perkin Elmer Lambda 9 spectrometer to assess the level of porosity. Photoluminescence was measured with an ISA U-1000 Raman spectrometer using a 5 mW 488 nm Ar-laser excitation.

The temperature of the substrate-mounting facility was controlled by a heater and cooling water (T = 16 ° C). Helium substrate backside cooling was also used to control the deposition temperature during plasma operation.

When electrical contacts were used with these void-column films, they were defined as a parallel strip (length 19 mm) arrangement (at 4 mm intervals) on the film surface to monitor conductivity changes in response to various gas environments. In the specific case of relative humidity (RH) measurements, the sample was placed in a glass tube on a Teflon stage with two Au probes in contact with the strip electrodes. RH inside the glass tube through a heating bubbler (bubbler), Then was gradually rises in the glass tube of 20 ℃ by flowing the N ₂ as a moisture carrier into the tube up to about 97% from about 2%. For reference, RH (TI-A; TOPLAS Co., Japan) was measured with an HP-4284A LCR-meter using a capacitive sensor, And tracked for void-column structures using a 4140B pA-meter / DC voltage source.

The observed morphology for conventional electrochemically prepared porous Si is based on the " microporous " (void width less than 20 A), " mesoporous ("quot; mesoporous " (pore width of 20-500 A) and " macroporous " (pore width of 500 A or more) (AG Cullis, LT Canham, PDJ Calcott, J. Appl. Phys. 1997). Whether the " conventional " porous silicon is microporous, mesoporous or macroporous depends on the starting material thickness, doping type and level, crystal orientation, wet corrosion time, According to this " pore size " classification, the films of the present invention are closest to " conventional " porous silicon, commonly referred to as microporous silicon, obtained from p ⁺ or p ^- silicon. When p ⁺ silicon is applied to anodization, long voids along the vertical direction to the silicon surface are formed with a width in the range of about 10 nm. However, morphology shows a significant degree of randomness because the pore itself is heavily branched and represents a very characteristic "fir tree" arrangement (MIJ Beale, JD Benjamin, MJ Uren, NG Chew, AG Cullis, J. Cryst Growth 73, 622 (1985)). In the case of anodized microporous p ^- silicon, the material exhibits an irregular, corrugated microstructure consisting of highly interconnected micropores ranging in size from less than 2 nm (Beale et al.).

The morphology of the film of the present invention is very different from these fir or coral structures. The nanostructures of the Si film deposited by the high density plasma tool method are composed of an array of bar-shaped columns that are perpendicular to the substrate surface and are located in a continuous void matrix. 1 shows a TEM photograph of the nanostructure of a film deposited at a temperature of 120 DEG C, a process pressure of 7.8 mTorr, and a microwave power of 500 W. FIG. Here, a typical column diameter is 10 nm, and a typical column interval is 3 nm. These columns in FIG. 1 exist as a concentrator (not seen at this very high magnification). From Fig. 1 the porosity of the film can be roughly estimated to be about 60%, but greater porosity in excess of 90% may be obtained and reproducibly obtained as estimated from near-UV (NUV) reflectance measurements. Careful inspection of the column revealed that the column was composed of granular crystalline particles whose size was the size of the column diameter in the parameter range when they were crystalline. In this case, the particles constituting the column are arranged on top of each other. The undulation in the gaps between columns (i. E., The change in void size) appears to be due to statistical variations in particle size. However, at a larger scale, the column spacing and size (e. G., Averaged across the film) and the void spacing between columns in the column body are generally uniform. The voids are interconnected, so that the column is generally isolated even in the case of lower porosity to form a continuous void network throughout the film. Thus, compared to the observed morphology of electrochemically corroded porous silicon, these deposited void-column network films exhibit obvious nanostructures and, most importantly, higher uniformity. The unique morphology of the film is represented in all films having a thickness of about 10 nm or more. The XRD pattern in FIG. 2 shows that the three films deposited at 100 ° C and various powers of 6, 8 and 10 mTorr were crystalline for 35 minutes.

(19 Thornton, J. Vac. Sci. Technol., 11, 666 (1974), J), introduced by BA Movchan and AV Demchishin, F. Met. Metalloved., 28, 653 Structural Zone Model developed by R. Messier, AP Giri, RA Roy, J. Vac. Sci. Technol., A2, 500 (1984) The film of our inventors was deposited / etched using a high-density plasma method, but if we used SZM, the structure of these porous-silicon films Is supposed to belong to what is called area 1 morphology.

In this zone 1, the film is composed of a tapered column (generally having a diameter of several tens nm) separated by voids (generally several nm in diameter). Due to the tapered column, this Zone 1 structure appears to have a thickness. In the case of the film of the present invention, a Zone 1 structure is expected because the deposition temperature used is very low relative to the melting point of the deposited material and the diffusion length of the molecules or atoms on the deposition surface is less than the average distance between the physical adsorption sites . Also, the kinetic energy of the impinging ions is less than or equal to the sputtering threshold (of the silicon film). Therefore, for these reasons it is expected that the deposition species will be immobilized where they are loaded. This is known as " ballistic " deposition. In these conditions, two factors are involved in the formation of voids: statistical roughening and self-shadowing. However, these mechanisms result in the formation of randomly shaped voids and tapers (" cauliflower-shaped ") columns, respectively. These conditions lead to morphology evolving according to the film thickness. The film of the present invention is not sputter deposited. These are produced by plasma deposition / corrosion. They have voids and columns that are very different from these expected results. In addition, the adjustment of the void size, the degree of porosity, and the column of films of the present invention are very different from what is expected. A feature of the present invention resides in its ability to provide controlled porous, column, and doped or undoped polycrystalline or amorphous materials in a void-column network structure that does not evolve with thickness. Generally, a single step process can not have all of these characteristics. Briefly, a feature of the present invention resides in its ability to take advantage of low surface diffusion for void generation, and its ability to take advantage of high density plasma reactions to promote corrosion and adjustable crystallinity despite such low surface mobility . On the other hand, in the case of a conventional PECVD process in the absence of high-density plasma chemistry, low surface mobility limits the structure to amorphous. Thus, it is expected that it would be impossible to obtain morphology that does not evolve according to the controlled high void fraction, controlled crystallinity, and thickness simultaneously.

Evolution of these films according to the void network and film thickness in amorphous-silicon films deposited by RF-sputtering has been extensively studied by Messier and co-workers (R. Messier and RC Ross, J. Appl. Phys. 53, 6220, (1982)). The film of the present invention can be adjusted to be polycrystalline silicon and the porosity can be up to about 90%. Messier et al. Used amorphous silicon, but did not show how to obtain the degree of porosity that the present technology can provide unless post-deposition wet corrosion is performed (R. Messier, SV Krishnaswamy, LR Gilbert, P. Swab, J. Appl. Phys. 51, 1611 (1980)). In the very low process-temperature method of the high-density plasma used here, it is assumed that deposition and hydrogen radical erosion (corrosion-induced deposition) play an important role in the formation of nanostructures. A possible mechanism is that once the crystalline nuclei are formed in the presence of high density hydrogen radicals, the bonds at these crystalline nuclei sites are stronger and resist the hydrogen radical corrosion, while the other bonds are weaker, It can be corroded. As a result, crystalline nuclei grow to induce the formation of a protruding column aligned in a regular form of the void-column network film. Likewise, if any material is charged between the columns, it is corroded because it is weakly bonded and removed. The reason why side growth is not allowed to form a column (i.e., a cone-shaped or cauliflower-shaped column) whose diameter increases as the film thickness increases in the process is not yet understood. This may be due to severe hydrogen corrosion which promotes highly directional growth. An amorphous layer free of voids is formed at the substrate interface before growth in the column starts. From Fig. 1, in the case of this sample, the thickness of this transition site is measured to be about 20 nm. The void-column network of the porous film is then coated on top of this transition layer.

A particular feature of the deposited silicon nitride-type (i.e., non-tapering morphology with non-tapered columns oriented perpendicular to the transition layer and penetrating through the continuous voids) of the porous silicon is that many factors Lt; / RTI > These include (a) the voltage between the plasma and the substrate, (b) the substrate temperature, (c) the plasma power and process pressure, (d) the magnetic field in the vicinity of the substrate, (e) the deposition gas and flow rate, And (g) a substrate surface. The impact of these multiple factors was unpredictable.

The ranges of some of the key parameters used in this test are listed in Table 1 below.

Process conditions Parameter range H ₂ flow rate (sccm) 1-500 SiH ₄ flow rate (sccm) 1-300 Microwave (2.45 GHz) Power (Watts) 100-1200 RF (13.56 MHz) substrate bias (Watts) 0-100 Process Pressure (mtorr) 2-15 Deposition temperature (캜) 20-250 Magnetic field strength near the substrate (Gauss) +800 to -600 (+ mark: same direction as upper magnet - mark: opposite to upper magnet)

These parameters are described in detail below.

The voltage between the plasma and the substrate (RF substrate bias)

The acceleration voltage (i.e., substrate bias) between the plasma and the substrate can be adjusted independently in a high density plasma (HDP) tool. These parameters are independently available in the HDP deposition machine and are variable. That is, in this class of tools, this voltage can be adjusted independently of the plasma power, unlike in a typical RF or DC plasma deposition system. In an electron cyclotron resonance (ECR) high density plasma tool used to describe a HDP deposited porous film, this voltage is adjusted independently of the plasma power by applying an RF bias between the plasma and the substrate.

As shown in the paper on thin film silicon deposition (S. Bae, AKKalkan, S. Cheng, and SJ Fonash, J. Vac. Sci. The presence of RF biases between the layers indicated that the column morphology was destroyed and that a continuous film with a non-pore structure was obtained. In fact, the purpose of the JVST paper was to show how to avoid porous-type films, and the purpose of this paper was to show how to remove the morphology of the column, which can be found by film. It was not known at the time of publication of this article that the column of the film did not taper and did not exhibit the typical callyflower morphology found in previous column silicon films and had fully adjustable porosity. It was also not known that the void structure of the present invention was unique and continuous voids. At the time of the publication of the paper, it was thought that the film in the column had a typical Zone I structure with a morphology and tapered column evolved by thickness. Thus, the purpose of the document at the time of the JVST paper was to show how to avoid the formation of columnar deformation of the deposited silicon film. As indicated by the JVST paper, column morphology can be avoided by applying an RF bias between the plasma and the substrate, and the effectiveness of this RF bias method is demonstrated in this paper. The avoidance of Zone I column formation by the increased energy of species reaching the growing film surface (increased RF substrate bias) is a behavior that could be expected from the structural zone model. The deposition species will have greater energy as the RF substrate bias increases, and the increase in surface mobility obtained will lead to a pore-free, column-free, homogeneous film. This is the expected and mentioned behavior in the JVST paper.

For the production of the thin film-deposited, column network material of the present invention, it has been found that the best film morphology (non-tapered, non-calcifiable column) is obtained when the voltage between the plasma and the substrate is at its lowest value 0 RF substrate bias). In the ECR system of the present invention, this is obtained when the RF bias voltage is zero for all plasma power levels.

Substrate (deposition) temperature

Increasing the substrate temperature during deposition also increases surface mobility. Thus, as expected from the structural zone model, porosity in the film degrades with increasing substrate temperature. However, it was not expected that the column would continue to be uniform (i. E., Non-tapered) without tendency to carry out callyflower-type growth over the temperature range tested (50 ° C <T <250 ° C) It was not mentioned in the paper. The film did not exhibit morphological evolution by film thickness. It should be noted that although temperatures over a defined range have been found to be tools for regulating porosity as would be expected, it has surprisingly been found that this is achieved without loss of the oriented, tapered uniform column projecting through a continuous void (pore) network. It is possible that This has not been anticipated in the prior art and has not been discussed.

Plasma (microwave) power / process pressure

Using the structural zone model, increasing the plasma microwave power was expected to lead to larger surface species of energy and thus to lower porosity. However, when all the factors except for plasma power and process pressure are fixed, the porosity does not decrease with power, and surprisingly it is shown that the oriented non-tapered uniform column protruding through the continuous void network continues and still does not exhibit evolution by film thickness Found. It can be expected that increasing the plasma power can alleviate column formation, or at least promote taper calf-type growth if the column has survived. What actually happened is a systematic reduction of the void size and a uniform orientation of the same column.

When changing the plasma power in the system, it was found that the pressure was not actually independent. Specifically, for a given process pressure and gas flow rate, the hydrogen plus silane ECR plasma used in this experiment is stable only when the incident microwave power is above a certain threshold level. At this threshold level or above, the incident power is all absorbed by the plasma. If the power level increases above this threshold level, the absorbed power changes only slightly, and the excess power is reflected. Thus, the absorbed net microwave power and process pressure are strongly connected. Figure 3 shows the trajectory of the absorbed power level as pressure changes with hydrogen and silane flow rates of 40 sccm and 2 sccm, respectively, for the particular high density plasma system used.

Figure 4 shows the optical reflectance spectrum of a film set deposited at 100 &lt; 0 &gt; C. Also, the various process pressures here correspond to specific power levels as shown in FIG. Peaks at about 275 nm characterize the film as crystalline. The spectrum exhibits interference at about 400 nm or more due to the reflected light from the substrate that is attenuated towards the lower wavelength as the optical absorption increases. Therefore, based on the dielectric-mixing theory, from the interference-free reflectance of the high-porosity film as shown in Fig. 4, when the other deposition parameters are kept constant, the porosity is changed according to the process pressure It can be deduced that it increases monotonically. The inset of FIG. 4 shows the porosity calculated based on the reflectivity at 380 nm.

Figure 5 shows AFM surface images of three films deposited at 100 ° C and various pressures (ie, 6, 8, and 10 mTorr). Here, the projected shape represents a focusing body of the column. Due to its size and shape, the AFM tip can not track the sudden drop between concentrators. From Figure 5, the concentrator density has been shown to increase systematically with power (i.e., as the pressure decreases). As shown in Figure 6 and discussed below, the photoluminescence (PL) appears for all of the samples in Figure 5, so the column size must be maintained in its range of several tens of nanometers for all of these samples. Thus, Figures 5 and 6 show that a reduction in pressure reduces the average porosity between the concentrator and the column.

As in the case of conventional electrochemically etched porous Si films, the aligned void-column films of the present invention exhibit photoluminescence. The photoluminescence spectra of the three films deposited at 100 &lt; 0 &gt; C and 6, 8 and 10 mTorr are shown in Fig. Here, the photoluminescent band has a peak at ~ 1.8 eV and has a maximum width at 1/2 maximum of ~ 0.3 eV, similar to that observed in porosity-Si (L. Tsybeskov, MRS Bulletin, April 1998, 33 1998).

Magnetic field near the substrate

The HDP system may have a magnetic field (MF) at or near the substrate location. This is true of the ECR high-density plasma deposition system of the present invention. The intensity of the magnetic field in the vicinity of the substrate was found to have an influence on the film porosity. Studies of the impact of magnetic fields on film morphology suggest that modulating the magnetic field at the deposition surface may be useful in enhancing film porosity if all other deposition factors remain constant. Preferably, adjusting the magnetic field perpendicular to the deposition surface may be useful in enhancing film porosity. A scanning electron micrograph taken on the film as shown in Fig. 7 demonstrates that the structure is more densely packed, i. E., Less porous, when MF is absent on and immediately above the deposition surface. Indeed, the magnetic field effects are not even considered in the structural morphological model of the film morphology.

Deposition gas and flow rate

As can be seen in Table 1 above, the range of flow rates was investigated for precursor gas hydrogen and silane. The gas composition and flow rate used to deposit the film in the column were found to affect morphology. Of course, the gas used for deposition must, for example, in the case of silicon, contain silicon-containing molecules. However, it has also been found that hydrogen is also important to obtain a unique column of film and a continuous void (void) structure. For example, as the plasma power increases, a greater amount of hydrogen radicals can be expected from the literature, and thus increased porosity can be expected with plasma power. However, the inventors have found that porosity actually decreases with plasma power, which proves that complex interactions occur. This role of hydrogen and power in the deposited porous film morphology has not been previously observed and reported in the literature.

The hydrogen radical will probably play a role in the nucleation process, which sets the position of the column growing through the continuous voids perpendicular to the transition layer. Hydrogen radical / impact species interactions lead to unexpected nucleation behavior compared to those discussed in the literature. Specifically, the nanostructure shown in Fig. 1 corresponds to a nucleation density of about 6x10 &lt; ¹¹ &gt; cm &lt;&quot; ^{2 &} gt ^; (column-forming region), which is a nanocrystalline- (HV Nguyen and RW Collins, Phys. Rev. B47, 1911 (1993)), which is about 3 × 10 ¹⁰ cm ^-2 . These larger nuclear densities, which have been shown to directly affect porosity by the present inventors and which are exhibited by higher powers, have never been considered in conventional structural zone models which are expected to lead to an understanding of morphology. The proposed model shows that this is due to hydrogen radical formation effects. The column growth nucleus density can be as high as 10 ¹¹ to 10 ¹² cm ^-2 .

Chamber Conditioning

The cleanliness of the chamber affects film yield in an obvious manner. For example, particles in the chamber are detrimental to film quality. However, the chemical state of the chamber walls (i.e., film coating) also affects the film. There are basic chamber / plasma species interactions that are uniquely present due to the use of high-density plasmas for deposition of these porous films. These wall / species interactions affect the rate of reaction and species balance that exist during film growth, and thus can affect porosity. For example, the silicon nitride coating on the chamber walls after each deposition can be beneficial to film reproducibility and quality. Exposure to H ₂ or O ₂ plasma chambers before voided-column network film deposition is another example of conditioning. In this case, these plasmas volatize (H ₂ or O ₂ ) species on the chamber walls (O ₂ ) and induce a stable and reproducible environment for subsequent porous silicon deposition.

Substrate surface

The state of the surface on which the porous film is to be deposited affects the resulting film. For example, when comparing silicon wafer, indium tin oxide (ITO), antireflection glass, metal-coated glass and silicon nitride-coated glass starting surfaces, porosity differences appear in the deposited film. In particular, films on ITO and antireflective glass are very similar and exhibit a slightly lower porosity compared to nitrided glass. Thus, larger porosity correlates with greater structural mismatch between the film and the substrate, which can lead to lower nuclear density.

The films of the present invention exhibit a number of properties reported only for previously wet-electrochemically produced porous silicon. For example, they exhibit reported gas and vapor sensitivities for electrochemically corroded porous silicon (I. Schecter et al., Anal. Chem. 67, 3727 (1995)). For preliminary investigation, the sensitivity of the films of the present invention to water vapor was studied. Figure 8 illustrates the typical behavior of the film with changes in RH. Depending on the pore size, a weak reaction is observed below the threshold moisture content, and a steep (usually exponential) increase is observed above this threshold humidity level. The expression of this steep behavior is controlled by pore size and stability / sensitization treatments. In the case of Figure 8, the Pd layer was deposited on the deposited porous Si and annealed at 600 ° C for 1 hour.

The increase in conductivity is due to capillary condensation of moisture inside the void. Similar behavior was observed for the ceramics and the charge transfer was thought to be through a proton (H ⁺ ), a hydronium ion (H ₃ O ⁺ ) or a hydroxyl ion (OH ^- ) (T. Hubert, MRS Bulletin, 49 (June 1999), BM Kulwicki, J. Am. Ceram Soc., 74, 697 (1991)). When the silicon surface interacts with humidity, the formation of chemically bonded hydroxyl ions leads to a high charge density and a strong electrostatic field. Thus, additional water molecules physically adsorbed on this chemisorbed layer can easily dissociate into ions due to their high electrostatic fields (2H ₂ O ↔ H ₃ O ⁺ + OH ^- ) (T. Hubert, MRS Bulletin, 49 (June 1999), BM Kulwicki, J. Am. Ceram Soc., 74, 697 (1991)). Proton transfer occurs when H ₃ O ⁺ liberates a proton to neighboring H ₂ O and this is transformed into H ₃ O ⁺ (Grotthuss chain reaction) (T. Hubert, MRS Bulletin, 49 (June 1999); BM Kulwicki , J. Am. Ceram. Soc., 74, 697 (1991)). The steep rise in conductivity will probably be associated with the growth of a molecular layer of water with increasing RH (JJ Mares et al., Thin Solid Films 255, 272 (1995)). Finally, saturation occurs following a steep increase in conductivity with increasing RH. It is believed that at this point complete filling of the void volume with the water condensed occurs. Thus, in the case of a given surface tension or absorption coefficient, saturation is expected to occur at higher RH for larger voids or pore sizes, as also shown by the Kelvin's relation to capillary condensation (T. Hubert , MRS Bulletin, 49 (June 1999); JJ Mares et al., Thin Solid Films 255, 272 (1995)).

Figure 9 shows the stabilized humidity response of three films deposited at 100 ° C and various pressures (6, 8 and 10 mTorr). Among these films, those deposited at 10 mTorr (the highest porous film) exhibit the most regular behavior. Figure 10 shows several measurements taken from this high porosity film, followed by several minutes, several hours, and several days, respectively. Obviously, reproducibility is important. The data in Figs. 8 to 10 are for a film subjected to the stabilization / reduction process. This process need not be used.

Mares et al. Reported a similar conductivity enhancement (grade 3) to obtain a similar S-shaped curve as in FIG. 8, obtained from porous Si produced electrochemically with a change in RH from 0 to 100% (JJ Mares et al., Thin Solid Films, 255, 272 (1995)). However, these measurements included high levels of instability that took several days to achieve stable results. This is because current can only be transported across the thickness of the porous silicon layer due to the presence of a unique silicon material that is the basis of the electrochemically fabricated porous silicon layer. If a side electric field is used for these electrochemically prepared samples, it will cause the classification of the current through the silicon wafer, which makes lateral monitoring of electrical properties impossible. Thus, there is a need for a sandwich monitoring structure with a conventional porous silicon disposed between two electrodes. This is a major drawback because the water vapor passes through the upper electrode before reaching the porous semiconductor layer. As a result, not only the reaction time but also the sensitivity is seriously destroyed.

On the other hand, if the porous film is present on the insulator, the electrical properties can be easily monitored laterally by the side contact arrangement, as is easily accomplished by the deposited void-column network material. This structure allows for direct interaction between the atmosphere and the monitored film in the region between the contact sites. As a result, the film shows the reaction time within one second in the case where the RH rapidly changes from 0 to 100% or vice versa. In addition, in the morphology of the present invention, the voids are interconnected so that the column is isolated even in the case of lower porosity and forms a continuous void network that is vertically aligned with the film / atmospheric interface through the film. This facilitates uniform and rapid mass transfer inside and outside the film. Electrochemically prepared porous silicon films lack this feature because voids are not necessarily interconnected.

The shift in RH where saturation occurs in FIG. 9 is a token of different void sizes for the three films. As discussed above for capillary condensation, an increase in void size is indicated by an increase in process pressure (reduction in power). This is in full agreement with our conclusions from AFM and PL data. Thus, this study confirms that the conductive behavior of the porous film by RH provides useful information on morphology. Because 10 mTorr samples have the highest porosity and thickness, this sample is expected to yield the best current when all void volumes are charged with condensed water. However, in reality, as can be seen from Fig. 9 (from 6 mTorr to 10 mTorr), the saturation current is opposite in that it decreases with the void volume (porosity x film thickness directly). This is probably due to the fact that in the case of the film of the present invention the main charge transport does not occur in the bulk liquid, but rather occurs near the silicon surface where water is most effectively dissociated by surface charge. The ionized fraction at the surface is expected to be only 1%, but this is a sixth grade larger than the fraction in liquid water (B. M. Kulwicki, J. Am. Ceram. Soc. 74, 697 (1991)). Thus, the 6-mTorr sample with the highest density of the column exhibits the highest saturation current due to its highest internal surface area. On the other hand, 10 mTorr films not only have the lowest internal surface area, but also have the maximum average spacing between the columns. The longer the interval, the lower the ionic concentration decreases from its value at the surface towards the center of the gap, and therefore more series resistance is applied.

Morphology, sensitivity and specificity can be adjusted using post-deposition processes in the in situ or external reaction systems. For example, Figure 11 illustrates the enhancement of porosity by post-deposition-corrosion hydrogen plasma erosion. Such porosity enhancement with plasma exposure time is due to the reduction of the diameter of the silicon column, the concentrator, or both. As mentioned above, the film may be deformed after deposition by elevated temperature exposure, chemical interaction, subsequent deposition, wet exposure and / or a particular plasma exposure. As a further example, F-terminated or Cl-terminated surfaces can be obtained in the porous film to avoid degradation. The film surface may be functionalized by chemical, biological or plasma treatment to make it more sensitive to certain detection targets other than water vapor.

These porous void-column network silicon films with controlled porosity as described herein can also be used in a variety of isolation, isolation layers, void formation and limited applications due to their ability to be fast, reproducible and controllably corrosive have. They can be used for chemical, electrical, physical and mechanical isolation. We call all forms of this application an "air gap", isolation or "release layer" application. In the case of electrical isolation, for example, these films can be oxidized to produce a column of SiO ₂ in a two-dimensional array (layer 3 in FIG. 12A). The resulting air / SiO ₂ material can have a very low dielectric constant as required in the case that the power storage should be minimized coupling. Specific applications are in interconnections in microelectronics. The capping layer can then be deposited on this two-dimensional array as shown in Figure 13, which shows two 2-D array layers (layer 3). Thereafter, there may be an electrical connection in the layer 1, the base layer and / or the substrate. Interconnection between these layers may be achieved by doping or otherwise inducing the conduit through the porous layer.

This electrical connection or circuitry is advantageous because of the excellent electrical isolation characteristics of a two-dimensional (2-D) air / SiO ₂ array, that is, due to the low dielectric constant of the porous isolating layer, Lt; RTI ID = 0.0 &gt; electrically chargeable coupling. For example, if the silicon oxide bridging structure contains 70% porosity, the effective dielectric constant of this structure may be 1.84.

Mechanical, physical and chemical sequestration may also be achieved by a unique deposited and controlled structured film that appears as a void-column network by removing this material at selected sites. For example, the capping layer 1 may be deposited directly on the film 3 where silicon may remain, or may chemically react to SiO ₂ , metal silicides or other silicon compounds. The capping layer may be formed without destroying or destroying the vacuum, and a nitride, oxide, metal or other non-porous (i.e., continuous) silicon layer or cap 1 may be deposited to form the substrate 5 For example, a 2-D void-column network or film 3 deposited on a semiconductor, glass, or plastic. Corrosion access holes 10 may then be defined using conventional methods, such as lithography, before or after capping deposition, as shown in Figures 12b and 12c. These holes 10 allow the caustic to enter the porous void-column network silicon (or SiO _2, etc.), which is removed at a predetermined site as shown in FIG. 12B. As a result, the isolation or restriction sites are defined by the removal of the porous material. The porous silicon void-column network material is easily removed by such corrosion because all areas of the porous material silicon are accessible due to the continuous network of voids or voids between the columns that allow for caustic access and reaction product removal. Figure 14 shows the actual " air gap " structure produced by the removal of this void-column network Si region. Here, the treatment process appears to generate a cavity between the insulator layers. In this particular example, the cavity was corroded within 20 minutes. Prior art methods of using polycrystalline silicon to generate cavities may employ multiple grades or use complex e-beam lithography to enhance corrosion (PJ French, J. Micromech. Microeng., 6 , 197 (1996)).

The removed sites (cavities or " air gaps ") as illustrated in Figure 14 can be used as well as tubes for applications such as chromatography, DNA classification, optical application and fluidics, as well as diaphragms, accelerometers, bolometers, Lt; RTI ID = 0.0 &gt; capacitive coupling. &Lt; / RTI &gt;

Figure 15 illustrates the use of a deposited porous film in another illustrated application: A support substrate for mass desorption spectroscopy analysis. The deposited porous silicon here serves as a medium for attachment of molecules for subsequent detection. Detection occurs by using a laser to desorb molecules from the absorbent porous silicon and cause ionization. The ions generated from these desorbed molecules are then identified using mass spectrometry. The identification of some molecules adsorbed on purpose on the deposited porous silicon film can be seen in the mass spectrometry scan of FIG. The use of lasers to desorb molecules from the substrate and subsequent mass spectrometry analysis were previously performed, but this required an organic " matrix " to bind the molecules to be detected. This is mass analysis by so-called laser desorption and ionization (MALDI) techniques. The inventors' technique avoids the use of organic matrix binder materials. As can be seen, laser exposure causes desorption and ionization leading to molecular identification. Electrochemically corroded porous silicon substrates have also been found to be effective in a limited mass range for such laser-desorption induced spectroscopic analysis. They also avoid the use of binders (Nature, vol. 399, p. 243-246, (1999)). However, these corroded porous silicon methods have the problems mentioned earlier: they require electrochemical corrosion, reversed contact and thick starting silicons to obtain the nanostructures necessary to bond the molecules to be detected . The films of the present invention have deposited nanostructures, do not require a corrosion step, and can be deposited on any substrate, including plastic.

In these and all other applications, the method for producing the deposited porous silicon as proposed in the present invention provides several distinct advantages over electrochemical wet etchants and prior art deposited materials. These benefits fall into four groups: (1) substrate variability, (2) porosity and film controllability, (3) consistency with porosity and thickness, and (4) plasma- Process flexibility.

In the case of the low temperature direct deposition method of the present invention, the porous semiconductor film can be obtained on any substrate including an insulator, a metal foil and a plastic. The films of the present invention can be doped or undoped and can have a thickness of about 10 nm or greater, preferably 10-20 nm. The electrochemical method requires that a porous semiconductor layer be obtained only on a conductive substrate or layer. The starting material must be doped and should have a sufficient thickness to ensure that the corroded material obtains the required morphology. Prior art deposition methods provide morphology that varies with the film thickness and can only reach the porosity of the film of the present invention after a separate erosion step has been performed and always produce an amorphous phase material. The plasma basic treatment process and parameters and conditioning used by the present inventors provide a controlled, porous and phase dry process for thin films deposited on any substrate with simultaneous corrosion and deposition.

As noted, the fact that these films can be deposited on an insulating structure facilitates their use in sensor structures. In addition, the distinct nanostructures of the present invention having a continuous uniform and uniform void network and void volume aligned perpendicular to the film surface can be used in applications such as electrical sensors, electrophoresis and chromatographic and mass-desorption applications, Facilitating mass transfer. This feature of aligned void-column network morphology with non-tapered columns and relatively uniformly continuous voids is found only in the porous silicon of the present invention. This means that the films of the present invention can be used in the fields of adsorption, desorption, transport and immobilization applications (for example, immobilizing and fixing species such as DNA for identification and sorting and fixing and contacting molecules for molecular electronics) Especially, make it excellent. By direct deposition methods, porous semiconductors can also be obtained on any type of optical material substrate, such as transparency, polarizability, and the like. This facilitates and extends the use of porous semiconductors in optical applications such as antireflection, optical cavities, and light trapping coatings. Finally, when a porous semiconductor is deposited on a flexible polymer substrate, a non-planar curved porous semiconductor layer can also be made available.

This method takes advantage of the plasma-based processing technology. For example, the chemical composition of the highly porous silicon film of the present invention can be controlled by the precursor gas incorporated into the plasma during the co-deposition-corrosion process. This makes it possible to produce porous Ge, Ge: C, Si: C, Si: O, Si: F and Si: Cl as well as intrinsic, n-type or p-type porosity-Si. In addition, the chemical composition of the film can vary during deposition, and thus throughout the thickness of the film. Conversely, due to the electrochemical corrosion of the already grown material, the chemical composition of the porous-silicon layer can not be determined at any other site than the final surface, and the control of such surface composition is limited by the electrolyte used. Since the films of the present invention grow under high vacuum, contamination due to air exposure can be prevented, but conventional porous silicon films can be easily contaminated because they are processed in wet chemicals.

Whether using standard electrochemical etching or using the plasma deposition method of the present invention, the resulting porous silicon material is terminated by a hydrogen atom at the direct completion of the preparation. However, at ambient conditions this hydrogen-terminated surface exhibits considerable sensitivity to room temperature oxidation and hydrogen loss. Therefore, decomposition of the porous silicon film can be avoided if stable surface passivation is immediately effected. This is accomplished by a vacuum-based process by using a multi-chamber system and performing coating, immersion, vapor exposure, etc. in separate chambers, or by replacing the chamber atmosphere in the same reaction system after film deposition-erosion. In this respect, the high-density plasma method of the present invention is highly applicable because it facilitates any kind of reaction at lower activation energies to facilitate plasma-based surface treatment. Generally, the chemistry of the surface can be controlled during or after deposition. For example, F-terminated or Cl-terminated surfaces in porous films can be obtained in situ, and such surfaces are believed to be more resistant to degradation. Of course, the porous film can be treated in an external reaction system and can become hydrophobic or hydrophilic by surface treatment. The film of the present invention can be functionalized by surface treatment.

While the inventors have shown and described several embodiments in accordance with the present invention, it will be clear to those skilled in the art that many obvious changes will occur to those skilled in the art. Accordingly, the inventors are not intended to be limited to the embodiments illustrated and described, but are to be understood to cover all modifications and variations that fall within the scope of the appended claims.

SUMMARY OF THE INVENTION [

The present invention provides a deposited porous film comprising a plurality of perturbations extending therefrom into voids having a porosity of up to about 90%. The plurality of perturbations are disposed substantially perpendicular to the substrate, or alternatively to the base layer. Many of the perturbations are bar-shaped columns, semiconducting and polycrystalline like a silicon material. Porosity is the result of continuous voids. The perturbation portion has a height adjustable by the film thickness and has a diameter of about 1 nm to about 50 nm. More particularly, the column has a diameter of about 3 nm to about 7 nm. Also, the perturbations are found in a concentrator having a diameter of about 50 to 500 nm or more.

The present invention also relates to a substrate; And a plurality of percussive portions extending therefrom into the void having a porosity of up to 90%, the porous film being disposed on the substrate. The composite structure may further comprise a coating layer such that the porous film is disposed on the coating layer. The coating layer may comprise at least one of an insulator such as an organic insulator, silicon nitride and silicon oxide; Or active materials such as piezoelectric materials, ferroelectrics, metals and semiconductors. The composite structure may further include a capping layer such that the porous film is disposed between the capping layer and the substrate. The capping layer may comprise at least one of an insulator, such as an organic insulator, silicon nitride and silicon oxide; Or active materials such as piezoelectric materials, ferroelectrics, metals and semiconductors. The porous film has a thickness of at least about 10 nm, wherein the film can vary from polycrystalline to amorphous. This deposited porous film is organized into a two-dimensional periodic array of rod-shaped perturbations. The porous film can be converted, for example, to be oxidized to SiO ₂ , or to react with the metal to form a silicide, or it can be nitrated with Si ₃ N ₄ . The film may also be doped or undoped. The substrate of the composite structure is selected from glass, metals including foil, insulators, plastics and semiconductor-containing materials. The substrate may optionally be coated with an atomic motion barrier, a thermal barrier, an electrically insulating or stress-controllable film. For example, the film is a silicon nitride barrier layer, wherein the thickness of the silicon nitride barrier layer may vary from a few hundred angstroms or less to about 5,000 nm. The film can be changed during deposition and throughout the film thickness.

The present invention also provides a method of forming a composite structure comprising a substrate and a porous film. The method includes depositing a porous film on a substrate through a high density plasma deposition. The porous film of the method comprises a plurality of percussive portions extending therefrom into voids having a porosity of up to about 90%. The method also includes the step of corroding the porous film, wherein the deposition and erosion steps preferably occur simultaneously. Corrosion can be carried out in the presence of a corrosive agent in a plasma such as hydrogen, chlorine, fluorine, HCl, HF, and derivative radicals thereof. The above-mentioned high density plasma deposition is performed in the presence of at least one precursor gas selected from hydrogen and a silicon-containing gas. More particularly, a silicon-containing gas is silane (SiH ₄ gas). The deposition step is conducted under excitation of microwave power in the range of about 100 watts to 1200 watts in the presence of a magnetic field in the range of about +800 to -600 Gauss at the substrate site at a temperature of about 250 DEG C or less. The deposition step is also performed without voltage applied between the plasma and the substrate. An additional step in this method may be to remove the porous layer at selected sites of the porous film by corrosion to create an air gap, release or isolation structure.

More particularly, the present invention relates to a process for preparing a substrate; Conditioning the surface of the deposition tool; Plasma deposition tools are used to generate ions, radicals and other excited species; Introducing power into the plasma chamber; Supplying a precursor gas into the plasma deposition tool to ignite the plasma; Further adjusting the deposition rate using an adjusting agent; And depositing a film on the substrate through plasma deposition.

The substrate may be further coated before deposition of the porous film, depending on the type of substrate provided. The substrate is coated using materials selected from materials useful for functions such as electrical isolation, planarizing, atomic motion barrier, stress conditioning, and thermal coupling. The substrate may be exposed to surface texturing such as liquid chemical corrosion or plasma chemical corrosion.

The plasma deposition tool used in the method is a high density plasma deposition tool. A specific high-density plasma deposition tool for this method is the electron cyclotron resonance tool.

Porosity can be controlled by substrate processing such as coating, plasma power, substrate-site magnetic field, gas composition, deposition temperature, plasma-substrate bias, chamber conditioning, process pressure, deposition gas and flow rate. The energy of the plasma species impacting the deposition / corrosion film is important and must be kept low. This regulation is ensured by a high density plasma system, for example the kinetic energy of the impact species in the ECR tool is expected to be <45 eV.

The present invention also contemplates adjustment on the column. For example, at high deposition pressures (e.g., 20 mTorr), the column becomes amorphous instead of polycrystalline in the case of silicon.

The present invention also relates to a process for producing a substrate by steps such as barrier coating; Conditioning the chamber; High density plasma deposition tools are used to generate ions, radicals and other excited species; Introducing power into the plasma chamber; Supplying a H ₂ gas and a precursor gas, such as SiH ₄ gas, into the deposition chamber into the plasma chamber to ignite the plasma; Maintaining the temperature for substrate deposition below about 250 ° C; Further adjusting the deposition rate using an adjustment such as a substrate-site field; And depositing a film on the substrate.

The microwave power introduced into the ECR plasma chamber is from about 100 watts to 1200 watts, preferably from about 340 watts to 640 watts. The microwave power used has a frequency of 2.45 GHz.

In the present invention, the H ₂ flow rate is between about 1 sccm and 500 sccm, preferably between about 10 and 100 sccm. In the present invention, the SiH ₄ flow rate is between about 1 sccm and 300 sccm, preferably between about 2 and 10 sccm.

More particularly, the present invention uses a high density plasma deposition tool with a precursor gas such as hydrogen diluted silane (H ₂ : SiH ₄ ); Introducing microwave power of about 100 to 1200 watts into the ECR chamber through a fused quartz window and a waveguide that minimizes the reflected power by tuning the tuner; Using a DC electromagnet to set a static magnetic flux density in the vicinity of the substrate of +800 to -600 Gauss; Supplying H ₂ gas at about 1 sccm to 500 sccm through a dispersal ring in an ECR plasma chamber; Injecting the SiH ₄ gas into the deposition chamber at about 1 sccm to about 300 sccm through the gas distribution ring (ring distribution) of from about 1.3 ㎝ position of the substrate and the top; Maintaining a temperature of less than 250 占 폚 for substrate deposition; And depositing a film on the substrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a sensor, a desorption spectroscopy structure, a gas detector, and a plasma display field, a dielectric field, a monitoring of lateral resistance and forming an air gap structure for tubes, sorting and chromatographic applications, Can be used in optical structures such as optoelectronic devices and solar cells for optical impedance applications. These applications generally include a substrate; And a composite structure having a porous continuous film disposed on the substrate, the composite structure including polycrystalline or amorphous silicon having a porosity of 90% or less.

Claims (49)

A porous film comprising a plurality of percussive portions extending into a void having a porosity of up to about 90%. The porous film of claim 1, wherein the plurality of perturbations are disposed substantially perpendicular to the substrate. The porous film of claim 1, wherein the plurality of perturbations are disposed substantially perpendicular to the base layer. The porous film of claim 1, wherein the plurality of perturbing portions are columnar-shaped columns. The porous film according to claim 1, wherein the perturbing part is a semiconductor. The porous film according to claim 1, wherein the perturbing part is polycrystalline or amorphous. The porous film of claim 6, wherein the polycrystalline or amorphous phase is a silicone material. The porous film of claim 1, having a thickness of about 10 nm or greater. 2. The porous film of claim 1, wherein the perturbation portion has a diameter of about 1 nm to about 50 nm. 10. The porous film of claim 9, wherein the perturbation portion has a diameter of about 3 nm to 7 nm. The porous film of claim 1, wherein the perturbation is present in a focusing body having a diameter of about 50 nm to 500 nm. The porous film of claim 1, wherein the porosity is adjustable by at least one of substrate coating, plasma power, process pressure, magnetic field, plasma-substrate bias, chamber conditioning, deposition gas, flow rate and deposition temperature. Board; And a plurality of percussive portions extending into voids having a porosity of up to 90%, the porous structure comprising a porous film disposed on a substrate. The composite structure according to claim 13, wherein the porous film further contains a substrate coating layer so as to be disposed on the substrate coating layer. 15. The composite structure according to claim 14, wherein the substrate coating layer is at least one coating material selected from the group consisting of an organic insulator, silicon nitride and silicon oxide. The composite structure according to claim 14, wherein the coating layer is at least one active material selected from the group consisting of a piezoelectric material, a ferroelectric material, a metal and a semiconductor. 14. The composite structure of claim 13, further comprising a capping layer such that the porous film is disposed between the capping layer and the substrate. 18. The composite structure of claim 17, wherein the capping layer is at least one insulating material selected from the group consisting of an organic insulator, silicon nitride, and silicon oxide. The composite structure according to claim 17, wherein the capping layer is at least one active material selected from the group consisting of a piezoelectric material, a ferroelectric material, a metal and a semiconductor. 14. The composite structure of claim 13, wherein the porous film has a thickness of at least about 10 nm. 14. The composite structure of claim 13, wherein the porous film is polycrystalline or amorphous. 22. The composite structure of claim 21, wherein the polycrystalline or amorphous porous film is structured with a two-dimensional periodic array of rod-shaped perturbations. 23. The composite structure of claim 22, wherein the rod-like perturbation portion has a diameter of about 1 to 50 nm. 23. The composite structure of claim 22, wherein the rod-like perturbation is present in a focusing body having a diameter of about 50 to 500 nm. 14. The composite structure of claim 13, wherein the substrate is selected from the group consisting of glass, metal foil, insulating material, plastic material and semiconductor-containing material. Depositing a porous film on the substrate through a high density plasma deposition at a temperature of less than 250 &lt; 0 &gt; C. 27. The method of claim 26, wherein the porous film comprises a plurality of percussive portions extending into a void having a porosity of up to about 90%. 27. The method of claim 26, further comprising the step of corroding the porous film. 29. The method of claim 28 wherein the deposition and erosion steps are performed simultaneously. 29. The method of claim 28, wherein the corrosion is carried out by hydrogen, chlorine, fluorine, HCl, HF and their derivative radicals. 27. The method of claim 26, wherein the high density plasma deposition is performed in the presence of a precursor environment comprising a silicon-containing gas. 32. The method of claim 31, wherein the precursor environment comprises at least one gas selected from the group consisting of hydrogen and a silicon-containing gas. 33. The method of claim 32 wherein the silicon-containing gas is silane. 27. The method of claim 26, wherein the deposition step is performed in the vicinity of the substrate in the presence of a magnetic field in the range of about +800 to -600 Gauss. 27. The method of claim 26, wherein the deposition step is performed in the presence of a microwave excitation frequency in the range of about 100 watts to 1200 watts. 27. The method of claim 26, wherein the deposition step is performed in the absence of a voltage applied between the plasma and the substrate. 27. The method of claim 26, wherein the composite structure further comprises a substrate coating layer so that the porous film is disposed on the substrate coating layer. 38. The method of claim 37, wherein the substrate coating layer is at least one coating material selected from the group consisting of an organic insulator, silicon nitride and silicon oxide. 38. The method of claim 37, wherein the coating layer is at least one active material selected from the group consisting of a piezoelectric material, a ferroelectric material, a metal, and a semiconductor. 27. The method of claim 26, wherein the composite structure further comprises a capping layer such that the porous film is disposed between the capping layer and the substrate. 41. The method of claim 40, wherein the capping layer is at least one insulating material selected from the group consisting of an organic insulator, silicon nitride, and silicon oxide. 41. The method of claim 40, wherein the capping layer is at least one active material selected from the group consisting of a piezoelectric material, a ferroelectric material, a metal, and a semiconductor. 27. The method of claim 26, wherein the porosity is adjustable by at least one of substrate coating, plasma power, process pressure, magnetic field, plasma-substrate bias, chamber conditioning, deposition gas, flow rate and deposition temperature. 27. The method of claim 26, wherein at least a portion of the porous layer in the porous film is removed by corrosion to create an air gap, release or isolation structure. Board; And a composite structure having a porous film disposed on the substrate, the composite structure including a plurality of sliding portions extending into a void having a porosity of 90% or less. 46. The sensor of claim 45, wherein the sensor is capable of monitoring lateral resistance, optical or genetic response. Board; And a composite structure having a porous film disposed on the substrate, the composite structure including a plurality of sliding portions extending into a void having a porosity of 90% or less. Board; And a composite structure having a porous film disposed on the substrate, the composite structure including a plurality of sliding portions extending into a void having a porosity of 90% or less. 49. The apparatus of claim 48, capable of performing desorption mass spectrometric analysis.