摘要:

The oxidation of a hydrogen terminated Si surface can locally be induced with a scanning tunnelling microscope (STM) operating in air or with a beam of free electrons in a controlled oxygen environment. The oxidation mechanism of both processes was studied and compared. The oxidation with the STM in air depends strongly on the applied tip‐substrate voltage and writing speed, but is not proportional to the tunnelling current. This is in contrast to the process with a beam of free electrons. The thickness of the electron beam induced oxide is studied as a function of electron energy, electron dose, and oxygen pressure. Oxide thicknesses of 0.5–3 nm are measured using Auger spectroscopy. The initial step of the oxidation process is the electron beam induced removal of hydrogen from the surface. The electron dose requirement for this step was determined as a function of electron energy. The dose is found to be minimal for 100 eV electrons, and is ≊4 mC/cm2. Oxide lines made with the STM on Si(110) were used as a mask to wet etch the pattern into the Si(110). With tetramethyl ammonium hydroxide, a selective anisotropic etch liquid, trenches with a width of 35 nm and a depth of 300 nm were made. We show that it is also possible to locally oxidize hydrogenated amorphous silicon (a‐Si:H) and use the oxide as an etching mask. Hydrogenated amorphous silicon has the advantage that it can be deposited in very thin layers on almost any substrate and therefore has great potential as STM and electron‐beam resist.

ISSN:0734-211X    

DOI:10.1116/1.587858

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Low‐voltage electron beam lithography has been considered for some time for high‐resolution lithography because of reduced proximity effects, increased resist sensitivities, and reduced substrate damage. An accelerating voltage of 1 kV is being considered for the operation of microcolumns that are being developed for use in an innovative, high‐speed, high‐resolution electron beam lithography system. The development of resists and processes for use at 1 kV then becomes one of the essential components in this developing technology. Since 1 keV electrons have a penetration depth of ∼60 nm in organic polymers, the resists used for electron beam exposures must be correspondingly thin. This makes the development of processes for pattern transfer a challenge. Here, we report on three resist and processing schemes for use at 1 kV which can be used to produce 50–100 nm wide structures. Structures as small as 50 nm wide with 3 to 1 aspect ratios, and trenches 300 nm deep and less than 100 nm wide have been successfully transferred into Si substrates. Despite the use of very thin resists, the transferred patterns do not suffer from noticeable defects.

ISSN:0734-211X    

DOI:10.1116/1.587859

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

A Monte Carlo simulation has been performed for photoelectrons and Auger electrons generated in Si or Ge doped polymethyl methacrylate (PMMA) resist (Si5xC5(1−x)H8O2or Ge5xC5(1−x)H8O2) films for the enhancement of dry etching resistance under MoLα x‐ray exposure. It is found that the addition of such heavy elements, especially Ge, into the resist is very effective for reducing the spatial spreading of energy absorption. Calculations for line and space patterns with an equal 100 nm width show that the interproximity effect between the patterns decreases significantly with an increasing content of heavy atoms doped. It is also shown that about the same resolution as obtained for a pure PMMA resist with an AlKα x ray (1.5 keV) can be achieved with a MoLα x ray (2.3 keV) by adding Ge atoms with a content ofx=0.1–0.2 into the resist.

ISSN:0734-211X    

DOI:10.1116/1.587860

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The advantages of a retarding field immersion lens for focusing low energy electrons and ions have been well chronicled. One recent development is a retarding field lens in which the sample is outside the retarding field (i.e., a nonimmersion lens). Thus, any sample roughness will not distort the focusing field. We describe here a simple model and analysis that indicates that the performance of such a lens can be almost as good as that of a retarding field immersion lens. For example, it should be possible to focus 1 keV electrons with an energy spread of 1 eV into a beam diameter of 4 nm using realistic values of maximum voltage and retarding field strength; the effective resolution under these conditions is estimated to be 1.4 nm.

ISSN:0734-211X    

DOI:10.1116/1.588192

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The effect of the remaining solvent on the diffusion of the catalytically active acid within the chemical amplification resists is discussed. A range of solvents was investigated from the viewpoint of sensitivity, diffusion, and resolution. The solvent remaining after the coating and baking processes is thought to one of the most probable factors among the several possible causes in the determination of the performance of the resists. It is also considered to result in the environmental instability which is currently one of the most serious problems in the use of the resists of this type. The remaining solvent drastically enhances the thermal diffusion of acid generated from photo‐acid generators upon photoanalysis. The log of the diffusion range of the acid is found to be proportional to the concentration of the remaining solvent. This phenomenon may be described by a theory which combines the hole theory of liquids and the free volume theory of polymers and was also found to be the correlation energy between resin, solvent, and acid. In practice, this enhancement of diffusion range by remaining solvent does not result in higher sensitivity but rather degrades the performance of the resists.

ISSN:0734-211X    

DOI:10.1116/1.588193

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

A pattern recognition algorithm is developed to estimate the top width and bottom width of trenches of semiconductor wafers simultaneously. A confocal microscope is used in this study because of its excellent depth resolution. The signals from the confocal microscope are compared to a set ofaprioriwaveforms with known trench dimensions. An optimal estimate is chosen. Principle component decomposition of the set of waveforms is used to achieve reduced storage and improved computational speed. An interpolation method is used to improve the accuracy of the estimate. Experimental results of deep trenches are provided to demonstrate the approach.

ISSN:0734-211X    

DOI:10.1116/1.588194

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The use of thin‐film interferometry to determine the thickness of thin films is extended from unpatterned to patterned films. We developed a two‐color thin‐film interferometer which is robust and suitable for shop‐floor use. With this new diagnostic, the etch rates of both the masking film and the underlying layer can be monitored. Several approaches to analyzing the thin‐film interferometry data from patterned samples are explored including a mechanistic model, a simplified sine wave model, and fast Fourier transforms. The relative advantages and disadvantages of each technique are described. Both the mechanistic and sine wave models are complicated by the fact that they are nonlinear functions of the etch rates. It was therefore useful to examine maps of the mean squared error of the fit of data to the sine wave model. The analysis techniques are applicable to samples that have one or more thin films, are patterned with features that are larger than the wavelength of light, λ, and where at least a thickness λ of each film is etched away. The analysis techniques are demonstrated on laboratory data sets of the etching of photoresist‐masked oxide films on silicon wafers.

ISSN:0734-211X    

DOI:10.1116/1.588195

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

A new algorithm method used to determine the correlation position between two marks for automatic alignment in microcircuit fabrication has been developed. This algorithm maintains the correlation technique advantage such as its high immunity to noise and poor contrast in the mark signal. The alignment overlay precision achieved is better than one pixel. By using this algorithm method, the 486‐33PC computer takes about 4 s to determine the correlation position without any special hardware. This article describes the method along with giving experimental results.

ISSN:0734-211X    

DOI:10.1116/1.588196

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Plasma deposition of monosubstituted organosilicon precursors can result in layers containing extensive Si–Si bonded backbones. When these films are simultaneously exposed to ultraviolet light and oxygen, the Si–Si bonds are scissioned and oxygen inserted to form Si–O–Si polymer chains. It is shown that these films can be deposited by a low‐pressure dc plasma source. The plasma is created by electronic excitation of Xe and methylsilane with an axial magnetic field to confine the plasma near the substrate surface. The plasma has a narrow spread of relatively low (10–20 eV) particle energies. In this way the production of undesirable gas phase reactions is limited. The ability to work at low pressure, with correspondingly low deposition rates, makes it possible to deposit thin resist layers which are suitable for nanolithographic applications.

ISSN:0734-211X    

DOI:10.1116/1.588197

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Diethyldiethoxysilane is an organosilicate that may offer new possibilities for SiO2deposition. In this study, the adsorption and decomposition of diethyldiethoxysilane (DEDEOS) was examined on Si(100)2×1 and porous silicon surfaces using laser‐induced thermal desorption (LITD), temperature‐programmed desorption (TPD), Fourier‐transform infrared (FTIR), and Auger electron spectroscopy techniques. The FTIR studies revealed that DEDEOS dissociatively adsorbs on porous silicon and deposits ethyl and ethoxy species. These species are observed to decompose via a β‐hydride elimination mechanism at ∼700 K. In agreement with this mechanism, TPD studies on Si(100)2×1 observed ethylene (C2H4) at ∼700 K and H2desorption at ∼800 K. Additionally, the controlled deposition of SiO2was achieved on Si(100)2×1 using repetitive cycles of DEDEOS adsorption at 300 K followed by thermal annealing at 820 K for 300 s. After the rapid deposition of an oxygen coverage of θO∼2.4 ML, the oxygen deposition rate decreased and reached a constant deposition rate of ∼0.04 ML oxygen per cycle after ten cycles. The constant reactivity of the growing SiO2film was attributed to dangling bond reactive sites resulting from β‐hydride elimination of the ethyl groups (SiCH2CH3→SiH+CH2=CH2) and subsequent H2desorption (2SiH→2Si+H2). DEDEOS was also utilized to grow SiO2films under high‐pressure chemical vapor deposition conditions. The rate of SiO2deposition displayed Arrhenius behavior with an activation barrier ofEact=49±6 kcal/mol. This activation barrier is similar to activation barriers measured earlier for SiO2growth using tetraethoxysilane (TEOS). The deposition rate of SiO2by DEDEOS was approximately 60 times slower than the deposition rate by TEOS at 943 K and 0.5 Torr.

ISSN:0734-211X    

DOI:10.1116/1.588198

出版商:American Vacuum Society    

年代:1995

数据来源: AIP