摘要:

Reactive ion etching (RIE) of compound semiconductors is well‐known to produce damaged surfaces that reduce quantum yield and produce excessive leakage currents. Therefore, it is desirable to develop procedures to passivate or remove such process‐induced damage. From a manufacturing perspective, it would be ideal to perform such postetch passivationinsitu. In this work, we use real‐time photoluminescence monitoring andexsitux‐ray photoelectron spectroscopy to evaluate the effectiveness ofinsituH2plasma passivation of GaAs after RIE in a BCl3/Cl2plasma. Because of reactor wall contamination, we conclude thatinsitupassivation, at least for this chemical etching system, is not practical; two chambers are needed, one for etching and another for passivation. However, RIE damage is removed effectively by first stripping the Cl‐contaminated GaAs surface using an acid solution and then exposing the resultant oxidized surface to the H2plasma. This procedure results in an elevated quantum yield that remains stable in air indefinitely.

ISSN:1071-1023    

DOI:10.1116/1.586189

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Recent studies of chemical vapor deposition of SiO2films on GaAs substrates show the existence of subcutaneous oxidation processes which degrade the electrical properties of the interface. To form SiO2/GaAs interfaces this work presents a different approach based on a direct writing technique that consists in the growth of the SiO2film by electron beam stimulated oxidation of ultrathin Si layers deposited onto the GaAs(100) surfaces. Modeling of the interface chemical evolution is performed by a detailed quantitative analysis of the Auger intensities. Subcutaneous oxidation is found to play an important role for Si films as thin as 1 monolayer (ML), and its kinetics is discussed by comparison with that of the SiO2growth. However, while a Ga oxide film clearly appears below the Si oxide layer for 1 Si ML deposits, no signs of Ga oxidation are found for Si films 2.5 ML thick, that providing an estimate for discussing the minimum thickness required to grow abrupt SiO2/GaAs interfaces.

ISSN:1071-1023    

DOI:10.1116/1.586190

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Silicon dioxide films with breakdown field strength ≳12 MV/cm and fixed charge density ∼3×1010cm−2were grown using an oxygen plasma generated by an electron cyclotron resonance source at 16 °C. This oxidation temperature is much lower than previously reported plasma oxidation of silicon, while the breakdown field and fixed charge density for these oxides are comparable to thermally grown oxide at high temperature. The oxidation rate was studied as a function of microwave power, pressure, rf power, source to sample distance, and oxidation time. The oxidation rate increases with microwave power but decreases with source distance and rf power. At pressure<5 mTorr, the oxidation rate increases rapidly with decreasing pressure. The oxide thickness increases with the oxidation time but the oxidation rate decreases. These oxide films were found to have oxygen to silicon ratio of 2 using x‐ray photoelectron spectroscopy. From the ellipsometry measurements, these films show a refractive index around 1.47. These results indicate that high quality oxide films with properties that are similar to that of thermal oxide can be grown at low temperature.

ISSN:1071-1023    

DOI:10.1116/1.586191

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Enhanced etching of a room temperature Si(100) surface is observed during exposure to a neutral hyperthermal chlorine beam. Etching is monitored by mass spectrometric detection of silicon chloride products (SiClx) in the scattered flux. The etchant beam is produced by laser vaporization of cryogenic chlorine films; it consists of ≥93% molecular chlorine with a variable kinetic energy distribution depending on laser energy. The sustained etching rate, based on detection of SiCl3+, is independent of energy when the maximum Cl2kinetic energy is less than 3 eV but increases by a factor of 3.6±1 when the maximum energy is ≊6 eV. No etch products are detected with thermal Cl2. The etching rate of the most energetic chlorine is greater than the thermal chlorine etching rate by a factor of ≥30.

ISSN:1071-1023    

DOI:10.1116/1.586192

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

One of the critical steps in top‐surface imaging lithographic processes such as diffusion enhanced silylated resist DESIRE is the dry development, i.e., the anisotropic oxygen plasma etching of the nonsilylated resist selective with respect to silylated resist. In this article the etch characteristics of the DESIRE process in a magnetically enhanced reactive ion etching etcher are described. The application of a magnetic field is shown to increase both the etch rate and the etch selectivity. The dependency of etch rates, etch selectivity, linewidth and residue formation on magnetic field, radio‐frequency (rf) power, oxygen pressure, and flow are reported. The expected linewidth variation with varying etch selectivity, due to sloped silicon profiles in the resist, is observed when the selectivity variation is due to varying rf power or oxygen flow. However, it is not observed when the selectivity variation is due to varying magnetic field. An explanation is given. The etch rate of silylated resist is shown to be dependent on the properties of the thin SiO2top layer formed during oxygen etching, which is dependent both on etching and on silylation conditions.

ISSN:1071-1023    

DOI:10.1116/1.586193

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Light scattering from latent images in photoresist is useful for lithographic tool characterization, process monitoring, and process control. In particular, closed‐loop control of lithographic processes is critical for high yield, low cost device manufacturing. In this work, we report use of pulsed laser diffraction from photoresist latent images in 0.24 μm pitch distributed feedback laser gratings. Gated detection of pulsed light scattering permits high spatial resolution probing using ultraviolet light without altering the latent image. A correlation between latent image and etched grating diffraction efficiencies is demonstrated and shows the value of ‘‘upstream’’ monitoring.  

ISSN:1071-1023    

DOI:10.1116/1.586194

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

The influence of diffraction on the shape and size of features printed using x‐ray proximity printing with a collimated x‐ray source (measured beam divergence of ∼0.2 mrad full width at half‐maximum) at mask to wafer gaps of 25 μm and above is described. Three major conclusions can be drawn from the results: (1) Diffraction can distort the shape of a printed feature, and the systematic shape changes observed in resist images can be explained using simple scaling based on Fresnel diffraction; (2) The linewidth change with exposure dose is independent of feature type and size, and depends only on the square root of the mask to wafer gap; and (3) The bias of each printed feature varies when all of the feature types and sizes are printed at the same dose. Resist images of 2.0–0.25 μm contact holes printed at mask to wafer gaps ranging from 25 to 515 μm are presented. The square contact holes on the mask print diamond shaped at a Fresnel number of 2.5. Isolated lines, spaces, and line‐space arrays ranging from 1.0 to 0.25 μm were printed in thin PMMA (0.1 μm thick) resist at gaps ranging from 25 to 80 μm over a series of exposure doses. A 10% increase in exposure dose results in a 16, 20, and 30 nm change in linewidth at gaps of 25, 40, 80 μm, respectively. When the 1.0–0.25 μm lines, spaces, and line‐space arrays are printed with a single dose at a 40 μm gap, the bias variation among the features appears to be approximately ±20 nm. However, this bias measurement is very sensitive to the metrology technique used, and systematic errors in these absolute measurements may be a significant contributor to the observed bias variation. All the experimental results are compared to calculated aerial images. Exposures in thick PMMA (0.5 μm) show trends similar to those observed in thin resist. However, as the thickness of the resist increases, the dose at which the printed linewidth has zero bias decreases, and approaches the dose required to clear a large open area.

ISSN:1071-1023    

DOI:10.1116/1.586195

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Extremely high quality vertical structures, suitable for integrated optical components, have been fabricated in GaAs using electron beam lithography and chemically assisted ion beam etching. By using the directly exposed electron beam resist as etch mask all quality degrading intermediate pattern transfers were eliminated, resulting in high resolution and reproducibility. In order to obtain a vertical mask profile and high durability, pattern corrected exposure and heat treatment of the electron beam resist was employed. The pattern correction of the resist exposure was studied using an exposure simulation program. Calculations, based on an estimation of the facet roughness using a scanning electron microscope, suggest optical scattering ratios as low as 0.6% and 7.1% for external and internal reflection of 850 nm light, respectively.  

ISSN:1071-1023    

DOI:10.1116/1.586196

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

In a manner suitable for large‐scale processing, vertical platinum structures having thicknesses (linewidths) down to 20 nm, heights up to 700 nm, an aspect ratio up to 13, and different geometric shapes have been fabricated on top of a silicon dioxide substrate by Pt deposition from the thermal decomposition of a platinum precursor molecule under gas phase collisionless conditions followed by ion‐assisted etching. Scanning electron microscopy analysis shows that the structures have very small grains, high uniformity, and very sharp contours, demonstrating a high degree of conformal deposition. Scanning Auger microscopy reveals platinum only on the structures. X‐ray diffraction and x‐ray photoelectron spectroscopy analysis of the as‐deposited platinum film show that the platinum film is polycrystalline and has no detectable impurity. Scotch tape test shows good bonding of the film. Mass spectrometric measurements suggest that substantial amounts of stable precursor fragments from partial decomposition of the parent precursor desorb from the substrate. The observed desirable film morphology and purity can be attributed to the favorable choice of template material, decomposition mechanism of the precursor, and the chemical beam conditions used.

ISSN:1071-1023    

DOI:10.1116/1.586197

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

As the microelectronics industry strives to achieve smaller device design geometries, control of linewidth, or critical dimension (CD), becomes increasingly important. Currently, CD uniformity is controlled by exposing large numbers of samples for a fixed exposure time which is determined in advance by calibration techniques. This type of control does not accommodate variations in optical properties of the wafers that may occur during manufacturing. In this work, a relationship is demonstrated between the intensity of light diffracted from a latent image consisting of a periodic pattern in the undeveloped photoresist and the amount of energy absorbed by the resist material (the exposure dose). This relationship is used to simulate exposure control of photoresist on surfaces having slight variations in optical properties, representative of those found in operating process lines. We demonstrate that linewidth uniformity of the developed photoresist can be greatly improved when the intensity of diffracted light from the latent image is used to control the exposure dose. Samples include a variety of photoresist materials and substrates with a wide range of optical properties. To verify the experimental observations, diffractions from the latent image grating structures is modeled using rigorous coupled wave analysis. The modeling is used to predict the diffraction from a latent image as a function of the substrate optical properties and the parameters of the latent image (i.e., linewidth, sidewall angle). Good agreement is obtained between theoretical and experimental observations. Conversely, the inverse problem is solved in which the parameters of the diffracting structure (the latent image) are determined from a measurement of the diffracted power. Therefore, the diffracted power can be monitored for the purpose of determining when the latent image will produce the proper CD upon development.  

ISSN:1071-1023    

DOI:10.1116/1.586198

出版商:American Vacuum Society    

年代:1992

数据来源: AIP