Anthony Yen | National Tsing Hua University (original) (raw)

Papers by Anthony Yen

Research paper thumbnail of Explosive phenomenon of AlCu/TiN and W-plugs multilevel interconnect system

The 'explosive phenomenon' of AlCu/TiN metal line (explosive defect) always be observed p... more The 'explosive phenomenon' of AlCu/TiN metal line (explosive defect) always be observed posterior to deposit oxide film by Plasma Enhanced Chemical Vapor Deposition (PECVD) and their profile look like distorted bamboo structure. From the Tunneling Electronic Microscope (TEM) analysis result and the defect distribution on the wafer, the defects were enhanced by the compressive stress of oxide film. The tungsten

Research paper thumbnail of System and Method for Combined Intraoverlay and Defect Inspection

Research paper thumbnail of Reduce mask overlay error by removing film deposited on blank of mask

Research paper thumbnail of 0.13-UM Optical Lithography for Random Logic Devices Using 248-NM Attenuated Phase-Shifting Masks

We report here a lithography process for 0.13 micrometers lines using a high NA 248 nm scanner an... more We report here a lithography process for 0.13 micrometers lines using a high NA 248 nm scanner and attenuated phase-shifting masks (AttPSM) employing optical proximity correction with optimized assisting features. Our current result indicate a common depth of focus of 0.5 micrometers and exposure latitude of 10 percent for lines with line/space ratios from 1:1.2 to isolated. The mask error

Research paper thumbnail of Characterization and correction of optical proximity effects in deep‐ultraviolet lithography using behavior modeling

Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society

We present the characterization of optical proximity effects and their correction in deep‐UV lith... more We present the characterization of optical proximity effects and their correction in deep‐UV lithography using an empirically derived model for calculating feature sizes in resist. The model is based on convolution of the mask pattern with a set of kernels determined from measuring the printed test structures in resist. The fit of the model to the measurement data is reviewed. The model is then used for proximity correction using commercially available proximity correction software. Corrections based on this model is effective in restoring resist linearity and in reducing line‐end shortening. It is also more effective in reducing optical proximity effects than corrections based only on aerial image calculations. © 1996 American Vacuum Society

Research paper thumbnail of Extension of deep-ultraviolet lithography for patterning logic gates using alternating phase shifting masks

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena, 1999

We present the combination of alternating phase-shifting masks and rule-based optical proximity c... more We present the combination of alternating phase-shifting masks and rule-based optical proximity correction (OPC) for the patterning of 0.13 μm polysilicon gate lines. Using the optimal process condition, a process window with 1.2 μm of depth of focus (DOF) and 15% exposure latitude is obtained for 0.13 μm isolated lines in resist. In addition, with the application of rule-based OPC, the common DOF for 0.13 μm lines of various line-to-space ratios can be improved from 0 to 0.6 μm.

Research paper thumbnail of <title>Optical proximity effects and correction strategies for chemical-amplified DUV resists</title>

Optical Microlithography IX, 1996

ABSTRACT Optical proximity effects (OPE) are narrowing the process window in the 0.25micrometers ... more ABSTRACT Optical proximity effects (OPE) are narrowing the process window in the 0.25micrometers - 0.18micrometers CD range. Hence optical proximity correction (OPC) might be required. These proximity effects and correction strategies are studied in detail in this work. First, an evaluation methodology is derived for the three types of OPE (linewidth differences with pitch, end-of-line effects and corner rounding). Hence, the influence of various parameters on OPE is investigated for negative tone and positive tone resists, since clear differences exist in OPE for dark field and bright field masks. Linewidth differences with pitch are small for negative tone resists, end-of-line effects are less pronounced for positive tone materials. Obviously, optical parameters have an important influence on OPE. Also, loading effects during etch processes deserve attention. Aerial image based proximity correction is evaluated. With respect to CD variations with pitch, important improvements are obtained for some resists, but not for all materials. End-of-line effects and corner rounding are improved by the use of OPC in all our experiments. Superior proximity correction results are expected with the expansion of aerial image based OPC by implementation of resist models.

Research paper thumbnail of An accurate method to determine the amount of out-of-band light in an EUV scanner

SPIE Proceedings, 2015

In this paper, we proposed a new design of the test mask to measure the amount of the out-of-band... more In this paper, we proposed a new design of the test mask to measure the amount of the out-of-band (OOB) light from an extreme-ultraviolet (EUV) light source by detuning the period of the multilayer (ML), rather than changing the material of the absorber, to suppress reflection of EUV light. The new OOB test mask also reflects essentially the same OOB light as that of the production mask at each wavelength in the whole OOB spectral range. With the help of the new OOB test mask, the contributions to the background intensity from in-band flare and OOB light can be correctly separated and an accurate optical-proximity-correction (OPC) model can be established.

Research paper thumbnail of Balancing lithographic performance and resist outgassing in EUV resists

Extreme Ultraviolet (EUV) Lithography IV, 2013

ABSTRACT Resolution (R), line-width roughness (L), and sensitivity (S) are three key indices desc... more ABSTRACT Resolution (R), line-width roughness (L), and sensitivity (S) are three key indices describing the performance of a resist. When optimizing a resist to compromise the RLS trade-off in extreme-ultraviolet lithography, outgassing of the resist also needs to be considered, because it will cause deposition of cleanable and non-cleanable contaminants on the surface of the projection optics and reduce the throughput of the exposure tool. In this paper, the dependence of outgassing of a resist on its compositions, such as types of photo-acid generator, quencher, and acid liable group as well as their loadings are investigated systematically through a set of specially prepared resist samples. The outgassing of these samples is tested on EUVOM-9000 from Litho Tech Japan. The lithographic performances of these samples are also characterized on the ASML NXE3100. Directions for optimizing resist lithographic performance under the constraint of resist outgassing are proposed.

Research paper thumbnail of The role resist plays in EUVL extensibility

SPIE Proceedings, 2012

In this paper, the impact of resist on the lithographic process window is investigated. To estima... more In this paper, the impact of resist on the lithographic process window is investigated. To estimate the resolution limit of EUVL due to the limitation from resist performance, a simplified resist model, called diffused aerial image model (DAIM), is employed. In the DAIM, the resist is characterized by the acid diffusion length, or more generally, resist blur. Lithographic process windows with resists of various blurs are then calculated for different technology nodes. It is concluded that the resist blur needs to be smaller than 8 nm to achieve a reasonable window for the technology node with the minimum pitch of 32 nm. The performance of current resists can barely fulfill this requirement. Investigation of a more refined resist model is also initiated.

Research paper thumbnail of Quencher distribution engineering for out-of-band insensitive EUV resists: experiments and stochastic simulation

Extreme Ultraviolet (EUV) Lithography IV, 2013

ABSTRACT We investigated the effect of quencher type and loading concentration in OoB-insensitive... more ABSTRACT We investigated the effect of quencher type and loading concentration in OoB-insensitive EUV resists via actual exposure on the latest EUV scanner and stochastic simulation using Prolith. Model resist samples with two quencher types, conventional base type and photo-decomposable base type, at variant loading concentrations were prepared and tested. Basic indicators of lithographic performance, such as depth of focus, energy latitude, and line-width roughness were significantly improved by 80 nm, 8.4% and 25%, respectively along with a moderate increase of sensitivity (ca. 5mJ/cm2) under the optimized quencher condition. Meanwhile, we further quantitatively analysis the outgassing-induced contamination growth to realize the quencher distribution engineering effect on outgassing issue in EUV lithography. In addition, stochastic simulation for EUV resist featuring various types of quenchers provides certain correlation with the experimental results.

Research paper thumbnail of <title>Optical proximity effects correction at 0.25 um incorporating process variations in lithography</title>

Optical Microlithography X, 1997

ABSTRACT We study the optical proximity effect and its correction using empirically derived model... more ABSTRACT We study the optical proximity effect and its correction using empirically derived models for DUV lithography taking into account random process variations. The sensitivity of corrected configurations to different sources of process variation (exposure dose, defocus) is evaluated. For correction at a centered condition (optimum dose, zero defocus), problems may arise in ill-conditioned areas (inside corners of T-shape features, butting line-ends, etc.), when going away from the best focus and/or exposure dose, within the exposure/defocus window. Correction for sharp corners (aggressive correction) shows a stronger sensitivity to defocus than less corner sharpening (conservative correction). Furthermore, we study what types of design configurations tend to print poorly with process variations and investigate alternative correction optimization schemes that stabilize the printing performance in such areas. Various optimization alternatives to improve performance within the process window are evaluated. Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Abstract Text Return: Query Results Return items starting with number Query Form Database: Astronomy Physics arXiv e-prints

Research paper thumbnail of Top-surface imaging and optical proximity correction: a way to 0.18-um lithography at 248 nm

SPIE Proceedings, 1996

... Anne-Marie Goethals, J. Vertommen, Frieda Van Roey, Anthony Yen, Alexander V. Tritchkov, Kurt... more ... Anne-Marie Goethals, J. Vertommen, Frieda Van Roey, Anthony Yen, Alexander V. Tritchkov, Kurt G. Ronse, Rik M. Jonckheere, Luc Van den Hove. Abstract. We present a description of a software tool and a methodology for easily creating photoresist development rate ...

Research paper thumbnail of Overlay similarity: a new overlay index for metrology tool and scanner overlay fingerprint methodology

Metrology, Inspection, and Process Control for Microlithography XXIII, 2009

For different CD metrologies like average CD from CD SEM and optical CD (OCD) from scatterometry,... more For different CD metrologies like average CD from CD SEM and optical CD (OCD) from scatterometry, CD point-to-point R2 has been well adopted as the CD correlation index. For different overlay metrologies like image-based box-in-box overlay and scatterometry-based overlay, we propose the cosine similarity as the correlation index of overlay. The cosine similarity is a measure of similarity between two

Research paper thumbnail of <title>On the extensibility of extreme UV lithography</title>

Extreme Ultraviolet (EUV) Lithography II, 2011

In this paper, definition of line/space patterns at 44-, 32-, and 22-nm pitches using extreme-ult... more In this paper, definition of line/space patterns at 44-, 32-, and 22-nm pitches using extreme-ultraviolet lithography (EUVL) is investigated by aerial image simulation. The results indicate that extending EUVL to the 22-nm pitch requires reducing the mask shadowing effect, which implies reducing the mask absorber thickness as well as maintaining the 6-degree angle of incidence on the mask, if the

Research paper thumbnail of Printability of buried mask defects in extreme UV lithography

SPIE Proceedings, 2011

A programmed-defect mask consisting of both bump- and pit-type defects on the LTEM mask substrate... more A programmed-defect mask consisting of both bump- and pit-type defects on the LTEM mask substrate has been successfully fabricated. It is seen that pit-type defects are less printable because they are more smoothed out by the employed MLM deposition process. Specifically, all bump-type defects print even at the smallest height split of 1.7 nm whereas pit-type defects print only at

Research paper thumbnail of Feasibility demonstration of 0.18 μm and 0.13 μm optical projection lithography based on CD control calculations

1996 Symposium on VLSI Technology. Digest of Technical Papers

ABSTRACT

Research paper thumbnail of Characterization and optimization of CD control for 0.25-um CMOS applications

SPIE Proceedings, 1996

Optical lithography, since many years the workhorse in manufacturing of integrated circuits, is b... more Optical lithography, since many years the workhorse in manufacturing of integrated circuits, is being pushed to its limits. The extension of photolithography has been made possible by improvements in resist schemes and by resolution enhancement techniques. Although the resolution capabilities are available, maintaining CD-control will be one of the major challenges for photolithography engineers in the future. Traditionally, focus and

Research paper thumbnail of Combination of OPC and AttPSM for patterning sub-0.18-um logic devices

Phase-shifting mask (PSM) and modified illumination techniques have shown promise in improving re... more Phase-shifting mask (PSM) and modified illumination techniques have shown promise in improving resolution and process latitude in optical lithography. Here we present a combination of attenuated PSM and optical proximity correction (OPC) for the patterning of 0.15 micrometers polysilicon lines. Using the combination method, we obtained a depth of focus of 0.9 micrometers DOF for 0.15 micrometers isolated lines, much

Research paper thumbnail of Negative transconductance and negative differential resistance in a grid-gate modulation-doped field-effect transistor

Applied Physics Letters, Jan 30, 1989

We report on transport measurements in grid-gate lateral-surface-superlattice (LSSL) field-effect... more We report on transport measurements in grid-gate lateral-surface-superlattice (LSSL) field-effect transistors on a modulation-doped GaAs/AlGaAs heterostructure. The LSSL is created by a 0.2 μm period Ti/Au grid on top of the AlGaAs layer, which presents a tunable, two-dimensional periodic potential modulation to the electrons traveling from source to drain. Current measurements at 4.2 K as a function of gate bias exhibit negative transconductance at a fixed drain bias below 15 mV, providing evidence of a superlattice effect (i.e., coherent back-diffraction). In addition, negative differential resistance is observed at a fixed gate bias and a drain bias around 100 mV, which could be a manifestation of sequential resonant tunneling.

Research paper thumbnail of Explosive phenomenon of AlCu/TiN and W-plugs multilevel interconnect system

The 'explosive phenomenon' of AlCu/TiN metal line (explosive defect) always be observed p... more The 'explosive phenomenon' of AlCu/TiN metal line (explosive defect) always be observed posterior to deposit oxide film by Plasma Enhanced Chemical Vapor Deposition (PECVD) and their profile look like distorted bamboo structure. From the Tunneling Electronic Microscope (TEM) analysis result and the defect distribution on the wafer, the defects were enhanced by the compressive stress of oxide film. The tungsten

Research paper thumbnail of System and Method for Combined Intraoverlay and Defect Inspection

Research paper thumbnail of Reduce mask overlay error by removing film deposited on blank of mask

Research paper thumbnail of 0.13-UM Optical Lithography for Random Logic Devices Using 248-NM Attenuated Phase-Shifting Masks

We report here a lithography process for 0.13 micrometers lines using a high NA 248 nm scanner an... more We report here a lithography process for 0.13 micrometers lines using a high NA 248 nm scanner and attenuated phase-shifting masks (AttPSM) employing optical proximity correction with optimized assisting features. Our current result indicate a common depth of focus of 0.5 micrometers and exposure latitude of 10 percent for lines with line/space ratios from 1:1.2 to isolated. The mask error

Research paper thumbnail of Characterization and correction of optical proximity effects in deep‐ultraviolet lithography using behavior modeling

Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society

We present the characterization of optical proximity effects and their correction in deep‐UV lith... more We present the characterization of optical proximity effects and their correction in deep‐UV lithography using an empirically derived model for calculating feature sizes in resist. The model is based on convolution of the mask pattern with a set of kernels determined from measuring the printed test structures in resist. The fit of the model to the measurement data is reviewed. The model is then used for proximity correction using commercially available proximity correction software. Corrections based on this model is effective in restoring resist linearity and in reducing line‐end shortening. It is also more effective in reducing optical proximity effects than corrections based only on aerial image calculations. © 1996 American Vacuum Society

Research paper thumbnail of Extension of deep-ultraviolet lithography for patterning logic gates using alternating phase shifting masks

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena, 1999

We present the combination of alternating phase-shifting masks and rule-based optical proximity c... more We present the combination of alternating phase-shifting masks and rule-based optical proximity correction (OPC) for the patterning of 0.13 μm polysilicon gate lines. Using the optimal process condition, a process window with 1.2 μm of depth of focus (DOF) and 15% exposure latitude is obtained for 0.13 μm isolated lines in resist. In addition, with the application of rule-based OPC, the common DOF for 0.13 μm lines of various line-to-space ratios can be improved from 0 to 0.6 μm.

Research paper thumbnail of <title>Optical proximity effects and correction strategies for chemical-amplified DUV resists</title>

Optical Microlithography IX, 1996

ABSTRACT Optical proximity effects (OPE) are narrowing the process window in the 0.25micrometers ... more ABSTRACT Optical proximity effects (OPE) are narrowing the process window in the 0.25micrometers - 0.18micrometers CD range. Hence optical proximity correction (OPC) might be required. These proximity effects and correction strategies are studied in detail in this work. First, an evaluation methodology is derived for the three types of OPE (linewidth differences with pitch, end-of-line effects and corner rounding). Hence, the influence of various parameters on OPE is investigated for negative tone and positive tone resists, since clear differences exist in OPE for dark field and bright field masks. Linewidth differences with pitch are small for negative tone resists, end-of-line effects are less pronounced for positive tone materials. Obviously, optical parameters have an important influence on OPE. Also, loading effects during etch processes deserve attention. Aerial image based proximity correction is evaluated. With respect to CD variations with pitch, important improvements are obtained for some resists, but not for all materials. End-of-line effects and corner rounding are improved by the use of OPC in all our experiments. Superior proximity correction results are expected with the expansion of aerial image based OPC by implementation of resist models.

Research paper thumbnail of An accurate method to determine the amount of out-of-band light in an EUV scanner

SPIE Proceedings, 2015

In this paper, we proposed a new design of the test mask to measure the amount of the out-of-band... more In this paper, we proposed a new design of the test mask to measure the amount of the out-of-band (OOB) light from an extreme-ultraviolet (EUV) light source by detuning the period of the multilayer (ML), rather than changing the material of the absorber, to suppress reflection of EUV light. The new OOB test mask also reflects essentially the same OOB light as that of the production mask at each wavelength in the whole OOB spectral range. With the help of the new OOB test mask, the contributions to the background intensity from in-band flare and OOB light can be correctly separated and an accurate optical-proximity-correction (OPC) model can be established.

Research paper thumbnail of Balancing lithographic performance and resist outgassing in EUV resists

Extreme Ultraviolet (EUV) Lithography IV, 2013

ABSTRACT Resolution (R), line-width roughness (L), and sensitivity (S) are three key indices desc... more ABSTRACT Resolution (R), line-width roughness (L), and sensitivity (S) are three key indices describing the performance of a resist. When optimizing a resist to compromise the RLS trade-off in extreme-ultraviolet lithography, outgassing of the resist also needs to be considered, because it will cause deposition of cleanable and non-cleanable contaminants on the surface of the projection optics and reduce the throughput of the exposure tool. In this paper, the dependence of outgassing of a resist on its compositions, such as types of photo-acid generator, quencher, and acid liable group as well as their loadings are investigated systematically through a set of specially prepared resist samples. The outgassing of these samples is tested on EUVOM-9000 from Litho Tech Japan. The lithographic performances of these samples are also characterized on the ASML NXE3100. Directions for optimizing resist lithographic performance under the constraint of resist outgassing are proposed.

Research paper thumbnail of The role resist plays in EUVL extensibility

SPIE Proceedings, 2012

In this paper, the impact of resist on the lithographic process window is investigated. To estima... more In this paper, the impact of resist on the lithographic process window is investigated. To estimate the resolution limit of EUVL due to the limitation from resist performance, a simplified resist model, called diffused aerial image model (DAIM), is employed. In the DAIM, the resist is characterized by the acid diffusion length, or more generally, resist blur. Lithographic process windows with resists of various blurs are then calculated for different technology nodes. It is concluded that the resist blur needs to be smaller than 8 nm to achieve a reasonable window for the technology node with the minimum pitch of 32 nm. The performance of current resists can barely fulfill this requirement. Investigation of a more refined resist model is also initiated.

Research paper thumbnail of Quencher distribution engineering for out-of-band insensitive EUV resists: experiments and stochastic simulation

Extreme Ultraviolet (EUV) Lithography IV, 2013

ABSTRACT We investigated the effect of quencher type and loading concentration in OoB-insensitive... more ABSTRACT We investigated the effect of quencher type and loading concentration in OoB-insensitive EUV resists via actual exposure on the latest EUV scanner and stochastic simulation using Prolith. Model resist samples with two quencher types, conventional base type and photo-decomposable base type, at variant loading concentrations were prepared and tested. Basic indicators of lithographic performance, such as depth of focus, energy latitude, and line-width roughness were significantly improved by 80 nm, 8.4% and 25%, respectively along with a moderate increase of sensitivity (ca. 5mJ/cm2) under the optimized quencher condition. Meanwhile, we further quantitatively analysis the outgassing-induced contamination growth to realize the quencher distribution engineering effect on outgassing issue in EUV lithography. In addition, stochastic simulation for EUV resist featuring various types of quenchers provides certain correlation with the experimental results.

Research paper thumbnail of <title>Optical proximity effects correction at 0.25 um incorporating process variations in lithography</title>

Optical Microlithography X, 1997

ABSTRACT We study the optical proximity effect and its correction using empirically derived model... more ABSTRACT We study the optical proximity effect and its correction using empirically derived models for DUV lithography taking into account random process variations. The sensitivity of corrected configurations to different sources of process variation (exposure dose, defocus) is evaluated. For correction at a centered condition (optimum dose, zero defocus), problems may arise in ill-conditioned areas (inside corners of T-shape features, butting line-ends, etc.), when going away from the best focus and/or exposure dose, within the exposure/defocus window. Correction for sharp corners (aggressive correction) shows a stronger sensitivity to defocus than less corner sharpening (conservative correction). Furthermore, we study what types of design configurations tend to print poorly with process variations and investigate alternative correction optimization schemes that stabilize the printing performance in such areas. Various optimization alternatives to improve performance within the process window are evaluated. Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Abstract Text Return: Query Results Return items starting with number Query Form Database: Astronomy Physics arXiv e-prints

Research paper thumbnail of Top-surface imaging and optical proximity correction: a way to 0.18-um lithography at 248 nm

SPIE Proceedings, 1996

... Anne-Marie Goethals, J. Vertommen, Frieda Van Roey, Anthony Yen, Alexander V. Tritchkov, Kurt... more ... Anne-Marie Goethals, J. Vertommen, Frieda Van Roey, Anthony Yen, Alexander V. Tritchkov, Kurt G. Ronse, Rik M. Jonckheere, Luc Van den Hove. Abstract. We present a description of a software tool and a methodology for easily creating photoresist development rate ...

Research paper thumbnail of Overlay similarity: a new overlay index for metrology tool and scanner overlay fingerprint methodology

Metrology, Inspection, and Process Control for Microlithography XXIII, 2009

For different CD metrologies like average CD from CD SEM and optical CD (OCD) from scatterometry,... more For different CD metrologies like average CD from CD SEM and optical CD (OCD) from scatterometry, CD point-to-point R2 has been well adopted as the CD correlation index. For different overlay metrologies like image-based box-in-box overlay and scatterometry-based overlay, we propose the cosine similarity as the correlation index of overlay. The cosine similarity is a measure of similarity between two

Research paper thumbnail of <title>On the extensibility of extreme UV lithography</title>

Extreme Ultraviolet (EUV) Lithography II, 2011

In this paper, definition of line/space patterns at 44-, 32-, and 22-nm pitches using extreme-ult... more In this paper, definition of line/space patterns at 44-, 32-, and 22-nm pitches using extreme-ultraviolet lithography (EUVL) is investigated by aerial image simulation. The results indicate that extending EUVL to the 22-nm pitch requires reducing the mask shadowing effect, which implies reducing the mask absorber thickness as well as maintaining the 6-degree angle of incidence on the mask, if the

Research paper thumbnail of Printability of buried mask defects in extreme UV lithography

SPIE Proceedings, 2011

A programmed-defect mask consisting of both bump- and pit-type defects on the LTEM mask substrate... more A programmed-defect mask consisting of both bump- and pit-type defects on the LTEM mask substrate has been successfully fabricated. It is seen that pit-type defects are less printable because they are more smoothed out by the employed MLM deposition process. Specifically, all bump-type defects print even at the smallest height split of 1.7 nm whereas pit-type defects print only at

Research paper thumbnail of Feasibility demonstration of 0.18 μm and 0.13 μm optical projection lithography based on CD control calculations

1996 Symposium on VLSI Technology. Digest of Technical Papers

ABSTRACT

Research paper thumbnail of Characterization and optimization of CD control for 0.25-um CMOS applications

SPIE Proceedings, 1996

Optical lithography, since many years the workhorse in manufacturing of integrated circuits, is b... more Optical lithography, since many years the workhorse in manufacturing of integrated circuits, is being pushed to its limits. The extension of photolithography has been made possible by improvements in resist schemes and by resolution enhancement techniques. Although the resolution capabilities are available, maintaining CD-control will be one of the major challenges for photolithography engineers in the future. Traditionally, focus and

Research paper thumbnail of Combination of OPC and AttPSM for patterning sub-0.18-um logic devices

Phase-shifting mask (PSM) and modified illumination techniques have shown promise in improving re... more Phase-shifting mask (PSM) and modified illumination techniques have shown promise in improving resolution and process latitude in optical lithography. Here we present a combination of attenuated PSM and optical proximity correction (OPC) for the patterning of 0.15 micrometers polysilicon lines. Using the combination method, we obtained a depth of focus of 0.9 micrometers DOF for 0.15 micrometers isolated lines, much

Research paper thumbnail of Negative transconductance and negative differential resistance in a grid-gate modulation-doped field-effect transistor

Applied Physics Letters, Jan 30, 1989

We report on transport measurements in grid-gate lateral-surface-superlattice (LSSL) field-effect... more We report on transport measurements in grid-gate lateral-surface-superlattice (LSSL) field-effect transistors on a modulation-doped GaAs/AlGaAs heterostructure. The LSSL is created by a 0.2 μm period Ti/Au grid on top of the AlGaAs layer, which presents a tunable, two-dimensional periodic potential modulation to the electrons traveling from source to drain. Current measurements at 4.2 K as a function of gate bias exhibit negative transconductance at a fixed drain bias below 15 mV, providing evidence of a superlattice effect (i.e., coherent back-diffraction). In addition, negative differential resistance is observed at a fixed gate bias and a drain bias around 100 mV, which could be a manifestation of sequential resonant tunneling.