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Showing papers on "Proximity effect (electron beam lithography) published in 1985"


Patent
08 Oct 1985
TL;DR: In this paper, a method of drawing a desired pattern on a target through exposure thereof with an electron beam was proposed, where a pattern area (51, 52) on the target surface is defined by first pixels (53) arranged in rows and columns and is exposed by a first electron beam.
Abstract: In a method of drawing a desired pattern on a target through exposure thereof with an electron beam, a pattern area (51, 52) on the target surface is defined by first pixels (53) arranged in rows and columns and is exposed by a first electron beam. A background area (56) other than the pattern area on the target surface is also defined by secondary pixels (58) which are arranged in rows and columns, and is exposed by a secondary electron beam to compensate for the proximity effect. The secondary pixels (58) have a size larger than that of the first pixels (53) and the second electron beam forms on the target surface a second beam spot (59) which is larger than the first beam spot (54) formed on the target surface by the first electron beam so that the background area is exposed in a reduced period of time.

25 citations


Patent
Lawrence V. Gregor1
26 Apr 1985
TL;DR: In this paper, a multi-layered resist structure and methods of producing them which can be used in electronic device lithography to produce micrometer and submicrometer geometries are described.
Abstract: The present invention discloses multi-layered resist structures and methods of producing them which can be used in electronic device lithography to produce micrometer and submicrometer geometries. The resist structure comprises two or more layers at least one of which is a metallic material and at least one of which is a radiation-sensitive material. The metallic layer exhibits both a high atomic number and a high density. The metallic material is positioned relative to the radiation-sensitive polymeric material so that it can be used to control reflection and backscatter of radiation used to create a latent image within the radiation-sensitive polymeric material. The thickness of the metallic layer is determined by the amount of reflection desired and the amount of backscatter permitted into the layer of radiation-sensitive polymeric material.

19 citations


Journal ArticleDOI
TL;DR: In this paper, a partial transmission Fresnel zone plate (PT-FZP) is proposed, in which part of the normally transparent zones is transparent, and the distance between transparent zones can be set large so that a zone plate with very high resolution can be fabricated by electron beam lithography because the proximity effect due to electron scattering in resist layer can be reduced.

11 citations


Journal ArticleDOI
TL;DR: In this paper, the backscattered electron energy distribution in resist on a Si substrate for beam energies (E) of 20, 40, 60, and 120 keV was measured using exposure of a 0.1 μ thick PMMA resist layer to determine constant deposited energy contours.
Abstract: Proximity effect from electron scattering is a major limitation to using e‐beam lithography for high density, submicron patterns. Conventional beam writers operate near 20 keV where the range of the backscattered electron energy distribution is about 2 μ, comparable to the feature size in integrated circuits. Exposure from backscattered electrons creates complex interactions between the exposures of adjacent features and requires extensive computation for correcting the local dose. We report experimental measurements of both the magnitude and range of the backscattered electron energy distribution in resist on a Si substrate for beam energies (E) of 20, 40, 60, and 120 keV. The measurements were made using exposure of a 0.1 μ thick PMMA resist layer to determine constant deposited energy contours. The ratio of the integrated energy deposited in the resist by the backscattered electrons to that deposited by the primary electrons, ηE is found to be about 0.8 and is insensitive to energy. The range of the di...

10 citations


Journal ArticleDOI
TL;DR: In this article, the effects of errors in the correction dose, the correction beam diameter, and the registration between the pattern and correction exposures have been calculated analytically, and it is shown that the allowable tolerances for these parameters are wide.
Abstract: The GHOST proximity effect correction scheme has been applied to a round beam lithography system and also to a shaped beam system. It is shown that the image contrast of the GHOST scheme is constant at all spatial frequencies at which forward scattering is insignificant: the flatness of the modulation transfer function corresponds to the removal of the proximity effect. The effects of errors in the correction dose, the correction beam diameter, and the registration between the pattern and correction exposures have been calculated analytically, and it is shown that the allowable tolerances for these parameters are wide.

10 citations


Patent
10 Jun 1985
TL;DR: In this article, the problem of pattern distortion due to the proximity effect was corrected by deriving the irradiation offset amount based on the back scattering electrons from the pattern's drawing area factor in each divided region.
Abstract: PURPOSE: To enable the pattern distortion due to the proximity effect to be easily corrected so that a fine pattern can be formed with high precision, by deriving the irradiation offset amount based on the back scattering electrons from the pattern's drawing area factor in each divided region, and calculating the irradiation amount of the electron beam according to the offset amount. CONSTITUTION: In irradiating the resist applied on a substrate with an electron beam to form a pattern, the pattern is divided into a plurality of regions, the irradiation offset amount based on the back scattering electrons of the electron beam is derived from the pattern's drawing area factor in each divided region 1, and the irradiation amount is determined which has been provided with irradi ation correction of the electron beam, according to the irradiation offset amount. The divided region 1 may be the whole pattern, or it may be a division provided by depending on the pattern density. With this, the process can be simplified, the corrected amount can be obtained in a short time which is, e.g., about 1/100 as compared with the conventional external proximity effect correction method, and a fine pattern can be formed with high precision. COPYRIGHT: (C)1986,JPO&Japio

6 citations


Journal ArticleDOI
TL;DR: In this article, a Monte Carlo simulation of electron diffusion based on a single scattering model including secondary electron production is presented, where the inelastic energy loss is corrected as suggested by Spencer and Fano.

5 citations


Patent
03 Apr 1985
TL;DR: In this paper, the authors proposed a method to prevent a proximity effect resulting from remnant charges and pattern strain by previously forming a position, to which a resist layer is not shaped, to the surface of the outer edge section of a mask blank and exposing the resist layer by electron beams while an electrode for grounding is brought into contact with the position.
Abstract: PURPOSE:To prevent a proximity effect resulting from remnant charges and pattern strain by previously forming a position, to which a resist layer is not shaped, to the surface of the outer edge section of a mask blank and exposing the resist layer by electron beams while an electrode for grounding is brought into contact with the position. CONSTITUTION:At least one or more of positions 9, to which resist layers are not formed, are formed previously outside a pattern forming prearranged position 10 in the surface of a blank block 5. Electron beams EB are projected to the surface of the resist layer 4 while electrodes 7 for grounding are brought into contact with Cr oxide layers 3 exposed to the positions 9 by pressure to expose a circuit pattern. According to the method, since the electrodes 7 are brought into contact with the layers 3, charged electric charges do not remain in a layer 4, the layers 3 and a layer 2 and escape to the ground through the electrodes 7, thus resulting in no possiblity in which defective patterns are generated.

5 citations


Journal ArticleDOI
TL;DR: In this paper, the exposure characteristics and the proximity effect in Ag2Se/GeSe4 inorganic photoresists have been examined through experiment and high γ and high contrast are confirmed.
Abstract: The exposure characteristics and the proximity effect in Ag2Se/GeSe4 inorganic photoresists have been examined through experiment. As a result, high γ and high contrast are confirmed. Reciprocity law failure is not observed. The self‐compensation effect of the proximity effect due to the lateral Ag diffusion is verified by measuring the linewidth deviation. In addition, a logarithmic dependence of the Ag‐photodoped depth on the exposure dose is derived from the relation between the threshold exposure dose and the removal time of the photodoped layer. This behavior can be explained by a model which demonstrates that the Ag‐photodoping is promoted by the recombination of photoexcited electron‐hole pairs in GeSe4.

5 citations


Journal ArticleDOI
TL;DR: In this article, a new approach to electron beam lithography for device fabrications is described, which transfers relief images formed at the superficial layer of a positive resist inversely to the bottom layer of the resist.
Abstract: A new approach to electron beam lithography for device fabrications is described. This technique transfers relief images formed at the superficial layer of a positive resist inversely to the bottom layer of the resist. The technique can drastically improve the resolution and linewidth accuracy of delineated patterns by reducing proximity effects and the influence of incident beam spread. Writing time can also be reduced. 0.2‐μm very large scale integration patterns and feature with 250‐A linewidth less than the incident beam size have been successfully produced.

5 citations


Patent
25 Dec 1985
TL;DR: In this article, a buffer memory is used to store drawing pattern data stored in a disk and then used for electron beam drawing in a stage control system and electron beam deflecting system.
Abstract: PURPOSE:To correct drawing pattern data as they are compressed without using a computer and to perform the electron beam drawing effectively, by using a proximity effect correcting circuit in combination with a hardware provided in the electron beam drawing device. CONSTITUTION:The drawing pattern data read in a disk 2 are temporarily stored in a buffer memory 3. Each proximity effect data area of the data thus stored is sent out to be developed to a shot data by a compressed data developing circuit 4, and delivered to a correcting system through a mode switching switch 5. The shot data is sent to a bit map memory 6 (11) which has been cleared to zero, where it is converted to a shot image 12 and recorded. Among the data written in the memory 6, only the data used actually are again developed by the developing circuit 4 to shot data 13 and the address of a proximity effect affecting range 14 is calculated by an irradiation quantity computing circuit 7 and sent to the memory 6. The memory 6 reads out these data successively in a work line unit 15 and convert them into bit number data. Simultaneously, the bit number data is multiplied by a proximity effect coefficient to obtain a quantity of proximity effect on the subject word line, and an appropriate irradiation is recorded in the disk 2. When all the necessary processing operation is finished, the switch 5 is changed over to the printing mode so that the pattern data in the memory 3 are developed by the developing circuit 4. The data are sent to a stage control system and electron beam deflecting system 9, and blanked by a blanking system 10 according to the data from the irradiation memory 8, so that the electron beam drawing is performed effectively.

Journal ArticleDOI
TL;DR: In this paper, the impact of the background on the edge control is directly related to fundamental physics through the Monte Carlo calculation, and the nominal edge is used as the critical aspect to be controlled.
Abstract: Proximity effect in electron‐beam lithography is studied with an emphasis on physical understanding. Computer simulation is used to explore correction schemes which specifically include the resist behavior and yet are theoretically manageable in formulating the pattern correction for mathematical analysis. Both energy density part way through the resist and relative importance of background on critical edge are investigated. It is shown that one‐third of the resist thickness from the substrate appears to be where the process parameters should be characterized, and that the total effective deposited energy at the nominal edge must be reduced as the background contribution increases. A mathematical model and design graphs are developed so that the impact of the background on the edge control is directly related to fundamental physics through the Monte Carlo calculation. The nominal edge is used as the critical aspect to be controlled and the constraint of constant bias can be applied.

Journal ArticleDOI
TL;DR: In this article, the impact of lateral diffusion of Ag in projection printing in a GexSe1−x resist system is explored and compared with simulations and experiments, showing that the proximity effects are predominantly those associated with the aerial image, even under low intensity exposure conditions which maximize lateral diffusion effects.
Abstract: Simulations and experiments are used to explore the impact of lateral diffusion of Ag in projection printing in a GexSe1−x resist system. The lateral transport of Ag makes more Ag available for photodoping in the bright areas than in the dark areas. This lateral diffusion which is responsible for the edge sharpening effect causes nearby features to interact not only in the aerial image but also in the competition for Ag. Proximity effects arising both from this diffusion and from the optical image itself are simulated and compared with experiments. Good agreement between simulation and experiment is found. Under normal use up to dose of 500 mW/cm2, the proximity effects are predominantly those associated with the aerial image, even under low‐intensity exposure conditions which maximize lateral diffusion effects. No unusual increase in the tendency for small defects to print was observed either for line features or contact holes. For very high doses proximity effects due to lateral diffusion can be observed.

Journal ArticleDOI
TL;DR: In this article, a high-voltage (100 kV) variable-shaped electron beam lithography system has been developed with the aim of improving the edge resolution in variable shape lithography to better than 1 μm even at high beam currents.
Abstract: A high‐voltage (100 kV) variable‐shaped electron beam lithography system has been developed With this system it is possible to improve the edge resolution in variable‐shape lithography to better than 01 μm even at high beam currents In addition the other advantages of high‐voltage lithography such as reduced proximity effect, improved line width control in lithography over steps in the substrate, and better profiles on thick resist overlayers are also obtained Experimental results are compared with simulation from a Monte Carlo based model of the electron column which predicts the benefits of working at higher beam voltage than the conventional 20 kV Results are presented which show current profiles and exposures in resist of patterns with sizes from 5 μm×5 μm to ∼1 μm×1 μm with sub 01 μm resolution at beam voltages of 70 kV and greater while maintaining a beam current of >3 μA

Journal ArticleDOI
TL;DR: In this paper, the authors proposed the GHOST solubility ratio (Srg) method for positive electron beam resist characterization, which removes the development time ambiguity inherent in resist characterization by means of a thickness remaining vs dose curve, and eliminates the experimental difficulty in characterization of resist based on measurements of unexposed solubilities rate.
Abstract: Positive electron beam resists can be characterized by the GHOST solubility ratio parameter Srg defined as the ratio of the solubility at the nominal exposure dose Qe to the solubility at the GHOST correction dose, [ηe/(1+ηe)]xQe. This parameter removes the development time ambiguity inherent in resist characterization by means of a thickness remaining vs dose curve, and eliminates the experimental difficulty in characterization of resist based on measurements of unexposed solubility rate. Modeling data indicate that the Srg parameter is a good measure of resist performance. GHOST proximity effect correction results on PMMA exposed at doses from 10 to 200 μC/cm2 illustrate experimentally the dependency of feature quality on the value of Srg. The Srg method is a general technique for resist characterization, and is valid whether or not proximity effect correction is used. This parameter has been used to compare the performance of PMMA, EBR‐9, CP‐3 and Microposit 2400. Electrical test measurements show tha...

Patent
16 Apr 1985
TL;DR: In this paper, a reticle with a pattern consisting of a photoelectron generating film brought to a porous state is minimized with the increase of pattern size and executing reduced exposure, where the hole diameter is formed in size such as approximately 0.2mumphi one.
Abstract: PURPOSE:To reduce the adverse effect of a proximity effect by forming a reticle with a pattern consisting of a photoelectron generating film brought ot a porous state so that the mean electron-beam generating efficiency of the pattern is minimized with the increase of pattern size and executing reduced exposure. CONSTITUTION:A large number of holes (circular holes from which gold is removed) are formed to a large pattern 14 for a gold thin-film to shape a porous film, and a small pattern 13 is left as it is a conventional compact film. The hole diameter is formed in size such as approximately 0.2mumphi one, and formed in size in an extent that the hole is not made sure when a reticle with these patterns is reduction-projected. Accordingly, a proximity effect is reduced because the number of photoelctrons discharged per the unit area of the large pattern 14 is made smaller than that of the small pattern 13. The gold thin- film having the porous film quality can be formed by adjusting a sputtering method, through which gold is applied, or etching (containing lift-off) the film after coating.

Patent
03 Apr 1985
TL;DR: In this article, a pattern is drawn while varying acceleration voltage in response to the size of the pattern, such that the pattern can be drawn in a short drawing time by drawing the pattern while varying the acceleration voltage.
Abstract: PURPOSE:To draw a pattern, which hardly displays a proximity effect and has high accuracy, in a short drawing time by drawing the pattern while varying acceleration voltage in response to the pattern. CONSTITUTION:A pattern is drawn while varying acceleration voltage in response to the size of the pattern. The pattern such as a pattern 1 (20mumX20mum) having size of not less than 1mum width is drawn is drawn by acceleration voltage of 10kv, and the pattern such as a pattern 2 (0.5mumX30mum) having size of less than 1mum width is drawn by using acceleration voltage of 80kv. Accordingly, exposure time may be reduced to one fourth times or less as long both the pattern 1 and the pattern 2 are exposed by 80kv, and the fine pattern in 0.5mum width can be formed by sufficient resolution because it is drawn by acceleration voltage of 80kv.

Journal ArticleDOI
TL;DR: In this paper, a fast correction program that has two new techniques for the proximity effect has been developed for highly accurate VLSI patterning on a negative resist, and a pattern accuracy of ± 0.1 µm and a uniform resist of the desired thickness were obtained.
Abstract: When applying a proximity-effect correction to VLSI patterning, the major challenge is to obtain a highly accurate pattern without excessive computation. A fast correction program that has two new techniques for the proximity effect has been developed for highly accurate VLSI patterning on a negative resist. The first technique is the effective definition of sample points where energy intensity is calculated to obtain a highly accurate pattern. The second is the use of the exposure-intensity reduction rate which corresponds to a change in the pattern dimensions to reduce the computation time. A pattern accuracy of ±0.1 µm and a uniform resist of the desired thickness were obtained. The computation time is proportional to the 1.2 power of pattern density.

Journal ArticleDOI
TL;DR: In this article, a new proximity effect correction technique for high accuracy resist exposure, denoted as Enhanced Proximity Effect Correction (EPEC), has been developed and succesfully implemented.

Journal ArticleDOI
A. Izrael1, J. Bellessa1, B Akamatsu1
TL;DR: In this article, a Monte-Carlo simulation and a simple model of interaction between the electrons and the resist were used to calculate the proximity effect at three different electron beam energies (100, 40 and 20 keV) for various pattern expositions.

Patent
25 Jun 1985
TL;DR: In this article, the effect of the proximity effect of a transfer pattern in a photo-electron image reduction projection type electron beam transfer method was reduced by forming a pattern for generating a photoelectricron image by using the quality of materials of two kinds having different photoelectron generating efficiency.
Abstract: PURPOSE:To reduce the effect of the proximity effect of a transfer pattern in a photoelectron image reduction projection type electron beam transfer method by forming a pattern for generating a photoelectron image by using the quality of materials of two kinds having different photoelectron generating efficiency and using the quality of a material having large photoelectron generating efficiency for a peripheral region. CONSTITUTION:A first layer 15 consisting of the quality of a material having a comparatively small work function, such as Si, Se, etc. is formed on a substrate 14, the surface thereof is shaped by the quality of a material generating no photoelectrons, and a resist 16 corresponding to a desired pattern is formed. The first layer 15 in a section where the resist 16 is not shaped is removed through etching, and a predetermined pattern composed of the first layer 15 is formed. A second layer 17 is shaped on the substrate 14 and the first layer 15 in the pattern section by using the quality of a material having a comparatively large work function, such as Au, Ag, etc., and a second resist 18 is formed at a position where the fringe section of the predetermined pattern is removed. The second layer 17 in a position where there is no resist 18 is removed through selective etching, and a reticle 1 having desired pattern constitution is manufactured.

Patent
24 Oct 1985
TL;DR: In this paper, the authors proposed a method to suppress increase in the number of exposure pattern as well as to prevent the generation of wasteful data transfer time caused by the restriction of capacity of an exposing buffer memory by a method wherein, utilizing a shape correcting method having a relatively small pattern dividing number, an arbitrary measurement correction is performed on the optional part located on the outer circumference of a pattern.
Abstract: PURPOSE:To suppress increase in the number of exposure pattern as well as to prevent the generation of wasteful data transfer time caused by the restriction of capacity of an exposing buffer memory by a method wherein, utilizing a shape correcting method having a relatively small pattern dividing number, an arbitrary measurement correction is performed on the optional part located on the outer circumference of a pattern. CONSTITUTION:A pattern data information group is sent to and stored in a buffer memory 2 from a central information processing device 1. Informations are sent to a pattern circumferential information generating circuit 3 and exposing period controlling circuit 4 successively, the internal exposure information is placed in a holding register 7 and an exposure period data holding register 8 in a compressed form. A shot pattern is successively generated along the outer circumference of a pattern by a shot information generating circuit 5, and the circuit 5 gives a directional width data to exposure shot forming device driving amplifiers 9a and 9b, and it gives also coordinate data to exposure shot deflectors 11a and 11b through a shot position correcting circuit 6. The exposure period data holding register 8 gives exposure period data to an electron beam breaker driving amplifier 10. As a result, the shape of the exposure pattern is changed by an electron beam exposing device A, and an exposure wherein proximity effect is corrected can be performed.

Journal ArticleDOI
TL;DR: In this paper, a new evaluation method based on the difference between the resist development energy and the exposure energy at points on the edge of each shape was introduced to clarify error factors from the exposure conditions, the proximity effect correction method, and the machine exposure fluctuation.
Abstract: To create submicrometer patterns with high accuracy on thick single-layer negative resist, error factors that degrade pattern accuracy have been investigated. Pattern accuracy was analyzed using a new evaluation method based on the difference between the resist development energy and the exposure energy at points on the edge of each shape. By introducing a new evaluation parameter, we were able to clarify error factors from the exposure conditions, the proximity effect correction method, and the machine exposure fluctuation. The evaluation parameter K is Q/Q_{0} where Q is the exposure dose appropriate for the desired resist thickness and Q 0 is the interface gel dose. It was found that the resist resolution and the rounding error of the exposure dose were serious error factors, especially in delineation on submicrometer patterns. To achieve 0.5-µm patterns with ±0.1-µm accuracy on 1-µm-thick negative resist, the resist evaluation parameter K must be less than 2, the rounding error of the exposure dose must be less than 2.5 percent of the dose, and the beam addressing unit (LSB) must be less than 0.025 µm.

Patent
04 Mar 1985
TL;DR: In this paper, the problem of correcting the proximity effect for obtaining the design pattern and for actual irradiation of electron beam was addressed by calculating the ratio of scattered electron beam intensity at the point where the influence of proximity effect can be neglegible to such intensity.
Abstract: PURPOSE:To previously inspect whether a proximity effect is adequately corrected or not and exposure pattern can be resolved or not by correcting proximity effect and determining exposure data based on the exposure condition for the specified design pattern data. CONSTITUTION:The data having a design pattern indicated by a solid line is stored in the memory. The pattern indicated by the broken line indicates the region for correcting the proximity effect for obtaining the design pattern and for actual irradiation of electron beam. For inspection of exposure pattern, the design pattern data is read from the memory and amount of correction is calculated. A plurality of sample points are provided on the design pattern, a scat- tered electron beam intensity on the sample points by electron beam irradiation for the exposure data is calculated and a ratio of scattered electron beam intensity at the point where the influence of proximity effect can be neglegible to such intensity is calculated. Using such ratio, a pattern size at the sampling point is calculated and evaluation is carried out whether the maximum and minimum values are in the preset range or not.