WO2005048338A1 - Procede et substrat semiconducteur permettant de transferer un modele d'un masque de phase a un substrat - Google Patents

Procede et substrat semiconducteur permettant de transferer un modele d'un masque de phase a un substrat Download PDF

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Publication number
WO2005048338A1
WO2005048338A1 PCT/FI2004/000677 FI2004000677W WO2005048338A1 WO 2005048338 A1 WO2005048338 A1 WO 2005048338A1 FI 2004000677 W FI2004000677 W FI 2004000677W WO 2005048338 A1 WO2005048338 A1 WO 2005048338A1
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WO
WIPO (PCT)
Prior art keywords
layer
pattern
substrate
etching
antireflective coating
Prior art date
Application number
PCT/FI2004/000677
Other languages
English (en)
Inventor
Tomi RYYNÄNEN
Petri Melanen
Pekka Savolainen
Original Assignee
Modulight, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Modulight, Inc. filed Critical Modulight, Inc.
Publication of WO2005048338A1 publication Critical patent/WO2005048338A1/fr

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Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/004—Photosensitive materials
    • G03F7/09—Photosensitive materials characterised by structural details, e.g. supports, auxiliary layers
    • G03F7/091—Photosensitive materials characterised by structural details, e.g. supports, auxiliary layers characterised by antireflection means or light filtering or absorbing means, e.g. anti-halation, contrast enhancement
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/0005—Production of optical devices or components in so far as characterised by the lithographic processes or materials used therefor
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/004—Photosensitive materials
    • G03F7/09—Photosensitive materials characterised by structural details, e.g. supports, auxiliary layers
    • G03F7/11—Photosensitive materials characterised by structural details, e.g. supports, auxiliary layers having cover layers or intermediate layers, e.g. subbing layers

Definitions

  • the present invention relates generally to semiconductor lasers.
  • the present invention relates to a novel and improved method and apparatus for fabricating of diffractive gratings for semiconductor lasers cost effectively and with high throughput.
  • High-speed semiconductor DFB (Distributed Feedback) and DBR (Distributed-Bragg-Reflector) lasers are crucial for high-speed optical communication links. These lasers can be directly modulated at frequencies reaching 10 to 20 GHz, and have important applications in WDM (wavelength division multiplexing) optical networks.
  • High performance DFB and DBR lasers demand that careful attention be paid to the design and manufacture of the grating which provides the optical feedback. Spatial-hole burning, side-mode suppression, radiation loss, laser linewidth, spontaneous emission in non-lasing modes, lasing wavelength selection and tunability, laser re- laxation oscillation frequency etc. are all features that are very sensitive to the grating design and manufacturing .
  • IL is a conceptually simple process where two coherent beams interfere to produce a standing wave, which can be re- corded in a photoresist.
  • the spatial-period of the grating can be as fine as half the wavelength of the interfering light, allowing for structures of the order of 100 nm from UV wavelengths, and features as small as 30-40 nm using a deep UV ArF laser.
  • the problems of IL are that it requires narrowband coherent illumination to produce grating, it is not stable, it is difficult to achieve alignment between the interference fringes and existing patterns on the substrate, presence of existing features on the substrate could interfere with the exposure, and IL is sensitive as regards the optic alignment with respect to the surface .
  • UV Photolithography is the process by which patterns on a semiconductor material can be defined using UV light.
  • the surface is cleaned to remove any traces of contamination from the surface of the wafer such as dust, organic, ionic and metallic compounds.
  • the cleaned wafer is subjected to priming, to aid the adhesion of the resist to the surface of the substrate material.
  • a resist is applied to the surface using a spin-coating machine.
  • the photo mask is created by a photographic process and developed onto a glass, substrate. Alignment of the mask is critical and must be achieved in x-y as well as rotationally.
  • the mask may be in contact with the surface, very close to the surface or used to project the mask onto the surface of the substrate. This technique is very sensitive to resist and mask structure .
  • X-ray lithography may be used for fabricating gratings.
  • interference lithography is used once to pattern an x-ray mask, which can be used repeatedly to transfer the patterns to substrates. X-rays typically emerge from the vacuum sys- tern through a thin nitride membrane window and illuminate the mask and sample.
  • x-ray lithography benefits from the very different way that x-rays interact with materials.
  • e-beam lithography In an electron-beam lithography system, a focused e- beam is traced over a surface to define almost any prescribed pattern. A combination of electromagnetic beam deflection and interferometrically controlled stage motion allows one to write patterns over a relatively large area.
  • One of the limitations of e-beam lithography is throughput. Because each pixel comprising the pattern must be exposed separately and sequentially, direct e-beam exposures are typically time- consuming. For this reason, e-beam lithography is primarily used for building prototype devices and for generating masks, which can be used repeatedly in a higher throughput system such as optical photolithography or x-ray lithography. A more serious limitation of e-beam lithography is the difficulty in achieving accurate pattern placement .
  • NSH near-field holography
  • the mask carries a grating with perfect pitch, which is produced with crossed laser beams and etched into a hard quartz sub- strate.
  • Near-field holography makes use of monochromatic and polarized light of high collimation that is impinging under an oblique angle onto a phase mask carrying the grating pattern. The zero diffraction or- der simply passes through the plate whereas the minus first (-1) diffraction order is diffracted under an angle that has the same value as the impinging beam, but is directed to the opposite side. Higher orders are suppressed.
  • the grating on the mask is etched in a way to give both beams the same intensity.
  • the resulting interference pattern has the same pitch as the original grating on the quartz mask and can be transferred into a photoresist layer of the same thickness as the line width transferred.
  • For the grating trans- fer to be successful it is important to prevent back reflection from the substrate surface as this severely disturbs the interference of the two diffracted beams, leading to intensity fluctuations that mirror the mask/substrate gap variations caused by uneven wafer topography (typically 1-2 ⁇ m) .
  • the reflection from glass substrates is very low and poses no problem.
  • semiconductor materials like InP the main material used for DFB lasers, are often highly, reflective under the light incidence of ca. 45° which is typically used.
  • an antireflective material has to be spun onto the substrate before the resist is applied.
  • Both polymer layers, antireflective material and photoresist form a good AR coating, which suppresses reflection, thus enabling successful grating transfer.
  • the main problem of NFH is the pattern transfer from the photoresist to BARC (bottom antireflection coating) . This is due to almost the same etching rate of these used materials. Especially this is a major problem when etching small period gratings.
  • the present invention relates to a method for transferring a pattern, e.g. a grating pattern from a phase mask to a substrate.
  • the invention is especially well suited for fabricating small period gratings for long wavelength semiconductor lasers.
  • the inventive process for transferring a pattern to a substrate which is provided with a layer structure comprising at least a photoresist layer and bottom antireflective coating (BARC) , comprises the steps of developing said pattern on the photoresist layer by UV light and transferring said developed pattern from photoresist layer to said substrate by etching.
  • This etching can be e.g. a reactive ion etching or other corresponding etching technique.
  • BARC is not needed if resist and dielectric thickness are properly adjusted (optimised) with respect of each other. In this case the process is simplified quite a lot. If the resulting grating is as good (or better) than using BARC, then it is clearly advantageous not to use BARC.
  • a first -dielectric layer between said photoresist layer and said bottom antireflective coating in order to differentiate the etching rate of the two adjacent materials, i.e. the photoresist layer and bottom antireflective coating.
  • the material of said first di- electric layer is selected so that the etching selectivity between said photoresist layer and said first dielectric layer, and between said bottom antireflective layer and said first dielectric layer is maximized.
  • the method further comprises the steps of etching said pattern from said developed photoresist into said first dielectric layer by using said photoresist layer as an etch mask; etching said pattern from said first dielectric layer into said bottom antireflective coating layer by using said first dielectric layer as an etch mask; and etching said pattern from said bottom antireflective coating layer into said substrate by using said bottom antireflective coating layer as an etch mask. Finally the remaining parts of said layers are removed or cleaned.
  • a second dielectric layer is arranged between said bottom antireflective coating and said substrate in order to differentiate the etching rate of the two adjacent materials, i.e. said bottom antireflective coating and said substrate.
  • the layer thickness for all - -layers in said layer structure are optimised for optimal output and pattern transfer from said photoresist layer to said substrate. This optimisation means minimising the reflectance from combination of all layers at exposure wave- length.
  • each layer does not need to be optimised separately (although can be done so) to produce minimum reflectivity but instead the combination of them is more important.
  • dielectric layer thickness is much less than thickness of photoresist and BARC to improve pattern transfer during the process (this depends also on the etching method and parameters chosen) .
  • photoresist thickness should be around half of the grating pitch (lOOnm) or less to allow small grating figures to be exposured and developed to the resist. In principle all layer thickness can be varied when taking into account these factors above .
  • the invention is directed to a semiconductor substrate for fabricating a grating pattern for a semiconductor laser device by using Near Field Holography technique, which semiconductor sub- strate is provided with a layer structure comprising a photoresist layer and a bottom antireflective coating on said substrate. Said photoresist layer is arranged on said antireflective coating.
  • said layer structure further comprises a first dielectric layer between said photoresist layer and said bottom antireflective coating in order to differentiate the etching rate of the two adjacent materials.
  • the material of said first dielectric layer is selected so that the etching selectivity between said photore- sist layer and said first dielectric layer, and between said bottom antireflective layer and said first dielectric layer is maximized.
  • said layer structure further comprises a second dielectric layer between said bottom antireflective coating and said substrate in order to differentiate the etching rate of the two adjacent materials, i.e. between said bottom antireflective coating and said substrate. It might further improve the etching selectivity when a thicker antireflective layer works as a mask for etching the second dielectric through, and the second dielectric layer works ultimately as a mask for semiconductor etching. In this case the etching profile might be better because the final etch mask is now thinner and keeps its form better than a thicker antireflective layer during the process.
  • the fabricating technique in accordance with the present invention is simple, cheap, stable, and efficient (has high throughput) compared to the interference lithography and other lithographic techniques. It also provides improved etching quality. The present also facilitates smaller gratings to be formed and better reproducibility compared to method where shadow masking is used to improve etching quality.
  • Fig 1 is a block diagram illustrating the process steps according to one embodiment of the present invention.
  • Figure 1 represents a simplified and idealistic presentation of grating fabrication using Near Field Holography (NFH) and tri-layer resist stack according to the present invention.
  • The. key part (and major difference compared to commonly used grating fabrication process done with NFH or interference lithography) of this invention is the NFH together with use of the dielectric layer in between the resist and BARC layers.
  • the reason for using dielectric layer is to facilitate high quality pattern transfer from resist to BARC.
  • Resist and BARC as carbonaceous polymers are essentially the same material from etching chemistry point of view and thus their etching rate is about the same. Instead, with certain etching methods, there is a high etching se- lectivity between the photoresist and dielectric layer and between dielectric layer and BARC layer.
  • Near field holography makes use of monochromatic and polarized light of high collimation that is impinging under an oblique angle onto a phase mask carrying the grating pattern. The zero diffraction order just passes through the plate whereas the first diffraction order is diffracted under an angle that has the same value as the impinging beam, but is di- rected to the opposite side.
  • the grating on the mask is etched in a way to give both beams the same intensity.
  • the resulting interference pattern has the same pitch as the original grating on the quartz mask and can be transferred into a photoresist layer of the same thickness as the line width transferred.
  • the target of the process according to the present invention presented in figure 1 is to fabricate a 200 nm grating pattern G into the semiconductor.
  • the semiconductor SC is covered with a tri-layer resist stack ST consisting of spinned bottom antireflective coating layer BARC, evaporated thin dielectric layer D (Si02 or SiN) and spinned (photo) resist layer (P) as the top layer.
  • the thickness of the BARC layer is optimised to minimize the back reflection of the exposure light from semiconductor to resist.
  • the resist layer is patterned using near field holography, step 1) in fig 1, and after that the pattern is transferred from developed re- sist P, step 2) into the dielectric layer D by using the resist layer P as an etch mask, step 3) .
  • this is accomplished e.g. by using 313 nm exposure for the photoresist.
  • Photoresist is less sensitive and power density output from mask aligner is smaller when compared to 365 nm light causing quite significant difference in process optimisation.
  • Bottom antireflection coating (BARC) is needed to minimize surface reflections of the exposure light.
  • 313 nm exposure light allows going down to 200 nm gratings with high quality phase masks.
  • the pattern is transferred into the BARC layer by using dielectric layer D as an etch mask, step 4) .
  • the pattern can be finally transferred into the semiconductor SC by using, both dielectric D and BARC layers as the etch mask, step 5.
  • the remaining parts of the tri-layer stack ST can be removed and the grating with period of e.g. 200 nm is formed/existing in semiconductor, step 6) .

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Architecture (AREA)
  • Structural Engineering (AREA)
  • Diffracting Gratings Or Hologram Optical Elements (AREA)

Abstract

La présente invention concerne un procédé pour transférer un modèle, p. ex. un modèle de réseau, d'un masque de phase à un substrat. Cette invention est particulièrement bien appropriée à la fabrication de réseaux de courte période pour lasers à semiconducteurs de grande longueur d'onde. Ce procédé pour transférer un modèle à un substrat, présentant une structure stratifiée composée d'au moins une couche de résine photosensible et d'une couche de fond antireflet (BARC), consiste à développer ledit modèle sur la couche de résine photosensible sous lumière ultraviolette et à transférer le modèle développé de la couche de résine photosensible au substrat par gravure, p. ex. par gravure ionique réactive ou par toute autre technique de gravure correspondante. Selon la présente invention, on utilise une première couche diélectrique, placée entre ladite couche de résine photosensible et la couche de fond antireflet, pour différencier le taux de gravure des deux matières adjacentes, c.-à-d. la couche de résine photosensible et la couche de fond antireflet.
PCT/FI2004/000677 2003-11-13 2004-11-12 Procede et substrat semiconducteur permettant de transferer un modele d'un masque de phase a un substrat WO2005048338A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI20031653 2003-11-13
FI20031653A FI20031653A (fi) 2003-11-13 2003-11-13 Menetelmä ja puolijohdesubstraatti kuvion siirtämiseksi vaihemaskista substraatille

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WO2005048338A1 true WO2005048338A1 (fr) 2005-05-26

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102445158A (zh) * 2011-09-23 2012-05-09 清华大学 一种制作高温散斑的方法
CN103837919A (zh) * 2014-03-06 2014-06-04 成都贝思达光电科技有限公司 一种基于双层胶纳米压印的光栅结构彩色滤光膜加工方法
CN111509073A (zh) * 2019-05-30 2020-08-07 中国科学院长春光学精密机械与物理研究所 一种柔性光电探测器件的制备方法及柔性光电探测器件

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6380067B1 (en) * 2000-05-31 2002-04-30 Advanced Micro Devices, Inc. Method for creating partially UV transparent anti-reflective coating for semiconductors
EP1235263A2 (fr) * 2001-02-22 2002-08-28 Texas Instruments Incorporated Modulation des caractéristiques d'un procédé de gravure par changement du gaz

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6380067B1 (en) * 2000-05-31 2002-04-30 Advanced Micro Devices, Inc. Method for creating partially UV transparent anti-reflective coating for semiconductors
EP1235263A2 (fr) * 2001-02-22 2002-08-28 Texas Instruments Incorporated Modulation des caractéristiques d'un procédé de gravure par changement du gaz

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
ZHANG F. ET AL: "CD control using SiON BARL processing for sub-0.25 [mu]m lithography", MICROELECTRONIC ENGINEERING, vol. 46, no. 1-4, May 1999 (1999-05-01), pages 51 - 54, XP004170666 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102445158A (zh) * 2011-09-23 2012-05-09 清华大学 一种制作高温散斑的方法
CN103837919A (zh) * 2014-03-06 2014-06-04 成都贝思达光电科技有限公司 一种基于双层胶纳米压印的光栅结构彩色滤光膜加工方法
CN111509073A (zh) * 2019-05-30 2020-08-07 中国科学院长春光学精密机械与物理研究所 一种柔性光电探测器件的制备方法及柔性光电探测器件
CN111509073B (zh) * 2019-05-30 2022-09-20 中国科学院长春光学精密机械与物理研究所 一种柔性光电探测器件的制备方法及柔性光电探测器件

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FI20031653A (fi) 2005-05-14
FI20031653A0 (fi) 2003-11-13

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