CN103197376B - Silicon waveguide preparation method based on polycrystalline silicon mask - Google Patents

Silicon waveguide preparation method based on polycrystalline silicon mask Download PDF

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CN103197376B
CN103197376B CN201310047054.9A CN201310047054A CN103197376B CN 103197376 B CN103197376 B CN 103197376B CN 201310047054 A CN201310047054 A CN 201310047054A CN 103197376 B CN103197376 B CN 103197376B
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silicon
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polysilicon
mask
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CN103197376A (en
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朱海柯
谢静雅
孙晓萌
周林杰
陈建平
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Shanghai Jiaotong University
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Shanghai Jiaotong University
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Abstract

The invention discloses a silicon waveguide preparation method based on a polycrystalline silicon mask. The method comprises the following steps of preparing a clean silicon-on-insulator (SOI) substrate, carrying out dry-oxygen oxidation for one time so as to generate a thin silica film, growing a thick polycrystalline silicon film layer on the silica film, carrying out glue coating, photoetching and etching on the polycrystalline silicon film to obtain the polycrystalline silicon mask, carrying out oxidation on a sample, and removing silicon oxide and polycrystalline silicon so as to obtain a silicon waveguide. The silicon waveguide is smooth in side wall, good in steep degree and flat in bottom and top, the whole technological process is simple and convenient, and technology cost is low.

Description

Based on the silicon waveguide preparation method of polysilicon mask
Technical field
The present invention relates to a kind of silicon waveguide preparation method based on polysilicon mask, belong to integrated optical communication field.
Background technology
The development of Modern optical communication technology proposes very high requirement to the material of optic communication device and structure.Silicon-based devices has high speed, low-power consumption, microminiaturized feature as Novel photonic devices, and Beijing semiconductor Suo Yujinzhong seminar of the Chinese Academy of Sciences reports and have developed the silica-based Mach-Zehnder modulators of the hypervelocity with 40G/s on the Optical Express magazine of 2012; The people such as the J.C.Rosenberg of IBM Corporation have issued the silicon-based modulator that power consumption only only has 1.8pJ/bit in the OFC meeting of 2011; Because silicon materials have higher refractive index (3.46), high index-contrast is defined with ambient air and as the earth silicon material of substrate, so light signal can be limited in very little space, thus achieving the microminiaturization of device, current silicon waveguide dimensions is all in sub-micron rank; Because silicon technology integrated technology is completely compatible with now very ripe integrated circuit CMOS technology integrated technology, thus be easy to realize large-scale integrated.So, use silicon materials to realize the direction that Modern optical communication device is future development.
The performance of silica-based optic communication device is determined by silicon waveguide to a great extent.Coarse silicon waveguide sidewalls produces very large scattering process by the light signal transmitted wherein, and signal power weakens greatly, adds loss, and the bit error rate becomes large.Because the height, the width that etch the silicon waveguide caused change, light propagation constant will be changed, affect device performance.The way of current preparation silica-based waveguides is mainly divided into two kinds, comprises dry etching method and oxidizing process.Dry etching method refers to that namely utilizing photoresist mask to carry out etching to silicon forms optical waveguide.If reactive ion etching (RIE), then silicon materials sidewall can with plasma generation physical-chemical reaction, cause sidewall roughness; If ion beam etching (IBE), then the physical bombardment of ion can make out-of-flatness bottom silicon materials, and etching depth is wayward; Adopt inductive couple plasma (ICP) etching, sidewall roughness can be made to reduce, improve sidewall steepness simultaneously.Another method preparing silicon waveguide is oxidizing process, and namely first formed on silicon and can stop the hard mask pattern that oxygen molecule spreads downwards, such oxygen can only carry out reaction with the silicon materials exposed and form monox, can obtain silicon waveguide after removing hard mask.
For the way being formed silicon waveguide by oxidation, current silicon nitride, monox, the silicon oxynitride of mainly adopting is as hard mask.For silicon nitride hard mask, because silicon nitride and silicon interface exist larger stress, when be oxidized occur in the side roof part of silicon waveguide time, the monox generated at the interface of silicon nitride and silicon will cause waveguide local deformation, thus affect the communication mode of light signal in silicon waveguide.For the situation of monox as hard mask, the membranous layer of silicon oxide generated owing to using CVD (chemical vapor deposition) loosens, poor to the barrier effect of oxygen, so the less silicon waveguide of difference in height can only be prepared, and the sidewall of waveguide compares inclination, increase the error between practical structures and design.For the situation of silicon oxynitride as hard mask, then it is the shortcoming simultaneously with above two kinds of hard masks.In order to improve the quality of monox waveguide, in conjunction with existing integrated technique, propose the present invention.
Summary of the invention
The object of the invention is to for above-mentioned the deficiencies in the prior art, a kind of silicon waveguide preparation method based on polysilicon mask is provided, the optical waveguide of preparation has that sidewall is smooth, verticality better, bottom with upper flat, technique is simple, cost is lower, with the advantage such as CMOS technology compatibility.
For achieving the above object, technical solution of the present invention is as follows:
Based on a silicon waveguide preparation method for polysilicon mask, it is characterized in that, the method comprises the steps:
Step one, carries out dry-oxygen oxidation process to silicon-on-insulator (SOI) sheet of cleaning, oxidizing temperature 850 ~ 950 DEG C, O 2flow 15 ~ 20sccm (standard state gas milliliter is per minute), N 2flow 45 ~ 60sccm, oxidization time 10 ~ 25min, form the silicon dioxide film that 20 ~ 30nm is thick;
Step 2, utilizes inductive couple plasma to strengthen chemical vapor deposition (ICP-PECVD) on silicon dioxide film, forms the thick polysilicon of one deck 100 ~ 400nm;
Step 3, the thick photoresist of spin coating 1 ~ 3 μm makes it cover polysilicon;
Step 4, carries out photoetching with stepper, focal length-1 ~ 0.5, time shutter 120ms ~ 160ms, forms photoresist image;
Step 5, removes not by the polysilicon that photoresist image covers by dark silicon inductive couple plasma (ICP) etching, SF 6flow 40 ~ 80sccm, C 4f 8flow 40 ~ 60sccm, plasma power 700 ~ 800W, etching time 30 ~ 35s, then, successively wash away remaining photoresist image with acetone and alcohol, form polysilicon mask;
Step 6, carries out dry-oxygen oxidation process again, oxidizing temperature 1000 ~ 1100 DEG C, O 2flow 15 ~ 20sccm, N 2flow 45 ~ 60sccm, oxidization time 30 ~ 45min, form oxide layer and remaining polysilicon mask;
Step 7, utilizes BOE solution removal oxide layer at room temperature 25 DEG C, utilizes alkaline solution to remove remaining polysilicon, obtains the silicon waveguide that 180 ~ 350nm is thick.
Principle of the present invention is that polysilicon generates fine and close silicon oxide film under dry-oxygen oxidation condition, stops that most oxygen molecule enters the silicon layer immediately below mask layer.There is no the part that polysilicon covers, oxygen molecule directly and pasc reaction form monox, the silicon of this part is consumed; And the part having polysilicon layer to cover, silicon and the oxygen reaction of its lower floor are considerably less, thus form the waveguide of ridge silicon.
Feature of the present invention is:
1, present invention uses polysilicon and carry out transition diagram.
2, in silicon oxide layer towards the oxygen that silicon waveguide sidepiece and top cross spread, due to polysilicon relative to silicon more easily and oxygen reaction, the base silicon that polysilicon is covered is not easily oxidized, thus ensure that the planarization of steep property with silicon waveguide top of silicon waveguide sidewalls.
3, the dry-oxygen oxidation method that the present invention uses can make oxidation reaction slowly, so remaining silicon face smooth even after reaction.
4, first time dry-oxygen oxidation formation thin silicon oxide, its object is to: one is isolation base silicon and the polysilicon grown afterwards, thus can as stop-layer during etch polysilicon; Two is after being formed as waveguide, restraining barrier during erosion removal polysilicon
Polysilicon quality prepared by the inductively coupled plasma enhancing chemical vapor deposition that 5, the present invention uses is good, controllability is strong.
6, the preparation method of the present invention's use is simple and convenient, complete and CMOS technology compatibility.
7, preparation method's cost of the present invention's use is lower, because the preparation cost of polysilicon itself is very low, and easily Macroscale homogenous deposit, therefore only need to use SiH in Film preparation process 4with H 2gas source, thus the operation and the maintenance cost that reduce equipment.
Accompanying drawing explanation
Fig. 1 is the process flow diagram of the silicon waveguide preparation method that the present invention is based on polysilicon mask.
Embodiment
Below in conjunction with drawings and Examples, the present invention will be further described, but should not limit the scope of the invention.
Embodiment 1
Based on a silicon waveguide preparation method for polysilicon mask, comprise the steps
Step one, prepares clean SOI sheet 1, puts into oxidation furnace and carry out a dry-oxygen oxidation, oxidizing temperature 900 DEG C, O 2flow 20sccm, N 2flow 60sccm, oxidization time 12min, generate the silicon dioxide film 2 that 20nm is thick.
Step 2, uses inductively coupled plasma enhancing chemical vapor deposition on silicon dioxide film, to form the polysilicon 3 of one deck 300nm, temperature of tray 350 DEG C, SiH 4(using Ar gas dilution) flow 10sccm, H 2flow 22sccm, ICP power 2100W, RF power 170W.
Step 3, the AZ6112 photoresist 4 that spin coating 1.1 μm is thick.
Step 4, uses stepper to carry out photoetching, focal length 0.4, time shutter 140ms, obtains the photoetching offset plate figure 5 that live width is 1 μm.
Step 5, uses dark silicon inductively coupled plasma etching to remove the polysilicon not having photoetching offset plate figure 5 to cover, SF 6flow 40sccm, C 4f 8flow 60sccm, ICP power 800W, etching time 32s, use acetone, alcohol wash away remaining photoresist, obtain polysilicon mask 6 after etching.
Step 6, dry-oxygen oxidation, oxidizing temperature 1100 DEG C, O 2flow 20sccm, N 2flow 60sccm, oxidization time 33min, obtain oxide layer 7 and remaining polysilicon mask 8.
Step 7, under room temperature (25 DEG C), use BOE solution (hydrofluorite: ammonium fluoride=1:20) to remove oxide layer, soak sample at twice, first time soak time 150s, take out sample, use acetone, second alcohol and water cleaning sample, second time soak time 90s, take out sample, use acetone, ethanol and washed with de-ionized water sample.Re-use the sodium hydroxide solution immersion sample 30s that concentration is 5%, take out sample, use washed with de-ionized water sample, obtaining wide is 1 μm, and height is 220nm silicon waveguide 9.
Embodiment 2
Based on a silicon waveguide preparation method for polysilicon mask, comprise the steps:
Step one, carries out dry-oxygen oxidation process to the SOI 1 of cleaning, oxidizing temperature 850 DEG C, O 2flow 15sccm, N 2flow 45sccm, oxidization time 25min, form the silicon dioxide film 2 that 30nm is thick;
Step 2, utilizes inductive couple plasma to strengthen chemical vapor deposition and on silicon dioxide film, forms the thick polysilicon of one deck 100nm 3, temperature of tray 350 DEG C, SiH 4flow 10sccm, H 2flow 15sccm, plasma power 2000W, radio-frequency power 200W;
Step 3, the thick photoresist 4 of spin coating 3 μm makes it cover polysilicon 3;
Step 4, carries out photoetching with stepper, focal length-1, time shutter 120msms, forms photoresist image 5;
Step 5, removes not by the polysilicon that photoresist image 5 covers with dark silicon inductively coupled plasma etching, SF 6flow 80sccm, C 4f 8flow 60sccm, plasma power 700W, etching time 30s, then, successively washes away remaining photoresist image with acetone and alcohol, forms polysilicon mask 6;
Step 6, carries out dry-oxygen oxidation process again, oxidizing temperature 1100 DEG C, O 2flow 20sccm, N 2flow 60sccm, oxidization time 30min, form oxide layer 7 and remaining polysilicon mask 8;
Step 7, utilizes BOE to lose liquid (hydrofluorite: ammonium fluoride=1:20) and removes oxide layer, utilize alkaline solution to remove remaining polysilicon, obtain the silicon waveguide 9 that 180nm is thick at room temperature 25 DEG C.
Embodiment 3
Based on a silicon waveguide preparation method for polysilicon mask, comprise the steps
Step one, carries out dry-oxygen oxidation process to the SOI 1 of cleaning, oxidizing temperature 950 DEG C, O 2flow 20sccm, N 2flow 60sccm, oxidization time 10min, form 20 thick silicon dioxide films 2;
Step 2, utilizes inductive couple plasma to strengthen chemical vapor deposition and on silicon dioxide film, forms the thick polysilicon of one deck 400nm 3, temperature of tray 350 DEG C, SiH 4flow 5sccm, H 2flow 25sccm, plasma power 2500W, radio-frequency power 200W;
Step 3, the thick photoresist 4 of spin coating 1 μm makes it cover polysilicon 3;
Step 4, carries out photoetching with stepper, focal length 0.5, time shutter 160ms, forms photoresist image 5;
Step 5, removes not by the polysilicon that photoresist image 5 covers with dark silicon inductively coupled plasma etching, SF 6flow 40sccm, C 4f 8flow 40sccm, plasma power 800W, etching time 35s, then, successively washes away remaining photoresist image with acetone and alcohol, forms polysilicon mask 6;
Step 6, carries out dry-oxygen oxidation process again, oxidizing temperature 1000 DEG C, O 2flow 15sccm, N 2flow 45sccm, oxidization time 45min, form oxide layer 7 and remaining polysilicon mask 8;
Step 7, utilizes BOE to lose liquid and removes oxide layer, utilize alkaline solution to remove remaining polysilicon, obtain the silicon waveguide 9 that 350nm is thick at room temperature 25 DEG C.

Claims (3)

1., based on a silicon waveguide preparation method for polysilicon mask, it is characterized in that, the method comprises the steps:
Step one, carries out dry-oxygen oxidation process to the SOI (1) of cleaning, oxidizing temperature 850 ~ 950 DEG C, O 2flow 15 ~ 20sccm, N 2flow 45 ~ 60sccm, oxidization time 10 ~ 25min, form the silicon dioxide film (2) that 20 ~ 30nm is thick;
Step 2, utilizes inductive couple plasma to strengthen chemical vapor deposition on silicon dioxide film, forms the thick polysilicon of one deck 100 ~ 400nm (3);
Step 3, the thick photoresist (4) of spin coating 1 ~ 3 μm makes it cover polysilicon (3);
Step 4, carries out photoetching with stepper, focal length-1 ~ 0.5, time shutter 120ms ~ 160ms, forms photoresist image (5);
Step 5, removes not by the polysilicon that photoresist image (5) covers with dark silicon inductively coupled plasma etching, SF 6flow 40 ~ 80sccm, C 4f 8flow 40 ~ 60sccm, plasma power 700 ~ 800W, etching time 30 ~ 35s, then, successively wash away remaining photoresist image with acetone and alcohol, form polysilicon mask (6);
Step 6, carries out dry-oxygen oxidation process again, oxidizing temperature 1000 ~ 1100 DEG C, O 2flow 15 ~ 20sccm, N 2flow 45 ~ 60sccm, oxidization time 30 ~ 45min, form oxide layer (7) and remaining polysilicon mask (8);
Step 7, utilizes BOE solution removal oxide layer at room temperature 25 DEG C, utilizes alkaline solution to remove remaining polysilicon, obtains the silicon waveguide (9) that 180 ~ 350nm is thick.
2. the silicon waveguide preparation method based on polysilicon mask according to claim 1, is characterized in that, described BOE solution is that 1:20 mixes by hydrofluoric acid solution and ammonium fluoride solution according to volume ratio.
3. the silicon waveguide preparation method based on polysilicon mask according to claim 1, is characterized in that, it is make temperature of tray 350 DEG C, SiH that described inductive couple plasma strengthens chemical vapor deposition 4flow 5 ~ 10sccm, H 2flow 15 ~ 25sccm, plasma power 2000 ~ 2500W, radio-frequency power 150 ~ 200W.
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CN103820863A (en) * 2014-02-25 2014-05-28 四川飞阳科技有限公司 Etching method of polycrystalline silicon on quartz substrate and manufacture method of planar optical waveguide
CN103926649A (en) * 2014-04-17 2014-07-16 四川飞阳科技有限公司 Manufacturing method of planar optical waveguide device
CN107807419A (en) * 2017-12-11 2018-03-16 中山大学 Radius of curvature is the preparation method and bent lightguide of the bent lightguide of wavelength magnitude

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4726879A (en) * 1986-09-08 1988-02-23 International Business Machines Corporation RIE process for etching silicon isolation trenches and polycides with vertical surfaces
CN1600901A (en) * 2003-09-25 2005-03-30 北京大学 Method for etching polysilicon based on inductively coupled plasma and for preparing superfine lines
CN101013181A (en) * 2007-02-12 2007-08-08 浙江大学 CMOS technique compatible silicon optical waveguide preparation method

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JP2002014242A (en) * 2000-06-28 2002-01-18 Oki Electric Ind Co Ltd Optical waveguide device

Patent Citations (3)

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Publication number Priority date Publication date Assignee Title
US4726879A (en) * 1986-09-08 1988-02-23 International Business Machines Corporation RIE process for etching silicon isolation trenches and polycides with vertical surfaces
CN1600901A (en) * 2003-09-25 2005-03-30 北京大学 Method for etching polysilicon based on inductively coupled plasma and for preparing superfine lines
CN101013181A (en) * 2007-02-12 2007-08-08 浙江大学 CMOS technique compatible silicon optical waveguide preparation method

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