CN109848569A - A kind of laser etching method of MEMS silicon structure - Google Patents
A kind of laser etching method of MEMS silicon structure Download PDFInfo
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- CN109848569A CN109848569A CN201711224703.2A CN201711224703A CN109848569A CN 109848569 A CN109848569 A CN 109848569A CN 201711224703 A CN201711224703 A CN 201711224703A CN 109848569 A CN109848569 A CN 109848569A
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Abstract
The invention belongs to micro-processing technology fields, are related to a kind of laser etching method of MEMS silicon structure；Method includes the following steps: laser beam carries out local irradiation to silicon materials surface through object lens, silicon materials are heated after absorbing portion of energy；Irradiation zone surface is melted into melting zone, and the part silicon materials being melted are vaporized into plume and melting splash, and the part being melted is scattered in silicon materials finished surface and forms solid splash；Laser irradiation terminates, and heat affected area and slight crack is presented in silicon materials condensation, silicon materials irradiation zone.The present invention can reduce re cast layer influence and the pollution of surrounding splash under conditions of not changing average laser beam power and pulsewidth, by reducing laser repetition rate, improving single pulse energy；It is compensated by defocusing amount, obtain maximum local irradiation intensity, the smallest etching diameter and mitigates etching splashing；By assisting vacuum environment, the dissipation during laser transfer is reduced, relatively high irradiation intensity is obtained and reduces heat affected area.
Description
Technical field
The invention belongs to micro-processing technology fields, are related to a kind of laser etching method of MEMS silicon structure.
Background technique
It is aided with surface etch technique in silicon MEMS gyro sensitive structure process to realize to the subtle of sensitive structure
Adjustment can effectively reduce the non-ideal factors such as frequency mismatch, the Spindle Deviation of process introducing to device overall performance
It influences, so as to improve device performance, improves yield rate.
Laser ablation has the characteristics that unstressed introducing, processing method are flexible, operation is convenient, at low cost, in silicon materials
It is widely used in the processing of surface.The common laser of laser ablation according to the difference of pulsewidth can be divided into nanosecond laser, picosecond swash
Light device, femto-second laser, wherein femto-second laser, the pulse of picosecond laser are very short, have peak power high, and fuel factor is small,
The advantages that machining accuracy is high, but overall processing efficiency is relatively low and expensive.Nanosecond laser overall cost is lower, but
Since pulsewidth limits, no image of Buddha femto-second laser realizes cold ablation like that, and easy region edge pattern is not in etching process
Rule, heat-affected zone is excessive, particulate matter splashes phenomena such as serious, causes etch areas dirty beyond scope of design, splashing particle
The problems such as dye chip, splash droplet cause lead short circuit.
Summary of the invention
For the above-mentioned prior art, the purpose of the present invention is to provide a kind of laser etching method of MEMS silicon structure, solutions
Certainly using nanosecond laser is poor to the etch topography occurred in silicon materials surface etch, heat-affected zone is big and particle contamination is serious
The problems such as, improve the processing effect of laser ablation.
In order to achieve the above object, the present invention uses following technical scheme.
The purpose of the present invention is to provide a kind of laser etching methods of MEMS silicon structure, method includes the following steps:
Step 1: laser beam carries out local irradiation to silicon materials surface through object lens, silicon materials are added after absorbing portion of energy
Heat；
Step 2: irradiation zone surface is melted into melting zone, the part silicon materials being melted are vaporized into plume and melting flies
Object is splashed, the part being melted is scattered in silicon materials finished surface and forms solid splash；
Step 3: laser irradiation terminates, heat affected area and slight crack is presented in silicon materials condensation, silicon materials irradiation zone.
The laser beam is generated by ultraviolet nanosecond laser etching system, parameters of laser beam value are as follows: wavelength: 355nm, average function
Rate: 3W, 20~150kHz of repetition rate, pulsewidth 45ns.
Relationship between the mean power of the laser beam, repetition rate and width parameter are as follows: mean power=pulse energy
Amount × repetition rate reduces repetition rate under fixed mean power, promotes pulse energy, reduces melting splash.
The repetition rate is 50kHz.
The repetition rate is 20kHz.
The laser beam is focused by object lens, and laser beam waist spot position acts on silicon materials surface.
In the ultraviolet nanosecond laser etching system focus process, laser beam defocusing amount is compensated, improves silicon materials
The laser irradiation intensity on surface.
Further, the defocusing amount of compensation is -700 μm~-900 μm.
Further, carrying out local irradiation etching environment to silicon materials surface using laser beam is vacuum environment.
Technical solution provided in an embodiment of the present invention has the benefit that
A kind of laser etching method of MEMS silicon structure of the present invention, larger for the heat affected area that occurs in etching process,
Melt splash the problems such as, under conditions of not changing laser average power and pulsewidth, by reduce laser repetition rate,
Re cast layer influence and the pollution of surrounding splash can be reduced by improving single pulse energy.
A kind of laser etching method of MEMS silicon structure of the present invention, is compensated by defocusing amount, obtains maximum local irradiation
Intensity, the smallest etching diameter simultaneously mitigate etching splashing.
A kind of laser etching method of MEMS silicon structure of the present invention reduces laser transfer process by assisting vacuum environment
In dissipation, obtain relatively high irradiation intensity and reduce heat affected area.
Detailed description of the invention
Fig. 1 is laser ablation silicon materials mechanism schematic diagram of the present invention；
Fig. 2 be laser repetition rate be 50Hz when etching effect schematic diagram；
Fig. 3 be laser repetition rate be 20Hz when etching effect schematic diagram；
Fig. 4 is laser optical spot position view with a tight waist；
Fig. 5 is influence curve schematic diagram of the different defocusing amounts to etch areas diameter；
Fig. 6 is not using the etching effect schematic diagram under defocusing amount compensation condition；
Fig. 7 is using the etching effect schematic diagram under defocusing amount compensation condition；
Fig. 8 is the etching effect schematic diagram under air environment；
Fig. 9 is the etching effect schematic diagram under vacuum environment；
In figure: 11- laser beam, 12- object lens, 13- silicon materials, 14- melting zone, 15- plume and melting splash, 16- are solid
Body splash, the heat affected area 17-, 18- slight crack, 21- beam waist spot position.
Specific embodiment
It elaborates With reference to embodiment to a kind of laser etching method of MEMS silicon structure of the present invention.
As shown in Figure 1, a kind of laser etching method of MEMS silicon structure of the present invention, comprising the following steps:
Step 1: laser beam 11 carries out local irradiation to 13 surface of silicon materials through object lens 12, silicon materials 13 absorb part energy
It is heated after amount；
Step 2: irradiation zone surface is melted into melting zone 14, part silicon materials 13 are vaporized into plume and melting splash
15, it is partially scattered in 13 finished surface of silicon materials and forms solid splash 16；
Step 3: laser irradiation terminates, silicon materials 13 are condensed, and heat affected area 17 and slight crack 18 etc. is presented.
The laser beam 11 is generated by ultraviolet nanosecond laser etching system, laser parameter value are as follows: wavelength: 355nm, function
Rate: 3W, 20~150kHz of frequency, pulsewidth 45ns.
As seen from Figure 1, during laser ablation, silicon materials 13 can occur to vaporize and melt two kinds of states of matter variations after heating,
Wherein vaporizing section determines the volume of etachable material removal, and puddle constitutes re cast layer and splash.
To advanced optimize etching technics, according to the energy mechanism of action of laser ablation, increase material surface in the short time
The energy of absorption can effectively increase the specific gravity of removal material vaporizing section, when short-time energy accumulation reaches a certain level, material
Material will be removed in a manner of completely vaporizing, and there will not be melt substance.The energy for increasing irradiation laser in short-term, can play increase
Evaporation of materials specific gravity reduces the effect of melting double teeming and splash.
Mean power, repetition rate and the pulsewidth of laser are to influence several principal elements of laser irradiation energy.
The configuration intrinsic as laser of the mean power of laser, can not generally change；Pulsewidth mainly influences laser spoke
According to peak power, pulsewidth is smaller, and peak power is bigger, and the minimum pulse width of laser is generally also fixed；Repetition rate is determined
The available irradiation energy of single pulse is determined, can be described as with the relationship of mean power: mean power=pulse energy
× repetition rate, this is major parameter of the laser for adjusting, and under fixed mean power, repetition rate is lower, pulse
Energy is bigger.
Fig. 2 and Fig. 3 gives the etching effect under 50kHz, 20kHz various lasers repetition rate, it is seen then that passes through reduction
Laser repetition rate, raising single pulse energy can reduce the influence and the pollution of surrounding splash of re cast layer.
To advanced optimize etching technics, the laser irradiation energy on reinforcing material surface is reducing laser repetition rate
On the basis of, it can also start with from the characteristics of optical path of laser beam.As shown in figure 4, laser beam 11 focuses reality by object lens 12
Energy in existing range of small is concentrated, and has the smallest etching diameter and maximum energy density in beam waist spot position 21.
The material vapor that laser action generates when material surface can generate a density gradient field on zone of action surface,
Since refractive index is related to density, faint transformation can occur for its direction of travel when this gradient fields of laser penetration, so that swashing
Deviate its original focal position in focusing (waist spot) position of light light beam.
Due to the presence of waist spot position deviation, the waist spot of laser beam is not fallen on material surface when etching system is focused,
The irradiation energy of unit area does not reach system maximum value at this time.The waist spot position in practical etching process is obtained, and is being
It recompenses in system focus process, the laser irradiation intensity of material surface can be further increased.Fig. 5 provides different defocusing amounts
The influence of (offset of practical focusing position relative system focus) to etch areas diameter.
According to Fig. 5 data it is found that defocusing amount is at -700~-900 μm, etch areas diameter is minimum, is now placed in laser
At spot with a tight waist, maximum local irradiation intensity and relatively preferably etching effect can be obtained.Fig. 6 and Fig. 7 shows different defocus
Etching effect figure under the conditions of amount, it can be seen that after being compensated by defocusing amount, etch areas diameter is obviously reduced, splashing situation
Also mitigated.
Gaseous environment locating for etching process also can laser irradiation intensity on material surface exist and influence, under vacuum environment
Dissipation during laser transfer is smaller compared with air environment, can get relatively high irradiation intensity and preferable material removal effect
Rate.
Experiment is performed etching under vacuum conditions, and is compared with the etching result under air environment, such as Fig. 8 and Fig. 9
Shown, its etch areas edge is more smooth under vacuum environment, and surrounding heat affecting trace obviously weakens, splash is less, and nothing
Droplet-like sputters trace.
Claims (9)
1. a kind of laser etching method of MEMS silicon structure, it is characterised in that: method includes the following steps:
Step 1: laser beam carries out local irradiation to silicon materials surface through object lens, silicon materials are heated after absorbing portion of energy；
Step 2: irradiation zone surface is melted into melting zone, the part silicon materials being melted are vaporized into plume and melting splash,
The part being melted is scattered in silicon materials finished surface and forms solid splash；
Step 3: laser irradiation terminates, heat affected area and slight crack is presented in silicon materials condensation, silicon materials irradiation zone.
2. a kind of laser etching method of MEMS silicon structure according to claim 1, it is characterised in that: the laser beam by
Ultraviolet nanosecond laser etching system generates, parameters of laser beam value are as follows: wavelength: 355nm, mean power: 3W, and repetition rate 20~
150kHz, pulsewidth 45ns.
3. a kind of laser etching method of MEMS silicon structure according to claim 2, it is characterised in that: the laser beam
Relationship between mean power, repetition rate and width parameter are as follows: mean power=pulse energy × repetition rate, fixed
Under mean power, reduction repetition rate is lower, promotes pulse energy, reduces melting splash.
4. a kind of laser etching method of MEMS silicon structure according to claim 3, it is characterised in that: the repetition rate
For 50kHz.
5. a kind of laser etching method of MEMS silicon structure according to claim 3, it is characterised in that: the repetition rate
For 20kHz.
6. a kind of laser etching method of MEMS silicon structure according to claim 3, it is characterised in that: the laser beam is logical
Object lens focusing is crossed, laser beam waist spot position acts on silicon materials surface.
7. a kind of laser etching method of MEMS silicon structure according to claim 6, it is characterised in that: the ultraviolet nanosecond
In laser etching system focus process, laser beam defocusing amount is compensated, improves the laser irradiation intensity on silicon materials surface.
8. a kind of laser etching method of MEMS silicon structure according to claim 7, it is characterised in that: the defocusing amount of compensation
It is -700 μm~-900 μm.
9. a kind of laser etching method of MEMS silicon structure according to claim 6, it is characterised in that: utilize laser beam pair
It is vacuum environment that silicon materials surface, which carries out local irradiation etching environment,.
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| US3560258A (en) * | 1966-07-22 | 1971-02-02 | Int Standard Electric Corp | Pattern deposit by laser |
| CN1567535A (en) * | 2003-06-26 | 2005-01-19 | 铼宝科技股份有限公司 | Method for manufacturing polysilicon of thin-film transistor |
| CN101421071A (en) * | 2006-02-23 | 2009-04-29 | 皮科德昂有限公司 | Method for producing high-quality surfaces and a product having a high-quality surface |
| CN101604604A (en) * | 2009-07-17 | 2009-12-16 | 武汉理工大学 | The method of the little processing and preparing field emissive cathode of a kind of 157nm deep ultraviolet laser |
| CN102009945A (en) * | 2010-11-11 | 2011-04-13 | 北京自动化控制设备研究所 | Method for machining micro-mechanical quartz tuning fork gyro sensitive structure |
| CN106915723A (en) * | 2015-12-25 | 2017-07-04 | 中国科学院上海微***与信息技术研究所 | The preparation method of the beam-mass block structure based on laser combination anisotropic etch |
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Application publication date: 20190607 |