CN108801162A - A kind of non-contact optical measurement method of thick photoresist film thickness - Google Patents
A kind of non-contact optical measurement method of thick photoresist film thickness Download PDFInfo
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- CN108801162A CN108801162A CN201810684915.7A CN201810684915A CN108801162A CN 108801162 A CN108801162 A CN 108801162A CN 201810684915 A CN201810684915 A CN 201810684915A CN 108801162 A CN108801162 A CN 108801162A
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- film thickness
- photoresist film
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- contact optical
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
- G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
Abstract
The invention belongs to micro-fabrication technology fields, a kind of non-contact optical measurement method of thick photoresist film thickness is provided, the refractive index that this method passes through the introducing glued membrane when carrying out photoresist thickness measure using light microscope, the virtual image observed that will steal a glance is converted into real image, obtains accurate film thickness.Its measuring process includes " substrate pretreatment-glued membrane making-glue thickness measurement-exposure, development ", solve the deficiency of measurement methods such as electrolysis, crystal a period of time method, interferometry, spectral scanning method, x-ray method and Ellipsometric and the limitation of application in the prior art, realize the accurate measurement of hundreds of microns of thick photoresist thickness, with having a wide range of application, simply, efficient feature can improve the dimensional accuracy and producing efficiency of metal micro structure electroforming film production.
Description
Technical field
The invention belongs to micro-fabrication technology field, it is related to the measurement method of film thickness in photoetching process, more particularly to
After a kind of spin coating, the measuring method of thick photoresist film thickness is measured before exposure imaging.
Background technology
Micro- galvanoplastics based on photoetching rubber moulding makes in the technique of metal microdevices, and the thickness of photoresist film determines electricity
The height of ingot metal micro-structure.In the manufacturing process of photoetching rubber moulding, the big thickness photoresist film for being hundreds of microns for thickness,
Inappropriate lithography process parameters often cause glued membrane front baking, exposure or rear baking time deficiency, photochemical reaction insufficient, aobvious
Qualified micro- electroforming glued membrane cavity is unable to get when shadow, eventually leading to microelectroforming technology can not carry out.Therefore high-quality to obtain
Micro- electroforming glued membrane cavity of amount needs the thickness for accurately measuring photoresist film before exposure, and is determined suitably according to glue thickness
The lithography process parameters such as exposure dose, rear baking and developing time, to improve success rate, the reduction micro- device of metal that photoresist molding is made
The development cost of part.
Currently, common measured film thickness method mainly has optical means and non optical method.Wherein non optical method
Include mainly electrolysis and quartz crystal method.Electrolysis is mainly used for measuring the thickness of metallic film.Quartz crystal method is mainly used
In the thickness for measuring physical vapor deposition film, and utilize the density of needs known film material when this method measurement film thickness.Therefore, non-
Optical means is not suitable for measuring the thickness of thick photoresist film.And optical means includes mainly interferometry, spectral scanning method, X
Ray method and Ellipsometric.Interferometry is to form the principle of equal thick interference fringe using coherent light interference to determine film thickness
's.However, for the photoresist film of big thickness, generally require to carry out multiple whirl coating, front baking just to obtain.Coherent light is through more
Larger mistake is easy tod produce when cannot occur clearly interference fringe when tunic, therefore the thickness of thick film is measured using interferometry
Difference.Spectral scanning method is also based on the interference theory of light, and by measuring reflection or the transmission spectrum curve of film to be measured, analysis is thin
The thickness of film is calculated in the spectral characteristic of film.But when using spectroscopy measurements, for different types of film to be measured
It needs to measure it using the spectrum of different-waveband, specific spectral band range is often very in practical measurement process
It is difficult to guarantee.X-ray method is to receive the photon energy size that is generated after X-ray based on detection film to calculate film thickness
's.But it is highly difficult for measuring the film of blending constituent or two layers or more of laminated film.In addition, generally using X-ray
Method measures the range of film thickness at several nanometers to hundreds of nanometers.Ellipsometric is using light beam at interface and film table
The phase of the polarised light occurred when being reflected on face and changing to determine film thickness for amplitude.This method is suitable for measuring transparent
Or weak absorbing isotropic thicknesses of layers, and measured film thickness range in a nanometer between tens microns.
In conclusion existing measurement method cannot be satisfied during making big thickness photoresist film, need exposing
The preceding accurate measurement request for measuring film thickness.The present invention proposes a kind of non-contact optical measurement side based on refractive index thus
Method.The visual thickness of glued membrane is obtained by adjusting microscopical thin accurate burnt spiral, then is determined by experiment photoresist to microscope
The product of the refractive index of light, the two is exactly the actual (real) thickness of glued membrane.This measurement method is simple and convenient, and error is smaller, equally
Suitable for the thickness measure of other transparent membranes, there is important practical value.
Invention content
In view of the problems of the existing technology the present invention, provides a kind of based on the non-contact of refractometry thickness film thickness
Formula measuring method, i.e., by during measuring thick film thickness using light microscope, introducing the refractive index of glued membrane,
It converts the virtual image being observed visually to real image, obtains accurate film thickness, the selection for follow-up lithography process parameters provides
With reference to.
In order to achieve the above object, the technical solution adopted by the present invention is：
A kind of non-contact optical measurement method measuring thick photoresist film thickness, this method in photoresist by exposing
Before, the thickness of thick photoresist is gone out using light microscope combination photoresist refractometry.It is different from common glue thickness measurement procedure
" substrate pretreatment-photoetching-glue thickness measures ", this method is using " substrate pretreatment-glued membrane making-glue thickness measurement-exposure is shown
Shadow ".Specific measuring process is as follows：
Step 1, substrate pretreatment
Metal substrate is roughly ground with the sand paper of different model, is refined, polishing treatment, its surface roughness Ra is made to be less than
0.04μm；Substrate surface is cleaned with acetone cotton balls；By the substrate of wiped clean be placed in acetone soln be cleaned by ultrasonic 15~
25min, then it is placed in 15~25min of ultrasonic cleaning in ethanol solution, it rinses through deionized water, be put into drying box after nitrogen drying
Drying；Metal substrate after drying is cooled to room temperature for use.
Step 2 makes glued membrane
Using sol evenning machine in metallic substrate surfaces spin coating SU-8 photoresists, low speed is set as 500~700rpm, duration
For 15~30s；High speed is set as 800~1000rpm, and the duration is 20~40s.The substrate for coating photoresist is placed in hot plate
Upper carry out front baking, using staged heating mode：20~40min to be dried at 65 DEG C, dries 20~40min at 75 DEG C, 85 DEG C of whens dry 1~
2h is cooled to room temperature after front baking.
It is thick to measure glue for step 3
First, the refractive index of photoresist is determined.Take two pieces of identical metal substrates with photoresist film.It is utilized after front baking
Light microscope measures visual thickness H ' in the different location of two prints respectively, utilizes tool microscope in phase after exposure imaging
Measure actual (real) thickness H with position, obtain two groups of different-thickness glued membranes visual thickness value and actual (real) thickness value since H' and H is full
Sufficient linear relationship, using H' as abscissa, H is that data point is depicted in rectangular coordinate system by ordinate, and passes through least square method
Fitting obtains linear equation, and the slope of straight line is exactly the refractive index n of SU-8 photoresists2。
Secondly, thick glued membrane is measured after determining refractive index.The thin accurate burnt spiral for adjusting light microscope, makes its focus
Glued membrane top and bottom are respectively focused on, the difference in height of the two is the visual thickness H ' of glued membrane.It is calculated according to formula (1)
The actual (real) thickness H of photoresist.
H=n2H' (1)
Step 4, exposure, development
Determine that exposure dose and time for exposure, time for exposure are 60~90s after photoresist film thickness measure, exposure dose is
480mJ/cm2~720mJ/cm2；Substrate after exposure is placed on after being carried out on hot plate and is dried, hot plate temperature is 85 DEG C, when drying afterwards
Between be 5~10min, be then cooled to room temperature；Developer solution develops to micro- electroforming glued membrane with photoresist, developing time be 6~
12min is rinsed well with deionized water, and nitrogen drying can be obtained the metal substrate with micro- electroforming film.
The effect and benefit of the present invention：Provide a kind of non-contact optical measurement side measuring thick photoresist film thickness
Method.Solve the deficiency of existing measurement method and the limitation of application, have the characteristics that it is simple, efficiently, have a wide range of application, can be accurate
The thickness for really measuring hundreds of micron lithography glue glued membranes improves metal to provide accurate exposure imaging parameter for subsequent technique
The making precision and success rate of micro-structure electroforming film.
Description of the drawings
Fig. 1 is the thick film thickness measuring principle schematic diagram based on refractive index；
Fig. 2 is the refractive index that least square method calculates SU-8 photoresists；
In figure：1 is air part, refractive index n1.2 be SU-8 glue, refractive index n2.3 be visual observation point.P is substrate
On a bit, i.e. the minimum point of SU-8 glued membranes, P' is the virtual image seen by person.X is the horizontal distance of the point and normal, and H' is
The virtual image to the vertical distance of glued membrane upper surface, the i.e. eye level of glued membrane, H be the point to glued membrane upper surface it is vertical away from
From the i.e. actual height of glued membrane.θ is the incidence angle of light, and i is the refraction angle of light.
Specific implementation mode
Describe the specific implementation mode of the present invention in detail below in conjunction with technical solution and attached drawing.
Attached drawing 1 is the thick film thickness measuring principle schematic diagram based on refractive index.In conjunction with the law of refraction and triangle letter of light
The actual (real) thickness of SU-8 glue known to number relationship is the product of visual thickness and its refractive index, i.e. formula (1).Measurement based on Fig. 1
Principle calculates the refractive index of 2075 photoresists of SU-8 using Fig. 2.A kind of experimental method measuring thick photoresist thickness, packet
Include that steps are as follows：
(1) substrate pre-processes
Metal copper base is roughly ground with the sand paper of different model, is refined, polishing treatment, keeps its surface roughness Ra small
In 0.04 μm；Substrate surface is cleaned with acetone cotton balls；The substrate of wiped clean is placed in acetone soln and is cleaned by ultrasonic 20min,
It is placed in ethanol solution again and is cleaned by ultrasonic 20min, rinsed through deionized water, be put into vacuum drying chamber and dry after nitrogen drying；
Metal copper base after drying is cooled to room temperature for use.
(2) glued membrane makes
Using desk-top sol evenning machine in 2075 photoresists of metallic copper substrate surface spin coating SU-8, low speed is set as 600rpm, holds
The continuous time is 18s；High speed is set as 900rpm, duration 30s.The copper base for coating photoresist is placed on hot plate and is carried out
Front baking, using staged heating mode：Dry 30min at 65 DEG C, 75 DEG C of whens dry 30min, and 85 DEG C of whens dry 2h, and front baking terminates postcooling
To room temperature.
(3) glue thickness measures
First, the refractive index of 2075 photoresists of SU-8 is determined.Take two pieces of identical copper bases with photoresist film.Before
Visual thickness H ' is measured in the different location of two prints respectively using light microscope after baking, is shown using tool after exposure imaging
Micro mirror measures actual (real) thickness H in same position, obtains the visual thickness value and actual (real) thickness value of a series of different-thickness glued membranes.H'
Meet linear relationship with H, using H' as abscissa, H is that data point is depicted in rectangular coordinate system by ordinate, and passes through minimum two
Multiplication is fitted to obtain linear equation：：The slope of y=1.6542x, straight line are exactly refractive index value
Secondly, after determining that the refractive index of 2075 photoresists of SU-8 is 1.6542, using light microscope to thick photoresist film
Thickness measures.The thin accurate burnt spiral for adjusting light microscope, makes its focus be respectively focused on glued membrane top and bottom, the two
Difference in height be glued membrane visual thickness.The thickness of glued membrane different location is calculated using formula (1), as shown in table 1.
1 SU-8 of table, 2075 photoresist visual thickness and actual (real) thickness
(4) it exposes, develop
The photoresist film thickness measured according to refractive index determines that exposure dose is 640mJ/cm2, time for exposure 80s, after
The baking time is 7min, and rear temperature of drying is 85 DEG C.Developed to micro- electroforming glued membrane with the special developer solution of SU-8 glue, developing time is
10min is rinsed well with deionized water, and nitrogen drying can be obtained the metal substrate with micro- electroforming film.
Claims (10)
1. a kind of non-contact optical measurement method of thick photoresist film thickness, it is characterised in that following steps：
Step 1, substrate pretreatment
Metal substrate is roughly ground, is refined, after polishing treatment, is cleaned by ultrasonic substrate surface；
Step 2 makes glued membrane
Using desk-top sol evenning machine in metallic copper substrate surface spin coating SU-8 photoresists, the copper base for coating photoresist is placed in hot plate
Upper carry out front baking；
It is thick to measure glue for step 3
3.1) refractive index of photoresist is determined：Take two pieces of identical metal substrates with photoresist film；Optics is utilized after front baking
Microscope measures visual thickness H ' in the different location of two metal substrate prints respectively, and tool microscope is utilized after exposure imaging
Measure actual (real) thickness H in same position, obtain two groups of different-thickness glued membranes visual thickness value and actual (real) thickness value due to H' and
H meets linear relationship, and using H' as abscissa, H is that data point is depicted in rectangular coordinate system by ordinate, and passes through least square
Method is fitted to obtain linear equation, and the slope of straight line is exactly refractive index value
3.2) thick glued membrane is measured after determining photoresist refractive index：The thin accurate burnt spiral for adjusting light microscope, makes its coke
Point is respectively focused on glued membrane top and bottom, and the difference in height of the two is the visual thickness of glued membrane；The actual (real) thickness of photoresist is
The product of visual thickness and its refractive index；
Step 4, exposure, development
Exposure dose and time for exposure are determined after photoresist film thickness measure；Substrate after exposure is placed on after being carried out on hot plate
It dries, is then cooled to room temperature；Developer solution develops to micro- electroforming glued membrane with photoresist, finally, is rinsed using deionized water dry
Only, nitrogen drying can be obtained the metal substrate with micro- electroforming film.
2. a kind of non-contact optical measurement method of thick photoresist film thickness according to claim 1, which is characterized in that
In step 2 when spin coating SU-8 photoresists：Low speed is set as 500~700rpm, and the duration is 15~30s；High speed is set as
800~1000rpm, duration are 20~40s.
3. a kind of non-contact optical measurement method of thick photoresist film thickness according to claim 1 or 2, feature exist
In drying before SU-8 photoresists are carried out using staged heating mode in step 2：Dry 20-40min at 65 DEG C, 75 DEG C of whens dry
20-40min, 85 DEG C of whens, dry 1-2h.
4. a kind of non-contact optical measurement method of thick photoresist film thickness according to claim 1 or 2, feature exist
In the time for exposure of SU-8 photoresists is 60~90s, exposure dose 480mJ/cm in step 42~720mJ/cm2。
5. a kind of non-contact optical measurement method of thick photoresist film thickness according to claim 3, which is characterized in that
The time for exposure of SU-8 photoresists is 60~90s, exposure dose 480mJ/cm in step 42~720mJ/cm2。
6. a kind of non-contact optical measurement method of thick photoresist film thickness according to claims 1 or 2 or 5, special
Sign is that the rear baking temperature of SU-8 photoresists is 85 DEG C in step 4, rear to dry the time for 5~10min.
7. a kind of non-contact optical measurement method of thick photoresist film thickness according to claim 3, which is characterized in that
The rear baking temperature of SU-8 photoresists is 85 DEG C in step 4, rear to dry the time for 5~10min.
8. a kind of non-contact optical measurement method of thick photoresist film thickness according to claim 4, which is characterized in that
The rear baking temperature of SU-8 photoresists is 85 DEG C in step 4, rear to dry the time for 5~10min.
9. a kind of non-contact optical measurement side of thick photoresist film thickness according to claims 1 or 2 or 5 or 7 or 8
Method, which is characterized in that the developing time described in step 4 is 6~12min.
10. a kind of non-contact optical measurement method of thick photoresist film thickness according to claim 6, feature exist
In the developing time described in step 4 is 6~12min.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111474822A (en) * | 2020-05-19 | 2020-07-31 | 中国科学院光电技术研究所 | Method for quickly correcting uniformity of optical substrate based on three-dimensional photoresist mask |
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| US5769540A (en) * | 1990-04-10 | 1998-06-23 | Luxtron Corporation | Non-contact optical techniques for measuring surface conditions |
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| CN103424995A (en) * | 2013-06-05 | 2013-12-04 | 上海理工大学 | Optimization method for photoresist layer of guide mode resonance optical filter |
| CN103436923A (en) * | 2013-05-28 | 2013-12-11 | 大连理工大学 | Method for increasing interfacial bonding strength between SU-8 photoresist and metal substrate by ultrasound |
| CN104576428A (en) * | 2013-10-16 | 2015-04-29 | 上海华虹宏力半导体制造有限公司 | Film thickness detection method |
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Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5769540A (en) * | 1990-04-10 | 1998-06-23 | Luxtron Corporation | Non-contact optical techniques for measuring surface conditions |
| CN101305259A (en) * | 2005-11-15 | 2008-11-12 | 株式会社尼康 | Plane position detection device, exposure device and method for manufacturing elements |
| CN101393881A (en) * | 2007-09-20 | 2009-03-25 | 东京毅力科创株式会社 | System and method for checking construction formed on semi-conductor wafer |
| CN103436923A (en) * | 2013-05-28 | 2013-12-11 | 大连理工大学 | Method for increasing interfacial bonding strength between SU-8 photoresist and metal substrate by ultrasound |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111474822A (en) * | 2020-05-19 | 2020-07-31 | 中国科学院光电技术研究所 | Method for quickly correcting uniformity of optical substrate based on three-dimensional photoresist mask |
| CN111474822B (en) * | 2020-05-19 | 2021-09-17 | 中国科学院光电技术研究所 | Method for quickly correcting uniformity of optical substrate based on three-dimensional photoresist mask |
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