Surface treatment method for lens support assembly of ultraviolet lithography equipment

Abstract

The invention discloses an ultraviolet lithography equipment lens holder assembly and a surface treatment method thereof, which realize that the gas release amount is less than or equal to 0.14 * 10 <-9 > Torr.L / s.cm < 2 >, the 193nm reflectivity is less than or equal to 2.7%, the irradiation-resistant life is more than 620 hours and the surface treatment time is less than or equal to 2 hours through femtosecond laser processing of a three-dimensional curved surface microstructure, sulfur-free gradient anodic oxidation and a nano composite antireflection layer preparation technology. And the photoetching imaging precision and the equipment stability are obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor manufacturing equipment, and in particular to an innovative structural design of a lens support assembly of an ultraviolet lithography device and a surface treatment method thereof. Background Art

[0002] The aluminum alloy mirror base and support frame of traditional UV lithography equipment have the following defects:

[0003] Material outgassing problem: The oxide film generated by the traditional sulfuric acid anodizing process will slowly release SO 2 and organic gases. Under ultraviolet light, these substances undergo photochemical reactions to generate solid pollutants, leading to lens fogging, reduced transmittance, and film damage. According to SEMI standard F72-1103, the outgassing rate of the vacuum chamber of the lithography machine is required to be less than 1×10 -9 Torr·L / s·cm 2 , while the measured gas release of traditional sulfuric acid anodized parts is 3.2×10 -9 Torr·L / s·cm 2 ;

[0004] Secondary reflection problem: The existing surface treatment process does not adequately suppress reflections in the deep ultraviolet band (such as 193nm / 248nm), and the reflectivity is generally >8%, which interferes with the original optical path and reduces the accuracy of photolithography.

[0005] index Traditional crafts Industry Demand Test Standards 193nm reflectivity (%) 8.6 ≤3 ISO 13697 <![CDATA[Gas release rate (Torr·L / s·cm 2 )]]> <![CDATA[3.2×10 -9 ]]> <![CDATA[<1×10 -9 ]]> ASTM E595 UV irradiation resistance life (hours) 200 ＞500 SEMI F47

[0006] Poor durability: After 200 hours of UV irradiation, traditional coatings began to peel off and the reflectivity drifted by >5%.

[0007] A Chinese patent (application number: 2019113320585) discloses a method for preparing a highly corrosion-resistant aluminum alloy anodized protective layer, but the sulfuric acid system is used and the sulfur pollution problem cannot be solved. The existing multi-layer dielectric film anti-reflection solution cannot solve the problem of matrix outgassing and structural stability coordination. Summary of the invention

[0008] The object of the present invention is to provide a surface treatment method for a lens support assembly of an ultraviolet lithography device to solve the problems raised in the above-mentioned background technology.

[0009] To achieve the above object, the present invention provides the following technical solution: a surface treatment method for a lens support assembly of an ultraviolet lithography device, characterized in that it comprises the following steps:

[0010] (1) Femtosecond laser processing: wavelength 1030nm, pulse width <500fs, power density >1×10 14 W / cm 2The femtosecond laser is used to process a three-dimensional curved array microstructure with a bottom diameter of 1-3μm and a depth of 1-3μm on the surface of the stent;

[0011] (2) Sulfur-free anodization: immerse the stent treated in step (1) in an electrolyte containing 30-50 g / L oxalic acid and 5-10 g / L boric acid, apply a gradient DC voltage at 18±2°C, increase the voltage to 100 V within the initial 5 minutes, and then increase the voltage by 5-10 V every 5 minutes, with a total treatment time of 30-60 min, to form a gradient oxide film with a porosity gradually changing from 15% to 45% from the substrate to the outside;

[0012] (3) Nanocomposite treatment: TiO 2 Nanoparticles (10-20nm) and Ta 2 O5 nanoparticles (15-25 nm) were dispersed in an acetic acid solution with a mass ratio of 1:1.3 at pH 4.5. -2 Pa vacuum and 80°C conditions for 2-4h to form a quarter-wavelength anti-reflection layer on the surface of the oxide film.

[0013] Preferably, the three-dimensional curved surface array microstructure in step (1) is a randomly distributed sawtooth groove, the center spacing between adjacent grooves is 0.8-2 μm, and the inclination angle of the groove side wall is 10-25°.

[0014] Preferably, the gradient voltage boosting process in step (2) comprises: the voltage is linearly increased from 0 V to 100 V in the first 5 minutes, then the voltage is stepped up to 120 V by increasing 5 V every 5 minutes, and finally the constant voltage of 120 V is maintained for 10-20 min.

[0015] Preferably, the gradient voltage boosting process in step (2) comprises: the voltage is linearly increased from 0 V to 100 V in the first 5 minutes, then the voltage is stepped up to 120 V by increasing 5 V every 5 minutes, and finally the constant voltage of 120 V is maintained for 10-20 min.

[0016] Preferably, a lens support assembly for an ultraviolet lithography device comprises:

[0017] The base layer is made of 6061-T6 aluminum alloy;

[0018] The gradient porosity oxide film layer covers the surface of the substrate layer, with the porosity increasing from 15% to 45% from the inside to the outside, and the thickness is 8-12μm;

[0019] A three-dimensional curved surface microstructure layer is disposed outside the oxide film layer and includes a curved surface groove array with a bottom diameter of 1-3 μm and a depth of 1-3 μm;

[0020] Nanocomposite anti-reflection layer, made of TiO 2 With Ta 2 O5 It is compounded in a mass ratio of 1:1.3, with a thickness of 45-55nm and an equivalent refractive index of 2.05-2.15 at a wavelength of 193nm.

[0021] Preferably, the TiO 2 With Ta 2 O 5 The lattice mismatch is less than 3%, and the porosity within the layer is less than 2%.

[0022] Preferably, the pore size of the inner region of the gradient porosity oxide film is 10-20 nm, the pore size of the outer region is 50-80 nm, and there is a transition zone with a thickness of 0.5-1 μm at the interface between the inner and outer layers.

[0023] Preferably, the surface roughness Ra of the three-dimensional curved microstructure layer is less than 10 nm, and the peak value of the bidirectional reflectance distribution function (BRDF) at a wavelength of 248 nm is less than 0.05 sr -1 .

[0024] Compared with the prior art, the invention has the following beneficial effects: the total outgassing amount of the lens holder processed by the device and process is reduced to 0.14×10 -9 Torr·L / s·cm 2 , Reflectivity: 193nm band reflectivity ≤2.7%, Lifespan: UV radiation resistance life>620 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the structure of the lens support assembly of the present invention.

[0026] Figure 2 Schematic diagram of the three-dimensional curved surface microstructure layer.

[0027] In the figure: 1 three-dimensional curved microstructure layer, 2 gradient pore oxide film layer, 3 nanocomposite anti-reflection layer, 101 curved groove array. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] See also Figure 1-2 The present invention provides a technical solution: a surface treatment method for a lens support assembly of an ultraviolet lithography device, comprising the following steps:

[0030] (1) Femtosecond laser processing: wavelength 1030nm, pulse width <500fs, power density >1×10 14 W / cm 2 The femtosecond laser is used to process a three-dimensional curved array microstructure with a bottom diameter of 1-3μm and a depth of 1-3μm on the surface of the stent;

[0031] (2) Sulfur-free anodization: immerse the stent treated in step (1) in an electrolyte containing 30-50 g / L oxalic acid and 5-10 g / L boric acid, apply a gradient DC voltage at 18±2°C, increase the voltage to 100 V within the initial 5 minutes, and then increase the voltage by 5-10 V every 5 minutes, with a total treatment time of 30-60 min, to form a gradient oxide film with a porosity gradually changing from 15% to 45% from the substrate to the outside;

[0032] (3) Nanocomposite treatment: TiO 2 Nanoparticles (10-20nm) and Ta 2 O5 nanoparticles (15-25 nm) were dispersed in an acetic acid solution with a mass ratio of 1:1.3 at pH 4.5. -2 Pa vacuum and 80°C conditions for 2-4h to form a quarter-wavelength anti-reflection layer on the surface of the oxide film.

[0033] The three-dimensional curved surface array microstructure in step (1) is a randomly distributed sawtooth groove, the center spacing of adjacent grooves is 0.8-2 μm, and the inclination angle of the groove side wall is 10-25°; the gradient boosting process in step (2) includes: the voltage is linearly increased from 0V to 100V in the first 5 minutes, then the voltage is increased to 120V in a stepwise manner with an increase of 5V every 5 minutes, and finally the 120V constant voltage treatment is maintained for 10-20 minutes; the suspension in step (3) also contains 0.1-0.5wt% of polyvinyl pyrrolidone dispersant, and TiO 2 With Ta 2 The Zeta potential difference of O5 nanoparticles is less than 5mV.

[0034] A lens support assembly for ultraviolet lithography equipment comprises:

[0035] The base layer is made of 6061-T6 aluminum alloy;

[0036] Gradient porosity oxide film layer 2, covering the surface of the substrate layer, with a porosity increasing from 15% to 45% from the inside to the outside, and a thickness of 8-12 μm;

[0037] The three-dimensional curved surface microstructure layer 1 is disposed outside the oxide film layer and comprises a curved surface groove array 101 with a bottom diameter of 1-3 μm and a depth of 1-3 μm;

[0038] Nanocomposite anti-reflection layer 3, made of TiO 2 With Ta2 O 5 It is compounded in a mass ratio of 1:1.3, with a thickness of 45-55nm and an equivalent refractive index of 2.05-2.15 at a wavelength of 193nm.

[0039] TiO in nanocomposite anti-reflection layer 3 2 With Ta 2 O 5 The lattice mismatch of the three-dimensional curved microstructure layer 1 is less than 3%, and the porosity in the layer is less than 2%; the pore size of the inner layer of the gradient porous oxide film layer 2 is 10-20nm, the pore size of the outer layer is 50-80nm, and there is a transition zone with a thickness of 0.5-1μm at the interface between the inner and outer layers; the surface roughness Ra of the three-dimensional curved microstructure layer 1 is less than 10nm, and the peak value of the bidirectional reflectance distribution function (BRDF) at a wavelength of 248nm is less than 0.05sr -1 .

[0040] During the gradient boost anodization process, the ion migration rate of the electrolyte (oxalic acid + boric acid) is dynamically adjusted with the voltage change:

[0041] Initial stage (0→100V): High electric field drives Al 3+ Rapidly migrate outward and react with OH in the electrolyte - Combined to form dense amorphous Al 2 O 3 (porosity 15%), forming the inner layer;

[0042] Gradient boost stage (100→120V): The voltage gradually increases, resulting in oxygen ions (O 2- ) migration rate exceeds Al 3+ , the growth direction of the oxide film turns to inward growth, the pores gradually expand and connect with each other (porosity 25-35%);

[0043] Constant voltage stage (120V): The chemical dissolution of the oxide film by the electrolyte is dominant, forming an outer layer with high porosity (45%).

[0044] The transition zone (0.5-1μm) is essentially an oxidation-dissolution rate competition zone caused by dynamic changes in voltage, and its thickness is jointly regulated by the voltage gradient (5V / 5min) and the electrolyte temperature (18±2℃).

[0045] Thickness control experimental data:

[0046]

[0047] By selecting a 5V / 5min voltage gradient and an electrolyte temperature of 18°C, a 0.5-1μm transition zone can be formed while ensuring a bonding strength of >25MPa, thus avoiding cracking of the film layer caused by interface stress concentration.

[0048] Nanoparticle dispersion stability experiment:

[0049] Dynamic Light Scattering (DLS):

[0050] Storage time (month) <![CDATA[TiO 2 Average particle size (nm)]]> <![CDATA[Ta 2 O 5 Average particle size (nm)]]> Proportional Dispersion Index (PDI) 0 18.3±2.1 23.7±3.2 0.12 3 19.8±2.5 24.9±3.5 0.15 6 21.4±3.0 26.1±4.1 0.18

[0051] Sedimentation experiment: After the suspension was left standing for 6 months, the bottom sediment volume was less than 0.5%, and the initial dispersion state could be restored by ultrasonic treatment for 30 seconds.

[0052] In summary, the precise control of the gradient oxide film transition zone (0.5-1 μm) and the long-term stability of the nanoparticle dispersion system (PDI < 0.2) are the key factors for achieving ultra-low outgassing (0.13×10 -9 ) and high anti-reflection (2.4%@193nm).

[0053] Embodiment 1:

[0054] Surface treatment methods

[0055] Substrate pretreatment: The 6061-T6 aluminum alloy bracket was ultrasonically cleaned (acetone and ethanol for 10 min each) and then dried;

[0056] Femtosecond laser processing:

[0057] Laser parameters: wavelength 1030nm, pulse width 400fs, power density 1.2×10 14 W / cm 2 ;

[0058] Processing path: Random spiral scanning to form a curved groove array with a bottom diameter of 2μm and a depth of 2.5μm;

[0059] Sulfur-free anodizing:

[0060] Electrolyte: oxalic acid 40g / L + boric acid 8g / L, temperature 18°C;

[0061] Voltage program: 0→100V (5min linear boost)→105V (5min)→110V (5min)→120V constant voltage for 20min;

[0062] Oxide film thickness: 10μm, porosity gradient 15%→45%;

[0063] Nanocomposite treatment:

[0064] Suspension: TiO 2 (15nm) and Ta 2 O 5 (20nm) was mixed at a ratio of 1:1.3, 0.3wt% PVP dispersant was added, pH = 4.5;

[0065] Dipping conditions: 10 -2 Pa vacuum, adsorption at 80℃ for 3h;

[0066] Anti-reflection layer thickness: 50nm, 193nm reflectivity 2.5%.

[0067] Example 2

[0068] Outgassing test standard: ASTM E595-15 "Test method for total mass loss and condensation of volatiles in a vacuum environment"

[0069] Test equipment: Vacuum release test system (Inficon Transpector MPH-100, ultimate vacuum degree ≤ 1×10 -8 Torr

[0070] Test conditions:

[0071] Sample size: 20mm×20mm×2mm (sample cut from the bracket after pretreatment)

[0072] Temperature control: 85℃ constant temperature (±0.5℃)

[0073] Test time: 24 hours (including 2 hours of heating stabilization period)

[0074] Gas detection: Quadrupole mass spectrometer (QMS) monitors H 2 O, CO, CO 2 , CH 4 The main gas release components

[0075] Test steps:

[0076] 1. The sample was pretreated in a vacuum oven at 50°C for 12 hours to remove surface adsorbed moisture;

[0077] 2. Place the sample in the test chamber and evacuate to 5×10 -8 Torr;

[0078] 3. Raise the temperature to 85°C and stabilize for 2 hours;

[0079] 4. Record the total amount of gas released within 22 hours and calculate the gas release rate according to the formula:

[0080] Q=∑(Pi·V) / t·A

[0081] in:

[0082] Pi: partial pressure of the i-th gas (Torr)

[0083] V: cavity volume (10L)

[0084] t: test time (79200 seconds)

[0085] A: Sample surface area (8cm 2 )

[0086] Test results:

[0087] Total gas release: 0.13×10 -9 Torr·L / s·cm 2 (Only 4% of traditional technology)

[0088] Gas composition distribution:

[0089] Element Proportion (%) source <![CDATA[H 2 The]]> 65.2 Oxide film adsorption and desorption of water <![CDATA[CO 2 ]]> 26.5 Oxalic acid decomposition products CO 5.3 Oxidation of residual organic matter

[0090] The high porosity (45%) of the outer layer of the gradient oxide film effectively adsorbs CO 2 , inhibiting the diffusion of gas into the vacuum chamber; the sulfur-free process completely eliminates SO 2 Release (traditional process accounts for > 30%), meet SEMI F72-1103 standard (<1×10 -9 Torr·L / s·cm 2 ).

[0091] Reflectivity test

[0092] Test standard: ISO 13697:2006 "Measurement method for reflectivity of optical laser components"

[0093] Test equipment: JAWoollam M-2000DI wide-spectrum ellipsometer (193-250nm band)

[0094] Test parameters:

[0095] Incident angle: 5° (simulating the collimated incident condition of the photolithography machine)

[0096] Spot size: 100μm×100μm

[0097] Data fitting: Cauchy model is used to calculate the equivalent refractive index and film thickness

[0098] Test steps:

[0099] 1. Calibration standard: fused quartz (193nm reflectivity 4.2%) is used as the reference standard;

[0100] 2. Sample surface cleaning: ultrapure water + nitrogen purge to ensure no particle contamination;

[0101] 3. Multi-point measurement: select 10 areas on the sample surface and take the average value after measurement;

[0102] 4. Data analysis: After deducting the influence of the substrate oxide film (refractive index 1.65@193nm), the reflective properties of the nanocomposite layer were evaluated separately.

[0103] Test results:

[0104]

[0105]

[0106] Anti-reflection mechanism: The nanocomposite layer reduces the reflectivity to 90% of the theoretical limit (conventional process > 8%) through the synergistic effect of quarter-wavelength interference (50nm thickness) and refractive index gradient (2.05→2.15);

[0107] Wide-band adaptability: The reflectivity at 248nm only increased by 0.4%, proving that the structure is universally applicable to the deep ultraviolet band.

[0108] UV radiation life test test standard: SEMI F47-0706 "UV radiation life test method for optoelectronic devices"

[0109] Test equipment: Xenon lamp accelerated aging instrument (wavelength matching 193nm, equipped with water-cooled light filtering system)

[0110] Test conditions:

[0111] Irradiation intensity: 100mW / cm 2 (3 times the working intensity of the equivalent lithography machine)

[0112] Environmental control: vacuum degree 5×10 -6 Torr, temperature 25±1℃

[0113] Cycle mode: Continuous irradiation for 500 hours (without interruption)

[0114] Test steps:

[0115] 1. Initial performance record: reflectivity (2.4%@193nm) and surface morphology (SEM observation) before testing irradiation;

[0116] 2. Dynamic monitoring: Pause the test every 50 hours to measure the reflectivity change and coating integrity;

[0117] 3. Endpoint analysis:

[0118] Reflectivity drift ΔR = |R_end-R_initial|;

[0119] Statistics of coating peeling area (observed under metallographic microscope at 1000 times magnification);

[0120] Surface roughness variation (AFM scan 5 μm × 5 μm area).

[0121] Test results:

[0122] Reflectivity drift: ΔR = 0.2% (from 2.4% to 2.6%), well below the industry failure threshold (ΔR > 5%);

[0123] Coating integrity: no macroscopic peeling (peeling area <0.01%), SEM showed that the nanoparticles remained densely stacked;

[0124] Surface morphology: AFM measured that Ra increased from the initial 0.6nm to 0.8nm (an increase of 33%), but still met the optical surface requirements of the lithography machine (Ra<1nm).

[0125] Failure mechanism analysis:

[0126] The main degradation mode is UV-induced TiO 2 The formation of lattice oxygen vacancies leads to a slight increase in the refractive index (n from 2.05 → 2.07);

[0127] Ta 2 The amorphous phase of O5 inhibits crack propagation and no interlayer delamination occurs (bonding strength tested by scratch method>30MPa).

[0128] In summary: The present invention is compared with the same industry:

[0129] index The present invention Prior art Beyond Gas release <![CDATA[0.13×10 -9 ]]> <![CDATA[<1×10 -9 ]]> 87％ 193nm reflectivity 2.4％ ≤3％ 20％ Radiation life >500 hours >500 hours

[0130] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A surface treatment method for a lens support assembly of an ultraviolet lithography device, characterized in that: The following steps are involved: (1) Femtosecond laser processing: wavelength 1030nm, pulse width <500fs, power density >1×10 14 W / cm 2 The femtosecond laser is used to process a three-dimensional curved array microstructure with a bottom diameter of 1-3μm and a depth of 1-3μm on the surface of the stent; (2) Sulfur-free anodization: immerse the stent treated in step (1) in an electrolyte containing 30-50 g / L oxalic acid and 5-10 g / L boric acid, apply a gradient DC voltage at 18±2°C, increase the voltage to 100 V within the initial 5 minutes, and then increase the voltage by 5-10 V every 5 minutes, with a total treatment time of 30-60 min, to form a gradient oxide film with a porosity gradually changing from 15% to 45% from the substrate to the outside; (3) Nanocomposite treatment: TiO2 nanoparticles (10-20 nm) and Ta2O5 nanoparticles (15-25 nm) were dispersed in an acetic acid solution with a pH of 4.5 at a mass ratio of 1:1.

3. -2 Pa vacuum and 80°C conditions for 2-4h to form a quarter-wavelength anti-reflection layer on the surface of the oxide film.

2. The surface treatment method according to claim 1, characterized in that: The three-dimensional curved surface array microstructure in step (1) is a randomly distributed sawtooth groove, the center spacing between adjacent grooves is 0.8-2 μm, and the inclination angle of the groove side wall is 10-25°.

3. The surface treatment method according to claim 1, characterized in that: The gradient voltage boost process in step (2) includes: the voltage is linearly increased from 0V to 100V in the first 5 minutes, then the voltage is stepped up to 120V by increasing 5V every 5 minutes, and finally the voltage is maintained at 120V for 10-20 minutes.

4. The surface treatment method according to claim 1, characterized in that: The suspension in step (3) further comprises 0.1-0.5 wt % of polyvinyl pyrrolidone dispersant, and the Zeta potential difference between the TiO2 and Ta2O5 nanoparticles is less than 5 mV.

5. A lens support assembly for ultraviolet lithography equipment, characterized in that: include: The base layer is made of 6061-T6 aluminum alloy; A gradient porosity oxide film layer (2) covers the surface of the substrate layer, with a porosity increasing from 15% to 45% from the inside to the outside, and a thickness of 8-12 μm; A three-dimensional curved surface microstructure layer (1), arranged outside the oxide film layer, comprising a curved surface groove array (101) with a bottom diameter of 1-3 μm and a depth of 1-3 μm; The nanocomposite anti-reflection layer (3) is composed of TiO2 and Ta2O5 in a mass ratio of 1:1.3, has a thickness of 45-55nm, and an equivalent refractive index of 2.05-2.15 at a wavelength of 193nm.

6. The lens support assembly according to claim 5, characterized in that: The lattice mismatch between TiO2 and Ta2O5 in the nanocomposite anti-reflection layer (3) is less than 3%, and the porosity in the layer is less than 2%.

7. The lens holder assembly according to claim 5, characterized in that: The pore size of the inner layer of the gradient porous oxide film (2) is 10-20 nm, the pore size of the outer layer is 50-80 nm, and there is a transition zone with a thickness of 0.5-1 μm at the interface between the inner and outer layers.

8. The lens holder assembly according to claim 5, characterized in that: The surface roughness Ra of the three-dimensional curved microstructure layer (1) is less than 10 nm, and the peak value of the bidirectional reflection distribution function (BRDF) at a wavelength of 248 nm is less than 0.05 sr-1.

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