JP2002343697A - Method and device for heating polymer material layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cure a pattern of a thick polymer material layer formed on a substrate. SOLUTION: A substrate holder 4 is disposed in a vacuum chamber 2. The substrate holder 4 holds a transparent glass substrate 6, on which a polymer material layer pattern is formed on its surface side at the periphery thereof, so that the polymer material layer pattern faces upward. A far-infrared radiation heater 22, that irradiates far-infrared radiation is disposed on top of the vacuum chamber 2, and a far-infrared radiation heater 22, that irradiates far-infrared radiation and a far-infrared radiation lamp 24 that irradiates far-infrared radiation, are disposed under the vacuum chamber 2. Light from these lamps 22, 24 is made incident via incident windows on the upper surface and the lower surface of the vacuum chamber 2, to have the polymer material layer cured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for heating a polymer layer formed on a substrate for baking or curing, and an apparatus used for the method. Baking refers to evaporating and removing a solvent, and curing refers to crosslinking and curing. As an example of the target polymer material layer, a photosensitive material (hereinafter, referred to as a resist) layer used in a method of manufacturing an article having a three-dimensional structure surface shape, and a patterned layer thereof may be mentioned. it can. The resist pattern is formed on the substrate in a three-dimensional structure according to the desired surface shape, and the resist pattern is engraved on the substrate to form the desired three-dimensional structure on the article. Is formed. In addition to the resist layer, ink, adhesives, paints, surface treatment films, and the like can be given as the target polymer material layer.

[0002]

2. Description of the Related Art In a process of manufacturing a semiconductor device, a resist pattern is used as a mask to etch an underlying insulating film or conductive film to form a pattern. It is about 0.2 to 0.5 μm. In the process, since the thickness of the resist layer was small, there was no problem of uneven evaporation during baking or occurrence of a hardened surface layer. For this reason, oven baking and hot plate baking were sufficient. Then, as a method of forming the surface hardened layer, UV (ultraviolet), DUV (far ultraviolet)
Hardening devices have been proposed. Although the resist is used in the field of plating, the maximum thickness of the resist for plating is about 5 μm. Here, since it is used as a block layer at the time of plating, the properties required for the resist layer may be any thickness as long as a desired plating thickness can be obtained. The condition was not a problem.

That is, in the conventional baking method, baking using an oven or a hot plate is mainly used, and there is no need to bake a thick film resist. Therefore, in order to uniformly evaporate and remove the solvent component of the thick resist layer using the conventional technique, baking may be performed at a slow speed,
It takes a considerable amount of time and the productivity is reduced. In addition, since the evaporation of the solvent component naturally occurs from the surface, the formation of a hardened surface layer is unavoidable. Once the hardened surface layer is formed, it acts as a barrier (e.g., a wall) for preventing the internal solvent from evaporating, thereby hindering the process. Was a factor.

[0004] A special surface shape represented by a spherical surface or an aspherical surface has been used for a refracting surface or a reflecting surface of an optical element. In recent years, a special surface shape has been required for a microlens and the like in connection with a liquid crystal display element and a liquid crystal projector.

Therefore, as a method of forming the refraction surface and the reflection surface without using molding or polishing, a method of forming a resist pattern and transferring the resist pattern to a substrate has been proposed (JP-A-7-230159; See Japanese Patent Application Laid-Open No. Hei 8-504515). According to the method, a layer of a photoresist (a typical example of a resist) is formed on the surface of an optical substrate, and the photoresist layer is exposed through an exposure mask having a two-dimensional transmittance distribution. To obtain a convex shape or a concave shape as the surface shape of the photoresist by the development of the photoresist, then anisotropically etching the photoresist and the optical substrate, engraving and transferring the photoresist surface shape to the optical substrate. As a result, a desired three-dimensional structure of a refraction surface and a reflection surface is obtained on the surface of the optical substrate.

When the surface shape of the photoresist is engraved on the optical substrate and transferred, the photoresist and the optical substrate are both etched by anisotropic etching. In order to transfer the surface shape of the photoresist to the optical substrate, an appropriate selection ratio is required between the etching rate of the optical substrate and the etching rate of the photoresist. Usually, since the etching rate of the photoresist with respect to the optical substrate is high, it is necessary to enhance the etching resistance of the photoresist.

Further, when RIE (reactive ion etching) or ICP (inductively coupled plasma) dry etching is used as anisotropic etching, the photoreaction is caused by a surface reaction between the photoresist and the plasma or a reaction due to collision of ions in the plasma. The resist is heated. Therefore, if the heat resistance of the photoresist is not sufficient, the photoresist flows and the shape of the photoresist pattern is damaged. Therefore, it is necessary to increase the heat resistance of the photoresist.

High-resolution positive resists recently developed with high integration and miniaturization have lower heat resistance than negative resists. In addition, recently developed resists for g-line (436 nm) and i-line (365 nm) have low heat-resistant temperatures.
In the process of forming a three-dimensional surface, the resist material requires plasma etching resistance in addition to heat resistance. As a method of improving heat resistance and plasma etching resistance, there is a method of increasing the temperature stepwise in post-baking, but sufficient heat resistance and plasma etching resistance cannot be obtained. In particular, as the thickness of the resist becomes larger, it becomes more difficult to evaporate and remove the solvent component, sufficient heat resistance and plasma etching resistance cannot be obtained, and the shape deformation during the heating process becomes large.

In the semiconductor process, the photoresist U
A V curing process has been used. In the UV curing process, a semiconductor wafer coated with a photoresist on the front side is placed on a wafer processing table with a built-in heater under reduced pressure, and heated from the back side of the wafer. (See Japanese Patent No. 2798792).

[0010] The wavelength of the ultraviolet light used in UV curing is 3
Light irradiation shorter than 00 nm is mainly used. This is because it is considered that the novolak resin and the photosensitive material are combined to cause a crosslinking reaction, thereby improving the heat resistance of the resist.

When the UV curing method is applied to the curing of a thick resist having a film thickness of 3 μm or more, a cured layer having a thickness of slightly more than 1 μm is formed on the surface (depending on conditions). When the resist layer is thin, this method is effective. However, when the resist layer is 3 μm or more, the surface hardened layer acts as a blocker to prevent evaporation and removal of the internal solvent component, and is used in a process of baking a thick resist layer uniformly. It becomes an inhibiting factor.

In general, no method has been proposed for baking a thick resist layer uniformly. From another viewpoint, there are few attempts to use a resist layer to produce a three-dimensional structure in a thick film state. Speaking strongly, there is a report on a three-dimensional structure fabrication method in which a UV-curable material (that is, a UV adhesive) that does not contain a solvent component is applied to a thick film in a micromachining method and cured with a special laser beam. In this case, there is no need to remove the solvent component as in the present case, so the baking step does not pose a problem.

[0013]

When a baking method using a hot plate or an oven is used for baking a thick film resist, it is impossible to remove a solvent component uniformly in the film thickness direction. In addition, baking requires a long time and productivity is poor.
A hardened layer is formed on the surface and functions to prevent evaporation of the solvent component. If the evaporation and removal of the solvent components are not uniform, thermal deformation due to heating, foaming, reduction in plasma resistance and inhomogeneity, generation of surface cracks, cracking of resist,
Many problems such as peeling from the substrate (poor adhesion) occur.

In the mechanism for heating the substrate, when the substrate is in the atmosphere, there are three methods of transmitting air: convection of air, heat transfer (contact between the substrate and a heating jig), and radiation. When the heating jig is placed in a vacuum, the gap between the heating plate and the substrate is also vacuumed, so that heat transfer by air convection is lost, and the way heat is transferred from the heating plate to the substrate is And radiation only. That is, heat is less likely to be transmitted from the heating plate to the substrate, and the temperature difference between the surface of the heating plate and the substrate increases.
Therefore, it is necessary to set the heating plate set temperature higher.

In the above-mentioned conventional UV curing method,
The resist is heated from the back of the substrate (the surface without the photoresist). That is, the thermal energy that contributes to the evaporation of the solvent in the resist is “supplied from the lower part of the resist”, whereas the vacuum environment that assists the evaporation of the solvent acts from the “resist surface”. Ultraviolet rays are similarly irradiated from the “resist surface”. The above-mentioned UV curing process is performed in a semiconductor process, and if it is intended to be directly applied to a process of curing a resist pattern having a three-dimensional structure having a large thickness, as the object of the present invention,
The following various problems occur.

Generation and Residual Bubbles in Resist The positive resist emits N ₂ gas when irradiated with ultraviolet rays. If a hardened layer is formed on the resist surface before it is completely released, the N ₂ gas remains as bubbles, causing the resist to burst. This is because ultraviolet irradiation is performed from the resist surface to form a surface hardened layer,
_This is because the path through which the _two gases evaporate is blocked. In particular, this problem becomes more conspicuous as the resist film thickness increases.

In the method to which the present invention is applied, since the resist is thick, the light is attenuated and the surface of the substrate (below the resist)
Hard to reach. In particular, when ultraviolet irradiation is performed from the resist surface, only the surface layer is cured,
It strongly absorbs light having a wavelength of 00 nm or less and prevents light from penetrating into the resist. The formation of the surface hardened layer also occurs when the organic solvent component is partially evaporated on the surface, that is, only by heating. As a result, there are problems that the solvent inside the resist does not evaporate sufficiently, the heat resistance does not improve, and the processing time becomes long. If the set temperature of the heating plate is increased to sufficiently heat the resist in a state where the heat resistance inside the resist does not reach the predetermined temperature, the resist pattern may be deformed or wrinkled.

In the conventional method, since the back surface of the substrate is heated by bringing the back surface into contact with the heating member, the back surface of the substrate may be damaged. Even if there is no problem in the case of a semiconductor wafer as in the related art, the transmission characteristics are affected in the case of a substrate on which an optical element is formed. If a gap is provided between the back surface of the substrate and the heating member in order to avoid this, there arises a problem that the temperature difference between the back surface of the substrate and the heating member increases. An object of the present invention is to solve the above problems and to provide a method and an apparatus for heating a thick polymer material layer formed on a substrate for baking or curing.

[0019]

According to the present invention, far-infrared rays are applied to the substrate and the polymer material layer for baking or curing the polymer material layer formed on the substrate surface.
By heating the thick polymer material layer with far infrared rays, baking or curing can be performed in a short time with uniform heat conduction to the polymer material. Baking includes at least one of any baking in a processing step including pre-baking, pre-hardening baking, post-hardening baking, and post-baking. The polymer material layer formed on the surface of the substrate includes both unpatterned and patterned ones. An example of the polymer material layer is a resist layer, which is applied to the surface side of the substrate or patterned according to a desired shape.

In the case of a resist layer, a resist is applied to a predetermined thickness on the surface of a substrate material on which a desired surface shape is to be formed, and a resist layer is formed. The mask pattern is exposed on the resist layer using the designed mask. As the substrate, various substrates, for example, a transparent glass substrate, a Si substrate, a Ga-As substrate, or the like can be used as a substrate to be processed. As a typical example, a thick resist film (20 to 25 μm) is formed on these substrates.
m) and pre-bake. The resist layer is exposed through a mask according to a desired shape. The desired shape is
It may be a line / space like a semiconductor or a three-dimensional structure. Also, it may be a structural part for micromachining. Next, development and rinsing are performed (PEB (post exposure bake) between exposure and development, if necessary). Then, if necessary, remove resist
Pre-baking is performed by the V hardening method (pre-baking may be omitted). That is, the surface layer is irradiated with ultraviolet rays in order to harden the surface layer and improve etching resistance and heat resistance. Further, post-bake of the present invention is performed by far infrared rays. In this post-baking, the substrate is preferably first heated in the air or under reduced pressure, and then a far-infrared ray (preferably 10 to 1000 μm wavelength range) capable of baking and curing the target resist layer under reduced pressure. )
Is irradiated. This far-infrared irradiation is applied from the front side of the substrate.
Or, it is performed from both sides of the front surface and the back surface.

In a preferred embodiment, the heater is simultaneously heated from the back side of the substrate. Preheating of the substrate is performed by heating the heater, and heating of the polymer material layer is realized by irradiating far infrared rays. Heating by far infrared rays
It is preferable to change the irradiation intensity and wavelength over time. By heating the heater and irradiating far-infrared rays from the back surface of the substrate, baking and curing of the polymer material layer are performed from the heated side of the polymer material layer (the interface between the polymer material layer and the substrate surface) to form a hardened surface layer. And uniform heating and high-precision temperature control can be realized by far-infrared irradiation.

When the temperature of the substrate is raised and far-infrared radiation is applied, the substrate heating rate is increased. When the far-infrared ray is heated, the far-infrared ray is not absorbed and passes through many substrate materials, so that the polymer material layer can be directly heated. This makes it possible to favorably heat the glass material having a low thermal conductivity or the polymer material layer when the substrate has a large thickness. In addition, by simultaneously performing heating from the upper surface of the substrate (the surface of the polymer material layer), heating can be performed from above and below, and uniform solvent component heating becomes possible.

After baking and curing under reduced pressure,
Can be processed in a short time. This is because the vapor pressure is reduced under reduced pressure, so that water and the solvent are easily evaporated, and the baking and curing speeds are increased. Further, the reduced pressure condition uniformly acts on all the interfaces, so that the baking and curing treatment can be made uniform.

By performing far-infrared heating as a substrate heating method, non-uniformity of heat conduction in a vacuum, difficulty in conducting heat, improvement in reproducibility, and the like are realized. It is important for the baking and curing process to raise the substrate temperature to the required heat-resistant temperature while irradiating far-infrared rays. In addition, the rising gradient when increasing the substrate temperature, the irradiation intensity of the far-infrared ray, the irradiation amount, the temporal timing, and the integrated far-infrared irradiation amount are important. Although there are many elements as described above, the method differs depending on the type, thickness, processing method, and the like of a polymer material such as a resist. That is, it depends on the molecular design, functional group structure, molecular weight, and the like of the polymer material constituting the resist. Because the improvement of heat resistance of polymer material is
This is because the crosslinking reaction proceeds by heating and the polymer material is polymerized. It is important to uniformly evaporate and remove the solvent component contained therein while preventing the polymer material from being partially polymerized.

A curing apparatus according to the present invention for realizing this curing method is a substrate holding apparatus which holds a substrate having a polymer material layer formed on the surface side at a peripheral portion of the substrate so that the polymer material layer faces upward. A mechanism and a far-infrared irradiation mechanism that is arranged above and below the substrate and irradiates the polymer material layer with far-infrared light in a wavelength range capable of heating the polymer material layer through the substrate,
A heater disposed below the substrate for heating the substrate, and an entrance window that houses the substrate and the substrate holding mechanism and receives the far infrared rays from the far infrared irradiation mechanism and the far infrared rays from the substrate heating mechanism. And a decompression container having an exhaust mechanism to reduce the pressure inside.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, far infrared rays for baking and curing a polymer material layer are from 10 μm to 1000 μm.
Are preferred. As a light source having such a wavelength, a far infrared heater, a far infrared laser, a heater with a ceramic plate, a semiconductor laser, an optical parametric oscillator, a Raman laser, or the like can be used.

One common and preferred example of a far-infrared light source is
It is a far infrared heater. By using the far-infrared rays, heating is performed from the polymer material portion in contact with the substrate, so that uniform solvent component heating can be performed regardless of the thickness of the polymer material layer. This is because the baking / curing speed, the thickness of the cured polymer material layer, solvent components (evaporation temperature, molecular weight, evaporation speed, vapor pressure, evaporation speed, etc.) and heat resistance vary depending on the type of polymer material.

When irradiating far-infrared rays from both above and below the substrate, far-infrared rays above and below the far-infrared rays may be radiated simultaneously, or they may be radiated sequentially by selecting a filter to change the wavelength. When sequentially irradiating, it is preferable to irradiate far-infrared rays on the long wavelength side first, and then irradiate far-infrared rays on the short wavelength side. Thereby, the curing speed of baking can be further increased and the uniformity can be improved.

It is preferable to use different wavelengths of far-infrared rays to be irradiated and to use different irradiation timings according to the target polymer material. This is because the irradiation energy, which is the irradiation intensity and irradiation time or the product of these (irradiation intensity x irradiation time), is more dominant than the substrate temperature,
Irradiating far-infrared rays in a time-division manner in accordance with a program while increasing the temperature while removing temperature stably and uniformly removes the solvent component, and increases the curing speed.

It is preferable that the irradiation intensity of the far-infrared ray is first reduced, and then the irradiation intensity is increased.
When the polymer material layer is thick, it foams when irradiated with strong far-infrared rays from the beginning, and the foam remains in the polymer material layer as it is or bursts, thereby damaging the polymer material pattern. In order to prevent this, it is preferable to first irradiate a weak far-infrared ray for a few seconds to about 30 seconds to release gas which causes foaming.

When the heat capacity of the substrate material is large, it is effective to heat the substrate with a separately prepared heater in order to heat the substrate in advance. By doing so, it is possible to eliminate the temperature difference between the substrate temperature and the polymer material, thereby preventing poor adhesion and foaming.

The feature of the heating device of the present invention is that the substrate holding mechanism holds the substrate at the periphery of the substrate, and the far-infrared ray irradiation device and the heater for heating the substrate are both arranged on the back surface of the substrate. Preferably, the far-infrared irradiating device and the heater are installed in parallel and arranged so as not to interfere with each other. Alternatively, it is preferable to use a heating apparatus having two chambers as shown in FIG. Further, it is preferable that an auxiliary reflection plate is provided so that the illuminance is uniform and a mechanism for rotating the substrate is provided.

The irradiation of far-infrared rays, the use time of the heater, and the setting of the vacuum decompression condition are set in the embodiment and as shown in FIG. After reaching a predetermined temperature, it is preferable to reduce the pressure in vacuum. Further, the far-infrared irradiation is time-divisionally performed while monitoring the evaporation state of the solvent component, and the irradiation is performed several times to maintain the internal temperature of the polymer material layer and evaporate the solvent component while gradually increasing the temperature. The ultimate temperature depends on the polymer material. Further, it is desirable that the vacuum pressure is maintained at an appropriate degree of vacuum while controlling the evaporation of the solvent component as shown in the examples.

[0034]

FIG. 1 shows an embodiment of a curing apparatus according to the present invention.
Reference numeral 2 denotes a vacuum chamber of a decompression container, in which a substrate holder 4 of a substrate holding mechanism is provided. The substrate holder 4 holds the transparent glass substrate 6 having the polymer material layer pattern formed on the surface side at the periphery of the substrate 6 so that the polymer material layer pattern faces upward.

The upper and lower surfaces of the vacuum chamber 2 are entrance windows of a synthetic quartz plate. Far-infrared rays as a heater for baking and curing the polymer material layer and far-infrared rays for heating the polymer material layer enter the vacuum chamber 2 through the lower entrance window, and the transparent glass substrate After 6, the polymer material layer pattern formed on the surface is irradiated. Far-infrared rays for baking and curing the polymer material layer enter the vacuum chamber 2 through the upper entrance window, and irradiate the polymer material layer pattern. The vacuum chamber 2 is provided with a vacuum pump 10 via a pressure control mechanism (valve) 8 for controlling an exhaust speed in order to reduce the pressure inside the vacuum chamber 2.

The vacuum chamber 2 is further provided with a nitrogen supply mechanism 12 for supplying nitrogen introduced when the vacuum chamber 2 is leaked (vacuum released), and a vent 14 for discharging the nitrogen from the vacuum chamber 2. I have.

The side of the vacuum chamber 2 is provided so that the work can be continued without breaking the vacuum in the vacuum chamber 2 when the substrate 6 is placed on the substrate holder 4 or taken out of the substrate holder 4. , A load lock chamber 16 is provided. Reference numeral 18 denotes a substrate carrier for accommodating the substrates 6 before and after the baking / curing process. The transfer robot 20 transfers the substrates between the substrate carrier 18 and the load lock chamber 16.

At the upper and lower portions of the vacuum chamber 2, an illuminating device is disposed. The illuminating device includes upper and lower far-infrared irradiation heaters 22 for irradiating far-infrared rays through an entrance window.
An infrared lamp 24 for heating the substrate from below. 26 is a power supply of the far infrared heater 22. Although not shown, the heater 22 and the far-infrared lamp 24
A shutter, a filter, and an auxiliary reflector for uniformizing the irradiation intensity are installed.

Reference numeral 30 denotes a power supply device for supplying necessary power to each unit. An outer frame surrounded by a broken line represents the entire curing device, and 32 is an air conditioning control device for controlling the cleanness of the entire curing device. As the far-infrared irradiation heater 22, a total of two lamps for industrial use (1000W) were used. The irradiation intensity can be varied by changing the irradiation distance. By using the far-infrared irradiation heater, the back surface of the substrate was not scratched. In addition, there is no difference in the substrate temperature depending on how the gap is provided between the substrate and the heater as in the case of using the contact type heater.

Example 1 As an example, a large-diameter microlens shown in FIG. 2 was manufactured. This lens is L
D is a microlens for collimating emitted light, center wavelength: 1480 nm, WD (working distance, ie, distance between LD (laser diode) and microlens): 0.4 mm, distance between microlens and second lens : 9.5mm, Substrate material: S-NPH
2. Substrate thickness: 1.1 mm, lens effective diameter: first surface side (aspherical cylinder shape): 370 μm, second surface side (aspherical toroidal shape): 496 μm, focal length (first
Surface): f (Y direction) = 0.489 (mm), f (X direction) = 0.994 (mm), numerical aperture (first surface): NA
A microlens with (Y direction) = 0.390 and NA (X direction) = 0.251 was manufactured.

In the case of the microlens of this embodiment, a density distribution mask is manufactured with a unit cell shape of 2 μm × 2 μm square, a dot shape of a circle (a method of increasing the area concentrically), and a dot arrangement at the center. did. Finally, the shape required for processing under the conditions of the final resist thickness: 21.5 μm and the selectivity at the time of etching: 1.68 (the shape obtained by reducing the target shape to 1 / α; Selectivity) by the density distribution mask method,
A density distribution mask was designed from the sensitivity curve.

Next, an example of a micro lens manufactured using the above-mentioned mask will be described. An S-NPH2 glass substrate was prepared, and a TGMR-950 resist (a product of Tokyo Ohka Co., Ltd.) was applied on the substrate to a thickness of about 25.0 μm. The application condition is 300 rpm (the final number of revolutions for making the film thickness uniform is 1500 rpm). Next, prebaking was performed using the vacuum far-infrared irradiation apparatus of the present invention. The pre-bake was performed by placing the substrate in the apparatus and starting at 1 atm and 25 ° C. Far-infrared irradiation was started at the same time as the start. At the same time, evacuation was started. Seven minutes after the start, the vacuum reached 0.1 Torr and the substrate temperature reached 80 ° C. Thereafter, far-infrared rays were irradiated while maintaining a vacuum of 0.1 Torr. Thirteen minutes after the start, the substrate temperature was set to 90 ° C. and the degree of vacuum was set to 0.1 Torr. This state was continued for another 7 minutes. The total time after the start is 20 minutes. At this point, the far-infrared irradiation was terminated. After the treatment for a total of 20 minutes, nitrogen was introduced to release the vacuum.
At the same time, the substrate temperature dropped. The substrate was taken out of the device while being sufficiently cooled. The substrate was exposed with a 1/5 stepper. Exposure conditions are defocus: 0 μm, irradiation amount: 390 mW × 6.4 seconds (illuminance: 2500 mJ).

After exposure under these conditions, PEB was not performed. Thereafter, development and rinsing were performed to form a resist pattern. The resist height at this time was 21.5 μm (3.5 μm reduced by development and rinsing (reduction)
did). Further, as a pretreatment of resist surface hardening, baking was performed at 90 ° C. for 30 minutes under atmospheric pressure using the baking apparatus of FIG.

By this operation, the plasma etching resistance and heat resistance of the resist are improved, and the resist can be processed in the next step. Further, post-baking was performed using a heater and a far-infrared ray irradiator with the reduced pressure / far-infrared ray irradiator shown in FIG. In this post-baking, the temperature was gradually increased from 25 ° C to 160 ° C. During this time, when the temperature reached 90 ° C., the pressure reduction was started. Substrate temperature is 160 ℃
When the pressure reached, the pressure was stopped, and the pressure was increased to the atmospheric pressure while gradually introducing nitrogen. From the time when the pressure returned to the atmospheric pressure, the accumulated time was maintained until the maintenance time became 120 minutes. In the baking and curing conditions of the far-infrared irradiation in the present embodiment, after the substrate 6 is carried in by the automatic transfer apparatus, the valve 8 for far-infrared irradiation or evacuation is opened to start evacuation.

The operation state of a general apparatus is shown below. In the vacuum device itself, roughing is performed to 1 Torr in 60 seconds.
(However, since the resist (containing a large amount of solvent components) is usually applied on the substrate to the desired thickness, the ultimate pressure and the time are different even after evacuation is started.) Maintain 0.95 Torr by pump. Normally, the substrate is heated by irradiating infrared rays from the infrared lamp 24 at the same time as the evacuation is started to start the substrate heating. Raise to and maintain 55 ° C. within 60 seconds. Thereafter, far infrared rays are irradiated from the far infrared irradiation heater 22 and baking is performed while slowly heating the resist. Next, while maintaining the temperature, irradiation with far infrared rays is continued to cure the resist. It goes without saying that the baking / curing time and the timing of evacuation greatly vary depending on the type and thickness of the resist, the thermal conductivity of the substrate, and the purpose of baking / curing.

For the baking and curing, the conditions are obtained in advance by experiments and input to a computer, and are externally controlled by a computer. When the shape of the resist was measured after the curing treatment, there was no change from that before the curing treatment. The substrate 6 that has been subjected to the post-baking (curing) process is set in an ICP dry etching apparatus, the reaction gas is CHF ₃ : 5.0 to 10.0 sccm, the degree of vacuum is 1.5 × 10 ⁻³ Torr, and BCL _{3 is} :
Dry etching was performed under the following conditions: 1.0 sccm, Ar: 0.5 sccm, substrate bias power: 1 kW, upper electrode power: 1.25 kW, substrate cooling temperature: -20 ° C. At this time, the etching was performed while changing the substrate bias power and the upper electrode power with time, and changing the selectivity to increase with time. The average etching rate of the substrate was 0.55 μm / min, and the average selectivity was 1.68. Lens height after etching is 36.0
It was 1 μm. The actual etching time required 65.5 minutes.

In this embodiment, the lens shapes of the first surface and the second surface are different. For this reason, density distribution masks corresponding to the respective masks were prepared. However, since the lens heights were almost the same, the processes for manufacturing the lenses on the first surface and the second surface were exactly the same. As a result, the light coupled by the biconvex microlens manufactured in this example had a light coupling efficiency of 94.8% on the surface of the second lens.

Example 2 As a second example, a large-diameter microlens shown in FIG. 3 was manufactured. In the present embodiment, the “microlens for condensing LD emission light” has a center wavelength of 850 nm and a WD (working distance, that is, a distance between the LD and the microlens) of 0.
15 mm, distance between microlens and fiber: 0.1
3 mm, substrate material: S-NPH2, substrate thickness: 1.0 m
m, lens effective diameter is on the first surface side (aspherical shape): 200 μm
m, effective lens diameter on the second surface side (spherical surface): 200 μm, focal length (first surface): f = 0.15 (mm), focal length (second surface): f = 0.30 (mm), Numerical aperture (first
Surface): NA = 0.3, numerical aperture (second surface): NA = 0.16
Of micro lenses.

In the case of the microlens of this embodiment, a density distribution mask is manufactured by setting the unit cell shape to a square of 2 μm × 2 μm, the dot shape to a circular shape (a method of increasing the area concentrically), and the dot arrangement to the center arrangement. did. Lastly, the shape required for processing under the conditions of the final resist thickness: 21.5 μm and the etching selectivity: α (the target shape is reduced to 1 / α, α is the selection at the time of etching) The density distribution mask was designed based on the sensitivity curve so that the ratio was realized by the density distribution mask method.

In the design of the density distribution mask, the resist height after development is designed to be substantially the same on the first and second surfaces. Naturally, since the target heights are different,
The selectivity is different in each aspect. Therefore, the design of the density distribution mask is different. For this reason, the sensitivity curves used are the same, but specifically, the slopes of the slopes and the reduction ratios are different.

Next, an example of a micro lens manufactured using the above-mentioned mask will be described. An S-NPH2 glass substrate was prepared, and the TGMR-950 resist (manufactured by Tokyo Ohka Co., Ltd.) was applied on the substrate to a thickness of about 25.0 μm. The application condition is 300 rpm (the final number of revolutions for making the film thickness uniform is 1500 rpm). Next, FIG.
After heating by heating with a heater at 60 ° C. for 5 minutes using the decompression / far-infrared heating device shown in (1), vacuum decompression is started. Next, the temperature is gradually increased to 90 ° C. by irradiating far infrared rays. During that time, evacuate to 0.1 To
Reduce the pressure gradually to rr. (Integration of 0.1 Torr is 1
(5 minutes hold: 20 minutes total). From the start of depressurization, far-infrared rays are irradiated for 15 minutes at 500 W in both directions.

This substrate was exposed with a 1/5 stepper.
Exposure conditions are: defocus: 0 μm, irradiation amount: 390 m
W × 6.4 seconds (illuminance: 2500 mJ). After exposure under these conditions, PEB was not performed. Thereafter, development and rinsing were performed to form a resist pattern. The resist height at this time was 21.5 μm (decreased by 3.5 μm by development and rinsing). Further, as a pretreatment of resist surface hardening, the present baking apparatus is used at 85 ° C. under atmospheric pressure.
Baking was performed for 20 minutes.

Further, the temperature was gradually increased from 25 ° C. to 160 ° C. by using a heater and a far-infrared ray irradiator in the vacuum / far-infrared ray irradiator shown in FIG. During this time, when the temperature reaches 90 ° C., the pressure reduction is started. When the substrate temperature reaches 160 ° C., the pressure reduction is terminated, and the pressure is increased to the atmospheric pressure while gradually introducing nitrogen. After returning to the atmospheric pressure, post-baking is performed while maintaining the accumulated time until the maintenance time reaches 60 minutes. Unlike the first embodiment, since the pre-baking is performed under the reduced pressure of vacuum, the integrated holding time at 160 ° C. may be short.

The substrate 6 having undergone the post-baking (curing) process is set in an ICP dry etching apparatus, and the reaction gas is CHF ₃ : 5.0 at a degree of vacuum of 1.5 × 10 ⁻³ Torr.
10.0 sccm, BCL ₃ : 1.0 sccm, Ar:
Dry etching was performed under the conditions of a flow rate of 0.5 sccm, a substrate bias power of 1 KW, an upper electrode power of 1.25 KW, and a substrate cooling temperature of −20 ° C. At this time, the etching was performed while changing the substrate bias power and the upper electrode power with time, and changing the selectivity to increase with time. The average etching rate of the substrate was 0.55 μm / min, and the average selectivity was 1.4 on the first surface.
0 and 1.24 on the second surface. The height of the lens after etching is 30.0 μm on the first surface and 26.7 μm on the second surface.
μm. Actual etching time is 5 on the first side
It took 6 minutes and 50 minutes on the second side.

In this embodiment, the first surface and the second surface have the same lens shape. However, the lens height is different. For this reason, density distribution masks corresponding to each were prepared,
Since the lens heights after the development rinsing are almost the same, the lens manufacturing process for the first surface and the second surface was performed exactly the same. The target shape was successfully obtained by changing the selectivity of the subsequent etching. As a result, the light coupled by the biconvex microlens manufactured in this example had a light coupling efficiency of 85% on the end face of the optical fiber.

Although the curing apparatus of FIG. 1 has one vacuum chamber, FIG. 4 shows a curing apparatus improved to two vacuum chambers for mass production. Reference numerals 41 and 42 denote vacuum chambers of a decompression container, each holding a substrate 46 therein, and irradiating far infrared rays to cure the polymer material. One vacuum chamber 41 is provided with a substrate receiving jig 47 for holding the substrate 40 in the center. The substrate receiving jig 47 holds the periphery of the substrate 46, and can irradiate far-infrared rays from both directions. Far-infrared irradiators 44, 44 are arranged above and below the substrate 46 held at the center, respectively, and the space where the substrate 46 is arranged is separated by the synthetic quartz plate entrance windows 41a, 41a, respectively. I have. The far-infrared rays pass through the entrance windows 41a, 41a and irradiate the polymer material of the substrate 46.

In the other vacuum chamber 42, a heating device 45 for placing and holding the substrate 46 at the center and heating the substrate 46 is disposed. The heating device 45 is a heating device for infrared heating or heater heating. Above the substrate 46 installed on the heating device 45, a far-infrared irradiation device 44 is provided through an entrance window 42a of a synthetic quartz plate. In this vacuum chamber 42 as well, far infrared rays are applied to the polymer material layer on the substrate 46 through the incident window 42.

A transfer chamber 40 for connecting the two vacuum chambers 41 and 42 is disposed between the two vacuum chambers 41 and 42.
They are connected to be openable and closable via 9, 49. Transfer room 4
An automatic transfer device 43, which is a transfer robot, is provided in the unit 0, and the substrate 46 is gripped by the hand 50 and can be set in or removed from the vacuum chambers 41 and 42. Each of the vacuum chambers 41 and 42 and the transfer chamber 40 is provided with an exhaust port 48 to reduce the pressure inside thereof, and is connected to a vacuum pump via a pressure control mechanism (valve) (not shown) for controlling the exhaust speed. It is connected.

The vacuum chambers 41 and 42 further include a nitrogen supply mechanism (not shown) for supplying nitrogen introduced when the vacuum chambers 41 and 42 leak, and a vent for discharging the nitrogen from the vacuum chambers 41 and 42. Are provided respectively. Although not shown, a shutter, a filter, and an auxiliary reflector for uniformizing irradiation intensity are installed in each far-infrared irradiation device 44. As each far-infrared irradiation device 44, an industrial (1000W) device was used. The irradiation intensity can be varied by changing the irradiation distance.

The operation of the curing device shown in FIG. 4 will be described. A substrate carrier (not shown) capable of accommodating 25 substrates is transferred to the automatic transporter 43 in the transport chamber 40 by the substrate 46.
Is automatically conveyed. Substrate 46 transferred to transfer chamber 40
Is first placed on a substrate heating device 45 in the vacuum chamber 42. Next, the substrate 46 is heated by the substrate heater 45.
Is heated. At this time, the gate valve 49 is closed, and the inside of the vacuum chamber 42 is evacuated as necessary. During this time, both the transfer chamber 40 and the vacuum chamber 41 are evacuated.

After the heating in the vacuum chamber 42 is completed, the gate valve 49 is opened, and the heated substrate 46 is transferred to the substrate receiving jig 4 in the vacuum chamber 41 by the automatic transfer machine 43.
7. Thereafter, while the gate valve 49 of the vacuum chamber 41 is closed and the inside of the vacuum chamber 41 is evacuated, far infrared rays are irradiated from above and below the substrate 46 by the far infrared irradiation device 44 to cure the polymer material. After the end of the predetermined processing, the substrate 46 is returned to the transfer chamber 40, the vacuum is leaked, and the substrate 46 is taken out. In this curing device, the entrance window was not stained, and the inside of the vacuum vessel was not stained, so that the maintenance time was reduced.

FIG. 5 shows an example of the processing in the curing apparatus of FIG. ,, Respectively show examples of evacuation. These conditions differ depending on the resist thickness, sensitivity, and process (whether pre-baking or post-baking), and appropriate conditions are set for each. Symbols A to F in FIG. 5 indicate the temperature of the substrate 46. Is a typical example, so this case will be described.

The substrate 46 is carried into the vacuum chamber 42,
The substrate heating by the substrate heating device 45 is started. When the substrate temperature reaches a predetermined temperature, for example, 80 ° C. (B), the inside of the vacuum chamber 42 is evacuated and far-infrared irradiation is started by the far-infrared irradiation device 44 in the vacuum chamber 42. At this time, the transfer chamber 40 and the other vacuum chamber 41 are simultaneously evacuated so as to have the same degree of vacuum. When the temperature reaches (C) after heating for a certain period of time and irradiation with far-infrared rays, the substrate 46 is moved to the vacuum chamber 4 by the automatic transporter 43.
2 to the vacuum chamber 41. In the vacuum chamber 41, the upper and lower far-infrared radiation devices 44, 44
Irradiate far infrared rays. After the evacuation is continued and the substrate temperature reaches the point (D), the irradiation amount of far-infrared rays is controlled to maintain the substrate temperature at the constant temperature at the point (D). After maintaining at this temperature for a predetermined time, the far-infrared irradiation ends. Thereafter, nitrogen is introduced into the vacuum chamber 41 to return the pressure to the atmospheric pressure, and the substrate 46 is carried out to the substrate carrier by the automatic carrier 43.

[0064]

According to the heating method of the present invention, the conventional baking method using a hot plate and an oven is changed to a baking method using far-infrared rays. Also,
Shorter processing time is possible compared to oven and hot plate. Then, the etching resistance is further improved while the baking is performed for a short time. The heating method of the present invention can be used for baking in general, irrespective of soft baking or hard baking. By using the baking / curing method by irradiation with far infrared rays and the ultraviolet curing device of the present invention, the following effects were obtained and various problems could be solved. Since heating was performed from the back side of the polymer material layer by irradiation with far-infrared rays, the temperature distribution in the substrate could be controlled, and generation and retention of bubbles in the resist could be suppressed. The temperature distribution in the substrate became smaller. The baking and curing of the resist became possible from the substrate side, and no bubbling, thermal deformation and wrinkling occurred, and the resist was not thermally deformed by heat. Complete curing was possible even when the resist thickness was 20 μm or more.
In this way, even if the resist is thick, the heat resistance is no longer insufficient.By performing far-infrared irradiation and heater heating from the side opposite to the side of the polymer material, the solvent and the resist itself are evaporated. The resist can be heated uniformly, and the baking / heating speed has been greatly improved. Curing conditions can be set according to the type of resist, and baking and curing of many resists have become possible, so that a curing effect can be obtained regardless of the type of resist.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a curing device of the present invention.

FIG. 2 is a front view showing a large-diameter microlens manufactured using the heating method of the present invention.

FIG. 3 is a front view showing another large-diameter microlens manufactured using the heating method of the present invention.

FIG. 4 is a schematic configuration diagram showing another embodiment.

FIG. 5 is a time chart illustrating an example of a process in the embodiment of FIG. 4;

[Explanation of symbols]

 2, 41, 42 Vacuum chamber 4 Substrate holder 6, 46 Substrate 10 Vacuum pump 22 Far infrared heater 24 Heater 40 Transfer chamber 43 Automatic transfer machine 44 Far infrared irradiation device 45 Substrate heating device

Continued on the front page F term (reference) 2H096 AA25 DA01 FA01 GB02 HA01 JA02 JA03 JA04 5F046 KA02 KA04 KA07 KA10

Claims (14)

[Claims] 1. A heating method for baking or curing a polymer material layer formed on a substrate surface, wherein the substrate and the polymer material layer are irradiated with far-infrared rays. 2. The heating method according to claim 1, wherein a pressure condition around the substrate to be processed at the time of the far-infrared irradiation, an irradiation time, a far-infrared irradiation direction, an integrated irradiation energy, and an irradiation timing are combined. 3. The baking includes at least one of all baking in a processing step including pre-baking, baking before hardening, baking after hardening, and post-baking, and setting baking conditions as necessary. The heating method according to claim 1 or 2, wherein the heating is performed. 4. The substrate is a substrate to be processed, the polymer material layer is a photosensitive material layer, and the photosensitive material layer is applied to the substrate surface and is not patterned, or a desired material layer. The heating method according to any one of claims 1 to 3, wherein the heating method is patterned into a shape. 5. The method according to claim 1, wherein the far infrared ray is from 10 μm to 1000 μm.
The heating method according to any one of claims 1 to 4, wherein the heating method has a wavelength of m. 6. The pressure condition is 750 Torr or less and 1 T.
The heating method according to claim 2, wherein the heating is performed under reduced pressure of orr or more. 7. The heating method according to claim 2, wherein the substrate is first heated by a heater or an infrared heater, and then irradiated with far infrared rays. 8. The heating method according to claim 2, wherein the irradiation intensity of the far infrared rays is first reduced, and then the irradiation intensity is increased. 9. The irradiation of the far-infrared rays sets the timing, the number of times of irradiation, and the integrated irradiation amount according to the removal rate or the removal amount of the solvent component contained in the polymer material.
9. The heating method according to any one of items 1 to 8. 10. The heating method according to claim 1, wherein the thickness of the polymer material layer is 3 μm or more. 11. The heating method according to claim 1, wherein the polymer material layer is formed on the surface of the substrate via a layer of a substance having a higher thermal conductivity than the substrate. 12. The method according to claim 2, wherein the far-infrared irradiation direction includes both directions of the front side and the back side of the substrate.
The heating method according to any one of the above. 13. A substrate holding mechanism for holding a substrate having a polymer material layer formed on its surface at a peripheral portion of the substrate so that the polymer material layer faces upward, and disposed above and below the substrate. A far-infrared irradiation mechanism for irradiating the polymer material layer with far-infrared rays in a wavelength range capable of heating the polymer material layer from both the lower surface side and the upper surface side of the substrate through the substrate; and A substrate heating mechanism for heating the polymer material layer through the substrate with a heater, and an entrance window that accommodates the substrate and the substrate holding mechanism and receives far infrared rays from the far infrared irradiation mechanism. And a decompression container provided with an exhaust mechanism to reduce the pressure inside. 14. A pressure condition around the substrate to be processed at the time of far-infrared irradiation, irradiation time, far-infrared irradiation direction,
2. A controller for controlling irradiation conditions of far-infrared irradiation including irradiation integrated energy and timing.
4. The heating device according to 3.