JP2000155207A - Manufacture of element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To etch the element so as to make a shape of a highly accurate rectangular stairway. SOLUTION: In film-forming by alternatively laminating a sputtered film 2 for forming a stairway part by etching and sputtered film 3 functioning as an etching stopper layer in each step with a etching rate different from that of the sputtered film 2 on a substrate 1 consisting of an optical glass, a metal and a synthetic resin, a second etching stopper layer 4 having a etching rate different from the prescribed two kinds of etching rates is formed between the substrate 1 and the lowest layered sputtered film 3 in the alternatively laminated films.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an element having a fine structure such as a step-like diffraction grating.

[0002]

2. Description of the Related Art A diffractive optical element is an optical element utilizing a light diffraction phenomenon, and can be constituted by diffraction gratings having various shapes and dimensions. For example, a method of manufacturing a step-shaped diffraction grating is described in JP-A-9-54420. In this case, an initial light-shielding film pattern is formed on a substrate,
The substrate exposed from the light-shielding film pattern is etched by a first depth, and a negative resist is applied thereon. Thereafter, a predetermined portion of the negative resist on the light-shielding film is exposed, and a mask pattern is formed by exposing and developing the entire surface of the substrate from the back surface. The light-shielding film exposed from the mask pattern is etched, and the substrate exposed from the mask pattern is further etched to a second depth. This is a mold manufacturing method in which the substrate is etched in two or more stages by repeating this process.

However, in the method of patterning from the back side of the substrate using a negative resist disclosed in Japanese Patent Application Laid-Open No. 9-54420, the aspect ratio to be etched increases as the number of steps increases, and the etching shape of a deep portion becomes tapered. Will come. As a result, since a corner-shaped etching residue is formed at the boundary between steps, there is a problem that a continuous rectangular step shape cannot be obtained. On the other hand, Japanese Patent Application Laid-Open No. 6-258510 discloses a method for manufacturing a diffractive optical element in which the cross section of a diffraction grating has a stepped shape. This diffractive optical element uses two kinds of materials having different reactivities to an etching gas. After the film thickness is sufficiently controlled and alternately laminated on the substrate, the two kinds of materials are patterned and etched by photolithography on the alternate layer to form a step-like diffraction grating.

An object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to provide a method of manufacturing an element for performing etching so as to have a rectangular step shape with high accuracy.

[0005]

However, when a diffraction grating having a stepped cross section is formed, in the above-described conventional example of Japanese Patent Application Laid-Open No. 6-258510, if patterning is performed three times, the step Misalignment occurs on the side wall opposite to the side wall. For this reason, the shape in which the side wall has a skirt with respect to the bottom surface of the staircase becomes remarkable, and there is a problem that a staircase shape in which the side wall forms a vertical rectangle cannot be obtained.

[0006]

According to a first aspect of the present invention, there is provided a method of manufacturing a device, comprising: forming a region corresponding to a lowermost step of a step-like element of a substrate by a required depth; After generating the lowermost surface of the step-like element by etching, etching a region corresponding to another step of the step-like element on the substrate to a required depth, thereby forming the step-like element. It is characterized in that the surface of the other step is generated.

According to a second aspect of the present invention, in the method of manufacturing an element, a film having a thickness corresponding to the height of the step-like element is formed on the substrate, and the step on the film on the substrate is formed. Etching the area corresponding to the lowermost step of the step-like element to a required depth to generate the lowermost surface of the step-like element, and then forming another step of the step-like key in the film on the substrate. The step corresponding to the step is etched by a necessary depth to generate the surface of the another step of the step-like element.

According to a ninth aspect of the present invention, in the method of manufacturing an element having a stepped cross section, the etching film and the etching stopper film formed on the substrate and having different etching rates from each other are provided. Two types are alternately formed to form an alternately laminated film, and a second etching stopper layer having an etching rate different from the two types of etching rates is provided between the substrate and the alternately laminated film to perform etching. It is characterized by the following.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the illustrated embodiment. FIG. 1 shows a sectional view of a four-step diffractive optical element according to the first embodiment, which is alternately laminated on a substrate 1 made of optical glass, metal or synthetic resin in order to form a step by etching. As a film, a sputtering layer (etching layer) 2 and an etching stopper layer 3 functioning as an etching stopper of each stage are alternately laminated and formed. A second etching stopper layer 4 is provided between the substrate 1 and the lowermost etching stopper layer 3 of the alternate laminated film.

In the present embodiment, an Si wafer is used as the substrate 1, an SiO ₂ film is used as the layer 2 which is one of the alternately laminated films formed on the surface of the substrate 1, and each of the layers 2 is used. Is formed by a normal sputtering film forming apparatus so that the thickness of the film becomes 600 nm. Further, as the layer 3 forming the other layer of the alternately laminated film, an Al ₂ O ₃ film having an etching rate different from that of the SiO ₂ film is formed using a similar sputtering film forming apparatus so that the film thickness becomes 10 nm. Film. The second etching stopper layer 4 is made of a metal film or a dielectric film having an extremely low etching rate with respect to an etching gas for etching the sputtered film (etching layer) 2 of the alternately laminated film and the etching stopper layer 3. For example, a Cr ₂ O ₃ film is used. This Cr ₂ O ₃ film is formed between the substrate 1 and the lowermost etching stopper layer 3 by using, for example, a normal vacuum film forming method.

FIG. 2 to FIG. 7 are schematic views showing the fabrication of the diffractive optical element shown in FIG. 1. First, a substrate 1 having a diameter of 8 inches and well washed is placed on a tank so that a film forming surface faces a target of a sputtering apparatus. Set in the sample holder inside. After sufficiently evacuating, oxygen gas and argon gas are introduced into the tank, and the pressure in the tank is set to 2 Pa. A high frequency of 400 W output is applied to the electrodes from an RF power source, and the second etching stopper layer 4 made of the above-mentioned Cr ₂ O ₃ film is uniformly formed on the surface so as to have a thickness of 100 nm. After the film formation, the vacuum in the tank is once released, the sample is put into a heating high-temperature furnace, and annealing is performed at 900 ° C. for 2 hours in an air atmosphere.

After sufficiently cooling, the sample is set again in the sputtering apparatus in the same manner as described above. The target was changed to Al and the mixture ratio of oxygen gas and argon gas was adjusted to be the same, and the second
The first etching stopper layer 3 is uniformly formed on the etching stopper layer 4 so as to have a thickness of 10 nm in the plane.

This time, the target was set to Si without releasing the vacuum.
The gas is exchanged for O ₂ , and the mixture ratio of oxygen gas and argon gas is adjusted so that the ratio of argon gas to oxygen is 10 so that the thickness of the sputtering film 2 on the etching stopper layer 3 becomes 600 nm in-plane. To form a uniform film. Subsequently, alternate layers of the layer 3 and the layer 2 are formed two more times, so that an alternate laminated film including six layers is formed on the second etching stopper layer 4.

Further, a four-step step shape is formed on such a sample by etching using the patterned photoresist 5. In FIG. 2, a photoresist 5 is formed on the alternately laminated film by a spinner, and a pattern having a step width of 1 μm corresponding to the fourth step is exposed and developed.

Next, this sample was set on an electrode of a normal RIE etching apparatus so that the film formation surface was etched, and after sufficiently evacuating, CF ₄ and CHF ₃ were introduced as etching gases. The pressure in the tank is set to 1 Pa. 100W output from high frequency power supply to electrode
Is applied for discharging, and etching is performed only for a predetermined time during which one layer 2 is etched from the sample surface. Further, the layer 3 is etched by changing the etching gas to CCl ₄ . This is alternately repeated three times, and as shown in FIG.
Is etched until is completely exposed. As a result, as shown in FIG.
The step patterning and etching are completed.

The sample is taken out of the etching apparatus, the resist 5 is peeled off, and as shown in FIG. 4, a photoresist 5 is formed on the alternately laminated film by a spinner again. This time, the step width 2.3 corresponding to the step width 2 μm corresponding to the second step and 0.3 μm as the patterning alignment accuracy is added.
Exposure and development at μm. At this time, the width of 0.3 μm is set so as to be on the side of the etching stopper layer which has already been etched and exposed.

As in the previous case, the sample is set in the etching apparatus, the layer 2 is etched for a predetermined time as shown in FIG. 5, and the layer 3 is etched by changing the etching gas in the same manner. The sample is taken out of the etching apparatus and the resist 5 is peeled off. Next, as shown in FIG. 6, a photoresist 5 is formed on the alternately laminated film by a spinner as in the previous case, and a step width of 1 μm corresponding to the third step is formed.
0.3 μm as patterning alignment accuracy
Exposure and development are performed with a step width of 1.3 μm in consideration of the above. At this time, the width of 0.3 μm is made to be on the layer 3 side already etched and exposed.

Further, as in the previous case, the etching apparatus
Set the pull, and as shown in FIG.
Etching for the specified time, and etching in the same way
The gas is changed and the layer 3 is etched. And sample
Out of the etching apparatus to remove the resist 5. Next
And Cr_TwoO_ThreeImmerse the etched sample in the stripper
Then, apply ultrasonic waves to only the second etching stopper layer 4.
Is peeled off and the surface is roughened by the second and third etching steps.
2 is removed, and the smooth substrate 1 is removed.
The surface is exposed to the groove bottom. Then wash thoroughly with pure water
N after flushing _TwoAfter drying with a blower, as shown in FIG.
Such a four-stage diffractive optical element is formed.

If an Al reflecting surface is formed on the diffraction grating surface by a usual vacuum evaporation apparatus, a four-stage reflective diffractive optical element can be manufactured. According to the manufacturing method of this embodiment, the step shape in cross section, in particular, the side wall facing the stair is perpendicular to the bottom surface, the etching bottom surface has no surface roughness, and the steps per one step in which both are smooth surfaces are uniform. Because a rectangular shape can be formed, a diffractive optical element having excellent diffraction characteristics can be stably manufactured at low cost. Note that the same effect can be obtained even if the sputtering film 2 and the etching stopper layer 3 constituting the staircase are not limited to the combination of the film materials described in the embodiments.

FIG. 8 is a sectional view of the second embodiment, and FIG.
In the embodiment, the Cr ₂ O ₃ film used as the _second etching stopper layer 4 was changed to an etching stopper layer 4 ′ made of a metal Cr film, and annealed at 400 ° C. for 2 hours in a N ₂ atmosphere in a heating high temperature furnace. Perform processing. This second
The first etching stopper layer 3 made of an Al ₂ O ₃ film and the SiO forming the step portion are formed on the etching stopper layer 4 ′ of FIG.
_A sputtering film (etching layer) 2 composed of _two films is alternately laminated twice, and a photolithography step and an etching step corresponding thereto are performed to produce a diffractive optical element.
Others are the same as the first embodiment.

In this way, as in the first embodiment, it is possible to manufacture a three-stage reflection type diffractive optical element having a rectangular shape with side walls perpendicular to the bottom surface and without unevenness and with uniform smooth steps. Second etching stopper layer 4 made of a metal Cr film
By using ', a reflectance close to that of the substrate 1 made of a Si wafer used in a normal photolithography process can be obtained, so that normal exposure conditions can be applied and production can be switched smoothly. it can. The same effect can be obtained with a diffractive optical element having a different number of stages.

In the first embodiment, the substrate 1 is
An antireflection film instead of an Al reflection film may be formed on a diffraction grating surface etched by changing from i-wafer to quartz using a normal vacuum deposition apparatus. Thus, a four-stage transmission diffractive optical element having the same characteristics as those of the first embodiment can be realized. A similar effect can be obtained for a transparent optical base material other than quartz used here.

Further, in the first embodiment, the etching layer 2 is formed directly on the second etching stopper layer 4 without forming the etching stopper layer 3, and thereafter the same as in the first embodiment. A four-stage diffractive optical element may be manufactured by forming an alternately laminated film with the etching stopper layer 3 in advance. In this case, without forming an Al reflective film on the diffraction grating surface, a UV curable resin was dropped on the mold as a mold, an optical glass was laminated thereon, and cured by irradiating ultraviolet light from the back or front surface of the diffraction grating. Later, the diffraction grating is obtained by peeling and replica transfer. Also, a diffraction grating can be obtained by pouring a thermoplastic resin into a mold and performing injection molding. Then, by forming an Al reflective film on the grating surface of the diffraction grating obtained by this molding to form a reflective diffractive optical element, a four-stage reflective diffractive optical element having the same characteristics as in the first embodiment. Can be realized with good reproducibility and at low cost.

In the first embodiment, the etching stopper layers 3 and the etching layers 2 are alternately stacked directly on the substrate 1 without forming the second etching stopper layers 4.
When a diffractive optical element is manufactured, phenomena such as formation of a groove corresponding to the fourth step counted from the top, that is, a small groove at the bottom, and roughening of the groove surface are observed. Can be vertical.

In the first embodiment, the annealing is performed after the second etching stopper layer 4 is formed because the etching stopper layer 3 and the sputtering film 2 are alternately stacked when they are alternately stacked. Partial film peeling occurs during the formation of the film, the film quality partially changes in the surface of the substrate 1, making desired patterning difficult, and the resist peeling and cleaning steps in the photolithography process. This is because the possibility that film peeling occurs in part also becomes small and eliminated.

Further, in the first embodiment, when an Al reflective film is formed on the diffraction grating surface to form a reflective diffractive optical element, the second etching stopper layer 4 is wet-etched after the etching is completed. Thus, there is no phenomenon that the lowermost groove surface corresponding to the fourth step counted from the top is roughened.

[0027]

As described above, according to the method for manufacturing a device according to the present invention, etching can be performed so as to form a highly accurate rectangular step shape. In the embodiment disclosed herein, when two types of etching films and an etching stopper film having different etching rates are alternately formed to form an alternately laminated film, the substrate and the alternately laminated film are firstly sandwiched. By providing the second etching stopper layer having an etching rate different from those of the two types, even if the alternately laminated film is exposed to the etching condition, the etching does not proceed to the substrate side beyond the stopper layer, so The side wall facing the side can form a rectangular shape having a step-shaped cross section perpendicular to the groove bottom surface, and good adhesion or durability to the substrate and the alternately laminated film can be obtained, which is used as an element type. In this case, the mold durability by molding transfer can be improved.
Further, since the groove bottom surface can be smoothed, it has excellent diffraction spectral characteristics, and it is possible to stably produce the film with good reproducibility at low cost.

[Brief description of the drawings]

FIG. 1 is a sectional view of a diffractive optical element according to a first embodiment.

FIG. 2 is a sectional view of a manufacturing process of the first embodiment.

FIG. 3 is a cross-sectional view of the manufacturing process of the first embodiment.

FIG. 4 is a cross-sectional view of the manufacturing process of the first embodiment.

FIG. 5 is a sectional view of a manufacturing step of the first embodiment.

FIG. 6 is a cross-sectional view of the manufacturing process of the first embodiment.

FIG. 7 is a sectional view of the manufacturing process of the first embodiment.

FIG. 8 is a sectional view of a diffractive optical element according to a second embodiment of the first embodiment.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 sputtering film 3 etching stopper layer 4, 4 'second etching stopper layer 5 photoresist

Claims (18)

[Claims] 1. The method according to claim 1, further comprising: etching a region corresponding to a lowermost step of the stepped element of the substrate to a required depth to generate the lowermost surface of the stepped element, and then forming the stepped element on the substrate. Forming a surface of the other step of the step-like element by etching a region corresponding to the other step to a required depth. 2. A film having a thickness corresponding to the height of a step-like element is formed on a substrate, and a region corresponding to a lowermost step of the step-like element in the film on the substrate is etched to a required depth. Then, after generating the lowermost surface of the step-like element, the region on the film on the substrate corresponding to the other step of the step-like wire is etched by a necessary depth. A method of manufacturing a device, comprising generating the surface of the another step of the step-like element. 3. The film comprises a multilayer film in which two materials having mutually different etching rates are alternately laminated.
Of the two materials, the layer of the material with the higher etching rate is the main part of the stepped element, and the layer of the material with the lower etching rate etches the layer of the material with the higher etching rate. 3. The method according to claim 2, wherein the method acts as a stopper when performing the operation. 4. The film comprises a multilayer film in which two materials having mutually different etching rates are alternately laminated.
Of the two materials, the layer of the material with the higher etching rate is the main part of the stepped element, and the layer of the material with the lower etching rate etches the layer of the material with the higher etching rate. A first stopper layer that acts as a stopper when the etching is performed, wherein the film is made of a material having an etching rate lower than that of the two materials, and acts as a stopper when etching both the two materials. 3. The method according to claim 2, wherein a stopper layer is provided on the substrate side of the multilayer film. 5. A method for manufacturing an element, comprising a step of manufacturing a diffraction grating by using the method according to claim 1. 6. A method for manufacturing an element, comprising: manufacturing a diffraction grating mold using the manufacturing method according to claim 1; and forming the diffraction grating using the mold. 7. An optical system comprising a diffractive optical element manufactured by using the manufacturing method according to claim 1. 8. An optical system comprising a diffractive optical element manufactured using a mold manufactured by using the manufacturing method according to claim 1. 9. A method for manufacturing an element having a stepped cross section, wherein two types of etching films and etching stopper films formed on a substrate and having different etching rates from each other are alternately formed to form an alternately stacked film. A method for manufacturing a device, wherein a second etching stopper layer having an etching rate different from the two types of etching rates is provided between the substrate and the alternately stacked films, and etching is performed. 10. The device according to claim 9, wherein after etching a deep groove in contact with said second etching stopper layer, a shallow groove corresponding to a step portion is sequentially etched from the upper side of said alternately laminated film. Method. 11. The method according to claim 9, wherein an annealing process is performed after forming the second etching stopper layer. 12. The method according to claim 9, wherein the second etching stopper layer exposed by forming the step-like shape is removed by etching. 13. A method of manufacturing a diffractive optical element by filling a resin and curing-transferring the element using the element manufactured by the method according to claim 9 as a mold. 14. An element manufacturing method, comprising a step of manufacturing a diffractive optical element by the method according to claim 9. 15. An element manufactured by the method according to claim 9. Description: 16. An exposure apparatus having the element according to claim 18. 17. A device manufacturing method including an exposure step using the exposure apparatus according to claim 15. 18. An optical element having an element manufactured by the method according to claim 9. Description: