JP2002283295A - Method of manufacturing microstructure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method suitable for manufacturing a microstructure by laminating a plurality of structural layers. SOLUTION: When combining a semiconductor substrate 20 for forming the first structural layer 101 becoming an actuator 6 and a glass substrate 96 for forming the second structural layer 102 becoming a prism via a separation layer 97 so that the respective structural layers 101 and 102 are opposed, an introducing passage 80 of an etchant is secured between microstructure groups 59 to be chipped. Thus, etching efficiency of the separation layer 97 is improved, and time required for a process of separating the substrate 96 by removing the separation layer 97 is shortened so that this microstructure can be manufactured in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a microstructure suitable for manufacturing a micromachine such as an optical switching device having a micron or submicron micro optical element.

[0002]

2. Description of the Related Art As a light valve of an image display device such as a projector, for example, an image display device that uses liquid crystal is known as an image display device capable of controlling light on / off. However, an image display device using this liquid crystal has a poor high-speed response characteristic and operates only at a response speed of at most several milliseconds. Therefore, a device for displaying a high-resolution image that requires a high-speed response, and further, an optical recording device such as an optical communication device, an optical operation device, a hologram memory, and an optical printer are realized by a switching device using liquid crystal. Difficult.

Therefore, there is a need for a switching device or an image display device capable of operating at a high speed. One of them is the development of a switching device which is a micromachine having a microstructure on the order of microns or a smaller submicron. Is being eagerly pursued.

[0004]

One effective method of manufacturing these micromachines is a method of forming the structure of the micromachine by dividing the structure into a plurality of structural layers using photolithography technology and laminating them. Then, by manufacturing by dividing into a plurality of structural layers, each structural layer can be manufactured by a manufacturing method and a material suitable for the function of the structural layer. Therefore, in the case of the above-mentioned optical switching device, for example, a hybrid microstructure including an actuator layer having high driving performance and an optical element layer having high optical performance can be manufactured by a manufacturing method of sequentially stacking them. Can be.

Further, when the manufacturing processes of the respective structural layers are different, the respective structural layers are manufactured with different devices or at different timings, and then the respective structural layers, for example, the actuator layer and the actuator layer are formed by a method such as substrate bonding. It has been studied to combine optical element layers to produce one microstructure such as an optical switching device. By separating the manufacturing process by including each structural layer from the substrate, there is an advantage that the manufacturing process is easily optimized and quality control is also facilitated. In particular, an expensive substrate manufactured up to the semiconductor circuit and the structure layer by the photolithography technique is not wasted, and the overall yield is greatly improved, so that the economic effect is large.

In this manufacturing method, it is necessary to remove one or both substrates after combining structural layers formed on different substrates. Therefore, the applicant of the present application has already applied for a method of providing a release layer between the structural layer and the second substrate and removing the substrate by chemically removing the release layer by etching. In a method of removing the peeling layer by etching, the substrate can be easily peeled by performing the dry process in particular, and the structure layer to be formed is not damaged. Further, it is excellent in that the peeled substrate can be reused.

Further, since the substrate can be separated at an etching rate as compared with the case where the substrate is mechanically peeled off, the substrate peeling process can be performed at a stable speed. However, there is an aspect that the peeling rate cannot be increased more than the etching rate. Reducing the manufacturing time is one important issue in the manufacturing method, and it is desirable that the time required for the process of peeling the substrate can also be reduced.

[0008] In the case where the above-mentioned microstructure is manufactured using a laminated structure layer, a micromachine having a microstructure is not formed individually, but a plurality of micromachines are formed on one wafer similarly to a semiconductor device. Chips are manufactured simultaneously. Therefore, the area of the substrate on which the structural layer is formed is also the same size as the wafer, for example, the wafer size is 5 inches or 8 inches in diameter. Then, after a chip-sized device including a plurality of switching elements is arranged on one wafer, elements are formed by combining a plurality of structural layers, and the elements are separated so as to operate individually. Each device (chip) is diced.

Therefore, since the peeling layer between the substrate and the structural layer is formed on the substrate surface, a diameter of 8 mm is required to separate the substrate.
An inch or 5 inch area of the release layer must be removed with an etchant. Since the structural layer is formed in the thickness direction of the substrate, the thickness is in the range of several μm to several tens μm, and the etching time is a few minutes at the longest.
On the other hand, in order to etch the peeling layer extending in the plane direction of the substrate, it is necessary to perform etching in units of several cm to several tens of cm. There is a degree of difference. Therefore, shortening the time for removing the release layer greatly contributes to shortening the time required for manufacturing the microstructure.

Therefore, in the present invention, in a method of forming each layer having a fine structure on a substrate using a release layer and combining them to manufacture a fine structure, the time for removing the release layer is reduced. It is an object of the present invention to provide a manufacturing method capable of performing the above. Further, it is an object of the present invention to provide a manufacturing method capable of producing a highly reliable and high quality microstructure in a short time with good yield.

[0011]

Therefore, in the present invention,
Instead of etching the release layer from the periphery of the substrate, the release layer can be etched from the inside of the substrate. That is, since the structural layer is formed on the entire surface of the substrate, if the release layer is to be removed by etching as it is, etching leaves the cross section of the release layer around the substrate where the cross section of the release layer is visible. Will be.
For this reason, when separating a substrate, it was necessary to wait for the peeling layer to be etched in cm units. On the other hand, in the present invention, not only the surroundings, but also the etching from the inside by actively forming the introduction path for guiding the etchant into the inside of the substrate as a structure,
The etching time is shortened, and finally, the substrate can be peeled off only by etching a length of the order of mm on the order of the chip area.

Therefore, the method for manufacturing a microstructure according to the present invention comprises a first step of forming a first structural layer on a first substrate and a second step of forming a second structural layer on a second substrate. And a third step of forming a plurality of microstructure groups to be later chipped by combining the first and second structural layers such that the first and second structural layers face each other. A release layer capable of separating the first and / or second structural layer from the first and / or second substrate is formed on the first substrate;
In the third step, a hollow introduction path leading to the release layer is formed avoiding the microstructure group, and the method further includes a fourth step of removing the release layer with an etchant supplied through the introduction path. The fourth step of removing the release layer in this manner
Before the step, the introduction path for guiding the etchant to the inside of the substrate, for example, to the central portion, so as not to hinder the manufacture of the microstructure group, is provided not only from the edge of the substrate but also from the introduction path. The exfoliation layer is exposed to the etchant also from the portion along the, and the exfoliation layer can be removed in a short time.

[0013] In the third step, if an introduction path connected to the edge of the substrate is formed through at least the central portion of the first and second substrates, an etchant is formed along the introduction path from the edge side in the fourth step. To the central portion, and the release layer can be etched from a portion along the introduction path. Further, by forming a plurality of introduction paths, the area where the peeling layer and the etchant come into contact from the beginning can be increased, so that the etching time can be shortened. Then, in the third step, the release layer and the etchant come into contact with each other without affecting the microstructure group to be chipped by forming an introduction path in a region that is cut off by dicing when the chip is formed. The area can be maximized, and the etched length can be reduced to about the chip size. For this reason,
The time for etching the release layer can be minimized. Therefore, the time for manufacturing the microstructure can be reduced, and the yield can be improved.

By providing the introduction paths in the region where the dicing is to be performed, the introduction paths of a sufficient number and area can be arranged on the wafer without affecting the arrangement of the fine structures on the wafer. Therefore, a sufficient number of microstructure groups can be arranged on the wafer without reducing the effective area for the production, and the productivity can be secured. For example, the introduction path can be provided by locally disposing an adhesive for attaching the first and second structural layers. Also, the first
And / or as a second structural layer, a side wall constituting the introduction path is formed on the release layer so that the material applied in the third step, such as an adhesive, remains inside the side wall in the third step. In this way, the introduction path may be ensured.

For example, xenon fluoride (XeF ₂ )
Is easy to handle with a gaseous etchant, and has a very small etching rate (selectivity) other than silicon, damaging surrounding materials and structures such as metals and resins that form other structural layers. Not useful. For this reason, silicon is adopted as the release layer,
It is effective that the substrate is made of glass or silicon oxide which is not etched by xenon fluoride. And even if it is said that the etching rate other than silicon is low, the etching other than the peeling layer may be an obstacle if it is etched for a long time, but if the manufacturing method of the present invention,
There is no such concern because the etching time is shortened.

Further, when the first and / or second structural layers are formed with a sacrifice layer made of the same material as the release layer, this sacrifice layer can be removed in the fourth step. In addition, the time required to manufacture a microstructure can be further reduced. Xenon fluoride is also convenient when removing the sacrificial layer because the etching rate of other elements than silicon is very small, and it is desirable to use silicon also as the sacrificial layer.

In this manufacturing method, a release layer can be easily formed in a known semiconductor process such as CVD.
Since the structure layer can be separated from the substrate by removing the release layer, it is suitable for forming a fine structure with high surface accuracy by controlling the shape or thickness of the release layer. Therefore, the manufacturing method of the present invention is suitable for forming an optical element for switching light in the structural layer, or for forming a switching element for switching another medium such as a gas. At that time, a fifth step of separating the element into desired units after removing the release layer is required. Then, in the manufacturing method of the present invention, the surface of the structural layer from which the substrate is separated is separated by the introduction path, for example, in units of the fine structure group, and has irregularities. Therefore, since it is not a flat surface, it is difficult to apply and pattern a photosensitive member such as a resist by spin coating. Therefore, by applying a photosensitive member such as a resist using a spray coat and patterning the same, element isolation can be easily performed as in the conventional case.

In the third step, a third structural layer can be formed between the first and second structural layers, and a part of the introduction path is also formed in the third structural layer. As a result, a large cross-sectional area of the introduction path can be ensured, and the circulation of the etchant can be promoted. At this time, it is possible to form a side wall of the introduction path by applying a resin including a gap material so as to surround the resin which is to be a part of the third structural layer. As the gap material, a spherical member having a predetermined tolerance diameter can be used, and the thickness of the third structural layer can be controlled by the size of the gap material. Further, when adjusting the alignment between the substrates before the curing, the gap material facilitates the relative movement of the substrates, and has an effect of assisting the alignment. In the case where the third structural layer is formed with a sacrifice layer made of the same material as the release layer, the sacrifice layer can also be removed in the fourth step.

Further, either one of the substrates can be used as a part of the fine structure manufactured by the present invention. In that case, for example, the release layer is formed only in the second step, and is removed in the fourth step. Further, the present invention also includes a manufacturing method in which the structural layers manufactured on the third substrate are stacked thereon and the third substrate is removed to sequentially stack the structural layers.

Substrates useful as part of the structure are semiconductor substrates such as silicon and germanium, for example,
If the first substrate is a semiconductor substrate, the first structural layer has a portion functioning as an actuator, and a circuit for driving the actuator can be incorporated in the first substrate. When a silicon substrate is used in combination with xenon fluoride, it is desirable to form an oxide film on the surface so as not to be affected by an etchant.

Further, the first structural layer may be a piezo actuator, but an electrostatic actuator which is easy to manufacture and uses less power by using silicon as a sacrificial layer is suitable. Then, the sacrificial layer can be removed in the fourth step. In addition, by forming the second structural layer as an element driven by an actuator, a microstructure including a plurality of switching elements can be provided. When the element is a plurality of optical elements, an optical switching device having high utility as an image display device or the like can be manufactured by the present invention. In this case, in the fifth step of separating the second structural layer into elements, as described above, it is desirable to apply a photosensitive member by spray coating and pattern the photosensitive member.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be further described with reference to the drawings. The invention of the present application is not limited to the switching device described in detail below, but can be manufactured extremely efficiently by applying the manufacturing method of the present invention. This microstructure device extracts evanescent light by bringing an extraction surface of a switching portion into contact with a total reflection surface of a light guide portion capable of transmitting light by total internal reflection, and extracts a microscopic light of about one wavelength or less of an optical element. It is an optical switching device capable of controlling the modulation of light at high speed by simple movements.
2 schematically shows a projector 180 as an example of an image display device using an image display device that performs switching by evanescent light.

The projector 180 includes a white light source 18
And a rotating color filter 182 that separates the light from the white light source 181 into three primary colors and makes the light enter the light guide plate (light guide) 1 of the image display unit (light switching unit) 55.
Display unit 55 that modulates and emits light of each color
And a projection lens 186 that projects the emitted light 185.
And Then, modulated light 185 for each color
Are projected onto a screen 189 and mixed with time to output a multi-tone multi-color image. The projector 180 further includes a control circuit 184 that controls the image display unit 55 and the rotating color filter 182 to display a color image. Image display unit 5
Reference numeral 5 denotes a light guide 1 and an image display device (optical switching device) 50 described in detail below. Data φ for displaying a color image and the like from the control circuit 184 are supplied to the image display device 50. Is done.

As described above, the projector 1 shown in FIG.
A light input / output unit 80 includes a light source 181 that supplies light for projection to the light guide 1 that transmits the light while totally reflecting the light, and a lens 185 that projects the light emitted from the light guide 1. An image display device 50 that modulates the projection light supplied to the guide 1 is provided. The image display device 50 controls the evanescent light leaking from the light guide 1 to display an image.

FIG. 2 shows an outline of an image display device 55 that modulates light using an evanescent wave (evanescent light). The image display device 55 includes a switching device 5 in which a light guide 1 and a plurality of optical switching elements (optical switching mechanisms) 10 are two-dimensionally arranged.
0, and each optical switching element 10 is an optical element capable of modulating light by approaching and separating from a light guide plate (light guide) 1 capable of transmitting the totally reflected light 2 by itself. A switching unit) 3 and an actuator 6 for driving the optical element 3. Then, the layer of the optical element 3 and the layer of the actuator 6 are stacked on the semiconductor substrate 20 on which the drive circuit for driving the actuator 6 and the digital storage circuit (storage unit) are built, and
Integrated as one optical switching device 50.

With reference to FIG. 2, the image display device 55 of the present embodiment using evanescent light will be described in more detail. When the individual optical switching elements 10 are described as a base, the optical switching elements 10 shown on the left side of FIG.
a is an ON state, and the optical switching element 10b shown on the right side is an OFF state. The optical element 3 has a surface (contact surface or extraction surface) 3a that is in close contact with the surface (total reflection surface) 1a of the light guide plate 1 that functions as a waveguide, and the surface 3a is in close contact with the total reflection surface 1a. A V-shaped prism (microprism 4) for extracting the leaked evanescent wave, a reflection film 46 for reflecting the light from the bottom surface of the prism 4 in a direction substantially perpendicular to the light guide plate 1, and a V-shaped prism And a support structure 5 for supporting the support structure 4.

The actuator 6 is of a type for electrostatically driving the optical element 3. For this purpose, an upper electrode (first electrode) that is mechanically connected to the support structure 5 of the optical element 3 and moves together with the optical element 3. 7 and a lower electrode (second electrode) 8 fixed to the semiconductor substrate 20 at a position facing the upper electrode 7. Further, the upper electrode 7 is supported by a support 11 extending upward from the anchor plate 9.

As shown in FIG. 2, the light guide plate 1 is supplied with the illumination light 2 from the light source at an angle at which the illumination light 2 is totally reflected by the total reflection surface 1a. Light is repeatedly totally reflected on the side 1a facing the light switching portion 3 and on the upper surface (emission surface), and the inside of the light guide plate 1 is filled with light rays. Therefore, in this state, the illumination light 2 is macroscopically confined inside the light guide plate 1 and propagates therein without any loss. On the other hand, microscopically, in the vicinity of the surface 1a of the light guide plate 1 which is totally reflected, the illuminating light 2 once leaks from the light guide plate 1 only for a very small distance of about the wavelength of light and changes its course again. The phenomenon of returning to the inside of the light guide plate 1 has occurred. The light leaked from the surface 1a in this manner is generally called an evanescent wave. This evanescent wave can be extracted by bringing another optical member close to the total reflection surface 1a at a distance of about the wavelength of light or less. The optical switching element 10 of the present embodiment is designed to modulate light transmitted through the light guide plate 1 at high speed, that is, to switch (on / off) using this phenomenon.

For example, the optical switching element 10 shown in FIG.
In a, since the optical element 3 is at the first position in contact with the total reflection surface 1a of the light guide plate 1, evanescent waves can be extracted by the surface 3a of the optical element 3. Therefore, the light 2 extracted by the micro prism 4 of the optical element 3 is reflected by the reflection film 4
At 6 the angle is changed to become the outgoing light 2a. The emitted light 2a is used as light 185 for projection of the projector 180 shown in FIG. On the other hand, in the optical switching element 10b, the optical element 3 is moved to the second position away from the light guide plate 1 by the electrostatic force acting between the electrodes 7 and 8. Therefore, the evanescent wave is not extracted by the optical element 3, and the light 2 does not exit from the inside of the light guide plate 1.

An optical switching element using an evanescent wave functions as a device capable of switching light by itself, but as shown in FIG.
It is configured so that it can be arranged in a three-dimensional direction, or even three-dimensionally. In particular, by arranging them two-dimensionally in a matrix or array, it is possible to provide a video device or an image display device 55 capable of displaying a two-dimensional image similarly to liquid crystal or DMD. In the optical switching device 50 using the evanescent light, the moving distance of the optical element 3 as the switching unit is on the order of submicron, so that the optical switching device 50 can be used as an optical modulator having a response speed one digit or more faster than that of liquid crystal. Projector 18 capable of high-speed operation using
It is possible to provide a zero or direct-view image display device. Further, the optical switching element 10 using the evanescent light allows the light to be moved by approximately 1 submicron order.
It can be turned on and off by 00%, and an image with very high contrast can be expressed. Therefore, it is easy to increase the temporal resolution,
A high-contrast image display device can be provided.

Further, the optical switching device 50
Now, the semiconductor integrated substrate 20 in which the driving circuit and the like are built
In this configuration, the actuators 6 and the optical elements 3 arranged in an array are stacked, and this can be provided by one chip. That is, as described above, a micromachine in which a microstructure such as the actuator 6 and the optical element 3 is constructed on the semiconductor substrate 20 or an optical switching device 50 as an integrated device and the light guide 1 are assembled. 55 can be supplied. By incorporating the image display device 55, it is possible to provide a projector that can display an image with a high operation speed, a high resolution, and a high contrast.

Such an actuator 6 and the optical element 3
The manufacturing method of the present invention is particularly suitable for manufacturing a micromachine having a structure in which are laminated. The stacked type micromachine is, of course, not limited to the above-described configuration. For example, the actuator 6 is not limited to the one having the pair of upper and lower electrodes of FIG. In addition to those having an intermediate electrode that moves between them, an actuator using a mechanism capable of supplying a driving force by another electric signal such as a piezoelectric element instead of an electrostatic actuator using an electrode pair Can also be configured. Therefore, in the present specification, for simplicity, a description will be given based on a micromachine in which an optical switching element is driven based on an electrostatic drive type actuator of upper and lower electrodes, but the configuration of the micromachine is not limited to this.

Incidentally, the optical switching device 50 having the above structure includes an actuator layer that emphasizes driving performance and an optical element layer that emphasizes optical performance, and these may be manufactured by the same manufacturing process. But,
It is more advantageous to manufacture each structural layer by a manufacturing process suitable for it. Therefore, as a manufacturing method,
A manufacturing method in which each of the structural layers is formed using two substrates, and after combining these, one substrate is removed is considered as a method for improving the yield.

FIG. 3 shows a semiconductor substrate as a first substrate 20 on which the optical switching elements 10 are arranged in an array.
Forming an optical switching device (image device) 5
0 is shown by a flow chart. 4 to 16 schematically show the respective processes. The process of the present example is a method of manufacturing a fine structure by manufacturing the structure layers of the fine structure on separate substrates and then combining the substrates so as to sandwich these structure layers. FIGS. 4 to 16 are intended to schematically explain the manufacturing process. For this reason, the optical switching device or the substrate on which the optical switching device is formed and the configuration on the wafer are partially deformed and shown. is there.
In the following manufacturing method, a semiconductor substrate on which a circuit can be formed is the first substrate 20, a glass substrate for forming an optical element is the second substrate 96, and only the glass substrate 96 is separated from the optical element. This is an example in which the semiconductor substrate 20 is used as a part of an optical switching device without being separated.

First, in step 120 of FIG. 3, a glass substrate is prepared as the second substrate 96 as shown in FIG.
A release layer 97 made of silicon is formed on the surface of the glass substrate 96. In this process, for example, the glass substrate 9
On the surface of No. 6, an inorganic material silane (SiH ₄ ) is deposited by a plasma CVD method at about 580 ° C. to form an amorphous silicon (a-silicon) release layer 97.

Next, in step 121, a second structural layer, that is, the optical element layer 3 is formed on the second substrate 96, and an etchant is introduced into the second structural layer later. The structure which becomes the introduction path of is formed. Therefore, as shown in FIG.
Using OS (tetraepoxide silane) as a plasma source, vapor deposition was performed under a low temperature condition of a substrate temperature of 300 ° C., and 3 μm
A silicon oxide layer 98 having a film thickness of about the same is formed.

For this purpose, as shown in FIG. 6, a resist (photoreactive member) 88 is spin-coated on the surface of the silicon oxide layer 98, and ultraviolet rays are passed through a gray mask 87 in which the structure as an optical element is incorporated in a gray scale. 86
Is irradiated. As a result, as shown in FIG. 7, the resist 88 is patterned into a desired pattern to be processed into an optical element.

Then, by performing RIE (reactive ion etching) on the silicon oxide layer 98 using the resist 88 as a mask, the shape of the resist 88 is transferred to the silicon oxide layer as shown in FIG. That is, the resist 8
8 is formed as it is on the silicon oxide layer 98, and the silicon oxide layer 98 is processed into the second structural layer 102.

In this example, the plurality of prisms 4 of the switching element 10 are configured as the second structural layer 102 in order to provide the device 50 having the plurality of optical switching elements 10 shown in FIG. 11 as one chip. V structure 42 is formed continuously.

In this process, the V structures 42 are formed as the second structure layer 102 shown in FIG. 8 and, at the same time, the protrusions 81 serving as side walls are formed at both ends of the structure 59 in which the V structures 42 are grouped. To process. These V structures 42
Are two-dimensionally arranged in a microstructure group 59, which is later separated into chip-based optical switching devices. For this reason, by forming the side walls 81 outside the chip unit structure 59, grooves are formed between the chip unit structures 59, which will later become the etchant introduction paths 80. Further, since the area where the introduction path 80 is formed corresponds to the area 79 which is later diced and cut off between the structures 59 in a chip unit, it is originally a necessary space. Substrate 9
It does not mean that the utilization efficiency of 6 is reduced.

Further, a V-shaped reflecting film 46 is formed by sputtering an Al-Nd material on the surfaces 42a of the plurality of V structures 42 of the second structural layer 102. In this way,
The step 121 of FIG. 3 for forming the second structural layer 102 constituting the V-shaped prism layer on the glass substrate 96 as the second substrate is completed, and the second structural layer 102 includes the V structure 42. In addition, a projection 81 serving as a side wall for forming the introduction path 80 is also formed.

On the other hand, before or after the step of forming the second structural layer on the second substrate, or at the same time, at step 122 in FIG. 3, the semiconductor substrate on which the CMOS circuit serving as the first substrate is formed is formed. The process of forming the first structural layer 101 for realizing the function as the actuator 6 on 20 is advanced. Then, in step 123 of FIG. 3, as shown in FIG. 9, the semiconductor substrate 20 of the first substrate and the glass substrate 96 of the second substrate are combined with the first structural layer 101 and the second structural layer 102. And stick them together (combination). Further, in the manufacturing method of this example, when bonding, a resin layer that joins the first structural layer 101 and the second structural layer 102 is used, and between these substrates 20 and 96, as shown in FIG. A part of the prism 4 shown and a support structure 41 serving as a support structure 5 for joining the prism 4 and the actuator 6 are formed as a third structural layer 103.

For example, first, the glass substrate 9 shown in FIG.
The surface of the reflective film 46 which is the interface (connection surface) of the second structural layer 102 on the side of the semiconductor substrate 20 and the surface of the actuator structure 6 which is the interface of the first structural layer 101 on the side of the semiconductor substrate 20 are coupling materials. Surface treatment. Thereafter, the first structural layer 10
First, a resin material serving as the third structural layer 103, for example, an epoxy (EP) material 71 is applied in units of chips, that is, in units of the fine structure group 59, and is divided into a plurality of points and applied by a syringe or the like. For example, the amount is about 0.3 mg per one point (site), and about 2.3 seconds when the application amount is controlled by time using the application apparatus used by the present inventor.

As described above, the resin material 71 is applied in the form of dots in units of the fine structure group 59, so that the introduction path 80 constituted by the side walls 81 provided outside the fine structure group 59 is formed. It can be used later as an introduction path for etchants. Further, the side wall 81 has a function of preventing the resin material 71 from inadvertently flowing into the introduction path 80. Therefore, the introduction path 80
Prevents the space from being filled with resin,
A sufficient resin material 71 is held on the region surrounded by the side wall 81, that is, on the fine structure group 59, so that the third structural layer 103 having a predetermined thickness is formed. In the manufacturing method of this example, the second structural layer 102 and the third structural layer 103 are not a structure having a continuous thickness,
The structure has a structure intermittently, and does not have a structure having a constant thickness over the entire substrate 96. However, by providing the side wall 81 at an appropriate position, it becomes possible to appropriately control the flow and thickness of the resin material 71 for joining the first structural layer 101 and the second structural layer 102. It is possible to manufacture a fine structure with high accuracy and no structural defects.

At the same time, the third structural layer 103 which does not become the support layer 41 such as the outer periphery of the substrate 20 is coated with a minute amount of the resin material 72 including the spherical gap material, for example, 0.0%.
It is desirable to apply an amount of about 6 mg / point (0.46 sec in time amount). As the resin material 72 including the gap material, Micropearl SP-2 manufactured by Sekisui Chemical Co., Ltd., which has been developed as a gap material for a liquid crystal panel.
03 etc. can be recommended. Gap materials such as micropearls also have high compressive strength and heat resistance, and by being sandwiched between the two substrates 96 and 20, the gap material allows the size of the gap between these substrates 96 and 20 to be adjusted. It is easy to control the relative combination size of the first structural layer 101 and the second structural layer 102. In this example, the thickness of the third structural layer 103 can be controlled by the gap material, and a fine structure with high dimensional accuracy can be provided. Further, since the first substrate 20 and the second substrate 96 come into contact with each other by interposing the granular gap material therebetween, even if the substrates 20 and 96 are bonded to each other, the substrate can be formed with a small resistance. It is possible to move the positions of each other, and it is easy to adjust the alignment.

As described above, the first substrate 20 and the second substrate 9
6 by pasting them together, as shown in FIG.
Between these substrates 20 and 96, the first structural layer 10
1, a microstructure in which the third structural layer 103 and the second structural layer 102 are stacked is completed. That is, the first substrate having the function as the actuator 6 on the first substrate 20 is provided.
Structure layer 101, a third structure layer 103 having a function as a support layer 41 thereon, and a third structure layer 103
On top of this, a second structural layer 102 having a function as an optical element 3 driven by the actuator 6 is sequentially stacked.

In such a combination, it is desirable to employ the following process. That is, after supporting and bonding the substrates 20 and 96 with a proper jig in a chamber in which the pressure is reduced to about 0.2 Torr or less, this state is maintained for several minutes. Heat to about 45 ° C. to lower the viscosity of the resin and increase the fluidity. Furthermore, 0.3MP by a pressure machine
The resin material 71 is spread as a whole by applying pressure to the extent that the support layer 41 made of resin is formed. Next, the bonded first and second substrates 20 and 96 are taken out of the chamber and set on an alignment device (aligner) having a UV exposure function. This UV exposure apparatus is also used for mask alignment in a semiconductor process, for example, a bond aligner B manufactured by Carl Seuss Japan Co., Ltd.
A6 or the like can be used. The exposure apparatus includes a stage capable of performing alignment between substrates, performs alignment adjustment of two substrates that are vertically stacked on the order of 1 μm, temporarily irradiates with UV, and performs first and second substrates. Fix the relative position of.

When the alignment is adjusted such that the first and second substrates are at the desired relative positions,
Take out from the alignment device, put in an oven or the like, and heat cure. In this example, the resin-made support layer 41 is cured by heating at 120 ° C. for 60 minutes, and the V-shaped structure 5 that connects the actuator 6 and the prism 4 is formed.

Thereafter, an operation of peeling the second substrate 96 in step 124 of FIG. 3 is performed. In this step, the first substrate 20 and the second substrate 20 shown in FIG.
The substrate 96 is set in a state where it is bonded, and an etchant of an appropriate concentration, xenon fluoride 99 in this example, is supplied into the chamber. The silicon release layer 97 exposed to the etchant 99 is removed, and the second glass release layer 97 is removed.
Substrate 96 is separated from the second structural layer 102, and the second substrate 96 can be removed. At this time, the etchant 99 is passed through the introduction path 80 constituted by the side wall 81 provided outside the chip unit structure 59 and the substrates 20 and 96
Can be guided to the joined interior. And
Release layer 9 in a shorter time than etching from the periphery of the substrate
7 can be removed.

FIG. 11 shows a first substrate 20 and a second substrate 9.
6 and the first structural layer 101 and the third structural layer 1
03 and a part of a state where the second structural layer 102 is stacked are schematically shown in an enlarged manner. Silicon sacrificial layer 60
The support structure 5 is formed by a resin support layer 41 on the actuator 6 on which the electrodes 7 and 8 are constructed. Further, the prism 4 is constituted by the V structure 42, and the structure as the optical switching element 10 in which the optical element 3 is driven by the actuator 6 is established. Then, the etchant 99 passes through the introduction path 80 outside the chip-based structure group 59.
Flows, and the release layer 97 is etched and removed. Accordingly, in step 124 of FIG. 3, the etching distance is a dimension of a chip unit, that is, on the order of cm to mm, and is several tens cm over the entire area of the substrate 96.
Compared to performing etching in units, the etching time can be reduced from a fraction to about a tenth.

In the structure shown in FIG. 11, the second structural layer 1
02, the wall structure 39 provided by the first structural layer 101 and the wall structure 49 formed by the third structural layer 103 form the periphery of the microstructure group 59 in chip units. It is a surrounding wall. Therefore, when the optical switching device 50 is diced by chip, it can be used as a support wall for laminating the light guide 1 shown in FIG. Also, this side wall 8
Due to 1, 39 and 49, the inside of the fine structure group 59 is isolated from the etchant 99 flowing through the introduction path 80, but the structure of this portion is not limited to the structure shown in FIG. For example, a space may be provided from the side wall 81 to the sacrifice layer 60 for forming the first structural layer 101, and the sacrifice layer 60 may be removed at the same time by an etchant flowing through the introduction path 80. Thereby, the step of removing the sacrificial layer 60 becomes unnecessary, and the manufacturing process can be further shortened. On the other hand, as in this example, the sacrificial layer 60
, The structure of the actuator 6 can be supported by the sacrificial layer 60 to the end, and it is also possible to prevent the actuator 6 from being damaged and leading to a product failure by a later assembling operation or the like. .

FIG. 12 schematically shows the entire substrate (wafer) viewed from above. In the manufacturing method of this example,
Since the side wall 81 is formed in units of the chip, that is, the fine group 59 to be a device, the introduction path 80 is formed so as to surround the fine structure group 59. Therefore, the second substrate 96 can be separated only by etching the separation layer 97 having an area of a chip unit. The arrangement of the introduction path 80 is not limited to this, and is not limited to, for example, the four sides of the microstructure loop 59,
It is also possible to form side walls in two directions and form a plurality of introduction paths 80 in parallel. Also, instead of forming the side walls 81 in units of the fine structure group 59, the walls of the substrate 96 are formed so as to divide the area of the substrate 96 into two or more parts, or the resin material 71 is applied, thereby forming the substrate. 96 rims 9
An introduction path 80 for guiding the etchant 99 from 6a to the central portion 96c can be formed. By forming a path for guiding the etchant 99 to the central portion 96c, the release layer 97 can be etched not only from the periphery but also from the inside, and the etching time can be reduced. Then, by forming the plurality of introduction paths 80, the area where the peeling layer 97 contacts simultaneously with the etchant 99 can be further increased, so that the etching time can be shortened.

Further, in the manufacturing method of this example, the selectivity of xenon fluoride 99 as an etchant is 10000: 1 for silicon to silicon oxide, which is almost the same for other substances. Therefore, it is possible to etch substantially only silicon, and the etching rate is as high as about 1 to 2 μm / min. Therefore, by providing the introduction path 80 for the etchant 99 as in this example, the process time for removing the release layer 97 for removing the substrate 96 can be significantly reduced.

Further, if etching is performed for a long time even if the selectivity is very large, the influence on other structures is not negligible, but in this example, the etching time is reduced by a factor of several to several tens. And the etching time can be reduced to such an extent that the effect of the etchant on other structures can be ignored. For this reason, a fine structure with higher accuracy and no structural defect can be manufactured in a short time with high yield.

As shown in FIG. 13, after the glass substrate 96 as the second substrate is peeled off, the second structural layer 102 laminated on the silicon substrate 20 has the fine structure group 5.
It is composed of 9 units. Therefore, as shown in step 125 of FIG. 3, it is necessary to perform pixel separation so that the microstructure group 59 is a unit of the optical switching element 10. At this time, in this example, since the introduction path 80 is provided, the surface of the structural layer is not flat, and is formed in an uneven shape. Therefore, when the resist is applied by spin coating, the thickness of the resist becomes constant. hard. Therefore, a technique of spray-coating a resist is adopted.

For the spray coating, for example, a pulse spray coating system manufactured by Nordson Corp. can be used. As shown in FIG. 14, the second structural layer 102 having an uneven shape is formed by using a spray coater. A resist 88 is applied to the surface. Then, a pixel pattern is formed on the resist 88 by the mask 87a. Using the patterned resist 88 as a mask, V
The structure 42 is made of a fluorine-based etchant such as C ₄ F ₈ +
Etching is performed with Ar + H ₂ , and the reflection film 46 made of Al—Nd is made of a chlorine-based etchant such as Cl ₂ and BCl ₃
The support layer 41 made of epoxy, which is the third structural layer 103, is subjected to RIE using O ₂ . Through these processes, the second and third structural layers 102 and 103 constituting the optical element 3 can be separated into individual elements, and a configuration in which each switching element 10 can be driven as shown in FIG. 15 appears. In addition, this O ₂
During the RIE process, the photoresist 88 for forming the image patterning can also be removed.

Then, as shown in step 126 of FIG. 3, the boundary of the fine structure group 59 is diced, and FIG.
A chip-shaped optical switching device 50 as shown in FIG.
Can be manufactured. By mounting the cover glass (light guide) 1 above the device 50,
An optical switch unit (image display device) 55 as shown in FIGS. 1 and 2 can be provided.

The introduction path 80 provided in the present invention is formed in a region 79 which is cut off by dicing when forming into chips. Therefore, a step of processing the introduction path 80 later is unnecessary. In addition, the area 7 which is originally diced
Since 9 is used as the introduction path 80, the area efficiency of the substrate 20 or 96 is not affected, and the number of chips that can be manufactured from one substrate is reduced, and the production efficiency is not reduced.

As described above, not only the optical switching device 50 of the present embodiment but also micromachines having a microstructure of a micron or sub-micron class are hardly manufactured individually. A plurality of devices (chips) are manufactured simultaneously on a wafer (substrate). Therefore, by employing the manufacturing method of this example, the step of removing the release layer in the manufacturing process can be shortened, and the productivity can be improved and the manufacturing cost can be reduced. In addition, since the speed of removing the release layer can be improved, the influence on the manufacturing time is reduced even if the number of steps of releasing from the substrate increases. Therefore, when manufacturing a microstructure of a multilayer structure, it is easy to manufacture by manufacturing a method suitable for manufacturing each structural layer on a large number of substrates, stacking them in order, and peeling the substrate. A complicated microstructure can be manufactured. The peeled substrate can be reused. Further, since the structure layer is separated from the substrate by etching, there is no influence such as damage to the structure of the structure layer when the structure layer is separated, and a very fine yield and a complicated fine structure can be manufactured.

Further, as described above, the first structural layer 10 is formed by using the two substrates 20 and 96 shown in FIG.
The first and second structural layers 102 are manufactured, and then one of the substrates 96 is removed. For this reason, the risk is very small as compared with a method of manufacturing a fine structure by sequentially stacking a plurality of structural layers on one substrate. For example, in each case, in addition to the semiconductor circuit, the structural layers are sequentially formed on the expensive substrate 20 manufactured up to the actuator layer by the photolithography technique.
In manufacturing, if there is a defect in the manufacturing process of the structural layer, all processes of manufacturing the substrate and the underlying structural layer up to that point are wasted. On the other hand, when the structure layer is manufactured in units of the substrate, defects in the manufacturing process do not spread to other structure layers, and the other structure layers and the semiconductor substrate are not wasted. Therefore, according to this manufacturing method, the yield of microdevices to be manufactured can be greatly improved, and a microstructure can be provided at low cost.

Further, the formation of the introduction path 80 for the etchant 99 according to the present invention is not limited to the above example. For example, as schematically shown in FIGS. 17 to 19, the first substrate 20 and the second A member serving as a side wall of the introduction path 80 may be provided in the third structural layer 103 formed when the substrate 96 is bonded. As shown in FIG. 17, a release layer 97 is formed on a second substrate 96, and a V
When the structures 42 are formed, they are arranged in groups 59 in chip units. Then, as shown in FIG. 18, when the first substrate 20 on which the first structural layer 101 serving as the actuator 6 is manufactured and the second substrate 96 are bonded, a resin material 71 serving as the support layer 41 is applied. At the same time, a resin including the gap material 72 is applied to a position around the microstructure group 59. That is, the resin 72 including the gap material is applied so as to surround the resin material 71. Then, these substrates 20 and 96 are attached to each other, and the first structural layer 101 and the second structural layer 102 are assembled with the third structural layer 103 interposed therebetween.

The resin 72 provided with the gap material is difficult to move because the fluidity is hindered by the gap material.
This prevents the resin material 71 constituting the support layer 41 from flowing inside. For this reason, the space isolated by the resin 72 containing the gap material becomes hollow, and this portion is later formed into the introduction path 8.
Available as 0. In addition, resin 7 containing a gap material
As described above, 2 controls the gap (interval) between the first substrate 20 and the second substrate 96 to facilitate the alignment.

For this reason, as shown in FIG. 19, when the first substrate 20 and the second substrate 96 are combined, an introduction path 80 is formed therebetween, and the introduction path 80 is formed in the same manner as described above.
, The exfoliation layer 97 from the glass substrate 96 is exposed to xenon fluoride 99 as an etchant in many regions, and the glass substrate 96 can be removed in a short time. After that, as shown in FIGS. 13 to 16, the optical switching device 50 and the image display device 55 as shown in FIG.

Furthermore, the introduction path 80 can be ensured only by setting the distance between the microstructure groups to be chips to a value that is not filled with the resin, without using the resin containing the gap material. However, as described above, if the flow of the resin is controlled to ensure the introduction path 80, the arrangement of the chips becomes easier, the area efficiency of the substrate can be improved, and a manufacturing method with high mass productivity can be provided.

Although the shape of the introduction path 80 is shown as an example of a substantially rectangular parallelepiped shape in the above description, the shape is not limited to this, and may be a columnar shape or the like, and becomes a path for the etchant (gas). Any shape may be used as long as the etchant efficiently contacts the layer. Further, in the above, an example in which silicon is used for the separation layer 97 and xenon fluoride is combined with the etchant is described. However, the present invention is not limited to this, and silicon oxide is used as the separation layer using hydrogen fluoride for the etchant. The combination of the etchant and the release layer is not limited to the above. However, as described above, xenon fluoride has a very high etching rate (selectivity) with respect to silicon and is easy to handle, so that it is one of the most desirable combinations at present.

Further, the method for producing a microstructure of the present invention comprises:
The present invention is not limited to the example applied to the optical switching device 50 using the evanescent light described above, but can be applied to a manufacturing method of a micromachine or the like that switches a transmitted optical signal in a space using a light shield. Alternatively, not only optical switching devices but also microswitching devices that operate media other than light,
It is possible to provide the manufacturing method of the present invention to micro machines for other uses, shorten the lead time of mass production base, and mass-produce micro machines with high product accuracy with good yield and low cost. Becomes

Further, in the above, the semiconductor substrate is used as one of the fine structures by using the semiconductor substrate as one of the substrates and incorporating a circuit for driving the actuator into the semiconductor substrate. For this reason, although an example is shown in which only the glass substrate as the second substrate is separated, it is of course possible to separate the first and second substrates, and the substrate is not part of the structure. The manufacturing method of the present invention can also be applied to the micromachine of (1). This manufacturing method can be said to be a manufacturing method suitable for manufacturing a fine structure having a free structure separated from the substrate while manufacturing using the substrate. This is a very effective manufacturing method for a small micromachine or a nanomachine of a smaller size.

[0068]

As described above, in the manufacturing method of the present invention, a plurality of microstructures having a micron or submicron order structure such as an optical switching device having an optical element are manufactured on a wafer. At this time, by ensuring the passage for introducing the etchant, the etching property of the separation layer for separating the microstructure from the substrate can be improved. Therefore, according to the present invention, for example, a process that required several hours to etch the release layer and remove the second substrate can be performed in several minutes. For this reason, the etching time can be reduced from １ ／ to 、, the process time can be significantly reduced, and a highly reliable and high quality microstructure can be easily manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a projector using a video display device using evanescent light.

FIG. 2 is a diagram showing an outline of a video display device (switching device) using evanescent light.

FIG. 3 is a flowchart schematically showing a manufacturing process of the switching device shown in FIG. 2;

FIG. 4 is a diagram showing a manufacturing process of the optical switching device shown in FIG. 2 and showing a state in which a release layer is formed on a second substrate.

FIG. 5 is a view showing a state in which silicon oxide for forming a prism layer is stacked on the second substrate shown in FIG.

FIG. 6 is a view showing a state in which a pattern is exposed to a prism layer and an introduction path on the silicon oxide layer shown in FIG. 5;

FIG. 7 is a view showing a state where a pattern of a prism layer and an introduction path is developed on a second substrate shown in FIG. 6 via a release layer.

FIG. 8 is a diagram showing a state where a prism layer and an introduction path are patterned on a second substrate shown in FIG. 7 via a release layer.

9 is a diagram showing a state where a semiconductor substrate (first substrate) in which an actuator layer is laminated on a semiconductor substrate and the glass substrate shown in FIG. 8 are combined.

FIG. 10 is a diagram showing a state in which an etchant is supplied through an introduction path and a release layer is etched.

FIG. 11 is an enlarged view showing a part of the optical switching device shown in FIG. 10;

FIG. 12 is a diagram showing the optical switching device shown in FIG. 10 as viewed from above.

FIG. 13 is a view showing a state where the glass substrate has been removed.

FIG. 14 is a diagram illustrating a state in which a unit of an optical switching element is patterned.

FIG. 15 is a diagram illustrating a state in which pixels are separated in units of an optical switching element.

FIG. 16 is a diagram showing a state in which an optical switching device which is diced and chipped is obtained.

FIG. 17 is a view illustrating a different manufacturing process of the present invention, and is a view illustrating a state in which a release layer is formed on a second substrate.

18 is a diagram showing a state where a semiconductor substrate (first substrate) in which an actuator layer is stacked on a semiconductor substrate and the glass substrate shown in FIG. 17 are combined.

FIG. 19 is a diagram showing a state in which an etchant is supplied through the introduction path shown in FIG. 18 and a peeling layer is etched.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light guide 2 Illumination light 3 Optical element (optical element layer) 4 Microprism (2nd structure) 5 V-type support structure (3rd structure) 6 Actuator part, 7 Upper electrode and spring structure 8 Lower electrode Reference Signs List 10 optical switching element 20 semiconductor substrate (first substrate) 41 support layer 42 V structure 46 reflective film 50 optical switching device 55 optical switching unit (image display device) 59 microstructure group 60 sacrifice layer 71 first resin material 72 gap Material 80 Introductory path 81 Convex part (side wall) forming introductory path 96 Glass substrate (second substrate) 97 Release layer 99 Etchant (xenon fluoride) 101 First structural layer (actuator layer) 102 Second structural layer 103 Third structural layer

Claims (24)

[Claims] A first step of forming a first structural layer on a first substrate; a second step of forming a second structural layer on a second substrate; A third step of forming a plurality of microstructure groups to be chipped later by combining the structural layers so as to face each other, and wherein the first and / or second substrates have the first and / or second substrates. Alternatively, a release layer capable of separating the second structural layer from the first and / or second substrate is formed, and in the third step, a hollow introduction path leading to the release layer avoiding the microstructure group. Is formed, and further comprising a fourth step of removing the release layer with an etchant supplied through the introduction path. 2. The method according to claim 1, wherein in the third step, the introduction path is formed through at least a central portion of the first and second substrates and connected to an edge of the substrate. Method. 3. The method according to claim 1, wherein in the third step, a plurality of the introduction paths are formed. 4. The method according to claim 1, wherein, in the third step, the introduction path is formed in a region that is cut off by dicing when forming a chip. 5. The microstructure according to claim 1, wherein in the first and / or second step, the first and / or second structural layer has a side wall that forms the introduction path. Production method. 6. The method according to claim 1, wherein the first and / or second structural layers are formed with a sacrifice layer made of the same material as the release layer interposed therebetween, and the sacrifice layer is also formed in the fourth step. A method for manufacturing a microstructure to be removed. 7. The method according to claim 1, wherein the release layer is made of silicon, and the etchant is xenon fluoride. 8. The method according to claim 1, wherein the first and / or second substrate is made of glass or silicon oxide. 9. The method according to claim 1, wherein the first and / or second structural layer is a layer forming a switching element. 10. The method according to claim 1, wherein the first and / or
Alternatively, a method for manufacturing a microstructure in which the second structural layer is a layer for forming an optical element. 11. The method according to claim 1, wherein the first and / or
Or a fifth step of separating the fine structure group of the second structural layer into a plurality of elements. In the fifth step, a fine structure in which a photosensitive member is applied by spray coating and patterned. How to make the body. 12. The method according to claim 1, wherein, in the third step, a third structural layer is formed between the first and second structural layers, and the third structural layer is also provided with the introduction path. A method for manufacturing a microstructure partially formed. 13. The side wall of the introduction path according to claim 12, wherein in the third step, a resin including a gap material is applied so as to surround the resin to be a part of the third structural layer. Manufacturing method of a fine structure. 14. The method according to claim 13, wherein the gap member is a spherical member having a diameter with a predetermined tolerance. 15. The method according to claim 13, wherein, in the third step, a thickness of the third structural layer is controlled by a size of the gap material. 16. The fine structure according to claim 12, wherein the third structural layer is formed with a sacrifice layer made of the same material as the release layer interposed therebetween, and the sacrifice layer is also removed in the fourth step. How to make the body. 17. The method according to claim 1, wherein the release layer is formed only in the second step. 18. The circuit according to claim 17, wherein the first substrate is a semiconductor substrate, the first structural layer has a portion functioning as an actuator, and the first substrate has a circuit for driving the actuator. A method for manufacturing a microstructure in which is incorporated. 19. The method according to claim 18, wherein the first structural layer is an electrostatic actuator. 20. The fine structure according to claim 18, wherein the first structural layer is formed with a sacrifice layer of the same material as the release layer interposed therebetween, and the sacrifice layer is also removed in the fourth step. How to make the body. 21. The method according to claim 18, wherein the second structural layer is a microstructure to be an element driven by the actuator. 22. The method according to claim 21, wherein the element is a plurality of switching elements. 23. The method according to claim 21, wherein the element is a plurality of optical elements. 24. The method according to claim 21, further comprising: a fifth step of separating the second structural layer into the elements. In the fifth step, a photosensitive member is applied by spray coating and patterned. Manufacturing method of a fine structure.