JP2004249403A - Method of manufacturing microstructure and microstructure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microstructure manufacturing method, and a microstructure for restraining deformation of a metallic body while simplifying a manufacturing process. <P>SOLUTION: When manufacturing the microstructure, first of all, a Ti conductive layer 8 is formed on an upper surface of a silicon substrate 6. Then, a cantilever 9 is formed on an upper surface of the conductive layer 8, and a mirror 10 is formed on this cantilever 9. Then, after patterning the conductive layer 8, a TiO<SB>2</SB>film 8a is formed on a surface of the conductive layer 8, and the conductive layer 8 is formed into a passive state to XeF<SB>2</SB>gas. Then, a recessed part 7 is formed on the silicon substrate 6 by etching the silicon substrate 6 by the XeF<SB>2</SB>gas. At this time, the conductive layer 8 is not directly etched by the XeF<SB>2</SB>gas, and the XeF<SB>2</SB>gas wraps around into a lower part of the conductive layer 8 according too etching of the silicon substrate 6, and the conductive layer 8 is etched from the under surface side. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a fine structure for manufacturing a fine structure such as an optical switch, and to a fine structure.
[0002]
[Prior art]
As a method of forming a concave portion on a substrate of a microstructure, an etching mask for XeF ₂ (xenon difluoride) gas, for example, an SiO ₂ film or a resist film is patterned on the substrate, and then a molecule of XeF ₂ gas is formed. There is known a method in which a substrate is etched by irradiating a flow onto the substrate (for example, see Patent Document 1).
[0003]
[Patent Document 1]
JP-A-61-181131
[Problems to be solved by the invention]
For example, an optical switch has a microstructure in which a metal driver such as a cantilever or a cantilever is provided on a substrate, and the above-described conventional technology is applied to a method for manufacturing such a microstructure. In such a case, the following problems occur.
[0005]
That is, when fabricating a fine structure of an optical switch using the above-described conventional technique, after forming a metal driver on an etching mask, the substrate is etched to form a concave portion into which a part of the metal driver enters. Will be formed. At this time, since the SiO ₂ film or the like serving as the etching mask is not etched by the XeF ₂ gas, the etching mask remains completely. Since the thermal expansion coefficient of the metal driving body is largely different from that of the SiO ₂ film or the like, if the etching mask remains as it is, depending on the material of the metal driving body, the metal driving body is deformed due to a temperature change. For this reason, after forming the concave portion in the substrate, a part of the etching mask may be removed by wet etching or the like. However, in this case, the number of laborious manufacturing processes increases by one, and the cost increases accordingly.
[0006]
An object of the present invention is to provide a method for manufacturing a fine structure and a fine structure capable of suppressing deformation of a metal body while simplifying a manufacturing process.
[0007]
[Means for Solving the Problems]
The present invention relates to a method for manufacturing a microstructure including a substrate having a concave portion opened on the upper surface and a metal body provided on the substrate, wherein the XeF ₂ gas is applied to the upper surface of the substrate. Forming a conductive layer made of a passivable metal, forming a metal body on the upper surface of the conductive layer, and forming a passivation film on the surface of the conductive layer after forming the metal body. A step of passivating the conductive layer with respect to the XeF ₂ gas, and a step of etching the substrate with the XeF ₂ gas to form a concave portion in the substrate.
[0008]
In the present invention, passivatable metal against XeF ₂ gas, per se is etched by XeF ₂ gas, no longer etched with XeF ₂ gas when passivated. By utilizing this, the conductive layer can have a function as an etching mask. That is, the surface of the conductive layer, after forming the passivation film which is resistant to XeF ₂ gas, when etching the substrate by XeF ₂ gas, the surface of the conductive layer is etched by XeF ₂ gas There is no. Thus, it is not necessary to form a silicon oxide film or the like having a large difference in thermal expansion coefficient from the metal body on the substrate as an etching mask. In addition, when the etching of the substrate by the XeF ₂ gas proceeds and the substrate under the conductive layer is etched, the conductive layer is etched from the lower surface of the conductive layer where the passivation film is not formed, and finally, the side of the substrate is etched. The conductive layer is removed by the etching amount. Therefore, the deformation of the metal body due to the temperature change can be sufficiently suppressed. Further, since the conductive layer is removed together with the etching of the substrate as described above, it is not necessary to perform the step of removing the conductive layer after the etching of the substrate. Therefore, the manufacturing process of the fine structure can be simplified as compared with the case where a silicon oxide film or the like is used as an etching mask.
[0009]
Preferably, a passivation film is formed on the surface of the conductive layer by introducing the XeF ₂ gas into the conductive layer and placing the conductive layer in oxygen. As described above, the material of the conductive layer itself is etched with the XeF ₂ gas. However, if the surface of the conductive layer has a fluorine F component, the oxygen O ₂ component easily permeates the surface of the conductive layer. Therefore, a passivation film (oxide film) having a desired thickness can be easily formed by first slightly etching the surface of the conductive layer with XeF ₂ gas and then placing the conductive layer in oxygen. According to such a method, a passivation film can be formed on the surface of the conductive layer by using an etching apparatus for etching a substrate with a XeF ₂ gas. Investment can be reduced.
[0010]
Preferably, the metal that can be passivated with respect to the XeF ₂ gas is Ti or Cr. In this case, when a metal body is formed on the upper surface of the conductive layer by electroplating, the conductive layer can be used as an electrode (cathode).
[0011]
Further, a microstructure according to the present invention is characterized by being manufactured by the method for manufacturing a microstructure described above. In this case, as described above, it is possible to obtain a fine structure in which the deformation of the metal body due to the temperature change is extremely small.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of a method for manufacturing a microstructure and a microstructure according to the present invention will be described with reference to the drawings.
[0013]
FIG. 1 is a vertical sectional view showing an optical switch including one embodiment of a microstructure according to the present invention. In FIG. 1, an optical switch 1 includes a platform 2 having an optical waveguide (not shown) for guiding an optical signal, and an electrode 3 made of nickel Ni or the like is provided on an upper surface of the platform 2. An insulating layer 4 made of a silicon oxide film (SiO ₂ film) or the like is provided on the electrode 3.
[0014]
An actuator structure 5 is disposed on the insulating layer 4. The actuator structure 5 has a silicon substrate 6, on which a recess 7 is formed. A cantilever 9 is fixed to the silicon substrate 6 via a conductive layer 8. The conductive layer 8 is formed of titanium Ti, and the cantilever 9 is formed of a metal such as Ni. The base of the cantilever 9 is placed on the insulating layer 4 in a state where the cantilever 9 is arranged to face the electrode 3. The tip side portion of the cantilever 9 is warped so as to enter the recess 7 formed in the silicon substrate 6. A mirror 10 that reflects an optical signal passing through the optical path in a predetermined direction is fixed to the tip of the cantilever 9. The mirror 10 is made of Ni or the like, like the cantilever 9. A titanium oxide film (TiO ₂ film) is formed on a portion of the surface of the conductive layer 8 that is not in contact with the cantilever 9.
[0015]
The electrode 3 and the cantilever 9 are connected via a voltage source 11. Then, by applying a predetermined voltage between the electrode 3 and the cantilever 9 by the voltage source 11, an electrostatic force is generated between the two and the tip side portion of the cantilever 9 is drawn to the electrode 3, Move the mirror 10 downward.
[0016]
In such an optical switch 1, in the initial state, the tip side portion of the cantilever 9 is warped upward. At this time, the optical switch 1 is in the ON state, and the input signal light is output as it is through an optical waveguide (not shown) formed on the platform 2. On the other hand, when a predetermined voltage is applied between the cantilever 9 and the electrode 3 by the voltage source 11, the mirror 10 descends due to the electrostatic force generated between them (see the two-dot chain line in FIG. 1). At this time, the optical switch 1 is in the off state, and the input signal light is reflected by the mirror 10.
[0017]
FIGS. 2 and 3 show a method of manufacturing the actuator structure 5. FIG. 2 illustrates a manufacturing process when the component is viewed from the side, and FIG. 3 illustrates a manufacturing process when the component is viewed from the top.
[0018]
In each figure, first, a silicon substrate 6 is prepared, and a conductive layer 8 is formed on the upper surface of the silicon substrate 6 by sputtering or the like (see FIGS. 2A and 3A). Note that the thickness of the silicon substrate 6 is about 2 mm, and the thickness of the conductive layer 8 is about 1 μm.
[0019]
Subsequently, the cantilever 9 is formed on the upper surface of the conductive layer 8 by, for example, photolithography and electroplating (see FIGS. 2B and 3B). At this time, the conductive layer 8 is used as an electrode (cathode) for electroplating. The thickness of the cantilever 9 is about 5 μm.
[0020]
Subsequently, the mirror 10 is formed on the cantilever 9 by, for example, SR (synchrotron radiation) lithography and electroplating (see FIGS. 2C and 3C). At this time, it is desirable to form a reflective film such as Au on the surface of the mirror 10 by plating or the like in order to increase the light reflectance of the mirror 10.
[0021]
Subsequently, the conductive layer 8 is patterned by, for example, photolithography (see FIGS. 2D and 3D). As a result, the conductive layer 8 existing below the tip end portion of the cantilever 9 is removed.
[0022]
Subsequently, a TiO ₂ film (passive film) 8a is formed on the surface (upper surface and side surface) of the conductive layer 8 (see FIGS. 2E and 3E). Ti, which is the material of the conductive layer 8, is etched with XeF ₂ (xenon difluoride) as it is. However, by providing the TiO ₂ film 8 a on the surface of the conductive layer 8, the conductive layer 8 is compared with XeF ₂ . Passivated and no longer etched.
[0023]
The formation process of the TiO ₂ film 8a is performed using a processing apparatus 12 as shown in FIG. The processing apparatus 12 is used for the main processing and the subsequent etching processing (described later) of the silicon substrate 6.
[0024]
The processing apparatus 12 has a chamber 14 for accommodating the components 13 shown in FIGS. 2D and 3D. In the chamber 14, a vacuum pump 15 for depressurizing the inside of the chamber 14 is provided. It is connected via a valve 16. Further, a XeF ₂ gas supply source 17 and a N ₂ gas supply source 18 are connected to the chamber 14 via valves 19 and 20, respectively. Further, an O ₂ gas supply source 21 is connected to the chamber 14 via a valve 22. The O ₂ gas supply source 21 is used only in the process of forming the TiO ₂ film 8a.
[0025]
FIG. 5 shows a processing procedure for forming the TiO ₂ film 8a on the surface of the conductive layer 8 using such a processing apparatus 12.
[0026]
In the figure, the component 13 is first placed on a support (not shown) in the chamber 14. In this state, the valve 20 is opened, and the inert nitrogen N ₂ gas from the N ₂ gas supply source 18 is introduced into the chamber 14 (procedure 51). Subsequently, the valve 16 is opened, and the inside of the chamber 14 is evacuated to a predetermined ultimate vacuum by the vacuum pump 15 (procedure 52). Subsequently, by opening the valve 19, the XeF ₂ gas XeF ₂ gas supply source 17 into the chamber 14 (Step 53). Subsequently, the inside of the chamber 14 is evacuated again to a predetermined ultimate vacuum degree by the vacuum pump 15 (step 54). XeF ₂ gas generates harmful hydrofluoric acid when it reacts with hydrogen H component in the atmosphere. For this reason, as described above, the inside of the chamber 14 is replaced with the N ₂ gas, vacuum is evacuated, and then the XeF ₂ gas is introduced into the chamber 14.
[0027]
By this sequence 51-54, which is a material of the conductive layer 8 Ti is continuously reacted with XeF _2, conductive layer 8 are etched. However, since the fluorine F component exists on the surface of the conductive layer 8 etched by XeF ₂ , the permeability of the oxygen O ₂ component increases.
[0028]
Therefore, steps 51 to 54 are repeated until the surface portion of the conductive layer 8 is etched to some extent (step 55). When the conductive layer 8 is etched by a predetermined amount, opening the valve 22, the O ₂ gas O ₂ gas supply source 21 into the chamber 14 (Step 56). As a result, a TiO ₂ film containing a fluorine F component is formed on the surface of the conductive layer 8. The above steps 51 to 56 are performed until a TiO ₂ film having a desired thickness is formed on the surface of the conductive layer 8 (step 57).
[0029]
In the above processing, the supply flow rate and the supply time of the XeF ₂ gas, the N ₂ gas, and the O ₂ gas are appropriately set in accordance with the conditions for forming the TiO ₂ film. TiO Also, suppressing the number of introduction cycles concentration and XeF ₂ gas XeF ₂ gas, in a state where the conductive layer 8 is not completely etched, the conductive layer 8 also by open to the atmosphere, the surface of the conductive layer 8 _Two films can be formed.
[0030]
Further, the TiO ₂ film 8a can be formed without using XeF ₂ gas. For example, a heat treatment for thermally oxidizing the component 13 in the air, a plasma treatment for generating plasma in a chamber containing the component 13 and putting oxygen into the chamber in that state, and a chemical treatment for dipping the component 13 in an acid solution or the like Alternatively, an oxidation furnace process for putting the component 13 in the oxidation furnace may be used.
[0031]
After the TiO ₂ film 8a is formed on the surface of the conductive layer 8 as described above, the silicon substrate 6 is etched from the upper surface using the processing apparatus 12. As a result, a concave portion 7 is formed in the silicon substrate 6 so as to be opened on the upper surface and into which the cantilever 9 enters (see FIGS. 2F to 3H and FIGS. 3F to 3H). FIG. 6 shows such an etching procedure.
[0032]
In the same figure, in a state where the part 13 shown in FIG. 2 (e) and FIG. 3 (e) is mounted on a support base (not shown) in the chamber 14, the same procedures 51 to 54 in FIG. Perform processing. That, _{N 2} gas introduced into the chamber 14 (Step 61) of the _{N 2} gas supply source 18 to evacuate the chamber 14 by the vacuum pump 15 (Step 62). Then, by introducing the XeF ₂ gas XeF ₂ gas supply source 17 to the chamber 14 (Step 63), evacuating the chamber 14 by the vacuum pump 15 (Step 64).
[0033]
Thereby, Si, which is the material of the silicon substrate 6, reacts with XeF ₂ , the surface of the silicon substrate 6 is gasified as SiF (silicon fluoride), and the silicon substrate 6 is etched. Then, the horizontal etching (side etching) of the silicon substrate 6 proceeds along with the etching of the silicon substrate 6 in the depth direction.
[0034]
At this time, since the TiO ₂ film 8a is formed and passivated on the surface of the conductive layer 8, the conductive layer 8 is not directly etched by the XeF ₂ gas. However, when the silicon substrate 6 under the conductive layer 8 is side-etched, the XeF ₂ gas flows under the conductive layer 8 and the conductive layer 8 is etched from the lower surface side. Thereby, the conductive layer 8 is removed toward the base end side of the cantilever 9 together with the side etching of the silicon substrate 6 under the conductive layer 8 (FIGS. 2F to 3H and 3F). )-(H)).
[0035]
The above procedures 61 to 64 are repeatedly performed until the silicon substrate 6 is etched by a predetermined amount (procedure 65). The supply flow rate and supply time of the XeF ₂ gas and the N ₂ gas are appropriately set according to the etching conditions.
[0036]
Here, as a comparative example, FIG. 7 shows a method of manufacturing an actuator structure using an etching mask formed of a SiO ₂ film.
[0037]
In the figure, first, an SiO ₂ film 82 serving as an etching mask is patterned on the upper surface of a silicon substrate 81 (see FIG. 7A). Subsequently, a conductive layer 83 is formed on the silicon substrate 81 (see FIG. 7B). Subsequently, a cantilever 84 is formed on the upper surface of the conductive layer 83 (see FIG. 7C), and a mirror 85 is formed on the cantilever 84 (see FIG. 7D). Subsequently, the conductive layer 83 existing below the tip end portion of the cantilever 84 is removed (see FIG. 7E).
[0038]
Subsequently, the silicon substrate 81 is etched with a XeF ₂ gas (see FIG. 7F). At this time, since the SiO ₂ film 82 is not etched by the XeF ₂ gas, the SiO ₂ film 82 remains as it is even after the etching process of the silicon substrate 81 is completed (see FIG. 7G).
[0039]
Incidentally, the thermal expansion coefficient of the SiO ₂ film 82 is significantly different from the thermal expansion coefficients of the cantilever 84 and the conductive layer 83 which are metal. Therefore, if the SiO ₂ film 82 is left as it is, the cantilever 84 is deformed due to a temperature change, and the amount of warpage of the cantilever 84 changes. In this case, since the driving condition of the cantilever 84 changes depending on the temperature, it may be difficult to design the cantilever 84. When the optical switch is completed in a state where the SiO ₂ film 82 remains as it is, when the cantilever 84 is driven, the SiO ₂ film 82 is largely moved together with the cantilever 84. However, there is a possibility that the operation of the optical switch is hindered.
[0040]
To avoid such a problem, a part of the SiO ₂ film 82 is removed by wet etching after the end of the etching process (see FIG. 7H). However, in this case, when evaporating the etching solution, the cantilever 84 sticks to the etching surface of the silicon substrate 81 due to the surface tension of the etching solution. It can take a lot of work.
[0041]
On the other hand, in the present embodiment, a TiO ₂ film (passive film) 8 a is formed on the surface of the conductive layer 8 so that the conductive layer 8 is not directly etched by the XeF ₂ gas. There is no need to form a SiO ₂ film on the silicon substrate 6. For this reason, since the wet etching does not need to be performed after the etching process of the silicon substrate 6 is completed, the cantilever 9 does not stick to the bottom surface of the concave portion 7 of the silicon substrate 6 and the cantilever 9 is attached to the silicon substrate 6. You can save the trouble of separating from. In addition, since the conductive layer 8 is removed in the base end direction of the cantilever 9 together with the side etching of the silicon substrate 6 with the XeF ₂ gas, the conductive layer 8 is separately formed after the etching of the silicon substrate 6 is completed. There is no need to do some removal. As described above, the manufacturing process of the actuator structure 5 is simplified, and the manufacturing cost can be reduced.
[0042]
Further, the conductive layer 8 and the cantilever 9 are made of metal, and their thermal expansion coefficients are close to each other. Further, the conductive layer 8 that is in contact with the root side portion of the cantilever 9 is formed on the side of the silicon substrate 6 as described above. Since the cantilever 9 is partially removed along with the etching, there is almost no deformation of the cantilever 9 due to a temperature change, and the amount of warpage of the cantilever 9 becomes substantially constant. In addition, since the conductive layer 8 is partially removed, the conductive layer 8 is not largely moved together with the cantilever 9 when the optical switch 1 is actually used. The operation of the device is prevented from being hindered.
[0043]
Note that the present invention is not limited to the above embodiment. For example, in the above embodiment, a passivation film is formed on the surface of a conductive layer formed of Ti. As a material of the conductive layer, the passivation film is etched with a XeF ₂ gas and is exposed to a XeF ₂ gas. As long as it is passivated, it is not particularly limited to Ti, but may be Cr, for example. The passivation film formed on the surface of the conductive layer is not limited to an oxide film, but may be a nitride film or the like.
[0044]
In addition, the present invention is not limited to the components of the optical switch as described above, but is applicable as long as it relates to a microstructure in which a metal body is provided on a substrate having a concave portion opened on the upper surface. .
[0045]
【The invention's effect】
According to the present invention, a conductive layer made of a metal that can be passivated with respect to XeF ₂ gas is formed on the upper surface of the substrate, and a metal body is formed on the upper surface of the conductive layer. By forming the active film, the conductive layer is passivated with respect to the XeF ₂ gas, and then the substrate is etched with the XeF ₂ gas. Therefore, the temperature is reduced while simplifying the manufacturing process of the microstructure. Deformation of the metal body due to a change or the like can be suppressed.
[Brief description of the drawings]
FIG. 1 is a vertical sectional view showing an optical switch including an embodiment of a microstructure according to the present invention.
FIG. 2 is a diagram illustrating a method of manufacturing the actuator structure illustrated in FIG. 1, illustrating a manufacturing process when components are viewed from the side.
FIG. 3 is a view illustrating a method of manufacturing the actuator structure illustrated in FIG. 1, illustrating a manufacturing process when components are viewed from above.
FIG. 4 is a schematic configuration diagram of a processing apparatus used for processing shown in FIGS. 2 (e) to (h) and FIGS. 3 (e) to (h).
FIG. 5 is a flowchart showing a procedure of a process of forming a TiO ₂ film on a surface of a conductive layer using the processing apparatus shown in FIG.
6 is a flowchart showing a procedure of a process of etching a silicon substrate using the processing apparatus shown in FIG.
FIG. 7 is a diagram illustrating, as a comparative example, a method of manufacturing an actuator structure using an etching mask formed of a SiO ₂ film.
[Explanation of symbols]
5 Actuator structure (microstructure), 6 Silicon substrate, 7 Depression, 8 Conductive layer, 8a Titanium oxide film (passive film), 9 Cantilever (metal body), 12 Processing device , 17 ... XeF ₂ gas supply source, 18 ... _{N 2} gas supply source, 21 ... _{O 2} gas supply source.

Claims (4)

A substrate having a concave portion opened on the upper surface, and a method of manufacturing a microstructure including a metal body provided on the substrate,
Forming a conductive layer made of a metal that can be passivated with respect to XeF ₂ gas on the upper surface of the substrate;
Forming the metal body on the upper surface of the conductive layer;
Forming a passivation film on a surface of the conductive layer after forming the metal body, thereby passivating the conductive layer with respect to the XeF ₂ gas;
Etching the substrate with the XeF ₂ gas to form the recess in the substrate. _2. The microstructure according to claim 1, wherein the passivation film is formed on a surface of the conductive layer by introducing the XeF ₂ gas into the conductive layer and placing the conductive layer in oxygen. 3. Production method. _{3. The} method according to claim 1, wherein the metal passivable with respect to the XeF2 gas is Ti or Cr. A microstructure manufactured by the method for manufacturing a microstructure according to claim 1.

Images