KR20040036362A - Micro mirror and manufacturing method thereof - Google Patents

Abstract

PURPOSE: A micromirror and its fabrication method are provided to improve processing accuracy without being influenced by changes of environment variables when forming a structure having a 45 degree slope. CONSTITUTION: An insulation film is located on an upper part of a silicon substrate(1). A silicon structure(3) has at least one slope located on an upper part of the insulation film. And a mirror(4) is located on the slope of the silicon structure. The slope has a slope angle of 45 degree. And the silicon structure is 9.74 degree off-axis. A metal electrode(5) is located on the silicon substrate revealed in a direction prolonged the direction where the slope is located, and a photo detector or a light emitting device is located on the metal electrode.

Description

Miniature mirror and manufacturing method thereof {MICRO MIRROR AND MANUFACTURING METHOD THEREOF}

The present invention relates to a micromirror and a method of manufacturing the same, and particularly to a micromirror and a method of manufacturing the micromirror that can improve the uniformity of the microstructure using a SOI (SILICON ON INSULATOR) substrate, and simplify the process to improve the mass productivity. It is about.

In general, a micromirror is used for an optical communication element using an optical fiber or the like, or for changing the path of light in a pickup optical system of an optical recording device.

The micromirror has a constant inclination angle according to the purpose of use, and a mirror having a mirror inclination angle of 45 ° is used to change the path of light to 90 °.

As described above, a conventional micromirror having a mirror inclination angle of 45 ° forms a structure having a 45 ° inclined surface by using a mechanical chemical polishing technique, and manufactures a micromirror by mirror treating the inclined surface of the structure, or on the inclined surface of the structure. It was prepared by attaching the mirror-treated thin plate.

However, such a method has a problem in that mass productivity is lowered and an additional assembly process is required, thereby increasing the manufacturing cost and lowering the yield.

In addition, conventionally, a 9.74 ° off-axis silicon substrate having a surface inclined 9.74 ° with respect to the (100) crystal direction is used to form a structure having an inclined surface.

The 9.74 ° off-axis silicon substrate is anisotropically etched to form a 45 ° inclined surface with respect to the surface of the 9.74 ° off-axis silicon substrate.

However, the above technique uses a timed etch that controls the etching time by controlling the height of the inclined surface, that is, the depth of etching.

The time etch ignores the etch rate that is changed according to the environmental variables such as temperature, concentration, and loading of the substrate to be etched, and performs etching for a predetermined time, thereby reproducing the process between processes. In the same wafer, variations in the depth of etching occur due to local temperature differences, concentration differences, defects in the substrate, and non-uniformity of impurity distributions according to positions, and thus the shape and shape of individual mirrors The reliability of the dimensional uniformity is lowered, which causes a decrease in the yield.

In particular, when etching the 9.74 ° off-axis silicon substrate from the surface, the surface in the etch depth direction becomes inclined and not parallel to the substrate surface as the etching proceeds.

That is, the surface of the etched 9.74 ° off-axis silicon substrate is not parallel to the surface of the unetched 9.74 ° off-axis silicon substrate.

This phenomenon occurs because the crystallization direction in which the etching proceeds fastest in the anisotropic silicon etching solution is different from the off-axis direction, and the etching residual surface and etching in the (111) crystal direction forming an angle of 45 ° with respect to the surface of the substrate. The angle formed by the surface of the substrate is out of 45 °.

This lowers the reliability of the processing accuracy according to the etching depth, and when the light emitting element or the light receiving element is formed in the etched substrate region, the optical path cannot be changed in the vertical direction, and thus cannot be used.

In addition, there is a problem that the etching surface is rougher than the etching surface obtained by etching the substrate in the conventional (100) crystal direction.

As described above, the conventional micromirror and the method of manufacturing the same control anisotropic etching in a time-etch manner to control the etching time to form an inclined surface of 45 °, and thus cannot form an accurate structure according to environmental variables. There was a problem that the reliability and yield of the process is lowered.

In addition, by anisotropically etching the 9.74 ° off-axis silicon substrate, the surface of the etched silicon substrate and the surface of the non-etched silicon substrate are not parallel to each other, thereby reducing processing accuracy and performing normal operation in the application of a micro mirror. There was a problem that could not be.

In view of the above problems, the present invention has an object to provide a micromirror and a method of manufacturing the same, which are not affected by changes in environmental variables when forming a structure having an inclined surface of 45 ° and can improve processing precision.

The present invention for achieving the above object is configured to use the buried insulating film as an etch stop film by using a silicon on insulator substrate in which the buried insulating film is located between the support substrate and the structure having the inclined surface. It features.

The use of the etch finish film enables the etching process irrespective of environmental variables, and is characterized in that it is configured to produce a structure having the inclined surface.

1 is a perspective view of a micromirror of the present invention.

Figure 2 is a plan view of Figure 1;

3 is a cross-sectional view in the A-B direction in FIG.

Figure 4 is a flow chart of the manufacturing process of the SOI substrate applied to the present invention.

5A to 5H are cross-sectional views of a manufacturing process of the present invention micro mirror.

Figure 6 is a perspective view of a light source mounted on the micro-mirror of the present invention.

Figure 7 is a plan view of Figure 6;

8 is a cross-sectional view in the A-B direction in FIG.

* Description of the symbols for the main parts of the drawings *

1: Silicon Substrate 2: Insulation Film

3: 9.74 ° off-axis silicon 4: mirror

5: electrode 11: SOI substrate

12: Hard mask layer

When described in detail with reference to the accompanying drawings, an embodiment of the present invention, the ultra-compact mirror and the manufacturing method as described above are as follows.

Fig. 1 is a perspective view of the micromirror of the present invention, Fig. 2 is a plan view of Fig. 1, and Fig. 3 is a sectional view in the A-B direction in Fig. 2, and a silicon substrate 1 as shown therein; An insulating film 2 positioned on an upper portion of the silicon substrate 1; 9.74 ° off-axis silicon (3) positioned on the insulating film (2) and having one surface at a 45 ° slope; A mirror 4 located on the mirror surface of the 9.74 ° off-axis silicon 3; It consists of an electrode 5 located on the exposed surface of the silicon substrate 1.

In the figures, D1 is the thickness of 9.74 ° off-axis silicon 3, D2 is the thickness of silicon substrate 1, and L is the length from the insulating film 2 of the exposed silicon substrate 1 to the end. .

The micromirror according to the present invention having the above-described structure is characterized in that the insulating film 2 is located under the structure having the mirror surface.

This prevents the etching from proceeding using the insulating film 2, thereby making it possible to accurately control the height of the inclined surface.

FIG. 4 is a flowchart of a process of forming a structure of the silicon substrate 1, the insulating film 2, and the 9.74 ° off-axis silicon 3, and has a uniform thickness of 9.74 ° off-axis silicon as shown in FIG. (3) A substrate and a silicon substrate 1 on which an insulating film 2 is deposited to a predetermined thickness are prepared.

At this time, since the silicon substrate 1 serves to support the structure, the crystal orientation may be any.

The silicon substrate 1 thus prepared and the 9.74 ° off-axis silicon 3 substrate are bonded to each other so that the insulating film 2 is positioned at the center, thereby producing a SOI substrate.

Next, a uniform SOI substrate is prepared by wrapping and polishing 9.74 ° off-axis silicon 3.

After the SOI substrate is prepared as described above, a micromirror is formed according to the manufacturing process described in FIG. 5 below.

5A to 5H are schematic cross-sectional views of a micromirror manufacturing process according to the present invention. As shown therein, an SOI substrate 11 including the silicon substrate 1, the insulating film 3, and 9.74 ° off-axis silicon 3 is stacked. Forming a hard mask layer 12 on the top and bottom of the, and forming a photoresist (PR) pattern to expose the central upper portion of the hard mask layer 12 formed on top of the 9.74 ° off-axis silicon (3) Step (Fig. 5A); The exposed hard mask layer 12 is removed through a chemical mechanical polishing process, and the exposed 9.74 ° off-axis silicon 3 is polished to be inclined at an angle of 45 °, so that polishing is performed when the insulating film 2 is exposed. Stopping and removing the photoresist (PR) pattern (FIG. 5B); Removing the exposed insulating film 2 (FIG. 5C); Removing the hard mask 12 (FIG. 5D); Applying photoresist PR1 on top of the structure, exposing and developing to expose a portion of one side of the inclined surface of the 9.74 ° off-axis silicon 3 and at the center of the exposed silicon substrate 1 Forming a pattern to expose (FIG. 5E); Depositing a metal on the inclined surface of the exposed 9.74 ° off-axis silicon 3 and on the silicon substrate 1 to form a mirror 4 and an electrode 5 (FIG. 5F); Removing the photoresist (PR1) pattern (FIG. 5g); A step of separating the area of the SOI substrate 11 where the mirror 4 is not formed (FIG. 5H) is performed.

Hereinafter, the method of manufacturing a micromirror according to the present invention configured as described above will be described in detail.

First, as illustrated in the flowchart of FIG. 4, the SOI substrate 11 is formed by bonding 9.74 ° off-axis silicon 3 with the silicon substrate 1 having the insulating film 2 formed thereon.

In this case, a silicon direct bonding method, which is a kind of silicon micromachining technology, may be used as a method of joining two substrates, and an oxide film containing a certain concentration of sodium impurities is deposited on the silicon substrate 1 as an embedded oxide film. After that, an anodic bonding technique may be used in which a high voltage is applied to bond the 9.74 ° off-axis silicon 3.

Then, as shown in FIG. 5A, hard mask layers 12 are formed on the top and bottom of the SOI substrate 11, respectively.

The hard mask layer 12 may be formed by an oxidation or deposition method, and the hard mask layer 12 may be a material having a significantly low etching rate in an etching solution in a silicon anisotropic etching process.

For example, a silicon oxide film, a silicon nitride film or a mixed thin film thereof may be used.

Next, the photoresist PR is applied on the hard mask layer 12 formed on the 9.74 ° off-axis silicon 3, exposed and developed to expose the upper center of the hard mask layer 12. A photoresist (PR) pattern to be exposed is formed.

Next, the hard mask layer 12 selectively exposed by the photoresist (PR) pattern is removed using a reactive ion etching method or an etching solution capable of selectively etching only the hard mask layer 12.

Next, as shown in FIG. 5B, the hard mask layer 12 is etched, and then the exposed 9.74 ° off-axis silicon 3 is etched using an anisotropic silicon etching solution (AQUEOS ANISOTROPIC SILICON ETCHANT).

Examples of the anisotropic silicon etching solution may be a KOH aqueous solution, an EDP (ETHYLENEDIAMINE PYROCATECHOL) aqueous solution, a TMAH (TETRA-METHYL AMMONIUM HYDROXIDE) aqueous solution, and in addition, an aqueous solution of a hydroxide (HYDROXIDE) series may be used. When etching is performed with such an etching solution, a (111) crystal plane with a significantly lower etch rate is revealed, and an inclined surface which forms an inclination of 45 ° with the surface of 9.74 ° off-axis silicon (3) in accordance with the etching depth. Will be revealed.

The etched crystal plane facing the 45 ° inclined plane is formed at an angle of 64.48 ° with 9.74 ° off-axis silicon 3.

As the etching proceeds and the insulating film 2 is exposed, the etching is stopped.

At this time, since the height of the 45 ° inclined surface formed by etching becomes the same as the thickness of the first 9.74 ° off-axis silicon (3), it is possible to accurately control the height of the inclined surface.

In addition, since the inclined plane is a (111) crystal plane, etching does not occur.

As described above, by controlling the etching process using an etch stop layer rather than a time etch method, a more accurate microstructure can be formed.

This is a process that is not affected by the environmental variables of the process, thereby improving the reproducibility between the processes. In addition, the yield is also improved by the control of the correct dimensions.

Then, the exposed insulating film 2 is removed as shown in Fig. 5C.

At this time, the insulating film 2 is a solution that selectively removes the insulating film 2 without etching the hydrofluoric acid solution or other silicon.

The insulating film 2 may be used in an unetched state. When the insulating film is etched, a more uniform etching surface can be obtained, and a heat dissipation problem due to the remaining of the insulating film 2 can be solved. However, depending on the field of application, the insulating film 2 may be used without etching.

Next, as shown in FIG. 5D, the hard mask layer 12 located at the top and bottom of the SOI substrate 11 is selectively removed.

In this case, the mirror may be manufactured as it is by mirror-treating the inclined surface of the 9.74 ° off-axis silicon 3 by adjusting a solution capable of selectively removing the hard mask layer 12.

Then, as shown in FIG. 5E, photoresist PR1 is applied to the upper portion of the structure, exposed and developed to expose a portion of one side of the inclined surface of the 9.74 ° off-axis silicon 3, and the exposure. The pattern which exposes the center upper part of the silicon substrate 1 which was formed is formed.

Next, as shown in FIG. 5F, metal is deposited on the inclined surface of the exposed 9.74 ° off-axis silicon 3 and the upper portion of the silicon substrate 1 so that the upper portion of the 9.74 ° off-axis silicon 3 is deposited. The mirror 4 is formed on the electrode, and the electrode 5 is formed on the silicon substrate 1.

In this case, the type and thickness of the metal to be deposited may be determined within a wavelength range of light used in the optical system to which the mirror is applied. In addition, a method of depositing a metal is deposited by using sublimation (EVAPORATION) or sputtering.

Next, as shown in Fig. 5G, the photoresist PR1 pattern is selectively removed. This uses acetone or solvent-based chemicals that selectively dissolve the photoresist PR1, and the metal deposited on the photoresist PR1 pattern is removed together.

Then, as shown in FIG. 5H, the manufactured micromirror is diced and separated into individual element units.

As described above, according to the present invention, the insulating film embedded in the SOI substrate is precisely designated by using the insulating film 2 at the time of forming the structure having the inclined surface by using the SOI substrate. It is possible to form a structure.

This provides a wider process latitude compared to the prior art, such as a change in the etching rate, the surface roughness of the etching bottom surface, and the angle formed between the etching bottom surface and the inclined surface. It is possible to improve the uniformity between the processes of the structure, between input wafers in the same process, and between devices on the same wafer, and to improve yield.

In addition, by reducing the need for strict process environment control of the conventional etching process, it is possible to lower the price of the process equipment, and to reduce the process cost. In addition, even when processing a large number of wafers at the same time is not affected by the environmental variables there is an effect that can be mass-produced.

FIG. 6 is a perspective view showing a light source mounted on the micromirror of the present invention shown in FIG. 1, FIG. 7 is a plan view of FIG. 6, and FIG. 8 is a sectional view of the AB direction of FIG. The laser diode 13, which is a light source, is disposed on the upper side of the X, and the light of the laser diode 13 is changed by 90 ° by the mirror 4 inclined at an angle of 45 ° to the plane and emitted.

That is, the surface vertical radiation laser light source can be manufactured. Such a surface vertical radiation laser light source can be used as a light source of a pickup optical system used in an optical recording device, and has high utility as a transceiver for optical communication.

As described above, according to the present invention, the micromirror and its manufacturing method accurately designate an insulating film embedded in an SOI substrate by using an etch finish film in which the etching is terminated when forming a structure having an inclined surface, thereby forming a uniform structure regardless of environmental variables. There is an effect that can be done.

In addition, by eliminating various variables generated during etching, a wider process latitude is provided than in the related art, thereby improving uniformity, improving reproducibility, and improving yield.

In addition, by reducing the need for strict process environment control of the existing etching process, it is possible to lower the price of the process equipment, and reduce the process cost. In addition, even when processing a large number of wafers at the same time is not affected by the environmental variables there is an effect that can be mass-produced.

Claims (12)

An insulating film positioned over the silicon substrate; A silicon structure having at least one inclined surface positioned above the insulating film; Miniature mirror, characterized in that comprising a mirror located on the inclined surface of the silicon structure. The micromirror according to claim 1, wherein the inclined surface is inclined at an inclination angle of 45 degrees. The micromirror according to claim 1, wherein the silicon structure is 9.74 ° off-axis silicon. The semiconductor device of claim 1, further comprising: a metal electrode disposed on an upper portion of the silicon substrate exposed in a direction extending in the direction in which the inclined surface is located; The micromirror further comprises a light receiving or light emitting element located above the metal electrode. The micromirror according to claim 4, wherein the metal electrode is located directly on the silicon substrate or on the extended insulating film. The micromirror according to claim 1, wherein the mirror is an inclined surface of a silicon structure or a metal located on the inclined surface. Preparing a silicon on insulator (SOI) substrate; Forming an etch stop layer above and below the SOI substrate; Etching a portion of the anti-etching layer on the SOI substrate to expose a silicon layer under the SOI substrate; Anisotropically etching the exposed silicon layer to form a silicon structure; Removing the etch stop layer and mirror-treating the inclined surface of the silicon structure to form a mirror. The method of claim 7, wherein preparing the SOI substrate comprises: preparing a 9.74 ° off-axis silicon substrate and a silicon substrate having an insulating layer formed on an upper surface thereof; Bonding the silicon substrate and the 9.74 ° off-axis silicon substrate so that an insulating layer is centrally located; And grinding the 9.74 ° off-axis silicon substrate to a predetermined thickness. 9. The method of claim 8, wherein the silicon substrate is used regardless of the crystal direction. 8. The method of claim 7, wherein forming the mirror is replaced by removing an etch stop layer and depositing a metal on the inclined surface. The method of claim 10, wherein the depositing of the metal on the inclined surface to form the mirror comprises forming the mirror and forming an electrode on the silicon substrate or the insulating layer to form an electrode. . 12. The method of claim 11, further comprising the step of attaching a light receiving or light emitting element on top of the electrode.