KR100947951B1 - Optical modulator and manufacturing method thereof - Google Patents

Abstract

PURPOSE: An optical modulator and a method for manufacturing the same are provided to improve the attachment and the adhesive on an interface between a lower electrode and a ribbon layer by forming the lower electrode and the ribbon layer with a nitride-based compound thin film. CONSTITUTION: An insulation layer(130) is stacked on a substrate(110). The insulation layer is composed of a nitride-based compound with an insulation property. A buffer layer(120) is formed between the substrate and the insulation layer. A recessed part is formed on one side of a ribbon layer(140) which oppose to the substrate. First electrodes(151) are composed of a nitride-based compound thin film with a conductive property. The first electrodes are located on the both side of the ribbon layer. A second electrode(153) applies a driving voltage between the first electrodes.

Description

Optical modulator device and manufacturing method thereof

The present invention relates to a MEMS device and a method of manufacturing the same, and more particularly, to an optical modulator device having a ribbon layer formed of a nitride compound thin film and a method of manufacturing the same.

MEMS (Micro Electro Mechanical System) refers to a micro electromechanical system or device, and MEMS technology is a technology for forming a three-dimensional structure on a substrate using semiconductor manufacturing technology. MEMS is applied to the optical field as one of various application fields. MEMS technology enables the fabrication of optical components smaller than 1mm, enabling ultra-compact optical systems. Micro-optical components such as optical modulator elements and micro lenses, which are miniature optical systems, have been adopted and applied to communication devices, displays, and recording devices due to advantages such as fast response speed, small loss, and ease of integration and digitization.

 An optical modulator element is a circuit or device for transmitting a signal to light (optical modulation) in a transmitter when a free space of an optical fiber or an optical frequency band is used as a transmission medium. The optical modulator element is divided into a direct method of directly controlling the on / off of light and an indirect method using reflection and diffraction of light, and the indirect method is divided into an electrostatic method and a piezoelectric method according to the method of being driven again.

In this case, in the indirect optical modulator device using light reflection and diffraction, light modulation is performed through diffraction (interference) generated by a path difference of incident light reflected regardless of the driving method. In particular, in the piezoelectric type optical modulator device, a path difference of reflected light is generated by using a vertical driving force by a piezoelectric driving body which contracts and expands according to a predetermined voltage applied thereto. Therefore, the role of the piezoelectric driver is very important in realizing the optical diffraction characteristic of the piezoelectric drive modulator.

1 shows an optical modulator element according to the prior art. Referring to FIG. 1, the optical modulator device according to the related art includes a substrate 110, an etching stop layer 120, a sacrificial layer 130, a ribbon layer 140, and a low temperature oxide layer 141 (LTO). For example, a silicon oxide (SiO _X ) layer, a Ti thin film 142, and a piezoelectric driver 150 (the first electrode 151, the piezoelectric layer 152, and the second electrode 153) are included. Here, the LTO layer 141 and the Ti thin film 142 may increase the adhesive force between the ribbon layer 140 made of silicon nitride-based material and the first electrode 151 made of metal material such as platinum (Pt). To intervene.

However, according to the prior art, the interface between the piezoelectric drive body 150 and the LTO layer 141 formed below the piezoelectric drive body 150 (that is, the bottom of the first electrode 151) during the long time driving of the optical modulator element (identification code of FIG. 4). (a) is separated, causing a defect of the optical modulator element. This is because the Ti thin film 142 laminated as a junction layer therebetween for the adhesion between the LTO layer 141 and the first electrode 151 deteriorates as the optical modulator element is driven for a long time. to be.

In addition, the Ti thin film 142 may be oxidized by diffused oxygen during a high temperature manufacturing process for stacking the piezoelectric layer 152 which is performed after the film formation process of the first electrode 151. Therefore, the Ti thin film 142 is oxidized by the diffused oxygen, thereby being easily separated from the LTO layer 141. Separation or deterioration between the LTO layer 141 and the first electrode 151 due to the deterioration of the Ti thin film 142 may result in deterioration of operating characteristics of the piezoelectric driving body 150. It adversely affects the diffraction characteristic and its reliability.

In addition, the manufacturing process of the optical modulator device according to the prior art has a high complexity of the process. This will be described with reference to FIGS. 2 and 3.

FIG. 2 is a manufacturing process diagram of the optical modulator device according to the related art shown in FIG. 1, and FIG. 3 is a detailed process diagram showing the subdivision of step (d) of FIG. 2.

In step (a) of FIG. 2, the etch stop layer 120 is formed on the substrate 110, and in step (b) of FIG. 2, the sacrificial layer 130 is formed on the etch stop layer 120. . Herein, the sacrificial layer 130 is subjected to a later process (see step (e) of FIG. 2), and the center portion of the ribbon layer 140 (hereinafter, simply referred to as 'ribbon') secures a driving space and the etch stop layer. It is partially etched so as to be spaced apart from the predetermined distance from 120.

For this reason, when a silicon (Si) substrate is used as the substrate 110 and an amorphous silicon thin film (a-Si thim film) is used as the sacrificial layer 130, an etch stop layer 120 ) Is a material having a high etching selectivity with respect to an etchant for etching amorphous silicon, which is a material constituting the sacrificial layer 130 as an etching target, in which the etchant is an etching solution or an etching gas. Silicon oxide (SiO _X ) and the like.

In step (c) of FIG. 2, the ribbon layer 140 is formed on the sacrificial layer 130. Here, the ribbon layer 140 may be formed using a material of silicon nitride series (Si _X N _Y ) such as Si ₃ N ₄ , and the ribbon may be formed by a later process (see step (e) of FIG. 2). For example, it may be selectively etched to form a shape having one or more open holes.

In step (d) of FIG. 2, the LTO layer 141 on both side ends of the ribbon layer 140, the Ti thin film 142 on the LTO layer 140, and the piezoelectric driver 150 on the Ti thin film 142. ). This process is described in more detail with reference to FIG. 3 as follows. In FIG. 3, the sacrificial layer 130, the etch stop layer 120, and the substrate 110 forming the lower portion of the ribbon layer 140 are omitted for convenience of illustration.

In steps (d)-(1) and (d)-(2) of FIG. 3, the LTO layer 141, the Ti thin film 142, the first electrode 151, and the piezoelectric layer are formed on the ribbon layer 140. 152 and the second electrode 153 are sequentially stacked.

Here, a lamination method such as LPCVD (Low Pressure Chemical Vapor Deposition) may be used for lamination of the LTO layer 141, and sputtering and electron beam evaporation (E-beam evaporation) for lamination of the Ti thin film 142. ), Chemical vapor deposition (CVD) deposition, atomic layer deposition (ALD) deposition, and the like may be used. In addition, an electrode material such as platinum (Pt), nickel (Ni), gold (Au), aluminum (Al), titanium (Ti), or the like may be used as the first electrode 151 or the second electrode 153. In the lamination, sputtering or electron beam evaporation may be used. In addition, piezoelectric materials such as PZT, PNN-PT, PLZT, AlN, and ZnO may be used as the piezoelectric layer 152, and the lamination may be performed by a high temperature rapid thermal annealing (RTA) process. have.

In steps (d)-(3) of FIG. 3, the second electrode 153 and the piezoelectric layer 152 deposited on the front surface of the first electrode 151 through steps (d)-(2) of FIG. 3. The second electrode 153 and the piezoelectric layer 152 are etched to be located only at predetermined portions of both side ends of the first electrode 151. At this time, the etching of the second electrode 153 and the piezoelectric layer 152 is dry etching or plasma etching using equipment such as dry etcher or plasma asher. This can be used.

In steps (d) and (4) of FIG. 3, after etching the second electrode 153 and the piezoelectric layer 152, a portion of the first electrode 151 and the Ti thin film 142 are etched. In this case, the etching of the first electrode 151 and the Ti thin film 142 may also be performed by dry etching or plasma etching using equipment such as dry etcher or plasma asher. ) May be used.

In steps (d)-(5) of FIG. 3, the central portion of the ribbon layer 140, that is, the LTO layer 141 stacked on the ribbon is etched. In this case, wet etching using wet station equipment may be used to etch the LTO layer 141.

As described above, the structure having the same shape as in step (d) of FIG. 2 may be formed through the process of steps (d)-(1) to (d)-(5) of FIG. 3.

Referring back to FIG. 2, in step (e) of FIG. 2, a portion of the sacrificial layer 130 (that is, a portion filled in the bottom surface of the center portion of the ribbon layer 140) is etched. In order to perform the etching process of the sacrificial layer 130, an etching process of forming one or more open holes in the ribbon may be preceded, and a portion of the sacrificial layer 130 is injected by injecting an etchant through the open holes formed as described above. Can be etched. Through this step, the ribbon is spaced apart from the etch stop layer 120 by a predetermined interval, thereby securing a driving space capable of moving up or down in accordance with the driving force transmitted from the piezoelectric driving body 150.

As can be seen through the description of Figures 2 and 3 described above, the manufacturing process of the optical modulator device according to the prior art requires at least eight lamination processes, and in addition, several etching processes are required, and the complexity of the manufacturing process is required. Very high. Therefore, the optical modulator device according to the prior art increases the stress between the plurality of laminated thin films due to the large number of stacks, and thus the position of the ribbon is greatly different for each of the fabricated optical modulator devices, so that the reliability of the optical diffraction characteristics of the optical modulator device is increased. However, there is a problem that adversely affects the accuracy.

Accordingly, the present invention provides an optical modulator device having a better and improved optical diffraction characteristic and reliability and a method of manufacturing the same.

In addition, the present invention provides an optical modulator device and a method of manufacturing the same that greatly improves the adhesion and bonding at the interface between the lower electrode and the ribbon layer by using a method of forming both the lower electrode and the ribbon layer of the same series of nitride compound thin film to provide.

In addition, the present invention provides an optical modulator device having a more improved uniformity and accuracy in forming a ribbon layer in the optical modulator device and a method of manufacturing the same.

The present invention also provides an optical modulator device capable of simplifying the manufacturing process and reducing the manufacturing cost, and a method of manufacturing the same.

Other objects of the present invention will be readily understood through the following description.

The present invention as described above, the substrate; An insulating layer laminated on the substrate as an insulating nitride compound; A buffer layer formed between the substrate and the insulating layer to assist growth of crystals of the insulating layer on the substrate; A ribbon layer disposed on the substrate, wherein a recess is formed on one surface of the substrate to face a center portion so as to be floating from the substrate; A first electrode formed of a conductive nitride film and positioned on both side ends of the ribbon layer; A second electrode formed of a conductive nitride film and formed to apply a driving voltage between the first electrodes; And a piezoelectric layer disposed between the first electrode and the second electrode, the piezoelectric layer generating a driving force to move the center portion of the ribbon layer up and down by contracting or expanding in correspondence with a driving voltage applied between the electrodes. Characterized in that made.

In addition, the substrate of the present invention is characterized in that the sapphire substrate.

In addition, the buffer layer of the present invention is characterized in that the aluminum nitride (AlN) thin film.

In addition, the ribbon layer of the present invention is characterized in that formed of a nitride compound thin film containing at least one element of aluminum (Al), indium (In) and gallium (Ga).

In addition, the ribbon layer of the present invention is characterized in that formed of an insulating treated nitride compound thin film.

In addition, the first electrode of the present invention is characterized in that it is formed of a nitride compound thin film containing at least one element of aluminum (Al), indium (In) and gallium (Ga).

In addition, at least one open hole is formed in the central portion of the ribbon layer of the present invention.

Further, a light reflection layer may be further formed on a portion of the center portion of the ribbon layer of the present invention in which the open hole is not formed and a corresponding portion of the upper surface of the substrate corresponding to the position where the open hole is formed. It features.

In addition, the present invention (A) growing a nitride compound having an insulating property on the substrate using a buffer layer; (B) depositing a rectangular parallelepiped sacrificial layer on a substrate; (C) laminating a ribbon layer on the substrate to surround the sacrificial layer; (D) stacking a first electrode layer of a conductive nitride compound, a piezoelectric layer, and a second electrode layer of a nitride compound having conductivity on the ribbon layer; (E) forming a piezoelectric driver by etching the first electrode layer, the piezoelectric layer and the second electrode layer; And (F) removing the sacrificial layer after forming the open hole in the ribbon layer.

In addition, the step (A) of the present invention, (A-1) forming a buffer layer to assist the growth of the crystal of the insulating layer on the substrate; And (A-2) forming an insulating layer of a nitride compound having an insulating property on the buffer layer.

In addition, the step (C) of the present invention is characterized in that the ribbon layer is formed by a method in which the ribbon layer of the nitride-based compound thin film overgrown on the substrate covers the sacrificial layer.

In addition, in the step (D) of the present invention, the first electrode, the piezoelectric layer, and the second electrode 153 may be stacked in an in-situ manner.

According to the optical modulator device according to the present invention, the manufactured optical modulator device has an effect of having better and improved optical diffraction characteristics and reliability.

In addition, the present invention has the effect of greatly improving the adhesion and bonding at the interface between the lower electrode and the ribbon layer by using a method of forming both the lower electrode and the ribbon layer of the same series of nitride compound thin film.

In addition, the present invention has an effect that the ribbon layer produced in forming the ribbon layer in the optical modulator device has a more improved uniformity and accuracy.

In addition, the present invention has the effect of simplifying the manufacturing process, reducing the manufacturing cost in manufacturing the optical modulator device.

Now, the optical modulator element of the present invention and a manufacturing method thereof will be described with reference to the drawings below.

5 is a side view showing an optical modulator device according to an embodiment of the present invention.

Referring to FIG. 5, an optical modulator device according to an exemplary embodiment of the present invention includes a substrate 110, a buffer layer 120, an insulating layer 130, a ribbon layer 140, and a piezoelectric driver 150. Here, the piezoelectric driver 150 includes a first electrode 151, a piezoelectric layer 152, and a second electrode 153.

Here, the substrate 110 is preferably a sapphire substrate, the buffer layer 120 is located on the substrate 110, the insulating layer 130 is located on the buffer layer 120.

The buffer layer 120 is insulated from the substrate 110 to assist the growth of the insulating layer 130 on the substrate 110 when the nitride compound is used as the insulating layer 130 when the substrate 110 is a sapphire substrate. Interposed between the layers 130 is made of aluminum nitride (AIN).

In addition, the insulating layer 130 is formed of a nitride compound thin film, and the nitride compound includes nitrogen (N) and at least one element of aluminum (Al), indium (In), and gallium (Ga). Substances can be used. For example, gallium nitride (GaN), aluminum gallium nitrogen (Al _X GaN _{X -1} where 0 ≦ x ≦ 1), indium gallium nitrogen (In _X GaN _{X −1} where 0 ≦ x ≦ 1), and the like. This is it. In addition, the insulating layer 130 may be insulated to ensure insulation. For example, the insulating layer 130 may be doped by iron (Fe), magnesium (Mg), or zinc (Zn) on the nitride compound thin film, or by using a method of controlling growth methods and conditions of the nitride compound thin film. May be insulated.

The insulating layer 130 is a sacrificial layer so that the etching can be stopped even through the etching process of the sacrificial layer (it does not remain in the final optical modulator element because it is all etched in the manufacturing process as can be seen in the process to be described later). It is composed of a material with high etching selectivity with respect to the etchant for etching the material to be used as.

As such, when a separate insulating layer 130 is interposed between the substrate 110 and the sacrificial layer as shown in FIG. 5, it is possible to prevent the etchant from inadvertently etching portions other than the sacrificial layer. . For example, assuming that a sapphire substrate is used as the substrate 110 and silicon oxide (SiO _X ) is used as the sacrificial layer, gallium nitride (GaN) may be used as the insulating layer 130.

Meanwhile, the ribbon layers 140 are positioned on both side ends of the insulating layer 130. The biggest difference between the ribbon layer 140 and the optical modulator device of the prior art is that the ribbon layer 140 is not supported by the sacrificial layer. That is, the ribbon layer 140 of the present invention may be supported by the sacrificial layer on its own substrate 110 without being supported on both sides thereof, and thus the ribbon layer 140 itself may be in a 'Π' shape (ie, a ribbon). The center part of the one surface which faces the board | substrate 110 in the layer 140 is recessed.

In one embodiment of the present invention, as the ribbon layer 140, a silicon nitride compound thin film is used, unlike the conventional silicon nitride-based material. This is due to the use of a conductive nitride film thin film as the first electrode 151 in one embodiment of the present invention, the ribbon layer 140 is similar to, and similar to, the material constituting the first electrode 151 Formation using a series of materials can greatly improve the bonding strength between the interfaces. This will be described in more detail together with the description of the first electrode 151.

As such, when the ribbon layer 140 is formed of a nitride compound thin film, the nitride compound includes at least one element of aluminum (Al), indium (In), and gallium (Ga) together with nitrogen (N). Material may be used. For example, gallium nitride (GaN), aluminum gallium nitrogen (Al _X GaN _{X -1} where 0 ≦ x ≦ 1), indium gallium nitrogen (In _X GaN _{X −1} where 0 ≦ x ≦ 1), and the like. This is it. In this case, the ribbon layer 140 may be insulated to ensure insulation. For example, the ribbon layer 140 may be doped with iron (Fe), magnesium (Mg), or zinc (Zn) in the nitride compound thin film, or by using a method of controlling growth methods and conditions of the nitride compound thin film. May be insulated.

Here, at least one open hole (not shown) is provided in the central portion (ie, the ribbon) of the ribbon layer 140. In this case, an upper light reflection layer (not shown) is formed on a portion where the open hole is not formed in the ribbon, and a lower light reflection layer (not shown) is formed on a corresponding portion of the insulating layer 130 corresponding to the position of the open hole.

Next, the piezoelectric drive body 150 is positioned on both side ends of the ribbon layer 140. The piezoelectric drive member 150 has a ribbon bottom or top using a contraction or expansion force of the piezoelectric layer 152 due to the piezoelectric effect generated according to the driving voltage applied between the first electrode 151 and the second electrode 153. Make it move. Accordingly, the piezoelectric layer 152 is a material exhibiting a piezoelectric effect in accordance with the applied voltage, for example, piezoelectric materials such as PZT, PNN-PT, PLZT, AlN, ZnO, or lead (Pb), zirconium (Zr), Piezoelectric electrolytic materials containing two or more elements such as zinc (Zn) or titanium (Ti) can be used.

In the present invention, the first electrode 151 is formed of a nitride compound thin film having conductivity. As the nitride compound to form the first electrode 151, a material including at least one element of aluminum (Al), indium (In), and gallium (Ga) together with nitrogen (N) may be used. For example, gallium nitride (GaN), aluminum gallium nitrogen (Al _X GaN _{X -1} where 0 ≦ x ≦ 1), indium gallium nitrogen (In _X GaN _{X −1} where 0 ≦ x ≦ 1) Etc. In this case, when using a nitride compound that does not contain a metal material, such as a gallium nitride (GaN) thin film as the first electrode 151, silicon (Si) or the like is used to increase the conductivity thereof and to improve utilization efficiency as an electrode. Of course, it can be doped (for example, doping so that it can be converted to n-type gallium nitride thin film).

As described above, specific advantages in the case where the first electrode 151 and the ribbon layer 140 are each formed of a nitride compound thin film will be described below.

In the conventional optical modulator device, a silicon nitride-based material (Si _X N _Y ) such as Si ₃ N ₄ is used as the ribbon layer 140, and a metal such as platinum (Pt) is used as the first electrode 151. Material was used. For this reason, when the first electrode 151 is directly formed on the ribbon layer 140, the bonding force at the interface thereof is not very good, and thus the piezoelectric drive body 150 including the first electrode 151 is separated from the ribbon layer 140. Falling separation was serious. Therefore, in the related art, in order to compensate for this, the LTO layer (see identification number 141 of FIG. 1) made of a material such as silicon oxide is laminated on the ribbon layer 140, and then again a Ti thin film (identification number 142 of FIG. 1). By laminating a thin layer), a method of improving the bonding force between the first electrode 151 formed of a metal material and the ribbon layer 140 was used.

However, even when the optical modulator device manufactured by the above-described prior art is driven for a long time, the problem of causing the defect of the optical modulator device is still not solved because the Ti thin film interposed therebetween deteriorates itself for improving bonding strength. In addition, the Ti thin film was easily oxidized by diffused oxygen during the high temperature manufacturing process for stacking the piezoelectric layer 152 which is subsequently performed after the deposition process of the first electrode 151. This is because there is no problem in bonding between the first electrodes 151 formed of the same metallic material because the Ti thin film is a metallic material, but for the same reason (metallic material), the Ti thin film is also easily oxidized or corroded.

Therefore, in the present invention, in order to solve the above-mentioned problems of the prior art, the ribbon is manufactured by using the nitride-based compound thin film having conductivity instead of the metal material and interviewing the first electrode 151. The layer 140 is also fabricated using the same or similar material as the first electrode 151. As such, when both the first electrode 151 and the ribbon layer 140 are made of a thin film of a nitride compound of the same kind or similar material, the interface bonding property can be greatly improved, and problems of oxidation and corrosion due to oxygen diffusion, etc. At the same time there is an advantage that can be solved. Particularly, in the case of a gallium nitride compound, there are some differences depending on the composition of the compound, but its thermal characteristics are stable, such as having a very high melting point (for example, 3000 ° C. or higher in the case of GaN). Therefore, the piezoelectric layer 152 may be hardly deteriorated even when the piezoelectric layer 152 is laminated in the manufacturing process sequence or the actual optical modulator device is driven after fabrication.

In addition, in the case of using the gallium nitride-based compound thin film as described above as the first electrode 151, when the GaN / PZT structure is formed together with the piezoelectric layer 152 composed of a piezoelectric material such as PZT, The crystallographic orientation of PZT is improved by the gallium nitride compound thin film, so that the piezoelectric efficiency of the piezoelectric layer 152 may be greatly increased. Here, the crystal orientation refers to the degree to which the piezoelectric material is deflected and rearranged according to its polarity by an electric field formed in the piezoelectric layer 152 according to the voltage applied between electrodes.

Accordingly, when the first electrode 151 is made of a thin film of a conductive nitride compound instead of a metal material, and the ribbon layer 152 is also made of the same type of material or similar material, It is possible to prevent deterioration of the piezoelectric driver 150 and the entire optical modulator element.

Meanwhile, in the present invention, the second electrode 153 is formed of a nitride compound thin film having conductivity. As the nitride compound to form the second electrode 153, a material including at least one of aluminum (Al), indium (In), and gallium (Ga) together with nitrogen (N) may be used. For example, gallium nitride (GaN), aluminum gallium nitrogen (Al _X GaN _{X -1} where 0 ≦ x ≦ 1), indium gallium nitrogen (In _X GaN _{X −1} where 0 ≦ x ≦ 1), and the like. This is it. In this case, when using a nitride compound that does not contain a metal material such as a gallium nitride (GaN) thin film as the second electrode 153, silicon (Si) or the like is used to increase the conductivity thereof and to improve utilization efficiency as an electrode. Of course, it can be doped (for example, doping so that it can be converted to n-type gallium nitride thin film).

As such, when the first electrode 151 and the second electrode 153 are formed of a conductive nitride thin film, the first electrode 151, the piezoelectric layer 152, and the second electrode 153 are formed in the same chamber. It can form in the same process and can shorten a process significantly.

Now, look at the operation of the optical modulator device shown in Figure 5 as follows.

The piezoelectric drive body 150 is a ribbon according to the degree of shrinkage or expansion of the piezoelectric layer 152 generated by the driving voltage applied between the two electrodes (that is, the first electrode 151 and the second electrode 153). Gives driving force to move up and down. For example, when the driving voltage is not applied to the piezoelectric driving body 150, the ribbon maintains its original position, and when an arbitrary driving voltage is applied, the ribbon moves up or down in accordance with the applied voltage. Will move. By utilizing the change in the position of the ribbon as described above, the optical modulator element can generate diffracted light (that is, modulated light) diffracted incident light.

For example, when the wavelength of light incident on the optical modulator element is λ, the distance between the upper light reflecting layer formed on the ribbon and the lower light reflecting layer formed on the insulating layer 130 is (2n) λ / 4 (n is a natural number). It is assumed that a first driving voltage is applied between electrodes. In this case, in the case of the 0th diffracted light, the total path difference between the light reflected from the upper light reflecting layer and the light reflected from the lower light reflecting layer is equal to nλ, so that the diffracted light has the maximum luminance due to constructive interference. In the case of light, the brightness of light has a minimum brightness due to destructive interference.

Then, it is assumed that a second driving voltage is applied between the electrodes such that the distance between the upper light reflecting layer formed on the ribbon and the lower light reflecting layer formed on the insulating layer 130 is (2n + 1) λ / 4 (n is a natural number). do. In this case, in the case of the 0th diffracted light, the total path difference between the light reflected from the upper light reflecting layer and the light reflected from the lower light reflecting layer is equal to (2n + 1) λ / 2. In the case of the first-order and -first-order diffracted light, the luminance of the light has the maximum luminance due to constructive interference.

In this way, the optical modulator device can load a signal on the light by adjusting the amount of diffracted light by using the result of the interference of the reflected light reflected by the upper light reflecting layer and the lower light reflecting layer, respectively, according to the driving voltage applied between the electrodes.

In this case, only the case where two driving voltages are applied such that the distance between the upper light reflecting layer and the lower light reflecting layer is (2n) λ / 4 or (2n + 1) λ / 4 is described. It is apparent that various sizes of driving voltages can be applied between the electrodes, which can be driven at intervals that can control the intensity (that is, the amount of light) of the diffracted light interfered with.

Hereinafter, a manufacturing process and an advantage of the manufacturing process of the optical modulator device according to an embodiment of the present invention shown in Figure 5 will be described in detail with reference to FIG.

FIG. 6 is a view schematically showing the entire manufacturing process of the optical modulator device shown in FIG.

In step (a) of FIG. 6, a buffer layer 120 having a thickness of 200 to 500 and an insulating layer 130 having a thickness of 1 to 3 μm are formed on the substrate 110.

Here, a sapphire substrate is used as the substrate 110, aluminum nitride (AIN) is used as the buffer layer 120, a nitride compound is used as the insulating layer 130, and preferably gallium nitride is used. do.

As described above, an organometallic compound vapor phase growth method (hereinafter referred to as MOCDVD method) is used as a method for growing a crystal of the nitride compound insulating layer 130 on the sapphire substrate 110.

In this method, a buffer layer 120 of aluminum nitride (AlN) having a thickness of 200 to 500 Angstroms is grown on the sapphire substrate 110 at a low temperature of 400 to 900 ° C.

Then, an organic compound gas is supplied as a reaction gas into the reaction vessel in which the sapphire substrate 110 is installed, and the substrate surface temperature is maintained at a high temperature of approximately 900 ° C to 1100 ° C to have a thickness of 1 to 3 μm on the sapphire substrate 110. The crystals of the nitride compound insulating layer 130 are grown. For example, when growing the insulating layer 130 of potassium nitride (GaN), trimethylgallium as the Ga source and ammonia gas as the N source are used. By growing the nitride compound on the aluminum nitride (AlN) layer which is the buffer layer 120 by this method, the insulating layer 130 having good crystallinity and surface morphology can be obtained.

At this time, in order to improve the insulation of the insulating layer 130, the temperature is increased, or Fe or C is doped.

In step (b) of FIG. 6, the sacrificial layer 135 is patterned to a predetermined thickness at a predetermined position on the substrate 110. For example, assuming that a sapphire substrate is used as the substrate 110, a silicon-based material or silicon oxide may be stacked as a sacrificial layer 130 at a specific position on the sapphire substrate. As such, in the case of using the sapphire substrate as the substrate 110, there is an advantage in that heat generated during operation in the fabricated optical modulator device may be easily released to the outside due to better thermal conductivity than the silicon substrate.

In this case, the predetermined position is a position corresponding to the position of the ribbon to be formed through the entire removal process of the sacrificial layer 135, and the predetermined thickness is the substrate 110 through the entire removal process of the sacrificial layer 135. It will be readily understood through the following description that the thickness is determined by the thickness corresponding to the separation distance between the ribbon and the). In this regard, a perspective view in which the sacrificial layer 135 is stacked on the substrate 110 is illustrated in FIG. 7. Referring to FIG. 7, the sacrificial layer 135 is formed in a rectangular parallelepiped shape having a longer side than a vertical side in the substrate 110. It can be seen that it is laminated.

In step (c) of FIG. 6, the ribbon layer 140 is formed on the substrate 110 and the sacrificial layer 135. At this time, the material constituting the ribbon layer 140 is a nitride compound.

Therefore, when the ribbon layer 140 is formed of a nitride compound thin film according to an embodiment of the present invention, it is assumed that the sacrificial layer 130 is formed of a silicon-based material or silicon oxide. Planar overgrowth method (ELOG: Epitaxial Lateral OverGrowth deposition method, abbreviated as ELOG method) may be used. It is assumed that the sapphire substrate 110 on which a silicon oxide (SiO _X ) thin film is patterned as a sacrificial layer 130 is grown at a specific position to grow a gallium nitride (GaN) thin film as a ribbon layer 140 thereon. As follows.

The gallium nitride (GaN) thin film has a single crystal ulzite structure and does not grow directly on the silicon oxide (SiO _X ) thin film. Instead, gallium nitride (GaN) thin films can be grown on sapphire substrates having the same ulzite structure. Therefore, when a sapphire substrate having a pattern formed by a silicon oxide thin film is loaded into a MOCVD chamber to overgrow the gallium nitride (GaN) thin film on the sapphire substrate at a high temperature, the gallium nitride (GaN) thin film directly grows on the silicon oxide thin film. However, the ribbon layer 140 made of the gallium nitride (GaN) thin film by the gallium nitride (GaN) thin film overgrown on the sapphire substrate is covered with the silicon oxide thin film (ie, the ELOG method). It may be formed on the sacrificial layer 130.

In step (d) of FIG. 6, the piezoelectric driving body 150 is formed on both side ends of the ribbon layer 140. Since the piezoelectric driver 150 is composed of the first electrode 151, the piezoelectric layer 152, and the second electrode 153, the piezoelectric driver 150 is sequentially stacked on the ribbon layer 140, and the ribbon is etched by etching the center portion thereof. To be positioned on both sides of layer 140. The optical modulator element including the completed piezoelectric driver 150 is shown in perspective view in FIG. 8.

Here, as described above, the first electrode 151 and the second electrode 153 may use a nitride compound thin film having conductivity. Thus, the advantages in the manufacturing process in the case of using the nitride compound thin film as the first electrode 151 and the second electrode 153 will be described below.

First, in the prior art, in order to improve the bonding strength between the first electrode 151 made of a metal material and the ribbon layer 140 made of a silicon nitride-based material, a process of laminating an LTO layer and a Ti thin film between the interfaces thereof Should be further proceeded. However, in the case of the present invention, since the first electrode 151 and the ribbon layer 140 are made of the same or similar material, there is no need to stack layers for improving the bonding strength. For this reason, the present invention has a significant improvement over the prior art in terms of simplification of the manufacturing process, manufacturing cost, manufacturing time.

In addition, in the prior art, the lamination methods of the LTO layer, the first electrode 151, the piezoelectric layer 152, and the second electrode 153 are different from each other, and thus, a manufacturing process thereof is complicated. That is, the deposition of LTO layer is performed by deposition method such as Plasma Enhanced Chemical Vapor Deposition (PECVD) or Low Pressure CVD (LPCVD), and the deposition of Ti thin film and the first electrode 151 by electron beam evaporation (E-beam evaporation). ), Sputtering, or the like, and when the piezoelectric layer 152 is laminated, a second electrode 153 is used, such as a sol-gel method or spin coating. In the case of lamination of the first electrode 151, a method such as E-beam evaporation or sputtering was used. Therefore, in the prior art, since different lamination methods are used for fabrication of each layer, the process cannot be continuously performed in one same reaction chamber, and the substrate is once taken out after one process. Was uncomfortable to be reloaded after resetting by another lamination method.

However, in the present invention, since the ribbon layer 140, the first electrode 151, and the second electrode 153 use a nitride compound thin film such as gallium nitride (GaN), the ribbon layer 140 and the first electrode ( The lamination process of the 151, the piezoelectric layer 152, and the second electrode 153 may be performed successively in an in-situ manner. The in-situ method means that the lamination process for two or more lamination materials is successively performed in one same reaction chamber without carrying out the substrate. In order for the in-situ method to be applied, it is essential that the lamination method is the same. For example, in the present invention, when the ribbon layer 140, the first electrode 151, the piezoelectric layer 152, and the second electrode 153 are stacked in the same manner, a method of metal organic CVD (MOCVD) may be used. . This is because MOCVD can be used in the same manner as the deposition method of the nitride compound thin film and piezoelectric materials such as PZT.

As described above, according to the manufacturing method of the optical modulator device of the present invention, further lamination of the LTO layer and the Ti thin film is unnecessary, and the ribbon layer 140, the first electrode 151, the piezoelectric layer 152, and the second When the electrode 154 is stacked, the process can be performed in a continuous process in the same reaction chamber according to the in-situ method, thereby simplifying the manufacturing process, as well as manufacturing cost and time advantages.

In step (e) of FIG. 6, the sacrificial layer was filled between the substrate 110 and the ribbon layer 140 so that the central portion (ie, ribbon) of the ribbon layer 140 can be suspended from the substrate 110. (135) Remove all. A process of forming at least one open hole in the ribbon for the entire removal process of the sacrificial layer 135 through this step should be preceded, and the optical modulator device after such a process is performed is shown in FIG. 9.

As shown in FIG. 9, an etching process of forming one or more open holes in the ribbon layer 140 is first followed, and thus, the sacrificial layer 130 is etched by injecting an etchant through the open holes formed in the ribbon. can do.

Through this step, as shown in FIG. 5, as shown in FIG. 5, the recessed portion in which the central portion of one surface facing the substrate 110 is recessed is formed so that both side ends thereof are positioned on the substrate 110 so that the ribbon layer 140 has its own shape. It is supported by the form.

The biggest advantage of the optical modulator device according to another embodiment of the present invention manufactured according to the above-described manufacturing process comes from this step. In the prior art optical modulator device, unlike the sacrificial layer 130 is laminated on the entire surface of the substrate 110 or the etch stop layer 120, the sacrificial layer 130 through the manufacturing process of the present invention The substrate 110 or the insulating layer 130 is laminated only at a position where a ribbon is to be formed later. For this reason, in the conventional optical modulator device, the width and the area of the portion removed through the etching process of the sacrificial layer 130 may be greatly different depending on the etching conditions and the surrounding process environment. . This causes a difference in the length of the ribbon or a difference in separation distance between the ribbon and the substrate in the fabricated optical modulator device, which makes it difficult to form a uniform ribbon. If the uniformity of the ribbon is not secured as described above, even when the same driving voltage is applied, the ribbon displacement may occur for each of the fabricated optical modulator elements, thereby degrading the optical diffraction characteristics and the efficiency of the optical modulator elements. There is a problem that can be done.

In contrast, in the case of the optical modulator device of the present invention, only the sacrificial layer 130 filled between the substrate 110 and the ribbon layer 140 is completely removed without affecting other portions due to the apparent difference in the etching selectivity. There is an advantage in that a ribbon having uniformity can be formed. Therefore, since the optical modulator device according to another embodiment of the present invention can secure the uniformity of the ribbon for the above-described reason, it is possible to greatly improve the optical diffraction characteristics and the efficiency of the optical modulator device by greatly reducing the displacement distribution. Therefore, there is an advantage that more stable operation is possible.

In addition, according to the optical modulator device according to another embodiment of the present invention, there is a great advantage in terms of the complexity of the manufacturing process compared to the prior art. In the prior art, a total of eight lamination processes and a total of seven etching processes should be performed based on the manufacturing process of FIGS. 2 and 3, whereas the optical modulator device of the present invention may have a maximum of five lamination processes and five times. Since it can be manufactured only by the etching process, it can be seen that it is greatly improved compared to the prior art in view of the manufacturing process, manufacturing cost and time.

In addition, as the number of thin films laminated for fabricating an optical modulator device increases as the prior art increases, the stress between the thin films increases in proportion to each other, so that the control of the stress is not easy. Therefore, when using a smaller number of thin films for the fabrication of the optical modulator device as in another embodiment of the present invention, there is also an advantage that can reduce the amount of stress generated between the thin films. In particular, in the case of the optical modulator device of the present invention, since the ribbon layer 140 itself is composed of a single thin film that can be self-supporting through both side ends, stress control is much easier.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art to which the present invention pertains without departing from the spirit and scope of the present invention as set forth in the claims below It will be easy to understand that it can be modified and changed.

1 is a side view showing an optical modulator device according to the prior art.

Figure 2 is a manufacturing process of the optical modulator device according to the prior art shown in FIG.

Figure 3 is a detailed process diagram showing a more detailed step (d) of FIG.

4 illustrates an interface between a lower electrode and an LTO layer.

5 is a side view showing an optical modulator device according to an embodiment of the present invention.

FIG. 6 is a schematic view showing the entire manufacturing process of the optical modulator element shown in FIG.

Figure 7 is a perspective view of the sacrificial layer laminated on the substrate in Figure 6 (b).

Figure 8 is a perspective view of the piezoelectric actuator is completed on the substrate in Figure 6 (d).

Figure 9 is a perspective view after forming the open hole in the ribbon layer in Figure 6 (e).

<Description of the symbols for the main parts of the drawings>

110 substrate 120 buffer layer

130: insulating layer 140: ribbon layer

150: piezoelectric drive 151: lower electrode

152: piezoelectric layer 153: upper electrode

Claims (12)

Board; An insulating layer laminated on the substrate as an insulating nitride compound; A buffer layer formed between the substrate and the insulating layer to assist growth of crystals of the insulating layer on the substrate; A ribbon layer disposed on the substrate, the ribbon layer having an indentation formed on one surface of the substrate so as to be positioned floating from the substrate; A first electrode formed of a conductive nitride film and positioned on both side ends of the ribbon layer; A second electrode formed of a conductive nitride film and formed to apply a driving voltage between the first electrodes; And And a piezoelectric layer disposed between the first electrode and the second electrode and generating a driving force to move the center portion of the ribbon up and down by contracting or expanding in correspondence with a driving voltage applied between the electrodes. Optical modulator elements. The method of claim 1, The substrate is an optical modulator device, characterized in that the sapphire substrate. The method of claim 1, The buffer layer is an optical modulator device, characterized in that the aluminum nitride (AlN) thin film. The method of claim 1, The ribbon layer is an optical modulator device, characterized in that formed of a nitride compound thin film containing at least one element of aluminum (Al), indium (In) and gallium (Ga). The method of claim 1, The ribbon layer is an optical modulator device, characterized in that formed of an insulating treated nitride compound thin film. The method of claim 1, The first electrode is an optical modulator device, characterized in that formed of a nitride compound film containing at least one element of aluminum (Al), indium (In) and gallium (Ga). The method of claim 1, At least one open hole is formed in the central portion of the ribbon layer. The method of claim 7, wherein The optical modulator further comprises a light reflection layer further formed on a portion of the center portion of the ribbon layer where the open hole is not formed and a corresponding portion of the upper surface of the substrate corresponding to the position where the open hole is formed. device. (A) growing an insulating nitride compound on a substrate using a buffer layer; (B) depositing a rectangular parallelepiped sacrificial layer on a substrate; (C) laminating a ribbon layer on the substrate to surround the sacrificial layer; (D) stacking a first electrode layer of a conductive nitride compound, a piezoelectric layer, and a second electrode layer of a nitride compound having conductivity on the ribbon layer; (E) forming a piezoelectric driver by etching the first electrode layer, the piezoelectric layer and the second electrode layer; And (F) manufacturing a light modulator device comprising the step of removing the sacrificial layer after forming an open hole in the ribbon layer. The method of claim 9, Step (A) is (A-1) forming a buffer layer on the substrate to assist the growth of the crystals of the insulating layer; And (A-2) A method of manufacturing an optical modulator element comprising the step of forming an insulating layer of an insulating nitride compound on the buffer layer. The method of claim 9, In the step (C), the ribbon layer is formed by a method in which the ribbon layer of the nitride-based compound thin film overgrown on the substrate covers the sacrificial layer. The method of claim 9, In the step (D), the stacking of the first electrode, the piezoelectric layer, and the second electrode 153 is performed in an in-situ manner.

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