KR19990039329A - Manufacturing method of thin film type optical path control device - Google Patents

Abstract

Disclosed is a manufacturing method of a thin film type optical path control apparatus capable of preventing damage to a mirror and improving light efficiency of incident light. After the sacrificial layer is formed and patterned on the active matrix, the support layer, the lower electrode, the strain layer, and the upper electrode are sequentially stacked on the sacrificial layer. The upper electrode, the strain layer, the lower electrode, and the support layer are sequentially patterned to form an actuator, and a mirror is formed using aluminum on top of the patterned support layer. The sacrificial layer is then removed using hydrogen fluoride (HF) vapor having a concentration of about 65 to 73%. Thus, the etching selectivity of hydrogen fluoride with respect to aluminum, which is a constituent of the mirror, is improved so that the mirror is not damaged while the sacrificial layer is etched. Therefore, the light efficiency of the light incident from the light source can be improved, and the image quality of the image projected on the screen can be improved.

Description

Manufacturing method of thin film type optical path control device

The present invention relates to a method for manufacturing a thin film type optical path control device using an Actuated Mirror Array (AMA), and more particularly, by adjusting the concentration of hydrogen fluoride (HF) used when etching a sacrificial layer. It relates to a method of manufacturing a thin film type optical path control device that can prevent damage to the mirror to improve the light efficiency of the incident light.

Optical path modulators or optical light modulators for projecting optical energy onto a screen may be applied to various fields such as optical communication, image processing, and information display devices. An image processing apparatus using such an optical modulator is generally divided into a direct-view image display device and a projection-type image display device according to a method of displaying optical energy on a screen. do.

An example of a direct-view image display device is a CRT (Cathode Ray Tube). The CRT device is called a CRT, which has excellent image quality but increases in weight and volume as the screen is enlarged, leading to an increase in manufacturing cost. There is. Examples of the projection image display apparatus include a liquid crystal display (LCD), a deformable mirror device (DMD), and an AMA. Such projection image display devices can be further divided into two groups according to their optical characteristics. That is, devices such as LCDs can be classified as transmissive spatial light modulators, while DMD and AMA can be classified as reflective spatial light modulators.

Transmission optical modulators, such as LCDs, have a very simple optical structure, which makes them thinner, lighter in weight, and smaller in volume. However, due to the polarity of the light, the light efficiency is low, there is a problem inherent in the liquid crystal material, for example, there is a disadvantage that the response speed is slow and the inside is easy to overheat. In addition, the maximum light efficiency of existing transmission light modulators is limited to a range of 1-2%, requiring dark room conditions to provide acceptable display quality. Therefore, optical modulators such as DMD and AMA have been developed to solve the above problems.

Although DMD shows a relatively good light efficiency of about 5%, the hinge structure employed in the DMD not only causes serious fatigue problems, but also requires a very complicated and expensive driving circuit. In the AMA, each of the mirrors installed therein reflects light incident from the light source at a predetermined angle, and the reflected light is projected on the screen through an aperture such as a slit or a pinhole. It is a device that can adjust the speed of light to form an image. Therefore, its structure and operation principle are simple, and high light efficiency (more than 10% light efficiency) can be obtained compared to LCD or DMD. In addition, the contrast of the image projected on the screen is improved to obtain a brighter and clearer image.

Each actuator of the AMA generates a deformation in accordance with the electric field generated by the applied electric picture signal and the bias signal. As the actuator deforms, each of the mirrors mounted thereon is tilted. Accordingly, the inclined mirrors reflect light incident from the light source at a predetermined angle to form an image on the screen. Piezoelectric materials such as PZT (Pb (Zr, Ti) O ₃ ) or PLZT ((Pb, La) (Zr, Ti) O ₃ ) are used as actuators for driving the respective mirrors. The actuator may also be configured as a warping material such as PMN (Pb (Mg, Nb) O ₃ ).

These AMA devices are largely divided into bulk type and thin film type. The bulk optical path control device is disclosed in US Pat. No. 5,085,497 to Gregory Um et al. The bulk optical path adjusting device is made by thinly cutting a multilayer ceramic to mount a ceramic wafer having a metal electrode formed therein in an active matrix in which a transistor is embedded, and then processing by a sawing method and installing a mirror thereon. However, the bulk optical path control device requires very high precision in design and manufacturing, and has a disadvantage in that the response of the deformation layer is slow.

Accordingly, a thin film type optical path control apparatus that can be manufactured using a semiconductor manufacturing process has been developed. The thin film type optical path control device is a patent application No. 96-42197 (Applicant's name: thin film type optical path control device that can control the stress of the membrane and a method of manufacturing the same) of the applicant filed a patent application of the Republic of Korea Patent Office on September 24, 1996 Is disclosed.

Figure 1 shows a cross-sectional view of the thin film type optical path control device described in the preceding application. Referring to FIG. 1, the thin film type optical path adjusting apparatus includes an active matrix 1 and an actuator 60 formed on the active matrix 1. The active matrix 1 includes a protective layer 10 stacked on the active matrix 1 and the drain pad 5, and an etch stop layer 15 stacked on the protective layer 10.

The actuator 40 has one side in contact with a portion where the drain pad 5 is formed below the etch stop layer 15, and the other side has a membrane 25 formed horizontally through the air gap 20, and a membrane. Lower electrode 30 stacked on top of 25, strained layer 35 stacked on top of lower electrode 30, upper electrode 40 stacked on top of strained layer 35, and the strained layer. In the via hole 45 formed from one side of the 35 to the drain pad 5 through the strained layer 35, the lower electrode 30, the membrane 25, the etch stop layer 15, and the protective layer 10. The lower electrode 30 and the drain pad 5 include a via contact 50 electrically formed with each other.

Hereinafter, a method of manufacturing the above-described thin film type optical path control apparatus will be described with reference to the drawings.

2A to 2D are manufacturing process diagrams of the apparatus shown in FIG. 1. Referring to FIG. 2A, an upper portion of an active matrix 1 having M x N (M, N is an integer) MOS transistors (not shown) embedded therein and a drain pad 5 extending from the drain of the transistor. The protective layer 10 is formed in the. The protective layer 10 is formed of phosphorus silicate glass (PSG) to have a thickness of about 1.0 to about 2.0 μm using a chemical vapor deposition (CVD) method. The protective layer 10 protects the active matrix 1 in which the MOS transistor is embedded during a subsequent process.

An etch stop layer 15 is formed on the passivation layer 10. The etch stop layer 15 is formed to have a thickness of about 1000 to 2000 kPa using a low pressure chemical vapor deposition (LPCVD) method. The etch stop layer 15 prevents the active matrix 1 and the protective layer 10 from being etched and damaged during the subsequent etching process.

The sacrificial layer 18 is stacked on the etch stop layer 15. The sacrificial layer 18 is formed of phosphorous silicate glass (PSG) having a high concentration of phosphorus (PG) to have a thickness of about 1.0 to 3.0 µm using the atmospheric pressure chemical vapor deposition (APCVD) method. In this case, since the sacrificial layer 18 covers the upper portion of the active matrix 1 in which the transistor is embedded, the surface flatness is very poor. Accordingly, the surface of the sacrificial layer 18 is planarized by polishing using a spin on glass (SOG) method or a chemical mechanical polishing (CMP) method. Subsequently, a portion of the sacrificial layer 18 is etched to expose a portion in which the drain pad 5 is formed below the etch stop layer 15.

Referring to FIG. 2B, the membrane 25 is stacked on the exposed etch stop layer 15 and the sacrificial layer 18 to have a thickness of about 0.1 to 1.0 μm. The membrane 25 is formed of silicon carbide (SiC) using a Plasma Enhanced CVD (PECVD) method.

The lower electrode 30 is stacked on the membrane 25. The lower electrode 30 is laminated with a metal such as platinum (Pt) or platinum-tantalum (Pt-Ta) so as to have a thickness of about 500 to 2000 kW using a sputtering method. Subsequently, the lower electrode 30 is iso-cutted so as to apply an independent first signal (image signal) for each pixel.

Referring to FIG. 2C, a strained layer 35 is stacked on the lower electrode 30. The strained layer 35 is formed of a piezoelectric material such as PZT or PLZT so as to have a thickness of about 0.1 to 1.0 탆, preferably about 0.4 탆 using a sol-gel method. Thereafter, the piezoelectric material constituting the strained layer 35 is subjected to heat treatment by a rapid heat treatment (RTA) method to cause phase shift. The strained layer 35 is applied with a second signal (bias signal) to the upper electrode 40 and a first signal is applied to the lower electrode 30 so that the potential difference between the upper electrode 40 and the lower electrode 30 is reduced. Deformation is caused by the electric field generated.

The upper electrode 40 is stacked on top of the strained layer 35. The upper electrode 40 is formed of a metal having electrical conductivity and reflectivity such as aluminum so as to have a thickness of about 500 to 2000 kPa using a sputtering method. The second signal (bias signal) is applied to the upper electrode 40 from the outside through a common electrode line (not shown). Since the upper electrode 40 has both electrical conductivity and reflectivity, the upper electrode 40 performs not only a function of a bias electrode generating an electric field but also a function of a mirror reflecting light incident from a light source.

Subsequently, the upper electrode 40 is patterned into a predetermined pixel shape. In this case, a stripe 55 is formed on a part of the upper electrode 40. The stripe 55 uniformly operates the upper electrode 40 so that light incident from the light source is diffusely reflected at the boundary between the portion of the upper electrode 40 that is deformed and the portion that is not deformed according to the deformation of the deforming layer 35. To prevent them. The strained layer 35 and the lower electrode 30 are patterned to have a predetermined pixel shape, respectively.

Referring to FIG. 2D, the strained layer 35, the lower electrode 30, the membrane 25, the etch stop layer 15, and the protective layer 10 from one side of the strained layer 35 to an upper portion of the drain pad 5. ) Is sequentially etched to form a via hole 45 from the strained layer 35 to the drain pad 5. Subsequently, a metal such as tungsten (W) or titanium (Ti) is deposited in the via hole 45 using a sputtering method, so that the bottom contact 30 and the drain pad 5 are electrically connected to each other. 50). Accordingly, the first signal transmitted from the outside is applied to the lower electrode 30 through the transistor, the drain pad 5, and the via contact 50 embedded in the active matrix 1. In addition, the second signal is applied to the upper electrode 40 so that the deformation layer 35 formed between the upper electrode 40 and the lower electrode 30 causes deformation, and accordingly the actuator including the deformation layer 35 ( 40) is bent upwards. Therefore, the upper electrode 40 on the actuator 40 is also bent in the same direction. Light incident from the light source is reflected by the upper electrode 40 bent at a predetermined angle, and then projected onto a screen to form an image.

Subsequently, the membrane 25 is patterned to have a predetermined pixel shape. Then, the sacrificial layer 18 is removed using 49% hydrogen fluoride (HF) vapor to form an air gap 20 at the position of the sacrificial layer 18, followed by washing and drying. Complete the AMA device.

However, in the above-described manufacturing method of the thin film type optical path control apparatus, when the sacrificial layer is removed using 49% hydrogen fluoride (HF) vapor, the upper electrode composed of aluminum and also serves as a mirror is damaged. The reflection area of the light incident from the light is reduced, resulting in a problem that the light efficiency is lowered. As a result, the image quality of the image projected on the screen is reduced. In addition, since the upper electrodes of the respective actuators are connected to each other, when one upper electrode is damaged, the actuator does not drive because the second signal is not applied to the actuators having the upper electrode as well as the actuators after the actuator having the upper electrode. There is a problem.

Accordingly, an object of the present invention is to adjust the concentration of hydrogen fluoride used to etch a sacrificial layer to relatively change the concentration of hydronium ion (H ₃ O ⁺ ) in hydrogen fluoride, thereby reducing fluorine. It is to provide a method for manufacturing a thin film type optical path control device that can improve the light efficiency by preventing the damage of the mirror by hydrogen fluoride.

1 is a cross-sectional view of a thin film type optical path control device previously applied by the present applicant.

2A to 2D are manufacturing process diagrams of the apparatus shown in FIG. 1.

3 is a plan view of a thin film type optical path control apparatus according to the present invention.

4 is an enlarged perspective view of the apparatus shown in FIG. 3.

FIG. 5 is a cross-sectional view taken along line A′A ′ of the apparatus shown in FIG. 4.

6A to 6C are manufacturing process diagrams of the apparatus shown in FIG. 5.

<Explanation of symbols for main parts of drawing>

100: active matrix 125: first metal layer

130: first protective layer 135: second metal layer

140: second protective layer 145: etch stop layer

150: sacrificial layer 160: support layer

165: lower electrode 170: strained layer

175: upper electrode 180: via hole

185: Beer contact 190: Actuator

195: mirror

In order to achieve the above object of the present invention, the present invention provides an active matrix including a first metal layer having M x N (M, N is an integer) MOS transistor embedded therein and having a drain pad extending from the drain of the transistor. Providing; Forming a sacrificial layer over the active matrix and patterning the sacrificial layer; Iii) forming a support layer on top of the patterned sacrificial layer, ii) forming a bottom electrode on top of the support layer, iii) forming a strained layer on top of the bottom electrode, iii) the strained layer Forming an upper electrode on an upper portion of the upper electrode, and iii) sequentially patterning the upper electrode, the deformation layer, the lower electrode, and the support layer to form an actuator; Forming a mirror on top of the patterned support layer; And removing the sacrificial layer using hydrogen fluoride (HF) vapor having a concentration of 65 to 73%.

In the thin film type optical path adjusting device according to the present invention, a second signal is applied to the upper electrode through a common electrode line from the outside, and at the same time, the lower electrode is provided with a transistor embedded in the active matrix, a drain pad of the first metal layer, and a via contact from the outside. Through the first signal is applied, an electric field is generated according to the potential difference between the upper electrode and the lower electrode. Due to this electric field, the strain layer formed between the upper electrode and the lower electrode causes deformation. The strained layer contracts in a direction orthogonal to the electric field, so that the actuator including the strained layer and the support layer is bent at an angle. The mirror reflecting the light incident from the light source is bent at the same angle as the actuator because it is formed above the central portion of the support layer. Accordingly, the mirror reflects the incident light at a predetermined angle, and the reflected light passes through the slit and is projected onto the screen to form an image.

According to the manufacturing method of the optical path control apparatus which concerns on this invention, a sacrificial layer is etched using the hydrogen fluoride vapor which has a density | concentration of about 65-73%. Accordingly, the etching selectivity of hydrogen fluoride with respect to aluminum, which is a constituent material of the mirror, is improved, so that the mirror is not damaged while the sacrificial layer is etched. Therefore, the light efficiency of the light incident from the light source can be increased, and as a result, the image quality of the image projected on the screen is improved.

Hereinafter, with reference to the accompanying drawings will be described in detail a manufacturing method of a thin film type optical path control apparatus according to a preferred embodiment of the present invention.

3 is a plan view showing a thin film type optical path control apparatus according to the present invention, FIG. 4 is an enlarged perspective view of the apparatus shown in FIG. 3, and FIG. 5 is an AA ′ line of the apparatus shown in FIG. 4. It shows a cut section.

3, 4, and 5, the thin film type optical path adjusting apparatus according to the present invention includes an active matrix 100, an actuator 170, and a mirror 160.

The active matrix 100 having M × N (M, N is an integer) P-MOS transistors includes a first metal layer 125 extending from a source 110 and a drain 120 of the MOS transistor. The first protective layer 130 formed on the first metal layer 125, the second metal layer 130 formed on the first protective layer 130, and the second protective layer formed on the second metal layer 130 ( 140, and an etch stop layer 145 formed on the second passivation layer 140. The first metal layer 125 includes a drain pad extending from the drain 120 of the MOS transistor, and the second metal layer 135 includes a titanium (Ti) layer and a titanium nitride (TiN) layer.

Referring to FIG. 4, one side of the actuator 190 is in contact with a portion of the etch stop layer 145 in which the drain pad of the first metal layer 125 is formed, and the other side thereof is horizontal through the air gap 155. The support layer 160, the lower electrode 165 formed on the support layer 160, the deformation layer 170 formed on the lower electrode 165, and the upper electrode 175 formed on the deformation layer 170. The strained layer 170, the lower electrode 165, the support layer 160, the etch stop layer 145, the second passivation layer 140, and the first passivation layer 130 are formed from one side of the strain layer 170. The via contact 185 is formed to connect the lower electrode 165 and the drain pad to the inside of the via hole 180 that is vertically formed to the drain pad of the first metal layer 125. The support layer 160 functions as a membrane supporting the actuator of the thin film type optical path adjusting device described in the previous application.

The support layer 160 has a shape in which a rectangular flat plate is integrally formed with the arms on the same plane between two rectangular arms formed in parallel from both support portions. The mirror 195 is formed on the rectangular flat plate of the support layer 160. Thus, the mirror 195 has the shape of a rectangular flat plate.

Hereinafter, a method of manufacturing a thin film type optical path control device according to the present invention will be described in detail with reference to the drawings.

6a to 6c show a manufacturing process of the thin film type optical path control apparatus according to the present invention.

Referring to FIG. 6A, after preparing an active matrix 100, which is an n-type doped silicon (Si) wafer, the active matrix 100 may be formed using a conventional device isolation process, for example, silicon partial oxidation (LOCOS). ) To form an isolation layer 105 for dividing the active region and the field region. Subsequently, after forming the gate 115 made of a conductive material such as polysilicon doped with impurities on the active region, p ⁺ source 110 and drain 120 are formed by an ion implantation process, thereby forming M ×. N (M, N is an integer) P-MOS transistors are formed.

After forming the insulating layer 118 made of oxide on the P-MOS transistor is formed, openings for exposing the top of one side of the source 110 and the drain 120, respectively by a photolithography process. Subsequently, a first metal layer 125 made of a metal such as titanium, titanium nitride, and tungsten (W) is deposited on the resultant, on which the openings are formed, and then the first metal layer 125 is patterned by a photolithography process. The first metal layer 125 patterned as described above includes a drain pad extending from the drain 120 of the P-MOS transistor to one side of the support of the actuator 190.

The first passivation layer 130 is formed on the first metal layer 125. The first passivation layer 130 is formed to have a thickness of about 8000 μs using the phosphorus silicate glass (PSG) using a chemical vapor deposition (CVD) method. The first protective layer 130 prevents damage to the active matrix 100 in which the MOS transistor is embedded during a subsequent process.

The second metal layer 135 is formed on the first passivation layer 130. In order to form the second metal layer 135, first, a titanium layer is formed by sputtering titanium (Ti) to a thickness of about 300 μm. Subsequently, titanium nitride is deposited on the titanium layer using physical vapor deposition (PVD) to form a titanium nitride layer. Since the light incident from the light source is incident not only to the mirror 195 but also to a portion other than the portion where the mirror 195 is formed, the second metal layer 135 prevents light leakage current from flowing in the active matrix 100. do. Subsequently, an opening 138 is formed in the second metal layer 135 by etching the portion of the second metal layer 135 where the via contact 185 is to be formed in a subsequent process through a photolithography process.

The second passivation layer 140 is formed on the second metal layer 135. The second protective layer 140 is formed to have a thickness of about 2000 GPa using in-silicate glass (PSG). The second protective layer 140 also prevents damage to the active matrix 100 in which the MOS transistor is embedded and the results formed on the active matrix 100 during the subsequent process.

An etch stop layer 145 is formed on the second passivation layer 140. The etch stop layer 145 prevents the active matrix 100 and the second passivation layer 140 from being etched due to a subsequent etching process. The etch stop layer 145 is formed by depositing nitride (Si ₃ N ₄ ) by a low pressure chemical vapor deposition (LPCVD) method to have a thickness of about 1000 ~ 2000Å.

The sacrificial layer 150 is formed on the etch stop layer 145. The sacrificial layer 150 serves to facilitate stacking of the thin films constituting the actuator 190, and is removed by hydrogen fluoride (HF) vapor after the actuator 190 is formed. The sacrificial layer 150 is formed by depositing phosphorus silicate glass (PSG) to a thickness of about 2.0 to about 3.0 μm using an atmospheric pressure chemical vapor deposition (APCVD) method. In this case, since the sacrificial layer 150 covers the upper portion of the active matrix 100 in which the P-MOS transistor is embedded, the surface flatness is very poor. Therefore, planarization is performed by polishing the surface of the sacrificial layer 150 such that the sacrificial layer 150 has a thickness of about 1.1 μm by using spin on glass (SOG) or chemical mechanical polishing (CMP). Let's do it. Subsequently, the portion of the first sacrificial layer 150 having the opening 138 formed under the second metal layer 135 is etched to expose a part of the etch stop layer 145, thereby anchoring the support of the actuator 190. Create the location where the anchor will be formed.

Referring to FIG. 6B, the support layer 160 is formed on the exposed etch stop layer 145 and on the sacrificial layer 150. The support layer 160 is formed to have a thickness of about 0.01 to 1.0 탆 using low pressure chemical vapor deposition (LPCVD).

The lower electrode 165 is formed on the support layer 160. The lower electrode 165 is formed of a metal such as platinum, tantalum, or platinum-tantalum to have a thickness of about 0.01 to 1.0 탆 using a sputtering method or a chemical vapor deposition method. Subsequently, the lower electrode 165 is separated for each pixel so that an independent first signal (image signal) is applied to each pixel (Iso-cut process). A first signal is applied to the lower electrode 165 through a transistor embedded in the active matrix 100, a drain pad of the first metal layer 125, and a via contact 185 from the outside.

A deformation layer 170 made of a piezoelectric material such as PZT or PLZT is formed on the lower electrode 165. The strained layer 170 is formed to have a thickness of about 0.01 to 1.0 탆 using a sol-gel method, a sputtering method, or a chemical vapor deposition method. Preferably, the strained layer 170 is formed to have a thickness of about 0.4 μm using PZT using a sol-gel method. In addition, the piezoelectric material constituting the strained layer 165 is heat-treated by rapid thermal treatment (RTA) to cause phase shift. The strained layer 170 is applied with a second signal (bias signal) to the upper electrode 175 and a first signal is applied to the lower electrode 165 to thereby reduce the potential difference between the upper electrode 175 and the lower electrode 165. Deformation is caused by the electric field generated.

The upper electrode 175 is formed on the strained layer 170. The upper electrode 175 is formed of a metal such as platinum, tantalum, or platinum-tantalum to have a thickness of about 0.01 to 1.0 탆 using a sputtering method or a chemical vapor deposition method. The second electrode (bias signal) is applied to the upper electrode 175 through a common electrode line (not shown) from the outside.

Referring to FIG. 6C, after the first photoresist (not shown) is coated on the upper electrode 175 by spin coating, the upper electrode 175 is shown in FIG. 4. Pattern it to have the shape of the letter 'c' on the mirror. Subsequently, after the first photoresist is removed, a second photoresist (not shown) is applied on the patterned upper electrode 175 and the strained layer 170 by spin coating, and then the strained layer ( 170 is patterned to have a mirror-shaped 'c' shape slightly wider than the upper electrode 175 (see FIG. 4). Subsequently, after removing the second photoresist and applying a third photoresist (not shown) on the upper electrode 175, the deforming layer 170, and the lower electrode 165 by spin coating, The lower electrode 165 is patterned to have a mirror-shaped 'c' shape slightly wider than that of the strained layer 170.

Subsequently, the strained layer 170, the lower electrode 165, the support layer 160, and the etch stop layer 145 are formed from a portion of the strained layer 170 in which the opening 138 of the second metal layer 135 is formed below. After etching the second protective layer 140 and the first protective layer 130 in order to form the via hole 180 from one side of the strained layer 170 to the drain pad of the first metal layer 125, Vias in which the drain pads of the first metal layer 125 and the lower electrode 165 are electrically connected to each other by using a sputtering method of a metal such as tungsten (W), platinum, aluminum, or titanium in the via hole 180. The contact 185 is formed. Thus, the via contact 185 is formed from the lower electrode 165 to the top of the drain pad in the via hole 180. The first signal transmitted from the outside is applied to the lower electrode 165 through the transistor embedded in the active matrix 100, the drain pad of the first metal layer 125, and the via contact 185.

Subsequently, after the fourth photoresist (not shown) is coated on the patterned lower electrode 165 and the via hole 180 by spin coating, portions extending from both supporting portions of the support layer 160 may be formed. The lower portion of the lower electrode 165 has a slightly rectangular shape, and the center portion of the support layer 160 formed integrally therewith is patterned to have a rectangular flat shape. That is, as shown in FIG. 4, the support layer 160 has a shape in which rectangular arms extend from both support portions, and a rectangular flat plate having a larger area between these arms is formed integrally with the arms on the same plane. Have Then, the fourth photoresist is removed. As a result of the patterning of the support layer 160 as described above, a portion of the sacrificial layer 150 is exposed.

Subsequently, a fifth photoresist (not shown) is coated on the exposed sacrificial layer 150 and the support layer 160 by a spin coating method, and then a rectangular flat plate is formed as a center of the support layer 160. It is patterned to be exposed. Then, a metal having reflective properties such as aluminum is deposited on the upper portion of the center portion of the rectangular exposed support layer 160 by a sputtering method or a chemical vapor deposition method with a thickness of about 0.3 to 2.0 μm. Subsequently, the deposited metal is patterned to form the mirror 195 such that the deposited metal has the same shape as the center portion of the rectangular exposed support layer 160, and then the fifth photoresist is removed.

Subsequently, the sacrificial layer 150 is removed using hydrogen fluoride (HF) vapor having a concentration from about 65% up to 73% to form an air gap 155 at the position of the sacrificial layer 150. In this case, the etching mechanism of the silicate glass (PSG) constituting the sacrificial layer 150 by hydrogen fluoride and the damage mechanism of aluminum constituting the mirror 195 are shown in Schemes 1 and 2 below.

SiO ₂ (PSG) + 6HF → H ₂ SiF ₆ + 2H ₂ O

2Al + 6H ₃ O ⁺ → 3Al ³⁺ + 3H ₂ O + H ₂ (↑)

The etching of the phosphorus silicate glass (PSG), which is a constituent material of the sacrificial layer 150 from Scheme 1, depends on the concentration of hydrogen fluoride (HF), and the damage of aluminum, which is a constituent material of the mirror 195, in Scheme 2 It can be seen that it depends on the concentration of H ₃ O ⁺ . Therefore, in order to minimize the damage of aluminum by hydrogen fluoride and to perform the etching of the sacrificial layer 150 smoothly, it is required to relatively reduce the concentration of hydronium ions (H ₃ O ⁺ ). Since hydrogen fluoride is a weak acid, when the concentration of hydrogen fluoride is increased to about 65-73% as in the conventional 49% of the present invention, the concentration of hydronium ions in hydrogen fluoride is relatively increased. The reduction may improve the etch selectivity of aluminum, which is a material of the mirror 195. As described above, when the concentration of hydrogen fluoride is increased to about 65 to 73%, the difference in the etching rate of the phosphorus silicate glass, which is a constituent of the sacrificial layer 150, and the aluminum, which is a constituent of the mirror 195, is about aluminum. The phosphorus silicate glass may be etched about 600 to 1000 μm while being etched about 1 μm to prevent the mirror 195 from being damaged when the sacrificial layer 150 is etched.

After etching the sacrificial layer 150 as described above, the cleaning and drying process is performed to complete the thin film type optical path control apparatus.

In the above-described thin film type optical path control device according to the present invention, a second signal is applied to the upper electrode 175 through a common electrode line from the outside, and at the same time, a transistor embedded in the active matrix 100 from the outside to the lower electrode 165. The first signal is applied through the drain pad and the via contact 185 of the first metal layer 155 to generate an electric field according to the potential difference between the upper electrode 175 and the lower electrode 165. Due to such an electric field, the deformation layer 170 formed between the upper electrode 175 and the lower electrode 165 causes deformation. The strained layer 170 contracts in a direction orthogonal to the electric field, and thus the actuator 190 including the strained layer 170 and the support layer 160 is bent at a predetermined angle. The mirror 195 reflecting the light incident from the light source is formed at an upper portion of the central portion of the support layer 160, and thus is bent at the same angle as the actuator 190. Accordingly, the mirror 195 reflects the incident light at a predetermined angle, and the reflected light passes through the slit to be projected onto the screen to form an image.

According to the manufacturing method of the optical path control apparatus which concerns on this invention, a sacrificial layer is etched using the hydrogen fluoride vapor which has a density | concentration of about 65-73%. Accordingly, the etching selectivity of hydrogen fluoride with respect to aluminum, which is a constituent material of the mirror, is improved, so that the mirror is not damaged while the sacrificial layer is etched. Therefore, the light efficiency of the light incident from the light source can be increased, and as a result, the image quality of the image projected on the screen is improved.

Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited thereto and may be improved or modified by those skilled in the art within the scope of the technical idea of the present invention.

Claims (1)

Providing an active matrix comprising a first metal layer with M × N (M, N is an integer) embedded therein and having a drain pad extending from the drain of the transistor; Forming a sacrificial layer over the active matrix and patterning the sacrificial layer; Iii) forming a support layer on top of the patterned sacrificial layer, ii) forming a bottom electrode on top of the support layer, iii) forming a strained layer on top of the bottom electrode, iii) the strained layer Forming an upper electrode on an upper portion of the upper electrode, and iii) sequentially patterning the upper electrode, the deformation layer, the lower electrode, and the support layer to form an actuator; Forming a mirror on top of the patterned support layer; And And removing the sacrificial layer by using hydrogen fluoride (HF) vapor having a concentration of 65 to 73%.