KR102186653B1 - A MEMS Device And The Manufacturing Method of the MEMS Device - Google Patents

Abstract

MEMS device according to an embodiment of the present invention, a sensor substrate having an infrared sensor; And a cap substrate bonded to the lower substrate to form a cavity. The cap substrate may include an upper substrate; An upper pattern having a Moth-eye structure formed on an upper surface of the upper substrate; A lower pattern having a moth-eye structure disposed to face the upper pattern and formed in a cavity region recessed from a lower surface of the upper substrate; A getter disposed around the lower pattern and disposed within the cavity area; A partition wall protruding from the lower surface of the upper substrate than the cavity region and having the same structure and material as that of the upper substrate and disposed to surround the cavity region; A cut portion recessed from a lower surface of the upper substrate than an arrangement plane of the cavity region and disposed to surround the partition wall; And an upper bonding pad disposed on a lower surface of the partition wall.

Description

MEMS Device And The Manufacturing Method of the MEMS Device

The present invention relates to a MEMS device, and more particularly, to an infrared sensor MEMS device having an infrared window having a high transmittance in the infrared band and having a high absorbance in the infrared band.

The bolometer is a kind of infrared sensor. The bolometer is formed on a lower substrate including a reflector and a signal processing unit. The bolometer absorbs incident infrared rays. When the temperature of the absorption plate of the bolometer increases, a change in resistance of the resistive layer due to the increase in temperature is detected, and energy of infrared rays is measured from the change in resistance.

The cap substrate includes a lower substrate and a separate upper substrate, and the cap substrate is packaged while forming a cavity by wafer bonding with the lower substrate.

One technical problem to be solved of the present invention is to provide a MEMS device for an infrared sensor having a high transmittance in a specific band of infrared rays (7 μm -20 μm).

A method of manufacturing a MEMS device according to an embodiment of the present invention includes forming an upper pattern having a Moth-eye structure on an upper surface of an upper substrate; Forming a preliminary lower pattern that is aligned with the upper pattern and has a Moth-eye structure and is disposed on a lower surface of the upper substrate; Simultaneously forming a cavity region including a lower pattern to which the preliminary lower pattern is transferred and a preliminary recess region surrounding the partition wall region by etching using an etching mask formed in the partition wall region surrounding the preliminary lower pattern; Forming a recess area for additionally etching the preliminary recess area; Forming an upper bonding pad in the partition area and a getter in the cavity area so as not to overlap with the lower pattern; Bonding a lower bonding pad of a lower substrate with an infrared sensor and the upper bonding pad of the upper substrate in a vacuum state; And cutting the recessed region of the upper substrate to expose an external connection pad of the lower substrate. The upper substrate and the lower substrate are silicon substrates.

In an embodiment of the present invention, the forming of the upper pattern having a Moth-eye structure on the upper surface of the upper substrate is arranged in a matrix form using a photo-lithography process on the upper surface of the upper substrate. Forming a preliminary upper photoresist pattern spaced apart from each other; Performing a thermal reflow process on the upper substrate on which the preliminary upper photoresist pattern is formed to form an upper photoresist pattern having a Moth-eye structure; Dry etching the upper photoresist pattern with an etching mask to form an upper pattern having a Moth-eye structure on the upper surface of the upper substrate; And removing the upper photoresist pattern.

In an embodiment of the present invention, the forming of the preliminary lower pattern aligned with the upper pattern and having a Moth-eye structure and disposed on the lower surface of the upper substrate may be performed on the lower surface of the upper substrate. Forming a preliminary lower photoresist pattern arranged in a matrix form and spaced apart from each other by using a photo-lithography process; Forming a lower photoresist pattern having a Moth-eye structure by performing a thermal reflow process on the upper substrate on which the preliminary lower photoresist pattern is formed; Forming a preliminary lower pattern having a Moth-eye structure on a lower surface of the upper substrate by dry etching the lower photoresist pattern with an etching mask; And removing the lower photoresist pattern.

In one embodiment of the present invention, the Moth-eye structure of the lower pattern may include a plurality of hemispheres disposed in contact with each other.

In one embodiment of the present invention, the Moth-eye structure of the lower pattern may include a plurality of cut ellipsoids disposed in contact with each other.

MEMS device according to an embodiment of the present invention, the upper substrate; An upper pattern having a Moth-eye structure formed on an upper surface of the upper substrate; A lower pattern having a moth-eye structure disposed to face the upper pattern and formed in a cavity region recessed from a lower surface of the upper substrate; A getter disposed around the lower pattern and disposed within the cavity area; A partition wall protruding from the lower surface of the upper substrate than the cavity region and having the same structure and material as that of the upper substrate and disposed to surround the cavity region; A cut portion recessed from a lower surface of the upper substrate than an arrangement plane of the cavity region and disposed to surround the partition wall; And an upper bonding pad disposed on a lower surface of the partition wall. A lower substrate; An infrared sensor disposed to face the cavity area of the upper substrate; And a lower bonding pad aligned with the upper bonding pad and disposed to surround the infrared sensor. The upper substrate and the lower substrate are silicon substrates.

In one embodiment of the present invention, the Moth-eye structure of the lower pattern may have a plurality of hemispherical shapes disposed in contact with each other.

In one embodiment of the present invention, the radius of curvature of the hemispherical shape of the lower pattern is sub-micrometer to several micrometres, and the hemispheres of the lower pattern may be aligned with the hemispheres of the upper pattern.

In an embodiment of the present invention, the Moth-eye structure of the lower pattern may be in the shape of a plurality of cut ellipsoids disposed in contact with each other.

MEMS device according to an embodiment of the present invention, a sensor substrate having an infrared sensor; And a cap substrate bonded to the lower substrate to form a cavity. The cap substrate may include an upper substrate; An upper pattern having a Moth-eye structure formed on an upper surface of the upper substrate; A lower pattern having a moth-eye structure disposed to face the upper pattern and formed in a cavity region recessed from a lower surface of the upper substrate; A getter disposed around the lower pattern and disposed within the cavity area; A partition wall protruding from the lower surface of the upper substrate than the cavity region and having the same structure and material as that of the upper substrate and disposed to surround the cavity region; A cut portion recessed from a lower surface of the upper substrate than an arrangement plane of the cavity region and disposed to surround the partition wall; And an upper bonding pad disposed on a lower surface of the partition wall. The sensor substrate may include a lower substrate; An infrared sensor formed on the lower substrate and disposed to face the cavity region of the upper substrate; And a lower bonding pad aligned with the upper bonding pad and disposed to surround the infrared sensor. The upper substrate and the lower substrate are silicon substrates.

In an embodiment of the present invention, the infrared sensor includes: a metal pad formed on an upper surface of the lower substrate and electrically connected to a detection circuit; A reflective layer formed on the upper surface of the lower substrate and reflecting an infrared band; An absorption plate that is formed to be spaced apart from the top of the reflective layer and absorbs infrared rays to change resistance; And an anchor formed on the metal pad to support the absorber plate and electrically connect the metal pad to the absorber plate.

In one embodiment of the present invention, the absorber plate may include a first insulating layer, an absorbing layer, a resistance layer, a second insulating layer, and an anti-reflection pattern that are sequentially stacked.

In one embodiment of the present invention, the anti-reflection pattern may be a mothed structure.

In one embodiment of the present invention, the Moth-eye structure of the lower pattern is a plurality of hemispheres disposed in contact with each other, and the radius of curvature of the hemispheres of the lower pattern is sub-micrometer to several microns. And hemispheres of the lower pattern may be aligned with hemispheres of the upper pattern.

The MEMS device according to an embodiment of the present invention is manufactured through a vacuum packaging process of the cap substrate and the MEMS device substrate. The cap substrate has an infrared window on which a pattern of a moth structure is formed. The upper pattern of the moth structure is formed on the upper surface of the cap substrate to perform an anti-reflective function, and the lower pattern of the moth structure is formed in a region recessed in the lower surface of the cap substrate to perform a band pass filter function. . The upper pattern and the lower pattern have a moth structure and provide excellent infrared transmission characteristics. In addition, the upper pattern and the lower pattern can reduce cost and improve productivity compared to non-reflective coating by a multilayer thin film process.

1A is a conceptual diagram illustrating a MEMS device according to an embodiment of the present invention.
1B is a plan view and a cross-sectional view showing a pattern of a moth-eye structure displayed on a cap substrate of the MEMS device of FIG. 1A.
FIG. 1C is a cross-sectional view illustrating a pattern of a moth-eye structure displayed on a cap substrate of the MEMS device of FIG. 1A.
2A and 2B show transmittance according to an embodiment of the present invention.
3A to 3L are cross-sectional views illustrating a method of manufacturing a MEMS device according to an embodiment of the present invention.
4A is a perspective view illustrating a sensor substrate including an infrared sensor according to an embodiment of the present invention.
4B is a cross-sectional view taken along line A-A' of FIG. 4A.
5A to 5H are cross-sectional views illustrating a method of manufacturing a sensor substrate according to an embodiment of the present invention.

The present invention relates to a method for manufacturing a microelectromechanical systems (MEMS) device, and to a wafer level vacuum packaging. Wafer-level vacuum packaging bonds the MEMS device substrate and the cap wafer. The MEMS device substrate may include an infrared sensor structure such as a bolometer and readout integrated circuits (ROIC). The cap substrate is bonded to the MEMS device substrate to create a vacuum cavity, and provides a window through which external infrared light can be transmitted.

The bolometer transmits infrared rays incident from the outside to the infrared absorbing layer, and when the temperature of the infrared absorbing layer increases, the increase in temperature of the infrared absorbing layer causes a change in resistance of the resistive layer. The change in resistance of the resistive layer is converted into infrared energy through a read integrated circuit. Accordingly, in order to efficiently transmit external infrared light to the infrared absorbing layer, an antireflection film for preventing surface reflection of the bolometer is required. The infrared window of the cap wafer typically uses an anti-reflective coating with a multilayer thin film structure.

In order to prevent surface reflection, anti-reflection (AR) coating with a multilayer thin film structure is used. The anti-reflective coating of a multilayered thin film structure lowers the reflectance at the surface by using the interference effect. The interference effect uses changes in the wavelength and intensity of light according to the refractive index and thickness. The anti-reflective coating of such a multilayer thin film structure has a stacked structure of several layers having different refractive indices (eg, 2 to 27 layers). In the process of laminating a multilayer thin film, there is a problem of high defect loss, poor mass production due to many lamination steps, and high cost. Since the thermal expansion coefficients of the plurality of stacked layers are different from each other, characteristics and lifespan are deteriorated by stress.

In order to prevent surface reflection, a nanostructured lattice pattern may be used. However, such a lattice pattern is difficult to apply to a cap substrate for forming a cavity. Specifically, a deep trench of tens of micrometers or more is required to construct a cavity in a cap wafer. It is very difficult to form a pattern of nanostructures in the deep trench. The cap substrate requires a cavity to accommodate the infrared sensor. The depth of the cavity is from tens of micrometers to hundreds of microbits. It is difficult to form a pattern of a moth-shaped structure in a hollow cavity through a photolithography process.

According to an embodiment of the present invention, in order to prevent surface reflection of external light, a moth-eye pattern of a microstructure is formed on both sides or lower surfaces of the surface of the MEMS device and/or the cap wafer of wafer level packaging. pattern) is formed. Accordingly, infrared light gradually recognizes the pattern of the moth structure as a surface having a refractive index change. In the case of infrared rays incident in the air at the interface between the air and the cap substrate, the moth-eye pattern minimizes reflection in the 7 μm to 14 μm wavelength range of Far Infrared (FIR), and 7 of Far Infrared (FIR). Transmission of wavelengths in the μm to 14 μm wavelength range can be maximized. The pattern of the spheroid structure can operate as a band pass filter having a high transmittance in the 7um to 14um wavelength region when incident from the cap substrate at the interface between the air and the cap substrate.

According to an embodiment of the present invention, a pattern having a Moth-eye structure is formed on both sides of the cap substrate or on one side of the cap substrate. The pattern of the Moth-eye structure improves infrared transmission and can extend the lifespan compared to the multilayer thin film, thereby minimizing deterioration of the packaging life of the MEMS device.

In addition, the Moth-eye structure is formed on one side of the recessed cavity in a simple manufacturing process and inexpensive manufacturing cost, so that mass production of the MEMS device can be secured.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. However, these examples are intended to illustrate the present invention in more detail, and it will be apparent to those of ordinary skill in the art that the present invention is not limited or limited by experimental conditions, material types, and the like. The present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed content may be thorough and complete, and the spirit of the present invention may be sufficiently conveyed to those skilled in the art. In the drawings, components are exaggerated for clarity. Parts indicated by the same reference numerals throughout the specification represent the same elements.

1A is a conceptual diagram illustrating a MEMS device according to an embodiment of the present invention.

1B is a plan view and a cross-sectional view showing a pattern of a moth-eye structure displayed on a cap substrate of the MEMS device of FIG. 1A.

FIG. 1C is a cross-sectional view illustrating a pattern of a moth-eye structure displayed on a cap substrate of the MEMS device of FIG. 1A.

1A, 1B, and 1C, the MEMS device 100 includes: a sensor substrate 102 having an infrared sensor 103; And a cap substrate 101 that is bonded to the sensor substrate 102 to constitute the cavity 104.

The cap substrate 101 may include an upper substrate 120; An upper pattern 130 having a Moth-eye structure formed on an upper surface of the upper substrate 120; Is aligned with the upper pattern 130 A lower pattern 140 having a Moth-eye structure formed in the cavity region 150 recessed from the lower surface of the upper substrate 120; A getter 170 disposed around the lower pattern 140 and disposed within the cavity region 150; A partition wall 180 protruding from the lower surface of the upper substrate 120 than the cavity region 150 and having the same structure and material as the upper substrate 120 and disposed to surround the cavity region 150; A cutting portion 184 that is disposed on the lower surface of the upper substrate 120 to be more depressed than the layout plane of the cavity area and disposed to surround the partition wall 180; And an upper bonding pad 182 disposed on a lower surface of the partition wall 180.

The sensor substrate 102 may include a lower substrate 110; An infrared sensor 103 formed on the lower substrate 110 and disposed to face the cavity region 150 of the upper substrate 120; And a lower bonding pad 116 arranged to surround the infrared sensor 103 and aligned with the upper bonding pad 182. The upper substrate 120 and the lower substrate 110 are silicon substrates.

The cap substrate 101 includes the upper substrate 120 and the upper pattern 130 formed on the upper surface of the upper substrate, and the lower pattern 140 formed in the recessed cavity region 150 of the lower surface of the upper substrate. , A partition wall 180 protruding from a lower surface of the upper substrate and a getter 170 formed in the cavity region. The cap substrate 101 is bonded to the sensor substrate 102 to form a cavity 104. The cavity 104 may be maintained in a vacuum state.

The upper substrate 120 may be a silicon substrate. The upper substrate 120 operates as a substrate for forming the upper pattern 130, the lower pattern 140, the cavity region, the partition wall 180, the recess region 160, and the cut portion 184. The upper substrate 120 may have a thickness of several hundred micrometers or more to sufficiently withstand even when a vacuum is formed in the cavity 104.

The upper pattern 130 is of the upper substrate 120 When the upper pattern 130 is formed on the upper surface and is projected on the same surface as the lower pattern 140, the lower pattern 140 may include or be aligned to be the same. The upper pattern 130 may have a Moth-eye structure. The moth structure of the upper pattern 130 may include a plurality of hemispheres 132 disposed in contact with each other. The hemispheres 132 may be made of the same material as the upper substrate 120. The hemispheres 132 may be arranged in a matrix form, or may be arranged in a honeycomb hexagonal form. The hemispheres may be disposed in contact with each other, and a radius or a radius of curvature of the hemisphere 132 may be sufficiently smaller than an infrared wavelength. Specifically, a radius of the hemisphere 132 in a far infrared (FIR) range of 7 μm to 14 μm may range from sub micrometers to several micrometers. The transmittance of infrared rays incident in the air to transmit through the upper pattern 130 of the upper substrate is almost independent of the radius of the hemisphere and may be constant in the range of 2 μm to 20 μm. The upper pattern 130 may perform an anti-reflection function. The upper pattern 130 may be formed to correspond to each unit cell of the infrared sensor or may be formed to correspond to the entire area of the infrared sensor.

The lower pattern 140 is arranged in alignment with the upper pattern 120 in the cavity region 150 recessed from the lower surface of the upper substrate 120, and may have a Moth-eye structure. The cavity area 150 may face the infrared sensor 103 of the sensor substrate. The lower pattern 140 may include a plurality of hemispheres arranged in a matrix form or a hexagonal form. The hemispheres may be disposed in contact with each other. The radius of curvature of the hemisphere may be a sub micrometer to several micrometers. The hemispheres of the lower pattern 140 may be aligned with the hemispheres of the upper pattern 130. For example, when the radius of the hemisphere of the lower pattern is 0.3 μm, the transmittance gradually decreases as it goes to the long wavelength region of 3 μm or more while showing the maximum transmittance in the 3 μm wavelength region. However, compared with the case without the moth-eye structure, the transmittance is high when the moth-moon structure is applied in the 3 μm to 20 μm wavelength range.

In addition, when the radius of the hemisphere of the lower pattern 140 is 0.6 μm, the transmittance may have a maximum value at a wavelength of about 7 μm. The transmittance increases rapidly up to a wavelength of 7 μm, and the transmittance may gradually decrease at a wavelength of 7 μm or more. That is, as the radius increases, higher transmittance is shown in the long wavelength region, and it can be seen that higher transmittance is exhibited in the 6 μm to 20 μm region as compared to the case without the moth structure, through which the lower pattern 140) The Moth-eye structure of can operate as a band-pass optical filter that blocks light below a specific wavelength and transmits light above a specific wavelength.

Referring to FIG. 1C, the Moth-eye structure of the upper pattern 130 and the lower pattern 140 may include a plurality of cut ellipsoids disposed in contact with each other. The ellipsoids of the moth-eye structure are expressed by a surface primitive formula representing a curved surface.

[Equation 1]

Where r is the radius, c is the reciprocal of the radius of curvature at r=0, κ is the conic constant, κ = 0 (spherical), κ>-1 (elliptical), κ=-1 (parabolic ), κ <-1 (hyperbolic) shape. A structure that maximizes transmittance in the wavelength band of the region of interest can be selected while changing these variables. In the case of an ellipsoid, the conic constant is -1<κ<0, so if the value is appropriately modulated in conjunction with the radius of curvature in this range, anti-reflection for each incident wavelength in the visible and infrared regions. You can maximize the effect.

The lower pattern 130 may be disposed in the cavity region 150 recessed from the lower surface of the upper substrate 120. The cavity area 150 may provide the cavity 104 accommodating an infrared sensor. The depression depth h1 of the cavity region 150 may be several micrometers to several hundred micrometers. The depression depth h1 of the cavity area may depend on the height of the infrared sensor 103. Typically, when detecting an infrared wavelength of 8 μm, the distance between the absorption layer 115 and the reflector 112 in the infrared sensor 103 may be 1/4 times (2 μm) of the infrared wavelength. Accordingly, the depression depth h1 of the cavity area may be greater than the height of the infrared sensor 103.

The partition wall 180 separates the recessed cavity area 150 and the recessed recess area 160, and may protrude from the lower surface of the upper substrate 120. The partition wall 180 may be disposed to surround the recessed cavity region 150 to provide a sealed cavity 104. The height of the partition wall 180 may have a depressed depth h1 of the cavity region 150 and a depressed depth h2 of the recess region 160.

The depression depth h2 of the recess region 160 is greater than the depression depth h1 of the cavity region 150 and may be several micrometers to several hundreds micrometers. As the recessed depth h2 of the recessed region 160 increases, the thickness of the upper substrate to be cut decreases. The depth difference h2-h1 may be several hundred micrometers. Accordingly, the external connection pad 117 may be exposed by cutting the recess region 160.

The upper bonding pad 182 may be disposed on the partition wall 180. The upper bonding pad 182 may perform eutectic bonding. The upper bonding pad 182 may be Au, In, Cu, Sn, or an alloy thereof.

The getter 170 may be disposed in the recessed cavity region 150 and may be disposed around the lower pattern 140. The getter 170 may be a metal or a metal alloy. The getter 170 may include at least one of Ti, Zr, Fe, Co, Al, and V. The getter 170 may maintain a vacuum state by adsorbing moisture or impurities.

The cut part 184 is a part where the upper substrate 120 is cut. The cut portion 184 may be disposed in the recess region 160 and may expose the external connection pad 117 disposed on the lower substrate 110. The substrate cutting may be performed using a sawing or laser dicing method.

The sensor substrate 102 may include a lower substrate 110; An infrared sensor 103 formed on the lower substrate and disposed to face the cavity region 150 of the upper substrate; And a lower bonding pad 116 arranged to surround the infrared sensor 103 and aligned with the upper bonding pad 182. The upper substrate 120 and the lower substrate 110 are silicon substrates.

The lower substrate 110 may be a silicon substrate. The lower substrate 110 may include a readout integrated circuit (ROIC) for driving an infrared sensor. The read integrated circuit may be a CMOS. An insulating layer 111 is disposed on the lower substrate 110 on which the read integrated circuit is formed.

The insulating layer 111 may insulate the read integrated circuit and the infrared sensor 103 formed on the lower substrate 110 from each other. The insulating layer 111 may be a silicon oxide layer.

The lower bonding pad 116 may be disposed to surround the infrared sensor 103. The lower bonding pad 116 may be disposed at a position facing the upper bonding pad 182 and combined with the upper bonding pad 182 to seal the cavity 104. The lower bonding pad 116 may perform eutectic bonding. The lower bonding pad 116 may be Au, In, Cu, Sn, or an alloy thereof.

The external connection pad 117 is disposed outside the lower bonding pad 116 and may perform electrical connection with an external circuit. The external connection pad 117 may be Al, Cu, or an alloy thereof. The external connection pad 117 may include a protective layer on its surface. The protective layer may be Ti or TiN. The protective layer may function to prevent oxidation and diffusion of the external connection pad.

The infrared sensor 103 may include a metal pad 113 formed on an upper surface of the lower substrate 110 and electrically connected to a read integrated circuit; A reflective layer 112 formed on the upper surface of the lower substrate and reflecting an infrared band; An absorption plate 115 formed to be spaced apart from the reflective layer 112 and absorbing infrared rays to change resistance; And an anchor 118 formed on the metal pad 113 to support the absorber plate 115 and electrically connect the metal pad 113 and the absorber plate 115 to each other. The infrared sensor 103 may be a microbolometer. The infrared sensor 103 may include a plurality of unit cells arranged in a matrix form. Each unit cell can operate as one pixel. Each unit cell may have a rectangular structure. The absorber plate 115 is floating in the air and may be supported by the anchor 118 by a cantilever 119.

The metal pad 113 may be electrically connected to a read integrated circuit formed in the lower substrate 110. The metal pad 113 may include a metal layer made of a metal such as Al that is sequentially stacked and TiN as a protective layer.

The metal pad 113 may provide an electrical connection capable of detecting a change in resistance of the absorber plate 115 through the anchor 118.

The reflective layer 112 may be disposed to be spaced apart from the absorber plate 115, and reflect infrared rays transmitted through the absorber plate 115 to be provided to the absorber plate 115 again. The reflective layer 112 may be formed of aluminum having a thickness greater than or equal to a skin depth.

The protective layer 112a is disposed on the reflective layer 112 in alignment with the reflective layer 112, and oxidation of the reflective layer 112 may be prevented. The protective layer 112a may be a conductive material and may be made of TiN. The thickness of the protective layer 112a may be sufficiently smaller than the thickness of the reflective layer 112.

The absorption plate 115 may be lifted and spaced apart from the reflective layer 112 and the protective film 112a by a predetermined distance d or more. The absorption plate 115 may absorb infrared rays incident from the outside or absorb infrared rays reflected from the reflective layer 112. The distance d between the absorption plate 115 and the reflective layer 112 may be 1/4 of the wavelength of infrared rays to be reflected.

The absorption plate 115 may include a first insulating layer 115a, an absorbing layer 115b, a resistance layer 115c, a second insulating layer 115d, and an anti-reflective pattern 115e sequentially stacked in a square plate shape. I can.

The first insulating layer 115a transmits an infrared band, is an insulator, and may be a silicon nitride film.

The temperature of the absorption layer 115b increases as it absorbs infrared rays. The absorbing layer 115b absorbs infrared rays well, and may be a metal material having high thermal conductivity. The absorption layer 115b may be a Ti, TiN, or NiCr alloy. The absorption layer 115b may be divided in half within the unit cell. Accordingly, the resistance layer 115c buried between the absorbing layers separated from each other may have a resistance change depending on the temperature.

The resistive layer 115c is a layer whose resistance changes according to temperature, and the resistive layer 115c may be amorphous silicon, single crystal silicon, vananium oxide, or silicon-germanium.

The second insulating layer 115d may protect and insulate the absorbing layer 115c and transmit infrared rays. The second insulating layer 115d may be a silicon nitride layer.

The non-reflective pattern 115e is formed on the second insulating layer 115d and may have a divided structure. The anti-reflective pattern 115e may be formed of a silicon oxide film or a silicon nitride film. When infrared rays are incident on the non-reflective pattern in a vacuum, the moth-eye structure may reduce a reflectance to provide an anti-reflection function. The anti-reflective pattern 115e may include a plurality of hemispheres arranged in a matrix form and in contact with each other. The radius of the hemisphere may be sufficiently smaller than the infrared wavelength. Preferably, the radius of the hemisphere may be sub micrometers to several micrometers (eg, 0.1 μm to 2 μm). The anti-reflective pattern 115e may provide a constant transmittance in a wavelength band of 7 μm to 14 μm. The antireflection pattern 115e may be disposed on the absorber plate 115 of the unit cell. An empty space between the absorbing plate 115 and the reflective layer 112 may be maintained in a vacuum state in a vacuum packaging process.

The anchor 118 is formed in a columnar shape on the upper portion of the metal pad 113 to separate the absorber plate 115 from the reflective layer 112 in a suspended state, and the absorber plate 115 Can support. The lower end of the anchor 118 may be buried in the second auxiliary insulating layer 111b. In addition, the anchor 118 electrically connects the metal pad 113 and the absorber plate 115. As the absorption layer 115b absorbs infrared rays, the temperature increases, and the resistance layer 115c receives energy from the absorption layer 115b and changes its resistance. The resistance layer 115c connected in series between the separated absorbing layers provides a resistance change. The change in resistance of the resistive layer 115c is read in a read driver circuit through the absorbing layer 115b, the anchor 118a, and the metal pad 113.

The anchor 118 may be formed by forming a contact hole and then filling the contact hole with a metal or a metal alloy. The anchor 118 may be formed of TiN. When the contact hole is not completely filled with an anchor forming material (eg, TiN), in the process of forming the absorbing layer, the resistive layer, and the second insulating layer, the absorbing layer 115b, the resistive layer 115c, And a material constituting the second insulating layer 115d may fill the rest of the contact hole.

The cantilever 119 may connect the absorber plate 115 to the anchor 118, respectively. The cantilever 119 has the same lamination structure as the absorber plate 115. In a unit cell, the number of anchors 118 is two, and when disposed at a pair of vertices of a square, the cantilever 119 connects one anchor and the separated vertices of the absorber to the corners of the absorber plate. Accordingly, the anchor 118 may extend in the direction of a vertex where the anchor 118 is not disposed.

2A and 2B show transmittance according to an embodiment of the present invention.

Referring to FIG. 2A, transmittances are displayed when infrared rays are incident on an upper surface of the upper substrate without a pattern in air and when infrared rays are incident on the upper pattern of the upper substrate in air. When infrared rays are incident on the unpatterned upper surface of the upper substrate in air (A), the transmittance increases to about 0.7 or more at a wavelength of 2 μm to 3 μm. Transmittance is constant at 0.7 level above 3 μm wavelength.

On the other hand, when the upper pattern 130 is formed on the upper surface of the upper substrate, when infrared rays are incident on the upper pattern 130 of the secondary substrate in the air (α), the transmittance is about 0.9 or more at 2 μm to 20 μm and is almost It is constant.

Referring to FIG. 2B, when infrared rays are incident into air (or vacuum) in the upper substrate (B), the transmittance increases to about 0.7 or more at a wavelength of 2 μm to 3 μm. The transmittance is constant at the level of 0.7 above 3 μm.

On the other hand, when the lower pattern 140 is formed on the lower surface of the upper substrate, when infrared rays enter the air from the lower pattern 140 of the upper substrate (β), the transmittance rapidly decreases below a specific threshold wavelength, Above the threshold wavelength, the transmittance gradually decreases. For example, when the lower pattern 140 includes a hemisphere having a moth structure, and the radius of the hemisphere is 0.3 μm, the threshold wavelength is about 3.5 μm. When the radius of the hemisphere is 0.6 μm, the threshold wavelength is about 7 μm. Compared with the case where there is no mothed structure, the transmittance is always high when the mothed structure is applied in the 3 μm to 20 μm wavelength range. In addition, the lower pattern 140 may operate as an infrared band pass filter.

When the upper substrate 120 has both the upper pattern 130 and the lower pattern 140, the total transmittance may be expressed as α X β.

3A to 3L are cross-sectional views illustrating a method of manufacturing a MEMS device according to an embodiment of the present invention.

3A to 3L, a method of manufacturing a MEMS device includes forming an upper pattern 130 having a Moth-eye structure on an upper surface of the upper substrate 120; Forming a preliminary lower pattern 140a aligned with the upper pattern 130 and having a Moth-eye structure and disposed on the lower surface of the upper substrate 120; The cavity region 150 including the lower pattern 140 to which the preliminary lower pattern 140a is transferred by etching using the etching masks 151 and 152 formed in the partition wall region surrounding the preliminary lower pattern 140a and the partition wall Simultaneously forming a preliminary recess region 160a surrounding the region; Forming a recess area 160 for additionally etching the preliminary recess area 160a; Forming an upper bonding pad 182 in the partition wall region and a getter 170 in the cavity region 150 so as not to overlap with the lower pattern 140; Bonding the lower bonding pad 116 of the lower substrate 120 with the infrared sensor 103 and the upper bonding pad 182 of the upper substrate in a vacuum state; And cutting the recessed region 160 of the upper substrate to expose the external connection pads 117 of the lower substrate. The upper substrate 120 and the lower substrate 110 are silicon substrates.

3A to 3C, an upper pattern 130 having a Moth-eye structure is formed on the upper surface of the upper substrate 120. Forming the upper pattern 130 having a Moth-eye structure on the upper surface of the upper substrate 120 is arranged in a matrix form using a photo-lithography process on the upper surface of the upper substrate and separated from each other. Forming a preliminary upper photoresist pattern 131a; Forming an upper photoresist pattern 131b having a moth-eye structure by performing a thermal reflow process on the upper substrate 120 on which the preliminary upper photoresist pattern 131a is formed; Forming an upper pattern 130 having a moth-eye structure on the upper surface of the upper substrate 120 by dry etching the upper photoresist pattern 131b with an etching mask; And removing the upper photoresist pattern 131b.

Again, referring to FIG. 3A, preliminary upper photoresist patterns 131a arranged in a matrix form and spaced apart from each other are formed on the upper surface of the upper substrate 120 using a photo-lithography process. The preliminary upper photoresist pattern 131a may be cylindrical masks arranged in a matrix form and spaced apart from each other.

Again, referring to FIG. 3B, the upper substrate on which the preliminary upper photoresist pattern 131a is formed is subjected to a thermal reflow process to form an upper photoresist pattern having a Moth-eye structure ( 131b) is formed. In the thermal reflow process, the upper photoresist pattern 131b having a Moth-eye structure is formed through a heat treatment process. The upper photoresist pattern 131b may be hemispheres disposed in contact with each other.

Referring again to FIG. 3C, the upper photoresist pattern 131b is then dry-etched with an etching mask to form an upper pattern 130 having a Moth-eye structure on the upper surface of the upper substrate 120. To form. Accordingly, the upper pattern 130 may have a shape of the upper photoresist pattern 131b. The dry etching may simultaneously etch the upper substrate and the upper photoresist pattern at a low selectivity. Accordingly, the dry etching may form a hemispherical moth structure.

Subsequently, the upper photoresist pattern 131b is removed.

3D to 3F, forming a preliminary lower pattern 140a aligned with the upper pattern 130 and disposed on the lower surface of the upper substrate 130 with a Moth-eye structure The steps of forming a preliminary lower photoresist pattern 141a arranged in a matrix form and spaced apart from each other by using a photo-lithography process on a lower surface of the upper substrate 120; Forming a lower photoresist pattern 141b having a Moth-eye structure by performing a thermal reflow process on the upper substrate on which the preliminary lower photoresist pattern 141a is formed; Forming a preliminary lower pattern 140a having a Moth-eye structure on the lower surface of the upper substrate by dry etching the lower photoresist pattern 141b with an etching mask; And removing the lower photoresist pattern 141b.

Again, referring to FIG. 3D, a preliminary lower photoresist pattern 141a arranged in a matrix form and spaced apart from each other is formed on the lower surface of the upper substrate 120 using a photo-lithography process. The preliminary lower photoresist pattern 141a may be arranged in a matrix form and may have a plurality of cylindrical shapes spaced apart from each other.

Referring again to FIG. 3E, the lower photoresist pattern 141b having a Moth-eye structure by performing a thermal reflow process on the upper substrate on which the preliminary lower photoresist pattern 141a is formed. Can be formed.

Again, referring to FIG. 3F, a preliminary lower pattern 140a having a Moth-eye structure may be formed on the lower surface of the upper substrate by dry etching the lower photoresist pattern 141b with an etching mask. . The preliminary lower pattern 140a has a moth structure, and may include a plurality of hemispheres or ellipsoids disposed in contact with each other. Subsequently, the lower photoresist pattern 141b may be removed. The preliminary lower pattern 140a may be entirely recessed later to form the lower pattern 140.

3G and 3H, including a lower pattern 140 to which the preliminary lower pattern 140a is transferred by etching using the etching masks 151 and 152 formed in the partition area surrounding the preliminary lower pattern 140a. The cavity region 150 and the preliminary recess region 160a surrounding the partition wall region may be simultaneously formed. The lower surface of the upper substrate 120 may be divided into a cavity region 150, a partition wall region surrounding the cavity region 150, and a preliminary recess region 160a surrounding the partition wall region.

Referring to FIG. 3G, a hard mask pattern 151 and a photoresist pattern 152 aligned with the hard mast pattern may be formed on the partition area. The hard mask pattern 151 may be an etching mask for performing dry etching of several tens of micrometers to several hundreds of micrometers. The hard mask pattern 151 may be a silicon oxide film or a silicon nitride film.

Referring to FIG. 3H, when dry etching is performed, the partition wall region is not etched, and the preliminary recess region 160a and the cavity region 150 may be etched to a level of about 100 micrometers. In addition, the preliminary lower pattern 140a may form the lower pattern 140 while maintaining its shape through the dry etching.

After performing the dry etching, the photoresist pattern 152 and the hard mask 151 may be removed.

Referring to FIG. 3I, a recess region 160 for additionally etching the preliminary recess region 160a may be formed. In order to form the recess region 160, an etching mask 161 may be formed to cover the partition wall region and the cavity region. The preliminary recess region 160a may be etched to a level of about 100 micrometers using the etching mask 161.

3J to 3L, a getter 170 is formed on the partition wall 180 of the partition wall region so as not to overlap with the lower pattern 140 in the upper bonding pad 182 and the cavity region 150. .

Again, referring to FIG. 3J, after forming a deposition mask 181 exposing the barrier rib region, an upper bonding pad 182 may be deposited to form the formation. Subsequently, the deposition mask 181 may be removed through a lift-off process.

Again, referring to FIGS. 3K and 3L, a deposition film 171 exposing a portion of the cavity region 150 is attached to the lower surface of the upper substrate 120. The deposition film 171 may be a dry film photoresist (DFR) or a shadow mask. The deposition film 171 may be floating without contacting the lower pattern 140. Subsequently, the getter 170 may be deposited by an evaporation deposition method or a sputtering deposition method. Subsequently, the deposition film 171 may be removed.

Referring again to FIG. 1A, the lower bonding pad 116 of the lower substrate 110 including the infrared sensor 103 and the upper bonding pad 182 of the upper substrate 120 are bonded in a vacuum state. Bonding of the lower bonding pad 116 of the lower substrate 110 and the upper bonding pad 182 of the upper substrate 120 may be Utetic bonding.

Subsequently, the recess region 160 of the upper substrate 120 is cut to expose the external connection pad 117 of the lower substrate. Accordingly, when the recess region 160 is cut, the cut portion 184 is formed. The cut of the recess region 160 of the upper substrate may be performed by a diamond sawing process.

Subsequently, the bonded upper substrate 120 and the lower substrate 110 are cut into individual MEMS devices by a diamond sawing process again.

4A is a perspective view illustrating a sensor substrate including an infrared sensor according to an embodiment of the present invention.

4B is a cross-sectional view taken along line A-A' of FIG. 4A.

4A and 4B, the sensor substrate 102 includes a lower substrate 110; An infrared sensor 103 formed on the lower substrate 110 and disposed to face the cavity region 150 of the upper substrate 120; And a lower bonding pad 116 arranged to surround the infrared sensor 103 and aligned with the upper bonding pad 182.

The lower substrate 110 may be a silicon substrate. The lower substrate 110 may include a readout integrated circuit (ROIC) for driving an infrared sensor. The read integrated circuit may be a CMOS. An insulating layer 111 is disposed on the lower substrate 110 on which the read integrated circuit is formed.

The insulating layer 111 may insulate the read integrated circuit and the infrared sensor 103 formed on the lower substrate from each other. The insulating layer 111 may be a silicon oxide layer as an interlayer insulating layer.

The lower bonding pad 116 may be disposed to surround the infrared sensor 103. The lower bonding pad 116 may be disposed at a position facing the upper bonding pad 182 and combined with the upper bonding pad 182 to seal the cavity 104. The lower bonding pad 116 may perform eutectic bonding. The lower bonding pad 116 may be Au, In, Cu, Sn, or an alloy thereof.

The external connection pad 117 is disposed outside the lower bonding pad 116 and may perform electrical connection with an external circuit. The external connection pad 117 may be Al, Cu, or an alloy thereof. The external connection pad 117 may include a protective layer on its surface. The protective layer may be TiN. The protective layer may function to prevent oxidation and diffusion of the external connection pad.

The infrared sensor 103 may include a metal pad 113 formed on an upper surface of the lower substrate 110 and electrically connected to a read integrated circuit; A reflective layer 112 formed on the upper surface of the lower substrate and reflecting an infrared band; An absorption plate 115 formed to be spaced apart from the top of the reflective layer 112 and to change resistance by absorbing infrared rays; And formed on the metal pad 113 to support the absorption plate 115 and to the metal pad ( 113) and an anchor 118 electrically connecting the absorption plate 115. The infrared sensor 103 may be a microbolometer, and the infrared sensor 103 is in a matrix form. Each unit cell may operate as a single pixel Each unit cell may have a rectangular structure The absorber plate 115 is floating in the air and a cantilever. It may be supported on the anchor 118 by a cantilever, 119.

The metal pad 113 may be electrically connected to a read integrated circuit formed in the lower substrate 110. The metal pad 113 may include a metal layer made of a metal such as Al that is sequentially stacked and TiN as a protective layer.

The metal pad 113 may provide an electrical connection capable of detecting a change in resistance of the absorber plate 115 through the anchor 118.

The reflective layer 112 may reflect infrared rays transmitted through the absorbing plate 115. The reflective layer 112 may be formed of aluminum having a thickness greater than or equal to a skin depth.

The protective layer 112a is disposed on the reflective layer 112 in alignment with the reflective layer, and oxidation of the reflective layer 112 may be prevented. The protective layer 112a may be a conductive material and may be made of TiN.

The absorbing plate 115 may be spaced apart from the reflective layer 112 and the protective layer 112a by a predetermined distance d or more. The absorbing plate 115 may absorb infrared rays incident from the outside or absorb infrared rays reflected from the reflective layer 112. The distance between the absorbing plate 115 and the reflective layer 112 may be 1/4 of an infrared wavelength to be reflected.

The absorber 115 may include a first insulating layer 115a, an absorbing layer 115b, a resistance layer 115c, a second insulating layer 115d, and an anti-reflective pattern 115e sequentially stacked in a square plate shape. have. The first insulating layer 115a transmits an infrared band, is an insulator, and may be a silicon nitride film.

The temperature of the absorption layer 115b increases as it absorbs infrared rays. The absorbing layer 115b absorbs infrared rays well, and may be a metal material having high thermal conductivity. The absorption layer 115b may be a Ti, TiN, or NiCr alloy. The absorption layer 115b may be divided in half within the unit cell. Accordingly, the resistance layer 115c buried between the absorbing layers separated from each other may have a resistance change depending on the temperature.

The resistive layer 115c is a layer whose resistance changes according to temperature, and the resistive layer 115c may be amorphous silicon, single crystal silicon, or silicon-germanium.

The second insulating layer 115d may protect and insulate the absorbing layer 115c and transmit infrared rays. The second insulating layer 115d may be a silicon nitride layer.

The non-reflective pattern 115e is formed on the second insulating layer 115d and may have a divided structure. The anti-reflective pattern 115e may be formed of a silicon oxide film or a silicon nitride film. When infrared rays are incident on the non-reflective pattern in a vacuum, the moth-eye structure may reduce a reflectance to provide an anti-reflection function. The anti-reflective pattern 115e may include a plurality of hemispheres arranged in a matrix form and in contact with each other. The radius of the hemisphere may be sufficiently smaller than the infrared wavelength. Preferably, the radius of the hemisphere is several microns from a submicrometer wavelength. The anti-reflection pattern may provide a constant transmittance in a wavelength band of 7 μm to 14 μm. The non-reflective pattern 115e may be disposed on the absorber plate 115 of the unit cell. An empty space between the absorbing plate 115 and the reflective layer 112 may be maintained in a vacuum state in a vacuum packaging process.

The anchor 118 is formed in a columnar shape on the upper portion of the metal pad 113, and the absorber plate 115 is spaced apart from the reflective layer 112 at a predetermined distance, and may support the absorber plate 115. . In addition, the anchor 118 electrically connects the metal pad 113 and the absorber plate 115. The temperature of the absorbing layer 115b increases as it absorbs infrared rays, and the resistance layer 115c receives energy from the absorbing layer and changes its resistance. The resistance layer 115c connected in series between the separated absorbing layers provides a resistance change. The change in resistance of the resistive layer is read in a read driver circuit through the absorbing layer, anchor, and metal pad.

The anchor 118 may be formed by forming a contact hole and then filling the contact hole with a metal or a metal alloy. The anchor 118 may be formed of TiN. When the contact hole is not completely filled with an anchor forming material (eg, TiN), in the process of forming the absorbing layer, the resistive layer, and the second insulating layer, the absorbing layer 118b, the resistive layer 118c, And a material constituting the second insulating layer 118d may fill the rest of the contact hole.

The cantilever 119 may connect the absorber plate 115 to the anchor, respectively. The cantilever has the same lamination structure as the absorption plate. In a unit cell, when there are two anchors and are arranged at a pair of vertices of a square, the cantilever 119 is the absorber plate 115 to connect the vertices of the one anchor 118 and the absorber plate 115. ) May extend in the direction of a vertex in which the anchor is not disposed.

5A to 5H are cross-sectional views illustrating a method of manufacturing a sensor substrate according to an embodiment of the present invention.

Referring to FIG. 5A, a read integrated circuit is formed on the lower substrate 110. An insulating layer 111 is formed as an interlayer insulating film on the lower substrate on which the read integrated circuit is formed. The insulating layer 111 may be a silicon oxide layer.

The reflective layer 112 and the metal pad 113 may be simultaneously formed on the insulating layer. The reflective layer and the metal pad may include an adhesive layer, a conductive layer, and a protective layer sequentially stacked. The adhesive layer may be Ti. The conductive layer may be aluminum, copper, or an alloy thereof. The protective layer 112a may be Ti/TiN. The reflective layer 112 and the metal pad 113 may be patterned through a photolithography process.

5B, after the reflective layer 112 and the metal pad 113 are patterned, a first auxiliary insulating layer 111a is deposited on the lower substrate 111 to form the reflective layer 112 and the metal pad. (113) can be covered. After the first auxiliary insulating layer 111a is planarized through a planarization process, the protective layer 112a may be exposed through an etching process without a mask.

Referring to FIG. 5C, a second auxiliary insulating layer 11b may be formed to cover the reflective layer 112 and the metal pad 113. Subsequently, patterning may be performed to expose the reflective layer 112 and the metal pad 113 through a photolithography process.

Referring to FIG. 5D, a sacrificial layer 219 may be deposited on the exposed reflective layer 112 and protective layer 112a. The sacrificial layer 219 is removed later. The sacrificial layer 219 may be an amorphous carbon layer or polyimide. The thickness of the sacrificial layer 219 may be several micrometers to tens of micrometers. A first insulating layer 115a may be deposited on the sacrificial layer 219. The first insulating layer 115a may be a silicon nitride layer.

A contact hole 218 for forming an anchor 118 may be formed on the metal pad 113 by patterning the first insulating layer 115a. The contact hole 218 may penetrate the first insulating layer 115a and the sacrificial layer 219 to expose the metal pad 113.

5E, a conductive material constituting the anchor 118 may be deposited. The anchor 118 may be TiN or Ti/TiN/W. After the conductive material is deposited, the conductive material may be patterned while leaving the contact plug filling the contact hole 218 to form the anchor 118.

Referring to FIG. 5F, the absorbing layer 115b may be formed to cover the anchor 118 and the first insulating layer 115a. The absorption layer 115b may be patterned to be separated into two in a unit cell. The absorption layer 115b may be TiN.

Referring to FIG. 5G, a resistive layer 115c, a second insulating layer 115d, and an anti-reflective pattern layer are sequentially formed on the absorbing layer 115b. The non-reflective pattern layer may be patterned to form the non-reflective pattern 115e. The anti-reflection pattern 115e may include a moth eye structure. The method of forming the non-reflective pattern 115e may be the same as that of the upper pattern or the lower pattern. The inside of the anchor 118 may be filled with an absorbing layer 115b, a resistive layer 115c, and a second insulating layer 115d. Accordingly, the anchor 118 may include an absorbing layer 115b, a resistive layer 115c, and a second insulating layer 115d.

The first insulating layer 115a, the absorbing layer 115b, the resistive layer 115c, the second insulating layer 115d, and the anti-reflective pattern 115e are etched through a photolithography process to form the sacrificial layer ( The 219 is exposed, and the absorber plate 115 is formed.

5H, the sacrificial layer 219 is removed through dry etching or wet etching.

* In the above, the present invention has been illustrated and described with respect to certain preferred embodiments, but the present invention is not limited to these embodiments, and the present invention claimed in the claims by a person of ordinary skill in the art to which the present invention pertains. It includes all of the various types of embodiments that can be implemented within the scope of the technical concept of.

100: MEMS device
101: cap substrate
102: sensor board
110: lower substrate
120: upper substrate
130: upper pattern
140: lower pattern
150: cavity
160: recess area
180: bulkhead

Claims (6)

An upper substrate;
An upper pattern having a Moth-eye structure formed on an upper surface of the upper substrate;
A lower pattern having a moth-eye structure disposed to face the upper pattern and formed in a cavity region recessed from a lower surface of the upper substrate;
A getter disposed around the lower pattern and disposed within the cavity area;
A partition wall protruding from the lower surface of the upper substrate than the cavity region and having the same structure and material as that of the upper substrate and disposed to surround the cavity region;
A cut portion recessed from a lower surface of the upper substrate than an arrangement plane of the cavity region and disposed to surround the partition wall;
An upper bonding pad disposed on a lower surface of the partition wall;
A lower substrate;
An infrared sensor disposed to face the cavity area of the upper substrate; And
Including; a lower bonding pad arranged to surround the infrared sensor and aligned with the upper bonding pad,
The upper substrate and the lower substrate are silicon substrates,
The infrared sensor is:
A metal pad formed on an upper surface of the lower substrate and electrically connected to a detection circuit;
A reflective layer formed on the upper surface of the lower substrate and reflecting an infrared band;
An absorption plate that is formed to be spaced apart from the top of the reflective layer and absorbs infrared rays to change resistance; And
An anchor formed on the metal pad to support the absorber plate and electrically connect the metal pad to the absorber plate,
The absorber plate includes a first insulating layer, an absorbing layer, a resistance layer, and a second insulating layer sequentially stacked,
The absorption layer is Ti, TiN, or NiCr,
The absorbing layer is divided in half within the unit cell,
The lower pattern of the Moth-eye structure and the upper pattern of the Moth-eye structure operate as a band pass filter in a wavelength region of far infrared rays. The method of claim 1,
The MEMS device, wherein the Moth-eye structure of the lower pattern is a plurality of hemispheres disposed in contact with each other. The method of claim 2,
The MEMS device, characterized in that the radius of curvature of the hemisphere of the lower pattern is sub-micrometer to several micrometers, and the hemispheres of the lower pattern are aligned with the hemispheres of the upper pattern. The method of claim 1,
The MEMS device, characterized in that the Moth-eye structure of the lower pattern has the shape of a plurality of cut ellipsoids arranged in contact with each other. The method of claim 1,
MEMS device, characterized in that the wavelength range of the far infrared rays is 7um ~ 14um. The method of claim 1,
Further comprising a non-reflective pattern of a mothed structure stacked on the second insulating layer,
The MEMS device, wherein the anti-reflection pattern is a silicon oxide film or a silicon nitride film.

Images