JP2016022550A - Semiconductor device and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device having an easy manufacturing process and a hollow sealing structure of a high degree of vacuum, and a manufacturing method of the device.SOLUTION: A semiconductor device comprises: a protective film 2 formed on one principal surface of a substrate 1; a space part 5 formed between the protective film 2 and the substrate 1; a sensor part arranged in the space part 5 and having a portion spaced from the substrate 1 and the protective film 2; a through hole 6 extending from the upper face of the protecting film 2 to the space part 5 from the substrate 1 and the protective film 2; and a sealing film 3 formed over the protective film 2 for sealing over the through hole 6. The space part 5 is in an evacuated pressure state, and the film thickness of the sealing film 3 over the through hole 6 is smaller than the film thickness of the sealing film 3 over the protective film 2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a semiconductor device and a manufacturing method thereof, and more particularly to a semiconductor device having a cavity sealed in a reduced pressure state and a manufacturing method thereof.

  2. Description of the Related Art In recent years, a device in which a micro electro mechanical system (hereinafter referred to as “MEMS”) consisting of a micron-sized mechanical structure and an electronic circuit is integrated on a single substrate is small and highly functional with excellent energy saving. As a high value-added device, it is attracting attention in various industrial fields such as information communication, medical care, and automobiles.

  Some of these MEMS devices require sealing under a very low pressure environment (so-called vacuum sealing).

  For example, an uncooled infrared sensor is a device that converts heat generated by absorption of collected infrared light into an electrical signal. To increase detection sensitivity, it is important to improve heat insulation between the infrared detector and the outside. It becomes. Specifically, it is desirable to seal the infrared sensor unit with as low a pressure as possible in order to prevent heat generated in the infrared detection unit from being dissipated by gas existing around the sensor unit.

  In addition, in inertial sensors and MEMS resonators equipped with minute driving parts, the operation is attenuated by the damping effect when gas is present in the atmosphere around the sensor parts. Is required.

  Therefore, as a method for realizing such vacuum sealing, for example, a bonding technique such as anodic bonding, direct bonding, eutectic bonding, or bonding of a cover wafer for sealing on a wafer on which a sensor is formed is performed. The method of sealing by sticking together in a reduced-pressure atmosphere is used.

  However, such a sealing method requires a separate process for bonding the cover wafer and the wafer on which the sensor portion is formed, since it is necessary to separately produce a cover wafer. In particular, there is a problem that the manufacturing cost becomes high.

  In order to solve this problem, a sacrificial film is formed around the sensor portion formed on the substrate, a film serving as a cover is formed on the sacrificial film, and a through hole is formed in the sacrificial film. A space portion is formed by removing the sacrificial film through the hole, and finally the through-hole is closed by a coating film formed by a low pressure chemical vapor deposition (hereinafter referred to as LPCVD) method. A method for sealing the part has been proposed. By using this manufacturing method, there is an effect that sealing can be performed in a reduced pressure state similar to the LPCVD atmosphere when forming the coating film (for example, Patent Document 1).

  Hereinafter, the semiconductor device disclosed in Patent Document 1 will be described with reference to a schematic cross-sectional view shown in FIG.

  As shown in FIG. 6, in a conventional semiconductor device, a sensor unit 40 made of polysilicon is provided on one surface side of a substrate 10 made of silicon. A protective film 20 made of polysilicon and a sealing film 30 made of polysilicon are provided so as to cover the sensor unit 40. The sensor unit 40, the protective film 20 and the substrate 10 are separated by the space 50, and the space 50 is kept in a reduced pressure state.

  Next, a method of manufacturing the conventional semiconductor device shown in FIG. 6 will be described with reference to a sectional process diagram shown in FIG.

  As shown in FIG. 7A, after forming the first sacrificial film 80a and the sensor unit 40 including the vibrator on one surface side of the substrate 10, the second sacrificial film 80b is formed around the sensor unit 40. Then, a protective film 20 serving as a cover is deposited on the second sacrificial film 80b.

  Next, as shown in FIG. 7B, a predetermined region of the protective film 20 is etched to form a through hole 60 that reaches the second sacrificial film 80b.

  Next, as shown in FIG. 7C, an etchant is introduced through the through hole 60, and the first sacrificial film 80a and the second sacrificial film 80b are selectively dissolved and removed, so that the space 50 is formed. Form.

  Next, as illustrated in FIG. 7D, the LPCVD method is used to form a sealing film 30 made of polysilicon on the protective film 20 to close the through hole 60 and seal the space 50. To do. As a result, the space 50 can be sealed under reduced pressure at the degree of vacuum during LPCVD used when the sealing film 30 is formed.

US Pat. No. 5,188,883

  However, in the method disclosed in Patent Document 1, since the degree of vacuum of the space 50 is determined by the atmospheric pressure during LPCVD (usually 13.3 Pa or higher), the space is vacuumed below the atmospheric pressure during LPCVD. Difficult to measure.

  Therefore, when the sensor unit is an infrared sensor, there is a problem that heat insulation from the surroundings is insufficient and the detection sensitivity is not sufficiently increased. Further, when the sensor unit is an inertial sensor or a MEMS resonator, there arises a problem that the operation attenuation due to the damping effect cannot be sufficiently suppressed.

  Therefore, in view of the above problems, the present invention achieves a hollow sealing structure with an easy manufacturing process and a high degree of vacuum, and a semiconductor device capable of suppressing the occurrence of problems such as a decrease in sensitivity of the sensor unit and operational attenuation, and its An object is to provide a manufacturing method.

  In order to solve the above problems, a semiconductor device of the present invention includes a protective film formed on one main surface of a substrate, a space formed between the protective film and the substrate, a substrate disposed in the space, And a sensor part having a portion spaced from the protective film, a through hole reaching the space part from the upper surface of the protective film, and a sealing film that is formed on the protective film and seals the through hole. The part is in a reduced pressure state, and the film thickness of the sealing film on the through hole is smaller than the film thickness of the sealing film on the protective film.

  The semiconductor device of the present invention further includes a reinforcing film formed on the protective film in contact with the outer peripheral portion of the sealing film and having an opening on the sealing film, and the Young's modulus of the material constituting the reinforcing film is The Young's modulus of the material constituting the sealing film is larger.

  In the semiconductor device of the present invention, the pressure in the space is preferably less than 13.3 Pa.

  In the semiconductor device of the present invention, the sealing film preferably includes at least one material of aluminum, copper, and germanium.

  In the semiconductor device of the present invention, it is preferable that the sealing film and the through hole are formed at a position away from the sensor portion by a predetermined distance in plan view.

  In the semiconductor device of the present invention, it is preferable that the outer periphery of the sealing film and the outer periphery of the through hole are separated by 10 μm or more at the shortest distance.

  In the semiconductor device of the present invention, the diameter of the through hole is preferably 1 to 5 μm.

  In the semiconductor device of the present invention, the sensor unit preferably includes any one of an infrared sensor, an inertial sensor, and a resonator.

  In the semiconductor device of the present invention, it is preferable that an electrode pad electrically connected to the sensor portion is provided on the protective film, and the electrode pad and the sealing film are made of the same material with the same film thickness.

  According to another aspect of the present invention, there is provided a method for manufacturing a semiconductor device, the step of forming a first sacrificial film at a predetermined position on one main surface of a substrate, the step of forming a sensor portion on the first sacrificial film, Forming a second sacrificial film on the first sacrificial film so as to cover the portion, and forming a protective film on the substrate so as to cover the first sacrificial film and the second sacrificial layer; A step of forming a sealing film at a predetermined position on the protective film, and a through hole that penetrates the sealing film and the protective film and reaches the second sacrificial film at a predetermined position of the sealing film. After the steps, the step of introducing the etchant from the through hole to remove the second sacrificial film and the first sacrificial film, forming a space between the protective film and the substrate, and the step of forming the space And heating the substrate in a reduced-pressure atmosphere to close the through hole with a sealing film and sealing the space portion, and the space portion In the step of forming the sensor portion has a portion separated from the substrate and the protective film.

  In the method for manufacturing a semiconductor device of the present invention, after the step of forming the sealing film, a reinforcing film is formed on the protective film so as to be in contact with the outer peripheral portion of the sealing film and to have an opening on the sealing film. It is preferable to further include a step of forming, and to form a through hole in a portion exposed from the opening of the sealing film.

  According to the semiconductor device and the manufacturing method thereof of the present invention, it is possible to achieve a hollow sealing structure with an easy manufacturing process and a high degree of vacuum, and to suppress the reduction in sensitivity of the sensor unit, the operation attenuation, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the semiconductor device which concerns on the 1st Embodiment of this invention, (a) is a top view, (b) is principal part sectional drawing in an AA cross section. It is principal part sectional drawing which shows the manufacturing process of the semiconductor device which concerns on the 1st Embodiment of this invention. It is principal part sectional drawing which shows the manufacturing process of the semiconductor device which concerns on the 1st Embodiment of this invention. It is a figure which shows the semiconductor device which concerns on the 2nd Embodiment of this invention, (a) is a top view, (b) is principal part sectional drawing in an AA cross section. It is principal part sectional drawing which shows a part of manufacturing process of the semiconductor device which concerns on the 2nd Embodiment of this invention. It is principal part sectional drawing which shows the semiconductor device which concerns on a prior art. It is principal part sectional drawing which shows the manufacturing process of the semiconductor device which concerns on a prior art.

Embodiments of the present invention will be described below with reference to the drawings. In addition, this invention is not limited to the following embodiment. Moreover, in each embodiment, the description is abbreviate | omitted by attaching | subjecting the same code | symbol to the same component.
(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1A is a top view showing the semiconductor device 100 according to this embodiment. Moreover, FIG.1 (b) is principal part sectional drawing in the cross section along the AA shown in Fig.1 (a).

  As shown in FIG. 1, a semiconductor device 100 according to this embodiment includes a substrate 1, a protective film 2 provided on one surface side of the substrate 1, and a substrate 1 and a gap at a predetermined position on the substrate 1. The sensor unit 4 is formed. A space 5 is formed between the substrate 1 and the protective film 2 so as to surround the sensor portion 4. In the protective film 2, a through hole 6 that reaches the space 5 from the upper surface of the protective film 2 is formed. A sealing film 3 is formed on the protective film 2 so as to close the through hole 6. That is, the space 5 is sealed with the sealing film 3.

  Hereinafter, the structure of the semiconductor device 100 disclosed in FIG. 1 will be described in detail.

  The substrate 1 is a p-type single crystal silicon (Si) substrate having a (100) plane on one surface. Although not shown, an electronic circuit element such as a transistor may be formed on the substrate 1.

The protective film 2 formed on the substrate 1 may be a single layer or an insulating film such as a silicon oxide film (SiO ₂ ), a silicon nitride film (SiN), a silicon oxynitride film (SiON), or a silicon carbide film (SiC). It is formed by stacking. Although not shown, a multilayer wiring may be formed in the insulating film. The thickness of the protective film 2 is preferably 1 to 10 μm.

  At least one sensor unit 4 is formed between the substrate 1 and the protective film 2. The sensor unit 4 is supported by the substrate 1 in the form of a cantilever beam via the support unit 4 a, and portions other than the support unit 4 a are formed apart from the substrate 1 and the protective film 2. An output signal or the like of the sensor unit 4 is sent to the outside of the space unit 5 through the support unit 4a. In addition, the sensor part 4 may be supported by the substrate 1 in a cantilever shape with the support part 4a formed only on one side.

  As the sensor part 4, it can be set as the non-cooling type | mold infrared sensor with which it is desirable to ensure thermal insulation with the surrounding environment. The sensor unit 4 may be a device that desirably suppresses the attenuation of the movable unit due to the damping effect of the surrounding atmosphere, such as a MEMS resonator or an inertial sensor. The sensor unit 4 may be any device as long as it is desirable that the surroundings have a reduced pressure atmosphere.

  A space 5 is formed around the sensor unit 4. The space 5 is in a reduced pressure state, and the pressure is maintained at less than 13.3 Pa. Thereby, when the sensor part 4 is an infrared sensor, the heat insulation is improved. In the case where the sensor unit 4 is a device having a movable part, the attenuation of the movable part of the device due to the damping effect is suppressed. In addition, the pressure of the space part 5 is so preferable that it is low. That is, the pressure in the space 5 is desirably 10 Pa or less, and more desirably 1.0 Pa or less.

  At a predetermined position of the protective film 2, at least one through hole 6 that reaches the space portion 5 from the upper surface side of the protective film 2 is formed. The through-hole 6 is cylindrical, and the diameter of the cylinder is preferably 1 to 5 μm. If the diameter of the cylinder is smaller than 1 μm, an etchant described later cannot be supplied sufficiently. On the other hand, if the diameter of the cylinder is larger than 5 μm, the through-hole 6 of the sealing film 3 cannot be blocked by a heat treatment process described later. The shape of the through hole 6 may be any shape as long as the maximum width of the opening is 1 to 5 μm. That is, the through hole 6 may have a triangular prism shape or a quadrangular prism shape.

  A sealing film 3 is formed on the protective film 2 so as to close the through hole 6. Here, the sealing film 3 is formed only on the surface of the protective film 2 and the through hole 6, and is not formed on the inner wall of the through hole 6. As a material of the sealing film 3, a material such as a metal material having a high thermal expansion coefficient and easy to thermocompression is preferable. In this embodiment, aluminum (Al) is used as the material of the sealing film 3, but copper (Cu) or germanium (Ge) can also be used in addition, and a laminated film of these materials. May be.

  The thickness of the sealing film 3 is desirably 0.5 μm or more and 3 μm or less. As will be described later, the through hole 6 formed in the sealing film 3 is closed by thermal expansion of the sealing film 3 in the heat treatment step. Therefore, after the substrate returns to room temperature, the sealing film 3a on the through hole 6 is stretched and thinned. That is, the film thickness of the sealing film 3 on the through hole 6 is smaller than the film thickness of the sealing film 3 on the protective film 2. Further, in a plan view, it is desirable that the outer periphery of the sealing film 3 and the outer periphery of the through hole 6 are separated by 10 μm or more at the shortest distance. Thereby, the thermal expansion in the in-plane direction of the sealing film 3 can be sufficiently ensured, and the through-hole 6 formed in the sealing film 3 can be closed. That is, it is desirable that the shortest distance from the outer periphery of the sealing film 3 to the outer periphery of the through hole 6 is at least 10 μm.

  In the present embodiment, the sealing film 3 and the through-hole 6 are formed at positions separated from the sensor unit 4 by a certain distance in plan view. Thereby, the sensor part 4 can be made hard to receive the influence at the time of the through-hole 6 formation. Note that when the above-described influence is slight, the sealing film 3 and the through hole 6 may be formed immediately above the sensor unit 4 in plan view.

  Next, a method for manufacturing the semiconductor device 100 according to the present embodiment will be described with reference to FIGS. 2 (a) to 2 (c) and FIGS. 3 (a) to 3 (c).

First, as shown in FIG. 2A, a silicon oxide film (SiO ₂ ) having a thickness of about 1 μm is formed on one surface side of a substrate 1 made of silicon by chemical vapor deposition (hereinafter referred to as CVD). Then, the silicon oxide film is patterned into a predetermined shape by a photolithographic etching technique to form a first sacrificial film 8a. Thereafter, a conductive film made of polysilicon having a thickness of about 500 nm is formed on the first sacrificial film 8a by a CVD method or the like, and the conductive film is patterned into a predetermined shape by a photolithographic etching technique to form the sensor unit 4. To do. Note that the conductive film may be doped with an impurity such as boron, phosphorus, or arsenic by a method such as ion implantation or thermal diffusion.

  Next, a silicon oxide film (SiO 2) having a thickness of about 500 nm is formed on the entire surface of the substrate 1 including the sensor unit 4 and the first sacrificial film 8a by CVD or the like. The silicon oxide film is patterned into substantially the same shape as the first sacrificial film 8a using an etching technique. Thereby, as shown in FIG. 2B, a second sacrificial film 8b covering the first sacrificial film 8a and the sensor portion 4 is formed. In this way, the sacrificial film 8 covering the entire periphery of the sensor unit 4 is formed. Thereafter, a protective film 2 made of a silicon nitride film (SiN) having a thickness of about 2 μm is formed on the entire surface of one surface of the substrate 1 by CVD or the like. In addition to the silicon nitride film, an insulating film such as a silicon oxynitride film (SiON) or a silicon carbide film (SiC) that can be selectively etched with the sacrificial film 8 may be used as the material of the protective film 2. Further, after the protective film 2 is formed, a planarization process such as chemical mechanical polishing (hereinafter referred to as CMP) may be performed.

  Next, as shown in FIG. 2C, an aluminum (Al) film having a thickness of about 2 μm is formed on the entire surface of the substrate 1 by a physical vapor deposition (hereinafter referred to as PVD) method or the like. Then, the sealing film 3 is formed by patterning the aluminum film into a predetermined shape by a photolithographic etching technique. Here, as the material of the sealing film 3, for example, copper (Cu) or germanium (Ge) may be used in addition to aluminum (Al). When a metal material such as aluminum is used as the material of the sealing film 3, an electrode pad that is electrically connected to the sensor portion can be formed simultaneously with the step of forming the sealing film 3. Thereby, simplification of a manufacturing process is realizable. The electrode pad is formed of the same material as the sealing film 3 at a predetermined position on the protective film 2.

  Next, a photoresist (not shown) having an opening is formed above the sacrificial film 8, and a predetermined region of the sealing film 3 corresponding to the opening is selectively etched using the photoresist as a mask. Thereby, the upper surface of the protective film 2 corresponding to the opening is exposed. Further, the upper surface of the sacrificial film 8 corresponding to the opening is exposed by selectively etching the protective film 2 whose upper surface is exposed by changing the etching conditions. Thereafter, the photoresist is removed. In this way, as shown in FIG. 3A, the through hole 6 penetrating the sealing film 3 and the protective film 2 is formed. Here, an opening is previously formed in the photoresist so that the diameter of the through hole to be formed is 1 to 5 μm.

  Next, an etchant capable of selectively dissolving and removing only the sacrificial film 8 flows from the through-hole 6 and the sacrificial film 8 is selectively etched and removed. In this way, a space 5 is formed between the protective film 2 and the substrate 1 as shown in FIG. Here, a gas such as hydrofluoric acid gas can be used as the etchant.

  Next, the sealing film 3 is thermally expanded or reflowed by placing the substrate 1 under a reduced pressure with a high degree of vacuum of less than 13.3 Pa and applying a heat treatment at 450 ° C. for 30 minutes. Thereby, as shown in FIG.3 (c), the through-hole 6 formed in the sealing film 3 is completely plugged when the sealing film 3 extends | stretches by thermal expansion from the circumference | surroundings. Thereby, the space part 5 is sealed in a reduced pressure state having a high degree of vacuum of less than 13.3 Pa, which is the same as the atmospheric pressure. Here, since the sealing film 3 in which the through-hole 6 is closed by thermal expansion at a high temperature returns to the original volume when the temperature decreases, the sealing film 3 is pulled in the vicinity of the through-hole 6 of the protective film 2 and has a thin film thickness. Become. Note that the lower the atmospheric pressure during heat treatment, the better. That is, the atmospheric pressure during the heat treatment is desirably 10 Pa or less, and more desirably 1.0 Pa or less.

  As described above, in the present embodiment, heat treatment is performed in a high-vacuum pressure-reduced atmosphere to thermally expand or reflow the sealing film 3 made of metal, thereby sealing the space portion 5 in a high-vacuum pressure-reduced state. Can be stopped. In particular, by adjusting the degree of vacuum of the atmosphere in which heat treatment or reflow is performed, the degree of vacuum of the space 5 can be controlled to an arbitrary degree of vacuum (specifically, less than 13.3 Pa), so that the manufacturing process is easy. In addition, the semiconductor device 100 having a sealing structure with a high degree of vacuum can be realized.

In the prior art, since the sealing film 30 is formed by the CVD method after the through hole 60 is formed, the sealing film 30 may enter and accumulate in the space 50 through the through hole 60. Therefore, the sealing film 30 that has entered and deposited in the space 50 may destabilize the characteristics of the sensor unit or cause deterioration. On the other hand, in the present embodiment, the through hole 6 is formed after the sealing film 3 is formed, and the through hole 6 formed in the sealing film 3 is sealed by heat treatment or reflow. The sealing film 3 does not enter and deposit on the substrate. Therefore, it is possible to prevent the characteristics of the sensor unit from becoming unstable or deteriorating.
(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to FIGS.

  FIG. 4A is a plan view showing the semiconductor device 200 according to this embodiment. Moreover, FIG.4 (b) is principal part sectional drawing in the cross section along the AA shown in Fig.4 (a).

  A feature of the semiconductor device 200 of the present embodiment is that the configuration of the semiconductor device 100 of the first embodiment is formed on the protective film 2 in contact with the outer peripheral portion of the sealing film 3, and an opening is formed on the sealing film 3. The reinforcing film 7 further includes 7a. Other configurations are the same as those of the semiconductor device 100 of the first embodiment.

  Specifically, the reinforcing film 7 is formed on the protective film 2 so as to surround the entire outer peripheral portion of the sealing film 3, and the vicinity of the outer peripheral portion of the sealing film 3 is covered with the reinforcing film 7. Further, in the region on the through hole 6 of the sealing film 3, the reinforcing film 7 has an opening 7 a, and the sealing film 3 is exposed from the reinforcing film 7. In addition, the material constituting the reinforcing film 7 has a Young's modulus greater than that of the material constituting the sealing film 3. That is, the reinforcing film 7 has higher rigidity than the sealing film 3 and is not easily deformed.

  Accordingly, since the reinforcement film 7 formed in contact with the outer peripheral portion of the sealing film 3 suppresses deformation of the sealing film 3 in the outer direction, in the heat treatment step for performing sealing, the sealing film It is possible to suppress the thermal expansion of 3 in the outward direction. For this reason, the sealing film 3 thermally expands more in the inner direction in which the through holes 6 are formed in the heat treatment step.

  As a result, the space 5 can be sealed even under heat treatment conditions at a lower temperature than the configuration of the semiconductor device 100 of the first embodiment. Thereby, the stress applied to the sealing film 3 when the substrate is returned to room temperature can be reduced, and the reliability of the semiconductor device 200 can be improved by suppressing cracks and the like of the sealing film 3. Moreover, in the case of the heat treatment conditions similar to those of the first embodiment, the sealing film 3 can be reliably sealed, and the manufacturing yield of the semiconductor device 200 can be improved.

  Here, as a material constituting the reinforcing film 7, for example, a material such as a silicon nitride film (SiN) or a silicon carbide film (SiC) can be used. The Young's modulus of the material constituting the reinforcing film 7 is preferably at least twice that of the material constituting the sealing film 3. Thereby, the deformation | transformation to the outer side direction of the sealing film 3 can fully be suppressed.

  In plan view, it is desirable that the outer periphery of the opening 7a of the reinforcing film 7 and the outer periphery of the through hole 6 be separated by 10 μm or more at the shortest distance. Thereby, the thermal expansion in the in-plane direction of the sealing film 3 can be sufficiently ensured, and the through-hole 6 formed in the sealing film 3 can be closed.

  Next, a method for manufacturing the semiconductor device 200 according to the present embodiment will be described with reference to FIG. FIG. 5 is a view for explaining a step of forming the reinforcing film 7 in the method for manufacturing the semiconductor device 200 of the present embodiment.

  In the method for manufacturing the semiconductor device 200 according to the present embodiment, after the steps from FIGS. 2A to 2C shown in the method for manufacturing the semiconductor device 100 according to the first embodiment are performed, the step of forming the reinforcing film 7 is performed. I do.

  Specifically, a silicon nitride film (SiN) of about 2 μm is formed on the entire surface of the substrate 1 by a CVD method or the like, and a predetermined region on the sealing film 3 of the silicon nitride film is removed by a photolithographic etching technique. Opening 7a is formed. In this way, as shown in FIG. 5, the reinforcing film 7 that is in contact with the outer peripheral portion of the sealing film 3 and has the opening 7 a on the sealing film 3 can be formed.

  Here, as the material of the reinforcing film 7, in addition to the silicon nitride film (SiN), a material having an etching resistance to an etchant that selectively etches the sacrificial film 8, for example, a silicon carbide film (SiC) or the like is used. Can do. Note that the reinforcing film 7 may be formed simultaneously with a passivation film for protecting the semiconductor device 200 from moisture and the like entering from the outside.

  Thereafter, by performing the same steps as the manufacturing method shown in FIGS. 3A to 3C of the first embodiment, the semiconductor device 200 according to this embodiment shown in FIG. 4 can be manufactured.

  In the semiconductor device 200 according to this embodiment, the same effect as that of the first embodiment can be obtained. Further, as described above, the reinforcing film 7 formed in contact with the outer peripheral portion of the sealing film 3 allows the space portion even under heat treatment conditions at a lower temperature than the configuration of the semiconductor device 100 of the first embodiment. 5 can be sealed, and the reliability of the semiconductor device 200 can be improved by suppressing cracks and the like of the sealing film 3. Moreover, in the case of the heat treatment conditions similar to those of the first embodiment, the sealing film 3 can be reliably sealed, and the manufacturing yield of the semiconductor device 200 can be improved.

  Further, since the reinforcing film 7 can be formed simultaneously with a passivation film on an electrode pad generally used in the prior art, it is not necessary to add a film forming process for the reinforcing film 7 and the manufacturing process can be simplified. .

  As described above, according to the first and second embodiments of the present invention, heat treatment is performed in a reduced-pressure atmosphere with a high degree of vacuum, and the sealing film 3 is thermally expanded toward the center of the through hole 6. The space part 5 surrounding the sensor part 4 can be sealed in a reduced pressure state with a high degree of vacuum. Therefore, the degree of vacuum of the space portion 5 can be controlled by adjusting the degree of vacuum of the atmosphere in which the heat treatment is performed. As a result, unlike the prior art, the degree of vacuum in the space 50 is not limited to the minimum pressure required to deposit the sealing film 30 by LPCVD. Further, there is no need for special equipment for bonding a cover wafer for sealing in a high vacuum atmosphere.

  Therefore, according to the semiconductor device and the manufacturing method thereof according to the first and second embodiments of the present invention, a manufacturing process is easy and a hollow sealing structure with a high degree of vacuum is achieved, and the sensitivity of the sensor unit is reduced. Occurrence of operational attenuation or the like can be suppressed.

  In the first and second embodiments, the protective film 2 is formed in contact with the substrate 1, but another film may be inserted between the substrate 1 and the protective film 2. Even in that case, the space 5 is formed between the substrate 1 and the protective film 2.

  In the first and second embodiments, a silicon substrate is used as the substrate 1, but a glass substrate or the like may be used.

  INDUSTRIAL APPLICABILITY The semiconductor device and the manufacturing method thereof according to the present invention can realize a semiconductor device that has a reduced pressure sealing structure that is easy in manufacturing process and has a high degree of vacuum. In particular, an infrared sensor, an inertial sensor, and a MEMS The present invention is useful as a semiconductor device including a microelectromechanical system having a cavity sealed with a high degree of vacuum, such as a resonator, and a manufacturing method thereof.

DESCRIPTION OF SYMBOLS 1,10 Substrate 2,20 Protective film 3,30 Sealing film 4,40 Sensor part 5,50 Space part 6,60 Through hole 7 Reinforcing film 8 Sacrificial film 8a, 80a First sacrificial film 8b, 80b Second Sacrificial film

Claims (11)

A protective film formed on one main surface of the substrate;
A space formed between the protective film and the substrate;
A sensor unit disposed in the space and having a portion spaced from the substrate and the protective film;
A through hole reaching the space from the upper surface of the protective film;
A sealing film formed on the protective film and sealing the through-hole,
The space is in a reduced pressure state;
A film thickness of the sealing film on the through hole is smaller than a film thickness of the sealing film on the protective film. The semiconductor device according to claim 1,
Further comprising a reinforcing film formed on the protective film in contact with the outer periphery of the sealing film and having an opening on the sealing film;
The Young's modulus of the material constituting the reinforcing film is larger than the Young's modulus of the material constituting the sealing film. The semiconductor device according to claim 1 or 2,
The pressure in the space is less than 13.3 Pa. The semiconductor device according to any one of claims 1 to 3,
The sealing film includes a material of at least one of aluminum, copper, and germanium. The semiconductor device according to any one of claims 1 to 4,
The sealing film and the through hole are formed at positions separated from the sensor unit by a predetermined distance in plan view. The semiconductor device according to any one of claims 1 to 4,
The outer periphery of the sealing film and the outer periphery of the through hole are separated by 10 μm or more at the shortest distance. The semiconductor device according to any one of claims 1 to 6,
The diameter of the through hole is 1 to 5 μm. The semiconductor device according to any one of claims 1 to 7,
The sensor unit includes any one of an infrared sensor, an inertial sensor, and a resonator. The semiconductor device according to any one of claims 1 to 8,
An electrode pad electrically connected to the sensor unit is provided on the protective film,
The electrode pad and the sealing film are made of the same material with the same film thickness. Forming a first sacrificial film at a predetermined position on one main surface of the substrate;
Forming a sensor portion on the first sacrificial film;
Forming a second sacrificial film on the first sacrificial film so as to cover the sensor portion;
Forming a protective film on the substrate so as to cover the first sacrificial film and the second sacrificial layer;
Forming a sealing film at a predetermined position on the protective film;
Forming a through-hole that penetrates the sealing film and the protective film and reaches the second sacrificial film at a predetermined position of the sealing film;
Introducing an etchant from the through hole to remove the second sacrificial film and the first sacrificial film, and forming a space between the protective film and the substrate;
After the step of forming the space portion, the substrate is heated in a reduced-pressure atmosphere to close the through hole with the sealing film, and the space portion is sealed, and
In the step of forming the space part, the sensor part has a part spaced apart from the substrate and the protective film. In the manufacturing method of the semiconductor device according to claim 10,
After the step of forming the sealing film, further comprising the step of forming a reinforcing film on the protective film so as to contact the outer periphery of the sealing film and to have an opening on the sealing film,
A method of manufacturing a semiconductor device, wherein the through hole is formed in a portion exposed from the opening of the sealing film.

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