JP6183012B2 - Semiconductor package - Google Patents

Description

  The present invention relates to a semiconductor package including a MEMS (Micro Electro Mechanical System) device having a movable portion formed of silicon.

  Conventionally, an acceleration sensor, a MEMS mirror, a high-frequency switch, and the like are known as a MEMS device having a movable part formed of silicon.

  As described in Patent Document 1, in a semiconductor package including a MEMS device, the movable portion is housed in the housing space of the semiconductor package and protected from factors (for example, foreign matter) that hinder normal operation.

JP 2005-332957 A

  By the way, since the movable part made of silicon is repeatedly driven, there is a possibility of fatigue failure due to repeated load, and there is a need to grasp the fatigue life of the movable part.

  However, in the conventional semiconductor package described in Patent Document 1, the fatigue life of the movable part is not particularly taken into consideration.

  In view of the above problems, an object of the present invention is to grasp the fatigue life of a movable part formed of silicon as a material in a semiconductor package including a MEMS device.

  The invention disclosed herein employs the following technical means to achieve the above object. Note that the reference numerals in parentheses described in the claims and in this section indicate a corresponding relationship with specific means described in the embodiments described later as one aspect, and limit the technical scope of the invention. Not what you want.

One of the disclosed inventions is a MEMS device (52) having a movable part (52a) formed of silicon as a material;
An accommodating portion (56) provided in the internal space (56a) in which the gas is enclosed so as to accommodate at least a movable portion of the MEMS device;
A humidity sensor (54) for detecting the relative humidity in the internal space is provided in order to grasp the fatigue life of the movable portion made of silicon and contained in the internal space together with the movable portion .

Although details will be described later, as a result of intensive studies, the inventor has found that the fatigue index n that determines the difficulty of crack growth depends on the relative humidity around the movable part (52a).
In the present invention, the relative humidity in the internal space (56a) can be detected by the humidity sensor (54). Therefore, the fatigue life of the movable part (52a) can be grasped from the output of the humidity sensor (54).

  For example, even if the leak gradually progresses due to aging, and the relative humidity of the internal space (56a) changes, the fatigue life of the movable part (52a) can be grasped from the output of the humidity sensor (54). .

It is a perspective view which shows schematic structure of a test piece. It is sectional drawing which follows the II-II line of FIG. It is a figure which shows schematic structure of a test apparatus. It is a figure which shows the result of the fatigue test in 95% RH. It is a figure which shows the result of the fatigue test in 50% RH. It is a figure which shows the result of the fatigue test in 35% RH. It is a figure which shows the result of the fatigue test in 5% RH. It is a figure which shows the relationship between the repetition number N until the destruction in (sigma) / (sigma) ₀ = 0.9, and the cumulative failure probability F. FIG. It is a figure which shows the relationship between the repetition number N until the destruction in (sigma) / (sigma) ₀ = 0.8, and the cumulative failure probability F. FIG. It is a figure which shows the relationship between the repetition number N until the destruction in (sigma) / (sigma) ₀ = 0.7, and the cumulative failure probability F. FIG. It is a figure which shows the relationship between the relative humidity in 25 degreeC, and the fatigue index n. It is a figure which shows the relationship between the relative humidity in 95 degreeC, and the fatigue index n. It is a figure which shows the relationship between absolute humidity and the fatigue index n. It is a figure which shows schematic structure of the semiconductor package which concerns on 1st Embodiment. It is a block diagram which shows schematic structure of the semiconductor package which concerns on 2nd Embodiment. It is a figure which shows schematic structure of a semiconductor package. It is a block diagram which shows schematic structure of the semiconductor package which concerns on 4th Embodiment. It is a figure which shows schematic structure of a semiconductor package. It is a figure which shows schematic structure of the semiconductor package which concerns on 6th Embodiment. It is a figure which shows a 1st modification. It is a figure which shows a 2nd modification.

  First, before describing the embodiment of the present invention, the background of the inventor's creation of the present invention will be described.

  The inventor creates a test piece 10 shown in FIGS. 1 and 2 to evaluate the fatigue life of a movable part for a MEMS (Micro Electro Mechanical System) device having a movable part formed of silicon as a material, The initial fracture strength was evaluated by the test apparatus 30 shown in FIG.

(Test pieces)
When a test piece having a sidewall patterned and etched by lithography is used, variation in fatigue life, that is, variation in the number N of repetitions until destruction is large. Such a large variation is considered to be due to the large influence of the stress concentration factor resulting from the roughness of the processed surface of the side wall by etching.

  Therefore, in this test, as shown in FIGS. 1 and 2, a test piece 10 having a membrane structure having no etching surface was prepared. The test piece 10 includes a substrate 12 made of silicon, a mask 18 provided on one surface of the substrate 12, and a membrane 20 having a multilayer structure provided on the back surface opposite to the one surface of the substrate 12.

The substrate 12 includes a weight portion 14 and a frame portion 16 surrounding the weight portion 14 with a predetermined gap. On the other hand, the membrane 20 includes a silicon nitride film 22 (Si ₃ N ₄ ), a silicon oxide film 24 (SiO ₂ ), and a polycrystalline silicon film 26. Since Si ₃ N ₄ has a strength about four times that of polycrystalline silicon, having the silicon nitride film 22 allows the membrane 20 to be moved from the polycrystalline silicon film 26 side in a test in which the weight portion 14 is vibrated up and down. Can be destroyed. Further, the silicon nitride film 22 functions as an etching stopper when the weight portion 14 and the frame portion 16 are formed. By having the silicon oxide film 24 which is compressive stress, the resonance frequency can be controlled to 3 kHz or less which is the maximum frequency of the vibration tester 34.

A planar square substrate 12 having a thickness of 400 μm and a side of 20 mm was prepared, and a silicon oxide film (SIO ₂ ) having a thickness of 2 μm was formed as a mask 18 on one surface side of the substrate 12. Further, a silicon nitride film 22 having a thickness of 600 nm and an internal stress of tensile was formed on the surface opposite to the one surface of the substrate 12 by LP-CVD. Further, on the silicon nitride film 22, a silicon oxide film 24 having a thickness of 300 nm and an internal stress of compression of −200 MPa was formed by plasma CVD. Further, a polycrystalline silicon film 26 having a thickness of 250 nm and an internal stress of 100 MPa was formed on the silicon oxide film 24. This polycrystalline silicon film 26 was obtained by depositing amorphous silicon at about 540 ° C. by LP-CVD and then crystallizing it by performing heat treatment at 950 ° C. for 3 hours in a nitrogen atmosphere. .

  Then, the weight portion 14 and the frame portion 16 were formed by etching the substrate 12 using the mask 18 and using the silicon nitride film 22 as an etching stopper. The weight portion 14 is arranged in the center of the substrate 12 and has a cylindrical shape with a diameter of 12 mm. Further, the frame portion 16 has an annular shape with a constant width (2 mm), and the center of the inner peripheral end coincides with the center of the weight portion 14. Thereby, the minimum space | interval between the weight part 14 and the frame part 16 became 2 mm. Thus, by having the weight portion 14, the resonance frequency can be reduced. In the following description, the mask 18 located on the surface of the weight portion 14 is also a part of the weight portion 14, and the mask 18 located on the surface of the frame portion 16 is also a part of the frame portion 16.

(Test equipment)
The test apparatus 30 shown in FIG. 3 is configured to deform the membrane 20 having the weight portion 14 in the center in the direction perpendicular to the membrane 20 by resonance vibration caused by external excitation. 26 enables application of high stress leading to breakage and high cycle test in a short time.

  This test apparatus 30 accommodates the test piece 10 and provides a predetermined temperature and humidity environment, a constant temperature and humidity chamber 32, a vibration tester 34 that applies vibration to the test piece 10, and an acceleration for detecting relative displacement. A total 36 and a laser displacement meter 38 are provided. Further, the test apparatus 30 includes a controller 40 that controls the driving of the vibration tester 34 and a data logger 42 that collects output data of the accelerometer 36 and the laser displacement meter 38. The accelerometer 36 is built in the vibration tester 34.

  A vibration tester 34 and a laser displacement meter 38 in which an accelerometer 36 is built together with the above-described test piece 10 are arranged inside the constant temperature and humidity chamber 32, and the frame portion 16 of the test piece 10 comes into contact with the mask 18 side. The vibration tester 34 was fixed as described above. Based on the control signal output from the controller 40, the vibration tester 34 vibrates in the thickness direction of the substrate 12, and thereby vibrates the test piece 10 in the thickness direction, that is, the out-of-plane direction.

  At the time of resonance, the weight part 14 and the frame part 16 are displaced in opposite phases, whereby the membrane 20 is deformed. Further, in the polycrystalline silicon film 26 of the membrane 20, the maximum stress application point 20 a to which the maximum stress is applied by deformation is surrounded by the alternate long and short dash line in FIGS. 1 and 2. Near the center of each side of the plane square.

  In this test, the maximum stress (hereinafter referred to as applied stress) applied to the membrane 20 was calculated using FEM analysis based on the relative displacement of the weight portion 14 with respect to the frame portion 16. The displacement of the frame portion 16 was calculated by assuming a sine wave from the acceleration amplitude and frequency of the accelerometer 36, and the displacement of the weight portion 14 was measured by a laser displacement meter 38. These values were collected by the data logger 42 and converted to the maximum stress of the membrane 20 from the relative displacement.

  During the test, the displacement of the weight portion 14 and the displacement of the frame portion 16 are also fed back to the controller 40 to maintain a constant relative displacement.

(Test results)
First, a ramping stress test was performed in order to calculate the reference stress σ ₀ used in the fatigue test.

  In this ramping stress test, the vibration acceleration of the vibration tester 34 was made constant in an environment of 25 ° C. and 50% RH, and the vibration frequency was increased at a rate of 300 Hz to 10 Hz / s to approach the resonance frequency. The applied stress was calculated from the relative displacement at the moment when the membrane 20 (polycrystalline silicon film 26) was broken by vibration. This test was performed on 14 specimens 10. Although illustration is omitted, as the frequency increases, the relative displacement also increases. When the frequency is 1.5 kHz and the relative displacement is around 300 μm, the membrane 20 of each test piece 10 has been destroyed.

The calculation result of the applied stress was in good agreement with the Weibull distribution, and the reference stress σ ₀ was calculated by fitting the calculation result with the Weibull distribution function. Specifically, the applied stress at which the cumulative failure probability F of the Weibull distribution function is 63% is defined as the reference stress σ ₀ . The reference stress σ ₀ was 2.58 GPa. In addition, the Weibull coefficient m was 15.2, and the intensity variation was small.

Next, a fatigue test was performed using the reference stress σ ₀ .

In this fatigue test, fixing is performed at a predetermined vibration frequency so as to generate a relative displacement that generates a stress σ of 90%, 80%, and 70% of the reference stress σ ₀ under a predetermined temperature and humidity condition. The number N, that is, the fatigue life was calculated. The temperature was 25 ° C., and the humidity was 95% RH, 50% RH, 35% RH, and 5% RH. The maximum cycle of the fatigue test was 2 × 10 ⁹ . The result (SN plot) of a fatigue test is shown in FIGS.

As shown in FIGS. 4-7, the variation in fatigue life was reduced compared to a specimen having a conventional etched sidewall. In particular 95% RH as shown in FIG. 4, 50% RH as shown in FIG. 5, in 35% RH as shown in FIG. 6, the variation of the fatigue life is less than 10 ^2, than the conventional variation 10 ³ at the same temperature the humidity It was greatly reduced. The broken lines shown in FIGS. 5 to 7 indicate the maximum cycle of 2 × 10 ^9, and the arrows in the drawings indicate the results of the test piece 10 that was not broken in the cycle up to 2 × 10 ⁹ .

8 to 10 are diagrams in which the results of the fatigue test described above are summarized as a relationship between the number N of repetitions until failure and the cumulative failure probability F, that is, as a Weibull plot. 8 shows σ / σ ₀ = 0.9, FIG. 9 shows σ / σ ₀ = 0.8, and FIG. 10 shows σ / σ ₀ = 0.7. As a result, it was found that the lower the relative humidity, the greater the number N of repetitions until failure, that is, the longer the fatigue life.

Here, fatigue life is modeled by Weibull statistics and Paris law. Since silicon is a brittle material and its strength varies, the fracture strength follows Weibull statistics. Equation 1 represents a Weibull distribution function, where F is a cumulative failure probability, σ ₀ is a reference stress, σ is an applied stress, and m is a Weibull coefficient.

On the other hand, the crack growth rate v is defined as shown in Equation 2 by the Paris law expressing the crack growth due to repeated stress. In Equation 2, a dimension of a crack, N is the number of repetitions, C is a constant, n represents fatigue index, [Delta] K _I is the stress intensity factor, K _IC is the fracture toughness value. The crack growth rate v is shown as the amount of progress of the crack dimension a per one stress application.

Since ΔK _I / K _IC <1, the smaller the fatigue index n, the greater the crack growth rate v. Here, the stress diffusion coefficient ΔK _I at the crack tip is expressed by Equation 3. In Equation 3, β is a coefficient depending on the crack shape.

Substituting Equation 3 into Equation 2 yields Equation 4.

When Equation 4 is integrated from the initial crack size a _i to the critical crack size a _{c at} which fracture occurs, Equation 5 can be obtained. Formula 5 shows the initial crack size a _i when a constant stress σ is repeatedly applied N times, the crack size reaches _ac and breaks.

Here, the material strength has a strength variation modeled by Weibull statistics, which can be expressed as a variation in the initial crack size a _i . By substituting Equation 3 into Equation 1, as shown in Equation 6, the cumulative fracture probability F at an arbitrary crack size a that has developed due to repeated stress can be obtained with respect to the initial crack size a _i .

Then, by substituting Equation 5 into Equation 6, Equation 7 representing a fatigue failure probability model due to repeated stress can be obtained. In other words, the cumulative failure probability F can be shown using the fatigue index n.

  Fatigue index n at each relative humidity was calculated by fitting the Weibull plot of the fatigue test shown in FIGS. FIG. 11 shows the relationship between the relative humidity and the fatigue index n. FIG. 12 shows the relationship between the relative humidity and the fatigue index n obtained as a result of the fatigue test similarly performed at 95 ° C. Further, FIG. 13 shows the relationship between absolute humidity and fatigue index n at 25 ° C. and 95 ° C. As shown in FIG. 12, in the test at 95 ° C., 95% RH cannot be measured due to the limit of the measuring apparatus, and measurement was performed at 70% RH instead.

  As shown in FIGS. 11 and 12, it was found that the fatigue index n increases as the relative humidity decreases. On the other hand, as shown in FIG. 13, the relationship between absolute humidity and fatigue index n is discontinuous. Therefore, it became clear that the fatigue characteristics that govern the fatigue life depend on the relative humidity, not the absolute humidity. And it became clear that fatigue life prolongs, so that relative humidity is low. Furthermore, from FIG. 11 and FIG. 12, the change with respect to the relative humidity of the fatigue index n is large at 35% RH or less. That is, it was revealed that the fatigue life can be effectively extended when it is 35% RH or less.

  As a result of preparing the test piece 10 in which the thickness of the silicon oxide film 24 is changed to 390 nm and the thickness of the polycrystalline silicon film 26 to 500 nm, and performing the same test, the Weibull coefficient m is It was found that the value was almost constant regardless of the relative humidity, and varied depending on the film thickness. That is, it has been clarified that the Weibull coefficient m depends on the thickness of the polycrystalline silicon film 26.

  Thus, it became clear that the fatigue index n, that is, the fatigue life, depends on the relative humidity. The present invention is based on the above test results. Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each embodiment, common or related elements are given the same reference numerals.

(First embodiment)
First, a schematic configuration of the semiconductor package 50 according to the present embodiment will be described with reference to FIG.

  As shown in FIG. 14, the semiconductor package 50 includes a MEMS device 52, a humidity sensor 54, and a housing portion 56.

  The MEMS device 52 has a movable portion 52a formed using silicon as a material. As such a MEMS device 52, a sensor, an optical device, a high frequency device, a power generation device, a fluid / analysis device, or the like can be adopted. More specifically, there are an acceleration sensor, an angular velocity sensor, a pressure sensor, a MEMS mirror, a variable spectrometer (Fabry-Perot interferometer), an RF switch, a variable capacitor, and the like.

  In the present embodiment, as an example, a capacitance type acceleration sensor having a known structure formed using an SOI (Silicon On Insulator) substrate is employed, and the movable portion 52a includes a weight portion, a movable electrode, and the like. Yes.

  The humidity sensor 54 is accommodated in an internal space 56a described later, and detects the relative humidity of the internal space 56a. As such a humidity sensor 54, a known sensor such as a resistance humidity sensor or a capacitive humidity sensor can be employed. In the present embodiment, the humidity sensor 54 is provided as a separate chip from the MEMS device 52.

  The accommodating part 56 is provided in the internal space 56a in which gas is enclosed so that at least the movable part 52a of the MEMS device 52 and the humidity sensor 54 can be accommodated. In other words, the accommodating part 56 is provided so that the movable part 52a and the humidity sensor 54 may be held hollow.

  The entire MEMS device 52 may be accommodated in the internal space 56a, or only a part of the MEMS device 52 including the movable portion 52a may be accommodated. Moreover, the constituent material of the accommodating part 56 is not specifically limited. For example, a semiconductor substrate such as metal, ceramic, or silicon, glass, or resin can be employed.

  As an example, the housing portion 56 of the present embodiment includes a metal base 58 having a substantially flat plate shape and a metal cap 60 having a bottomed cylindrical shape, and the base 58 and the cap 60 are, for example, a resistor. It is welded and sealed. The closed space formed by the base 58 and the cap 60 is an internal space 56a, and the entire MEMS device 52 and the humidity sensor 54 are disposed in the internal space 56a. The internal space 56a is filled with a gas capable of measuring relative humidity. The gas whose relative humidity can be measured includes at least water vapor. Thus, if it is set as the structure which hold | maintains the MEMS device 52 hollow, the movable part 52a can be protected from a foreign material. Moreover, the drive environment of the movable part 52a can be stabilized.

  A MEMS device 52 and a humidity sensor 54 are fixed to the base 58. In addition, a terminal 62 for electrically connecting the MEMS device 52 and the humidity sensor 54 to the outside is attached to the base 58 by glass sealing or the like. A portion of the terminal 62 that protrudes from the base 58 to the internal space 56 a and the pads of the MEMS device 52 and the humidity sensor 54 are electrically connected via a bonding wire 64.

  The accommodating portion 56 in which the MEMS device 52 and the humidity sensor 54 are accommodated is disposed on one surface of the wiring board 66. The wiring board 66 is formed by arranging wirings 68 made of a conductive material on an electrically insulating base material. The terminal 62 is inserted into the insertion hole of the wiring board 66 (base material), and is electrically connected to the wiring 68 in this inserted state.

  A processing circuit unit 70 is mounted on the wiring board 66 at a position different from the housing unit 56. The processing circuit unit 70 is electrically connected to the MEMS device 52 and the humidity sensor 54 via the wiring 68. The processing circuit unit 70 includes a MEMS device driving circuit and an output processing circuit, a humidity sensor 54 driving circuit, and an output processing circuit such as temperature compensation. Note that the drive circuit and the output processing circuit can be configured on the same chip as the MEMS device 52 and the humidity sensor 54.

  Next, effects of the semiconductor package 50 according to the present embodiment will be described.

  In the present embodiment, the relative humidity in the internal space 56a can be detected by the humidity sensor 54 accommodated in the internal space 56a. As described above, the fatigue life of silicon depends on the relative humidity. Therefore, the fatigue life of the movable part 52 a in the MEMS device 52 can be grasped from the output of the humidity sensor 54.

  For example, even if the leak gradually progresses due to deterioration over time and the relative humidity of the internal space (56a) changes gradually, the fatigue life of the movable part 52a can be grasped from the output of the humidity sensor 54.

(Second Embodiment)
In the present embodiment, description of portions common to the semiconductor package 50 shown in the first embodiment is omitted.

  In this embodiment, as shown in FIG. 15, the semiconductor package 50 includes a heater 72 that generates heat when energized, and the heater 72 is provided so that the heat of the heater 72 is transmitted to the gas in the internal space 56a. It is characterized by. In the example shown in FIG. 15, a driving circuit for the heater 72 is formed in the processing circuit unit 70, and energization of the heater 72 is controlled by a driving signal output from the processing circuit unit 70.

  An example of the arrangement of the heaters 72 is shown in FIG. In FIG. 16, the heater 72 is fixed to the base 58 as a single element and is electrically connected to the processing circuit unit 70 via the terminal 62 and the wiring 68.

  Next, effects of the semiconductor package 50 according to the present embodiment will be described.

  In the present embodiment, the heater 72 can increase the temperature of the gas sealed in the internal space 56a. Relative humidity decreases with increasing temperature. Therefore, the relative humidity in the internal space 56 a can be lowered by the heat of the heater 72. In other words, the heat of the heater 72 can extend the fatigue life of the movable portion 52a and ensure a desired fatigue life.

  In addition, the fatigue life of the movable portion 52a can be grasped as described in the first embodiment while the temperature of the internal space 56a is changed by the heater 72. That is, it is possible to grasp the life while extending the fatigue life of the movable portion 52a.

  The energization pattern of the heater 72 is not particularly limited. For example, the constant current may be always energized, or on and off may be repeated at a predetermined cycle.

  Further, the arrangement of the heaters 72 is not limited to the example of FIG. The heater 72 can also be formed integrally with the MEMS device 52 and the humidity sensor 54 (in one chip). Further, a heater 72 may be disposed on the outer wall of the housing portion 56 so that the gas in the internal space 56 a can be warmed through the housing portion 56.

(Third embodiment)
In the present embodiment, the description of the parts common to the semiconductor package 50 shown in the second embodiment is omitted.

  The first feature of the present embodiment is that energization of the heater 72 is controlled based on the output of the humidity sensor 54 so that the relative humidity in the internal space 56a is equal to or lower than a predetermined relative humidity. Further, the second feature is that energization of the heater 72 is controlled so that the relative humidity is 35% RH or less. The configuration of the semiconductor package 50 is basically the same as that shown in FIGS.

The humidity sensor 54 outputs a substantially constant value regardless of the temperature by the temperature compensation circuit described above. That is, if the relative humidity is the same, a substantially constant value is output regardless of the temperature.
Therefore, the processing circuit unit 70 feedback-controls energization to the heater 72 so as to keep a predetermined relative humidity or less based on the relative humidity detected by the humidity sensor 54. In the present embodiment, energization to the heater 72 is controlled so as to keep 0% RH or more and 35% RH or less.

  Next, effects of the semiconductor package 50 according to the present embodiment will be described.

  In the present embodiment, the processing circuit unit 70 feedback-controls energization to the heater 72 so that the relative humidity in the internal space 56a is kept below a predetermined relative humidity. As described above, the fatigue index n increases as the relative humidity decreases. Therefore, if the heat of the heater 72 keeps the predetermined relative humidity or less, the fatigue life of the movable portion 52a can be extended.

  Further, even when the leak gradually progresses and the relative humidity originally changes, the heater 72 is feedback-controlled based on the relative humidity, so that the relative humidity in the internal space 56a is kept below a predetermined relative humidity. can do. Thereby, the fatigue life of the movable part 52a can be extended.

  Further, in the present embodiment, the energization of the heater 72 is controlled so as to be 35% RH or less. As described above (see FIGS. 11 and 12), the fatigue index n increases as the relative humidity decreases, and increases significantly particularly at a relative humidity of 35% or less. Therefore, if it is made 35% RH or less, the fatigue life of the movable part 52a can be more effectively extended.

  Further, the fatigue life of the movable portion 52a can be grasped while the temperature of the internal space 56a is changed by the heater 72.

  In the present embodiment, an example is shown in which the energization to the heater 72 is controlled so that the predetermined humidity is 35% RH or less, but the reference humidity is not limited to 35% RH or less. Since the fatigue life is extended as the relative humidity is lower, the energization to the heater 72 may be controlled so as to be, for example, 50% RH or less.

(Fourth embodiment)
In the present embodiment, description of portions common to the semiconductor package 50 shown in the first embodiment is omitted.

  In this embodiment, as shown in FIG. 17, the semiconductor package 50 is further provided with a temperature sensor 74 that is housed in an internal space 56a and detects the temperature of the internal space 56a. In FIG. 17, the temperature sensor 74 is loaded on the configuration shown in the first embodiment.

  An example of the arrangement of the heaters 72 is shown in FIG. In FIG. 18, a chip thermistor is employed as the temperature sensor 74. The temperature sensor 74 is fixed to a base 58 that constitutes the housing portion 56, and is electrically connected to the processing circuit portion 70 via a terminal 62 and a wiring 68.

  Next, effects of the semiconductor package 50 according to the present embodiment will be described.

  In the present embodiment, since the temperature of the internal space 56a can be measured by the temperature sensor 74, the output of the humidity sensor 54 can be corrected based on the temperature measurement result. As a result, the detection accuracy of the relative humidity is further improved, and as a result, the fatigue life of the movable portion 52a can be grasped more accurately.

  Further, as shown in FIGS. 11 and 12, when the relative humidity is the same at 35% RH or more, the fatigue index n shows almost the same value regardless of the temperature. The index n is different. According to this embodiment, since the temperature of the internal space 56a can be measured by the temperature sensor 74, the fatigue life of the movable portion 52a can be grasped with higher accuracy.

  The arrangement of the temperature sensor 74 is not limited to the example of FIG. The temperature sensor 74 can also be formed integrally (in one chip) with the MEMS device 52 and the humidity sensor 54.

  Further, in the second embodiment and the third embodiment described above, the temperature sensor 74 may be provided.

(Fifth embodiment)
In the present embodiment, description of portions common to the semiconductor package 50 shown in the first embodiment is omitted.

  In the first embodiment, no particular mention is made of the gas sealed in the internal space 56a. In this embodiment, nitrogen, oxygen, or a rare gas is sealed in the internal space 56a as part of the gas. The gas is a part of the gas sealed in the internal space 56a, and since there is water vapor other than the gas, the relative humidity can be detected. Note that examples of rare gases (also referred to as inert gases) include helium, neon, argon, and krypton.

  Next, effects of the semiconductor package 50 according to the present embodiment will be described.

  In this embodiment, nitrogen, oxygen, or a rare gas is sealed as a part of the gas, and these gases hardly contain water vapor. Therefore, the relative humidity in the internal space 56a can be lowered. Thereby, the fatigue life of the movable part 52a can be extended.

  The same effect can be obtained even when dry air having a low relative humidity is enclosed.

  In the second, third, and fourth embodiments described above, the gas may be sealed.

(Sixth embodiment)
In the present embodiment, description of portions common to the semiconductor package 50 shown in the first embodiment is omitted.

  In the present embodiment, as shown in FIG. 19, the semiconductor package 50 further includes a moisture absorbent 76 accommodated in the internal space 56 a.

  As the hygroscopic agent 76, mesoporous silica, zeolite, silica gel or the like can be employed. The mesoporous silica can be deposited on the MEMS device 52, for example. Moreover, about zeolite or a silica gel, it can fix to the accommodating part 56, for example.

  In the present embodiment, silica gel is employed as the hygroscopic agent 76, and the hygroscopic agent 76 is fixed to the bottom inner wall of the cap 60.

  Next, effects of the semiconductor package 50 according to the present embodiment will be described.

  In the present embodiment, since the moisture absorbent 76 disposed in the internal space 56a retains moisture, the relative humidity in the internal space 56a can thereby be reduced. And the fatigue life of the movable part 52a can be extended.

  In the second embodiment, the third embodiment, the fourth embodiment, and the fifth embodiment described above, the hygroscopic agent 76 may be disposed.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  The configuration in which the movable portion 52a and the humidity sensor 54 are held in the hollow is not limited to the above-described CAN package. A ceramic package having a cavity structure can also be adopted. For example, in the first modification shown in FIG. 20, the base 58 and the cap 60 that constitute the housing portion 56 are made of ceramic. The terminal 62 is fixed to the peripheral edge of the base 58 and pulled out to the outside. The base 58 and the cap 60 are connected by a low melting point sealing glass 78, thereby sealing the internal space 56a. The terminal 62 drawn out from the internal space 56 a is electrically connected to the processing circuit unit 70 through the wiring 68.

  Further, as shown in the second modification shown in FIG. 21, a mold package having a cavity structure can also be adopted. In FIG. 21, a humidity sensor 54 is also formed on the substrate that constitutes the MEMS device 52. And the accommodating part 56 (cap) which consists of silicon | silicone is joined to the silicon which comprises the NENS device 52 so that the movable part 52a and the humidity sensor 54 may be held hollow. The MEMS device 52 including the humidity sensor 54 is fixed to an island 80 of the lead frame. The processing circuit unit 70 is also fixed to the same island 80.

  The MEMS device 52 and the humidity sensor 54 are electrically connected to the lead 84 via the bonding wire 82. The MEMS device 52 including the humidity sensor 54, the housing portion 56, the island 80, the bonding wire 82, and a part of the lead 84 are integrally sealed with a sealing resin body 86.

  Thus, if the accommodating part 56 is fixed to the MEMS device 52 and the movable part 52a is held hollow, the volume of the internal space 56a can be reduced. Therefore, in the configuration including the heater 72 and the hygroscopic agent 76, the effect of the heater 72 and the hygroscopic agent 76 can be enhanced. In this case, an internal space 56a is formed by the space of the accommodating portion 56 and the space around the movable portion 52a in the MEMS device 52, and gas is sealed in the internal space 56a.

  In addition, a configuration in which the sealing resin body 86 is not provided in FIG. 21, that is, a configuration in which the housing portion 56 made of silicon is bonded to the MEMS device 52 including the humidity sensor 54 can be employed. Moreover, the structure by which the accommodating part 56 which consists of glass is joined to the MEMS device 52 is also employable.

  The MEMS device 52 including the humidity sensor 54, that is, a configuration in which the MEMS device 52 and the humidity sensor 54 are formed on the same chip can be applied to each of the above-described embodiments.

  Further, the silicon constituting the movable portion 52a is not limited to single crystal silicon, but may be polycrystalline silicon or amorphous silicon.

DESCRIPTION OF SYMBOLS 10 ... Test piece, 12 ... Board | substrate, 14 ... Weight part, 16 ... Frame part, 18 ... Mask, 20 ... Membrane, 20a ... Maximum stress application point, 22. ..Silicon nitride film, 24... Silicon oxide film, 26... Polycrystalline silicon film, 30... Test apparatus, 32. Accelerometer, 38 ... laser displacement meter, 40 ... controller, 42 ... data logger, 50 ... semiconductor package, 52 ... MEMS device, 52a ... movable part, 54 ... Humidity sensor, 56... Housing, 56 a .. internal space, 58... Base, 60... Cap, 62. ... Wiring, 70 ... Processing circuit, 72 ... Heater 74 ... Temperature sensor, 76 ... Hygroscopic agent, 78 ... Glass for sealing, 80 ... Island, 82 ... Bonding wire, 84 ... Lead, 86 ... Sealing resin body ,

Claims (8)

A MEMS device (52) having a movable part (52a) formed of silicon as a material;
An accommodating portion (56) provided in an internal space (56a) in which gas is enclosed so as to accommodate at least the movable portion of the MEMS device;
A humidity sensor (54) for detecting the relative humidity in the internal space in order to grasp the fatigue life of the movable portion made of silicon and housed in the internal space together with the movable portion, Semiconductor package.   The semiconductor package according to claim 1, further comprising a heater (72) provided so as to generate heat when energized and to transmit the heat to the gas in the internal space (56a).   The energization of the heater (72) is controlled based on the output of the humidity sensor (54) so that the relative humidity in the internal space (56a) is equal to or lower than a predetermined relative humidity. 2. The semiconductor package according to 2. A MEMS device (52) having a movable part (52a) formed of silicon as a material;
An accommodating portion (56) provided in an internal space (56a) in which gas is enclosed so as to accommodate at least the movable portion of the MEMS device;
A humidity sensor (54) that is housed in the internal space together with the movable part and detects relative humidity in the internal space;
A heater (72) provided to generate heat by energization and to be transmitted to the gas in the internal space (56a) ,
Wherein as the relative humidity in the interior space (56a) is less than or equal to a predetermined relative humidity, the semiconductor package on the basis of the output of the humidity sensor (54), energization of the heater (72) is characterized Rukoto controlled . 5. The semiconductor package according to claim 3, wherein the predetermined relative humidity or lower is 35% RH or lower. The semiconductor package according to any one of claims 1 to 5 , further comprising a temperature sensor (74) housed in the internal space (56a) and detecting a temperature of the internal space. 7. The semiconductor package according to claim 1 , wherein nitrogen, oxygen, or a rare gas is sealed in the internal space as a part of the gas. The semiconductor package according to claim 1 , further comprising a hygroscopic agent (76) accommodated in the internal space.

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