JP2014016177A - Heater structure of sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heater structure of a sensor which further suppresses the separation of a heater part and occurrence of cracks and further enhances a long-term reliability.SOLUTION: In a heater structure of a sensor in which a heater part 5 is formed in insulating layers (a first insulating layer 3 and second insulating layer 4) formed on a semiconductor substrate 2, a thermal stress relaxing layer 6 which has a thermal expansion coefficient between the heater part 5 and the insulating layers 3 and 4 and is formed of a material having a higher thermal transmission ratio than the insulating layers 3 and 4, is arranged in contact with the heater part 5.

Description

  The present invention relates to a sensor heater structure.

  2. Description of the Related Art Conventionally, as a general sensor heater structure, a heater portion (micro heater) formed on an insulating layer formed on a semiconductor substrate is known (for example, Patent Document 1).

  In this case, since the difference in thermal expansion coefficient between the heater portion made of platinum and the insulating layer made of silicon oxide film, silicon nitride film, etc. is large, the boundary between the heater portion and the insulating layer is large when the heater portion is heated. There was a problem that stress was generated. Insulating layers made of silicon oxide film, silicon nitride film, etc. have low thermal conductivity, so when the heater part is heated suddenly, the heat of the heater part is unevenly distributed, resulting in a large temperature difference in the insulating layer. There is also a problem that local thermal stress is generated. Thus, if a large thermal stress is generated between the heater part and the insulating layer, the heater part may be peeled off or cracks may be generated, and the long-term reliability of the sensor may be impaired. .

  Therefore, by providing a hafnium oxide layer (thermal stress relaxation layer) that has a thermal expansion coefficient between the heater part and the insulating layer in contact with the heater part, thermal stress generated between the heater part and the insulating layer is reduced. However, there has been proposed one that can suppress the peeling and cracking of the heater portion (see, for example, Patent Document 2).

JP 2007-132762 A JP 2001-091486 A

  However, in the above prior art (Patent Document 2), although the problem of thermal stress due to the difference in thermal expansion coefficient can be solved, the hafnium oxide layer is a material having a low thermal conductivity. There was a problem that the problem of thermal stress due to was not solved as before.

  Accordingly, an object of the present invention is to obtain a sensor heater structure that can further suppress the occurrence of peeling and cracking of the heater portion and can further improve long-term reliability.

  In order to achieve the above object, a first feature of the present invention is that in a heater structure of a sensor in which a heater portion is formed on an insulating layer formed on a semiconductor substrate, heat between the heater portion and the insulating layer is obtained. The gist is that a thermal stress relaxation layer formed of a material having an expansion coefficient and higher thermal conductivity than the insulating layer is disposed in contact with the heater portion.

  The gist of the second feature of the present invention is that the thermal stress relaxation layer is disposed so as to be within a projection plane of a diaphragm formed on the semiconductor substrate.

  According to a third feature of the present invention, the insulating layer has a two-layer structure including a first insulating layer and a second insulating layer having different thicknesses, and the thermal stress relaxation layer includes the first insulating layer. The gist is that it is provided on the thin layer side of the insulating layer and the second insulating layer.

  According to a fourth aspect of the present invention, the thermal stress relaxation layer includes any one insulating material of aluminum nitride, boron nitride, diamond-like carbon, and silicon carbide, or a composite material containing any one insulating material. The gist is that it is formed.

  A fifth feature of the present invention is that a plurality of the heater parts are provided side by side on the semiconductor substrate, and the thermal stress relaxation layer is arranged separately for each predetermined region of each heater part. It is a summary.

  According to the present invention, the thermal stress relaxation layer formed of a material having a thermal expansion coefficient between the heater portion and the insulating layer and having a higher thermal conductivity than the insulating layer is disposed in contact with the heater portion. Therefore, it is possible to relieve the thermal stress due to the difference in thermal expansion coefficient, and it is possible to prevent the thermal stress from locally increasing by giving the thermal stress relaxation layer a higher thermal conductivity. Therefore, it becomes possible to further suppress the occurrence of peeling and cracking of the heater portion, and it is possible to obtain a sensor heater structure that can further improve long-term reliability.

It is the top view which showed the heater structure of the sensor concerning 1st Embodiment of this invention. It is sectional drawing which showed the heater structure of the sensor concerning 1st Embodiment of this invention. It is explanatory drawing of the insulating material which comprises the thermal stress relaxation layer of the heater structure of the sensor concerning 1st Embodiment of this invention, Comprising: (a) is a linear expansion coefficient, thermal conductivity, and resistance of platinum and a silicon oxide film. (B) is a diagram showing the physical property values of the thermal stress relaxation layer, (c) is the linear expansion coefficient, thermal conductivity and resistance of aluminum nitride, boron nitride, diamond-like carbon and silicon carbide. It is the figure which showed the rate. It is the figure explaining the creation process of the heater structure of the sensor concerning 1st Embodiment of this invention later on in order of (a)-(d). It is the figure which followed the preparation process of the heater structure of the sensor concerning 1st Embodiment of this invention later on in order of (e)-(h). It is the top view which showed the heater structure of the sensor concerning 2nd Embodiment of this invention. It is sectional drawing which showed the heater structure of the sensor concerning 2nd Embodiment of this invention. It is sectional drawing which showed the heater structure of the sensor concerning 3rd Embodiment of this invention. It is sectional drawing which showed the modification of the heater structure of the sensor concerning 3rd Embodiment of this invention. It is the top view which showed the heater structure of the sensor concerning 4th Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The heater structure of the sensor of the present invention can be applied to all sensors that require heating, such as a flow sensor, a gas flow sensor, a temperature sensor, a humidity sensor, and a gas sensor.

[First embodiment]
1 to 4 are diagrams showing a heater structure of a sensor according to the first embodiment of the present invention.

  As shown in FIGS. 1 and 2, the sensor chip 1 of the present embodiment includes a semiconductor substrate 2, a first insulating layer 3 and a second insulating layer 4 having a two-layer structure stacked on the semiconductor substrate 2, At least a heater portion 5 formed between the first insulating layer 3 and the second insulating layer 4 is provided. For example, when the sensor chip 1 is configured as a flow rate sensor, a temperature-sensitive resistor (thermal element) is provided in parallel on both sides of the heater unit 5 and the sensor chip 1 is configured as a gas sensor. A gas sensitive layer is provided on the second insulating layer 4.

  In the present embodiment, the first insulating layer 3 and the second insulating layer 4 are formed of a silicon oxide film (SiO 2), and the heater unit 5 is formed of platinum (Pt).

  Here, in this embodiment, the thermal expansion coefficient between the heater unit 5 and the insulating layer (the first insulating layer 3 and the second insulating layer 4) is higher than that of the insulating layers 3 and 4. The thermal stress relaxation layer 6 formed of a material is arranged in contact with the heater unit 5.

  Specifically, as shown in FIGS. 1 and 2, in the present embodiment, the thermal stress relaxation layers 6 are formed on the upper and lower surfaces of the heater unit 5, and the electrode unit 52 serving as a predetermined region of the heater unit 5. The film is formed so as to cover at least the bellows-like dense portion 51 except for the above.

  Further, as shown in FIG. 3A, from the linear expansion coefficient, thermal conductivity, and resistivity of platinum (Pt) and silicon oxide film (SiO 2), as shown in FIG. 3B as an example in this embodiment. The physical property value is used as a standard for the thermal stress relaxation layer 6. As shown in FIG. 3C, in this embodiment, the thermal stress relaxation layer 6 is made of any one of aluminum nitride (AIN), boron nitride (BN), diamond-like carbon (DLC), and silicon carbide (SiC). Or a single insulating material.

  In the present embodiment, the physical property values shown in FIG. 3B are used as references for the thermal stress relaxation layer 6, but the present invention is not limited to this. The thermal stress relaxation layer 6 is formed of a composite material containing any one insulating material of aluminum nitride (AIN), boron nitride (BN), diamond-like carbon (DLC), and silicon carbide (SiC). It may be.

  Next, with reference to FIG. 4, the manufacturing method of the heater structure of the sensor concerning this embodiment is demonstrated.

  First, as shown in FIG. 4A, a first insulating layer 3 made of a silicon oxide film (SiO2) is formed on the upper and lower surfaces of a semiconductor substrate 2 which is a silicon wafer by a film forming means such as thermal oxidation treatment or CVD. Form.

  Next, as shown in FIG. 4B, a thermal stress relaxation layer 6 is formed on one surface (upper surface) of the semiconductor substrate 2 by a method such as sputtering. Then, patterning is performed by a method such as photolithography so that the thermal stress relaxation layer 6 is left in a portion that becomes the heater portion 5 (the bellows-like dense portion 51).

  Next, as shown in FIG. 4C, a platinum film to be the heater unit 5 is formed by sputtering or the like, and a wiring pattern of the heater unit 5 is formed by a method such as photolithography.

  Next, as shown in FIG. 4D, a thermal stress relaxation layer 6 is formed again on the wiring pattern of the heater portion 5 by a method such as sputtering. Then, patterning is performed by a method such as photolithography so that the thermal stress relaxation layer 6 is left on the bellows-like dense portion 51 of the heater portion 5.

  Next, as shown in FIG. 4E, a second insulating layer 4 made of a silicon oxide film (SiO 2) is formed by film forming means such as CVD.

  Next, as shown in FIG. 4 (f), in order to form the electrode pad 53, the second insulating layer 4 at a position corresponding to the electrode portion 52 of the heater portion 5 is opened by photolithography to open the opening portion 41. Form. At this time, protection is provided so that the first insulating layer 3 located on the back side is not removed together.

  Next, as shown in FIG. 4G, an electrode pad 53 made of gold (Au) is formed by sputtering or vapor deposition, and a pattern is formed by photolithography.

  Finally, as shown in FIG. 4 (h), the first insulating layer 3 on the opposite surface (lower surface) side of the semiconductor substrate 2 is opened, and a recess 7 is provided using an etching solution such as TMAH. A diaphragm 8 is formed on 2.

  And it is cut and used for sensor chip 1 by dicing. Electric power is supplied to the heater unit 5 by wire bonding of the electrode pad 53.

  As described above, according to the heater structure of the sensor of the present embodiment, the thermal expansion coefficient between the heater unit 5 and the insulating layers (the first insulating layer 3 and the second insulating layer 4) and the insulating layer A thermal stress relaxation layer 6 made of a material having a higher thermal conductivity than 3 and 4 is disposed in contact with the heater unit 5. Therefore, it is possible to relieve the thermal stress due to the difference in thermal expansion coefficient, and it is possible to suppress the thermal stress from being locally increased by giving the thermal stress relaxation layer 6 a high thermal conductivity. . Therefore, peeling of the heater part 5 and generation of cracks can be further suppressed, and a sensor heater structure that can further improve long-term reliability can be obtained.

  In the present embodiment, the thermal stress relaxation layer 6 is formed of any one insulating material or a composite material containing any one insulating material of aluminum nitride, boron nitride, diamond-like carbon, and silicon carbide. Has been. Therefore, it is possible not only to suppress the local increase in thermal stress by making the heat distribution uniform, but also to increase the resistivity and ensure the insulation. Therefore, it is possible to obtain a sensor heater structure that can further improve long-term reliability.

[Second Embodiment]
5 and 6 are diagrams showing a second embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals, and redundant description will be omitted.

  The sensor heater structure of the present embodiment is mainly different from the sensor heater structure of the first embodiment in that the thermal stress relaxation layer 6 of the sensor chip 1A is a projection surface of the diaphragm 8 formed on the semiconductor substrate 2. It is that it is arranged so as to fit in.

  That is, in the sensor chip 1 of the first embodiment, as shown in FIG. 2, the thermal stress relaxation layer 6 is disposed so as to protrude from the diaphragm 8 to the position where it overlaps the semiconductor substrate 2. May escape to the semiconductor substrate 2. As described above, when the heat of the heater unit 5 escapes to the semiconductor substrate 2 via the thermal stress relaxation layer 6, the heater unit 5 may not rise to a predetermined temperature for causing the detection unit (not shown) to function. Heater efficiency will deteriorate.

  On the other hand, in this embodiment, as shown in FIGS. 5 and 6, the thermal stress relaxation layer 6 is disposed so as to be within the projection plane of the diaphragm 8. Therefore, it is possible to prevent the heat of the heater unit 5 from escaping to the semiconductor substrate 2 through the thermal stress relaxation layer 6, and the heater unit 5 cannot be raised to a predetermined temperature or the heater efficiency is deteriorated. Can be suppressed.

  Also according to this embodiment described above, the same operations and effects as those of the first embodiment can be achieved.

  In the present embodiment, the thermal stress relaxation layer 6 is disposed so as to be within the projection plane of the diaphragm 8 formed on the semiconductor substrate 2. Therefore, when the thermal stress relaxation layer 6 is formed of a material having high thermal conductivity, the heat of the heater portion 5 is easily escaped, but there is an advantage that it can be suppressed. That is, it is possible to suppress the heat of the heater unit 5 from escaping to the semiconductor substrate 2 through the thermal stress relaxation layer 6.

[Third embodiment]
FIG. 7 is a diagram showing a third embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  The sensor heater structure of the present embodiment is mainly different from the sensor heater structure of the first embodiment in that the thermal stress relaxation layer 6 of the sensor chip 1B includes the first insulating layer 3 and the second insulating layer. 4 is provided on the thin layer side.

  That is, in this embodiment, as shown in FIG. 7, the first insulating layer 3 and the second insulating layer 4 have different thicknesses, and the first insulating layer 3 is more than the second insulating layer 4. It is formed so as to be thick. In such a case, the heater portion 5 is formed between the first insulating layer 3 and the second insulating layer 4, but on the upper side and the lower side of the heater portion 5, the second located on the upper side. Since the insulating layer 4 is thinner, it is considered that cracks are likely to occur on the upper boundary surface.

  Therefore, in this embodiment, by providing the thermal stress relaxation layer 6 on the second insulating layer 4 side, which is the thin layer side, generation of cracks on the thin layer side where the strength is further reduced can be suppressed. is there.

  In this embodiment, since the thermal stress relaxation layer 6 is provided only on the second insulating layer 4 side which is the thin layer side, the lower surface of the heater portion 5 which is the first insulating layer 3 side is exposed to heat. The stress relaxation layer 6 is not in contact, and the thermal stress relaxation layer 6 exists only on the upper surface side.

  Also according to the present embodiment described above, the same operations and effects as the first and second embodiments can be obtained.

  Further, in the present embodiment, the insulating layer has a two-layer structure including the first insulating layer 3 and the second insulating layer 4 having different thicknesses, and the thermal stress relaxation layer 6 is the first insulating layer 3. The second insulating layer 4 is provided on the thin layer side. Therefore, there is an advantage that generation of cracks at the boundary surface on the thin layer side where the strength is lowered can be more reliably suppressed.

  In the present embodiment, the first insulating layer 3 is formed so as to be thicker than the second insulating layer 4, but the second insulating layer as in the modification shown in FIG. 4 may be formed to be thicker than the first insulating layer 3. In this case, the thermal stress relaxation layer 6 of the sensor chip 1C is provided only on the first insulating layer 3 side which is the thin layer side. The thermal stress relaxation layer 6 is not in contact with the upper surface of the heater portion 5 on the second insulating layer 4 side, and the thermal stress relaxation layer 6 exists only on the lower surface side.

[Fourth embodiment]
FIG. 9 is a diagram showing a fourth embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  The sensor heater structure of the present embodiment is mainly different from the sensor heater structure of the first embodiment in that a plurality of heater portions 5 are provided side by side on the semiconductor substrate 2, and a thermal stress relaxation layer is provided. 6 is arranged separately for each predetermined region of each heater unit 5.

  That is, in this embodiment, as shown in FIG. 9, a pair of heater parts 5 (the first heater part 5A and the second heater part 5B) are arranged in parallel, and the pair of thermal stress relaxation layers 6, 6 Are arranged separately for each bellows-like dense part (predetermined region) 51 of each heater part 5A, 5B. At this time, in the present embodiment, both of the pair of thermal stress relaxation layers 6 and 6 are arranged so as to be within the projection plane of the diaphragm 8.

  Thus, in this embodiment, since the thermal stress relaxation layer 6 is separated for each of the heater portions 5A and 5B of the sensor chip 1D, it is advantageous when, for example, it is desired to vary the heating temperature for each of the heater portions 5A and 5B. It is.

  That is, when it is desired to operate the first heater unit 5A at a heating temperature of 500 ° C. and the second heater unit 5B at a heating temperature of 300 ° C., if the thermal stress relaxation layer 6 is integrated, each heater unit 5A, The heating temperature of 5B will be neutralized.

  On the other hand, in this embodiment, since the thermal stress relaxation layer 6 is separated for each of the heater portions 5A and 5B, it can be operated at the heating temperature for each of the heater portions 5A and 5B.

  Also according to the present embodiment described above, the same operations and effects as the first and second embodiments can be obtained.

  In the present embodiment, a plurality of heater portions 5 are provided side by side on the semiconductor substrate 2 (in this embodiment, the first heater portion 5A and the second heater portion 5B), and a thermal stress relaxation layer is provided. 6 is arranged separately for each bellows-like dense part (predetermined region) 51 of each heater part 5A, 5B. Therefore, for example, when it is desired to change the heating temperature for each of the heater units 5A and 5B, it is possible to prevent the heating temperature of each of the heater units 5A and 5B from being neutralized. There is an advantage that it can be operated at temperature.

  In the present embodiment, the first heater unit 5A and the second heater unit 5B are used as the heater unit 5. However, three or more heater units 5 may be used.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various modifications can be made.

  For example, in the above embodiment, the insulating layer is formed of a silicon oxide film (SiO 2) heater portion of platinum (Pt), but may be formed of other materials. In this case, the thermal stress relaxation layer can be appropriately changed as a material having a thermal expansion coefficient between the heater portion and the insulating layer and a higher thermal conductivity than the insulating layer.

2 Semiconductor substrate 3 First insulating layer (insulating layer)
4 Second insulating layer (insulating layer)
5 Heater part 6 Thermal stress relaxation layer 8 Diaphragm

Claims (5)

In the heater structure of the sensor in which the heater portion is formed on the insulating layer formed on the semiconductor substrate,
A thermal stress relaxation layer formed of a material having a thermal expansion coefficient between the heater portion and the insulating layer and having a higher thermal conductivity than the insulating layer is disposed in contact with the heater portion. Sensor heater structure.   2. The sensor heater structure according to claim 1, wherein the thermal stress relaxation layer is disposed so as to be within a projection plane of a diaphragm formed on the semiconductor substrate. The insulating layer has a two-layer structure including a first insulating layer and a second insulating layer having different thicknesses,
3. The sensor heater structure according to claim 1, wherein the thermal stress relaxation layer is provided on a thin layer side of the first insulating layer and the second insulating layer.   The thermal stress relaxation layer is formed of any one insulating material of aluminum nitride, boron nitride, diamond-like carbon, and silicon carbide, or a composite material containing any one insulating material. The heater structure of the sensor according to any one of claims 1 to 3. A plurality of the heater parts are provided side by side on the semiconductor substrate,
5. The sensor heater structure according to claim 1, wherein the thermal stress relaxation layer is arranged separately for each predetermined region of each heater portion. 6.

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