JPH06345495A - Anode joining method - Google Patents

Abstract

PURPOSE:To provide an anode joining method capable of obtaining accelerating sensor, etc., having hardly any temperature dependance in the aspect of accuracy even in both cases in the case of lowering the temperature from high temperature state in joining to temperature used and the case of having the change of temperature in the range of temperature used. CONSTITUTION:In the anode joining method for subjecting a semiconductor member in which a beam-like elastic spring 6 and a weight part 5 supported by the beam-like elastic spring 6 are formed to anode joining with a glass member in which an electrode is formed at the position opposite to the weight part by heating and application of voltage, a layer for preventing joining is formed in a part of contact face between the semiconductor member and the glass member. The forming part is a part in which heat stress directly exerts an influence upon the beam elastic spring if joining is carried out in this part. Since joining is not carried out in a part in which joiningpreventing layer is formed and joining part 3 is formed in other part, the joining is finally carried out in a part in which heat stress does not directly exert an influence upon beam-like elastic spring 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anodic bonding method, and more particularly to relaxation of thermal stress in the anodic bonding method used for manufacturing various sensors.

[0002]

2. Description of the Related Art The anodic bonding method for joining a semiconductor member and a glass member by heating and applying a DC voltage has advantages such that the semiconductor member and the glass member can be joined without weight, and an airtight joint can be obtained. However, since it has a bonding strength comparable to that of a low melting point glass bonding method in which low melting point glass is bonded as an adhesive, it is widely applied in the fields of manufacturing acceleration sensors and pressure sensors.

When the anodic bonding method is used for manufacturing these sensors, there is a constraint that not only the bonding strength is sufficient, but also the function of the manufactured sensor should not be affected by manufacturing conditions. In particular, in recent years, semiconductor processing technology has been used to reduce the size and weight of the semiconductor, and as a result, higher precision and higher reliability have become issues, and the conditions imposed on the anodic bonding method become strict.

9 and 10 show a conventional anodic bonding method, and show an example of manufacturing a capacitance type acceleration sensor by using the anodic bonding method. In the capacitance type acceleration sensor, an upper structural material 1 such as glass and a lower structural material 2 such as single crystal silicon are bonded and anodically bonded by heating at 400 ° C. and 800 V and applying a voltage. The joint portion 3 is formed on the entire surface of the contact portion (shown by the diagonal lines in FIG. 9) in order to join the upper structural material 1 and the lower structural material 2 with sufficient strength.

However, when the entire contact portion between the upper structural material and the lower structural material is used as the bonding portion for anodic bonding in this way, the thermal expansion coefficients of the different materials are different.
When the ambient temperature changes after joining, a large internal stress is generated in the beam-shaped elastic spring 6 supporting the weight portion 5 which is a movable portion due to the difference in the coefficient of thermal expansion of these structures. As a result, an error is given to the amount of displacement generated on the electrode surfaces 7 and 9 by the normal external force, which affects the accuracy. There are two types of temperature change here. That is, one is the case where the temperature is decreased from the high temperature state at the time of joining to the use temperature, and the other is the temperature change in the use temperature range.

As described above, the conventional anodic bonding method has a problem that the function of the acceleration sensor or the like is affected when the sensor or the like is manufactured. Therefore, in the past, in order to prevent adverse effects due to temperature changes during anodic bonding,
For example, a method has been proposed in which a notch groove is provided on the back surface of the supporting portion of the beam to absorb thermal stress (Japanese Patent Laid-Open No. 1-301174). Further, as a measure for eliminating the influence of temperature change in the operating temperature range, (a) the apparent thermal expansion coefficients of the materials are made to coincide with each other (JP-A-3-131176). (B) A heating means is provided to maintain a constant temperature. When heated and used (JP-A-1-302772) (c) A method is adopted in which a protrusion is provided on a part of the mounting base to float and support the sensor chip (JP-A-1-301176). There is.

[0007]

However, Japanese Patent Laid-Open No. 1-33
The method of Japanese Patent No. 01174 has a problem that it can absorb the stress acting in the direction perpendicular to the groove but cannot absorb the stress acting in the direction parallel to the groove. Further, the provision of the groove lowers the strength, resulting in a disadvantageous effect on the impact force.

Further, in the method (a), it is almost impossible to actually find a substance having the same thermal expansion, considering that the materials that are the premise of the anodic bonding method are the semiconductor member and the glass member. Further, the method (b) has a large waste of providing a heating means separately, and cannot be used until the set temperature is reached after the heating is started. Further, in the method (c), floating the sensor chip causes the chip itself to be in a cantilever state, and vibration may occur, which may impair accuracy.

As described above, the conventional anodic bonding method cannot cope with both the temperature change from the bonding temperature of the manufactured sensor and the temperature change in the operating temperature range, and has a problem in each case. The present invention has been made in view of the above-mentioned conventional problems, and the object thereof is accuracy in both cases of lowering the temperature from the high temperature state at the time of joining to the use temperature and the case where there is a temperature change within the use temperature range. It is to provide an anodic bonding method that can obtain an acceleration sensor or the like having less temperature dependency in the above, and can be used for a wider range of applications.

[0010]

In order to achieve the above object, the anodic bonding method of the present invention is an anodic bonding method in which a semiconductor member and a glass member are anodic bonded by heating and voltage application. Prior to forming a metal film for bonding prevention in at least a region directly affected by thermal stress of the glass member to prevent anodic bonding in the region of the semiconductor member and the glass member where the metal film is formed, the metal It is characterized in that the semiconductor member and the glass member are anodically bonded in a region other than the region where the film is formed.

[0011]

As described above, according to the anodic bonding method of the present invention, when the semiconductor member and the glass member are bonded together, the bonding is not carried out over the entire contact surface as in the conventional case, but the bonding is carried out at a limited partial location. Is. As described above, when the materials of the members are different, such as the semiconductor material and the glass material, their thermal expansion coefficients are also different. Therefore, when the ambient temperature changes after the anodic bonding, the difference in the thermal expansion coefficient of these members causes these differences. Thermal stress is generated between the members, exerting an action on the other member at the joint portion, and in the form of thermal strain at the non-joint portion. Conventionally, joining is performed on the entire contact surface of the component member, so that, for example, in an acceleration sensor, this thermal strain is concentrated on the beam-shaped elastic spring, which is the portion where strain is most likely to occur at the non-joining portion.

According to the present invention, the metal film for preventing bonding is formed on a part of the contact surface between the semiconductor member and the glass member, and the part where the metal film for bonding is formed is heated if the bonding is performed at that part. The part where the stress will directly affect is selected. For example, in the acceleration sensor described above, it is an extension of the lengthwise method of the beam-shaped elastic spring, or a peripheral position separated from the center of the weight portion by a predetermined distance. If the joining is performed in this state, the joining is not performed on the portion where the metal film for preventing the joining is formed, so that the joining is performed on the portion where the thermal stress does not directly affect. Therefore, it is possible to reduce the influence of the thermal stress generated by the temperature change when the temperature is lowered from the high temperature state at the time of joining to the use temperature and the thermal stress generated by the temperature change during the use.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the anodic bonding method of the present invention will be described below with reference to the drawings, taking manufacturing of an acceleration sensor as an example.

First Embodiment The overall structure of the first capacitive acceleration sensor to which the anodic bonding method of this embodiment is applied is the same as the conventional one. That is, as shown in FIG. 10, the upper structural material 1 and the lower structural material 2 are joined at the contact surface 3. The lower structural member 2 is composed of a fixed portion 4, a weight portion 5, a beam-like elastic spring 6 supporting the weight portion 5, and a movable electrode 7 arranged on the upper surface of the weight portion 5.
In addition, the upper structural material 1 includes the cover glass 8 and the fixed electrode 9.
It consists of Conventionally, the upper structural material 1 and the lower structural material 2 are joined together over the entire contact surface. Four
After being joined in a high temperature state of 00 ° C. and a voltage applied state of 800 V, the temperature is lowered to a working temperature near room temperature, so that thermal stress occurs due to the difference in thermal expansion coefficient between the upper structural member 1 and the lower structural member 2, The influence is generated in the form of thermal strain on the beam-like elastic spring 6 where strain is likely to occur in the unjoined portion. As a result, the weight portion 5 is displaced, the distance between the movable electrode 7 and the fixed electrode 9 is changed, and the initial capacitance is changed. Further, a similar phenomenon occurs even when the temperature changes within the operating temperature range. However, in this case, the temperature change may be both rising and falling.

FIG. 1 shows the bonding positions of the upper structural member 1 and the lower structural member 2 in the acceleration sensor bonded by the anodic bonding method of the first embodiment. The joining position is a shaded area in the figure. As is clear from comparison with FIG. 9, the upper structural material 1 and the lower structural material 2 are joined not in the entire contact surface but in only a limited partial area. In order to perform the bonding only in such a limited region, chromium, palladium, or the like may be formed by a vapor deposition method, a sputtering method, or the like before the bonding is performed on the contact surface other than the bonding portion 3 shown by the hatching in FIG.
It suffices to form a metal film for preventing bonding of platinum or the like.
In the region where the metal film for preventing bonding is formed, electrostatic attraction does not act even when a voltage is applied, and the upper structural material 1 and the lower structural material 2
Since they do not come into close contact with each other, joining is not performed on that portion, and eventually joining is performed only on the shaded portion in FIG. In the acceleration sensor of FIG. 1, the beam has a shape extending in a cross shape from the center of the weight. However, there is no joint on the extension of the beam in the longitudinal direction. The stress caused by the difference in the coefficient of thermal expansion of the structural material acts on other members at the joint. Therefore, the beam is not directly affected by this stress, the amount of displacement generated in the weight portion is reduced, and as a result, the fluctuation of the initial capacity is reduced.

Second Embodiment FIG. 2 shows an example of a second acceleration sensor to which the anodic bonding method of this embodiment is applied. The acceleration sensor of FIG. 2 is different from the acceleration sensor of FIG.
A beam extends in four directions from the end of the. In this case as well, as shown in the figure, a joining portion (hatched portion in the figure) is provided at a position deviated from the extension line in the longitudinal direction of the beam 6, and the other regions are formed by vapor deposition or sputtering before joining. A metal film for preventing bonding of chromium, palladium, platinum, etc. is formed in advance. Also in this case, since there is no joint portion on the extension line of the beam 6 in the longitudinal direction, the stress generated by the difference in the coefficient of thermal expansion of the structural material does not directly affect the beam 6. Therefore, the amount of displacement generated in the weight portion 5 is reduced, and as a result, the variation in the initial capacity is reduced, so that the variation in the initial capacity with respect to the temperature change can be alleviated.

Third Embodiment FIG. 3 shows an example of a third acceleration sensor to which the anodic bonding method of this embodiment is applied. In this third acceleration sensor, the beam 6 extends in parallel with the weight portion 5, and the beam 6 does not exist in the direction perpendicular to this. In such an acceleration sensor, the joining position may be set in parallel with the longitudinal direction of the beam 6 as shown in FIG. 3, and the joining preventing metal film may be formed in another region. Also in this case, since the joint region is selected in parallel with the beam 6, there is no joint on the extension line of the beam 6 in the longitudinal direction. Therefore, the stress caused by the difference in the coefficient of thermal expansion of the structural material is directly applied to the beam. Does not affect Therefore, the amount of displacement generated in the weight portion 5 is reduced, and as a result, the variation in the initial capacity is reduced, so that the variation in the initial capacity with respect to the temperature change can be alleviated. It should be noted that in FIG. 3, the bonding region is formed continuously, but as long as sufficient bonding strength is obtained, it is also possible to set it at several points arranged on a straight line instead of being continuous. .

Fourth Embodiment In the third embodiment described above, in the third acceleration sensor in which the beam 6 extends parallel to the weight portion 5 and the beam does not exist in the direction perpendicular to the weight portion 5, the length of the beam 6 is long. Although the bonding position is set parallel to the direction and the bonding preventing metal film is formed in another region, the bonding region can be set in another position. FIG. 4 shows an example in which the joining position is set so as to surround the weight portion 5 at a position near the weight portion 5, that is, the center of the movable portion. In this case as well, it goes without saying that the metal film for preventing bonding is formed in other regions where bonding is not performed. When the joint region is set in this way, the thermal strain is released in the peripheral portion where the joint is not performed, so that the beam 6 is not directly affected. Furthermore, since the joint is made at a position close to the center of the movable portion, it is possible to suppress the fluctuation of the initial capacity due to the temperature change.

Fifth Embodiment In the above-mentioned fourth embodiment, the joining position is set so as to surround the weight portion 5, but as shown in FIG. 5, it is parallel to the longitudinal direction of the beam 6 and the movable portion. It is also possible to set the joining position at a position close to the center. In this case, although the joint strength is slightly inferior to that in FIG. 4, since there is no joint on the extension line of the beam 6 in the longitudinal direction, the effect of the stress caused by the difference in the coefficient of thermal expansion of the structural material is more effective. Can be removed selectively.

Sixth Embodiment In the fifth embodiment described above, due to the structure of the acceleration sensor,
When the joint position cannot be set parallel to the longitudinal direction of the beam 6, as shown in FIG.
The joining position can also be set at a position close to the center of the movable part. Also in this case, as in the fourth embodiment, the thermal strain is released in the peripheral portion where the joining is not performed, so that the beam 6 is not directly affected.

Seventh Embodiment In the above-described first to sixth embodiments, an example in which the joining position is set in consideration of the joining strength is shown, but when a small joining strength is sufficient (for example, only low acceleration is used). When measuring (for example), it is also possible to join at only one place near the center of the movable part as shown in FIG. 7 or 8. Even in these cases, since the thermal stress is released in the other three directions in which the joining is not performed, the beam 6 is not directly affected.

As described above, according to the anodic bonding method of the present embodiment, when constructing an acceleration sensor or the like with two or more types of structures by bonding, the internal stress caused by the difference in the coefficient of thermal expansion of the structural materials is relaxed. Therefore, the temperature dependence in terms of accuracy can be reduced. In addition, each of the above-described embodiments is a case of a two-layer structure in which glass is bonded to the upper surface of a processed silicon substrate, but it can be applied to a case of a three-layer structure or more. That is, for example, when bonding glass to the upper surface and the lower surface of the processed silicon substrate, by limiting those bonding locations to the locations as described above,
The internal stress caused by the difference in the coefficient of thermal expansion of the structural material can be relaxed, and the temperature dependence in terms of accuracy can be reduced.

Further, as to the jointed portions, FIGS.
It is also possible to appropriately combine the joint portions shown in. For example, “a portion deviated from the longitudinal direction of the beam-shaped elastic spring and close to the center of the weight portion” or “a portion close to the center of the weight portion and along one side of the rectangle”. Depending on the situation, a larger effect can be expected by combining in this way.

Further, in this embodiment, the case where the invention is applied to the acceleration sensor is shown, but the invention can be applied to a sensor such as a pressure sensor which requires joining.

[0025]

As described above, according to the anodic bonding method of the present invention, the thermal stress caused by the difference in the coefficient of thermal expansion of the structural material can be relaxed, so that the temperature dependence of the accuracy of various sensors can be reduced. Can be reduced. Therefore, the anodic bonding can be applied to a sensor or the like which has not been suitable for the anodic bonding in the related art, and its application can be expanded.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a bonding position in a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a joining position in the second embodiment of the present invention.

FIG. 3 is an explanatory diagram of a joining position in a third embodiment of the present invention.

FIG. 4 is an explanatory diagram of a joining position in a fourth embodiment of the present invention.

FIG. 5 is an explanatory diagram of a joining position in a fifth embodiment of the present invention.

FIG. 6 is an explanatory diagram of a joining position in a sixth embodiment of the present invention.

FIG. 7 is an explanatory diagram of a joining position in a seventh embodiment of the present invention.

FIG. 8 is an explanatory diagram of another joining position in the seventh embodiment of the present invention.

FIG. 9 is an explanatory diagram showing a bonding position in a conventional anodic bonding method.

FIG. 10 is a configuration diagram of a capacitive acceleration sensor.

[Explanation of symbols]

 1 Upper Structural Material 2 Lower Structural Material 3 Joined Part 5 Weighted Part 6 Beam Elastic Spring 7 Movable Electrode 8 Cover Glass 9 Fixed Electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hirofumi Funabashi, Aichi Prefecture, Aichi Prefecture, Nagakute Town, Oita, Nagakage 1 1 at 41 Yokochi, Toyota Central Research Institute Co., Ltd. 1 in 41 Chuo-dori, Toyota Central Research Institute Co., Ltd. (72) Inventor Motohiro Fujiyoshi, Nagakute-cho, Aichi-gun, Aichi Prefecture Nagatoji 1-41 in Toyota Chuo Research Laboratory (72) Inventor Susumu Sugiyama Aichi 1 in 41 Central Road, Nagakute, Nagakute Town, Aichi District, Toyota Central Research Institute Co., Ltd. (72) Inventor, Minoru Nakagawa 1 in 41 Central Road, Nagakute Town, Aichi District, Aichi County, Toyota Central Research Center Co., Ltd. (72) Inventor Yasuaki Tsurumi 1 41st Yokomichi, Nagakute-cho, Aichi-gun, Aichi-gun 1st of Yokomichi Toyota Central Research Institute Co., Ltd.

Claims (1)

[Claims] 1. A anodic bonding method for anodic bonding a semiconductor member and a glass member by heating and applying a voltage, wherein a metal film for bonding prevention is formed at least in a region directly affected by thermal stress of the glass member prior to anodic bonding. To prevent anodic bonding in the region of the semiconductor member and the glass member in which the bonding prevention metal film is formed, and the semiconductor member and the glass in regions other than the region in which the bonding prevention metal film is formed. An anodic bonding method, characterized in that a member is anodically bonded.