JP2016146420A - Determination method for anode junction conditions - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a three-layer substrate while maintaining satisfactory bondability, without depositing movable ions and with energy as little as possible.SOLUTION: Primary anode junction is performed at any junction temperature T1 between a lowest junction temperature TL and a highest junction temperature TH and at a junction voltage V1 that is obtained from a current equal to or higher than a minimum current density IL. A junction voltage at which the minimum current density IL can be obtained is defined as a lowest reference voltage VL and a relation between VL and the junction temperature is calculated as a first relation line I. Secondary anode junction is performed, a junction voltage at which deposition of movable ions is started is defined as a highest reference voltage VH and a relation between the highest reference voltage VH and the junction temperature is calculated as a second relation line II. A region S1 surrounded by the first relation line I, the second relation line II, the lowest junction temperature TL and the highest junction temperature TH is defined as a target region and secondary anode junction conditions P2 (T2 and V2) are determined from a region S2 where the conditions are weaker than primary anode junction conditions P1 (T1 and V1) in the target region S1.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method for determining anodic bonding conditions when manufacturing a three-layer substrate having a glass substrate interposed therebetween.

  Conventionally, as an example of a three-layer substrate configured with a glass substrate interposed therebetween, there is a pressure sensor having a three-layer structure including a sensor chip (silicon substrate), a glass pedestal, and a silicon tube. In the three-layer structure pressure sensor, the sensor chip, the glass pedestal, and the silicon tube are joined by anodic bonding (see, for example, Patent Document 1).

Anodic bonding is a direct bonding method in which a third material is not interposed between bonding members, and glass containing movable ions (metal cations such as Na ⁺ and K ⁺ ) and silicon or metal are overlapped. In this state, when high temperature and high voltage are applied, electrostatic attraction acts on the interface, and covalent bonding occurs to bond the two. Using this technique, a sensor chip, a glass pedestal, and a silicon tube are joined to obtain a three-layer pressure sensor. In addition, when anodic bonding is performed, the bonding portion is heated, and the heating temperature at this time is called the bonding temperature. The applied voltage is called a junction voltage.

[First anodic bonding (primary anodic bonding)]
First, as shown in FIG. 5, the glass pedestal 12 and the silicon tube 13 are overlapped, the upper surface of the glass pedestal 12 is the negative electrode side (cathode side), the lower surface of the silicon tube 13 is the positive electrode side (anode side), A high voltage is applied in a state where the bonding temperature has been reached, and the glass pedestal 12 and the silicon tube 13 are anodically bonded. Thereby, the joined body (glass pedestal / silicon tube joined body) 14 of the glass pedestal 12 and the silicon tube 13 is formed.

[Second anodic bonding (secondary anodic bonding)]
Next, as shown in FIG. 6, the sensor chip (silicon substrate) 11 and the glass pedestal / silicon tube assembly 14 are overlapped, and the upper surface of the sensor chip 11 is placed on the positive electrode side (anode side), and the glass pedestal / silicon tube. The lower surface of the bonded body 14 (the lower surface of the silicon tube 13) is set to the negative electrode side (cathode side), and a high voltage is applied in a state where the bonding temperature is reached, so that the sensor chip 11 and the glass pedestal / silicon tube bonded body 14 are connected. Anodized. Thereby, the joined body (sensor chip / glass pedestal / silicon tube joined body) 15 of the sensor chip 11 and the glass pedestal / silicon tube joined body 14 is formed, and the pressure sensor 200 having a three-layer structure is obtained.

  As a manufacturing method of the pressure sensor 200, in order to efficiently produce the pressure sensor 200 in large quantities, a wafer in which a plurality of sensor chips 11 are created (sensor chip wafer) and a wafer in which a plurality of glass pedestals 12 are created (glass pedestal). Wafer) and a wafer (silicon tube wafer) on which a plurality of silicon tubes 13 are formed are bonded to form a three-layer wafer bonded body, and the three-layer wafer bonded body is cut by dicing to form a plurality of pressure sensors 200. The method of obtaining is adopted. That is, the primary anodic bonding and the secondary anodic bonding described above are performed at the wafer level.

However, when primary anodic bonding and secondary anodic bonding are performed in this way by applying a voltage in the opposite direction on the same axis (axis passing through the three-layer structure), mobile ions (Na ⁺ , K) are formed in the primary anodic bonding. ⁺ ) Is moved (see FIG. 7A), a deficient layer of mobile ions is generated in the vicinity of the bonding surface (primary bonding surface) between the glass pedestal 12 and the silicon tube 13, and the deficient layer is formed in the secondary anodic bonding. When mobile ions (Na ⁺ , K ⁺ ) gather on the surface (see FIG. 7B), sodium and the like are segregated in the glass pedestal 12 to cause cracks in the glass pedestal 12 and reduce the strength of the glass pedestal 12. Invite.

Therefore, in Patent Document 1, in order to prevent this, after performing primary anodic bonding in the same manner as described above (see FIG. 8A), the secondary anodic bonding is performed as shown in FIG. 8B. The upper surface of the sensor chip 11 is the positive electrode side, the side surface of the glass pedestal 12 is the negative electrode side, and a high voltage is applied in a state where the bonding temperature has been reached, and the sensor chip 11 and the glass pedestal / silicon tube assembly 14 Are anodically bonded. This anodic bonding using the side surface of the glass pedestal 12 is referred to as a side anodic bonding method. Thereby, the movable ions (Na ⁺ , K ⁺ ) in the glass pedestal 12 are prevented from moving to the joining surface of the primary anodic bonding, and the strength of the glass pedestal 2 is prevented from being lowered.

JP 2009-135190 A

  However, when the side surface anodic bonding method is employed, one electrode is taken from the side surface side, and particularly when bonding is performed at the wafer level, the distance between the electrodes becomes remarkably long, and current does not easily flow. For this reason, it is necessary to apply a high voltage for a long time, and energy consumption increases.

  The present invention has been made in order to solve such a problem, and the object of the present invention is to maintain a good bondability, and with as little energy as possible without precipitation of mobile ions. Another object of the present invention is to provide a method for determining anodic bonding conditions that makes it possible to manufacture a three-layer substrate.

  In order to achieve such an object, the present invention includes a primary anodic bonding process in which one surface of a glass substrate is anodically bonded to the first substrate using the first substrate as an anode and the glass substrate as a cathode, The first substrate of the joined body of the first substrate and the glass substrate bonded by the next anodic bonding step is used as the cathode, the second substrate is used as the anode, and the second substrate is anodically bonded to the other surface of the glass substrate. In the method of determining anodic bonding conditions for determining anodic bonding conditions when manufacturing a three-layer substrate through a secondary anodic bonding process, the minimum and maximum bonding temperatures are determined as the minimum and maximum bonding temperatures during anodic bonding. The primary voltage is a junction voltage at which a current exceeding the minimum current density necessary for ensuring good jointability can be obtained at any junction temperature between the minimum junction temperature and the maximum junction temperature. Anodic bonding in anodic bonding process The lowest reference voltage in a temperature range including at least the minimum junction temperature and the maximum junction temperature is the minimum reference voltage, which is the minimum reference voltage for obtaining the minimum current density necessary to ensure one step and good bondability. A second step for obtaining the relationship between the voltage and the bonding temperature as a first relationship line, and anodic bonding in the secondary anodic bonding step for the bonded body of the first substrate and the glass substrate bonded by the first step. And the highest reference voltage in the temperature range including at least the lowest junction temperature and the highest junction temperature, where the highest reference voltage is the junction voltage at which mobile ions begin to precipitate from the vicinity of the junction surface between the glass substrate and the first substrate. And a region surrounded by the first relationship line, the second relationship line, the lowest junction temperature, and the highest junction temperature as a target region. In the target area Conditions than anodic bonding conditions in step is characterized and a fourth step of determining the anodic bonding conditions in the secondary anodic bonding process from the weak region.

  In the present invention, when conditions suitable as anodic bonding conditions in the secondary anodic bonding process cannot be determined, the anodic bonding conditions in the first process may be reset. That is, it is preferable to reset the junction temperature and the junction voltage in the first step.

  Further, in the present invention, the anodic bonding conditions in the secondary anodic bonding process are determined from the region where the conditions are weaker than the anodic bonding conditions in the first process in the target region. The junction temperature and the junction voltage in the secondary anodic bonding process are determined from the region where both the junction temperature and the junction voltage are lower than the junction temperature and the junction voltage in the first step in the target region.

  In the present invention, good bondability means that the base material is destroyed without breaking at the joint surface (interface) when it breaks. In multi-layer anodic bonding, it is assumed that there is good bonding property that no mobile ions are precipitated near the bonding surface.

  According to the present invention, at any junction temperature between the minimum junction temperature and the maximum junction temperature, and at a junction voltage that can obtain a current equal to or higher than the minimum current density necessary to ensure good bondability, Anodic bonding in the primary anodic bonding process is performed as the first process, and a minimum reference voltage is set as a minimum reference voltage, which is a minimum reference voltage required to secure a good bonding property, and at least a minimum bonding temperature In a temperature range including between the highest bonding temperature, the relationship between the lowest reference voltage and the bonding temperature is obtained as a first relationship line, and the bonded body of the first substrate and the glass substrate bonded in the first step The anodic bonding in the secondary anodic bonding process is performed, and the maximum reference voltage is defined as the bonding voltage at which mobile ions start to precipitate from the vicinity of the bonding surface between the glass substrate and the first substrate, and at least the minimum bonding temperature and the maximum bonding temperature Temperature including In the range, the relationship between the highest reference voltage and the junction temperature is obtained as the second relationship line, and the region surrounded by the first relationship line, the second relationship line, the lowest junction temperature, and the highest junction temperature is set as the target region. Since the anodic bonding conditions in the secondary anodic bonding step are determined from the region where the conditions are weaker than the anodic bonding conditions in the first step in the target region, the state in which good bondability is maintained and It is possible to manufacture a three-layer substrate with as little energy as possible without depositing mobile ions.

It is a figure which shows an example of a three-layer board | substrate. It is a figure which shows the 1st anodic bonding (primary anodic bonding) and the 2nd anodic bonding (secondary anodic bonding) at the time of manufacturing this three-layer substrate. It is a flowchart which shows the outline | summary of the determination procedure of the anodic bonding conditions at the time of manufacturing this three-layer board | substrate. It is a figure which shows the object area | region enclosed by the 1st relationship line, the 2nd relationship line, the minimum junction temperature, and the maximum junction temperature. It is a figure explaining the first anodic bonding (primary anodic bonding). It is a figure explaining the second anodic bonding (secondary anodic bonding). It is a figure explaining a mode that a mobile ion precipitates. It is a figure explaining a side anodic bonding system.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a pressure sensor 100 having a three-layer structure as an example of a three-layer substrate. In the figure, reference numeral 1 denotes a sensor chip (silicon substrate), 2 denotes a glass pedestal, 3 denotes a silicon tube, and a joined body of the glass pedestal 2 and the silicon tube 3 by the first anodic bonding (primary anodic bonding) ( A glass pedestal / silicone tube assembly) 4 is formed. Further, a joined body (sensor chip / glass pedestal / silicon tube joined body) 5 of the sensor chip 1 and the glass pedestal / silicon tube joined body 14 is formed by the second anodic joining (secondary anodic joining).

  That is, as shown in FIG. 2 (a), the glass pedestal 2 is a glass substrate referred to in the present invention, the silicon tube 3 is a first substrate referred to in the present invention, and the glass pedestal 2 and the silicon tube 3 are overlaid, The upper surface of the glass pedestal 2 is the negative electrode side (cathode side), the lower surface of the silicon tube 3 is the positive electrode side (anode side), and a high voltage is applied in a state where the bonding temperature is reached. And the glass pedestal / silicon tube joined body 4 are formed.

  Further, as shown in FIG. 2B, the sensor chip 1 is used as the second substrate in the present invention, the sensor chip 1 and the glass pedestal / silicon tube assembly 4 are overlapped, and the upper surface of the sensor chip 1 is added. The electrode side (anode side), the lower surface of the glass pedestal / silicon tube assembly 4 (the lower surface of the silicon tube 3) is the negative electrode side (cathode side), and a high voltage is applied in a state where the bonding temperature has been reached. 1 and the glass pedestal / silicon tube joined body 4 are anodically joined to form a sensor chip / glass pedestal / silicon tube joined body 15.

  As a method for manufacturing the pressure sensor 100, in order to efficiently produce the pressure sensor 100 in large quantities, a wafer (sensor chip wafer) in which a plurality of sensor chips 1 are created and a wafer (glass pedestal) in which a plurality of glass pedestals 2 are created. Wafer) and a wafer (silicon tube wafer) on which a plurality of silicon tubes 3 are formed are bonded to form a three-layer wafer bonded body, and the three-layer wafer bonded body is cut by dicing to form a plurality of pressure sensors 100. The method of obtaining is adopted.

  FIG. 3 is a flowchart showing an outline of a procedure for determining anodic bonding conditions when manufacturing the pressure sensor 100. Hereinafter, a method for determining the primary anodic bonding conditions and the secondary anodic bonding conditions when manufacturing the pressure sensor 100 will be described with reference to this flowchart. In the following description, it is assumed that primary anodic bonding and secondary anodic bonding are performed at the wafer level.

First, the lower limit value and the upper limit value of the bonding temperature at the time of anodic bonding are set to a minimum bonding temperature TL (for example, TL = 300 ° C.) and a maximum bonding temperature TH (for example, TH = 380 ° C.). Junction at which a current equal to or higher than a minimum current density IL (for example, IL = 1.5 A / m ² ) necessary for ensuring good bonding performance can be obtained at an arbitrary bonding temperature T1 between the temperature TH. At the voltage V1, anodic bonding (primary anodic bonding) between the glass pedestal 2 and the silicon tube 3 is performed (step S101, FIG. 2A). In addition, the upper limit value of the bonding temperature at the time of anodic bonding is determined from the product specifications.

  Thus, after anodically bonding the glass pedestal 2 and the silicon tube 3, it is confirmed whether or not the bonding property is good (step S102). If the bondability is not good (NO in step S102), the anodic bonding between the glass pedestal 2 and the silicon tube 3 is repeated by changing the bonding temperature T1 and the bonding voltage V1, that is, changing the primary anodic bonding conditions. Hereinafter, the junction temperature T1 is referred to as a primary junction temperature, and the junction voltage V1 is referred to as a primary junction voltage.

  If the bondability is good (YES in step S102), the minimum reference voltage VL is set as the minimum reference voltage VL to obtain the minimum current density IL necessary for ensuring good bondability, and at least the minimum junction temperature TL and the maximum In a temperature range including between the junction temperature TH, the relationship between the lowest reference voltage VL and the junction temperature is obtained as a first relationship line I (step S103).

  Specifically, the junction voltage that can obtain the minimum current density IL necessary to ensure good jointability at several points in the temperature range of the minimum junction temperature TL and the maximum junction temperature TH was obtained and obtained. A first relation line I is obtained by plotting a graph in which the junction voltage is the lowest reference voltage VL, the horizontal axis is the junction temperature T, and the vertical axis is the junction voltage V, and the plotted points are connected (see FIG. 4). ).

  Then, the joined body of the glass pedestal 2 and the silicon tube 3 determined to have good bondability in step S102 is a glass pedestal / silicon tube joined body 4, and the glass pedestal / silicon tube joined body 4 and the silicon chip 1 Anodic bonding (secondary anodic bonding) is performed (step S104, FIG. 2B).

  In this step S104, the secondary anodic bonding is repeatedly performed while changing the anodic bonding conditions, and the highest standard is set to the bonding voltage at which mobile ions start to precipitate from the vicinity of the bonding surface (primary bonding surface) between the glass pedestal 2 and the silicon tube 3. The relationship between the highest reference voltage VH and the junction temperature T is obtained as a second relationship line II in the temperature range including at least the minimum junction temperature TL and the maximum junction temperature TH.

  Specifically, at several points in the temperature range of the lowest bonding temperature TL and the highest bonding temperature TH, the bonding voltage at which mobile ions begin to precipitate from the vicinity of the bonding surface (primary bonding surface) between the glass pedestal 2 and the silicon tube 3 is set. The second relationship line II is obtained by plotting the obtained junction voltage in a graph with the junction voltage T as the maximum reference voltage VH and the junction temperature T as the horizontal axis and the junction voltage V as the vertical axis. (See FIG. 4).

  Then, a region surrounded by the first relationship line I, the second relationship line II, the lowest junction temperature TL, and the highest junction temperature TH (region S1 indicated by a dotted line in FIG. 4) is set as a target region, and this target region S1 The secondary anodic bonding condition P2 (T2, V2) is determined from the region where the condition is weaker than the primary anodic bonding condition P1 (T1, V1) (step S105).

  Specifically, the primary junction temperature T1 and the primary junction voltage V1 set in step S101 are set as primary anodic bonding conditions, and the junction temperature and the primary junction temperature T1 and the primary junction voltage V1 in the target region S1 are set. From the region where both of the junction voltages are low (region S2 indicated by the mesh line in FIG. 4), the optimum junction temperature T2 and junction voltage V2 considering the safety factor and the energy consumption are determined as the secondary anodic junction conditions. Hereinafter, the junction temperature T2 is referred to as a secondary junction temperature, and the junction voltage V2 is referred to as a secondary junction voltage.

  In the present embodiment, since the side anodic bonding method is not adopted, the distance between the electrodes is short, and the secondary anodic bonding conditions in the target region S1 are all energy saving as compared with the side anodic bonding method. Furthermore, since the optimum secondary anodic bonding condition P2 (T2, V2) in consideration of the safety factor and the energy consumption is determined from the region S2 where the conditions are weaker than the primary anodic bonding condition P1 (T1, V1). Furthermore, energy saving is achieved.

  The safety factor is determined by defining a pair of the secondary junction temperature T2 and the secondary junction voltage V2 on the first relationship line I, that is, the secondary junction temperature T2 and the secondary junction voltage V2 in the line of the lowest reference voltage VL. If this pair is determined, the current density is insufficient because it is a marginal line, and there is a possibility that good jointability may not be obtained. Therefore, a pair of the secondary junction temperature T2 and the secondary junction voltage V2 is determined not in the first relationship line I but in a region above the first relationship line I considering the safety factor. In addition, considering the decrease in energy consumption due to the voltage drop and the increase in energy consumption due to the temperature rise, the energy consumption should be combined with the safety factor to be advantageous in terms of energy consumption. A pair of the secondary junction temperature T2 and the secondary junction voltage V2 is determined.

  After determining the secondary anodic bonding condition P2 (T2, V2) in this way, the secondary anodic bonding is actually performed under the determined secondary anodic bonding condition P2 (T2, V2). If good bondability is obtained (YES in step S106), and if no mobile ions are deposited on the primary bonding surface (YES in step S107), the primary anodic bonding condition P1 (T2, V2) set in step S101 is obtained. ) And the secondary anodic bonding condition P2 (T2, V2) determined in step S105, the primary anodic bonding condition P1 (T1, V1) and the secondary anodic bonding condition P2 (T2, V2) when the pressure sensor 100 is manufactured. (Step S108).

  In the case where good bondability is not obtained by secondary anodic bonding (NO in step S106), and when mobile ions are deposited on the primary bonding surface (NO in step S107), step Returning to S105, the secondary anodic bonding condition P2 (T2, V2) is determined again.

  In Step S105, when an appropriate condition cannot be determined as the secondary anodic bonding condition P2 (T2, V2), the process returns to Step S101 to set the primary anodic bonding condition P1 (T1, V1). Try again.

[Extension of the embodiment]
The present invention has been described above with reference to the embodiment. However, the present invention is not limited to the above embodiment. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the technical idea of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Sensor chip (silicon substrate), 2 ... Glass base, 3 ... Silicon tube, 4 ... Glass base / silicon tube joined body, 5 ... Sensor chip / glass base / silicon tube joined body, 100 ... Pressure sensor.

Claims (3)

A primary anodic bonding step of anodic bonding one surface of the glass substrate to the first substrate using the first substrate as an anode and the glass substrate as a cathode;
The first substrate of the joined body of the first substrate and the glass substrate bonded by the primary anodic bonding step is used as a cathode, the second substrate is used as an anode, and the second substrate is used as the second substrate. In a method for determining anodic bonding conditions for determining anodic bonding conditions when a three-layer substrate is manufactured through a secondary anodic bonding step of anodic bonding two substrates,
The lower limit value and the upper limit value of the bonding temperature at the time of anodic bonding are set as the minimum bonding temperature and the maximum bonding temperature, and in order to ensure good bonding performance at an arbitrary bonding temperature between the minimum bonding temperature and the maximum bonding temperature. A first step of performing anodic bonding in the primary anodic bonding step at a bonding voltage at which a current equal to or higher than the minimum current density necessary for the above is obtained;
The lowest reference voltage is a junction voltage at which a minimum current density necessary for ensuring good jointability is obtained, and at least in the temperature range including between the lowest junction temperature and the highest junction temperature. A second step for obtaining a relationship between the voltage and the junction temperature as a first relationship line;
Anodic bonding in the secondary anodic bonding step is performed on the bonded body of the first substrate and the glass substrate bonded in the first step, and a bonding surface between the glass substrate and the first substrate The junction voltage at which mobile ions begin to precipitate from the vicinity is defined as the maximum reference voltage, and the relationship between the maximum reference voltage and the junction temperature is a second relationship at least in a temperature range including between the minimum junction temperature and the maximum junction temperature. A third step as a line;
A region surrounded by the first relationship line, the second relationship line, the minimum junction temperature, and the maximum junction temperature is set as a target region, and the anodic bonding condition in the first step in the target region is set. And a fourth step of determining an anodic bonding condition in the secondary anodic bonding step from a region where the conditions are weak. In the method for determining anodic bonding conditions according to claim 1,
A method for determining an anodic bonding condition, wherein when an appropriate condition as an anodic bonding condition in the secondary anodic bonding process cannot be determined, the anodic bonding condition in the first process is reset. In the method for determining anodic bonding conditions according to claim 1 or 2,
The anodic bonding conditions are a bonding temperature and a bonding voltage,
The fourth step includes
The junction temperature and junction voltage in the secondary anodic bonding step are determined from a region where both the junction temperature and junction voltage are lower than the junction temperature and junction voltage in the first step in the target region. A method for determining anodic bonding conditions.

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