JPH11220141A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a semiconductor device having a substrate for filling inert gas or vacuum sealing at high yield and simplified processes. SOLUTION: When a cap substrate 7 is mounted on a sensor substrate 1 through a recess formed in the cap substrate 7, a cavity part 10 is formed. By providing a communicating groove 9a, which communicates the cavity part 10 and its outer part is provided. Then, evacuation or inert gas filling can be performed through this communicating groove 9a. This communicating groove 9a is embedded, when the cap substrate 7 and the sensor substrate 1 are compressed and dissipates, when the cap substrate 7 and the sensor substrate 1 are subjected to eutectic bonding. As a result, the evacuation or the gas filling can be surely performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly, to a method of manufacturing a semiconductor device in which a protective cap for covering a functional element is bonded in an inert gas or vacuum. . In particular, it is preferable to apply the present invention to an acceleration sensor or the like used for side slip prevention control in a vehicle.

[0002]

2. Description of the Related Art A semiconductor acceleration sensor or the like utilizing a surface micromachining technology has a movable portion (vibrating portion) on a silicon chip, and a physical quantity such as acceleration is converted into an electric signal by displacement of the movable portion (vibrating portion). It is designed to be converted and taken out. In such a semiconductor device, the movable portion is covered with a cap to protect the movable portion (vibrating portion). In other words, the cap protects the movable part (vibrating part) from water pressure and water flow when dicing and cutting from the wafer to the chip, and prevents resin from entering the inside of the movable part when performing resin molding.

[0003] However, in consideration of high sensitivity of the sensor, stabilization of characteristics, avoidance of air damping, etc., an inert gas or vacuum is suitable as an atmosphere around the movable part. A cap that can be sealed in an atmosphere is indispensable. For this reason, conventionally, the atmosphere around the movable portion is set to an inert gas or a vacuum atmosphere, and the sensor substrate (substrate on which the sensor is formed) on which the cap substrate (substrate serving as a cap) is mounted is bonded to the bonding chamber. The cap substrate is bonded to the sensor substrate by heating in a state where the inside of the bonding chamber is in an inert gas atmosphere or in a vacuum, or an inert gas filling hole or a vacuum exhaust hole is provided after bonding. A method is adopted in which the atmosphere around the part is made an inert gas or a vacuum atmosphere, and then the holes are sealed by film formation.

[0004]

However, the conventional method has the following problems. That is, according to the former method, since the gap between the cap substrate and the sensor substrate cannot be secured due to the weight of the cap substrate, there is a problem that the inert gas cannot be sufficiently filled or exhausted inside the cap due to the conductance. is there. In this case, the pressure inside the cap may vary or may not reach the target pressure.

Further, according to the latter method, it is impossible to fill with an inert gas because the film must be formed in a vacuum state to some extent. There is a problem that it becomes necessary. Therefore, an object of the present invention is to provide a semiconductor device having a substrate for filling with an inert gas or vacuum sealing.
It is an object of the present invention to provide a method for manufacturing a semiconductor device which can be manufactured with a high yield and in a reduced number of steps.

[0006]

In order to achieve the above object, the following technical means are employed. In the invention according to claims 1 to 4, a cavity (10) between the first semiconductor substrate (7) and the second semiconductor substrate (1) formed by the recess (7a), and the cavity Forming a communication groove (9a) that communicates with the outside of the part, evacuation or gas filling of the cavity through the communication groove, and sandwiching the first semiconductor substrate and the second semiconductor substrate The method includes a step of filling the communication groove formed in the bonding film by applying pressure in the direction to cut off the cavity and the outside thereof.

As described above, before the first and second semiconductor substrates are joined, the communication groove is temporarily formed, and vacuum evacuation or gas filling is performed through the communication groove. By pressurizing in a direction sandwiching the gap, the communication groove is filled to shut off the cavity from the outside, so that vacuum evacuation or gas filling can be performed reliably. In addition, since the communication groove is filled and disappears when the pressure is applied, the manufacturing process can be simplified without having to seal the communication groove by film formation.

Accordingly, a semiconductor device having a substrate for filling with an inert gas or vacuum sealing can be manufactured with a high yield and with a reduced number of steps. Specifically, as described in claim 2, at least one communication groove may be formed in parallel with the joint surface between the first semiconductor substrate and the second semiconductor substrate. It is also possible to The shape of the communication groove may be any shape as long as the communication groove allows the hollow portion to communicate with the outside.

In the eutectic bonding using the bonding film, Au-Si based on gold contained in the bonding film and silicon contained in the first and second semiconductor substrates.
This can be done with a eutectic layer. In a case where a structure having a low mechanical strength (for example, an acceleration sensor (2) is formed on the second semiconductor substrate), the invention according to claims 1 to 3 is applied. It is preferable to apply.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention. FIG. 1 is a sectional view of an acceleration sensor to which one embodiment of the present invention is applied, and the structure of the acceleration sensor will be described. FIG. 1A is a cross-sectional view in a direction passing through the acceleration sensor, and FIG.
It is sectional drawing in the -A arrow direction.

As shown in FIG. 1, a movable part (sensing part) 2 of an acceleration sensor is formed in a predetermined area of a sensor substrate 1. The sensor substrate 1 includes a silicon substrate 3, an insulating film 4 formed on the silicon substrate 3, a movable part 2, an SOI substrate 5 used for forming the movable part 2, and a movable part 2.
And an electrode portion 6 electrically connected to the first electrode. The cap substrate 7 is mounted on the sensor substrate configured as described above, and the movable portion is covered by the cap substrate 7.

The cap substrate 7 includes a cap wafer 8 and a bonding film 9 formed on one surface of the silicon substrate. A concave portion 7a is formed in the cap substrate 7, and the movable portion 2 is covered by the concave portion 7a in a state where a predetermined hollow portion 10 is formed between the cap substrate 7 and the sensor substrate 1. . This cavity 10
The inside is filled with an inert gas (or is in a vacuum state), and consideration is given to increasing the detection sensitivity of the sensor, stabilizing the characteristics, and avoiding air damping.

The bonding film 9 is formed on the surface of the cap substrate 7 where the concave portion 7a is formed, and the cap substrate 7 and the sensor substrate 1 are formed by eutectic bonding of the bonding film 9.
And are combined. The bonding film 9 is made of a Ti film or an Au film. When the cap substrate 7 and the sensor substrate 1 are pressurized, these films are eutectic bonded.
The cap substrate 7 and the sensor substrate 1 are joined.

As shown in FIG. 1B, a concave portion 8a which is partially etched away is formed in the cap wafer 8, and the details of the concave portion 8a will be described later. Next, a method for manufacturing the acceleration sensor shown in FIG. 1 will be described with reference to FIGS.

[Step shown in FIG. 2A] First, a wafer (hereinafter referred to as a cap wafer) substrate 8 for forming the cap substrate 1 is prepared, and a thermal oxide film is formed on the front and back surfaces of the cap wafer 8. 12 are formed at 5000.degree. And the surface side is patterned by photoetching. Then, using the oxide film 12 as a mask, a concave portion 8a is formed in the cap wafer 8 by etching.

When the cap wafer 8 is a Si substrate,
It can be formed by dry etching using an oxide film as a mask. The recess 8a is used to form a communication groove for introducing an inert gas (or a communication groove for evacuating). The concave portion 8a may be formed not only at right angles to the side of the cap having the concave portion, but also obliquely or around the joint.

[Step shown in FIG. 2 (b)] A thermal oxide film 13 is formed on the front and back surfaces of the cap wafer 8 at 5000.degree., And the front surface is patterned by photoetching. Then, etching is performed by using the thermal oxide film 13 as a mask to form irregularities on the cap wafer 8. More specifically, as shown in a top view of the cap wafer 8 shown in FIG. 5 (a view of FIG. 2B as viewed from above in FIG. 2), a concave portion 7a for protecting the movable portion 2 of the sensor. And a dicing blade 22 when dicing the cap wafer 8 in a later step.
A concave portion 7b for securing a gap (between sensing portions) required to avoid contact between the sensor wafer 20 and the sensor wafer 20 (see FIG. 3C).

[Step shown in FIG. 2 (c)] The thermal oxide film 13 used as a mask is removed on both the front and back surfaces using an HF aqueous solution.
Ti14 and Au1 required to form a plating film
5 is continuously formed in a vacuum by a vapor deposition method or a sputtering method. At this time, the film thickness of Ti14 and Au15 is set to 1000 °.

Next, a plating process is performed on the entire surface of the Au surface by electrolytic plating to form an Au film 16. However, Au
Is not limited to plating, but may be formed by vapor deposition or sputtering. At this time, the thickness of the Au film 16 is 3.5 μm. Further, Ti17 having a reducing action and Au18 for preventing its oxidation are continuously formed in a vacuum. At this time, the thickness of Ti17 is set to 50 to 800 °.
For example, if the thickness of the Ti film 17 is 1000 ° or more, a large amount of Ti silicide other than titanium oxide is formed, and the bonding strength is reduced.

The film thickness of Au18 is such that Ti in Au is Si
The angle is set to 200 ° in consideration of diffusion to the surface. Thus, Ti14, Au15,
The Au film 16 and the Ti film 17 are formed to form the bonding film 9. At this time, the recess 8 described above is formed in the cap wafer 8.
Since a is formed, the concave portion 9a remains even when the bonding film 9 is formed, and the concave portion 9a becomes a communication groove for introducing an inert gas (or evacuation). . Hereinafter, the concave portion 9a is referred to as a communication groove 9a. The communication groove 9a is formed so that each of the recesses 7a for protecting the movable portion 2 of the sensor communicates with the outside through the recess 7b, as in FIG. Thus, the cap substrate 7 is completed.

Next, alignment lines for dividing the cap substrate 7 are formed. That is, as shown in FIG. 6, the edges of the formed projections are set as reference lines L1 and L2, and the predetermined distances ΔL1 and ΔL from the reference lines L1 and L2.
Dicing cuts are made at positions separated by two (dicing lines L3 and L4). Although two dicing cut lines are formed in FIG. 3, if the facet cutting accuracy of the cap substrate 7 is reliable, the dicing cut line can be used as a reference alignment line. In this case, only one facet may be perpendicular to the facet.

[Step shown in FIG. 3A] Next, the movable part 2
The portion where the silicon is exposed in the sensor substrate 1 on which is formed is brought into contact with the bonding film 9 of the cap substrate 7. At this time, since the communication groove 9a is formed in the cap substrate 7, when the movable portion 2 is covered with the cap substrate 7, the cavity 1 formed by the cap substrate 7 and the sensor substrate 1 is formed.
0 indicates a state of communication with the outside. And the communication groove 9a
(Or vacuum evacuation) of an inert gas.

[Step shown in FIG. 3 (b)]
The temperature is set to 00 ° C., the pressure applied to the cap substrate 7 and the sensor substrate 1 is set to ² gf / mm ² , and the holding is performed for 10 minutes. Thereby, soft Au or the like is pressed, and the Au 15, the Au film 16, and the Ti film 17 become the Au-Si eutectic layer 20. Then cool. At the time of this pressurization, the communication groove 9a is Au-Si
It is filled with the eutectic layer 23 and disappears. The sensor substrate 1 and the cap substrate 7 are joined by the Au-Si eutectic layer 23, and the inside of the cavity 10 is sealed with an inert gas or vacuum.

FIGS. 7A and 7B are cross-sectional views of the cap substrate 7 and the sensor substrate 1 before and after this bonding step.
(B). As shown in this figure, it can be seen that the communication groove 9a is open before the joining step, and the communication groove 9a is filled and disappears after the joining. [Step shown in FIG. 3C] Next, the cap substrate 7 is diced and cut by a dicing blade 22 in order to separate the cap portion 7c and the unnecessary cap portion 7d. At this time, the cutting direction is perpendicular to the facet as shown in FIG. 8A, and the cut interval and the cut position are determined based on the alignment lines L3 and L4 formed earlier. At this time, since the lines L3 and L4 are formed, dicing can be easily performed even if there is no pattern such as a scribe line on the back surface of the cap substrate 7. Thereby, as shown in FIG. 8A, the dicing line L5 which is one of the dicing lines of the cap substrate 7 is cut.

[Step shown in FIG. 4A] Next, an adhesive sheet 23 for dicing and cutting is attached to the back surface of the cap substrate 7. Here, it is expected that air is trapped when the adhesive sheet 23 is adhered, and the air-trapped portion is not fixed by the adhesive sheet and is scattered after the dicing cut. Because of this, air can be exhausted from there, so if this is rubbed lightly after pasting, this problem can be avoided.

[Step shown in FIG. 4B] This figure is a cross-sectional view in which the cross-sectional directions of the sensor substrate 1 and the cap substrate 7 are changed by 90 degrees. As shown in this figure, the cap substrate 7 together with the adhesive sheet 23 is diced and cut again by the dicing blade 22 to divide the unnecessary portion 7e. The cutting direction is perpendicular to the line L5 as shown in FIG. 8B, and the cut interval and the cut position are determined on the basis of the alignment line, similarly to the formation of the line L5. Thus, the dicing cut line L6 is formed. In the drawing, the adhesive sheet 23 is indicated by oblique lines.

In this dicing step, the adhesive sheet 23 is cut with the adhesive sheet 23 adhered to the cap substrate 7, so that unnecessary materials 7 e are scattered during the dicing cut to damage the electrodes 6 and the like on the surface of the sensor substrate 1 and the dicing blade 2.
2 can be prevented from being damaged. That is, the unnecessary object 7e is fixed to the adhesive sheet 23, and the above-described problem can be avoided. In the present embodiment, the order of cutting is performed in the order of the lines L5 and L6, but there is no problem even if the order in the dicing cut direction is reversed.

[Step shown in FIG. 4C] Next, the adhesive sheet 23 is peeled off from the divided cap substrate 7. At this time, the cap unnecessary portion 7e is removed together with the adhesive sheet 23, and the cap 7c is placed on the sensor substrate 1 as shown in FIG.
Will be mounted. Next, the sensor substrate 1 is diced and cut along the scrub line to form a sensor chip. Thus, the acceleration sensor shown in FIG. 1 is completed.

As described above, introduction of the inert gas (evacuation)
By performing the following, the hollow portion 10 formed by the sensor substrate 1 and the cap substrate 7 is communicated with the outside, and the communication groove 9a which disappears at the time of joining after the introduction of the inert gas (evacuation) is provided. The inside of the part 10 can be completely made into an inert gas atmosphere (or a vacuum state). For this reason, the space for introducing the inert gas cannot be secured by the weight of the cap substrate 7, and the inside of the cap 7c (the cavity 10) cannot be filled with the inert gas or evacuated sufficiently due to the influence of the conductance. Problem does not occur. Further, there is no variation in the pressure inside the cap 7c, and the pressure does not reach the target pressure. Further, unlike the case where an inert gas introduction hole is formed after bonding, an inert gas can be reliably introduced into the cap 7c, and the hole is closed by film formation as in the case where a vacuum exhaust hole is provided. Since no process is required,
It is also possible to omit a process for forming a film and to simplify a semiconductor device manufacturing process.

As described above, according to the method of the present embodiment,
A semiconductor device having a cap substrate for filling with an inert gas or vacuum sealing can be manufactured with a high yield and with a reduced number of steps. (Other Embodiments) In this embodiment, the sensor wafer is described as the first semiconductor substrate and the cap wafer is described as the second semiconductor substrate.
Alternatively, a wafer including circuit elements may be used as the second semiconductor substrate. This form is a multi-chip called Chip On Chip and has an advantage that the effective area can be reduced.

According to the present invention, a protective cap in an inert gas or vacuum atmosphere can be manufactured on a chip on which a structure having low mechanical strength is formed with a high yield.
Moreover, the groove used for filling with an inert gas or vacuum evacuation disappears and is sealed by the Au-Si eutectic layer generated at the time of joining, so that the process can be simplified. In addition, unlike the direct wafer bonding, it is hardly affected by the surface roughness at the time of bonding,
Since high-temperature heat treatment is unnecessary, it can be applied to various processes.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an acceleration sensor manufactured by applying one embodiment of the present invention.

FIG. 2 is a diagram showing a manufacturing process of the acceleration sensor shown in FIG.

FIG. 3 is a diagram illustrating a manufacturing process of the acceleration sensor continued from FIG. 2;

FIG. 4 is a view illustrating a manufacturing process of the acceleration sensor continued from FIG. 3;

FIG. 5 is a diagram showing a state before and after bonding a cap wafer and a sensor substrate 1;

FIG. 6 is a diagram for explaining a cutting position alignment line when dicing and cutting the sensor substrate 1 and the cap wafer.

FIG. 7 is an explanatory diagram showing a dicing cut state of the cap substrate.

FIG. 8 is an explanatory diagram showing a dicing cut state of the sensor substrate 1.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sensor board, 2 ... Movable part, 3 ... Cap wafer,
4 insulating film, 5 SOI film, 6 electrodes, 7 cap substrate, 7a, 7b recess, 7c cap, 9 bonding film, 9a communication groove, 14 Ti, 15 Au, 16 ... A
u film, 17 ... Ti film, 18 ... Au film, 20 ... Au-Si
Eutectic layer.

Claims (5)

[Claims] A first portion having a concave portion formed on one surface side;
When the semiconductor substrate (8) is mounted on the second semiconductor substrate (1) via the bonding film (9), the first semiconductor substrate and the second semiconductor substrate formed by the concave portion Forming a communication groove (9a) communicating between the cavity (10) and the outside thereof; a step of evacuating or filling the interior of the cavity with the communication groove; By pressing in a direction sandwiching the first semiconductor substrate and the second semiconductor substrate, the first film is pressed by the bonding film.
Eutectic bonding between the semiconductor substrate and the second semiconductor substrate, and filling the communication groove to cut off the cavity from the outside. 2. The bonding film is formed on one of the first semiconductor substrate and the second semiconductor substrate, and the communication groove is formed on the first semiconductor substrate and the second semiconductor substrate. 2. The method of manufacturing a semiconductor device according to claim 1, wherein at least one semiconductor device is formed in parallel with a bonding surface of the semiconductor device. 3. The eutectic bonding using the bonding film is performed using an Au—Si eutectic layer including gold included in the bonding film and silicon included in the first and second semiconductor substrates. The method for manufacturing a semiconductor device according to claim 1, wherein: 4. The semiconductor device according to claim 1, wherein the second semiconductor substrate is provided with a structure having a low mechanical strength, and the structure is disposed in the cavity. 4. The method for manufacturing a semiconductor device according to any one of items 3 to 3. 5. A plurality of elements (2) formed for each chip
When a second semiconductor substrate for a cap having a recess formed thereon for covering each of the plurality of elements is mounted on a first semiconductor substrate (1) having Forming a cavity (10) between the first semiconductor substrate and the second semiconductor substrate and a communication groove (9a) communicating the outside thereof; and forming a vacuum in the cavity through the communication groove. Exhausting or filling with gas, and pressurizing the first semiconductor substrate and the second semiconductor substrate in a direction sandwiching the first semiconductor substrate and the second semiconductor substrate.
Eutectic bonding between the semiconductor substrate and the second semiconductor substrate, and filling the communication groove to cut off the cavity from the outside; and the first semiconductor substrate and the second semiconductor substrate. And dicing the semiconductor chip into chips.