JPH0496353A - Sealing structure, manufacture thereof and semiconductor device - Google Patents

Abstract

PURPOSE:To relax thermal stress, and to realize high reliability at low cost by forming sealing structure composed of a cap being sealed with a base and organizing a sealing space and forming the side face of the cap in expansible curved structure. CONSTITUTION:A bellows-shaped curved structure 4a is formed to the side face section of a cap 14 sealing a semiconductor element 3 between the cap 4 and a base 1. Consequently, the curved structure 4a is easily expanded and contracted and deformed in the direction of the laminating of the base 1, the semiconductor element, etc., and the direction of the plane of the base 1 without damaging the airtight sealing state of the semiconductor element 3. As a result, even when thermal deformation such as expansion and contraction is generated in the semiconductor element 3, bump electrodes 2 and further the cap 11 at the time of heating, cooling and the change of an ambient temperature by the operation of the semiconductor element 3 and opeeration stoppage, the curved structure 4a in the cap 4 follows up to these deformation and is deformed easily. Accordingly, the working of large thermal stress to the semiconductor element 3 and the bump electrodes 2 and sealing sections with the cap 4 and the base 1 is avoided.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a sealing structure, a method for manufacturing the same, and a semiconductor device, and particularly relates to a technique effective when applied to sealing a semiconductor element using flip chip technology. .

[Conventional technology]

For example, in the packaging technology of semiconductor devices, from the viewpoint of responding to demands such as increased heat generation due to higher integration of semiconductor elements and improved packaging density, conventionally, for example, Japanese Patent Application Laid-Open No. 62-249429 Encapsulation techniques as disclosed have been proposed.

In other words, a semiconductor element is mounted on a package substrate using so-called flip-chip technology, which is connected via a plurality of solder bumps, and is sealed with a cap having a U-shaped cross section that is sealed to the package substrate by brazing or the like. . Then, the internal dimensions of the cap are set so that the top surface of the semiconductor element (the back side of the connection surface by solder bumps) and the top inner surface of the cap are in contact with each other, and the contact interface between the two is filled with a desired metal layer, etc. to form a sealing structure. That is.

By the way, the use of aluminum nitride (Aj!N), for example, is becoming common as a material for the cap constituting the conventional sealing structure as described above, for the following reasons. That is, (1) it has a coefficient of thermal expansion close to that of a semiconductor element made of silicon or the like, (2) it has excellent strength and relatively low hardness and is easy to process, and (3) it can be sintered under normal pressure.

[Problem to be solved by the invention]

However, in the above-mentioned conventional technology, aluminum nitride, which is a material for the cap, is expensive, which is a factor in increasing the manufacturing cost of the sealing structure.

In addition, since the semiconductor element is confined and sealed inside the rigid structure made up of the package paste and the cap, the semiconductor element and solder bumps can be easily bonded due to temperature changes caused by heat generated during operation. Thermal stress acts on the solder bumps and the package base, resulting in a decrease in reliability, such as failure of continuity due to unintentional breakage of the joint between the solder bump and the package base.

In order to avoid this, it is necessary to strictly design/manufacture the dimensions of the cap, but such measures will further increase the manufacturing cost of the cap as described above.

Therefore, an object of the present invention is to provide an inexpensive and highly reliable sealing structure.

Another object of the present invention is to provide a method for manufacturing a sealed structure that allows a sealed structure of a desired shape to be easily obtained at low cost.

Still another object of the present invention is to provide an inexpensive and highly reliable semiconductor device.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means to solve the problem]

A brief overview of typical inventions disclosed in this application is as follows.

That is, the sealing structure according to the present invention is a sealing structure consisting of a paste and a cap that is sealed to the paste and forms a sealed space, and the side surface of the cap has a curved structure that can be expanded and contracted. It is.

Further, the method for manufacturing a sealing structure according to the present invention includes a pace,
A method for manufacturing a sealing structure comprising a cap that is sealed to the paste to form a sealing space, the method comprising: forming a desired sealing structure on the surface of a mold body having at least one convex portion or concave portion imitating the contour shape of the cap; The first step is to deposit and form a film made of a substance.
and a second step of obtaining the cap by removing the mold.

Further, a semiconductor device according to the present invention is obtained by sealing a semiconductor element using a sealing structure obtained by the method for manufacturing a sealing structure according to claim 4.5 or 6.

Further, the semiconductor device of the present invention includes a paste, a semiconductor element bonded to the paste via a solder bump, and a joint between the base and the semiconductor element sealed between the paste and the semiconductor element. The frame material has a structure in which an expandable and contractible curved structure is formed on the side surface of the frame material.

[Effect]

According to the above-described sealing structure of the present invention, even when a semiconductor element is mounted on the base side via solder bumps and the back side is connected to the cap in a sealed state, the temperature of the semiconductor element and the cap increases. Dimensional changes due to changes are absorbed by the expansion and contraction deformation of the curved structure provided in the cap, thereby avoiding large thermal stress from acting on semiconductor elements, solder bumps, and the like. Furthermore, it is no longer necessary to use expensive aluminum nitride or the like as a material for the cap in order to bring the coefficient of thermal expansion close to that of the material of the semiconductor element. As a result, a highly reliable sealing structure with few occurrences of failures due to breakage of the encapsulated semiconductor element or solder bumps can be realized at low cost.

Further, according to the method for manufacturing a sealing structure according to the present invention, even if the cap has a complicated shape with a curved structure such as a bellows shape, the cap can be manufactured without going through complicated processing or assembly steps. By depositing a film made of a desired substance on the surface of a mold according to the shape by a method such as electroless plating, it can be easily formed at low cost.

Further, according to the semiconductor device according to claims 6 and 7 of the present invention, the semiconductor device is formed of a desired metal or the like and has a curved structure such as a bellows shape that is effective for alleviating thermal stress acting on semiconductor elements, solder bumps, etc. By adopting a sealing structure using a cap made of aluminum nitride, it is possible to obtain high reliability at a lower cost than when using a sealing structure with a cap made of expensive materials such as aluminum nitride. can.

Further, according to the semiconductor device according to claim 8 of the present invention, the semiconductor element and the base are sealed by a stretchable frame material, and the frame material is made of an inexpensive metal or the like, thereby reducing the cost. This makes it possible to improve reliability by alleviating thermal stress. Furthermore, the frame material is made of a shape memory alloy, bimetal, etc. that is set to expand at a temperature near the melting point of the solder bump, and after assembly, the frame material is stretched by heating to a temperature around the melting point of the solder bump. According to
By making the shape of the solder bump into a drum shape, stress concentration at the joint between the solder bump and both the semiconductor element and the base is alleviated, and the reliability of the joint by the solder bump can be further improved.

[Example 1] Hereinafter, an example of a sealing structure and its manufacturing method, which is an example of the present invention, and a semiconductor device using the same will be described in detail with reference to the drawings.

FIG. 1 is a schematic cross-sectional view schematically showing an example of the configuration of a sealing structure and a semiconductor device using the same, which is an embodiment of the present invention, and FIGS. It is a schematic sectional view showing an example of a manufacturing method in order of steps.

First, the sealing structure of this embodiment and the structure of a semiconductor device using the same will be explained with reference to FIG.

For example, in the base 1, which is made of ceramics such as alumina or mullite, and has a multilayer wiring structure (not shown) formed therein, the upper surface where the surface electric bridge is exposed and where electricity is distributed is made of, for example, Pb-3n solder. Bump electrode 2
Semiconductor element 3 is electrically and mechanically connected and fixed by face-down bonding technology.

On the upper surface of the base 1, a cap 4 made of, for example, nickel, copper, cobalt, gold, or an alloy thereof is provided in a peripheral region surrounding the mounted semiconductor element 3. Pb-Ag-5n
A semiconductor device is constructed by sealing the semiconductor element 3 through a bonding layer 5 made of Pb-Ag-In-based solder or the like.

A filling layer 6 made of, for example, the same material as the bonding layer 5 described above is interposed in the gap between the semiconductor element 3 and the cap 4, and heat generated during the operation of the semiconductor element 3 is transferred to the filling layer 6.
The structure is such that it is efficiently dissipated to the outside via the cap 4.

A plurality of mounting bump electrodes 7 are arranged on the bottom surface of the base 1, and the mounting bump electrodes 7 are the bump electrodes inside the multilayer wiring structure and sealing structure (not shown) provided inside the base 1. 2, it is connected to an integrated circuit inside the semiconductor element 3.

Then, by performing face-down bonding to a mounting board (not shown) via the mounting bump electrode 7, the semiconductor device is mounted on the mounting board (not shown).

The arrangement pitch of the bump electrodes 2 and the mounting bump electrodes 7 that are connected to each other is set to be equal to each other, or so that the mounting bump electrodes 7 are larger.

Further, the bump electrode 2 in the above structure. Filled layer 6. Joining 15. The melting temperature of the bump electrode 7 for mounting is set to be the highest for the bump electrode 2, the filling layer 6 and the bonding layer 5 are the same or higher, and the melting temperature of the bump electrode 7 for mounting is set to be the lowest. . Therefore, it is possible to accurately join each part according to the assembly order without melting each other.

In case 2, a bellows-like curved structure 4a, for example, is provided on the side surface of the cap 4 that seals the semiconductor element 3 between it and the base 1, without impairing the hermetically sealed state of the semiconductor element 3. , the base 1 and the semiconductor element 3 are easily expanded and deformed in the stacking direction and in the planar direction of the base 1.

For this reason, for example, when heating and cooling the semiconductor element 3 due to activation and deactivation, or fluctuations in environmental temperature, the semiconductor element 3, the bump electrodes 2, and even the cap 4
Even if thermal deformation such as expansion and contraction occurs in the cap 4, the curved structure 4a of the cap 4 easily deforms following these deformations, so that the semiconductor element 3, the bump electrodes 2, and even the cap 4 and the base 1 are It is possible to reliably avoid applying large thermal stress to the sealing portions, etc.

As a result, failures such as malfunctions caused by damage to the semiconductor element 3 and bump electrodes 2 due to thermal stress, and failures such as poor airtightness due to breakage of the sealing part, are prevented, and the sealing structure and semiconductor device reliability will definitely improve.

In addition, for the purpose of achieving both the rigidity of the cap and the relaxation of thermal stress as in the past, for example, a material such as aluminum nitride, which has a good thermal expansion coefficient matching with silicon, which is the material of the semiconductor element 3, is used. It is not necessary to use expensive ceramics or the like, and the cap 4 can be made of an inexpensive metal or the like having sufficient sealing performance, and the manufacturing cost of the sealing structure and the semiconductor device can be reduced.

Next, an example of the method for manufacturing the cap 4 used in the sealing structure and semiconductor device illustrated in FIG. 1 is shown in FIGS. 2(a) to 2(a).
This will be explained in detail with reference to (C).

First, as shown in FIG. 4(a), a rubber mold 8 having a plurality of protrusions imitating the internal shape of the cap 4 formed at a predetermined pitch on the surface is formed by an existing process, and further,
In order to stabilize the shape, a shaping plate 9 that matches the undulations of the rubber mold 8 is combined.

In this case, since the rubber mold 8 is an electrically insulating material, electroless plating is used.

That is, in order to form an electroless plating film on a nonconductor, it is necessary to adsorb the catalyst species that will become the precipitation nuclei of the plating onto the surface of the rubber mold 8, so a pretreatment is performed, for example, by one of the following methods. .

l) First, the surface of the rubber mold 8 is coated with stannous ions (Sn2゛).
sensitization by immersion in a solution containing
g) and then activating by immersing it in a solution containing palladium ions (Pd'').The purpose of sensitization is to first form strongly adsorbed tin ions on the surface of the rubber mold 80. , and upon activation,
A catalyst species is formed by a reaction between palladium ions and tin ions on the surface of the rubber mold 80 [two-liquid method].

1i) A catalyst species is formed on the surface of the rubber mold 80 by immersing the rubber mold 8 in a suspension containing a mixture of l& ions and palladium ions [-liquid type].

After such processing, for example, nickel, copper.

Electroless plating of cobalt, gold, alloys thereof, etc. is performed to form a single-layer or multi-layer plating layer 40 of a desired material on the surface of the rubber mold 8 to a desired thickness. This state is shown in FIG. 2(b).

Next, the shaping plate 9 is removed from the rubber mold 8, and the rubber mold 8 is dissolved and removed using, for example, a solvent.

Thereafter, the plated layer 40 is cut into predetermined dimensions to obtain individual caps 4.

As described above, according to the manufacturing method of this embodiment, the curved structure 4a, which is difficult to manufacture by ordinary machining, for example.
A large number of caps 4 can be obtained simultaneously without any seams, and the manufacturing process can be easily automated.

Therefore, it is possible to mass-produce the cap 4 having the curved structure 4a while maintaining high strength and quality, and it is possible to reliably reduce the manufacturing cost of the sealing structure and semiconductor device using the cap 4.

In addition, in the above explanation, as an example of a method for removing the rubber mold 8 from the plating layer 40, a case was explained in which dissolution with a solvent is performed. Alternatively, a method may be used in which the plating layer 40 is mechanically peeled off by controlling the plating layer 40 .

Further, the individual caps 4 obtained by dividing the plating layer 40 may be plated with gold or other metal, if necessary, to improve strength and corrosion resistance.

Furthermore, as a pretreatment, instead of forming the catalyst species described above, a method such as forming an initial thin film corresponding to the catalyst species by, for example, a vapor deposition technique, and then performing normal electroplating may be used.

[Embodiment 2] FIG. 3 is a schematic cross-sectional view of essential parts schematically showing an example of the configuration of a semiconductor device according to another embodiment of the present invention.

In the case of this second embodiment, the semiconductor element 3 is mounted on the upper surface of the base 1 via the bump electrodes 2, and the bonding surface of the bump electrodes 2 on the semiconductor element 3 and the base 1
A cylindrical frame 10 whose both ends are sealed between the upper surface of the
is provided to seal the bonding region between the semiconductor element 3 and the base 1 and protect it from the outside.

Further, the frame 10 is provided with a bellows-shaped curved structure 10a that can be freely expanded and contracted, and the base 1. Bump electrode 2° semiconductor element 3. Furthermore, the frame 10 itself is configured so that thermal deformation is absorbed by the easy deformation of the curved structure 10H.

This causes harmful thermal stress to be applied to the semiconductor element 3 and the bump electrodes 2. The effect on the base 1 and the like is avoided, and the reliability of the semiconductor device is improved.

Further, the frame 10 having a complicated shape such as the curved structure 108 can be manufactured in large quantities and at low cost by the manufacturing method exemplified in the first embodiment described above.

On the other hand, a bump electrode 2 for bonding a semiconductor element 3 to a base 1
Since the bump electrode 2 has a spherical shape, a wedge-shaped space is formed around the joint between the bump electrode 2, the base 1, and the semiconductor element 3, resulting in a constricted state and contributing to stress concentration at the joint. There is.

Therefore, the frame 10 is made of, for example, a shape memory alloy, a bimetal, or the like that is designed to expand and deform near the melting temperature of the bump electrode 2.

After assembling as shown in FIG. 13, the frame 10 is expanded as shown in FIG. 4 by heating near the melting temperature of the bump electrode 2 to separate the base 1 and the semiconductor element 3. As a result, the molten spherical bump electrode 2 is solidified into a drum-shaped bump electrode 2a.

This eliminates stress concentration at the joints between the bump electrodes 2a, the semiconductor element 3, and the base 1, and increases the strength of the joints, thereby improving the reliability of the operation of the semiconductor device.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. Nor.

For example, when forming a cap, the shape of the mold body is not limited to providing a convex portion that imitates the inner circumferential shape of the cap, but also providing a concave portion that imitates the outer circumferential shape, and forming a desired shape on the inner circumferential surface of the concave portion. Alternatively, a film made of a substance may be deposited.

Furthermore, the method for forming a film made of a desired substance on the surface of the mold is not limited to electroless plating or electrolytic plating, but may also be, for example, chemical vapor deposition or sputtering.

〔Effect of the invention〕

Among the inventions disclosed in this application, the effects obtained by typical inventions are briefly described below.

That is, according to the sealing structure of the present invention, thermal stress is alleviated by the curved structure provided on the cap, and there is no need to use a specific expensive material for the purpose of alleviating thermal stress, so the cost is low. high reliability can be achieved.

Further, according to the manufacturing method of the sealing structure of the present invention, caps having arbitrary complicated shapes such as curved structures can be manufactured in large quantities at low cost using desired materials, and are easily reliable at low cost. A sealing structure with high properties can be obtained.

Further, according to the semiconductor device according to the present invention as set forth in claims 6 and 7, the curved structure provided in the cap constituting the sealing structure alleviates the occurrence of thermal stress. Since there is no need to use specific expensive materials, high reliability can be achieved at low cost.

Further, according to the semiconductor device according to the present invention as set forth in claim 8, the joint portion such as the solder bump that joins the semiconductor element and the base is reliably sealed by the frame constituting the sealing structure, and, for example, By stretching the frame through a heating operation after assembly and changing the shape of the spherical solder bumps into a drum shape with less stress concentration, the fatigue strength of the joint can be reliably improved, achieving high reliability at low cost. can do.

[Brief explanation of the drawing]

FIG. 1 schematically shows an example of the configuration of a sealing structure and a semiconductor device using the same, which is an embodiment of the present invention. FIG. 3 is a schematic cross-sectional view showing an example of the structure of a semiconductor device according to another embodiment of the present invention, and FIG. 4 is a schematic cross-sectional view showing an example of its operation. FIG. 2 is a schematic cross-sectional view of main parts shown in FIG. 1...Base, 2.2a...Bump electrode, 3...
Semiconductor element, 4... Cap, 4a... Curved structure,
5... Bonding layer, 6... Filling layer, 7... Bump electrode for mounting, 8... Rubber mold, 9... Shaping plate, 10...
Frame, 10a... Curved structure, 40... Plating layer (cap). Figure 3 Figure 4 10: Frame 10a: Curved structure agent Patent attorney Daikazu Tsutsui

Claims (1)

[Claims] 1. A sealing structure consisting of a base and a cap that is sealed to the base to form a sealed space, characterized in that the side surface of the cap has a curved structure that can be expanded and contracted. Sealed structure with 2. The sealing structure according to claim 1, wherein the cap is made of a bimetal or a shape memory alloy and is configured to spontaneously expand and contract at a desired temperature. 3. A method for manufacturing a sealed structure comprising a base and a cap sealed to the base to form a sealed space,
A first step of forming a film made of a desired substance on the surface of a mold body having at least one convex or concave portion imitating the contour shape of the cap, and removing the mold body to remove the cap. a second step of obtaining a sealed structure. 4. The method of manufacturing a sealing structure according to claim 3, wherein the cap is obtained by forming a multilayer film of a desired material on the surface of the mold body by electroless plating. 5. The method of manufacturing a sealing structure according to claim 3 or 4, wherein the mold body is made of an elastic material. 6. A semiconductor device comprising a semiconductor element sealed using the sealing structure according to claim 1 or 2. 7. A semiconductor device obtained by sealing a semiconductor element using a sealing structure obtained by the method for manufacturing a sealing structure according to claim 3 or 4. 8. A base, a semiconductor element bonded to the base via solder bumps, and a frame member sealed between the base and the semiconductor element to seal the joint between the base and the semiconductor element. A semiconductor device comprising: an expandable and contractible curved structure formed on a side surface of the frame member. 9. The frame material is made of a bimetal or a shape memory alloy that spontaneously expands at the melting temperature of the solder bump, and the solder bump assumes an hourglass shape by stretching the frame material by heating after assembly is completed. 9. The semiconductor device according to claim 8.