JPH04103149A - Package sealing method and semiconductor device - Google Patents

Abstract

PURPOSE:To improve a package sealed part in airtightness by a method wherein a preform brazing material provided with second brazing material layers formed on the front and the rear of an inner first brazing material layer is used, where the first brazing material layer is different from tire second brazing material layer in composition. CONSTITUTION:A brazing material 5b excellent in wettability formed on both the front and the rear of a preform brazing material 5 is made to come into close contact with a metallization layer 9 formed on the inner face of a cap 4 and another metallization layer 8 formed on the back of a semiconductor element 3 to form a thermal conductive filling layer 11 which joins the back of the semiconductor element 3 and the inner layer of the cap 4 together. A part of a brazing material 5a which serves as the center layer of the preform material 5 and is excellent in airtightness and strength is squeezed out from a gap between the back of the semiconductor element 3 and the cap 4 by a load 10 is made to move along a route shown by an arrow. In result, the brazing material 5a is supplied to a gap between a metallization layer 6 formed on a base 1 and a metallization layer 7 on the cap 4. By this setup, a sealing bonding layer 12 is formed to hermetically seal up the base 1 and the cap 4.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a package sealing technique and a semiconductor device, and particularly to a package sealing technique used for a semiconductor device.

[Conventional technology]

For example, as an example of a method of sealing a semiconductor device, a semiconductor element is mounted on a base made of ceramics or the like via multiple solder bumps, and then a cap with a concave cross section is sealed to the base to seal the base hermetically. structure is known.

By the way, when a semiconductor element is mounted via a solder bump as described above, heat generated from the semiconductor element during operation is not efficiently dissipated because the heat transfer area in the solder bump is small.

For this reason, as described in Japanese Patent Application Laid-Open No. 62-249429, for example, the height of the semiconductor element including the solder bumps is increased so that the gap between the back surface of the semiconductor element and the cap becomes minute. The relationship between the back surface of the semiconductor element and the internal dimension of the cap is set, and the minute gap between the back of the semiconductor element and the cap is filled with a brazing material or the like and the bond is made, thereby efficiently dissipating heat through heat conduction through the bond. A structure has been proposed that allows

[The invention tries to solve i! Title]

However, in semiconductor devices with the above-mentioned sealing structure, due to the assembly procedure, the melting point of the solder bump that mounts the semiconductor element on the base is higher than the melting point of the sealing part of the package or the joint for heat conduction. Since there is a restriction that the melting point of the solder used must be low, for example, when a solder other than the eutectic composition is used in the sealing part, there is a problem that the airtightness deteriorates due to the formation of dendrites.

In addition, when a preform brazing filler metal of a single composition such as - is directly used as the solder to form the sealing part,
A natural oxide film formed on the surface while being left in the air gets caught up in the sealing part and forms a leakage path, which also contributes to the deterioration of airtightness.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for sealing a package that can improve the airtightness of a sealed portion.

Another object of the present invention is to provide a method for sealing a package that can both improve the airtightness of the sealed portion and improve heat dissipation in the joint portion forming the heat conductive portion. It is in.

Another object of the present invention is to provide a 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 package sealing method according to the present invention is a package sealing method that performs at least one of airtightly sealing the sealed portion of the component of the package and bonding the component to the object to be sealed in the package. In this case, a preform brazing material having second brazing material layers having a composition different from that of the internal first brazing material layer is used on both the front and back surfaces.

Further, the single conductor device of the present invention includes a base on which a semiconductor element is mounted, and a cap sealed to the base, and the semiconductor element and the cap are bonded using a brazing material. The device melts a preform brazing material having a second brazing material layer having a composition different from that of the internal first brazing material layer on both the front and back surfaces while being pressed between a semiconductor element and a cap. , the bonding between the semiconductor element and the cap using the second brazing filler metal on both the front and back surfaces, and the sealing between the base and the cap using the first brazing filler metal extruded from the bonded portion are performed simultaneously. 7 [Function] According to the package sealing method of the present invention described above, for example, between the sealed object mounted on the base that constitutes the package and the cap that also constitutes the package,
A preform brazing filler metal with a multilayer structure in which a second brazing filler metal with a composition with good wettability is coated on both the front and back sides of a II brazing filler metal that has excellent strength and airtightness is melted under pressure, and both the front and back sides are melted. The object to be sealed and the cap are joined by the second brazing material layer with good wettability, and the base and the cap are bonded together by the internal first brazing material extruded from the joint, which has excellent strength and airtightness. By performing this sealing, the airtightness of the sealed portion of the package is reliably improved.

In addition, it is possible to supply a brazing material with an optimal composition to each of the sealing parts that require high airtightness and the joint parts that require high adhesion for heat dissipation. It is possible to achieve both improved airtightness in the sealed portion and improved heat dissipation characteristics due to high adhesion in the bonded portion.

Further, according to the semiconductor device of the present invention, heat is effectively dissipated at the joint between the cap and the semiconductor element by the second brazing material having good wettability, and heat is extruded from the joint in a molten state and oxidized. The first brazing filler metal, which does not contain films and has excellent strength and airtightness, can achieve high airtightness and strength at the sealing part between the base and the cap, increasing the reliability of the operation of the semiconductor device. will improve.

[Example 1] Hereinafter, an example of a package sealing method and a semiconductor device according to an embodiment of the present invention will be described in detail with reference to the drawings! ! Hustle.

FIGS. 1(a) to (C) show an embodiment of the present invention, 1<
FIG. 3 is a schematic cross-sectional view showing a method for sealing a cage in order of steps.

Note that the package sealing method of this embodiment will be described with reference to a case where it is applied to a sealing process in a semiconductor device, as an example.

First, FIG. 1(a) shows an example of the power distribution state of each component of a semiconductor device prior to the sealing method of this embodiment.

As shown in FIG. 5A, a multilayer wiring structure (not shown) is formed to interconnect connection electrodes (not shown) exposed on both the front and back surfaces, and on a base 1 made of mullite or other ceramics, Multiple Bamboo Electric Bridges 2
A semiconductor element 3 having an integrated circuit structure having a desired function is mounted thereon.

At a position facing the base 1, for example, a material having a substantially concave cross-sectional shape and a coefficient of thermal expansion approximately equal to that of silicon constituting the semiconductor element 3 is sealed to the peripheral edge of the base 10. Sealed space (cavity)
A cap 4 is arranged.

A preform brazing material 5 is arranged between the semiconductor element 3 mounted on the base 1 and the cap 4.

For example, chromium (C
r), adhesion layers such as titanium (Ti), tungsten (111), nickel (Ni), copper ccu), platinum (p
t), a barrier layer such as palladium (Pd) or molybdenum (MO), and an anti-oxidation layer such as gold (^U) on the outermost surface.
A metallization 7 is formed.

Similarly, metallization 8 and metallization 9 having the same structure as the metallizations 6 and 7 are formed on the back surface of the semiconductor element 3 and the inner peripheral surface of the cap 4 facing thereto, respectively.

In this case, the preform brazing material 5 has a multilayer structure consisting of a central plate-shaped brazing material 5a and brazing materials 5b attached to both the front and back surfaces of the brazing material 5a.

The surface brazing material 5b is made of, for example, Pb-5 with good wettability.
n I such as solder! (Sn)-containing solder, while the internal brazing filler metal 5a is made of, for example, Pb-^g solder, which has excellent airtightness and strength.
It is composed of eutectic solder that does not contain tin, that is, it has a composition that does not generate dendrites.

Note that the brazing filler metal 5a and the brazing filler metal 5b are not limited to the above-mentioned solder, as long as they satisfy the above-mentioned high airtightness, strength, good wettability, etc.
Other compositions may also be used.

Next, same one! As shown in I(b), the preform brazing material 5 is sandwiched between the semiconductor element 3 mounted on the base 1 and the cap 4, and acts in the stacking direction of the base 1 and the cap 4. It is compressed by a load 10 and heated to the melting temperature of the preform brazing material 5.

At this time, the brazing filler metal 5b, which has a good wetting method and constitutes both the front and back surfaces of the preform brazing filler metal 5, is in close contact with the metallization 9 on the inner surface of the cap 4 and the metallization 8 on the back side of the semiconductor element 3, and has resistance to heat transfer. The back surface of the semiconductor element 3 and the cap 4 can be bonded without creating voids that increase the
A thermally conductive filling layer 11 is formed to join the inner surface of the substrate.

At the same time, the preform brazing material 5 is pushed out from the gap between the back surface of the semiconductor element 3 and the cap 4 by the load 10.
A part of the brazing filler metal 5a, which has a composition excellent in airtightness and strength, and which constitutes the central layer of the A pure brazing filler metal 5a is supplied to the gap between the metallization 6 formed on the edge of the base 1 and the corresponding metallization 7 of the cap 4, and hermetically seals the base 1 and the cap 4. A sealing bonding layer 12 is formed.

At this time, the volume of the sealed space composed of the cap 4 and the base 1 is reduced, but air is removed from the gap between the metallization 7 of the cap 4 and the metallization 6 of the base 1, and from the inside of the cavity. Due to the flow of the filler material 5a supplied into the gap between the sealed portion of the base 1 and the cap 4, no pressure difference is created between the inside and outside of the cavity.
A semiconductor device exhibiting a sealed state as shown in FIG. 3(C) is obtained.

As the atmosphere for the above-mentioned heating, for example, an inert gas containing 10 ppm or less of oxygen (02) or a gas to which 10 to 20% hydrogen (H2) is added is used.

As described above, according to the package sealing method of the present embodiment and the semiconductor device assembled using the method, the semiconductor element 3 and the cap 4 are heated using the brazing material 5b, which has good wettability and does not easily cause voids. They are joined by the conductive filling layer 11, and heat is efficiently dissipated through the joint. Further, the base 1 and the cap 4 are reliably sealed by a sealing bonding layer 12 made of a brazing filler metal 5a having a composition excellent in strength and airtightness.

As a result, the airtightness of the package formed by sealing the cap 4 to the base 1 is ensured. In addition, in a semiconductor device in which a semiconductor element 3 is sealed inside the package,
The heat generated from the semiconductor element 3 is efficiently dissipated to the outside of the package through the thermally conductive filling layer 11 without voids, preventing overheating during operation, and preventing moisture from leaking due to poor airtightness of the sealing part. Corrosion of the bump electrodes 2 due to intrusion is reliably avoided, and reliability is improved.

In addition, in the above explanation, the case where the sealing work is performed with the base 1 set down and the cap 4 set up is explained, but the same effect is not limited to this, and the same effect can be obtained even if the vertical relationship between the two is reversed. is obtained.

[Embodiment 2] FIGS. 2(a) to 2(C) are schematic cross-sectional views showing an example of a package sealing method and a semiconductor device assembly operation according to another embodiment of the present invention in the order of steps.

In the case of the second embodiment, the base 1a on which the semiconductor element 3 is mounted via the bump electrodes 2 is made of ceramic or the like with a concave cross section, and the cap 4a is made flat. This is different from the case of Example 1.

In the second embodiment, the assembly and sealing work is performed with the base 1a facing up and the cap 4a facing down.

As a result, as in the case of the first embodiment, the thermally conductive filling layer 11 that joins the back surface of the semiconductor element 3 and the cap 4a.
is made of the brazing filler metal 5b with good wettability,
The brazing material 5 is capable of efficiently dissipating heat generated from the semiconductor element 3, and has excellent strength and airtightness and is extruded from the gap between the semiconductor element 3 and the cap 4a.
The sealing bonding layer 12 constituted by a can improve the airtightness of the sealed portion.

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, the composition of the brazing material constituting the preform brazing material is not limited to those exemplified in each of the above embodiments.

Furthermore, the materials and structures of the base and cap are not limited to those exemplified in each of the above embodiments.

〔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 package sealing method of the present invention, for example, a first brazing filler metal having excellent strength and airtightness is placed between the cap and the object to be sealed mounted on the base of the package. A preform brazing material with a multi-layer structure, in which a second brazing material with a composition with good wettability is coated on both the front and back sides, is melted under pressure. It joins the object to be sealed and the cap, and has excellent strength and airtightness.
．． By sealing the base and the cap using the brazing material No. 1, the airtightness of the sealed portion of the package is reliably improved.

In addition, it is possible to supply brazing filler metals with compositions that have optimal physical properties for sealing parts that require high airtightness and joint parts that require high adhesion for heat dissipation, making it possible to seal packages. It is possible to achieve both an improvement in airtightness at the joint portion and an improvement in heat dissipation characteristics due to high adhesion at the joint portion.

Furthermore, the semiconductor device of the present invention has good wettability! Effective heat dissipation at the joint between the cap and the semiconductor element by the second brazing material, and the first brazing material, which is extruded from the joint in a molten state and does not contain an oxide film and has excellent strength and airtightness. , high airtightness and strength can be achieved at the sealed portion between the base and the cap, and the reliability of the operation of the semiconductor device is improved.

[Brief explanation of drawings]

1(a) to 1(C) are schematic cross-sectional views showing step by step a method for sealing a package according to an embodiment of the present invention. !
l (a) to (C) illustrate an example of a package sealing method and a semiconductor device assembly work that are other embodiments of the present invention.
It is a schematic sectional view shown in order of steps. 1, la...base, 2...bump electrode, 3...
Semiconductor element, 4, 4a... Cap, 5... Preform brazing filler metal, 5a... Brazing filler metal (first brazing filler metal), 5
b... Brazing metal (second brazing metal), 6, 7, 8.9...
- Metallization, 10... Load, 11... Thermal conductive filling layer, 12... Sealing bonding layer. Figure 1 (a) Mu agent patent attorney Daiwa Tsutsui Figure (b) (C) 11: Gaiden! 4th brother layer diagram (a)

Claims (1)

[Scope of Claims] 1. A package sealing method that performs at least one of hermetically sealing a sealed portion of a component of a package and bonding an object to be sealed in the package and the component, the method comprising: A package sealing method characterized in that a preform brazing material is used, which has second brazing material layers on both sides having a composition different from that of the first internal brazing material layer. 2. The constituent elements are a base and a cap, and the object to be sealed is a semiconductor element mounted on the base,
The preform brazing material is melted while being pressed between the semiconductor element and the cap, and the semiconductor element and the cap are bonded by the second brazing material layer on both the front and back surfaces, and the bonded portion is 2. The package sealing method according to claim 1, wherein the base and the cap are sealed by the first brazing material extruded from the inside. 3. The second brazing filler metal on both the front and back surfaces of the preform brazing filler metal is made of a brazing filler metal having a composition that has good wettability to the adhered surfaces of the cap and the semiconductor element, and the first brazing filler metal inside is The package sealing method according to claim 1 or 2, characterized in that the package is made of a brazing material having a composition excellent in airtightness and stress resistance. , 4. A semiconductor device comprising a base on which a semiconductor element is mounted and a cap sealed to the base, the semiconductor element and the cap being joined by a brazing material, the front and back sides A preform brazing material having a second brazing material layer having a composition different from the internal first brazing material layer on both sides is melted while being pressed between the semiconductor element and the cap, and A semiconductor device in which bonding of the semiconductor element and the cap using a second brazing material and sealing of the base and the cap using the first brazing material extruded from the bonding portion are performed simultaneously.