JP2841259B2 - Ceramic container for semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic container body for accommodating and hermetically sealing a semiconductor element, and a sealed ceramic container.

[0002]

2. Description of the Related Art In order to protect a semiconductor element, it is common practice to put it in a container to form a hermetically sealed structure.
Alumina ceramic (Al2O3), which is an electrically insulating material, is generally used for a container body for housing a semiconductor element, and a metallized layer of a high melting point metal (for example, tungsten) is provided on the upper surface for bonding with a lid. Provided. On the other hand, on the lid, Kovar (Fe-Ni-Co alloy) and 42 alloy (42% Ni-
Metals such as Fe alloys are used (coefficient of thermal expansion: alumina = 7.3 × 10−6 / deg, Kovar = 7.2 × 10−6 / deg, 4
2 alloy = 8.8 x 10-6 / deg: temperature range 30-600 ° C). For joining with the ceramic container body, the sealing metal ring is fixed to the metallized layer of the container body in advance by brazing,
After the semiconductor element is die-bonded to the container body and wire-bonded with an aluminum wire or the like, the ring and the lid are joined by low-temperature brazing or seam welding,
It has a desired hermetic sealing structure.

In recent years, the size of semiconductor devices housed in containers has been increasing in order to achieve higher integration and more functions of semiconductor devices. Accordingly, when a silicon chip is mounted on the alumina container body, the difference in thermal expansion coefficient between silicon and alumina (coefficient of thermal expansion; silicon = 3.5 × 10−6 / deg, alumina = 6.7 × 10−6 / deg: temperature range) 30-400 ° C.), a thermal stress is generated between the silicon chip and the alumina container main body, which may cause a problem that the silicon chip is peeled off.

[0004]

In order to solve such a drawback, in order to match the coefficient of thermal expansion between silicon and the container body, aluminum nitride (AlN), which is a ceramic having a lower coefficient of thermal expansion than alumina, is added to a ceramic container body. ), Mullite, silicon nitride (Si3N4), glass ceramic, and the like. However, when the above-described ceramic having a low coefficient of thermal expansion is bonded and sealed to a ring or a lid made of a sealing metal in the same manner as in the related art, there are the following problems. First, when the sealing ring is brazed and fixed to the container body (when using a silver brazing material: about 800 ° C), the thermal stress caused by the difference in the coefficient of thermal expansion between the container body and the sealing ring causes
Cracks enter the container body, lowering the yield,
The sealing reliability of the container with a ring may be reduced. Secondly, when the container body with the ring and the lid are joined (when using gold-tin-based brazing material: about 300 ° C), thermal stress is generated due to the difference in the coefficient of thermal expansion between the container body and the lid. In some cases, peeling of the ring portion or cracking of the container body may prevent the hermeticity of the container from being maintained, resulting in a lack of reliability.

In view of the above problems, the present invention provides a hermetically sealed structure for joining a sealing ring and a lid to a semiconductor element container using ceramics. An object of the present invention is to alleviate thermal stress caused by a difference in expansion coefficient by interposing a buffer layer between a container body and a sealing ring, thereby improving yield and preventing a decrease in reliability regarding airtightness. Since the coefficient of thermal expansion is generally non-linear, the coefficient of thermal expansion varies depending on the temperature range to be considered. It should be noted that the difference in the coefficient of thermal expansion due to the difference in the joining temperature depending on the material of the brazing material.

[0006]

SUMMARY OF THE INVENTION The present invention is directed to a method for applying a thermal stress to an upper surface.
A ceramic container for a semiconductor element having a sealing ring fixed with a buffer ring interposed therebetween , wherein the thermal stress buffering phosphorus is provided.
When the width of the sealing ring is h and the width of the sealing ring is H, the thermal stress buffering ring and the sealing member satisfying the following relational expression.
It is characterized by using a ring . h> 0.15H The interposed thermal stress buffering ring is made of one layer of a low Young's modulus material or a low thermal expansion material, or the container body side is made of a low thermal expansion material, and the sealing ring side is made of a low Young's modulus material. It is characterized by having a two-layer structure. In the case of two layers, a low thermal expansion coefficient material whose thermal expansion coefficient is relatively close to that of the container body is connected to the container body side to reduce the thermal expansion difference between the sealing ring and the lid. This is because a low Young's modulus material is bonded to the sealing ring to absorb thermal stress.

The dimensions of each layer of the ring are determined by the dimensions of the main body of the ceramic container, the purpose, the dimensions of the lid, the material, and the like.
The width of the ring is greater than 15% of the width of the sealing ring,
Preferably, the thickness of the sealing ring is greater than 20% of the thickness. When two layers are used, it is preferable that the width of the smaller layer is larger than 15% of the width of the sealing ring, and the thickness of the smaller layer is larger than 20% of the thickness of the sealing ring. If the ratio is smaller than this ratio, the thermal stress buffering effect of the ring decreases, causing peeling of the ring portion and airtight failure due to generation of cracks, brazing work becomes difficult, and the ring is used for brazing. When setting it on a jig, the ring is likely to deform,
This is because the workability is also reduced.

The present invention is intended to reduce the thermal stress caused by the difference in the coefficient of thermal expansion between the ceramic container body and the sealing ring or lid by interposing the thermal stress buffering ring. Therefore, it is not limited to the above-mentioned materials. However, in a preferred embodiment, the material of the ceramic container body is aluminum nitride, mullite, silicon nitride (Si3N4), which is called a low thermal expansion ceramic material.
Glass ceramic is preferred, but other ceramics for containers having a lower coefficient of thermal expansion than alumina may be used. Also,
The present invention can be used even with alumina depending on the material of the sealing ring and the lid.

When the sealing ring is fixed with a silver-based or copper-based brazing material, Kovar is preferable. However, the coefficient of thermal expansion of alloy 42 or the like is approximately 12.0 × 10 −6 / deg or less (temperature range: 30 ° C.). -80
Materials of 0 ° C) are also suitable. However, since the fixing temperature differs depending on the brazing material, the material of the sealing ring is selected in consideration of the temperature range of the thermal expansion coefficient depending on the brazing material to be used. Further, ceramic is a material that is not usually used as a sealing material.However, by metalizing the upper and lower surfaces of the ring, it can be joined to a thermal stress buffering ring or a lid, and has a thermal expansion coefficient similar to that of the above metal. If present, it can be used as a sealing ring.

[0010] Rings of low Young's modulus materials include copper, silver, gold,
A material such as niobium having a Young's modulus of 13000 kg / mm2 or less is preferable. When the ring of low thermal expansion material is fixed to the container body with silver or copper brazing material, the coefficient of thermal expansion of molybdenum, tungsten, copper-tungsten alloy, tungsten carbide, etc. is approximately 6 × 10−6 / deg. Below (Temperature range: 30
A material of -800 ° C) is preferred, but is selected taking into account the temperature range as well as the sealing ring.

As the lid, a sealing material such as Kovar or 42 alloy is suitable, but other metals can also be applied. Further, the peripheral portion on one side of the ceramic plate may be metallized, and this portion may be joined to the ring portion. The metallized layer of the ceramic container body and the thermal stress buffering ring, and the connection between the rings are preferably silver-based and copper-based brazing materials, but may be other brazing materials. In addition, gold-tin-based brazing material is suitable for joining the lid and the sealing ring, but other gold-based brazing materials or so-called solder may be used, or a direct sealing method such as a seam welding method may be used. .

[0012]

According to the present invention, a thermal stress buffering ring is interposed between a container body and a joining ring, and the buffering ring is formed of one layer of a low Young's modulus material or a low thermal expansion material, or the container side has a low thermal expansion coefficient. The material and the sealing ring are made of two layers of low Young's modulus material, so that the thermal stress caused by the difference in the coefficient of thermal expansion between the ceramic container body and the sealing ring or lid can be reduced, and the ceramic container and the ring Alternatively, it has an action of preventing the lid body from being subjected to excessive thermal stress.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a first embodiment of the present invention. A ceramic container main body 1 for housing a semiconductor element is made of aluminum nitride ceramic, and a concave portion 10 for housing and installing a semiconductor element is provided at a central portion, and a high melting point material (for example, tungsten) is provided on an upper surface of the container main body. Is provided as a main component. On the metallized layer, a thermal stress buffer ring 3 made of a low Young's modulus material or a low thermal expansion material is provided with a silver brazing material (not shown).
Further, a sealing ring 4 made of an alumina ceramic metallized on both sides with Kovar of a metal to be sealed and brazed thereon is similarly brazed and fixed (not shown). On the two-layered ring thus fixed, a lid 5 made of Kovar, a metal to be sealed, is joined by a seam welding method or a gold brazing material (not shown), and the container is hermetically sealed.

In this case, the material and dimensions (width, thickness) of the thermal stress buffering ring 3 and the dimensions (width, thickness,
(Thickness) was prepared. The airtightness is evaluated after adhesion of the buffer ring and sealing ring, after joining the lid, and thermal shock test (MIL-STD-883C, COND. C × 15 cycles)
Thereafter, the amount of helium leak was measured by a helium leak detector. Further, the appearance was inspected by a fluorescent flaw detection method. As a comparative example, as shown in FIG. 2, the same evaluation was performed for a filter having only the Kovar sealing ring 4 and no buffer ring. Here, the portions denoted by the same reference numerals as those in FIG. 1 indicate the same contents.

The results are shown in Table 1.

[Table 1] Here, the outer dimensions of the ring and the lid used for Nos. 1 to 8 and 17 were 75 mm square, the thickness of the lid was 0.5 mm, and the lid and the ring were brazed with gold-tin-based brazing material. Are joined. On the other hand, the outer dimensions of the ring and the lid used in Nos. 9 to 16 and No. 18 are 50 mm square, and the thickness of the lid is 0.3 mm, and they are directly joined to the ring by the seam welding method.

As can be seen from Table 1, copper having a low Young's modulus or molybdenum being a material having a low thermal expansion coefficient is obtained by interposing a thermal stress buffering ring 3 between a container body 1 and a sealing ring 4 of Kovar. Airtightness was improved compared to Comparative Example 1 (Nos. 17 and 18) without a buffer ring, and good results were obtained, especially after the lid was joined and after the thermal shock test, and the thermal stress was reduced. I understand. Numbers 8 and 16
It can be seen that the same effect can be obtained by using an alumina ceramic provided with a metallized layer on both sides of the sealing ring.

The width h and the thickness t of the thermal stress buffer ring 3 made of a low Young's modulus material or a low thermal expansion material are h ≦ 0.15H and t ≦ 0 with respect to the width H and the thickness T of the sealing ring 4. .
It can be seen that at 2T, the effect of relaxing the thermal stress cannot be obtained. This indicates that a certain size of the buffer ring is required for the sealing ring in order to obtain the buffer effect. The cracks detected by the fluorescent flaw detection method on the outer peripheral portion of the metallized layer 2 on the upper surface of the ceramic reached the concave portion 10 of the container, confirming the results of the helium leak test.

A second embodiment will be described with reference to FIG. Ceramic container 1 for housing semiconductor element, metallized layer 2
The lid 5 is the same as in the first embodiment. Molybdenum as the first thermal stress buffering ring 3A, copper as the second buffering ring 3B, and Kovar as the sealing ring 4 are sequentially brazed on the tungsten metallized layer 2 with a silver brazing material (not shown). ing. The Kovar lid 5 is sealed to the sealing ring 4 by a seam welding method, and together with Comparative Example 2 in the case of one layer of Kovar sealing ring,
The same tests and evaluations as in Example 1 were performed.

The results are shown in Table 2.

[Table 2] As is clear from the results in Table 2, the thermal stress buffer ring was
The layered structure can also reduce the thermal stress. When the smaller one of the widths or thicknesses of the rings 3A1 or 3A2 is denoted by h and t, respectively, the width H of the sealing ring,
It can be seen that sufficient airtight sealing cannot be achieved unless h> 0.15H and t> 0.2T with respect to the thickness T. This is shown in Table 1.
This indicates that the buffering effect cannot be exerted unless the dimensions of the buffer ring are not less than a certain value.

[0020]

As described in detail above, a thermal stress buffer ring is interposed between the ceramic container body and the sealing ring,
Since the thermal stress buffer ring is made of one layer of a low Young's modulus material or a low thermal expansion material, or two layers of a low thermal expansion material layer on the container body side and a low Young's modulus material layer on the sealing ring side,
A container for hermetically sealing a semiconductor element having excellent airtightness, which can relieve thermal stress caused by a difference in coefficient of thermal expansion between a ceramic container and a sealing ring or lid, and does not cause deformation or peeling of a ring portion and cracking of the container. And a semiconductor hermetically sealed package.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing first and second comparative examples of the present invention.

FIG. 3 is a sectional view showing a second embodiment of the present invention.

[Explanation of symbols]

 1. Ceramic semiconductor element container body. 2 Metallization layer. 3, 3A, 3B thermal stress buffer ring. 4, sealing ring 5 lid. 10 Container recess.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-283549 (JP, A) JP-A-4-72636 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 23/10 H01L 23/08

Claims (8)

(57) [Claims] 1. A thermal stress buffer ring is interposed on the upper surface and fixed.
Ceramic container present a semiconductor device having a the sealing ring
The width of the thermal stress buffer ring is h,
When the width of the ring is H, the thermal stress buffer ring and the sealing
A ceramic container body for a semiconductor element, characterized by using a ring . h> 0.15H 2. The thermal stress buffer ring is made of a material having a Young's modulus.
2. The ceramic container body for a semiconductor device according to claim 1 , wherein the material is a material having a low Young's modulus of 13000 kg / mm ² or less . 3. The material of said thermal stress buffer ring is 30 to 8
The coefficient of thermal expansion in the temperature range of 00 ° C. is 6 × 10 ⁻⁶ /
The ceramic container body for a semiconductor element according to claim 1 , wherein the material is a material having a low coefficient of thermal expansion of not more than deg . 4. When the thickness of the thermal stress buffer ring is t and the thickness of the sealing ring is T, the thermal stress buffer ring and the sealing ring satisfy the following relational expression.
4. The method according to claim 1, wherein
A ceramic container body for a semiconductor element according to any one of the above . t> 0.20T 5. the thermal stress buffer ring has a two-layer, a low thermal expansion material layer on the container body side, according to claim 1 to claim, characterized in that arranged a low Young's modulus material layer for sealing ring side 3
A ceramic container body for a semiconductor element according to any one of the above . 6. The width H of the sealing ring and the thickness T of the sealing ring, where h is the width of the smaller layer and t is the thickness of the smaller layer of the two thermal stress buffering rings. against, h> 0.15H, t> 0.20T ceramic container body for a semiconductor device according to claim 5, characterized in that a. 7. A container body material is, in any one of claims 1 to 6 characterized in that it is a low expansion ceramic
A ceramic container body for a semiconductor element as described in the above . 8. The cover according to claim 1, wherein
A ceramic container for a semiconductor element, which is joined to the container body described in the above .