JP2534145B2 - Method for manufacturing silicon nitride package for semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention accommodates a semiconductor element, hermetically seals the semiconductor element from the outside to protect the semiconductor element, and at the same time burys an electric conductor to provide an input / output terminal with a semiconductor. Regarding ceramic packages.

[Conventional technology]

Conventionally, a ceramic package has been widely used as an airtight container for incorporating a semiconductor integrated circuit into a semiconductor device. Alumina ceramics have been the mainstream for this type of ceramic package.

However, with the recent increase in the size of silicon chips, a problem that the silicon chips are cracked due to a mismatch in the coefficient of thermal expansion between alumina and silicon has arisen, and there is a need to solve the problem. When aluminum nitride is used as the ceramic instead of alumina, the coefficient of thermal conductivity is high and the coefficient of thermal expansion is close to that of a silicon chip, but its color is white or translucent white. The transmission of the light adversely affected the IC memory. Further, since a black material is required for an optical functional component such as an image sensor, a black silicon nitride sintered body is attracting attention because it has a thermal expansion coefficient close to that of silicon.

[Problems to be Solved by the Invention]

As described above, a black insulating material having a coefficient of thermal expansion close to that of silicon (see FIG. 1) as a ceramic material for a package, a coefficient of thermal expansion more favorable than that of other alumina or aluminum nitride, and excellent in light shielding property. Another object of the present invention is to provide a silicon nitride-based package having excellent mechanical strength.

[Means for solving the problem]

The present invention has been made in order to solve the above problems, and relates to a silicon nitride package embedded in or formed on a surface of a silicon nitride sintered body that uses a refractory metal as a conductive portion. If necessary, a through hole may be provided in the silicon nitride molded body, and a high melting point metal may be filled therein to form an interlayer circuit.

Accordingly, the present invention provides a method for manufacturing the above package, the first method is a step of mixing a refractory metal with a binder to form a sheet, and punching the sheet with a mold to form a conductive portion. It is a method for manufacturing a silicon nitride based package, which comprises a step of forming and a step of superposing the punched conductive portion and the silicon nitride based molded body in a predetermined arrangement, pressure sintering and integrating. Here, when the pressure sintering is performed by hot pressing, a dense sintered body is formed under the conditions of a firing temperature of 1600 to 1850 ° C, a holding time of 0.5 to 2 hours, and a pressure of 150 to 300 kg / cm ^2. Obtainable.

When pressure sintering is performed by gas pressure sintering (in a nitrogen atmosphere), the firing temperature is 1600 to 1850 ° C and the holding time is 0.5 to 5
A dense sintered body can be obtained under the conditions of pressure for 5 to 100 kg / cm ² for time.

By setting the thickness of the conductive portion made of a refractory metal by the above method to 10 to 100 μm, a conductive portion which is also electrically satisfactory is formed.

Further, the second method comprises a step of punching a high melting point metal foil with a die to form a conductive portion, and a step of pressure-sintering the punched conductive portion and the silicon nitride compact in a predetermined arrangement. Is a method for manufacturing a silicon nitride package.

Also, in the second method, the thickness of the conductive portion is 50 to 200 μm.
Can be manufactured.

[Operation] Since the package of the present invention is made of a material such as a silicon nitride chamber, which has a coefficient of thermal expansion close to that of silicon, the problem of thermal expansion coefficient mismatch with a silicon chip does not occur.
There is no crack in the silicon chip.

Further, since a refractory metal such as tungsten (W) or molybdenum (Mo) is used for forming the conductive portion of the package, it is possible to provide a package that withstands high temperatures and cooperates with silicon nitride. Further, in the first method of the present invention, a sheet made of a high melting point metal with a binder is punched out with a mold to form a conductive portion. Is obtained.

According to the second method, since the metal foil is used as the conductive part, the conductivity of the conductive part is uniform, and a thin package that does not cause anxiety can be obtained.

〔Example〕

Hereinafter, each manufacturing method of the present invention and the method of the comparative example and the packages obtained thereby will be described.

I. Examples 1 to 3 and Comparative Example 1 FIG. 2 is an exploded perspective view showing an example of a manufacturing process according to the first method of the present invention, in which a refractory metal and a binder are formed on the silicon nitride chamber compact 1a. The punched conductive portion (circuit) 2a of the sheet is formed, and the punched conductive portion (entire surface) 2b of the sheet made of a refractory metal and a binder is further provided on the silicon nitride molded body 1b, and the sheets are stacked and sintered. They are integrated into a package.

Example 1 90% by weight of silicon nitride (α-Si ₃ N ₄ ) powder having an average particle size of 0.7 μm, 4.5% by weight of alumina (Al ₂ O ₃ ) powder, 5% by weight of yttrium oxide (Y ₃ O ₃ ) powder, and 0.5% by weight of iron (Fe) component (in the form of methoxide) was mixed in alumina trommel using ethyl alcohol as a solvent for 10 hours, and wax was further added and mixed for 1 hour.
Granulated particles having an average particle size of 100 μm were produced.

Next, this granulated particle is 1500 kg / cm with a 100 × 80 mm mold.
Molding was carried out at a pressure of ² to obtain a silicon nitride molded body 1a of 100 × 80 × 5 mm. A conductive portion (circuit) 2a formed by punching out a tungsten sheet (a mixture of tungsten powder having an average particle size of 13 μm, a binder and a solvent, and molding the sheet into a sheet having a thickness of 100 μm) in a pattern shown in FIG. 2 on this surface. Was set up. Separately, using the same granulated particles as in the case of the above-mentioned molded body 1a, a frame-shaped silicon nitride molded body (100 × 80 × 5 mm, internal dimensions 80 × 60 × 5 mm) 1b was similarly molded and molded. It is placed on the surface of the conductive portion (circuit) 2a manufactured from the above-mentioned tungsten sheet, again integrated under pressure of 2000 kg / cm ² , and a tungsten sheet manufactured in the same manner as in the case of the above-mentioned circuit 2a is further provided on the surface. The punched out size was used as the conductive part (entire surface) 2b. (See FIG. 2) As described above, the silicon nitride material and the tungsten sheet forming the conductive portion are superposed and arranged.
By treating in a nitrogen atmosphere at 600 ° C for 3 hours,
The binder contained in the silicon nitride compact is removed, boron nitride is applied to the surface, and the central space is
A silicon nitride compact formed by applying boron nitride on the surface in advance (although the same quality as the silicon nitride compact forming the package, the size is set to fill the space, and the package is baked). It is used as an auxiliary means for forming a bond and is called a dummy below.
Min, and sintered under the condition of 200 kg / cm ² to obtain a package. The sintered body of the molded silicon nitride chamber forming this package was manufactured separately after removing the dummy at the center, removing the boron nitride on the surface by barrel polishing, and nickel-plating and gold-plating the conductive portion. A silicon nitride cap is placed on the surface of the package and joined by silver brazing,
Airtightness was tested using gas, but it was below the same level as conventional alumina (10 ^-8 atm cc / sec).

In addition, a 50 x 50 x 0.5 mm silicon chip is used inside the Au-Si
A brazing material was used and bonded by heating at 400 ° C. for 3 minutes, and cracks at the time of bonding and cracks after thermal cycles (room temperature to 300 ° C. 5 cycles) were examined.

Example 2 In the same manner as in Example 1, a silicon nitride molded body 1a, 1b and a tungsten sheet constituting a conductive portion (circuit) 2a were superposedly arranged in the middle, and pressure integration was performed at 2000 kg / cm ^2. Then, a tungsten sheet was punched out into a predetermined size to form a conductive portion (entire surface) 2b on the surface thereof.
Using the polymerization arrangement, 600 ℃ × 3 hours,
The binder was removed in a nitrogen atmosphere, and the package was obtained by gas pressure sintering in a nitrogen atmosphere at 75 atm at 1850 ° C. for 3 hours. After that, barrel polishing was performed to finish the surface, the conductive portion (metallized portion) was plated with nickel and gold, and a cap was joined in the same manner as in Example 1 to perform an airtightness test, but there was no problem. Further, when the lead strength with a thickness of 1 mmφ was measured on the plated metallized surface of the metallized portion, it was found to be sufficient strength of 20 kg / cm ² .

However, the lead strength was measured by soldering the lead wire to the metallized surface, pulling the other end of the lead with a spring meter, and dividing the load when the metallized surface was peeled by the peeled area to obtain the adhesion strength.

Comparative Example 1 99.7% by weight of high-purity alumina with 99.995% purity and 0.30% by weight of reagent grade magnesium carbonate (MgCO ₃ ) converted into MgO were deionized with a polyethylene ball mill and 99.995% pure alumina spheroid. Water, polyvinyl alcohol and polyethylene glycol were added and mixed for 15 hours, and then granulated particles having an average particle size of 50 μm were produced by a spray dryer.

Next, except that an alumina molded body is produced by using these particles, a material obtained by polymerizing with a conductive portion (circuit) of a tungsten sheet is pressed and integrated at 2000 kg / cm ² in the same manner as in Example 1, and tungsten is further formed on the surface. The sheet is punched out to a specified size and the conductive part (overall surface) is placed, and these polymerized products are decompressed at 30 ° C and temperature 1630 ° C x 2 in an ammonia decomposition gas atmosphere.
A package was obtained by firing under the conditions of time.

The conductive portion of this package was plated with nickel and gold, and the hermeticity was tested in the same manner as in Example 1, but there was no problem.

On the other hand, a 50 x 50 x 0.5 mm silicon chip is Au-
Using Si brazing material, bond by heating at 400 ℃ for 3 minutes,
When cracks were examined after thermal cycles (room temperature to 300 ° C., 5 cycles), 1/20 silicon chips were cracked.

II. Example 3 and Comparative Example 2 FIG. 4 is an exploded perspective view showing an example of a manufacturing process according to the second method of the present invention, in which a refractory metal foil is punched out on the silicon nitride compact 1a and the conductive portion 2e is formed. (Circuit) is provided, and a high melting point metal foil is punched out on the silicon nitride molded body 1b to form a conductive portion 2f (solid).
Is provided, and these are stacked and sintered together to form a package.

Example 3 90% by weight of silicon nitride (α-Si ₃ N ₄ ) powder having an average particle size of 0.7 μm, 4.5% by weight of alumina (Al ₂ O ₃ powder), 5% by weight of yttrium oxide (Y ₂ O ₃ ) powder, and 0.5% by weight of iron (Fe) component (in the form of methoxide) was mixed in alumina trommel using ethyl alcohol as a solvent for 10 hours, and then wax was added and mixed for 1 hour. 100 μm granulated particles were produced.

The granulated particles were molded with a mold of 10 × 80 mm at a pressure of 1500 kg / cm ² to obtain a silicon nitride compact 1a of 100 × 80 × 5 mm, the surface of which is shown in FIG. Punching conductive part 2e made of tungsten foil (tungsten thickness 100 μm)
(Circuit) is provided.

Next, separately using the same granulated particles as in the case of the molded body 1a, a frame-shaped silicon nitride molded body (100 × 8
0 × 5 mm, internal dimensions 80 × 60 × 5 mm) 1b punched out the conductive part 2
It is placed on the surface of e, integrated again under pressure of 200 kg / cm ² , and the conductive portion 2f is further placed on the surface of the tungsten foil (third part).
See figure).

Polymerize the silicon nitride material forming bodies 1a and 1b, the punched conductive portion 2e (circuit), and the punched conductive portion 2f (entire surface) in a predetermined arrangement as described above, and treat at 600 ° C. for 3 hours in a nitrogen atmosphere. Then, remove the binder, apply boron nitride on the surface, and insert a dummy (not shown) formed by applying boron nitride in advance in the central space, using a carbon mold, 1800 ℃ × It was sintered for 30 minutes by hot pressing under the condition of 200 kg / cm ² to obtain a package.

After removing the dummy inserted in the central part of the sintered body, the surface boron nitride was removed by barrel polishing, the metallized part was nickel-plated and then gold-plated, and a separately manufactured cap was placed on the surface of the package. , Welded by silver brazing and tested gas tightness using He gas, but it was less than the same level as conventional alumina (10 ^-8 atm cc / sec).

In addition, a 50 x 50 x 0.5 mm silicon chip is used inside the Au-Si
A brazing material was used and bonded by heating at 400 ° C. for 3 minutes, and cracks at the time of bonding and cracks after a thermal cycle (room temperature-300 ° C. 5 cycles) were examined, and no defects were found.

Comparative Example 2 99.7% by weight of high-purity alumina having a purity of 99.995% and 0.30% by weight of reagent grade magnesium carbonate (MgCO ₃ ) converted into MgO were deionized with a polyethylene ball mill and a 99.995% pure alumina ball stone. Water, polyvinyl alcohol and polyethylene glycol were added and mixed for 15 hours, and then granulated particles having an average particle size of 50 μm were produced by a spray dryer.

Next, a conductive part (circuit) made of a tungsten foil is formed in the middle in the same manner as in Example 3 except that the particles are used under pressure at 2000 kg / cm ² and integrated to obtain an alumina molded body as in Example 3. Was prepared and polymerized in the same manner as in Example 3, and a conductive portion (entire surface) made of a tungsten foil was further arranged on the surface.

In this way, the alumina molded body provided with the conductive portion was subjected to an ammonia decomposing gas atmosphere at a dew point of 30 ° C and a temperature of 1630 ° C x 2
A package was obtained by firing under the conditions of time.

The conductive portion of this package was plated with nickel and gold, and the hermeticity was tested in the same manner as in Example 3, but the He leak did not pass 10 ⁻⁸ atm.cc/sec.

Looking at the interface between the metal conductor and the ceramic, the metal conductor was abnormally deformed and cracks were generated in the ceramic part. This is because although the alumina shrinks due to firing, the metal conductor tungsten does not shrink,
It was found that the distortion caused cracks and reduced airtightness.

Hereinafter, Examples and Comparative Examples of the present invention are described in detail,
What is shown in FIGS. 2 to 4 is an example of the present invention, and the mounting state of the lead frame and the silicon chip is omitted. The silicon nitride compact may be a single layer or a multilayer.
The package lid is glass-sealed in the case of a silicon nitride molding, but is silver brazed in the case of metal.

However, since the lid is made of glass in the package of the image sensor, it is not necessary to provide a conductive portion in the upper frame of the silicon nitride molding.

〔The invention's effect〕

The ceramic used in the package according to the present invention is silicon nitride, and its coefficient of thermal expansion is very close to that of silicon, and the coefficient of thermal conductivity is equal to or higher than that of the alumina package used so far. The strength shows a doubled value (anti-deposition strength 90 kg / mm ² ), or the color is black, and it is possible to provide a suitable package for an optical functional component such as an image sensor.

[Brief description of drawings]

FIG. 1 shows thermal expansion-temperature curves of various packaging materials, and FIGS. 2 and 3 are exploded perspective views for explaining an embodiment of the present invention. 1a, 1b …… Silicon nitride molded product 2a …… Punched conductive part (circuit) of sheet made of high melting point metal and binder 2b …… Punched conductive part (solid) of sheet made of high melting point metal and binder 2e… … Punched conductive part of high melting point metal foil (circuit) 2f …… Punched conductive part of high melting point metal foil (entire surface)

Claims (2)

(57) [Claims] 1. A method of manufacturing a silicon nitride package for a semiconductor device, comprising a conductive portion made of a refractory metal embedded in or formed on a silicon nitride fired body, the refractory metal being mixed with a binder. A step of forming into a sheet, a step of punching the sheet with a mold to form a conductive portion, and a punching of the punched conductive portion and a silicon nitride molded body are superposed in a predetermined arrangement to perform pressure sintering integration. A method of manufacturing a silicon nitride package for a semiconductor device, comprising: 2. A method of manufacturing a silicon nitride package for a semiconductor device, wherein a conductive portion made of a refractory metal is embedded in or formed on a silicon nitride fired body, and a refractory metal foil is punched with a die. And a step of forming a conductive part, and a step of superposing the punched conductive part and the silicon nitride molded body in a predetermined arrangement and pressure-sintering them together to form a semiconductor device. A method for manufacturing a silicon nitride package.