JP2652014B2 - Composite ceramic substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a semiconductor element and comprising a composite ceramic substrate of mullite ceramics and aluminum nitride ceramics.

2. Description of the Related Art In recent years, the amount of heat generated from a semiconductor element tends to increase with the increase in density and speed of the semiconductor element, and improvement in heat dissipation of a semiconductor device is desired. Also, due to the increase in the size of the element, distortion, peeling, destruction, etc. of the element due to thermal stress generated due to the difference in thermal expansion between the element and the element fixing part have become problems, and thermal expansion has been performed to ensure reliability against these. It is also desired that the coefficient be close to that of the element.

Conventionally, a semiconductor device having an alumina ceramics-metal composite structure using a metal such as copper tungsten for an element fixing portion has been used to improve the heat dissipation.

However, recently, there is a growing demand for electrical insulation, and therefore, beryllia ceramics, aluminum nitride ceramics, and the like have attracted attention as materials having both electrical insulation and high thermal conductivity.

Beryllia ceramics have already been commercialized as a composite with alumina ceramics. There are major obstacles in production such as

Aluminum nitride ceramics, on the other hand, have a thermal expansion coefficient close to that of the element and have no problem in fixing the element, but when combined with alumina ceramics, direct bonding is impossible due to the thermal stress generated by the difference in thermal expansion between the two. It is. In order to alleviate this, it is necessary to provide a stress relaxation layer between the two, so that the process becomes complicated and the reliability is remarkably lacking in some cases.

Although it is possible to manufacture a semiconductor device using only aluminum nitride ceramics, there are problems in that simultaneous firing with a conductor is difficult and the device becomes too expensive.

Problems to be Solved by the Invention The present invention has been made in consideration of the above points, and has excellent heat dissipation in a semiconductor device, a close thermal expansion coefficient with an element, and high-density and high-speed wiring. An object of the present invention is to provide a composite ceramic substrate having a substrate at low cost.

B. Means for Solving the Problems The present invention comprises an aluminum nitride ceramic substrate for fixing a semiconductor element and a mullite ceramic substrate having a wiring conductor in a surface layer or an inner layer, and the aluminum nitride ceramic substrate and the mullite ceramic substrate are A composite ceramics substrate characterized by being joined with brazing material, solder, or glass.

Effect Mullite ceramics has a thermal expansion coefficient close to that of aluminum nitride ceramics and a lower dielectric constant than alumina ceramics, making it suitable as a wiring board. , Easily manufactured using conventional techniques. Also, the manufacturing cost is lower than manufacturing with only aluminum nitride ceramics. Therefore, by combining mullite ceramics and aluminum nitride ceramics, semiconductor devices with good heat dissipation, low thermal expansion, etc. The device can be obtained at low cost and can be used for large-sized devices with high output.

Table 1 shows aluminum nitride ceramics (AI
Material properties of N), mullite ceramics (mullite) and alumina.

The present invention can be applied to all types of semiconductor devices, from circuit board type to package type semiconductor devices.

The present invention uses mullite ceramics for parts using conventional alumina ceramics, metals used where high thermal conductivity is required, beryllia ceramics,
Alternatively, aluminum nitride ceramics are used instead of alumina ceramics. The connection between the aluminum nitride ceramic substrate and the mullite ceramic substrate
The following known methods can be used.

Before fixing the semiconductor element to the aluminum nitride substrate, a high-temperature brazing material can be used. A W paste is printed on a predetermined portion of each green substrate before firing, and each ceramic substrate is fired. After the firing, Ni plating is performed on the W conductor layer of each substrate, and an Ag brazing material (melting point: 800 ° C.) is sandwiched between the substrates and joined at about 900 ° C. in a hydrogen-nitrogen atmosphere.

In the case of glass printing, a glass paste is printed on a predetermined portion of each substrate, and after drying, bonding is performed at about 400 ° C. in the atmosphere.

After fixing the semiconductor element to the aluminum nitride substrate, bonding is performed using eutectic solder having a melting point of 300 ° C. or lower.
Ag-Pd paste is printed at a predetermined position after firing of each substrate,
Bake at about 900 ° C in air. After fixing the element with Au / Si or Ag-containing glass, a solder paste is printed on the Ag-Pd joint surface, and joined through a reflow furnace at a maximum temperature of 300 ° C.

In the case of a semiconductor element on an aluminum nitride substrate, a W layer is formed at the same time as the simultaneous baking, and then joined by Au / Si brazing material as Ni plating and gold plating. In addition, it can also be joined with an Au / Si brazing material by a thin film method of sputtering Ti / Ni / Au.
In addition, Ag-containing glass, Ag-containing resin, and the like can be used.

First Embodiment FIG. 1 is a sectional view of an embodiment applied to a PGA (pin grid array) of the present invention. MgO or GaO to mullite powder
A sheet with a thickness of 0.6 mm was prepared by a doctor blade method by dispersing and dissolving a mixture containing an auxiliary agent and the like together with a binder in an organic solvent to form a slurry. After a predetermined pattern was printed thereon with W paste, five sheets were laminated by heating and pressing. Thereafter, the resultant was punched into a predetermined shape, and simultaneously fired in a mixed gas of nitrogen and hydrogen at 1580 ° C. for 2 hours to obtain a mullite ceramic substrate 1 having five inner conductor patterns.

On the other hand, a slurry obtained by adding an auxiliary agent to aluminum nitride powder was formed into a slurry, and a sheet was formed by a doctor blade method. A predetermined pattern was printed thereon by using a W paste, punched into a predetermined shape, and fired at 1800 ° C. for 2 hours in a nitrogen gas or a mixed gas of nitrogen and hydrogen to obtain an aluminum nitride ceramics substrate 2.

The thus obtained mullite substrate 1 and aluminum nitride substrate 2 were subjected to Ni electroless plating, and then the aluminum nitride substrate 2 together with the pins 3 were combined with the mullite substrate 1 and an Ag-Cu solder 4.
By sintering at 850 ° C. for 10 minutes in a mixed gas of nitrogen and hydrogen to perform bonding and electroless plating of Ni and Au.
Thereafter, the semiconductor element 5 was mounted with an Au-Si eutectic solder 6. Next, the connection between the semiconductor element 5 and the conductor was performed by using the Au wire 7 by a heating ultrasonic bonding method. Finally, the mullite cap 8 was sealed using Au-Sn eutectic solder 9 to form a composite PGA. Aluminum nitride substrate 2
First, the sheet is punched out, baked, and then subjected to pattern printing using W, Mo or Mo.W paste, baked in a mixed gas of nitrogen and hydrogen at 1650 ° C., and then subjected to NiB electroless plating to form a mullite substrate 1. Good PG even after joining
A is obtained.

Embodiment 2 FIG. 2 is a sectional view of an embodiment applied to a circuit board on which a chip carrier of the present invention is mounted. A mullite ceramic and an aluminum nitride ceramic sheeted in the same manner as in Example 1 were punched out into a predetermined shape and fired to obtain a substrate. An AgPd paste was baked on the mullite substrate 1 at 850 ° C. in the air to form a conductor pattern 10. Then, a resistor 11 was formed in the air at 850 ° C. using a resistor paste, and the overcoat glass 12 was baked in the air at 520 ° C. to obtain a HIC subassembly substrate 13.

Aluminum nitride substrate 2 for mounting semiconductor element 5
Then, a conductor pattern 10 was formed using an AgPd paste at 850 ° C. in the air. The semiconductor element 5 was mounted thereon with an Au-Si eutectic solder 6 and further bonded with an Au wire 7 to obtain a chip carrier 14. After bonding the chip carrier 14 to the HIC subassembly substrate 13 by soldering, a resin 15 for sealing a semiconductor element was coated to obtain a composite HIC substrate.

C. Effect of the Invention As described above, according to the present invention, an aluminum nitride ceramics substrate having excellent heat dissipation properties is used for a fixed portion of a semiconductor element, and as a wiring substrate, the thermal expansion coefficient is substantially equal to that of an aluminum nitride ceramics substrate, The use of a mullite substrate with a lower dielectric constant than the alumina and having inner or surface conductor wiring and a low dielectric constant is advantageous for high transmission speed with little transmission delay, and uses a complex joint for joining both substrates. Instead, since it is a composite substrate that can be joined by a known brazing material, solder, glass, or the like, a large-sized substrate that can cope with high density and high speed can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment in which the present invention is applied to a PGA (pin grid array). FIG. 2 is a sectional view of an embodiment in which the present invention is applied to a circuit board on which a chip carrier is mounted. 1 ... Mullite ceramic substrate, 2 ... Aluminum nitride ceramic substrate, 3 ... Pin, 4 ... Ag-Cu brazing, 5 ... Semiconductor element, 6 ... Au-Si eutectic brazing, 7 ...
Au wire, 8 ... cap, 9 ... Au-Sn eutectic solder,
10: Conductor pattern, 11: Resistor, 12: Overcoat glass, 13: HIC sub-assembly board, 14:
Chip carrier, 15 resin

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsu Nishiyama, Narumi-cho, Midori-ku, Nagoya-shi, No. 3, Narumi-cho, Co., Ltd. References JP-A-59-158538 (JP, A) JP-A-61-7647 (JP, A) JP-A-61-35539 (JP, A) JP-A-62-16548 (JP, A)

Claims (1)

(57) [Claims] 1. An aluminum nitride ceramic substrate for fixing a semiconductor element, and a mullite ceramic substrate having a wiring conductor on a surface layer or an inner layer, wherein the aluminum nitride ceramic substrate and the mullite ceramic substrate are joined by brazing material, solder, or glass. A composite ceramic substrate characterized by being formed.