JPH0439231B2 - - Google Patents

Abstract

PURPOSE:To obtain the substrate for mounting of the semiconductor elements in high density by a method wherein the substrate is made of the material the same with the semiconductor elements to remove the difference between the coefficients of thermal expansion. CONSTITUTION:When a comparatively soft polymer of polyimide, etc., is used as an insulating film for construction of a multilayer wiring on the Si substrate, concentration of stress at the connecting part of a chip and the substrate can be prevented. The polymer has the larger coefficient of thermal expansion than Si usually, while when it is formed in a thin film, behavior of thermal expansion thereof nearly follows that of Si. Therefore even when the Si chip is connected electrically to the wiring on the polymer film formed on the Si substrate using solder balls, break off of the connecting part to be caused according to thermal expansion is not generated. Accordingly, formation of the chip in a large area, provision of connecting pins in high density can be facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a board for mounting semiconductor elements, and in particular, to a high-density board that mounts a large number of Si semiconductor LSIs (Large-Scale Integrated Circuits) and performs connections between LSI chips and connections to the outside of the board. It is effective when used on mounting boards.

Conventionally, IC (integrated circuit) chips were packaged one by one, the DIL (Dual in Line) pins were extracted, and the chips were mounted on an epoxy printed circuit board. In this method, the area occupied by the packaging was large compared to the area of the IC chip, and there was a limit to the high density of IC packaging. Recently, in order to avoid this problem and increase the density of IC chip mounting, a method of directly connecting IC chips to a ceramic multilayer substrate has been used. In this ceramic board mounting method, CCB (Controlled Collapse Bonding), which usually uses small solder balls, is used to electrically connect the IC chip and the ceramic board.
law is used. This solder connection technique has a problem in that the difference in thermal expansion coefficient between the Si used for the chip and the alumina used for the substrate causes large stress to act on the connecting solder balls, making the connections easy to break. This tendency becomes more severe when the area of the chip is increased or the diameter of the solder balls is decreased, which hinders the increase in the area of the chip and the increase in the number of connection pins, which in turn becomes a factor that hinders the high integration of the chip. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a substrate for mounting semiconductor elements without the above-mentioned drawbacks.

The structure of the present invention to achieve the above object is to use Si as the substrate material and eliminate the difference in thermal expansion coefficient between the IC chip and the substrate material. Therefore, by using a relatively soft polymer such as polyimide as an insulating film for realizing multilayer wiring, stress concentration at the connection between the chip and the substrate can be prevented. Polymers usually have a larger coefficient of thermal expansion than Si, but are thinner, so the thermal expansion behavior of polymer films formed on Si plates roughly follows that of Si.
Therefore, when a Si chip is electrically connected to a wiring on a polymer film formed on a Si substrate using a solder ball, there is almost no chance of breakage of the connection due to thermal expansion. Therefore, it becomes easy to increase the area of the chip and increase the number of connection pins with high density.

The present invention will be specifically described below using examples with reference to the drawings.

Example As shown in FIG. 1a, a silicon plate with a thickness of 2 mm was used as the substrate 1. A through hole 11 with a diameter of 1 mm was made in this using a laser or an electron beam. Next, as shown in FIG. 1b, the substrate 1 was subjected to an oxidation treatment to form a SiO ₂ coating 2 on the substrate surface and inside the through hole 11. As shown in FIG. Next, a conductive paste 3 was filled into the through holes, dried and solidified, and a flattening process was performed. Next, the first
As shown in Figure c, polyimide isondroquinazolinedione (a type of polyimide, hereinafter abbreviated as PIK) was deposited by spin coating, and a 10 μm thick
A PIK film 4 was formed. Through-holes were made at predetermined locations in the PIK film, and aluminum wiring 5 was applied. Furthermore, as shown in Figure 1d, PIK film formation,
A second wiring layer 51 was formed by repeating the through-hole drilling and aluminum wiring steps. Necessary surface treatment was performed on the connection pad of the aluminum wiring section on the top surface of the second wiring layer. Connect the silicon IC chip 6 to the connection pad using CCB.

As explained above, according to the present invention, the difference in thermal expansion between the silicon chip and the wiring board can be made very small. Therefore, the stress acting on the connecting portion between the two can be reduced, and the reliability of the wiring board can be significantly improved. Furthermore, since a relatively soft polymer insulating film is placed between the above two layers, multilayer wiring can be easily formed. This has made it easier to mount multiple IC chips on a single wiring board.

[Brief explanation of drawings]

FIGS. 1A to 1D are explanatory diagrams schematically showing the structure of a semiconductor mounting board and its manufacturing process as an embodiment of the present invention. 1...Si substrate, 11...Through hole, 2...
Oxide film, 3...conductor paste, 4...polymer resin layer, 5 and 51...Al wiring layer, 6...silicon IC chip.

Claims (1)

[Claims] 1. A semiconductor substrate, a soft polymer layer formed on the semiconductor substrate, a wiring formed on the soft polymer layer, and electrically connected to a predetermined location of the wiring by solder. What is claimed is: 1. A semiconductor device comprising a semiconductor substrate and an IC chip, wherein the semiconductor substrate and the IC chip are made of the same material. 2. The semiconductor device according to claim 1, wherein the soft polymer is polyimide. 3. The semiconductor device according to claim 1 or 2, wherein the semiconductor substrate is made of silicon.