JPH03111729A - Pressure measuring apparatus - Google Patents

Abstract

PURPOSE:To make it possible to measure pressure in an IC package highly accurately by providing a spiral shaped diffused resistor which is formed on the surface of a semiconductor chip by impurity diffusion. CONSTITUTION:This apparatus is used for measuring pressure in an IC package wherein a silicon chip 11 that is a semiconductor chip is sealed with a resin. A double-spiral shaped diffused resistor 13 is provided on the surface of the semiconductor chip 11 by the diffusion of impurities. The diffused resistor 13 is formed so that the resistor is distributed uniformly on the surface of the chip 11. The pressure in the IC package is measured based on the change in resistivity of the diffused resistor 13. The change in resistivity of the diffused resistor 13 appears as the result of the piezoelectric resistance effect due to the strain in the circumferential direction generated in the diffused resistor 13. The length of the double-spiral shaped diffused resistor can be made very long in a small forming region. Therefore, the amount of the change in resistivity with respect to the strain along the surface of the chip 11 can be made large. As a result, the measurement of the pressure with the double-spiral shaped diffused resistor 23 can be performed highly accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION C. Industrial Application Field The present invention relates to a pressure measuring device for measuring pressure within an IC package.

[Conventional technology]

If a semiconductor integrated circuit element, in which a chip containing a circuit element is sealed in an IC package, absorbs moisture during the period after manufacture and before it is mounted on a circuit board, the internal parts may deteriorate due to evaporation of moisture when immersed in a solder bath during mounting. The pressure increases, causing deformation and cracking of the IC package. For this reason, integrated circuit devices have traditionally been wrapped and stored in aluminum foil after manufacturing to prevent moisture absorption, but this requires careful handling, resulting in high costs. be. For this reason, the development of IC packages with improved durability against internal pressure caused by evaporation of absorbed moisture is underway. In other words, by preventing cracks from occurring in the IC package even if absorbed moisture evaporates during mounting, it becomes easier to handle integrated circuit devices, reducing costs, and improving the reliability of integrated circuit devices. It is possible to improve the elasticity.

In developing an IC package with such high durability, we measure to what extent the pressure inside the IC package rises due to evaporation of moisture during solder mounting. If possible, the strength of the encapsulant that will become the IC package can be determined based on this measurement result.

As a technique that can be applied to measure the pressure within an IC package, there is a technique for stress measurement that applies a piezoresistance effect. The piezoresistance effect is a phenomenon in which the specific resistance of a crystal changes according to the strain that occurs when an external force is applied to the crystal.

An example configuration for the stress measurement is shown in FIG.

Diffused resistors R1 to R4 are formed on the surface of a silicon chip l by patterning them by impurity diffusion. The diffused resistors R1-R4 are arranged extending in four different directions on the surface of the silicon chip 1 at an angle of 45 degrees with respect to each other. When an external force is applied to the silicon chip 1, the resistance values of the diffused resistors R1 to R4 change corresponding to the strain at this time, and the stress parallel to the surface of the silicon chip 1 is calculated by calculation based on the change in each resistance value. σ8. σ7 and the stress σ1 perpendicular to the surface of the silicon chip 1 can be determined. Therefore, if the stress σ is known, the pressure inside the IC package can be determined.

[Problem to be solved by the invention]

However, in the above-described configuration, in order to measure the pressure inside the IC package, that is, the stress σ, it is necessary to use 4
There is a problem that different types of diffused resistors R1 to R4 are required, and therefore the pattern for forming the diffused resistors becomes complicated, and the process of forming them on the surface of the silicon chip 1 becomes complicated. In addition, the above-mentioned technique applies stress σ8 in three orthogonal directions. σ,
.

In order to obtain σ8, linear diffused resistors R1 to R4 are used, and since the formation area of each diffused resistor R1 to R4 cannot be made too large, the length of each diffused resistor R1 to R4 is relatively short. For this reason, distortion of the silicon chip 1 cannot be detected with high precision. Therefore, the structure for measuring stress as described above is not necessarily suitable for measuring the pressure increase due to evaporation of water within an IC chip.

An object of the present invention is to provide a pressure measuring device that solves the above-mentioned technical problems and can measure the pressure inside an IC package with high precision.

[Means to solve the problem]

The pressure measuring device of the present invention is characterized in that it includes a spiral diffusion resistance r formed on the surface of a semiconductor chip by impurity diffusion.

[Effect]

According to the configuration of the present invention, the pressure within the IC package acts perpendicularly to the surface of the semiconductor chip, so that the semiconductor chip is subjected to strain that contracts in a direction perpendicular to the surface and expands in a direction along the surface.

This strain in the direction along the surface is the strain in the radial direction of the spirally shaped diffused resistor formed on the surface of the semiconductor chip, and due to this radial strain, the diffused resistor is distorted in its circumferential direction. The specific resistance of the diffused resistance changes due to the piezo effect. The spiral-shaped diffused resistor has the advantage that its length can be very long in a small formation area, and therefore the amount of change in its resistivity changes greatly with respect to the circumferential distortion. In other words, the amount of change in specific resistance with respect to the strain of the semiconductor chip is large. As a result, compared to conventional technology that measures pressure by calculation using linear diffusion resistance,
This makes it possible to measure pressure with much higher precision.

Moreover, there is no need to form diffused resistors extending in four different directions on the surface of a semiconductor chip as in the past, and only one type of spiral pattern diffused resistor can be formed, which can complicate the formation process. Therefore, it is advantageous to reduce costs.

〔Example〕

FIG. 1 is a plan view showing the basic configuration of a pressure measuring device according to an embodiment of the present invention, and FIG. 2 is a plan view showing an enlarged part of the configuration. Further, FIG. 3 is a sectional view showing the overall configuration. This device consists of an IC package 12 (a first
Illustrations are omitted in the figures and FIG. 2. ) is used to measure the pressure within ), and is a double spiral-shaped diffused resistor 13 formed on the surface of the silicon chip 11 by impurity diffusion.
It is equipped with The diffused resistors 13 are formed so as to be uniformly distributed on the surface of the silicon chip 11, and both ends of each are connected to the IC package 12 via wiring 14 and bonding wires 15 formed on the surface of the silicon chip 11.
It is connected to the wood frame 16 led out. 1
7 is a die pad that supports the silicon chip 11.

FIG. 4 is an explanatory diagram showing the principle for pressure measurement. FIG. 4 (1) shows a simplified cross-sectional view of the silicon chip 11, and FIG. 4 (2) shows the silicon chip 11. 11
A simplified plan view of is shown.

When the IC package 12 containing moisture is heated, the moisture inside evaporates, thereby applying pressure P perpendicularly to the surface of the silicon chip 110. As a result, silicon chip 1
1 contracts in the direction along the pressure P, and expands in the direction crossing the pressure P (that is, the direction parallel to the surface on which the diffusion resistance 12 is formed). In other words, a single silicon chip has a strain ε that shrinks in the thickness direction of the silicon chip 11.
Strain a extending in the radial direction of the spirally shaped diffused resistor 13.

occurs. Due to this radial strain ε, the diffusion resistance 1
3, a strain ε occurs in the circumferential direction (that is, the direction in which the diffused resistor 13 extends), and as a result, the specific resistance of the diffused resistor 13 changes due to the piezoresistance effect described above.

Therefore, if a known value of pressure is applied to the IC package 12 and the relationship between the pressure and the amount of change in resistivity is calibrated in advance, the pressure P can be measured as a change in the resistivity of the diffusion resistor 13. . FIG. 5 shows an example of the results of calibrating the relationship between the pressure P and the amount of change ΔR/R in the specific resistance of the diffusion resistor 13.

As described above, according to this embodiment, the double spiral-shaped diffused resistors 13 are uniformly distributed and formed on the surface of the silicon chip 11, and from the change in the specific resistance of the diffused resistors 13, I'm trying to measure pressure. The change in resistivity of the diffused resistor 13 is a change realized as a result of the piezoresistance effect due to the circumferential strain that occurs in the diffused resistor 13, and the double spiral-shaped diffused resistor has a very long length in a small formation area. Silicon chip 1
It is possible to increase the amount of change in specific resistance with respect to strain along the surface of 1. Thereby, the pressure P can be measured with high precision by the double spiral diffusion resistor 13.

Moreover, in this embodiment, since the plurality of diffused resistors 13 are uniformly distributed on the surface of the silicon chip 11, the pressure distribution within the IC package 12 can also be accurately measured. Furthermore, since only a plurality of diffused resistors 13 of one type of pattern are formed as shown in FIG.
The formation process does not become complicated, and it can also contribute to cost reduction.

FIG. 6 is a sectional view showing the basic configuration of another embodiment of the invention. In FIG. 6, parts corresponding to those shown in FIG. 3 described above are designated by the same reference numerals. In this embodiment, silicon chips lla and llb are fixed on both sides of the die pad 17, and silicon chips lla and llb are fixed on both sides of the die pad 17.
A plurality of diffused resistors 13 are formed on each surface of la and llb.

With this configuration, the pressure distribution inside the IC package 12 on both sides of the die pad 17 can be measured.

In the above-mentioned embodiment, a double spiral diffused resistor 13 was used, but the diffused resistor only needs to be spiral, and does not necessarily have to be double spiral.

〔Effect of the invention〕

As described above, according to the pressure measuring device of the present invention, by forming the diffused resistance formed on the surface of the semiconductor chip in a spiral shape, the length can be made very long in a small formation area, and therefore The amount of change in specific resistance with respect to strain can be increased. As a result, it is detected as a change in the resistivity of the spirally diffused resistance ■c
The pressure inside the package can now be measured with high precision.

Moreover, there is no need to form diffused resistors extending in four different directions on the surface of a semiconductor chip as in the past, and it is only necessary to form a single type of spiral pattern diffused resistor, so the formation process is not complicated. Therefore, it is also advantageous for cost reduction.

[Brief explanation of drawings]

Fig. 1 is a plan view showing the basic configuration of an embodiment of the present invention, Fig. 2 is a plan view showing an enlarged part of the same, Fig. 3 is a cross-sectional view showing the overall structure, and Fig. 4 5 is an explanatory diagram showing the principle of pressure measurement, FIG.
The figure is a sectional view showing the basic configuration of another embodiment of the present invention, and FIG. 7 is a plan view showing the configuration for stress measurement. 11...Silicon chip (semiconductor chip), 12...
・IC package, 13... Diffusion resistance diagram

Claims (1)

[Claims] A pressure measuring device for measuring the pressure inside an IC package in which a semiconductor chip is sealed with resin, the pressure measuring device comprising a spiral diffusion resistance formed by impurity diffusion on the surface of the semiconductor chip. .