JPH01235699A - Production of ic card and ic chip - Google Patents

Abstract

PURPOSE:To enhance the anti-rupture strength of an IC chip against the bending of an IC card to a great extent, by a method wherein a micro-crack layer caused by a mechanical abrasion on the reverse side of the IC chip is removed by etching. CONSTITUTION:An IC chip is formed by providing electrodes 2, a diffusion layer 3, and the like on the surface of an IC chip 1 in a wafer processing. On the reverse surface of the IC chip 1, a removal layer 4 consisting of a mechanical abrasion layer 5 to be ground with a #4000 or #8000mesh and a chemical abrasion layer 6 to be removed by chemical etching is formed. Here, a micro-crack layer 6' is a flow caused by a mechanical abrasion and assumed to have a 5mum thickness more or less, therefore being completely included in the chemical abrasion layer 6 having a thickness of the order of 10mum, which is removed by chemical etching. In this manner, the micro-crack layer 6' is perfectly removed. Then, the anti-rupture strength of the IC chip is approximately three times that of a chemical etching-free IC chip, thereby remarkably improving an IC chip anti-rupture strength.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an IC card whose IC chip is less likely to be damaged when the IC card is bent.

(Prior Art) In recent years, so-called IC cards, such as credit cards or bank cash cards, have become popular, and these cards have a built-in IC chip equipped with a microcomputer EPROM or the like.

However, the IC used in such IC cards
Since the chip is equipped with a microcomputer, E2FROM, etc., a relatively large chip size of about 5 square meters or more is required. Furthermore, I.C.
The thickness of the chip is 0.2 rtr because the thickness of the entire card is limited to about 0.76 wm according to standards such as ISO.
It must be kept below about m. Therefore, since the IC chip itself has a relatively large area and is thin, it has a structure that is easily broken, and since IC cards are used in people's pockets, they are subject to stress such as bending. The bending strength of the steel is an important issue.

Conventionally, as a countermeasure against such inter-injection, there is one disclosed in, for example, Japanese Patent Laid-Open No. 62-275788.

Figure 2 is an explanatory diagram of a conventional micro crack.
Figure (a) shows rectangular IC chips A and B made from an IC wafer.
It shows the direction to cut out. A large number of parallel horizontal lines in the figure indicate that linear scratches (micro scratches) generated during backside grinding (pack grinding) of the IC wafer remain.

FIG. 2(b) is an explanatory diagram showing that the bending rupture strength of IC chips A and B differs depending on the cutting direction. That is, case A in which the IC chip grinding direction is parallel to the longitudinal direction of the IC chip shows that the bending strength is far superior to case B in which the grinding direction is perpendicular to the IC chip.

(Problem to be Solved by the Invention) However, according to the method disclosed in the above publication, the breaking strength is at most several hundred grams, and I
The strength against bending of the C card is not sufficient.

It is thought that in the above method, scratches (microcracks) generated during back grinding (pack grinding) remain, and the inherent breaking strength of a silicon single crystal IC chip is not achieved.

(Means for Solving the Problems) The present invention resides in an IC card equipped with an IC chip in which scratches (microcracks) that occur during back grinding (pack grinding) are completely removed by chemical etching. . There is also a method for manufacturing such an IC chip.

(Function) The IC chip of the present invention is back-grinded (pack-grinded).
The scratches (microcracks) caused by this process have been completely removed. Therefore, the weak points of conventional IC chips have been eliminated, and this IC chip has improved bending strength up to the inherent breaking strength of silicon single crystal.

(Example) The wafer process of IC wafers, that is, the process of forming ICs on wafers by photolithography, diffusion, vapor deposition, etc., is completely unchanged from the conventional process.

IC wafer that has completed the wafer process, conventional I
Back surface grinding (pack grinding) is performed by mechanical polishing as in the case for C cards.

In the wafer process, an IC wafer with a thickness of 560μ can be polished to a target thickness of 2 by one polishing using a diamond-containing sialumina abrasive (≠4000 mesh), which is a mechanical grinding method.
Grind to 30μ before 00μ. Next, a diamond-filled alumina abrasive ≠ 80, which is a similar mechanical grinding method, is used.
10μ before the target value of 200μ by polishing with 00 mesh
Grind until. Thereafter, the diffusion surface (surface) of the IC wafer is affixed to a metal or sapphire plate with wax or pitch. Then, chemical etching of 10 μm is performed to adjust the IC wafer thickness to the target value of 200 μm and to give it a mirror finish. The etchant is general] UshiINO32 HF: CH3CO0H=
A solution with a composition of 5:1:2 saturated with Work 2 was used. Next, the IC wafer is removed from the metal or sapphire plate, the wax is removed with Triclean, and the wafer is diced. The process of mounting the IC chip onto the IC card after dicing is no different from the conventional method.

In this example, dicing is performed after chemical etching, but 1 mechanical polishing and dicing are performed.

It is also possible to perform the chemical etching in the same order as the chemical etching, and there seems to be no difference in the effect.

FIG. 1 is a sectional view of an IC chip according to an embodiment of the present invention. On the surface of the IC chip 1, an electric maple 2.degree. diffusion layer 3 and the like are formed in a wafer process to produce an IC. The back surface of the IC chip 1 has a mechanical polishing layer 5 which is ground by ≠4000.48000 mesh and a chemical polishing layer 6 which is removed by chemical etching. Both layers are removed by a removal layer 4.
It is.

Here, the microcrack layer 6' is considered to be scratches caused by mechanical polishing, and its thickness is considered to be about 5 μm at most. Therefore, 1 is removed by chemical etching.
It is completely included in the chemical polishing layer 6 with a thickness of about 0μ, and the microcrack layer 6' is completely removed.

FIG. 4 is an explanatory diagram of the experimental results of IC chip breaking strength, in which the horizontal axis represents the chemical etching time and the vertical axis represents the IC chip breaking strength.

FIG. 5 is an explanatory diagram showing a method for measuring IC chip breaking strength. A load Wl is applied to the IC chip 1 via the probe 10.
By applying l, the breaking strength of the IC chip 1 is measured. Here, back pressing means pressing the back side of the IC chip 1 with the front side facing down, and pressing the front side means pressing the front side of the IC chip 1 with the back side facing down. The horizontal axis in FIG. 4 means that time t0 means etching time O minutes, and jlet
2... means that the etching time becomes longer, that is, the layer removed by chemical etching becomes thicker.

Therefore, what Figure 4 means is that in surface pressing, by performing chemical etching for t3 (minutes), the IC chip breaking strength improves to about three times that of no chemical etching, and thereafter remains almost constant. That's true. This shows that the microcrack layer 6' is completely removed by the etching time t3 (minutes), which has the effect of significantly improving the breaking strength of the IC chip. Here, the chemical etching time ta (minutes) corresponds to an etching thickness of 5 .mu., so the chemical etching removal thickness of 10 .mu. in the above-mentioned embodiment is a sufficient f straightness.

In FIG. 3, since the etching rate is high in the section to-t2, the etching speed is high in the section from t2 to t5 in the micro-crack layer 6'.
Since the etching rate in the section corresponding to is relatively slow, it is considered that this is related to the etching of a silicon single crystal layer without microcracks. In addition, the micro crack layer 6
It is clear that the thickness of ′ varies depending on the polishing method.
It is recognized that the downfeed grinding method, in which the silicon wafer is ground from the top surface, produces fewer microcracks than the one-feed grinding method, in which the silicon wafer is ground from the side.

FIG. 5 is a sectional view of a 1C card according to an embodiment of the present invention. The IC chip 1 has a sharp back surface 7 bonded with resin onto a metal plate, for example, a stainless steel plate with a thickness of 0.2 mm, thereby forming a lid 22. The electrical terminals of the IC chip are taken out using bumps 19 or wire bonds, and
It is taken out to the terminal electrode 17 through the through hole 16 of No. 5. The mounting of the IC chip on the IC card is no different from the conventional method. In the present invention, the micro-crack layer 6' is removed by chemical etching, but instead of etching removal, It is conceivable to fix the p-microcrack layer by alloying. That is, after mechanical polishing, Ni and Ti are deposited on the back surface of the IC wafer.

A metal such as NiCr is deposited and alloyed with silicon by heating. It is thought that the metal penetrates into the microcrack layer and becomes fixed, thereby improving the IC chip breaking strength.

(Effects of the Invention) As explained above, according to the present invention, the IC chip mounted on the IC card has the micro-crack layer formed by mechanical polishing on the back surface of the chip removed by etching treatment. The IC chip breaking strength is significantly improved against bending of the IC card.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an IC chip according to an embodiment of the present invention, and FIG.
The figure is an explanatory diagram of conventional micro cracks, Figure 3 is an explanatory diagram of the experimental results of IC chip breaking strength, Figure 4 is an explanatory diagram of the method for measuring IC chip breaking strength, and Figure 5 is a cross-sectional view of an IC card. be. DESCRIPTION OF SYMBOLS 1... IC chip, 4... Removal layer, 5... Mechanical polishing layer, 6... Chemical polishing layer, 6'... Micro crack layer. Patent applicant: Oki Electric Industry Co., Ltd. ) Figure 5 Procedural Amendment (Mutsu) 1 Indication of the case 1988 Patent Application No. 061913 2 Name of the invention IC card and IC chip manufacturing method 3 Person making the amendment Relationship with the case Patent Application Residence , place (
Address: 105) 1-7-12 Toranomon, Minato-ku, Tokyo Name (029) Representative of Oki Electric Industry Co., Ltd.
Director and President Kosugi Kosugi Hikari 4 Agent Address (〒108) 4-10-3 Shibaura, Minato-ku, Tokyo
Column of "Brief explanation of the drawings" and drawing 6, contents of amendment, attached sheet 6, contents of amendment (1) "To be a topic of the day" on page 2, line 15 of the specification. be corrected to ``This will be an issue.'' (2) In the 16th line of page 4 of the Ministry of Foreign Affairs, the word "Lingraphy" is corrected to "Lingraphy." (3) On page 5, line 20 of the Ministry of Foreign Affairs, the phrase ``changeable'' is amended to ``changeable''. (4) On page 6, line 19 of the ministry, the words “Figure 4” were replaced with “
◇ (5) In the second line of page 7 of the same book, the text ``Figure 5'' is corrected to ``Figure 4''. (6) In the 9th line of the same page of the same book, the text "Figure 4" is corrected to read "Figure 3." (7) In lines 18 to 19 of page 8 of the same Ministry, the phrase ``The sharp back surface 7 is glued with resin to form the lid 22'' has been replaced with ``The back surface 2 is glued with resin. The lid is on the 18th floor.'' (8) In the third line of page 10 of the same book, the phrase ``conventional micro-crack'' is amended to read ``conventional''. (9) Correct all appendixes of the drawing “Figure 5”. *Cross-sectional view of IC card Figure 5

Claims (2)

[Claims] (1) An IC card equipped with an IC chip, characterized in that the IC chip has microcracks caused by mechanical polishing on the back surface of the chip removed by etching treatment. (2) After completion of the wafer process, the method includes a step of removing the back surface of the IC wafer by mechanical polishing, and a step of removing the back surface of the IC wafer, including the micro-crack layer generated by the mechanical polishing, by etching treatment. A method for manufacturing an IC chip.