JP2010012578A - Manufacturing method for silicon substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To develop a simple through-hole formation technique which can alternate a conventional through-hole formation technique and has high productivity since it is necessary that a device such as a dry-etching method and a laser method uses an expensive through-hole formation technique with low productivity when forming a through-hole for a penetration electrode on a silicon substrate. <P>SOLUTION: In a manufacturing method for a silicon substrate for forming the through-hole or a non-through-hole by a drill while locally cooling the silicon substrate, the number of rotation of the drill is a range of 8,000-50,000 rpm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a semiconductor element substrate made of silicon, and more particularly to a method of forming through holes necessary for three-dimensional high-density mounting of semiconductor elements in a silicon wafer.

  It is an indispensable demand to improve the integration density of semiconductor devices and perform signal processing at high speed. For this purpose, it is necessary to develop a technique for miniaturizing a semiconductor chip to operate at high speed and mounting the semiconductor chip itself at a high density.

  As one of high-density mounting techniques, a system is known in which a plurality of semiconductor chips are stacked on a plastic substrate or a ceramic substrate through a thin insulating substrate. The electrical connection between the stacked semiconductor chips is generally achieved by wire bonding the connection pads formed on the outer periphery of the semiconductor chip, and finally the whole is molded with a resin to form a semiconductor device product. Become. However, in the wire bonding method, the connection pads can be arranged only at the periphery of the semiconductor chip and the number of pads is limited, and high-speed signals can be transmitted at high density due to problems such as wire line inductance. Not very suitable.

  Also, as a method similar to the above in that the semiconductor chips are stacked, a silicon substrate is used as the insulating intermediate substrate, and an electrode penetrating from the front surface to the back surface of the substrate is formed, and this is connected to the upper and lower semiconductor chip connection electrodes. (For example, refer to Patent Document 1). In this stacked configuration, the semiconductor chip and the silicon substrate are made of the same material, so the thermal stress generated at the connection between the semiconductor chip and the silicon substrate is less than that between the semiconductor chip and the plastic substrate, so that highly reliable bonding is possible. The wiring distance can be shortened.

  Further, as an advanced technique, a technique is disclosed in which the intermediate substrate is omitted and a through electrode is directly formed on the semiconductor chip itself, and the through electrodes are connected to each other vertically (see, for example, Patent Document 2). Here, in each semiconductor chip, a two-dimensional integrated circuit and a through electrode penetrating the chip are formed side by side on the surface. The through electrode is formed such that a part of the through electrode is exposed on the back surface, and this protruding portion is joined to a through electrode pad formed on the surface of another semiconductor chip, and a three-dimensional semiconductor integrated circuit is obtained as a whole by repeating this. . This technique is excellent in that an ideal semiconductor device having a short wiring length can be obtained by connecting the bottom through electrode to the electrode pad of the multilayer wiring board and finally packaging.

In addition, after forming the through-hole for the through-hole in the silicon substrate, an insulating film such as silicon oxide is formed on the inner wall of the hole by chemical vapor deposition. Thereafter, a seed layer is generally formed by an electroless plating method, and this seed layer is used as a cathode, and a metal film such as copper or aluminum is provided on the inner side wall to form a through electrode. In addition, the inside of a hole is filled with metal by a damascene method, and silicon is removed from the back surface by etching to cue the metal portion to form a through electrode.
JP-A-5-144978 JP 2003-17558 A

Before forming a penetrating electrode in the silicon substrate, it is necessary to form a hole penetrating vertically in the silicon substrate. One method for forming the through hole is a dry etching method. First, a resist pattern having an opening at a location corresponding to the penetrating portion is formed on the silicon substrate by a regular photolithography method on the silicon substrate, and the silicon in the opening portion is made of a fluorocarbon gas such as SF ₆ . This is a method of removing in the vertical direction by dry etching.

  However, in this method, when a hole is etched deeply, a single resist layer is not sufficient, and a multi-layer process such as adding a hard mask made of an inorganic material is often required. In addition, even if etching proceeds in the vertical direction, etching also enters in the side wall direction, so it is necessary to employ a Bosch process that alternately repeats protection and etching of the side wall, which requires a very long time for processing. There is also a problem.

  In addition, since a dangerous chlorofluorocarbon gas is used, the dry etching apparatus has a very complicated structure, cannot be easily maintained, and requires a large amount of maintenance. In addition, the dry etching method has a problem that the size of the substrate that can be processed is limited due to the specifications of the apparatus.

  There is a laser method as another method. However, since silicon is melted and removed by irradiating a YAG laser beam at a desired position, there is a problem that dross and dissolved powder are reattached around the processed portion. Furthermore, it has the same problem as the dry etching method that the laser apparatus is expensive and the productivity is low.

  Accordingly, an object of the present invention is to provide a method for manufacturing a silicon substrate using a through hole forming technique that is simple and high in productivity, instead of an expensive and low productivity through hole forming technique in which an apparatus such as a dry etching method or a laser method is expensive. Is to provide.

  The present invention has been made in view of the above problems. The invention of claim 1 is directed to a through-hole or non-penetration in a silicon substrate with a rotating drill while locally cooling a contact portion between the silicon substrate and the drill. A method for manufacturing a silicon substrate is characterized in that a hole is formed.

  In the manufacturing method of the present invention, by performing the drill while cooling the silicon substrate, the generation of frictional heat caused by the rotating drill coming into contact with the silicon substrate is suppressed, so that the silicon melts and the melted portion becomes the hole opening. It does not re-solidify and adhere to the hole sidewall. Therefore, a through hole having excellent vertical shape is formed.

  The invention according to claim 2 is the method for producing a silicon substrate according to claim 1, wherein the number of rotations of the drill is in the range of 8,000 rpm to 50,000 rpm.

If the number of rotations of the drill is set within such a range, it is possible to suppress the occurrence of chipping or cracking in the back surface opening. Therefore, it is possible to suppress the opening diameter from being enlarged due to the chipping or cracking in the opening formed on the back surface side of the silicon substrate.
The invention according to claim 3 is characterized in that the silicon substrate is placed on a substrate mounting base, and the substrate mounting base is cooled by a cooling medium to perform local cooling. Item 3. A method for manufacturing a silicon substrate according to Item 2.
The invention according to claim 4 is characterized in that the local cooling is performed by spraying cooling water onto a contact portion between the silicon substrate and the drill. It is what.

  The invention according to claim 5 is characterized in that the local cooling is performed by spraying liquid nitrogen onto a contact portion between the silicon substrate and the drill. It is what.

  According to the present invention, since it has the operation described above, it is possible to use a very simple mechanical means of drilling without using a dry etching method or a laser method with low productivity and high cost. It can be set as the manufacturing method of the silicon substrate which can form a through-hole or a non-through-hole in a silicon substrate. In particular, the drilling method is easier to adjust the depth of squeezing holes in the silicon substrate than the punching method using molds belonging to the same mechanical means, so it is suitable for forming non-through holes. Can be mentioned.

The drill method has been considered unfavorable as a technique for squeezing through-holes in a single crystal substrate such as a silicon substrate, resulting in enlargement of the back opening and damage to the inner wall. However, it was found that by drilling at an appropriate number of rotations, a practical through hole and a non-through hole having a side wall free from shape collapse and melt adhesion can be mechanically formed.
Hereinafter, this will be described in accordance with an embodiment.

  First, a silicon wafer having a thickness of 300 μm and a diameter of 6 inches and an NC drilling apparatus were prepared. The drilling apparatus had a substrate mounting base, and a silicon wafer was mounted on the base. At this time, the silicon wafer was fixed to the substrate by a suction chuck method. The fixing may be performed by an electrostatic chuck method or by placing a magnet on a silicon wafer and attracting the magnet to the substrate.

  Using a drill with a pointed tip and a diameter of 50 μm, the silicon wafer was squeezed. During the squeezing, the number of rotations (rpm) of the drill was changed to 2,000 rpm, 5,000 rpm, 8,000 rpm, 10,000 rpm, 20,000 rpm, 50,000 rpm, 100,000 rpm, and squeezing was performed.

In addition, when squeezing holes, in addition to changing the rotation speed of the drill as described above, the shape of the through hole was observed depending on whether or not the contact portion between the drill and the silicon wafer was cooled.
First, without performing local cooling by spraying liquid nitrogen, a drilling process was performed on the silicon substrate under the above conditions to form a through hole in the silicon substrate. As a result, the silicon wafer was cracked when the drill was rotated at a low speed of 2,000 rpm and 5,000 rpm. On the other hand, when the number of rotations of the drill reached high speeds of 50,000 rpm and 100,000 rpm, the shape of the hole collapsed on the back surface of the silicon wafer when the drill penetrated. In addition, although the same squeezing hole was performed with the drill blade which changed the front-end | tip shape of a drill, the difference in the shape of the hole by the difference in front-end | tip shape was not seen. In general, when squeezing holes without local cooling, silicon melts and re-condenses on the edge of the through hole of the silicon substrate and the side wall of the through hole, and the shape is It was hard to say good.

  Next, the silicon substrate was drilled under the same conditions as described above while cooling by blowing liquid nitrogen to the portion where the rotating drill was in contact with the silicon substrate, thereby forming a through hole in the silicon substrate. In this case, almost no adhesion of silicon coagulum was found in the through holes.

Table 1 collectively shows the observation results around the through-holes when the squeezed holes were formed with a drill having a diameter of 50 μm while performing local cooling by spraying liquid nitrogen. It is clear that the shape depends on the number of rotations of the drill. Moreover, although the photograph from the surface or the back surface of the through-hole formed with the 50 μm diameter drill is shown in FIGS. 1 (a) and (b), local cooling is performed and the number of revolutions of the drill is 8,000 rpm, 10,000 rpm. , 20,000 rpm, and 50,000 rpm, the shape was sufficiently practical. Although fine burrs and the like were observed around the through-holes, the burrs and the like were minute ones having no problem that can be removed and shaped by light etching. In addition, FIG.1 (c) is a front view at the time of seeing a hole from the back side, when local cooling is carried out and drilling is carried out at a high rotational speed of 100,000 rpm. Yes. FIG. 1 (d) shows a photograph when a hole is made without local cooling, and melting occurs at the edge of the hole.

The photograph at the time of squeezing a hole in a silicon substrate by drilling under local cooling according to the present invention. (A) Top view and top perspective view, (b) Rear front view, (c) Front view photograph of the squeezed hole when the drill rotation speed is 100,000 rpm, (d) When there is no local cooling Squeezed hole front view photograph.

Claims (5)

  A method for manufacturing a silicon substrate, comprising forming a through hole or a non-through hole in a silicon substrate with a rotating drill while locally cooling a contact portion between the silicon substrate and the drill.   2. The method of manufacturing a silicon substrate according to claim 1, wherein the number of revolutions of the drill is in the range of 8,000 rpm to 50,000 rpm. The silicon substrate according to claim 1 or 2, wherein the silicon substrate is placed on a substrate mounting base, and the substrate mounting base is cooled by a cooling medium to perform local cooling. Manufacturing method. 3. The method for manufacturing a silicon substrate according to claim 1, wherein the local cooling is performed by spraying cooling water on a contact portion between the silicon substrate and the drill. The method for manufacturing a silicon substrate according to claim 1, wherein the local cooling is performed by spraying liquid nitrogen onto a contact portion between the silicon substrate and a drill.