JPH06325991A - Method of manufacturing semiconductor device - Google Patents

Abstract

PURPOSE:To provide a method of manufacturing a semiconductor device that uses a thinned silicon wafer of which the thickness is selected at a requisite minimum, and that further secures a mechanical strength required for a step in a wafer process, and that is finally finished as a chip piece having an optimum thickness. CONSTITUTION:A silicon substrate 3 is joined to a silicon wafer 1 having a specific thickness determined by the specifications of a semiconductor device via a silicon oxide film 2, and this substrate having an join structure is brought into a wafer process to make devices 5 in the silicon wafer 1. Thereafter, the wafer is diced to the silicon oxide film 2 along scribe lines and further this silicon substrate 3 is plasma-etched, so that the silicon oxide film 2 is removed by hydrofluoric acid cleaning to cut it into individual pieces.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device.

[0002]

2. Description of the Related Art As is well known, a normal semiconductor device is manufactured by subjecting a silicon wafer to a series of wafer processes to form a large number of devices and then dicing the wafer into individual chips. Manufactured. In addition, semiconductor elements include surface devices such as DRAMs that make elements using the surface portion of a wafer as an active region, and vertical devices that make full use of the bulk as represented by MOSFETs. Wafers used for these semiconductor elements are required to have an appropriate thickness that is determined by aspects such as the on-resistance and heat dissipation characteristics of the element, and ideally the minimum thickness required to form the active region of the semiconductor element. Is desirable.

However, the handling of the wafer between the steps of the wafer process, and the cracking of the wafer due to the thermal stress due to the heat treatment and the film forming process,
In order to avoid chipping and secure the necessary mechanical strength, in reality, thick silicon wafers with a certain thickness allowance are put into the wafer process for manufacturing. is there. In addition, in order to increase the productivity of semiconductor devices, the diameter of wafers is becoming larger and larger in recent years, but on the other hand, in order to secure the necessary mechanical strength, the diameter of wafers has become larger. The thickness also increases.

[0004]

By the way, in a semiconductor element manufactured from a large-diameter wafer, a chip piece cut into pieces by dicing by the thickness of the wafer is
The thickness of the chip becomes relatively large with respect to the chip size, and the chip looks like a dice in appearance. Therefore, when the chip is mounted on the ceramic substrate, there is a large difference in height between the chip and the conductor pattern on the substrate side, and there are problems such as the wire coming into contact with the chip due to dripping of wire loops during wire bonding. It is easy to occur.

In this regard, conventionally, a recess is dug in the upper surface of the ceramic substrate, and the chip is mounted in the recess to reduce the height difference between the bonding pad of the chip and the conductor pattern, or by sandblasting or the like. This is dealt with by adopting methods such as reducing the thickness, but since these methods require man-hours and labor, improvement measures are desired.

The present invention has been made in view of the above points, and an object thereof is to solve the above-mentioned problems, to use a thin silicon wafer whose thickness is selected to be a necessary minimum, and in the wafer process, from the viewpoint of steps. It is an object of the present invention to provide a method for manufacturing a semiconductor device, which is capable of finally finishing into individual chips having an optimum thickness while ensuring the required mechanical strength.

[0007]

In order to achieve the above object, in the manufacturing method of the present invention, a silicon substrate is bonded to a silicon wafer having a predetermined thickness determined from the specifications of semiconductor elements via a silicon oxide film, After the substrate having this bonded structure is put into a wafer process to form elements on the silicon wafer, the wafer is diced along the scribe line until it reaches a silicon oxide film, and then the silicon substrate, the silicon oxide The film shall be removed and divided into individual chips.

In carrying out the manufacturing method, a method of removing the silicon substrate by plasma etching,
Another method is to remove the silicon oxide film by cleaning with a hydrofluoric acid solution.

[0009]

In the above-mentioned manufacturing method, in the wafer process, since the substrate having the structure in which the silicon wafer and the reinforcing silicon substrate are bonded to each other through the silicon oxide film is put in, it is required in the processing of the process step. The mechanical strength is ensured. Then, with respect to the wafer in which the elements are formed on the silicon wafer through the wafer process, after the silicon wafer is scribed and scribed until the wafer oxide film is reached in the next dicing process, the silicon wafer is further scribed from the back surface side. SF
_The wafer is divided into individual chips by removing the silicon substrate by plasma etching with ₆ gas, and then removing the silicon oxide film by cleaning with a hydrofluoric acid (HF) solution. Here, since the silicon substrate and the silicon oxide film bonded to the silicon wafer in the previous step have already been removed from the chip pieces that are separated from the wafer and made into chips, the surface such as on-resistance and heat dissipation characteristics is finally obtained. Finished to the optimum thickness required by

[0010]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 shows a substrate structure to be put into a wafer process. In the figure, reference numeral 1 denotes the type of semiconductor device, a silicon wafer having a minimum thickness determined from such specifications, 2 silicon oxide film (SiO _2), 3 silicon reinforcing as the supporting substrate of the silicon wafer 1 The substrate is a substrate, and the silicon substrate 3 is bonded to the back surface of the silicon wafer 1 via the silicon oxide film 2. The numerical values shown in the figures represent specific thickness dimensions of the substrate. Further, FIG. 3 shows a cross-sectional structure of an element formed on a silicon wafer 1 through a series of wafer processes on the above-mentioned bonded substrate. In addition, as shown in FIG.
After the device is built in, the surface of the silicon wafer 1
In order to protect it from the hydrofluoric acid cleaning solution described later, the silicon nitride film (Si
-N) is completely covered, and the bonding pad portion is formed of copper (Cu) which is not attacked by the hydrofluoric acid (HF) solution.

1 (a) to 1 (e), a manufacturing process for obtaining a chip piece by introducing the substrate having the bonded structure shown in FIG. 2 into a wafer process will be described. First, in (a), the substrate having the bonded structure described in FIG. 2 is put into a wafer process, and a large number of the elements shown in FIG. 3 are arranged on the surface of the silicon wafer 1 in a grid pattern.

Next, in the dicing step (b), the substrate after the wafer process is cut to a depth from the side of the silicon wafer 1 to the silicon oxide film 2 along the scribe line (street). Dicing is performed so that the groove 4 is formed and the element 5 is shredded. Continued (c)
In the etching step, the substrate is turned upside down, the silicon substrate 3 is removed by plasma etching with SF ₆ gas, and then the silicon oxide film 2 is removed in the cleaning step with the hydrofluoric acid solution in (d). During the cleaning with the hydrofluoric acid solution, the above-mentioned silicon nitride film with high corrosion resistance (Si-
N), protect the device with copper (Cu). Then, when the silicon oxide film 2 is removed, the chip 6 is divided into individual pieces as shown in (e), and finally the chip having an optimum thickness corresponding to the thickness of the silicon wafer 1 is finished.

[0013]

As described above, according to the present invention, a silicon substrate having a predetermined thickness determined by the specifications of semiconductor elements is bonded to a silicon substrate via a silicon oxide film,
After the substrate having this bonding structure is put into a wafer process to form an element on the silicon wafer, the wafer is diced until it reaches a silicon oxide film along a scribe line, and further the silicon substrate,
By removing the silicon oxide film and dividing it into individual chips, it is possible to finally finish the chips to the optimum thickness while ensuring the mechanical strength required from the wafer process step, and the on-resistance. A semiconductor element with high device performance in terms of heat dissipation is obtained.

[Brief description of drawings]

FIG. 1 is an explanatory view of a semiconductor device manufacturing process according to an embodiment of the present invention, in which (a) is a structural diagram of a substrate to be put into a wafer process, (b) is a dicing process diagram, and (c) is a silicon substrate. Etching process diagram for removal, (d) process diagram of hydrofluoric acid solution cleaning process for removing silicon oxide film, (e) diagram showing individual chip pieces

FIG. 2 is a structural diagram of a bonded substrate to be put into a wafer process.

FIG. 3 is a structural cross-sectional view of an element built in the bonded substrate stack of FIG.

[Explanation of symbols]

 1 silicon wafer 2 silicon oxide film 3 silicon substrate 4 kerf 5 element 6 chip

Claims (3)

[Claims] 1. A silicon substrate having a predetermined thickness determined from the specifications of a semiconductor device is bonded to a silicon substrate via a silicon oxide film, and the substrate having this bonding structure is put into a wafer process to form a device on the silicon wafer. After that, the wafer is diced along the scribe line until it reaches the silicon oxide film, and further, the silicon substrate and the silicon oxide film are removed and divided into individual chips. Method. 2. A method of manufacturing a semiconductor device according to claim 1, wherein the silicon substrate is removed by plasma etching. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the silicon oxide film is removed by cleaning with a hydrofluoric acid solution.