TW201802906A - Wafer processing method - Google Patents

Abstract

[Problem] An object of the present invention is to provide a method for processing a wafer capable of performing plasma etching without lowering the quality of a device. [Solution] According to the present invention, a method for processing a wafer can be provided, which is to divide a wafer into individual devices. The wafer is a device in which a passivation film is layered on a positive area to divide a predetermined line into a semiconductor substrate. A plurality of front surfaces are formed, and the processing method of the wafer is at least composed of the following steps: a semiconductor substrate exposing step, positioning a cutter at a predetermined division line to remove a passivation film or a metal film laminated on the predetermined division line, Exposing the semiconductor substrate along a predetermined division line; and a division step, using the passivation film covering the device as a shielding film, and dividing the semiconductor substrate that has been exposed at the division line by plasma etching.

Description

Processing method of wafer

FIELD OF THE INVENTION The present invention relates to a method of processing a wafer by dividing a wafer into individual devices by so-called plasma etching.

BACKGROUND OF THE INVENTION A wafer that is divided by a predetermined division line and has a plurality of devices such as ICs and LSIs formed on the front surface of a semiconductor substrate is divided into individual devices by a dicing device, a laser processing device, and the like, and is used in On electrical equipment such as mobile phones and personal computers.

In addition, as a method for improving the flexural strength of a device, and capable of dividing a wafer into individual devices at a time, a method of plasma etching has been proposed (see, for example, Patent Document 1). . Prior Art Literature Patent Literature

Patent Document 1: Japanese Patent Laid-Open No. 2002-093752

SUMMARY OF THE INVENTION The problem to be solved by the invention is based on the plasma etching technique described in the above-mentioned Patent Document 1. Although the production efficiency is expected to be improved, and the flexural strength of the divided device is improved, it is on the front side of the wafer. It is difficult to form a resist film for protecting devices to a uniform thickness. When the applied resist film (1 to 5 μm) is subjected to plasma etching, if the resist film is thinner When the etching is performed partially, there is a problem that the device is partially exposed and the quality of the device is lowered. In addition, when a metal film including a TEG (test element group) is laminated on a predetermined division line, there is also a problem that plasma etching is blocked and division cannot be performed by plasma etching.

The present invention has been made in view of the above-mentioned facts, and its main technical problem is to provide a method for processing a wafer capable of performing plasma etching without degrading the quality of a device. Means to solve the problem

In order to solve the above-mentioned main technical problems, a method for processing a wafer may be provided according to the present invention. The method is to divide a wafer into individual devices. The wafer is a device having a passivation film in a positive area. A plurality of divided lines are formed on the front surface of the semiconductor substrate. The method for processing the wafer is composed of at least the following steps: The semiconductor substrate is exposed, and the cutter is positioned at the predetermined division line to remove the build-up layer. A passivation film or a metal film at a predetermined line to expose the semiconductor substrate along the predetermined division line; and a division step of using the passivation film covering the device as a shielding film and etching the semiconductor substrate that has been exposed at the predetermined division line by plasma. Divide.

The passivation film can be formed by any one of a SiO ₂ film, a Si ₃ N ₄ film, and a polyimide film. The semiconductor substrate is a silicon substrate, and a gas used in plasma etching can be set. The above-mentioned wafer processing method is performed using a fluorine-based gas. Invention effect

The processing method of the wafer of the present invention is to divide the wafer into individual devices. The wafer is a device in which a passivation film is layered on a positive area to divide a predetermined line to form a plurality of lines on the front surface of a semiconductor substrate. The method for processing a circle is composed of at least the following steps: a semiconductor substrate exposing step, positioning the cutter at a predetermined division line to remove a passivation film or a metal film laminated on the predetermined division line, and exposing the semiconductor substrate along the predetermined division line; And the dividing step, the passivation film covering the device is used as a shielding film, and the semiconductor substrate that has been exposed at the predetermined division line is divided by plasma etching, whereby the division can be scheduled as a barrier when performing plasma etching. The passivation film on the line or the metal film composed of TEG is removed in advance, and the passivation film laminated on the front surface of the device is used as a masking film during plasma etching, so it is not necessary to form a uniform coating. A difficult resist film (1 to 5 μm) can also suppress a reduction in quality when plasma etching is performed using the resist film as a shielding film.

Embodiments for Carrying Out the Invention Hereinafter, preferred embodiments of the wafer processing method of the present invention will be described in detail with reference to the attached drawings.

As shown in FIG. 1, the wafer 10 to be processed in this embodiment is formed by a semiconductor substrate (silicon substrate) 10a and a device 14, which is formed on the front side of the semiconductor substrate 10a. In the area defined by the plurality of predetermined division lines 12, as shown in a partially enlarged sectional view in FIG. 1 (a), a passivation film 16 (for example, , A silicon dioxide film (SiO ₂ )), and the passivation film 16 has a function of protecting the device 14 from external pollution and entry of impurities. It is known that the passivation film 16 is laminated by a plasma CVD method, and the details are omitted here. The wafer processed by the method for processing a wafer according to the present invention is not necessarily limited to the wafer shown in FIG. 1 (a). A passivation film is formed, and a wafer including a TEG (test element group) metal film 18 is formed as an object (see FIG. 1 (b)).

After the wafer 10 to be processed is prepared, a semiconductor substrate exposing step is performed by using a dicing device 20 (only a part of which is shown) shown in FIG. 2 to expose the semiconductor substrate 10 a along a predetermined division line 12. The cutting device 20 is provided with a cutting blade 22 that can be rotated at a high speed by a rotating spindle (not shown). The worker places the prepared wafer 10 with the front surface covered with the passivation film 16 on the holding mechanism 24 of the dicing apparatus 20, and operates a suction mechanism (not shown) to perform suction holding.

After aligning the position of the cutting blade 22 of the cutting device 20 with the planned division line 12 of the wafer 10, the cutter 22 is positioned at one end of the planned division line 12, and the rotary spindle is driven. The cutting blade 22 is rotated and the holding mechanism 24 is relatively moved in the direction indicated by the arrow X to perform cutting along the planned division line 12. As a result, as shown in FIG. 2 as a partially enlarged sectional view, a cutting process is performed along a predetermined division line 12 of the wafer 10 to form a thickness corresponding to at least the passivation film 16 (or the metal film 18) (in this embodiment) 5 μm), and the semiconductor substrate 10 a of the wafer 10 is exposed to a depth. After the cutter 22 reaches the other end of the planned division line 12, the holding device 24 is appropriately moved and rotated to adjust the cutting position to the position of the unprocessed planned division line 12, and to all the planned division lines 12 The same cutting process is performed to expose the semiconductor substrate 10a. Thereby, the passivation film 16 is removed along the planned division line 12, or when the metal film 18 including TEG is formed, the metal film 18 is removed, and the semiconductor substrate 10a is exposed along all the planned division lines 12. .

After the semiconductor substrate exposure step is performed as described above, a dicing step is performed, which is a plasma etching for dicing the wafer 10 into individual devices. For the plasma etching, a plasma etching apparatus 40 shown in FIG. 3 can be used, for example. This plasma etching apparatus 40 includes a gas supply unit 41 that supplies a fluorine-based gas, and includes a chamber 42 that performs an etching process inside. As the fluorine-based gas, for example, SF ₆ and C ₄ F ₈ can be supplied from the gas supply unit 41 into the chamber 42.

As shown in the figure, an etching gas supply mechanism 43 connected to the gas supply unit 41 is disposed on the upper side of the chamber 42 where plasma etching is performed, and a workpiece to be etched is disposed on the lower side. Work table 44 of the wafer 10.

The etching gas supply mechanism 43 is provided with a gas flow path 43a inside, and has a lower surface 43b formed by a porous member to supply to the exposed surface side (side where the device 14 is formed) of the wafer 10 held on the stage 44. Function of etching gas. It should be noted that the etching gas supply mechanism 43 is configured to be driven upward and downward in the chamber 42 by a movement mechanism (not shown).

On the other hand, the work clamp table 44 rotatably supports its shaft portion by the chamber 42 and connects a suction source (not shown) to the upper surface 44b configured to have air permeability through the suction path 44a. The bottom of the chamber 42 is provided with an exhaust port 45 connected to a gas exhaust portion (not shown), and the exhaust port 45 functions to reduce the pressure in the chamber or exhaust used gas. Further, a high-frequency power source 46 is connected to the etching gas supply mechanism 43 and the work table 44 so that a high-frequency voltage can be supplied and the etching gas in the chamber 42 is plasmatized. The plasma etching apparatus 40 in this embodiment is configured as described above. The following describes the division steps performed by the plasma etching apparatus 40.

First, the wafer 10 on which the semiconductor substrate exposure step has been performed is held on the frame F by a protective tape T having adhesiveness and flexibility. The wafer 10 is transferred into the chamber 42 from a loading / unloading port of a chamber 42 (not shown). The wafer 10 that has been carried into the chamber 42 is placed on the work clamp table 44 with the front side of the passivation film 16 that functions as a shielding film during the etching process being formed facing upward, and is suction-fixed. After the wafer 10 is placed on the work table 44 and the chamber 42 is set as a closed space, the internal air is exhausted to reduce the pressure.

After the pressure in the chamber 42 has been reduced, the etching gas supply mechanism 43 is lowered by a moving mechanism (not shown) to adjust the distance from the wafer 10, and the etching gas is passed through the etching gas supply mechanism 43 from the gas supply unit 41 to cause the etching gas (SF ₆ ) is ejected into the chamber 42, and the high-frequency power source 46 is operated to apply a high-frequency voltage between the etching gas supply mechanism 43 and the work table 44 so that the etching gas that has been supplied into the chamber 42 (SF ₆ ) Plasmaization. Then, the bottom of the exposed region 10b of the semiconductor substrate from which the passivation film 16 (or the metal film 18) has been removed from the front surface of the wafer 10 is etched for a predetermined time by the plasma etching effect. After cutting the bottom of the semiconductor exposed region 10b by a predetermined amount in this way, the etching gas supplied from the gas supply unit 41 is switched to C ₄ F ₈ as another etching gas, and the high-frequency power supply is operated to cause the newly supplied The etching gas is plasmatized. Thereby, the low wall of the exposed region 10b of the semiconductor substrate can be removed, and a protective film laminated by plasma polymerization can be sequentially formed on the side wall. After that, the same was performed, and the SF ₆ and C ₄ F ₈ were repeatedly supplied while being etched. By performing the etching for 10 to 15 minutes in this way, anisotropic etching can be performed as shown in a schematic cross-sectional view in FIG. 3 (b), and a good divided trench 10c extending vertically downward can be formed. Then, by etching only the thickness corresponding to the semiconductor substrate 10a, the wafer 10 can be divided into individual devices 14 to complete the dividing step. In addition, this plasma etching method is generally known as a Bosch process. The etching apparatus shown in the figure is a schematic diagram, and other configurations have been omitted.

After dividing grooves are formed along all dividing lines 12 by this dividing step, the frame F holding the wafer 10 is transferred to a picking step (not shown). Then, by using an expansion mechanism (not shown) that expands the protective tape T in a radial direction, the protective tape can be expanded, and the devices 14 that have been divided into individual pieces can be easily picked up.

Although the wafer processing method according to the present invention can be implemented by the above-mentioned embodiment, the present invention is not limited to the invention. In this embodiment, although silicon is used as the material of the semiconductor substrate, it is not limited to this, and other semiconductor substrates such as gallium arsenide (GaAs) may be used.

In this embodiment, although a silicon dioxide (SiO ₂ ) film is used as the passivation film 16, the invention is not limited to this, and a polyimide film or a silicon nitride film (Si ₃ N ₄ ). In addition, in the plasma etching of the present embodiment, the dividing step is performed by an etching method known as a so-called Bosch method of supplying SF ₆ and C ₄ F ₈ alternately, but it is not limited to this. Other generally known plasma etching methods can also be used. When performing plasma etching, it is desirable to select an etching condition that will be anisotropic etching. The thickness of the semiconductor substrate 10a (for example, 200 to 300 μm) and the member that functions as a masking film as the passivation film 16 may be considered. Ratio of etching rate of selected film material (for example, Si: SiO ₂ film = 700: 1, Si: polyimide film, Si: silicon nitride film (Si ₃ N ₄ ) = 100: 1 Etc.), the thickness of the passivation film (for example, 1 to 5 μm) that functions as a shielding film before the semiconductor substrate 10 a is divided is selected, and the etching conditions are appropriately adjusted. In addition, since plasma etching is a well-known technique, more detailed description is omitted here.

10‧‧‧ wafer
10a‧‧‧ semiconductor substrate
10b‧‧‧Semiconductor substrate area
10c‧‧‧ divided trench
12‧‧‧ divided scheduled line
14‧‧‧device
16‧‧‧ passivation film
18‧‧‧ metal film
20‧‧‧ cutting device
22‧‧‧Cutter
24‧‧‧ holding agency
40‧‧‧ Plasma Etching Device
41‧‧‧Gas Supply Department
42‧‧‧ chamber
43‧‧‧Etching gas supply mechanism
43a‧‧‧Gas circulation path
43b‧‧‧ lower surface
44‧‧‧Working table
44a‧‧‧Attraction path
44b‧‧‧ Top surface
45‧‧‧ exhaust port
46‧‧‧High Frequency Power
F‧‧‧Frame
LB‧‧‧Laser Ray
T‧‧‧protective tape
X‧‧‧ direction

1 (a) and 1 (b) are explanatory diagrams illustrating a wafer to be processed in the wafer processing method of the present invention. FIG. 2 is an explanatory diagram for explaining a semiconductor substrate exposure step in the present invention. 3 (a) and 3 (b) are explanatory diagrams for explaining an outline of a plasma etching apparatus for performing a dividing step in the present invention.

10‧‧‧ wafer

10a‧‧‧ semiconductor substrate

10c‧‧‧ divided trench

14‧‧‧device

16‧‧‧ passivation film

40‧‧‧ Plasma Etching Device

41‧‧‧Gas Supply Department

42‧‧‧ chamber

43‧‧‧Etching gas supply mechanism

43a‧‧‧Gas circulation path

43b‧‧‧ lower surface

44‧‧‧Working table

44a‧‧‧Attraction path

44b‧‧‧ Top surface

45‧‧‧ exhaust port

46‧‧‧High Frequency Power

F‧‧‧Frame

T‧‧‧protective tape

Claims (2)

A wafer processing method is to divide a wafer into individual devices. The wafer is a device in which a passivation film is layered on a positive area to divide a predetermined line to form a plurality of lines on a front surface of a semiconductor substrate. The processing method is composed of at least the following steps: a semiconductor substrate exposing step, positioning the cutter at a predetermined division line to remove a passivation film or a metal film laminated on the predetermined division line, and exposing the semiconductor substrate along the predetermined division line; And a slicing step, the passivation film covering the device is used as a shielding film, and the semiconductor substrate that has been exposed at a scheduled line is singulated by plasma etching. For example, the method for processing a wafer according to claim 1, wherein the passivation film is any one of a SiO ₂ film, a Si ₃ N ₄ film, and a polyimide film; the semiconductor substrate is a silicon substrate; and a gas used in plasma etching. It is a fluorine-based gas.