JPH03153026A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To make etching rate fast and to reduce damage by a method wherein a high frequency is applied to an electrode of a dry etching apparatus on which a wafer has been placed, and an application of the high frequency is changed over to an electrode faced with the wafer when the residure of a layer to be etched reaches 25% or lower. CONSTITUTION:A wafer is placed on one of electrodes arranged in parallel; a high frequency is applied; a plasma is generated; an etching operation is executed by using a dry etching apparatus. A gas is introduced into an etching chamber; after that, a pressure is set to a set value; a high-frequency power supply (103) connected to an electrode (101) on which the wafer has been placed is turned on. An etching operation is executed for, e.g. 50sec. After that, it is changed over to a high-frequency power supply (104) connected to an electrode (102) faced with the wafer; residual polycrystalline silicon is etched.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a method for manufacturing a semiconductor device, and in particular to a dry etching apparatus.

[Prior Art] A device that performs etching by applying high frequency waves to a gas introduced into a reaction chamber to generate plasma is generally called a plasma etching device. What is applied is a cathode type reactive ion etching device (hereinafter referred to as cathode type RIE).
An apparatus that applies a high frequency to an electrode facing the wafer is called an anode type plasma etching apparatus (hereinafter referred to as an anode type PE). In cathode type RIE (Figure 3), the self-bias potential is large and ions are easily accelerated, resulting in a high etching rate. Also, since the ions are incident perpendicularly, an anisotropic shape can be obtained, but the ion incidence energy is large, so damage may occur. The problem is that it's big.

For example, when polycrystalline silicon is etched under the conditions shown in Table 1, a perfectly anisotropic shape can be obtained at an etching rate of 3450 people/min. However, when the lifetime (minority carrier survival time: in the case of an N-type semiconductor, the time from when a hole is generated until it disappears) was measured, it decreased to 15 to 20% of the reference value.

Table 1 On the other hand, since the sheath potential of anode type PE is not as large as that of cathode type RIE, the gas ratio must be changed (increase the amount of gas that facilitates the formation of a sidewall protective film to prevent side etching from progressing).Anisotropic shape However, the damage can be reduced, but the etching speed will be reduced.

For example, when polycrystalline silicon was etched under the conditions shown in Table 2, the etching rate was 2230 people/min, and the lifetime was 70 to 85% of the reference value.

Table 2 [Problem to be solved by the invention 1 If cathode type RIE is used as in the prior art, the etching speed is fast and an anisotropic shape can be obtained, but the damage is large, and if anode type PE is used, the damage is small. However, the problem was that the etching speed was slow.

The present invention solves these problems and aims to provide an etching method that has a high etching speed and causes little damage.

[Means for Solving the Problems] The method for manufacturing a semiconductor device of the present invention is a dry etching apparatus in which a wafer is placed on one side of electrodes placed in parallel, and a high frequency is applied to generate plasma to perform etching.a) Etching is performed by applying high frequency to the electrode on which the wafer is placed.

b) Etching is performed by switching the application of high frequency to the electrode facing the wafer when the remaining amount of the layer to be etched becomes 25% or less.

[Function] By performing etching by switching the application of high frequency using the same device, the deposits that occur during the first etching and adhered to the side walls are altered by the influence of the outside air, and their original function as a side wall protective film is lost. (No problem occurs, and it can be used as a sidewall protective film in the second etching as well.

〔Example〕

The present invention will now be described in detail based on examples.

Figure 1 shows the etching apparatus used in this example, in which an electrode (101) on which a wafer is placed and an electrode (102) facing it are placed in parallel, and high frequency power sources (103, 104) are connected to each. It is designed so that it can be switched during etching.

Using this equipment, polycrystalline silicon deposited by 4,000 people was etched under the conditions shown in Tables 3 and 4. First, after introducing gas into the etching chamber and setting the pressure to the set value, the wafer was placed on the etching chamber. Electrode (lot)
Turn on the high frequency power source (103) connected to the wafer and perform etching for 50 seconds (approximately 3000 times) under the conditions shown in Table 3. After that, switch to the high frequency power source (104) connected to the electrode (102) facing the wafer and etching. The remaining polycrystalline silicon was etched to the end under condition 4.

Table 3 Table 4 When etching is performed as described above, the shape becomes vertical, and the damage is 65 to 8 when examined in terms of lifetime.
0%, good etching characteristics comparable to those of anode type PE were obtained.

Note that the etching conditions are not limited to those shown in Table 3.4 (they differ depending on the material to be etched and the etching equipment.In addition, two high-frequency power supplies are installed and can be switched over). However, the present invention is not limited to this, and may be switched by a switch as shown in FIG.

In this way, by switching the high-frequency application electrode in the same device, the deposition generated during the first etching is not altered by the influence of the outside air and loses its original function as a sidewall protective film, and the second etching is It can also be used as a sidewall protective film for etching.

[Effects of the Invention] By successively performing the first etching with a high etching speed and the second etching with a small damage according to the present invention, it is possible to perform etching with a small damage and a high etching speed. are doing.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an etching apparatus in this embodiment. FIG. 2 is a schematic diagram of the second etching apparatus in this embodiment. FIG. 3 is a schematic diagram of an etching apparatus in the prior art. 101.201.301 ... lower electrode 102
．． 202.302 ... Upper electrode 103.104
．． 203.303...High frequency power supply 105.205.
305 106.206.306 107.207.307 208 ・ ・ ・ ・ ・Gas inlet, gas inlet, wafer, switch or higher

Claims (1)

[Scope of Claims] A dry etching apparatus in which a wafer is placed on one side of electrodes placed in parallel and etching is performed by applying high frequency waves to generate plasma, which includes: a) applying high frequency waves to the electrode on which the wafer is placed to perform etching; Do this. b) A method for manufacturing a semiconductor device, characterized in that when the remaining amount of the layer to be etched becomes 25% or less, application of high frequency waves to an electrode facing the wafer is switched to perform etching.