JPH04251922A - Magnetron reactive ion etching apparatus - Google Patents

Abstract

PURPOSE:To generate magnetron motion of electron by applying a vertical magnetic field to an opposed plane of parallel flat electrodes for conducting the etching using high density plasma generated between the electrodes and to realize excellent high speed reactive ion etching (RIE) with excellent size control by generating plasma more stably under the etching gas pressure lower than that of the conventional apparatus. CONSTITUTION:The title magnetic reactive ion etching apparatus comprises a evacuatable reaction vessel 1 providing therein a pair of parallel plate type electrodes 2, 3 where a substrate 6 to be processed is placed on the one opposed electrode, a ring type electromagnet 7 provided to surround the reaction vessel 1 and a plurality of permanent magnets 10 arranged between the reaction vessel 1 and electromagnet 7 so that the neighboring magnets are inversely polarized with each other.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a dry etching apparatus having parallel plate type electrodes, and in particular applies a perpendicular magnetic field to opposing surfaces of the electrodes to cause electron magnetron movement. The present invention relates to a magnetron reactive ion etching (RIE) device that performs etching using high-density plasma generated between electrodes.

0002

2. Description of the Related Art Dry etching such as reactive ion etching has become mainstream for forming etching patterns with excellent vertical shapes necessary for increasing the density of semiconductor devices. In order to improve the vertical shape of the etching pattern,
It is effective to lower the pressure of the etching gas, thereby increasing the mean free path of the gas ions and strengthening the anisotropy. However, when the gas pressure decreases, the stability of the plasma decreases. In contrast, stable plasma can be generated even at low gas pressures by applying a magnetic field to the space where plasma is generated and causing magnetron movement of electrons.

0003

[Problem to be Solved by the Invention] Conventional magnetron-type RIE equipment employs a configuration in which a large number of magnets are placed on the back side of the substrate to be processed, and a number of magnets are used to improve the uniformity of etching on the substrate. The arrangement of the magnets requires some ingenuity, and a complicated mechanism is required to rotate or translate the magnets back and forth parallel to the substrate surface. These problems become more common as the substrates to be processed become larger.
Increase the difficulty.

[0004] Furthermore, in the conventional magnetron RIE apparatus as described above, the etching gas is
Although it is possible to lower the pressure to a Torr table, the etching rate decreases as the pressure is lowered, and the vertical formability is not necessarily sufficient. The present invention
Magnetron R under even lower gas pressure than before
The purpose is to enable IE and thereby improve vertical formability.

[0005]

[Means for Solving the Problems] The above object is to provide a reaction tank that can be evacuated and that is equipped with a pair of parallel plate electrodes on which a substrate to be processed is placed on one opposing surface. A ring-shaped electromagnet is provided so as to surround the reactor, and a plurality of permanent magnets are arranged between the reaction tank and the electromagnet so that adjacent ones have opposite polarities. This is achieved by the magnetron RIE device according to the present invention.

[0006]

[Operation] A ring-shaped electromagnet and multiple permanent magnets are placed around the reaction tank in a magnetron RIE device. This increases the magnetic field strength between the parallel plate electrodes, making it possible to generate high-density plasma even under lower gas pressure than conventional devices. As a result, vertical etching patterns can be formed at high speed.

[0007] Placing a multipolar magnetic field around the reaction vessel of a magnetron type etching apparatus is disclosed in Japanese Patent Application Laid-open No. 1983
Although this is disclosed in Japanese Patent No. 21833, it is not described that a multipolar magnetic field and an electromagnet are provided together as in the present invention. The above publication describes problems with conventional magnetron-type etching equipment, namely, the anisotropy of the vertical etching pattern within the surface of the substrate to be processed, and the ionization of the substrate caused by the arrangement of the magnets to avoid this. The purpose is to reduce damage. Therefore, an etching gas of about 10-3 Torr is used, and the magnetic field strength at the cathode surface, that is, near the substrate to be etched, is about 180 Gauss even when the multipole magnetic field is provided.

In contrast, the present invention enables magnetron RIE under an etching gas pressure of 10-4 Torr, as shown in the embodiments described later.
This makes it possible to form etching patterns with excellent vertical shapes at a practical speed. This is due to the fact that a multipolar magnetic field consisting of multiple permanent magnets and an electromagnet are installed together, making it possible to increase the magnetic field strength between the electrodes compared to conventional methods.

[0009]

[Embodiment] FIG. 1 is an explanatory diagram of an embodiment of the magnetron RIE apparatus of the present invention, and FIG. 2 is a sectional view taken along the line X-X in FIG. 2 and 3 are provided. The electrode 2 is grounded, and a substrate 6 to be processed, ie, a wafer, is placed on the electrode 3, which is connected to a high frequency power source 4 via a blocking capacitor 5. An annular electromagnet 7 is provided around the reaction tank 1 so as to surround it. As a result, there is a gap between parallel plate electrodes 2 and 3.
A magnetic field perpendicular to the electrode plane is applied. In the same figure, reference numeral 8 denotes a shielding plate made of quartz glass, for example, to prevent the plasma generated between the parallel plate electrodes 2 and 3 from coming into contact with the inner wall of the reaction chamber 1. The above is the same as the conventional magnetron RIE device.

In the present invention, the reaction tank 1 and the electromagnet 7
A plurality of permanent magnets 10 are arranged between. For example, as shown in FIG. 2, the permanent magnets 10 are arranged so that each magnetic pole faces parallel to the planes of the parallel plate electrodes 2 and 3, and adjacent ones have opposite polarities. ing.

[0011] Due to the multipolar magnetic field composed of the permanent magnet 10,
The strength of the magnetic field between the parallel plate electrodes 2 and 3 is higher than in the past, and uniform and high-density plasma is stably generated even under low gas pressures on the order of 10-4 Torr. therefore,
The mean free path of the ions becomes longer and the proportion of ions that are incident perpendicularly to the six surfaces of the substrate to be processed increases, making it easier to obtain a vertically shaped etching pattern. Moreover,
Since the magnetic field generated by the permanent magnet 10 forms a uniform plasma in the center, the surface of the substrate 6 to be processed is etched with good uniformity. These enable etching with excellent shape controllability.

Magnetron RIE of the present invention shown in FIG.
An example in which etching was performed using the apparatus will be described below. The magnetic field strength distribution in the direction perpendicular to the electrode plane between the parallel plate electrodes 2 and 3 with a mutual distance of 20 cm is as shown in FIG. The horizontal axis in FIG. 3 is the distance from the parallel plate electrode 2, which is the anode.

Example 1 Etching of lower layer resist in tri-level resist As shown in FIG. 4(a),
For example, a lower resist 13, an intermediate bath 14, and an upper resist 15 are sequentially applied onto a base 12 made of polysilicon. These materials and layer thicknesses are as follows.

[0014]
material
Layer thickness Upper layer resist 1
5 OFPR (manufactured by Tokyo Ohkasha)
1μm intermediate layer 14
OCD type 7 (manufactured by Tokyo Ohkasha) 0
．． 3μm lower resist 13
OFPR (manufactured by Tokyo Ohkasha) 2μm
After patterning the upper resist 15 as shown in Figure 4(b) using normal lithography technology, the CF
By the well-known reactive RIE using a mixed gas of 4 and CHF3 as an etchant, as shown in Fig. 4(c),
Etch the intermediate layer 14. After removing the upper resist layer 15, using the intermediate layer 14 as a mask,
The lower resist layer 13 was etched as shown in FIG. 4(d). The etching conditions at this time are as follows.

[0015]
Etching conditions Etching gas and pressure Oxygen (O2), 3 x 10-4
Torr High frequency bias frequency
13.56 MHz High frequency bias power 200 W As a result, a good vertical etching pattern with no undercut or taper shape was obtained. The etching rate at this time was 3000 Å/min. Incidentally, in a conventional device that does not have the permanent magnet 10, stable plasma is not generated at the above pressure, and etching is impossible.

FIG. 5 shows the results of investigating the amount of undercut when changing the etching gas pressure in the above case. This undercut amount is the value that occurs when overetching reaches 50%. As shown in the figure, it was observed that when the gas pressure exceeded 1 x 10-3 Torr, dimensional shifts occurred due to a rapid increase in undercuts. On the other hand, when the gas pressure is lowered to 1 x 10-4 Torr or less, the vertical shape is good, but the etching rate is about 1000 Å/min, which is not practical. This is because the exhaust capacity reaches its limit, making it impossible to supply a sufficient flow rate of etching gas.
Therefore, the concentration of active species contributing to etching is reduced.

Example 2 Etching of polysilicon As shown in FIG. 6(a), a 0.1 μm thick Si
After depositing a polysilicon layer 18 with a thickness of 0.4 μm on the O2 film 17, a resist layer 19 is formed. The sheet resistance of the polysilicon layer 18 is 20Ω square, and the resist layer 19 is made of OFPR (manufactured by Tokyo Ohka Co., Ltd.) with a thickness of 1 μm.
It was coated on. The resist layer 19 is patterned as shown in FIG. 6(b) using ordinary lithography technology, and the polysilicon layer 18 exposed from the resist layer 19 is patterned using the magnetron RIE apparatus shown in FIG. ) was etched as shown. The etching conditions at this time are as follows.

[0018]
Etching conditions Etching gas and pressure Chlorine (Cl2), 7×10
-4Torr high frequency bias frequency
13.56MHz High frequency bias power 200W
As a result, a good vertical etching pattern with no undercuts or tapers was obtained. The etching rate at this time was 3000 Å/min.
Met.

FIG. 7 shows the results of investigating the amount of undercut when changing the etching gas pressure in the above case. This undercut amount is the value that occurs when overetching reaches 50%. As shown in the figure, it was observed that when the gas pressure exceeded 5 x 10-3 Torr, undercuts rapidly increased and dimensional shifts occurred. On the other hand, when the gas pressure is lowered to 1 × 10-4 Torr or less, the vertical shape is good, but the etching rate is 1
000 Å/min, making it impossible to obtain a practical speed. This is because, as described above, it is no longer possible to supply a sufficient flow rate of etching gas, and the concentration of active species contributing to etching is therefore reduced.

Example 3 Aluminum Etching As shown in Figure 8(a), P with a thickness of 1.0 μm was etched.
1.0 μm thick on the SG (phosphosilicate glass) layer 20
After depositing an Al-Si (1%) layer, a resist layer 22 is formed. The resist layer 22 is formed by applying OFPR (manufactured by Tokyo Ohka Co., Ltd.) to a thickness of 1 μm. The resist layer 22 is patterned as shown in FIG. 8(b) using ordinary lithography technology, and the Al-Si 21 exposed from the resist layer 22 is patterned using the magnetron RIE apparatus shown in FIG. 1, as shown in FIG. 8(c). ) was etched as shown. The etching conditions at this time are as follows.

[0021]
Etching conditions Etching gas and pressure Cl2 +BCl3, 1
×10-3Torr High frequency bias frequency 13.56MHz
High frequency bias power 20
0 W As a result, the etching rate at this time was 6000 Å/min. In addition, conventionally, the etching selectivity ratio between the resist mask and the Al film was about 3 to 4;
For this reason, a dimensional shift was unavoidable.
As a result of the above, an etching selectivity of 5 or more was obtained, making it possible to perform etching with good dimensional control. That is, in the past, it was necessary to increase the substrate bias in order to obtain a vertical shape, which inevitably led to a decrease in the selectivity of the resist mask, but according to the present invention, the magnetic field at the 6 positions of the substrate By increasing the strength, high-density plasma is generated even at low pressure, making it difficult to obtain a vertical shape even if the substrate bias is low.

FIG. 9 shows the results of investigating the amount of undercut when changing the etching gas pressure in the above case. As shown in the figure, it was observed that when the gas pressure exceeded 5 x 10-3 Torr, undercuts increased rapidly and dimensional shifts occurred. On the other hand, the gas pressure is set to 1×10-4To
When lowered to below rr, the vertical shape is good, but
The etching rate is about 2000 Å/min, which is not a practical rate. This is because, as described above, it is no longer possible to supply a sufficient flow rate of etching gas, and the concentration of active species contributing to etching is therefore reduced.

[0023]

[Effect of the invention] According to the present invention, the reaction tank 1 and the electromagnet 7
By arranging a plurality of permanent magnets 10 between
It is possible to stably generate high-density, uniform plasma under lower pressure than with conventional equipment, and as a result, it has the effect of making it possible to obtain vertical etching patterns with good dimensional control.

[Brief explanation of the drawing]

[Fig. 1] An explanatory diagram of an embodiment of the magnetron RIE device of the present invention

[Figure 2] Cross-sectional view of reaction tank 1 in Figure 1

[Figure 3]
Example of magnetic field strength distribution in the device shown in Figure 1

[Fig. 4] Explanatory diagram of the first embodiment of etching using the apparatus of the present invention

[Figure 5] Supplementary explanatory diagram for the etching in Figure 4

[Fig. 6] Explanatory diagram of a second embodiment of etching using the apparatus of the present invention

[Figure 7] Supplementary explanatory diagram for etching in Figure 6

[Fig. 8] Explanatory diagram of the third example of etching by the apparatus of the present invention

[Figure 9] Supplementary explanatory diagram for etching in Figure 8

[Explanation of symbols]

1 Reaction tank 2, 3 Parallel plate type electrode 6 Substrate to be processed 7 Electromagnet 10 Permanent magnet 12 Groundwork 13 Lower layer resist 14 Middle class 15 Upper layer resist 17 SiO2 film 18 Polysilicon layer 19, 22 Resist layer 20 PSG layer 21　Al-Si

Claims (2)

[Claims] Claims: 1. A reaction tank 1 which can be evacuated and which is provided with a pair of parallel plate electrodes 2 and 3 on which a substrate to be processed 6 is placed on one opposing surface, and which surrounds the reaction tank 1. A ring-shaped electromagnet 7 provided in this manner, and a plurality of permanent magnets 10 arranged between the reaction tank 1 and the electromagnet 7 such that adjacent ones have opposite polarity to each other. A magnetron reactive ion etching device characterized by: [Claim 2] The electromagnet 7 is connected to the parallel plate electrodes 2 and 3.
and the permanent magnet 10 applies a magnetic field parallel to the opposing surfaces of the parallel plate electrodes 2 and 3 and point symmetrical with respect to the center of the parallel plate electrodes 2 and 3. 2. The magnetron reactive ion etching apparatus according to claim 1, further comprising a magnetron reactive ion etching apparatus.