JPS6230891A - Dry etching method - Google Patents

Abstract

PURPOSE:To execute efficient dry-etching with less damages and at a high selection ratio by etching a substrate with the high-density plasma in a mirror or cusp magnetic field then etching the substrate with the neutral radicals of the cusp magnetic field. CONSTITUTION:A reactive gas is introduced from an introducing pipe 1 into a plasma generating chamber 2 and microwaves 4 are introduced via a waveguide 3 into the chamber; at the same time, a magnetic field is impressed by coils 5, 9 connecting to DC power sources 10, 12 to form the plasma by which the substrate 8 disposed in a sample chamber 7 is dry-etched. Electric current in the same direction is first passed to the coils 5, 9 to form the mirror magnetic field (not shown) in the chamber 7 by which the plasma ions are increased in the concn. and the high-speed anisotropic etching is executed in the above-mentioned method. The current is thereafter changed over by a switch 11 to pass the current in the opposite direction, thereby forming the cusp magnetic field 34. The substrate 8 is disposed to the neutral plane 40 of the magnetic field 34 and the low-damage high-selection ratio etching is executed by utilizing the neutral radicals.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a dry etching method for etching a substrate with plasma ions. This invention relates to a dry etching method that utilizes radicals to achieve low damage and high selectivity etching.

[Background of the invention]

In semiconductor processes using plasma, reaction speed can be improved by concentrating the plasma density. An example of this is a deposited film manufacturing method disclosed in Japanese Patent Laid-Open No. 57-45224. This is as shown in FIG.
, 109 in the same direction, the plasma gas ions confined in the region B cause the substrate 1 to
06 to form a deposited film efficiently.

With the miniaturization of semiconductor LSI circuit patterns, etching methods such as those described above (sputter etching using plasma ions have become mainstream), but the ions incident on the substrate cause element damage and decrease in selectivity. Therefore, it is recommended that most of the etching process be performed by sputter etching using ions as mentioned above, and the rest be etched by neutral radicals, which is free from the influence of ions. However, this cannot be done with the above-mentioned conventional technology.

In other conventional techniques, using commercially available RF plasma,
Most of the etching process is performed by sputter etching using ions, and the rest is performed by chemical dry etching, which causes less damage. However, the method that uses high-density plasma using microwaves and performs the above two-step etching Not disclosed.

[Purpose of the invention]

The present invention was created in view of the above circumstances.
The above-mentioned step etching is performed mainly using microwaves using only high-density ions generated by plasma confinement and neutral radicals, resulting in low damage during etching.
It is an object of the present invention to provide a dry etching method that makes it possible to improve the selectivity.

[Summary of the invention]

In order to achieve the above object, the present invention creates a mirror magnetic field or a cusp magnetic field by exciting a pair of opposing coils in the same direction or in opposite directions in a plasma generation chamber, and first applies high-density plasma ions to the substrate. After performing sputter etching by arranging the mirror magnetic field or the internal pressure of the cusp a field in the presence of , the substrate was etched by neutral radicals at a position within the cusp field not affected by the plasma ions to complete dry etching. This method is characterized by a dry etching method.

[Embodiments of the invention]

Hereinafter, preferred embodiments for carrying out the method of the present invention will be described based on the drawings.

First, the outline of this embodiment will be explained with reference to FIG. 1 and FIG.
At the same time, it is introduced into the microwave plasma generation chamber 2. Coils 5 and 9 are arranged facing each other on the outer circumferential side of the microwave plasma generation chamber 2 . A DCt source 10 is connected to the coil 5, and a DCz source 12, which will be described later, is connected to the coil 9. A substrate 8 to be etched is disposed in a sample chamber Z in the microwave plasma generation chamber 2 at a position sandwiched between the coils 5 and 9.

Plasma is generated in the microwave plasma generation chamber 2 by the excitation of the coils 5 and 9, but when the coils 5 and 9 are excited in the same direction, a portion 50 with high Goto density is generated as shown in FIG. .51 and a region 52 with low magnetic flux density sandwiched therebetween (i.e., the mirror magnetic field 55 is formed).
The plasma ion concentration in this area increases because the plasma ions are confined in the ion. As shown in the figure, the substrate 8 is disposed in the area where the plasma ion concentration is high, so the substrate 8 is subjected to reactive sputter etching due to the high concentration of plasma ions.
When the coil 9 is excited in the opposite direction to the coil 5 after performing etching of about 80% or more under the conditions described above, a cusp magnetic field 54 is formed as shown in FIG. Cusp magnetic field 5
4, as will be described later, since plasma ions hardly cross the cusp neutral surface 40, as shown in the figure (this cusp neutral surface 40
By arranging the substrate 8 at a position below 0, etching is performed using only neutral radicals that are hardly affected by ions.

The following nine embodiments will be described in more detail.

As shown in Fig. 5<c)t<b), the charged particle inserted into the cusp magnetic field 54 reaches Zttbr slightly beyond the cusp neutral plane ao (Z == o), assuming that its traveling direction is Z.
It is well known that loci such as the f+ line in FIG. 5(α) and the spiral line in FIG. 5(b) are formed within a range not exceeding the position n. In other words, this fact is based on, for example, Schumann, Kluba, and plasma physics.

7, p. 245 (1965) (W, Schwurm
a214. tigKltbiver, Plazrna
Physics, 7.2 & 5.1965). As mentioned above, 7. Since plasma ions do not exist below t tLrn, etching should be performed in this area using only neutral radicals that are not affected by ions.

. In short, the DC power supply 12 connected to the coil 9 will be explained.

The DC source 12 is connected to a changeover switch 11. Rectifier 15. power tube 1
4. Slow down and slow up to suppress the coil electromotive force corresponding to -Ltt when the switching tr switch 11 is operated by the voltage control λ1 circuit 15 etc., and the coil 9 is made the same as the coil 5. direction or opposite direction π
Encourage @. Further, the voltage control circuit 15 outputs the voltage reference signal 17 set by the setting device 16 and the output '11 from the voltage divider 18.
It is formed so that it compares it with the signal 19 and outputs a single power ffi dynamic signal 20, and also sets the rise and fall times of the voltage arbitrarily by adjusting the capacitance of the capacitor 21.

In the real t@ column, coil 9 has a diameter of 240 m? 7L, length 120m77L, and number of turns 1700, the inductance L will be approximately 6.6X10-'H,
When a current of 1 OA is passed through the coil 9, the rise and fall times of about 1 second can be set to make the back electromotive force at the rise and fall of the t current due to the inductance L to be 10 V or less.

Next, the etching method of this embodiment will be explained in more detail.

Inside the plasma generation chamber 2, D is generated by applying a high frequency voltage across the substrate as in normal reactive sputter etching.
Ions are made to enter the substrate 8 by C bias voltage, or
Alternatively, the substrate 8 is set at a potential of 70°, and ions are stimulated by an electric field corresponding to the plasma potential (about 20 V), and the ions are made incident on the substrate 8. As described above, the coil 519 is energized in the same direction until the etching time of 80 minutes has elapsed to perform reactive sputter etching, thereby performing high-speed, anisotropic patterning. Next, the current in the coil 9 is lowered, the polarity is reversed with the changeover switch 11, and the current is raised again to form the above-mentioned cusp magnetic field 54, which is generated only by the neutral radicals that diffuse without being affected by the magnetic field. Continue directional etching. For example, when etching D = 0.5 μm as shown in FIG. 4 (α) in 1 minute at 100 mm,
The time required for the above switching ((+, 2D position)) is approximately 4 minutes after the start of etching. Although the timing of this switching may be determined based on time as described above, it may also be determined based on plasma emission spectroscopy.

Isotropic etching using only neutral radicals is a chemical reaction, so the selectivity to the underlying layer is high (and no damage occurs due to ion injection).

After performing anisotropic etching as shown in FIG. 4(α), isotropic etching is performed as described above to obtain etching as shown in FIG. 4(b).

In this case, as shown in the figure (0.2D side etching and an R part are formed at the bottom. These values are extremely small, so there is no particular problem. However, when performing 0.2D side etching, the resist pattern is enlarged by this amount in advance. This can also be avoided by keeping it in place.

FIG. 5 shows another embodiment of the invention. In the figures, the same reference numerals as in FIG. 1 etc. indicate the same parts or parts with the same functions.

In this embodiment, unlike in FIG.
Excited in the opposite direction, the plasma generation chamber 2 always forms a cusp magnetic field 54.

The substrate 8 is supported by a shaft 5 slidably in the plasma generation chamber 2.
Connect to 5. Further, the shaft 55 is movable by an eccentric cam 44 rotated by a motor 45. Note that a motor drive circuit 42 and a timer 41 are respectively engaged with the motor 45.

With the above structure, the substrate 8 is first placed at a position above the cusp center surface 40 in the figure (indicated by the two-dot chain line) where it is affected by plasma ions, and the first step of pattern etching is performed. Next, the motor 45 is driven, and the shaft 55 is moved by the cam 44 to the illustrated position below the cusp neutral surface 40 (
Adjustments such as the timing of moving the board 8 (solid line) are performed by the motor drive circuit 42. This is done by the timer 41. At the position below the cusp neutral plane 40, the second step of etching by neutral radicals is carried out similarly to the above embodiment.

As described above, by performing the two-step etching, it is possible to reduce damage and improve the selectivity, thereby increasing throughput and yield.

Note that although microwaves are used as the plasma generation source in the above embodiments, the present invention is not limited to this, and RF or the like may also be used.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, high-speed, anisotropic etching and subsequent (low-damage, high-selectivity etching with neutral radicals) can reduce damage and improve selectivity, thereby improving product quality. This has the effect of improving yield and throughput.

[Brief explanation of drawings]

Fig. 1 is a front cross-sectional view showing the configuration of the present invention-Jetume example and the cusp magnetic field, Fig. 2 is a front cross-sectional view showing the configuration of the embodiment and the mirror magnetic field, and Fig. 5 (α) is a charged particle in the cusp magnetic field. 5(b) is a front view showing the moving state of charged particles in the cusp magnetic field, and FIG. 4(cL) is an example of pattern etching. FIG. 4(h) is a cross-sectional view showing an example of etching by neutral radicals, FIG. 5 is a front sectional view showing the structure and operation of another practical example of the present invention, and FIG. The figure is a front sectional view showing an example of the prior art. 1... Introduction 'R12... Microwave plasma generation chamber, 5... Waveguide, 4... Microwave, 5.9...
Coil, 730. Sample chamber, 8... Substrate, 10, 12...
...DCC temperature source 11...changeover switch, 15...rectifier, 14...1 power tube, 15...'1 pressure control circuit,
16... Setting device, 17... Voltage reference signal, 181.
2 Voltage divider, 19... Output power signal, 20... Power tube drive (No.・
...Cusp neutral surface, 41...Timer, 42...Motor drive circuit, 45...Motor, 44...Cam. 7・'7 5,-.

Claims (1)

[Claims] 1. In a dry etching method in which a substrate placed in a plasma generation chamber is etched by plasma, high density mirror magnetic fields or cusp magnetic fields are generated in the plasma generation chamber by exciting opposing coils in the same or opposite directions. A dry etching method characterized in that after etching the substrate with plasma ions, the substrate is etched with neutral radicals of the cusp magnetic field that are hardly affected by the plasma ions to complete the dry etching.