JP2000012524A - Dry etching - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dry etching method which can realize a high selectivity and a residue minimization simultaneously. SOLUTION: In the dry etching method, a high frequency voltage is modulated in an amplitude modulation(AM) manner and then applied as a bias voltage in a plasma etching apparatus. It is desirable in the AM modulation that the amplitude have a minimum of 50 V or more and a maximum of 100 V or more, the high frequency voltage to be modulated be a sinusoidal or pulsed voltage of 2 MHz or more, and one cycle period of the modulation be 10 ms or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a plasma processing method, and more particularly to a method for applying a bias voltage to an object to be processed.

[0002]

2. Description of the Related Art FIG. 2 shows the configuration of the most typical RF bias means among the bias applying means of a conventional plasma processing apparatus. The workpiece 1 is connected to a high frequency power supply 4 via a ceramic 2 for electrostatic adsorption and a high frequency matching circuit 3. A sine-wave high frequency voltage is applied from the high frequency power supply 4. At this time, since electrons supplied from the plasma 5 are several hundred times larger than ions, negative charges are accumulated on the sample side of the ceramic 2 for electrostatic chuck.

Due to this negative charge, a negatively shifted voltage appears on the workpiece as shown in FIG. The negative voltage accelerates positive ions as etching species and vertically enters the object to be processed, thereby enabling vertical processing. As the high frequency voltage, a frequency of 400 KHz, 800
KHz, 2 MHz and 13.56 MHz are mainly used. In addition, at the experimental level, "1995 Dry Process Symposium Proceedings p33-37"
There is also a method in which the RF bias is modulated on / off as shown in FIG.

As another idea, a method of applying a voltage having a pulse waveform as a bias has been devised in Japanese Patent No. 1095402 and Japanese Patent Application Laid-Open No. 6-61182. But,
There has not been a method of AM modulating a high frequency bias.

[0005]

When a sample having a mask 8 formed on a material to be etched 7 formed on a base material 6 like a sample structure shown in FIG. It has been difficult to achieve both selectivity of the material to be etched with respect to the mask material and reduction of the etching residue (residue) of the material to be etched. When a high-frequency bias voltage of 2 MHz or more is applied or when a pulse-like bias voltage is applied, high selectivity can be obtained, but there is a problem that residues tend to occur. Meanwhile, 2
When a low-frequency bias of less than MHz is applied or when the bias is modulated on / off, a residue hardly occurs, but there is a problem that selectivity to a mask material is low.

The present invention solves this trade-off and provides a highly selective and low residue etching method.

[0007]

According to the method of the present invention, in a plasma etching apparatus, a high-frequency voltage which is AM-modulated as shown in FIG. 1 is applied as a bias voltage. A
The M modulation has a minimum amplitude of 50 V or more and a maximum amplitude of 100 V.
V or more. Also, as the modulated high-frequency voltage,
It is desirable to use a sine wave voltage or a pulse voltage of 2 MHz or more. Further, it is desirable that the cycle of one cycle of modulation is 10 ms or less.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) FIG.
It is an example of an apparatus in which the bias of the present invention is applied to an ECR etching apparatus. In this device, a 450 MHz UHF wave generated by a UHF power supply 9 is transmitted through a coaxial line 10, a matching device 11,
The antenna is introduced into the processing chamber 13 through the antenna 12, and has a structure capable of generating high-density plasma by the introduced UHF wave and electron cyclotron resonance generated by the coil 14. The bias voltage was generated by AM-modulating a sinusoidal signal generated by the oscillator 15 using a signal generated by the signal generator 16 and amplifying the signal by an amplifier. The bias voltage is applied to the sample 1 to be etched via the high-frequency matching device 3 and the ceramic 2 for electrostatic attraction.

As a sample to be etched, titanium or titanium nitride (Ti) as a material to be etched is formed on a CVD oxide film as a base material deposited on a gate wiring on a Si wafer.
N), titanium, aluminum / copper / silicon mixed crystal (Al
-Cu-Si), titanium nitride (TiN), and a resist mask formed thereon.

Using Cl ₂ gas plasma, 0.4 Pa,
Etching was performed under the condition of a UHF power of 800 W while applying the modulation bias of the present invention. Here, the bias is
As shown in FIG. 1, the frequency of the modulated high frequency is 13.56.
MHz, amplitude is 100 V and 200 V, one cycle of modulation is 1 ms, duty at 200 V (Duty)
A high frequency voltage having a ratio of 10% was used. FIG. 6 shows an electron micrograph of the surface of the sample after etching.

For comparison, a conventional high frequency bias (amplitude 1)
FIG. 7 shows a simulated electron micrograph of the sample surface after etching in the case of applying a voltage of 00 V and a frequency of 13.56 MHz. With the bias of the conventional method, an island-like residue is observed on the surface of the sample after etching, whereas with the bias of the present invention, both the size and the number of the residue are reduced. This effect is remarkable when etching a material containing copper.

In the case of the bias of the present invention, the etching rate of the photoresist of the mask material and the Al of the material to be etched.
FIG. 8 shows the relationship between the etching rates of —Cu—Si. It has been found that the bias of the present invention maintains high selectivity equal to or higher than the conventional 13.56 MHz bias. In addition, it was found that this bias maintains high selectivity similarly for the underlying CVD oxide film.

FIG. 9 shows the relationship between the cycle of one cycle of modulation and the etching rate of Al-Cu-Si as a material to be etched. High A in a region where the cycle of one cycle is 10 ms or less
It can be seen that an etching rate of 1-Cu-Si can be obtained. In the present embodiment, the amplitude of the bias voltage is 100 V
And 200 V, the same effect can be obtained by setting the voltage at the small amplitude to 50 V or more and the voltage at the high amplitude to 100 V or more. In this embodiment, a sinusoidal voltage having a frequency of 13.56 MHz is used as the modulated high-frequency voltage. However, a similar effect can be obtained by using a sinusoidal voltage or a pulsed voltage of 2 MHz or more.

In this embodiment, the material to be etched is Al-Cu
-Si, mask material is photoresist, base material is CVD
Although the case of the oxide film has been described, similar effects can be obtained with other materials to be etched, other mask materials, and other base materials.

[0015]

According to the present invention, high selectivity and low residual etching can be achieved at the same time. In particular, by setting the frequency of the modulated high-frequency voltage to 2 MHz or more, the selection ratio 4
The above high selectivity is maintained. In addition, high-speed workability is achieved by setting the cycle of one modulation cycle to 10 ms or less.

[Brief description of the drawings]

FIG. 1 is a waveform diagram of a bias voltage applied to a sample in one embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a conventional plasma etching apparatus using an RF bias.

FIG. 3 is a wafer bias waveform diagram of a conventional RF bias.

FIG. 4 is a cross-sectional view showing a sample structure to be processed.

FIG. 5 is a longitudinal sectional view showing an example of an S-ECR apparatus for performing the method of the present invention.

FIG. 6 is a simulated view of an electron micrograph of a sample surface etched according to the present invention.

FIG. 7 is a simulated view of an electron micrograph of a sample surface etched by applying a conventional high-frequency bias.

FIG. 8 is a measurement diagram of a relationship between an etching rate of Al—Cu—Si and a resist etching rate.

FIG. 9 is a measurement diagram showing the relationship between the cycle of one cycle of modulation and the etching rate of Al—Cu—Si.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Workpiece, 2 ... Electrostatic chuck, 3 ... High frequency matching circuit, 4 ... High frequency power supply, 5 ... Plasma, 6 ... Base material, 7
... material to be etched, 8 ... mask, 9 ... UHF power supply, 1
0: Coaxial line, 11: Matching device for UHF, 12: Antenna, 13: Processing room, 14: Coil, 15: Oscillator, 16
... signal generator.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Shinichi Taji 1-280 Higashi Koikekubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. 4K057 DA13 DA20 DB04 DB05 DB11 DB15 DD01 DM18 DM19 DM20 DN01 5F004 AA02 BA16 BB11 CA03 CA06 DA04 DB09 DB12

Claims (6)

[Claims] In a plasma etching method for supplying plasma to an object placed in a reduced-pressure processing chamber and applying a bias voltage to the object, a voltage obtained by amplitude-modulating a high-frequency voltage is used as the bias voltage. A dry etching method characterized by the above-mentioned. 2. A dry etching method according to claim 1, wherein the amplitude-modulated voltage has a minimum amplitude of 50 V or more and a maximum amplitude of 100 V or more. 3. The dry etching method according to claim 1, wherein the high frequency bias voltage to be modulated is a sinusoidal bias voltage having a frequency of 2 MHz or more or a pulsed voltage. 4. A dry etching method according to claim 1, wherein a cycle of one cycle of the amplitude modulation is 10 ms or less. 5. An object according to claim 1, wherein the object to be treated is a base material,
A dry etching method having a laminated structure of a material to be etched and a mask material made of more than two kinds of materials, wherein the material to be etched contains aluminum or copper. 6. A dry etching method, wherein the mask material according to claim 5 is a photoresist.