JP3355444B2 - Dry etching method for photomask - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method applied to a photomask manufacturing process used for manufacturing semiconductor devices and the like.

[0002]

2. Description of the Related Art Conventionally, in dry etching of an IC substrate, a rotating magnetic field is formed by an electromagnetic coil in an etching chamber, and the IC substrate covered with a pattern material is etched there. The IC substrate used for this is
On a Si wafer, a layer of poly-Si, oxide layer + poly-Si is formed as a pattern material (Kevin G. Donoho
e: "Si trench etching by Precision 5000 Etch", Semiconductor World 7 (8) pp. 97-103 (1988)).
In the case of a photomask, the substrate is a quartz substrate, and the pattern material is a Cr film, a Cr film with an antireflection film, or an SiO ₂ film such as SOG (sol-gel SiO ₂ by spin coating). An etching method using an etching apparatus has not been proposed. In general, it goes without saying that different pattern materials will result in different etching conditions, but the difference in the optimum etching conditions due to differences in etching requirements and performance goals will be significant. It has been impossible to estimate an etching method for a photomask using different pattern materials and a photomask substrate.

When etching is performed using a dry etching apparatus having a rotating magnetic field by an electromagnetic coil, the ionization and dissociation efficiency of plasma are increased even at a low pressure due to a magnetron discharge by the magnetic field, and the DC bias applied to the substrate is increased by increasing the magnetic field intensity. It is known that the DC bias can be reduced even with relatively high RF power, and that etching with a high etching rate and low damage can be performed. Further, by rotating the magnetic field, uniform etching can be expected over the entire substrate.

[0004]

Conventionally, a structure to be etched is a structure in which a pattern material such as a poly-Si layer, an oxide layer and a poly-Si layer is formed on a substrate of an Si wafer. Requirements and performance targets are, for example, in the case of silicon trench etching, opening width ≧ 0.5 μm,
Opening depth ≧ 10 μm, selectivity (Si to thermal oxide film) ≧ 20:
1. The uniformity within the wafer is ≦ ± 3%, CD loss (critical dimension loss) <0.1 μm, and the side wall angle is 85 to 90 ° in shape control. However, in the etching for the photomask, it is etched. Structure is Cr on quartz substrate
Film, Cr film with Cr oxide antireflection film, or SiO such as SOG
_Two films, for example, the pattern is a linear pattern with a line width of 2 to 4
μm, in-plane uniformity within 120 mm x 120 mm square, line width of 3
σ ≦ 0.06 μm, CD loss 0.08 μm, etching depth 0.1-0.4 μm, selectivity (Cr or SiO ₂ to resist) of 1.4-3 or more. The content of the etching is different from the example. Therefore, it is necessary to optimize the dry etching conditions unique to the photomask, and by analogy with the conventional etching conditions,
It is difficult to find the desired dry etching conditions.

An object of the present invention is to provide a photomask etching method capable of obtaining a highly accurate photomask using a dry etching apparatus having a rotating magnetic field by an electromagnetic coil.

[0006]

According to the first aspect of the present invention, a Cr film is formed on an RF electrode surface in an etching chamber of a dry etching apparatus having a rotating magnetic field by a reaction gas inlet, a vacuum exhaust port, and two pairs of electromagnets. Alternatively, a photomask substrate provided with a photoresist covered with a pattern material of a Cr film with an antireflection film and having a pattern formed thereon is attached, the magnetic field strength of the electromagnet is 57 to 110 Gauss, and the etching is performed. Indoors
The reaction gas is Cl2 + O2, and the gas composition ratio is O2 / (Cl2 + O2).
2) 10 to 25%, the gas pressure is 0.05 to 0.3 T
orr ( 6.7 to 40 Pa ), and the RF power density of the electrode is 0.2
The pattern material was etched by reactive ion etching under the condition of 0 to 0.32 W / cm2. Ma
According to the invention of claim 2, the reaction gas inlet and the vacuum
Dry with rotating magnetic field due to exhaust port and two pairs of electromagnets
SiO2 film on RF electrode surface in etching chamber of etching equipment
Covered with a pattern material and forming a pattern thereon
Attach a photomask substrate provided with a photoresist
The magnetic field strength of the electromagnet is 50 to 150 gauss;
The reaction gas in the combustion chamber is CHF3 + O2, and its gas composition ratio O2 /
(CHF3 + O2) 5-8%, gas pressure 0.03-
0.05 Torr (4-7 Pa), and the RF power density of
Under the condition of 20 to 0.32 W / cm2, reactive ion etching
The pattern material was etched by the etching.

[0007]

When dry etching of a photomask substrate is performed by using a dry etching apparatus having a rotating magnetic field, plasma controllability is good, the magnetic field strength on the photomask substrate surface is high, and thus plasma ionization and dissociation efficiency are high. Although generally expected from a dry etching apparatus having a rotating magnetic field that can keep the DC bias voltage applied to the photomask substrate low even at a low pressure, the magnetic field strength, the reaction gas pressure, the RF power density, and the like can be obtained. By setting the etching conditions of the reaction gas composition as described above, the selectivity of the etching material to the resist is improved, the processing accuracy of the pattern is improved, and the in-plane uniformity of the photomask is improved. A photomask can be obtained.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
In FIGS. 1 and 2, reference numeral 1 denotes a dry etching apparatus used for carrying out the present invention. An etching chamber 2, a transfer chamber 3, and a substrate cassette table 4 are accommodated in a panel 12 constituting the outer periphery of the dry etching apparatus 1, and the electromagnets 5, 6, 7, 8 provided with the etching chamber 2 on the outer periphery thereof are provided. It was installed inside. The electromagnet is a rectangular ring-shaped coil,
The electromagnets 5 and 6, 7 and 8 are paired with each other, and a low-frequency current whose phase is shifted by 90 °, for example, flows through these electromagnets. The coils of each pair of electromagnets are wound in the same direction, and the combined magnetic field generated by the electromagnets 5 and 6 and the electromagnets 7 and 8 is parallel to the substrate as indicated by the dotted arrows in FIGS. It is configured to rotate at the same frequency as the frequency of the low-frequency current in the plane. In the etching chamber 2, a flat RF power source connected to an RF power source 9 via a capacitor 13 is provided.
An electrode 10 and a plate-shaped counter electrode 14 were provided, and the photomask substrate 11 was placed on the RF electrode 10 through a substrate delivery port 15 formed on the side of the etching chamber 2.

The photomask substrate 11 is formed as shown in FIG.
As shown in one example, Cr,
A photoresist 1 in which a pattern material 11b such as Cr and SiO ₂ with an antireflection film is thinly applied and a pattern is formed thereon
1c is a general one provided. AZ-1350 (commercially available) similar to the IC substrate is used for the photoresist 11c. The counter electrode 14 and the etching chamber 2 are kept at the ground potential. In order to supply an etching reaction gas such as Cl ₂ + O ₂ into the etching chamber 2, a gas supply system 16 having a gas cylinder and a mass flow controller is provided at the reaction gas inlet 30. Exhaust system 1 equipped with a vacuum pump to control gas pressure
7 was connected to a vacuum exhaust port 18 of the etching chamber 2. As the reaction gas, CHF ₃ + O ₂ is used in addition to the Cl ₂ + O ₂ .

A plurality of the photomask substrates 11 are placed in a cassette case 19, which is placed on a substrate cassette table 4, and is transferred from the cassette case 19 by a transfer robot 21 via a partition valve 20 during etching. It is brought into the chamber 3 and then the vacuum valve 22 and the substrate transfer port 15
Is placed on the RF electrode 10 in the etching chamber 2 via the. The transfer robot 21 is a known robot, and is a two-joint robot having a knot 26 and a knot 28 and a motor shaft 24.
It is configured such that the reciprocating rotational movement of the distal end portion of the transport arm 29 is performed by combining the rotational movements of the knot 26 and the knot 28. The movement of the first arm 25 and the second arm 27 is restricted in a horizontal plane. The movement of the tip of the transfer arm 29 between the cassette case 19 and the transfer chamber 3 via the partition valve 20 and the etching chamber 2 via the substrate transfer port 15
The movement of the tip of the transfer arm 29 between the RF electrode 10 in the inside and the transfer chamber 3 is caused by the linear reciprocation of the motor shaft 24 and the joint movement of the arms 25, 27, 29 of the robot at the joints 26 and 28. It is performed by The transfer of the substrate between the vacuum valve 22 on the front surface of the substrate transfer port 15 and the partition valve 20 on the cassette case 19 side is performed by a half-rotational movement of the transfer arm 29 of the transfer robot about the motor shaft 24 in the horizontal plane. . When the motor 23 provided outside the transfer chamber 3 is rotated, the transfer arm 29 having a flat plate shape places the photomask substrate 11 thereon, and the cassette case 19 and the RF electrode 1 are placed.
It reciprocates to transport between zero.

When etching the pattern material of the photomask substrate 11 on the RF electrode 10, the etching chamber 2
A process in which the inside is evacuated by an exhaust system 17, a reaction gas is introduced from a reaction gas inlet 30, two pairs of electromagnets 5, 6, 7 and 8 are excited, and RF power is applied to the RF electrode 10 to excite plasma. Go through. The two pairs of electromagnets 5 and 6 and 7 and 8 are supplied with the same low-frequency alternating current in the same direction, respectively.
And 6, and by shifting the phases of the currents flowing through 7 and 8 by 90 °, a rotating magnetic field is formed in a plane parallel to the photomask substrate 11. The plasma generated between the RF electrode 10 and the counter electrode 14 is generated by the rotating magnetic field.
Gathered on the surface of the substrate, the density thereof increased, and the introduced reactant gas was efficiently dissociated.
Reactive ion etching is performed in a state where only a bias voltage is generated. In this case, the photomask substrate 11
Unlike IC substrate, it is not silicon but synthetic quartz,
The pattern material applied to the substrate is poly S
i, Cr, S with anti-reflective coating instead of oxide layer + poly-Si
Since it is iO ₂ etc., even if the reaction gas is introduced and etched under the same conditions as the dry etching for the IC substrate, the selectivity of the etching material to the resist and the in-plane uniformity of the photomask are poor, but the magnetic field strength From 50 to 150 gauss, and the reaction gas pressure in the etching chamber 2 from 0.03 to
By setting the pressure to 0.3 Torr (4 to 40 Pa) and the RF power density of the electrode 10 to 0.20 to 0.32 W / cm ² , the selectivity and dimensional uniformity are improved, and high accuracy is achieved. Is obtained.

A specific embodiment of the present invention is as follows.

Example 1 A photomask substrate 11 having a thickness of 6.35 mm and a thickness of 152
A Cr layer having a thickness of about 750 Å is provided as a pattern material on the surface of a square synthetic quartz substrate of × 152 mm, or a Cr layer having a Cr oxide antireflection film having a thickness of about 300 Å is further provided thereon. Layer or two layers,
AZ-1350 photoresist was applied on the pattern material layer. A linear pattern having a line width of 2 to 4 μm was formed on the photoresist. Reactive ion etching of the photomask substrate 11 was performed by setting the etching conditions as shown in Table 1.

[0014]

[Table 1]

The photomask substrate 11 is mounted on the surface of the RF electrode 10 in the etching chamber 2 shown in FIGS. 1 and 2, and Cl ₂ + O ₂ is introduced as a reaction gas through a reaction gas inlet 30. When the composition ratio O ₂ / (Cl ₂ + O ₂ ) is 10
-25%, the reaction gas pressure is 0.05-0.3 Torr (6.
7 to 40 Pa), and the magnetic field strength (the amplitude of the rotating magnetic field) is 57 to 1
The reactive ion etching of the photomask substrate 11 was performed by changing the magnetic field rotation speed to 10 Hz, the power density of the RF electrode 10 to 0.2 to 0.32 W / cm ^2, and 10 gauss. In this case, the dependence of the etching rate and the selectivity of the pattern material and the photoresist on the magnetic field are shown in FIG. 4, the dependence on the reaction gas composition ratio is shown in FIG. 5, the dependence on the reaction gas pressure is shown in FIG. FIG. 7 shows the power density dependence. Also,
FIG. 8 shows the magnetic field dependence of the DC self-bias and the electron density of the plasma, FIG. 9 shows the dependence of the reaction gas composition ratio, FIG. 10 shows the dependence of the reaction gas pressure, and FIG. 10 shows the power density dependence of the RF electrode 10. 11 respectively. FIG. 12 shows the magnetic field strength dependency of the in-plane uniformity 3σ, and FIG. 13 shows the CD gain (a CD loss with a negative sign) and the pressure dependency of the in-plane uniformity 3σ.
FIG. 14 shows the RF power density dependency, and FIG. 15 shows the electrode spacing dependency.

In this case, the etching rates of the pattern material and the photoresist (AZ-1350) are 22 to 3 respectively.
At 5 mn / min and 6 to 27 nm / min, the selectivity between the pattern material and the photoresist becomes 1.3 to 1.8 or more by observing the cross-sectional shape of the etching (FIGS. 4 to 7). The in-plane uniformity 3σ (actual value of line width−three times the variance of the average line width) was 0.06 μm or less. Further, the CD loss (critical dimension loss = design dimension−actual measurement dimension) is smaller than 0.08 μm (FIGS. 13 to 14),
The bias voltage is 15 to 150 V, and the electron density is (2.8 to
8) At 10 ⁹ / cm ³ (FIGS. 8 to 10), the pattern shape was good.

FIG. 24 shows that the magnetic field strength is 100 Gauss, the magnetic field rotation speed is 1 Hz, the gas composition ratio O ₂ / (Cl ₂ + O ₂ ) is 20%,
At a reaction gas pressure of 0.10 Torr (13 Pa), an RF power density of 0.22 W / cm ² , a single Cr layer having a thickness of about 750 Å is provided on the surface of the quartz substrate 11 as a pattern material. An example of a cross-sectional shape by SEM (scanning electron microscope) photograph of a pattern formed on a substrate coated with a photoresist of AZ-1350 and subjected to reactive ion etching is shown. FIG. 25
The following shows an example of a cross-sectional shape of an SEM photograph of a pattern formed by applying a ZEP 810 electron beam resist in place of the above-mentioned photoresist and performing reactive ion etching under the same conditions as above.

On the other hand, the reaction gas is Cl ₂ + O ₂ and the pressure of the reaction gas is 0.05 to 0.3 Torr as in the above case.
(6.7 to 40 Pa), and the gas composition ratio O ₂ / (Cl ₂ + O ₂ ) is 10% or less or 2 even when the magnetic field rotation speed is 1 Hz.
5% or more, and the magnetic field strength is 57 Gauss or less or 11
0 gauss, when the RF power density 0.20 W / cm ² or less, or 0.32 W / cm ² or more, the selectivity of 0.8 to 2.
8. The in-plane uniformity is also 0.05 to 0.13, but one of them is worse than the above case, the CD loss is 1 μm or more,
The bias voltage is 40 to 300 V, and the electron density is (3 to 7.
7) At 10 ⁹ / cm ³ , any of these numerical values was worse than the above case, and the pattern shape was also poor.

In the first embodiment, the distance between the RF electrode 10 and the opposing electrode 14 was changed in the range of 40 to 80 mm. This spacing was found to be appropriate in the range of 40 to 60 mm (FIG. 15).

Embodiment 2 The material and shape of the photomask substrate 11 are the same as those in Embodiment 1.
Using the same material as that described above, a 150 Å thick SnO ₂ layer is provided as an etching stopper layer on the substrate surface, and SOG (sol-gel SiO ₂ by spin coating) having a thickness of 4000 is further formed on the surface thereof as a second pattern material.
Angstrom. Next, a pattern of Cr as the first pattern material was formed under the conditions of Example 1. A photoresist of AZ-1350 was applied on the second pattern material, and a linear pattern having a line width of 2 to 4 μm was previously formed thereon. Then, reactive ion etching was performed with the etching conditions set as shown in Table 2.

[0021]

[Table 2]

This photomask substrate 11 is attached to the surface of the RF electrode 10 in the etching chamber 2 shown in FIGS. 1 and 2 as in the case of the first embodiment, and CHF ₃ + O ₂ is supplied as a reaction gas through the reaction gas inlet 30. The gas composition ratio O ₂ / (CHF ₃ + O ₂ ) is 5 to 8% and the reaction gas pressure is 0.0
3 to 0.05 Torr (4 to 7 Pa), magnetic field strength (amplitude of rotating magnetic field) 50 to 150 gauss, magnetic field rotation speed 1 Hz, power density of RF electrode 10 changed to 0.2 to 0.30 W / cm ² Then, reactive ion etching of the photomask substrate 11 was performed. In this case, the etching rates of the pattern material and the photoresist (AZ-1350) are 23 to 4 respectively.
At 8 nm / min and 0.8 to 15 nm / min, the selectivity between the pattern material and the photoresist became 3 or more. The DC bias voltage is 70 to 220 V, and the electron density is (7 to 11) × 10 ⁹
/ Cm ³ , the pattern shape was good.

On the surface of the photomask substrate 11, a 150 .ANG. Thick film is used as an etching stopper.
A SnO ₂ layer is provided, on which a second pattern material 40
An SOG layer having a thickness of 60 Å is applied thereon, and a Cr layer having a thickness of 1000 Å is provided thereon as a first pattern material. A photoresist (resist A) of AZ-1350 is applied to form a line having a line width of 2 to 4 μm. A pattern was formed. Next, a photoresist (resist B) of AZ-1350 is applied on the pattern of Cr as the first pattern material under the conditions of Example 1 to form a linear pattern having a line width of 2 to 4 μm. Reactive etching was performed. The etching conditions were a magnetic field of 100 gauss and a reaction gas composition ratio of O.
₂ / (CHF ₃ + O ₂ ) = 7%, reaction gas pressure 0.10 Torr
(13 Pa) and an RF power density of 0.22 W / cm ² . FIG. 26 shows an example of a pattern shape based on this SEM photograph.

On the other hand, even when the reaction gas pressure of CHF ₃ + O ₂ is 0.03-0.05 Torr and the magnetic field rotation speed is 1 Hz, the gas composition ratio O ₂ / (Cl ₂ + O _{2) is the same as above.} )
5% or less or 8% or more, a magnetic field strength of 50 Gauss or less or 150 Gauss or more, and an RF power density of 0.2
When the 0 W / cm ² or less, or 0.30 W / cm ² or more, selectivity ratio becomes 0.6 to 3, both worse than for the, DC bias voltage 20～450V, electron density (5
11) × 10 ⁹ / cm ³ , these numerical values were generally worse than in the above case, and the pattern shape was also poor.

In each of these examples, when the magnetic field intensity was increased, the electron density monotonically increased and the DC bias voltage monotonously decreased. This indicates that the ionization and dissociation efficiency of the plasma are improved by the increase in the magnetic field strength (FIGS. 8 and 20). When the magnetic field intensity was increased, the etching rate of Cr in Example 1 showed one maximum value in the magnetic field intensity range of 0 to 150 Gauss (FIG. 4), and the etching rate of SOG in Example 2 decreased monotonically. (Fig. 1
6). This is a behavior that cannot be predicted at all from the tendency that the silicon etching rate described in the above-mentioned Kevin G. Donohoe monotonically increases as the magnetic field intensity increases. Further, in both Examples 1 and 2, the electron density and the reaction gas composition
The DC bias voltage does not change much (FIGS. 9 and 2).
1), the etching rate and selectivity of Cr and photoresist of Example 1 changed relatively slowly (FIG. 5), and the etching rate and selectivity of SOG and photoresist of Example 2 changed greatly, Is 3 or more, the range of the gas composition ratio is extremely narrow as 5 to 8% (FIG. 17).

In the above embodiment, C was used as the pattern material.
Although r and Cr with an oxide-based anti-reflection film of Cr are used, other known pattern materials with an anti-reflection film such as Cr with a nitride-based anti-reflection film of Cr may be used. Further, instead of the SOG pattern material used in the above embodiment, an SiO ₂ film formed by sputtering or vapor deposition may be used. AZ- for photoresist
It is possible to use a photoresist other than 1350 or an electron beam resist other than ZEP810. Further, in the above embodiment, an example in which a linear pattern is formed in a photoresist has been described, but the method of the present invention can be applied to a pattern other than a linear pattern, for example, in which a contact hole is formed.

[0027]

As described above, according to the present invention, a dry etching apparatus having a rotating magnetic field by an electromagnet is used for dry etching of a photomask substrate. Since the voltage is low and the damage to the photoresist is small,
Selectivity is improved, magnetic field strength is 50-150 gauss, reaction gas pressure is 0.03-0.3 Torr, RF power density is 0.2
By setting the thickness to 0 to 0.32 W / cm ² , there is an effect that a CD loss is small in the pattern material of the photomask and high-precision etching with good in-plane uniformity can be performed to obtain a high-precision photomask. .

[Brief description of the drawings]

FIG. 1 is a plan view in which a part of a dry etching apparatus used for carrying out the present invention is cut away.

FIG. 2 is a sectional view taken along line AA of FIG. 1;

FIG. 3 is a cross-sectional view of a photomask substrate.

FIG. 4 is a characteristic diagram showing a relationship between an etching rate and a selectivity and a magnetic field.

FIG. 5 is a characteristic diagram showing a relationship between an etching rate and a selection ratio and a reaction gas composition ratio.

FIG. 6 is a characteristic diagram showing a relationship between an etching rate and a selection ratio and a reaction gas pressure.

FIG. 7 is a characteristic diagram showing a relationship between an etching rate and a selection ratio and an RF power density.

FIG. 8 is a characteristic diagram showing a relationship between an electron density and a self-bias voltage.

FIG. 9 is a characteristic diagram showing a relationship between an electron density, a self-bias voltage, and a reaction gas composition ratio.

FIG. 10 is a characteristic diagram showing a relationship between an electron density, a self-bias voltage, and a reaction gas pressure.

FIG. 11 is a characteristic diagram showing a relationship between electron density, self-bias voltage, and RF power density.

FIG. 12 is a characteristic diagram showing a relationship between in-plane uniformity and magnetic field strength.

FIG. 13 is a characteristic diagram showing a relationship between in-plane uniformity and CD gain and pressure.

FIG. 14 is a characteristic diagram showing the relationship between in-plane uniformity and CD gain and RF power density.

FIG. 15 is a characteristic diagram showing the relationship between in-plane uniformity, CD gain, and electrode spacing.

FIG. 16 is a characteristic diagram showing a relationship between an etching rate, a selectivity, and a magnetic field.

FIG. 17 is a characteristic diagram showing a relationship between an etching rate, a selection ratio, and a reaction gas composition ratio.

FIG. 18 is a characteristic diagram showing a relationship between an etching rate, a selection ratio, and a reaction gas pressure.

FIG. 19 is a characteristic diagram showing a relationship between an etching rate, a selectivity, and RF power density.

FIG. 20 is a characteristic diagram showing a relationship between an electron density, a self-bias voltage, and a magnetic field.

FIG. 21 is a characteristic diagram showing a relationship between an electron density, a self-bias voltage, and a reaction gas composition ratio.

FIG. 22 is a characteristic diagram showing a relationship between an electron density, a self-bias voltage, and a reaction gas pressure.

FIG. 23 is a characteristic diagram showing a relationship between an electron density, a self-bias voltage, and an RF power density.

FIG. 24: SEM of a photomask substrate after etching
Cross section photo sketch

FIG. 25: SEM of a photomask substrate after etching
Cross section photo sketch

FIG. 26: SEM of a photomask substrate after etching
Cross section photo sketch

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Dry etching apparatus 2 Etching chamber 5, 6, 7, 8 Electromagnet 9
RF electrode 11 Photomask substrate 11b Pattern material 11c Photoresist 18 Vacuum exhaust port 30 Reaction gas inlet

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yaichiro Watanabe 4-Ichimitsu, Mizuhara, Itami-shi, Hyogo Mitsubishi Electric Machinery Co., Ltd. Within the SSI Research Laboratory (72) Inventor Akihiko Shig 2562 Terao, Chiba, Chichibu, Saitama -3 (72) Yasuo Inventor 6744-3 Yokoze, Yokoze-cho, Chichibu-gun, Saitama (72) Inventor Atsushi Hayashi 2129-7 Yokoze, Yokoze-cho, Chichibu-gun, Saitama No. 202, Palaisheim 202 (56) References 30424 (JP, A) JP-A-3-222415 (JP, A) JP-A-4-268727 (JP, A) JP-A-4-318926 (JP, A) JP-A-5-6875 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03F 1/00-1/16 H01L 21/302

Claims (3)

(57) [Claims] An RF electrode surface in an etching chamber of a dry etching apparatus having a rotating magnetic field generated by a reaction gas inlet and a vacuum exhaust port and two pairs of electromagnets is provided with a Cr film or a Cr having an antireflection film.
A photomask substrate provided with a photoresist covered with a pattern material of a film and having a pattern formed thereon is attached, the magnetic field strength of the electromagnet is 57 to 110 gauss, the reaction gas in the etching chamber is Cl2 + O2, and the gas composition is Ratio O
2 / (Cl2 + O2) 10-25%, and the gas pressure is 0.1% .
The pattern material is etched by reactive ion etching under the conditions of 0.5 to 0.3 Torr ( 6.7 to 40 Pa ) and an RF power density of the electrode of 0.20 to 0.32 W / cm2. Dry etching method for photomask. 2. A reaction gas inlet, a vacuum exhaust port and two pairs of
Of dry etching equipment with rotating magnetic field by electromagnet
The RF electrode surface in the etching chamber is made of SiO2 film pattern material.
Photoresist covered and patterned on it
Attach a photomask substrate provided with
Degree of 50-150 Gauss, reactive gas in the etching chamber
Is CHF3 + O2 and its gas composition ratio O2 / (CHF3 + O2)
5-8%, the gas pressure is 0.03-0.05 Torr (4
７7 Pa), and the RF power density of the electrode is set to 0.20 to 0.32 W /
Under the condition of cm2, the pattern was
A dry etching method for a photomask, which comprises etching an etching material . 3. The electromagnet of claim 2, wherein the two pairs of electromagnets are provided outside the etching chamber, and one pair of electromagnets and the other pair of electromagnets are provided orthogonally.
Or the dry etching method of the photomask according to claim 2 .