CN104205308B - Dry-etching method - Google Patents

Abstract

The present invention provides a low-cost dry etching method, which can efficiently manufacture a silicon substrate with a textured structure, the textured structure can effectively prevent light scattering, and can also be well covered when forming a prescribed thin film in a subsequent process Film-forming. It includes a first step of introducing a first etching gas containing a fluorine-containing gas, a halogen-containing gas, and oxygen into a film-forming chamber (12) under reduced pressure in which a silicon substrate (W) is placed, and applying electric power for discharging to etch silicon. the substrate surface; and a second step of introducing a second etching gas containing a fluorine-containing gas into a film-forming chamber under reduced pressure in which the silicon substrate etched in the first step is disposed, applying electric power for discharge, and further Etch the surface of the silicon substrate.

Description

dry etching method

technical field

The present invention relates to a dry etching method for forming a textured structure on the surface of a silicon substrate, in particular to a dry etching method for forming a texture structure on the surface of a silicon substrate in the manufacturing process of a crystalline solar cell, which has the effect of preventing light scattering with high efficiency. dry etching method for textured structures.

Background technique

In crystalline solar cells using single crystal or polycrystalline silicon substrates, conventional methods have been to dry-etch the surface of the silicon substrate to form concavities and convexities, and then roughen the surface (impart a textured structure) so that the light incident on the surface of the silicon substrate is reduced. The reflection of light is reduced to realize the improvement of photoelectric conversion efficiency. Furthermore, it is known that, for example, in Patent Document 1, when slicing a silicon ingot to obtain a silicon substrate for a crystalline solar cell, dry etching is used to perform a unified process from the process of removing the damaged layer of the silicon substrate generated during slicing to the formation of a textured structure. process.

In the above-mentioned patent document 1, in the processing chamber of the dry etching device, at first, in order to remove the damaged layer _on the surface of the silicon substrate produced during slicing, for example oxygen and SF gas for removing the damaged layer are introduced into a predetermined flow rate, and the high-frequency power supply Power is applied to the base holding the silicon substrate, and the damaged layer is removed by dry etching on the surface of the silicon substrate. Next, oxygen gas, Cl ₂ gas and NF ₃ gas for forming textures are introduced into the processing chamber, power is applied from a high-frequency power supply to the base, and the surface of the silicon substrate is dry-etched, thereby forming a silicon substrate on the surface of the silicon substrate from which the damaged layer has been removed. Texture structure.

However, as described above, when a textured structure is formed on the surface of the silicon substrate by dry etching, reaction products generated during etching accumulate on the surface of the silicon substrate after etching. In addition, the silicon surface becomes uneven, and its top and bottom become sharp sharp parts (that is, jagged when viewed in cross-section). At this time, if an anti-reflection film is formed on the surface of the silicon substrate in a subsequent process, for example, using a vacuum film forming device, the top and bottom cannot be efficiently formed, resulting in problems such as poor coverage.

Therefore, it has been proposed to remove the reaction product by wet etching using an etchant such as a mixed solution of hydrofluoric acid and nitric acid, and to round the top and bottom to make them smooth. However, additional equipment for wet etching is required for round grinding, which not only lowers productivity, but also requires waste liquid treatment, etc., resulting in an increase in cost.

prior art literature

patent documents

Patent Document 1: Patent Publication No. 2011-35262

Contents of the invention

The technical problem to be solved by the invention

In view of the above, the technical problem to be solved by the present invention is to provide a low-cost dry etching method, which can efficiently manufacture a silicon substrate with a textured structure, and the silicon substrate can effectively prevent light scattering, and then In the case of forming a predetermined thin film in the process, it can be formed into a film with good coverage.

means of solving technical problems

In order to solve the above-mentioned technical problems, the present invention provides a dry etching method for forming a textured structure on the surface of a silicon substrate, which is characterized in that: it includes a first step, which is introduced into a film-forming chamber under reduced pressure in which a silicon substrate is arranged. The first etching gas containing fluorine-containing gas, halogen-containing gas, and oxygen is applied to etch the surface of the silicon substrate with electric power for electric discharge; the second process is formed under reduced pressure on which the silicon substrate that has been etched in the first process is placed. In the film chamber, the second etching gas containing fluorine-containing gas is introduced, and the electric power for discharge is applied to further etch the surface of the silicon substrate.

According to the present invention, a textured structure is formed on the surface of the silicon substrate in the first process. That is, in the processing chamber, introduce halogen-containing gases (flow ratio 25-70%) such as CF ₄ and other fluorine-containing gases (flow ratio 20-60%), Cl ₂ and other halogen gases or hydrogen halide gases such as HBr (flow ratio 25-70%), oxygen The first etching gas (flow ratio: 10 to 40%) applies high-frequency power, for example, to a substrate stage holding a silicon substrate in the processing chamber. As a result, plasma is formed in the processing chamber, and active species or ion species in the plasma are incident on the surface of the silicon substrate for etching. At this time, the silicon oxide or hydrocarbon-based fluoride accumulated on the substrate surface acts as a mask, and the silicon surface is etched into a concave-convex shape, and the surface is roughened and has a textured structure.

Next, the texture structure formed on the surface of the silicon substrate in the second step is cleaned in a vacuum atmosphere to remove silicon oxide and hydrocarbon-based fluoride deposited on the surface of the silicon substrate during the etching in the first step. and other reaction products. That is, a second etching gas composed of, for example, a fluorine-containing gas such as CF ₄ is introduced into the processing chamber, and high-frequency power is applied to the substrate stage holding the silicon substrate in the processing chamber. Thus, the reaction products accumulated on the surface of the silicon substrate are removed by the active species and ion species in the plasma. At this time, the wall surface (including the shield plate) of the vacuum chamber defining the processing chamber is also cleaned. At this time, the etching gas may also contain oxygen.

In this way, in the present invention, the formation of the texture structure and the cleaning of the surface of the silicon substrate after the first process are performed separately by dry etching, so that the texture structure can be efficiently produced on the silicon substrate. Furthermore, since wet etching is not used, high productivity can be achieved, and cost reduction can be achieved.

In the present invention, it is preferable to further include a third step of introducing any one of a fluorine-containing gas and a halogen-containing gas into a film-forming chamber under reduced pressure in which the silicon substrate etched in the second step is disposed. The third etching gas with oxygen added as its main component further etches the surface of the silicon substrate by applying electric power for discharge. Thereby, the rounding process is continuously performed on the textured structure formed on the surface of the silicon substrate. That is, the third etching gas including fluorine _- containing gas (flow rate ratio: 40-95%) and oxygen gas (flow rate ratio: 5-60%) is introduced into the processing chamber, and applied to the substrate table holding the silicon substrate in the processing chamber. high frequency electricity. Thus, the active species and ion species in the plasma are incident on the surface of the silicon substrate to etch, and the top and bottom of the textured structure on the surface of the silicon substrate formed in the first step are rounded. At this time, the purpose of adding oxygen is to control the etching rate to obtain the most suitable shape by adjusting the flow rate of oxygen. As a result, dry etching can be performed up to the rounding of the texture structure, and even when a predetermined thin film is formed in a subsequent process, a film can be formed with good coverage.

In the present invention, it is preferable that in the same processing chamber, the application of electric power for discharge is not stopped, the introduction of the halogen-containing gas and oxygen in the first etching gas into the processing chamber is stopped, and the first etching gas is switched to the second etching gas, and the process is continuously performed. The first process and the second process. In addition, it is preferable that in the same processing chamber, the application of electric power for discharge is not stopped, the introduction of oxygen gas is resumed, the second etching gas is switched to the third etching gas, and the second step and the third step are continuously performed. By performing unified dry etching in such a same processing chamber, further improvement in productivity and reduction in cost can be achieved.

In the present invention, it is preferable to further include a third step of introducing any one of a fluorine-containing gas and a halogen-containing gas into a film-forming chamber under reduced pressure in which the silicon substrate etched in the first step is disposed. The main component is the third etching gas to which oxygen is added, and the electric power for discharge is applied to further etch the surface of the silicon substrate, and the surface of the silicon substrate etched in the third step is further etched by the second step. At this time, the formation of the texture structure, the rounding of the texture structure, and the cleaning of the surface of the silicon substrate after the third step are respectively performed by dry etching, so that the texture structure can be efficiently produced on the silicon substrate. Furthermore, since wet etching is not used, high productivity can be achieved, and cost reduction can be achieved.

In the present invention, it is also possible to switch from the first etching gas to any one of the fluorine-containing gas and the halogen-containing gas in the first etching gas introduced into the processing chamber without stopping the application of electric power for discharge in the same processing chamber. Up to the third etching gas, the first step and the third step are continuously performed. In addition, the third process and the second process may be continuously performed in the same processing chamber without stopping the application of electric power for discharge, switching from the third etching gas to the second etching gas. By performing unified dry etching in the same processing chamber as described above, further improvement in productivity and reduction in cost can be achieved.

In addition, the oxygen introduction in the first process and the third process can also be carried out through a single gas introduction system with a flow control device, and the flow control device can be controlled to control the oxygen flow ratio in the first process in the range of 10 to 40%. Inside, the oxygen flow ratio in the third process is controlled within the range of 5-60%. Here, if the oxygen flow ratio in the first step (the flow ratio of the oxygen in the first etching gas to the total flow of the first etching gas introduced into the processing chamber) is out of the above range, there is a problem that a textured structure cannot be formed. , On the other hand, if the oxygen flow ratio in the third step is out of the above-mentioned range, there is a problem that the etching rate is too fast or too slow, and the etching shape cannot be controlled.

Description of drawings

FIG. 1 is a schematic structural view of a dry etching device implementing a dry etching method according to an embodiment of the present invention.

2( a ) and ( b ) are SEM photographs of the substrate obtained in Example 1 of the present invention.

3( a ) to ( c ) are SEM photographs of the substrate obtained in Example 2 of the present invention.

detailed description

Hereinafter, a dry etching method according to an embodiment of the present invention will be described with reference to the accompanying drawings. The dry etching method takes a single crystal or polycrystalline silicon substrate (hereinafter simply referred to as substrate W) used in a crystalline solar cell as the processing object, and forms a texture on the surface thereof. structure. In addition, the structure of a crystalline solar cell is well known, so a detailed description thereof will be omitted here.

FIG. 1 shows a dry etching apparatus EM capable of implementing the dry etching method of this embodiment. The following description will be made with the direction of the shower plate facing the substrate W as below and the direction of the substrate W facing the shower plate as above.

The dry etching device EM has a vacuum chamber 1, which is divided into a film forming chamber 12. The vacuum chamber 1 can be decompressed and maintained at a specified vacuum degree through a vacuum exhaust device 11. The vacuum exhaust device 11 has a rotary pump, a turbine Molecular pump, etc. A substrate stage 2 is provided in a lower space of the film formation chamber 12 . An output 31 from a high-frequency power supply 3 is connected to the substrate stage 2 . A shower plate 4 is provided on an upper portion of the film forming chamber 12 so as to face the substrate stage 2 . The shower plate 4 is held by the lower end of the annular support wall 13, and the support wall 13 protrudes from the inner wall surface of the vacuum chamber 1, and a gas introduction system 5 is provided to the part divided by the support wall 13 and the shower plate 4. An etching gas is introduced into the space 41 .

The gas introduction system 5 has a confluence ventilation pipe 51 communicated with the space 41, and the gas pipelines 53a, 53b, 53c are respectively separated from flow control devices 52a, 52b, 52c with closing functions such as mass flow controllers and connected with the confluence ventilation pipe 51, And communicate with the first to third gas sources 54a, 54b, 54c respectively. Thus, the flow rate of the gas can be controlled and introduced into the processing chamber 12 according to the type of gas. In this embodiment, the first process, the second process, and the third process are continuously implemented. The gas in the first gas source 54a is composed of fluorine-containing gases such as CF ₄ , NF ₃ , SF ₆ , and CxHyFz. The gas in the second gas source 54b The gas is composed of halogen gas such as Cl ₂ or hydrogen halide gas such as HBr, and the gas of the second gas source 54b is composed of oxygen. The etching method of the first embodiment using the above-mentioned dry etching apparatus EM will be specifically described below.

First, in the state where the processing chamber 12 has reached a predetermined degree of vacuum (for example, 10 ^-5 Pa), the substrate W is transported by a vacuum robot (not shown) and held on the substrate stage 2. The flow control valves 52 a to 52 c of 5 introduce the first etching gas from the first to third gas sources 54 a , 54 b , and 54 c from the space 41 through the shower plate 4 into the processing chamber 12 . As the first etching gas, it is composed of CF ₄ as a fluorine-containing gas, Cl ₂ as a halogen-containing gas, and oxygen, and the flow rate ratio of the fluorine-containing gas to the total flow of gas introduced into the processing chamber 12 is set at 20 to 60. %, the flow ratio of the halogen-containing gas to the total flow of the gas is set in the range of 25 to 70%, and the flow ratio of the oxygen to the total flow of the gas is set in the range of 10 to 40% (at this time, The pressure in the processing chamber 12 under reduced pressure is 30 to 250 Pa). The flow rate ratio of each gas can be appropriately set within the above-mentioned range according to the size of the processing chamber 12 or other process conditions (the same is true in the third step). In conjunction with this, electric power for discharging is applied to the substrate stage 2 via the high-frequency power supply 3 . The applied power at this time is appropriately set so that the power density becomes 0.5 to 1.8 W/cm ² . Thus, a textured structure is formed on the surface of the substrate W in the first process. That is, plasma is formed in the processing chamber 12 , and active species or ion species in the plasma are incident on the surface of the substrate W for etching. At this time, since the oxygen element accumulated on the surface of the substrate acts as a mask, the silicon surface is etched into a concave-convex shape and roughened into a textured structure.

After performing the etching in the above-mentioned first step for a predetermined time, a cleaning treatment is performed next as a second step. That is, the discharge power applied by the high-frequency power supply 3 is not stopped, the flow control device 52b is closed to stop introducing Cl ₂ as a halogen-containing gas into the processing chamber 12, and the flow control device 52c is closed to stop introducing oxygen gas into the processing chamber 12, thereby Switching from the first etching gas to the second etching gas. This second step removes reaction products such as silicon oxides and hydrocarbon-based fluorides (also referred to as "etching residue") deposited on the surface of the substrate during etching in the first step. At the same time, the inner wall surface (including the protective plate) of the vacuum chamber 1 defining the processing chamber 12 is also cleaned.

After performing the etching in the above-mentioned second step for a predetermined time, the second step is then implemented. That is, the discharge power applied by the high-frequency power supply 3 is not stopped, the flow control device 52c is turned off, and the introduction of oxygen gas into the processing chamber 12 is restarted, switching from the second etching gas to the third etching gas. At this time, the flow ratio of the fluorine-containing gas relative to the total flow of the gas introduced into the processing chamber 12 is set in the range of 40 to 95%, and the flow ratio of oxygen to the total flow of the gas is set in the range of 5 to 60%. (At this time, the pressure in the processing chamber 12 under reduced pressure is 20 to 150 Pa).

Through this third step, the textured structure formed on the surface of the substrate W is rounded. That is, the top and bottom of the textured structure on the surface of the silicon substrate formed in the first step are rounded by the active species or ion species in the plasma incident on the surface of the substrate W. At this time, the purpose of adding oxygen is to control the etching rate by adjusting the flow rate of oxygen to obtain the most suitable shape. In addition, when the texture structure is covered with the reaction product in the third step, the above-mentioned second step may be performed again.

Control the flow control device so that the oxygen flow ratio of the first process is in the range of 10-40%, and the oxygen flow ratio of the third process is in the range of 5-60%, so that the texture structure formation of the first process can be efficiently carried out And the rounding process of the third process. In addition, if the oxygen flow ratio in the first step (the flow ratio of oxygen to the total flow of the first etching gas introduced into the processing chamber) is outside the above range, there is a problem that the texture cannot be formed. On the other hand, if the third If the oxygen flow ratio of the process (the flow ratio of oxygen to the total flow of the third etching gas introduced into the processing chamber 12) is outside the above range, the etching rate is too fast or too slow, and the etching shape cannot be controlled.

Next, the etching method of the second embodiment using the dry etching apparatus EM described above will be described. The etching method of the second embodiment is the same as the etching method of the above-mentioned first embodiment except that the order of the second step and the third step is reversed. Here, it is preferable to continuously perform the first step, the third step, and the second step in the same processing chamber by switching the etching gas without stopping the discharge power applied by the high-frequency power supply 3 . Conditions such as the gas flow rate in each step are the same as those in the first embodiment described above, so detailed description thereof will be omitted here. According to this embodiment, since the cleaning is performed at the end, it can be reliably ensured that the texture structure after the rounding process is covered by the reaction product. On the other hand, since the reaction product formed on the surface of the substrate in the first step contains silicon, the reaction product is also etched during the rounding process in the third step, so there is a possibility that the third step may not be enough until the desired surface state is obtained. The processing time up to now is longer than that of the above-mentioned first embodiment. In addition, any one of the first embodiment and the second embodiment may be appropriately selected in consideration of steps before and after dry etching on a solar cell production line, various conditions of dry etching, and the like.

From the above, when forming a texture structure and rounding the texture structure by a single dry etching apparatus EM, thereby exerting the effect of suppressing light scattering, and forming a predetermined thin film in a subsequent process, It is also possible to produce textured structures with good coverage and good film formation on silicon substrates efficiently. In addition, since wet etching is not used, high productivity can be achieved, and cost reduction can be achieved. In addition, a step of removing a damaged layer generated on the substrate W during slicing when the silicon ingot is sliced to obtain the substrate W may be performed in the same processing chamber 12 before the above-mentioned first step. At this time, since the above-mentioned conventional example can be used for the conditions of dry etching, a detailed description thereof will be omitted here.

Next, an example performed using the dry etching apparatus EM shown in FIG. 1 will be described. In the first embodiment, a polysilicon substrate obtained by a known method is used as the substrate, and the conditions of the first process are: CF ₄ , Cl ₂ and oxygen are used as the first etching gas, and the flow rate of the CF ₄ :Cl ₂ :oxygen is set to 300:1000:200sccm (the flow ratio at this time is 20:67:13%), the pressure of the processing chamber 12 during etching is set to 60Pa, the applied power from the high-frequency power supply 3 is set to 2kW, and the process is performed for 90 seconds. described above. The conditions of the second step are: using CF ₄ as the second etching gas, the flow rate of this CF ₄ is set to 300 sccm, the pressure of the processing chamber 12 during etching is set to 60 Pa, and the applied power from the high-frequency power supply 3 is set to 1.5 kW, The washing process was performed for 10 seconds. The condition of the third process is: with CF ₄ and oxygen as the third etching gas, the flow of this CF : oxygen is set to 300:50 _sccm (the flow ratio at this time is 86:14%), the pressure of the processing chamber during etching It was set at 60 Pa, the applied electric power from the high-frequency power supply 3 was set at 1.0 kW, and the above-mentioned processing was performed for 10 seconds. FIG. 2( a ) shows a SEM photograph of the substrate immediately after the second step, and FIG. 2( b ) shows a SEM photograph of the substrate immediately after the third step. From this, it can be seen that a textured structure can be efficiently produced on a silicon substrate by dry etching.

In the second example, a polysilicon substrate obtained by a known method was used as the substrate, and the first step, the third step, and the second step were sequentially carried out. At this time, the conditions of the first process are: CF ₄ , Cl ₂ and oxygen are used as the first etching gas, the flow ratio of the CF ₄ :Cl ₂ :oxygen is set to 60:30:10%, and the processing chamber 12 during etching The pressure was set in the range of 20 to 150 Pa, the applied power from the high-frequency power supply 3 was set to 29.5 kW, and the processing time was set to 75 seconds. The condition of the 3rd process is: with CF ₄ and oxygen as the 3rd etching gas, this CF : the flow ratio of oxygen is set as 90: ₁₀ %, the pressure of the treatment chamber during etching is set in the scope of above-mentioned 20～150Pa, The applied power from the high-frequency power source 3 was set to 15 kW, and the processing time was set to 15 seconds. The condition of the second process is: with CF ₄ as the second etching gas, the CF ₄ is set to introduce the same flow rate as that of the third process, and the pressure of the processing chamber 12 during etching is set in the above-mentioned range of 20-150Pa, from high The applied power of the frequency power source 3 was set to 15 kW, and the processing time was set to 10 seconds. Fig. 3 (a) shows the SEM photo of the substrate just after the first process has been implemented, Fig. 3 (b) shows the SEM photo of the substrate just after the third process has been implemented, and Fig. 3 (c) shows the SEM photo of the substrate just after the third process has been implemented. SEM photograph of the substrate after the second process. Therefore, after the first process, the entire surface of the substrate is covered by the reaction product, and after the second process, the top and bottom of the texture structure are rounded, and the reaction product remains on the top (white bright part in the photo), but the third process After the reaction product on the top was completely removed, it can be seen that the texture structure can be efficiently produced on the silicon substrate by dry etching.

As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. In the above-mentioned embodiment, the dry etching apparatus EM capable of implementing the dry etching method of the present invention has been described by taking the application of power to the substrate stage 2 as an example. Other types of dry etching equipment such as dry etching equipment using inductively coupled discharge.

In the above-mentioned embodiment, the first process, the second process and the third process are implemented by a single dry etching processing apparatus EM, but they may be implemented separately, and further, the implementation of the halogen-containing gas is stopped in the second process. The method is described as an example, but it is also possible to stop the fluorine-containing gas. Furthermore, although in the above-mentioned embodiment, fluorine-containing gas, halogen-containing gas and oxygen are used as different gas sources, it is also possible to use a mixed gas of fluorine-containing gas and oxygen, a mixed gas of halogen-containing gas and oxygen as the gas source .

In the above-mentioned embodiment, the embodiment in which oxygen gas is stopped in the second step has been described as an example, but the flow control device 52c may be controlled so that the amount of oxygen introduced in the second step is lower than that in the first step. At this time, the flow ratio of the halogen-containing gas to the total flow of gas introduced into the processing chamber 12 is set in the range of 60 to 90%, and the flow ratio of oxygen to the total flow of the gas is set in the range of 10 to 40% (at this time , the pressure in the processing chamber 12 under reduced pressure is set at 40 to 150 Pa).

Explanation of reference signs

EM, dry etching device, 12, processing chamber, 2, substrate table, 3, high-frequency power supply, 4, shower plate, 5, gas introduction system, 52a～52c, mass flow controller (flow control device), 53a～ 53c, gas pipes, 54a-54c, (each for fluorine-containing gas, halogen-containing gas, and oxygen) gas sources, W, substrate (silicon substrate).

Claims (7)

1. a dry-etching method, for forming texture structure, described dry-etching method at silicon substrate, it is special Levy and be, comprise:

First operation, it imports containing fluoro-gas in film forming room under the decompression being configured with silicon substrate, contains First etching gas of halogen G&O, applies electric discharge electric power and etches silicon substrate；

Second operation, it etches the silicon substrate that is over, one-tenth under decompression to being configured with in the first operation Film is indoor, imports the second etching gas containing fluoro-gas, applies electric discharge electric power and etches silica-based further Plate surface；And

3rd operation, it etches the silicon substrate that is over, one-tenth under decompression to being configured with in the second operation Film is indoor, imports in fluoro-gas and Halogen gas that any one for main component and with the addition of oxygen wherein 3rd etching gas of gas, applies electric discharge electric power and etches silicon substrate further.

Dry-etching method the most according to claim 1, it is characterised in that:

In same process chamber, do not stop applying electric discharge electric power, stop in this process chamber, import the first etching Halogen G&O in gas, is switched to the second etching gas from the first etching gas, is carried out continuously One operation and the second operation.

Dry-etching method the most according to claim 1 and 2, it is characterised in that:

In same process chamber, do not stop applying electric discharge electric power, start again at importing oxygen, from the second erosion Carve gas and be switched to the 3rd etching gas, be carried out continuously the second operation and the 3rd operation.

4. a dry-etching method, for forming texture structure, described dry-etching method at silicon substrate, it is special Levy and be, comprise:

First operation, it imports containing fluoro-gas in film forming room under the decompression being configured with silicon substrate, contains First etching gas of halogen G&O, applies electric discharge electric power and etches silicon substrate；

3rd operation, it etches the silicon substrate that is over, one-tenth under decompression to being configured with in the first operation Film is indoor, imports in fluoro-gas and Halogen gas that any one for main component and with the addition of oxygen wherein 3rd etching gas of gas, applies electric discharge electric power and etches silicon substrate further；And

Second operation, it etches the silicon substrate that is over, one-tenth under decompression to being configured with in the 3rd operation Film is indoor, imports the second etching gas containing fluoro-gas, applies electric discharge electric power and etches silica-based further Plate surface.

Dry-etching method the most according to claim 4, it is characterised in that:

In same process chamber, do not stop applying electric discharge electric power, stop in this process chamber, import the first erosion Carve in the fluoro-gas in gas and Halogen gas any one, be switched to the 3rd etching from the first etching gas Gas, is carried out continuously the first operation and the 3rd operation.

6. according to the dry-etching method described in claim 4 or 5, it is characterised in that:

In same process chamber, do not stop applying electric discharge electric power, be switched to the second erosion from the 3rd etching gas Carve gas, be carried out continuously the 3rd operation and the second operation.

7. according to the dry-etching method described in claim 1 or 4, it is characterised in that:

Import in the first operation and the 3rd operation by having the pure gas import system of volume control device Oxygen, with the flow-rate ratio of total flow of the oxygen in etching gas and the etching gas importing process chamber for oxygen stream Amount ratio, controls volume control device by the oxygen flow in the first operation than the scope controlled in 10～40%, will Oxygen flow in 3rd operation is than the scope controlled in 5～60%.