JP4167544B2 - Plasma etching method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a processing gas for performing plasma etching under a substantially normal pressure, and a plasma etching method and apparatus using the processing gas, and in particular, to be processed such as an electronic device having a silicon compound and polycrystalline or amorphous silicon. The present invention relates to a processing gas suitable for selective etching of polycrystalline or amorphous silicon.
[0002]
[Prior art]
For example, elements such as TFT (Thin Film Transistor) are incorporated in FPD (Flat Panel Display) and LCD panels. In general, in a TFT, a gate electrode is patterned on a glass substrate, the gate electrode is covered with an insulating film, and a semiconductor layer is formed on the insulating film. For the insulating film, SiO₂Silicon compounds such as SiN and SiN are used. For the semiconductor layer, polycrystalline silicon such as polysilicon or amorphous silicon such as amorphous silicon is used. A part of this semiconductor layer is etched, and a source electrode and a drain electrode are formed thereon.
In manufacturing the TFT having the above structure, it is important not to etch the underlying insulating film when the semiconductor layer is etched.
[0003]
In Patent Document 1, as a processing gas, oxygen and 20% or less of CF with respect to oxygen are used._FourAnd performing a microwave downflow plasma etching in a vacuum environment.
Patent Document 2 describes general contents of plasma etching under normal pressure.
Non-Patent Document 1 discloses CF as a processing gas._FourDescribes that microwave plasma etching is performed in a 30 Pa vacuum vessel using oxygen added at 63 to 83%.
In addition, wet etching using dilute hydrofluoric acid is also known.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 3-29322 (first page)
[Patent Document 2]
JP 2000-58508 A (first page)
[Non-Patent Document 1]
Toshiba Technical Collection (Issue No. 97-0502, VOL.15-52)
[0005]
[Problems to be solved by the invention]
In the case of wet etching, a subsequent process of washing with water and drying is necessary, which is complicated. On the other hand, even in the case of dry etching, in the case of a vacuum system such as Patent Document 1 and Non-Patent Document 1, not only the apparatus is increased in size but also a long time is required for evacuation, resulting in poor throughput.
[0006]
On the other hand, the atmospheric pressure plasma etching as in Patent Document 2 is advantageous because there is no such problem of post-processing and throughput. However, what kind of processing gas is used for the object to be processed having a silicon compound typified by the TFT and polycrystalline or amorphous silicon under the normal pressure environment can select polycrystalline or amorphous silicon. In addition, it is not known whether etching can be performed at a good etching rate.
[0007]
[Means for Solving the Problems]
  The present invention has been made in view of the above circumstances, and plasma-etches an object to be processed having a silicon compound that should not be etched and polycrystalline or amorphous silicon that should be etched under a substantially normal pressure.MethodAnd halogen compound 0.1-20 vol%, water (water vapor) or hydroxyl group-containing compound 0.5-3 vol%, Preferably 1.7-1.8 vol%, Balance oxygen (including unavoidable impurities; the same shall apply hereinafter)Apply plasma to the workpiece under normal atmospheric pressureFeatures. ThisThisTherefore, polycrystalline or amorphous silicon can be selectively etched, the silicon compound can be hardly damaged, and the etching rate can be increased.
It is preferable that the halogen compound is approximately 0.1 vol% with respect to the entire processing gas.
[0008]
In particular, when the halogen compound is in the vicinity of 0.1 vol%, the water or hydroxyl group-containing compound is in the vicinity of 1.7 vol% to 1.8 vol%, and the balance is oxygen, the selective etching property of polycrystalline or amorphous silicon is extremely good. The silicon compound can be hardly damaged, and the etching rate is sufficiently good.
[0009]
Here, the halogen compound is set to 0.1 vol% or more because it is difficult to obtain a good etching rate if it is less than 0.1 vol%, and it is set to 20 vol% or less if it exceeds 20 vol%. This is because the silicon compound is easily etched and it is difficult to ensure the selective etching property of polycrystalline or amorphous silicon.
[0010]
With respect to water or a hydroxyl group-containing compound, 0.5 vol% or more is set to less than 0.5 vol% when OH radicals (OH^*) Is generated too much and it is difficult to obtain a good etching rate. The reason why it is 3 vol% or less is that if it exceeds 3 vol%, condensation (liquefaction) is liable to occur in the piping system and the device is easily damaged. This is because the object to be treated may get wet as well as the etching rate. On the other hand, if the temperature is raised to prevent condensation, the etching rate may be impaired.
[0011]
The normal pressure (pressure near atmospheric pressure) in the present invention is 1.333 × 10.^Four~ 10.664 × 10^FourSays the range of Pa. Among them, 9.331 × 10^Four~ 10.397 × 10^FourThe range of Pa is preferable because pressure adjustment is easy and the apparatus configuration is simple.
[0012]
The object to be processed in the present invention is, for example, a semiconductor device such as a TFT or an electronic device.
An example of polycrystalline silicon to be etched is polysilicon.
Examples of amorphous silicon to be etched include amorphous silicon.
Examples of silicon compounds that should not be etched include SiO.₂, SiC and SiN. SiC and SiN are SiO₂Since it is harder to etch, the selectivity (selective etching property) of polycrystalline or amorphous silicon becomes higher. Since SiN is particularly difficult to be etched, the selectivity is further increased.
[0013]
As the halogen compound, a fluorine compound is preferably used, but a chlorine compound may be used.
Examples of fluorine compounds include CF_Four, C₂F₆, C_ThreeF₆, C_ThreeF₈, C_FourF₈, NF_Three, SF₆Is mentioned. In addition to selecting one of these compounds, a mixed gas formed by selecting a plurality of compounds may be used.
[0014]
The “water” as a component of the processing gas is, of course, the gas phase (water vapor).
Among water and a hydroxyl group-containing compound, water is superior in terms of cost and handleability.
Examples of the hydroxyl group-containing compound include alcohol (C_nH_{2n + 1}OH (CH_ThreeOH, C₂H_FiveOH etc.) is desirable. The alcohol as the hydroxyl group-containing compound is desirably a lower one having n or less carbon atoms of “6”. For example, methanol (CH_ThreeThe binding energy of OH) is 85 kcal / mol, which is smaller than 120 kcal / mol of water, and can generate more OH radicals.
[0015]
  The present invention also provides:A method for plasma-etching an object to be processed having a silicon compound that should not be etched and polycrystalline or amorphous silicon that should be etched, under a substantially normal pressure, comprising a halogen compound of 0.1 to 20 vol% and a hydroxyl group-containing compound It is characterized by a plasma etching method in which a processing gas comprising 0.5 to 3 vol% and the balance oxygen is converted to plasma at a substantially normal pressure and applied to a workpiece.
The hydroxyl group-containing compound is preferably a lower alcohol.
Water or a hydroxyl compound that should be one component of the processing gas is stored in a liquid phase, and the liquid is vaporized, and the flow rate ratio (that is, a halogen compound of 0.1 to 20 vol%, water) is added to the other components of the processing gas. Alternatively, a hydroxyl group-containing compound may be added in an amount of 0.5 to 3 vol%, and the remaining oxygen), and the obtained processing gas may be plasmatized under substantially normal pressure and applied to the object to be processed. Thereby, the polycrystalline or amorphous silicon to be processed can be etched with a high selectivity and a high etching rate.
[0016]
Here, “other components of the processing gas” refers to a halogen compound, oxygen, or a mixed gas thereof. That is, after adding water or a hydroxyl compound to one of the halogen compound and oxygen (preferably oxygen), it may be mixed with the other (preferably a halogen compound). Water or a hydroxyl compound may be added to the mixed gas.
[0017]
  Furthermore, the present invention providesAn object to be processed having a silicon compound to be etched and polycrystalline or amorphous silicon to be etched.Plasma etchingDoA device for supplying halogen compounds and oxygen, and an additive component comprising water or a hydroxyl group-containing compoundofAn adding means and a processing unit;A processing gas path is connected to the supply means, and the addition means has an addition path that allows the additive component to pass through in a gas phase and merges with the processing gas path, and is provided at a junction of the processing gas path and the addition path. The gas from the processing gas path and the additive component in the gas phase from the addition path merge,Halogen compound 0.1-20 vol%,Additive components0.5-3 vol%, remaining oxygenThe obtained processing gas is made into plasma at substantially the normal pressure in the processing section and applied to the object to be processed, and the flow path cross-sectional area of the processing gas path is The ratio of the flow path cross-sectional area of the addition path is substantially equal to the ratio of the gas flow rate in the processing gas path and the gas flow rate in the addition path.Features a plasma etching apparatus. Thereby, polycrystalline or amorphous silicon can be etched with a high selectivity and a high etching rate.
[0018]
Here, the supply means may store the halogen compound and oxygen in a mixed state, or store them separately and mix them in the supply process to the processing unit. In the case of separate storage of the latter, after adding an additive component to either one of the halogen compound and oxygen (preferably oxygen), it may be mixed with the other (preferably halogen compound). After adding oxygen and oxygen, an additive component may be added to the mixed gas.
[0019]
The means for adding water or a hydroxyl group-containing compound may be a method of injecting and bubbling other components of the processing gas into the liquid raw material of the additive component. The liquid raw material is vaporized by heating or the like, and this is converted into other components of the processing gas. A mixing method may be used, and various other methods may be used.
[0020]
It is preferable to control the condensation point (dew point) of the additive component to be equal to or lower than the atmospheric temperature of the etching environment in the processing section. Thereby, reliquefaction (condensation) of the additive component can be prevented. The above control may be performed using a dew point meter. A specular dew point meter is preferably used as the dew point meter because it can be controlled with high accuracy. Further, the pipe containing the additive component after vaporization may be heated to prevent reliquefaction in the pipe. As the heating means, a ribbon heater may be wound around the pipe, and the pipe (addition path) may be accommodated in a heating container (a constant temperature bath) as described later.
[0021]
  As an addition method using a thermostatic bath, the adding means is configured to add the additive component.In liquid stateA stored liquid reservoir;AboveFrom the liquid reservoirWithout being mixed with other components of the process gasVaporized additive components to a flow rate that should satisfy the flow rate ratioTo the addition pathAn additive amount control unit,Said liquidBody reservoirAnd saidAddition control unitAnd saidAdditive routeWhenThe junctionWhenA container (constant temperature bath) containing,TheMoreoverIt is desirable that the inside of the container be maintained at a temperature higher than the vaporization temperature of the additive component. Thereby, it is possible to reliably prevent the additive component from the additive amount control unit from being liquefied before the addition, and a desired additive amount can be reliably obtained. As a result, the final flow ratio of each component of the processing gas can be surely set to a desired value, and the selection ratio and etching rate of polycrystalline or amorphous silicon can be reliably increased.
[0022]
  As an addition method by bubbling, the adding means adds the additive component.Store in liquid state
I gotA bubbling tank,A diversion ratio adjusting unit, and a branch path is branched from the processing gas path, and a downstream end of the branch path is disposed in the liquid in the bubbling tank, and the diversion ratio adjusting unit isGas from the supply meansSaid branchThe diversion ratio to the roadBy adjustingThe flow rate ratio of the additive component is satisfiedThe addition path extends from the bubbling tank, and a gas mixture from the gas from the branch path and the additive component vaporized in the gas is passed through the addition path. The ratio of the gas flow rate in the processing gas path between the branching part of the branching path and the junction part is substantially equal to the ratio of the flow rate of the mixed gas in the addition path.It is desirable. Thereby, a desired addition amount can be obtained reliably. As a result, the final flow ratio of each component of the processing gas can be surely set to a desired value, and the selection ratio and etching rate of polycrystalline or amorphous silicon can be reliably increased.
  here,"processingGas path "and"Branch`` Road '' is the processing gasOther than additive ingredientsEither a component, that is, a halogen compound or oxygen, or a mixed gas thereof is passed.
[0023]
  In the junction, theprocessingBy setting the cross-sectional area ratio of the gas path and the addition path to be substantially equal to the flow rate ratio in these paths, the gas flow velocities of the processing gas path and the addition path that merge together are substantially equal. The additive component can be smoothly mixed with the processing gas from the processing gas path.
[0024]
In the merging portion, the downstream end of one of the gas passage and the addition passage (preferably the passage on the smaller flow rate side) is connected to the other passage inside the other passage (preferably the passage on the higher flow rate side). It is desirable that it is coaxially accommodated so as to open in the downstream direction of the other path, and the merged gas path is connected to the other path in a straight line. Accordingly, the mixing can be performed more smoothly, the gas can be prevented from staying around the joining portion, and the re-liquefaction of the added component due to the stay can be surely prevented. As a result, the final flow rate ratio of each component of the processing gas can be more reliably set to a desired value. As a result, the selectivity and etching rate of polycrystalline or amorphous silicon can be increased more reliably.
[0025]
The processing unit includes, for example, a pair of electrodes and an electric field applying unit that applies an electric field between the electrodes. By applying an electric field, discharge plasma is generated between the electrodes, and a plasmatized space is formed. In the present invention, this plasmatized space has a substantially normal pressure. The discharge form is preferably glow discharge, but may be corona discharge, creeping discharge, or arc discharge. The processing gas is guided to the plasmaization space to be converted into plasma (excitation, radicalization, activation, ionization, etc.), and is applied to the object to be processed, so that polycrystalline or amorphous silicon is selectively etched.
[0026]
The present invention may adopt a so-called remote type in which a plasma process gas is blown out from a plasma generation space and applied to an object to be processed, and the object to be processed is arranged inside the plasma generation space, that is, between a pair of electrodes. You may employ what is called a direct type exposed to plasma.
[0027]
The electrode structure composed of the pair of electrodes is not particularly limited, and may be a parallel plate type or coaxial cylindrical type electrode structure, may be a combination of a roll electrode and a plate electrode, and a roll electrode and a portion along the electrode. It may be a combination with a concave electrode having a cylindrical concave surface. Examples of the material of the electrode include simple metals such as iron, copper, and Al, alloys such as stainless steel and brass, and intermetallic compounds. It is preferable that the electrodes have a structure in which the distance between the plasma spaces (between the electrodes) is constant in order to avoid occurrence of arc discharge due to electric field concentration.
[0028]
At least one of the pair of electrodes needs to have a solid dielectric disposed on the surface facing the other electrode. It is preferable that the solid dielectric is in close contact with the one electrode and completely covers the facing surface. If there is a portion where the electrodes directly face each other without being covered by the solid dielectric, arc discharge is likely to occur therefrom. The solid dielectric may be in the form of a plate, sheet, or film that can be separated and easily separated as an electrode, or a film coated on the electrode surface by a thermal spraying method. The thickness of the solid dielectric is preferably 0.01 to 4 mm. If the solid dielectric is too thick, a high voltage may be required to generate discharge plasma, and if it is too thin, dielectric breakdown may occur when a voltage is applied, and arc discharge may occur. The material of the solid dielectric may be either organic or inorganic. For example, plastic such as polytetrafluoroethylene and polyethylene terephthalate, glass, metal oxide such as silicon dioxide, aluminum oxide, zirconium dioxide, and titanium dioxide, titanium Examples include double oxides such as barium acid. The relative dielectric constant of the solid dielectric is preferably 2 or more (25 ° C. environment, the same applies hereinafter). Specific examples of the solid dielectric having a relative dielectric constant of 2 or more include polytetrafluoroethylene, glass, and metal oxide film. Further, in order to stably generate a high density discharge plasma, it is preferable to use a solid dielectric having a relative dielectric constant of 10 or more. The upper limit of the relative dielectric constant is not particularly limited, but an actual material of about 18,500 is known. Examples of the solid dielectric having a relative dielectric constant of 10 or more include a metal oxide film mixed with 5 to 50% by weight of titanium oxide and 50 to 95% by weight of aluminum oxide, or a metal oxide film containing zirconium oxide. Can be mentioned.
[0029]
The distance between the electrodes is appropriately determined in consideration of the thickness of the solid dielectric, the magnitude of the applied voltage, etc., but is preferably 0.1 to 5 mm. If the distance between the electrodes is less than 0.1 mm, the gap may be too narrow and installation may be difficult. On the other hand, if it exceeds 5 mm, it is difficult to generate uniform discharge plasma. If it is the range of 0.5-3 mm, the stable discharge will be obtained and it is more preferable.
[0030]
The electric field applying means is preferably a pulse electric field applying means using a pulse wave, which may be a high frequency or microwave. In particular, a pulse electric field having a rise time and / or a fall time of 10 μs or less is preferable. If it exceeds 10 μs, the discharge state tends to shift to an arc and becomes unstable, and it becomes difficult to maintain a high-density plasma state. The shorter the rise time and fall time, the more efficiently the ionization of the gas during plasma generation, but it is practically difficult to make it less than 40 ns. A more preferable range of the rise time and the fall time is 50 ns to 5 μs. Here, the rise time is a time during which the voltage (absolute value) continuously increases, and the fall time is a time during which the voltage (absolute value) continuously decreases. The electric field strength of the pulse electric field is preferably 10 to 1000 kV / cm, and more preferably 20 to 300 kV / cm. When the electric field strength is less than 10 kV / cm, it takes too much time for processing, and when it exceeds 1000 kV / cm, arc discharge tends to occur. The frequency of the pulse electric field is preferably 0.5 kHz or more. If it is less than 0.5 kHz, the plasma density is low, and the process takes too much time. The upper limit is not particularly limited, and may be 13.56 MHz which is commonly used, or may be a high frequency band such as 500 MHz which is used experimentally. In consideration of ease of matching with the load and handling, 500 kHz or less is preferable. By applying such a pulse electric field, the processing speed can be greatly improved. Moreover, it is preferable that one pulse duration in a pulse electric field is 200 microseconds or less, and 3 to 200 microseconds is more preferable. If it exceeds 200 μs, it tends to shift to arc discharge. Here, one pulse duration means a continuous ON time of one pulse in a pulse electric field composed of repetition of ON / OFF.
[0031]
Furthermore, it is desirable that the plasma etching apparatus of the present invention includes a workpiece temperature adjusting means for adjusting the temperature of the workpiece to 70 to 100 ° C. As a result, undercutting and side etching of the etched portion can be suppressed, and residues on the object to be processed (substrate) can be suppressed, and the device can be sufficiently miniaturized.
[0032]
Furthermore, it is desirable that the processing section is provided with an exhaust mechanism that sucks and exhausts the gas after the etching process. As a result, undercut and side etching of the etched portion can be suppressed, and the device can be sufficiently miniaturized. Note that this suction exhaust exhausts not only the processed gas but also by-products generated by etching.
[0033]
In addition, you may decide to wash | clean the to-be-processed object after an etching for the improvement of surface property. This cleaning may be dry cleaning using plasma, wet cleaning using pure water or the like, and acid cleaning may be used in some cases.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows an atmospheric pressure plasma etching apparatus M1 according to the first embodiment of the present invention. First, the workpiece 9 which is a processing target of the atmospheric pressure plasma etching apparatus M1 will be described. The workpiece 9 (object to be processed) has a thin plate shape. In the drawing, the thickness and size of the work 9 are drawn with considerable exaggeration. The work 9 is to be a TFT (thin film transistor), and is configured by sequentially laminating a glass substrate 9a, a gate electrode 9b, a gate insulating film 9c, and a semiconductor layer 9d from the bottom. The gate insulating film 9c is made of SiO.₂(Silicon compound). The semiconductor layer 9d is made of polysilicon (polycrystalline silicon). The semiconductor layer 9d may be made of amorphous silicon (amorphous silicon).
[0035]
The atmospheric pressure plasma etching apparatus M1 uses the SiO of the gate insulating layer 9c.₂In the semiconductor layer 9d, the polysilicon is selectively etched. After this etching step, the work 9 is further laminated with a source electrode, a drain electrode, and the like to complete the TFT.
[0036]
The atmospheric pressure plasma etching apparatus M1 will be described in detail.
The apparatus M1 includes a processing gas supply unit 1 and an etching processing unit 3. The etching processing unit 3 includes a processing chamber 30 in which a work 9 to be etched is placed, and a nozzle head 31 provided in the processing chamber 30. The inside of the processing chamber 30 is at normal pressure and normal temperature.
[0037]
The nozzle head 31 is disposed above the set table 39 and is opposed to the workpiece 9 set on the table 39. Although not shown in detail, a pair of electrodes is provided inside the nozzle head 31. One hot electrode is connected to a pulse power source (electric field applying means), and the other earth electrode is grounded. A pulse electric field is applied between the electrodes by a pulse power supply. As a result, glow discharge occurs between the electrodes, and the space between the electrodes becomes a plasma space.
[0038]
A suction nozzle 32 is attached around the nozzle head 31. A suction pump 33 is connected to the suction nozzle 32 via a suction pipe 34. The suction nozzle 32 and the suction pump 33 constitute an “exhaust mechanism”.
[0039]
The work set table 39 incorporates a work heater 35 (processing object temperature adjusting means). The work 9 is heated to a desired temperature by the heater 35. Note that the work heater 35 may be provided outside the chamber 30, and the work 9 may be placed in the chamber 30 after being heated by the heater 35.
[0040]
The processing gas supply unit 1 of the atmospheric pressure plasma etching apparatus M1 will be described.
The processing gas supply unit 1 includes a processing gas supply means 10 and a vaporizer 20 (addition means) connected to the supply means 10. The processing gas supply means 10 includes two processing gas component tanks 11 and 13 and two processing gas component MFCs (mass flow controllers) 14 and 15. CF_FourThe tank 11 has CF as a processing gas component._FourGas (halogen compound, fluorine compound) is stored. CF in this tank 11_FourThe MFC 14 is connected. MFC 14 receives CF from tank 11_FourThe mass of the gas is measured to obtain a desired flow rate. The oxygen tank 13 stores oxygen gas as a processing gas component. An oxygen MFC 15 is connected to the tank 13. The MFC 15 measures the mass of the oxygen gas from the tank 13 to obtain a desired flow rate. The pipes from the outlet ports of the two MFCs 14 and 15 merge with each other. As a result, CF_FourAnd a mixed gas of oxygen can be obtained. The mixed gas pipe 50 after the merging / mixing is connected to the inlet port 21 described later of the vaporizer 20._INIt is linked to.
[0041]
The vaporizer 20 includes a thermostatic chamber 21 (container), a water storage tank 22 (liquid storage unit) and a water vapor MFC 23 (addition amount control unit) accommodated in the thermostatic chamber 21. The thermostatic chamber 21 is thermally insulated from the outside. The constant temperature bath 21 incorporates a heater 40 (heating means in the bath). Thereby, the whole inside of the thermostatic chamber 21 is maintained at a constant temperature. This temperature is set to be higher (for example, 110 ° C.) than the vaporization temperature under normal pressure of water.
[0042]
  An inlet port 21IN for connection with the mixed gas pipe 50 is provided on the outer surface of the thermostatic chamber 21. Inside the thermostatic chamber 21, an in-tank mixed gas pipe 25 (from the supply means) extends from the inlet port 21IN.processingGas path) is piped. The tank mixed gas pipe 25 is provided with an air control valve V25.
[0043]
The water storage tank 22 in the thermostatic chamber 21 stores, for example, liquid phase pure water (liquid raw material to be added to the gas phase) having an electric conductivity of 0.1 μS / cm. In the tank 22 above the water surface, only water vapor (gas phase additive component) evaporated from water is present, and impure gas such as air is hardly contained. Inside the thermostatic chamber 21, a pre-metering steam pipe 24 extends from the upper end of the tank 22 toward the MFC 23. The steam pipe 24 has two air control valves V₂₄₁, V₂₄₂Are sequentially provided from the upstream side. Each valve V₂₄₁, V₂₄₂Ribbon heaters 41 and 42 (valve heating means) are wound around. These valves V₂₄₁, V₂₄₂A discharge pipe 29 extends from the water vapor pipe 24 between the discharge ports 21 disposed on the outer surface of the thermostatic chamber 21._EXIt is connected to. The exhaust pipe 29 has an air control valve V₂₉Is provided. A pressure sensor P is provided at the joint between the steam pipe 24 and the discharge pipe 29.₁Is provided. A purge port 21 is provided on the outer surface of the thermostatic chamber 21._PGThe purge port 21 is provided._PGA purge pipe 28 extending from the valve V₂₄₂It is connected to the steam pipe 24 on the downstream side. The purge pipe 28 includes an air control valve V.₂₈Is provided.
[0044]
The downstream end of the steam pipe 24 is connected to the inlet port of the steam MFC 23. The MFC 23 measures the mass of water vapor from the water vapor pipe 24 and thus from the water storage tank 22 to obtain a desired flow rate.
[0045]
An addition pipe 26 (addition path) extends from the outlet port of the MFC 23. The downstream end of the addition pipe 26 joins the tank mixed gas pipe 25. The full length region of the addition pipe 26 including the merging portion is accommodated in the thermostatic chamber 21. In addition pipe 26, air control valve V₂₆Is provided. Valve V₂₆A ribbon heater 43 (valve heating means) is wound around.
[0046]
Inside the thermostatic chamber 21, a post-merging gas pipe 27 (a post-merging gas path) extends from the merging portion of the pipes 25 and 26. The post-merging gas pipe 27 is connected to the outlet port 21 disposed on the outer surface of the thermostatic chamber 21._OUTIt is connected to. This outlet port 21_OUTA processing gas supply pipe 51 extends from the plasma processing space 3 and is connected to the plasma forming space of the etching processing unit 3. A ribbon heater may be wound around the outer circumference of the processing gas supply pipe 51 to heat the pipe 51.
[0047]
The junction structure between the pipes 25 and 26 will be described in further detail.
As shown in FIG. 2, the mixed gas pipe 25 in the tank and the post-merging gas pipe 27 are constituted by a single straight common gas pipe 20P. The common gas pipe 20P has substantially the same cross-sectional area over the entire length. The downstream end of the addition pipe 26 is joined to the middle part of the common gas pipe 20P. The gas pipe 20P on the upstream side from this joint is provided as the in-tank mixed gas pipe 25, and the gas pipe 20P on the downstream side is provided as the post-merging gas pipe 27.
[0048]
The ratio of the cross-sectional area of the common gas pipe 20P, that is, the mixed gas pipe 25 in the tank and the cross-sectional area of the flow path of the addition pipe 26 is determined by the mixed gas (CF_Four(+ Oxygen) flow rate and the ratio of the water vapor flow rate in the addition pipe 26 are set to be substantially equal. The addition pipe 26 penetrates the pipe wall of the common gas pipe 20P and enters the pipe 20P, and the pipe axis L of the pipe 20P._20XIt is bent in an L shape on the top. Thereby, the downstream end of the thin addition pipe 26 is coaxially formed with the thick common gas pipe 20P and is opened toward the downstream after-treatment gas pipe 27 side.
[0049]
The operation of the atmospheric pressure plasma etching apparatus M1 configured as described above will be described. A purge gas such as nitrogen gas is previously purged from the purge port 21._PGThe inside of the pipes 24, 26 and the like is purged by feeding from the inside. Furthermore, the discharge port 21_EXAnd a vacuum pump is connected to suck and exhaust the unknown gas in the tank 22 and the pipes 24 and 26 above the water surface.
[0050]
Then, by turning on the heater 40, the temperature chamber 21 is heated to a desired temperature (for example, 110 ° C.) higher than the vaporization temperature of water. As a result, the water storage tank 22 and pure water therein are also heated. In this heating process, the valve V₂₄₁, V₂₉While opening valve V₂₄₂Keep closed. Thereby, the inside of the water storage tank 22 is maintained at a normal pressure. Also, the ribbon heaters 41 to 43 are turned on and the valves V of the steam pipes 24 and 26 are turned on.₂₄₁, V₂₄₂, V₂₆Are individually heated to a desired temperature (for example, 120 ° C.) higher than the internal space of the thermostatic chamber 21.
[0051]
When the inside of the thermostatic chamber 21 and the water storage tank 22 reaches equilibrium at a desired 110 ° C., the water in the tank 22 is at 100 ° C. As a result, water evaporates and vaporizes, and the inside of the tank 22 above the water surface is filled with saturated water vapor. Here, the valve V of the steam pipes 24 and 26₂₄₁, V₂₄₂, V₂₆open. (Valve V₂₈, V₂₉Is closed. Thus, saturated steam is sent from the tank 22 through the pre-metering steam pipe 24 to the MFC 23. At this time, since the steam pipe 24 is also heated to 110 ° C., water vapor does not condense (reliquefy) on the inner peripheral surface of the steam pipe 24. Furthermore, valve V₂₄₁, V₂₄₂Is heated to a higher temperature of 120 ° C.₂₄₁, V₂₄₂It is possible to reliably prevent condensation in the interior.
[0052]
In parallel, the valve V of the mixed gas pipe 25 in the tank_{twenty five}And CF of tank 11_FourThe gas is sent to the MFC 14 and O in the tank 13₂Send gas to MFC15.
[0053]
The three MFCs 14, 15, 23 cooperate with each other to_FourThe flow rate ratio of oxygen, water vapor, and oxygen to their total flow rate_FourIt adjusts so that it may become 0.1-20 vol%, water vapor | steam 0.5-3 vol%, and remainder oxygen. In particular, CF_FourIt is preferable to adjust so that it may become 0.1 vol%, water vapor | steam 1.7vol%-1.8vol%, and remainder oxygen.
[0054]
CF_FourAnd oxygen are respectively sent from the MFCs 14 and 15 and then joined together in the pipe 50. This mixed gas (CF_Four+ Oxygen) is at the inlet port 21_INTo the tube 25.
[0055]
On the other hand, the water vapor is sent from the MFC 23 to the addition pipe 26. Since the addition pipe 26 is maintained at a high temperature of 110 ° C. over its entire length, water vapor does not condense on the inner peripheral surface of the addition pipe 26. As a result, the flow rate ratio of water vapor can be reliably maintained as it is. Furthermore, valve V₂₆Is heated to a higher temperature of 120 ° C.₂₆Condensation does not occur inside, and the accuracy of the flow rate ratio of water vapor can be further increased.
[0056]
Then, the water vapor flows into the pipe 20P, and the mixed gas (CF_Four+ Oxygen). At this time, the flow rate of water vapor coming out of the tube 26 is substantially equal to the flow rate of the mixed gas outside the tube 20P due to the relationship between the flow rate ratio and the flow path cross-sectional area of the tubes 25 and 26. Thereby, water vapor can be stably mixed with the processing gas. Moreover, since the downstream end opening of the addition pipe 26 faces the downstream merged post-treatment gas pipe 27, the steam flux φ₁Is the gas flux φ of the post-merging gas pipe 27₂It can be absorbed more smoothly by being sucked into the inside. Furthermore, since the downstream end of the addition pipe 26 is accommodated coaxially in the common gas pipe 20P, water vapor can be mixed more uniformly. Thereby, it is possible to prevent the water vapor from locally staying around the joining portion, and it is possible to reliably prevent the condensation of water vapor due to the stay. As a result, a processing gas having a flow rate ratio adjusted by the MFCs 14, 15, and 23 can be obtained.
[0057]
According to the vaporizer 20, since the heating means for vaporization in the water storage tank 22 and the heating means for preventing condensation in the pipes 24 and 25 are constituted by the common heater 40, the number of parts can be reduced. In addition, the configuration can be simplified.
[0058]
The processing gas that has passed through the pipe 27 in the vaporizer 20 is passed through the processing gas supply pipe 51. Since the water vapor partial pressure in the pipe 51 is extremely small, no condensation occurs in the pipes 27 and 51, and the flow rate ratio is maintained. Then, the processing gas is introduced into the interelectrode space (plasmaization space) in the nozzle head 31 of the etching processing unit 3.
[0059]
On the other hand, the workpiece 9 is heated to 70 to 100 ° C. by the workpiece heater 35 (processing object temperature adjusting means) and then set below the nozzle head 31.
A pulse electric field is applied between the electrodes. As a result, glow discharge occurs between the electrodes, and the processing gas is turned into plasma. The plasma-ized processing gas flow is blown from the nozzle head 31 to the workpiece 9. Thereby, the semiconductor layer 9d, that is, polysilicon can be etched. Processing gas is CF_FourSince it is precisely adjusted to be 0.1-20 vol%, water vapor 0.5-3 vol%, and the remaining oxygen, the polysilicon 9d can be selected and etched reliably, and the SiO of the gate insulating layer 9c₂It is possible to prevent the damage from reaching much, and the etching rate can be increased. Moreover, since the temperature of the workpiece 9 is 70 to 100 ° C., the undercut and side etching amount of the side edge of the polysilicon 9d can be suppressed.
[0060]
Furthermore, by operating the suction pump 33, the processed gas around the etching site and the by-product generated by the etching can be sucked by the suction nozzle 32 and exhausted. Thereby, undercut and side etching amount can be further suppressed.
[0061]
Next, another embodiment of the present invention will be described. In the following embodiments, the same reference numerals are given to the drawings for the same configurations as those in the above-described embodiments, and the description will be simplified.
FIG. 3 shows a second embodiment of the present invention. The second embodiment is different from the first embodiment described above in the configuration of the adding means. Specifically, the atmospheric pressure plasma etching apparatus M2 according to the second embodiment includes a processing gas supply unit 1A and an etching processing unit 3 having the same configuration as that of the first embodiment. The processing gas supply unit 1A includes a processing gas supply means 10 having the same configuration as that of the first embodiment and a bubbling device 12 (addition means).
[0062]
  The bubbling device 12 includes a branch valve 18 (a diversion ratio adjusting unit) and a bubbling tank 17 interposed in the mixed gas pipe 50. The branch valve 18 allows the mixed gas pipe 50 (i.e. from the supply means 10).processingGas path) is branched into first and second branch pipes 50a and 50b.(The branch path 50a is branched from the processing gas paths 50 and 50b.)
[0063]
  In the bubbling tank 17, water to be added to the processing gas is stored in a liquid phase. In the water of the bubbling tank 17, the first branch pipe 50a (first gas path), Branch) Is inserted and opened at the downstream end. An addition pipe 52 (addition path) extends from the upper end of the bubbling tank 17. This addition pipe is connected to the second branch pipe 50b (second gas path)., Processing gas path) A processing gas supply pipe 51 (processing gas path after the merging) extends from the merging portion and is connected to the inter-electrode space of the nozzle head 31 of the etching processing portion 3.
[0064]
The branch valve 18 can adjust the flow rate of the processing gas from the pipe 50 to the first branch pipe 50a and the flow rate to the second branch pipe 50b (that is, the diversion ratio of the pipes 50a and 50b). When the flow rate to the first branch pipe 50a is increased, the amount of water vaporized in the bubbling tank 17 increases. Conversely, when the flow rate to the first branch pipe 50a is reduced, the amount of water vaporized in the bubbling tank 17 is reduced. Thereby, it is possible to adjust the water vapor in the processing gas so as to be surely 0.5 to 3 vol%. As a result, the polysilicon of the work 9 can be etched with a high selectivity and a high etching rate.
Instead of the branch valve 18, a flow control valve is provided in each of the first and second branch pipes 50 a and 50 b or in any one of the first and second branch pipes 50 a and 50 b. Also good.
[0065]
The present invention is not limited to the above embodiment, and various modifications can be made.
For example, a hydroxyl group-containing compound (for example, a lower alcohol such as methyl alcohol or ethyl alcohol) may be used as a gas phase additive component instead of water. Also in this case, the hydroxyl group-containing compound is set to 0.5 to 3 vol% with respect to the entire flow rate of the processing gas.
The process gas component constitution of the present invention is SiO₂It can also be applied to the case where other silicon compounds such as SiC and SiN are used as materials that should not be etched, and amorphous silicon such as amorphous silicon is etched instead of polycrystalline silicon such as polysilicon. It can also be applied to the case of substances to be used.
CF as a processing gas component halogen compound_FourInstead of C₂F₆, C_ThreeF₆, C_ThreeF₈, NF_Three, SF₆Other fluorine compounds may be used, and a chlorine compound may be used. These CF_FourCF for other halogen compounds_FourThe same flow rate ratio of 0.1 to 20 vol% can be applied.
Only oxygen gas is introduced into the adding means 20 and 12 to add water vapor, and then this humidified oxygen is converted into CF._FourThe processing gas may be obtained by mixing the above. In the second embodiment, the structure of the joining part of the second branch pipe 50b and the addition pipe 52 is the same as the structure of the joining part of the mixed gas pipe 25 in the tank and the addition pipe 26 of the first embodiment shown in FIG. You may comprise.
The object to be processed of the present invention is not limited to the TFT, and can naturally be applied to other electronic devices.
[0066]
【Example】
An embodiment relating to the selective etching property and the etching rate according to the component composition of the processing gas will be described.
<Example 1>
Plasma etching was performed in a normal pressure / normal temperature environment using the same apparatus as in FIG. Process gas component is CF_Four: 20 vol%, O₂: 79.3 vol%, H₂O: 1.7 vol%. H₂The flow rate ratio of O was confirmed using a specular dew point meter immediately before entering the processing unit 3.
The results are shown in FIG. Polysilicon etching rate ER₁ER₁= 4500 Å / min, SiO₂Etching rate ER₂ER₂= 3500 Å / min, polysilicon selection ratio r₁R₁= ER₁/ ER₂= 1.28. In FIG. 4, the line with an etching depth of about 1700 mm represents the polysilicon layer 9d and the SiO 2 layer.₂Is the boundary of the layer 9c, and from 0 to the boundary line is a polysilicon etching region.₂This is an etching region.
As a result, CF_FourIs 20 vol% or less, polysilicon selection ratio r₁R₁What can be> 1, ie SiO₂It has been found that polysilicon can be etched more than. It has been found that the etching rate of polysilicon can be increased sufficiently.
[0067]
<Example 2>
Process gas configuration is CF_Four: 0.1 vol%, O₂: 98.2 vol%, H₂The plasma etching was performed under the same conditions as in Example 1 except that O was 1.7 vol%.
The results are shown in FIG. Polysilicon etching rate ER₁ER₁= 2500 Å / min and SiO₂Etching rate ER₂ER₂= 246Å / min, polysilicon selectivity r₁R₁= 10.1. Thus, it has been found that the selective etching property of polysilicon is extremely good, only the polysilicon can be etched, and the etching rate is sufficiently good.
In addition, according to Example 1 and Example 2, CF_FourThe smaller the ratio, the polysilicon selectivity r₁It was found that can be increased. On the other hand, polysilicon etching rate ER₁Was also found to be smaller.
[0068]
<Comparative Example 1>
Process gas configuration is CF_Four: 80 vol%, O₂: 18.3 vol%, H₂The plasma etching was performed under the same conditions as in Example 1 except that O was 1.7 vol%.
Result, polysilicon etching rate ER₁ER₁= 700 Å / min, SiO₂Etching rate ER₂ER₂= 6000 kg / min, polysilicon selection ratio r₁R₁= 0.1.
<Comparative example 2>
Process gas configuration is CF_Four: 90 vol%, O₂: 8.3 vol%, H₂The plasma etching was performed under the same conditions as in Example 1 except that O was 1.7 vol%.
Result, polysilicon etching rate ER₁ER₁= 700 Å / min, SiO₂Etching rate ER₂ER₂= 9000Å / min, polysilicon selection ratio r₁R₁= 0.08.
According to Comparative Examples 1 and 2, when CF4 exceeds 20 vol%, polysilicon selectivity r₁Is r₁<1, and SiO from polysilicon₂It was found that this is easier to etch.
[0069]
<Comparative Example 3>
Process gas is O₂: 100 vol%, and the other conditions were the same as in Example 1, and plasma etching was performed.
As a result, it was found that the etching rate was practically infinite and etching was impossible.
<Comparative example 4>
Process gas configuration is CF_Four: 98.2 vol%, H₂The plasma etching was performed under the same conditions as in Example 1 except that O: 1.8 vol%.
As a result, it was found that the etching rate was practically infinite and etching was impossible.
[0070]
Next, an example of the effect of suppressing side etching by heating the workpiece will be described.
<Example 3>
Plasma etching was performed under the same conditions as in Example 1 except that the workpiece temperature was 70 ° C.
As a result, as shown in FIG. 5, the amount of side etching of the polysilicon was 2 μm or less.
<Example 4>
Plasma etching was performed under the same conditions as in Example 1 except that the workpiece temperature was 100 ° C.
As a result, as shown in FIG. 5, the amount of side etching of the polysilicon was 2 μm or less.
<Comparative Example 5>
Plasma etching was performed under the same conditions as in Example 1 except that the workpiece temperature was 50 ° C.
As a result, as shown in FIG. 5, the side etching amount of polysilicon was 5 μm or less.
Thus, it has been found that the side etching amount can be suppressed if the workpiece temperature is set to 70 ° C. to 100 ° C.
[0071]
Next, an example of the side etching suppression effect by the exhaust mechanism will be described.
<Example 5>
In Example 1, when the suction pump 33 was operated to perform suction and exhaust from the suction nozzle 32, the side etching amount of polysilicon was 1 μm or less. On the other hand, when the suction pump 33 was stopped, the side etching amount was 5 μm.
Thus, it has been found that side etching can be suppressed by exhausting.
[0072]
【The invention's effect】
As described above, according to the present invention, it is possible to reliably selectively etch polycrystalline or amorphous silicon out of the silicon compound and polycrystalline or amorphous silicon to be processed, and damage the silicon compound. Therefore, the etching rate can be increased.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an atmospheric pressure plasma etching apparatus according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view of a connection portion between a common gas pipe and an addition pipe of the apparatus.
FIG. 3 is a schematic configuration diagram of an atmospheric pressure plasma etching apparatus according to a second embodiment of the present invention.
4 is a graph showing the results of Example 1 and Example 2. FIG.
5 is a graph showing the results of Examples 3 and 4 and Comparative Example 5. FIG.
[Explanation of symbols]
M1, M2 atmospheric pressure plasma etching equipment
3 Etching processing part
9 Workpiece (object to be processed)
9c Gate insulating layer (SiO₂(Silicone compound layer)
9d Semiconductor layer (polysilicon (polycrystalline silicon) layer)
10 Process gas supply means (CF₄(Halogen compound) and oxygen supply means)
12 Adding means
17 Bubbling tank
18 Branching valve (Diversion ratio adjuster) s
20 Vaporizer (addition means)
21 Thermostatic bath (container)
22 Water storage tank (liquid storage part)
23 Water vapor MFC (addition control unit)
25 Mixed gas pipe in tank (from supply meansprocessingGas path)
26 Addition pipe (addition path)
27 Post-merging gas pipe (gas path after merging)
32 Suction nozzle 32 (component of exhaust mechanism)
33 Suction pump (component of exhaust mechanism)
35 Work heater (Process temperature control means)
50 Mixed gas pipe (from supply meansprocessingGas path)
50a First branch pipe (BranchRoad)
50b Second branch pipe (Processing between branch and junctionGas path)
52 Addition pipe (addition path)

Claims (7)

A method for plasma-etching an object to be processed having a silicon compound that should not be etched and polycrystalline or amorphous silicon that should be etched, under a substantially normal pressure,
A plasma etching method characterized in that a processing gas comprising a halogen compound of 0.1 to 20 vol%, water or a hydroxyl group-containing compound of 1.7 to 1.8 vol%, and the remaining oxygen is converted into plasma at a substantially normal pressure and applied to the object to be processed. . The plasma etching method according to claim 1, wherein the halogen compound is approximately 0.1 vol% with respect to the entire processing gas. A method for plasma-etching an object to be processed having a silicon compound that should not be etched and polycrystalline or amorphous silicon that should be etched, under a substantially normal pressure,
  A plasma etching method, characterized in that a processing gas comprising a halogen compound of 0.1 to 20 vol%, a hydroxyl group-containing compound of 0.5 to 3 vol%, and the balance oxygen is converted to plasma under a substantially normal pressure and applied to an object to be processed. The plasma etching method according to claim 1, wherein the hydroxyl group-containing compound is a lower alcohol. An apparatus for plasma etching a workpiece having a silicon compound not to be etched and polycrystalline or amorphous silicon to be etched,
A means for supplying a halogen compound and oxygen, a means for adding an additive component consisting of water or a hydroxyl group-containing compound, and a treatment section,
A processing gas path is connected to the supply means,
The addition means has an addition path for passing the additive component in the gas phase and merging with the processing gas path,
The gas from the processing gas path and the gas phase additive component from the addition path merge at the junction of the process gas path and the addition path, and the halogen compound is 0.1 to 20 vol%, and the additive component A processing gas composed of 0.5 to 3 vol% and the balance oxygen is obtained, and the obtained processing gas is the processing gas.
In the part, it is turned into plasma under almost normal pressure and applied to the workpiece.
In the junction, the ratio of the cross-sectional area of the processing gas path to the cross-sectional area of the addition path is substantially equal to the ratio of the gas flow rate in the processing gas path and the gas flow rate in the addition path. A plasma etching apparatus characterized by that. A flow rate at which the addition means should satisfy the flow rate ratio of a liquid storage part that stores the additive component in a liquid state and an additive component that has been vaporized without being mixed with other components of the processing gas from the liquid storage part An addition amount control unit to be sent to the addition path, and a container that houses the liquid storage unit, the addition amount control unit, the addition path, and the merging portion, 6. The plasma etching apparatus according to claim 5, wherein the plasma etching apparatus is maintained at a temperature higher than a vaporization temperature of the additive component . The adding means further includes a bubbling tank that stores the added component in a liquid state, and a diversion ratio adjusting unit, and a branch path branches from the processing gas path, and a downstream end of the branch path is the bubbling tank Disposed in the liquid, and the diversion ratio adjustment unit adjusts the diversion ratio of the gas from the supply means to the branch path so as to satisfy the flow rate ratio of the additive component, and from the bubbling tank The addition path extends, and a gas mixture from the gas from the branch path and the additive component vaporized in the gas is passed through the addition path.
The flow passage cross-sectional area ratio is substantially equal to the ratio of the gas flow rate in the processing gas passage between the branching portion of the branch passage and the merge portion and the flow rate of the mixed gas in the addition passage. The plasma etching apparatus according to claim 5 , wherein the apparatus is a plasma etching apparatus.

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