JP2006156992A - Plasma processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an etching method that allows etching with a high selectivity ratio relative to a photoresist, and a CVD film formation method that allows an α-CF film to be formed at a high deposition rate. <P>SOLUTION: A plasma processing method is used for processing a target object by using plasma of a process gas containing a fluorocarbon compound. A fluorocarbon compound having at least one triple bond within a molecule and a CF<SB>3</SB>group bonded by at least one single bond adjacent to the triple bond, such as 1,1,1,4,4,4-hexafluoro-2-butyne or 1,1,1,4,4,5,5,5-octafluoro-2-pentyne, is used. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a plasma processing method, and more particularly to a plasma processing method applicable to an etching process or a film forming process in a manufacturing process of a semiconductor device.

When plasma etching is performed using a silicon oxide film such as a SiO ₂ film formed on a substrate to be processed using a photoresist as a mask, examples of etching gas include octafluorocyclopentene (c-C ₅ F ₈ ), hexafluoro-1, Fluorocarbon compound gas (CF gas) such as 3-butadiene (1,3-C ₄ F ₆ ) has been used. (For example, Patent Document 1 and Patent Document 2).

However, in recent years, with the progress of thinning of a photoresist mask, etching with a high selectivity to photoresist is required. That is, increasing the selectivity of the silicon oxide film to the photoresist in etching (silicon oxide film etching rate / photoresist etching rate) is a problem. However, c-C ₅ F ₈ described in Patent Document 1 and 1,3-C ₄ F ₆ described in Patent Document 2 are not sufficiently satisfactory from the viewpoint of the photoresist selectivity. .

In addition, in the case of c-C ₅ F ₈ and 1,3-C ₄ F ₆ , when the gas flow rate is increased to increase the etching rate, by-products (depots) accumulate in the etching holes and gradually There has been a problem in that the etching rate is lowered and eventually causes an etching stop in which the etching stops.

On the other hand, a low dielectric constant amorphous CF film (α-CF film) is formed on a silicon substrate or an insulating film such as a SiO ₂ film by CVD (Chemical Vapor Deposition) using a CF-based gas such as c-C ₅ F ₈ gas. ) Is known. However, in the case of the conventional CF-based gas, since the film forming speed is not sufficient, provision of a technique capable of forming a film at a higher speed has been demanded.
JP 2002-134479 A (Claims) JP 2001-267294 A (Claims)

  Accordingly, a first object of the present invention is to provide an etching method that enables etching of a silicon oxide film using a CF-based gas with a high selectivity to photoresist. In addition, a second object of the present invention is to provide a CVD film forming method capable of forming an α-CF film at a high film formation rate using a CF-based gas.

In order to solve the above-described problem, according to a first aspect of the present invention, there is provided a plasma processing method for processing an object to be processed using plasma with a processing gas containing a fluorocarbon compound,
The plasma treatment method, wherein the fluorocarbon compound is a compound containing in the molecule at least one triple bond and a CF ₃ group bonded by at least one single bond adjacent to the triple bond. Is provided.

In the plasma processing method of the first aspect, the plasma processing is performed by etching a silicon-containing oxide film formed on an object to be processed using a photoresist formed and patterned thereon as a mask. Is preferred. In this case, the etching selectivity to the photoresist is preferably 4.8-6. Moreover, it is preferable that the residence time of the process gas in the said etching is 0.01 to 0.1 second. Further, the fluorocarbon compound is preferably 1,1,1,4,4,4-hexafluoro-2-butyne. The processing gas preferably further contains one or more rare gases selected from the group consisting of He, Ne, Ar and Xe. Further, it is preferable that the processing gas further contains O ₂ .

  In the plasma processing method of the first aspect, it is preferable that the plasma processing is to form an α-CF film on an object to be processed. In this case, the fluorocarbon compound is 1,1,1,4,4,4-hexafluoro-2-butyne or 1,1,1,4,4,5,5,5-octafluoro-2- Pentine is preferred.

  According to a second aspect of the present invention, there is provided a plasma processing apparatus that operates on a computer and performs the plasma processing method according to any one of claims 1 to 9 when executed. There is provided a control program characterized by controlling.

According to a third aspect of the present invention, there is provided a computer storage medium storing a control program that operates on a computer,
A computer storage for controlling the plasma processing apparatus so that the plasma processing method according to any one of claims 1 to 9 is performed at the time of execution. A medium is provided.

According to the plasma processing method of the present invention, by using a fluorocarbon compound gas having a triple bond and a CF ₃ group bonded by at least one single bond adjacent to the triple bond, a high anti-photoresist It becomes possible to etch the silicon oxide film at a selective ratio or to form a CF film at a high film formation rate.

In particular, 1,1,1,4,4,4-hexafluoro-2-butyne is used in place of fluorocarbon compounds such as c-C ₅ F ₈ and 1,3-C ₄ F ₆ which have been used conventionally. By using this, it becomes possible to etch a silicon oxide film such as SiO ₂ with a high photoresist selection ratio. Furthermore, in the case of etching using 1,1,1,4,4,4-hexafluoro-2-butyne, while preventing the etching stop by setting the residence time to 0.01 to 0.1 seconds, A high photo resist selection ratio of about 4.8-6 can be obtained. Therefore, the plasma processing method of the present invention can be suitably used as an etching process for forming holes or trenches in an oxide film such as SiO ₂ or SiOF in the manufacturing process of a gate electrode or the like in a semiconductor device, for example.

Further, 1,1,1,4,4,4-hexafluoro-2-butyne or 1,1,1,4,4,5,5,5-octafluoro-2-pentyne as the fluorocarbon compound By using this, it is possible to efficiently form a CF film at a high deposition rate. Therefore, the plasma processing method of the present invention is a CVD film forming process in which a CF film as a low-k film is deposited on a silicon substrate or an interlayer insulating film such as SiO ₂ in the manufacturing process of a gate electrode of a semiconductor device, for example. Can be suitably used.

In the plasma processing method of the present invention, a processing gas containing a fluorocarbon compound is used as the processing gas. The fluorocarbon compound contained in the process gas is a compound containing at least one triple bond in the molecule and a CF ₃ group bonded by at least one single bond adjacent to the triple bond. The compound represented by general formula (I) is illustrated.

［式中、Ｒは、ＣＦ_３基、Ｃ_２Ｆ_５基などの有機残基、または無機残基を示す］

[Wherein, R represents an organic residue such as CF ₃ group or C ₂ F ₅ group, or an inorganic residue]

Among the compounds represented by the general formula (I), 1,1,1,4,4,5,5,5-octafluoro-2-pentyne (hereinafter referred to as the substituent R is a C ₂ F ₅ group) may be referred to as _"2-C 5 _{F 8"),} the substituent R is a CF ₃ group 1,1,1,4,4,4-hexafluoro-2-butyne (hereinafter, _{"2-C 4} F ₆ ”is sometimes preferred).

As is apparent from the above general formula (I), the fluorocarbon compound used in the present invention has CF ₃ bonded in the molecule by at least one triple bond and at least one single bond adjacent to the triple bond. Therefore, the triple bond is easily cleaved in the plasma, and the CF ₃ group adjacent to the cleavage site is easily released. Since the released CF ₃ group is very unstable and easily polymerized, in etching, the produced polymer is deposited on the surface of the photoresist film and acts as a resist protective film. A CF film is formed by depositing on a deposition target such as a silicon substrate or a silicon oxide film at a high rate.

Examples of an object to be etched when the plasma processing method of the present invention is applied to etching include a silicon oxide film such as a SiO ₂ film and a SiOF film, as well as a SiOC film and a SiOCH film.

In addition, when the plasma processing method of the present invention is applied to CVD film formation, the film formation target is, for example, a silicon layer, a polysilicon layer of a gate electrode, an interlayer insulating film or a SiO ₂ film as a gate insulating film, a SiOF film, etc. The silicon oxide film can be used.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing an enlarged main part of a longitudinal section of a semiconductor wafer (hereinafter simply referred to as “wafer”) W in order to explain an example of an etching process according to the first embodiment of the present invention. . As shown in FIG. 1A, a silicon oxide film 102 such as SiO ₂ as an insulating film is formed on a silicon substrate 101 constituting the wafer W, and a photoresist film 103 is formed thereon as a mask. Is formed. The photoresist film 103 is made of, for example, a material such as poly-hydroxystyrene for Kr-F resist, poly-methyl methacrylate (PMMA) for Ar-F resist, and is patterned into a predetermined shape. The silicon oxide film 102 is exposed at the bottom of the opening 110 (portion corresponding to the groove or hole) constituting the pattern.

Etching is performed to remove the silicon oxide film 102 in the photoresist opening 110 using the plasma processing apparatus 1 (see FIG. 2), as shown in FIG. As an etching gas used for the removal of the silicon oxide film 102, and _2-C 4 _{F 6} or the like fluorocarbon compound gas, He, Ne, Ar, is a mixed gas containing a rare gas such as Xe Preferably, further _{O 2} A mixed gas containing is more preferable. Specifically, for example, plasma etching is performed using a gas containing 2-C ₄ F ₆ , Ar, and O ₂ . The etching can be terminated when, for example, the depth of the opening 110 ′ (groove or hole) reaches a predetermined depth. Etching is preferably performed under the condition that the etching rate is 450 nm / min or more. Further, it is preferable that the selectivity ratio with respect to photoresist expressed by [etching rate of silicon oxide film 102] / [etching rate of photoresist film 103] is 4.8 to 6.

  FIG. 2 schematically shows a plasma processing apparatus suitably used in the etching process according to the first embodiment. The plasma processing apparatus 1 can be used as a capacitively coupled parallel plate etching apparatus in which electrode plates are opposed in parallel in the vertical direction and a high frequency power source is connected to both.

  The plasma processing apparatus 1 has a chamber 2 formed into a cylindrical shape made of aluminum, for example, whose surface is anodized (anodized), and the chamber 2 is grounded. In the chamber 2, a wafer W made of, for example, silicon and having a predetermined film formed thereon as a target object is placed horizontally, and a susceptor 5 functioning as a lower electrode is supported by the susceptor support 4. It is provided in the state. A high pass filter (HPF) 6 is connected to the susceptor 5.

  A temperature control medium chamber 7 is provided inside the susceptor support 4, and the temperature control medium is introduced into the temperature control medium chamber 7 through the introduction pipe 8 and circulated so that the susceptor 5 can be controlled to a desired temperature. It is like that.

  The upper center portion of the susceptor 5 is formed into a convex disk shape, and an electrostatic chuck 11 having substantially the same shape as the wafer W is provided thereon. The electrostatic chuck 11 has a configuration in which an electrode 12 is interposed between insulating materials. When a DC voltage of, for example, 1.5 kV is applied from a DC power source 13 connected to the electrode 12, the electrostatic chuck 11 has a Coulomb force. The wafer W is electrostatically adsorbed.

  The insulating plate 3, the susceptor support 4, the susceptor 5, and the electrostatic chuck 11 are heated to a predetermined pressure (back pressure) with a heat transfer medium, for example, He gas, on the back surface of the wafer W that is the object to be processed. A gas passage 14 for supplying the wafer W is formed, and heat transfer is performed between the susceptor 5 and the wafer W through the heat transfer medium so that the wafer W is maintained at a predetermined temperature. .

  An annular focus ring 15 is disposed at the upper peripheral edge of the susceptor 5 so as to surround the wafer W placed on the electrostatic chuck 11. The focus ring 15 is made of an insulating material such as ceramics or quartz, and acts to improve etching uniformity.

  An upper electrode 21 is provided above the susceptor 5 so as to face the susceptor 5 in parallel. The upper electrode 21 is supported on the upper portion of the chamber 2 via an insulating material 22, constitutes a surface facing the susceptor 5, and has a large number of discharge holes 23, for example, an electrode plate 24 made of quartz, The electrode 24 is composed of a conductive material, for example, an electrode support 25 made of aluminum whose surface is anodized. The interval between the susceptor 5 and the upper electrode 21 can be adjusted.

A gas introduction port 26 is provided at the center of the electrode support 25 in the upper electrode 21, and a gas supply pipe 27 is connected to the gas introduction port 26. Further, a valve is connected to the gas supply pipe 27. 28 and a mass flow controller 29 are connected to a processing gas supply source 30, and an etching gas for plasma etching is supplied from the processing gas supply source 30. In FIG. 2, only one processing gas supply source 30 is representatively shown, but a plurality of processing gas supply sources 30 are provided, for example, a fluorocarbon compound such as 2-C ₄ F ₆ Gas, a rare gas such as Ar, O _{2 and the} like are independently controlled in flow rate and supplied into the chamber 2.

  An exhaust pipe 31 is connected to the bottom of the chamber 2, and an exhaust device 35 is connected to the exhaust pipe 31. The exhaust device 35 includes a vacuum pump such as a turbo molecular pump, and is configured so that the inside of the chamber 2 can be evacuated to a predetermined reduced pressure atmosphere, for example, a predetermined pressure of 1 Pa or less. Further, a gate valve 32 is provided on the side wall of the chamber 2 so that the wafer W is transferred to and from an adjacent load lock chamber (not shown) with the gate valve 32 opened. It has become.

  A first high frequency power supply 40 is connected to the upper electrode 21, and a matching unit 41 is provided on the feeder line. Further, a low pass filter (LPF) 42 is connected to the upper electrode 21. The first high-frequency power source 40 has a frequency in the range of 50 to 150 MHz. By applying such high-frequency high-frequency power, a high-density plasma in a preferable dissociated state in the chamber 2. Can be formed, and plasma treatment under low pressure conditions becomes possible. Furthermore, the frequency of the first high frequency power supply 40 is preferably 50 to 80 MHz, and typically, a condition of 60 MHz or its vicinity is adopted as shown in FIG.

  A second high frequency power supply 50 is connected to the susceptor 5 as the lower electrode, and a matching unit 51 is provided on the power supply line. The second high frequency power supply 50 has a frequency in the range of several hundred kHz to several tens of MHz, and damages the wafer W by applying a high frequency power having a frequency in such a range. And an appropriate ionic effect can be provided. As the frequency of the second high frequency power supply 50, for example, a condition such as 13.56 MHz or 800 KHz is adopted as shown in FIG.

  Each component of the plasma processing apparatus 1 is connected to and controlled by a process controller 60 having a CPU. The process controller 60 includes a user interface 61 including a keyboard for a command input by a process manager to manage the plasma processing apparatus 1, a display for visualizing and displaying the operating status of the plasma processing apparatus 1, and the like. It is connected.

  Further, the process controller 60 stores a recipe in which a control program (software) for realizing various processes executed by the plasma processing apparatus 1 under the control of the process controller 60 and processing condition data are recorded. A storage unit 62 is connected.

  Then, if necessary, in response to an instruction from the user interface 61, an arbitrary recipe is called from the storage unit 62 and is executed by the process controller 60, so that the plasma processing apparatus 1 performs the process under the control of the process controller 60. Desired processing is performed. In addition, recipes such as the control program and processing condition data may be stored in a computer-readable storage medium such as a CD-ROM, a hard disk, a flexible disk, a non-volatile memory, or the like. For example, it is possible to transmit the data from time to time via a dedicated line and use it online.

  Next, a process of etching the silicon oxide film 102 formed on the silicon substrate 101 by the plasma processing apparatus 1 configured as described above will be described.

  First, the wafer W having the silicon oxide film 102 and the patterned photoresist film 103 is loaded into the chamber 2 from a load lock chamber (not shown) with the gate valve 32 opened, and placed on the electrostatic chuck 11. To do. The wafer W is electrostatically adsorbed on the electrostatic chuck 11 by applying a DC voltage from the DC power source 13.

Next, the gate valve 32 is closed, and the inside of the chamber 2 is evacuated to a predetermined vacuum level by the exhaust device 35. Thereafter, the valve 28 is opened, and a fluorocarbon compound (CxFy; x, y is an arbitrary integer) such as 2-C ₄ F ₆ as an etching gas from the processing gas supply source 30. Hereinafter, the same meanings are used. And Ar and O ₂ are introduced into the processing gas supply pipe 27, the gas inlet 26, and the hollow portion of the upper electrode 21 while being adjusted to a predetermined flow ratio by the mass flow controller 29, and discharged from the electrode plate 24. Through the holes 23, as shown by arrows in FIG. Here, the processing gas flow rate is, for example, 2-C ₄ F ₆ / Ar / O ₂ = 10 to 50/0 to 1500/10 to 50 mL / min, preferably about 18 to 20/300/20 mL / min. Can do.

Etching is preferably performed so that the etching rate is 450 nm / min or more. Further, the residence time of the processing gas is preferably about 0.01 to 0.1 seconds, and more preferably 0.01 to 0.03 seconds, from the viewpoint of increasing the selectivity of the photoresist to the etching. .
Here, the residence time means the residence time of the etching gas in the portion that contributes to the etching in the chamber 1, and the lower electrode area (in the case of FIG. 2, the sum of the area of the wafer W and the area of the focus ring 15). The effective chamber volume obtained by multiplying the distance between the upper and lower electrodes (that is, the volume of the space in which the processing gas is converted into plasma) is V [m ³ ], the exhaust speed is S [m ³ / sec], and the pressure in the chamber is p [Pa], where the total flow rate of the processing gas is Q (Pa · m ³ / sec), the residence time τ [sec] can be determined based on the following equation.
τ = V / S = pV / Q

  Then, the pressure in the chamber 2 is maintained at a predetermined pressure, for example, about 1 to 8 Pa, preferably about 2.0 Pa, and the first high frequency power supply 40 applies the upper electrode 21 to 500 to 3000 W, preferably about 2200 W, High frequency power of 1000 to 3000 W, preferably about 1800 W is supplied from the second high frequency power supply 50 to the susceptor 5 as a lower electrode, and the etching gas is turned into plasma to etch the silicon oxide film 102. The back pressure is preferably set to about 666.5 / about 3332.5 Pa at the center / edge of the wafer W. Further, as the process temperature, for example, the temperature of the upper electrode 21 = 60 ° C; the temperature of the side wall of the chamber 2 = 50 ° C; the temperature of the susceptor 5 = -10 ° C is preferable.

  FIG. 3 is a schematic diagram for explaining an example of a CVD film forming process according to the second embodiment of the present invention. As shown in FIG. 3A, on the wafer W, for example, a polysilicon layer 105 constituting a gate electrode and a silicon oxide film 106 as an interlayer insulating film are formed.

For example, as shown in FIGS. 3A and 3B, the CVD film is formed by forming a CF film 107 as a low-k film on the silicon oxide film 106 using the plasma processing apparatus 1 (see FIG. 2). This is done for the purpose of forming. In the formation of the CF film 107, it is preferable to use a mixed gas containing, for example, a fluorocarbon compound and a rare gas such as He, Ne, Ar, Kr, or Xe as a film forming gas, and a mixed gas containing O _2. It is more preferable to use a gas. For example, plasma CVD is performed using a gas containing 2-C ₄ F ₆ and / or 2-C ₅ F ₈ and Ar and O ₂ . The CVD can be terminated when, for example, the CF film 107 reaches a predetermined film thickness.

  In the CVD film forming process according to the second embodiment, as in the first embodiment, the plasma processing apparatus 1 of FIG. 2 can be suitably used as a CVD apparatus, and here, it is different from the first embodiment. I will focus on the points to do.

  When the plasma processing apparatus 1 is used as a plasma etching apparatus, high frequency power is supplied from the second high frequency power supply 50 to the susceptor 5 as a lower electrode. However, when the plasma processing apparatus 1 is used as a CVD apparatus, only the upper electrode 21 is predetermined. The plasma processing is performed without supplying high frequency power to the susceptor 5.

  In the CVD film forming process, the wafer W having the polysilicon layer 105 and the silicon oxide film 106 is loaded into the chamber 2 from a load lock chamber (not shown) with the gate valve 32 opened, and mounted on the electrostatic chuck 11. Put. The wafer W is electrostatically adsorbed on the electrostatic chuck 11 by applying a DC voltage from the DC power source 13.

Next, the gate valve 32 is closed, and the inside of the chamber 2 is evacuated to a predetermined vacuum level by the exhaust device 35. Thereafter, the valve 28 is opened, and a fluorocarbon compound (CxFy) such as 2-C ₄ F _6, 2-C ₅ F ₈ , Ar, and O ₂ is used as a film forming gas from the processing gas supply source 30. 2 is introduced into the processing gas supply pipe 27, the gas inlet 26, and the hollow portion of the upper electrode 21 while being adjusted to a predetermined flow rate ratio by the mass flow controller 29, and the arrow in FIG. As shown in FIG. 2, the wafer W is uniformly discharged. Here, the processing gas flow rate can be, for example, CxFy / Ar / O ₂ = 10-50 / 0 to 1500/10 to 50 mL / min, preferably about 40/300/20 mL / min. The residence time of the processing gas is preferably about 0.01 to 0.1 seconds, for example, and more preferably 0.01 to 0.03 seconds.
Here, the residence time means a residence time in a portion that contributes to film formation in the chamber 1 of the film formation gas, and the area of the lower electrode (in the case of FIG. 2, the area of the wafer W and the area of the focus ring 15). The total chamber) is multiplied by the distance between the upper and lower electrodes, that is, the effective chamber volume (that is, the volume of the space where the processing gas is turned into plasma) is V [m ³ ], the exhaust speed is S [m ³ / sec], When the pressure is p [Pa] and the total flow rate of the processing gas is Q (Pa · m ³ / sec), the residence time τ [sec] can be obtained based on the following equation.
τ = V / S = pV / Q

  Then, the pressure in the chamber 2 is maintained at a predetermined pressure, for example, about 1 to 8 Pa, preferably about 2.0 Pa, and the first high frequency power supply 40 applies the upper electrode 21 to 500 to 3000 W, preferably about 2200 W, A high frequency power of 0 to 1000 W, preferably 0 W is applied from the second high frequency power supply 50 to the susceptor 5 as a lower electrode, and the film forming gas is converted into plasma to form the CF film 107 on the silicon oxide film 106. . Further, as the process temperature, for example, the temperature of the upper electrode 21 = 60 ° C .; the temperature of the side wall of the chamber 2 = 50 ° C .; the temperature of the susceptor 5 = 20 ° C. is preferable.

  Next, a test for confirming the effect of the present invention will be described. The structural formula of the fluorocarbon compound (CxFy) used in the following tests is shown below.

A film thickness in which an SiO ₂ film as a silicon oxide film 102 is formed on a silicon substrate 101 by thermal oxidation with a film thickness of 2000 nm, and an opening 110 is formed with a diameter corresponding to a hole, with the same structure as in FIG. A sample wafer having a photoresist film 103 of 660 nm was prepared. For the photoresist film 103, a poly-methylmethacrylate (PMMA) X-ray mask photoresist was used.

  Etching is performed on the sample wafer by using the plasma processing apparatus 1 having the same configuration as in FIG. 2 (however, the volume of the chamber 2 is 70 L) to form holes having diameters of 0.1, 0.15, and 0.3 μm. In each case, the etching rate was measured and the selectivity for the photoresist was calculated. Note that the photoresist selectivity was calculated by distinguishing between flat and facet. Here, “flat” means the result of measuring the etching rate based on the film thickness of the flat surface of the photoresist film 103 (total thickness of the photoresist film 103), and “facet” means the corner portion of the photoresist 103. This means the result of calculating the etching rate on the basis of the film thickness obtained by subtracting the thickness of the shoulder drop portion from the total thickness of the photoresist film 103 when scraping (so-called shoulder drop) occurs due to the action of ion sputtering or the like.

As a fluorocarbon compound that is a component of the etching gas, 2-C ₄ is a compound containing at least one triple bond in the molecule and a CF ₃ group bonded by at least one single bond adjacent to the triple bond. the F ₆ was used. For comparison, 1,3-C ₄ F ₆ , which is a structural isomer of the above fluorocarbon compound, was used.

Gas flow rate, securing the Ar and _{O 2} flow _rate, to change the flow rate of C 4 _{F 6,} and the _{C 4 F 6 / Ar / O} 2 = 18~24 / 300 / 20mL / min (sccm). The pressure in the chamber 2 was about 2.0 Pa (15 mTorr), high-frequency power of 2200 W was supplied to the upper electrode 21 and 1800 W was supplied to the susceptor 5 as the lower electrode, and etching was performed by turning the etching gas into plasma. The back pressure is about 666.5 / about 3332.5 Pa (5/25 Torr) at the center / edge of the wafer W, and the process temperature is the upper electrode 21 = 60 ° C., the side wall of the chamber 2 = 50 ° C .; = −10 ° C., etching time was 3 minutes.

With respect to the etching rate and the photoresist selection ratio, the results when the formed hole diameter is 0.1 μm are shown in FIG. 4, the results when the hole diameter is 0.15 μm, and the results when the hole diameter is 0.3 μm. Each is shown in FIG. 6 (both are measurement results in a flat state).
FIG. 7 shows the photoresist selection ratio of flat and facet at each hole diameter when the flow rate of C ₄ F ₆ is 20 mL / min.

4 to 7, 2-C ₄ F ₆ having at least one triple bond in the molecule and a CF ₃ group bonded by at least one single bond adjacent to the triple bond is an isomer thereof. Compared with a certain 1,3-C ₄ F ₆ , the selectivity ratio with respect to the photoresist was high. In particular, in the case of the flat type, the difference in the selectivity ratio between the two with respect to the photoresist diameter significantly increased as the hole diameter increased. Regarding the etching rate, no significant difference was observed between 2-C ₄ F ₆ and 1,3-C ₄ F ₆ .
From the above results, it is shown that by using 2-C ₄ F ₆ , etching with high selectivity to photoresist can be performed while maintaining the etching rate equal to 1,3-C ₄ F _6. It was.

Next, 2-C ₅ F ₈ and 2 as fluorocarbon compounds (CxFy) having at least one triple bond in the molecule and a CF ₃ group bonded by at least one single bond adjacent to the triple bond. -C ₄ F ₆ and their structural isomers c-C ₅ F ₈ , 1,3-C ₅ F ₈ (octafluoro-1,3-pentadiene) and 1,3-C ₄ F ₆ are used. Etching was performed on the sample wafer using the plasma processing apparatus 1. Here, holes having a diameter of 0.15 μm were formed, the etching rate was measured, and the selectivity for the photoresist was calculated.

The gas flow rate was set to CxFy / Ar / O ₂ = 14 to 24/300/20 mL / min (sccm) by fixing the Ar and O ₂ flow rates and changing the CxFy flow rate. The pressure in the chamber 2 was about 2.0 Pa (15 mTorr), high-frequency power of 2200 W was supplied to the upper electrode 21 and 1800 W was supplied to the susceptor 5 as the lower electrode, and etching was performed by turning the etching gas into plasma. The back pressure is about 666.5 / about 3332.5 Pa (5/25 Torr) at the center / edge of the wafer W, and the process temperature is the upper electrode 21 = 60 ° C., the side wall of the chamber 2 = 50 ° C .; = −10 ° C., etching time was 3 minutes.

The results are shown in FIG. In FIG. 8, ◯ indicates that the etching performance is good, Δ indicates that the etching performance is slightly lowered, and × indicates that the etching is impossible and the etching is stopped halfway. From this result, 2-C ₄ F ₆ , which is a fluorocarbon compound containing at least one triple bond in the molecule and a CF ₃ group bonded by at least one single bond adjacent to the triple bond, is It was shown that the resist selection ratio is high, and the etching stop hardly occurs even when the flow rate is increased.

Further, from FIG. 8, 2-C ₄ F ₆ is a high anti-photoresist with a flow rate of about 20 to 22 mL / min (sccm) under the condition that the volume of the chamber 2 is 70 L and the pressure is about 2.0 Pa (15 mTorr). From the fact that the selection ratio was obtained, it was found that if the residence time of the processing gas is in the range of about 0.01 to 0.1 seconds, a high photoresist selection ratio can be obtained.

  On the other hand, in the case of other fluorocarbon compounds, although the etching rate generally tends to be high, the selectivity ratio with respect to the photoresist is low and it is difficult to cope with the thinning of the photoresist film. It was done.

Next, application to a CVD film forming process will be described. Similarly to the one shown in FIG. 3A, a CVD film formation test was performed on a stacked body having a structure in which a SiO ₂ film was stacked as the silicon oxide film 106 on the polysilicon layer 105.

In the CVD film formation, a CF film as a low-k film was formed on the silicon oxide film 106 using the plasma processing apparatus 1 having the same configuration as in FIG. As a film forming gas, a gas containing a fluorocarbon compound (CxFy), Ar, and O ₂ was used.

In the CVD film forming process, the flow rates of Ar and O ₂ are fixed, the flow rate of the fluorocarbon compound is changed, and the gas flow rate ratio is CxFy / Ar / O ₂ = 10-50 / 300/20 mL / min (sccm). did. The pressure in the chamber 2 was about 2.0 Pa (15 mTorr), high frequency power of 2200 W was supplied to the upper electrode 21, and high frequency power was not supplied to the susceptor 5 as the lower electrode. The process temperature was set to upper electrode 21 = 60 ° C., chamber 2 side wall = 50 ° C .; susceptor 5 = 20 ° C.

The results are shown in FIG.
From FIG. 9, 2-C ₅ F ₈ , which is a fluorocarbon compound containing at least one triple bond in the molecule and a CF ₃ group bonded by at least one single bond adjacent to the triple bond, It was shown that the deposition rate was highest at a flow rate of 10 to 50 mL / min (sccm), followed by the deposition rate of 2-C ₄ F ₆ having the same structure. The deposition rate of the two compounds was also superior to c-C ₅ F ₈ and 1,3-C ₄ F ₆ which are these structural isomers. On the other hand, in the case of c-C ₄ F ₈ (octafluorocyclobutane) and C ₃ F ₈ (octafluoropropane), which are other fluorocarbon compounds, the deposition rate was inferior.

As mentioned above, although embodiment of this invention was described, this invention is not restrict | limited to the said embodiment, A various deformation | transformation is possible.
For example, in the above embodiment, a capacitively coupled parallel plate etching apparatus is used. However, any plasma processing apparatus such as an inductively coupled apparatus may be used as long as plasma can be formed with a gas pressure within the range of the present invention. Can be used.

1 is a schematic diagram of a wafer cross-sectional structure for explaining a first embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS Drawing which shows the outline | summary of the plasma processing apparatus of this invention. The schematic diagram of the wafer cross-section used for description of 2nd Embodiment of this invention. C ₄ F ₆ gas flow rate and the etching rate and the pair photoresist selectivity ratio graph showing the hole diameter 0.1 [mu] m. _C 4 _{F 6} gas flow rate and the etching rate and the pair photoresist selectivity ratio graph showing the hole diameter 0.15 [mu] m. C ₄ F ₆ gas flow rate and the etching rate and the pair photoresist selectivity ratio graph showing the hole diameter 0.3 [mu] m. C ₄ F ₆ graph showing the relationship between the hole diameter and the pair photoresist selectivity of gas. The figure which plotted the selectivity with respect to photoresist for every CxFy gas kind with respect to an etching rate. The graph figure which shows the gas flow rate and deposition rate for every CxFy gas kind.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Plasma processing apparatus 2; Chamber 60; Process controller 61; User interface 62; Memory | storage part 101; Silicon substrate 102; Silicon oxide film 103; Photoresist film 105; Polysilicon layer 106; Silicon oxide film 107; CF film 110; Aperture

Claims (11)

A plasma processing method of processing an object to be processed using plasma with a processing gas containing a fluorocarbon compound,
The plasma treatment method, wherein the fluorocarbon compound is a compound containing in the molecule at least one triple bond and a CF ₃ group bonded by at least one single bond adjacent to the triple bond. .   2. The plasma treatment according to claim 1, wherein the silicon-containing oxide film formed on the object to be processed is etched using a patterned photoresist formed thereon as a mask. 3. Plasma processing method.   The plasma processing method according to claim 2, wherein the etching selectivity to the photoresist is 4.8-6.   The plasma processing method according to claim 3, wherein a residence time of the processing gas in the etching is 0.01 to 0.1 seconds.   The plasma processing method according to claim 4, wherein the fluorocarbon compound is 1,1,1,4,4,4-hexafluoro-2-butyne.   The plasma processing method according to claim 5, wherein the processing gas further includes one or more rare gases selected from the group consisting of He, Ne, Ar, and Xe. The plasma processing method according to claim 6, wherein the processing gas further contains O ₂ .   2. The plasma processing method according to claim 1, wherein the plasma processing is to form an [alpha] -CF film on an object to be processed.   The fluorocarbon compound is 1,1,1,4,4,4-hexafluoro-2-butyne or 1,1,1,4,4,5,5,5-octafluoro-2-pentyne. The plasma processing method according to claim 8, wherein:   A control program that operates on a computer and controls the plasma processing apparatus so that the plasma processing method according to any one of claims 1 to 9 is performed at the time of execution. A computer storage medium storing a control program that runs on a computer,
A computer storage for controlling the plasma processing apparatus so that the plasma processing method according to any one of claims 1 to 9 is performed at the time of execution. Medium.

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