JP2010263244A - Plasma processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma processing method, capable of quickly and surely removing a material attached to an end section of a processing subject, such as a wafer and preventing damages due to plasma to each component inside a chamber. <P>SOLUTION: In the plasma processing method, when a plasma processing device 1 that applies a first high frequency power to an upper electrode 5 to generate a plasma and applies a second high-frequency power, having a lower frequency than that of the first high-frequency power to a lower electrode 4 of a wafer W, is used to remove a deposit D attached to an end section of the wafer W, placed on the lower electrode 4 with an oxygen gas plasma; a pressure of the oxygen gas is set to 400 to 800 mTorr; and the oxygen gas is converted into a plasma by the upper electrode 5, in a state in which the wafer W is separated from the lower electrode 4. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a plasma processing method for performing predetermined plasma processing such as plasma etching (hereinafter simply referred to as “etching”) on an object to be processed such as a semiconductor wafer (hereinafter simply referred to as “wafer”). .

  2. Description of the Related Art Conventionally, in a manufacturing process of a semiconductor device or an LCD, plasma processing such as various film forming processes or etching processes is performed on an object to be processed such as a wafer or an LCD substrate.

  For example, when etching is performed, an object to be processed (for example, a wafer) W having a layer structure as shown in FIG. As shown in FIG. 4A, the wafer W has a diffusion prevention film 51, an interlayer insulating film 52, an insulating film (for example, a silicon oxide film) 53, and a resist film 54 on the surface from the lower layer to the upper layer. Then, using the etching gas plasma, the silicon oxide film 53 is etched according to the pattern 54A formed on the resist film 54 in the order of FIGS. 4A and 4B to form, for example, a trench 53A for wiring. Form. Next, ashing is performed on the wafer W to remove the resist film 54 and expose the silicon oxide film 53 as shown in FIG. Further, although not shown, a via hole is formed in the interlayer insulating film in a later process.

  For such etching, for example, a parallel plate type plasma processing apparatus is used as the plasma processing apparatus. This type of plasma processing apparatus includes, for example, a chamber having an airtight structure, a mounting table on which a wafer is mounted in the chamber and also serving as a lower electrode, and an upper electrode disposed above the mounting table. Then, high frequency power is applied to generate plasma in the chamber, and the silicon oxide film 53 is etched with a predetermined pattern 54A through the resist film 54 as described above to form a trench 53A for wiring. Further, ashing after etching is performed in the same chamber or in another chamber. FIG. 5 is an example of a cross-sectional view showing the end of the mounting table of the plasma processing apparatus.

  The mounting table 61 shown in FIG. 5 is formed of a conductive material, for example, aluminum whose surface is anodized. An electrostatic chuck 62 for fixing the wafer W is disposed on the mounting surface of the mounting table 61. In this electrostatic chuck 62, an electrode 62B is interposed between sheet-like insulators 62A, and a DC voltage is applied to the electrode 62B to electrostatically attract the wafer W with Coulomb force. Further, a focus ring 63 is disposed on the outer peripheral edge of the mounting table 61, and the focus ring 63 surrounds the wafer W fixed on the mounting table 61 via the electrostatic chuck 62.

  By the way, since the mounting table 61 is made of aluminum, if there is a part that is directly exposed to the plasma formed above the wafer W, the part is sputtered by the plasma, and the wafer W is not desirable to contain aluminum or the like. A film may be formed. Therefore, as shown in FIG. 5, the diameter of the mounting surface (portion where the electrostatic chuck 62 is disposed) of the mounting table 61 is formed slightly smaller (for example, about 4 mm) than the diameter of the wafer W. The mounting surface of the focus ring 63 is formed to be larger than the outer diameter of the wafer W so that the top surface of the mounting table 61 is not directly exposed to plasma when viewed from above.

  However, when the mounting table 61 is configured as shown in FIG. 5, a by-product due to etching of the silicon oxide film or the resist film goes around to the back side of the end of the wafer W, and particularly on the back side of the end of the wafer W. A by-product may be deposited in the form of a thin film as a polymer or the like on an inclined portion (hereinafter referred to as “bevel portion”) on the back surface. If a polymer or the like is deposited on the bevel part, this deposit (a material such as a polymer) is peeled off from the bevel part in the subsequent process, causing particles, or a step is formed by the deposit and the focus is not adjusted during resist exposure. May cause trouble. Therefore, it is necessary to prevent the generation of such deposits as much as possible.

  Therefore, in order to remove such deposits, for example, the wafer is transferred from the etching chamber to another chamber, and ashing is performed in the other chamber to remove the resist film and remove the deposit at the edge of the wafer. It has been removed.

  As another method for removing deposits, for example, plasma processing for removing deposits on the back side of the wafer by raising an inert gas plasma in a state where the wafer is lifted and supported by a pin in an etched chamber. A method has been proposed (Patent Document 1). Further, this document proposes a method of supplying an oxidizing gas (for example, oxygen gas) instead of an inert gas to form an oxide film on the back side of the wafer and preventing the adhesion of impurities by this oxide film. Yes. In these cases, the pressure in the chamber is set to 50 to 300 mTorr, and plasma processing is performed by applying high frequency power of 25 to 100 W to the mounting table.

  Also, as a processing method similar to Patent Document 1, after CVD film formation, a wafer is pushed up and held by a pin to the position immediately below the gas shower head in the same chamber, and a purge gas is supplied from the gas shower head to the surface of the wafer. There has been proposed a substrate processing method and a substrate processing apparatus in which an etching gas such as an F-based gas is supplied from another gas supply unit into a chamber to form plasma and remove deposits on the back surface and side surfaces of the wafer (Patent Document 2). ).

US Pat. No. 4,962,209 (columns 2 to 3 and Example 1) JP-A-9-28359 (paragraphs [0040] to [0042])

  However, in the method of removing the deposit at the wafer edge in the ashing chamber, an ashing chamber is required in addition to the etching chamber, which increases the apparatus cost and the apparatus size. Since the wafer is transferred from the etching chamber to the ashing chamber, there is a problem that throughput is lowered. In the case of the method of lifting the wafer with pins as in Patent Documents 1 and 2, since the high frequency power for generating plasma is applied to the lower electrode even when the deposit on the edge of the wafer is removed, ions in the plasma are There was a risk of violently colliding with the lower electrode side and damaging various components in the chamber.

  On the other hand, since the mask pattern has become extremely fine in recent years and it has become difficult to perform etching according to the pattern, a parallel plate plasma of a two-frequency application type that applies high-frequency power with different frequencies to the upper and lower electrodes. A high-frequency power having a high frequency is applied to the upper electrode in order to generate plasma, and a high-frequency power having a lower frequency than that of the upper electrode is used to attract ions in the plasma to the lower electrode. Apply. However, since the high frequency power applied to the lower electrode is set to be low both in frequency and applied power, the wafer is lifted from the lower electrode by using pins as in Patent Documents 1 and 2, and the deposit at the edge of the wafer is removed. However, this method has a problem that the deposit cannot be sufficiently removed.

  The present invention has been made to solve the above-described problems, and can quickly and surely remove substances adhering to the end of an object to be processed such as a wafer by etching and ashing performed continuously in the same chamber. Another object of the present invention is to provide a plasma processing method capable of preventing damage to each component in the chamber due to plasma.

  In the plasma processing method according to claim 1 of the present invention, etching is performed on an object to be processed held by a holding body in one chamber, and a substance attached to an end of the object to be processed is etched. Ashing is performed continuously after the ashing, and is removed by plasma generated from the oxygen gas supplied into the chamber. The pressure of the oxygen gas in the chamber is different from that during the ashing. A step of setting to 400 to 800 mTorr, and a step of converting oxygen gas into plasma in a state in which the object to be processed is separated from the holding body.

  In the plasma processing method according to claim 2 of the present invention, the first high frequency power is applied to the plasma generating means in one chamber to generate plasma, and the second has a frequency lower than that of the first high frequency power. Using the plasma processing apparatus that applies the high frequency power of the processing object to the mounting table, an etching is performed on the processing object placed on the mounting table in the chamber to end the processing object A method of removing a substance adhering to a part by plasma generated from oxygen gas supplied into the chamber continuously after ashing after the etching and ashing are continuously performed, the oxygen gas in the chamber The step of setting the pressure of 400 to 800 mTorr, which is different from the time of the ashing, and the generation of the plasma with the object to be processed being separated from the mounting table The stage is characterized in that it comprises a a step of plasma to the oxygen gas.

  The plasma processing method according to claim 3 of the present invention is characterized in that, in the invention according to claim 2, an upper electrode disposed above the mounting table is used as the plasma generating means. is there.

  According to a fourth aspect of the present invention, in the plasma processing method according to the second or third aspect, the frequency of the first high-frequency power is set to 13.56 MHz or more, and the second high-frequency power is set. The power frequency is set to 3.2 MHz or less.

Further, in the plasma processing method according to claim 5 of the present invention, in the invention according to claim 4, the density of the first high-frequency power applied to the upper electrode is 2.83 to 4.25 W / cm ² . The density of the second high frequency power applied to the mounting table is set to 0.28 W / cm ² or less.

  The plasma processing method according to claim 6 of the present invention is the invention according to any one of claims 1 to 5, wherein the residence time of the oxygen gas is set to 50 to 260 milliseconds. It is a feature.

  The plasma processing method according to claim 7 of the present invention is characterized in that, in the invention according to any one of claims 1 to 6, the flow rate of the oxygen gas is set to 600 to 1500 sccm. To do.

  According to the present invention, it is possible to quickly and surely remove substances adhering to the end of an object to be processed such as a wafer by etching and ashing performed continuously in the same chamber. A plasma processing method capable of preventing damage due to plasma can be provided.

It is sectional drawing which shows the outline of one Embodiment of the plasma processing apparatus of this invention. FIG. 2 is a schematic diagram for explaining an embodiment of the method of the present invention using the plasma processing apparatus shown in FIG. 1, wherein (a) shows a susceptor after ashing, and (b) shows an embodiment of the method of the present invention. It is a figure which shows a susceptor at the time of removing the deposit of a wafer edge part. It is a graph which shows the result when the processing conditions of the plasma processing apparatus shown in FIG. It is process drawing for demonstrating an etching process, (a) is a figure which shows the state just before an etching, (b) is a figure which shows the state after an etching, (c) is a figure which shows the state after ashing. It is sectional drawing which expands and shows a part of susceptor of a plasma processing apparatus.

Hereinafter, the present invention will be described based on the embodiment shown in FIGS.
First, the plasma processing apparatus used in this embodiment will be described with reference to FIG. For example, as shown in FIG. 1, the plasma processing apparatus 1 is configured as a two-frequency application type parallel plate type plasma processing apparatus. For example, a silicon oxide film (SiO ₂ film) in the wafer W shown in FIG. Etch according to the pattern.

  As shown in FIG. 1, the plasma processing apparatus 1 includes a chamber 2 formed of a metal such as aluminum whose surface is anodized and grounded for safety, and an insulator 3 at the bottom of the chamber 2. And a lower electrode 4 (hereinafter referred to as “susceptor” or “lower electrode” as appropriate) 4, an upper electrode 5 disposed above the susceptor 4, and the plasma processing method of the present invention. A control device (not shown) having a program for execution is provided, and under the control of the program of the control device, a series of plasma processing is performed for removing etching of the wafer W, ashing and deposits on the edge of the wafer. A first high frequency power source 7 is connected to the upper electrode 5 via a matching unit 6, and a second high frequency power source 9 is connected to the lower electrode 4 via a matching unit 8. Further, a low pass filter (LPF) 10 is connected to the upper electrode 5, and a high pass filter (HPF) 11 is connected to the susceptor 4.

  An electrostatic chuck 12 is provided on the susceptor 4, and a wafer W is placed thereon. The electrostatic chuck 12 is configured by interposing an electrode 12A between insulators, and applies a DC voltage from a DC power source 13 connected to the electrode 12A, thereby electrostatically adsorbing the wafer W with Coulomb force. A focus ring 14 surrounding the wafer W is disposed on the outer peripheral edge of the susceptor 4. The focus ring 14 is made of Si or the like, and improves etching uniformity.

  In addition, a plurality of (for example, three) pins 15 (see FIG. 2) are provided in the susceptor 4 so as to be movable up and down, and the wafers that have entered the chamber 2 from the susceptor 4 and the loading / unloading port via these pins 15 are conveyed. The wafer W is transferred to and from a mechanism (not shown). As will be described later, these pins 15 continuously etch and ash the wafer W under the control of the control device, and then rise by a predetermined dimension and hold the position for a predetermined time. Thus, the deposit D at the edge of the wafer W is removed.

  Further, a refrigerant flow path 4A is formed in the susceptor 4, and a refrigerant (for example, an ethylene glycol aqueous solution) flows from an inflow pipe 16A connected to the inlet, and the refrigerant flows from an outflow pipe 16B connected to the outlet. The refrigerant flows out and circulates in the refrigerant flow path 4A to cool the susceptor 4. A gas flow path 4B that penetrates the electrostatic chuck 12 and opens at a plurality of locations is formed in the susceptor 4, and a heat transfer gas having high thermal conductivity such as He gas is supplied into the gas flow path 4B. Thus, the heat is transferred between the electrostatic chuck 12 and the wafer W from the opening of the gas flow path 4B to enhance the heat transfer between the susceptor 4 and the wafer W.

The upper electrode 5 includes a showerhead-like electrode plate 5A and a support 5B that supports the electrode plate 5A, and is supported on the upper portion of the chamber 2 via an insulator 17. The upper electrode 5 and the lower electrode 4 are separated by, for example, 10 to 60 mm. A gas inlet 5C is provided at the center of the support 5B, and a processing gas supply source 19 is connected to the gas inlet 5C via a gas supply pipe 18. A mass flow controller 20 and a valve 21 are sequentially arranged in the gas supply pipe 18 from the upstream side to the downstream side. The processing gas supply source 19 has a plurality of gas sources used as an etching gas. As the etching gas, conventionally known gases such as C ₅ F ₈ , Ar, and O ₂ can be used.

  On the other hand, an exhaust pipe 22 is connected to the bottom of the chamber 2, and an exhaust device 23 is connected to the exhaust pipe 22. In addition, a gate valve 24 is provided at the loading / unloading port on the side wall of the chamber 2, and the wafer W is placed between the adjacent load lock chamber (not shown) and the chamber 2 through the loading / unloading port where the gate valve 24 is opened. Transport.

Next, an embodiment of the plasma processing method of the present invention using the plasma processing apparatus 1 will be described with reference to FIGS. First, the gate valve 24 is opened, and the wafer W is loaded into the chamber 2 and placed on the electrostatic chuck 12. Next, after the gate valve 24 is closed and the inside of the chamber 2 is depressurized by the exhaust device 23, the valve 21 of the gas supply pipe 18 is opened, and for example, C ₅ F ₈ , Ar, and O ₂ are supplied from the processing gas supply source 19. These gases are supplied from the upper electrode 5 into the chamber 2 as an etching gas at a predetermined flow rate (for example, a flow rate of C ₅ F ₈ / Ar / O ₂ = 140/650/24 sccm) by the mass flow controller 20 and etching gas. Is set to a predetermined pressure. In this state, for example, a first high-frequency power having a frequency of 60 MHz is applied from the first high-frequency power supply 7 to the upper electrode 5 and a second high-frequency power having a frequency of 2 MHz is applied from the second high-frequency power supply 9 to the lower electrode 4. The plasma is formed into an etching gas by the first high-frequency power, and ions in the plasma are drawn into the lower electrode 4 by the second high-frequency power to increase the anisotropy of etching by ion assist, so that SiO ₂ in the wafer W is increased. The film is etched through the resist film to form, for example, a wiring trench. At this time, the DC power supply 13 is applied to the electrode 12 </ b> A in the electrostatic chuck 12 to electrostatically attract the wafer W onto the electrostatic chuck 12.

As described above, when the SiO ₂ film is etched by the etching gas composed of C ₅ F ₈ , Ar, and O ₂ , by-products are generated from the SiO ₂ film and the resist film, and schematically shown in FIG. As shown, a polymer or the like is deposited on the edge of the wafer W to form a deposit. Subsequently, after the residual gas in the chamber 2 is replaced with a chemically inert gas such as nitrogen gas, oxygen gas is supplied into the chamber 2 to bring the inside of the chamber 2 to a predetermined pressure (for example, 20 to 800 mTorr). Then, the first high frequency power is applied to the upper electrode 5 and the second high frequency power is applied to the lower electrode 4 to remove the resist film by ashing, and the SiO ₂ film in which the trench for wiring is formed is displayed. Let it come out.

  Thereafter, in order to transfer the wafer W to the next process, the pins are raised and the wafer W is lifted from the susceptor 4 by, for example, 1 to 18 mm (18 mm in this embodiment) and held as shown in FIG. . In this state, oxygen gas is continuously supplied into the chamber 2, and first high frequency power is applied to the upper electrode 5 under conditions different from those during ashing, and second high frequency power is applied to the susceptor 4 to supply oxygen gas. Plasma is generated, and deposits at the end of the wafer W lifted from the electrostatic chuck 12 are removed by the plasma.

  When removing the deposit, the pressure of the oxygen gas in the chamber 2 is preferably set to 400 to 800 mTorr, for example, and the residence time of the oxygen gas in the chamber 2 is preferably set to 50 to 260 msec. When the pressure of oxygen gas is less than 400 mTorr, the removal time of the deposit at the end of the wafer W becomes longer, and when it exceeds 800 mTorr, the stabilization time of the pressure in the chamber 2 becomes longer and it takes time to remove the deposit. There is a risk that the throughput will decrease. Further, the shorter the residence time of the oxygen gas, the shorter the removal time of the deposit, but if it is less than 50 msec, a flow rate of 1500 sccm or more is required in the pressure range of 400 to 800 mTorr, which is not preferable in terms of consumption. If it exceeds 260 milliseconds, the removal time of the deposit becomes longer.

Here, the residence time of oxygen gas is calculated using the following equation (1). Further, when calculating the residence time, it is assumed that the gas outside the wafer W does not contribute to the etching and is not considered in the calculation. In the following equation (1), τ is the residence time (seconds), V is the volume (L) of the chamber 2, S is the exhaust speed of the oxygen gas (L / second), and p is the pressure of the oxygen gas in the chamber 2 (Torr) ), Q is the total flow rate (sccm) of oxygen gas.
τ = V / S = pV / Q (1)

When removing the deposit on the back side of the edge of the wafer W, the upper electrode 5 is supplied to the upper electrode 5 at a frequency of 13.56 MHz or more from the first high frequency power source 7 to 2000 to 3000 W (2.83 in terms of power density). It is preferable to apply a high frequency power of ˜4.25 W / cm ² ). If the frequency of the first high-frequency power is less than 13.56 MHz, a sufficient plasma density cannot be obtained, which is not preferable. Further, if the first high-frequency power is less than 2000 W, the deposit removal throughput decreases, and if the power exceeds 3000 W, overetching tends to occur and parts in the chamber 2 may be damaged.

Further, high frequency power of 200 W (0.28 W / cm ² in terms of power density) or less is applied from the second high frequency power source 9 to the lower electrode 4 at a frequency of 3.2 MHz or less. When the frequency of the second high-frequency power exceeds 3.2 MHz or the power exceeds 200 W, the self-bias potential of the lower electrode 4 becomes high, and ions are strongly attracted to the plasma. And there is a risk of causing damage to the surrounding parts by plasma, which is not preferable.

  Accordingly, the higher the applied power to the upper and lower electrodes 4 and 5, the higher the removal rate of the deposits. However, the components in the chamber 2 are easily consumed, and the etching characteristics are deteriorated (for example, a shoulder drop such as a hole). Yes, the applied power has an upper limit. In addition, when removing deposits, the larger the oxygen gas flow rate, that is, the shorter the oxygen gas residence time at the same pressure, the greater the removal rate. From the viewpoint of increasing consumption, naturally the oxygen gas flow rate is also increased. There is an upper limit.

  Incidentally, since the optimum conditions for ashing are different from the optimum conditions for removing deposits, the deposits are removed after ashing as described above. At the time of ashing, it is necessary to set the applied power of the upper electrode 5 to be large and the applied power to the lower electrode 4 to be set small, and it is also necessary to set the flow rate of oxygen gas to be smaller than that in the case of deposit removal. In ashing, for example, the pressure of the oxygen gas in the chamber 2 is set to 20 mTorr, the flow rate of the oxygen gas is set to 300 sccm, the upper electrode 5 is set to 1500 W, and the power of the lower electrode 4 is set to 400 W, so that ashing can be performed smoothly. it can.

  After removing the deposits at the edge of the wafer as described above, the residual gas in the chamber 2 is replaced with an inert gas such as nitrogen gas, and then the gate valve 24 is opened to carry out the processed wafer W from the chamber 2. And then transported to the next process.

  As described above, according to the present embodiment, oxygen gas is converted into plasma by the upper electrode 5 while the wafer W is lifted from the susceptor 4 in the chamber 2, and the deposit D is generated from the end of the wafer W by the plasma P. At the time of removal, since the pressure of the oxygen gas in the chamber 2 is set to 400 to 800 mTorr, even if the frequency and power of the second high-frequency power source 9 applied to the lower electrode 4 are low, the oxygen gas is applied to the end of the wafer W. The deposited deposit D can be removed quickly and reliably, and damage to each component in the chamber 2 due to plasma can be prevented. Further, it is possible to prevent subsequent contamination of the wafer transfer mechanism and contamination in the subsequent process.

  Further, according to the present embodiment, the frequency of the first high-frequency power applied to the upper electrode 5 is set to 13.56 MHz or higher, and the frequency of the second high-frequency power applied to the lower electrode 4 is set to 3.2 MHz or lower. Since the setting is made, it is possible to remove the deposits at the edge of the wafer in a shorter time and increase the throughput, and it is possible to more reliably prevent the consumption of each component in the chamber 2.

  Further, since the residence time of the oxygen gas in the chamber 2 is set to 50 to 260 msec, the deposits at the wafer end can be more reliably removed. Further, since the etching and ashing are continuously performed on the wafer W prior to the removal of the deposit, a series of processes from the etching, the ashing, and the removal of the deposit on the edge of the wafer can be performed efficiently. The throughput of these series of steps can be increased.

Next, specific examples of the present invention will be described. In this embodiment, four 300 mm wafers whose surfaces are covered with a resist film are prepared, and the silicon oxide film is etched under the following conditions in accordance with the etching conditions using a plasma processing apparatus. A by-product was deposited as a deposit on the edge of the wafer to create a sample wafer.
[Etching conditions]
(1) Frequency of the first high frequency power source applied to the upper electrode: 60 MHz
(2) First high frequency power applied to the upper electrode: 1500 W
(3) Frequency of the second high frequency power source applied to the lower electrode: 2 MHz
(4) Second high frequency power applied to the lower electrode: 1500 W
(5) Susceptor temperature: -10 ° C
(6) Pressure in the chamber: 120 mTorr
(7) Etching gas flow rate:
C ₅ F ₈ = 140 sccm, Ar = 650 sccm, O 2 = 24 sccm
(8) Processing time: 230 seconds

Example 1
In this example, the relationship between the pressure of oxygen gas in the chamber 2 and the first and second high-frequency powers when the wafer deposits are removed by etching was examined. That is, the initial film thickness of the sample wafer deposit was observed with a scanning electron microscope (hereinafter referred to as “SEM”) and measured based on the photograph. Thereafter, after placing the sample wafer on the susceptor 4 in the chamber 2, the flow rate of oxygen gas is controlled to 1200 sccm and supplied based on the experimental design method (DOE) as shown in Table 1 below. The second high-frequency power and the oxygen gas pressure in the chamber 2 were swung in the range of level 1 to level 4, and the deposit at the edge of the wafer was removed by etching for 5 seconds. Thereafter, the sample wafer is taken out from the chamber 2, and the remaining film thickness / reduced film thickness of the deposits on the notches A and B and the tops A and B of each wafer are measured based on SEM observation photographs. And in Table 3 below. FIG. 3 shows the measurement results in Table 1 and Table 2 below. In Tables 1 and 2 below, the unit of film thickness is angstrom.

  In Table 2, Table 3 and FIG. 3 below, the notch refers to the notch portion of the wafer at the wafer edge, and the top refers to the portion 180 ° opposite to the notch of the wafer edge. Say. And notch A points out the back side of a notch part, and notch B points out the inclined part (bevel part) of the back side of a notch part. Top A refers to the back side of the top portion, and top B refers to an inclined portion (bevel portion) on the back side of the top portion.

  According to the results shown in FIG. 3 in which Table 2 and Table 3 are summarized, the higher the pressure of oxygen gas in the chamber 2, the greater the reduction in the thickness of the deposit on the wafer edge, and the faster the removal rate. I understood. Further, as shown in FIG. 3, it was found that the larger the electric power of the upper electrode 5, the larger the amount of decrease in the film thickness of the deposit at the edge of the wafer, and the faster the removal rate. However, as shown in FIG. 3, it has also been found that the voltage of the lower electrode 4 is not as effective as the other factors described above in removing the deposit at the edge of the wafer as shown in FIG.

Example 2
When the deposit is actually removed, it is necessary to evaluate the processing speed by the time obtained by adding the pressure stabilization time in the chamber 2 in addition to the time for simply removing the deposit. Therefore, in this example, based on the result obtained in Example 1, the applied voltage of the upper electrode was set to 2000 W, and the oxygen gas pressure in the chamber was varied as shown in Table 4 below to stabilize each pressure. The sedimentation time at each pressure and the deposit removal time at each pressure (cleaning time in Table 4 below) were measured, and the total time of both was evaluated as the actual processing time.

  According to the results shown in Table 4 above, it was found that the processing time at 600 mTorr was the shortest among 400 mTorr, 600 mTorr and 800 mTorr. That is, the deposit removal time becomes shorter as the pressure becomes higher, but the pressure stabilization time becomes shorter as the pressure becomes lower. Therefore, in order to minimize the processing time, it is necessary to optimize the pressure in the chamber. Therefore, a preferable pressure range of the oxygen gas is 400 to 800 mTorr.

Example 3
In this embodiment, as shown in Table 5 below, the wafer was processed for 5 seconds by varying the oxygen gas flow rate, and the relationship between the oxygen gas flow rate in the chamber and the deposit removal rate was determined by SEM of the top A and top B of the wafer. Observed. And the residual film thickness of the deposit of each site | part was measured based on the observation photograph of SEM, and the removal rate was calculated | required from this residual film thickness and processing time. These measurement results are shown in Table 5 below. In Table 5 below, the remaining film thickness and removal rate are shown as remaining film thickness / removal rate. The unit of film thickness is angstrom, and the unit of removal rate is angstrom / second.

  According to the results shown in Table 5 above, it was found that the higher the oxygen gas flow rate, the higher the deposit removal rate. From the viewpoint of deposit removal rate and oxygen gas consumption, the flow rate of oxygen gas is preferably in the range of 600-1500 sccm. Further, from the result when the oxygen gas flow rate is 1200 sccm, it was found that the higher the second high-frequency power of the lower electrode 4 is, the higher the deposit removal rate is.

  According to Examples 2 and 3 described above, it was found that the pressure range of oxygen gas is preferably 400 to 800 mTorr, and the flow rate range of oxygen gas is preferably 600 to 1500 sccm. Thus, when the oxygen gas residence time in the preferred pressure range and preferred flow rate range of the oxygen gas was calculated using the formula (1), the results shown in Table 6 below were obtained. According to the results in Table 6 below, it was found that the residence time of oxygen gas is preferably 50 to 260 milliseconds.

  In addition, this invention is not restrict | limited at all to the said embodiment, The plasma processing apparatus of this invention is included by this invention, if it has a program specification which can implement the method of this invention. For example, in the above-described embodiment, the case of the plasma processing apparatus that generates plasma by applying high-frequency power having different frequencies to the upper and lower electrodes has been described. However, plasma processing that applies high-frequency power to either one of the upper and lower electrodes The present invention can also be applied to an apparatus, a plasma processing apparatus that applies high-frequency power having a different frequency to the upper and lower electrodes, or a plasma processing apparatus in which a magnetic field forming means is added to these plasma processing apparatuses.

DESCRIPTION OF SYMBOLS 1 Plasma processing apparatus 2 Chamber 4 Susceptor (mounting table and lower electrode, holder)
5 Upper electrode (plasma generating means)
7 First high frequency power supply 9 Second high frequency power supply 15 Pin (separation means)
W Wafer P Plasma D Deposit (Material)

Claims (7)

  Etching is performed on the object to be processed held by the holding body in one chamber, and the substance adhering to the end of the object to be processed is continuously etched and ashed, and then continuously after ashing. A method of removing the oxygen gas supplied from the oxygen gas supplied into the chamber by plasma, the step of setting the pressure of the oxygen gas in the chamber to 400 to 800 mTorr, which is different from that during the ashing, And a step of converting oxygen gas into plasma in a state in which the object to be processed is separated.   A plasma processing apparatus for generating a plasma by applying a first high-frequency power to plasma generating means in one chamber and applying a second high-frequency power having a frequency lower than that of the first high-frequency power to a mounting table for the object to be processed. Etching and ashing the substance adhered to the end of the object to be processed by etching the object to be processed placed on the mounting table in the chamber. A method of removing the oxygen gas from the oxygen gas supplied into the chamber after ashing by plasma, and setting the pressure of the oxygen gas in the chamber to 400 to 800 mTorr different from that during the ashing. And the step of converting the oxygen gas into plasma by the plasma generating means in a state where the object to be processed is separated from the mounting table. The plasma processing method characterized by that example.   The plasma processing method according to claim 2, wherein an upper electrode disposed above the mounting table is used as the plasma generating means.   4. The plasma processing method according to claim 2, wherein the frequency of the first high-frequency power is set to 13.56 MHz or more, and the frequency of the second high-frequency power is set to 3.2 MHz or less. . The density of the first high-frequency power applied to the upper electrode is set to 2.83 to 4.25 W / cm ² , and the density of the second high-frequency power applied to the mounting table is set to 0.28 W / cm ² or less. The plasma processing method according to claim 4, wherein:   The plasma processing method according to any one of claims 1 to 5, wherein a residence time of the oxygen gas is set to 50 to 260 milliseconds.   The plasma processing method according to claim 1, wherein a flow rate of the oxygen gas is set to 600 to 1500 sccm.

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