JP2014107405A - Plasma processing apparatus and plasma processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma processing apparatus capable of performing uniform plasma processing by reducing the reactivity of the peripheral part of a processed substrate, without using a straightener wall or a sacrifice material of high radical consumption.SOLUTION: A plasma processing apparatus comprises: a processing container 2 for housing a substrate G and performing plasma processing; a substrate mounting table 4 for mounting the substrate G in the processing container; process gas supply mechanisms 20, 28 for supplying process gas into the processing container; an exhaust mechanism 30 for exhausting the processing container 2; a high frequency power supply 14a; i.e., a plasma source for generating plasma of process gas in the processing container 2; and trap gas supply mechanisms 16, 19 supplying trap gas, for trapping active species in the plasma, to the periphery of the substrate G on the substrate mounting table 4.

Description

  The present invention relates to a plasma processing apparatus and a plasma processing method for performing plasma processing such as plasma etching.

  In the manufacturing process of flat panel displays (FPD) and semiconductor devices, plasma processing such as etching, sputtering, and CVD (chemical vapor deposition) is frequently used for a substrate to be processed.

  For example, when plasma etching is performed as plasma processing, a processing gas is dissociated and activated by plasma, and an active species such as a generated radical reacts with an etching target film.

  When the etching target film has a high chemical reactivity, the etching rate tends to be high in the peripheral portion of the substrate to be processed due to the influence of loading, and this often limits the uniformity of etching.

  As a technique for suppressing the tendency of the etching rate to increase at the peripheral portion, a flow straightening wall that is a vertical side wall is disposed so as to surround the substrate to be processed to suppress the flow of processing gas at the peripheral portion of the substrate to be processed. Is known (for example, Patent Document 1). Further, a method of reducing the influence of loading by arranging a member having a large amount of radical consumption as described in Patent Document 2 as a sacrificial material in the outer region of the substrate to be processed can be considered.

JP 2003-243364 A Japanese Patent Laid-Open No. 5-190502

  However, when a rectifying wall is used, it is necessary to optimize the rectifying wall in accordance with the type of etching target film and etching conditions (recipe), which is complicated. In addition, when using a sacrificial material with a large amount of radical consumption, the sacrificial material is a consumable item, so it is necessary to replace it periodically, which requires labor and cost for replacement. Further, in both techniques, when a plurality of etching layers are processed continuously, the other etching target film is affected, and process inconvenience may occur.

  The present invention has been made in view of such circumstances, and performs uniform plasma processing by reducing the reactivity of the peripheral portion of the substrate to be processed without using a rectifying wall or a sacrificial material with a large amount of radical consumption. It is an object of the present invention to provide a plasma processing apparatus and a plasma processing method.

  In order to solve the above problems, according to a first aspect of the present invention, there is provided a plasma processing apparatus for performing plasma processing on a substrate, a processing container for accommodating the substrate and performing plasma processing, and the inside of the processing container A substrate mounting table for mounting the substrate, a processing gas supply mechanism for supplying a processing gas into the processing container, an exhaust mechanism for exhausting the processing container, and generating plasma of the processing gas in the processing container And a trap gas supply mechanism for supplying a trap gas for trapping active species in the plasma to a peripheral portion of the substrate on the substrate mounting table. To do.

  According to a second aspect of the present invention, there is provided a plasma processing method for performing plasma processing on a substrate, wherein a processing gas is supplied into the processing container in a state where the substrate is mounted on the substrate mounting table in the processing container, A plasma of a processing gas is generated in the processing container to perform plasma processing on the substrate, and at that time, a trap gas for trapping active species in the plasma is supplied to a peripheral portion of the substrate. A plasma processing method is provided.

  In the first aspect and the second aspect, the plasma treatment may be a plasma etching treatment. The processing gas may be a gas including at least one of F, Cl, and O, and the trap gas may be a hydrogen gas. Moreover, the ratio of the number of atoms of the trap gas to the number of atoms of the active species in the processing gas can be 17 to 80%.

When the plasma treatment is a plasma etching treatment, the etching target can be any one of a Si film, a SiN _x film, and an Al film formed on the substrate. When the etching target is a Si film, F may be used as the active species, and the ratio of the number of atoms of the trap gas to the number of atoms of the active species in the processing gas may be 40 to 80%. When the etching object is a SiN _x film, F and O are used as active species, and the ratio of the number of atoms of the trap gas to the number of atoms of the active species in the processing gas is 17.1 to 4.3.3%. Good. When the etching target is an Al film, Cl may be used as the active species, and the ratio of the number of atoms of the trap gas to the number of atoms of the active species in the processing gas may be 40 to 80%.

  In the first aspect, the trap gas supply mechanism may be provided around the substrate of the substrate mounting table. Further, the processing gas supply mechanism has a shower head that supplies the processing gas in a shower shape toward the substrate on the substrate mounting table in the processing container, and the trap gas supply mechanism is arranged around the shower head. May be provided.

  According to a third aspect of the present invention, there is provided a storage medium that operates on a computer and stores a program for controlling a plasma processing apparatus, wherein the program is executed when the plasma processing method according to the second aspect is performed. The storage medium is characterized by causing a computer to control the plasma processing apparatus.

  According to the present invention, a trap gas for trapping active species in plasma is supplied to the peripheral portion of the substrate on the substrate mounting table during plasma processing. Therefore, when the plasma processing rate is large at the outer peripheral portion of the substrate, the processing rate of that portion can be reduced, and the uniformity of the plasma processing distribution can be improved.

It is sectional drawing which shows the plasma etching apparatus as a plasma processing apparatus which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows partially the substrate mounting base in the plasma etching apparatus of FIG. It is a top view which shows the substrate mounting base in the plasma etching apparatus of FIG. It is sectional drawing which shows the other example of a trap gas discharge nozzle. It is sectional drawing which shows the further another example of a trap gas discharge nozzle. It is sectional drawing which shows the plasma etching apparatus as a plasma processing apparatus which concerns on the 2nd Embodiment of this invention. 6 is a schematic diagram for explaining Experimental Example 1. FIG. is a diagram showing the relationship between the supply amount and the etching distribution to the substrate peripheral portion of the H ₂ gas as a trap gas when the plasma etching an a-Si film. Is a diagram showing the relationship between the supply amount and the etching distribution to the substrate peripheral portion of the H ₂ gas as a trap gas when the plasma etching the SiN _x film. The Al film is a diagram showing the relationship between the supply amount and the etching distribution to the substrate peripheral portion of the H ₂ gas as a trap gas when the plasma etching. the amount of H ₂ gas supplied to the substrate peripheral portion of the etching of the a-Si film is a diagram showing a relationship between the emission spectrum of the plasma. It is sectional drawing which shows the laminated structure of the etching object in the case of the LTPS contact etching assumed in Experimental example 2. FIG. Is a diagram showing an etching profile of the SiO ₂ film by the presence or absence of supply of the H ₂ gas is trapped gas in Experiment 2. 6 is a diagram showing an etching distribution of a SiN _x film depending on whether or not a H ₂ gas that is a trap gas in Experimental Example 2 is supplied. FIG. Is a diagram showing an etching profile of a-Si film with and without the supply of the H ₂ gas is trapped gas in Experiment 2. It is a figure which shows the result of Experimental example 3.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
In the present invention, a plasma etching apparatus will be described as an example of a plasma processing apparatus.

<First Embodiment>
First, the first embodiment will be described.
FIG. 1 is a sectional view showing a plasma etching apparatus as a plasma processing apparatus according to the first embodiment of the present invention, FIG. 2 is a sectional view partially showing a substrate mounting table in the plasma etching apparatus of FIG. It is a top view which shows the substrate mounting base in the plasma etching apparatus of FIG.

  As shown in FIG. 1, the plasma etching apparatus 1 is configured as a capacitively coupled plasma etching apparatus that performs etching on an FPD glass substrate (hereinafter simply referred to as “substrate”) G. Examples of the FPD include a liquid crystal display (LCD), an electroluminescence (EL) display, a plasma display panel (PDP), and the like. The plasma etching apparatus 1 includes a chamber 2 as a processing container that accommodates a substrate G that is a substrate to be processed. The chamber 2 is made of, for example, aluminum whose surface is anodized (anodized), and is formed in a square tube shape corresponding to the shape of the substrate G.

  A substrate mounting table 4 that functions as a lower electrode is provided at the bottom of the chamber 2 via an insulating plate 3 made of an insulating material. The substrate mounting table 4 is made of metal, such as aluminum, and has a base 5 made of metal, for example, aluminum, and has a convex portion 5a formed at the upper central portion and a flange portion 5b around the convex portion 5a, and a convex portion. And an insulating member 6 having a mounting surface for the substrate G provided on 5a. A planar attracting electrode 6a is provided inside the insulating member 6, and these constitute an electrostatic chuck for electrostatically attracting the substrate G. A shield ring 7 made of a frame-shaped insulator is provided on the flange portion 5b so as to surround the substrate G placed thereon. An insulating ring 8 is provided so as to surround the periphery of the substrate 5. The insulating member 6, the shield ring 7, and the insulating ring 8 are made of insulating ceramics such as alumina, for example.

  A power supply line 12 for supplying high-frequency power is connected to the base material 5. The power supply line 12 is branched, and a matching device 13a and a first high-frequency for plasma generation (source) are connected to one branch line. A power source 14a is connected, and the other branch line is connected to a matching unit 13b and a second high-frequency power source 14b for bias application. For example, 13.56 MHz high frequency power for plasma generation is applied to the base material 5 from the first high frequency power supply 14a, whereby the substrate mounting table 4 functions as a lower electrode. Further, a high frequency power of, eg, 3.2 MHz for bias is applied to the base material 5 from the second high frequency power supply 14b, and thereby ions in the plasma can be effectively drawn into the substrate G. Note that a single high-frequency power source that combines plasma generation and bias application may be provided. A DC power source 15 is connected to the adsorption electrode 6a, and a DC voltage is applied to the adsorption electrode 6a so that the substrate G is adsorbed on the mounting surface of the insulating member 6 by Coulomb force.

On the upper surface of the shield ring 7, hydrogen gas (H ₂ gas) is discharged as a trap gas for trapping active species (radicals) in the plasma so as to surround the mounting surface of the substrate G on the entire circumference thereof. A trap gas discharge nozzle 16 having a frame shape is provided. A plurality of gas discharge ports 17 are formed on the entire upper surface of the trap gas discharge nozzle 16. A gas flow path 18 is connected to the trap gas discharge nozzle 16, and a trap gas supply source 19 for supplying hydrogen gas as a trap gas is connected to the other end of the gas flow path 18. Then, hydrogen gas, which is a trap gas, reaches the trap gas discharge nozzle 16 from the trap gas supply source 19 via the gas flow path 18 and is discharged from the plurality of gas discharge ports 17. Supplied to the periphery.

  The substrate mounting table 4 is provided with a plurality of lifter pins (not shown) for transferring the substrate G so as to protrude and retract with respect to the upper surface of the substrate mounting table 4 (that is, the upper surface of the insulating member 6). The transfer of the substrate G is performed with respect to the lifter pins in a state of protruding upward from the upper surface of the substrate mounting table 4.

  A shower head 20 that supplies a processing gas into the chamber 2 and functions as an upper electrode is provided above the chamber 2 so as to face the substrate mounting table 4. In the shower head 20, a gas diffusion space 21 for diffusing a processing gas is formed therein, and a plurality of discharge holes 22 for discharging the processing gas are formed on the lower surface or the surface facing the substrate mounting table 4. The shower head 20 is grounded, and forms a pair of parallel plate electrodes together with the substrate mounting table 4.

  A gas inlet 24 is provided on the upper surface of the shower head 20, and a processing gas supply pipe 25 is connected to the gas inlet 24. A processing gas supply source 28 is connected to the processing gas supply pipe 25. ing. The processing gas supply pipe 25 is provided with a valve 26 and a mass flow controller 27. A processing gas for etching is supplied from the processing gas supply source 28. As the processing gas, a processing gas generally used in this field can be used, and an optimum material is used depending on a film to be processed. As such a processing gas, a gas containing at least one of F, Cl, and O can be typically used. Each of these forms active species (radicals) containing highly reactive F, Cl, and O.

  Exhaust pipes 29 (only two are shown) are connected to the four corners of the bottom wall of the chamber 2, and an exhaust device 30 is connected to the exhaust pipe 29, and a pressure regulating valve (not shown) is provided. The exhaust device 30 includes a vacuum pump such as a turbo molecular pump, and is configured to be able to evacuate the chamber 2 to a predetermined reduced pressure atmosphere. A loading / unloading port 31 for loading / unloading the substrate G is formed on the side wall of the chamber 2, and a gate valve 32 for opening / closing the loading / unloading port 31 is provided. The substrate G is carried in and out of the chamber 2 by the transfer means.

  The plasma etching apparatus 1 also includes a control unit 40 having a process controller including a microprocessor (computer) for controlling each component of the plasma etching apparatus 1. The control unit 40 includes a keyboard for performing an input operation such as command input for managing the plasma etching apparatus 1 by an operator, a user interface including a display for visualizing and displaying the operating status of the plasma etching apparatus 1, and plasma A control program for realizing various processes executed by the etching apparatus 1 under the control of the process controller, and a program for causing each component of the plasma processing apparatus to execute processes according to the processing conditions, that is, a processing recipe are stored. And a storage unit. The processing recipe is stored in a storage medium in the storage unit. The storage medium may be a hard disk or semiconductor memory built in the computer, or may be portable such as a CDROM, DVD, or flash memory. Moreover, you may make it transmit a recipe suitably from another apparatus via a dedicated line, for example. Then, if necessary, a desired process in the plasma etching apparatus is performed under the control of the process controller by calling an arbitrary process recipe from the storage unit according to an instruction from the user interface and causing the process controller to execute it. Is called.

Next, a processing operation in the plasma etching apparatus 1 having the above configuration will be described. The following processing operations are performed under the control of the control unit 40.
First, the inside of the chamber 2 is evacuated by the exhaust device 30 to a predetermined pressure, the gate valve 32 is opened, and a transfer means (not shown) is held from a transfer chamber (not shown) held in an adjacent vacuum via the loading / unloading port 31. (Not shown), the substrate G is carried in, the lifter pin (not shown) is raised, the substrate G is received thereon, and the lifter pin is lowered to place the substrate G on the substrate platform 4. After the transfer means is retracted from the chamber 2, the gate valve 32 is closed.

  In this state, the processing gas is supplied from the processing gas supply source 28 into the chamber 2 through the processing gas supply pipe 25 and the shower head 20, and the pressure in the chamber 2 is adjusted to a predetermined degree of vacuum by the pressure adjustment valve. To do.

  Then, a high frequency power for plasma generation is applied from the first high frequency power supply 14a to the substrate mounting table 4 (base material 5) via the matching unit 13a, and the substrate mounting table 4 as the lower electrode and the shower head as the upper electrode. A high-frequency electric field is generated between the chamber 20 and the processing gas in the chamber 2 is turned into plasma. Further, a high frequency power for bias is applied from the second high frequency power supply 14b to the substrate mounting table 4 (base material 5) via the matching unit 13b, and ions in the plasma are effectively drawn into the substrate G. At this time, by applying a DC voltage from the DC power source 15 to the adsorption electrode 6a, the substrate G is adsorbed and fixed on the mounting surface of the substrate mounting table 4 (insulating member 6) by plasma using Coulomb force.

  Thereby, the plasma etching process with respect to the predetermined film | membrane of the board | substrate G advances. At this time, as the processing gas, an optimum material is used depending on the film to be processed. A gas containing at least one kind can be used.

  In the plasma etching process, a large amount of unreacted process gas exists in the peripheral part of the substrate G. Therefore, if the etching target film has high chemical reactivity, the loading effect causes the peripheral part of the substrate G to have a high chemical reactivity. Etching rate becomes high.

Therefore, in the present embodiment, hydrogen gas is used as a trap gas for trapping active species (radicals) in the plasma, and a plurality of gases provided from the trap gas supply source 19 to the trap gas discharge nozzle 16 via the gas flow path 18. The liquid is supplied from the discharge port 17 to the periphery of the substrate G. As a result, active species (radicals) are trapped in the periphery of the substrate G. Specifically, when active species (radicals) containing highly reactive F, Cl, and O are present, these react with hydrogen gas around the substrate G to react with HF, HCl, and H ₂ O. Such components do not contribute to the etching and are discharged from the chamber 2. For this reason, the amount of active species (radicals) is reduced in the peripheral portion of the substrate G where the etching rate is high, the etching rate is lowered, and the etching rate is made uniform in the plane of the substrate G.

  As described above, when active species (radicals) containing highly reactive F, Cl, and O are used, by supplying hydrogen gas as a trap gas to the periphery of the substrate G, these active species (radicals) are trapped. However, even other hydrogen sources such as hydrogen radicals can function as a trap gas. In addition, a trap gas other than hydrogen can be used as long as it can generate a component that does not contribute to etching by reacting with active species (radicals).

  As the trap gas flow rate increases, the effect of trapping active species (radicals) increases. Therefore, the distribution of the etching rate of the substrate G can be controlled by controlling the trap gas flow rate. In this case, it is preferable that the trap gas flow rate is such that the atomic weight of the trap gas is 17 to 80% with respect to the atomic weight of the active species.

As a specific example, when etching an amorphous silicon (a-Si) film, SF ₆ gas can be suitably used as a processing gas. However, when hydrogen (H ₂ ) gas is used as a trap gas, active species are used. It is preferable to supply hydrogen gas at a flow rate such that the H atomic weight is 40 to 80% with respect to the F atomic weight which is (radical). In addition, in the etching of the SiN _x film, a mixed gas of SF ₆ gas and oxygen (O ₂ ) gas can be suitably used as a reactive species, but when hydrogen (H ₂ ) gas is used as a trap gas, It is preferable to supply hydrogen gas at a flow rate such that the H atomic weight is 17.1 to 4.3.3% with respect to the atomic weights of F and O which are active species (radicals). Further, when etching the Al film, BCl ₃ and Cl ₂ can be preferably used. However, when hydrogen (H ₂ ) gas is used as a trap gas, the amount of Cl atoms as active species (radicals) is reduced. It is preferable to supply hydrogen gas at a flow rate such that the H atomic weight is 40 to 80%.

  After the processing is completed, the first high-frequency power supply 14a and the second high-frequency power supply 14b are turned off, the power supply to the suction electrode 6a is stopped to release the electrostatic suction, and the substrate G is removed by lift pins (not shown). The substrate G is lifted up, the gate valve 32 is opened, and the processed substrate G is unloaded from the loading / unloading port 31.

  In this embodiment, a trap gas for trapping active species (radicals) is supplied to the peripheral portion of the substrate G, and the amount of active species (radicals) in the peripheral portion of the substrate G is reduced. Plasma etching with high in-plane uniformity can be performed at a reduced rate. As described above, the etching rate of the peripheral portion of the substrate G can be reduced without using a rectifying wall or a sacrificial material. Therefore, according to the type of etching target film and the etching conditions (recipe) when the rectifying wall is used. Problems such as the need to optimize the rectifying wall, troubles and costs due to periodic replacement when using sacrificial materials, and processing multiple etching layers that are both problematic The problem of affecting other etching target films can be solved.

  The supply form of the hydrogen gas as the trap gas is not limited to the form shown in FIG. For example, as shown in FIG. 4, the trap gas discharge nozzle 16 may be attached to the side surface of the shield ring 7, and as shown in FIG. 5, the trap gas discharge nozzle 16 is placed on the outer periphery of the shower head 20. The hydrogen gas may be supplied to the peripheral portion of the substrate G from above the substrate G.

<Second Embodiment>
Next, a second embodiment of the present invention will be described.
FIG. 6 is a sectional view showing a plasma etching apparatus as a plasma processing apparatus according to the second embodiment of the present invention.

  As shown in FIG. 6, this plasma etching apparatus 1 'is configured as an inductively coupled plasma etching apparatus. In FIG. 6, the same reference numerals are given to the same parts as those in FIG. 1 to simplify the description.

In the chamber 2 ′ of the plasma etching apparatus 1 ′, the top wall 52 is made of a dielectric material such as ceramics or quartz such as Al ₂ O ₃ , and a processing gas supply is provided in a lower portion of the top wall 52. The structure is the same as that of the chamber 2 except that a shower casing 51 having a cross shape is fitted.

  The shower housing 51 is made of a conductive material, for example, anodized aluminum. The shower casing 51 is formed with a gas channel 53 extending horizontally, and a plurality of gas discharge holes 54 extending downward are communicated with the gas channel 53. On the other hand, a gas inlet 24 is provided at the center of the top surface of the top wall 52, and a processing gas supply pipe 25 is connected to the gas inlet 24 as in the apparatus of FIG. A processing gas supply source 28 is connected to the.

  A radio frequency (RF) antenna 55 is provided along the top surface of the ceiling wall 52, and a feeding line 56 is connected to the high frequency antenna 55, and the matching line 57 and plasma generation (source) are connected to the feeding line 56. The first high-frequency power source 58 is connected. When a high frequency power having a frequency of 13.56 MHz, for example, is supplied from the first high frequency power supply 58 to the high frequency antenna 55, an induction electric field is formed in the chamber 2 ', and is discharged from the shower casing 51 by this induction electric field. The processed gas is turned into plasma.

  On the other hand, a power supply line 12 is connected to the base material 5 of the substrate mounting table 4, and only the matching unit 13 b and the second high frequency power supply 14 b for applying bias are connected to the power supply line 12.

  In such a plasma etching apparatus 1 ′, the substrate G is placed on the substrate mounting table 4 in the same manner as in the first embodiment, and the processing gas supply source 28, the processing gas supply pipe 25, and the shower casing 51 are placed. The processing gas is supplied into the chamber 2 'through the pressure and the pressure in the chamber 2' is adjusted to a predetermined degree of vacuum by the pressure adjusting valve. Next, high-frequency power is applied from the first high-frequency power source 58 to the high-frequency antenna 55, thereby forming an induction electric field in the chamber 2 ′ via the top wall 52 made of a dielectric. Due to the induction electric field thus formed, the processing gas is turned into plasma in the chamber 2 ′, high-density inductively coupled plasma is generated, and the substrate G is subjected to plasma etching. At this time, high-frequency power for bias is applied from the second high-frequency power source 14b to the substrate mounting table 4 (base material 5) via the matching unit 13b, and ions in the plasma are effectively drawn into the substrate G, and the DC power source By applying a DC voltage from 15 to the attracting electrode 6a, the substrate G is attracted and fixed to the placing surface of the substrate placing table 4 (insulating member 6) by Coulomb force via plasma.

  Even when etching is performed by such inductively coupled plasma, a large amount of unreacted processing gas exists in the periphery of the substrate G. Therefore, if the etching target film has high chemical reactivity, the loading effect causes the substrate G to be etched. The etching rate in the peripheral part of the film becomes high.

  Therefore, as in the first embodiment, hydrogen gas is supplied to the peripheral portion of the substrate G as a trap gas for trapping active species (radicals) in the plasma. As a result, active species (radicals) are trapped in the periphery of the substrate G. For this reason, the amount of active species (radicals) is reduced in the peripheral portion of the substrate G where the etching rate is high, the etching rate is lowered, and the etching rate is made uniform in the plane of the substrate G.

<Experimental example>
Next, experimental examples will be described.
(Experimental example 1)
Here, as shown in FIG. 7, in a capacitively coupled plasma etching apparatus that etches a 550 × 650 mm substrate, hydrogen gas is discharged in a range of 500 mm to a portion corresponding to the shield ring on the short side of the substrate mounting table. A gas discharge nozzle 16 is provided, and the following film etching process is performed with a predetermined process gas while supplying hydrogen gas at a predetermined flow rate from a plurality of gas discharge ports formed in the gas discharge nozzle. At this time, the distribution of the etching rate from the edge of the substrate where hydrogen gas was supplied to the center of the substrate was measured.

· The a-Si film etching F radical susceptible a-Si film the influence of the base condition as follows, was etched by hydrogen gas _{(H 2} gas) flow rate is varied in 0,25,50Sccm.

Base conditions Pressure: 60mTorr
Source power: 3000W
Bias power: 300W
Process gas and flow rate:
SF ₆ 100 sccm
Ar 200sccm

FIG. 8 shows the distribution of the etching rate when such an a-Si film is etched.
As shown in this figure, when etching is performed by the conventional method without supplying H ₂ gas, the etching rate of the outer peripheral portion of the substrate becomes very high, and the uniformity (variation) of the etching rate is 17.9%. It was. On the other hand, by supplying H ₂ gas to the periphery of the substrate, it is possible to control only the etching rate at the outer periphery of the substrate without substantially affecting the etching rate to the center, and the flow rate of H ₂ gas is increased. It turns out that the etching rate of a board | substrate outer peripheral part falls so that it is so. When the H ₂ gas flow rate is 25 sccm, the uniformity (variation) of the etching rate becomes very small at 5.8%. When the H ₂ gas flow rate is 50 sccm, the etching rate at the outer periphery of the substrate further decreases, and the uniformity (variation) increases to 17.2%. It can be made lower than the etching rate at the center of the substrate, and it can be seen that the etching distribution can be controlled by the H ₂ flow rate.

SiN _x film etching For SiN _x films that are easily affected by F radicals and O radicals, etching was performed with the base conditions set as follows and the hydrogen gas (H ₂ gas) flow rate varied between 0, 25, and 50 sccm. .

Base conditions Pressure: 60mTorr
Source power: 3000W
Bias power: 300W
Process gas and flow rate:
SF ₆ 200sccm
O ₂ 100 sccm

FIG. 9 shows an etching rate distribution during etching of such a SiN _x film.
As shown in this figure, when etching is performed by a conventional method without supplying H ₂ gas, the etching rate of the outer peripheral portion of the substrate becomes very high, and the uniformity (variation) of the etching rate is 15.8%. It was. On the other hand, by supplying H ₂ gas to the periphery of the substrate, it is possible to control only the etching rate at the outer periphery of the substrate without substantially affecting the etching rate to the center, and the flow rate of H ₂ gas is increased. It turns out that the etching rate of a board | substrate outer peripheral part falls so that it is so. When the H ₂ gas flow rate is 50 sccm, the uniformity (variation) in the etching rate is very small at 5.3%. The effect is large even when the H ₂ gas flow rate is 25 sccm, and the uniformity (variation) is 6.4%.

· The Al film etching Cl radical sensitive Al film, the base condition as follows, was etched by hydrogen gas _{(H 2} gas) flow rate is varied in 0,50,100Sccm.

Base conditions Pressure: 20 mTorr
Source power: 1500W
Bias power: 50W
Process gas and flow rate:
BCl ₃ 200 sccm
Cl ₂ 300 sccm

FIG. 10 shows the etching rate distribution during the etching of such an Al film.
As shown in this figure, when etching is performed by a conventional method in which H ₂ gas is not supplied, the etching rate of the outer peripheral portion of the substrate becomes very high, and the uniformity (variation) of the etching rate is 34.0%. It was. On the other hand, by supplying H ₂ gas to the peripheral portion of the substrate, the etching rate of the outer peripheral portion of the substrate can be controlled, and the etching rate of the outer peripheral portion of the substrate decreases as the flow rate of H ₂ gas increases. I understand. It can be seen that the uniformity (variation) of the etching rate is greatly improved to 19.5% when the H ₂ gas flow rate is 100 sccm. Even when the H ₂ gas flow rate is 50 sccm, the uniformity (variation) is 28.8%, and an improvement effect is obtained. Although the rectifying wall is often used for Al films that are susceptible to loading, it has been confirmed that the uniformity can be improved without supplying a rectifying wall by supplying H ₂ gas as a trap gas to the periphery of the substrate. It was done.

(Verification of trap gas supply)
Next, a result of verifying an appropriate range of the trap gas supply amount with respect to the processing gas flow rate from the above results will be described.
The above results were obtained by providing a gas discharge nozzle that discharges H ₂ gas, which is a trap gas, on one side of the substrate, and grasping the influence of the trap gas on the etching rate by supplying H ₂ gas, which is a trap gas, from there. In reality, however, the supplied processing gas is discharged from the central portion of the substrate through four sides (2400 mm perimeter). For this reason, the following verification has taken a method of calculating the trap gas flow rate that is required relative to the processing gas by converting the processing gas amount per side where the trap gas is supplied.

In addition, the above results are obtained by reacting F, Cl, O, which are highly reactive reactive species (active species) in the processing gas, with H ₂ gas, which is a trap gas supplied to the periphery of the substrate. It is considered that a compound that does not contribute to etching, such as HF, HCl, and H ₂ O, is discharged from the chamber to reduce the reactive species in the periphery of the substrate. In fact, as shown in the emission spectrum of plasma around the substrate when the a-Si film is etched in FIG. 11, the emission of H having a wavelength of 656.5 nm increases as the flow rate of H ₂ gas increases. The emission of F with a wavelength of 704 nm decreases. Therefore, the following verification results are based on this point.

-Etching of a-Si film In the above experimental example, SF ₆ gas is used as a processing gas at 100 sccm. Therefore, if all the gas is dissociated by plasma, the volume is 7 times, and the volume flow rate is 100 sccm for S and 600 sccm for F. It will be said that. Further, as described above, since the processing gas supplied to the substrate is exhausted through the four sides, if the entire circumference of the substrate is 2400 mm, the converted amount of F per 500 mm of the substrate side is 125 sccm. On the other hand, since H ₂ gas as a trap gas is 25 to 50 sccm, when all of them are dissociated, the volume is doubled and H is 50 to 100 sccm. When converted to the atomic weight ratio, the H atomic weight is in the range of 40 to 80% with respect to the F atomic weight.

Etching of SiN _x film In the above experimental example, SF ₆ gas is used as a processing gas at 200 sccm and O ₂ gas is used at 100 sccm. Therefore, assuming that these are all dissociated by plasma, S is 200 sccm and F is 1200 sccm. , O is 200 sccm, and the volume flow rate of F and O is 1400 sccm. Therefore, the converted amount of active species (radicals) per 500 mm side of the substrate is 291.7 sccm. On the other hand, since the _{H 2} gas is trapped gas is 25～50Sccm, when they are dissociated all, H is 50～100Sccm. When converted to the atomic weight ratio, the H atomic weight is in the range of 17.1 to 4.3.3% with respect to the active species (radical) atomic weight.

-Etching of Al film In the above experimental example, 200 sccm of BCl ₃ gas and 300 sccm of Cl ₂ gas are used as the processing gas. If these are all dissociated by plasma, the volume flow rate of Cl is 1200 sccm. . Therefore, the converted amount of Cl per 500 mm side of the substrate is 250 sccm. On the other hand, since the _{H 2} gas is trapped gas is 50～100Sccm, when they are dissociated all, H is 100～200Sccm. When converted to the atomic weight ratio, the H atomic weight is in the range of 40 to 80% with respect to the Cl atomic weight.

In the above experimental example, the processing gas amount was converted into the atomic flow rate supplied per substrate side, and the relatively required trap gas flow rate was calculated. Actually, since the trap gas supply area is installed around the substrate, the necessary trap gas flow rate can be defined relative to the processing gas input amount.
From the above, H ₂ which is a trap gas so that the ratio of the H atomic weight is within a range of 17 to 80% with respect to the atomic weight of F, Cl, O in the processing gas supplied per unit time. It was confirmed that supplying the gas was effective in controlling the etching rate in the peripheral portion of the substrate.

(Experimental example 2)
Next, a description will be given of the result of an experiment assuming an actual process using a capacitively coupled plasma etching apparatus having the same configuration as that of FIG. The substrate size is 730 × 920 mm, and the trap gas is supplied around the substrate.

Here, an experiment was performed assuming LTPS (low temperature polysilicon) contact etching. The low temperature polysilicon contact etching is performed on a laminated structure in which a SiO ₂ film 102, a SiN _x film 103, and a SiO ₂ film 104 are laminated on a polysilicon (p-Si) film 101 as shown in FIG. Conventionally, in the etching of the polysilicon layer, the etching distribution at the outer peripheral portion is high, and the polysilicon film is likely to be etched off at the outer peripheral portion of the substrate. Therefore, in this experimental example, with respect to the a-Si film having the etching characteristics equivalent to those of the SiO ₂ film, the SiN _x film, and the polysilicon film, H ₂ gas is supplied from the shower head together with other gases, and H ₂ Etching was performed under the following conditions when the gas was supplied as a trap gas to the periphery of the substrate.

Etching conditions Pressure: 10 mTorr
Source power: 5000W
Bias power: 5000W
Process gas and flow rate (shower head):
C ₄ F ₈ 60 sccm
Ar 100sccm
H ₂ 100 sccm, 0 sccm
Trap gas (H ₂ gas) flow rate (substrate periphery): 0 sccm, 100 sccm
In this case, the ratio of the atomic weight of H, which is a trap gas, to the atomic weight of F, which is an active species, is 41.7%.

The distribution of the etching rate (etching amount) at the time of etching these films is shown in FIGS. FIGS. 13 and 14 show the results of the SiO ₂ film and the SiN _x film, respectively, and the in-plane uniformity of the etching rate is good regardless of whether or not the H ₂ gas is supplied to the periphery of the substrate. On the other hand, FIG. 15 shows the result of the a-Si film. When H ₂ gas was not supplied to the peripheral portion of the substrate, the etching rate at the outer peripheral portion of the substrate increased and the in-plane uniformity of the etching rate was 44%. However, the uniformity was significantly improved to 10% by supplying H ₂ gas to the periphery of the substrate.

Therefore, by supplying H ₂ gas as a trap gas to the periphery of the substrate, the etching of the SiO ₂ film and the SiN _x film is hardly affected, the chemical reactivity is strong, and the etching rate of the outer periphery of the substrate is increased. It was confirmed that only the high a-Si film can improve the etching distribution. Therefore, it can be said that this method is a very effective method for the etch-off of the polysilicon film that is likely to occur at the outer peripheral portion of the substrate in LTPS (low temperature polysilicon) contact etching.

(Experimental example 3)
Next, an inductively coupled plasma etching apparatus having the same configuration as in FIG. 6 except that a trap gas supply nozzle for supplying H ₂ gas as a trap gas is provided on the side surface of the shield ring as shown in FIG. The results of etching will be described. The substrate size is 1850 × 1500 mm.

Also in this experimental example, an experiment was performed assuming LTPS (low temperature polysilicon) contact etching. Specifically, C ₂ HF ₅ gas, H ₂ gas, and Ar gas were used as the processing gas, and the etching distribution of the SiO ₂ film and the Si film with or without the H ₂ gas as the trap gas was investigated.

The result is shown in FIG. FIG. 16 shows the etching rate of a quarter portion of the substrate, C is the center of the substrate, LC is the center of the long side, SC is the center of the short side, and Edge is the corner of the substrate. FIG. 16A shows the result of etching without using a trap gas, with the processing gas being C ₂ HF ₅ : 300 sccm, H ₂ : 180 sccm, and Ar: 240 sccm. FIGS. 16B and 16C show the results of eliminating H ₂ : 180 sccm in the processing gas and letting it flow out of the trap gas discharge nozzle in the periphery of the substrate. Note that the ratio of the atomic weight of H, which is a trap gas, to the atomic weight of F, which is an active species, in the cases of FIGS. 16B and 16C is 24% and 72%.

As shown in FIG. 16A, when the H ₂ gas as the trap gas is not supplied to the peripheral portion of the substrate, the etching distribution of the SiO ₂ film is relatively uniform, but the etching rate of the outer peripheral portion of the substrate is the Si film. Is high. On the other hand, in FIGS. 16B and 16C in which H ₂ gas contained in the processing gas of FIG. 16A is supplied as a trap gas to the periphery of the substrate, the Si film is not disturbed in the etching distribution of the SiO ₂ film. The etching distribution has been improved. Further, it was confirmed that the effect was greater in (c) at 540 sccm than in (b) where the flow rate of H ₂ gas to the peripheral portion of the substrate was 180 sccm.

  In the case of etching a laminated film including a highly chemical etching target film, the etching should be performed with a recipe that supplies a trap gas only to a film etching step that requires control of the etching rate on the outer periphery of the substrate. It can also be.

  The present invention can be variously modified without being limited to the above embodiment. For example, in the above-described embodiment, the plasma etching is described as an example of the plasma processing.

  In the above embodiment, the capacitively coupled type and inductively coupled plasma processing apparatuses are exemplified. However, the present invention is not limited to this, and plasma can be generated by other methods such as microwave plasma as long as plasma can be generated in the chamber. It may be a device that performs.

Furthermore, the trap gas is not limited to H ₂ gas, but may be any gas that can be trapped by reacting with active species such as radicals. The etching target film is not limited to that in the above embodiment.

  Furthermore, in the above-described embodiment, an example in which the present invention is applied to a glass substrate for FPD has been described. However, it is needless to say that the present invention can be applied to other substrates such as a semiconductor substrate.

1,1 '; Plasma etching equipment (plasma processing equipment)
2, 2 '; Chamber (processing vessel)
4; Substrate mounting table 5; Base material 6; Insulating member 7; Shield rings 14a and 58; First high frequency power supply 14b; Second high frequency power supply 16; Trap gas discharge nozzle 17; Gas discharge port 18; Trap gas supply source 20; Shower head 25: Process gas supply pipe 28: Process gas supply source 29: Exhaust pipe 30: Exhaust device 31; Loading / unloading port 40; Control unit 55; High-frequency antenna G; Substrate

Claims (19)

A plasma processing apparatus for performing plasma processing on a substrate,
A processing container for accommodating a substrate and performing plasma processing;
A substrate mounting table for mounting the substrate in the processing container;
A processing gas supply mechanism for supplying a processing gas into the processing container;
An exhaust mechanism for exhausting the inside of the processing container;
Plasma generating means for generating plasma of the processing gas in the processing container;
A plasma processing apparatus comprising: a trap gas supply mechanism that supplies a trap gas for trapping active species in the plasma to a peripheral portion of the substrate on the substrate mounting table.   The plasma processing apparatus according to claim 1, wherein the plasma processing is a plasma etching processing.   The plasma processing apparatus according to claim 2, wherein the processing gas is a gas containing at least one of F, Cl, and O, and the trap gas is hydrogen gas.   The plasma processing apparatus according to claim 2, wherein a ratio of the number of atoms of the trap gas to the number of atoms of the active species in the processing gas is 17 to 80%. 5. The plasma processing apparatus according to claim 3, wherein an etching target of the plasma etching process is any one of a Si film, a SiN _x film, and an Al film formed on a substrate.   6. When the etching target is a Si film, F is used as an active species, and the ratio of the number of atoms of the trap gas to the number of atoms of the active species in the processing gas is 40 to 80%. The plasma processing apparatus according to 1. When the etching target is a SiN _x film, F and O are used as active species, and the ratio of the number of atoms of the trap gas to the number of atoms of the active species in the processing gas is 17.1 to 4.3.3%. The plasma processing apparatus according to claim 5.   6. When the etching target is an Al film, Cl is used as an active species, and the ratio of the number of atoms of the trap gas to the number of atoms of the active species in the processing gas is 40 to 80%. The plasma processing apparatus according to 1.   The plasma processing apparatus according to claim 1, wherein the trap gas supply mechanism is provided around a substrate of the substrate mounting table.   The processing gas supply mechanism has a shower head that supplies the processing gas in a shower shape toward the substrate on the substrate mounting table in the processing container, and the trap gas supply mechanism is provided around the shower head. The plasma processing apparatus according to claim 1, wherein the plasma processing apparatus is provided. A plasma processing method for performing plasma processing on a substrate,
In a state where the substrate is placed on the substrate mounting table in the processing container, a processing gas is supplied into the processing container, plasma of the processing gas is generated in the processing container, and plasma processing is performed on the substrate. And a trap gas for trapping active species in the plasma is supplied to a peripheral portion of the substrate.   The plasma processing method according to claim 11, wherein the plasma processing is a plasma etching processing.   The plasma processing method according to claim 12, wherein the processing gas is a gas containing at least one of F, Cl, and O, and the trap gas is a hydrogen gas.   14. The plasma processing method according to claim 12, wherein a ratio of the number of atoms of the trap gas to the number of atoms of the active species in the processing gas is 17 to 80%. The plasma processing method according to claim 13 or 14, wherein an etching target of the plasma etching processing is any one of a Si film, a SiN _x film, and an Al film formed on a substrate.   16. When the etching target is a Si film, F is used as an active species, and the ratio of the number of atoms of the trap gas to the number of atoms of the active species in the processing gas is 40 to 80%. The plasma processing method as described in any one of Claims 1-3. When the etching target is a SiN _x film, F and O are used as active species, and the ratio of the number of atoms of the trap gas to the number of atoms of the active species in the processing gas is 17.1 to 4.3.3%. The plasma processing method according to claim 15.   16. When the etching target is an Al film, Cl is used as an active species, and the ratio of the number of atoms of the trap gas to the number of atoms of the active species in the processing gas is 40 to 80%. The plasma processing method as described in any one of Claims 1-3.   A storage medium that operates on a computer and stores a program for controlling a plasma processing apparatus, wherein the program performs the plasma processing method according to any one of claims 11 to 18 at the time of execution. And a computer that controls the plasma processing apparatus.