JPH0992643A - Plasma treating device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To selectively supply a chemical seed required for a plasma treatment to a substrate and to increase treatment speed and improve a treatment shape by providing a filter at a site where a means for introducing a source gas to a discharge room and a vacuum bath which is connected to the discharge room and where a substrate is placed inside are connected. SOLUTION: A down flow etching device generates plasma in a discharge room 103 where a process gas 101 is introduced by a gas storage 101 using microwave generated by a microwave power supply 102 and generates a charged particle or a chemical seed, where the excited chemical seed flows into a vacuum bath 104 for treating a substrate where a substrate to be treated is placed via a transportation pipe 107 in that a porous filter 108 is placed. The vacuum bath 104 is exhausted by an exhaust device 109. On the other hand, ions are reduced when passing the porous filter 108 and hence do not reach the vacuum bath 104, thus eliminating the need for providing a long transportation pipe and hence miniaturizing a device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus and a processing method, and more particularly to a plasma processing apparatus and a processing method capable of controlling the type and amount of excited chemical species.

[0002]

2. Description of the Related Art Conventionally, in a downflow etching apparatus which is a plasma processing apparatus, as shown in the apparatus configuration diagram of FIG.
In the discharge chamber 13, the kind of gas introduced into the discharge chamber and the flow rate of the gas are controlled by the gas reservoir 11 for introducing the chemical species generated by plasma. All the chemical species excited in the discharge chamber 13 are in the vacuum chamber 14 on which the substrate to be processed is placed.
Have been introduced to. Therefore, chemical species other than the chemical species effective for the etching process and the chemical species having the property of suppressing the etching are also supplied to the vacuum chamber 14, so that the etching performance such as high-speed etching and high selectivity is improved. Was stagnant.

For example, when oxygen (O ₂ ) is added to carbon tetrafluoride (CF ₄ ) in the etching of polycrystalline silicon, the etching rate increases until the O ₂ flow rate becomes equal to the CF ₄ flow rate. However, if O ₂ is added in the same amount or more, the etching rate will decrease. This is because as O ₂ is added, the number of chemical species effective in etching the polycrystalline silicon increases, but when the O ₂ flow rate is higher than the flow rate of CF ₄ , the chemical species forming a deposited film on the polycrystalline silicon etch. It is considered that the number of chemical species that is effective for is increased.

Further, CDE (Chemical Vapor Depos) using a chemical species as an etchant
in a plasma device such as an ion chamber) so that ions generated in the discharge chamber do not reach the substrate directly.
Since the transport pipe 17 between the vacuum chamber 3 and the vacuum chamber 14 was lengthened and bent several times, the entire apparatus was enlarged.

In addition, RIE (Reactive Ion)
Even in a plasma etching apparatus such as Etching), control of the type and amount of chemical species is important for achieving high selectivity and high speed. However, it is difficult to control the type of chemical species obtained by introducing a reactive gas into the vacuum vessel in which a wafer is introduced and generating plasma in the vacuum vessel as in the past, and it is difficult to control only the gas species and amount, and high selectivity is achieved. , Getting high speed was not easy.

[0006]

As described above, the conventional etching apparatus does not contribute to the etching process because the type of chemical species generated from plasma is controlled by controlling the type and flow rate of gas. Since chemical species are also supplied to the substrate to be treated, it is difficult to achieve high processing speed and high selectivity.

The present invention has been made in consideration of the above circumstances, and is a plasma processing apparatus capable of selectively and efficiently supplying chemical species necessary for plasma processing to a substrate, achieving a high processing speed and obtaining a good processing shape. Another object of the present invention is to provide a plasma processing method.

[0008]

In order to solve the above-mentioned problems, the present invention is connected to a discharge chamber for generating plasma, means for introducing a source gas into the discharge chamber and the discharge chamber, and a substrate to be treated is provided inside. There is provided a plasma processing apparatus comprising: a vacuum chamber to be placed and a filter provided at a portion where the discharge chamber and the vacuum chamber are connected to each other.

In this plasma processing apparatus, it is preferable to provide means for controlling the temperature of the filter in order to more appropriately control the chemical species introduced into the vacuum chamber. Also,
A means for generating plasma may be provided in the vacuum chamber.

Further, the above filter is preferably a porous filter having a large surface area. Furthermore, the surface of the filter is preferably made of a material whose main component is carbon.

In order to solve the above problems, the second aspect of the present invention is to introduce a source gas into the discharge chamber, generate plasma in the discharge chamber, and excite chemical species from the source gas. And a step of introducing the excited chemical species into a vacuum chamber through a filter.

[0012]

FIG. 1 is a schematic configuration diagram of a downflow etching apparatus which is an embodiment of a plasma processing apparatus of the present invention. This device is equipped with a microwave power source 102
Gas sump 101 using microwaves generated at
Plasma is generated in the discharge chamber 103 into which the process gas 101 is introduced, and charged particles and chemical species are generated.
The chemical species excited here have a hole diameter of 10 μm and a thickness of 100 μm.
Transport pipe 10 in which a porous filter 105 having the inner hole surface covered with a material containing carbon as a main component having the above holes is installed.
It is configured to flow into the vacuum chamber 104 for processing the substrate on which the substrate to be processed is placed via 7. The vacuum chamber 104 is exhausted by an exhaust device 109.

On the other hand, the ions disappear when passing through the porous filter 108 and do not reach the vacuum chamber 104.
Therefore, it is not necessary to record a long transport pipe 17 as in the conventional case, which can contribute to downsizing of the device. It is possible to control the composition of the chemical species so as to improve the etching performance with respect to the substrate 105 that is etched by the porous filter 108.

In order to show the effect of this embodiment,
FIG. 2 shows the results of measuring the etching characteristics of polycrystalline silicon in the conventional downflow etching apparatus without the porous filter 108 shown in FIG. 8 and the downflow etching apparatus with the porous filter 108.
The partial pressure of carbon tetrafluoride was 0.12 Torr and the microwave power was 1 kW. Carbon tetrafluoride and oxygen were used as process gases, and the flow rate of carbon tetrafluoride was kept constant and the flow rate of oxygen was increased. An etching rate in a conventional downflow etching apparatus in which a porous filter is not installed is shown by a one-dot chain line, and an etching rate according to this embodiment is shown by a solid line in FIG. According to the conventional apparatus, when the oxygen flow rate is increased, the etching rate increases, but it decreases when the flow rate with carbon tetrafluoride becomes equal to the flow rate of oxygen. According to the present embodiment, the etching rate does not decrease but gradually increases, and particularly when P _o2 / P _CF4 is 2 to 3, high-speed etching of 2000 Å / min is possible. Further, when P _o2 / P _CF4 is about 1.5 or more, a high speed which cannot be achieved by the conventional technique is obtained.

FIG. 3 is a schematic diagram of a downflow etching apparatus used for CDE which is an embodiment of the plasma processing apparatus of the present invention. This device is equipped with a microwave power source 10
Plasma is generated in the discharge chamber 103 into which gas is introduced from the gas source 101 by the microwave generated in 2 to generate charged particles and chemical species. The chemical species generated here flow into a vacuum chamber 104 for processing a substrate through a transport pipe 107 in which a porous filter 108 made of an insulating material having a hole diameter of 10 μm and a thickness of 100 μm is installed. On the other hand, C
Unwanted ions in DE disappear due to the porous filter 108 and do not reach the vacuum chamber 104. With this porous filter 108, it is possible to control the composition of chemical species so as to improve the etching performance.

In this embodiment, the hole diameter is 10 μm and the heat is 10
The temperature control means 110 is provided in the porous filter 108 in which the inner pore surface of the 0 nm pore is covered with a material containing carbon as a main component. The temperature of the filter 108 is controlled in order to further publicize the relative ratio of chemical species passing through the porous filter 108. FIG. 4 shows the relative ratio of the chemical species when carbon tetrafluoride and oxygen are used as the process gas and the temperature of the filter is set to 25 degrees and -50 degrees. Chemical species that are effective in etching by lowering the filter temperature, such as F and CF
It was possible to increase ₃ and reduce CF and CF ₂ which are chemical species having a low effect on etching. FIG. 5 shows the dependence of the etching rate of polycrystalline silicon on the partial pressure ratio of oxygen and carbon tetrafluoride at this time. The solid line shows what was done with the porous filter set at -50 degrees, and the dotted line shows what was done with the porous filter set at 25 degrees. Here, the partial pressure ratio of carbon tetrafluoride is 0.12 Tortr, and the discharge chamber 103
The microwave power supplied to the device was 1 kW. As can be seen from this graph, by lowering the temperature of the porous filter 108, chemical species such as C and CF can be reduced and the etching rate can be improved.

FIG. 6 is a schematic diagram of a downflow etching apparatus showing an embodiment of the plasma processing apparatus of the present invention. This device is a device in which a porous filter 108 is installed in a vacuum chamber 104 for processing a substrate. By providing the outlet of the transport pipe 107 equipped with the porous filter corresponding to the size of the substrate 105 to be treated, it is possible to uniformly supply the chemical species to the substrate 105 to be treated so as to be spatially uniform. I can.

In this embodiment, the porous filter is made of n ⁺ type silicon having a high electron donating property. As a result, the adsorption probability is increased, and C or C that hinders etching
Eliminate F efficiently. For example, when using CF ₄ and O ₂ gas in the etching of polycrystalline silicon, F _{produced, C, CF, CF 2,} CF 3, contributes to the etching of the COF radicals F, CF _2, CF ₃ is Although it passes through the porous filter, C and CF that contribute to the deposition are adsorbed on the filter and the passing amount is reduced. Thus, the relative amount of chemical species effective for etching is increased and the etching rate is improved. Further, in the etching of the nitride film and the oxide film using CF ₄ , O ₂ , and N ₂ gas, the etching rate of the oxide film is also reduced, so that etching with a high selection ratio can be performed. This is because the silicon atoms on the nitride film are etched by the chemical species F and the chemical species CF _2, etc., and then the chemical species of N coming to the surface of the nitride film pull out the N remaining on the nitride film and desorb it as N _2. Therefore, silicon atoms again appear and etching progresses. Here, since the nitrogen atom has a low adsorption probability, it is hardly captured by the filter, and the etching rate does not decrease. On the other hand, in the case of an oxide film, the abstraction of oxygen atoms after the abstraction of silicon atoms is difficult to be performed by the chemical species N, and the chemical species C that should abstract oxygen atoms is reduced by the porous filter, so that etching is performed. It's hard to progress. Therefore, since the etching rate of the oxide film can be increased without decreasing the etching rate of the nitride film, it is possible to perform processing with a high selection ratio.

Fluorocarbon-based deposits adhering to the filter generate oxygen plasma and can be cleaned by keeping the filter temperature at 300.degree. FIG. 7 is a schematic configuration diagram of a plasma etching apparatus showing an embodiment of the plasma processing apparatus of the present invention.

In this apparatus, a parallel plate type lower electrode 206 is used.
The substrate 105 to be processed is placed on the
Wafer 105 by applying 0 KHz RF power from RF power supply
An electric field is generated on the surface that accelerates the ions. On the other hand, a porous filter 208 covered with a material containing carbon as a main component is installed on the electrodes facing each other and is kept at the ground potential. The porous filter 208 is used as the heater 20.
5 is heated to about 250 ° C. Further, a coil 201 is wound around the outer circumference of the vacuum container 104, and for example, 2
RF of 0 MHz is applied to induce plasma 202 in the vacuum container 104.

The processing method using this apparatus will be described below. First, as shown in FIG. 7B, the surface of the substrate 105 to be processed is a thick oxide film (SiO 2) formed on the Si substrate 301.
₂ ) 302 (about 1 μm) is processed using the resist 303 as a mask, and after etching the oxide film, a high selection ratio (etching rate of SiO ₂ 302 of Si 301 is set so that the underlying Si substrate 301 is not etched as much as possible). Thickness ratio) is required.

After subjecting C ₄ F ₈ and CO gas to μ discharge (plasma 204), they are introduced into a vacuum container through a filter 208. On the other hand, Ar gas is directly introduced into the vacuum container through the introduction port 203.

The mixed gas of C ₄ F 8 and CO is C ₂ F ₄ , CF, CF ₂ , CF ₃ ,
It is decomposed into ions and chemical species such as F, COF, C and O. In the downflow region away from the plasma, the ions quickly disappear and the active species are transported. This chemical species is introduced into the vacuum vessel through filter 208.

Since this filter is heated to 250 ° C. and the surface of its pores is covered with a material containing carbon as a main component, the active species collide with the inner wall many times in the pores when passing through the filter. CF ₂ , CF, C containing C here
_Although chemical species such as ₂ F ₄ pass through as they are, CF ₃ or F or O, which is a chemical species containing a large amount of F, reacts with C to form C ₂ F _2.
It becomes ₄ , CF, CO, etc. and is discharged to the vacuum container. As a result, the ratio of C introduced into the vacuum container 104 and contained in the chemical species increases.

In etching SiO ₂ , the chemical species C
F (χ = 1, 2, 3) is the main etching species and is included in the chemical species. Even if the proportion of C increases, the etching rate does not decrease. On the other hand, the etching rate of Si is determined by the amounts of F and CF ₃ in CF ₂ . F and CF ₃
This is because Si easily reacts with F to form SiF ₄ . On the other hand, when CF or CF ₂ reacts with Si, some Si
It forms a F ₄ leaving the C and CF on the Si surface, Si-
C, Si-CF is formed on the surface, and then CF or CF ₂ supplied causes a polymerization reaction on the surface to stop the etching. That is, the selection ratio can be improved by changing the chemical species to contain a large amount of C.

In the embodiment of the present invention, C ₄ F ₈ , CO, Ar
Gas flow rate of 15,120,150 SCCM
(Cc1 min), the pressure in the vacuum container is 60 mTorr,
20 MHz RF power 1.2 kW, 800 KHz RF power 500 W, wafer mounting electrode temperature 50 ° C. SiO
₂ Etching rate 5800 Å / min, Si
The etching rate was 50 Å / min, and the selectivity 116 was obtained. Here, when the temperature of the porous filter was at room temperature, the etching rate of Si increased and the selectivity fell to 5, and when the gas was supplied without passing through the filter, the selectivity was 40. Here, the reason why the selection ratio is lowered when a filter at room temperature is used is CF, CF
It is considered that radicals containing a large amount of C such as ₂ are adsorbed in the filter and are hardly supplied, whereas F and CF ₃ almost pass through the filter as they are.

By controlling the temperature of the filter as described above, the selection ratio can be arbitrarily controlled. The hole diameter of the porous filter 108 is preferably 0.1 μm or more and 10 μm or less, and the thickness thereof is preferably 10 μm or more and 50 mm or less.

Further, the shape of the filter is not limited to a porous one, and a plurality of mesh-like filters or plate-like substances are superposed and a chemical species is adsorbed between the plates. Any filter having a surface with which it can collide may be used.

Further, since the transport pipe 107 is not provided, the discharge chamber 1
03 and the vacuum chamber 104 are directly connected to communicate with each other, and a device in which a filter 208 is provided at the connecting portion is also included in the present invention.

The present invention is not limited to the form applied to the above etching apparatus. In addition to the etching apparatus, a chemical species is used for processing and it is necessary to control the type and amount of the chemical species, for example, CVD (Chemical).
It can also be applied to the al Vapor Deposition) method and the like.

[0031]

According to the plasma processing apparatus of the present invention, since the relative ratio of the chemical species from the plasma can be controlled to a desired ratio, the processing speed can be increased and an excellent processing shape can be obtained. .

[Brief description of drawings]

FIG. 1 is a device configuration diagram for describing a first embodiment of the present invention.

FIG. 2 is an etching characteristic diagram for explaining the first embodiment of the present invention.

FIG. 3 is an apparatus configuration diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram showing a relative ratio of chemical species for explaining a second embodiment of the present invention.

FIG. 5 is an etching characteristic diagram for explaining the second embodiment of the present invention.

FIG. 6 is a device configuration diagram for explaining a third embodiment of the present invention.

FIG. 7 is a device configuration diagram for explaining a fourth embodiment of the present invention.

FIG. 8 is an apparatus configuration diagram for explaining a conventional plasma processing apparatus.

[Explanation of symbols]

11, 101 ... Process gas 12, 102 ... Microwave power source 13, 103 ... Discharge chamber 14, 104 ... Vacuum tank 15, 105 ... Substrate to be treated 16, 106, 206 ... Substrate support stand 17, 107 ... Transport pipes 108, 208 ... Porous filter 19, 109 ... Exhaust device 110 ... Temperature control device 202, 204 ... Plasma 301 ... Si substrate 302 ... SiO ₂ film 303 ... Resist

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H05H 1/46 H05H 1/46 B

Claims (4)

[Claims] 1. A discharge chamber for generating a plasma, a means for introducing a source gas into the discharge chamber and the discharge chamber, and a vacuum chamber in which a substrate to be processed is placed, the discharge chamber and the vacuum chamber. A plasma processing apparatus, comprising: a filter provided in a portion to be treated. 2. The plasma processing apparatus according to claim 1, further comprising means for controlling the temperature of the filter. 3. The plasma processing apparatus according to claim 1, further comprising means for generating plasma in the vacuum chamber. 4. A step of introducing a source gas into the discharge chamber, a step of generating plasma in the discharge chamber to excite chemical species from the source gas, and the excited chemical species to a vacuum chamber through a filter. And a step of introducing the plasma treatment method.