US20090008362A1

US20090008362A1 - Plasma processing apparatus and plasma processing method

Info

Publication number: US20090008362A1
Application number: US12/167,434
Authority: US
Inventors: Manabu Matsuo
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2007-07-04
Filing date: 2008-07-03
Publication date: 2009-01-08
Also published as: JP2009016540A

Abstract

A plasma processing apparatus includes a microwave-absorbing heat-generating member disposed along an inside surface of a plasma processing chamber to absorb microwaves and generate heat, wherein the microwave-absorbing heat-generating member is heated by microwaves without exciting plasma, and wherein, after that, a substrate to be processed is loaded into the plasma processing chamber and then plasma is excited to process the substrate.

Description

FIELD OF THE INVENTION AND RELATED ART

This invention relates to a plasma processing apparatus and a plasma processing method in which a semiconductor substrate used for semiconductor device manufacture is accommodated in a vacuum processing container, while microwaves are introduced thereinto to excite plasma to perform a treatment such as etching or ashing of the semiconductor substrate.
In the semiconductor device manufacture, an oxide film or the like formed on the surface of a semiconductor is selectively etched, and ions are locally implanted while using a material such as phosphor, arsenic or boron as a dopant.
Furthermore, electrons or electron holes are generated within the semiconductor to change the conductivity of the semiconductor. The above process is repeated to produce a predetermined circuit element.
A photoresist which is comprised of a resin having photosensitivity is used as mask material for this selective etching and local ion implantation.
This photoresist is removed after the etching and ion implantation processes because it is no more necessary.
For the removal of the photoresist, a microwave plasma processing apparatus in which a gas is excited by microwaves to produce plasma and active species (radicals, ions or ozone) generated by the plasma are used to remove the photoresist.
This microwave plasma processing apparatus comprises a plurality of vacuum processing containers, and semiconductor substrates to be processed are accommodated in these vacuum processing containers.
Under predetermined conditions of the type of gas, temperature, pressure and microwave output control, the unnecessary photoresist on the semiconductor substrate to be processed is transformed into a low boiling-point gaseous product such as steam, carbon dioxide or carbon monoxide, for example.
Thus, the unnecessary photoresist is transformed into a gaseous product by means of active species (radicals, ions or ozone) generated by the excited plasma.
Furthermore, it is moved out of the vacuum processing container, and the photoresist on the semiconductor substrate is removed. This process is called an incineration step or ashing step.
In the ashing step, the unnecessary photoresist is gasified by the active species (radicals, ions or ozone) generated by the plasma, whereby it is removed.
In this ashing step, there is a possibility that the sublimation of the photoresist once gasified contacts the low-temperature inner wall of the vacuum processing container and is solidified and accumulated, and it falls on the substrate as particles.
As a measure for this problem, Japanese Laid-Open Patent Application No. 5-211125 has proposed a “vapor phase epitaxy device” in which an electric heat source is introduced to heat the inner wall of the vacuum processing container up to 100 deg. Celsius or higher. However, since an electric voltage must be applied continuously, the electrical power consumption is very large.
If the removed resist falls on the substrate as particles in the vacuum processing container as described above, the product yield of the semiconductor substrate will be slowed down.

SUMMARY OF THE INVENTION

The present invention provides a plasma processing apparatus and a plasma processing method by which fall of particles in the vacuum processing container is reduced and the product yield loss of the semiconductor substrate is reduced.
In accordance with an aspect of the present invention, there is provided a plasma processing apparatus, comprising: a plasma processing chamber; a substrate supporting member configured to support a substrate disposed inside said plasma processing chamber to be processed there; a gas introducing system configured to introduce a gas into said plasma processing chamber; an exhausting system configured to evacuate the plasma processing chamber; a microwave introducing member configured to introduce microwaves into said plasma processing chamber; and a microwave-absorbing heat-generating member disposed along an inside surface of said plasma processing chamber and configured to absorb microwaves and generate heat.
In accordance with another aspect of the present invention, there is provided a plasma processing method, comprising the steps of: a first step of controlling a pressure inside a plasma processing chamber by controlling a flow rate of a gas introduced into the plasma processing chamber and a flow rate of a gas exhausted out of the plasma processing chamber, without placing a substrate, to be processed, in the plasma processing chamber, and introducing microwaves into the plasma processing chamber without generating plasma therein so that a microwave-absorbing heat-generating member disposed along an inside surface of the plasma processing chamber generates heat based on the microwaves; and a second step of controlling the pressure inside the plasma processing chamber by controlling the flow rate of a gas introduced into the plasma processing chamber and the flow rate of a gas exhausted out of the plasma processing chamber, while placing the substrate, to be processed, in the plasma processing chamber, and introducing microwaves into the plasma processing chamber to generate plasma therein, such that the substrate is processed by the generated plasma; wherein said first and second steps use the same source of emitting the microwaves.
A plasma processing apparatus of the present invention may include a vacuum processing container in which microwaves are introduced from a microwave emission source in a reduced pressure state to generate plasma, a gas introduction system for introducing a gas for generating active species in the vacuum processing container with the plasma, into the vacuum processing container, an exhaust system for exhausting the vacuum processing container, a substrate table disposed inside the vacuum processing container, for carrying thereon a substrate to be processed, and a microwave-absorbing heat-generating member disposed along the inside surface of the vacuum processing container and configured to absorb microwaves and generate heat to rise its temperature.
In accordance with the present invention, the fall of particles in the vacuum processing container is reduced, and the product yield loss of the semiconductor substrate is reduced.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a first processing step in a plasma processing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a second processing step in a plasma processing apparatus according to an embodiment of the present invention.

FIG. 3 is a flow chart illustrating the procedure in the plasma processing method according to an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be described with reference to the attached drawings.

Embodiment 1

Referring to FIG. 1 and FIG. 2, a plasma processing apparatus and a plasma processing method according to an embodiment of the present invention will be explained.
A vacuum processing container 1 is a container in which microwaves are introduced in a reduced pressure state from a microwave generator 2 a which is a microwave emission source, to produce plasma in a plasma region 10.
A microwave waveguide 2 is a member for introducing microwaves into the vacuum processing container 1 from the microwave generator 2 a which is the microwave emission source.
In response to introduction of microwaves into the vacuum processing container 1, plasma is generated in the plasma region 10.
A gas port 7 which is a gas introducing means functions to introduce a gas for generating active species with the plasma into the vacuum processing container 1.
An exhaust port 6 which is exhausting means for evacuating the vacuum processing container 1 is connected with an exhausting mechanism to evacuate the vacuum processing container 1 and to control the inside pressure thereof at a predetermined level.
A stage 4 is a table disposed inside the vacuum container 1, on which a substrate 9 to be processed is placed.
The plasma processing apparatus of the present embodiment comprises a gate 5 through which a dielectric member 3 and a substrate 9 to be processed are transferred into and out of the vacuum processing container, the dielectric member 3 being effective to transmit microwaves into the processing container having a pressure difference with the waveguide.
Furthermore, the plasma processing apparatus comprises a ring-shaped microwave-absorbing heat-generating member 8 which is disposed in the vacuum processing container 1 and which absorbs microwaves and generates heat, to rise its temperature.
The surface of the microwave-absorbing heat-generating member 8 is coated with any one of aluminum nitride, alumina, silicon carbide, quartz and yttria.
The material composition, volume, capacity and thickness of the microwave-absorbing heat-generating member 8 are chosen so that the temperature reached by the heating due to the microwave irradiation for a predetermined time inside the vacuum processing container 1 becomes uniform throughout the whole of the microwave-absorbing heat-generating member 8.
Next, referring to FIG. 1 and FIG. 3, the plasma processing method according to this embodiment of the present invention will be explained.
The plasma processing method of the present embodiment is a process for processing a substrate 9 by use of the plasma processing apparatus mentioned hereinabove. It performs a first processing step and a second processing step to be described below. In the first and second processing steps, the same microwave generator 2 a (microwave emission source) is used.
In the first processing step, a gas is introduced into the vacuum processing container 1 while being controlled, without inserting the substrate 9 into the vacuum processing container 1. Also, the gas inside the vacuum processing container 1 is exhausted while being controlled, to control the pressure inside the container 1.
Then, microwaves are introduced into the vacuum processing container 1 so as not to generate plasma therein, and the microwave-absorbing heat-generating member 8 generates heat due to the microwaves and rises its temperature.
As shown in FIG. 3, in the first processing step, the inside pressure of the vacuum processing container 1 is controlled through controlled gas introduction and controlled gas exhausting, such that the pressure is so controlled that no plasma is generated in response to introduction of microwaves (step 101).
Then, microwaves are introduced into the vacuum processing container 1 through the microwave introduction tube 2 at a predetermined output (step 102).
Whether or not the heat generation and temperature rise of the microwave-absorbing heat-generating member 8 are in a predetermined time or at predetermined temperature is checked (step 102).
If it is not the predetermined time or predetermined temperature, the introduction of microwaves is continued (step 103).
If it is the predetermined time or predetermined temperature, the introduction of microwaves is interrupted (step 104).
In this first processing step, microwaves are introduced into the vacuum processing container 1 while there is no substrate 9 placed inside the vacuum processing container 1. Thus, the microwave does not cause plasma excitement.
Furthermore, the microwave-absorbing heat-generating member 8 disposed inside the vacuum processing chamber 1 is irradiated with microwaves, by which heat is generated and the temperature thereof raised up.
The microwaves emitted from the microwave generator 2 a which is the microwave emission source are introduced into the vacuum processing container 1 through the microwave waveguide 2.
The microwaves are then transmitted through a dielectric member 3 which functions to transmit the microwaves into the vacuum chamber 1 having a pressure difference with the waveguide 2, and the microwaves then enter the vacuum processing container 1 which is controlled under a pressure condition not generating plasma.
The microwaves are absorbed by the ring-like microwave-absorbing heat-generating member 8 inside the vacuum processing container 1. In response, the microwave-absorbing heat-generating member 8 generates heat and the temperature thereof rises.
The temperature rise of the microwave-absorbing heat-generating member 8 is controlled in terms of a preset time or while being directly monitored.
After the temperature of the microwave-absorbing heat-generating member 8 reaches a predetermined level, the introduction of the microwaves through the microwave waveguide 2 is stopped, and a substrate 9 to be processed is conveyed through the gate 5 into the container by means of a conveying system for the substrate 9. The substrate 9 is then placed on the stage 4.
In the second processing step, the substrate 9 is introduced into the vacuum processing container 1, and a gas is introduced into the vacuum processing container 1 while being controlled. Also, the vacuum container 1 is exhausted while being controlled, so as to control the pressure inside the vacuum processing container 1.
Then, microwaves are introduced into the vacuum processing container 1 in the state causing plasma generation therein, to generate the plasma and to process the substrate 9 thereby.
After the microwave-absorbing heat-generating member 8 generates heat and raise its temperature in the first processing step, preferably the introduction of microwaves may be interrupted and then the second processing step may be initiated.
The first and second steps may be performed as a cycle and may be carried out repeatedly for a predetermined time and under predetermined conditions of pressure, output and temperature. The process may be repeated while monitoring a predetermined measurement subject.
The temperature reached by the microwave-absorbing heat-generating member 8 at the first processing step may be measured, and at least one of the microwave emission time and emission output may be controlled so that the predetermined temperature is reached.
As shown in FIG. 3, in the second processing step, the substrate 9 is introduced into the vacuum processing container 1 and, while controlling the pressure based on the controlled gas introduction and controlled gas exhausting, a state that plasma can be generated in response to the introduction of microwaves is accomplished (step 105).
Then, microwaves are introduced into the vacuum processing container 1 at a predetermined output through the microwave introduction tube 2. In response, plasma is generated and whether or not the substrate 9 is processed for a predetermined time or the end point is detected by an end point detecting means (not shown) is checked (step 106).
If the substrate 9 is not processed for a predetermined time or the end point is not detected by the end point detecting means (not shown), the process is continued (steps 105 and 106). The substrate is processed until it is processed for a predetermined time or the end point is detected by the end point detecting means (not shown) (step 107).
After the process is completed, the substrate 9 is unloaded from the vacuum processing container 1 (step 108).
Whether or not the process should be continued or not is checked (step 109), and the process is finished (step 110) or it goes back to step 101 of the first processing step.
A gas is introduced into the vacuum processing container through the gas port 7 in order that plasma is excited by active species, while the inside of the vacuum processing container is evacuated through the exhaust port 6, whereby a predetermined pressure is established inside the vacuum processing container 1 as the plasma generating condition. Then, microwaves are introduced into the container through the microwave guide tube 2.
Plasma is generated between the dielectric member 3, which transmits microwaves into the vacuum container 1 having a pressure difference with the microwave guide 2, and the stage 4 which carries the substrate 9 thereon. Based on active species produced thereby, the photoresist on the substrate 9 which is the object of processing is ashed. The ring-like microwave-absorbing heat-generating member 8 which absorbs microwaves and raise its temperature is provided along the inside surface of the vacuum processing container.
With this arrangement, any sublimation of the photoresist is not solidified or accumulated on the inner wall of the vacuum processing container 1, such that fall of them as particles can be prevented.
The microwave-absorbing heat-generating member 8 of ring-like shape made of microwave-absorbing heat-generating ceramics as a measure for the particle solidification and collection, is provided inside the vacuum processing container 1, and microwaves are introduced into the vacuum processing container 1 without generating plasma.
Furthermore, after the ring-like microwave-absorbing heat-generating member 8 is heated to a temperature of 100° C. or higher with which solidification and accumulation hardly occurs, the substrate 9 is introduced into the vacuum processing container 1. While controlling the gas quantity and pressure, plasma processing is carried out.
During the plasma processing, since the pressure is normally in a pressure range of 100 Pa to 300 Pa, heat is hard to radiate and the ring-like microwave-absorbing heat-generating member 8 can substantially hold its temperature during the processing.
As a result, contact of the sublimation of the photoresist being once gasified with the low-temperature inner wall of the vacuum processing container 1 and solidification and accumulation thereon can be well reduced.
As compared with the conventional method in which an electric heating source is used to heat the inner wall of the vacuum processing container 1 as a measure for the solidification and collection, the power consumption during the standby time can be reduced.
The present embodiment is particularly effective to the use in which a heating process is necessary at the same time in an etching step using microwave plasma and a CVD step.
While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims.
This application claims priority from Japanese Patent Application No. 2007-176182 filed Jul. 4, 2007, for which is hereby incorporated by reference.

Claims

1. A plasma processing apparatus, comprising:

a plasma processing chamber;

a substrate supporting member configured to support a substrate disposed inside said plasma processing chamber to be processed there;

a gas introducing system configured to introduce a gas into said plasma processing chamber;

an exhausting system configured to evacuate the plasma processing chamber;

a microwave introducing member configured to introduce microwaves into said plasma processing chamber; and

a microwave-absorbing heat-generating member disposed along an inside surface of said plasma processing chamber and configured to absorb microwaves and generate heat.

2. A plasma processing apparatus according to claim 1, wherein the surface of said microwave-absorbing heat-generating member is coated with at least one of aluminum nitride, alumina, silicon carbide, quartz and yttria.

3. A plasma processing apparatus according to claim 1, wherein a material composition, volume, capacity and thickness of said microwave-absorbing heat-generating member are chosen so that the temperature reached by the heating based on the microwave irradiation inside said plasma processing chamber in a predetermined time becomes uniform throughout the whole of said microwave-absorbing heat-generating member.

4. A plasma processing method, comprising the steps of:

a first step of controlling a pressure inside a plasma processing chamber by controlling a flow rate of a gas introduced into the plasma processing chamber and a flow rate of a gas exhausted out of the plasma processing chamber, without placing a substrate, to be processed, in the plasma processing chamber, and introducing microwaves into the plasma processing chamber without generating plasma therein so that a microwave-absorbing heat-generating member disposed along an inside surface of the plasma processing chamber generates heat based on the microwaves; and

a second step of controlling the pressure inside the plasma processing chamber by controlling the flow rate of a gas introduced into the plasma processing chamber and the flow rate of a gas exhausted out of the plasma processing chamber, while placing the substrate, to be processed, in the plasma processing chamber, and introducing microwaves into the plasma processing chamber to generate plasma therein, such that the substrate is processed by the generated plasma;

wherein said first and second steps use the same source of emitting the microwaves.

5. A plasma processing method according to claim 4, wherein, in said first step, after the microwave-absorbing heat-generating member generates heat, introduction of the microwaves is interrupted and, thereafter, said second step is carried out.

6. A plasma processing method according to claim 4, wherein said first step and said second step are performed as a cycle and carried out repeatedly for a predetermined time and under a predetermined condition of pressure, output and temperature, and wherein the cycle is repeated while monitoring a predetermined measurement subject.

7. A plasma processing method according to claim 4, wherein a temperature reached by the microwave-absorbing heat-generating member in the first step is measured and at least one of an emission time and an emission output of the microwaves is controlled so that a predetermined temperature is reached by the microwave-absorbing heat-generating member.