TWI645440B - Plasma processing device, thermal electron generator, plasma ignition device and method - Google Patents

Abstract

The invention provides a plasma processing device, a thermoelectron generator, a plasma ignition device and a method thereof, which are used to improve the plasma ignition. Among them, the plasma processing device includes: a chamber with a processing space inside; a gas inlet serving as a channel for the processing gas to enter the chamber; a thermionic generator that generates and delivers thermoelectrons into the chamber; an RF power source that drives the thermionic impact Process gas to generate plasma.

Description

Plasma processing device, thermal electron generator, plasma ignition device and method

The present invention relates to a plasma processing device, a plasma ignition device and method, and a thermoelectron generator applicable in the above device and method.

Generally, during semiconductor processing, a plasma etching process is used to remove or etch material along fine lines that form a pattern on a semiconductor substrate or within vias or contacts. A plasma etching process is typically used to position a semiconductor substrate with a protective layer (such as a photoresist layer) of a stacked pattern in a processing chamber. In addition, during semiconductor processing, a plasma enhanced chemical vapor deposition (PECVD) process can be used to deposit materials to fill patterned trenches, vias, contacts, or three of them on a semiconductor substrate.

For example, in a plasma etching process, once a substrate is positioned indoors, an ionizable, dissociable gas mixture can be introduced into the chamber at a predetermined flow rate, while a vacuum pump is throttled to achieve environmental processing pressure. Thereafter, a plasma is formed when a portion where the gas particles exist is ionized after colliding with a charged electron (electron moving at a high speed). In addition, hot electrons are used to dissociate some of the particles in the mixture of gas particles and produce reactive particles (s) that are suitable for exposed surface etching chemical reactions. Once the plasma is formed, any exposed surface of the substrate is etched by the plasma. The process is adjusted to achieve optimal conditions, including the desired concentration of reactants and the number of ions, to etch various features in the exposed areas of the substrate (eg, trenches, via contacts, etc.). In such a substrate material at a desired position, for example, comprise etching silicon dioxide (SiO _2), polysilicon, and silicon nitride.

Traditionally, various techniques have been applied to excite a gas into a plasma to process a substrate as described above during the fabrication of a semiconductor device. In particular, capacitively coupled plasma (CCP) processing systems or inductively coupled plasma (ICP) processing systems have been commonly used for plasma excitation.

The process of exciting an ionizable, dissociable gas mixture into a plasma that meets the process requirements is also commonly referred to as plasma ignition. The ignition time of the plasma affects the processing time of the process flow. In addition, for different batches of the same substrate, it is always desirable that their plasma ignition times in the same process flow tend to be the same.

The object of the present invention is to provide a plasma processing device, a thermoelectron generator, a plasma ignition device and a method thereof, which can effectively improve the plasma ignition.

According to an aspect of the present invention, a plasma processing apparatus is provided, which includes: a chamber having a processing space inside; a gas inlet as a passage for the processing gas to enter the chamber; a thermoelectron generator that generates and transports thermionic electrons into the chamber And a radio frequency power source that drives the hot electrons to strike a processing gas to generate a plasma.

Preferably, the chamber includes a top wall, a side wall and a bottom wall, and at least a part of the thermoelectron generator is disposed in the top wall or the side wall or the bottom wall.

Preferably, at least a portion of the thermionic generator has been extended into the processing space of the chamber.

Preferably, the plasma processing device is an inductively coupled plasma processing device.

Preferably, the plasma processing device is a capacitively coupled plasma processing device.

Preferably, the thermionic generator includes a heating wire; the amount of the generated heating electrons is controlled by adjusting a heating voltage applied to the heating wire.

According to another aspect of the present invention, a thermoelectron generator for assisting plasma ignition in a plasma processing device is provided. The thermionic generator is disposed in the plasma processing device and is used to generate and deliver thermoelectrons to the plasma processing device. Chamber.

Preferably, the thermionic generator includes: a casing with a gap inside; an electric heating wire located in the casing and generating thermoelectrons after being heated by heating; an electric field that drives the generated thermoelectrons to enter the chamber through the casing.

Preferably, the void is in a vacuum state.

Preferably, at least a part of a portion where the casing is in contact with the cavity is made of an electron-permeable material, and the thermoelectron enters the cavity through this part.

Preferably, the electron permeable material is glass, quartz or sapphire.

According to yet another aspect of the present invention, a plasma ignition device is provided, which includes: a chamber; a thermionic generator as described above; and a radio frequency power source.

Preferably, the plasma ignition device further includes a first electrode and a second electrode located in the cavity and oppositely disposed, and a radio frequency power source is applied to the first electrode or the second electrode.

Preferably, the plasma ignition device further includes a coil disposed outside the cavity, and a radio frequency power source is applied to the coil.

According to still another aspect of the present invention, a plasma ignition method is provided, which includes: passing a processing gas into a chamber; generating and delivering thermionic electrons into the chamber using a thermionic generator; and driving a thermionic impact by a radio frequency power source. Process the gas and ignite the plasma.

Compared with the conventional technology, the invention has the following advantages: the plasma ignition can be effectively improved, so that the plasma ignition time in the same process step tends to be the same.

2‧‧‧ chamber

20‧‧‧ processing space

22‧‧‧ sidewall

24‧‧‧ top wall

26‧‧‧ bottom wall

4‧‧‧Thermal electron generator

42‧‧‧shell

44‧‧‧ Electric wire

461‧‧‧Positive electrode

463‧‧‧Negative electrode

48‧‧‧ through electronic window

FIG. 1 is a schematic structural diagram of a plasma ignition device according to an embodiment of the present invention; FIG. 2 is a schematic flowchart of an embodiment of a plasma ignition method or a plasma treatment method according to the present invention.

The device and method of the present invention will be described below with reference to specific embodiments and drawings. It should be emphasized that this is only an exemplary explanation and does not exclude other embodiments using the present invention.

The conventional theory generally believes that the concentration and distribution of the plasma generated in the chamber is mainly caused by the RF power source. Different types of plasma processing devices usually use different RF frequencies. Power source. Taking a capacitively coupled plasma processing device as an example, the frequency of an optional RF power source can usually reach 60 MHz, and it is usually applied to the upper electrode or the lower electrode. Another example is the inductively coupled plasma processing device. The frequency of the optional RF power source can be 13.56 MHz, and it is usually applied to the coil above the top insulation window. 〉 And the distribution of processing gas. When the gas distribution is not adjustable or difficult to adjust, to improve the ignition condition of the plasma (for example, to reduce the ignition time or increase the plasma concentration), it is usually the only way to adjust the RF power source. Generally speaking, the higher the output power of the RF power source, the higher the plasma concentration. A lot of practice also shows that the above-mentioned law or theory holds in most cases. However, there are a few examples that do not conform to the above rules. For example, sometimes the same device runs the same process option at different locations (for example, where the device's manufacturer is located and where the chip maker that purchased the device), and the measured plasma ignition times can be quite different.

The inventors have worked to solve the above problems. The inventor found that the reasoning of the conventional theory deviates from the actual result because the understanding of the factors affecting the ignition effect of the plasma is not comprehensive or has been omitted. Conventional theory generally believes that the applied RF power source will cause the processing gas in the chamber to generate a small amount of charged particles (the earliest charged particles are often referred to as the initial charged particles). These charged particles (mainly electrons) continuously impact the surrounding gas molecules under the acceleration of the electric field generated by the RF power source, so that they ionize to generate more charged particles and plasma, and eventually cause the entire plasma to ignite. However, the inventor's research shows that the above-mentioned initial charged particles are not the result of the action of the RF power source, but are generated by the decay of cosmic rays or surface radioactive elements. The geographical location of the device and the heavy metal materials surrounding the device can affect the number of initially charged particles in the chamber, and then affect the ignition time of the plasma, or even make it difficult to ignite. When the initial number of charged particles is substantially constant, the same concentration of processing gas is applied to the same RF power source, and a constant plasma ignition effect (including the ignition time, the concentration of the obtained plasma, etc.) is naturally obtained; increase the power of the RF power source , Of course, it is naturally possible to improve the plasma by increasing the impact energy and frequency of charged particles. Lighting effect. However, when there are too few initially charged particles in the chamber due to environmental changes, even if the power of the RF power source is greatly increased, it is difficult to ignite the plasma, or the ignition time is too long. This successfully explains the above phenomenon (the same device has different ignition effects in different places).

Based on the above-mentioned new theory of the inventor, the inventor proposes a new type of plasma processing device or plasma ignition device which is added with a thermionic generator, which can use the thermionic generator to control the number of initial charged particles in the chamber. Thus, a more stable or better plasma ignition effect is obtained. A large number of experiments have also proved that the number of initial charged particles introduced by humans (for example, using a hot electron generator) is much larger (for example, when it is twice the number of the latter). At this time, changes in the surrounding environment could hardly affect the ignition effect of the plasma. This greatly guarantees the stability of plasma ignition. In addition, in a working environment where it is not possible or convenient to further increase the power of the RF power source, the ignition speed can be increased by manually increasing the number of initially charged particles (mainly electrons) in the chamber.

FIG. 1 is a schematic structural diagram of a plasma ignition device according to an embodiment of the present invention. The ignition device can be a simple plasma generation device for generating plasma and transmitting it to another subsequent device; it can also be a more complex system (such as plasma etching device, plasma deposition device, etc.) Plasma processing device), that is, it includes both a plasma generating device and other components, such as an etching table. In this way, the generated plasma can flow directly to the etching table in the same chamber and directly fixed to the etching table. The substrate on the surface is etched. As shown in FIG. 1, the plasma ignition device includes a chamber 2 surrounded by a plurality of walls (such as a side wall 22, a top wall 24 and a bottom wall 26). A processing space 20 is provided inside the chamber 2. The chamber 2 can be evacuated. Except for the necessary passages such as the gas inlet and exhaust port, the other parts of the chamber are kept closed and isolated from the outside during processing. The gas inlet (not shown) serves as a channel for the processing gas to enter the chamber, and can be connected to an external gas source (not shown) for continuously supplying the processing gas to the chamber 2 during the processing. The exhaust port (not shown) is connected to an external pump for The plasma or exhaust gas generated during the process (if the generated plasma is directly used in the chamber 2 for processing semiconductor substrates to generate waste gas) is discharged from the chamber 2 and is also used to perform the air pressure in the chamber 2 control.

The plasma ignition device is provided with a thermionic generator 4 to generate and deliver the thermionic electrons into the chamber 2. When the plasma ignition effect needs to be improved, the thermoelectron generator 4 can be turned on to generate and output a predetermined number of thermoelectrons to the chamber 2. If the influence of the environment on the ignition time is completely eliminated, the number of thermionic electrons generated by the thermionic generator 4 can be set to be twice or more than the number of electrons that can be naturally generated in a normal environment. If it is only to shorten the ignition time, there is no need to strictly control the number of thermionic electrons generated by the thermionic generator 4.

The thermoelectron generator 4 can be disposed in the processing space 20 of the chamber 2. In order to prevent plasma corrosion, the exposed shell of the thermoelectron generator 4 can be made of plasma-resistant materials (such as glass, quartz, sapphire, etc.). At least a part of the thermoelectron generator 4 may also be disposed in a wall of the chamber (such as the top wall 24, the side wall 22, and the bottom wall 26). In order to ensure that the generated thermoelectrons can better enter the chamber 2, at least a part of the thermoelectron generator 4 (especially the end of the thermoelectron generator used to emit thermoelectrons) has been extended into the processing space 20 of the chamber 2. .

The thermionic generator 4 used herein may be a conventional device that generates thermoelectrons by using a heating wire to generate electricity by heating. In order to ensure that the hot electrons can escape from the heating wire continuously, an electric field can be applied to the hot electrons, so that the hot electrons can be stably delivered to the chamber. As shown in FIG. 1, the thermoelectron generator 4 in this embodiment includes: a housing 42 having a gap inside; a heating wire 44 located in the housing 42 and generating thermoelectrons after being heated by heating; an electric field to drive the generated heat The electrons enter the chamber 2 through the housing 42.

The housing 42 may be generally made of an insulating material. The gap inside the housing 42 is drawn In a vacuum state, the hot electrons generated by the heating wire 44 will not collide with gas molecules in the process of passing through the above-mentioned gap, and thus no unnecessary particles and plasma will be generated. That is, it is possible to prevent plasma generation in the thermionic generator.

The material of the electric heating wire 44 may be tungsten wire or other high temperature resistant material. When heated to a red heat state by electric current, the hot electrons can be excited.

The elements that provide the electric field can be the high-voltage positive electrode 461 and the negative electrode 463. As shown in FIG. 1, the hot electrons are accelerated by the electric field between the high-voltage positive and negative electrodes 461 and 463, and enter the chamber 2 at high speed through the transmission window 48 Inside. The transparent electronic window 48 may be a part of the lower surface of the casing 42, and the material for the transparent window 48 may be glass, quartz, sapphire, or the like.

The amount of thermionic electrons generated can be controlled by adjusting the heating voltage applied across the heating wire 44. The energy of the hot electrons can be controlled by adjusting the voltage applied between the high-voltage positive and negative electrodes 461, 463. The voltage applied between the high-voltage positive and negative electrodes 461, 463 may be several hundreds to tens of thousands of volts. And can be adjusted according to actual needs.

The plasma ignition device is further provided with a radio frequency power source (not shown) for driving the hot electrons to impinge on the processing gas. The impact of hot electrons can cause the processing gas molecules to dissociate electrons and positively charged particles. The dissociated electrons can also impact the processing gas molecules at high speed under the action of the RF power source, thereby forming the plasma required for the process and achieving plasma ignition.

The plasma can be ignited either inductively or capacitively. For an inductively-coupled plasma ignition device or a plasma processing device, it also includes a coil disposed outside the chamber 2. The RF power source is usually applied to the coil, and the frequency used may generally be 13.56 MHz. For a capacitively-coupled plasma ignition device or a plasma processing device, it further includes a first electrode and a second electrode located in the chamber 2 and oppositely disposed, and a radio frequency power source is applied to the first electrode or the second electrode. The frequency can be as high as 60MHz.

FIG. 2 shows an embodiment of the plasma ignition method or the plasma treatment method of the present invention. The flow chart of the embodiment. As shown in FIG. 2, the plasma ignition method includes the following steps: introducing a processing gas into the chamber 2; generating and transmitting the thermionic electrons into the chamber 2 by using a thermionic generator 4; Gas, ignite the plasma.

The above method can be implemented by using the foregoing equipment of the present invention, or can be implemented by using other existing equipment and components, which is not limited herein.

Although the content of the present invention has been described in detail through the above-mentioned preferred embodiments, it should be recognized that the above description should not be considered as limiting the present invention. Various modifications and alternatives to the present invention will be apparent to those having ordinary knowledge in the field to which the present invention pertains after reading the foregoing. Therefore, the protection scope of the present invention should be defined by the scope of the attached patent application.

Claims (9)

A plasma processing device includes: a chamber having a processing space inside; a gas inlet as a channel for the processing gas to enter the chamber; a thermoelectron generator that generates and transports thermoelectrons to the chamber, and sets the thermoelectron generator The number of hot electrons generated is twice or more than the number of electrons that can be naturally generated in a normal environment to completely eliminate the influence of the environment on the ignition time. The hot electron generator includes a heating wire by adjusting the heating applied to the heating wire. Voltage to control the number of generated thermoelectrons; wherein the chamber includes a top wall, a side wall and a bottom wall, and at least a part of the thermoelectron generator is disposed in the top wall, the side wall or the bottom wall, and the thermoelectron is generated At least a portion of the device has been extended into the processing space of the chamber; and a radio frequency power source that drives the hot electrons to impinge on the processing gas to generate a plasma. The plasma processing device according to item 1 of the scope of the patent application, wherein the plasma processing device is an inductively coupled plasma processing device. The plasma processing device according to item 1 of the scope of the patent application, wherein the plasma processing device is a capacitively coupled plasma processing device. A thermoelectron generator for assisting plasma ignition in a plasma processing device, wherein the thermoelectron generator is provided in the plasma processing device and is used to generate and deliver thermoelectrons to a chamber of the plasma processing device, and set the The number of thermionic electrons generated by a thermionic generator is twice or more than the number of electrons that can be naturally generated in a normal environment to completely eliminate the influence of the environment on the ignition time. The thermionic generator includes a heating wire, which is applied by adjusting to The heating voltage of the electric heating wire controls the number of thermionic electrons generated; the thermionic generator includes: a housing with a gap inside, wherein the gap is in a vacuum state; a heating wire is located in the housing, and is generated after being heated by electricity Thermal electrons; and an electric field that drives the generated thermal electrons through the housing and into the chamber. According to the thermoelectric generator described in item 4 of the scope of patent application, at least a part of a portion where the casing is connected to the chamber is made of an electron transmitting material, and the thermoelectrons enter the chamber through the part. The thermoelectron generator according to item 4 of the scope of patent application, wherein the electron transmitting material is glass, quartz or sapphire. A plasma ignition device, comprising: a cavity; the thermoelectron generator according to any one of items 4 to 6 of the scope of patent application; a radio frequency power source; a first electrode located in the cavity and oppositely disposed, and a second electrode Electrode, the RF power source is applied to the first electrode or the second electrode. The plasma ignition device as described in item 7 of the scope of patent application, further comprising a coil disposed outside the cavity, and the RF power source is applied to the coil. A plasma ignition method includes the following steps: passing a processing gas into a chamber; generating and transmitting thermionic electrons into the chamber using a thermionic generator; and driving the thermionic electrons to impinge on the processing gas by an RF power source to ignite electricity The number of thermionic electrons generated by the thermionic generator is set to be twice or more than the number of electrons that can be naturally generated in a normal environment to completely eliminate the influence of the environment on the ignition time.