HK1263038A1 - Plasma reactor having divided electrodes - Google Patents

Description

Plasma reactor with split electrodes

Statement regarding federally sponsored research or development

Is free of

Background

A Chemical Vapor Deposition (CVD) technique used in a process of manufacturing an Integrated Circuit (IC) such as a semiconductor is a technique of applying energy such as heat or power to a gaseous raw material including a chemical to increase the reactivity of the raw material gas and induce a chemical reaction so that the raw material gas is adsorbed on a semiconductor wafer to form a thin film or an epitaxial layer, and is mainly used for producing a semiconductor, a silicon oxide film, a silicon nitride film, or an amorphous silicon thin film.

Generally, during the manufacturing process, if the production is performed at a relatively low temperature, the yield of the semiconductor is improved due to the reduction in the number of product defects. However, the chemical vapor deposition technique causes a chemical reaction by applying energy using heat or light, resulting in an inevitable increase in temperature, making it difficult to improve the yield of semiconductors.

As a method for solving the problem of temperature-induced defects, a Plasma Enhanced Chemical Vapor Deposition (PECVD) method enables chemical vapor deposition even at low temperatures. In the PECVD method, a chemical reaction is induced to deposit a thin film by chemically activating a reactant using plasma instead of applying heat, electricity, or light to increase the reactivity of a raw material gas. To achieve this in PECVD, the reactants are converted into plasma by increasing chemical activity by supplying RF power from an RF oscillator to a raw material gas existing in a gaseous state to generate a chemical reaction at a low temperature.

Generally, as the frequency of the RF power becomes higher, a higher deposition rate can be obtained using the PECVD method. The increase in high deposition rate under Very High Frequency (VHF) conditions leads to an increase in productivity, effectively reducing the manufacturing cost in the semiconductor manufacturing process. Thus, PECVD processes are typically performed under VHF conditions to improve manufacturing efficiency. For example, the RF frequency is generally supplied by an RF oscillator at a high frequency of 10MHz or higher, and preferably at a high frequency of 13.56MHz, 27.12MHz, or 40.68 MHz.

PECVD processes, which are performed in typical semiconductor manufacturing, can be performed under high frequency conditions due to the relatively small size of the semiconductor wafer. However, when a semiconductor wafer is large, for example, when the wafer is larger than a semiconductor wafer used in a typical process for manufacturing such as a solar cell, there arises a problem that it is difficult to constantly maintain a wide plasma corresponding to a large-area wafer surface. In other words, larger wafers suffer from plasma non-uniformity problems.

The non-uniform plasma is caused by standing waves generated from large area wafers used in solar cell manufacturing processes. The standing wave is a combination of waves that appear when waves having the same amplitude and frequency move in opposite directions, and refers to a wave that vibrates only in a stopped state without traveling. Thus, the plasma lacks uniformity due to the standing wave formed along the surface of the plasma electrode resulting in a variation in the intensity of the RF power on the electrode surface.

Since plasma non-uniformity occurs due to standing waves in the plasma reactor under high frequency conditions, the characteristics and deposition rate or etching rate of a thin film formed at a location where the density of plasma is relatively low are different from those formed at a location where the density of plasma is high, thereby reducing the overall productivity of such a large wafer.

Disclosure of Invention

The present invention relates to a plasma reactor, and more particularly, to a plasma reactor for generating plasma used in manufacturing products having a large wafer surface area, such as thin film solar cells. A plasma electrode unit in a plasma reactor is divided into a plurality of sections, and RF power is sequentially applied to the divided plasma electrode sections in response to a determined phase angle to solve a standing wave problem on the plasma electrode. Without the split plasma electrode, the high frequency RF power applied to form plasma over a large area corresponding to a large crystal surface area may cause plasma imbalance due to a standing wave phenomenon.

According to an aspect of the present invention, there is provided a plasma reactor for processing plasma, the plasma reactor comprising a plasma electrode unit, a process gas inlet, a wafer, an RF power unit, and a phase control unit, wherein: the plasma electrode unit is divided into a plurality of parts or a plurality of electrodes; the process gas inlet is used for injecting process gas to the lower part of the separated plasma electrode unit; the wafer is disposed at a lower end of the plasma electrode unit, and deposits a process gas converted into plasma on the wafer; an RF power unit for supplying RF power; and a phase control unit for sequentially applying the RF power to each of the separated portions of the plasma electrode unit.

The phase control unit matches a split portion of the plasma electrode unit with a specific phase angle of the RF power in advance, receives the RF power from the RF power unit, detects a phase of the RF power, and applies the RF power to the split portion or the split electrode of the plasma electrode unit that matches the detected phase angle of the RF power.

The split plasma electrode unit includes at least a first plasma electrode, a second plasma electrode, a third plasma electrode and a fourth plasma electrode spaced apart from each other. The phase control unit sequentially matches the split portions of the plasma electrode unit with phase angles of 0 ° (360 °), 90 °, 180 °, and 270 ° of the RF power to previously set the plasma electrode unit.

The separate parts or the separate electrodes of the plasma electrode unit are spaced apart from each other by the same distance corresponding to the shape of the wafer, are horizontally disposed in parallel in the same plane, and are insulated from each other by an insulator.

The plasma reactor may further comprise a plurality of process gas inlets for injecting process gases into the separation section of the plasma electrode unit.

The plasma reactor may further include a chamber including a partition wall extending downward such that the process gas injected into the lower portion of the separate part or the separate electrode of the plasma electrode unit is partitioned (shield), and the chamber is opened downward to deposit the formed plasma on the wafer disposed below.

It should be understood that different embodiments of the present invention, including those described in accordance with different aspects of the present invention, are intended to be universally applicable to all aspects of the present invention. Any embodiment may be combined with any other embodiment unless it is not appropriate. All examples are illustrative and not restrictive.

The plasma reactor with the split electrodes according to the present invention solves the standing wave problem and the plasma imbalance problem in the plasma reactor, preventing these problems from occurring due to the use of high frequency RF power applied on a large area wafer in the manufacture of, for example, solar cells. The efficiency and productivity of the manufacture of such products are improved even in plasma reactors using large area wafers.

Drawings

Other features and advantages of the present invention will become apparent from the following detailed description of the invention, taken in conjunction with the accompanying drawings, in which:

fig. 1 shows a portion of a plasma reactor with a split plasma electrode according to an exemplary embodiment of the invention;

FIG. 2 schematically shows a diagram of a plasma electrode unit of the plasma reactor of FIG. 1 depicting the RF frequency of the RF power and a particular phase angle assigned to the RF frequency, wherein the RF frequency of the RF power is a control reference for a phase control unit of the plasma reactor of FIG. 1; and

fig. 3 schematically shows the split plasma electrode of fig. 1 respectively connected to a plurality of output terminals of the phase control unit.

Detailed Description

This application claims priority to U.S. provisional patent application No. 62/329,488, filed 2016, 4, 29, which is hereby incorporated by reference in its entirety.

The embodiments described in the specification and the configurations shown in the drawings correspond to only exemplary embodiments of the present invention, and do not represent all technical spirit of the present invention.

The present invention relates to a plasma reactor, and more particularly, to a plasma reactor for generating plasma used in manufacturing products having a large wafer surface area, such as thin film solar cells. The plasma electrode unit in the plasma reactor is divided into a plurality of portions or electrodes, and RF power is sequentially applied to the split plasma electrode portions in response to a phase angle to solve the standing wave problem associated with the plasma electrodes of the related art plasma reactor. Without the divided plasma electrode unit, the high frequency RF power applied to form plasma over a large area corresponding to a large wafer surface area may cause plasma imbalance due to a standing wave phenomenon.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Fig. 1 shows a portion of a plasma reactor with a split electrode according to an embodiment of the invention.

As shown in the drawing, the plasma reactor with split electrodes according to the present invention includes a buffer chamber 40, a process chamber 50, a plasma electrode unit 10, a gas supply unit (not shown), an RF power supply unit 20, and a phase control unit 30, wherein: introducing a process gas into the buffer chamber 40 to generate a plasma; the generated plasma is activated in the processing chamber 50; the plasma electrode unit 10 is divided into a plurality of parts or a plurality of electrodes 11, 12, 13, 14 and formed above the buffer chamber 40, the plasma electrode unit 10 for converting the process gas into plasma when the RF power is applied to the plasma electrode unit 10; a gas supply unit for supplying a process gas into the buffer chamber 40; an RF power supply unit 20 for supplying RF power applied to the plasma electrode unit 10; the phase control unit 30 serves to control the RF power applied to each plasma electrode of the divided plasma electrode unit 10.

The plasma reactor having the divided electrodes according to the present invention is configured to operate with a wafer substrate 60 and a substrate support 70 for supporting the substrate, wherein plasma generated from the buffer chamber 40 by the divided plasma electrodes 11, 12, 13, 14 and activated in the process chamber 50 is deposited on the wafer substrate 60.

In the plasma reactor having the split electrodes according to the present invention, the RF power supplied by the RF power supply unit 20 is supplied to each electrode in the split plasma electrode unit 10 via the phase control unit 30, and the RF power is sequentially supplied to each of the split plasma electrodes corresponding to a specific phase angle or range of phase angles of the RF power detected by the phase control unit 30.

As shown in fig. 1, the plasma electrode unit 10 according to an exemplary embodiment of the present invention is divided into four discrete electrodes 11, 12, 13, 14, but the present invention is not limited thereto, and the plasma electrode unit 10 may have a smaller or greater number of electrodes in other embodiments of the present invention. In the embodiments to be described below, an embodiment including the plasma electrode unit 10 divided into four parts (i.e., the first electrode 11, the second electrode 12, the third electrode 13, and the fourth electrode 14) of fig. 2 will be described.

The configuration of the split plasma electrode unit 10 is set to solve the standing wave problem caused by supplying VHF RF power to the large-area electrode corresponding to the large-area wafer 60, and the configurations of the split plasma electrode units 10 are separated from each other to receive power, respectively, and the configuration of the split plasma electrode unit 10 does not cause the standing wave problem compared to the whole electrode unit according to the related art. In an exemplary embodiment of the present invention, the divided plasma electrode unit 10 may be insulated by a known insulator for insulating each electrode 11, 12, 13, 14 from each other.

Further, in an exemplary embodiment of the present invention, the process chamber 50 and the buffer chamber 40 may have a plurality of process gas inlets corresponding to the split plasma electrode unit 10. A plurality of process gas inlets are assigned to each electrode of the plasma electrode unit 10 to inject respective process gases corresponding to each of the discrete electrodes. To this end, the process chamber 50 and the buffer chamber 40 may include one or more partition walls extending downward between the electrodes such that the process chamber 50 is partially divided into separate gas regions. The lower side of the buffer chamber 40 is opened to deposit plasma on the substrate within the process chamber 50.

The split plasma electrode unit 10 is configured to sequentially receive high frequency power from the source 20 via the phase control unit 30 at the plurality of electrodes 11, 12, 13, 14.

The phase control unit 30 is a constituent element for controlling the RF power applied to each of the four electrodes of the split plasma electrode unit 10, and includes a phase detection circuit to detect the phase of the received RF power. The phase control unit 30 controls the RF power to be applied to the plasma electrode unit 10 according to a specific phase angle of the RF power, i.e., phase angles of 0 °, 90 °, 180 °, and 270 ° in the case of four discrete electrodes, respectively. Therefore, RF power is sequentially applied to the four electrode parts of the split plasma electrode unit 10 according to the phase or the range of the phase. Thus, in the example of a split plasma electrode unit having four discrete electrodes, when the received RF power is substantially equal to 0 °, the first electrode will have RF power applied by the phase control unit. As used herein, "substantially equal" may mean 0 +/-40 or some lesser range. Thus, each electrode receives RF power sequentially, energizing only one electrode at a time.

Thereby, the process gas reacts in each electrode portion or electrode in the split plasma electrode unit 10 to generate plasma, and finally generates plasma corresponding to the entire large area wafer 60. In this case, since plasma is generated by each of the electrode portions of the divided plasma electrode unit 10, respectively, each reaction region is relatively small. Therefore, it is not necessary to apply the high frequency RF power, thereby solving the problem of non-uniformity of plasma related to the related art and forming uniform plasma corresponding to the large area wafer 60.

Fig. 2 shows a diagram depicting the RF power frequency as a control reference for the phase control unit 30 and schematically shows the discrete electrodes 11, 12, 13, 14 of the plasma electrode unit 10 assigned to the respective frequency phase angles. Fig. 3 schematically shows separate plasma electrode units respectively connected to a plurality of output terminals of the phase control unit 30. Although the plurality of electrodes 11, 12, 13, 14 are schematically depicted in fig. 1 and 2 as being arranged in a linear array, this is for ease of illustration only. In practice, for use with large wafers, which may be rectangular or square, the electrodes are preferably arranged in a grid pattern such as that shown in FIG. 3.

As shown, the phase control unit 30 detects the phase of the RF power applied to the phase control unit 30. The phase control unit 30 matches specific phase angles (e.g., 0 ° (360 °), 90 °, 180 ° and 270 °) of the detected RF power with the split plasma electrode unit 10, and then, controls the frequency of the current applied to the split plasma electrode unit 10 by the phase control unit with reference to the phase angle according to the above-described control.

The phase control unit 30 includes an integrated circuit including a rectifying circuit for processing the applied power, a phase angle detection circuit, and a plurality of output terminals each connected to a corresponding electrode of the split plasma electrode unit 10 to output power corresponding to the detected phase and a control reference. Therefore, if the RF power is applied to the phase control unit 30, the phase angle is detected by the phase angle detection circuit via the rectification circuit in the phase control unit 30, and the RF power is applied to one of the split plasma electrodes corresponding to the detected phase angle.

As shown in fig. 3, in an exemplary embodiment of the present invention, 5KW of RF power having a frequency of 60MHz (relatively low compared to VHF) was applied to the separate plasma electrodes, respectively. The RF power applied to each of the separated insulated plasma electrodes generates plasma, but since activation is sequentially and uniformly performed, the same effect as that obtained when a total of 20KW of power is supplied to the conventional electrode can be obtained.

The plasma reactor having the split electrodes according to the present invention solves the standing wave problem and the plasma unbalance problem occurring due to the use of the large-area wafer 60 such as in the manufacture of solar cells, by the above configuration. Accordingly, the present invention solves all the disadvantages of the plasma reactor according to the related art, and improves the manufacturing efficiency of products even in the plasma reactor using the large area wafer 60, thereby improving productivity.

Although an exemplary embodiment of a plasma reactor with a split electrode according to the present invention has been described in detail, it is only a specific example for illustrating the general concept of the present invention and is not intended to limit the scope of the present invention. It should be clearly understood by those skilled in the art to which the present invention pertains that modifications based on the technical spirit of the present invention may be made in embodiments other than the disclosed embodiments.

Claims (6)

1. A plasma reactor for generating a plasma, the plasma reactor comprising:

a buffer chamber;

a split plasma electrode unit including a plurality of discrete electrodes and disposed within the buffer chamber;

at least one process gas inlet for receiving a respective process gas and for injecting the respective process gas into the buffer chamber proximate the discrete electrode;

a process chamber in which a plasma can be formed by selectively energizing the process gas through the discrete electrodes;

a substrate support provided at a lower end of the process chamber to support a substrate on which the plasma is deposited;

an RF power unit for supplying RF power; and

a phase control unit for sequentially applying the RF power received from the RF power unit to each of the discrete electrodes in the split plasma electrode unit.

2. The plasma reactor of claim 1 wherein the phase control unit associates each discrete electrode in the split plasma electrode unit with a phase angle or range of phase angles of the RF power, the phase control unit detecting the phase of the RF power received from the RF power unit and selectively applying the RF power to the discrete electrode of the plasma electrode unit associated with the detected phase angle of the RF power.

3. The plasma reactor according to claim 2,

the split plasma electrode unit includes first, second, third and fourth plasma electrodes spaced apart from each other in a substantially horizontal plane, an

The phase control unit sequentially associates each discrete electrode in the split plasma electrode unit with one of phase angles of the RF power of substantially 0 ° (360 °), 90 °, 180 °, and 270 °.

4. The plasma reactor according to claim 1, wherein the discrete electrodes of the split plasma electrode unit:

spaced from each other in a substantially horizontal plane;

arranged corresponding to the shape of a wafer to be disposed on the substrate support; and

are insulated from each other by insulators.

5. The plasma reactor of claim 1 wherein said at least one process gas inlet comprises a plurality of process gas inlets, each process gas inlet associated with a respective discrete electrode of said plurality of discrete electrodes.

6. The plasma reactor of claim 5, further comprising:

a dividing wall extending downwardly from a top of the buffer chamber and between the plurality of discrete electrodes within the buffer chamber for dividing the process gases from each other, the buffer chamber being downwardly open to allow the process gases to be energized by the respective discrete electrodes and thereby form the plasma within the process chamber.