Patent Application
20080210166
The present invention relates to plasma enhanced chemical vapor deposition (PECVD) devices, and particularly to a PECVD device which includes an anode electrode having multiple sub-electrodes.
Generally, thin film deposition includes two types: physical vapor deposition (PVD) and chemical vapor deposition (CVD). PVD does not contain any chemical reaction, and mainly includes an evaporation method and a sputtering method. CVD is to form a thin film on a substrate through gaseous chemical reaction, and generally includes atmospheric pressure CVD (APCVD), low pressure CVD (LPCVD), and plasma enhanced CVD (PECVD). PECVD uses plasma as activating energy to promote the chemical reaction, thus a high temperature is required. The plasma is a mixture matter consisting of ions, electrons, and neutral particles. PECVD is now well developed and widely used.
Referring to
Reaction gases are introduced into the chamber 11 through the gas supply pipe 111. Most of the reaction gases are converted into plasma consisting of ions, electrons, and neutral particles by the RF electric power formed between the first and second electrodes 12, 13. The reaction gases are excited by the plasma, and react with each other. Resultant of the chemical reaction is deposited on a substrate (not shown) disposed on the second electrode 13, thus a thin film is formed on the substrate. Waste gases are exhausted through the exhausting pipe 112.
The uniformity of the thin film is essentially determined by the uniformity of a consistency of the plasma. However, the plasma is apt to cluster because of its natural electric characteristic, thus the consistency of the plasma is generally non-uniform. In addition, the consistency of the plasma can be affected by conditions such as a temperature, a pressure, and a flow speed of the reaction gases. Therefore, a thickness of the deposited thin film formed by the PECVD device is liable to be unsatisfactory. What's more, with the trend of the substrate becoming larger, the uniformity of the thickness of the deposited thin film becomes worse.
What is needed, therefore, is a PECVD device that can overcome the above-described deficiencies.
In one preferred embodiment, a PECVD device includes a first electrode, a second electrode parallel to the first electrode, and a radio frequency (RF) circuit providing energy for the two electrodes. The first electrode includes at least two separated sub-electrodes. The RF circuit includes an RF power supply source and at least two variable resistors. The RF power supply source is connected to the at least two sub-electrodes via the at least two variable resistor respectively.
Other novel features and advantages of the present PECVD device will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
Reference will now be made to the drawing figures to describe various embodiments of the present invention in detail.
Referring to
Referring to
The RF circuit 23 is disposed outside the chamber 24, and includes an RF power supply source 230 and three variable resistors 231, 232, 233. One end of the RF power supply source 230 is connected to the second electrode 22, and the other end of the RF power supply source 230 is connected to the three sub-electrodes 211, 212, 213 via the three variable resistors 231, 232, 233 respectively. The RF circuit 23 has a working frequency of 13.56 MHz.
An example of a prescribed thin film which can be formed with the aid of the PECVD device is an amorphous silicon film (a-Si film). SiH4 and H2 gases are normally used as reaction gases in the formation of the amorphous silicon film. When the PECVD device is used to produce thin films on the substrate, a thin film for test is deposited. A consistency of the plasma can be calculated by measuring thicknesses of different regions of the test-needed thin film. The variable resistors 231, 232, 233 are adjusted such that electric fields are made uniform corresponding to each of the sub-electrodes 211, 212, 213. Thus, the consistency of the plasma becomes uniform and balanced. Then thin films can be deposited on the substrate uniformly.
Unlike the conventional PECVD device, because the first electrode 21 of the present PECVD device includes three separated sub-electrodes 211, 212, 213, and each sub-electrode is connected to the power supply source 230 via the corresponding variable resistor, the consistency of the plasma of different regions corresponding to the sub-electrodes 211, 212, 213 can be adjusted respectively by adjusting the three variable resistors 231, 232, 233. Therefore, even other conditions, such as a temperature and a pressure, are not uniform, a uniform consistency of the plasma is still acquired. Thus, a uniform thin film can be formed by using the PECVD device. In addition, because a consistency of the plasma corresponding to any one of sub-electrodes 211, 212, 213 can be adjusted independently by adjusting the variable resistors 231, 232, 233, if a prescribed thin film with different thicknesses in different regions is desired, it can be easily deposited through only one deposition process employing the PECVD device by adjusting the variable resistors 231, 232, 233 accordingly.
Referring to
In further and/or alternative embodiments, any sub-electrode can have a triangle shape, or any other suitable shape. What's more, the number of the sub-electrodes can be two, four, or more. Referring to
It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set out in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 96104973 | Feb 2007 | TW | national |
