1. Field of the Invention
The present invention relates to an inductively coupled plasma (ICP) etching system and a method of manufacturing a semiconductor device using such an etching system.
2. Background Art
In the manufacture of a semiconductor device, a thin film(s) such as an epitaxial layer is dry etched using a patterned resist as a mask. Such dry etching is performed in an etching system which generates an inductively coupled plasma. [See, e.g., Japanese Laid-Open Patent Publication No. 8-316210 (1996).]
The electrical characteristics of a semiconductor device depend greatly on the shape of its etched features, e.g., the shape of the edges of the etched layers. However, it has been very difficult to etch a layer or film into a controlled shape, or desired shape, without changing the process conditions, such as the ion energy and the amount of radicals, or without changing the mask material or mask pattern, during the process.
The present invention has been devised to solve the above problems. It is, therefore, an object of the present invention to provide an etching system capable of etching a layer or film into a controlled shape with ease without changing the process conditions and masks. An other object of the present invention is to provide a method of manufacturing a semiconductor device using such an etching system.
According to one aspect of the present invention, an etching system comprises: a vacuum chamber; a stage for mounting a workpiece thereon, said stage being disposed within said vacuum chamber; a first electrode provided within said vacuum chamber and above said stage; a second electrode provided between said first electrode and a ceiling of said vacuum chamber; gas supply means for introducing a process gas into said vacuum chamber; a variable capacitance element connected to said second electrode; and a radio frequency power supply connected to said first electrode and connected through said variable capacitance element to said second electrode; wherein said radio frequency power supply supplies radio frequency power to said first and second electrodes to produce an inductively coupled plasma from said process gas within said vacuum chamber.
Thus, the present invention allows a thin film to be etched into a controlled shape with ease without changing the process conditions and masks.
Other and further objects, features and advantages of the invention will appear more fully from the following description.
The vacuum chamber 10 contains a stage 22 for mounting a workpiece 20 thereon and also contains an ICP electrode 24 (referred to in the appended claims as a “first electrode”) disposed above the stage 22. Between the ICP electrode 24 and the ceiling 12 of the vacuum chamber 10 is disposed a planar electrode 26 (referred to in the appended claims as a “second electrode”) including a plurality of radially extending antennas.
A radio frequency power supply 28 is connected to the stage 22 through a matching box 30, and a radio frequency power supply 32 is connected to the ICP electrode 24 through a matching box 34. The radio frequency power supply 32 is also connected to the planar electrode 26 through the matching box 34 and a variable capacitor 36 (referred to in the appended claims as a “variable capacitance element”). The capacitance of the variable capacitor 36 can be varied, for example, between 10 pF and 1 F.
The operation of this etching system will now be described. The radio frequency power supply 32 supplies radio frequency (RF) power to the ICP electrode 24 and the planar electrode 26 while the radio frequency power supply 28 supplies RF power to the stage 22, thereby producing inductively coupled plasmas from the process gas within the vacuum chamber 10. The plasma thus produced by the ICP electrode 24 is used to dry etch the workpiece 20. The laser beam interferometric end point detector 14 detects the etching end point in this etching process by means of laser interferometry.
It should be noted that reaction products of the plasma etching attach to the inner walls of the vacuum chamber 10. Especially those attached to the ceiling 12 of the vacuum chamber 10 act to absorb light, thereby preventing the laser beam interferometric end point detector 14 from detecting the etching end point. In order to avoid this, the plasma generated by the planar electrode 26 is used to sputter off, or remove, the attached reaction products from the ceiling 12. The sputtered reaction products then attach to the etched sidewalls of the workpiece 20 again, thus contributing to the formation of the desired shape of the workpiece 20. That is, these sputtered reaction products act to adjust (or reduce) the amount of side etching of the workpiece 20.
It should be noted that changing the capacitance of the variable capacitor 36 results in a change in the power supplied to the planar electrode 26 and hence a change in the amount of reaction products sputtered off from the ceiling 12 of the vacuum chamber 10. This means that the capacitance of the variable capacitor 36 may be varied to etch the workpiece 20 into a controlled shape (or desired shape).
There will now be described a method of manufacturing a semiconductor device according to the present embodiment.
This method begins by sequentially forming an n-AlGaInP cladding layer 40, a multiquantum well active layer 42, an AlGaInP detection layer 44, and a p-AlGaInP cladding layer 46 (referred to in the appended claims as a “thin film”) on top of one another on a GaAs substrate 38 (referred to in the appended claims simply as a “substrate”) by use of an MOCVD or MBE crystal growth apparatus, as shown in
Next, a resist 48 is formed on the p-AlGaInP cladding layer 46 and patterned by photolithography, etc., as shown in
Then as shown in
According to the present embodiment, in the above dry etching process, the capacitance of the variable capacitor 36 may be varied to adjust the shape of the ridge 50, namely, the angles of the etched sidewalls of the ridge 50 relative to the surface of the detection layer 44 (or the angles formed by opposing sidewalls of the ridge). More specifically, when the capacitance of the variable capacitor 36 is high, the ridge 50 is formed to a trapezoidal shape in cross section as shown in
As described above, in the manufacture of a semiconductor device the present embodiment allows a layer or thin film to be etched into a ridge of a controlled shape with ease without changing the process conditions and masks. Accordingly, since the electrical characteristics of the semiconductor device depend on the angles of the sidewalls of the ridge relative to the surface of the underlying detection layer (or the angles formed by opposing sidewalls of the ridge), the ridge may be formed by etching to such a shape that the semiconductor device has the desired electrical characteristics.
Thus, according to the method of the present embodiment for manufacturing a semiconductor device, the workpiece 20 can be etched into a controlled shape by adjusting the RF power supplied from the radio frequency power supply 56 to the planar electrode 26. Except for this feature the present embodiment is similar to the first embodiment and hence retains the advantages of the first embodiment.
Although preferred embodiments of the present invention have been described in connection with the manufacture of a GaAs-based compound semiconductor device, it is to be understood that the invention may be applied to the manufacture of GaN-based and In P-based compound semiconductor devices and to etching insulating films.
Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.
The entire disclosure of a Japanese Patent Application No. 2008-161967, filed on Jun. 20, 2008 including specification, claims, drawings and summary, on which the Convention priority of the present application is based, are incorporated herein by reference in its entirety.
Number | Date | Country | Kind |
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2008-161967 | Jun 2008 | JP | national |