JP3582916B2 - Plasma etching equipment - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to plasma etching, and more particularly to a plasma etching apparatus for locally etching the surface of an object to be etched.
[0002]
[Prior art]
In the past, when plasma etching the surface of an object to be etched such as a silicon wafer, it has been widely proposed to expose the object to be etched in a reactive gas excited by plasma and to etch the entire surface of the object to be etched to a predetermined thickness. Have been.
[0003]
On the other hand, in recent years, instead of a technique for simultaneously etching the entire surface of the object to be etched, the surface of the object to be etched such as a silicon wafer or SOI (silicon-on-insulator) is locally etched and thinned (thinning). A downstream type plasma etching apparatus for flattening has been proposed (for example, JP-A-6-5571).
[0004]
The proposed plasma etching apparatus includes an insulator that defines a plasma chamber cavity, a unit that supplies a reactive gas into the plasma chamber cavity, a high-frequency power supply unit that converts the reactive gas into a plasma, and an object to be etched. And an XY position moving means for moving an object to be etched.
[0005]
The XY position moving means is housed and fixed in a housing, and the bottom of the housing is provided with an exhaust means for evacuating a reaction product to vacuum. According to the plasma etching apparatus having the above structure, the object to be etched 1 is locally moved, for example, the protrusion 2 is etched as shown in FIG. It becomes possible.
[0006]
The local etching by the plasma etching method is effective for flattening and smoothing an object to be etched.
However, high-energy ions generated in the plasma collide with atoms constituting the object to be etched, react with the atoms, and are contaminated 3 due to damage to the surface of the object to be etched or ion penetration into the inside of the object to be etched. That is inevitable.
[0007]
For this reason, it is conceivable to reduce the ion energy by reducing the plasma power to prevent surface damage and internal contamination of the object to be etched. The energy has not dropped so much and the expected effect has not been obtained.
[0008]
Further, a decrease in ion energy causes a decrease in the etching rate, and is not realistic as a method for solving the above-mentioned problem.
For this reason, an inefficient method has to be adopted such that the damage or the contaminant layer generated by the etching is removed by polishing again by a mechanical / chemical method.
[0009]
[Problems to be solved by the invention]
The present invention proposes a plasma etching apparatus capable of performing local etching, which can perform a high-speed etching process without damaging the surface of an object to be etched.
[0010]
[Means for Solving the Problems]
The plasma etching apparatus for locally etching an object to be etched with a plasma etching gas according to the present invention includes: an electromagnetic wave generating unit configured to irradiate an etching gas with an electromagnetic wave to generate plasma; A plasma etching gas conduit having a telescoping nozzle for locally guiding the surface, and a holder for holding the object to be etched, and further comprising a holder between the center of the plasma etching gas generation region and the object to be etched. In order to perform ion etching with the distance shortened and then perform neutral radical etching with the distance increased, the expansion / contraction nozzle of the plasma etching gas conduit and the holder are vertically moved in conjunction with each other to generate plasma etching gas. Distance changing means for changing the distance between the region and the surface of the workpiece It is provided.
According to this plasma etching apparatus, ion etching is performed in a state in which the distance between the center of the plasma etching gas generation region and the object to be etched is reduced, and then neutral radical etching is performed in a longer distance. Damage to the surface of the object to be etched due to ion bombardment in the ion etching and invading impurities are removed by neutral radical etching.
[0011]
【Example】
A plasma etching apparatus according to the present invention will be described with reference to FIG. In the plasma etching apparatus 10 shown in FIG. 1, a magnetron 4 generates a microwave of 2.45 GHz. The microwave generated from the magnetron 4 is guided to the waveguide 6.
[0012]
Reference numeral 5 denotes a quartz reaction tube. The quartz reaction tube 5 is connected to the waveguide 6. When an etching gas supplied to the quartz reaction tube 5, for example, a mixed gas of CF4 and O2 is irradiated with microwaves generated by the magnetron 4 from a coupling window provided on a gas flow path, the etching gas is turned into plasma, An etching gas generation region 12 is formed.
At this time, it is necessary to change the power of the microwave depending on the diameter of the quartz reaction tube 5, but it is turned into plasma with a power in the range of 100W to 500W. Hereinafter, the etching gas converted into plasma in the plasma etching gas generation region 12 will be described as a plasma etching gas.
[0013]
Reference numeral 9 denotes a vertically movable holder for holding the object 8 to be etched. The holder 9 also serves as an electrode for applying a negative bias voltage described later.
The quartz reaction tube 5 includes a plasma etching gas conduit 5a including a nozzle 5b that blows out a plasma etching gas, and is configured to be able to expand and contract in accordance with the vertical movement of the holder 9.
[0014]
As an example, the expansion / contraction mechanism is configured by forming a portion of the plasma etching gas conduit 5a with a double tube, and providing an expansion / contraction nozzle 5c so that the outer tube can be moved up and down with a sleeve shape. This will be described later with reference to FIG.
[0015]
The components excluding the magnetron 4 are housed in a quartz chamber 7, and the inside of the chamber 7 is evacuated from an exhaust port 13 by a vacuum exhaust device (not shown), and 0.5 to 1.3 Torr, preferably about 1 Torr. It is kept in.
[0016]
The ions generated in the plasma etching gas generation region 12 collide with an object to be etched disposed downstream, for example, the silicon wafer 8, and cause an etching reaction.
In this case, if the switch 14 is turned on and a negative bias voltage 11 is applied to the holder 9 to efficiently extract ions, the etching rate is improved.
Here, the mixed gas, SF6, NF3 and other fluorocarbon-based gases are used as the etching gas. Further, argon may be mixed with the etching gas.
[0017]
In the etching apparatus, the chamber 7 is evacuated to 1 Torr, a mixed gas of CF4 and O2 is used as an etching gas, and a microwave of 100 to 150 W is irradiated to convert the mixed gas into a plasma. When the distance between the center of the waveguide 12 (the center line of the waveguide 6 and the center line of the quartz reaction tube intersect) and the silicon wafer 8 was set to 20 mm or less and the silicon wafer 8 was locally etched, about 50 μm / min. High etching rate was obtained. In addition, when the surface of the silicon wafer at this time was observed with an electron microscope, there were countless traces of damage due to ion bombardment. Impurities were detected in trace amounts.
[0018]
Next, by lowering the holder 9 and extending the plasma etching gas conduit 5a, the distance between the plasma etching gas generation region 12 and the silicon wafer 8 is set to, for example, 50 mm or more, and the active species are almost neutral radicals. In this state, neutral radical etching was performed on the portion where the ion etching was performed earlier.
At this time, the distance between the plasma outlet of the nozzle tip 5b of the plasma etching gas conduit 5a and the surface of the silicon wafer is kept constant.
[0019]
Although the etching rate by this neutral radical etching was about 1 to 30 μm / min, the surface was in a mirror-like state, and no surface damage was observed when observed with an electron microscope. No impurities were observed.
Thus, damage near the surface caused by ion etching can be removed by neutral radical etching thereafter.
[0020]
FIG. 2 shows a cross section of a main part of a drive mechanism for vertically moving a telescopic nozzle 5c and a holder 9 constituting the plasma etching gas conduit 5a.
In FIG. 2, a vertical (Z-axis) moving shaft 18 driven by a motor 24 provided outside the chamber is provided to move the holder 9 and the telescopic nozzle 5c up and down in conjunction with each other. The moving shaft 18 can be moved up and down by being guided by a shaft guide 19 fixed to the inner wall of the chamber 7.
[0021]
The vertical support shaft 15 is connected to the holder support rod 15 via a connector 20 and the telescopic nozzle 5c via a connector 21. The motor 24 drives the telescopic nozzle 5c and the holder support. The rod 15 moves up and down in conjunction with the movement. Thus, the distance between the center of the plasma etching gas generation region 12 and the holder 9 can be changed.
[0022]
On the other hand, an XY drive stage for moving the holder 9 back and forth and right and left is provided at the upper end of the holder support bar 15.
The X stage 16 that moves in the left-right direction (X-axis direction) has an upper end of the holder supporting rod 15 and a sliding mechanism provided on the X stage 16, for example, a dovetail and a dovetail groove. It is configured to be able to slide left and right at the upper end of the.
The X stage 16 can be moved right and left by rotating a ball screw 25 via a flexible rotating shaft 22 connected to a motor 23 provided outside the chamber 7.
[0023]
Further, the movement of the holder 9 in the front-rear direction (Y direction) is achieved by moving a Y stage 17 provided orthogonally on the X stage 16 in the same manner as the movement of the X stage 16 by a motor (not shown), a flexible rotary shaft, a ball screw, and the like. And move it back and forth.
The X stage 16 and the Y stage 17 are also provided with a sliding mechanism with, for example, a dovetail and a dovetail groove, and the Y stage 17 is moved orthogonally to the X stage 16.
Here, an insulating plate 9a is provided for electrically insulating the Y stage 17 and the holder 9 from each other.
[0024]
By using the driving mechanism, it is possible to arbitrarily perform the positioning of the local etching position of the workpiece 8 (FIG. 1) and the adjustment of the ion etching distance and the neutral radical etching distance.
[0025]
【The invention's effect】
According to the plasma etching apparatus of the present invention, high-energy ion etching in the vicinity of the plasma generation region and subsequent neutral radical etching can be combined to realize low-damage plasma etching at a high etching rate.
[Brief description of the drawings]
FIG. 1 is a sectional view of a main part of a plasma etching apparatus of the present invention.
FIG. 2 is a sectional view of a main part of a driving mechanism of the plasma etching apparatus of the present invention.
FIG. 3 is a cross-sectional view of a surface state of an object to be etched;
[Explanation of symbols]
Reference Signs List 4 magnetron 5 quartz reaction tube 5a plasma etching gas conduit 5c telescopic nozzle 6 waveguide 8 workpiece 9 holder 11 negative bias 12 plasma etching gas generation region 22 flexible rotating shaft

Claims (1)

A plasma etching apparatus for locally plasma-etching an object to be etched ,
An electromagnetic wave generating means for irradiating the etching gas with an electromagnetic wave to produce plasma,
A plasma etching gas conduit having a telescoping nozzle for locally guiding the plasmatized etching gas to the surface of the workpiece,
In a plasma etching apparatus comprising a holder for holding an object to be etched,
The ion etching is performed in a state where the distance between the center of the plasma etching gas generation region and the object to be etched is short, and then the neutral etching is performed by increasing the distance. A plasma etching apparatus, further comprising a distance changing means for moving a nozzle and the holder up and down in conjunction with each other to change a distance between a plasma etching gas generation region and a surface of an object to be etched.

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