JP4368615B2 - Local dry etching method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for improving edge roll-off and reducing edge exclusion in numerically controlled dry etching processing of a semiconductor wafer.
[0002]
[Prior art]
Conventionally, a local dry etching method is known as one processing method for flattening the surface of a semiconductor wafer. In the local dry etching method, the activated species gas generated by plasma is ejected from the nozzle, and the ejected activated species gas is sprayed on the surface of the semiconductor wafer. Since silicon or the like reacts with the active species gas and is removed as a gaseous compound, the surface material of the semiconductor wafer is thinned. At this time, when the nozzle is relatively moved along the surface of the semiconductor wafer, the amount of thinning removed from the surface can be controlled according to the speed. The relative movement is usually performed by scanning, a scanning pitch corresponding to the surface irregularities of the semiconductor wafer obtained in advance is determined, and the surface of the semiconductor wafer is planarized by controlling the scanning speed. An apparatus for this purpose is called a local dry etching apparatus, and these movements are usually controlled by numerical control.
[0003]
The semiconductor wafer is a substantially disk-shaped plate body, and a bevel surface is formed on the front and back of the entire periphery of the semiconductor wafer, and a part of a flat portion inside the bevel surface is a wiring pattern forming surface. FIG. 1 is a partially enlarged sectional view around a semiconductor wafer. The edge roll-off A refers to a state in which the height of the flat surface P is lower than the original and falls like a shoulder in the vicinity of the boundary between the flat surface P for forming the wiring pattern and the bevel surface B. . Edge roll-off A often occurs in a polishing process prior to a local dry etching process.
[0004]
The local dry etching apparatus is provided with information including edge roll-off A information along with unevenness on the center side of the flat portion of each semiconductor wafer, and local dry etching is performed based on this information. Since the change in thickness is steep, the difference in scanning speed between this part and the inner part thereof becomes very large. Note that the unevenness to be removed by local dry etching is at the nanometer level, and the above “steepness” means that it is sharper than this.
[0005]
FIG. 2 is a graph showing a change in machining allowance a necessary for eliminating (flattening) the edge roll-off portion in a conventional dry etching process and a change in machining allowance b that can be actually handled by the apparatus. As shown in this figure, since the scanning speed cannot be changed as in the required change in the machining allowance a, the amount of thinning of the edge roll-off A cannot be reduced. Cannot sufficiently remove the edge roll-off A. Note that the bevel surface B itself is not included in the target of local dry etching.
[0006]
In recent years, in order to improve the yield of semiconductors, it is desired to form as many wiring patterns as possible on the flat portion P. However, the edge roll-off A is subjected to local dry etching processing to eliminate this as described above. Therefore, the area where the wiring pattern cannot be formed, that is, the edge exclusion E cannot be reduced.
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 04-246184 [Patent Document 2]
Japanese Patent Laid-Open No. 09-022934 [Patent Document 3]
Japanese Patent Laid-Open No. 09-027482 [Patent Document 4]
Japanese Patent Laid-Open No. 11-260806 [Patent Document 5]
JP 2000-36488 A [Patent Document 6]
JP 2002-231700 A [Patent Document 7]
JP 2002-252210 A [Patent Document 8]
JP 2002-299321 A [Non-Patent Document 1]
Michihiko Yanagisawa, “Numerically controlled dry planarization of silicon wafers”, Journal of the Abrasive Processing Society, October 2000, Vol. 44, No. 10, p437-440
[0008]
[Problems to be solved by the invention]
In view of the above problems, the present invention provides a local dry etching method capable of reducing edge exclusion by removing the edge roll-off using a gas flow controller which is a simple jig in local dry etching . The issue is to provide.
[0011]
[Means for Solving the Problems]
The above problem is solved by the following means. That is, solutions of the present invention, in a vacuum chamber, a semiconductor wafer by Rukoto sending relatively the said nozzle and the semiconductor wafer along the surface of the semiconductor wafer while blowing activated species gas from a nozzle surface of a semiconductor wafer In the local dry etching method for processing the surface, a wafer hole having an inner wall surface that can accommodate a semiconductor wafer, and one end of the wafer hole are overhanging into the wafer hole, By covering the semiconductor wafer with a gas flow controller having an inner flange portion having a clearance between the upper surface of the stored semiconductor wafer, the flow rate of the activated species gas flowing into the edge roll-off portion of the semiconductor wafer is reduced. , inhibiting than the thinned amount of the edge roll-off section and cutout of the other part Is a local dry etching method characterized.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described using an embodiment of the local dry etching apparatus 1 and the gas flow controller 6. FIG. 3 is a schematic diagram for explaining the outline of the local dry etching apparatus 1 which is an example of the embodiment of the present invention. The local dry etching apparatus 1 includes a vacuum chamber 11 and a wafer table 12 in the vacuum chamber 11, and the wafer table 12 places and fixes the semiconductor wafer W by an electrostatic chuck (not shown). The wafer table 12 is supported by an X-axis feeding device 121, a Y-axis feeding device 122, and a Z-axis feeding device 123, and is numerically controlled in the X, Y, and Z axis directions by a feed control unit (not shown).
[0013]
A nozzle 13 is opened in the vacuum chamber 11, and activated species gas is blown out from the nozzle 13. An active species gas generator 14 is provided outside the vacuum chamber 11 and in the middle of the nozzle 13. A microwave produced by a microwave generator (not shown) is irradiated to an intermediate portion of the nozzle 13 in the active species gas generator 14.
[0014]
The upper end of the nozzle 13 is coupled to gas cylinders 151 and 152 through a pipe 16. Valves 153 and 154 are provided in the vicinity of the outlets of the gas cylinders. By opening and closing these valves, gas in an arbitrary cylinder can be supplied to the upper end of the nozzle 13. Each cylinder is filled with SF ₆ gas, NF ₃ gas, CF ₄ gas, or the like, which is a source of active species.
[0015]
The vacuum chamber 11 is provided with a door 171 for carrying a semiconductor wafer from the left carry-in chamber 2 and a door 172 for carrying the semiconductor wafer etched in the vacuum chamber 11 to the right carry-out chamber 3. Yes. A vacuum pump (not shown) is connected to the vacuum chamber 11 so that the inside is evacuated (reduced pressure) and can be adjusted to an optimum degree of vacuum.
[0016]
A gas flow controller 6 is provided on the wafer table 12. The gas flow controller 6 includes a gas flow controller main body 61 and a driving device 62 for moving the gas flow controller main body 61 up and down. An arbitrary mechanism such as a piston cylinder mechanism, a screw feed mechanism, and a cam feed mechanism can be used for the drive device 62.
[0017]
FIG. 4 is a cross-sectional view for explaining an outline of the gas flow controller main body 61. The gas flow controller main body 61 is made of aluminum, magnesium, or a compound thereof and has a thin circular outer shape, but the outer shape is arbitrary. A wafer hole 613 having a cylindrical inner wall surface 612 for accommodating the semiconductor wafer W is formed in the gas flow controller main body 61. From the upper surface side (upper side) of the wafer hole 613, the inside of the wafer hole 613 is formed. An inner flange portion 614 extending toward is provided. The wafer hole 613 is deeper than the thickness of the semiconductor wafer W, and has a clearance with the inner flange portion 614. The inner flange portion 614 has a hole 617 so as to overhang the upper surface of the semiconductor wafer W. Another hole 616 provided in the gas flow controller main body 61 is a mounting hole (for example, a screw hole) for coupling the gas flow controller main body 61 to the driving device 62.
[0018]
The operation and action will be described below. The vacuum chamber 11, the carry-in chamber 2, and the carry-out chamber 3 are preliminarily depressurized to a predetermined degree of vacuum and become equal pressure. The driving device 62 of the gas flow controller 6 is driven to push up the gas flow controller main body 61 that supports and fixes the semiconductor wafer. At this time, the semiconductor wafer W is left on the wafer table 12. The door 172 is opened, and the semiconductor wafer W that has been processed is gripped by a transfer device (not shown) and placed in the carry-out chamber 3. The door 172 is closed.
[0019]
Next, the door 171 is opened, and a transfer device (not shown) carries a new semiconductor wafer W from the carry-in chamber 2 into the vacuum chamber 11, places it on the wafer table 12, and sucks and holds it by an electrostatic chuck. The door 171 is closed. The driving device 62 operates to lower the gas flow controller main body 61 onto the semiconductor wafer W newly placed on the wafer table 12. The semiconductor wafer W is fitted into the wafer hole 613 of the gas flow controller main body 61, and the inner flange portion 614 covers the periphery of the upper surface of the wafer so as to overhang.
[0020]
The valve 153 or the valve 154 is opened, and the original gas in the gas cylinder 151 or the gas cylinder 152 flows into the upper portion of the nozzle 13 through the pipe 16. By irradiation with microwaves from a microwave generator (not shown), the gas in the nozzle 13 is turned into plasma in the active species gas generator 14 to generate active species gas. The activated species gas flows downward and is ejected from the tip of the nozzle 13. The activated species gas ejected is sprayed toward the surface of the semiconductor wafer W.
[0021]
At the same time, the wafer table 12 is sent to a predetermined height position by the Z-axis feeding device 123, and thereafter, the X-axis feeding device 121 and the Y-axis feeding device 122 are given a pitch feed corresponding to the scanning pitch and a scanning feed therebetween. . The scanning pitch is a constant value calculated corresponding to the surface unevenness of the upper surface of the semiconductor wafer, which is measured in advance, and the scanning feed speed is a different speed for each place calculated corresponding to the unevenness. These movements are controlled by a numerical control device (not shown). The activated species gas ejected from the nozzle 13 scans the surface of the semiconductor wafer W, whereby the surface irregularities are removed and the thickness is reduced to a predetermined thickness. When the processing of the semiconductor wafer W is completed, it is transferred to the carry-out chamber 3 as described above.
[0022]
Although the overall operation is as described above, the flow of the activated species gas is affected by the inner flange portion 614 when scanning the vicinity of the peripheral portion of the semiconductor wafer W because the inner flange portion 614 is overhanging. It will be. As a result, the flow rate of the activated species gas flowing into the edge roll-off portion is extremely reduced as compared with the others. For this reason, the amount of thinning from the edge roll-off portion is greatly suppressed as compared with other portions. As a result, regarding the machining allowance of the edge roll-off portion, it is possible to reduce the thickness to a very small amount close to the necessary machining allowance as shown in FIG.
[0023]
The overhang amount d of the inner flange portion 614 and the clearance h between the inner flange portion 614 and the upper surface of the semiconductor wafer W are determined by experiments. FIG. 5 and FIG. 6 are graphs showing one example of the relationship between the overhang amount d and the removal rate suppression rate and the relationship between the clearance and the removal rate suppression rate at a certain point of the edge roll-off part, respectively. is there.
[0024]
From these graphs, when the overhang amount d of the inner flange portion 614 is increased, the amount of active species gas that reaches the edge roll-off portion is reduced, and therefore the rate of removal of the metal removal is increased and the clearance h is increased. If it is made smaller, the pressure in this space will rise and it will become difficult for the active species gas to enter, and it will be understood that the rate of removal of the metal removal increases. The amount of the overhang d of the inner flange portion 614 is in the range of 0.5 mm to 3.0 mm, and the amount of the clearance h between the inner flange portion 614 and the upper surface of the semiconductor wafer W is in the range of 0.1 mm to 1.0 mm. Is preferable.
[0025]
In this way, the gas flow controller is provided at the wafer hole with the inner wall surface that can accommodate the semiconductor wafer, and at one end of the wafer hole, and is overhanging toward the inside of the wafer hole. An internal flange portion having a clearance between the upper surface of the wafer and a gas flow controller suppresses the amount of thinning of the edge roll-off portion in local dry etching, thereby reducing edge exclusion of the semiconductor wafer. can do.
[0026]
【The invention's effect】
According to the gas flow controller of the present invention, the flow rate of the activated species gas flowing into the edge roll-off portion can be extremely reduced as compared with other portions, so that the thickness of the edge roll-off portion is suppressed, and the edge of the semiconductor wafer is reduced. There is an effect that the exclusion can be reduced. In addition, this gas flow controller has a simple structure, and there is an effect that it is not necessary to make a major modification to the conventional apparatus.
[Brief description of the drawings]
FIG. 1 is a partial enlarged cross-sectional view around a semiconductor wafer, for explaining edge roll-off.
FIG. 2 is a graph showing a change in machining allowance a necessary for eliminating (flattening) an edge roll-off portion in a conventional dry etching process and a change in machining allowance b that can be actually handled by the apparatus.
FIG. 3 is a schematic diagram for explaining an outline of a local dry etching apparatus which is an example of an embodiment of the present invention.
4 is a cross-sectional view for explaining an outline of a gas flow controller main body 61. FIG.
FIG. 5 is a graph showing one example of the relationship between the overhang amount d and the thinning amount suppression rate at a certain point of the edge roll-off portion.
FIG. 6 is a graph showing one example of the relationship between the clearance and the removal rate suppression rate at a certain point of the edge roll-off portion.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Local dry etching apparatus 11 Vacuum chamber 12 Wafer table 121 X-axis feeding apparatus 122 Y-axis feeding apparatus 123 Z-axis feeding apparatus 13 Nozzle 14 Active species gas generator 151, 152 Gas cylinder 153, 154 Valve 16 Pipe 171, 172 Door 2 Carrying in Chamber 3 Unloading chamber 6 Gas flow controller 61 Gas flow controller main body 612 Inner wall surface 613 Wafer hole 614 Inner flange 616 Hole 617 Hole 62 Drive device A Edge roll-off B Bevel surface E Edge exclusion P Flat portion, flat surface W Semiconductor Wafer d Overhang amount h Clearance

Claims (1)

In a vacuum chamber, in the local dry etching method for processing the surface of a semiconductor wafer by isosamples along the surface of the semiconductor wafer feeding relatively the said nozzle and the semiconductor wafer while blowing activated species gas from a nozzle surface of a semiconductor wafer ,
Between a wafer hole having an inner wall surface that can accommodate a semiconductor wafer and an upper surface of the semiconductor wafer that is provided at one end of the wafer hole and overhangs into the wafer hole. By covering the semiconductor wafer with a gas flow controller having an inner flange portion having a clearance, the flow rate of the activated species gas flowing into the edge roll-off portion of the semiconductor wafer is reduced, and the thickness of the edge roll-off portion is reduced. A local dry etching method characterized in that the amount is reduced as compared with the thickness of other portions .

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