Patent Application
20070000873
This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2005-193136, filed Jun. 30, 2005, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a substrate processing method of polishing a peripheral portion of a substrate to-be-processed (referred to as “substrate”, hereinafter), such as a semiconductor wafer. More specifically, the present invention relates to a substrate processing method of removing a SiN (silicon nitride) film deposited on a peripheral portion and to a semiconductor device manufacturing method.
2. Description of the Related Art
In a semiconductor device manufacturing process, material films deposited on a peripheral portion (an edge portion, bevel portion, and notch portion) become sources of contamination in subsequent processing steps. Thus, such material films have to be removed, however it is difficult to remove those material films by etching such as CDE (Chemical Dry Etching).
To overcome the problem, a method of polishing a wafer peripheral portion is recently employed to remove such a material film deposited on the peripheral portion of a wafer to become a source of contamination (Japanese Patent Application KOKAI Publication No. 2003-234314, for example). According to this method, a wafer is rotated, and concurrently, a polishing tape is applied on the peripheral portion of the wafer, thereby polishing the peripheral portion of the wafer. In this manner, the material film deposited on the peripheral portion of the wafer to become a source of contamination can be removed.
However, a problem exists in the above-described method. That is, in the case that the material film deposited on the peripheral portion of the semiconductor wafer is SiN, the SiN film is generally firmly adhered on the peripheral portion, and thus it takes a long polishing time to remove the SiN film from the peripheral portion. Especially, when polishing is carried out by using an expensive polishing tape coated with diamond abrasive, it is preferable that the polishing is completed as short a time as possible in order to reduce the amount of use of the tape. However, when the mechanical polishing force onto the wafer peripheral portion are increased to reduce the polishing time, there are included defects resulting from, for example, wafer slippage, thereby leading to a problem of causing cracking of the wafer in subsequent heat treatment.
According to an aspect of the present invention, there is provided a substrate processing method of polishing a peripheral portion of a substrate to-be-processed by sliding a polishing member and the peripheral portion of the substrate to each other to remove a SiN film deposited on the peripheral portion of the substrate, the method comprising:
supplying a solution containing at least one of polyethyleneimine and tetramethylammonium hydroxide to a slide portion between the peripheral portion of the substrate and the polishing member.
According to another aspect of the present invention, there is provided a semiconductor device manufacturing method comprising:
forming an insulation film containing SiN above a semiconductor wafer;
forming a resist pattern on the insulation film;
forming a trench passing through the insulation film and extending in a surface region of the semiconductor wafer by etching the insulation film and the semiconductor wafer, using the resist pattern as a mask;
removing the resist pattern; and
removing an undesired portion of the insulation film deposited on a peripheral portion of the semiconductor wafer by sliding the peripheral portion of the semiconductor wafer and a polishing member to each other while supplying a solution containing at least one selected from polyethyleneimine and tetramethylammonium hydroxide to a slide portion between the peripheral portion of the semiconductor wafer and the polishing member.
Embodiments of the present invention will be described below with reference to the drawings.
A polishing mechanism 20 is set for a semiconductor wafer 10 placed in the horizontal direction on a stage, not shown, to polish a bevel portion 11 of the wafer 10. The stage is rotatable about the axis of the wafer 10. A SiN film is deposited on edge, bevel, and notch portions, which are included in a peripheral portion of the wafer 10.
The polishing mechanism 20 comprises a polishing tape (i.e., polishing member) 21 coated with abrasive, a feed roller 22 for feeding the polishing tape 21, a take-up roller 23 for taking up the polishing tape 21, a feed side guide roller 24, and a take-up side guide roller 25. The polishing tape 21 is fed from the feed roller 22, is guided by the guide rollers 24 and 25, and is taken up by the take-up roller 23.
The polishing tape 21 is imparted predetermined tensions between the guide rollers 24 and 25, and concurrently, is pressed against the bevel portion 11 of the wafer 10 between the guide rollers 24 and 25. During the process of polishing the bevel portion 11 by the rotation of the stage, the polishing tape 21 is continuously and slowly fed from the feed roller 22, is guided by the guide rollers 24 and 25, and is taken up by the take-up roller 23.
A nozzle 30 is provided above a surface of the wafer 10 toward a slide portion between the bevel portion 11 of the wafer 10 and the polishing tape 21. During the process of polishing, a polishing liquid is supplied from the nozzle 30 toward the slide portion between the bevel portion 11 of the wafer 10 and the polishing tape 21.
The polishing mechanism 20 can be tilted overall in the state where the polishing tape 21 is in contact with the bevel portion 11 of the semiconductor wafer 10, so that polishing can be done not only for an outermost edge, but also for the entirety of the bevel portion 11.
In an example of the present embodiment, in order to remove a SiN film of 220 nm thick deposited on the bevel portion 11 of the semiconductor wafer 10 made of a silicon wafer, a polishing tape 21 formed by adhering diamond abrasive having a particle size of #4000 (JIS) by a binder on a tape base (width: 80 mm; thickness: 50 μm; and length: 50 μm) of PET (polyethylene terephthalate) was used. The bevel portion 11 was polished by using the polishing tape 21 in a manner that the stage on which the wafer 10 was placed is rotated at 500 rpm about the axis of the wafer 10 and the wafer 10 was rotated at 500 rpm. Concurrently, the polishing tape 21 was pressed at a load of 6N against the bevel portion 11. During the process of polishing, the polishing tape 21 was fed from the feed roller 22 at a rate of 10 mm/min, and a corresponding length of the polishing tape 21 was taken up by the take-up roller 23.
Conventionally, pure water is supplied during polishing; however, in the example, an aqueous solution containing 3 wt % (“wt %” represents the weight percent, which hereinafter will be indicated simply as “%”) polyethyleneimine (PEI) as an auxiliary polishing agent was supplied from the nozzle 30. As a consequence, although 60 seconds was needed to remove 220 nm thick SiN film in the case where the pure water was supplied, the time was reduced to 30 seconds by supplying the PEI-containing solution.
In a similar manner, the SiN film on an edge portion 12 of the wafer 10 was removed by tilting the polishing mechanism 20 with respect to the radial direction of the wafer 10 so that the polishing tape 21 contacts the edge portion 12 of the wafer 10.
It is considered that the time used for SiN film removing with the use of the PEI-containing solution is reduced for the reason that debris resulting from the polishing is not easily deposited on the polishing tape 21 because of surfactant effects of the PEI to thereby reduce deterioration in the polishing capability due to deposition of the debris on the polishing tape 21. It is also considered that the time used for SiN film removing with the use of the PEI-containing solution is reduced for the reason that since the PEI-containing solution is alkaline, also the Si substrate under the SiN-film is etched to thereby increase the rate of removing of the SiN film. Actually, the polishing rate with the use of the PEI-containing solution for Si is 1.2 times as high as the polishing rate achieved with the use of the pure water. Even with the use of, for example, TMAH (tetramethylammonium hydroxide) or a mixture of PEI and TMAH, effects similar to those as described above can be obtained.
However, even in the case of alkaline solutions, when, for example, a KOH alkaline solution is used, although the polishing rate for Si increases, the deposition of the debris onto the polishing tape 21 does not change from the case where the pure water is used, and thus the SiN film removing rate is not enhanced. Alternatively, when a polycarboxylic acid type surfactant, which is an acid surfactant, is used, while contamination of the polishing tape 21 decreases, the polishing rate for the Si substrate under the SiN film is not enhanced, and thus the SiN-film removing rate is not enhanced.
The following table shows polishing characteristics of the solutions.
From the Table, it can be known that the PEI solution and the TMAH solution is appropriate for polishing of the substrate peripheral portion having the SiN deposition.
When the PEI is used as the auxiliary polishing agent, the content of the PEI is preferably in the range of 0.1% to 50%. Similarly, when the TMAH is used as the auxiliary polishing agent, the content of the TMAH is preferably in the range of 0.1% to 25%. These ranges are preferable for the reasons that when the content of the auxiliary polishing agent is excessively small, the time necessary for removing the SiN film cannot be reduced so much, on the other hand, when the content of the auxiliary polishing agent is excessively large, the viscosity of the solution increases to the extent of possibly making it difficult to supply the polishing liquid through the nozzle 30.
Thus, according to the present embodiment, the solution containing the PEI or TMAH as the auxiliary polishing agent is supplied when the bevel portion 11 and edge portion 12 of the semiconductor wafer 10 are polished, and thus the SiN film deposited on the bevel portion 11 and edge portion 12 of the wafer 10 can be removed in a short time. Consequently, defect occurrence is suppressed, throughput is enhanced, and processing cost is reduced.
In the present embodiment, a notch portion 13 of the semiconductor wafer 10 is polished. Different from the case of the first embodiment, the stage is not rotated about the axis of the wafer 10, but is swung by a predetermined angle range, with the end of the notch portion 13 as being an axis, in the circumferential direction of the wafer 10. Alternatively, the configuration may be such that the entirety of the polishing mechanism 20 moves in a vertical direction (i.e., a direction extending from the front surface side to the reverse surface side of the wafer 10 or its opposite direction) in a predetermined distance range in the state where the polishing tape 21 is in contact with the notch portion 13.
As shown in
In an example of the present embodiment, a polishing tape 21 similar to that used in the first embodiment was used to remove a 220 nm thick SiN film deposited on the notch portion 13. However, the width of the polishing tape 21 used in the present case was 3 mm so as to be fed into the notch portion 13. The polishing tape 21 was pressed at a load of 100 gf against the notch portion 13, and concurrently, the stage was swung by an angle of ±30 degrees about the axis being the end of the notch portion 13 in the circumferential direction of the wafer 10, so that the notch portion 13 was polished by the polishing tape 21. Similarly as in the first embodiment, during the process of polishing, the polishing tape 21 was fed at the rate of 10 mm/min from the feed roller 22, and a corresponding length of the polishing tape 21 was taken up by the take-up roller 23.
Conventionally, pure water is supplied during polishing; however, in this example, a solution containing 4% TMAH as an auxiliary polishing agent was supplied from the nozzle 30. As a consequence, although 60 seconds was needed to remove 220 nm thick SiN film in the case where pure water was supplied, the time was reduced to 40 seconds by supplying the TMAH-containing solution.
With the second embodiment, by use of the TMAH-containing solution, a reduction effect of the SiN removing time similar to that in the first embodiment was obtained. Similarly as in the first embodiment, it is considered that the time can be reduced for the reasons that adhesion of the debris resulting from the polishing onto the polishing tape 21 can be suppressed, and etching of the Si substrate under the SiN film can be implemented.
In the embodiments described above, the PEI used as the auxiliary polishing agent may be of the type formed in the manner that hydrogen atoms in a polymer skeleton are substituted with a substituent, and the TMAH may be contained in the form of salts in the solution. Even with the use of these auxiliary polishing agents, similar effects as in the embodiments described above can be expected.
Further, in the first embodiment described above, a polishing member construction including a polishing member 52, such as a polishing tape, mounted to a polishing head 51 may be used, as shown in
In the present embodiment, a manufacturing method of a semiconductor device, more specifically, a DRAM (Dynamic Random Access Memory) cell, will be described below in relation to removal of an undesired SiN film formed on a peripheral portion of a semiconductor wafer during forming of a trench capacitor.
With reference to
After forming the resist pattern 64 on the SiO2 film 63 of the laminated insulation film, as described above, the SiO2 film 63, the SiN film 62, and silicon wafer 10 are sequentially etched by RIE (Reactive Ion Etching), with the resist pattern 64 being used as a mask, to form trenches 67 for forming the capacitor of the DRAM cell, as shown in
The protrusions including the material film 68 of the SiN film 62 and the SiO2 film 63 remaining on the bevel portion 10a and the edge portion 10b of the wafer 10 become sources of contamination in subsequent processing steps. Thus, the protrusions generated on the bevel portion 10a and the edge portion 10b have to be removed. In order to remove the protrusions including the remaining material film 68, as shown in
Subsequently, as usual, an impurity is introduced in the inner wall of the trenches, and then, a SiON (silicon oxynitride) film 71 is formed on the inner wall of the trenches as a dielectric film of a capacitor. Thereafter, as shown in
Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-193136 | Jun 2005 | JP | national |
