Patent Application
20100213170
The present invention relates to an etching method and an etching apparatus.
Priority is claimed on Japanese Patent Application No. 2007-165043, the contents of which are incorporated herein by reference.
Plasma etching apparatuses are widely employed.
In the etching apparatus 1 described above, the upper surface of the plate 53 is arranged at a position lower than the upper surface of the table 52; thus, a side surface of the table 52 is exposed. As a result, an etching gas excited by plasma flows into a gap formed between the plate 53 and the substrate 90, and the gas acts on the side surface of the table 52. Then, the side surface of the table 52 undergoes a generation of particles, thereby contaminating the substrate 90. In particular, in a case that the substrate 90 is heated at a high temperature of 400° C. or more, aluminum nitride which has a high degree of heat conductivity may be employed for the table 52, but unfortunately, the aluminum nitride is a material which easily undergoes generation of particles.
The present invention is made in view of the aforementioned circumstances, and an object thereof is to provide an etching method and an etching apparatus that can prevent a subject substrate from being contaminated by particles.
In order to achieve the above-described object, the present invention employs the following.
That is, an etching method of the present invention uses an apparatus including a chamber in which an etching gas is excited by plasma; a table arranged in the chamber which heats a subject substrate mounted thereon, and a frame member which includes etching-endurable material, which is arranged around the table, and which has an upper surface arranged at a position lower than an upper surface of the table, the etching method including: arranging the subject substrate on the upper surface of the table such that a peripheral part of the subject substrate projects above the table; and arranging the subject substrate such that a ratio H/G of a height from the upper surface of the frame member to a bottom surface of the subject substrate and a projecting length from a side surface of the table to an outer circumference of the subject substrate is 1.5 or more
According to this etching method, the etching gas excited by plasma hardly flows into the gap formed between the frame member and the subject substrate. Therefore, generation of particles caused by the etching gas which acts on the side surface of the table can be suppressed. Accordingly, the subject substrate can be prevented from contamination due to the particles.
The table may include a material having aluminum nitride as a major component.
Aluminum nitride has a high degree of heat conductivity and is desired to be used for heating the subject substrate, but easily undergoes a generation of particles. However, according to the etching method of the present invention, the generation of particles due to the etching gas which acts on the side surface of the table can be suppressed. Therefore, even if the table includes a material having aluminum nitride as a major component, generation of particles may be suppressed and the subject substrate can be prevented from contamination.
The subject substrate may be arranged such that the height defined from the upper surface of the frame member and the bottom surface of the subject substrate becomes 1.0 mm or more.
Then, even if etching products having conductive properties deposit on the upper surface of the frame member, an abnormal electrical discharge between the etching products and the subject substrate can be prevented.
A noble metal coating and a ferroelectric film formed on the subject substrate may be etched by the etching gas.
The noble metal coating and the ferroelectric film may configure a storage device such as a ferroelectric memory.
The noble metal coating may include at least one of Pt (platinum), Ir (iridium), IrO2 (iridium oxide), and SrRuO3 (strontium ruthenium oxide).
The ferroelectric film may include at least one of PZT (Pb(Zr,Ti)O3, lead zirconate titanate), SBT (SrBi2Ta2O9; strontium bismuth tantalate), BTO (Bi4Ti3O12; bismuth titanate), and BLT ((Bi,La)4Ti3O12; bismuth lanthanum titanate).
At the time of etching the noble metal coating and the ferroelectric film, etching products having conductive properties easily deposit on the upper surface of the frame member. Therefore, in the present invention using the above configuration, an abnormal electrical discharge between the etching products deposited on the frame member and the subject substrate can be prevented.
The present invention provides an etching apparatus including: a chamber in which an etching gas is excited by plasma; a table arranged in the chamber, the table heating a subject substrate which is mounted on the table; and a frame member arranged around the table which includes etching-endurable material, wherein: the frame member has an upper surface which is arranged at a position lower than an upper surface of the table; and an external form of the table is set such that, above the frame member, a peripheral part of the subject substrate arranged on the upper surface of the table projects, and is set such that a ratio H/G becomes 1.5 or more. Here, “G” denotes the height defined from the upper surface of the frame member to a bottom surface of the subject substrate, and “H” denotes the projecting length defined from a side surface of the table to an outer circumference of the subject substrate.
According to this etching apparatus, the etching gas excited by plasma hardly flows into the gap formed between the frame member and the subject substrate. Therefore, generation of particles caused by the etching gas which acts on the side surface of the table can be suppressed. Accordingly, the subject substrate can be prevented from contamination due to the particles.
According to the present invention, an etching gas excited by plasma hardly flows into a gap formed between a frame member and a subject substrate, thus, it is possible to suppress generation of particles due to the etching gas which acts on a side surface of the table. Therefore, the subject substrate can be prevented from being contaminated by particles.
Hereinafter, an etching apparatus according to an embodiment of the present invention will be described in detail with reference to Drawings. It should be noted that in each of the figures referred to in the following explanation, each member is suitably modified such that the sizes there of are recognizable. In the following embodiment, an explanation is made with a reactive ion etching apparatus of inductively coupled type taken as an example.
As shown in
As an example of a device fabricated on the substrate 90 by using the etching apparatus 1, a ferroelectric memory such as FeRAM (Ferroelectric Random Access Memory) may be fabricated.
The lower side electrode 102 and the upper side electrode 104 are each formed as a film. As materials of the lower side electrode 102 and the upper side electrode 104, noble metals such like Pt (platinum), Ir (iridium), IrO2 (iridium oxide), and SrRuO3 (strontium ruthenium oxide) may be employed. As materials of the ferroelectric layer 103, ferroelectrics such like PZT (Pb(Zr,Ti)O3, lead zirconate titanate), SBT (SrBi2Ta2O9; strontium bismuth tantalate), BTO (Bi4Ti3O12; bismuth titanate), and BLT ((Bi,La)4Ti3O12; bismuth lanthanum titanate) may be employed.
In the FeRAM 100, the direction of spontaneous polarization of the ferroelectric layer 103 can be modified by applying an electric field to the ferroelectric layer 103 by creating an electric potential difference between the lower side electrode 102 and the upper side electrode 104. Since the direction of the spontaneous polarization can be maintained after discharging the electric potential difference between the lower side electrode 102 and the upper side electrode 104, it is possible to store binary data, 0 or 1, according to the direction of the spontaneous polarization.
Hereinafter, with reference to
Firstly, processes of mounting a substrate 90 on an upper surface of a center portion 52a of a table 52, chucking the substrate 90 by electrostatic chuck using a second electrode 41, and heating the substrate 90 at 400° C. or more by the table 52 are carried out. Next, processes of reducing a pressure in a chamber 10 using a vacuum discharging system 70, and introducing an etching gas into the chamber 10 from an etching gas application device 60 are performed. For example, a halogen gas, a perfluoro carbon gas or the like is introduced as the gas for etching a ferroelectric layer or electrodes of FeRAM.
Next, a first high-frequency power source 34 is driven so as to supply a high-frequency current to a first electrode 31 and an antenna 33. Then, the etching gas in the chamber 10 is excited to a plasma state. Further, a second high-frequency power source 42 is driven so as to supply a high-frequency current to a second electrode 41. Then, the etching gas excited to the plasma state moves toward the substrate 90. As a result, the etching gas collides with the ferroelectric layer or the electrodes provided on the surface of the substrate 90 for etching. Here, the substrate 90 ejects etching products such as component materials of the ferroelectric layer or the electrodes, and reactant materials resulted from chemical reaction of these component materials with the etching gas.
The etching product including the component materials of the electrodes (i.e., noble metal) has conductive properties. This etching product deposits on a surface of a deposition preventing board 20, and on an upper surface of a plate 53. As shown in
Meanwhile, since the upper surface of the plate 53 is arranged at a position lower than the upper surface of the table 52, a side surface of the center portion 52a of the table 52 is exposed. Therefore, the etching gas excited by plasma in a center area of the chamber 10 flows into a gap 92 formed between the plate 53 and the substrate 90, and acts on the side surface of the table 52. In particular, since the second electrode 41 is arranged at a position in the vicinity of the side surface of the table 52, ions of the etching gas are attracted to the side surface of the table 52 by the second electrode 41. As a result, the side surface of the table 52 undergoes a generation of particles. More specifically, from the table 52 consisted of AIN, particles of AIN, AlO and the like are generated. Then, the substrate 90 may be unfortunately contaminated by these particles.
The etching gas which acts on the side surface of the table 52 is gas which has flowed into the gap 92 formed between the plate 53 and the substrate 90. Therefore, if it becomes difficult for the etching gas to flow into the gap 92, the etching gas which acts on the side surface of the table 52 can be reduced The following methods may be suggested for making it difficult for the etching gas to flow into the gap 92, that is, (1) a method of narrowing the gap G (height) defined from the upper surface of the plate 53 to the bottom surface of the substrate 90, and (2) a method of extending the overhang amount (projecting length) H defined as the length from the side surface of the table 52 to the outer circumference of the substrate 90. However, if employing the method (1) to narrow the gap G, the abnormal electrical discharge between the etching products 110 deposited on the upper surface of the plate 53 and the substrate 90 is likely to occur. If employing the method (2) to extend the overhang amount H, it becomes tough for bias application or heat application from the table 52 to reach outer region of the substrate 90. As a result, it is difficult to fabricate a device on the outer region of the substrate 90, and the yield will be reduced.
For the above reasons, the present inventors carried out experiments by variously changing the gap G and the overhang amount H, and counting the number of particles deposited on the surface of the substrate 90. More specifically, the experiments were carried out by using substrates 90 having 8 inches of diameter, setting the gap G to three patterns of 1.2 mm, 0.9 mm, and 0.3 mm, and setting the overhang amount H to five patterns of 1 mm, 2 mm, 3 mm, 5 mm, and 8.5 mm.
The experiments were carried out on 25 pieces of the substrate 90 by etching electrode layers consisted of Ir. In these experiments, mixed gases of HBr/O2/C4F8 were introduced as an etching gas, the pressure was maintained at 0.5 Pa, the antenna power was set to 1400 W, and the bias power was set to 1300 W.
Next, the experiments were carried out by mounting on the table 52, the substrate 90 for which particles were to be counted, and exposing the substrate 90 to plasma.
More specifically, Ar gas was introduced into the chamber 10, the pressure was maintained at 0.5 Pa, the antenna power was set to 1400 W, and the bias power was set to 0 W.
Then, the surface of the substrate 90 was scanned by a laser, and particles were counted based on the scattering light. Based on the phenomenon that the intensity of the scattering light varies depending on the particle size, the number of particles with grain size of 0.2 μm or more was counted. The result thereof is shown in Table 1.
As described above, it was confirmed that (1) upon narrowing the gap G, and (2) upon extending the overhang amount H, the number of particles reduced.
The embodiment employs a configuration in which the substrate 90 is arranged on the upper surface of the table 52 so that the ratio H/G becomes 1.5 or more, for carrying out etching process. With this arrangement, it becomes difficult for the etching gas excited by plasma to flow into the gap 92 formed between the plate 53 and the substrate 90. Therefore, generation of particles caused by the etching gas which acts on the side surface of the table 52 can be suppressed, and the substrate can be prevented from contamination due to the particles.
In particular, it is preferable to set the gap G defined from the upper surface of the plate 53 to the bottom surface of the substrate 90 (the upper surface of the table 52) to 1mm or more. With this configuration, even if the etching products 110 with conductive properties deposit on the upper surface of the plate 53, an occurrence of an abnormal electrical discharge between the etching products 110 and the substrate 90 can be prevented.
The technical range of the present invention is not limited to the above-described embodiment, and includes various modifications of the above-described embodiment within the scope of the intention of the present invention. That is, specific materials or configurations suggested in the embodiment are merely examples and can be suitably modified.
According to the present invention, an etching gas excited by plasma hardly flows into a gap formed between a frame member and a subject substrate, and thus, generation of particles caused by an etching gas which acts on a side surface of a table can be suppressed. Therefore, the substrate can be prevented from contamination due to the particles.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-165043 | Jun 2007 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2008/061215 | 6/19/2008 | WO | 00 | 3/8/2010 |
