Etching a substrate: processes – Gas phase etching of substrate – With measuring – testing – or inspecting
Reexamination Certificate
2002-02-25
2004-09-21
Norton, Nadine G. (Department: 1765)
Etching a substrate: processes
Gas phase etching of substrate
With measuring, testing, or inspecting
C216S059000, C438S706000, C438S710000, C438S725000
Reexamination Certificate
active
06793833
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an etching method of organic insulating films, and particularly to an etching method suitable for etching organic insulating films used in the production of semiconductor devices.
2. Description of the Related Art
[Prior Art 1]
As a method for etching an organic insulating film while preventing the microtrenching without using etch stop layer, for example, the method of WO 01/15213 A1 (JP-A-2001-60582) is known. The gazette of the above-mentioned patent gives the following description.
Thus, the wafer temperature is maintained at 20-60° C., in accordance with the processing. Then, a gaseous mixture of N
2
, H
2
and Ar is introduced into the processing chamber. The inner pressure of the processing chamber is adjusted to 500 mTorr or more substantially, and preferably 500-800 mTorr substantially. Then, a radio-frequency voltage having a frequency of 13.56 MHz and a power of 600-1,400 W is applied to the lower electrode, and a radio-frequency power having a frequency of 60 MHz and a power of 600-1,400 W is applied to the upper electrode. By taking such a measure, a high-density plasma is generated in the processing chamber and, due to the plasma, contact holes of a desired shape are formed in the insulating layer between layers of wafer made of an organic low-dielectric constant material.
Further, the same gazette as above makes the following mention, too.
A treating gas containing at least a nitrogen atom-containing gas and a hydrogen atom-containing gas is introduced into the processing chamber, and the inner pressure of the vacuum processing chamber is adjusted substantially to 500 mTorr or more to carry out etching of the organic layer film formed on the wafer to be etched placed in the processing chamber. As the material constituting the organic film, a low-dielectric constant material having a relative permittivity of 3.5 or less is preferable. The inner pressure of the vacuum processing chamber is preferably kept at 500-800 mTorr substantially.
By using a gas containing at least a nitrogen atom-containing gas and a hydrogen atom-containing gas as the processing gas and adjusting the inner pressure of the vacuum processing chamber substantially to 500 mTorr or higher, microtrenching can be prevented without using etch stop layer and the mask-selection ratio can be enhanced. Such a technique is especially effective for processes which require to stop the etching in the midst of an organic layer film, such as the dual damascene process, or the like.
It is possible to use N
2
as the nitrogen atom-containing gas or to use H
2
as the hydrogen atom-containing gas, if desired. In the gazette referred to above, there are mentioned some examples in which the N
2
/H
2
flow rate ratio (N
2
/H
2
) is 400 sccm/400 sccm, 200 sccm/200 sccm, and 100 sccm/300 sccm.
[Prior Art 2]
As another method for etching an organic insulating film, the method of JP-A-2000-252359 is known. The following description is given in the gazette thereof.
An insulating film (insulating film) between layers made of an organic dielectric film such as polyallyl ether is subjected to etching, while forming a CN group-containing reaction product, etc. by the use of an NH group-containing ion or radical generated from a gas plasma made from a mixture of hydrogen and nitrogen or an ammonia-containing gas.
The etching process of the insulating film between layers is carried out by means of ECR type (Electron Cyclotron Resonance type) plasma etching apparatus under conditions of, for example, a substrate-provided electrode temperature of 20° C., a &mgr;-wave power (2.45 GHz) of 2,000W, a pressure of 0.8 Pa, an RF power of 300 W, by using NH
3
as an etching gas at a flow rate of 100 sccm.
In the etching process mentioned above, it is also possible, if desired, to carry out the etching process by the use of a gas plasma comprising a gaseous mixture of hydrogen and nitrogen at a flow rate (N
2
+H
2
) of, for example, 100 sccm at a H
2
/N
2
flow rate ratio of, for example, 75/25 sccm.
By carrying out the etching using NH group-containing ion or radical, an insulating film containing an organic dielectric film can be subjected to an anisotropic etching without forming a damage layer causing defective conduction, while suppressing side etching, while maintaining a high etch rate of about 450 nm/minute, without bringing about a reduction of throughput, and rapidly.
By such a technique, it is also possible to etch an insulating film containing an organic insulating film to open contact holes. This technique is applicable also to an etching process for forming trench for interconnect wiring such as damascene process, or to an etching process for simultaneously opening trench for interconnect wiring and contact hole such as dual damascene process, etc.
Further, if etching process of insulating film between layers is carried out under various conditions [(a) N
2
=100 sccm, (b) N
2
/H
2
=50/50 sccm and (c) H
2
=100 sccm] and emission spectra are measured, an NH peak observable neither in the case (a) using N
2
gas nor in the case (c) using H
2
gas is observed in the case (b) using N
2
/H
2
mixture. Further, as for CN peak, the peak intensity observed in the case (b) using N
2
/H
2
mixture is higher than the peak intensity in the case (a) using N
2
gas and in the case (c) using H
2
gas.
Further, if the flow rate ratio of etching gas is so varied that N
2
/H
2
=100/0 to 50/50 to 0/100 sccm and the relative etch rate (the etch rate at N
2
/H
2
=100/0 sccm is taken as 1) and the emission spectral intensity ratios between the light-emitting components (CN, NH, N
2
, CH, H) at varied flow rate ratios are measured, it is found that the etch rate and the emission spectral intensity ratio between CN and NH are roughly the same in the behavior.
SUMMARY OF THE INVENTION
In the recent years, a damascene process using copper has been used as a method for forming a wiring on semiconductor elements. As an application of the damascene process, a dual damascene process can be referred to. In the prior dual damascene, an etch stop layer has been used for preventing the sub-trenching which is sometimes called “microtrenching”, at the time of forming a trench for interconnect wiring leading to the organic insulating film functioning as an insulating film between layers. Since an etch stop layer has a high dielectric constant, however, it is attempted today to lower the dielectric constant without using any etch stop layer.
According to the former prior art mentioned above (JP-A-2001-60582), etching of organic layer film is performed while keeping the inner pressure of vacuum processing chamber at 500 mTorr (ca. 66.5 Pa) or above, and preferably at 500-800 mTorr. According to this etching method, however, inner pressure of the processing chamber is very high, and hence this method is expected to have the following problems: (1) in the case of samples having a large diameter such as 300 millimeter wafer, the waste gas generated as a reaction product from the wafer surface cannot sufficiently be removed at the central part of wafer, so that the etch rate within the wafer surface is not uniform, (2) the quantity of reaction product is so large that controlling the shape of trench and hole is difficult, and (3) the quantity of reaction product is so large that inside of processing chamber is apt to be soiled, which reduces reproducibility of the etching treatment. Accordingly, a measure for solving these problems have to be taken when the processing is to be carried out at a high processing pressure.
On the other hand, the latter prior method (JP-A-2000-252359) is known as a method for etching an organic insulating film at a low processing pressure (0.8 Pa) which makes it unnecessary to consider the above-mentioned problems in the etching process at a high processing pressure. The latter prior method, however, pays no consideration for the problem occurring when an organic insulating film of dual
Fukuyama Ryooji
Mizumura Michinobu
Ohmoto Yutaka
Watanabe Katsuya
Ahmed Shamim
Norton Nadine G.
LandOfFree
Etching method of organic insulating film does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Etching method of organic insulating film, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Etching method of organic insulating film will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3200964