Semiconductor device manufacturing: process – Chemical etching – Liquid phase etching
Reexamination Certificate
2001-02-23
2003-04-22
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Chemical etching
Liquid phase etching
C438S748000, C438S750000, C438S627000, C438S686000
Reexamination Certificate
active
06551945
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a process for manufacturing a semiconductor device comprising removal of an undesired ruthenium containing metal adhering to a semiconductor substrate.
2. Description of the Related Art
Recently, a high dielectric-constant film such as Ta
2
O
5
has been used in place of a conventional silicon oxide or nitride film as a capacitance insulating film for a DRAM or FeRAM. Such a high dielectric-constant film permits us to ensure a required accumulated capacitance in a small occupied area and to improve a degree of memory-cell integration.
When using such a high dielectric-constant film and polysilicon as an electrode material sandwiching a capacitance film, oxygen is liberated from the high dielectric-constant film during heating a semiconductor device to oxidize the electrode material. There, therefore, exists a dielectric film (silicon oxide film) having a lower dielectric constant than the high dielectric-constant film between the electrode materials, leading to reduction in a capacitance. Thus, when using a high dielectric-constant film, it is important to select a material which does not become an insulating film due to oxidation as an electrode material sandwiching a capacitance film. It is because once a part of an electrode becomes an insulating film by oxidation, it constitutes a part of a capacitance film, resulting in a reduced capacitance. Ruthenium has recently attracted attention as an electrode material meeting the above requirement. Ruthenium is preferable because it retains conductivity even after oxidation, thus does not cause capacitance reduction and is inexpensive.
However, forming an electrode using ruthenium may lead to peeling of a ruthenium containing metal such as ruthenium and ruthenium oxide adhering to the end face or the rear face of a silicon substrate. The peeled metal may adhere to a device forming area or may cause cross contamination between devices or wafers via a carrying system. Recently, a procedure such as forming an electrode film within a narrow hole has been frequently employed for reducing an occupied area for a capacitor. It requires even forming of a thin ruthenium film, so that it is often essential to use CVD exhibiting good coverage as a deposition method, where adhesion of the ruthenium containing metal to the end and/or the rear faces of the silicon substrate becomes more prominent.
A ruthenium containing metal is known as a so-called lifetime killer to a semiconductor device. In particular, it may cause a variety of problems; for example, it adversely affects device operation due to reduction in carrier mobility and varying a threshold voltage of a transistor with time. A ruthenium containing metal is diffused at a higher rate in a silicon substrate than platinum also known as a lifetime killer. A trace amount of the ruthenium containing metal remaining on the silicon substrate surface may give prominent adverse affects on device properties. As described above, an undesired ruthenium containing metal remaining on a silicon substrate surface may deteriorate reliability of a device.
Therefore, when using ruthenium as an electrode material, it is important to remove an undesired ruthenium containing metal by treatment with an etchant. There have been, however, no etchants capable of dissolving and removing a ruthenium containing metal. For example, aqua regia used for forming a platinum electrode may not be used as a remover for a ruthenium containing metal due to its insufficient dissolving ability.
For effectively removing a ruthenium containing metal, a remover for ruthenium must not only dissolve the ruthenium containing metal but also effectively preventing the dissolved ruthenium containing metal from re-adhering to a silicon substrate.
SUMMARY OF THE INVENTION
In the light of the above situation, an objective of this invention is to provide a process for manufacturing a semiconductor device comprising depositing a ruthenium film wherein an undesired ruthenium containing metal may be adequately dissolved and removed and re-adhesion of the dissolved ruthenium containing metal may be effectively prevented.
To solve the above problems, this invention provides
[1] a process for manufacturing a semiconductor device, comprising the steps of:
depositing an insulating film in a device forming area on a semiconductor device;
depositing a barrier metal film on the insulating film;
depositing a first ruthenium film on the barrier metal film;
removing a ruthenium containing metal adhering to an area other than the device forming area using a first remover containing (a) at least one compound selected from the group consisting of salts containing chlorate, perchlorate, iodate, periodate, salts containing bromine oxide ion, salts containing manganese oxide ion and salts containing tetravalent cerium ion and (b) at least one acid selected from the group consisting of nitric acid, acetic acid, iodic acid and chloric acid;
removing the residual first remover using a first washing,
sequentially depositing a capacitance insulating film and a second ruthenium film after patterning the first ruthenium film,
removing a ruthenium containing metal adhering to an area other than the device forming area using a second remover containing (a) at least one compound selected from the group consisting of salts containing chlorate, perchlorate, iodate, periodate, salts containing bromine oxide ion, salts containing manganese oxide ion and salts containing tetravalent cerium ion and (b) at least one acid selected from the group consisting of nitric acid, acetic acid, iodic acid and chloric acid; and
removing the residual second remover using a second washing;
[2] a process for manufacturing a semiconductor device, comprising the steps of:
depositing an insulating film in a device forming area on a semiconductor substrate,
depositing a barrier metal film on the insulating film;
depositing a first ruthenium film on the barrier metal film;
removing a ruthenium containing metal adhering to an area other than the device forming area using a first remover containing (a) at least one compound selected from the group consisting of salts containing chlorate, perchlorate, iodate, periodate, salts containing bromine oxide ion, salts containing manganese oxide ion and salts containing tetravalent cerium ion and (b) at least one acid selected from the group consisting of nitric acid, acetic acid, iodic acid and chloric acid;
sequentially depositing a capacitance insulating film and a second ruthenium film after patterning the first ruthenium film,
removing a ruthenium containing metal adhering to an area other than the device forming area using a second remover containing (a) at least one compound selected from the group consisting of salts containing chlorate, perchlorate, iodate, periodate, salts containing bromine oxide ion, salts containing manganese oxide ion and salts containing tetravalent cerium ion and (b) at least one acid selected from the group consisting of nitric acid, acetic acid, iodic acid and chloric acid; and
removing the residual second remover using a second washing;
[3] a process for manufacturing a semiconductor device, comprising the steps of:
depositing an insulating film in a device forming area on a semiconductor substrate,
depositing a barrier metal film on the insulating film;
depositing a first ruthenium film on the barrier metal film;
sequentially depositing a capacitance insulating film and a second ruthenium film after patterning the first ruthenium film,
removing a ruthenium containing metal adhering to an area other than the device forming area using a second remover containing (a) at least one compound selected from the group consisting of salts containing chlorate, perchlorate, iodate, periodate, salts containing bromine oxide ion, salts containing manganese oxide ion and salts containing tetravalent cerium ion and (b) at least one acid selected from the group consisting of nitric acid, acetic acid, iodic acid and chloric acid
Aoki Hidemitsu
Watanabe Kaori
NEC Corporation
Rocchegiani Renzo N.
Smith Matthew
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