Semiconductor device manufacturing: process – Chemical etching – Liquid phase etching
Reexamination Certificate
1998-08-26
2001-05-15
Elms, Richard (Department: 2824)
Semiconductor device manufacturing: process
Chemical etching
Liquid phase etching
C438S963000, C438S906000, C510S175000
Reexamination Certificate
active
06232239
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to semiconductor fabrication, and more particularly, to a method for cleaning the contact holes of semiconductor devices to eliminate unwanted impurities and deposits introduced during the contact hole formation process.
2. Description of the Related Art
Contact holes are apertures formed through layers of a semiconductor device for the purpose of filling them with conducting material such as aluminum and thereby electrically coupling one layer to another layer. By way of example, such a contact hole can be formed to connect an upper electrode with a lower electrode in a multilayered unit cell structure of a semiconductor device.
Contact holes are conventionally formed using photo-etching techniques that are well known in the art. Such a process has several drawbacks, however. First, the chemical reaction of the etched region and the ambient oxygen in the atmosphere causes a native oxide film to grow on the lower side of the contact hole. Second, a chemical reaction between the carbon of the photoresist mask used during lithography with the reaction gas used in the dry-etching process causes a polymer to form on the sidewalls of the contact hole. These unwanted deposits deteriorate the electrical characteristics of the semiconductor device. Third, impurities such as copper (Cu), Gold (Au) and other materials are known to exist in the contact hole after formation for a variety of reasons. Such deposits are known to cause failure of the semiconductor device.
To address these problems, a cleaning process is carried out on the contact holes in order to remove the native oxide film, the polymer, or impurities such as Cu and Au. In the conventional cleaning process, the semiconductor wafer is bathed in a first cleaning process at 120° C. in a cleaning composition composed of H
2
SO
4
and H
2
O
2
in respective weight percents of 80/20 or 85/15. The profile of the inside wall of the contact hole is maintained in this first cleaning process. Then, the wafer is bathed in a second cleaning process at 25° C. for 45-90 seconds in a cleaning composition composed of H
2
SO
4
and H
2
O
2
in respective weight percents of 99.5/0.5.
Because of the small size of the contact holes and the surface tension of the cleaning solutions used, it is difficult to introduce the cleaning solution into the lower end of the contact hole. This becomes even more of a problem as device sizes are reduced due to improvements in lithographic techniques. Consequently, despite these cleaning processes, the native oxide film and other impurities still remain on the lower side and sidewalls of the contact hole. This results in a degradation of the electrical characteristics of the semiconductor devices.
Accordingly, the need exists for a better method for removing unwanted deposits and impurities from contact hole formation during the manufacture of semiconductor devices.
SUMMARY OF THE INVENTION
The present invention is directed to provide a method for cleaning the contact holes of a semiconductor device, which obviates one or more problems due to the limitations and disadvantages of the related art.
Another object of the present invention is to provide a method for cleaning the contact holes of a semiconductor device, wherein the cleaning composition is sufficiently introduced down to the lower side of the contact hole so that the cleaning efficiency is greatly improved.
To achieve these and other advantages and in accordance with the purpose of the present invention as embodied and broadly described, the method of cleaning contact hole comprises the step of bathing the semiconductor device in a solution having concentrations of between about 25 to 35 weight percent of Isopropyl Alcohol (IPA), 2 to 4 weight percent of H
2
O
2
, 0.05 to 0.25 weight percent of HF, and the remaining percent of deionized water. Such bathing is preferably carried out with the solution maintained at a constant temperature of between about 20 to 25° C. for about 1 to 5 minutes.
Contact holes are used in a variety of semiconductor devices, the following of which are only by way of example:
The contact hole can be coupled to an impurity region on a semiconductor substrate functioning as the source region or drain region of a MOS transistor. Films, on the semiconductor substrate, that have the contact hole pass through them comprise a sequentially-deposited oxide film and a borophosphorsilicate glass (BPSG) film, or a sequentially-deposited first oxide film, a silicon nitride film, a second oxide film, a first Tetra-ethyl-orthosilicate (TEOS) film, and a second TEOS film.
In another embodiment, the contact hole can be coupled to the gate electrode formed on a semiconductor substrate, whereby the contact hole passes through a second oxide film, a first TEOS film, and a second TEOS film.
In yet another embodiment, the contact hole is coupled to a titanium silicide film formed on a semiconductor substrate, whereby the contact hole passes through an oxide film, a first TEOS film, and a second TEOS film.
Also, the contact hole can be coupled to a sublayered-structure of the semiconductor device, whereby the contact hole passes through a sequentially-deposited first oxide film, a first BPSG film, a polysilicon film, a tungsten silicide film, a first silicon nitride film, a second BPSG film, a second silicon nitride film, and a second oxide film. In addition, the contact hole can be coupled to the sublayer structure through a BPSG film, or a double-layer of a first BPSG film and a second BPSG film. Alternately, the structure can be a sequentially-deposited first oxide film, a first BPSG film, a second oxide film, a second BPSG film, and a third BPSG film.
The cleaning solution is sufficiently introduced deep inside the contact hole by controlling the concentration of IPA in the cleaning solution. In addition, metallic impurities existing inside the contact hole are removed by controlling the concentration of H
2
O
2
of the cleaning solution. Finally, the native oxide film located on the lower side of the contact hole is removed and the profile of the contact hole is controlled by controlling the concentration of HF of the cleaning solution.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 5650041 (1997-07-01), Gotoh et al.
patent: 5650664 (1997-07-01), Sakamoto
patent: 5782984 (1998-07-01), Lim et al.
patent: 5876509 (1999-03-01), Nam
patent: 5972862 (1999-10-01), Torii et al.
patent: 5981375 (1999-11-01), Terada
patent: 5989970 (1999-11-01), Ohkawa et al.
patent: 5990507 (1999-11-01), Mochizuki et al.
patent: 6017784 (2000-01-01), Ohta et al.
Wet Chemical Cleaning for Damaged Layer Removal Inside Deep Sub-Micron Contact Hole, Miyamoto et al., 1998, IEEE/SEMI Advanced Semiconductor Manufacturing Conference.
Hwang Kyung-Seuk
Kim Eun-a
Lim Kwang-shin
Park Sang-o
Elms Richard
Marger & Johnson & McCollom, P.C.
Pyonin Adam
SamSung Electronics., Co., Ltd.
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