Cleaning and liquid contact with solids – Processes – For metallic – siliceous – or calcareous basework – including...
Reexamination Certificate
1998-10-22
2001-04-10
Carrillo, Sharidan (Department: 1746)
Cleaning and liquid contact with solids
Processes
For metallic, siliceous, or calcareous basework, including...
C134S002000, C134S017000, C134S019000, C134S025400, C134S026000, C134S028000, C134S029000, C134S030000, C134S036000, C134S041000, C134S902000
Reexamination Certificate
active
06214129
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for cleaning a member to be cleaned such as silicon wafer during a process for producing semiconductor parts by using a hydrochloric acid-hydrogen peroxide mixture.
BACKGROUND OF THE INVENTION
Hitherto, in a process of producing semiconductor parts, for making surface of wafer clean, i.e. without adhesive organic impurities, micro particles and metallic impurities, there are employed a cleaning method and device in which there is used a sulfuric acid-hydrogen peroxide mixture of sulfuric acid and hydrogen peroxide, an ammonia-hydrogen peroxide mixture of aqueous ammonia and hydrogen peroxide, a hydrochloric acid-hydrogen peroxide mixture of hydrochloric acid (HCl) and hydrogen peroxide (H
2
O
2
) and pure water (H
2
O), or ultrapure water.
Among them, the cleaning method with the hydrochloric acid-hydrogen peroxide mixture is important because metallic impurities such as Al, Fe, Ni, Cr and Cu can be removed, which may cause problems in performances of semiconductor devices such as leakage at junction, threshold voltage, thickness change of oxide film, breakdown of insulating film.
In the above method, though such metallic impurities can be removed, there is a problem that hydrogen peroxide is decomposed to generate bubbles of oxygen and the oxygen bubbles accelerate adhesion of micro particles such as silicon oxide, silicon, metal oxide and organic materials onto a wafer, which results in that a yield of desired device is lowered and, further, reliability of the device is lowered.
The reason why the particles adhere onto the wafer is not apparent but regarded in the followings.
In case of hydrophilic (lyophilic) particles such as silicon oxide, a flow of the hydrochloric acid-hydrogen peroxide mixture becomes turbulent flow due to the difference between a velocity of rising bubbles and a flow velocity of the hydrochloric acid-hydrogen peroxide mixture in which particles are dispersed, and thus when colliding the particles with a wafer, the vector of velocity of the particle to the wafer is increased as compared as in the state of laminar flow without bubbles.
In case of hydrophobic (lyophobic) particles, the hydrophobic particles let their contact surface area with the hydrochloric acid-hydrogen peroxide mixture decrease to be attracted onto the gas-liquid interface of the mixture. On the other hand, an exposed portion of the silicon wafer without oxide film thereon is hydrophobic (lyophobic) and also lets its contact surface area with the hydrochloric acid-hydrogen peroxide mixture decrease to adsorb the bubbles thereon. As a result, the bubbles stay on the exposed surface portion of wafer, and the hydrophobic micro particles are easy to move from the surface of bubbles and adhere onto the exposed wafer surface which is more stable in surface energy.
Then, in JP-A-775510/ 1988, for example, there is disclosed a cleaning method by using the cleaning device as shown in a diagrammatical view of FIG.
1
. In
FIG. 1
, numeral
1
designates a cleaning bath to clean a member to be cleaned such as wafer and the bath contains the hydrochloric acid-hydrogen peroxide mixture. Numeral
2
designates an outside bath into which the hydrochloric acid-hydrogen peroxide mixture is overflowed from the cleaning bath
1
, and numeral
3
designates a piping for circulating and supplying the hydrochloric acid-hydrogen peroxide mixture. Numeral
4
designates a pump for circulating the hydrochloric acid-hydrogen peroxide mixture and numeral
5
designates a filter for removing the particles contained in the hydrochloric acid-hydrogen peroxide mixture. Numeral
7
designates a supplying port and numeral
8
designates a discharging port. The hydrochloric acid-hydrogen peroxide mixture in the outside bath
2
is cleaned by the filter
5
and returned into the cleaning bath
1
.
According to the technical method described in the above-mentioned publication, means
6
for trapping bubbles is provided between the filter
5
and a supplying port
7
to decrease an amount of bubbles which come into the cleaning bath
1
.
By the method, however, the generation of oxygen due to decomposition of hydrogen peroxide cannot be sufficiently inhibited and the adhesion of micro particles onto the exposed surface portion of wafer cannot be prevented.
Then, an object of the present invention is to provide a cleaning method in which the adhesion of micro particles onto a member to be cleaned can be prevented by decreasing an amount of generation of bubbles.
SUMMARY OF THE INVENTION
According to the present invention, in a method for cleaning a member to be cleaned by dipping the member into a cleaning bath to which a hydrochloric acid-hydrogen peroxide mixture comprising hydrochloric acid, hydrogen peroxide and water is supplied through a filter and a supplying port;
the improvement comprises that a temperature of the hydrochloric acid-hydrogen peroxide mixture is controlled within the range of 20° to 45° C.
In the case, it is preferable that means for trapping bubbles in the hydrochloric acid-hydrogen peroxide mixture is provided at least between the filter and the supplying port.
Also, it is preferable that a pressure in the cleaning bath is more than 1 atm.
Further, it is preferable that a ratio of X/Y is not higher than 0.1 in which X is a total volume of bubbles generated per minute while the member to be cleaned is dipped in the hydrochloric acid-hydrogen peroxide mixture and Y is an amount of the hydrochloric acid-hydrogen peroxide mixture in the cleaning bath.
REFERENCES:
patent: 3281915 (1966-11-01), Schramm
patent: 3869313 (1975-03-01), Jones et al.
patent: 4808259 (1989-02-01), Jillie, Jr. et al.
patent: 5238500 (1993-08-01), Bergman
patent: 5242831 (1993-09-01), Oki
patent: 63077510A (1988-04-01), None
patent: 63-77510 (1988-04-01), None
patent: 3228327 (1991-10-01), None
Ohmi et al. “Total room temp wet cleaning for Si substrate surface”. J. Electrochem. Soc. 143(9) 2957-2954, 1996.
Ishimura Muneyuki
Kan Kazuyuki
Nakaoka Yasuyuki
Wake Setsuo
Burns Doane , Swecker, Mathis LLP
Carrillo Sharidan
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