Low metallic impurity SiO based thin film dielectrics on...

Details Low metallic impurity SiO based thin film dielectrics on... Low metallic impurity SiO based thin film dielectrics on...

2001-06-26

2003-09-02

Ghyka, Alexander (Department: 2812)

Semiconductor device manufacturing: process

Coating of substrate containing semiconductor region or of...

By reaction with substrate

C438S769000, C438S787000, C438S790000, C427S443200, C427S435000

Reexamination Certificate

active

06613697

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to a room temperature wet chemical growth (RTWCG) process of SiO-based dielectric coatings on semiconductor substrates and layers including but not restricted to Si, Ge, III-V and I-III-VI, and II-VI compound semiconductors and, specifically, to the RTWCG of SiO-based films on Si in the manufacture of silicon-based electronic and photonic (optoelectronic) device applications. One particular application involves the use of this room temperature wet chemical growth process to make SiO based thin film oxide layers with low metallic and non-metallic impurity concentration for use in the next generations IC microelectronic devices.
Silicon dioxide (SiO
2
) forms the basis of the planar technology. In industrial practice dielectric coatings for electronic and photonic devices layers are most frequently formed by thermal oxidation of Silicon (Si) in the temperature range 900 to 1200° C. SiO
2
is also deposited by chemical vapor deposition (CVD) techniques at lower temperatures (200 to 900° C.) on various substrates.
Thermal and CVD-grown SiO
2
based layers are used as diffusion masks, to passivate device junctions, as electric insulation, as dielectric material in Si technology, and as capping layers for implantation-activation annealing in III-V compound semiconductor technology, to name a few.
The growth of dielectric films at low temperatures is very attractive for most device applications due to reduced capital cost, and high output and technological constraints associated with the growth of dielectric thin films using conventional high-temperature growth/deposition techniques.
Dielectric films for microelectronic/photonic (optoelectronic) devices are well known in the art and are usually deposited at near room temperature on various substrates using physical vapor deposition processes including conventional (nonreactive) or reactive resistive, induction or electron beam evaporation, reactive or nonreactive dc or RF magnetron and ion-beam sputtering processes.
Room temperature growth of dielectric layers on semiconductor surfaces using anodic oxidation is known in the art. For silicon, using anodic oxidation up to 200 nm SiO
2
layers can be grown on the underlying Si substrates. The anodic oxidation process consumes about 0.43 of the thickness of the oxide from the underlying Si substrate, and is not compatible with most metallization schemes. This limits its application as a replacement of thermal or vacuum deposited SiO
2
.
Deposition of SiO
2
dielectric layers from solutions is known in the art using organo-metallic solutions. In this procedure, the dielectric layer is applied onto the substrate either by dipping the substrate into the solution or by spinning the substrate after a small amount of the solution is applied onto the surface. In both cases the substrate is then placed in an oven to drive off the solvent.
Researchers from Japan, China and Taiwan describe processes for deposition of SiO
2
and SiO
2−x
F
x
layers on glass and silicon surfaces using a room temperature (30 to 50° C.) solution growth. The growth of liquid-phase deposited (LPD) SiO
2
, initially proposed by Thomsen et al. for deposition of SiO
2
on the surface of soda lime silicate glass, is based on the chemical reaction of H
2
SiF
6
with water to form hydrofluoric acid and solid SiO
2
. The initial H
2
SiF
6
solution is saturated with SiO
2
powder (usually in a sol-gel from). Before immersing the glass into the solution, a reagent that reacts with the hydrofluorosilicilic acid, such as boric acid, was added to the solution. Boric acid reacts with the hydrofluorosilicilic acid and makes the solution supersaturated with silica.
One of the major disadvantages of SiO
2
LPD method described above is a very low deposition rate of about 8 nm/hour to about 24 nm/hour, which makes it impractical for growing dielectric layers for most semiconductor device applications. Deposition rates of up to 110 nm/hour are claimed by Ching-Fa Yeh et al. in the hydrofluorosilicilic acid-water system and the composition of the resulting films was reported to be SiO
2−x
F
x
where x is about 2%. Our own experimentation using the LPD method, seems to indicate that the LPD SiO
2
has poor adhesion to the Si surfaces, and the maximum growth rate we obtained is smaller than the reported values (less than 25 nm/hour). Even assuming that the reported 110 nm/hour deposition rates are possible, these deposition rates are still too low since assuming that the deposition rate is constant with the deposition time, it will require about 9 hours to deposit an oxide with a thickness of about 1 &mgr;m needed for ULSI interlevel dielectric.
The U.S. Pat. No. 6,080,683, entitled “Room Temperature Wet Chemical Growth Process of SiO Based Oxides on Silicon” issued Jun. 27, 2000 and the U.S. applications Ser. No. 09/602,489 entitled “Room Temperature Wet Chemical Growth Process of SiO Based Oxides on Silicon” and U.S. applications Ser. No. 09/891,832 entitled “Method of Making Thin Films Dielectrics Using a Process for Room Temperature Wet Chemical Growth of SiO Based Oxides on a Substrate” which were filed on Jun. 23, 2000 and Jun. 26, 2001, respectively as a continuation-in-part of the above patent, describe a room temperature wet chemical growth (RTWCG) process and method for growth of a silicon oxide layer on a semiconductor substrate to produce a silicon oxide layer comprising:
a) providing a substrate;
b) providing a reaction mixture comprising a silicon source, a pyridine compound, and an aqueous reduction oxidation solution;
c) a catalyst to enhance the reaction, and
d) reacting the mixture with the substrate to form said silicon oxide layer;
High growth rates of SiOX oxides according to related art described above are grown on planar or porous silicon using, commercial grade organic and inorganic silicon sources, a pyridine compound, such as N-n butylpyridinium chloride (C
9
H
14
CIN), redox aqueous solutions based on Fe
2+
/Fe
3
, an organic or inorganic homogeneous catalyst, and non-invasive additives to adjust the pH of the growth solution. By using the above growth solutions formulations, the SiO based oxide layers grown on various semiconductor substrates have a lower growth rate and a higher metallic and non-metallic impurity concentration, and inferior electric and dielectric properties compared with the SiO-based oxide layers grown using the solution growth formulations described in this patent application.
The term RTWCG process of SiO-based dielectric layers as used herein means a room temperature (e.g. 10-40° C.) wet chemical growth process for silicon oxide layers. While this layer is referred to in this application as a “silicon oxide layer”, this means a layer which is Si
x
O
y
X
z
(SiOX) layers where x is from 0.9 to 1.1, y is from 0.9 to 1.1 and z is from 0.01 to 0.2, where Si stands for silicon, O stands for oxygen, and X is either fluorine, (F), carbon (C), nitrogen (N) or a combination of these with iron (Fe), palladium (Ti) or other trace amount of metallic and non-metallic contaminants, depending on the redox system, catalyst, and the non-invasive additives being used.
One useful definition of a “catalyst” is a compound that promotes the reaction wherein the metallic ion of the reduction oxidation solution is subject to a change in its electron state such as from Fe
2+
to Fe
3+
. Also, a homogeneous catalyst is a catalyst which is dissolved in the reaction solution.
SUMMARY OF THE INVENTION
This invention relates to a room temperature wet chemical growth (RTWCG) process of silicon oxide (SiO) based thin film dielectrics with low metallic and non-metallic impurity concentration on semiconductor substrates and, specifically, to the RTWCG of SiO-based films in the manufacture of silicon-based electronic and photonic (optoelectronic) device applications.
It is an object of the invention to provide a silicon oxide-based thin film dielectrics with low metallic and non-metallic impurity concentration on a semiconductor substrates using

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