U.S. patent application number 09/886389 was filed with the patent office on 2002-02-07 for method for fabricating a capacitor in a semiconductor device.
Invention is credited to Choi, Hyung-Bok, Hong, Kwon.
Application Number | 20020016036 09/886389 |
Document ID | / |
Family ID | 19674486 |
Filed Date | 2002-02-07 |
United States Patent
Application |
20020016036 |
Kind Code |
A1 |
Hong, Kwon ; et al. |
February 7, 2002 |
Method for fabricating a capacitor in a semiconductor device
Abstract
A method for fabricating a capacitor of a semiconductor device,
comprising the steps of forming a seed layer over a semiconductor
substrate, forming multiple oxide layers on the seed layer, wherein
wet etching of the multiple oxide layer decreases as the layer go
up, forming a first opening exposing the seed layer by selectively
dry etching the multiple oxide layer, forming a second opening by
wet etching the lateral surface of the first opening where is the
width of the first opening is expanded, wherein the lower part of
the second opening is larger than the upper part, forming a bottom
electrode on the seed layer exposed at the bottom of the second
opening, whereby the bottom electrode has an identical shape with
the second opening, wherein the bottom electrode is formed with the
ECD (Electro-Chemical Deposition) technique, exposing the seed
layer by removing the multiple oxide layer, removing the exposed
seed layer, forming a dielectric layer on the bottom electrode and
forming a top electrode on the dielectric layer.
Inventors: |
Hong, Kwon; (Ichon-shi,
KR) ; Choi, Hyung-Bok; (Ichon-shi, KR) |
Correspondence
Address: |
JACOBSON HOLMAN PLLC
400 SEVENTH STREET N.W.
SUITE 600
WASHINGTON
DC
20004
US
|
Family ID: |
19674486 |
Appl. No.: |
09/886389 |
Filed: |
June 22, 2001 |
Current U.S.
Class: |
438/243 ;
257/E21.019; 257/E21.251; 257/E21.252; 257/E21.578 |
Current CPC
Class: |
H01L 21/31111 20130101;
H01L 28/91 20130101; H01L 21/76804 20130101; H01L 21/31116
20130101 |
Class at
Publication: |
438/243 |
International
Class: |
H01L 021/8242 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 28, 2000 |
KR |
2000-36046 |
Claims
What is claimed is:
1. A method for fabricating a capacitor of a semiconductor device,
comprising the steps of: forming a seed layer over a semiconductor
substrate; forming multiple oxide layers on the seed layer, wherein
wet etching rate of the multiple oxide layer decreases as the layer
go up; forming a first opening exposing the seed layer by
selectively dry etching the multiple oxide layer; forming a second
opening by wet etching the lateral surface of the first opening
where is the width of the first opening is expanded, wherein the
lower part of the second opening is larger than the upper part;
forming a bottom electrode on the seed layer exposed at the bottom
of the second opening, whereby the bottom electrode has an
identical shape with the second opening, wherein the bottom
electrode is formed with the ECD (Electro-Chemical Deposition)
technique; exposing the seed layer by removing the multiple oxide
layer by wet etching; removing the seed layer by dry etching;
forming a dielectric layer on the bottom electrode; and forming a
top electrode on the dielectric layer.
2. The method as recited in claim 1, wherein the seed layer is
formed with a material selected from the group consisting of Pt,
Ru, Ir, Os, W, Mo, Co, Ni, Au and Ag layer.
3. The method as recited in claim 1, wherein the bottom electrode
is formed with a material selected from the group consisting of Pt,
Ru, Ir, Os, W, Mo, Co, Ni, Au and Ag layer.
4. The method as recited in claim 1, wherein the bottom electrode
is formed at a current density of 0.1 mA/cm.sup.2 to 10
mA/cm.sup.2.
5. The method as recited in claim 1, wherein the multiple oxide
layers are formed step by step by decreasing concentration of
dopant in each layer of the multiple oxide layers.
6. The method as recited in claim 5, wherein the dopant is a
material selected from the group consisting of B, P, As and Ga.
7. The method as recited in claim 1, wherein the wet etching is
performed at a temperature of 4.degree. C. to 80.degree. C. for 1
second to 3600 seconds.
8. The method as recited in claim 7, wherein the wet etching is
performed by using HF contained solution.
9. The method as recited in claim 8, wherein the wet etching is
performed by using mixed solution of the HF solution and H.sub.2O,
wherein the volume of H.sub.2O is less than 1000 times of the
volume of the HF solution.
10. The method as recited in claim 9, wherein the wet etch is
performed by using a mixed solution of the NH.sub.4F solution and
HF, wherein the volume of NH.sub.4F is less than 500 times of the
volume of the NH.sub.4F/HF solution.
11. The method as recited in claim 1, wherein the multiple oxide
layers are formed by increasing, step by step, depositing
temperature of each layer of the multiple oxide layers, wherein
each layer of the multiple oxide layers have an identical dopant
concentration.
12. The method as recited in claim 11, wherein the dopant is a
material selected from the group consisting of B, P, As and Ga.
13. The method as recited in claim 12, wherein the wet etching is
performed at a temperature of 4.degree. C. to 80.degree. C. for 1
second to 80 seconds.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method for manufacturing
a capacitor in a semiconductor device; and, more particularly, a
method for fabricating a capacitor having a bottom electrode, of
which on upper part is smaller than a lower part.
DESCRIPTION OF THE PRIOR ART
[0002] An ECD (Electro-Chemical Deposition) technique is used to
deposit the Pt layer for a bottom electrode of a capacitor, of
which size is decreased according to the increase of the
integration density of the semiconductor device. To form the Pt
layer for the bottom electrode, a Pt seed layer is formed on a
semiconductor substrate, on which a predetermined lower structure
is formed, and an oxide layer pattern having an opening exposing
the Pt seed layer is formed. The Pt layer is deposited on the Pt
seed layer exposed in the opening.
[0003] At this time, a profile of a bottom electrode is determined
by a profile of the opening in the oxide pattern formed by dry
etch. The opening has the profile that the lower part of the
opening is relatively smaller than the upper part, by the
characteristic of dry etch. As described in FIG. 1, the lower part
of the bottom electrode is smaller than the upper part, according
to the profile of the opening. Thereby, the electrical
characteristics of capacitor are deteriorated, because the step
coverage of the dielectric layer and the top electrode, deposited
on the bottom electrode, is poor.
SUMMARY OF THE INVENTION
[0004] It is, therefore, an object of the present invention to
provide a method for fabricating a capacitor improving an
electrical characteristic in a semiconductor device.
[0005] In accordance with an aspect of the present invention, there
is provided a method for fabricating a capacitor of a semiconductor
device, comprising the steps of: forming a seed layer over a
semiconductor substrate; forming multiple oxide layers on the seed
layer, wherein wet etching rate of the multiple oxide layer
decreases as the layer go up; forming a first opening exposing the
seed layer by selectively dry etching the multiple oxide layer;
forming a second opening by wet etching the lateral surface of the
first opening where is the width of the first opening is expanded,
wherein the lower part of the second opening is larger than the
upper part; forming a bottom electrode on the seed layer exposed at
the bottom of the second opening, whereby the bottom electrode has
an identical shape with the second opening, wherein the bottom
electrode is formed with the ECD (Electro-Chemical Deposition)
technique; exposing the seed layer by removing the multiple oxide
layer by wet etching; removing the seed layer by dry etching;
forming a dielectric layer on the bottom electrode; and forming a
top electrode on the dielectric layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] The above and other objects and features of the present
invention will become apparent from the following description of
preferred embodiments taken in conjunction with the accompanying
drawings, in which:
[0007] FIGS. 1 to 5 are cross-sectional views showing a capacitor
fabricating process of a semiconductor device according to the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0008] Hereinafter, a method for fabricating a capacitor of a
semiconductor device according to the present invention will be
described in detail referring to the accompanying drawings.
[0009] As described in FIG. 1, an insulating layer 12 and a
reflecting protection layer 13 are formed on a semiconductor
substrate 11, on which a predetermined structure has been formed.
The reflecting protection layer 13 is formed with a material of
which etching selectivity is higher than the insulating layer 12.
The insulating layer 12 is formed with an oxide layer and the
reflecting protection layer 13 is formed with an oxide-nitride
layer (SION) according to the preferred embodiment of the present
invention.
[0010] Next, a contact hole, exposing a predetermined region of the
semiconductor, is formed by selectively etching the reflecting
protection layer 13 and the insulating layer 12. Therefore, a
polysilicon layer is formed on the entire structure, at thickness
of 500 .ANG. to 3000 .ANG., and then a polysilicon plug 14 is
formed through a blanket etching process until the polysilicon is
remained only in the contact hole at depth of 500 .ANG. to 2000
.ANG. from the upper surface of the reflection protecting layer
13.
[0011] A Ti layer is formed on the entire structure, including the
polysilicon plug 14, at thickness of 100 .ANG. to 300 .ANG.. A
thermal treatment is performed to form TiSi.sub.x 15 layer on the
polysilicon plug 14 by the reaction between the surface of the
polysilicon plug 14 and the Ti layer. Thereafter, the Ti layer
remaining on the reflecting protection layer 13 is removed by a wet
etching process.
[0012] A diffusion barrier layer 16 is formed on the entire
structure for completely burying the contact hole. The diffusion
barrier layer 16 is formed with one of TiN layer, TiSiN layer,
TiAlN layer, TaSiN layer or TaAlN layer. A CMP process is performed
until the upper surface of the reflecting prevention layer is
revealed, thereby the diffusion barrier layer 16 remains only on
the TiSix layer 15 in the contact hole.
[0013] A seed layer 17 for forming a Pt layer is formed on the
reflecting protection layer 13 and the diffusion barrier layer 16.
The seed layer 17 is formed with one of Pt, Ru, Ir, Os, W, Mo, Co,
Ni, Au or Ag at thickness of 50 .ANG. to 1000 .ANG..
[0014] As described in FIG. 2, a first oxide layer 18 and a second
oxide layer 19 are successively formed on the seed layer 17. Even
if the oxide layer is formed with double steps according to the
preferred embodiment of the present invention, the oxide layer can
be formed with multiple layers, such as triple layer and so on.
[0015] In the multiple oxide layers, the wet etching rate of each
layer decreases as the layers go up. Namely, in case of forming the
double oxide layers according to the preferred embodiment of the
present invention, the wet etching rate of the first oxide layer 18
is faster than that of the second oxide layer 19.
[0016] In order to decrease the wet etching rates of the multiple
oxide layers, as the layers go up, two methods of forming the
multiple oxide layers may be used. One method is to decrease the
dopant concentration of multiple oxide layers, as the layers go up.
The other method is to increase the deposition temperature of
multiple oxide layers, of each layer is doped with an identical
dopant, as the layers go up. The multiple oxide layers are doped
with at least one of B, P, As or Ga. Total thickness of the
multiple oxide layer is 500 .ANG. to 20000 .ANG. in the preferred
embodiment of the present invention.
[0017] A first opening 31 exposing the seed layer 17 is formed by
selectively dry-etching.
[0018] As shown in FIG. 3, the second oxide layer 19 and the first
oxide layer 18 are etched, by using wet etchant, to form a second
opening 32, which is larger than the first opening. The first oxide
layer 18 is etched more rapidly than the second oxide layer 19 in
the etching process, because the etch rate of the first oxide layer
18 is faster than that of the second oxide layer 19. Thereby, it is
possible to obtain the second opening 32, of which the lower part
is larger than the upper part. The second oxide layer 19 and the
first oxide layer 18 are etched with a mixed solution of HF and
H.sub.2O, or a mixed solution of NH.sub.4F and H.sub.2O, at
temperature of 4.degree. C. to 80 .degree. C., for 1 second to 3600
seconds, according to the preferred embodiment of the present
invention. The volume of H.sub.2O is less than 1000 times of the
volume of the HF solution, in the mixed solution of HF and
H.sub.2O, and the volume of NH4F is less than 500 times of the
volume of the mixed solution of NH.sub.4F and HF.
[0019] Subsequently, a first metal layer is formed on the seed
layer 17 by using an ECD technique, and the first metal layer is
completed with wet etching of the first oxide layer 18 and second
oxide layer 19. The first metal layer is formed with one of Ru, Ir,
Os, W, Mo, Co, Ni, Au or Ag layer at condition of current density
of 0.1 mA/cm.sup.2 to 10 mA/cm.sup.2.
[0020] It is possible to form the bottom electrode, of which lower
part is larger than the upper part, by forming the first metal
layer in the second opening 32, of which lower part is also larger
than the upper part. The bottom electrode of the capacitor
fabricated according to the present invention is shown in FIG.
3.
[0021] As described in FIG. 4, the seed layer 17 is exposed by
removing the multiple oxide layers and the exposed seed layer 17 is
removed for insulation between bottom electrodes.
[0022] As described in FIG. 5, a dielectric layer 21 is formed on
the entire structure including the bottom electrode, and a rapid
thermal annealing process is implemented for improving a dielectric
characteristic. A second metal layer, e.g., Pt layer, is formed on
the dielectric layer 21 and a top electrode 22 is formed by
patterning the second metal layer. The dielectric layer 21 is
formed with a (Ba, Sr)TiO.sub.3 (BST) layer at temperature of
300.degree. C. to 600.degree. C., to thickness of 150 to 500. Also,
the rapid annealing process is implemented at nitrogen gas
atmosphere of temperature of 500.degree. C. to 700.degree. C. for
30 seconds to 180 seconds in the ambient of nitrogen. The second
metal layer is formed by using a CVD technique or a sputtering
technique.
[0023] As described in the above, when the dielectric layer and the
top electrode are formed on the bottom electrode according to the
present invention, the characteristic of the step coverage may be
improved and, also, an electrical characteristic of the device may
be improved.
[0024] While the present invention has been described with respect
to the particular embodiments, it will be apparent to those skilled
in the art that various changes and modifications may be made
without departing from the spirit and scope of the invention as
defined in the following claims.
* * * * *