U.S. patent application number 11/022166 was filed with the patent office on 2005-06-23 for apparatus and method for wafer planarization.
This patent application is currently assigned to DongbuAnam Semiconductor Inc.. Invention is credited to Kim, Sang Kwon.
Application Number | 20050133156 11/022166 |
Document ID | / |
Family ID | 34675990 |
Filed Date | 2005-06-23 |
United States Patent
Application |
20050133156 |
Kind Code |
A1 |
Kim, Sang Kwon |
June 23, 2005 |
Apparatus and method for wafer planarization
Abstract
An apparatus and a method for wafer planarization is disclosed.
A disclosed apparatus comprises a liquid nitrogen supply tube; a
nitrogen gas transfer tube linked to the nitrogen gas supply tank
by valve; an etchant supply tube linked with the nitrogen gas
transfer tube; a spray nozzle part linked with the nitrogen gas
supply tube; and a chamber with a spray nozzle attached to the
upper part of the chamber and a wafer rotating equipment placed in
the lower part. A disclosed apparatus and a method has advantage to
planarize an entire surface of wafer by spraying high pressure of
etchant vapor into a wafer surface rotating at high speed.
Inventors: |
Kim, Sang Kwon; (Suwon-si,
KR) |
Correspondence
Address: |
THE LAW OFFICES OF ANDREW D. FORTNEY, PH.D., P.C.
7257 N. MAPLE AVENUE
BLDG. D, 3107
FRESNO
CA
93720
US
|
Assignee: |
DongbuAnam Semiconductor
Inc.
|
Family ID: |
34675990 |
Appl. No.: |
11/022166 |
Filed: |
December 23, 2004 |
Current U.S.
Class: |
156/345.12 ;
257/E21.219 |
Current CPC
Class: |
H01L 21/02019 20130101;
H01L 21/30604 20130101; H01L 21/6708 20130101 |
Class at
Publication: |
156/345.12 |
International
Class: |
C23F 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 23, 2003 |
KR |
10-2003-0095812 |
Claims
What is claimed is:
1. An apparatus for wafer planarization comprising: a liquid
nitrogen supply tank; a nitrogen gas transfer tube linked with the
liquid nitrogen supply tank by a valve; an etchant supply tube
linked with the nitrogen gas transfer tube; an etchant supply tank
for containing etchant linked with the etchant supply tube; and a
chamber with a spray nozzle part linked with the nitrogen gas
transfer tube attached to the upper part thereof and a wafer
rotating equipment placed in the lower part thereof.
2. The apparatus as defined by claim 1, wherein a sensor to detect
the remaining volume of the etchant is attached to the etchant
supply tank.
3. The apparatus as defined by claim 1, wherein the exit of the
etchant supply tube comprises a nozzle.
4. The apparatus as defined by claim 1, wherein the spray nozzle
part comprises plural nozzles.
5. The apparatus as defined by claim 1, wherein the wafer rotating
equipment comprises: a rotation actuator with a motor; a lift for
loading and unloading a wafer at the upper part of the rotation
actuator; a wafer stage at the upper part of the lift on which the
wafer is positioned; a clamp at the upper edge of the stage to fix
the wafer; and a cleaning nozzle to supply de-ionized water to the
wafer.
6. A method for wafer planarization comprising: emitting nitrogen
gas to a nitrogen gas transfer tube; mixing the emitted nitrogen
gas and etchant; planarizing a wafer by spraying the mixed etchant
from a spray nozzle part linked with the nitrogen gas transfer tube
onto the entire surface of the wafer; and cleaning the wafer.
7. The method as defined by claim 6, wherein the nitrogen gas is
emitted at high pressure from a liquid nitrogen supply tank into
the nitrogen gas transfer tube.
8. The method as defined by claim 6, wherein mixing the emitted
nitrogen gas and the etchant comprises: rising of the etchant,
which is stored and, diluted with de-ionized water in an etchant
supply tank, by pressure difference between the nitrogen gas
transfer tube at low pressure and an etchant supply tube at high
pressure linked with the nitrogen gas transfer tube and the etchant
supply tank; and mixing fine particles of the etchant sprayed
through a nozzle at the end of the etchant supply tube with the
emitted nitrogen gas.
9. The method as defined by claim 6, wherein planarizing the wafer
comprises: transforming the etchant sprayed from the spray nozzle
part into vapor by means of the nitrogen at high pressure; spraying
uniformly the etchant in vapor onto the entire surface of the wafer
rotating at high speed; and etching anisotropically the wafer in
the same direction as that of the wafer rotation.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an apparatus and a method
for wafer planarization and, more particularly, to an apparatus and
a method used to planarize the entire surface of a wafer by
spraying high-pressure etchant vapor into the wafer surface, which
can substitute an existing CMP (Chemical Mechanical Polish)
process.
[0003] 2. Background of the Related Art
[0004] FIG. 1a through FIG. 1c illustrate a conventional spin type
wafer processing equipment.
[0005] Referring to FIG. 1a, a spin type of wafer processing
equipment to substitute the existing CMP equipments comprises a
wafer chuck 10 on which a wafer is loaded and a chemical supply
line 14 to supply etching chemical solution to an upper part of the
wafer chuck. Once a wafer 12 is loaded on the wafer chuck, this
wafer chuck rotates and the chemical solution is dropped and
supplied to this rotating wafer through the chemical supply line.
The chemical supply line moves back and forth across the wafer. 14a
and 14b represent chemical supply lines placed between the wafer
center and wafer edge.
[0006] Referring to FIG. 1b, the virtual line 18 shows moving path
of the chemical supply line 14. A centrifugal force by wafer
rotation affects the chemical supplied to wafer, so the chemical
moves from first supplied points to wafer edges. Therefore, the
result of a wafer processing such as etching, strip and cleaning is
different by the regions on a wafer.
[0007] Referring to FIG. 1c, during the wafer rotation, wafer
processing chemical on the center of wafer has high relative
velocities to the wafer and experiences a centrifugal force
directed outward this wafer. Accordingly, the chemical moves fast
to the first region (R1) at a distance of radius r from the first
supplied point. Outside this R1 region, the relative velocity
between the chemical and the wafer 12 is near 0 and the movement
toward wafer edge becomes very slow even though the chemicals still
get affected by the centrifugal force. That is, the chemical
arriving at the second region (R2) between the first region (R1)
and the edge moves together with the wafer without fast movement
directed to the wafer edge. This difference in moving speed of
chemicals by the regions on a wafer, results in different reaction
time by the regions. The reaction time is longer on the first
region (R1) than on the second region (R2). Owing to the reaction
time difference, on a wafer, processing time is short for the first
region (R1) and long for the second region (R2). Therefore, the
first region (R1) is processed thickly and the second region (R2)
thinly.
[0008] This spin type wafer processing equipment has advantage that
wafer surface can be planarized without using existing CMP
equipment. By avoiding mechanical polishing by the friction with
the polishing pad of the CMP equipment, the defects like scratch
can be prevented. Furthermore, slurry needs not be used, so
production cost and the expense for processing byproducts can be
saved.
[0009] However, for the above-described spin type wafer processing
equipment, etching chemical have a enough reaction time only for
limited wafer region, so it is difficult to evenly planarize the
entire surface of the wafer. To solve this problem, it is necessary
to repeat the wafer processing with changing processing conditions.
For example, during an at the above oxide etching process, after
the first process is performed the second etching process should be
performed under the condition that the first region (R1) with
thicker oxide is given a longer reaction time and the second region
(R2) with thinner oxide is given a shorter reaction time. This
two-step process becomes a main reason for increasing the wafer
processing time and lowering semiconductor equipment
productivity.
SUMMARY OF THE INVENTION
[0010] Accordingly, the present invention is directed to an
apparatus and a method for wafer planarization that substantially
obviates one or more problems due to limitations and disadvantages
of the related art.
[0011] An object of the present invention is to provide an
apparatus and a method used to planarize the entire surface of a
wafer by spraying high pressure etchant vapor into the wafer
surface which can substitute an existing CMP (Chemical Mechanical
Polish) process to substantially obviate one or more problems due
to limitations and disadvantages of the related art.
[0012] To achieve this object, in accordance with the purpose of
the invention, as embodied and broadly described herein, an
apparatus for wafer planarization comprises: a liquid nitrogen
supply tank; a nitrogen gas transfer tube linked with the liquid
nitrogen supply tank by a valve; an etchant supply tube linked with
the nitrogen gas transfer tube; an etchant supply tank for
containing etchant linked with the etchant supply tube; and a
chamber with a spray nozzle part linked with the nitrogen gas
transfer tube attached to the upper part thereof and a wafer
rotating equipment placed in the lower part thereof.
[0013] Additionally, to achieve the object of the present
invention, a method for wafer planarization comprises: emitting
nitrogen gas into a transfer tube; mixing the emitted nitrogen gas
with etchant; planarizing a wafer by spraying the mixed etchant on
the entire surface of wafer through a spraying nozzle part of
chamber; and cleaning the wafer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The accompanying drawings, which are included to provide a
further understanding of the invention and are incorporated in and
constitute a part of this application, illustrate embodiment(s) of
the invention and together with the description serve to explain
the principle of the invention. In the drawings;
[0015] FIG. 1a through FIG. 1c illustrate a conventional spin type
wafer processing equipment.
[0016] FIG. 2a and FIG. 2b illustrate a wafer planarization
equipment using high pressure etchant vapor in accordance with the
teachings of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0017] Reference will now be made in detail to the preferred
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings.
[0018] FIG. 2a and FIG. 2b illustrate a wafer planarization
equipment using high pressure etchant vapor.
[0019] FIG. 2a is a sketch illustrating a wafer planarization
apparatus of the present invention. This wafer planarization
apparatus comprises a supply part to provide high pressure etchant
and a chamber part 50 for wafer planarization. The supply part
comprises a liquid nitrogen (LN.sub.2) supply tank 20, an etchant
supply tank 30 and a spraying nozzle part 40 and the chamber part
comprises a wafer rotating equipment 45 and a cleaning unit not
shown.
[0020] Referring to FIG. 2a, liquid nitrogen at ultra low
temperature is stored in the storing tank 20 at high pressure. When
a tank valve opens, the pressure decreases so fast that the triple
point at which all three phases of solid, liquid and gas can
coexist is formed and high pressure is generated. This high
pressure makes nitrogen gas vaporized from the liquid nitrogen emit
into a nitrogen gas transfer tube 21. This transfer tube 21 is
linked to an etchant supply tube 33, which is in turn linked to the
etchant supply tank 30 containing etchant. At the confluence of the
nitrogen gas transfer tube 21 and the etchant supply tube 33, low
pressure is generated due to the nitrogen gas moving through the
transfer tube at high speed. Thus, there is significant pressure
difference between the confluence at low atmospheric pressure and
the etchant supply tube 33 at atmospheric pressure. This
significant pressure difference makes the etchant 31 in the etchant
supply tank 30 rise through the etchant supply tube 33 and mix with
the nitrogen gas. The etchant 31 is stored, dilated with de-ionized
water and a sensor 32 attached to the etchant supply tank 30 can
detect the remaining volume of the etchant in the store tank. In
addition, the exit of the etchant supply tube 33 at the confluence
is made of a nozzle so that the etchant rising through this supply
tube 33 transforms into fine particles and these particles are
mixed with the nitrogen gas. This nitrogen gas plays a role as
carrier. The fine particles of the etchant are carried by this
nitrogen gas, pass through the transfer tube 21 linked to the
chamber part 50, and then arrive at the spray nozzle part 40
attached to the upper part of the interior of chamber part 50.
There may be plural nozzles in the spray nozzle part 40 so that the
etchant can be sprayed uniformly on the entire surface of a wafer
through these nozzles. The etchant is sprayed onto the rotating
wafer at a high speed as fume of fire particles at a high pressure,
due to the fine holes of the nozzles and the high pressure of the
nitrogen gas.
[0021] Further processes for etching are as follows. For example,
silicon oxide (SiO.sub.2) is positioned on a wafer surface and an
etchant is hydrofluoric acid (HF). The silicon oxide reacts with
the hydrofluoric acid (HF) as vapor as below.
SiO.sub.2+HF.fwdarw.SiO.sub.4.Arrow-up bold.+H.sub.2O.Arrow-up
bold.
[0022] The above reaction causes only an isotropic etching which is
inappropriate to planarization. Therefore, to induce an anisotropic
etching, the wafer is rotated at high speed. By rotating the wafer
at high speed and spraying uniformly the etchant of fire particles
in vapor, the wafer is etched anisotropically in the same direction
as that of the wafer rotation and planarized.
[0023] FIG. 2b represents the wafer rotating equipment 45. A wafer
51 is put between the top of a clamp 52 and a wafer stage 53 for a
fixation by a lift 54 for a loading and an unloading. The clamp 52
is positioned at the upper edge of the stage 53 to fix the wafer.
The stage 53 is positioned at the upper part of the lift on which
the wafer is positioned. The lift 54 is positioned at the upper
part of the rotation actuation. The wafer 51 then rotates by a high
speed rotation actuator 55 with a motor. After the wafer 51 is
planarized by the etchant in vapor, it is cleaned with de-ionized
water sprayed from a cleaning nozzle (not shown).
[0024] The foregoing embodiments are merely exemplary and are not
to be construed as limiting the present invention. The present
teachings can be readily applied to other types of apparatuses. The
description of the present invention is intended to be
illustrative, and not to limit the scope of the claims. Many
alternatives, modifications, and variations will be apparent to
those skilled in the art.
* * * * *