U.S. patent application number 12/400363 was filed with the patent office on 2009-09-17 for semiconductor device production method and semiconductor production apparatus.
Invention is credited to Shin-ichi IMAI, Masakai Kitabata, Tomoya Tanaka.
Application Number | 20090229985 12/400363 |
Document ID | / |
Family ID | 41061823 |
Filed Date | 2009-09-17 |
United States Patent
Application |
20090229985 |
Kind Code |
A1 |
IMAI; Shin-ichi ; et
al. |
September 17, 2009 |
SEMICONDUCTOR DEVICE PRODUCTION METHOD AND SEMICONDUCTOR PRODUCTION
APPARATUS
Abstract
A semiconductor device production method of the present
invention first collects data including an initial volume of
plating solution, volume of replenished solution, number of wafers
processed, value of current applied and volume of waste solution in
a step of filling a metal plating film in a via hole or a trench
formed in an insulating film on a semiconductor substrate. Then, a
cumulative charge during the plating is calculated based on the
obtained current value. Also, a total volume of plating solution is
calculated. Furthermore, an amount of decomposition products of
suppressors contained in the plating solution based on the
calculated total volume of plating solution, the volume of waste
solution and the calculated cumulative charge. The semiconductor
substrate is plated only when the amount of decomposition products
is equal to or smaller than a predetermined threshold.
Inventors: |
IMAI; Shin-ichi; (Osaka,
JP) ; Tanaka; Tomoya; (Toyama, JP) ; Kitabata;
Masakai; (Toyama, JP) |
Correspondence
Address: |
MCDERMOTT WILL & EMERY LLP
600 13TH STREET, NW
WASHINGTON
DC
20005-3096
US
|
Family ID: |
41061823 |
Appl. No.: |
12/400363 |
Filed: |
March 9, 2009 |
Current U.S.
Class: |
205/82 ; 204/279;
205/81 |
Current CPC
Class: |
C25D 21/12 20130101;
C25D 17/001 20130101; H01L 21/76877 20130101; H01L 21/2885
20130101; C25D 21/18 20130101 |
Class at
Publication: |
205/82 ; 205/81;
204/279 |
International
Class: |
C25D 21/12 20060101
C25D021/12; C25D 17/00 20060101 C25D017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 11, 2008 |
JP |
2008-060835 |
Claims
1. A semiconductor device production method having a step of
filling a metal plating film in a via hole or a trench formed in an
insulating film on a semiconductor substrate, the step of filling
the metal plating film comprising the steps of: collecting data
including an initial volume of plating solution, volume of
replenished solution, number of wafers processed, value of current
applied and volume of waste solution; calculating a cumulative
charge during the plating based on the value of current applied;
calculating a total volume of plating solution; and calculating an
amount of decomposition products of suppressors contained in the
plating solution based on the calculated total volume of plating
solution, the volume of waste solution and the calculated
cumulative charge.
2. The semiconductor device production method according to claim 1,
further comprising the steps of: discharging a predetermined volume
of plating solution when the amount of decomposition products
exceeds a predetermined value; and replenishing plating
solution.
3. A semiconductor production apparatus for filling a metal plating
film in a via hole or a trench formed in an insulating film on a
semiconductor substrate, comprising: a unit circulating plating
solution; a unit replenishing plating solution; a unit discharging
the plating solution; a unit collecting data including an initial
volume of plating solution, volume of replenished solution, number
of wafers processed, value of current applied and volume of waste
solution; a unit calculating a cumulative charge during the plating
based on the value of current applied; a unit calculating a total
volume of plating solution; and a unit calculating an amount of
decomposition products of suppressors contained in the plating
solution based on the calculated total volume of plating solution,
the volume of waste solution and the calculated cumulative
charge.
4. The semiconductor production apparatus according to claim 3,
wherein the unit discharging the plating solution discharges a
predetermined volume of plating solution when the amount of
decomposition products exceeds a predetermined value.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims the benefit of Japanese
Patent Application No. 2008-060835 filed Mar. 11, 2008, the subject
matter of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a semiconductor device
production method and a semiconductor production apparatus and
particularly to a plating method and a plating apparatus used in a
metal wiring process for semiconductor devices.
[0004] 2. Description of the Related Art
[0005] FIG. 9 is a schematic diagram showing a structure of a prior
art electroplating apparatus. This electroplating apparatus
comprises a circulation line 101, a plating tank 102, a cathode
104, an anode 105, a wafer 106, a filter 107, an additive
concentration measurement unit 108, a CPU 109, and an additive
supply unit 110.
[0006] In prior art electroplating, metal-plating is performed
while additives are supplied (reference is made, for example, to
Japanese Laid-Open Patent Application No. 2001-152398). The
concentration of additives are measured based on the
current-potential curve in some cases (for example, Kimiko OYAMADA
et al., "Plating Time Dependence of Filling Ability with Additives
by Copper Electroplating", Journal of Japan Institute of
Electronics Packaging, Vol. 7, No. 3, pp. 261-265 (2004)).
[0007] FIG. 10 is a flowchart of the prior art plating process. As
shown in FIG. 10, the prior art plating process comprises the steps
of replenishing the plating solution (S101), measuring the additive
concentration (S102), starting a recipe (S103), loading a wafer
(S104), plating (S105), unloading the wafer (S106), and ending the
recipe (S107).
[0008] In prior art plating, the concentration of constituents of
additives, such as brightener, leveler and suppressor, contained in
the plating solution are measured during electroplating. Each
constituent is added as needed so to maintain the concentration in
a specific range during electroplating.
[0009] Specifically, the concentrations of constituents of
additives are measured based on the current-potential curve of the
plating solution containing the additive obtained at the CV (cyclic
voltammetry) electrode placed in the plating solution within the
plating apparatus.
SUMMARY OF THE INVENTION
[0010] It is difficult in the prior art electroplating method and
electroplating apparatus to measure and assess the concentration of
all constituents present in the plating solution including
by-products produced in the course of plating. Therefore, it is
difficult to fill a metal in the wiring regions consisting of
nanoscale microstructures in semiconductor devices without creating
any voids.
[0011] The purpose of the present invention is to fill a metal in
wiring regions consisting of nanoscale microstructures in a
semiconductor device without creating any voids and seams so as to
reduce electric defects, thereby improving the production yield of
semiconductor devices.
[0012] In order to achieve the above purpose, a semiconductor
device production method of the present invention first collects
data including an initial volume of plating solution, volume of
replenished solution, number of wafers processed, value of current
applied and volume of waste solution in a step of filling a metal
plating film in a via hole or a trench formed in an insulating film
on a semiconductor substrate. Then, a cumulative charge during the
plating is calculated based on the obtained current value. Also, a
total volume of plating solution is calculated. Furthermore, an
amount of decomposition products of suppressors contained in the
plating solution based on the calculated total volume of plating
solution, the volume of waste solution and the calculated
cumulative charge.
[0013] It is preferable in the above semiconductor device
production method that a predetermined volume of waste solution
when the amount of decomposition products exceeds a predetermined
value and fresh plating solution be replenished.
[0014] A semiconductor production apparatus of the present
invention is used to fill a metal plating film in a via hole or a
trench formed in an insulating film on the semiconductor substrate.
The semiconductor production apparatus of the present invention
comprises a unit circulating plating solution, a unit replenishing
plating solution and a unit discharging the plating solution. The
apparatus further comprises a unit collecting data including an
initial volume of plating solution, volume of replenished solution,
number of wafers processed, value of current applied and volume of
waste solution, a unit calculating a cumulative charge during
plating based on the obtained current value, a unit a total volume
of plating solution and a unit calculating an amount of
decomposition products of suppressors contained in the plating
solution based on the calculated total volume of plating solution,
the volume of waste solution and the calculated cumulative
charge.
[0015] It is preferable for the above semiconductor production
apparatus that the unit discharging the plating solution discharges
a predetermined volume of plating solution when the amount of
decomposition products exceeds a predetermined value.
[0016] The present invention prevents defective filling due to
fluctuations in the plating solution composition by calculating and
controlling the amount of by-products (the amount of decomposition
products) produced during electroplating, thereby improving the
production yield of semiconductor devices.
[0017] The foregoing and other objects, features, aspects and
advantages of the present invention will become more apparent from
the following detailed description of the present invention when
taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a schematic diagram showing a structure of an
electroplating apparatus relating to a first embodiment of the
present invention.
[0019] FIG. 2 is a graphical representation showing a relationship
between a calculated amount of by-products in plating solution and
defects occurrence.
[0020] FIG. 3 is a schematic illustration showing a defective
filling of a via hole and trench.
[0021] FIG. 4 is a schematic illustration showing a mechanism of a
defective filling of a via hole and trench.
[0022] FIG. 5 is a graphical representation showing liquid
chromatography measurements based on the calculated amount of
by-products in the plating solution.
[0023] FIG. 6 is a flowchart of an electroplating process relating
to a second embodiment of the present invention.
[0024] FIG. 7 is a graphical representation showing waste solution
ratios simulation results relating to a third embodiment of the
present invention.
[0025] FIG. 8 is a graphical representation showing a method of
determining a waste solution ratio relating to the third embodiment
of the present invention.
[0026] FIG. 9 is a schematic diagram showing a structure of a prior
art electroplating apparatus.
[0027] FIG. 10 is a flowchart of the prior art electroplating
process.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
First Embodiment
[0028] A first embodiment of the present invention is described
hereafter with reference to FIG. 1.
[0029] FIG. 1 is a schematic diagram showing the structure of an
electroplating apparatus relating to the first embodiment. The
electroplating apparatus comprises a plating chamber 21 having a
partition 22. An anode 14 is placed at the bottom of the plating
chamber 21. Facing the anode 14, a cathode 10 holds a wafer 11 in a
manner such that the surface to be treated is oriented toward the
anode 14. A filter 13 and a diffusion plate 12 are provided between
the anode 14 and cathode 10 in this order from the anode 14. The
electroplating apparatus of this embodiment further comprises a
circulation line 3 and a sub-circulation line 4 as the plating
solution circulation path. The circulation line 3 is a circulation
path allowing the plating solution from the top end of the plating
chamber 21 to re-enter between the diffusion plate 12 and filter 13
via a plating tank 2 and a filter 7. The sub-circulation line 4 is
a circulation path allowing the plating solution from the bottom of
the plating chamber 21 to re-enter between the filter 13 and anode
14 via a filter 8. A supply valve 9 for introducing fresh plating
solution into the circulation line 3 is provided on the circulation
line 3 upstream of the plating tank 2. A waste valve 5 for
discharging plating solution from the circulation path is provided
on the sub-circulation line 4 upstream of the filter 8. A control
unit 1 controls opening/closing of the supply valve 9 and waste
valve 5 based on data obtained by a monitoring unit 6, described
later. In this embodiment, the control unit 1 further controls
operations of the electroplating apparatus.
[0030] In FIG. 1, in the case that the electroplating apparatus is
used for plating copper, the plating solution is circulated and the
wafer 11 is rotated at a rotating speed of 5 to 100 rpm while a
current of 1 A to 50 A is applied to the wafer 11 placed on the
cathode 10 so as to form a plating film. The plating solution
circulates through the main circulation line 3 including the
plating tank 2 during the plating. The plating solution gathering
near the anode 14 circulates through the sub-circulation line (SAC:
separate anode chamber line) 4 near the anode 14. Here, the plating
solution mainly consists of copper sulfate and additives.
[0031] Here, three additives are used, including a suppressor,
accelerator (brightener), and leveler. The additives play an
important role in filling copper in microstructures. Their role is
briefly described hereafter.
[0032] The suppressor consists of PEG (poly(ethylene glycol))-PPG
(poly(propylene glycol)) polymers (high molecules) and suppresses
the growth of copper film. The accelerator (brightener) consists of
sulfur-containing organic substances and accelerates the growth of
copper film. The leveler consists of amine-based organic compounds
and s the growth of copper film in an area of the wafer surface
where the electric field concentrates and does not suppress the
growth of copper film in an area of the wafer surface where the
electric field does not concentrate. Therefore, the leveler serves
to improve the smoothness of the copper film.
[0033] It is very important to control the composition of the
plating solution for filling a copper film in nanoscale
microstructures such as vias, contact holes, and trenches without
creating gaps and defects such as voids and seams. However, it has
been found that the composition of the plating solution changes as
a result of electrolysis in the course of electroplating.
Furthermore, it is not sufficient to simply control the
concentrations of the above additives for predetermined value
ranges in order to fill a metal in nanoscale microstructures. This
is because the three additives are electrolyzed into different
substances (by-products) including those having different molecular
structures.
[0034] Speaking of the additive concentration control, the supply
valve 9 on the circulation line 3 is opened to add fresh plating
solution to the plating solution for controlling the additive
concentration. Such concentration control has conventionally been
used because of the belief that the by-products have no or little
influence on filling properties. However, investigation by the
inventor of the present application revealed that defective filling
occurs in vias of nanoscale microstructures, as mentioned above.
Moreover, it is difficult to measure an amount of the by-products
during a plating processing. In the electroplating apparatus, shown
in FIG. 1, invented by the inventor of the present application, the
monitoring unit 6 collects data such as an initial volume of
plating solution, a volume of replenished solution, a number of
wafers processed, a value of current applied, a value of voltage
applied, processing time, a number of rotations, a volume of waste
solution and the like, and the control unit 1 calculates the amount
of by-products (hereafter, also referred to as the amount of
decomposition products) produced as a result of electrolysis based
on a model using the data. Here, "the volume of replenished
solution" is a volume of plating solution replenished on the basis
of "the initial volume of plating solution". "The volume of waste
solution" is a volume of plating solution discharged on the basis
of "the initial volume of plating solution".
[0035] The monitoring unit 6 and control unit 1 can be realized for
example by dedicated arithmetic circuits, or hardware including a
processor and memory such as RAM (random access memory) and ROM
(read only memory) and software stored in the memory and running on
the processor. In this embodiment, the monitoring unit 6 and
control unit 1 are realized by a computer and programs running on
the computer. The monitoring unit 6 can acquire the data described
above from various sensors that acquire such data directly or based
on the operation states of the electroplating apparatus
indirectly.
[0036] The model used by the control unit 1 for calculating the
amount of decomposition products (the amount of by-products) is
described hereafter. In this embodiment, as shown in FIG. 1, one
wafer is processed in one plating operation. Therefore, the number
of plating operations is equal to the number of wafers processed.
In such a case, the amount of decomposition products N.sub.bn
contained in the plating solution after the n-th wafer processing
is expressed by the model equation (1) below in which is N.sub.b0
is the amount of decomposition products present in the initial
plating solution, G.sub.n is the amount of decomposition products
produced in the n-th wafer processing; V.sub.2 is the total volume
of plating solution (shell volume); and V.sub.1 is the volume of
waste solution in each discharge.
N bn = ( N b 0 + G 1 ) ( V 1 V 2 ) n + G 2 ( V 1 V 2 ) n - 1 + + G
n ( V 1 V 2 ) ( 1 ) ##EQU00001##
[0037] The above model equation particularly obtains the amount of
decomposition products produced (G.sub.n) in each wafer processing
using a cumulative charge (integrated current value) calculated
from the value of current applied to the wafer processed (for
example, calculated using the number of wafers processed and the
value of current applied) and calculates the amount of
decomposition products remaining after each discharging waste
solution based on the volume of waste solution in relation to the
total volume of plating solution. Then, each amount of
decomposition products remaining between discharges is cumulated to
obtain the amount of decomposition products contained in the
plating solution after the n-th wafer processing (N.sub.bn). The
amount of decomposition products produced during the subsequent
plating operation is added to the amount of decomposition products
N.sub.bn to obtain the amount of decomposition products at the time
of the subsequent plating operation. The data (particularly the
current value) used for calculating the amount of decomposition
products N.sub.bn should be obtained at least at a sampling rate
higher than 2 Hz. This is because there is some influence on the
accuracy of calculation of the amount of by-products. For example,
sampling rates higher than 2 Hz increase the calculation accuracy
more than 3%. In the above equation (1), the total volume of
plating solution (V.sub.2) and the volume of waste solution
(V.sub.1) are constant. However, when volume of waste solution and
the volume of replenished solution in each operation are different,
the amount of decomposition products can be calculated using their
respective values.
[0038] FIG. 2 is a graphical representation showing a relationship
between the calculated amount of by-products and the occurrence of
electrically defective chips due to seams and voids. In FIG. 2, the
amount of by-products (amount of decomposition products) is plotted
as ordinate. FIG. 2 shows that defective chips occur when the
amount of by-products exceeds a specific value. In other words, it
was found that by-products are produced as the plating solution is
electrolyzed in the course of the above described wafer processing
and defects such as seams and voids occur depending on the amount
of by-products. Such behavior of the by-products indicates that the
by-products possess an ability of suppressor. The inventors of the
present application have found out this new knowledge. In the
electroplating apparatus of this embodiment, a maximum volume of
plating solution to be filled is 200 L.
[0039] FIG. 3 is an illustration showing a result of physical
analysis of an electrically defective chip (the defective part was
identified and its cross-section was observed). A contact 35 has a
diameter of 60 to 70 nm. An interlayer insulating film 32
corresponding to the total depth of a trench 34 and the contact 35
has a thickness of 200 to 300 nm. FIG. 3 also shows an interlayer
insulating film 31 that is an under layer for the interlayer
insulating film 32 and a metal plating layer filled in a trench 33
formed in the interlayer insulating film 31.
[0040] In FIG. 3, the depth of the trench 34 is smaller than 100
nm. Therefore, the contact 35 has an aspect ratio up to
approximately 5. There is difficulty in filling when a contact has
a diameter of 100 nm or smaller and an aspect ratio of 3 or higher.
The electrically defective chip had a void 41 on the sidewall of
the trench 34 as shown in FIG. 3. Furthermore, a seam 42 occurred
in the contact 35. Neither the seam 42 nor the void 41 was
prevented even if the copper concentration in the plating solution
was increased from 10 mg/L to 100 mg/L.
[0041] The mechanism of occurrence of defective filling in vias is
described hereafter.
[0042] FIG. 4 is a schematic illustration showing a mechanism of
change in the via filling properties in association with alteration
in the plating solution. Investigation by the inventor of the
present application revealed that it is important to control
by-products 52 produced as a result of electrolysis of the
suppressor 51 for obtaining good via filling properties. A
phenomenon was observed that indicates that molecules having
molecular weights lower than the original PEG-PPG polymers are
produced as the suppressor 51 is consumed through electrolysis.
Molecules having lower molecular weights are the above described
by-products 52. As mentioned above, the by-products 52 possess an
ability suppressing the growth of copper film as does the
suppressor 51. With lower molecular weights, the by-products 52
have larger diffusion coefficients and a larger amount of
by-products 52 can reach the small via bottom (the bottom of the
contact 35 in FIG. 4). This leads to defective filling in vias and
contact holes. In other words, the by-products 52 presumably reach
the via bottom earlier and suppress the growth of metal film from
the via bottom (bottom filling), thereby causing defects such as
seams and voids.
[0043] Therefore, even if fresh plating solution is added to
control the amounts of three additives, it is impossible to control
the by-products produced in the above mechanism or reduce defective
filling. A fundamental solution removes the by-products from the
plating solution and bring them to the outside, namely discharging
waste solution. Hence, it is most important to control the volume
of waste solution. In the electroplating apparatus of this
embodiment, the waste valve 5 on the SAC line 4 is opened to
release the plating solution when the amount of by-products
calculated by the above equation (1) exceeds a predetermined value.
In this structure, the by-products are discharged by releasing the
plating solution and the amount of by-products present in the
plating solution and responsible for voids and seams can be
reduced.
[0044] FIG. 5 is a graphical representation showing the amount of
by-products that was calculated by the above equation (1) and the
amount of by-products in the plating solution actually measured by
liquid chromatography (off line measurement). FIG. 5 shows that the
amount of by-products in the plating solution increases as the
calculated amount of by-products increases. In this measurement,
the specific molecular structures of by-products to be detected are
not identified. Therefore, the plating solution was sampled based
on the calculated amount of by-products, and the molecules having
molecular weights different from the suppressor were measured by
liquid chromatography.
[0045] In liquid chromatography, an intensity of refractive-index
for a column retention time is observed. Molecules having such
different molecular weights emerge in retention times different
from those in which the suppressor is observed; therefore, they can
be detected separately. In actual observation, peaks supposedly for
by-products other than the suppressor were observed in times longer
than the retention time (observation time) in which the suppressor
was observed. This liquid chromatography was of the size exclusion
mode. In this mode, molecules having smaller molecular weights
enter the column deep inside and have difficulty coming out of the
column, lengthening their column retention time. In measurement,
peaks were observed in the longer retention times. Therefore, the
detected by-products presumably had molecular weights smaller than
the suppressor and the above inventor's model was verified.
Second Embodiment
[0046] A second embodiment provides a filling method creating no
defects such as voids and seams based on the first embodiment of
the present invention.
[0047] FIG. 6 is a flowchart of a plating process presenting the
second embodiment. When the electroplating apparatus starts a
recipe for plating, first, the monitoring unit 6 measures the
concentrations of the three additives (S1). The monitoring unit 6
orders the control unit 1 to replenish plating solution in the case
of NG in which the measurements are outside predetermined value
ranges. The control unit 1 being ordered opens the supply valve 9
and replenishes a predetermined volume of plating solution (S1NG,
S2). When the replenishment is completed, the monitoring unit 6
measures the concentrations of the additives once again (S1). The
replenishment of plating solution is repeated until the
concentrations of the additives are within the above predetermined
ranges. When the replenished volume exceeds the total volume of
plating solution, the control unit 1 stops the replenishment of
plating solution. When the concentrations of the additives become
within the above ranges (S1OK), the monitoring unit 6 collects
apparatus data such as the initial volume of plating solution,
volume of replenished solution, number of wafers processed, value
of current applied, value of voltage applied, processing time,
number of rotations, and volume of waste solution (S3). The control
unit 1 calculates the amount of by-products based on the equation
(1) using the collected apparatus data (S4). When the amount of
by-products exceeds a predetermined value range, the control unit 1
opens the waste valve 5 and discharges the solution (S4NG, S5).
After the discharging, the monitoring unit 6 collects the apparatus
data, and the control unit 1 calculates the amount of by-products
using the data once again (S4). The control unit 1 repeats the
discharge of plating solution until the amount of by-products
becomes within the predetermined value range (S4NG, S5). When the
amount of by-products becomes within the predetermined value range,
the control unit 1 loads a wafer into the apparatus (S6) and places
it on the cathode electrode. Then, the wafer is metal-plated (S7)
and unloaded after the plating is completed (S8); then, the recipe
ends.
[0048] What is important here is that the steps of measuring the
concentrations of additives, which is conventionally performed
outside the recipe, and determining whether the concentrations are
appropriate are newly provided and, furthermore, the mechanism and
step of replenishing plating solution when the concentrations of
additives are outside predetermined value ranges (S1NG) is
provided. What is more important is that the step of collecting
apparatus data, calculating the amount of by-products, and
determining whether the mount is appropriate is newly provided and,
furthermore, the mechanism and step of discharging the solution
when the amount of by-products is outside a predetermined value
range (S4NG) is provided. Because these are performed within the
recipe, it is possible to feedback the calculated result using the
apparatus data collected in situ. Then, the volume of replenished
solution and the volume of waste solution are controlled according
to the amount of by-products. Therefore, the accuracy of
calculation of the amount of by-products is significantly
improved.
[0049] In the above explanation, the recipe start (operation start)
is the initial point. However, needless to say, the calculation
accuracy will not be so different even if the initial point is when
a lot is engaged in the apparatus (track-in).
Third Embodiment
[0050] A third embodiment of the present invention will be
described hereafter. The third embodiment of the present invention
relates to an electroplating method in which the optimum volume of
waste solution is determined. The plating solution is expensive and
it is preferable that the volume of waste solution is minimized.
Then, in this embodiment, a technique of determining the optimum
volume of waste solution based on the quantity of wafers to be
processed, namely the amount of by-products to be produced, total
volume of plating solution, and volume of waste solution, will be
described.
[0051] FIG. 7 is a graphical representation showing results of
simulating the amount of by-products in the plating solution in
relation to the number of times of discharging waste solution.
Here, the amounts of by-products were calculated for the cases when
volume ratios of waste solution to the total volume of plating
solution (hereafter, referred to as a waste solution ratio) were 8%
and 29% with the initial amount of by-products being "1". The waste
solution ratios were randomly determined.
[0052] FIG. 7 shows that the by-products are not sufficiently
released at the waste solution ratio of 8% so that the by-products
in the plating solution continue to increase. On the other hand,
increase in the amount of by-products is suppressed at the waste
solution ratio of 29%. This suggests that there must be an optimum
waste solution ratio. Then, increase in the amount of by-products
in relation to the waste solution ratio is obtained based on the
above calculation results as follows.
[0053] FIG. 8 is a graphical representation for explaining increase
in the amount of by-products in relation to the waste solution
ratio. In FIG. 8, the waste solution ratio is plotted as abscissa
and the amount of by-products is plotted as ordinate.
[0054] As predicted above, FIG. 8 shows that the increase is
smaller as the waste solution ratio is raised. The original amount
of by-products is "1." The waste solution ratio to keep the amount
of by-products "1" or smaller is 34%. Therefore, 34% of the total
volume of plating solution should be discharged at each discharge
to prevent the amount of by-products in the plating solution from
increasing. Needless to say, the amount of by-products in the
plating solution can be reduced as the number of times of
discharging waste solution is increased when the waste solution
ratio is higher than 34%.
[0055] In this embodiment, the volume of waste solution can
previously be determined as described above. Defective filling due
to abnormal apparatus states can be prevented by storing the
obtained value in the monitoring unit 6 in FIG. 1 as a threshold
and stopping the plating apparatus when the waste solution ratio is
lower than the threshold. At least 34% of plating solution should
be discharged at least to fill copper in microstructures having
contacts of 100 nm or smaller in diameter as shown in FIG. 3
without creating any defects such as voids and seams.
[0056] In the above embodiments, copper is filled. However,
needless to say, the same is true for other metal films such as
silver and aluminum.
[0057] As described above, the present invention prevents defective
filling due to change in the composition of plating solution and
improves the production yield of semiconductor devices.
[0058] The present invention is not restricted to the above
embodiments. Various modifications and applications are available
without departing from the technical idea of the present invention.
For example, in the above embodiments, the present invention is
applied to a semiconductor production apparatus having a
circulation line and a sub-circulation line. The invention of the
present application is applicable to a semiconductor production
apparatus having only one circulation line as shown in FIG. 9.
[0059] The semiconductor device production method and semiconductor
production apparatus of the present invention is capable of
obtaining the amount of by-products to be produced by calculation
and can use this capability for controlling the amount of
by-products for a constant value, therefore providing a useful
production technique for the semiconductor device wiring process in
which metals are filled in nanoscale microstructures. The present
invention also has applications in plating process for MEMSs.
* * * * *