U.S. patent application number 10/742883 was filed with the patent office on 2004-07-15 for semiconductor device manufacturing system for etching a semiconductor by plasma discharge.
This patent application is currently assigned to Kabushiki Kaisha Toshiba. Invention is credited to Matsumoto, Takanori, Narita, Masaki, Sato, Fumio, Shimonishi, Satoshi.
Application Number | 20040137746 10/742883 |
Document ID | / |
Family ID | 13602979 |
Filed Date | 2004-07-15 |
United States Patent
Application |
20040137746 |
Kind Code |
A1 |
Matsumoto, Takanori ; et
al. |
July 15, 2004 |
Semiconductor device manufacturing system for etching a
semiconductor by plasma discharge
Abstract
A semiconductor device manufacturing system has a vacuum chamber
which is provided with a cathode electrode for holding a substrate
to be processed and into which a reactive gas for generating
discharging plasma by the application of a high-frequency electric
power is introduced, a measuring circuit which measures at least
one of the impedance of a system including the plasma, the
peak-to-peak voltage of a high-frequency signal applied to the
plasma, and a self-bias voltage applied to the cathode electrode,
and a sense circuit which compares the measured value from the
measuring circuit with previously prepared data and senses the
change of processing characteristics with time for the substrate in
using the discharging plasma or the cleaning time of the inside of
the vacuum chamber.
Inventors: |
Matsumoto, Takanori;
(Yokkaichi-shi, JP) ; Shimonishi, Satoshi;
(Kawasaki-shi, JP) ; Sato, Fumio; (Oita-shi,
JP) ; Narita, Masaki; (Yokohama-shi, JP) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER
LLP
1300 I STREET, NW
WASHINGTON
DC
20005
US
|
Assignee: |
Kabushiki Kaisha Toshiba
Kawasaki-shi
JP
|
Family ID: |
13602979 |
Appl. No.: |
10/742883 |
Filed: |
December 23, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10742883 |
Dec 23, 2003 |
|
|
|
09527681 |
Mar 17, 2000 |
|
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|
6685797 |
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Current U.S.
Class: |
438/706 ;
438/689 |
Current CPC
Class: |
H01J 37/32082
20130101 |
Class at
Publication: |
438/706 ;
438/689 |
International
Class: |
H01L 021/302; H01L
021/461 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 19, 1999 |
JP |
11-076352 |
Claims
What is claimed is:
1. A semiconductor device manufacturing system comprising: a vacuum
chamber provided with a cathode electrode for holding a substrate
to be processed and into which a reactive gas for generating
discharging plasma by the application of a high-frequency electric
power is introduced; a high-frequency power supply connected to
said cathode electrode, for applying a high-frequency electric
power to said cathode electrode; a measuring circuit connected to
said cathode electrode, for measuring at least one of the impedance
of a system including said plasma, the peak-to-peak voltage of a
high-frequency signal applied to said plasma, and a self-bias
voltage applied to said cathode electrode; and a sense circuit for
receiving the measured value from said measuring circuit, and for
sensing the change of processing characteristics with time for said
substrate by comparing said measured value with previously prepared
data.
2. The system according to claim 1, wherein said reactive gas is an
etching gas for etching said substrate to be processed.
3. The system according to claim 1, further comprising an impedance
matching circuit provided between said high-frequency power supply
and said cathode electrode of said vacuum chamber, for effecting
the impedance matching between the output of said high-frequency
power supply and a load on the high-frequency power supply.
4. A semiconductor device manufacturing system comprising: a vacuum
chamber provided with a cathode electrode for holding a substrate
to be processed and into which a reactive gas for generating
discharging plasma by the application of a high-frequency electric
power is introduced; a high-frequency power supply connected to
said cathode electrode, for applying a high-frequency electric
power to said cathode electrode; a measuring circuit connected to
said cathode electrode, for measuring at least one of the impedance
of a system including said plasma, the peak-to-peak voltage of a
high-frequency signal applied to said plasma, and a self-bias
voltage applied to said cathode electrode; and a report circuit for
receiving the measured value from said measuring circuit, for
sensing that said measured value has departed from a preset range,
and for reporting the cleaning time of the inside of said vacuum
chamber.
5. The system according to claim 4, wherein said reactive gas is an
etching gas for etching said substrate.
6. The system according to claim 4, further comprising an impedance
matching circuit provided between said high-frequency power supply
and said cathode electrode of said vacuum chamber, for effecting
the impedance matching between the output of said high-frequency
power supply and a load on the high-frequency power supply.
7. A semiconductor device manufacturing system comprising: a vacuum
chamber provided with a cathode electrode for holding a substrate
to be processed and into which a reactive gas for generating
discharging plasma by the application of a high-frequency electric
power is introduced; a high-frequency power supply connected to
said cathode electrode, for applying a high-frequency electric
power to said cathode electrode; a measuring circuit connected to
said cathode electrode, for measuring at least one of the impedance
of a system including said plasma, the peak-to-peak voltage of a
high-frequency signal applied to said plasma, and a self-bias
voltage applied to said cathode electrode; and a control circuit
for receiving the measured value from said measuring circuit, for
supplying an output based on said measured value to said
high-frequency power supply, and for controlling the output of said
high-frequency power supply in such a manner that the measured
value of said measuring circuit is kept at a specific value.
8. The system according to claim 7, wherein said reactive gas is an
etching gas for etching said substrate.
9. The system according to claim 7, further comprising an impedance
matching circuit provided between said high-frequency power supply
and said cathode electrode of said vacuum chamber, for effecting
the impedance matching between the output of said high-frequency
power supply and a load on the high-frequency power supply.
10. A semiconductor device manufacturing system comprising: a
vacuum chamber provided with a cathode electrode for holding a
substrate to be processed and a reactive gas intake and into which
a reactive gas for generating discharging plasma by the application
of a high-frequency electric power is introduced through said
intake; a high-frequency power supply connected to said cathode
electrode, for applying a high-frequency electric power to said
cathode electrode; an electronic valve provided at said intake in
such a manner that the intake of said reactive gas introduced into
said vacuum chamber is controlled; a measuring circuit connected to
said cathode electrode for measuring at least one of the impedance
of a system including said plasma, the peak-to-peak voltage of a
high-frequency signal applied to said plasma, and a self-bias
voltage applied to said cathode electrode; and a control circuit
for receiving the measured value from said measuring circuit, for
supplying an output based on said measured value to said valve, and
for controlling the operation of said valve in such a manner that
said measured value of said measuring circuit is kept at a specific
value.
11. The system according to claim 10, wherein said reactive gas is
an etching gas for etching said substrate.
12. The system according to claim 11, wherein said etching gas
includes O.sub.2 gas and the operation of said valve is controlled
by said control circuit in such a manner that the intake of said
O.sub.2 gas introduced into said vacuum chamber is changed.
13. The system according to claim 10, further comprising an
impedance matching circuit provided between said high-frequency
power supply and said cathode electrode of said vacuum chamber for
effecting the impedance matching between the output of said
high-frequency power supply and a load on the high-frequency power
supply.
14. A semiconductor device manufacturing system comprising: a
vacuum chamber provided with a cathode electrode for holding a
substrate to be processed, a reactive gas intake, and a reactive
gas outlet, and into which a reactive gas for generating
discharging plasma by the application of a high-frequency electric
power is introduced through said intake; a high-frequency power
supply connected to said cathode electrode, for applying a
high-frequency electric power to said cathode electrode; an
electronic valve provided at said outlet in such a manner that the
pressure in said vacuum chamber is adjusted; a measuring circuit
connected to said cathode electrode for measuring at least one of
the impedance of a system including said plasma, the peak-to-peak
voltage of a high-frequency signal applied to said plasma, and a
self-bias voltage applied to said cathode electrode; and a control
circuit for receiving the measured value from said measuring
circuit, for supplying an output based on said measured value to
said valve, and for controlling the operation of said valve in such
a manner that the measured value of said measuring circuit is kept
at a specific value.
15. The system according to claim 14, wherein said reactive gas is
an etching gas for etching said substrate to be processed.
16. The system according to claim 14, further comprising an
impedance matching circuit provided between said high-frequency
power supply and said cathode electrode of said vacuum chamber for
effecting the impedance matching between the output of said
high-frequency power supply and a load on the high-frequency power
supply.
17. A semiconductor device manufacturing system comprising: a
vacuum chamber provided with a cathode electrode for holding a
substrate to be processed and into which a reactive gas for
generating discharging plasma by the application of a
high-frequency electric power is introduced; a high-frequency power
supply connected to said cathode electrode, for applying a
high-frequency electric power to said cathode electrode; a cooling
gas carrying path provided at said cathode electrode and into which
a cooling gas is introduced to cool said substrate; an electronic
valve provided at said cooling gas carrying path in such a manner
that the pressure of said cooling gas introduced into said cooling
gas carrying path is adjusted; a measuring circuit connected to
said cathode electrode, for measuring at least one of the impedance
of a system including said plasma, the peak-to-peak voltage of a
high-frequency signal applied to said plasma, and a self-bias
voltage applied to said cathode electrode; and a control circuit
for receiving the measured value from said measuring circuit, for
supplying an output based on said measured value, and for
controlling the operation of said valve in such a manner that the
measured value of said measuring circuit is kept at a specific
value.
18. The system according to claim 17, wherein said reactive gas is
an etching gas for etching said substrate to be processed.
19. The system according to claim 17, further comprising an
impedance matching circuit provided between said high-frequency
power supply and said cathode electrode of said vacuum chamber, for
effecting the impedance matching between the output of said
high-frequency power supply and a load on the high-frequency power
supply.
20. A method of manufacturing semiconductor devices, comprising the
steps of: causing a cathode electrode provided in a vacuum chamber
to hold a substrate; generating discharging plasma in said vacuum
chamber by introducing a reactive gas into said vacuum chamber and
applying a high-frequency electric power to said cathode electrode;
measuring at least one of the impedance of a system including said
plasma, the peak-to-peak voltage of a high-frequency signal applied
to said plasma, and a self-bias voltage applied to said cathode
electrode; and sensing the change of processing characteristics
with time for said substrate by comparing said measured value with
previously prepared data.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No. 11-076352,
filed Mar. 19, 1999, the entire contents of which are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] This invention relates to a semiconductor device
manufacturing system, and more particularly to a system for
processing a semiconductor substrate by plasma discharge used in,
for example, a reactive ion etching (RIE) system with a
high-frequency power supply.
[0003] In a dry etching system used in the process of manufacturing
semiconductor devices, a substrate on whose surface a given mask
pattern has been formed is placed in a vacuum reactive chamber. A
reactive gas is introduced into the vacuum reactive chamber and at
the same time, discharging plasma is generated, thereby causing
reactive ions to etch the substrate.
[0004] At that time, high-vapor-pressure reaction products are
generally produced as a result of the reaction between the reactive
ions and the etched layer. The reaction products are exhausted.
Depending on the pressure in the vacuum chamber, the type of
reactive gas, the flow rate, and the amount of energy of the
reactive ions, the rate of reaction with the etched film and the
types of reaction products differ.
[0005] In a system for processing a semiconductor substrate by
plasma discharge, one means for clearly verifying the presence or
absence of the change of processing conditions with time and the
degree of the change with time, if any, is to process a substrate
in such a manner that it has a shape with a high aspect ratio.
[0006] The shape with a high aspect ratio is, for example, a
contact hole, a via hole, or a trench. As a typical example,
problems encountered in a case where a conventional dry etching
system is used in the process of forming trenches for trench
capacitors in the memory cells of, for example, a DRAM will be
explained.
[0007] FIGS. 1A and 1B are sectional views of a substrate in the
process of forming a trench for trench capacitor.
[0008] As shown in FIG. 1A, a TEOS (Tetraethyl orthosilicate) film
12 is first formed on an Si substrate 11 to be processed. Then,
patterning is done to form a mask pattern, thereby forming a sample
of the substrate.
[0009] Next, after each lot processing of semiconductor substrates
by a magnetron RIE system, a sample of the substrate as shown in
FIG. 1A is placed in a vacuum reactive chamber. Reactive gases HBr,
O.sub.2, and NF.sub.3 are introduced into the vacuum reactive
chamber at flow rates of 100, 10, and 70 sccm, respectively. Then,
plasma discharge is effected at a pressure of about 200 mTorr
(about 26.6 Pa) with a high-frequency power supply output of about
1000 W, thereby causing reactive ions to etch the sample.
[0010] As a result of this, a trench 13 for trench capacitor is
formed at the Si substrate 11 as shown in FIG. 1B. Here, .theta. is
the taper angle at the top of the trench 13 and D is the diameter
of the bottom of the trench.
[0011] FIG. 2 shows the relationship between the number of lots of
substrates processed by a conventional RIE system and the diameter
D (.mu.m) of the trench bottom. The number of substrates processed
in one lot is, for example, 24 to 25.
[0012] As seen from FIG. 2, as the number of substrates processed
increases, the diameter D of the trench bottom decreases. The
reason is that, as the number of substrates processed increases,
the degree of the taper at the top of the trench decreases, making
the taper angle .theta. smaller gradually.
[0013] The cause of this is not clear, but the following phenomenon
is considered to be taking place.
[0014] In processing a trench for trench capacitor, SiBr.sub.x,
SiBr.sub.yO.sub.z, and SiF.sub..alpha. are mainly produced as
reaction products. Although most of them are exhausted, part of
them adhere to the relatively low-temperature parts of the vacuum
chamber or decompose again into substances with lower vapor
pressures and adhere to the inside of the vacuum chamber.
[0015] These deposits are estimated to be of the SiO.sub.2 family.
When the deposits build up to form a film, they are exposed to
degassing or plasma, which causes the film to decompose again. As a
result, the actual flow rate of each process gas in the atmosphere
in the vacuum chamber differs from the set flow rate, preventing
the desired shape and etching rate from being achieved.
[0016] As described above, because the diameter of the trench
bottom is closely related to the condition of the deposited film on
the inside of the vacuum chamber, a grasp of the condition of the
deposited film would help determine the time the inside of the
vacuum chamber should be cleaned. It is, however, impossible to
grasp the condition of the inner surface of the vacuum chamber from
the outside.
[0017] At present, the standard value of the diameter D of the
trench bottom for trench capacitor is 0.1 .mu.m. In this situation,
the vacuum chamber is opened to atmosphere and cleaned manually
every, for example, eight lots on the basis of the data in FIG. 2.
However, it is not clear whether the method is the best.
[0018] As described above, with the conventional dry etching system
for manufacturing semiconductor devices, it is impossible to
externally grasp the condition of the inner surface and others of
the vacuum chamber. For example, in processing a trench for trench
capacitor, the change of the diameter of the trench bottom with
time dependent on the number of substrates processed is impossible
to grasp and therefore the suitable cleaning time of the inside of
the vacuum chamber cannot be determined.
BRIEF SUMMARY OF THE INVENTION
[0019] It is, accordingly, an object of the prevention is to
provide a semiconductor device manufacturing system which enables
the change of the diameter of the trench bottom with time dependent
on the number of substrates processed in processing a trench and
the condition of the inner surface and others of the vacuum chamber
to be grasped from the outside, making it possible to determine the
suitable cleaning time of the inner surface of the vacuum chamber
and control the processing of the shape of a substrate, which
thereby suppresses the change with time.
[0020] According to a first aspect of the present invention, there
is provided a semiconductor device manufacturing system comprising:
a vacuum chamber provided with a cathode electrode for holding a
substrate to be processed and into which a reactive gas for
generating discharging plasma by the application of a
high-frequency electric power is introduced; a high-frequency power
supply connected to the cathode electrode, for applying a
high-frequency electric power to the cathode electrode; a measuring
circuit connected to the cathode electrode, for measuring at least
one of the impedance of a system including the plasma, the
peak-to-peak voltage of a high-frequency signal applied to the
plasma, and a self-bias voltage applied to the cathode electrode;
and a sense circuit for receiving the measured value from the
measuring circuit, and for sensing the change of processing
characteristics with time for the substrate in using the
discharging plasma by comparing the measured value with previously
prepared data.
[0021] According to a second aspect of the present invention, there
is provided a semiconductor device manufacturing system comprising:
a vacuum chamber provided with a cathode electrode for holding a
substrate to be processed and into which a reactive gas for
generating discharging plasma by the application of a
high-frequency electric power is introduced; a high-frequency power
supply connected to the cathode electrode, for applying a
high-frequency electric power to the cathode electrode; a measuring
circuit connected to the cathode electrode, for measuring at least
one of the impedance of a system including the plasma, the
peak-to-peak voltage of a high-frequency signal applied to the
plasma, and a self-bias voltage applied to the cathode electrode;
and a control circuit for receiving the measured value from the
measuring circuit, for supplying an output based on the measured
value to the high-frequency power supply, and for controlling the
output of the high-frequency power supply in such a manner that the
measured value of the measuring circuit is kept at a specific
value.
[0022] According to a third aspect of the present invention, there
is provided a semiconductor device manufacturing system comprising:
a vacuum chamber provided with a cathode electrode for holding a
substrate to be processed and a reactive gas intake and into which
a reactive gas for generating discharging plasma by the application
of a high-frequency electric power is introduced through the
intake; a high-frequency power supply connected to the cathode
electrode, for applying a high-frequency electric power to the
cathode electrode; a valve provided at the intake in such a manner
that the intake of the reactive gas introduced into the vacuum
chamber is controlled; a measuring circuit connected to the cathode
electrode for measuring at least one of the impedance of a system
including the plasma, the peak-to-peak voltage of a high-frequency
signal applied to the plasma, and a self-bias voltage applied to
the cathode electrode; and a control circuit for receiving the
measured value from the measuring circuit, for supplying an output
based on the measured value to the valve, and for controlling the
operation of the valve in such a manner that the measured value of
the measuring circuit is kept at a specific value.
[0023] According to a fourth aspect of the present invention, there
is provided a semiconductor device manufacturing system comprising:
a vacuum chamber provided with a cathode electrode for holding a
substrate to be processed and into which a reactive gas for
generating discharging plasma by the application of a
high-frequency electric power is introduced; a high-frequency power
supply connected to the cathode electrode, for applying a
high-frequency electric power to the cathode electrode; a measuring
circuit for measuring at least one of the impedance of a system
including the plasma, the peak-to-peak voltage of a high-frequency
signal applied to the plasma, and a self-bias voltage applied to
the cathode electrode; and a report circuit for receiving the
measured value from the measuring circuit, for sensing that the
measured value has departed from a preset range, and for reporting
the cleaning time of the inside of the vacuum chamber.
[0024] According to a fifth aspect of the present invention, there
is provided a semiconductor device manufacturing system comprising:
a vacuum chamber provided with a cathode electrode for holding a
substrate to be processed, a reactive gas intake, and a reactive
gas outlet, and into which a reactive gas for generating
discharging plasma by the application of a high-frequency electric
power is introduced through the intake; a high-frequency power
supply connected to the cathode electrode, for applying a
high-frequency electric power to the cathode electrode; an
electronic valve provided at the outlet in such a manner that the
pressure in the vacuum chamber is adjusted; a measuring circuit
connected to the cathode electrode for measuring at least one of
the impedance of a system including the plasma, the peak-to-peak
voltage of a high-frequency signal applied to the plasma, and a
self-bias voltage applied to the cathode electrode; and a control
circuit for receiving the measured value from the measuring
circuit, for supplying an output based on the measured value to the
valve, and for controlling the operation of the valve in such a
manner that the measured value of the measuring circuit is kept at
a specific value.
[0025] According to a sixth aspect of the present invention, there
is provided a semiconductor device manufacturing system comprising:
a vacuum chamber provided with a cathode electrode for holding a
substrate to be processed and into which a reactive gas for
generating discharging plasma by the application of a
high-frequency electric power is introduced; a high-frequency power
supply connected to the cathode electrode, for applying a
high-frequency electric power to the cathode electrode; a cooling
gas carrying path provided at the cathode electrode and into which
a cooling gas is introduced to cool the substrate; an electronic
valve provided at the cooling gas carrying path in such a manner
that the pressure of the cooling gas introduced into the cooling
gas carrying path is adjusted; a measuring circuit connected to the
cathode electrode, for measuring at least one of the impedance of a
system including the plasma, the peak-to-peak voltage of a
high-frequency signal applied to the plasma, and a self-bias
voltage applied to the cathode electrode; and a control circuit for
receiving the measured value from the measuring circuit, for
supplying an output based on the measured value, and for
controlling the operation of the valve in such a manner that the
measured value of the measuring circuit is kept at a specific
value.
[0026] Additional objects and advantages of the invention will be
set forth in the description which follows, and in part will be
obvious from the description, or may be learned by practice of the
invention. The objects and advantages of the invention may be
realized and obtained by means of the instrumentalities and
combinations particularly pointed out hereinafter.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0027] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate presently
preferred embodiments of the invention, and together with the
general description given above and the detailed description of the
preferred embodiments given below, serve to explain the principles
of the invention.
[0028] FIGS. 1A and 1B are sectional views of a substrate in the
process of forming a trench for trench capacitor;
[0029] FIG. 2 shows the relationship between the number of
substrates processed and the diameter of the trench bottom in a
conventional dry etching system;
[0030] FIG. 3 is a schematic block diagram showing the
configuration of an RIE system according to a first embodiment of
the present invention and its peripheral circuit;
[0031] FIG. 4A shows the relationship between the number of lots of
substrates processed, the peak-to-peak voltage of a high-frequency
signal, and the diameter of the trench bottom in the system of FIG.
3;
[0032] FIG. 4B shows the relationship between the peak-to-peak
voltage of the high-frequency signal and the diameter of the trench
bottom in the system of FIG. 3;
[0033] FIG. 5 is a schematic block diagram showing the
configuration of an RIE system according to a second embodiment of
the present invention and its peripheral circuit;
[0034] FIG. 6A shows the relationship between the output of a
high-frequency power supply and the peak-to-peak voltage of the
high-frequency signal in the system of FIG. 5;
[0035] FIG. 6B shows the relationship between the peak-to-peak
voltage of the high-frequency signal and the taper angle .theta. at
the top of the trench in the system of FIG. 5;
[0036] FIG. 7 is a schematic block diagram showing the
configuration of an RIE system according to a third embodiment of
the present invention and its peripheral circuit;
[0037] FIG. 8A shows the relationship between the flow rate of a
reactive gas and the peak-to-peak voltage of a high-frequency
signal in the system of FIG. 7;
[0038] FIG. 8B shows the relationship between the peak-to-peak
voltage of the high-frequency signal and the taper angle at the top
of the trench in the system of FIG. 7;
[0039] FIG. 9 is a flowchart to help explain a method of
manufacturing semiconductor devices using the system of FIG. 5 or
7;
[0040] FIG. 10 is a schematic block diagram showing the
configuration of an RIE system according to a fourth embodiment of
the present invention and its peripheral circuit;
[0041] FIG. 11 shows the relationship between the pressure in the
vacuum reactive chamber and the taper angle .theta. at the top of
the trench in the system of FIG. 10;
[0042] FIG. 12 is a schematic block diagram showing the
configuration of an RIE system according to a fifth embodiment of
the present invention and its peripheral circuit; and
[0043] FIG. 13 shows the relationship between the pressure of a
cooling gas to adjust the temperature of the substrate to be
processed and the taper angle at the top of the trench in the
system of FIG. 12.
DETAILED DESCRIPTION OF THE INVENTION
[0044] Hereinafter, referring to the accompanying drawings,
embodiments of the present invention will be explained. The same
reference symbols designate the corresponding parts throughout all
the views and repetitious explanation will be avoided.
[0045] FIG. 3 shows a magnetron RIE system, a type of dry etching
system according to a first embodiment of the present invention,
and a control circuit for controlling the operation of the
system.
[0046] In FIG. 3, numeral 20 indicates an RIE system. The RIE
system 20 is provided with a vacuum reactive chamber 21. In the
vacuum reactive chamber 21, a cathode electrode 23 for holding a
substrate to be processed is provided. When a high-frequency power
supply, explained later, applies a high-frequency electric power to
the cathode electrode 23 and a reactive gas is introduced,
discharging plasma 24 develops inside the vacuum reactive chamber
21. In the vacuum reactive chamber 21, a gas intake 25 for
introducing a reactive gas and an outlet 26 for exhausting the gas
from the vacuum reactive chamber 21 are provided. Three branch
paths 27, 28, 29 are provided at the gas intake 25. When a mixed
gas of three types of gases, for example, HBr, O.sub.2, and
NF.sub.3, is used as etching gas, these three types of gases are
carried through the three branch paths 27, 28, 29. In the branch
paths 27, 28, 29, electronic valves 30, 31, 32 for adjusting the
flow rate of the gases are provided respectively. At the outlet 26,
there is provided an electronic valve 33 for controlling the amount
of exhaust to adjust the pressure in the vacuum reactive chamber
21.
[0047] A high-frequency power supply 34 including, for example, a
magnetron is connected to the cathode electrode 23. The output of
the high-frequency power supply 34 is supplied to the cathode
electrode 23. An impedance matching circuit (or matching
controller) 35 is provided between the high-frequency power supply
34 and the cathode electrode 23. The matching controller 35 is for
effecting the impedance matching between the output of the
high-frequency power supply 34 and the load side.
[0048] The matching controller 35 is composed of, for example, two
variable capacitors 36, 37, and an inductance 38. The values of the
two variable capacitors 36, 37 are controlled automatically by an
automatic control loop (not shown) in such a manner that the
reflected power returning to the high-frequency power supply 34
always becomes the smallest, thereby achieving impedance
matching.
[0049] Further connected to the cathode electrode 23 are a Vpp
measuring circuit 39 for measuring the peak-to-peak voltage Vpp of
a high-frequency signal applied to the plasma 24, a Vdc measuring
circuit 40 for measuring a self-bias voltage Vdc applied to the
cathode electrode 23, and an impedance (Z) measuring circuit 41 for
measuring the impedance (Z) of a system including the plasma
24.
[0050] Then, the voltage Vpp measured at the Vpp measuring circuit
39, the voltage Vdc measured at the Vdc measuring circuit 40, and
the impedance (Z) measured at the impedance measuring circuit 41
are inputted to a sense/report circuit 42. The sense/report circuit
42 has the function of comparing the outputs (or measurements) of
the Vpp measuring circuit 39, the Vdc measuring circuit 40, and the
impedance measuring circuit 41 with previously prepared data,
sensing the change of processing characteristics with time for the
substrate 22 to be processed, and determining and reporting the
cleaning time of the inside of the vacuum chamber 21, and outputs a
sense signal and a report signal.
[0051] The matching controller 35 is so controlled that the total
of impedance as a physical quantity to be monitored is, for
example, 50.degree. in the part including the matching controller
34 and beyond that when viewed from the high-frequency power supply
34, that is, the system including the plasma on the vacuum reactive
chamber 21 side. For example, if the impedance of the system
including the plasma is 30.degree., the values of the two
capacitors 36, 37 are adjusted by the automatic control loop so
that the impedance of the matching controller 35 itself may be
20.degree.. Since the impedance of the system including the plasma
varies, depending on the etching condition of the substrate in
etching the substrate or the change of the state in the vacuum
reactive chamber 21, it is possible to control of the shape of the
substrate and grasp the buildup of the deposited film on the inner
surface of the vacuum reactive chamber 21 on the basis of the
result of monitoring the impedance of the system including the
plasma.
[0052] Ordinary lot processing was done using the RIE system in
FIG. 3. After each lot process, a sample of the substrate as shown
in FIG. LA was placed in the vacuum reactive chamber 21. HBr gas,
O.sub.2 gas, and NF.sub.3 gas were introduced as reactive gases
into the vacuum reactive chamber at flow rates of about 100, 10,
and 70 sccm, respectively. Discharging plasma 24 was generated at a
pressure of about 200 mToor (about 26.6 Pa) in the vacuum reactive
chamber with the high-frequency power supply 34 outputting about
1000 W, thereby causing reactive ions to etch the sample. As a
result, a trench 13 for trench capacitor was formed in the Si
substrate 11 as shown in FIG. 1B.
[0053] At that time, the relationship between the number of lots of
substrates processed and the diameter D of the trench bottom in the
RIE system was examined. In addition, the relationship between the
number of lots processed and the peak-to-peak voltage Vpp of a
high-frequency signal applied to the cathode electrode 23 in the
vacuum reactive chamber was examined. The results of these are
shown in FIG. 4A.
[0054] Examinations as described above were made several times
using the same mask pattern under the same etching conditions. FIG.
4B shows the result of examining the relationship between the
peak-to-peak voltage Vpp of the high-frequency signal at that time
and the diameter D of the trench bottom.
[0055] It can be seen from FIGS. 4A and 4B that there is a
correlation between the diameter D of the trench bottom and the
peak-to-peak voltage Vpp of the high-frequency signal and the
diameter D of the trench bottom can be almost determined by
measuring the Vpp with the Vpp measuring circuit 39.
[0056] As described above, the reason why the diameter D of the
trench bottom correlates with the peak-to-peak voltage Vpp of the
high-frequency signal is not clear, but can be considered as
follows.
[0057] When the shape of the trench has got thinner for some
reason, the opening area of the Si substrate to be etched
decreases. Because the main reaction products are estimated to be
SiBr.sub.x, SiBr.sub.yO.sub.z, SiF.sub..alpha., and the like, as
the amount of Si in the substance to be etched decreases, the
amount of reaction products decreases accordingly. As a result, the
frequency of collision between ions and reaction products
decreases, resulting in a decrease in the impedance of the system
including the plasma 24. If the output of the high-frequency power
supply is W, the equation W=Vpp.sup.2/Z holds. In this case,
because W is constant (in this embodiment, about 1000 W), Vpp is
also expected to decrease.
[0058] Between the self-bias voltage Vdc applied to the cathode
electrode 23 holding the substrate 22 and the peak-to-peak voltage
Vpp of the high-frequency signal, the fact that Vdc is almost equal
to Vpp/2 is generally true. As a result, it is easily estimated
that the diameter D of the trench bottom is determined by measuring
the Vdc with the Vdc measuring circuit 40 as is the Vpp.
[0059] With the RIE system of the first embodiment, there is
provided the sense/report circuit 42 that compares the outputs
(measurements) of the measuring circuits 39, 40, and 41 with the
previously prepared data and senses and reports the change of
processing characteristics with time for a substrate to be
processed or the cleaning time of the inside of the vacuum reactive
chamber. The sense signal makes it possible to externally grasp the
change of the diameter of the trench bottom dependent on the number
of substrates processed in processing a trench for trench
capacitor. Furthermore, the report signal enables the condition and
the like of the inner surface of the vacuum reactive chamber to be
grasped indirectly from the outside, which makes it possible to
determine the suitable cleaning time of the inside of the vacuum
reactive chamber.
[0060] FIG. 5 shows a magnetron RIE system, a type of dry etching
system according to a second embodiment of the present invention,
and a control circuit for controlling the operation of the
system.
[0061] The RIE system of the second embodiment differs from that of
FIG. 3 in an additional high-frequency power supply control circuit
43 that receives the sense signal outputted from the sense/report
circuit 42 and controls the output of the high-frequency power
supply 34.
[0062] In the RIE system of the second embodiment, on the basis of
the sense signal outputted according to one or two or more of the
value of Vpp measured by the Vpp measuring circuit 39, the value of
Vdc measured by the Vdc measuring circuit 40, and the value of the
impedance measured by the Z measuring circuit 41, the
high-frequency power supply control circuit 43 is controlled. In
addition, the output of the high-frequency power supply 34 is
controlled on the basis of the output of the high-frequency power
supply control circuit 43. In this way, the impedance Z, the
peak-to-peak voltage Vpp of the high-frequency electric power, and
the self-bias voltage Vdc are controlled. Then, shape control in
processing a substrate can be performed by controlling the output
of the high-frequency power supply 34 in such a manner that each of
the measured values is kept at a desired constant value.
[0063] After each lot processing of semiconductor substrates was
carried out using the RIE system of FIG. 5, a sample of the
substrate as shown in FIG. 1A was placed in the vacuum reactive
chamber. HBr gas, O.sub.2 gas, and NF.sub.3 gas were introduced as
reactive gases through the branch paths 27, 28, 29 into the vacuum
reactive chamber at flow rates of about 100, 10, and 70 sccm,
respectively. Discharging plasma 24 was generated at a pressure of
about 200 mToor (about 26.6 Pa) in the vacuum reactive chamber with
the output of the high-frequency power supply 34 being applied to
the cathode electrode 23, thereby causing reactive ions to etch the
sample.
[0064] At that time, dry etching was done changing the output
(RF-Power) (W) of the high-frequency power supply 34, thereby
examining how the peak-to-peak voltage Vpp of the high-frequency
signal changed. At the same time, how the taper angle .theta. at
the top of the trench as shown in FIG. 1B changed was also
examined. The results are shown in FIGS. 6A and 6B.
[0065] It can be seen from FIGS. 6A and 6B that the output of the
high-frequency power supply 34 and the peak-to-peak voltage Vpp of
the high-frequency signal and the taper angle .theta. of the trench
have one-to-one correspondence and therefore the taper angle
.theta. can be controlled by the high-frequency output.
[0066] The reason is not clear. The equation W=Vpp.sup.2/Z
generally holds. When the amount of reaction products generated is
almost constant, Z is almost constant. Therefore, Vpp is
proportional to W and the value of Vpp is estimated to be
determined.
[0067] Furthermore, part of the reaction products adhere to the
sidewall of the trench to make a sidewall protective film. The
taper angle .theta. at the top of the trench is controlled by the
amount of the sidewall protective film. As the sidewall protective
film gets thicker, the taper angle .theta. becomes smaller.
[0068] In addition, since Vdc is generally equal to Vpp/2, an
increase in Vpp increases Vdc, which increases the energy at which
reactive ions arrive at the substrate. As a result, the sidewall
protective film inside the trench is estimated to be scraped away,
making the taper stand more straight.
[0069] With the RIE system of the second embodiment, the value of
Vpp is measured by the Vpp measuring circuit 39, the value of Vdc
is measured by the Vdc measuring circuit 40, and the value of Z is
measured by the Z measuring circuit 41. The high-frequency power
supply control circuit 43 is controlled on the basis of the sense
signal outputted from the sense/report circuit 42 according to the
result of the measurements. The output of the high-frequency power
supply 34 is controlled to an arbitrary value in such a manner that
the measured value of Vpp, Vdc, or Z is kept at a specific set
value. Controlling the high-frequency power supply circuit 43 and
the output of the high-frequency power supply 34 this way enables
the shape of the trench to be controlled.
[0070] FIG. 7 shows a magnetron RIE system, a type of dry etching
system according to a third embodiment of the present invention,
and a control circuit for controlling the operation of the
system.
[0071] The RIE system of the third embodiment differs from that of
FIG. 1 in an additional gas flow-rate control circuit 44 that
receives the sense signal outputted from the sense/report circuit
42 and controls the flow rate of each of the gases by controlling
the opening and closing of the electronic valves 30, 31, 32. The
output of the gas flow-rate control circuit 44 is supplied to each
of the electronic valves 30, 31, 32.
[0072] In the RIE system constructed as described above, after each
lot processing of semiconductor substrates, a sample of the
substrate as shown in FIG. 1A was placed in the vacuum reactive
chamber. HBr gas, O.sub.2 gas, and NF.sub.3 gas were introduced as
reactive gases through the branch paths 27, 28, 29 into the vacuum
reactive chamber. Discharging plasma 24 was generated at a pressure
of about 200 mToor (about 26.6 Pa) in the vacuum reactive chamber
with the output (RF-Power) of the high-frequency power supply 34
being applied to the cathode electrode 23, thereby causing reactive
ions to etch the sample.
[0073] At that time, dry etching was done by introducing HBr gas
and NF.sub.3 gas at flow rates of about 100 and 70 sccm
respectively, and changing a flow rate of O.sub.2 gas, thereby
examining how the peak-to-peak voltage Vpp of the high-frequency
signal changed. At the same time, how the taper angle .theta. at
the top of the trench as shown in FIG. 1B changed was also
examined. The results are shown in FIGS. 8A and 8B.
[0074] It can be seen from FIGS. 8A and 8B that the flow rate of
the O.sub.2 gas and the peak-to-peak voltage Vpp of the
high-frequency signal and the taper angle .theta. of the trench
have one-to-one correspondence and therefore control can be
performed on the basis of the flow rate of the O.sub.2 gas.
[0075] The reason is not clear. The equation W Vpp.sup.2/Z
generally holds. An increase in the flow rate of the O.sub.2 gas
increases the amount of reaction products of the SiBr.sub.yO.sub.2
family generated, which increases the impedance Z. In this case,
therefore, W is almost constant. From this, the value of Vpp can be
considered to have decreased.
[0076] Furthermore, since the magnitude of the impedance z depends
on the amount of reaction products, a similar effect is easily
estimated to be produced in a case where a process gas including a
bromine-containing gas, such as HBr containing Br and F composing
reaction products and a fluorine-containing gas, such as NF.sub.3,
is used.
[0077] With the RIE system of the third embodiment, the value of
Vpp is measured by the Vpp measuring circuit 39, the value of Vdc
is measured by the Vdc measuring circuit 40, and the value of Z is
measured by the Z measuring circuit 41. On the basis of the results
of the measurements, the gas flow-rate control circuit 44 is
controlled and the valves 30 to 32, particularly the valve 31 for
controlling the flow rate of O.sub.2 gas, are controlled. In this
way, the flow rate of each process gas is controlled to an
arbitrary value in such a manner that the measured value of Vpp,
Vdc, or Z is kept at a specific set value, which enables the shape
of the trench to be controlled.
[0078] Next, a method of processing a substrate using the RIE
system in FIG. 5 or 7 will be explained briefly by reference to a
flowchart in FIG. 9.
[0079] When the processing of a substrate is started, the supply of
each process gas and the output of the high-frequency power supply
are first started.
[0080] At least one of the measured values of the impedance Z of
the part including the system and plasma 24, the peak-to-peak
voltage Vpp of the high-frequency signal applied to the plasma 24,
and the self-bias voltage Vdc developing at the cathode electrode
23 is taken in by the sense/report circuit 42.
[0081] Then, it is judged whether those measured values are equal
to the previously set values. The judgment is made at the
sense/report circuit 42. If the measured value is equal to the set
value, the supply of the process gas and the output of the
high-frequency power supply are stopped at the time when the set
process end time has been reached, which completes the process.
[0082] When the set process end time has not been reached, the
measured value is taken in again by the sense/report circuit 42,
which judges whether the measured value is equal to the set
value.
[0083] If the measured value is different from the set value, the
process condition, such as the process gas or the output of the
high-frequency power supply, is adjusted in real time. Then, it is
judged whether a measured value equal to the set value has been
obtained. At this time. If a measured value equal to the set value
has not be obtained, a process stop signal is transmitted to the
high-frequency power supply 34 or valves 30 to 32, which forces the
process to end. At the same time, the sense/report circuit 42
outputs the report signal that reports that the cleaning time has
been reached.
[0084] Monitoring the impedance Z, peak voltage Vpp, and self-bias
voltage Vdc makes it possible to clearly grasp, from the outside of
the vacuum chamber, the change of substrate processing
characteristic in the vacuum chamber with time and the cleaning
time of the inside of the vacuum chamber. In addition, keeping the
result of monitoring at an arbitrary value enables shape control of
processing, which makes it possible to suppress the change with
time.
[0085] FIG. 10 shows a magnetron RIE system, a type of dry etching
system according to a fourth embodiment of the present invention,
and a control circuit for controlling the operation of the
system.
[0086] The RIE system of the fourth embodiment differs from that of
FIG. 1 in an additional pressure control circuit 45 that receives
the sense signal outputted from the sense/report circuit 42 and
controls the pressure in the vacuum reactive chamber by controlling
the opening and closing of the electronic valve 33 provided at the
outlet 26. The output of the pressure control circuit 45 is
supplied to the valve 33.
[0087] After each lot processing of semiconductor substrates using
the RIE system of the fourth embodiment, a sample of the substrate
as shown in FIG. 1A was placed in the vacuum reactive chamber 21.
Reactive gas was introduced into the vacuum reactive chamber 21.
Then, the inside of the vacuum reactive chamber was kept at a
specific pressure and the output of the high-frequency power supply
34 was applied, thereby generating discharging plasma 24, which
causes reactive ions to etch the sample.
[0088] At that time, dry etching was done changing the pressure in
the vacuum reactive chamber 21, thereby examining how the taper
angle .theta. at the top of the trench as shown in FIG. 1A changed.
The results are shown in TABLE 1 and FIG. 11.
1 TABLE 1 PRESSURE (mTorr) TAPER ANGLE .theta. (.degree.) 100 88.42
150 88.17 200 88.09
[0089] It can be seen from TABLE 1 and FIG. 11 that as the pressure
in the vacuum reactive chamber 21 decreases, the taper angle
.theta. increases. The reason is considered as follows. As the
pressure in the vacuum reactive chamber decreases, ions begin to
have the same direction and the frequency of collision between ions
or between ions and other particles, such as atoms, decreases. As a
result, because the kinetic energy accelerated by an electric field
is not lost because of collisions, the energy at which ions arrive
at the substrate increases, which produces the effect of scraping
the sidewall protective film easily as when the output of the
high-frequency power supply 34 is increased.
[0090] Therefore, the taper angle .theta. can be controlled to a
desired value by inputting the sense signal from the sense/report
circuit 42 to the pressure control circuit 45, adjusting the amount
of exhaust from the vacuum reactive chamber 21 by controlling the
opening and closing of the valve 33 according to the output of the
pressure control circuit 45, thereby adjusting and keeping the
pressure in the vacuum reactive chamber 21 at a desired constant
value.
[0091] FIG. 12 shows a magnetron RIE system, a type of dry etching
system according to a fifth embodiment of the present invention,
and a control circuit for controlling the operation of the
system.
[0092] In the RIE system of the fifth embodiment, a cooling gas
intake 51 is provided on the reverse side of the cathode electrode
23, or on the opposite side to the surface on which a substrate 22
to be processed is placed. A cooling gas, such as He gas, is
introduced through the intake 51. The cooling gas introduced
through the intake 51 erupts from the surface of the cathode
electrode 23 on which the substrate 22 is placed, thereby cooling
the substrate 22.
[0093] Furthermore, an electronic valve 52 for adjusting the flow
rate of the cooling gas introduced through the intake 51 is
provided at the cooling gas intake 51. The opening and closing of
the valve 52 is controlled according to the output of the gas
flow-rate control circuit 53 that receives the sense signal
outputted from the sense/report circuit 42. In general, the inside
of the vacuum reactive chamber 21 where discharging plasma is being
generated is as high as about 120.degree. C. The substrate 22 in
the chamber is also at about the same temperature. When a cooling
gas, such as He gas, is erupted toward the back of the substrate
22, the temperature of the substrate 22 is adjusted according to
the flow rate of the cooling gas.
[0094] After each lot processing of semiconductor substrates using
the RIE system of the fifth embodiment, a sample of the substrate
as shown in FIG. 1A was placed in the vacuum reactive chamber 21.
Reactive gas was introduced into the vacuum reactive chamber 21.
Then, the vacuum reactive chamber was kept at a specific pressure
and the cooling gas was introduced through the valve 52, thereby
lowering the temperature of the substrate 22 to a specific
temperature. Thereafter, the output of the high-frequency power
supply 34 was applied to the cathode electrode 23, thereby
generating discharging plasma 24, which causes reactive ions to
etch the sample.
[0095] At that time, dry etching was done changing the temperature
of the substrate 22, thereby examining how the taper angle .theta.
at the top of the trench as shown in FIG. 1B changed. The results
are shown in TABLE 2 and FIG. 13. The flow rate (pressure) of the
cooling gas is shown as the values related to the temperature.
2 TABLE 2 PRESSURE (Torr) TAPER ANGLE .theta. (.degree.) 10 88.36
15 88.25 20 88.19
[0096] It can be seen from TABLE 2 and FIG. 13 that, as the
pressure of the cooling gas increases, the taper angle .theta.
increases. The reason is considered as follows. As the pressure of
the cooling gas is increased, the temperature of the substrate
drops, increasing the amount of deposits of reaction products
(sediment and sidewall protective films), which produces the effect
of decreasing the taper angle .theta. as when the flow rate of
O.sub.2 gas is increased.
[0097] Therefore, the taper angle .theta. can be controlled to a
desired value by adjusting and keeping the temperature of the
substrate at a desired constant value.
[0098] As described above, with a semiconductor device
manufacturing system according to the present invention, it is
possible to externally grasp the change of the diameter of the
trench bottom with time dependent on the number of substrates
processed in processing, for example, a trench for trench capacitor
and the condition of the inner surface and others of the vacuum
reactive chamber, making it possible to determine the suitable
cleaning time of the inside of the vacuum reactive chamber and
control the processing of the shape of a substrate, which thereby
suppresses the change with time.
[0099] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *