U.S. patent application number 11/274321 was filed with the patent office on 2006-03-23 for plasma treatment method.
Invention is credited to Takazumi Ishizu, Saburo Kanai, Yoshiaki Satou, Kazue Takahashi.
Application Number | 20060060300 11/274321 |
Document ID | / |
Family ID | 18467244 |
Filed Date | 2006-03-23 |
United States Patent
Application |
20060060300 |
Kind Code |
A1 |
Takahashi; Kazue ; et
al. |
March 23, 2006 |
Plasma treatment method
Abstract
A plasma treatment method of etching a substrate to be processed
by using a gas plasma in a treatment chamber. The method includes
exhausting reaction products obtained by etching and released into
a vapor phase as a gas from the treatment chamber, wherein the
reaction products on an outer periphery of the substrate are more
efficiently exhausted and setting a deposition probability of the
reaction products in a central part of a plane of the substrate to
be low and setting a deposition probability of the reaction
products in a peripheral part of a plane of the substrate to be
high. The setting of the deposition probability is effected by
setting a temperature in the central part of the substrate higher
than a temperature in the peripheral part of the substrate.
Inventors: |
Takahashi; Kazue;
(Kudamatsu-shi, JP) ; Kanai; Saburo; (Hikari-shi,
JP) ; Satou; Yoshiaki; (Tokuyama-shi, JP) ;
Ishizu; Takazumi; (Hikari-shi, JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET
SUITE 1800
ARLINGTON
VA
22209-3873
US
|
Family ID: |
18467244 |
Appl. No.: |
11/274321 |
Filed: |
November 16, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10288481 |
Nov 6, 2002 |
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11274321 |
Nov 16, 2005 |
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09218038 |
Dec 22, 1998 |
6482747 |
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10288481 |
Nov 6, 2002 |
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Current U.S.
Class: |
156/345.24 ;
257/E21.311 |
Current CPC
Class: |
H01J 37/32834 20130101;
H01L 21/6875 20130101; H01J 37/3244 20130101; H01J 2237/3322
20130101; C23F 4/00 20130101; H01L 21/32136 20130101 |
Class at
Publication: |
156/345.24 |
International
Class: |
H01L 21/306 20060101
H01L021/306 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 26, 1997 |
JP |
9-359971 |
Claims
1. A plasma treatment apparatus for etching a substrate to be
processed by using a gas plasma in a treatment chamber, comprising:
an electrode disposing the substrate to be processed thereon; a
vacuum pump for exhausting reaction products obtained by etching
and releasing into a vapor phase as a gas from the treatment
chamber; the vacuum pump providing a more efficient exhaustion of
the reaction products from the outer periphery and redistributing
the amount of reaction products between the central part of the
substrate and the peripheral part of the substrate; and a
controller for regulating pressure of the heat transfer gas
supplied to each part between the substrate and the electrode by
independent passages provided for the respective parts to which the
heat transfer gas is supplied, and for controlling a temperature
distribution in a plane of the substrate to be processed to
increase the temperature in the central part greater than that of
the peripheral part to provide increased uniformity of the
re-irradiation effect of the reaction products.
2. A plasma treatment apparatus for etching a substrate to be
processed by using a gas plasma in a treatment chamber according to
claim 1, wherein the vacuum pump provides more efficient exhaustion
of the reaction products from substantially the entire outer
periphery.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. application Ser.
No. 10/288,481, filed Nov. 6, 2002, which, is a continuation of
U.S. application Ser. No. 09/218,038, filed Dec. 22, 1998 (now U.S.
Pat. No. 6,482,747), the entire subject matter of which is
incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to plasma treatment for
performing etching or the like on a substrate to be treated; and,
more particularly, the invention relates to a plasma treatment
method and plasma treatment apparatus in which the treatment
characteristics in the central part of the substrate and those in
the peripheral part of the substrate to be treated are
uniformized.
[0003] Various methods have been devised for the operation
conventional plasma treatment apparatuses in order to uniformize
the plasma density (ion current value) and ion energy (RF bias
voltage) in the plane of a substrate (wafer) and to uniformize the
substrate temperature. For example, the Japanese unexamined patent
No. 7-18438 discloses a technique for uniformizing the temperature
distribution in the substrate by forming roughness on the surface
of an insulating material on a substrate supporting face of a flat
electrode, changing the density or depth of the rough surface of
the insulating material, and distributing the electrostatic
adsorption.
[0004] As the substrate size increases and the etching size becomes
finer, however, the influence of the distribution of etching
reaction products in the central part of the substrate and those in
the peripheral part of the substrate become significant.
[0005] FIG. 15 is a diagram showing the behavior of etching
reaction products. As shown in the diagram, etching reaction
products, such as Al, Cl, C, and the like, react with a plasma
etching gas (ions and radicals) on a substrate (wafer) 2 to be
treated, evaporate in a vapor phase, and become Al.sub.2Cl.sub.6 or
the like. The reaction products exhibit a complicated behavior in
that they are directed again at the substrate 2 to be treated, or
they are dissociated again in the plasma and the dissociated
species are directed at the substrate 2. That is, etched Al on the
bottom of the substrate is released as reaction products into a
vapor phase and a part of them is dissociated again in the plasma
and is again directed at the substrate 2. A photo resist 25 is
likewise etched so that the substrate is again irradiated with the
reaction products of the resist. Electrically neutral species among
the species dissociated from the reaction products in the plasma
are directed also at the side walls of an area to be etched and are
deposited. Such species, such as species which are obtained by
etching the bottom face and are directly deposited on the side
walls, species directed at the side walls sputtered by the incident
ions including physical or chemical elements, and the like, are
deposited, thereby forming a side wall protection layer 26.
[0006] Among the effects, with respect to the re-irradiation of the
reaction products, non-uniformity of the amount of irradiation in
the plane of the substrate tends to occur for the following reason.
The reaction products obtained by etching and which are released
into a vapor phase are exhausted as a gas from the etching chamber.
The further out one goes on the substrate, the more the reaction
products are exhausted efficiently. As shown in FIG. 16, therefore,
in the density distribution of the reaction products in the vapor
phase, that is, the re-irradiation amount distribution of the
reaction products, inevitably, the density or the re-irradiation
amount is high in the central part of the substrate and is low in
the peripheral part thereof.
[0007] As mentioned above, in a peripheral part of the substrate,
the amount of the reaction products is smaller than that in the
central part of the substrate since they are exhausted together
with the etching gas. In case of metal etching, if the side wall
protection layer is thick, the etch rate on the side walls due to
the ion assisted reaction becomes low. Because of this, when
describing a process for a trench as an example, the shape of a
part to be etched becomes a so-called tapered shape in which the
width is reduced as the etch depth increases. On the contrary, when
the side wall protection layer is too thin, the side walls are
etched and the part to be etched becomes wider than a target width.
Consequently, in order to obtain a vertical shape at an etched
part, the amount of deposition of the side wall protection layer
has to be optimized so as to obtain a proper thickness and prevent
the side walls from becoming fat or thin.
[0008] On the other hand, with reduction in the etching size, the
need for good processing accuracy with respect dimensions
increases. For example, when about 1/10 of a design dimension is a
permissible level, the permissible level is .+-.0.05 .mu.m for the
design dimension of 0.5 .mu.m. With reduction in the dimension to
0.25 .mu.m and 0.13 .mu.m, the permissible levels become .+-.0.025
.mu.m and .+-.0.013 .mu.m, respectively. In order to achieve such a
required specification, factors exerting an influence on the
processing dimension have to be made clear and to be accurately
controlled.
[0009] With the reduction in the etching size, also in dense and
sparse patterns in which fine patterns and sparse patterns which
are not so dense mixedly exist, the need for a good processing
accuracy with respect to dimensions has become increasingly
important.
SUMMARY OF THE INVENTION
[0010] It is an object of the present invention to provide a plasma
treatment method and a plasma treatment apparatus in which the
influence on treatment characteristics of the reaction products in
a plasma treatment, such as etching, is offset, so that uniform
treatment characteristics can be obtained in the plane of a
substrate.
[0011] It is another object of the present invention to provide a
plasma treatment method and a plasma treatment apparatus which
improves the uniformity in the substrate plane of a shape to be
processed in consideration of the influences of reaction products
at the time of plasma treatment, such as etching.
[0012] It is a further object of the present invention to provide a
plasma treatment method and a plasma treatment apparatus which can
obtain an etching treatment characteristic in which there is no
variation in processing dimension in dense and sparse patterns.
[0013] According to a feature of the invention, in a plasma
treatment method of performing etch treatment on a substrate to be
processed by using a gas plasma via a mask in a treatment chamber,
plasma treatment is performed while maintaining the in-plane
uniformity of a side wall protection layer formed on the side walls
of a part to be etched in the substrate.
[0014] According to another feature of the invention, in a plasma
treatment method of treating a substrate to be processed by using a
gas plasma via a mask in a treatment chamber, plasma treatment is
performed while equalizing the amount of deposition of a side wall
protection layer formed on the substrate to be processed in the
center of the substrate with that in an outer part of the
substrate, thereby maintaining the in-plane uniformity of the side
wall protection layer.
[0015] According to a further feature of the invention, in a plasma
treatment method of treating a substrate to be processed with a gas
plasma by using a resist as a mask in a treatment chamber, plasma
treatment is performed on the substrate while maintaining the
uniformity of the amount of deposition of reaction products which
are generated by a reaction between the substrate to be processed
and the plasma and are directed at and deposited on the substrate
in the plane of the substrate to be processed, thereby forming a
side wall protection layer having a uniform plane on the
substrate.
[0016] According to still another feature of the invention, in a
plasma treatment method of performing plasma treatment on a
substrate to be processed with a gas plasma by using a resist as a
mask in a treatment chamber, the plasma treatment is performed
while maintaining the in-plane uniformity of a side wall protection
layer formed on the substrate by controlling the temperature of the
substrate.
[0017] It is yet another feature of the invention that the plasma
treatment is performed on the substrate to be processed while
adjusting the pressure, flow rate, and mixing ratio of a process
gas in the treatment chamber.
[0018] It is another feature of the invention that the plasma
treatment is performed on the substrate to be processed while
regulating the amount of the reaction products exhausted from the
treatment chamber.
[0019] It is another feature of the invention that the plasma
treatment is performed on the substrate to be processed while
adjusting the kind of process gas or the pressure of the process
gas in the treatment chamber.
[0020] It is another feature of the invention that variation in a
deposition amount of reaction products in the plane of the
substrate to be processed is maintained within .+-.10%.
[0021] It is another feature of the invention that the diameter of
the substrate to be processed is 200 mm or larger and a pattern
formed on the substrate to be processed is 0.35 .mu.m or
smaller.
[0022] According to another feature of the invention, in a plasma
treatment apparatus for treating a substrate to be processed by
using a gas plasma, there is a substrate holding electrode on which
the substrate to be processed is placed and which controls the
temperature of the substrate so that temperatures in the central
and peripheral parts of the substrate are different and has a
function of maintaining an in-plane uniformity of a deposition
amount of reaction products in the plane of the substrate.
[0023] In the case of etching, usually, it is an objective to
perform etching vertically and faithfully with respect to the
processing dimension via a mask. In this case, etching in a
direction vertical to the etching direction, that is, etching of
side walls exerts an influence on the processing dimension. In the
etching of side walls, when the etch pressure is high, injected
ions also contribute to the etching. When the etch pressure is
sufficiently low, the ion injection can be almost ignored. In such
a state where the ion injection can be almost ignored, the etching
of side walls largely depends on a chemical reaction between the
side walls and radicals. The chemical reaction depends on the
temperature and the density and kind of radicals irradiated and
deposited. In the case of etching, reaction products which suppress
the chemical reaction are deposited on the side walls. It can be
said that the amount of the deposition, that is, the thickness of
the side wall protection layer, determines the side wall etch rate.
In other words, the control of the thickness of the side wall
protection layer is the key to improvement in the processing
accuracy.
[0024] Consequently, in the etching of a finer pattern on which the
influence of the reaction products is large, especially, it is
necessary to consider distribution characteristics in which the
reaction products in the vapor phase are not uniform in the plane
of the substrate and the amount of the reaction products is smaller
in the peripheral part of the substrate, and to obtain a plasma
distribution and a substrate temperature distribution which make
the in-plane distribution of the side wall protection layer uniform
by offsetting such influence.
[0025] According to the invention, in a plasma treatment method of
treating a substrate to be processed with a gas plasma via a mask
in a treatment chamber, the substrate is subjected to plasma
treatment while maintaining the in-plane uniformity of the side
wall protection layer formed on the substrate. By maintaining the
in-plane uniformity of the side wall protection layer on the
substrate to be processed, the etch rate of the side walls by an
ion assisted reaction becomes uniform. Even in the case of a fine
pattern, a vertical shape of the etched part can be easily
obtained.
[0026] In order to maintain the in-plane uniformity of the side
wall protection layer formed on the substrate to be processed, for
example, the temperature distribution in the substrate plane is
controlled. The higher the substrate temperature is, the lower will
be the probability that the reaction products which are directed
again at the substrate will be deposited on the side walls of the
part to be etched or the like. That is, when the substrate
temperature is constant, the deposition probability of the reaction
products in the plane of the substrate becomes constant.
Consequently, the amount of deposition on the side walls of the
treated part, that is, the thickness of the side wall protection
layer is proportional to the re-irradiation amount of the reaction
products. As a result, the deposition amount of reaction products
on the substrate increases in the center of the substrate and the
shape of the treated part and that of a peripheral part become
different.
[0027] In order to solve the problem and maintain the in-plane
uniformity of the side wall protection layer on the substrate to be
processed, at the time of the plasma treatment, for example, the
temperature is controlled so that the temperature in the center of
the substrate is higher as compared with that in the peripheral
part. Since the deposition probability of the reaction products is
low when the temperature in the center of the substrate is high,
even if the re-irradiation amount of the reaction products is
large, the amount of reaction products deposited on the side walls
of the etched part is therefore small. The temperature of the
substrate is regulated to have a characteristic such that the
temperatures in and out of the substrate plane are different so
that the amount of the reaction products deposited on the side
walls in the substrate plane becomes uniform. Thus, the treatment
characteristics in the substrate plane can be made uniform.
[0028] When the substrate temperature is changed, not only will the
deposition probability of the reaction products change, but also
the deposition probability of the etching gas plasma (especially,
radicals) changes. The rate of etch reaction itself also changes.
Consequently, since the amount of the reaction products being
generated changes, it is necessary to control the substrate
temperature distribution in accordance with the conditions of the
plasma treatment, such as etching.
[0029] For maintaining the uniformity in the plane of the side wall
protection layer, there are various methods of controlling the
temperature distribution in the substrate plane. For example, the
surface of the electrode is divided into a part which comes into
contact with the back face of the wafer and a part (trenches) which
does not come into contact with the back face, and the in-plane
temperature of the wafer can be controlled by utilizing the fact
that the overall heat transfer coefficient in the contact part and
that in the trenches are different. The overall heat transfer
coefficient can be also changed by varying the depth of the
trenches.
[0030] Further, the overall heat transfer coefficient can be
controlled by coating the trench with a film. Further, by adjusting
the kind and thickness of the film coated on the trench, the
temperature can be changed according to the process. By coating
with a film, cleaning can be carried out easily. The film does not
have to be made of plastics, but can be made of a metal or
ceramics. The film has to be thin. The temperature of the wafer
also can be controlled by coating a part which is in contact with
the back face of the wafer with the film.
[0031] According to the invention, a plasma treatment method and a
plasma treatment apparatus can be provided, in which the influence
on the etching characteristics of the reaction products in the
plasma treatment is offset and in which uniform treatment
characteristics can be obtained in the substrate plane.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 is a diagram showing an example of control
characteristics of an in-plane temperature of a substrate according
to the invention;
[0033] FIG. 2 is a vertical cross section showing the essential
part of an electrode in a plasma etching apparatus according to an
embodiment of the invention;
[0034] FIG. 3 is a plan view of the essential part of the electrode
of FIG. 2;
[0035] FIG. 4 is a schematic diagram showing a state where an
aluminum wiring is being etched according to the method of the
invention;
[0036] FIG. 5 is a diagram showing the relation among substrate
temperature, and generation amount and re-irradiation distribution
of reaction products at the time of plasma etching according to the
invention;
[0037] FIG. 6 is a graph showing the relation among the depth of
recessed parts (or trenches) of an electrostatic adsorption
electrode and pressure loss (Pa) on the back face of the
electrode;
[0038] FIG. 7 is a graph showing the relation between pressure (Pa)
on the back face of the electrode and an overall heat transfer
coefficient (W/m.sup.2.times.K) by gas molecules;
[0039] FIG. 8 is a diagram showing the relation between a distance
(d) between the back face of the substrate and the surface of the
electrode and the overall heat transfer coefficient by gas
molecules when the pressure is constant;
[0040] FIG. 9 is a vertical cross section of an electrode according
to another embodiment of the invention;
[0041] FIG. 10 is a diagram showing the electrode according to
another embodiment of the invention;
[0042] FIG. 11 is a diagram showing the electrode according to
another embodiment of the invention;
[0043] FIG. 12 is a diagram illustrating a method of controlling
the temperature in the substrate plane according to another
embodiment of the invention;
[0044] FIG. 13 is a diagram showing the relation between the
pressure on the back face of the substrate and the overall heat
transfer coefficient;
[0045] FIG. 14 is a diagram illustrating an etching treatment
method according to another embodiment of the invention;
[0046] FIG. 15 is a diagram for showing the behavior of etching
reaction products at the time of plasma etching in accordance with
a conventional technique;
[0047] FIG. 16 is a diagram showing the relation among substrate
temperature, and generation amount and re-irradiation distribution
of reaction products at the time of the plasma etching in
accordance with the conventional technique; and
[0048] FIG. 17 is a schematic diagram of a plasma etching apparatus
of the type to which the invention is applied.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0049] Embodiments of the present invention will be described in
detail hereinbelow.
[0050] FIG. 17 is a schematic diagram of a plasma treatment
apparatus of the type to which the invention may be applied. The
apparatus of FIG. 17 is an etching apparatus employing a plasma
generating method using electron cyclotron resonance produced by a
microwave. The invention also can be applied to apparatuses of
other systems as long as it is a plasma treatment apparatus, and so
the invention is not limited to the apparatus of FIG. 17.
[0051] Shown in FIG. 17 are an etching chamber 1; a substrate 2
placed on an electrode 3; an RF generator 4 for applying an RF bias
to the substrate; a wave guide 5 for guiding a microwave to the
etching chamber 1; a quartz window 6; an electromagnetic coil 7 for
forming an electron cyclotron resonance region in the etching
chamber by applying a magnetic field to the microwave; a vacuum
pump 8; a pressure regulating valve 9; and a sensor 10, such as a
pressure sensor.
[0052] The electrode 3 is an electrostatic adsorption electrode and
a part of the electrode surface serves as an electrostatic
adsorption face which is in contact with the back face of the
substrate 2. As shown in FIGS. 2 and 3, recessed parts 34, 35, and
36 are formed between annular electrostatic adsorption faces 31,
32, and 33 of the electrostatic adsorption electrode 3. Reference
numeral 38 denotes a supply port for the supply of a heat transfer
gas to the back face of the substrate, and 39 indicates a passage
to carry a medium for cooling the electrode. The depth (d) of the
recessed parts 34, 35, and 36 becomes smaller as one goes from the
center to the outer side of the electrostatic adsorption electrode
3 in accordance with the order of d3>d2>d1. In the case where
trenches are formed on the electrostatic adsorption face in place
of the recessed parts, it is sufficient to decrease the depth from
the center to the outer side of the electrostatic adsorption
electrode 3.
[0053] As mentioned above, since the depth (d) of the recessed
parts 34, 35, and 36 is decreased from the center to the outer side
of the electrostatic adsorption electrode 3, the electrostatic
adsorption electrode 3 has the function of maintaining the
temperature in the central part of the substrate at the time of
etching treatment so that it is higher than that in the peripheral
part, as shown in FIG. 1. When the temperature in the central part
of the substrate is high at the time of etching treatment, the
deposition probability of the reaction products becomes low.
Consequently, even if the amount of re-irradiation of the reaction
products is large, the amount of the reaction products deposited on
the side walls of the etched part decreases. The difference between
the high and low temperatures of the substrate is adjusted so that
the amount of the reaction products deposited on the side walls of
the etched part is uniform. In this manner, as will be described
hereinbelow, the etching characteristics in the substrate plane can
be uniformized.
[0054] The mechanism of the plasma treatment will be described by
an etching operation applied to an aluminum wiring film as an
example.
[0055] FIG. 4 is a schematic diagram showing an aluminum wiring
film that is being etched. As an aluminum wiring, a film 22 for
preventing diffusion, called a barrier, is formed on an SiO.sub.2
oxide film 21 as an underlayer. On the film 21, an aluminum wiring
film 23 is formed. The barrier 22 is made of Ti or TiN and the
aluminum wiring is made of an alloy such as Al--Cu or Al--Si--Cu.
The composition ratio of Cu and Si or Cu is usually about 0.5 to
1.5%.
[0056] Further, a cap layer 24 made of TiN or the like is formed on
the aluminum wiring. The cap layer 24 has thereon a resist 25.
Since light reflected directly from the aluminum wiring is too
strong when a fine pattern is exposed by lithography, the cap layer
24 is provided as a reflection preventing film for preventing
deterioration in the resolution of the exposure.
[0057] The aluminum is etched using chlorine gas. Usually, since it
is also necessary to etch a natural oxide film of aluminum, a mixed
gas of BCl.sub.3/Cl.sub.2 is used. Aluminum and chlorine evaporate
as Al.sub.2Cl.sub.6. This reaction easily occurs even at an
ordinary temperature and progresses even when chlorine gas and
aluminum come into contact with each other.
[0058] As shown in FIG. 4, therefore, when intending to obtain a
vertical shape anisotropically by using the resist as a mask, the
side walls of the aluminum wiring film have to be prevented from
being etched. In the plasma etching, however, since the mixed gas
of BCl.sub.3/Cl.sub.2 reaches a plasma state, in addition to Cl
ions and the like, neutral activated species such as Cl radicals
are generated. Since the neutral activated species are not
influenced by the electric field or the magnetic field, they flit
about in random directions in the etching chamber and a number of
them are directed at the side walls. Consequently, the reaction
between the Cl radicals and the aluminum side walls has to be
prevented. A side wall protection layer 26 functions to prevent
this.
[0059] Although the Cl radicals and Al react with each other, in
order to obtain a vertical shape and to perform etching at a higher
speed, an RF bias is applied by the RF generator 4 to the substrate
2, thereby allowing ions to be directed vertically at the
substrate. The ions are accelerated by the RF bias, reach a high
energy state, and are directed at the etching bottom of the
aluminum wiring film. By ion irradiation, Cl adsorbed on the
etching bottom promptly reacts with Al. Etching in which the ion
kinetic energy is transformed to the reaction between Cl and Al on
the etching bottom is called ion assisted etching.
[0060] The aluminum etched on the bottom is released as reaction
products into the vapor phase. A part of the reaction products
dissociates again in the plasma and is again directed at the
substrate. Since the resist is likewise etched, the substrate is
also irradiated with the reaction products of the resist.
Electrically neutral species among species which are obtained by
dissociation of those reaction products in the plasma are directed
also at the side walls of the etched part. Such species, such as
species obtained by etching the bottom face and which are directly
deposited on the side walls, species directed at the side walls
sputtered by the incident ions including physical or chemical
elements, and the like, are deposited, thereby forming the side
wall protection layer. Among them, due to the re-irradiation of the
reaction products, non-uniformity in the plane of the substrate
easily occurs for the following reason. The reaction products
released into the vapor phase by the etching are exhausted as a gas
from the etching chamber. As described with reference to FIG. 16,
the reaction products on the outer periphery of the substrate are
more efficiently exhausted. When the substrate temperature
distribution is uniform in the plane, inevitably, the density
distribution of the reaction products in the vapor phase is higher
over the center of the substrate and is lower in the peripheral
part thereof.
[0061] According to the invention, therefore, by setting the
temperature in the central part of the substrate higher, as shown
in FIG. 1, the deposition probability of the reaction products is
changed in the plane of the substrate, as shown in FIG. 5, and the
deposition amount of the reaction products serving as the side wall
protection layer is uniformized in the plane of the substrate. That
is, the deposition probability of the reaction products is set to
be low in the central part of the plane of the substrate and is set
to be high in the peripheral part thereof. As a result, the
thickness distribution characteristic of the side wall protection
layer can be uniformized in the plane of the substrate, as shown in
FIG. 5.
[0062] In order to obtain the characteristic to make the
temperature in the central part of the substrate higher as compared
with that in the peripheral part of the substrate, for example, the
depth (d) of the recessed parts 34, 35, and 36 (or trenches)
decreases sequentially from the central part to the outer side of
the electrostatic adsorption electrode 3.
[0063] FIG. 7 shows the relation between pressure (Pa) on the back
face of the substrate and the overall heat transfer coefficient
(W/m.sup.2.times.K) by the gas molecules. It will be understood
from FIG. 7 that the higher the pressure on the back face is, the
larger the overall heat transfer coefficient is. Consequently, the
relation between the distance (d) between the back face of the
substrate and the surface of the electrode and the overall heat
transfer coefficient by the gas molecules when the pressure is set
to be constant is obtained as shown in FIG. 8.
[0064] Using the characteristics of FIG. 8, therefore, by setting a
varying depth (d) of the recessed parts 34, 35, and 36 (or
trenches) on the surface of the electrostatic adsorption electrode
from the center to the outer side, the temperature distribution as
shown in FIG. 1 can be obtained.
[0065] In practice, it is sufficient to set the depth (d) of each
of the recessed parts 34, 35, and 36 (or trenches) on the surface
of the electrostatic adsorption electrode so that the deposition
amount of the reaction products in the plane of the substrate can
be maintained at an in-plane uniformity of .+-.10%.
[0066] The method according to the invention can be especially
effective when applied to a case where the diameter of the
substrate is 200 mm or larger and a pattern formed on the substrate
is 0.35 .mu.m or smaller.
[0067] In order to set the depth (d) of the recessed parts 34, 35,
and 36 (or trenches) on the surface of the electrostatic adsorption
electrode so as to be changed from the center to the outer side, as
shown in FIG. 9, it is also possible to preliminarily set the depth
of the recessed parts to be uniform and to adjust the depth
thereafter by arranging spacers 37 having different
thicknesses.
[0068] Instead of changing the thickness of the spacers 37, it is
also possible to change the thermal conductive characteristics by
coating the gap (trench) between the electrode surface and the
substrate with a polyimide film or the like, thereby obtaining a
predetermined temperature distribution in the plane of the
substrate. Further, the temperature can be changed according to the
processes by adjusting the kind or thickness of a film. By sticking
the film again, cleaning can be easily done. The film does not have
to be made of plastics material, but can be made also of a metal or
ceramics.
[0069] As shown in FIG. 10, the width W (W1, W2, and W3) of the
recessed parts 34, 35, and 36 (or trenches) on the surface of the
electrostatic adsorption electrode is changed so as to become
narrower from the center of the electrode to the outer side
thereof, thereby making it possible to obtain a temperature
distribution in the plane of the substrate as shown in FIG. 1.
Further, as shown in FIG. 11, both the depth (d) (d1, d2, d3) and
the width W (W1, W2, W3) of the recessed parts 34, 35, and 36 (or
trenches) on the electrostatic adsorption surface are sequentially
changed from the center of the electrode to the outer side, thereby
making it possible to obtain the temperature distribution in the
substrate plane as shown in FIG. 5.
[0070] Another method also can be employed. As shown in FIG. 12,
the temperature in the substrate 2 is measured by sensors 42, 43,
and 44 and the pressure of gas for heat transfer, which is supplied
between the substrate 2 and the electrode 3 via the passage 38, is
controlled by a valve 46 via a controller 45 on the basis of the
measured temperatures, thereby making it possible to obtain the
temperature distribution in the plane of the substrate as shown in
FIG. 1.
[0071] The pressure of the gas for heat transfer to the back face
of the substrate can be increased by increasing the flow of the
heat transfer gas. On the other hand, the pressure to the back face
and the overall heat transfer coefficient have the relation as
shown in FIG. 13. The depth of the recessed part (or trench) of the
electrostatic adsorption electrode 3 and the pressure loss (Pa) on
the back face of the electrode have the relationship as shown in
FIG. 6. It will be understood from FIG. 6 that the larger the
trench depth (d) is, the smaller the pressure loss .DELTA.Pa is.
Consequently, the supply pressure of the heat transfer gas is
adjusted so that a pressure loss occurs due to the shapes of the
radial recessed parts or trenches of the electrostatic adsorption
electrode 3 which communicate with the recessed parts 34, 35, and
36, and the pressure of the heat transfer gas to the recessed parts
34, 35, and 36 is properly regulated, thereby making it possible to
obtain the temperature distribution in the substrate plane as shown
in FIG. 1.
[0072] Independent passages for supplying the heat transfer gas
also can be provided for the respective recessed parts 34, 35, and
36 so that the pressures of the heat transfer gas supplied to the
recessed parts 34, 35, and 36 can be adjusted.
[0073] Further, as another embodiment of the invention, as shown in
FIG. 14, by etching the substrate 2 while regulating the exhaust
amount of the reaction products from the etching chamber 1 by
exhaust means 50, the deposition amount of the reaction products
can be made uniform in the substrate plane.
[0074] A method of adjusting a process gas in order to uniformize
the deposition amount of the reaction products in the substrate
plane during the etching will now be described. That is, the
process gas is adjusted by changing the parameters in the range and
the manner described below. [0075] (1) kinds of gasses: BCl.sub.3,
Cl.sub.2 [0076] addition gases: CHF.sub.3, CF.sub.4,
CH.sub.2F.sub.2, Ar+CH.sub.4 [0077] (2) gas flow rate [0078]
BCl.sub.3; 10 ml/min to 100 ml/min [0079] Cl.sub.2; 50 ml/min to
400 ml/min [0080] (3) gas pressure: 0.1 Pa to 6 Pa [0081] (4)
microwave (2.45 GHz) output: 200 W to 2000 W [0082] (5) RF output:
10 W to 500 W (frequency to be used: 100 KHz to 13.56 MHz) [0083]
(6) substrate temperature range: 50.degree. C. to 100.degree. C.
[0084] (7) resist is used as a mask
[0085] Within the above parameter adjustment range, in order to
reduce the difference (the density in the center of the substrate
is high and that in the peripheral part is low) in the density
distribution of the reaction products in the plane, the following
methods can be used.
[0086] (1) reduction in the gas pressure (0.1 Pa to 1 Pa)
[0087] The gas pressure is lowered, the gas residence time is
shortened, and the volatility of the products is increased, thereby
reducing the number of re-deposition times of the reaction products
after etching. In such a state, since the number of collisions with
other gas molecules is small in both the center and the peripheral
part of the substrate until the reaction products are exhausted, a
difference does not easily occur between the exhaust speed in the
center of the substrate and that in the peripheral part.
Consequently, the variation in the deposition amount distribution
of the reaction products in the plane of the substrate is
reduced.
[0088] (2) increase in both the gas flow rate and the chlorine flow
ratio (>80%)
[0089] By shortening the gas residence time by an increase in the
flow rate, the volatility of the products is increased and the
number of deposition times of the reaction products after etching
is reduced.
[0090] By reducing BCl.sub.3 ions having a large mass, the amount
of deposition on the side walls from the resist by the ion attack
is decreased, thereby reducing the variation in the in-plane
reaction product deposition density distribution.
[0091] (3) increase in the whole substrate temperature (70.degree.
C. to 100.degree. C.)
[0092] By increasing the temperature of the whole substrate, the
number of re-deposition times can be reduced.
[0093] Although the increase itself in the substrate temperature
does not directly contribute to solve a solution in-plane vibration
problem, when the temperature in the substrate is controlled, for
example, when the substrate temperature is increased, the
probability of deposition of the irradiated reaction products
decreases. Consequently, the deposition amount itself of the
in-plane reaction products is reduced, so that the absolute value
of the variation in the deposition density distribution of the
reaction products in the substrate plane can be reduced.
[0094] (4) reduction in the plasma density (decrease in the
microwave output)
[0095] By lowering the density of the plasma, the amount of
reaction products is suppressed and the variation in the in-plane
reaction product deposition density distribution is reduced.
[0096] (5) reduction in the energy of ions directed at the
substrate (decrease in the RF output)
[0097] By decreasing the RF output, the amount of the deposition on
the side walls from the resist by the ion attack is reduced and the
variation in the in-plane reaction product deposition density
distribution is reduced.
[0098] By optimizing the parameters so as to be applicable to
various areas to be etched, preferably, to a wiring process of a
semiconductor in which the diameter of the substrate is 200 mm or
larger and a pattern formed on the substrate is 0.35 .mu.m or
smaller, etching which does not cause a variation in the processing
dimension in the plane of the substrate can be performed.
[0099] Also, in so-called dense and sparse patterns in which fine
patterns and sparse patterns which are not so fine mixedly exist in
almost the same place on the substrate, the variation in the
processing dimension can be reduced. That is, the finer the pattern
becomes, the more the incident particles enter deep inside the
pattern and the probability of deposition on the side walls is
reduced, so that the side wall protection layer becomes thinner.
According to the invention, however, the uniformity in the dense
and sparse patterns can be also achieved in a way similar to that
of the uniformization of the side wall protection layer in the
plane of the substrate.
[0100] As mentioned above, according to the invention, a plasma
treatment method and a plasma treatment apparatus can be provided,
in which the influence exerted on the etching characteristics of
the reaction products during the plasma treatment is offset and
uniform treatment characteristics in the substrate plane are
obtained.
[0101] According to the invention, the in-plane distribution of the
plasma treatment characteristics can be uniformized by a simple
method, for instance, by changing the temperature in the substrate
plane, so that an effect can be attained wherein the yield of the
devices is improved. Since the substrate temperature can be changed
according to the process, there is also an advantage that the
invention is applicable to various specifications in the treatment
of etching or the like.
[0102] According to the invention, further, a plasma treatment
method and a plasma treatment apparatus can be provided, which can
obtain etching treatment characteristics causing no variation in
the processing dimension in the dense and sparse patterns.
* * * * *