Method and device for chemically treating substrates

A method for treating substrates includes chemically treating at least one substrate in a container with at least one treatment fluid and washing said at least one substrate with a washing fluid in the same container. Subsequently, the at least one substrate is dried.

BACKGROUND OF THE INVENTION 
The invention relates to a method for chemically treating substrates in 
which at least one substrate is subsequently subjected to a chemical 
treatment, a washing step, and a drying step, and a device for performing 
the aforementioned chemical treatment. 
To date an automatic wet treatment device has a series of tubs or of 
reservoirs for a sequence of chemical wet processes. After completion of a 
certain chemical process sequence the substrate, for example, a silicon 
wafer, is immersed in a separate washing, respectively, rinsing tub and 
subsequently dried. 
The drying of the substrate can, for example, be performed with a 
centrifuge, but can also be carried out during the slow removal of the 
substrate from the washing tub. 
From European document 0 385 536 the so-called Marangoni dryer is known. In 
the method disclosed in this patent a vapor is applied to the substrate in 
addition to the slow removal of the substrate from the bath, whereby the 
vapor does not condense on the substrate, but diffuses into the liquid. At 
the liquid meniscus of the substrate surface a concentration gradient will 
result and thus a surface tension gradient. This gradient results in a 
liquid movement away from the substrate into the liquid (Marangoni effect) 
and leads to a residue-free drying of the substrate. 
From U.S. Pat. No. 4,722,752 a device and a method are known for rinsing 
and drying wafers, whereby the wafer is enclosed in a cassette. The wafers 
are removed from the rinsing bath separate from the cassette and are 
subsequently inserted into the cassettes that have been slowly removed and 
dried also. 
The described device, respectively, methods have the following 
disadvantages: The rinsing reservoir in each case is a separate bath from 
the other process reservoirs and serves only for rinsing the substrate. 
However, an individual and separate rinsing reservoir means an increased 
space requirement. Furthermore, the substrate must be moved through the 
surface of the fluid used for the chemical treatment into the air and 
subsequently must be inserted into the rinsing fluid which, and this may 
have disadvantageous effects with respect to the particle contamination of 
the substrate, as is well known in the art. This is especially true for 
hydrophobic surfaces, for example, after HF treatment. Furthermore, the 
insertion into, respectively, removal of the substrates from the various 
baths for chemical treatment, respectively, the rinsing step results in an 
increased time expenditure. Also, the known devices, respectively, methods 
always require a cassette (carrier) for handling the substrates. 
It is therefore an object of the invention to provide a method for 
chemically wet treating, respectively, a device for such a method which 
economizes the process sequence of an automatic wet treatment device, 
i.e., saves time and space. A further object of the invention is to 
minimize the contamination of the substrate during such a sequence of 
chemical wet processes. Finally, a further object of the invention is to 
make obsolete the need for a cassette or similar holding device for the 
substrate in connection with the insertion of the substrate into 
respectively, the removal of the substrate from the reservoirs. 
SUMMARY OF THE INVENTION 
This object is inventively solved by performing the chemical treatment and 
the washing process in the same reservoir. 
The inventive method is primarily characterized by the steps of: 
chemically treating at least one substrate in a container with at least one 
treatment fluid; 
washing the at least one substrate with a washing fluid in the same 
container; and 
drying the at least one substrate. 
The method advantageously further comprises the step of replacing the at 
least one treatment fluid used in the chemical treatment step with the 
washing fluid. The step of replacing preferably includes the step of 
displacing the at least one treatment fluid with the washing fluid. 
The washing step includes the step of introducing the washing fluid into 
the container and simultaneously draining the at least one treatment 
fluid. The washing fluid is expediently introduced at a location that is 
different from a location of draining the at least one treatment fluid. 
The location of introducing the washing fluid is at the bottom of the 
container. 
Draining of the at least one treatment fluid is carried out by allowing the 
at least one treatment fluid to flow over the upper edges of the 
container. 
Preferably, the step of chemically treating includes the step of 
sequentially treating the substrate with at least two of the treatment 
fluids. 
Between individual treatments of the sequential treating step the substrate 
is preferably intermediately dried. The step of intermediately drying 
includes the step of removing the substrate from the treatment fluid. The 
step of intermediately drying may include the steps of slowly lifting the 
substrate from the container and applying a vapor that diffuses into the 
treatment fluid and does not condense on the substrate. The mixture of the 
vapor and the treatment fluid has a surface tension that is smaller than 
the surface tension of the treatment fluid. 
The at least two treatment fluids are selected from the group consisting of 
a chemical treatment fluid and a rinsing fluid. 
Preferably, a first chemical treatment fluid, a rinsing fluid, and a second 
chemical treatment fluid are sequentially used. 
It is expedient to use a first and a second chemical treatment fluid 
sequentially. 
The step of sequentially treating the substrate includes the step of 
replacing at least partially the previous treatment fluid with the 
subsequent treatment fluid. The step of replacing the previous treatment 
fluid is at least partially displaced by the subsequent treatment fluid. 
The chemical treatment step includes the step of introducing the subsequent 
treatment fluid into the container and simultaneously draining the 
previous treatment fluid from the container. 
The treatment fluids are introduced at a location that is different from a 
location of draining the treatment fluids. The location of introducing the 
treatment fluids is preferably at the bottom of the container. 
Draining of the treatment fluids is preferably carried out by allowing the 
treatment fluids to flow over the upper edges of the container. 
The method advantageously further comprises the step of removing the 
substrate from the washing fluid, wherein the step of drying is performed 
during the step of removing. The step of drying includes the steps of 
slowly lifting the substrate from the container and applying a vapor that 
diffuses into the washing fluid and does not condense on the substrate. 
The mixture of the vapor and the washing fluid has a surface tension that 
is smaller than the surface tension of the washing fluid. 
The treatment fluid can be hydrofluoric acid or ozone. 
The step of washing includes the step of applying mega sound. 
The invention also relates to a method of inserting into and removing from 
a container at least on substrate and includes the steps of: 
securing the at least on substrate on a receiving device; 
lowering the at least one substrate into the container with the receiving 
device and lifting the at least one substrate from the container with the 
receiving device. 
Preferably, this method further comprises the steps of providing a blade at 
the receiving device and providing supports at the receiving device. In 
the step of lifting the at least one substrate is raised to a point where 
guides at a hood secure the at least one substrate. 
Advantageously, the method further comprises the steps of providing 
moveable holders and, after lifting of the at least one substrate, 
positioning the moveable holders underneath the at least one substrate for 
securing the at least one substrate in its position. 
The invention also relates to a device for chemically treating at least one 
substrate in a container with at least one treatment fluid, washing the at 
least one substrate with a washing fluid in the same container, and drying 
the at least one substrate. The inventive device comprises: 
a first container; 
a device for introducing a fluid into the container; 
a device for removing the fluid from the container; and 
a receiving device for receiving at least one substrate. 
The device for removing has an overflow. 
The device preferably further comprises a second container surrounding the 
first container. 
Advantageously, leveling screws are provided for leveling the container. 
The device for introducing advantageously comprises a diffusor. 
The device for introducing comprises a pump with an inlet mechanism. 
Preferably, a vaporization device positioned above the first container is 
provided. 
The device further comprises a hood positioned above the first container 
and the vaporization plant. The hood has a guide for the at least one 
substrate. The guide has two parts for holding the at least one substrate 
laterally. At least one of the two parts has a slanted edge. 
The receiving device expediently comprises a blade and supports. 
Above the container moveable holders for the at least one substrate are 
provided which, after lifting of the at least one substrate, are moveable 
into a position under the at least one substrate. 
The device may further comprise a means for emitting mega sound. 
Advantageously, the chemical treatment and the washing process are 
performed within the same container by adding to, respectively, by 
(partially) replacing the fluid for the chemical treatment with a further 
such fluid and/or replacing with a washing fluid. Preferably, in a 
sequential chemical process a rinsing fluid is first introduced before 
replacing the fluid for the chemical treatment with a further such fluid 
and the substrate, respectively, the substrates are removed from the 
container and simultaneously dried. Subsequently, the rinsing fluid is 
replaced by a further fluid for chemical treatment and the substrate is 
again introduced into the container. 
In a preferred embodiment of the invention the drying process takes place 
during the removal of the substrate from the rinsing or washing fluid. 
This encompasses usually a very slow removal of the substrate from the 
rinsing or washing fluid. 
In order to make this process more efficient, it is advantageous to use a 
vapor on the substrate which does not condense on the substrate but mixes 
with the washing fluid. Preferably, the mixture has a smaller surface 
tension than the rinsing or washing fluid which means that a force is 
provided that forces the washing fluid adhering to the substrate back into 
the container. 
The replacement of the fluid for chemical treatment with the washing fluid 
in a preferred embodiment is carried out by displacement. A drainage of, 
for example, the fluid for chemical treatment and a subsequent 
introduction of the rinsing or washing fluid would result in subjecting 
the substrate to an increased particle contamination in the air. The 
displacement of one fluid with another, for example, with the washing 
fluid, has the advantage that the substrate does not have to pass through 
a phase border and is not exposed to air. Of course, it is possible that a 
plurality of fluids for chemical treatment can be replaced by displacement 
before the washing step. Especially in connection with the replacement of 
a fluid for chemical treatment with a further such treatment fluid, the 
replacement can be a partial replacement, i.e., a mixing. 
Preferably, the washing fluid is introduced into the container and 
simultaneously the mixture of the fluid for chemical treatment and the 
fluid is drained. 
The introduction of the rinsing or washing fluid and the drainage of the 
fluid for chemical treatment takes place preferably at different locations 
of the container. For example, this results in an optimization of the 
replacement of one fluid with another fluid in a timely fashion. 
The introduction of the washing fluid preferably takes place at the bottom 
of the container while the drainage of the mixture is carried out by 
overflow. The drainage thus does not require an additional pumping device. 
With the introduction at the bottom of the container, i.e., far removed 
from the location of drainage, the smallest possible amount of introduced 
washing fluid is drained off. Also, with respect to gravity, this 
arrangement can be additionally advantageous, for example with an 
additional temperature gradient. This is advantageous with respect to 
economical considerations and is also time-saving. 
In a preferred embodiment of the invention the fluid for chemical treatment 
is diluted hydrofluoric acid. A treatment in diluted hydrofluoric acid 
(HF) serves to remove the oxide layer on a substrate surface and to 
provide a hydrophobic, hydrogen-passivated surface that is required for 
some subsequent processes. 
In a further preferred embodiment of the invention the fluid for chemical 
treatment is ozone. A treatment with ozone is performed when it is desired 
to again grow a chemical oxide on the substrate surface, for example, 
after treatment with HF for cleaning purposes, and to thus provide a 
hydrophilic surface. 
The object of the invention is furthermore solved inventively such that in 
a method for introducing and/or removing at least one substrate into, 
respectively, from the container, the substrate is secured within the 
container by a receiving device and is inserted and removed with the 
receiving device. 
An advantage of the invention is that a cassette as a holder for the 
substrate for insertion and removal of the substrate is no longer needed. 
The inventive method thus does not need a carrier. Accordingly, the known 
disadvantages of a carrier in connection with the drying step (no drying 
takes place at the contact locations of the carrier in the substrate) are 
avoided. The inventive receiving device is not a carrier but simply a 
support movable back and forth for one or more substrates. A carrier-free 
drying not only eliminates the step of drying the carrier, but also 
reduces with respect to the rinsing or washing process the required time 
as well as the consumption of rinsing or washing fluid. Also, the 
entrainment of chemicals into the dryer is reduced with the carrier-free 
process. 
Advantageously, the receiving device is comprised of a two-part support 
device and a separate, vertically movable blade. 
Preferably, the receiving device removes the substrate from the container 
to such a location that it can be guided, respectively, held by guides 
that are arranged on opposite inner sides of a hood. 
In a preferred embodiment movable holders are provided that secure the 
substrate after removal from the container in their position above the 
container in a dry state. The movable holders below, respectively, within 
the hood are designed such that, when the substrate is secured by the 
movable holders, the hood can be opened, respectively, closed without 
problems and without changing the position of the substrate. The movable 
holders are always dry and have contact only with the already dried 
substrates. 
Advantageously, the inventive method provides for an enhancement of the 
washing, respectively, cleaning step by ultrasound, respectively, 
megasound. Advantageously, for this purpose the container is provided with 
piezoelements in order to generate sound waves for cleaning the substrate. 
Such a "mega-sonic" system is advantageous in this context because the 
particle contamination of the substrate is reduced to a minimum with the 
inventive method. Thus, an extremely thorough cleaning of the substrate is 
achieved. 
The object of the invention is also inventively solved by a device for 
chemically treating that comprises: 
an introduction device for a fluid into the container; 
a drainage device for fluid from the container; 
a receiving device for the substrate. 
Preferably, in addition to the (inner) container at its outer sides an 
outer container is provided that serves, for example, as a safety 
reservoir. 
For leveling the container with respect to a uniform overflow of the fluid 
to be replaced, leveling screws are advangtaeously provided. 
Advantageously, the introduction device is a diffusor, preferably at the 
bottom of the container. This is, for example, expedient for the 
aforementioned ozone (O.sub.3). 
In the case of a liquid, for example, diluted hydrochloric acid, a pump in 
combination with an inlet mechanism, preferably also at the bottom of the 
container, is advantageous. 
In a preferred embodiment a hood is provided above the container in order 
to protect the container, respectively, also the dried substrate from 
particle contamination and in order to provide a tight vapor atmosphere in 
the area above the container. For introducing the vapor, the hood is 
provided with an integrated diffusor, i.e., a perforated diffusor plate 
integrated into the hood for the introduction, respectively, distribution 
of an IPA (Isopropyl alcohol)/N.sub.2 mixture. In this manner, a 
homogenous and identical vapor atmosphere for all substrates is produced 
within the process chamber so that the process conditions for each wafer 
are identical. The mixing of IPA with nitrogen takes place in a bubbler. 
Preferably, the substrate is secured within the container with the 
receiving device that is comprised of a blade-shaped part, the so called 
blade, and, for example, two supports. The blade and the supports are 
movable relative to one another and the blade is advantageously positioned 
between the two supports. The supports are located within the container, 
while the blade can also be removed from the fluid. 
In a preferred embodiment of the invention the hood is provided with guide 
means above the container. The guide means is advantageously connected to 
the inner side of the hood at two oppositely arranged sides. The 
substrate, for example, a silicon wafer, can be guided, respectively 
secured in this guide means. 
The guide means is connected to opposite sides of the hood. It is 
groove-shaped for receiving a plurality of substrates. Thus, the use of a 
cassette for securing the substrate is obsolete. 
Preferably, the guide within the hood is of a two-part construction whereby 
at least one edge of the receiving means is slanted in order to facilitate 
receiving of the substrate. 
Advantageously, at least one part of the guide has a slanted edge for easy 
reception of the substrate. This also simplifies opening and closing of 
the hood. 
In a preferred embodiment of the invention, movable holders are provided 
which can be introduced from the exterior below the hood and above the 
container into a position above the container. They have an arc-shaped 
depression. The movable holders as well as the receiving device in the 
hood and the assembly of blade and the two supports can by themselves hold 
the substrate within the container. When the substrate is resting on the 
arc-shaped depression of the movable holders and when it is secured by the 
guide means within the hood, the hood can be opened without entraining the 
substrate. The substrate is then held only by the movable holders until 
the operator removes them for further treatment.

DESCRIPTION OF PREFERRED EMBODIMENTS 
FIG. 1 shows a device for chemical wet treatment 1 of substrates, 
especially of a wafer 2. The device 1 is comprised of an outer container 5 
and an inner container 10. The outer container 10 has an outer annular 
chamber 6 and an inner annular chamber 7. Above the inner container 10 a 
hood 12 with an opening mechanisms 13 is provided for covering the inner 
container 10. The hood 12 has a chamber delimited by a diffusor plate 14 
into which can be introduced, for example, an IPA/N.sub.2 mixture. The 
inner container 10 comprises a narrow cylinder 18 located at the lower end 
of the inner container 10. A frusto-conical intermediate section 20 widens 
the diameter of the inner container 10 to a wider cylinder 19. The edge at 
the upper end of the inner container 10 is in the form of a slanted outer 
edge 23. This improves the properties of the upper edge of the inner 
container 10 with respect to overflow of the fluid. With leveling screws 
4, that connect the inner container 10 to the outer container 5 and that 
are arranged within the chamber 6 of the outer container, the inner 
container 10 can be leveled in order to guarantee a uniform overflow of 
the fluid over the entire length of the container. The inner container 10 
at its bottom 11 is provided with two inlet devices, a diffuser 25 and an 
inlet mechanism 26, arranged atop one another. The diffusor 25 is arranged 
above the inlet mechanism 26. The diffusor 25 is connected with a line 30 
to a fluid container 35 that preferably contains ozone (O.sub.3). In the 
drawings the flow direction of the ozone is indicated by an arrow. The 
inlet mechanism 26 is connected with a line 31 to a pump 36. The pump 36 
pumps facultatively from the fluid reservoir 37, respectively, 38 via the 
lines 39, respectively, 40 a fluid for chemical treatment for the wafers 
2, for example, diluted hydrofluoric acid. In FIG. 1, the arrow represents 
the direction of fluid of the pumped fluid within the line 31. Within the 
inner container 10 right and left support devices 43, 44 are also provided 
which are attached to two securing devices 46, 47 that are displaceable 
parallel in the vertical direction within the inner container 10. The 
right and left supports 43, 44 are provided with an arc-shaped cutout 60, 
61 for receiving the wafer 2. In the center between the two supports 43, 
44 a so-called blade 42 is provided, i.e., an elongate element with a 
pointed edge. The blade 42 is, for example, made of quartz glass and is 
movable independent of the right and left supports 43, 44 in the vertical 
direction. In FIG. 1 it can be seen that the blade 42 has lifted the wafer 
2 from the inner container 10 and the wafer 2 is secured by a holder 51 
above the inner container 10 within the hood 12. The guide means or wafer 
receiving device 51, in analogy to the supports 43, 44, has a groove shape 
in order to simultaneously hold a plurality of wafers without a cassette. 
To facilitate insertion of the wafer 2 into the guide means 51, one inner 
edge 52 of the guide means 51 is slanted. The wafer or wafers 2 are 
secured or guided by the guide means 51. The outer container 5 is closed 
off in the upward direction by a cover 8 that has an opening 9. The outer 
container 5, which serves as a safety reservoir, is comprised of a narrow 
cylinder 48 which is connected with an intermediate section 50, in the 
form of a disk with a central circular opening, to the wider cylinder 49. 
The wider cylinder 49 forms the outer shell of the inner annular chamber 
7, respectively, the inner shell of the outer annular chamber 6 from which 
the overflowing fluid can be drained, respectively, pumped through the 
opening 9. 
FIG. 2 shows the first step of the process sequence represented in FIGS. 2 
to 9. In FIG. 2 it is shown that a wafer packet, represented by one wafer 
2, is fed to the device with a gripping device 90. The hood 12 that is 
connected to the guide means 51, has been opened by the automatic cylinder 
15. The blade 42 and the right and left supports 43, 44 are ready to 
receive the wafer 2. For this purpose, the blade 42 is slightly lowered 
relative to the supports 43, 44 so that the tip of the blade 42 is 
positioned on a circular line defined by the arc-shaped cutouts 60, 61 on 
which later on the wafer 2 will rest. 
FIG. 3 illustrates the lowering of the wafer 2 into the inner container 10, 
which is, for example, filled with HF. 
FIG. 4 shows that the hood 12 above the container 10 is closed and the 
wafer 2 is being lowered into the inner container 10 into a low position 
approximately at the level of the intermediate section 20, whereby the 
blade 42 and the right and left supports 43, 44 are moved downward at the 
same speed. 
In FIG. 5 the drying step of the wafer 2 is represented, i.e., the removal 
of the wafer 2 from the inner container 10. Inventively, between the steps 
represented in FIGS. 4 and 5 the chemical treatment fluid HF is replaced 
by another fluid, whereby as a last step preferably a washing fluid is 
introduced. Preferably, above the inner container 10 the wafer is exposed 
to a vapor which does not condense on the wafer 2; however, the mixture of 
washing fluid and vapor has a reduced surface tension relative to the 
washing fluid alone. For this step, the hood 12 is still in the closed 
position. Advantageously, the blade 42 is moved at a constant speed 
upwardly, whereby the two supports 43, 44 are moved at half the speed, so 
that they stay behind. 
In FIG. 6 the supports 43 and 44 are stopped, a further lifting of the 
wafer 2 takes place only with the blade 42. It is shown that the wafer 2, 
before removal only by the blade 42, is still in contact with the washing 
fluid within the container 10. 
In FIG. 7 the end of the drying process is represented, i.e., the wafer is 
completely removed from the inner container 10 and is secured by the blade 
42 and the guide means 51. 
FIG. 8 illustrates that before opening the hood 12 the movable holders 70, 
71 are introduced into the space above the inner container 10 in order to 
secure the wafer 2 from below in their position during, respectively, 
after opening of the hood 12, i.e., the removal of the guide means 51. The 
wafers 2 can be secured only by the movable holdes 70, 71, i.e., the blade 
42, the supports 42, 43, and the wafer guide means 51 are no longer needed 
for further securing the wafer 2. The movable holder 70, 71 have 
arc-shaped cutouts in order to secure the wafer 2 in their position. It is 
also shown in FIG. 8 that the blade 42 is again submerged within the inner 
container 10 in its initial position (compare FIG. 2) below the right and 
left supports 43 and 44. 
In FIG. 9 the hood 12 is opened and the gripping device 90 removes the 
wafer 2 from the device 1 for further processing. FIGS. 2 to 9 thus show a 
cyclical process. 
The invention has been explained with the aid of preferred embodiments. 
However, to a person skilled in the art numerous deviations, respectively, 
other embodiments are obvious without leaving the gist of the present 
invention. 
The present invention is, of course, in no way restricted to the specific 
disclosure of the specification and drawings, but also encompasses any 
modifications within the scope of the appended claims.