Real time monitor of reacting chemicals in semiconductor manufacturing

A method and apparatus provide for monitoring and controlling a chemical process with a chemical substance adapted for treatment of a semiconductor device. The chemical substance is held in a container. The process of monitoring is provided by transmitting a light or other electromagnetic energy from a source located within the container through the chemical substance. The electromagnetic energy transmitted through the chemical substance is sensed with a photosensor or a photosensor fiber located within the container. A comparison to a standard is made of the result of the sensing by spectrum analysis, with a passband filter between the source and the photosensor. The sensor may comprise a wavelength adjustable photosensor or a multiple wavelength photosensor.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a method and apparatus for monitoring and 
controlling a chemical process for manufacturing semiconductor devices and 
more particularly to detection of the condition of a chemical substance 
employed in such a chemical process. 
2. Description of Related Art 
In-line real-time testing of chemicals using density, color, spectroscopy, 
pH, etc. is generally known and used in many industries, including the 
chemical and semiconductor industries. 
U.S. Pat. No. 5,262,961 of Farone for "Method for Monitoring and 
Controlling a Chemical Process" shows a method of monitoring and 
controlling a chemical process by measuring the concentration of the 
process reactants and products using spectrometric technology, but not in 
a semiconductor manufacturing process. 
U.S. Pat. No. 5,401,664 of Larson et al "Analytical Method for Determining 
Concentration of Decomposition Products in Solvent Used for Solvent 
Extraction" describes an analytical method for determining the 
concentration of extraction. However, this invention does not appear to be 
a real time measurement. 
Current methods of detecting the life-time of reacting chemicals are as 
follows: 
1. Chemical analysis of contaminated elements added in the chemical, which 
is really time-consuming way, and is not applicable to sudden chemical 
variation. 
2. Unscientific life-time estimate with respect to numbers of runs or lots 
passed through the chemical, which must be not a cost effective method. 
SUMMARY OF THE INVENTION 
An object of this invention is a real-time monitoring of reacting chemicals 
to discover a problem ahead of scheduled chemical change, or to alarm the 
abnormality of chemicals to minimize resultant impacts. 
Another object of this invention real time monitoring of reacting chemicals 
using chemical life time estimation including estimation by analysis of 
contaminated elements in a laboratory, estimation by runs or by time and 
estimation by real time monitoring. 
Still another object of this invention is real time monitoring of reacting 
chemicals by real time spectrum analysis of chemicals. 
An additional object of this invention is real time monitoring assemblies 
for monitoring chemicals for use in real time spectrum analysis. 
In accordance with this invention, a method for monitoring and controlling 
a chemical process includes the following steps. Place a chemical 
substance in a container adapted for treating semiconductor devices. 
Transmit electromagnetic energy from a source through the chemical 
substance. Sense the electromagnetic energy transmitted through the 
chemical substance. Compare the result of the sensing with a standard. 
Preferably, sensing is provided with a wavelength adjustable photosensor 
and a passband filter between the source and the photosensor and the 
comparing comprises spectrum analysis. Sensing is provided with a multiple 
wavelength photosensor. 
It is further preferred that sensing is provided with a multiple wavelength 
photosensor and the comparing comprises spectrum analysis. 
Further in accordance with this invention a method for monitoring and 
controlling a chemical process is provided by the following steps. Place a 
chemical substance adapted for use in treatment of semiconductor devices 
in a container adapted for use in treatment of semiconductor devices. 
Transmit an electromagnetic energy from a source located within the 
container through the chemical substance. Sense the electromagnetic energy 
transmitted through the chemical substance with a sensor located within 
the container. Then, compare the result of the sensing with a standard. 
Preferably, sensing is provided with a photosensor and a passband filter 
between the source and the photosensor and the comparing comprises 
spectrum analysis; and sensing is provided with a wavelength adjustable 
photosensor; and the comparing comprises spectrum analysis. 
In accordance with another aspect of the invention, apparatus for 
monitoring and controlling a chemical process with a chemical substance 
adapted for use in treatment of semiconductor devices in a container 
includes means for transmitting an electromagnetic energy from a source 
through the chemical substance adapted for use in treatment of 
semiconductor devices, means for sensing the electromagnetic energy 
transmitted through the chemical substance, and means for comparing the 
result of the sensing with a standard. 
Preferably, the means for sensing comprises a multiple wavelength 
photosensor or a wavelength adjustable photosensor and a passband filter 
between the source and the photosensor and the means for comparing employs 
spectrum analysis. 
In accordance with still another aspect of this invention apparatus is 
provided for monitoring and controlling a chemical process. A chemical 
substance adapted for use in treatment of semiconductor devices is 
retained in a container adapted for use in treatment of semiconductor 
devices. Means are provided for transmitting an electromagnetic energy 
from a source located within the container through the chemical substance 
as well as means for sensing the electromagnetic energy transmitted 
through the chemical substance with a sensor located within the container. 
There are also means for comparing the result of the means for sensing 
with a standard. Preferably, the means for sensing comprises a photosensor 
and a passband filter between the source and the photosensor and the means 
for comparing employs spectrum analysis. Preferably, there is a wavelength 
adjustable photosensor or a multiple wavelength photosensor and a passband 
filter between the source and the photosensor.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1A shows semiconductor manufacturing apparatus with means for 
measuring the optical spectrum of a chemical substance 10 contained in a 
transparent chemical tank 8 to determine whether the chemical substance 10 
is of normal or abnormal condition, i.e. deviating from the normal or 
average condition from the point of view of the spectrum of 
electromagnetic radiation transmitted through the chemical substance 10. A 
source of electromagnetic radiation, in this case a light source 12 is 
located below the tank 8. There is a fiber optical line 14 above the tank 
8 which is connected via line 16 to a spectrum scanner 18. 
Scanner 18 compares the spectrum with respect to a light source through 
normal and abnormal chemicals, to find the intensity of variation specific 
wavelengths between them. Comparing the new chemical (H.sub.2 SO.sub.4) 
with old chemical (H.sub.2 SO.sub.4) which has been run through 40 lots, 
the intensities of some wavelengths listed in Table I as follows: 
TABLE I 
a: 406 nm 
b: 437 nm 
c: 487 nm 
d: 548 nm 
The intensities vary, as seen in FIGS. 1B and 1C where the X axis comprises 
optical wavelengths of the electromagnetic spectrum from 200.0 nm to 600.0 
nm and the Y axis is intensity measured as amplitude percentage (Amp %). 
In the case of FIG. 1B, a display is shown in the spectrum mode. The four 
wavelengths in Table I are marked by lines which extend above the top of 
the chart. The amplitude is 1.2% and the number of runs equals "0" for the 
new chemical which is an aqueous solution of sulfuric acid (H.sub.2 
SO.sub.4). The time is 35.7 seconds which means the scanning time of the 
spectrum referred to the H.sub.2 SO.sub.4 runs is 35.7 sec. 
Gain is 4,1 which means "4" is the working coarse gain for the spectrum 
intensity and "1" is the working fine gain for the spectrum intensity. HV 
is 660 Volts, which means the working high voltage set for spectrum 
intensity and 660 Volts is the standard setting suggested by the 
operations guide. Line is 548.0 nm, which is the chosen wavelength 
referred to the amplitude of intensity (1.2%), is 548 nm. In FIG. 1B, 
there are zoom percentages of ZX1 and ZX5 ZX1 ZY5, ZX1 means the zoom 
percentage is 100% in the X axis direction. ZY5 means the zoom percentage 
is 500% in the Y axis direction. 
In the case of FIG. 1C, a display is shown in the spectrum mode. The data 
at the four wavelengths in Table I are marked a, b, c, d but are shorter 
than in FIG. 1B. The amplitude is 0.0% which is less than the amplitude of 
1.2% in FIG. 1B. The number of runs again equals "0" for the new chemical 
which is an aqueous solution of sulfuric acid (H.sub.2 SO.sub.4). The time 
is again 35.7 seconds. Gain is again 4,1 and HV is again 660 Volts as 
above. Line is only 206.0 nm as compared with 548.0 nm, which means that 
there are no specific wavelengths chosen for the purpose of showing the 
four peaks a, b, c, d clearly. ZX1 ZY5 is as above. 
FIG. 2A shows similar apparatus to that in FIG. 1A for measuring the 
optical spectrum of a different chemical substance 10' contained in a 
transparent chemical tank 8 to determine whether the chemical substance 
10' is of normal or abnormal condition, i.e. deviating from the normal or 
average condition from the point of view of the spectrum of 
electromagnetic radiation transmitted through the chemical substance 10'. 
A source of electromagnetic radiation, in this case a light source 12 is 
located below the tank 8. There is a fiber optical line 14 above the tank 
8 which is connected via line 16 to a spectrum scanner 18. The output of 
the spectrum scanner 18 is connected via line 19 to block 20 marked "used 
chemical (H.sub.2 SO.sub.4)" which has been through runs of 40 lots. 
In the case of FIG. 2B, a display is shown in the spectrum mode. The four 
wavelengths in Table I are marked by lines which extend above the top of 
the chart. The amplitude is 0.4% and the number of runs equals "40" for 
the used chemical which is an aqueous solution of sulfuric acid (H.sub.2 
SO.sub.4). The time is 29.5 seconds which means the current scanning time 
of the spectrum referred to the H.sub.2 SO.sub.4 80 runs is 29.5 seconds. 
The time is less than the 35.7 seconds. in FIGS. 1B and 1C, which means 
shorter scanning time only. Gain is 4,1; HV is 660 Volts; Line is 548.0 
nm; and ZX1 ZY5 are as explained above. 
In the case of FIG. 2C, a display is shown in the spectrum mode. The data 
at the four wavelengths in Table I are marked a, b, c, d but are shorter 
than in FIG. 2B. The amplitude is 0.0% which is less than the amplitude of 
0.4% in FIG. 2B. The number of runs again equals "40" for the new chemical 
which is an aqueous solution of sulfuric acid (H.sub.2 SO.sub.4). The time 
is again 29.5 seconds. 
Gain is 4,1, HV is 660 Volts, and ZX1 ZY5, are as explained above, whereas 
in this case, Line is only 206.0 nm as compared with 548.0 nm. 
It should be noted that the solution 10' in FIG. 2A is far more opaque than 
the solution 10 in FIG. 1A because something remained in 10' after 80 
runs. 
Referring to FIGS. 3A and 3B, the light source 12 and the tank are similar 
to FIGS. 1A and 2A and they contain normal (new) chemical solution 20 and 
abnormal (used) chemical solution 20' respectively. The photosensor 34 is 
connected via lines 38 and 37 between spectrum or alarm circuits 40 and 
ground. Suitable photo-sensors 34 are used with sensitivities at 
wavelengths which indicate that a chemical change timing or alarm point 
has been reached. As an example of an embodiment of this aspect of the 
invention, FIGS. 3A and 3B show a photo-sensor 34 which includes a 437 nm 
passband filter. 
FIG. 3B shows photo-sensor 34 darkened by the intensity of abnormal 
chemical drop to the trigger point of the chemical change timing or alarm 
function because of the opaque nature of the old chemical solution 20'. 
FIGS. 4A and 4B show alternative kinds of photosensors and light source 
assemblies. 
FIG. 4A shows a chemical tank 8 containing a solution 60, in which an 
assembly 66 is housed with a light source 42 and a photosensor 44. The 
fluid flow between the light source 42 and the photo-sensor 44 in an 
assembly which includes the light source and the sensor. 
FIG. 4B shows a chemical tank 8 containing a solution 60', in which is 
located a light source 52 at the bottom of the tank in the solution and a 
photosensor 54 at the surface of the solution 60' in the solution. 
Structures of alternative types of assemblies which can be used in the 
arrangements such as FIGS. 4A and 4B are shown in FIGS. 4C and 4D. 
In FIG. 4C, an assembly 80 includes a transparent conduit (pipe) 82 having 
a coaxial passageway 81 therethrough for carrying a fluid flowing as 
indicated by the arrow. Housed within the walls of the conduit 82 on 
opposite sides of the passageway 81 are a light source LS1 and a 
photosensor PS1 which aligned so that the light reaching the sensor PS1 is 
a function of the opacity or tranmissivity of the fluid flowing through 
the passageway 81. 
In FIG. 4D, an assembly 90 includes a transparent body 92 having a 
passageway 91 therethrough for carrying a fluid flowing as indicated by 
the arrow. Housed within the walls of the body 92 on opposite sides of the 
passageway 91 are a light source LS2 and a photosensor PS2 which are 
aligned so that the light reaching the sensor PS2 is a function of the 
opacity or tranmissivity of the fluid flowing through the passageway 91. 
FIGS. 5A and 5B show photosensors for different kinds of wavelengths. 
FIG. 5A shows a chemical tank 8 containing a solution 70, housing an 
assembly 66 with a light source 62 and a wavelength adjustable photosensor 
64, such as a monochromator. Conventional electronics comprising spectrum 
and endpoint control apparatus are employed. 
FIG. 5B shows a chemical tank 8 containing a solution 70', housing an 
assembly 76 with a light source 72 and a multiple wavelength adjustable 
photosensor 74. With a set of specific wavelength filters it is possible 
to choose any one of the wavelengths to be a working channel or any 
combination the wavelengths. 
SUMMARY 
This invention provides the advantages as follows: 
1. Real-time monitoring of reacting chemicals. 
2. Spectrum analysis of new and used chemicals. 
3. Use of selected photo-sensors and similar assemblies. 
The real time monitor can be used in wet etching, cleaning or semiconductor 
related process equipment. Apparatus in accordance with this invention can 
be put inside or outside a treatment tank or used in any way possible to 
generate a signal to provide an alarm indicating abnormality of the 
optical characteristics of the chemical being processed. 
While this invention has been described in terms of the above specific 
embodiment(s), those skilled in the art will recognize that the invention 
can be practiced with modifications within the spirit and scope of the 
appended claims, i.e. that changes can be made in form and detail, without 
departing from the spirit and scope of the invention. Accordingly all such 
changes come within the purview of the present invention and the invention 
encompasses the subject matter of the claims which follow.