Surface condition judging apparatus

A parallel light beam having a predetermined diameter is projected onto an aluminum deposition film formed on a semiconductor wafer in a direction normal to the wafer surface. Light reflected by the aluminum deposition film is converted into reflected light intensity data by a plurality of photoelectric conversion elements arranged in a spherical surface with the center thereof at the center of the parallel light beam incidence spot. The reflected light intensity data are stored in a RAM in a microprocessor. The data stored in the RAM are displayed as a reflected light intensity distribution plot on a display unit for comparison with a standard reflected light intensity distribution plot, whereby the bonding property of the aluminum deposition film is judged.

BACKGROUND OF THE INVENTION 
This invention relates to an apparatus for judging the surface condition of 
a metal such as an aluminum film deposited on a semiconductor wafer. 
To form an aluminum deposition film on a semiconductor wafer is an 
indispensable step in the manufacture of a semiconductor product. Between 
the surface of a pad made of such aluminum deposition film formed on a 
discrete semiconductor device or chip and an external terminal provided on 
a lead frame, thin aluminum or gold leads are bonded. The aluminum 
deposition film thus is required to always have a satisfactory bonding 
property with respect to aluminum or gold thin leads. The judgement of the 
bonding property usually has been made by visually inspecting the surface 
of the aluminum deposition film that is formed on a semiconductor wafer. 
The aluminum deposition film generally has a mirror like smooth surface, 
that is, its bonding property generally is satisfactory. If gas such as 
CO.sub.2 remains in a deposition apparatus in the depositing step, the 
film deposited on the wafer has a rough surface, that is, its bonding 
property is deteriorated. This rough surface looks whitish and thus 
permits distinguishment of the unsatisfactory bonding property. However, a 
deposition film which has a satisfactory bonding property although its 
surface is whitish may be formed depending upon conditions at the time of 
the deposition. For example, when aluminum is deposited while maintaining 
a comparatively high wafer temperature or when it is deposited to a 
thickness in excess of 2 .mu.m its crystal growth occurs on the wafer. The 
deposition film in this case has a whitish surface, but its bonding 
property is satisfactory. When the bonding property is judged by visual 
inspection, a surface of crystal growth is often rejected in spite of its 
satisfactory bonding property because its surface looks whitish. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide a surface condition judging 
apparatus, which can accurately judge the surface condition of a metal 
such as an aluminum deposition film with respect to the bonding property 
thereof, the judgement being difficult by visual inspection. 
According to the invention, the above object is attained by a surface 
condition judging apparatus, which comprises a housing for accommodating 
an inspection item in a state shielded against external light, light 
projecting means for projecting a parallel light beam onto the surface of 
the item in the housing in a direction at a predetermined angle to the 
surface of the item, photoelectric conversion means provided in a 
spherical surface having a predetermined radius and having the center 
located at a predetermined point on the surface of the item, for obtaining 
electric signals having magnitudes corresponding to the intensity of light 
reflected at said predetermined point of the item surface in directions of 
various reflection angles, an analog/digital converter for converting the 
electric signals from said photoelectric conversion means into digital 
signals, and an operational control section for obtaining a reflected 
light intensity distribution data representing the relation between the 
reflection angle and the intensity of reflected light from the digital 
signals and comparing the reflected light intensity distribution data with 
a standard reflected light intensity distribution data to thereby judge 
the surface condition of the inspection item.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The invention now will be described in detail in conjunction with preferred 
embodiments thereof with reference to the drawings. Referring to FIG. 1, 
there is shown a box-like housing 1, which can serve as a dark box to 
shield external light and is provided with a door (not shown). In the 
housing 1, a table 3 is provided on the bottom. A semiconductor wafer 2 
having an aluminum film deposited thereon, the surface condition of which 
is to be judged, is horizontally set on the table 3. The semiconductor 
wafer 2 can be inserted into the housing 1 by opening the door mentioned 
above. The top wall 1a of the housing 1 is formed with a central 
see-through hole 4. A cylindrical optical unit 5 is mounted on top of the 
housing 1. The optical unit 5 has an opening 5a which communicates with 
the see-through hole 4 formed in the top wall 1a. In the optical unit 5, a 
light source lamp 6, lenses 7a and 7b and a mirror 8 are disposed in the 
mentioned order along a light path. Light emerging from the light source 
lamp 6 is converted through the lenses 7a and 7b into a parallel light 
beam A having a circular sectional profile. This light beam A is reflected 
by the mirror 8 to be directed through the opening 5a and see-through hole 
4 into the housing 1 so that it is incident on the wafer 2 set on the 
table 3 in a direction normal to the wafer surface. 
Eight arcuate supports 10a to 10h are secured to the inner surface of the 
top wall 1a of the housing 1 via mounting members 9a to 9h. As is shown in 
FIG. 2, the supports 10a to 10h are radially spaced apart by an equal 
angle of 45.degree. with respect to a center position C. The center 
position C is the center of the spot of the parallel light beam A incident 
on the surface of the wafer 2 provided with an aluminum film in the normal 
direction thereto. The eight arcuate supports 10a to 10h lie in a 
spherical surface, the center of which is the center C of the incident 
light beam spot. The light beam A passes through a space defined by one 
end of the supports 10a to 10h. The supports 10a to 10h each supports five 
photoelectric conversion elements 11-i (i=1, 2, . . . , 40) such as 
photodiodes, phototransistors and solar batteries and the like. The 
individual photoelectric conversion elements 11-i have their 
light-receiving surfaces directed toward the incident light beam spot 
center C. The directions in which the photoelectric conversion elements 
11-35 to 11-31 on the arcuate support 10g, for example, make respective 
angles of 10.degree., 20.degree., 30.degree., 40.degree. and 50.degree. 
with respect to the normal line P passing through the center C. The 
photoelectric conversion elements on the other arcuate supports 10a to 10f 
and 10 h are similarly disposed. 
As shown in FIG. 3, output signals from the individual photoelectric 
conversion elements 11-i are amplified by respective amplifiers 12-i (i=1, 
2, . . . , 40), and the amplified outputs are supplied to a multiplexer 
13. The photoelectric conversion units 11-1 to 11-40 as a whole constitute 
a photoelectric conversion unit 14. The output of the multiplexer 13 is 
coupled through an amplifier 15 to an analog/digital (A/D) converter 16. 
The multiplexer 13 simultaneously receives the signals from the amplifiers 
12-1 to 12-40 and sequentially supplies the received signals, for instance 
in the order of the signals from the amplifiers 12-1, 12-2, . . . , 12-40, 
to the amplifier 15 under the control of a central processing unit (CPU) 
18 of a microcomputer hereinafter described. 
The A/D converter 16 produces digital signals having voltages corresponding 
to the intensities of light received by the photoelectric conversion 
elements 11-1 to 11-40. These digital signals are led through an interface 
17a to the CPU 18. The CPU 18 supplies a switching control signal to the 
multiplexer 13 via a bus CB so that the signals from the individual 
photoelectric conversion elements 11-1 to 11-40 be sequentially supplied 
to the CPU 18. A random access memory (RAM) 19 and a read only memory 
(ROM) 20 are connected to the CPU 18 via a bus SB. Digital data 
representing the intensities of light received by the elements 11-i are 
sequentially stored in the RAM 19 in memory locations thereof specified by 
the CPU 18. In the ROM 20, data of preliminarily obtained, standard 
reflected light intensity distribution curves or plots as shown in FIG. 4 
are stored. In FIG. 4, plot I is obtained with an aluminum deposition film 
having a mirror like smooth surface. Plot II is obtained with a film 
deteriorated from residual gas and having a whitish surface. Plot III is 
obtained with a crystal growth film having a whitish surface. 
The operation of this embodiment will now be described with reference to 
FIGS. 1 to 4. First, the CPU 18 clears the RAM 19. The CPU 18 then 
supplies a switching control signal to the multiplexer 13. As a result, 
the output from the outermost photoelectric conversion element 11-1 on the 
arcuate support 10a is first supplied to the A/D converter 16, and the 
corresponding digital data is stored in the leading address memory 
location of the RAM 19. This first stored data represents the intensity of 
reflected light incident on the arcuate support 10a in a direction at an 
angle of 50.degree. with respect to the normal line P. After the first 
data has been stored in the RAM 19, the multiplexer 13 is switched under 
the control of the control signal from the CPU 18 while at the same time 
the second address memory location of the RAM 19 is specified. As a 
result, data obtained from the output of the element 11-2 is stored in the 
second address memory location. Like, data corresponding to the outputs of 
the elements up to the element 11-40 are stored in the RAM 19. 
After the data representing the intensities of reflected light incident on 
all the elements 11-1 to 11-40 have been stored in the RAM 19, the CUP 18 
reads out the standard reflected light intensity distribution data as 
shown in FIG. 4 from the ROM 20 and displays the read-out data on a 
display unit 22. The CPU 18 then reads out the measurement data concerning 
the surface condition of the aluminum film deposited on the wafer 2, 
having been stored in the RAM 19, and produces a display plot from the 
read-out data. In the display plot producing process, the CPU 18 
calculates the arithmetic mean value of the data obtained from the outputs 
of the elements 11-1, 11-20, 11-21 and 11-31, the light incidence angle of 
which is 50.degree., and plots the calculated value on the display unit 22 
at a position corresponding to a reflection angle of -50.degree.. The CPU 
18 also calculates the arithmetic mean value of the data obtained from the 
outputs of the elements 11-10, 11-11, 11-30 and 11-40, the light incidence 
angle of which is again 50.degree., and plots the calculated value at a 
position corresponding to a reflection angle of +50.degree.. Likewise, the 
CPU 18 plots the arithmetic mean values of the data for the elements on 
the supports 10a, 10d, 10e and 10g, which have the light incidence angles 
of 40.degree., 30.degree., 20.degree. and 10.degree., at positions 
corresponding to reflection angles of -40.degree., -30.degree., 
-20.degree. and -10.degree., and plots the arithmetic mean values of the 
data for the elements on the supports 10b, 10c, 10f and 10h, which have 
the incidence angles of 40.degree., 30.degree., 20.degree. and 10.degree., 
at positions corresponding to reflection angles of +40.degree., 
+30.degree., +20.degree. and +10.degree.. In FIGS. 1 and 2, five 
photoelectric conversion elements 11-i are shown provided on each of the 
arcuate supports 10a to 10h to simplify the description. However, if nine 
photoelectric conversion elements with respective light incidence angles 
of 10.degree., 20.degree., 30.degree., 40.degree., 50.degree., 60.degree., 
70.degree., 80.degree. and 90.degree. are provided on each arcuate 
support, comparison between each standard plot shown in FIG. 4 and the 
measurement data plot can be obtained over the entire reflection angle 
range. However, as is obvious from FIG. 4, a characterizing portion of 
each of the plots I to III resides in an angle range between 0.degree. and 
50.degree., so that judgement can be obtained sufficiently with the 
arrangement of FIGS. 1 and 2. 
If the plot of the measurement data displayed on the display unit 22 
closely resembles the standard plot I, it means that the surface of the 
aluminum film on the pertinent wafer 2 is a mirror surface having lustre. 
In this embodiment, no measurement data can be obtained for the reflection 
angle of 0.degree. in FIG. 4 for no photoelectric conversion element is 
provided in a position on the path of the parallel light beam A. However, 
it can be readily estimated that the measurement data plot has a central 
portion having a very high peak value like the standard plot I. When the 
measurement data plot is like the plot I, the inspected aluminum 
deposition film can be judged to be normal and have satisfactory bonding 
property. 
If the inspected aluminum deposition film is deteriorated by residual gas 
and has a whitish surface, the corresponding measurement data plot is like 
the standard plot II, with the intensity of reflected light gradually 
decreasing from the maximum value for the reflection angle of 0.degree.. 
In this case, the bonding property of the deposition film surface is 
judged unsatisfactory. 
If the inspected aluminum deposition film has a crystal growth surface, the 
surface is whitish like the surface of the deposition film deteriorated by 
residual gas. In this case, however, the corresponding measurement data 
plot is like the standard plot III, having maxima for reflection angles 
around .+-.20.degree. to .+-.30.degree.. The bonding property in this case 
is thus judged to be satisfactory in spite of the fact that the film has a 
whitish surface. 
In the above arrangement, a mean values of the data obtained from the 
outputs of a plurality of elements 11-i with each definite light incidence 
angle has been calculated and plotted on the display unit 22. However, 
practically sufficient judgement of the deposition film surface can be 
obtained from a plot obtained directly from the data of the outputs of the 
elements 11-31 to 11-40 on line Y--Y in FIG. 2 over the reflection angle 
range between -50.degree. and 50.degree.. 
In the meantime, the light intensity of the light source lamp 6, the input 
light intensity versus output voltage characteristic of the photoelectric 
conversion elements 11-i, the input versus output characteristic of the 
amplifiers 12-1 to 12-40, etc. are subject to changes in long use. The 
difference between the characteristics when the standard reflected light 
intensity distribution data on a calibration specimen are stored in the 
ROM 20 and the characteristics when the measurement is done on the same 
calibration specimen is obtained to correct the measurement data, thus 
allowing more accurate judgement. An equation for executing the correction 
may be stored in the ROM 20, and the CPU 18 may be adapted to effect the 
correction using the equation to obtain corrected data to the display 22. 
First, before storing the standard data in the ROM 20, which may be a 
programmable ROM, the amplification factor of the amplifiers 12-1 to 12-40 
is adjusted to make up for the fluctuations of the photoelectric 
characteristic of the photoelectric conversion elements 11-i and obtain a 
uniform photoelectric characteristic. When this adjustment is made, the 
outputs of the photoelectric conversion elements 11-i supplied to the 
multiplexer 13 have the same apparent level with the same light intensity. 
Under this condition, a calibration specimen (not shown) is substituted for 
the inspection wafer 2 on the table 3. The calibration specimen is a white 
diffuser having a coating of barium sulfate or magnesium oxide powder. It 
diffuses the incident light substantially 100%. The diffused light is 
received by the photoelectric conversion elements 11-i. The intensities of 
light incident on the photoelectric conversion elements 11-i at this time 
are referred to as standard light intensities Xi. Data representing the 
standard light intensities Xi (i=1, 2, . . . , 40) are stored in the ROM 
20. 
Next, the 100% diffuser is replaced with another 0% calibration specimen 
which has a mirror surface and regularly reflects incident light without 
any diffusion. At this time, the intensities of light incident on the 
photoelectric conversion elements 11-i are referred to as standard light 
intensities xi (i=1, 2, . . . , 40). Data representing the standard light 
intensities xi are again stored in the ROM 20. 
The data stored in the ROM 20, which were obtained using the 0% and 100% 
diffusion reflectors and represent the standard light intensities xi and 
Xi, are used as standard data. If there is subsequently no change in the 
characteristic of the individual elements such as amplifiers 12-1 to 
12-40, the same data as the standard data would be obtained when 
calibration is made using the same 0% and 100% diffusion calibration 
specimens. Without any change in the characteristic of the elements, a 
plot 26 as shown in FIG. 5 is obtained. In the graph of the Figure, the 
ordinate is taken for the standard light intensity data xi and Xi stored 
in the ROM 20, and the abscissa is taken for the light intensity data yi 
and Yi obtained at the time of a subsequent calibration using the same 
calibration specimen. The plot 26 contains points K (xi, yi) and L (Xi, 
Yi) and has a slope angle of 45.degree.. If subsequently there occurs any 
change in the characteristics of the elements, for instance a change in 
the light intensity of the light source lamp 6 and the gain of the 
amplifier 15, and/or the table 3 is tilted, different light intensity data 
yi' and Yi' would be obtained at the time of the subsequent calibration 
for the same calibration specimen. In this case, a plot 27 connecting 
points M (xi, yi') and N (Xi, Yi') results. This plot 27 is referred to as 
measurement data plot. If light intensity data Zi' is obtained in the 
subsequent measurement for the wafer 2, this data Zi' should be corrected 
to a data zi on the standard light intensity plot 26. 
The measurement data plot 27 can be obtained from an equation 
##EQU1## 
Since a co-ordinate point S (zi, Zi'), where zi is the standard data 
obtained under the standard condition and Zi' is the light intensity data 
obtained when the measurement is to be made, appears on the measurement 
data plot or a correction curve 27, the light intensity data Zi' which is 
subject to changes in long use, may be corrected to the corrected data zi 
being obtained under the standard condition. 
FIG. 6 shows a flow chart illustrating the procedure of the correction. 
Prior to making the judgement of the surface condition of an aluminum 
deposition film the standard light intensity data xi, Xi are stored in the 
ROM 20. Then, the 100% diffusion calibration specimen is set on the table 
3, in a step 28. Then, in a step 29 light from the light source lamp 6 is 
projected onto the 100% diffusion calibration specimen to obtain 
measurement data representing the intensities Yi' of reflected light 
incident on the photoelectric conversion elements 11-i. In a subsequent 
step 30, the Yi' measurement data are stored in the RAM 19. Thereafter, 
the 0% diffusion calibration specimen is set on the table 3 in a step 31. 
Measurement data representing the light intensities yi' is then obtained 
in a step 32. The obtained data yi' is stored in the RAM 19 in a step 33. 
Afterwards, the inspection wafer 2 is set on the table 3 in a step 34. 
Measurement data Zi' are obtained in a step 35. These data are stored in 
the RAM 19 in a step 36. In a subsequent step 37, the CPU 18 reads out a 
predetermined calculation program and standard light intensity data xi, Xi 
to obtain corrected data zi. The corrected data zi are obtained for all 
the photoelectric elements 11-i. These data Zi (i=1, . . . , 40) are 
plotted on the display unit 22 in a step 38. The displayed measurement 
data plot is compared with the standard plots I to III as shown in FIG. 4. 
In this way, the judgement of the bonding property of the aluminum film 
deposited on the wafer 2 is effected. 
While the calibration specimens having the diffusion factors of 100% and 0% 
have been used for the calibration described above, it is possible to use 
calibration specimens having different diffusion factors, for instance 80% 
and 20%, as well. Further, three or more calibration specimens having 
different diffusion factors may be used. In this case, the correction of 
the measurement data may be made by obtaining the measurement data plot 
using the least mean square method. Further, while in the above embodiment 
the judgement of the bonding property of the aluminum deposition film has 
been effected by an inspector from the reflected light intensity 
distribution plot displayed on the display unit 22, this is by no means 
limitative; the CPU 18 may be arranged to effect a processing for 
judgement as well following a judgement program which may be preliminarily 
stored in the ROM 20. At any rate, since the measurement data have been 
compensated for changes in conditions in the inspection from those at the 
time of obtaining the standard data stored in the ROM 20 before they are 
compared with the standard data, the accuracy of judgement can be 
extremely increased. Further, the photoelectric conversion elements 11-i 
may be provided not on the arcuate supports 10a to 10h but outside the 
housing 1 and connected to their respective light receiving positions 
inside the housing via optical fibers. Further, the elements 11-i can be 
arranged at any desired angles. 
In the above embodiment, the inspection wafer 2 and photoelectric 
conversion unit 14 were held stationary. It is possible, however, to let 
the surface of the wafer 2 be scanned by the parallel light beam A, for 
instance with a movement of the table 3. 
This is realized in an embodiment shown in FIG. 7. In the Figure, the parts 
corresponding to those in FIGS. 1 and 2 are designated by like reference 
symbols. Referring to FIG. 7, a table 3 is mounted on top of a vertical 
shaft 53. The shaft 53 is journalled in bearings 54 and 55, which are 
mounted in respective upper and lower bearing support portions 51 and 52 
of a support 50 which is in turn secured to the bottom of a housing 1. As 
shown in FIG. 8, the table 3 has a disc-like shape and is concentric with 
the shaft 53. The table 3 is supported on a top flange 56 of the shaft 53, 
and a thrust bearing 57 is provided between the flange 56 and the bearing 
54. 
A rotary encoder 59 which serves as a position detector is mounted on the 
outer surface of the bottom 1b of the housing 1. A shaft of the rotary 
encoder 59 is coupled by a shaft joint 58 to the lower end of the shaft 
53. The shaft 53 has an integral pulley 60 which intervenes between the 
upper and lower bearings 54 and 55. The pulley 60 is coupled by an endless 
belt 61 to a pulley 62 which is mounted on a shaft 64 of a motor 63. The 
motor 63 is mounted on a motor support 65 which is secured to the bottom 
1b such that its shaft 64 extends parallel to the shaft 53. Parallel light 
beam A from a lamp 6 is incident on the table 3 in the vertical direction 
parallel to the shaft 53. The center C of the incidence spot of the light 
beam A is spaced apart a predetermined distance from the center of the 
table 3. 
A wafer 2 to be inspected is set on the table 3 such that it is found on a 
circular scanning orbit 66 which is traced by the circular incidence spot 
of the parallel light beam A when the table 3 is rotated as shown in FIG. 
8. A 100% diffusion calibration specimen 67 and a 0% diffusion calibration 
specimen 68 are also set on the table 3 such that their centers are found 
on the circular scanning orbit 66. The wafer 2 and calibration specimens 
67 and 68 are positioned by positioning pins 69a to 69g, and they are 
prevented by these positioning pins from being deviated by centrifugal 
forces exerted to them while the table 3 is in rotation. The calibration 
specimens 67 and 68 have substantially the same thickness as the wafer 2. 
A photoelectric conversion unit 14, as shown in FIG. 9, is mounted on the 
inner surface of the top wall 1a of the housing 1 in the manner as 
described before in connection with FIG. 2. 
FIG. 10 is a block diagram showing the electric circuitry of the embodiment 
of FIG. 7. In the Figure, the parts corresponding to those in FIG. 3 are 
designated by like reference symbols. Here, the output of an A/D converter 
16 is supplied to a bus SB through an input/output interface 17. A 
switching control signal to a multiplexer 13 is supplied from a CPU 18 
through the input/output interface 17. The output of the rotary encoder 59 
as the position detector is supplied to the CPU 18 through the 
input/output interface 17. A motor driving control signal from the CPU 18 
is supplied to the motor 63 through the input/output interface 17. 
The operation of this embodiment will now be described with reference to 
FIGS. 7 to 10. 
First, the light intensity of the lamp 6, the gain of the amplifiers 12-1 
to 12-40 and 15, the angle of the table 3 with respect to the parallel 
light beam A, etc. are adjusted to ideal or optimum conditions (which are 
hereinafter referred to as standard conditions). Under the standard 
conditions, the calibration specimens 67 and 68 are set on the table 3 in 
the housing 1 and properly positioned with the positioning pins 69c to 
69g. Then, the motor 63 is driven to move the table 3 to a position to 
project the parallel light beam A onto each of the centers 70 and 71 of 
the calibration specimens 67 and 68 in the vertical direction. The 
intensities of reflected light incident on the photoelectric conversion 
elements 11-i are photoelectrically converted into electric signals of 
corresponding magnitudes. Digital values corresponding to these electric 
signals are stored in the ROM 20 in predetermined memory locations for the 
respective photoelectric conversion elements 11-i using a ROM writer (not 
shown). Of the stored data, those obtained with the 100% diffusion 
calibration specimen 67 are the standard light intensity data Xi (i=1, 2, 
. . . , 40) while those obtained with the 0% diffusion calibration 
specimen 68 are the standard light intensity data xi. When carrying out 
the inspection of the wafer 2 later, the wafer 2 is set on the table 3 and 
properly positioned with the positioning pins 69a and 69b. Then, the 
parallel light beam A from the lamp 6 is projected onto the surface of the 
wafer 2. This is of course done with the housing 1 held in the state of a 
dark box. In this state, a measurement start signal is supplied to the CPU 
18 through the input/output interface 17. As a result, the CPU 18 produces 
a control signal SA, which is supplied through the input/output interface 
17 to the motor 63 to rotate the motor 63. The rotation of the motor 63 is 
transmitted to the shaft 53 via the endless belt 61, thus causing rotation 
of the table 3 about the shaft 53 in the direction of arrow 72 in FIG. 8. 
While the shaft 53 is being rotated, the rotary encoder 59 provides a 
rotational position signal PS which is supplied to the CPU 18 through the 
input/output interface 17. In the ROM 20, standard position data that are 
obtained when the centers 70 and 71 of the calibration specimens 67 and 68 
and the region 73 of specimen 2 are in register with the path of the 
parallel light beam A, have been stored. The rotational position signal PS 
is instantaneously compared with these standard position data. When a 
coincidence of the compared data is detected, a strobe signal is supplied 
to the multiplexer 13 through a bus CB to actuate a selection switch 
therein. At the same time, the photoelectric conversion elements 11-i 
receive light reflected by the region 70, 71 or 73 and produce electric 
signals of magnitudes corresponding to the intensities of the incident 
light. These electric signals are amplified by the amplifiers 12-1 to 
12-40 to be supplied as simultaneous signals to the multiplexer 13. The 
light intensity data concerning the light reflected by the region 70, 71 
or 73 are thus sequentially coupled from the multiplexer 13 through the 
amplifier 15 to the A/D converter 16 for conversion into digital data. The 
digital data thus obtained are transferred through the input/output 
interface 17 to the CPU 18. The CPU 18 stores these data in the RAM 19 in 
memory locations for the individual photoelectric conversion elements 
11-i. The data stored in the RAM 19 are the measurement data Yi' 
concerning the light reflected by the region 73 of the aluminum film 
formed on the wafer 2, the data Yi' concerning the light reflected from 
the region 70 of the 100% calibration specimen 67 and the data yi' 
concerning the light reflected from the region 71 of the 0% calibration 
specimen 68. When the storage of these data in the RAM 19 has been 
completed, a stop signal SA' is supplied to the motor 63 to stop the table 
3. The conditions under which the inspection of the wafer 2 are carried 
out, i.e., the light intensity of the lamp 6, the gain of the amplifiers 
12-1 to 12-40, the angle of the table 3, etc., may be different from the 
standard conditions as mentioned above. In this case, the measurement data 
Zi' are corrected to data zi as shown in FIG. 5 that would be obtained 
under the standard conditions. This is again done by the CPU 18. More 
particularly, the CPU 18 substitutes the standard data xi and Xi stored in 
the ROM 20 and the measurement data yi', Yi' and Zi' for each of the 
photoelectric elements 11-i stored in the RAM 19 into the equation (1) 
stored in the ROM 20 to obtain the corrected data zi which would be 
obtained under the standard conditions. 
The corrected data zi calculated by the CPU 18 are stored in the RAM 19 and 
are also displayed as corrected measurement light intensity distribution 
plot on the display unit 22. In the ROM 20, standard light intensity 
distribution data, which were obtained with light reflected by a wafer 
having the "normal" deposition film in the measurement under the standard 
conditions, are stored. The plot of the standard data is displayed 
simultaneously with the measurement data plot on the display unit 22. The 
inspector thus can readily and accurately judge whether the inspected 
deposition film surface is "normal" or "rejected" from the comparison of 
shapes and levels of the two plots. 
As has been described, with the above embodiment of the surface condition 
judging apparatus, in which a plurality of calibration specimens and the 
inspection wafer are held in the same plane such that they can be moved 
relative to the position of light incidence, the measurement data can be 
corrected to those that would be obtained under the standard conditions. 
Accurate and quick judgement of the surface condition, thus can be 
obtained from the comparison of the light intensity distribution plot 
based on the corrected measurement data and the standard light intensity 
distribution plot obtained under the standard conditions. 
In the preceding embodiments, a plurality of photoelectric elements 11-i 
have been disposed in a spherical surface with the center thereof at the 
center C of the incident light beam spot such that they have predetermined 
light incidence angles with respect to the normal line P passing through 
the center. FIGS. 11 to 13 show a further embodiment, which uses a single 
photoelectric conversion element which can be moved along an arcuate orbit 
with the center thereof at the incident light beam spot center C for 
obtaining measurement data. In the Figures, the corresponding parts to 
those in FIGS. 1 and 7 are designated by like reference symbols. 
Referring to FIGS. 11 and 12, a motor 80 is mounted on one side wall 1c of 
a housing 1. The axis of the motor shaft 81 lies in the surface of a wafer 
2 set on a table 3. A crankshaft 83 is coupled to the motor shaft 81. A 
photoelectric conversion element 11 is provided at the free end of the 
crankshaft 83. When the motor 80 is driven, the free end of the crankshaft 
83 is moved along an arc 84 with the center thereof at the center C of the 
spot formed by the parallel light beam A. At the top of the arcuate orbit 
84, the photoelectric conversion element 11 thus crosses the parallel 
light beam A. The motor 80 is provided with a rotary encoder 85 for 
detecting the rotational position. The encoder 85 provides a signal 
representing the angular position of the photoelectric conversion element 
11 with respect to the parallel light beam A. As shown in FIG. 13, this 
signal is supplied to a CPU in an operation control section 23 through an 
interface 86. 
In operation, assume that a start signal is supplied to the CPU in the 
section 23 when the photoelectric conversion element 11 is at a position 
Ta in FIG. 12. At this time, the motor 80 is not moved, and the encoder 85 
is providing an angular position signal corresponding to +90.degree.. A 
RAM memory location for this angular position is specified, and the output 
data from the photoelectric conversion element 11 is coupled through an 
amplifier 12 and an A/D converter 16 and stored in the specified memory 
location of the RAM. When this operation has been completed, a driving 
signal for driving the motor 80 for a predetermined angle, for instance 
10.degree., is supplied from the CPU, thus moving the photoelectric 
conversion element to an angular position corresponding to +80.degree.. A 
signal representing this angular position of 80.degree. is supplied from 
the encoder 85 to the CPU through the interface 86. By this position 
signal the next RAM memory location is specified, and the output data of 
the element 11 at this time is stored in the specified memory location. In 
the above way, the operation of obtaining and storing light intensity data 
is carried out until data obtained when the element 11 is at a position Tb 
is stored. When this operation has been completed, the CPU reads out the 
data stored in the RAM and also the standard data stored in the ROM and 
supply these data to the display unit 22 for display so that the surface 
condition of the aluminum film deposited on the inspected wafer 2 may be 
judged. 
The measurement operation described above has been based on a linear 
scanning, for instance along line Y--Y in FIG. 2. To cover a 
two-dimensional measurement scope as in the case of FIG. 2, the scanning 
from the position Ta to the position Tb in FIG. 12 may be carried out 
repeatedly with the table 3 at successive rotational positions. For 
example, after the scanning along the line Y--Y in FIG. 2 has been 
completed, the table 3 may be rotated by 45.degree.. Now, the scanning can 
be made substantially along line R1--R1 in FIG. 2. This may be done until 
the entire scope is covered. 
In the preceding embodiments, the parallel light beam A is directed to the 
surface of the wafer 2 in the normal direction. This permits obtaining 
substantially symmetrical reflected light data with respect to the normal 
line P as shown in FIG. 4 so that the judgement can be readily made. 
However, this is not essential in this invention, and the parallel light 
beam A may be made to be incident on the surface of the wafer 2 in a 
direction at an angle to the normal line P to the wafer surface. 
FIG. 14 shows a further embodiment, in which the parallel light beam makes 
an angle of 30.degree. with the normal line to the wafer surface. In the 
Figure, the parts corresponding to those in the preceding embodiments are 
designated by like reference symbols. Referring to FIG. 14, the parallel 
light beam A from the mirror 8 is incident on a wafer 2 in a direction at 
an angle of 30.degree. with respect to the normal line P to the surface of 
the wafer 2. If the aluminum deposition film on the wafer 2 has a mirror 
surface, practically all the incident light is reflected in a direction at 
angle of 30.degree. with respect to the normal line to be incident on the 
photoelectric unit 14. Here, however, the individual photoelectric 
elements 11-i are arranged in a spherical surface, the center C' of which 
is not the center C of the incident light beam spot. However, the light 
receiving surfaces of the elements 11-i are directed toward the incident 
light beam spot center C. Therefore, the light intensity distribution data 
obtained from the outputs of the photoelectric elements 11-31 and 11-40 
disposed on the opposite sides of the axis of the reflected parallel light 
beam A' passing through the center C are not symmetrical with respect to 
this axis. However, if the standard light intensity distribution data 
stored in the ROM are obtained under the same conditions as in FIG. 4, 
sufficient judgement of the deposition film can of course be obtained from 
the measurement data plot displayed in superimposition upon the standard 
plot based on the standard data stored in the ROM.