Optics: measuring and testing – By polarized light examination – Of surface reflection
Reexamination Certificate
2001-05-24
2002-11-26
Robinson, Mark A. (Department: 2872)
Optics: measuring and testing
By polarized light examination
Of surface reflection
C356S237200
Reexamination Certificate
active
06486952
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to a semiconductor device, and in particular to a semiconductor testing device that measures the electrical field distribution or the voltage distribution or each measured point during testing of a device under test (DUT).
2. Description of Related Art
An example of conventional technology for this type of semiconductor testing apparatus is described in a paper by Shinagawa et al., “Handy-type high impedance probe using an EOS,” The 15
th
Light Wave Technology Research Conference, 1995, pp. 123-129. In addition, the structure of another conventional semiconductor test apparatus is shown in FIG.
7
. In this figure, the semiconductor test apparatus has a light source
101
, and a pulsed laser is emitted under control of the light source drive circuit
113
. The light pulse emitted by the light source
101
is condensed by the condenser lens
102
, and condensed onto the electrooptic element
103
.
The electrical field generated by the voltage input into and output from each pin of the DUT
105
is also present in the electrooptic element
103
. While the light pulse condensed by the condenser lens
102
transits the electrooptic element
103
, the polarization thereof changes (modulates) due to the electrical field generated by the measured device
105
.
This light pulse is reflected by the reflecting plate
104
provided on the lower surface of the electrooptic element
103
, and after transiting the wavelength plate
106
and the analyzer
107
, this light is condensed on the electrooptic converter
109
by the condenser lens
108
. The analyzer
107
has the property of changing the polarity component of the light to an intensity component, and the signal component of the light polarized by the electrooptic element
103
is converted to an intensity signal (amplitude information) due to transiting the analyzer
107
.
The optoelectric converter
109
converts the intensity (amplitude) of the light to the intensity (amplitude) of the electric signal. The electrical field generated by the voltage signal in each of the pins of the measured device
105
is made proportional to the level of the voltage signal, and thereby the amplitude of the electric signal generated in the optoelectric converter
109
is made proportional to the voltage in the measured device
105
. This electric signal is amplified by the amplifying circuit
110
, and converted to a digital signal by the A/D converting circuit
111
.
The trigger signal St is a trigger signal that represents the measurement from the measured device and the like. Based on the A/D conversion timing signal Sc output from the timing generation circuit
114
in synchronicity with this signal, the measurement data of the measured device
105
is input by the A/D conversion circuit
111
, A/D converted, and the electrical field and the voltage value are calculated and displayed by the calculation/display circuit
112
.
The timing operation of the semiconductor apparatus shown in
FIG. 7
is shown in FIG.
8
. As shown in this figure, in the case that the light source
101
emits a continuous light, at the timing represented by the AID conversion timing signal Sc, in sequence, the data is input into the A/D conversion circuit
111
, A/D converted, and the digital data that has been A/D converted is sent to the calculation/display circuit
112
. In this case, the output timing of the trigger signal St serves as the data input commencement timing.
Next, in the case that the light source emits a pulsed light, each time the trigger signal St is input, the pulsed emitted light timing signal Sp from the timing generation circuit
114
is output such that each time the phase is delayed by &dgr;t, and the light pulse is emitted from the light source
101
by controlling the drive of the light source drive circuit
113
by the pulsed light emission light timing signal Sp.
In the A/D conversion circuit
111
, data is input by the A/D conversion timing output from the timing generating circuit
114
, A/D conversion is carried out, and the digital data that has been A/D converted is sent to the calculation/display circuit
112
.
In the case that the light source
101
is driven so as to emit pulsed light, the measuring signal of the measured device
105
requires a return signal synchronized with the trigger signal
23
. This method is an existing technology called sequential sampling.
In the calculation/display circuit
112
, the digital data obtained by the A/D conversion circuit
111
is multiplied by the sensitivity of the measurement system, converted to a voltage or electrical field at the measurement point of the measured device
105
, and displayed as a data value, waveform, or a time series.
The conventional technology for the semiconductor test apparatus described above is disclosed in Japanese Patent Application, No. Hei 09-273156. In addition, similar functions for the light source
101
, condensing lens
102
, the electrooptic element
103
, reflecting plate
104
, wavelength plate
106
, analyzer
107
, condenser lens
108
, and the optoelectric conversion
109
are disclosed in this publication.
In the above-described EOS (Electro-Optic Sampling)-type semiconductor test apparatus, measurement of only one point on the measured device is possible, and for example, there is the problem that even in the case that the pins of the integrated circuit are arranged in a row, they must be measured by moving the irradiating position of the light beam emitted from the light source for each pin in sequence, and much time must be consumed.
Furthermore, in the case that the distribution of the voltage of electrical field of the entire measured device is measured, there are the problems that the light beam must be swept in two dimensions relative to the measured point, and due to measuring by sweeping the light beam in two dimensions, the system structure becomes complicated, and the measuring time becomes long.
In addition, in the above-described EOS-type semiconductor test apparatus, in the case that a plurality of measured points are to be measured, measurement must be conducted by moving the light beam in sequence, and thus in the case that many points in the measured device are measured simultaneously (at the same time), there is the problem that a plurality of sensors is necessary.
SUMMARY OF THE INVENTION
In light of the above-described circumstances, it is an object of the present invention to provide a semiconductor test apparatus that can measure the voltage distribution and the electrical field distribution of the measured device in one or two dimensions, and can implement a reduction in the measuring time.
In order to attain the above objectives, in a semiconductor test apparatus wherein a light beam emitted from a light source irradiates a measured part of a measured device via an electrooptic element arranged above the measured device and the electrical field distribution or the voltage distribution in the measured part of the measured device is calculated by electrically detecting the change in the state of the polarization of this reflected beam, a first aspect of the invention is characterized in comprising a first optical system wherein light emitted from the light source is shaped into a line-shaped light beam and irradiates a desired measurement line on the measured device via the electrooptic element, a second optical system that maintains as-is the shape of the line-shaped light beam reflected from the desired measurement line on the measured device after transiting the electrooptic element, and modulates the change in polarity of the line-shaped light beam to a change in intensity of the light, a light receiving device that receives the line-shaped light beam emitted from the second optical system and converts the light beam at each of the measured points to an electrical signal depending on the strength of each light beam reflected at each of the measured points on the desired measurement line on the measured device and outputs the result
Ando Electric Co. Ltd.
Robinson Mark A.
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