JP2010251521A - Electric characteristics measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device that quickly measures electric characteristics of a semiconductor thin film on an insulating substrate without contacting. <P>SOLUTION: The semiconductor thin film has a photoconductive layer formed in a ring shape when irradiated with light in the ring shape. A probe coil is wound around the light, and connected to a high-frequency power source. When a high frequency is applied from the probe coil, the coil is coupled to the conductive layer by an induction magnetic field to generate power loss. When the power loss of the high frequency is measured, the loss corresponding to the number of carriers is measured. When the light is ceased, the number of carriers decreases and the loss decreases correspondingly. Based on one simple lifetime of carriers, the number of carriers decreases according to e<SP>-t/τ</SP>. Here, (t) is a time and τ is the lifetime. Representing the decrease as a time function of the loss, the lifetime is known from the speed of the decrease. The lifetime is shorter as the number of defects of a semiconductor is large, and then usable for quality control of the semiconductor film. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an apparatus for measuring electrical characteristics of a semiconductor thin film on an insulating substrate.

There are devices that use a semiconductor thin film on an insulating glass substrate or a resin substrate. Examples are liquid crystal devices, organic EL devices, and solar cells. There is also an example of making a three-dimensional device by laminating semiconductor thin films (Patent Document 1).
These devices use a semiconductor layer on a substrate. The device manufacturing apparatus wants to form a semiconductor layer while maintaining the characteristics stably. However, for that purpose, it was necessary to extract and analyze the substrate. If the product is pulled out, it will be damaged. Inserting a substrate only for analysis purposes reduces line throughput. Producing a device and analyzing it takes time. These analyzes are a factor of cost increase.
Suspending the production line leads to an increase in production costs, so there is an idea that production will be expected. However, after the lot is manufactured, if it is found that the characteristics of the semiconductor film deviate from the manufacturing standard, the entire lot becomes defective and the cost increases.
Therefore, there is a demand for knowing the characteristics of the semiconductor thin film without stopping the production line in a short time during the production.

  Conventionally, workers at the manufacturing site have judged the quality by visually observing the substrate. This is because the human eye was sensitive to detecting uniformity and abnormality without contact.

If contact is allowed, there is an objective way to know the electrical properties of the thin film. There is a four-probe method as a general method for analyzing the electrical characteristics of a thin film. This is shown in FIG. The thin film 11 to be measured gives the sheet resistance of the film accurately when it is sufficiently lower in resistance than the substrate 10. The four needles 12 are arranged on a straight line at equal intervals, a constant current is passed to the other two, and the voltage is measured with the two of them. Since the current flows two-dimensionally, it becomes a fixed pattern (a pattern of a symmetrical mirror image effect).
Since this method is a contact method, a defect is given to the semiconductor film.

  FIG. 8 shows a method in which an electrode 13 is provided on the thin film 11 to be measured, a structure similar to that of a device is produced, and current and voltage characteristics are known. It takes too much time to feed back the analysis result to the production line.

JP 2008-218468 A

As described above, the human eye is sensitive, but the manufacturing method depending on the personality and ability of the person is not scalable. Therefore, there is an adverse effect that the factory cannot be expanded to the world. Further, even when it is determined that there is a problem, there is a problem that it is not possible to determine when it started.
Therefore, it is necessary to make a determination by a method that does not depend on a person. It must be done without stopping the flow of the product, it must be done on the product substrate without using a substrate for analysis, it must be done without touching the substrate because it is a product, There was also a problem that there were restrictions.

  This invention solves the said problem, and makes it a subject to provide the apparatus which measures the electrical property of the semiconductor thin film on an insulated substrate rapidly, non-contactingly.

  The invention according to claim 1 is an apparatus for measuring electrical characteristics of a semiconductor thin film on an insulating substrate, wherein the thin film can be irradiated with light, and a coil is formed so as to surround the light. The electrical characteristics of the thin film are measured by electromagnetically coupling the thin film irradiated with high-frequency current to the coil and measuring the reflection or transmission characteristics of the power. Measuring device.

  The invention according to claim 2 is the apparatus according to claim 1, wherein the light is one of ultraviolet light, visible light, infrared light, or a combination thereof.

  The invention according to claim 3 is the apparatus according to claim 1 or 2, wherein the light hits a beam or a ring.

  The invention according to claim 4 is the apparatus according to claims 1 to 3, characterized in that it displays or outputs the value of the time change of the electrical characteristics after the light irradiation is turned off.

  The invention according to claim 5 is the apparatus according to claims 1 to 4, wherein the value obtained by normalizing the value of the change with the value before turning off the light irradiation is displayed or output.

  The invention according to claim 6 is a device manufacturing apparatus in which the measurement apparatus is mounted so that the electrical characteristics of the semiconductor thin film on the glass substrate can be measured.

  The invention according to claim 7 is a device manufacturing apparatus in which the measurement apparatus is mounted so that the electrical characteristics of the semiconductor thin film on the resin substrate can be measured.

  The invention according to claim 8 is the device manufacturing apparatus according to claims 6 and 7, wherein the thin film is a thin film containing silicon.

  The invention according to claim 9 is a four-probe measuring device for measuring electrical characteristics of a thin film on an insulating substrate, and can irradiate the thin film with light on and off. It is a four-probe measuring device that measures changes in electrical characteristics.

  The invention according to claim 10 is the four-probe measurement apparatus according to claim 9, wherein the light is any one of ultraviolet light, visible light, and infrared light, or a combination thereof.

A schematic diagram of the configuration of the apparatus to be solved is shown in FIG. When light 34 is irradiated in a ring shape, a photoconductive layer 35 can be formed in a ring shape on the semiconductor thin film.
Since there is an insulating substrate 10 as compared with the semiconductor thin film 11, a conductor in which a photoconductive layer 35 is formed by generating carriers of electrons and holes in a portion that is strongly irradiated with light is formed.
A probe coil 31 is wound around the light and connected to a high-frequency power source 32.
When a high frequency is passed from the probe coil 31, the coil is coupled by the conductive layer 35 and the induction electromagnetic field 33. Since the conductivity of the conductive layer 35 is higher than that of the surrounding semiconductor layer that is not irradiated with light, a current is induced and an induced current flows. This current results in power loss.

When high-frequency power loss is measured, the loss corresponding to the number of carriers is measured. When the light is cut, the number of carriers decreases and the loss is attenuated accordingly. When the carrier has a simple lifetime, it decays according to ^{et-t / τ} . t is time and τ is lifetime. If attenuation is displayed as a time function of loss, the lifetime can be found from the rate of attenuation. Since the lifetime is shortened when the number of defects in the semiconductor is large, it can be used for quality control of the semiconductor film.
Here, since the coupling between the coils is easy to understand, the conductive layer is described in a ring shape. However, since the probe coil is also coupled to the conductive layer on the surface, there is a difference in the degree of coupling due to the loss due to electromagnetic coupling.

  According to the first to fifth aspects of the present invention, an apparatus for irradiating a semiconductor thin film on an insulating substrate with light and measuring the lifetime of the thin film carrier or its index without contacting the thin film. Is possible.

  According to the inventions according to claims 6 to 8, when the substrate is a large glass substrate of several meters, the quality of the actual product device substrate of the flowing production line can be immediately managed without stopping the manufacturing process. become. By changing the wavelength of the diode light used to match the light absorption characteristics of the thin film, or by using multiple types, it is possible to evaluate the solar spectrum. Becomes easier.

According to the ninth and tenth aspects of the present invention, the function of measuring the lifetime can be added to the four-probe device generally used for measuring the electric resistance of the thin film.
The invention according to the present application has the advantages as described above.

FIG. 1 is a schematic diagram showing electromagnetic coupling between a photoconductive layer on an insulating substrate and a coil. FIG. 2 is a schematic diagram of the configuration of the thin film electrical property measuring apparatus of the present invention. FIG. 3 shows an example of a transmission loss response. FIG. 4 is a schematic diagram of the configuration of the thin film electrical property measuring apparatus of the present invention that applies ring-shaped light. FIG. 5 shows a four-probe resistance measuring apparatus that can turn on / off light irradiation. FIG. 6 is an example of a change in sheet resistance. FIG. 7 is a schematic diagram of the four-probe method. FIG. 8 is a schematic diagram showing the current-voltage method.

A schematic diagram of the configuration of the apparatus to be solved is shown in FIG. FIG. 2 is a schematic diagram of a structure in which light is irradiated in the form of a beam. The beam shape may be round or square.
There is an insulating substrate 10 having a sufficiently high resistance compared to the thin film 11 to be measured. There is a transparent cylindrical light guide 42 on which a light emitting diode 43 is provided. Although one diode is shown here, it may be one or two or more. A power source 44 is connected to the diode 43, and a switch SW45 is provided. In this way, the light 47 is controlled by the SW 45 and strikes the thin film 11. When the substrate is a semiconductor, electrons and holes are generated in a portion that is strongly irradiated with light, and carriers are generated. It becomes a conductor in which the photoconductive layer 48 is formed.

It is effective to select light according to the energy band gap of the semiconductor layer.
When the semiconductor is silicon, visible light or ultraviolet light is suitable. Infrared light is preferred when the semiconductor is a material with a small band gap. In the case of a solar cell device, since it is desired to investigate the effect of absorbing light in the sunlight spectrum, ultraviolet light, visible light, and infrared light may be mixed using a plurality of diodes.

A probe coil 49 is wound around the light guide 42 and is connected to the network analyzer 41 by a coaxial cable 40.
When a high frequency is passed from the probe coil 49, the conductive layer 48 is electromagnetically coupled. Since the conductivity of the conductive layer is higher than that of the surrounding semiconductor layers, a current is induced and an induced current flows. This current results in power loss.
The analyzer 41 measures the high frequency power transmittance. When SW45 is on and light is applied, a current depending on the intensity of light is induced, and a transmittance corresponding to the power loss is output.

When the SW 45 is cut, the light irradiation of the diode is turned off stepwise. The number of generated carriers gradually decreases according to the lifetime of the carriers. When it is a simple lifetime, it decays according to ^{et-t / τ} . t is time and τ is lifetime. Displaying the attenuation as a function of transmission time reveals the rate of attenuation. Since the lifetime is shortened when the number of defects in the semiconductor is large, it can be used for quality control.

An example of transmittance response is schematically shown in FIG. The transmittance was normalized by the transmittance before cutting light.
As the carrier decays with time and becomes high resistance and power loss decreases, the reflectivity increases and the transmissivity attenuates. Since the decrease rate of the number of carriers starts depending on e ^{−t / τ} , the time for which the straight line crosses the transmittance = 1/10 (−10 dB) gives an index corresponding to the lifetime τ of the thin film carrier. Different thin films A and B give different τ _A and τ _B. When not normalized, the absolute value of the loss varies depending on the light intensity, the absorptivity and quantum efficiency of the thin film, and the mobility of the thin film. Assuming that the transmittance of different thin films A and B is T _A and T _B with constant light, this value represents the characteristics of the light response of the thin film, and may be used as an evaluation index of the characteristics of the thin film.

  The lifetime obtained here includes both electrons and holes and cannot be distinguished. However, since the lifetime measured by the numerical value depending on the disappearance rate of the semiconductor carrier is given, it can be used as a management index of the quality of the material. Further, curve B in FIG. 3 indicates that there are curves B1 and B2 having different inclinations. This indicates that carriers with different lifetimes have been generated, and the B2 line with this different slope is moved to the origin (time = 0, loss = 0 dB), and the time across different -10 dB is different. It can also be used for evaluation as a kind of lifetime.

  FIG. 4 schematically shows an example of another apparatus configuration for obtaining the lifetime of a thin film in a non-contact manner. Transparent acrylic is processed into a ring shape and processed into a ring-shaped light guide 67. The ring end face 69 has a donut ring shape with an outer diameter of 3 cm and a width of 7 mm. This shape may be a circle, a square or an ellipse. An acrylic fiber may also be used. The ring may not be connected.

  Two diodes 63 and 64 are mounted on the light guide 67 and are connected to the power supply 44 through the switch SW45. WS45 may be a transistor or a relay. The diodes may be diodes of different colors, may be the same, or may be three or more or one.

  The light from the diode is guided by an acrylic ring-shaped guide 67 and irradiated from the ring end face 69 toward the thin film 11. Since the center of the guide is shielded by black paper 66, ring-shaped light is produced. The light guide 67 has a coil guide 65, and a probe coil 49 is wound between the guides. Two terminals of the coil are connected to the network analyzer 31 by a coaxial cable 40. The network analyzer supplies power to the coil 49 by transmitting a high frequency. The transmission power with respect to the input power can be measured and output as the transmittance.

When light strikes, the ring-shaped light 67 forms the ring-shaped conductive layer 68, which consumes power from the probe coil by magnetic field inductive coupling and causes power loss. Since this loss power does not return to the analyzer, it becomes the transmitted power transmitted.
This transmitted power is expressed as a transmittance and displayed as a function of time. A straight line is obtained when the transmittance is normalized and expressed by the transmittance just before the light of the diode is cut, and the transmittance after the cut is expressed by dB. Reading the time when crossing −10 gives the lifetime τ.

  FIG. 5 shows an example of a four-probe resistance measuring instrument capable of turning light on and off. Four needles 12 are accommodated in the light irradiation box 72. In the light-on state, the thin film 11 becomes a photoconductive layer and is a conductor film. When SW45 is turned off, the resistance increases as the number of carriers decreases. Since the increase represents a decrease in the number of carriers, obtaining the lifetime is an indicator of the quality of the thin film.

An example of the ascending curve is shown in FIG.
The curve is shown by the sheet resistance value normalized by the sheet resistance value when SW45 is off. The time that the straight line portion of the curve A crosses the standardized sheet resistance value 1 gives an index corresponding to the carrier lifetime τ _A of the thin film A.
Similarly, different thin films B give different τ _B.

  The four-probe method with an on / off mechanism for light irradiation is a contact-type measurement method. Although this point is different from the remote method shown in FIG. 2, it is convenient as a method of knowing the carrier lifetime index.

  An apparatus configuration for obtaining the lifetime of the thin film by contact is schematically shown in FIG. A clear acrylic is processed into a ring shape. The ring end face 49 has a donut ring shape with an outer shape of 3 cm and a width of 7 mm. This shape may be a circle, a square or an ellipse. An acrylic fiber may also be used. The ring may not be connected.

  Two diodes 43 and 44 are mounted on the light guide, and are connected to the power supply 24 via the switch SW25. WS may be a transistor or a relay. The diodes may be diodes of different colors, may be the same, or may be three or more or one.

  The light from the diode is guided by an acrylic guide 47 and irradiated from the ring end face 49 toward the thin film 11. Since the center of the guide is shielded by black paper 46, ring-shaped light is produced. The light guide 47 has a coil guide 45, and the probe coil 29 is wound between the guides. The two terminals of the coil are connected to a network analyzer 31 by a coaxial cable 30. The network analyzer supplies a power to the coil 29 by transmitting a high frequency. The transmission power with respect to the input power can be measured and output as the transmittance.

When light strikes, a ring-shaped photoconductive layer 48 is formed, which consumes power from the probe coil due to magnetic field inductive coupling and causes power loss. Since this loss power does not return to the analyzer, it becomes the transmitted power transmitted.
This transmitted power is expressed as a transmittance and displayed as a function of time. A straight line is obtained when the transmittance is normalized and expressed by the transmittance just before the light of the diode is cut, and the transmittance after the cut is expressed by dB. Reading the time when crossing −10 gives the lifetime τ.

  Since the present invention can quickly measure the electrical characteristics of a thin film semiconductor formed on an insulating substrate or an insulating flexible substrate within a manufacturing process at low cost, it can be applied to manufacturing cost reduction and manufacturing management. It can also be used for production management of optical spectral response by selecting the wavelength of light.

10 High Resistance or Insulating Substrate 11 Thin Film 12 to be Measured Four Needles 13 Electrode 31 Probe Coil 32 High Frequency Power Supply 33 Inductive Magnetic Field 34 Light 35 Ring-shaped Photoconductive Layer 40 Coaxial Cable 41 Network Analyzer 42 Light Guide 43 Light Emitting Diode 44 Power supply 45 Switch SW
47 Light 48 Photoconductive layer 63 Light-emitting diode 64 Light-emitting diode 65 Coil guide 65
66 Black paper as shielding film 67 Transparent acrylic ring-shaped light guide 68 Ring-shaped photoconductive layer 69 Ring end surface 72 Light irradiation box

Claims (10)

An apparatus for measuring the electrical properties of a semiconductor thin film on an insulating substrate, capable of irradiating the thin film with light, and without a coil contacting the substrate so as to surround the light A measuring device that is disposed and electromagnetically coupled to a thin film irradiated with light through a high-frequency current to the coil, and measures the electric characteristics of the thin film by measuring the reflection or transmission characteristics of power. The apparatus according to claim 1, wherein the light is ultraviolet light, visible light, infrared light, or a combination thereof. 3. An apparatus according to claim 1, wherein the light strikes in the form of a beam or a ring. The apparatus according to claim 1, wherein a value of a time change of the electric characteristic after the light irradiation is turned off is displayed or output. 5. The apparatus according to claim 1, wherein a value obtained by normalizing the value of the change with a value before turning off the light irradiation is displayed or output. A device manufacturing apparatus in which the measurement apparatus is mounted so that the electrical characteristics of a semiconductor thin film on a glass substrate can be measured. A device manufacturing apparatus in which the measurement apparatus is mounted so that the electrical characteristics of the semiconductor thin film on the resin substrate can be measured. The device manufacturing apparatus according to claim 6, wherein the thin film is a thin film containing silicon. A four-probe measuring device that measures the electrical characteristics of a thin film on an insulating substrate, which can irradiate the thin film with light and measures changes in electrical characteristics when the light is turned on and off 4 probe measuring device. The four-probe measuring apparatus according to claim 9, wherein the light is one of ultraviolet light, visible light, infrared light, or a combination thereof.