JP2013045794A - Film resistance value measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film resistance value measuring method capable of efficiently measuring a resistance value of an oxide semiconductor film in a substrate surface just after film formation.SOLUTION: A film resistance value measuring method includes: a process in which an oxide semiconductor film is formed by depositing an object W to be measured on a substrate surface and the oxide semiconductor film is locally heated just after the film formation; and a process in which a resistance value is measured in the heated area using a probe 6 for measuring the resistance value. As the oxide semiconductor film, for example, a transparent oxide semiconductor film made of an In-Ga-Zn-O-based material can be used.

Description

  The present invention relates to a film resistance value measuring method, and more specifically, in order to manage the film thickness and film quality of a transparent oxide semiconductor film formed on a substrate surface, the resistance value of the oxide semiconductor film immediately after film formation is determined. It relates to a thing for measuring efficiently.

  Transparent oxide semiconductors are known to have high electron mobility and excellent electrical properties. Among them, an In—Ga—Zn—O-based material containing indium, gallium, zinc, and oxygen as constituent elements (among others) Hereinafter, an amorphous IGZO film made of “IGZO” has an electron mobility higher than that of amorphous silicon, and a field effect transistor using this amorphous IGZO film as a channel layer has an on / off ratio. Have high electrical characteristics. For this reason, in recent years, application to TFTs, light emitting devices, etc. (semiconductor devices) has been promoted.

  Here, for the formation of the amorphous IGZO film, it is suitable to use a reactive sputtering method into which oxygen gas is introduced in consideration of mass productivity. When an amorphous IGZO film is formed by this sputtering method, the carrier concentration changes by several orders of magnitude even if the oxygen partial pressure changes only slightly (several percent), and a constant carrier concentration can be obtained with good reproducibility. It is known to be difficult. In addition, when the amorphous IGZO film is heated in a later step, the electrical characteristics such as the carrier concentration further change (the heat resistance of the electrical characteristics is low).

  Thus, Patent Document 1 discloses that an IGZO film formed by a sputtering method is annealed at a predetermined temperature so that the electrical characteristics of the film hardly change even if heat treatment is applied after the film formation. Specifically, after an amorphous IGZO film is formed on the surface of a substrate such as a glass substrate by reactive sputtering, the glass substrate is accommodated in a heating furnace. And after evacuating the inside of a heating furnace, a glass substrate is heated. In this case, the annealing temperature is 200 to 500 ° C, preferably 250 ° C to 350 ° C. As a result, the resistance values of the amorphous IGZO film are aligned to a substantially uniform predetermined value within the substrate surface.

  By the way, when an amorphous IGZO film is formed by sputtering, the resistance value (1E + 16Ω / □ or more) of the amorphous IGZO film immediately after the film formation is much higher than that of other transparent conductive films such as ITO and IZO. It is known that the resistance value of an amorphous IGZO film immediately after film formation cannot be measured with a conventional resistance value measurement probe that measures the resistance value by the four-terminal method or the two-terminal method. This is considered to be due to the reason that the amorphous IGZO film is photo-degraded by being irradiated with plasma light during film formation. On the other hand, if the resistance value of the amorphous IGZO film immediately after film formation in the substrate surface can be measured, the film yield and the film quality of the amorphous IGZO film at the time of film formation can be controlled, which is advantageous. Become.

JP 2010-238770 A

  In view of the above points, an object of the present invention is to provide a film resistance value measuring method capable of efficiently measuring the resistance value of an oxide semiconductor film in a substrate surface immediately after film formation.

  In order to solve the above-described problems, the present invention provides an oxide semiconductor film formed on a substrate surface as a measurement object, and a step of locally heating the oxide semiconductor film immediately after the film formation and the heated region. And measuring a resistance value using a resistance value measuring probe.

  According to the present invention, since the oxide semiconductor film is locally heated, the resistance value is reduced to a range in which the resistance value is measured with a conventional resistance value measurement probe at the heated portion. Then, the resistance value is measured in the range where the resistance value is reduced by the heating, and the operation of the local heating and the measurement of the heating location is repeated over the entire surface of the substrate, thereby the substrate surface. The resistance value of the oxide semiconductor film formed in the step is measured over the entire surface. In this case, unlike the conventional example in which the substrate on which the oxide semiconductor film is formed is stored in a heating furnace and annealed, changes in film thickness and film quality based on differences in film formation conditions are captured from changes in resistance value. Is possible. As a result, the resistance value of the oxide semiconductor film can be efficiently measured, and the film thickness and film quality of the oxide semiconductor film during film formation can be managed. In addition, if heating temperature shall be the temperature in the range of 100-250 degreeC, it will become possible to catch the change of resistance value reliably reliably. In the present invention, a transparent oxide semiconductor film made of, for example, an In—Ga—Zn—O-based material can be used as the oxide semiconductor film.

  In the present invention, in order to effectively heat the transparent oxide semiconductor film to a temperature within the above range in a short time, the transparent oxide semiconductor film is locally heated by blowing hot air or a lamp. It is preferable to use a heater. In addition, local heating of the oxide semiconductor film may be performed in an inert gas atmosphere or air.

1 is a schematic perspective view of a measuring apparatus that can measure the resistance value of an oxide semiconductor film by applying the present invention. The graph which shows the result of invention experiment.

  Hereinafter, with reference to the drawings, the object to be measured W is a transparent oxide semiconductor film made of an In—Ga—Zn—O-based material formed by sputtering on the substrate surface, and the resistance of the transparent oxide semiconductor film immediately after film formation is described below. The film resistance value measuring method of the embodiment of the present invention for measuring the value (Rs) will be described.

  FIG. 1 shows an example of a measuring apparatus that can implement the film resistance value measuring method of the present embodiment. The measuring apparatus includes a base plate 1 that is horizontally supported by legs 1a installed on the floor surface. On the base plate 1, a measuring object W is placed with the transparent oxide semiconductor film formed side up. Positioning is held. Further, the base plate 1 is provided with a portal frame 2 arranged so as to straddle the measurement object W placed on the base plate 1. The portal frame 2 has two horizontal horizontal directions orthogonal to each other as an X-axis direction and a Y-axis direction, and a pair of left and right guide rails 3L and 3R which are fixed on the base plate 1 and which are long in the X-axis direction. The portal frame 2 is supported so as to be movable, and is moved relative to the base plate 1 in the X-axis direction.

  The portal frame 2 is composed of columns 21 and 21 on both sides in the Y-axis direction that are erected through a slider, and a beam 22 that is long in the Y-axis direction and is provided between the upper ends of both columns 21 and 21. On one side of the beam 22 in the X-axis direction, a Y-axis stage 4 is supported so as to be movable in the Y-axis direction via a linear motor (not shown) so as to reciprocate in the Y-axis direction. The Y-axis stage 4 is provided with a holder 5 that is supported by a pair of left and right guide rails 5L and 5R that extend in the vertical direction via a slider (not shown). It comes to move.

  The holder 5 is provided with a resistance measurement probe 6 and a hot air jet nozzle 7 at a predetermined interval in the Y-axis direction. As the probe 6 for measuring the resistance value, a so-called double ring method composed of two ring electrodes can be used. A voltage is applied between the inner ring electrode and the outer ring electrode, and the flowing current is measured. Measured with an ammeter, the resistance value is determined from this measured current. On the back surface of the measurement object, a guard electrode is installed and directly taken into the controller side, and the current flowing to the back surface of the measurement object is dropped to the ground to improve the measurement accuracy. Note that the method of measuring the resistance value is not limited to the above, and for example, a probe by a so-called four-terminal method or two-terminal method may be provided on the Y-axis stage.

  On the other hand, the nozzle end of the nozzle 7 has a rectangular outline with a predetermined area, and the nozzle end is disposed so as to be directed downward (opposite the measurement object W) in the Z-axis direction. The nozzle 7 is also connected to a blower duct (not shown) connected to an airflow generator (not shown) such as a sending fan with a heating mechanism. The hot air generated by the airflow generator is supplied to the nozzle 7 through the air duct, and the hot air is blown and heated only on the surface of the measurement object W facing the nozzle end. . The diameter of the opening at the tip of the nozzle 7 is preferably in the range of 50 to 100 mm so that a change in resistance value can be captured. Further, although the atmospheric air is usually used as a gas to be blown only on a predetermined range of the measurement object W, an inert gas such as argon or nitrogen may be used.

  Hereinafter, a method for measuring a film resistance value of a transparent oxide semiconductor film made of an In—Ga—Zn—O-based material using the above measurement apparatus will be described. First, an amorphous IGZO film is formed on a substrate surface such as a glass substrate or a silicon wafer by a known reactive sputtering method in which oxygen gas is introduced. In addition, since a well-known thing can be utilized as the sputtering apparatus for film-forming and its film-forming conditions, detailed description is abbreviate | omitted here.

  When the amorphous IGZO film is formed on the surface of the substrate with a predetermined film thickness, the substrate (measurement object W) is taken out from the vacuum chamber of the sputtering apparatus, and positioned and held on the base plate 1 of the measurement apparatus. In this case, the portal frame 2 is in a retracted position separated from the measurement object W in the X direction, and the Y-axis stage 4 is also in the retracted position.

  Next, the portal frame 2 is moved in the X-axis direction, and the nozzle end of the nozzle 7 provided on the Y-axis stage 4 is positioned immediately above the corners of the measurement object W in the X-axis direction and the Y-axis direction (see FIG. 1 and the upper right side). In this state, hot air is blown locally from the nozzle 7 for jetting hot air to the measuring object W for a predetermined time. In this case, the measuring object W is heated to a temperature in the range of 100 to 250 ° C. If the temperature of the object to be measured W is lower than 100 ° C., there is a problem that the measurement cannot be performed because the resistance remains high. On the other hand, if the temperature exceeds 250 ° C., the structure of the oxide semiconductor is relaxed by reacting with the heat treatment atmosphere. As a result, there arises a problem that it becomes impossible to detect a change in resistance value based on a difference in film forming conditions.

  When the measuring object W is heated to a predetermined temperature, the Y-axis stage 4 is moved by a predetermined pitch toward the other side (that is, the probe 6 is moved so as to be positioned immediately above the heated range). . Then, the Y-axis stage 4 is moved downward, the probe 6 is brought into contact with the measurement object, and the resistance value within the range is measured. At this time, hot air is locally blown for a predetermined time in a predetermined range shifted by one pitch in the Y-axis direction from the measurement target W from the hot air injection nozzle 7 to prepare for the next measurement. May be. Next, after measuring the resistance value at predetermined pitches in the Y-axis direction, the portal frame 2 is moved by a predetermined distance in the X-axis direction, and the resistance value is measured in the Y-axis direction as described above. Then, the above operation is repeated, and the resistance value is measured over the entire surface of the measuring object W.

  According to the above, since the amorphous IGZO film (transparent oxide semiconductor film) is locally heated, the heating point is lowered to a range where the resistance value is measured with a conventional probe. And the resistance value is measured with the probe 6 in the range where the resistance value has decreased due to heating, and this operation is repeated over the entire surface of the substrate, whereby the amorphous IGZO film formed on the surface of the measuring object W is measured. The resistance value is measured over the entire surface. In this case, unlike the conventional example in which the substrate on which the amorphous IGZO film is formed is stored in a heating furnace and annealed, changes in film thickness and film quality based on differences in film formation conditions and the like are captured from changes in resistance value. It becomes possible. As a result, the resistance value of the oxide semiconductor film can be efficiently measured, and the film thickness and film quality of the oxide semiconductor film during film formation can be managed.

  The following experiment was conducted to confirm the above effects. First, a silicon wafer was used as a substrate, and an amorphous IGZO film having a thickness of 50 nm was formed on the surface of the silicon wafer by reactive sputtering in which oxygen gas was introduced. In this case, the sputtering conditions such as the input power to the target and the pressure at the time of film formation were the same except for the oxygen partial pressure at the time of film formation, and the film was formed on three silicon wafers (Sample 1: Oxygen partial pressure). 0.02 Pa, Sample 2: Oxygen partial pressure: 0.15 Pa, Sample 3: Oxygen partial pressure 0.3 Pa).

  Next, the silicon wafer immediately after the formation of the amorphous IGZO film was transferred to the measurement apparatus, and the resistance value was measured. In this case, the power consumption of the air flow generator for generating warm air is set to 500 to 3000 W, the silicon wafer is locally heated to 200 ° C., and a known probe 6 using a double ring method is used. It was.

  FIG. 2 is a graph when the resistance value is measured under the above conditions. In addition, when it was going to measure resistance value with the said probe 6 without heating, none of the samples 1-3 could measure the resistance value. On the other hand, if heated by blowing warm air, the resistance value can be measured with the probe 6 and it is confirmed that the (sheet) resistance value (Ω / □) changes due to the difference in film formation conditions. It was done. Thus, it can be seen that the present invention can be applied to efficiently measure the resistance value of the amorphous IGZO film and manage the film thickness and quality of the amorphous IGZO film during film formation.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. In the above-described embodiment, the case where the amorphous IGZO film is locally heated with warm air has been described as an example. However, the present invention is not limited to this and can be heated using a lamp heater or the like. In the above-described embodiment, the example in which the resistance value is measured in the atmosphere has been described as an example.For example, the base plate and each component provided in the base plate are housed in an airtight container, and the inside of the airtight container is measured when the resistance value is measured. It can be an inert gas atmosphere. According to this, there is an advantage that the oxidation-reduction reaction due to the hot air treatment can be reduced and the change in the resistance value due to the structure relaxation can be suppressed.

  6 ... Resistance value measuring probe, 7 ... Hot air blowing nozzle (heating means), W ... Measurement object (a film in which an amorphous IGZO film is formed on the substrate surface).

Claims (4)

The measurement object is an oxide semiconductor film formed on the substrate surface, and the oxide semiconductor film immediately after film formation is locally heated;
And measuring a resistance value using a resistance value measurement probe in the heated region.   The film resistance value measuring method according to claim 1, wherein the local heating of the oxide semiconductor film is performed by blowing hot air.   2. The film resistance value measuring method according to claim 1, wherein the local heating of the oxide semiconductor film is performed by a lamp heater.   The film resistance value measuring method according to claim 1, wherein the oxide semiconductor film is locally heated in an inert gas atmosphere or air.

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