JP2005221298A - Absorbance analyzer, absorbance analyzing method, flow cell and semiconductor device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an absorbance analyzer constituted so as to eliminate the leak of a liquid from a slide part accompanying an increase in flow pressure at the time of reduction of an optical path length and capable of precisely analyzing the absorbance characteristics of the liquid by obtaining a predetermined optical path length with high reproducibility. <P>SOLUTION: The absorbance analyzer is constituted so as to be equipped with a pair of light transmissible flat plates 11a and 11b for forming an optical path through which the liquid flows, an optical path altering mechanism 13 for moving at least one flat plate to alter the length of the optical path, a light source 2 for emitting the incidence light to the optical path, an optical sensing means 3 for sensing the intensity of the transmitted light from the optical path, an analyzing means 4 for analyzing absorbance characteristics from the intensity of incident light and transmitted light and a position adjusting means 5 for adjusting the position of at least one of the pair of the flat plates 11a and 11b. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention belongs to the technical field of analyzing light absorption characteristics of a liquid, and particularly relates to the formation of an optical path length.

  For example, in liquid absorption analysis that contributes to the manufacture of semiconductor devices, it is necessary to select an optimal optical path length in accordance with the absorbance of the liquid. In the conventional absorption analysis method, it is desirable to measure when the transmittance T at the liquid concentration c is 20 to 70% (absorbance A is 0.15 to 0.69), so select an appropriate optical path length. A possible flow cell is used. Specifically, a flow cell configured to form a plurality of measurement chambers whose optical path lengths are sequentially changed, or a movable piece that is slidable in the radial direction of the flow path is provided on one side surface. A flow cell having a configuration in which the optical path length is changed based on the advance and retreat is used (for example, see Patent Document 1).

Japanese Patent Laid-Open No. 10-26584 (FIGS. 1 and 2)

  However, in the conventional flow cell in which a plurality of measurement chambers whose optical path lengths are sequentially changed are formed, the optical path lengths of the respective measurement chambers are fixed. It is necessary to secure the optical path length so as not to hinder the flow of light. However, if the optical path length is made too short in preparation for a liquid having a large absorbance, the flow of the liquid is inhibited, so there is a limit to shortening the optical path length.

  Further, in a flow cell having a configuration in which a movable piece that is slidable in the radial direction of a conventional flow path is provided on one side and the optical path length is changed based on the advance and retreat of the movable piece, The fluid flow pressure applied to the fluid increases. Therefore, if the optical path length is made very short, the fluid pressure becomes extremely high, so that the liquid leaks from the sliding part of the movable piece, or the moving direction of the movable piece is shifted and the upstream and downstream sides of the liquid flow. Thus, there is a problem that a predetermined optical path length cannot be obtained with good reproducibility, and the accuracy of absorption spectrometry is lowered.

  The present invention has been made to solve the above-mentioned problems, eliminates liquid leakage from the sliding portion due to an increase in the fluid pressure when shortening the optical path length, and has a predetermined optical path length. The present invention provides an absorption spectrometer and an absorption analysis method capable of accurately analyzing the light absorption characteristics of a liquid by obtaining a high reproducibility.

  The absorption spectrometer according to the present invention is an absorption spectrometer capable of analyzing the light absorption characteristics of a liquid. The optical path length is changed by moving at least one flat plate and a pair of light-transmitting flat plates forming an optical path through which the liquid can flow. The optical path length changing mechanism, the light source for generating the incident light to the optical path, the light detecting means for detecting the intensity of the transmitted light from the optical path, and analyzing the light absorption characteristics from the intensity of the incident light and the transmitted light Analyzing means, and position adjusting means for adjusting the position of at least one of the pair of flat plates.

  Further, the light absorption analysis method according to the present invention is an absorption light analysis method for analyzing the light absorption characteristics of a liquid. By changing the optical path length, it is possible to relieve the change in the flow pressure by providing a flow path that can bypass the liquid when changing the optical path length, irradiate the optical path with incident light, detect the intensity of transmitted light from the optical path, The light absorption characteristics are analyzed from the intensity of incident light and transmitted light.

  According to the present invention, the change in the flow pressure of the liquid flow associated with the optical path length is alleviated, the optical path length is made uniform between the upstream side and the downstream side, and liquid leakage from the sliding portion is eliminated. An absorption analyzer and an absorption analysis method can be provided that can accurately analyze the absorption characteristics.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram for explaining Embodiment 1 of an absorption spectrometer to which the present invention is applied. 2A and 2B are schematic views for explaining the flow cell 1 used in the absorption spectrometer 100, where FIG. 2A is a cross-sectional view and FIG. 2B is a plan view. The flow cell 1 includes a pair of light-transmitting flat plates 11a and 11b that form an optical path, a cylinder 13 as an optical path length changing mechanism that changes the optical path length, a flat plate 11a that is fixedly held, and an optical path length changing mechanism. And a holding member 12 that is slidably held. It is assumed that the liquid flows in the flow cell 1 in the direction of the arrow shown in the figure. The operation of an actuator or the like that presses the wide bottom of the cylinder 13 is controlled, and the cylinder 13 is moved like a piston to move the flat plate 11b and change the optical path length. The cylinder 13 may be further provided on the flat plate 11a side (not shown), and the flat plates 11a and 11b may be moved by moving each cylinder 13 like a piston. The actuator preferably has a moving distance.

The light source 2 generates incident light to the flow cell 1, and the light detector 3 detects the intensity of transmitted light from the flow cell 1. Regarding the relationship between the incident light intensity I ₀ and the transmitted light intensity I, the following Lambert-Beer equation is known.
I = I ₀ exp (−αcL)
Here, α is the molar extinction coefficient of the sample, c is the molar concentration of the sample, and L is the optical path length.

The analysis unit 4 analyzes the light absorption characteristics from the incident light intensity I ₀ and the transmitted light intensity I. Absorption characteristics refer to transmittance (T = I / I ₀ ), absorbance (A = log (I / I ₀ ) = − αcL), transmission spectrum, absorption spectrum, and the like. Generally, from the light detection performance of the light detector 3, T = 0.2 to 0.7 in the transmittance measurement and A = 0.15 to 0.69 in the absorbance measurement. It is preferable to appropriately adjust the sample concentration and the optical path length. The analysis part 4 should just analyze the light absorption characteristic according to the objective suitably.

  The parallel adjustment unit 5 is connected to a piezoelectric element 14 attached to the cylinder 13. Here, the parallel adjusting unit 5 and the two piezoelectric elements 14 constitute position adjusting means for adjusting the position of at least one of the flat plates so that the pair of flat plates are parallel when the optical path length is changed. To change the optical path length, first, the cylinder 13 is displaced in the vertical direction in the figure to move the flat plate 11b, and an approximate optical path length is set. Here, the liquid as the sample flows through the optical path from the left to the right in the drawing, and particularly when the optical path length is very short, for example, 300 μm or less, the fluid pressure causes the upstream and downstream sides of the liquid flow. In some cases, the optical path length is different. That is, the effective optical distance between the flat plate 11a and the flat plate 11b is not uniform and becomes unstable.

  Further, the phase of the reflected light slightly generated from the flat plate 11a and the flat plate 11b in the optical path is not uniform. Accordingly, the transmitted light reaching the light detector 3 has a portion where the light is strengthened and a portion where the light is weakened due to optical interference between the incident light and the reflected light having a non-uniform phase. Therefore, the transmitted light intensity detected by the light detector 3 is an average value including a portion where the light is strengthened and a portion where the light is weakened. In addition, the ratio between the light strengthening portion and the light weakening portion also varies depending on the optical path length. Thus, if the flat plate 11a and the flat plate 11b are not parallel, the transmitted light intensity varies, and the accuracy of the spectroscopic analysis decreases.

  Therefore, the parallel adjustment unit 5 applies a voltage to both ends of the piezoelectric elements 14 provided on the upstream side and the downstream side of the liquid flow to perform fine adjustment of the optical path length, and at the same time, the flat plate 11a and the flat plate 11b. Make parallel. These piezoelectric elements 14 expand or contract in the moving direction of the flat plate 11b when a voltage is applied. At this time, it is assumed that the displacement of the bottom portion of the cylinder 13 is suppressed, and the displacement of the side portion of the cylinder 13 is not suppressed. When the piezoelectric element 14 expands and contracts, the contact portion with the piezoelectric element 14 on the side of the cylinder 13 similarly expands and contracts. As a result, the upper side of the cylinder 13 in the figure is displaced, and accordingly, the flat plate 11b is also displaced. Whether the piezoelectric element 14 expands or contracts depends on the direction of remanent polarization in the piezoelectric element 14 and the polarity of the applied voltage, and the amount of expansion or contraction can be adjusted by the voltage value. The polarity and voltage value of the voltage applied to each piezoelectric element 14 can be controlled independently. Thereby, the displacement direction and the displacement amount of the piezoelectric element 14 can be independently adjusted on the upstream side and the downstream side.

  FIG. 3 is a schematic diagram for explaining an example of a specific parallel adjustment method. In the first stage, a voltage is applied to the upstream and downstream piezoelectric elements 14 so that both have the same displacement direction and the same displacement amount, and the transmitted light intensity is detected. At this time, the flat plate 11b is translated in the vertical direction as shown in FIG. The wavelength used for detecting the transmitted light intensity is preferably a wavelength that is not absorbed by the liquid, unlike the wavelength that substantially evaluates the light absorption characteristics of the liquid that is the sample. With such a wavelength, since the transmitted light intensity is high, it can be accurately determined whether or not the pair of flat plates are parallel. In addition, the displacement range of the piezoelectric element 14 at this time is preferably λ / 2n or more when the wavelength λ is set and the refractive index n of the liquid is set. Within this displacement range, either the peak at which the transmitted light intensity is maximum or minimum can be detected.

  In the second stage, the parallel adjusting unit 5 selects the optical path length that is the maximum or minimum peak of the transmitted light intensity detected in the first stage, and controls the upstream and downstream piezoelectric elements 14 independently, The flat plates 11a and 11b are adjusted in parallel. Here, the case of the maximum peak will be described. The two piezoelectric elements 14 are relatively displaced by reversing the displacement directions of the upstream and downstream piezoelectric elements 14 or by fixing one piezoelectric element 14 and displacing the other piezoelectric element 14. For example, as shown in FIG. 3B, the illustrated left end of the flat plate 11b is fixed and the illustrated right end is moved up and down. The relative displacement range at this time is preferably λ / 4n or more in the vertical direction of the drawing. In this manner, the two piezoelectric elements 14 are relatively displaced and the transmitted light intensity is detected. The parallel adjustment unit 5 regards the state where the transmitted light intensity is maximum in the relative displacement range as the state where the transmitted light intensity change due to the light interference is the smallest, and with this, the optical path lengths on the upstream side and the downstream side are the same. It is determined that they are equivalent, that is, the flat plate 11a and the flat plate 11b are parallel. The optical path length may be measured by an interferometric method using light in this parallel state.

  In addition, when the optical path length having the minimum transmitted light intensity peak is selected, the parallel adjustment unit 5 changes the transmitted light intensity change due to light interference in a state where the transmitted light intensity is minimum in the relative displacement range described above. It is the smallest state, and it is determined that the flat plate 11a and the flat plate 11b are parallel.

  Therefore, even if the optical path length is shortened so as to be affected by the flow pressure, the parallel adjustment unit 5 can adjust the flat plate 11a and the flat plate 11b in parallel. Therefore, the optical path length can be made uniform, and the light absorption characteristics of the liquid can be analyzed with high accuracy. In particular, in this embodiment, a pair of flat plates can be adjusted in parallel at an arbitrary optical path length by utilizing the optical interference phenomenon of transmitted light.

  In the first stage, when the piezoelectric element 14 is not used but the peak at which the transmitted light intensity is maximum or minimum is detected using the cylinder 13, the piezoelectric element 14 is located upstream or downstream. One may be sufficient. Although the piezoelectric element 14 has been described as the moving means here, any other moving means may be used. Further, it is preferable that the moving means at that time can grasp the moving distance.

Embodiment 2. FIG.
4A and 4B are schematic views of the flow cell 1 for explaining the second embodiment. FIG. 4A is a cross-sectional view and FIG. 4B is a plan view. In this embodiment, a spacer 15 is added to the flow cell 1 in the first embodiment. In the figure, the spacer 15 is provided on a part of the outer edge side of the optical path so as not to obstruct the optical path of the incident light on the flat plate 11a, and the liquid can secure a flow path through the gap of the spacer 15 to change the flow pressure. I am trying to relax. Further, by making the width of the spacer 15 shorter than the diameter of the flow path in the radial direction of the flow path, a change in fluid pressure can be mitigated by providing a flow path that can bypass the liquid.

  Next, the operation will be described. Here, when changing the optical path length to be short, the cylinder 13 moves the flat plate 11b until the flat plate 11b and the spacer 15 come into contact with each other. Since the width of the spacer 15 is shorter than the diameter of the flow path in the radial direction of the flow path, the liquid is bypassed and the change in the flow pressure can be reduced. In this case, the parallel adjustment unit 5 in the first embodiment is not necessarily required, and the spacer 15 serves as a position adjustment unit that guides ensuring a predetermined optical path length with good reproducibility. Therefore, the piezoelectric element 14 described in FIG. 4 is a portion that is not necessarily required in the second embodiment.

  Since the optical path length corresponding to the height of the spacer 15 is set in this way, the optical path length can be set with high accuracy even when the cylinder 13 is reciprocally displaced.

  In addition, although the example which provided the spacer 15 in the flat plate 11a was demonstrated, you may provide in the flat plate 11b. Furthermore, the shape and arrangement of the spacer 15 can be designed as appropriate, and the spacer 15 and the flat plate 11a (11b) may be the same member.

Embodiment 3 FIG.
5A and 5B are schematic views of the flow cell 1 for explaining the third embodiment. FIG. 5A is a cross-sectional view and FIG. 5B is a side view. In this embodiment, the holding member of the flow cell 1 can be deformed with the movement of the flat plate by the optical path length changing mechanism, and the sliding portion between the flat plate or the cylinder and the holding member is eliminated. Others are the same as in the first embodiment.

  In the figure, the holding member 16 holds a pair of flat plates 11a and 11b. In the flow cell 1, when the flat plate 11b is located at the position where the optical path length is maximum, the flow path shape of the holding member 16 is rectangular. When the optical path length is changed, the holding member 16 is deformed so that the joint portion with the flat surface 11b is pushed in as the flat plate 11b is moved by the cylinder 13 as shown in FIG. Therefore, the holding member 16 does not slide with the flat plate 11b or the cylinder 13. Further, it can be seen that as the flat plates 11a and 11b are pushed, the holding member 16 is deformed, and two flow paths that allow the liquid to bypass the inside of the holding member 16 are secured. Further, since the holding member 16 has a flexible structure, the holding member 16 may swing when the cylinder 13 is displaced. In this case, a guide mechanism for stably displacing the cylinder 13 in the vertical direction in the figure may be provided. The guide mechanism is a member having, for example, a suitable groove formed in the cylinder 13 in the displacement direction and a protrusion that fits into the groove.

  As described above, since there is no sliding portion between the holding member 16 and the flat plate 11b or the cylinder 13, there is no liquid leakage from the flow cell 1. Therefore, the inside of the absorption spectrometer 100 is not contaminated. Furthermore, there is no dust generation due to sliding from the flow cell 1. Therefore, it is suitable for use in a clean room, and the cleanliness can be maintained. Note that the piezoelectric element 14 illustrated in FIG. 5 is a portion that is not necessarily required in the third embodiment.

Embodiment 4 FIG.
FIG. 6 is a configuration diagram of a plating apparatus for explaining the third embodiment. The plating tank 200 contains a plating solution containing a gold sulfite complex, and a plating process is performed by immersing the object to be plated in the plating solution. The plating tank 200, the plating solution replenishment tank 300, the liquid feed pump 400, and the filter 500 are connected by piping. The plating solution is circulated through the plating solution replenishing tank 300, the liquid feeding pump 400, and the filter 500 to the plating treatment tank 200 by the conveying force of the liquid feeding pump 400. A pipe connecting the plating tank 200 and the plating solution replenishment tank 300 is branched, and the plating solution can be collected toward the absorption analyzer 100. Here, any one described in the first to third embodiments is used as the absorption spectrometer 100. In particular, the absorbance analyzer 100 according to the third embodiment is suitable for use in a clean room because there is no dust generation from the flow cell 1. The plating solution sampling position is not limited to this, and the plating solution may be collected directly from the plating bath 200 or the plating solution replenishment bath 300.

  Next, an example in which a plating solution containing a gold sulfite complex is used in a plating step when manufacturing a semiconductor device using this plating apparatus will be described. First, in this plating process, the abnormal precipitation of gold due to the deterioration of the plating solution is because the gold sulfite complex is first oxidized and decomposed, and the monovalent gold ions generated there change to gold colloid by the disproportionation reaction. Has been estimated. Therefore, in order to evaluate the degree of deterioration of the plating solution, it is preferable to analyze both the gold sulfite complex and the gold colloid.

  The state of the gold sulfite complex can be analyzed from the absorption characteristics at wavelengths of 220 to 240 nm where sulfite ions are absorbed. Further, the state of the gold colloid can be analyzed from the light absorption characteristics at a wavelength of 300 to 320 nm where trivalent gold ions, which are by-products during the production of the gold colloid, are absorbed. Here, the product of the molar extinction coefficient of sulfite ions and the molar concentration is two orders of magnitude larger than the product of the molar extinction coefficient of trivalent gold ions and the molar concentration. Therefore, in order to make the absorbance at a wavelength of 220 to 240 nm where sulfite ions are absorbed and the absorbance at a wavelength of 300 to 320 nm where trivalent gold ions are absorbed to the same order, the absorbance characteristics at a wavelength of 220 to 240 nm are used. It is necessary to make the optical path length for analysis shorter by two orders of magnitude or more than the optical path length for analyzing light absorption characteristics at wavelengths of 300 to 320 nm.

  FIG. 7 is an absorption spectrum in this embodiment, FIG. 7 (a) is an example when the optical path length is long, FIG. 7 (b) is an example when the optical path length is short, and FIG. 7 (c) is an optical path length. Is a composite spectrum of FIG. 7 (a) and FIG. 7 (b).

  In FIG. 7A, an absorption peak is observed at a wavelength of 310 nm, and the state of the gold colloid can be known. However, the absorbance at a wavelength of 220 to 240 nm is saturated, and the state of the gold sulfite complex cannot be known. On the other hand, in FIG. 7B, the state of the gold sulfite complex can be known, for example, a shoulder is observed at a wavelength of 220 to 240 nm. However, substantially no absorption can be observed at wavelengths of 300 to 320 nm.

  Therefore, the optical path length is normalized as shown in FIG. 7C, and FIG. 7B is selected for wavelengths 220 to 240 nm and its peripheral wavelengths, and FIG. 7A is selected for wavelengths 300 to 320 nm and its peripheral wavelengths. A synthetic spectrum was created. Thus, if the optical path length is continuously changed during the plating process and the composite spectrum of FIG. 7C is calculated, the change with time of the plating solution can be analyzed with high accuracy. Therefore, the state of the plating solution can be known in real time, and as a result, the yield of semiconductor devices is improved. In particular, in a plating solution using a gold sulfite complex, if the optical path length when analyzing the light absorption characteristics at a wavelength of 220 to 240 nm is 100 μm or less, and the optical path length when analyzing the light absorption characteristics at a wavelength of 300 to 320 nm is 10 mm or more, plating The degree of deterioration of the liquid can be accurately evaluated.

  The present invention can be widely used in a fluid spectroscopic analysis apparatus and a spectroscopic analysis method.

1 is a configuration diagram of an absorption spectrometer for explaining Embodiment 1. FIG. 4 is a schematic diagram of a flow cell for explaining the first embodiment. FIG. 5 is a schematic diagram of a parallel adjustment method for explaining the first embodiment. FIG. FIG. 4 is a schematic diagram of a flow cell for explaining a second embodiment. FIG. 5 is a schematic diagram of a flow cell for explaining a third embodiment. FIG. 6 is a configuration diagram of a plating apparatus for explaining a fourth embodiment. 6 is an absorption spectrum for explaining the fourth embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Flow cell, 2 light source, 3 photodetector, 4 analysis part, 5 parallel adjustment part, 11a-11b flat plate, 12 holding member, 13 cylinder, 14 piezoelectric element, 15 spacer, 16 holding member, 100 Absorption spectrometer.

Claims (17)

  In an absorption spectrometer capable of analyzing light absorption characteristics of a liquid, a pair of light-transmitting flat plates that form an optical path through which liquid can flow, an optical path length changing mechanism that changes an optical path length by moving at least one flat plate, and an optical path A light source for generating incident light to the light, a light detecting means for detecting the intensity of the transmitted light from the optical path, an analyzing means for analyzing the light absorption characteristics from the intensity of the incident light and the transmitted light, and a pair of flat plates And a position adjusting means for adjusting the position of at least one of the flat plates.   2. The absorption spectrometer according to claim 1, wherein the position adjusting means determines that the pair of flat plates are parallel when the change in transmitted light intensity due to light interference is the smallest.   3. The absorption analyzer according to claim 2, wherein the position adjusting means includes a piezoelectric element that expands or contracts in a moving direction of the flat plate that is moved by the optical path length changing mechanism.   2. The absorbance analyzer according to claim 1, wherein the position adjusting means has a spacer provided on at least one flat plate and on the outer edge side from the optical path.   2. The absorption spectrometer according to claim 1, wherein the optical path length changing mechanism is moved by an actuator capable of grasping the moving distance.   The absorption spectrometer according to claim 3, wherein a plurality of piezoelectric elements are provided and each of the piezoelectric elements can be controlled independently.   2. The absorption spectrometer according to claim 1, wherein the holding member that holds the pair of flat plates is deformable as the flat plate is moved by the optical path length changing mechanism.   In an absorption spectrophotometric method for analyzing the light absorption characteristics of a liquid, the liquid is circulated through an optical path formed by a pair of light-transmitting flat plates, the optical path length is changed by moving at least one flat plate, and the optical path length is changed. An absorption analysis characterized by providing a flow path that can bypass liquid, irradiating the light path with incident light, detecting the intensity of transmitted light from the light path, and analyzing the light absorption characteristics from the intensity of the incident light and transmitted light Method.   9. The method according to claim 8, wherein when the optical path length is changed, the pair of flat plates are determined to be parallel when the change in transmitted light intensity due to light interference is the smallest.   When the optical path length is changed, the pair of flat plates are made parallel by contacting the moved flat plate with a spacer provided on at least one flat plate and on the outer edge side of the optical path. The absorption analysis method according to claim 8.   In a flow cell for analyzing light absorption characteristics of a liquid, the flow cell has a pair of light-transmitting flat plates that form an optical path through which the liquid can flow, and a spacer provided on at least one of the flat plates. A flow cell characterized in that the optical path length can be changed by moving the lens.   A flow cell for analyzing light absorption characteristics of a liquid, comprising: a pair of light-transmitting flat plates that form an optical path through which a liquid can flow; and a holding member that holds the pair of flat plates. An optical path length can be changed, and the holding member can be deformed as the flat plate moves. In the manufacturing method of the semiconductor device which has a plating process using the plating solution containing a gold sulfite complex, the optical path length when analyzing the light absorption characteristics of the plating solution with a wavelength of 220 to 240 nm, and the plating solution with a wavelength of 300 to 320 nm. Shorter than the optical path length when analyzing the light absorption characteristics,
Distributing the plating solution to an optical path formed by a pair of light-transmitting flat plates, changing the optical path length by moving at least one flat plate, and providing a flow path that can bypass the plating solution when the optical path length is changed. A method of manufacturing a semiconductor device, comprising: irradiating incident light on an optical path; detecting intensity of transmitted light from the optical path; and analyzing light absorption characteristics from the intensity of incident light and transmitted light.   14. The method of manufacturing a semiconductor device according to claim 13, wherein when the optical path length is changed, it is determined that the pair of flat plates are parallel when a change in transmitted light intensity due to optical interference is the smallest.   When the optical path length is changed, the pair of flat plates are made parallel by contacting the moved flat plate with a spacer provided on at least one flat plate and on the outer edge side of the optical path. A method for manufacturing a semiconductor device according to claim 13.   16. The method of manufacturing a semiconductor device according to claim 14, wherein the holding member that holds the pair of flat plates is deformed as the flat plates move. 16. The optical path length when analyzing light absorption characteristics at wavelengths of 220 to 240 nm is 100 μm or less, and the optical path length when analyzing light absorption characteristics at wavelengths of 300 to 320 nm is 10 mm or more. A method for manufacturing a semiconductor device.

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