JP2006091309A - Etch back method, method for manufacturing inorganic polarizer by using this method, etching stop control device for realizing these methods, and inorganic polarizer to be manufactured - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately control the flatness of pattern surface formed by burying and stacking a metal on a fine recessed pattern and the height of the pattern by etch-back. <P>SOLUTION: An aluminium film 14 is stacked on the surface of a substrate 10 on which a fine grating pattern 12 is formed so as to cover the grating pattern 12, a resist layer 16 is applied to the surface of the aluminium film 14 and an aperture 18 is formed in an area of the resist layer 16 except an area in which the grating pattern 12 is formed. The resist layer 16 and the aluminium film 14 are etched back, and after prescribed set time (control time) from time that the differential value of plasma strength of plasma generated from SiF exceeds a prescribed value, etching is stopped. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing an element having fine irregularities on the surface of an element region, such as an inorganic polarizer and a semiconductor device, a control device used therefor, and a manufactured inorganic polarizer.

  An inorganic polarizer is a lattice-like pattern in which light handled by grooves parallel to each other on the substrate surface is arranged at equal intervals at a pitch that causes polarization separation (in the present invention, “lattice-like” refers to a number of strip-like patterns parallel to each other. It is an arrayed metal) embedded in the groove. An example of an inorganic polarizer to be manufactured by the present invention is a lattice-shaped pattern having grooves on the surface of a quartz glass substrate having a width about the wavelength of light.

The present invention is also directed to a method of embedding a metal in a through hole or a wiring groove provided in an interlayer insulating film in order to form a multilayer wiring in the semiconductor field.
In the semiconductor field, when a multilayer wiring having a fine wiring layer is formed, an interlayer insulating film is deposited on a polysilicon or aluminum wiring serving as a lower wiring. Since the interlayer insulating film is normally deposited by the CVD (Chemical Vapor Deposition) method, the unevenness of the lower layer wiring appears as the unevenness of the surface of the interlayer insulating film as it is. If a metal film for the upper layer wiring is deposited in this state, and patterning is attempted by photolithography, the pattern accuracy is lowered due to surface irregularities, and it becomes difficult to form fine wiring.

  Therefore, the surface of the interlayer insulating film under the upper wiring is flattened. In the planarization step, two types of different interlayer insulating films are formed on the lower wiring, and a resist layer is applied on the uneven surface of the interlayer insulating film. Since the resist layer is hardened after being applied by spin coating or the like, the unevenness of the interlayer insulating film can be filled and a flat surface can be obtained. In this state, the etching rate is set so that the resist and the interlayer insulating film have substantially the same etching rate, and etch back is performed by dry etching to flatten the surface of the interlayer insulating film. A metal film for upper wiring is deposited on the flattened interlayer insulating film, and the metal film is patterned by photolithography and etching to form upper wiring (see Patent Documents 1 and 2).

In the above-described etch bag in the semiconductor multilayer wiring, the etch back is stopped in a state where an interlayer insulating film having a predetermined thickness is left. Therefore, as a method for detecting the end point of etching, while monitoring the emission spectrum intensity of plasma during dry etching, two different types of interlayer insulating films are etched from the upper layer to expose the lower layer insulating film. Thus, the end point of etching is determined by capturing the time when the intensity of the spectrum unique to the lower interlayer insulating film changes.
Japanese Patent Laid-Open No. 5-55220 JP-A-6-85089

  When embedding metal in grooves of fine lattice patterns of inorganic polarizers or through holes and wiring grooves of multilayer wiring, the metal for embedding from above the lattice pattern, through holes, wiring grooves, etc. before the metal is embedded When the film is deposited and etched back as it is, the irregularities on the surface of the metal film remain in the buried metal layer, thereby degrading the performance of the device. Therefore, it is conceivable to apply a method of etching back after applying a resist and flattening the surface, as in the flattening method in the semiconductor field.

  In inorganic polarizers, for example, an aluminum film is deposited as a metal film on a lattice pattern formed on the surface of a quartz glass substrate, for example, and a resist is applied thereon to planarize the surface, followed by etching as in the semiconductor field. Will give back. In this case, when the metal layer is etched and the quartz glass of the substrate is exposed, the end point of etching is determined based on the change in the spectral intensity peculiar to the plasma. It is time to expose.

Etching back is performed in the same manner when a metal is embedded in a through-hole or a wiring groove of a multilayer wiring, and the point in time when the interlayer insulating film is exposed is set as the etching end point.
However, in general, etchback is a just-etched state in which the substrate surface and interlayer insulating film are exposed so that the metal remains in unnecessary places and does not adversely affect the optical or electrical characteristics. Usually, the process is continued until an overetching state in which etching is further advanced. As a result, in a fine lattice pattern such as an inorganic polarizer, the lattice characteristics are lowered by over-etching or the surface of the lattice pattern is damaged, so that the optical characteristics are deteriorated.

Accordingly, a first object of the present invention is to provide a method for controlling the layer height with high accuracy by flattening the surface of the inorganic polarizer or multilayer wiring having such a fine surface pattern after the metal is embedded by etch back. That is.
The second object of the present invention is to provide an inorganic polarizer produced by such a controlled method.
A third object of the present invention is to provide an etching stop control device capable of performing such etch back with good controllability.

The etch back method of the present invention includes the following steps (A) to (E) to etch a layer to be etched.
(A) A step of depositing an etching target layer having a material region different from that of the substrate surface on the substrate surface over the element region with respect to a substrate having an element region having a concave portion on the surface in a partial region of the substrate surface;
(B) A step of applying a resist layer which is a photosensitive material layer so that the surface becomes flat on the layer to be etched,
(C) providing an opening for detecting a spectral peak in the resist layer in a region other than the element region;
(D) etching the resist layer and the layer to be etched entirely by dry etching, and detecting when the substrate surface is exposed to the opening based on plasma emission generated by the dry etching; ) A stopping step of stopping the etching after a predetermined time from the detection time in the step (D).

Detection at the time when the substrate surface is exposed at the opening in the step (D) can be performed by comparing the differential value of the spectral peak value caused by the substance on the substrate surface in the plasma emission with a preset value.
The etching in the step (D) is preferably performed by setting etching conditions in a direction in which the etching rates of the resist layer, the layer to be etched, and the substrate are equal.

As an example of a specific application of the present invention, an inorganic polarizer provided with a lattice pattern having grooves embedded with metal, which are arranged at equal intervals with a pitch that causes polarization separation to occur in parallel with each other on the substrate surface. The method of manufacturing can be mentioned. In that case, the etch-back method of the present invention is used as a method for planarizing the metal embedded in the grooves of the grid pattern in accordance with the grid surface. The element region in the etch back method is a region where a lattice pattern is formed, and the layer to be etched is a metal layer embedded in a groove of the lattice pattern and a metal layer deposited on the substrate surface.
Here, the lattice pattern having grooves arranged at equal intervals only means that the pitch of the lattice is constant, and the width of the concave portion and the convex portion constituting the lattice may be equal, It means that they do not have to be equal. For example, when the pitch of the grating is 100 nm, the width of the concave portion and the convex portion are both equal to 50 nm, and the width of the concave portion and the convex portion is not equal. For example, the width of the concave portion is 60 nm and the width of the convex portion It also means that those having a thickness of 40 nm are included.

As an example of an inorganic polarizer, the substrate is quartz glass, the metal is aluminum or an aluminum alloy, a gas containing a fluorine compound is used as an etching gas, and the detection at the time when the substrate surface is exposed to the opening is a spectral peak of SiF. This can be done by comparing the differential value of the value with a preset value.
The inorganic polarizer of the present invention is produced by this method.

  The etching stop control device of the present invention inputs differential data at a specific wavelength of the plasma spectrum from the plasma monitor device of the dry etching device, and compares the differential value with a reference value set in advance. Comparing means for detecting the time when it exceeded, and measuring time from the time when the differential value exceeded the reference value in the comparing means, and when the preset control time is reached, the etching operation of the dry etching apparatus is stopped Drive stopping means.

In the etch-back method of the present invention, the time point when the element region is exposed by etching is not detected and the end point of etching is not detected, but the time point when the etching reaches the substrate surface at the opening is based on the plasma emission. Then, the etching is stopped after a predetermined time from that point. The opening is for detecting a spectrum peak caused by a substance on the substrate surface in plasma emission. The point in time when this spectral peak is detected is not the end point at which the etchback reaches the surface of the device region, but is an earlier stage. In the present invention, the time point before the end point of the etch back is detected, and the end point is set by the subsequent time setting. Therefore, by setting the time, the surface of the element region can be flattened, and overetching and damage to the element region can be suppressed.
Moreover, since over-etching can be suppressed, the method of the present invention is suitable for the production of finer products.
In the method of the present invention, it is not necessary to form a film for detecting the etching end point. If a film for detecting the etching end point is formed, the etching gas must be switched and introduced to remove the film after detecting the film for detecting the etching end point. Such switching of the etching gas is not required.

  If the detection at the time when the substrate surface is exposed to the opening is performed by comparing the differential value with a preset value rather than by the spectral peak value due to the substance on the substrate surface, the detection at that time is performed. It becomes possible to carry out more accurately.

Further, the etch back is performed by setting the etching conditions in a direction in which the etching rates of the resist layer, the layer to be etched, and the substrate are equal, the flatness of the surface of the element region can be further improved.
The etch back method can be applied to the production of an inorganic polarizer. In that case, if the substrate is quartz glass, the metal is aluminum or an aluminum alloy, a gas containing a fluorine compound is used as an etching gas, and detection is performed using the differential value of the spectral peak value of SiF, there is no opening. Although it is difficult to detect a peak because the SiF spectral peak gradually rises, the SiF spectral peak can be easily detected by providing an opening. Further, even if there is a variation in the thickness of the aluminum film, which is difficult to measure the film thickness, the etch back control is excellent by detecting the plasma spectrum of the opening. As a result, the optical properties of the obtained inorganic polarizer can be improved.
By using the etching stop control device of the present invention, controlled etch back can be automatically executed.

1A and 1B show a polarizer as an example of an article manufactured by applying the present invention. FIG. 1A is a perspective view, and FIG. 1B is a perspective cross-section showing a part of a lattice pattern of the polarizer. FIG.
The substrate 2 is a flat quartz glass substrate, and a fine lattice pattern 4 serving as a polarizer is formed at the center of the surface of the substrate 2. The surface of the lattice pattern 4 may be formed at the same height as the surface of the other part of the substrate 2 or may be formed so as to protrude from the surface of the other part of the substrate 2 as shown. is there.

  As shown in an enlarged view of (B), the lattice pattern 4 is a substrate in which a large number of grooves 6 having a constant width are formed in parallel with each other at a constant pitch. An aluminum layer is embedded in the groove 6 as a high reflectivity metal layer, and the surface of the aluminum layer embedded in the groove 6 and the surface of the quartz glass portion 8 that is the same as the substrate existing between the grooves 6 have the same height. Thus, the surface of the polarizer composed of these surfaces is a flat surface with suppressed surface roughness.

The pitch of the grating pattern is formed to be less than or equal to the wavelength of the light to be handled. When the light passes through this polarizer, the polarization component parallel to the grating pattern is reflected, and the polarized light is transmitted by transmitting the vertical component. Made.
The metal layer embedded in the groove 6 only needs to have a high reflectivity, and in addition to aluminum, an aluminum alloy, gold, silver, or an alloy of these metals can also be used. The substrate 2 is not limited to a quartz glass substrate, and a glass substrate such as a heat resistant glass substrate or an optical glass substrate can be used as well.

  As an example of the dimensions of this polarizer, the substrate 2 is a thin plate having a thickness of 1 mm, a width of 20 mm, and a length of 25 mm. The region in which the lattice pattern 4 is formed is a rectangle having a width of 15 mm and a length of 20 mm. The groove 6 has a width of 50 nm, a depth of 120 to 130 nm, and an interval of the grooves 6 of 50 nm. Six patterns are repeated. Of course, the dimensions are only examples, and the grating pattern 4 may be changed as long as it has the optical characteristics as a polarizer.

The present invention is not limited to the polarizer as shown in FIG. 1, but can be applied to an optical element having fine irregularities on the surface of the substrate and having the concave portions embedded with a material other than the substrate.
The present invention can also be applied to articles other than optical elements, such as embedding through holes for connecting fine wiring layers of multilayer wiring or upper and lower wirings in a semiconductor device.

Next, an example of a method for manufacturing the polarizer of FIG. 1 will be described with reference to FIG.
(A) From aluminum film deposition to resist layer formation:
The object to be processed is one in which a fine lattice pattern 12 is formed on the surface of a substrate 10 having a flat surface, for example, a quartz glass substrate. The lattice pattern 12 is formed integrally with the substrate 10. In this example, the lattice pattern 12 is formed so as to protrude from the surface of the other part of the substrate 10. They may be formed at the same height.

  As illustrated with reference to FIG. 1, the lattice pattern 12 is formed by, for example, grooves having a width of 50 nm and a depth of 120 to 130 nm formed at a pitch of 100 nm. The grid pattern 12 can be formed by forming a resist pattern on the surface of the substrate 10 by photolithography and etching the substrate 10 using the resist pattern as a mask.

  First, a highly reflective metal film is deposited on the surface of the substrate 10 so as to cover the lattice pattern 12. In this embodiment, an aluminum film 14 is deposited as a high reflectivity metal film. The thickness of the aluminum film 14 is not particularly limited, but is 200 to 600 nm, for example, and can be deposited by vapor deposition or sputtering.

  Next, a resist layer 16 is applied on the aluminum film 14. The resist layer 16 is not particularly limited, and may be a photosensitive material that is generally used in lithography such as a semiconductor manufacturing process, as long as it can be patterned so as to reduce the surface roughness as compared to the lower layer and provide an opening. All can be used if present. As an example, NPR-8100 (manufactured by Nagase Kasei Kogyo Co., Ltd.) having a viscosity of 5 cp is mixed with LB thinner at a ratio of 1: 2. The resist coating method is a spin coating method, for example, coating is performed at a rotation speed of 3500 rpm for 30 seconds.

Thereafter, the resist 16 is subjected to a pre-baking process, for example, at 95 ° C. for 120 seconds by an automatic hot plate.
In order to provide the opening 18 in a region other than the region where the lattice pattern 12 is formed, the resist 16 is exposed through a mask and developed to form the opening 18 in the resist 16.
Thereafter, post-baking treatment is performed at 200 ° C. for 1 hour in a clean oven. As a result, the resist 16 is cured. The thickness of the resist 16 after curing was 0.12 μm. This completes the etch-back sample.

(B) Etch back treatment:
The dry etching apparatus for etch back is not particularly limited as long as the progress of etching can be monitored by plasma light. As such a dry etching apparatus, an RIE (reactive ion etching) apparatus, an ICP (inductively coupled plasma etching) apparatus, an ECR (electron cyclone resonance plasma etching) apparatus, or the like can be used. Shall be used.
The resist layer 16 is formed, and the sample provided with the opening 18 is attached to an etching apparatus, and is etched according to the following procedure.

(B-1) Cleaning:
Prior to etching, the inside of the etching apparatus is cleaned. In the cleaning process, for example, O ₂ is supplied at 200 sccm and discharged for 20 minutes.

(B-2) Dummy etching:
In order to stabilize the etching of the sample, dummy etching is performed using a dummy substrate. The dummy etching conditions are set to be the same as those of sample etching described later, and are performed for about 10 minutes.

(B-3) Cleaning:
After the dummy etching, for example, O ₂ is flowed at 200 sccm, discharged for 10 minutes, and cleaning is performed again.
Then, leave it for 20 minutes or more.
Up to this point, the sample is stored in a vacuum-carrying substrate transfer chamber of the load lock mechanism and kept waiting, and is transferred into the etching apparatus for the next sample etch back process.

(B-4) Sample etchback:
Thereafter, the sample is etched back.
Etching conditions are set as follows, for example.
Etching gas:
CHF ₃ = ₃ sccm,
Ar = 20 sccm,
Cl ₂ = 8 sccm,
BCl ₃ = 4 sccm,
Pressure = 1 Pa,
RF power = 100W.

  In the etch back of the sample, spectral data of the plasma monitor is acquired, and the intensity at the peak wavelength of the plasma spectrum generated from SiF in the spectrum is differentiated. When the differential value exceeds a predetermined value, the opening 18 is obtained. It is determined that the quartz glass substrate 10 is exposed inside.

(C) Removal of residual aluminum film:
Thereafter, by continuing the etching for a predetermined set time (control time), the aluminum film remains in the grooves of the lattice pattern 12, and the aluminum film on the other part of the surface of the substrate 10 is completely removed, and the inorganic polarizer is removed. Is completed.

  This control time is experimentally obtained in advance so that the aluminum film remains in the grooves of the lattice pattern 12 and all the other portions of the aluminum film on the substrate surface are removed and set in the control unit of the etching apparatus. Keep it.

Thereafter, the sample is transferred into the substrate transfer chamber that is evacuated by the load lock mechanism.
Thereafter, O ₂ is flowed into the etching apparatus at 200 sccm, discharged for 10 minutes to perform a cleaning process, and then left for 10 minutes or more.
Thereafter, the sample is transferred into the etching apparatus and subjected to argon treatment. The purpose of the argon treatment of the sample is to remove the chlorine-based gas adhering to the sample in order to prevent oxidative corrosion of the aluminum material by the chlorine-based gas when the sample is taken out into the atmosphere. The conditions for the argon treatment are set as follows, for example.
Ar = 10 sccm,
Pressure = 1 Pa,
RF power = 100W.
After the argon treatment, the sample is transferred into the substrate transfer chamber and taken out.

FIGS. 3 to 5 show an embodiment in which the etch-back process is automatically executed using the etching stop control device of the present invention.
FIG. 3 shows an outline of the etching stop control device together with the etching device as a block diagram. Reference numeral 20 denotes an etching apparatus. Specifically, the etching apparatus may be an arbitrary etching apparatus that can be used for dry etching, such as an RIE apparatus, an ICP apparatus, or an ECR apparatus. A plasma monitor 22 receives light emitted from plasma in the etching apparatus 20 and detects its spectrum. The plasma monitor 22 can also differentiate and output the plasma intensity at a specific wavelength in the detected spectrum data, for example, the plasma spectrum wavelength by the SiF component. Reference numeral 26 denotes comparison means for inputting the differentiated plasma output value and comparing it with a reference value set in advance in the reference value setting unit 28 to detect when the differential value exceeds the reference value. 30 indicates a stop signal to the drive circuit 34 of the etching apparatus 20 when the comparison means 26 detects a time point exceeding the reference value and a control time set in the control time setting unit 32 in advance from that time point. Drive stop means for outputting and stopping etching. The etching stop control device includes a comparison unit 26, a reference value setting unit 28, a drive stop unit 30, and a control time setting unit 32.

The operation of this etching stop control device will be described with reference to the flowchart of FIG.
A sample as shown in FIG. 2A is put into an etching apparatus, and etching is started. In the etching, as described in the etching process of FIG. 2B, processing steps such as a cleaning process, a dummy etching process, and an argon process may be set as necessary.

In the sample etching process, the plasma monitor 22 detects the plasma spectrum. The spectrum data is shown, for example, in the uppermost diagram of FIG.
The plasma monitor 22 has a function of differentiating the time course of the plasma intensity at the peak wavelength of the plasma generated from the component generated by the reaction between the etching gas and the quartz glass substrate, such as SiF, among the spectrum data. The time history of the plasma intensity at the specific wavelength is shown in the middle diagram of FIG. 5, for example, and the differential waveform is shown in the lower diagram of FIG.

  The comparison means 26 of the etching stop control device takes in the differential waveform, and the value is set in advance for the differential waveform (the reference value is “100” in the example of FIG. 5, but is set appropriately). ) Is detected. The drive stop means 30 generates a stop signal to the drive circuit 34 when a predetermined set time (control time) is exceeded from that time, and stops the etching.

  The control time set in advance in the control time setting unit 32 depends on the resist film thickness, etching conditions, and the like. From the time when the differential value of the plasma intensity exceeds a predetermined reference value, the groove or recess of the element In this case, it is experimentally obtained in advance as the time for the aluminum film to remain and all the unnecessary aluminum film to be removed.

  The improvement of the surface roughness in one Example and the optical characteristic of the optical element obtained are shown. In the process shown in FIG. 2, the surface roughness of the region where the element 12 is present on the surface of the aluminum film 14 in the state where the aluminum film 14 is deposited on the element 12 is 4 to 7 nm.

  When the aluminum film 14 is etched back without providing the resist 16 and aluminum remains in the groove of the element 12, the surface roughness of the aluminum film 14 remains on the surface of the element 12, and the surface of 5 to 7 nm is left. Roughness was observed.

  On the other hand, when the resist layer 16 is formed on the aluminum film 14 according to the present invention, the opening 18 is provided and the etch back is performed, the surface roughness on the element 12 at the final stage shown in FIG. Improved to ~ 3 nm. The surface roughness was measured by AFM (atomic force microscope).

  Spectral characteristics (TE, TM) and control time (time from when the differential value of plasma intensity at a specific wavelength exceeds a preset reference value until etching is stopped) of the inorganic polarizer obtained by the example The relationship is shown in FIG. TE and TM are polarization transmittances. As shown in FIG. 1, TE polarization is polarized light whose polarization direction is parallel to the grating line direction, and TM polarization is polarized light whose polarization direction is orthogonal to the grating line direction. Polarized light, which was measured with a spectrophotometer (measurement wavelength = 450 nm). In FIG. 6, the vertical axis represents the transmittance, and the horizontal axis represents the control time (seconds).

  According to FIG. 6, TE increases with the control time, but TM does not change from around 21 seconds of control time. The control time is preferably set at a place where the TE is low and the TM is high. In this example, the condition is satisfied in a long time from about 21 seconds. However, if the control time is long, overetching is performed on the surface of the inorganic polarizer. In this example, the optimal control time is considered to be about 21 seconds circled in FIG. TE at a control time of 21 seconds was 0.5% and TM was 78%.

  INDUSTRIAL APPLICABILITY The present invention can be used for manufacturing an optical element, a semiconductor element or the like by embedding a metal in a fine unevenness on the surface of an element region such as an inorganic polarizer or a semiconductor device.

FIG. 1 shows a polarizer as an example of an article manufactured by applying the present invention, (A) is a perspective view, and (B) is a perspective sectional view showing a part of a lattice pattern of the polarizer. . It is process sectional drawing which shows one Example of the method of manufacturing the polarizer of FIG. It is a block diagram which shows the outline | summary of an etching stop control apparatus with an etching apparatus. It is a flowchart figure which shows operation | movement of the same etching stop control apparatus. It is a figure which shows the spectrum data obtained from a plasma monitor, and its differential waveform. It is a graph which shows the relationship between the spectral characteristics of the polarizer obtained in one Example, and control time.

Explanation of symbols

2,10 Substrate 4,12 Lattice pattern 6 Groove of lattice pattern 8 Quartz glass portion same as substrate 10 Substrate 14 Aluminum film 16 Resist layer 18 Opening 20 Etching apparatus 22 Plasma monitor 26 Comparison means 28 Reference value setting section 30 Drive stop means 32 Control time setting unit 34 Drive circuit

Claims (7)

An etch-back method for etching an etching target layer including the following steps (A) to (E).
(A) A step of depositing an etching target layer having a material region different from that of the substrate surface on the substrate surface over the element region with respect to a substrate having an element region having a concave portion on the surface in a partial region of the substrate surface;
(B) applying a resist layer so that the surface is flat on the layer to be etched;
(C) providing an opening for detecting a spectral peak in the resist layer in a region other than the element region;
(D) etching the resist layer and the layer to be etched entirely by dry etching, and detecting when the substrate surface is exposed to the opening based on plasma emission generated by the dry etching; ) A stopping step of stopping the etching after a predetermined time from the detection time in the step (D). The detection of the time when the substrate surface is exposed to the opening in the step (D) is performed by comparing a differential value of a spectral peak value caused by a substance on the substrate surface in the plasma emission with a preset value. Item 2. The etch back method according to Item 1. The etching back method according to claim 1, wherein the etching in the step (D) is performed by setting an etching condition in a direction in which etching rates of the resist layer, the layer to be etched, and the substrate are equal. In a method of manufacturing an inorganic polarizer having a lattice pattern having grooves embedded with metal in which light beams handled in parallel with each other on the substrate surface are arranged at equal intervals with a pitch causing polarization separation,
As a method of embedding metal in the lattice pattern groove, the element region according to claim 1 is an area where the lattice pattern is formed, and the metal for embedding the layer to be etched in the lattice pattern groove is on the substrate surface. An inorganic polarizer manufacturing method using the etch-back method according to any one of claims 1 to 3 as a deposited metal layer. The substrate is quartz glass, the metal is aluminum or an aluminum alloy, a gas containing a fluorine compound is used as the etching gas, and detection when the substrate surface is exposed to the opening is a differential value of the spectral peak value of SiF. The method for producing an inorganic polarizer according to claim 4, wherein the method is carried out by comparison with a preset value. 6. An inorganic polarizer having a lattice-like pattern having grooves embedded with metal, arranged on a substrate surface in parallel with each other at a pitch that causes polarization separation, and the light treated parallel to each other. An inorganic polarizer produced by the production method of Comparison means for inputting differential data at a specific wavelength of the plasma spectrum from a plasma monitor device of a dry etching apparatus, comparing with a preset reference value, and detecting when the differential value exceeds the reference value ,
Drive stop means for measuring the time from the time when the differential value exceeds the reference value in the comparison means, and stopping the etching operation of the dry etching apparatus when a preset control time is reached;
Etching stop control device.

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