JPH0430512A - Dummy wafer - Google Patents

Abstract

PURPOSE:To enable equipment of sufficient repetition durability and excellent sensitive characteristic by overlaying a silicon wafer substrate with a resin layer containing an specific organic photochromic material as the first layer, a layer made of a polymer resin of specific oxygen permeability ad the second layer, and a antireflection film as the third layer. CONSTITUTION:A substrate of silicon wafer or the like is overlaid with a layer made of a resin containing an organic photochromic material of 5-80 wt% selected from a group made of spiropyrane based compound, spironaphthooxazine based compound, and fulgide based compound as the first layer. It is overlaid with a layer made of a polymer resin with an oxygen permeability of 1 X 10<-10> cm<3>.cm/cm<2>.s.cmHg or less as the second layer and an antireflection film as the third layer. The organic photochromic material is a spiropyrane compound represented by a formula (where R1 is a nonsubstituted or substituted alkyl group of a carbon number 1-22; R2 and R acid are substituted groups selected from among oxygen atom, hydroxy group, amino group, alkoxy group, aryl group, halogen group, cyano group, carboxy group, and nitro group; and m, n an integer of 0-4).

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a dummy wafer used in an apparatus for manufacturing semiconductor devices such as ICs or LSIs.

(Prior Art) Conventionally, exposure apparatuses for manufacturing semiconductor devices such as ICs or LSIs have been required to have two basic performances: resolution performance and overlay performance. The former is the ability to form fine patterns on a photoresist surface coated on a semiconductor substrate (hereinafter referred to as a "wafer").
The latter is the ability to accurately align and transfer the pattern on the photomask with respect to the pattern formed on the eight sides of the sea urchin in the previous process.

Depending on the exposure method, the exposure device can e.g. contact,
It is broadly classified into proximity, mirror 1:1 projection, stepper, X-ray aligner, etc., and the optimal superimposition method for each has been devised and implemented.

Generally, for semiconductor device manufacturing, an exposure method that has a good balance between resolution performance and overlay performance is preferable, and for this reason, reduction projection type exposure apparatuses, so-called steppers, are often used at present.

The resolution performance required for future exposure equipment is 0.5
The exposure methods that can achieve this performance include, for example, a stepper using an excimer laser as a light source, a proximity type aligner-1 using X-rays as an exposure source, and an EB direct writing method. There are three methods. Of these, the former two methods are preferable from the viewpoint of productivity.

On the other hand, the overlay accuracy is generally 1/3 to 1/3 of the minimum line width for printing.
A value of 115 is required, and achieving this accuracy is generally as difficult or more difficult than achieving resolution performance.

In general, the following error factors exist in relative positioning, that is, alignment, between the pattern on the reticle surface and the pattern on the eight surfaces.

(1-1) The cross-sectional shape, physical properties, or optical characteristics of the pattern (or mark) on the eight faces of the sea urchin vary widely depending on the type of device or process.

(1-2) In order to reliably perform alignment with a predetermined accuracy in response to a variety of processes, the alignment detection system (optical system, signal processing system) must have a degree of freedom.

(1-3) In order to give the alignment optical system a degree of freedom, it is necessary to configure the projection lens and the alignment optical system independently, and as a result, the alignment between the reticle and the wafer becomes indirect.

In general, it is important to keep these error factors as small as possible (and maintain a good balance).

Next, specific examples of the above-mentioned error factors will be explained.

(2-1) By setting the alignment light to the same wavelength as the exposure wavelength, a TTL on-axis alignment system can be constructed. In such an alignment system, the projection lens has good aberration correction for this wavelength, so, for example, the alignment optical system can be placed above the reticle, and the projected image of the wafer pattern and the pattern on the reticle surface can be It is possible to align both while simultaneously observing them within the same field of view. Furthermore, exposure can be performed at the position where alignment has been completed. Therefore, there are no systematic error factors in this method.

However, this method has disadvantages in terms of process, such as there being no choice in the alignment wavelength, and in processes such as absorption resist, the signal light from the wafer is extremely attenuated.

(2-2) In an off-axis type stepper, the wafer alignment optical system can be freely designed without being subject to any restrictions of the projection lens, and this degree of freedom can enhance process adaptability. However, with this method, it is not possible to observe the reticle and wafer simultaneously; the reticle is aligned in advance to a predetermined standard using a reticle alignment microscope, and the wafer is aligned using a wafer alignment microscope (hereinafter referred to as "wafer microscope"). Alignment is performed to the reference inside the microscope.

For this reason, error factors exist between the reticle and the wafer. Furthermore, after wafer alignment, the wafer must be moved a predetermined distance (this is referred to as the "reference length" or rBase Line J) in order to overlap the pattern on the sea urchin with the projected image of the reticle. Therefore, this method results in an increase in system error factors.

In an apparatus using an alignment method that includes such system errors, it is necessary to strive to keep these error factors stable, and at the same time, periodically check and correct the amount. For example, the reference length, which is the distance between the optical axis of the projection lens and the optical axis of the alignment microscope, usually has a value of several tens of millimeters. In general, even if strict temperature control is carried out to suppress the thermal expansion of the material that connects this gap, the
It changes over time in units of m to 0.014 zm. Factors that cause such changes over time include, in addition to the above-mentioned reference length, the projection magnification of the lens, the alignment position of the reticle, and the array coordinate system of the wafer stage.

Therefore, when overlapping a reticle as a first object and a wafer as a second object, there are various error factors in overlay, such as changes in the magnification of the projection optical system over time, changes over time in the reference length, etc. In order to provide an exposure apparatus that can satisfactorily correct system errors such as changes in the arrangement coordinates of the wafer is being sought. For example, in an exposure device that exposes and transfers a pattern on a first object surface irradiated by an illumination system onto a second object surface placed on a movable stage,
An alignment pattern provided on the first object surface is irradiated, and an image of the alignment pattern is placed on the movable stage in place of the second object. formed on a third object surface having a reversible photosensitive material;
By detecting the imaging state of the image of the alignment pattern formed on the object surface, a system error is determined when the pattern on the first object surface is exposed and transferred onto the second object surface. .

That is, first, a pattern on a reticle surface as a first object is exposed and transferred onto a dummy wafer surface as a third object, and the image formation state of the transferred image at that time is used for alignment of a wafer as a second object. Detection is performed using a wafer alignment microscope, and based on the detection results at this time, system errors in the entire device are automatically or semi-automatically corrected within the device itself.

(Problems to be Solved by the Invention) The photosensitive material for dummy wafers is required to have the following characteristics.

■ Excellent coloring sensitivity for faster processing.

■Colored objects must have a certain level of contrast while capturing data using visible light in order to automatically correct system errors caused by the system.

■Have sufficient repeat durability.

Candidates for photosensitive materials that meet these conditions ■～■ are:
Examples include photosensitive resists, inorganic photochromic materials, and organic photochromic materials.

However, since photosensitive resists must undergo a development process after exposure, they cannot be automated and cannot be used repeatedly.

Inorganic photochromic materials have poor coloring sensitivity and cannot be processed at high speeds.

Furthermore, although organic photochromic materials have excellent coloring sensitivity, they fade quickly, and the contrast falls below the required level while data is being captured by exposing it to visible light.

In addition, there are many side reactions other than the desired coloring and decoloring reactions (there are drawbacks such as poor repeatability), and there are many complex synthetic routes for compounds (and material costs are high). There are also drawbacks.

As mentioned above, even if conventional materials are used, each has different drawbacks, and a photosensitive material that meets the purpose cannot be obtained.

The purpose of the present invention is to solve the problems in the conventional example described above.
To provide a dummy wafer using an organic photochromic material with excellent coloring sensitivity as a photosensitive material, in which the colored material has a contrast above a certain level during automatic correction of system errors, and has sufficient repeated durability. There is a particular thing.

(Means for solving problems) The above objects are achieved by the present invention as described below.

That is, the present invention consists of a resin containing 5 to 80% by weight of an organic photochromic material as a first layer on a substrate such as a silicon wafer, and the photochromic material is a spiropyran compound, a spironaphthoxazine compound, or a fulgide compound. The second layer has an oxygen permeability of 1.0xlO-10crrf.
This dummy wafer is characterized in that it is provided with a layer made of a polymer resin having a temperature of cm/C-.s-cmHg or less, and further provided with an antireflection film layer as a third layer.

(Function) The inventor discovered that the coloring sensitivity of the ultraviolet light used in the light source of semiconductor device exposure equipment is relatively high! As a result of repeated studies looking at the organic photochromic materials that can be used, we have found that among the organic photochromic materials, spiropyran compounds, spironaphthoxazine compounds, and fulgide compounds have a sensitivity suitable for use in dummy wafers.

In addition, as a result of investigating the cause of repeated durability failure,
It was discovered that the decomposition of the photochromic material by oxygen in the air is a factor, and as a countermeasure to this, a second layer with an oxygen permeability of 1.0 x 10-10 crd cm was formed on the first layer of the photochromic material. /crr?
・s ・cm) It has been found that by providing a polymer resin layer of 1 g or less, the repeated durability of the photochromic material can be improved.

Furthermore, it has been found that by providing a thin film having antireflection properties against exposure light as the third layer, excellent sensitivity characteristics that cannot be achieved with the first and second layers alone can be obtained.

(Preferred Embodiments) Next, the present invention will be described in more detail by citing preferred embodiments.

When forming the first layer on a substrate such as a silicon wafer,
After coating a coating solution in which a polymer resin and an organic photochromic material are dissolved in an organic solvent onto a substrate such as bare silicon or a silicon wafer that has undergone a process such as vapor deposition, the solvent contained in the resin is removed by heating and drying. do.

Further, when forming the second layer to be laminated on the first layer, first, a coating solution prepared by dissolving a resin with low oxygen permeability in a suitable solvent is coated on the substrate on which the first layer is formed. This solvent makes the substance of the first layer insoluble, and by overcoating a resin that is soluble in this solvent and has a low oxygen permeability, the second layer can be easily formed due to its insolubility in the first layer. You can.

After coating, it is heated and dried to increase the adhesion with the first layer.

Organic photochromic materials that can be used here include:
Examples of spiropyran compounds, spironaphthoxazine compounds, and fulgide compounds include the following general formula (wherein R is an unsubstituted or substituted alkyl group having 1 to 22 carbon atoms, R2 and R3 are hydrogen atoms) ,
It represents a substituent selected from an alkyl group, an alkoxy group, an aryl group, a hydroxy group, an amine group, a halogen group, a cyano group, a carboxy group, and a nitro group, and m and n represent integers of O to 5. ), and in particular, the following general formula (r) (where R1 is an unsubstituted or substituted alkyl group having 1 to 22 carbon atoms, R2 and R8 are a hydrogen atom, an alkyl group, an alkoxy group) , represents a substituent selected from an aryl group, a hydroxy group, an amino group, a halogen group, a cyano group, a carboxy group, and a nitro group, and m and n represent integers from O to 4. Those substituted with a nitro group have excellent coloring sensitivity, and among them, 1.3.3-trimethylindolino-6'-nitrobenzo of the following formula where R is a methyl group and R2 and R3 are hydrogen atoms. Bililosbilane is preferable because it has excellent sensitivity, is easy to synthesize, is relatively easy to obtain, and has a low material cost.

In addition, spironaphthoxazine compounds are represented by the following general formula (n) (where R2 is an unsubstituted or substituted alkyl group having 1 to 22 carbon atoms, R2 and R1 are hydrogen atoms, alkyl groups, alkoxy groups, It represents a substituent selected from an aryl group, a hydroxy group, an amino group, a halogen group, a cyano group, a carboxy group, and a nitro group, and m and n represent integers from O to 5. preferable.

In addition, as a fulgide compound, the following general formula (in the formula, R
1 to R1 represent a substituent selected from a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, a hydroxy group, an amino group, a halogen group, a cyano group, a carboxy group, a nitro group, and the like. ) is preferable.

Examples of the polymer resin used in the first layer include polymethyl methacrylate, polycarbonate, polystyrene, polybutyl methacrylate, etc., which have high transparency in the ultraviolet and visible regions.

In particular, polymethyl methacrylate is preferred because it has the best transparency and provides excellent resolution when reading a positioning pattern marked on a dummy wafer.

Examples of solvents include toluene, xylene, dioxane, cyclohexanone, cyclopentanone, butyl acetate, propyl acetate, methyl benzoate, methyl lactate, n-butyl cellosolve acetate, diethylene glycol monomethyl acetate, diacetone alcohol, methyl isobutyl ketone, etc. Examples include solvents with low volatility at temperatures of 100°C or higher. Further, the combined solid content concentration of the polymer and photochromic material in the coating solution is preferably in the range of 1 to 40% by weight. That is, if it is less than 1% by weight, the viscosity of the solution will be low (when coated in, it will be difficult to obtain a sufficient film thickness to obtain the desired color density, and if it exceeds 40% by weight, the viscosity of the solution will be too high). This is because coating suitability deteriorates and it becomes difficult to form a thin film.

The content of photochromic material in the first layer is 5 to 8
0% by weight is preferred. That is, if it is less than 5% by weight, the concentration of the photochromic material is too thin and the desired coloring feeling is not achieved.
If the concentration exceeds 80% by weight, the concentration of the photochromic material is too high and becomes insoluble in organic solvents.
Or even if it melts, it will crystallize within the thin film after coating and become opaque. Further, the content is preferably 20 to 60% by weight. As the coating method, a spin code method is preferable because it is convenient for coating silicon wafers.

The thickness of the first layer is preferably 0.1 to 5 LLm, preferably 0.
．． A thickness of 3 to 2 μm is desirable. That is, if it is less than 0.1 μm, the concentration of the photochromic material will be too thin when observed from above, making it impossible to obtain the desired contrast, and if it exceeds 5 μm, the contrast will improve, but with a stepper etc., the depth of focus with respect to the resist is usually 1 μm. This is because there is a risk that the mark line width during marking exposure may become unclear since the marking is designed to a certain extent.

The resin used for the second layer has an oxygen permeability of 1.0×10-”
crd ・cm/cm” ・s Polyvinyl alcohol, partially saponified polymer of polyvinyl acetate, cellulose, polyacrylonitrile, polyvinylidene chloride, nylon, etc. or copolymers thereof, which have high light transmittance in the visible and ultraviolet region of 1 cmHg or less, or Blends or copolymers of vinyl monomers and other polymerizable monomers constituting these may be mentioned.

Further, the thickness of the second layer is preferably 0.1 to 2 μm, and 0.1 to 2 μm.
If it is less than LLm, the desired oxygen barrier property cannot be obtained, and 2μ
This is because if it exceeds m, errors such as out of focus are likely to occur during marking exposure due to the difference in refractive index between the first layer and the second layer. After coating the second layer, it is desirable to increase the Z adhesion to the first fake by heating and drying it at an appropriate temperature.

Further, the composition of the first layer is not necessarily limited to the two components of the photochromic material and the polymer resin, and it is preferable to improve the performance by adding additives.

For example, the coloring sensitivity can be improved by adding a small amount of a triplet sensitizer such as benzophenone, Michler's ketone, naphthalene, anthracene, etc. within about 5% by weight.

Furthermore, repeatability can be improved by adding a tertiary amine compound or the like which is a deactivator for singlet oxygen, which is also a factor in the decomposition of photochromic materials.

In addition, phenolic compounds and polar compounds such as bisphenol A, long-chain alkylamide, carboxylic acid salts, carboxylic acid esters, and dividroxybenzophenone can be added to improve sensitivity, repeatability, and storage stability of coloring. desirable.

Further, the material for forming the third anti-reflection film layer has a refractive index lower than the refractive index of the polymer material forming the second layer (here, the refractive index for the exposure wavelength used). Preferably, the material is a good material (for example, an inorganic substance with a relatively low refractive index such as MgF or 5i02, or a material with a relatively low refractive index such as a fluorinated alkyl-containing acrylate or a fluorinated alkyl-containing epoxy).

As a film forming method, when forming a film of an inorganic substance, the vacuum evaporation method at room temperature, which is commonly used for plastic lenses, is preferable, and when forming a film of an organic substance, the first layer and the second layer It is preferable to prepare a coating liquid in the same manner as above and form a film by, for example, a spin code method. Also, the film thickness is 0
A thickness of about 0.01 to 0.2 μm is good (and it is more preferable to calculate and determine the optimum film thickness using the following formula from the exposure wavelength and the refractive index of the third layer).

ηXd=χ/4 η: Refractive index of the third layer at the exposure wavelength d: Film thickness λ: Exposure wavelength (Example) Next, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1 In the above chemical formula (II), I'1l=CH3, )12=
100 parts by weight of spironaphthoxazine with R3=H, 100 parts by weight of polymethyl methacrylate with a molecular weight of 600,000
An ethyl cellosolve acetate solution was prepared in which the total concentration of these solid components was 18% by weight in terms of parts by weight.

3 g of this 1M was coated on a silicon wafer at 25° C. using a spinner under the conditions of 300 rpm x 10 sec for the first time and 2000 rpm x 60 sec for the second coat.

Thereafter, heat treatment was performed for 20 minutes in a clean oven set at 98±2°C to form a first layer. The thickness of this first layer (coat film) was about 1 μm.

Next, the silicon wafer on which this first layer was formed was placed on a spinner (without exposing it to ultraviolet rays), and 1% of polyvinyl alcohol (degree of polymerization 1,000, degree of saponification 99 mo1%) was heated.
0% by weight aqueous solution at 300rpm x 30se for the first time
c, second coating was performed at 6000 rpm for 60 seconds. Thereafter, heat treatment was performed for 40 minutes in a clean oven set at 98±2°C.

The thickness of the second layer of this dummy wafer was about 1 μm. In addition, the oxygen permeability of polymethyl methacrylate used for the first layer is 1.15X10-10crd・cm/crr
L s-cmHg, and the oxygen permeability of the polyvinyl alcohol used for the second layer is 0°0089X10-"c
Go・cm/cGo・S・cmHg.

Furthermore, this wafer was placed in a vacuum evaporation chamber and heated at 60°C for 10-'
8 g of F2 was deposited under Torr conditions. The thickness of this third layer was approximately 0.05 μm.

In the manner described above, a dummy wafer of Example 1 having the first to third layers was obtained.

Next, the 36 filter of the 400W high pressure mercury lamp was cut.
When the above wafer was irradiated with 5 nm ultraviolet light and colored until saturated, the saturation exposure amount was 270 mJ/cr.
The saturation absorbance at rf is 1.5, and λmax =
580nm observation halogen lamp (1011I1w/
crr? ) was irradiated onto a colored object, the absorbance was 0.
．． The decay time to 5 was about 20 seconds. Also, 90℃3
The color is faded by heat treatment for a minute, and then colored by the above process.
This was repeated until the saturation absorbance decreased to 1.0, and the number of repetitions was 100.

Example 2 In place of the compound of chemical formula (U) in Example 1 above, 1 with chemical formula (I) where R+=CH5, Ra=H, and Ra=H
, 3,3-trimethylindoline-6'nitrobenzovirillospyran, and the other operations were the same as in the first formation method of Example 1 to form the first layer.

The silicon wafer on which the first layer was formed was set on a spinner without being exposed to any ultraviolet rays, and the second and third layers were formed in the same manner as in the method of forming the second and third layers in Example 1.
formed a layer. The saturation exposure amount of the obtained dummy wafer was 2
The saturated absorbance was 1.7 at 20 mJ/crrf, and the decay time to the saturated absorbance of 0.5 by halogen lamp irradiation was about 1,000 seconds.

Furthermore, when coloring was repeated 20 times, the saturated absorbance decreased to 1.0.

Example 3 R=C in the chemical formula (rI[) as a photochromic material
H3,R2=R,=H, polybutyl methacrylate having a molecular weight of 300,000 was used in a ratio of 120 parts by weight to 100 parts by weight of the tafurgide compound, and a cyclopentanone solution having a solid content concentration of 15% by weight was prepared. This was coated using a spinner in the same manner as in Example 1 to form a first layer, and the silicon wafer on which this first layer was formed was then set on a spinner without irradiating it with ultraviolet rays. The second and third layers were formed in the same manner as in the method for forming the second and third layers in Section 1.The saturated exposure amount of the obtained dummy wafer was 360 mJ/cnf, the saturated absorbance was 1.4, and a halogen lamp was used. The decay time to saturated absorbance of 0.5 due to irradiation was about 120 seconds.

Further, when fading was performed until the saturated absorbance decreased to 1.0, the number of repetitions was about 10.Example 4 The silicon wafer prepared in Example 2 was passed through a reticle using a stepper (manufactured by Canon, FPA- 4500), and exposed a linear pattern with a line width of 2 μm to 80 m using a rainbow laser beam of max = 248 nm.
Printing exposure was carried out at J/crrr. Next, the pattern was inspected on a monitor using an observation microscope, and the contrast of the exposed area to the unexposed area was measured from the video signal, which was 82%.
The value of was obtained.

Comparative Example 1 A dummy wafer of Comparative Example 1 was obtained by forming a first layer on a silicon wafer using the first layer forming method of Example 1 described above.

When the above wafer was subjected to repeated discoloration and fading in the same manner as in Example 1, the number of repetitions was 30 times.

Comparative Example 2 A dummy wafer of Comparative Example 2 was obtained by forming a first layer on a silicon wafer using the first layer forming method of Example 2 described above.

When the above wafer was used to repeat the same fading process as in Example 2, the number of repetitions was 5 times.

Comparative Example 3 Polyvinyl alcohol overcoating was performed in the same manner as in Example 1, using diphenylthiocarbazinophenylmercury, which is a type of dithizone compound, as a photochromic material in place of the compound (n) of Example 1. Furthermore, M
A dummy wafer on which gF 2 was deposited was created.

Even when irradiated with ultraviolet rays in the same manner as in Example 1, almost no coloring occurred, and the desired sensitivity could not be obtained.

Comparative Example 4 As a photochromic material, 20 parts by weight of tetrabenzopentacene, which is a type of fused polycyclic compound, and a molecular weight of 1
100 parts by weight of polystyrene of 100,000 ml in toluene solvent
A dummy wafer was prepared by dissolving 0% by weight of the solution, coating it on a silicon wafer in the same manner as in Example 1, further overcoating with polyvinyl alcohol, and further vapor-depositing NgF 2 .

When irradiated with ultraviolet rays in the same manner as in Example 1, the saturation exposure amount was 7. OOOmJ/C- had a saturation absorbance of 0.2, and the coloring sensitivity was very low.

Comparative Example 5 A dummy wafer of Comparative Example 5 was obtained by forming a first layer and a second layer on a silicon wafer using the method for forming the first layer and second layer of Example 1 described above.

When the same coloring test as in Example 1 was conducted using the above wafer, the saturation exposure amount was 300 mJ/cm', which was longer than in Example 1.

Comparative Example 6 A dummy wafer of Comparative Example 6 was obtained by forming a first layer and a second layer on a silicon wafer using the method for forming the first layer and second layer of Example 2 described above.

When the same coloring test as in Example 2 was conducted using the above wafer, the saturation exposure amount was 250 mJ/cm' and the irradiation time was longer than in Example 2.

(Effects of the Invention) As explained above, the dummy wafer according to the present invention has the following effects.

(1) By selecting a spiropyran compound, a spironaphthoxazine compound, or a fulgide compound as the first layer photochromic material, it has sufficient coloring sensitivity to ultraviolet rays, so it can be used as a resist in semiconductor exposure equipment such as a stepper. It is possible to perform marking under high-speed conditions similar to those used for exposure, and it is possible to improve alignment accuracy without adversely affecting semiconductor manufacturing efficiency.

(2) Furthermore, by coating the first layer with a similar compound and overcoating with a layer with low oxygen permeability as the second N, it is possible to prevent decomposition of the photochromic material and improve repeatability. Since a large number of markings can be made on a dummy wafer, the cost of dummy wafers can be reduced, and the storage of dummy wafers does not require a large amount of space.

(3) Furthermore, as the first layer photochromic material, 1,
If 3.3-trimethylindolino-6' nitrospirate penzobisosubiran is used, it is possible to provide a dummy wafer with excellent sensitivity and at low cost.

(4) Furthermore, by providing an anti-reflection film layer as the third layer, it becomes possible to efficiently (without waste) absorb the exposure light into the photochromic material. Inspection time can be shortened.

Claims (7)

[Claims] (1) On a substrate such as a silicon wafer, 5~
It is made of a resin containing 80% by weight of an organic photochromic material, the photochromic material forms a layer selected from the group consisting of a spiropyran compound, a spironaphthoxazine compound, and a fulgide compound, and the second layer has an oxygen permeability. 1.0 x 10^-^1^0cm^2cm
1. A dummy wafer comprising a layer made of a polymer resin having a temperature of /cm^2・s・cmHg or less, and further provided with an antireflection film layer as a third layer. (2) The organic photochromic material has the general formula (I) ▲ Numerical formula, chemical formula, table, etc. ▼ (I) (In the formula, R_1 is an unsubstituted or substituted alkyl group having 1 to 22 carbon atoms, R_2 and R_3 are hydrogen atoms, Represents a substituent selected from an alkyl group, a hydroxy group, an amino group, an alkoxy group, an aryl group, a halogen group, a cyano group, a carboxy group, and a nitro group, and m and n represent integers from 0 to 4.)
The dummy wafer according to claim 1, which is a spiropyran compound represented by: (3) The dummy wafer according to claim 1, wherein the spiropyran compound is 1,3,3-trimethylindolino-6'-nitrobenzopyrillospiran. (4) The dummy wafer according to claim 1, wherein the first layer resin is polymethyl methacrylate. (5) The dummy wafer according to claim 1, wherein at least one component of the polymer resin of the second layer is polyvinyl alcohol or a copolymer of polyvinyl alcohol and another polymer. (6) The dummy wafer according to claim 1, wherein the first layer contains at least one compound in addition to the photochromic material and the polymer resin. (7) The dummy wafer according to claim 1, wherein the third layer is an antireflection film made of a deposited film of MgF_2 or SiO_2.