JPH045815A - Dummy wafer and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a photochromic material layer whose stability is excellent and whose absorbance is high by a method wherein a resin layer containing an organic photochromic material is formed on a substrate; a heat treatment is executed in a vacuum; a polyvinyl alcohol layer is formed and the substrate is heated in a vacuum. CONSTITUTION:The following are formed on a substrate in the following order: a first layer composed substantially of a resin containing 30 to 80wt.% of an organic photochromic material; and a second layer composed substantially of polyvinyl alcohol whose oxygen transmission factor is at 1X10<-10> cm<3>.cm/ cm<2>.s.cmHg or lower and which does not contain H2O substantially. When the first layer is formed, the substrate is coated with a coating liquid formed by dissolving the resin and the organic photochromic material in an organic solvent, and, after that, a heat treatment is executed in a vacuum. When the second layer is laminated on the first layer, the substrate on which the first layer has been formed is coated with a coating liquid formed by dissolving polyvinyl alcohol in a solvent which does not dissolve the first layer. After this coating operation, the substrate is heat-treated in a vacuum.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a dummy wafer used in an apparatus for manufacturing semiconductor devices such as ICs or LSIs, and a method for manufacturing the same. [Conventional technology] Conventionally, in exposure equipment for manufacturing semiconductor devices such as IC or LSI, there are two factors: resolution performance and overlay performance.
Two basic performance improvements are required. The former is the ability to form fine patterns on the photoresist surface coated on the semiconductor substrate (hereinafter referred to as "wafer"), and the latter is the ability to form fine patterns on the pattern formed on the wafer surface in the previous process. On the other hand, it is the ability to accurately align and transfer the pattern on the photomask. Exposure apparatuses are broadly classified into, for example, contact, proximity, mirror 1:1 projection, stepper, and X-ray aligner, depending on their exposure method, and the optimum overlaying method has been devised and implemented for each of them. Generally, for the manufacture of semiconductor devices, an exposure method that has a good balance between resolution performance and overlay performance is preferable, and for this reason, reduction projection type exposure devices, 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 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 a pattern on a reticle surface and a pattern on a wafer surface. (1-1) The cross-sectional shape, physical properties, or optical characteristics of a pattern (or mark) on a wafer surface vary widely depending on the type of device or process. (1-2) In order to ensure alignment with a predetermined accuracy in response to various 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 minimize these error factors 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 the alignment optical system can be placed above the reticle, for example, and the projected image of the wafer pattern and the pattern on the reticle surface can be Both can be aligned while simultaneously observing 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, in this method, there is no choice in the alignment wavelength, and in processes such as absorption resist, the signal light from the wafer is extremely attenuated, and has disadvantages in terms of the process. (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 must be aligned in advance to a predetermined standard using a reticle alignment microscope, and the wafer must be aligned using a wafer alignment microscope (hereinafter referred to as "wafer microscope"). Alignment is performed to the reference inside the microscope. Therefore, an error factor exists between the reticle and the wafer. Furthermore, after wafer alignment, in order to overlap the wafer pattern with the projected image of the reticle, a predetermined distance (this is
The wafer must be moved. 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 try to maintain these error factors stably, 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, is usually several tens of mm.
is the value of In general, even if strict temperature control is carried out to suppress the thermal expansion of the material that connects this space, it is generally between 0.1 μm and 0.1 μm. O1
It changes over time in units of μm. Factors that cause such changes over time include, in addition to the reference length mentioned above, the projection magnification of the lens, the alignment position of the reticle, and the arrangement 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 magnification over time of the projection optical system, changes over time in the reference length, and changes in the reference length over time. In order to provide an exposure system that can consistently perform highly accurate overlay by correcting system errors such as changes over time in the arrangement coordinates of the wafer X and Y stages, we use so-called dummy wafers to correct system errors 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, and is sensitive to the irradiation light of the alignment pattern and can be written and erased. 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, system errors in the entire device are automatically or semi-automatically corrected within the device itself. [Problems to be Solved by the Invention] Incidentally, the photosensitive material for dummy wafers is required to have the following characteristics. - Excellent coloring sensitivity with ultraviolet light for faster processing. ■In order to automatically correct system errors caused by machines,
Colored objects must have a certain level of contrast while capturing data using visible light. ■Have sufficient repeated 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 require visual processing after exposure, they cannot be automated and cannot be used repeatedly. Inorganic photochromic materials have poor coloring sensitivity and cannot be processed at high speed. Furthermore, although organic photochromic materials have excellent coloring sensitivity, they fade quickly, resulting in less than the required contrast while capturing data by exposing them to visible light, and they decompose rapidly, making it difficult to improve their durability over repeated use. There is a drawback that there is no As mentioned above, even if conventional materials are used, each has different drawbacks, and a desired photosensitive material cannot be obtained. The present inventor has conducted various studies on the drawbacks of the organic photochromic material, which is one of the photosensitive materials, and its overcoat member, and has clarified the cause of the drawbacks as follows. ■If even a small amount of organic solvent remains in the layer containing the organic photochromic material, the stability of the colored product may decrease and the color may fade more quickly. ■Beta is required to remove the organic solvent and adhere the organic photochromic material layer to the wafer, but if this is done in air, the organic photochromic material will decompose with the oxygen in the air and the coloring density will drop. ■Organic photochromic materials decompose due to oxygen in the air, resulting in poor durability over repeated use. ■Organic photochromic materials decompose due to moisture in the air, resulting in poor durability over repeated use. In view of the above-mentioned problems, an object of the present invention is 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 while automatically correcting system errors. An object of the present invention is to provide a dummy wafer having sufficient repeated durability and a method for manufacturing the same.

[Means to solve the problem]

The present invention includes a step of forming a first layer substantially made of a resin containing 30 to 80% by weight of an organic photochromic material on a substrate, and a first vacuum heating of the substrate provided with the first layer. A dummy wafer comprising a heating step, a step of forming a second layer substantially made of polyvinyl alcohol on the first layer, and a second vacuum heating step of vacuum heating the substrate provided with the first layer and the second layer. This is a manufacturing method. The present invention also provides a first layer (on a substrate) consisting essentially of a resin containing 30 to 80% by weight of an organic photochromic material.
organic photochromic material layer), and oxygen permeability is I
This is a dummy wafer having, in this order, a second layer (overcoat layer) substantially made of polyvinyl alcohol that has a temperature of less than X 10-"cm3 cm/cm2-s-cmHg and does not substantially contain H2O.First layer When forming the film, a coating liquid in which a resin and an organic photochromic material are dissolved in an organic solvent is coated on a substrate such as bare silicon or a silicon wafer that has been subjected to a process such as vapor deposition, and then heat-treated in a vacuum. By removing the solvent contained in the binder without causing decomposition of the organic photochromic material, it is possible to increase the color density and prolong the time until fading.When laminating the second layer on the first layer, the first layer is A coating liquid in which polyvinyl alcohol (hereinafter referred to as PVA) is dissolved in an insoluble solvent is coated on the substrate on which the first layer is formed.As a coating method, a known coating technique may be applied as appropriate.After coating heat-treats the substrate in vacuum.This increases the adhesion between the first layer and the second layer, and removes oxygen and moisture (H2O and 0H-) in the air contained in the material of the second layer. By removing these, it is possible to suppress the decomposition of the photochromic material due to oxygen and moisture.If a surfactant is mixed into the material in either the first layer or the second layer, it will be difficult to heat the material. Oxygen and moisture can be quickly removed by drying, and more preferably alcohols such as methanol and ethanol or commercially available surfactants can be used as the surfactant.The amount added is determined to suppress the generation of bubbles in each layer. A preferable example of the organic photochromic material that can be used in the present invention is the organic photochromic material that can be used in the present invention. ) spironaphthoxin, (II) benzobirilosbilane, (m) fulgide, etc. (I) (U) (where R, = H, alkyl, alkoxy, R2 =
H, halogen, alkyl, nitro, nitroalkoxy,
R3=H, alkyl, alkoxycarbonylalkyl) The resin used for the first layer is preferably a polymeric resin that is highly transparent in the ultraviolet and visible regions, such as polymethyl methacrylate, polycarbonate, polystyrene, and the like. The solvent is preferably a low-volatility solvent with a boiling point of 100° C. or higher, such as toluene, xylene, ethyl cellosolve acetate, diethyl glycol monomethyl acetate. Further, it is preferable that the concentration of the solid content of the resin and the organic photochromic material in the solution is 40% or less. In the first layer, the ratio of the organic photochromic material to the resin is preferably 30 to 80% by weight, more preferably 80 to 200 parts by weight based on 100 parts by weight of the resin. As the coating method, a spin code method is preferable because it is convenient for coating silicon wafers. The polymer used for the second layer is preferably one having an oxygen transmittance of 1.0×1Cm3・Cll1/Cm2・5-CmHg or less and a high light transmittance in the visible ultraviolet region,
Polyvinyl alcohol that satisfies this condition and is soluble in polar solvents such as water and alcohol is preferably used. Furthermore, in order to improve durability (2) polyvinyl alcohol can be acetalized to improve hardness and repeat durability.
This can be done by reacting in a solution at 40 to 50°C using PVA and replacing it with the OH group of PVA. In addition, the film thickness of the second layer is 0.1 to 2 μm to prevent errors in the position of the first layer marks due to refraction in the second layer.
It is desirable that the range is within the range of m. After coating the second layer, vacuum beta is applied at high temperature to increase the adhesion with the first layer, but at that time the organic photochromic material in the first layer is also decomposed. The acetalized polyvinyl alcohol in the second layer also does not decompose. The vacuum heating conditions for the first layer and the second layer are 10-3 to 10
-'Torr, 90 to 100°C, and about 30 minutes are preferable. By using a vacuum instead of an inert gas atmosphere for the heat treatment, not only oxygen and organic solvents in each layer but also extremely small amounts of residual moisture can be removed. Organic solvents are quickly removed from the coating film, and gases such as carbon dioxide, oxygen, and nitrogen are removed relatively quickly, but water adsorbed on the coating film surface tends to remain the most difficult to remove. . The present invention uses not only vacuum but also heating to remove even moisture. [Example] Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 In the above chemical formula (1), R1=Me, R2=R3=
For 100 parts by weight of spironaphthoxazine as H,
A proportion of 100 parts by weight of polymethyl methacrylate having a molecular weight of 2 million was added, and 3% by weight of methanol was added to prepare an ethyl cellosolve acetate solution having a total concentration of these solids of 18% by weight. 3 g of this solution was placed on a silicon wafer at 25°C using a spinner, the first time was 300 rpm for 10 seconds, the second time was 2 times.
Coating was carried out under the conditions of 000 rpm x 60 seconds. After that, a vacuum evaporator (vacuum degree 5X 1
The first layer was formed by heat treatment for 20 minutes at a temperature of O-IeTorr (output: 0.2 kW). The thickness of this first layer (coat film) was 0.93 μm, and the difference in unevenness was 30 to 50 nm. Next, the silicon wafer on which the first layer was formed was set on a spinner without exposing it to any ultraviolet rays, and polyvinyl alcohol (manufactured by Kishida Chemical Co., Ltd., polymerization degree 1000, saponification degree 99) was placed on a spinner.
10% aqueous solution of mo1%) was heated at 300 rpm for the first time
30sec, 2nd 6000rpm x 60sec
It was coated under the following conditions. Thereafter, heat treatment was performed for 40 minutes under the same conditions as for the first layer in a vacuum evaporator set at 98±2° C. to obtain a dummy wafer having the first layer and the second layer. Furthermore, the dummy wafer was immersed for 15 minutes in a treatment solution consisting of 20.6 g of sulfuric acid, 25.3 g of sodium sulfate, 9.5 g of formalin, and 44.6 g of water to acetalize it, and then dried by heating. A dummy wafer of No. 1 was obtained. The thickness of the second layer of this dummy wafer was 1.0 μm, and the difference in unevenness was 80 to 1100 nm. The oxygen permeability of polymethyl methacrylate used in the first layer is 1.15.
X 1 leaf 1ecm"cm/cm"s-cmHg,
The oxygen permeability of the polyvinyl alcohol used in the second layer is 0.0089X 1×10-18 am”-cm/am2
・It was below s-CmHg. In addition, the moisture permeability of the second layer is several percent for one month at a relative humidity of 80%.
Met. When a dummy wafer was irradiated with an 800 mJ ultraviolet light source to obtain a saturated amount of color, the saturated absorbance was 5.0.
The decay time until the saturation absorbance reached 1.0 with 600 nm light was about 20 seconds. Further, when the coloring and fading process was repeated 150 times, the saturated absorbance decreased to 1.0. In this example, the ratio of the organic photochromic material in the first layer was 50%, but even if this was set to 80%, there was no difference in the absorbance and the number of repetitions. Due to the hardening effect of the present invention, not only water resistance was improved, but also acid resistance and oil resistance were improved, and the surface strength of the overcoat member (second layer) was increased. Example 2 In place of the compound of chemical formula (I), R in chemical formula (I[)
1, 3.3″ with 1=Me, R2=H, R3=NO2
A dummy wafer of Example 2 was prepared in the same manner as in Example 1, except that -trimethylindolino-6''-nitrobenzobyrillospiran was used, and acetalization was performed before vacuum heating of the second layer. It is preferable to perform vacuum heat treatment after acetalization because the solvent and moisture in each layer can be removed more thoroughly.The obtained dummy wafer had a saturated absorbance of 7.0 and 600
The decay time to saturation absorbance 1.0 with nm light is 200
It was 0 seconds. Further, when the coloring and fading process was repeated 50 times, the saturated absorbance decreased to 1.0. As described above, it has been confirmed that the dummy wafers of the examples have 50 to 200% higher durability than dummy wafers produced by conventional manufacturing methods. In addition, by combining vacuum heat treatment and polyvinyl alcohol acetalization, the mechanical strength and environmental resistance of the dummy wafer can be increased, and the optical properties are maintained without deteriorating the spectral transmittance characteristics of the overcoat material. can do. Further, the repeat durability can be sufficiently improved without acetalizing polyvinyl alcohol. [Effects of the Invention] According to the present invention, a dummy wafer having a photochromic material layer with excellent stability and high absorbance was obtained. This makes alignment work extremely easy and allows for highly accurate alignment.

Claims (1)

[Claims] 1. Forming a first layer substantially consisting of a resin containing 30 to 80% by weight of an organic photochromic material on a substrate; heating the substrate provided with the first layer in vacuum; a first vacuum heating step; a step of forming a second layer substantially made of polyvinyl alcohol on the first layer; a second vacuum heating of vacuum heating the substrate provided with the first layer and the second layer; A method for manufacturing a dummy wafer including a process. 2. The method according to claim 1, further comprising the step of acetalizing the polyvinyl alcohol between the step of forming the second layer and the second vacuum heating step. 3. On the substrate, a first layer consisting essentially of a resin containing 30 to 80% by weight of an organic photochromic material, and an oxygen permeability of 1×10^-^1^8 cm^3 cm/cm^
A dummy wafer having, in this order, a second layer substantially consisting of polyvinyl alcohol having a temperature of 2·s·cmHg or less and substantially free of H_2O. 4. The dummy wafer according to claim 3, wherein the polyvinyl alcohol is acetalized polyvinyl alcohol.