Method for double-sided exposure of optical transparent quartz wafer

Abstract

The invention relates to the technical field of micro-nano machining photoetching, in particular to a method for double-sided exposure of an optical transparent quartz wafer, the double-sided polished transparent substrate quartz wafer has high permeability, can penetrate through all or part of visible spectrum illumination radiation to achieve the optical transparent effect, and can be applied to the field of photolithography. Meanwhile, the photoresist has a very strong ultraviolet light transmission effect, the quartz wafer is a transparent substrate, and after the photoresist on the front surface is irradiated by ultraviolet light, the ultraviolet light is transmitted to the back surface of the wafer and is absorbed, so that the product obtained in this way has higher precision than that of exposure twice on a single surface due to the fact that a double-layer pattern is obtained on the single-layer transparent quartz wafer; meanwhile, the technological process is simplified, the efficiency is improved, and the technical problems that in the prior art, double-sided exposure of the optical transparent quartz wafer depends on expensive precision equipment with a complex structure, so that the technological cost is high, and the flow is tedious are solved.

Description

Technical Field

[0001] The invention relates to the technical field of micro-nano processing lithography, and in particular to a method for double-sided exposure of an optically transparent quartz wafer. Background Art

[0002] Exposure is the use of light to project the pattern on the mask onto the photoresist through an optical system to achieve pattern transfer. It is one of the important processes in the integrated circuit lithography process. With the continuous updating and iteration of semiconductor products, single-sided lithography can no longer meet the growing manufacturing needs, and the development of double-sided lithography is particularly important. At present, double-sided lithography is mostly completed using double-sided exposure machines. According to the different alignment principles, it can be roughly divided into two types: one is to use an infrared microscope to align the substrate with the mask on the other side, and a special infrared imaging device is required to achieve it, with low accuracy and an alignment accuracy of 2-3um; the other is to use two sets of objective lenses to simultaneously observe and align the upper and lower surfaces of the substrate and the mask, but this method is more expensive.

[0003] In summary, the double-sided exposure of optically transparent quartz wafers used in the prior art relies on complex and expensive precision equipment, resulting in high process costs and cumbersome procedures. Summary of the invention

[0004] The purpose of the present invention is to provide a method for double-sided exposure of an optically transparent quartz wafer, aiming to solve the technical problem that the double-sided exposure of an optically transparent quartz wafer used in the prior art relies on complex and expensive precision equipment to complete, resulting in high process costs and cumbersome procedures.

[0005] To achieve the above object, the present invention adopts a method for double-sided exposure of an optically transparent quartz wafer, comprising the following steps:

[0006] Step 1: Select a quartz wafer and apply photoresist on both sides of the quartz wafer;

[0007] Step 2: Fix the mask on the substrate stage of the proximity lithography machine, align the mask with the quartz wafer through the automatic alignment system, and project the pattern on the mask onto the quartz wafer through the optical system;

[0008] Step 3: Use ultraviolet light from a proximity photolithography machine to irradiate the front side of the quartz wafer. After the photoresist on the front side is irradiated by ultraviolet light, the ultraviolet light is transmitted to the back side of the transparent wafer and is fully absorbed, thereby obtaining a double-sided exposed quartz wafer;

[0009] Step 4: Develop the double-sided exposed quartz wafer with a developer, and then clean it to obtain a double-sided patterned quartz wafer with markings.

[0010] The selected quartz wafer is a double-sided polished optically transparent substrate quartz wafer, and the method of coating the photoresist on both sides of the optically transparent substrate quartz wafer is a spin coating process.

[0011] The photoresist coated on the front and back sides of the optically transparent substrate quartz wafer is a positive photoresist with a thickness of 1.5-2 μm.

[0012] 4. The method for double-sided exposure of an optically transparent quartz wafer as claimed in claim 3, characterized in that:

[0013] When the front side of the quartz wafer is irradiated with ultraviolet light of a proximity photolithography machine, the wavelength of the ultraviolet light of the proximity photolithography machine is 420nm-450nm, and the ultraviolet light curve is i line + h line.

[0014] The specific method of developing the double-sided exposed quartz wafer with a developer and then washing it to obtain a double-sided patterned quartz wafer with markings is as follows:

[0015] The double-sided exposed quartz wafer is immersed in TMAH developer, and the developing method is immersion. Then, the surface of the quartz wafer is cleaned to obtain a double-sided patterned quartz wafer with markings.

[0016] The cleaning liquid used to clean the developed quartz wafer is deionized water.

[0017] The invention discloses a method for double-sided exposure of an optically transparent quartz wafer. The method comprises the following steps: selecting a quartz wafer, coating the front and back surfaces of the quartz wafer with photoresist, fixing a mask plate on a substrate stage of a proximity photolithography machine, aligning the mask and the quartz wafer by an automatic alignment system, projecting a pattern on the mask plate onto the quartz wafer by an optical system, irradiating the front surface of the quartz wafer with ultraviolet light, and transmitting the ultraviolet light to the back surface of the transparent wafer after the photoresist on the front surface is irradiated with the ultraviolet light, and then completely absorbing the ultraviolet light, thereby obtaining a double-sided exposed quartz wafer, developing the double-sided exposed quartz wafer with a developer, and then washing the double-sided exposed quartz wafer to obtain a double-sided patterned quartz wafer with markings. The double-sided exposure method of the invention is disclosed. The polished transparent substrate quartz wafer has high transmittance and can achieve optical transparency by transmitting all or part of the visible spectrum light radiation. At the same time, because the photoresist has a strong ultraviolet light transmission effect, the quartz wafer is a transparent substrate. After the front photoresist is irradiated with ultraviolet light, the ultraviolet light is transmitted to the back of the wafer and absorbed. The product obtained in this way has a double-layer pattern on a single-layer transparent quartz wafer, which has higher accuracy than twice exposure on one side. At the same time, it also simplifies the process flow and improves efficiency. It solves the technical problem that the double-sided exposure of the optically transparent quartz wafer used in the prior art relies on complex and expensive precision equipment to complete, resulting in high process costs and cumbersome processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 It is a flow chart of the steps of the method for double-sided exposure of an optically transparent quartz wafer of the present invention.

[0020] Figure 2 It is a schematic diagram of spin coating of a transparent quartz wafer according to the present invention.

[0021] Figure 3 It is a schematic diagram of transparent quartz wafer exposure of the present invention.

[0022] Figure 4 It is a line graph of the transmittance of the photoresist of the present invention at different wavelengths.

[0023] Figure 5 It is a schematic diagram of transparent quartz wafer development of the present invention.

[0024] Figure 6 These are the final front and back effect diagrams of the transparent quartz wafer after double-sided exposure of the present invention. DETAILED DESCRIPTION

[0025] Embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0026] See also Figure 1 to Figure 6 ,in Figure 1 is a flow chart of the steps of the method for double-sided exposure of an optically transparent quartz wafer of the present invention, Figure 2 is a schematic diagram of the spin coating of a transparent quartz wafer of the present invention, Figure 3 is a schematic diagram of transparent quartz wafer exposure of the present invention, Figure 4 is a line graph of the transmittance of the photoresist of the present invention at different wavelengths, Figure 5 is a schematic diagram of transparent quartz wafer development of the present invention, Figure 6 These are the final front and back effect diagrams of the transparent quartz wafer after double-sided exposure of the present invention.

[0027] The present invention provides a method for double-sided exposure of an optically transparent quartz wafer, comprising the following steps:

[0028] S1, selecting a quartz wafer, and coating the front and back sides of the quartz wafer with photoresist respectively;

[0029] For this specific embodiment, the selected quartz wafer is a double-sided polished optically transparent substrate quartz wafer, which can transmit all or most of the visible spectrum light radiation, or can transmit the full spectrum light mixed with different proportions of red, yellow and blue. As the name suggests, the optically transparent quartz wafer of the present invention can transmit all or part of the visible spectrum light radiation to achieve the effect of optical transparency;

[0030] The photoresist coated on both sides of the optically transparent quartz wafer is a positive photoresist with a thickness of 1.5-2μm. Figure 2 The method of coating photoresist on both sides of the optically transparent substrate quartz wafer is a spin coating process; specifically, the wafer is placed on a turntable, vacuum-adsorbed wafer, photoresist is suspended in the center of the wafer, and it is spread naturally. The photoresist is first rotated at a low speed to cover the edge of the wafer, and then the excess photoresist at the edge is thrown off at a high speed. The setting of the rotation speed depends on the properties of the photoresist (viscosity, evaporation rate, surface tension, wafer size, etc.). Generally speaking, the faster the speed of the photoresist and the longer the time, the thinner the photoresist.

[0031] S2, fix the mask on the substrate stage of the proximity lithography machine, align the mask and the quartz wafer through the automatic alignment system, and project the pattern on the mask onto the quartz wafer through the optical system;

[0032] For this specific implementation method, combined with Figure 3 , a proximity lithography machine is used as the exposure device. A certain air gap is left between the mask and the photoresist in the proximity lithography machine. The proximity exposure avoids direct contact and friction between the mask and the photoresist, plays a certain protective role on the mask, and prolongs the service life of the mask;

[0033] Compared with proximity lithography machines, the mask plate and the wafer in contact lithography machines are in close contact. The direct contact between the mask plate and the photoresist will affect the quality of the mask plate. The photoresist is easy to adhere to the mask plate, and the contact friction will also cause certain damage to the mask plate.

[0034] Therefore, the proximity lithography machine has the advantages of easy operation, simple process and long service life.

[0035] S3, irradiating the front side of the quartz wafer with ultraviolet light from a proximity photolithography machine. After the photoresist on the front side is irradiated with ultraviolet light, the ultraviolet light is transmitted to the back side of the transparent wafer and is fully absorbed, thereby obtaining a double-sided exposed quartz wafer;

[0036] According to this specific implementation method, the designed mask is fixed on the substrate stage of the exposure device, the mask and the wafer are aligned by an automatic alignment system, the pattern on the mask is projected onto a transparent quartz wafer coated with photoresist by an optical system, and UV ultraviolet light is used to irradiate the front side of the wafer. Since the photoresist has a strong ultraviolet light transmission effect and the quartz wafer is a transparent substrate, after the front side photoresist is irradiated with ultraviolet light, the ultraviolet light is transmitted to the back side of the wafer and absorbed;

[0037] Thus, the exposure is performed once, and the result of exposure on both the front and back sides is obtained. At the same time, the product obtained by the double-sided exposure method of the present invention has a higher precision than that of exposing one side twice, because a double-layer pattern is obtained on a single-layer transparent quartz wafer. At the same time, the process flow is simplified, the efficiency is improved, and the market acceptance is relatively high;

[0038] In addition, according to actual needs, appropriate process parameters such as exposure energy, exposure intensity and exposure time can be comprehensively evaluated.

[0039] Combination Figure 4 , Figure 4 The figure shows the line graph of UV transmittance at different wavelengths when the quartz wafer is exposed on both sides. The UV wavelength, incident light intensity and transmitted light intensity can be measured using a UV spectrophotometer and an illuminometer. The statistics are summarized as follows: Figure 4 shown.

[0040] UV transmittance refers to the degree of UV light transmission of a material, usually expressed as T, T = I / I0, where I0 is the intensity of incident light and I is the intensity of transmitted light. In the 190nm to 380nm band, UV transmittance is 0, and in the 380nm to 780nm band, it is maintained between 80% and 90%; in the 420nm to 450nm band, UV transmittance increases slowly. In addition, different UV wavelengths have different absorbances.

[0041] Absorbance is the logarithm of the ratio of the incident light intensity before the light passes through the medium to the transmitted light intensity after the light passes through the medium, expressed as A, that is, A = lg (I0 / I). The present invention refers to the ultraviolet light incident on the front of the quartz wafer and then transmitted to the back of the quartz wafer. The wavelength of the UV light in the present invention is lower than 450nm, and is Figure 4 The UV light wavelength can be preferably selected to be 420nm to 450nm, and the UV light transmittance is 80% to 83%.

[0042] S4, developing the double-sided exposed quartz wafer with a developer, and then washing it to obtain a double-sided patterned quartz wafer with markings.

[0043] For this specific implementation method, combined with Figure 5, completely immerse the exposed quartz wafer in TMAH developer, then rinse with deionized water, and use the property that positive photoresist can be dissolved in the exposed area to obtain a double-sided patterned quartz wafer with markings. The development time depends on the type of photoresist, the thickness of the photoresist, the exposure amount, and the concentration of the developer. Generally, the development time for photoresist with a thickness of less than 2μm is no more than 2min.

[0044] Combination Figure 6 , Figure 6 (a) is the final front view of the transparent quartz wafer after exposure. Figure 6 (b) is the final back side effect of the transparent quartz wafer after exposure. The front side of the wafer is marked with "UP" and "+++" after ultraviolet exposure, and the back side of the wafer is also marked with corresponding marks after exposure to transmitted ultraviolet light. Thus, a single exposure achieves double-sided patterning results. This double-sided exposure method avoids the misalignment of marks or patterns caused by exposing the two sides separately, and is completed in one exposure, which not only simplifies the process flow, improves production efficiency, but also reduces production costs.

[0045] A method for double-sided exposure of an optically transparent quartz wafer of the present embodiment is used. A quartz wafer is selected, and photoresist is coated on the front and back sides of the quartz wafer respectively. The mask is fixed on a substrate stage of a proximity photolithography machine. The mask and the quartz wafer are aligned by an automatic alignment system. The pattern on the mask is projected onto the quartz wafer by an optical system. The front side of the quartz wafer is irradiated with ultraviolet light of the proximity photolithography machine. After the photoresist on the front side is irradiated with ultraviolet light, the ultraviolet light is transmitted to the back side of the transparent wafer and is fully absorbed, thereby obtaining a double-sided exposed quartz wafer. The double-sided exposed quartz wafer is developed with a developer, and then washed to obtain a double-sided patterned quartz wafer with markings. The double-sided exposed quartz wafer of the present invention is used. The surface-polished transparent substrate quartz wafer has high transmittance and can achieve optical transparency by transmitting all or part of the visible spectrum light radiation. At the same time, because the photoresist has a strong ultraviolet light transmission effect, the quartz wafer is a transparent substrate. After the front photoresist is irradiated with ultraviolet light, the ultraviolet light is transmitted to the back of the wafer and absorbed. The product obtained in this way has a double-layer pattern on a single-layer transparent quartz wafer, which has higher accuracy than twice exposure on a single side. At the same time, it also simplifies the process flow and improves efficiency. It solves the technical problem that the double-sided exposure of the optically transparent quartz wafer used in the prior art relies on complex and expensive precision equipment to complete, resulting in high process costs and cumbersome processes.

[0046] What is disclosed above is only a preferred embodiment of the present invention, and it certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A method for double-sided exposure of an optically transparent quartz wafer, characterized in that: The following steps are involved: Step 1: Select a quartz wafer and apply photoresist on the front and back sides of the quartz wafer respectively; Step 2: Fix the mask on the substrate stage of the proximity lithography machine, align the mask with the quartz wafer through the automatic alignment system, and project the pattern on the mask onto the quartz wafer through the optical system; Step 3: Use ultraviolet light from a proximity photolithography machine to irradiate the front side of the quartz wafer. After the photoresist on the front side is irradiated by the ultraviolet light, the ultraviolet light is transmitted to the back side of the transparent wafer and is fully absorbed, thereby obtaining a double-sided exposed quartz wafer; Step 4: Develop the double-sided exposed quartz wafer with a developer, and then clean it to obtain a double-sided patterned quartz wafer with markings.

2. The method for double-sided exposure of an optically transparent quartz wafer according to claim 1, characterized in that: The selected quartz wafer is a double-sided polished optically transparent substrate quartz wafer, and the method of coating the photoresist on both sides of the optically transparent substrate quartz wafer is a spin coating process.

3. The method for double-sided exposure of an optically transparent quartz wafer as claimed in claim 2, characterized in that: The photoresist coated on both sides of the optically transparent quartz substrate is a positive photoresist with a thickness of 1.5-2 μm.

4. The method for double-sided exposure of an optically transparent quartz wafer as claimed in claim 3, characterized in that: When the front side of the quartz wafer is irradiated with ultraviolet light of a proximity photolithography machine, the wavelength of the ultraviolet light of the proximity photolithography machine is 420nm-450nm, and the ultraviolet light curve is i line + h line.

5. The method for double-sided exposure of an optically transparent quartz wafer as claimed in claim 4, characterized in that: The double-sided exposed quartz wafer is developed with a developer and then cleaned to obtain a double-sided patterned quartz wafer with markings as follows: The double-sided exposed quartz wafer is immersed in TMAH developer, and the developing method is immersion. Then, the surface of the quartz wafer is cleaned to obtain a double-sided patterned quartz wafer with markings.

6. The method for double-sided exposure of an optically transparent quartz wafer according to claim 5, characterized in that: The cleaning solution used to clean the developed quartz wafer is deionized water.

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