CN116047869A

CN116047869A - Processing method of photoetching mother board for electroforming and micro-fluidic chip

Info

Publication number: CN116047869A
Application number: CN202211721910.XA
Authority: CN
Inventors: 宋娇阳; 王博; 杨文军; 罗明辉
Original assignee: Beijing Targeting One Biotechnology Co ltd; Xinyi Manufacturing Technology Beijing Co ltd
Current assignee: Beijing Targeting One Biotechnology Co ltd; Xinyi Manufacturing Technology Beijing Co ltd
Priority date: 2022-12-30
Filing date: 2022-12-30
Publication date: 2023-05-02

Abstract

The invention provides a processing method of a photoetching motherboard for electroforming and a micro-fluidic chip, wherein the processing method comprises the following steps: an exposure component forming step, namely placing a mask on a first side surface of a transparent glass substrate, and spin-coating negative photoresist on one side of the mask far away from the glass substrate to form an exposure component consisting of the glass substrate, the mask and the photoresist; an exposure component transferring step, namely transferring the exposure component into a first photoetching clamping groove of a placing platform of a photoetching machine, and enabling a glass substrate of the exposure component to face one side of a UV light source of the photoetching machine; and an exposure step, namely controlling the photoetching machine to start the UV light source for photoetching, and forming a photoetching mother board for electroforming after the exposure component is exposed. The groove formed at the negative photoresist after exposure is in an inverted trapezoid shape, namely, the bottom edge close to one side of the glass substrate is shorter and the bottom plate far away from one side of the glass substrate is longer, so that the subsequent injection molding and demolding can be facilitated, and the pulling phenomenon of a pulling die can be effectively avoided.

Description

Processing method of photoetching mother board for electroforming and micro-fluidic chip

Technical Field

The invention belongs to the technical field of photoetching, and particularly relates to a processing method of a photoetching mother board for electroforming and a microfluidic chip.

Background

The combination of UV-LIGA (ultraviolet lithography, electroforming) technology and traditional injection molding industry is a common manufacturing mode in the field of microfluidic chips at present. The manufacturing die of the traditional injection molding industry is limited by the limitation of processing precision, the minimum precision is 100 mu m generally, and the structure of 10-100 mu m cannot be prepared. Although the foreign precision manufacturing mould has a high-precision preparation technology, the mould manufacturing and repairing cost is extremely high, the development, verification and small-volume production cost of each time reaches more than one million, and the mould manufacturing mould is difficult to bear by small and medium enterprises. Therefore, a plurality of domestic scientific research universities and production research enterprises use the UV-LIGA technology to prepare injection molding mold cores, and the mold cores are embedded into an injection molding system, so that the development cost is greatly reduced under the condition that the photoetching-electroforming technology can perfectly ensure the microstructure quality, and the microfluidic chip has wider application prospects in biology and chemistry.

In order to adapt to electroforming in the UV-LIGA technology, the photoresist of the photoetching mother board needs to have certain structural strength, and can keep stable structure in electroforming liquid at 50 ℃ for 30 days, so that negative photoresist such as SU-8/AZ and the like is selected. Because of the negative photoresist photoetching characteristics of the optical diffraction phenomenon, the grooves are in a positive trapezoid shape when the silicon wafer is used for conventional exposure, and the drawing strain phenomenon can occur in the subsequent injection and demolding.

Disclosure of Invention

Therefore, the technical problem to be solved by the invention is to provide a processing method of a photoetching mother board for electroforming and a microfluidic chip, so as to overcome the defect that the photoetching mother board used for electroforming in the prior art is spin-coated with negative photoresist, and the groove is in a positive trapezoid shape after conventional exposure due to the optical diffraction phenomenon, so that the pulling phenomenon occurs in the subsequent injection and demolding.

In order to solve the above problems, the present invention provides a method for processing a lithographic master for electroforming, comprising the steps of:

an exposure component forming step, namely placing a mask on a first side surface of a transparent glass substrate, and spin-coating negative photoresist on one side of the mask far away from the glass substrate to form an exposure component consisting of the glass substrate, the mask and the photoresist;

an exposure component transferring step, namely transferring the exposure component into a first photoetching clamping groove of a placing platform of a photoetching machine, and enabling a glass substrate of the exposure component to face one side of a UV light source of the photoetching machine;

and an exposure step, namely controlling the photoetching machine to start the UV light source for photoetching, and forming a photoetching mother board for electroforming after the exposure component is exposed.

In some embodiments, after the exposing component transferring step, before the exposing step, further comprises:

and an exposure assembly leveling step of adjusting the glass substrate in the exposure assembly to be parallel to the contact plane of a mechanical pressing component of the photoetching machine.

In some embodiments, the placement platform comprises a second platform and a first platform arranged above a second photoetching clamping groove provided on the second platform, wherein the first photoetching clamping groove is constructed on the top surface of the first platform, and a plurality of soft rubber mats which are arranged at intervals in the circumferential direction are connected on the bottom surface of the first platform; and/or, in the exposure module leveling step, a glass white sheet is arranged between the glass substrate and the contact plane.

In some embodiments, a plurality of circular grooves are formed on the bottom surface of the first platform, and each soft rubber pad is correspondingly embedded in each circular groove.

In some embodiments, the electroforming lithographic master plate is used to manufacture a microfluidic chip, the second stage is a four inch substrate of the lithographic machine, the first stage is a five inch substrate, and the microfluidic chip has a length of 80mm and a width of 40mm.

In some embodiments, the mask is integrally formed with the glass substrate, and the mask and the glass substrate are integrally formed to form a mask blank.

In some embodiments, in the exposing component forming step, before spin-coating the negative photoresist, further comprising:

and cleaning, plasma treatment and high-temperature heating treatment are sequentially carried out on the original mask plate.

In some embodiments, the plasma treatment is specifically: treating with high power vacuum plasma for 15 min at 200-300 w; or the high-temperature heating treatment is specifically heating treatment for 30min at 150-170 ℃.

In some embodiments, the spin-on thickness of the negative photoresist is 50-200 μm.

The invention also provides a micro-fluidic chip which is manufactured and formed by adopting the electroforming photo-etching mother plate, and the electroforming photo-etching mother plate is manufactured and formed by adopting the processing method of the electroforming photo-etching mother plate.

The processing method of the photoetching mother plate for electroforming and the micro-fluidic chip are different from the traditional front exposure mode, the mask plate is positioned on one side of the transparent glass substrate, the negative photoresist is spin-coated on one side of the mask plate far away from the glass substrate, the UV light source irradiates and exposes the negative photoresist through the glass substrate and the mask plate sequentially from one side of the glass substrate, and due to the diffraction effect of light at the glass substrate, the groove formed at the exposed negative photoresist is in an inverted trapezoid shape, namely, the bottom edge close to one side of the glass substrate is shorter and the bottom plate far away from one side of the glass substrate is longer, so that the subsequent injection and demolding can be facilitated, and the occurrence of the drawing strain phenomenon is effectively avoided.

Drawings

FIG. 1 is a schematic diagram showing steps of a method for processing a lithographic master for electroforming according to an embodiment of the invention;

FIG. 2 is a schematic diagram of an exposure module according to an embodiment of the invention;

FIG. 3 is a schematic diagram of a three-dimensional structure of a mask blank formed after an integrated molding of a glass substrate and the mask in an embodiment of the present invention;

FIG. 4 is a schematic structural diagram of a first platform and a second platform according to an embodiment of the present invention;

FIG. 5 is a schematic diagram showing a state of the exposure module before transferring to the lithography machine for exposure according to an embodiment of the present invention;

FIG. 6 is a schematic diagram of the relative dimensional relationship between a conventional microfluidic chip and an electroformed master disk in the market, wherein the area of the microfluidic chip beyond the effective area of the electroformed master disk is designated at a.

The reference numerals are:

11. masking plate; 12. a glass substrate; 13. negative photoresist; 21. a first platform; 211. a first photolithographic clamping groove; 212. a soft rubber pad; 213. a suction hole; 22. a second platform; 221. a second photolithographic clamping groove; 3. a glass white piece.

Detailed Description

Referring to fig. 1 to 6 in combination, according to an embodiment of the present invention, there is provided a method of processing a photolithographic master for electroforming, including the steps of:

an exposure component forming step of placing a mask 11 on a first side surface of a transparent glass substrate 12, and spin-coating negative photoresist 13 on one side of the mask 11 far away from the glass substrate 12 to form an exposure component 1 consisting of the glass substrate, the mask and the photoresist, as shown in fig. 1;

an exposure module transferring step of transferring the exposure module 1 into a first lithography clamping groove 211 of a placement platform of a lithography machine, and directing a glass substrate of the exposure module 1 to one side of a UV light source (not shown) of the lithography machine, namely, an upper area of the exposure module 1 in the orientation shown in FIG. 5, so that back exposure of the exposure module can be formed;

and an exposure step, namely controlling the photoetching machine to start a UV light source for photoetching, and forming a photoetching mother board for electroforming after the exposure component is exposed.

In the technical scheme, unlike the traditional front exposure mode, the mask 11 is positioned on one side of the transparent glass substrate 12, the negative photoresist 13 is spin-coated on one side of the mask 11 far away from the glass substrate 12, the negative photoresist 13 is irradiated and exposed by the UV light source from one side of the glass substrate 12 sequentially through the glass substrate 12 and the mask 11, and due to the diffraction effect of light at the glass substrate 12, the groove formed at the exposed negative photoresist 13 is inverted trapezoid (taking the position of the negative photoresist 13, the mask 11 and the glass substrate 12 placed from top to bottom as a reference), namely, the bottom edge close to one side of the glass substrate 12 is shorter and the bottom plate far away from one side of the glass substrate 12 is longer, so that the subsequent smooth demolding of injection molding can be facilitated, and the occurrence of the pulling phenomenon is effectively avoided.

In the process combining the UV-LIGA technology and the traditional injection molding technology, because the electroforming process needs to keep the environment at 50 ℃ for tens of days, the photoresist needs to have strong anti-swelling and anti-wrinkle performance, the physical structure needs to be firm, the negative photoresist generally adopts SU-8/AZ negative photoresist, the negative photoresist is reserved after the front transparent part of the negative photoresist develops, the opaque part is developed and removed, the groove position forms a positive trapezoid after the front exposure in the prior art, the injection molding and demolding are influenced to cause poor injection molding and drawing, the back exposure technology is adopted, the negative photoresist is not placed on the front surface but exposed on the back surface, the groove position of the negative photoresist after the exposure is inverted trapezoid, and the smooth injection molding and demolding can be ensured.

After spin-coating negative photoresist (namely, the negative photoresist 13 is formed by the glass substrate 12 and the mask 11) on a mask original sheet (namely, a component formed by the glass substrate 12 and the mask 11), when an application scene is a micro-fluidic chip, the photoresist thickness is concentrated to 50-200 μm, namely, the spin-coating thickness of the negative photoresist 13 is 50-200 μm, the method of removing photoresist edge bulge by using a common photoresist remover is not applicable at all, the photoresist surface thickness is controllable due to spin-coating randomness, but the height difference of the maximum of 10 μm exists at different positions of the edge bulge, and the photoresist offset is slightly inclined in a photoetching machine to influence the photoetching quality, and based on the phenomenon, after the transferring step of the exposure component and before the exposing step, the method further comprises the following steps: an exposure module leveling step of adjusting the glass substrate 12 in the exposure module to be parallel to a contact plane of a mechanical pressing member (not shown) provided in the lithography machine. That is, before the exposure module is exposed, leveling is performed to make the glass substrate 12 parallel to the contact plane, specifically, horizontal, so that the photolithography quality can be improved. In a specific embodiment, referring to fig. 4, the placement platform includes a second platform 22 and a first platform 21 disposed above a second photoresist slot 221 formed in the second platform 22, the first photoresist slot 211 is configured on a top surface of the first platform 21, and a plurality of soft rubber pads 212 circumferentially spaced apart are connected to a bottom surface of the first platform 21, when the exposure module is specifically leveled, the exposure module is placed in the first photoresist slot 211 to make its position stable and reliable, then a mechanical pressing component of the lithography machine is controlled to slowly descend, and since the contact plane has a contact plane in a horizontal direction, the contact plane will apply a force to a top plane of the exposure module 1, the plurality of soft rubber pads will compensate for height fluctuation of a photoresist edge, and achieve an automatic leveling purpose while dispersing pressure, that is, achieve an adaptive negative photoresist thick photoresist edge height difference, further increase the lithography precision and stability, and the plurality of soft rubber pads 212 may be set at least three or four along a circumferential direction at intervals, for example. In a specific embodiment, the bottom surface of the first platform 21 is configured with a plurality of circular grooves, each soft rubber pad 212 is correspondingly embedded in each circular groove, and the soft rubber pads 212 are connected in an embedding manner rather than a bonding manner, so that adverse effects on leveling caused by thickness differences of adhesive layers can be avoided. With continued reference to fig. 4, the bottom surface of the first stage 21 is configured as a disk structure capable of being accommodated in the second photolithographic card slot 221, the soft rubber pad 212 is connected to the bottom surface of the disk structure, and the disk structure is further configured with a suction hole 213 communicating with the first photolithographic card slot 211, and the suction hole 213 communicates with a vacuum adsorption structure provided in the second photolithographic card slot 221, so that the exposure module 1 in the first photolithographic card slot 211 can be reliably positioned by a vacuum pump.

In another preferred embodiment, the application scenario of the lithography machine with smaller dimensions can be further expanded by designing the dimensions of the first platform 21 and the second platform 22, specifically, dPCR micro-fluidic chips (hereinafter referred to as chips) are used for matching, most of the chip length is in the range of 77-80mm, at least 2mm is needed to be added to each side of the mold core after electroforming for matching with the injection mold cavity, and the length direction needs at least 81-84mm, while if the current four-inch lithography system (lithography machine) is used, the lithography scope of the lithography machine and the silicon wafer glass size are limited, the maximum scope is not more than 100mm, the width of the conducting ring and the edge narrowing width are removed during electroforming, and only 86mm effective mold core scope is left in the range of 100mm-8mm-6mm, so that the length is limited. If the chip width is wider than 40mm (shown in fig. 6), the chip width is directly beyond the effective leveling range of the mold core after electroforming, and the chip cannot be used. Of course, six-inch lithography machines can perfectly solve the problem, but the price of six-inch lithography machines is in millions (the price is usually 200-400 ten thousand yuan), and the cost is obviously too high. Based on the above problems, the lithographic motherboard for electroforming is used for manufacturing a microfluidic chip, the length of the microfluidic chip is 80mm, the width of the microfluidic chip is 40mm, the second platform 22 is a four-inch substrate of a lithographic apparatus, the first platform 21 is a five-inch substrate, namely, the first platform 21 is used for leveling and simultaneously designing the size of the lithographic motherboard to be five inches, the five-inch substrate can be placed, the effective diameter of the lithographic motherboard after expansion is increased to 125-14=111 mm, the effective area of lithography and electroforming is greatly increased, the UV-LIGA technical threshold is greatly reduced, and the lithographic motherboard is very suitable for industrialized mass production.

In the exposure module leveling step, a glass white piece 3 is arranged between the glass substrate 12 and the contact plane, and the glass white piece 3, namely, a glass plate without a mask, is used for replacing the original mask in the traditional front exposure process, and although a common photoetching machine mostly has a mask photoetching mode or not, the exposure of negative photoresist thick photoresist needs contact exposure, and at the moment, the stability of a photoetching system can be increased by contacting the glass white piece 3 with a mother board to be photoetched.

The traditional back explosion technology needs to transfer a mask plate to the bottom of a glass substrate, the method needs a complex photoetching process, a transfer pattern is generally a chromium metal layer, chromium corrosive liquid and chromic acid washing liquid are needed to be configured for processing a glass substrate, a chromium layer and a sacrificial layer photoresist, a large amount of chemicals such as fuming nitric acid, sulfuric acid, ceric ammonium nitrate, perchloric acid, potassium dichromate and the like are needed, the technology is complex and dangerous, the quality of the transfer mask pattern is not very reliable, the probability of pinhole occurrence when the pattern falls off is not low due to the complex technology, the flow and the interference factors, the yield is only 30-50%, and the material cost is over 2000 yuan when the mask pattern is simply transferred once. Based on the defects of the conventional technology, in a preferred embodiment, the mask 11 and the glass substrate 12 are integrally formed, and then the mask 11 and the glass substrate 12 are integrally formed to form a mask original sheet, and the mask original sheet can be purchased in an outsourcing mode, that is, the invention initiates a technical route for directly using a mask finished product to carry out photoetching, and because of different preparation principles, the directly purchased mask does not have defects such as pinholes and the like caused by dropping of a chromium layer, completely bypasses a complex chemical treatment process, directly processes the mask, for example, customizes a mask with the thickness of 1.5mm, then cuts the mask, and cuts the mask into five-inch mask original sheets for later use (shown in fig. 3).

In the exposure-component forming step, before spin-coating the negative photoresist 13, further comprising: the original piece of the mask plate is sequentially subjected to cleaning, plasma treatment and high-temperature heating treatment, and the original piece of the mask plate is subjected to cleaning and modification treatment, so that the original piece and negative glue have binding force, and meanwhile, the defect of the original primer (the primer does not need to be coated on a glass substrate in a spinning way) on a subsequent electroforming link is removed. Wherein, the plasma treatment specifically comprises the following steps: treating with high power vacuum plasma for 15 min at 200-300 w; or heating at 150-170deg.C for 30min to ensure reliable combination of the original sheet and the negative adhesive.

The invention also provides a micro-fluidic chip, which is formed by adopting the electroforming photoetching mother board, and the electroforming photoetching mother board is formed by adopting the processing method of the electroforming photoetching mother board.

It will be readily appreciated by those skilled in the art that the above advantageous ways can be freely combined and superimposed without conflict.

The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention. The foregoing is merely a preferred embodiment of the present invention, and it should be noted that it will be apparent to those skilled in the art that modifications and variations can be made without departing from the technical principles of the present invention, and these modifications and variations should also be regarded as the scope of the invention.

Claims

1. A processing method of a lithographic mother plate for electroforming is characterized by comprising the following steps:

an exposure component forming step, namely placing a mask (11) on a first side surface of a transparent glass substrate (12), and spin-coating negative photoresist (13) on one side of the mask (11) far away from the glass substrate (12) to form an exposure component (1) formed by the glass substrate, the mask and the photoresist;

an exposure component transferring step of transferring the exposure component (1) into a first photoetching clamping groove (211) of a placing platform of a photoetching machine, and enabling a glass substrate of the exposure component (1) to face to one side of a UV light source of the photoetching machine;

2. The method of processing a lithographic master for electroforming according to claim 1, further comprising, after the exposure module transferring step and before the exposing step:

and an exposure assembly leveling step of adjusting the glass substrate (12) in the exposure assembly to be parallel to the contact plane of a mechanical pressing component of the lithography machine.

3. The method of processing a photolithographic master for electroforming according to claim 2, wherein the placement stage includes a second stage (22) and a first stage (21) placed on a second photolithographic card slot (221) provided in the second stage (22), the first photolithographic card slot (211) being configured on a top surface of the first stage (21), and a plurality of soft rubber pads (212) arranged at intervals in the circumferential direction being connected to a bottom surface of the first stage (21); and/or, in the exposure module levelling step, a glass white sheet (3) is arranged between the glass substrate (12) and the contact plane.

4. A method of manufacturing a photolithographic master for electroforming according to claim 3, wherein a plurality of circular grooves are formed in the bottom surface of the first stage (21), and each of the soft rubber pads (212) is fitted in each of the circular grooves.

5. A method of processing a photolithographic master for electroforming according to claim 3, wherein the photolithographic master for electroforming is used to fabricate a microfluidic chip, the second stage (22) is a four inch substrate of the photolithographic machine, the first stage (21) is a five inch substrate, and the microfluidic chip has a length of 80mm and a width of 40mm.

6. The method according to claim 1, wherein the mask plate and the glass substrate are integrally formed, and the mask plate and the glass substrate are integrally formed to form a mask plate blank.

7. The method of processing a photolithographic master for electroforming according to claim 6, characterized by further comprising, in the exposure module forming step, before spin-coating the negative photoresist (13):

8. The method for processing a master plate for electroforming according to claim 7,

the plasma treatment specifically comprises the following steps: treating with high power vacuum plasma for 15 min at 200-300 w; or the high-temperature heating treatment is specifically heating treatment for 30min at 150-170 ℃.

9. The method of processing a photolithographic master for electroforming according to claim 1, wherein the spin-coating thickness of the negative photoresist (13) is 50-200 μm.

10. A microfluidic chip fabricated and formed using the lithographic master for electroforming, wherein the lithographic master for electroforming is fabricated and formed using the method for fabricating the lithographic master for electroforming according to any one of claims 1 to 9.