CN1288069C

CN1288069C - Method for integral micromachining multilayer composite structure

Info

Publication number: CN1288069C
Application number: CN 200410024889
Authority: CN
Inventors: 陈文元; 姜勇; 赵小林; 丁桂甫; 张卫平
Original assignee: Shanghai Jiaotong University
Current assignee: Shanghai Jiaotong University
Priority date: 2004-06-03
Filing date: 2004-06-03
Publication date: 2006-12-06
Anticipated expiration: 2024-06-03
Also published as: CN1583543A

Abstract

The present invention relates to a method for integrally micromachining a multilayer composite structure, which belongs to the technical field of a micro-electro-mechanical system. The present invention adopts an SU-8 glue and quasi-LIGA machining method, uses a multilayer etching technology to reduce the error of relative positions among the multilayer structure, uses a surface activating technology to activate the surface of a metal electro-casting layer so as to enhance the binding force of a new electro-casting layer and the metal electro-casting layer, uses a seed layer technology to electro-cast a large electro-casting figure on a small electro-casting figure so as to realize an integral machining. Finally, a three micro composite structure with high interlayer relative position precision and strong binding force is manufactured. Based on the SU-8 glue and quasi-LIGA technology as the trunk of machining processes, the present invention uses the multilayer etching technology in a photoetching process to solve the problem of low relative position precision among the multilayer structure, uses the surface activating technology and the seed layer technology in an electro-casting pre-processing process to solve the problem of weak interlayer binding force, finally realizes the integral machining of the multilayer composite structure, and widens the machining range of the quasi-LIGA technology.

Description

The method of integrated little processing multilayer labyrinth

Technical field

The present invention relates to a kind of method of little processing multilayer labyrinth, particularly a kind of method of using the integrated little processing multilayer labyrinth of high-aspect-ratio process technology.Be used for micro-electromechanical system field.

Background technology

Accurate LIGA (ultraviolet photolithographic, little electroforming, little high-aspect-ratio process technology of duplicating) is technology commonly used in the high-aspect-ratio processing, be widely used in the manufacture field of MEMS, find by literature search, Li, Bo, Deng the people at The International Society for Optical Engineering (international optical engineering meeting), v 5344,2004, " the Low stressed high-aspect-ratioultra-thick SU-8 UV-LIGA process for the fabrication of a micro heatexchanger " that delivers on the p 147-154, (using the accurate LIGA technology processing low-grade fever converter of the thick SU-8 glue of high-aspect-ratio of low stress) uses the thick SU-8 photoresist of high-aspect-ratio of low stress, adopt accurate LIGA technology processing MEMS (MEMS) device, thick SU-8 glue-line is through behind the photoetching development, as little electroforming mould, electroforming material is selected Ni for use, the single layer structure MEMS device that machines, size is accurate, and the vertical direction edge is steep.This method is the method for common accurate LIGA processes individual layer MEMS device, promptly Jia Gong structure only is applicable to individual layer, vertical vertical in form and can not vicissitudinous accurate three-dimensional structure, if run into the complex three-dimensional structure, it can only be earlier a plurality of accurate three-dimensional structures with the part hierarchical design, layering processing then, be assembled into the part that needs at last, but this method can increase the difficulty of accurate assembly work of later stage, and rigging error and mismatch error are big, the globality of mechanism is not strong, influences actual operate as normal.

Summary of the invention

The objective of the invention is to, the deficiency that can only add the working drawing said three-dimensional body at common accurate LIGA technology, a kind of method of integrated little processing multilayer labyrinth is provided, makes the part that machines have characteristics such as interlayer is made a concerted effort by force, relative positional accuracy is high, mismatch error is little, globality is strong.

The present invention is achieved by the following technical solutions, the present invention adopts SU-8 glue and traditional accurate LIGA processing method, do the photoetching reference pattern in the substrate bottom surface, the litho machine of double-sided exposure function is all used in every layer of SU-8 glue photoetching later on, be as the criterion with the photoetching reference pattern of substrate bottom surface and focus, reduce the error of relative position between sandwich construction by this multilayer cover lithography, substrate put into contain NaOH 700-800 grams per liter, under 120-130 ℃ of temperature, heated 10-30 minute in the solution of NaNO2 (or NaNO3) 200-500 grams per liter, to activate loosening oxidation film layer.After the washing, put into HCl 300-500 grams per liter again, the H2SO4200-300 grams per liter, if corrosion is 1-2 minute in the solution of fourth 0.5-3 grams per liter, take out washing, like this with regard to activated metal electroformed layer surface, adhesion between itself and new electroformed layer is strengthened, soak substrate with watery hydrochloric acid, clean the Ni passivation layer, sputter Cu metallic film is as Seed Layer, new electroformed layer is directly grown on this layer Seed Layer, realize that by this method electroforming produces big electroforming figure on the little electroforming figure, thereby realize integrated processing, finally produce interlayer relative positional accuracy height, three little labyrinths that adhesion is strong.

Below the inventive method is further described:

1, multilayer cover lithography reduces the error of relative position between sandwich construction

The integrated process technology of multilayer is on the structured metal layer that one deck has been electroplated, electroforming produces new one deck structure again, electroforming is layer by layer got on, if therefore the relative positional accuracy between the sandwich construction solves with the focusing benchmark in front, cumulative errors can be very big, directly influences the interlayer positional precision of last whole mechanism.The present invention adopts at substrate back processing focusing photoetching reference pattern, uses the litho machine with double-sided exposure function, gets rid of the Su-8 photoresist earlier, focus according to substrate back photoetching reference pattern, behind the photoetching development, electroforming Ni, planarizing process is made every layer of structure.Reduce the error of relative position between sandwich construction like this, fundamentally solved interlayer relative positional accuracy problem.

2, surface active technology activation metal plating laminar surface

Carry out before the new electroforming at every turn, substrate is put into contained NaOH 700-800 grams per liter, heating 10-30 minute under 120-130 ℃ of temperature in the solution of NaNO2 (or NaNO3) 200-500 grams per liter is to activate loosening oxidation film layer.After the washing, put into HCl 300-500 grams per liter again, H2SO4 200-300 grams per liter if corroded 1-2 minute in the solution of fourth 0.5-3 grams per liter, takes out washing, observes the Ni surface brightness, and the surface-brightening unanimity enters next step electroforming process.Electroformed layer surface metal material is carried out activation processing, make it combine closely, strengthen engaging force with new electroformed layer.Increasing the interlayer adhesion with this is eager to excel.

3, Seed Layer technology

When the figure of new electroformed layer is greater than its preceding one deck electroformed layer figure, directly electroforming is impossible, can only adopt the Seed Layer technology, promptly at preceding one deck integral surface sputter layer of metal film, as Seed Layer, the figure of new electroforming is directly grown on this layer metal seed layer.Choosing of seed layer materials is most important, must decide according to the material of the double layer of metal that Seed Layer connected, promptly require seed layer materials close, require seed layer materials electric conductivity strong again with the metal material character that is connected, character is active relatively, and the Seed Layer surface passivation layer is removed easily.Ni does electroforming material, uses Cu as the Seed Layer between the Ni electroformed layer.Soak substrate with watery hydrochloric acid, clean the Ni passivation layer, sputter Cu metal film is as Seed Layer, new electroformed layer is directly grown on this layer Seed Layer, because Cu is close with the Ni chemical property, can both finely combine with levels Ni, and good conductivity, chemical property is active relatively, for the passivation layer that produces on the Seed Layer Cu film, also is easy to remove by methods such as pickling.

The present invention will be organically combined togather based on accurate LIGA technology, multilayer cover lithography, surface active technology and the Seed Layer technology of SU-8 glue, based on the accurate LIGA technology of SU-8 glue trunk as manufacturing procedure, in photo-mask process, use multilayer cover lithography, solved the relative positional accuracy problem between sandwich construction, in the electroforming pretreatment procedure, use surface active technology and Seed Layer technology, solved interlayer adhesion problem, the range of work of accurate LIGA technology has been widened in the integrated processing of the final multilayer labyrinth of realizing.

Description of drawings

Fig. 1 the inventive method flow chart

The specific embodiment

For understanding technical scheme of the present invention better, be further described below in conjunction with drawings and Examples.

Embodiment:

Process two three-deckers that cooperatively interact and use, first and third layer pattern is greater than second layer figure in this structure, and electroforming material is Ni, uses the double-sided exposure litho machine, and concrete processing method is as follows:

Earlier make the photoetching reference pattern in the substrate bottom surface, later photo-mask process is a benchmark with it all.

Shown in A among Fig. 1, ground floor gets rid of photoresist SU-8, after the reference pattern photoetching of bottom surface, developing, and electroforming Ni, planarizing process is carried out to the electroformed layer surface in the electroforming back that finishes.

Shown in B among Fig. 1, after second layer whirl coating, photoetching (is benchmark with the bottom surface figure), the development, surface activation process is carried out on the Ni surface, substrate put into contain NaOH 700～800 grams per liters, under 120～130 ℃ of temperature, heated 10～30 minutes in the solution of NaNO2 (or NaNO3) 200～250 grams per liters, to activate loosening oxidation film layer.After the washing, put into HCl 300～500 grams per liters again, H2SO4 200～300 grams per liters if corroded 1～2 minute in the solution of fourth 0.5～3 grams per liter, take out washing, observe Ni surface-brightening unanimity in the packing ring figure, can prepare to enter the electroforming process of the second layer.

Shown in C among Fig. 1, after second layer electroforming is finished, carry out planarizing process.

Shown in D among Fig. 1 because the 3rd layer electroforming figure is greater than the electroforming figure of the second layer, so can not be on the electroforming second time figure direct growth, must the sputtering seed layer.Electroforming material is Ni, makes seed layer materials with Cu, before the sputter, soaks substrate with watery hydrochloric acid, cleans and removes the Ni passivation layer, and sputter Cu film is as Seed Layer.

Shown in E among Fig. 1, whirl coating, photoetching (is benchmark with the bottom surface figure), development on the Cu film use dilute hydrochloric acid solution to soak substrate before the electroforming, remove Cu film passivation layer, then the 3rd layer of Ni of electroforming.

Shown in F among Fig. 1, after the 3rd layer of Ni carried out leveling, remove photoresist, substrate is put into acetone soln soak, place 200 ℃ of high-temperature oxydation stove constant temperature then, and logical oxygen, use the concentrated sulfuric acid to handle at last, spinning off from glue up to whole gear collection (abovely respectively goes on foot the processing time, concrete condition according to SU-8 glue thickness is decided), and photoresist is removed and is finished on the gear collection, again through after cleaning, and completion of processing.

This example is the processing method of three-decker, also can process structure more than three layers according to the method.In addition, handle substrate through overactivation and depassivation layer and should put into the electroforming of electroforming pond immediately, reduce the time that contacts with air, during electroforming process carries out, also should reduce the number of times that takes out Substrate checking and observation as far as possible, the probability of electrodeposited coating possibility passivation is dropped to minimum, thereby guarantee that the interlayer adhesion is unaffected.

Use this mechanism that this processing method machines, surfacing, the edge is steep, and the interlayer combination is firm, interlayer relative positional accuracy height, physical dimension adheres to specification fully.

Claims

1, a kind of method of integrated little processing multilayer labyrinth, it is characterized in that, adopt SU-8 glue and traditional accurate LIGA processing method, do the photoetching reference pattern in the substrate bottom surface, the litho machine of double-sided exposure function is all used in every layer of SU-8 glue photoetching later on, be as the criterion with the photoetching reference pattern of substrate bottom surface and focus, reduce the error of relative position between sandwich construction by this multilayer cover lithography, substrate put into contain NaOH 700-800 grams per liter, under 120-130 ℃ of temperature, heated 10-30 minute in the solution of NaNO2 or NaNO3 200-500 grams per liter, to activate loosening oxidation film layer; After the washing, put into HCl 300-500 grams per liter again, the H2SO4200-300 grams per liter, if corrosion is 1-2 minute in the solution of fourth 0.5-3 grams per liter, take out washing, like this with regard to activated metal electroformed layer surface, adhesion between itself and new electroformed layer is strengthened, soak substrate with watery hydrochloric acid, clean the Ni passivation layer, sputter Cu metallic film is as Seed Layer, new electroformed layer is directly grown on this layer Seed Layer, realize that by this method electroforming produces big electroforming figure on the little electroforming figure, thereby realize integrated processing, finally produce interlayer relative positional accuracy height, three little labyrinths that adhesion is strong.