CN100468637C - Method for producing air bridge of compound semiconductor microwave high power device - Google Patents
Method for producing air bridge of compound semiconductor microwave high power device Download PDFInfo
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- CN100468637C CN100468637C CNB2007100181473A CN200710018147A CN100468637C CN 100468637 C CN100468637 C CN 100468637C CN B2007100181473 A CNB2007100181473 A CN B2007100181473A CN 200710018147 A CN200710018147 A CN 200710018147A CN 100468637 C CN100468637 C CN 100468637C
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Abstract
The invention discloses an air bridge production method of compound semi-conductive microwave large powder device, mainly for resolving the problems of prior art which air bridge has low arch height, narrow width, and low reliability. And the production comprises that respectively coating remove adhesive and photo-etching adhesive with different pre-bake temperatures on a substrate, and etching a bridge area and an electrode area, to form a sacrificial layer, then baking the substrate at 135-145Deg. C for 15-25min, to form the sacrificial layer into arch structure, depositing a plating start layer at 80-100nm on the sacrificial layer, coating a photo-etching adhesive on the plating start layer, etching a bridge area and an electrode area, then in non-cyanide plating liquid, using plating method, to plate an Au layer on the etched bridge area and electrode area, at least, removing the mask photo-etching adhesive, removing Au and Ti of the plating start layer, removing the sacrificial layer, to obtain an arch air bridge. The invention has the advantages with high arch height, wide width, and high reliability.
Description
Technical field
The invention belongs to microelectronics technology, relate to the compound semiconductor microwave high power device manufacture craft, the method for producing air bridge in specifically a kind of compound semiconductor microwave high power device.
Background technology
With carborundum SiC, gallium nitride GaN is that the third generation wide bandgap semiconductor of representative has good characteristics such as big energy gap, high critical field strength, high heat conductance, high carrier saturation rate, heterojunction boundary two-dimensional electron gas height, makes its extremely people's attention.In theory, utilize the device such as metal Schottky-based field effect transistor MESFET, high electron mobility transistor (HEMT), heterojunction bipolar transistor HBT of these material that incomparable excellent properties is arranged aspect microwave high power.Particularly entered since the nineties, because the employing of resilient coating technology and the breakthrough of p type doping techniques are flourish in the whole world for the microwave high power device research boom on basis to third generation wide bandgap semiconductor.
The microwave high power device of making on third generation semiconductor material with wide forbidden band is considered the device high frequency characteristics, must adopt air bridge technology that unsettled port in the high power device is coupled together.With GaN HEMT is example, and GaN HEMTs HIGH-POWERED MICROWAVES device grid must be divided into a plurality of parallel short grid, different with phase place on the resistance that reduces grid and the grid.Referring to ChuK K, Design and Fabrication of AlGaN/GaN Based HFETs for Microwave applications, UMINO.9967478.Multi-gate structure require to adopt air bridges (air-bridge), chip is counter adorns (flip-chip) or through hole technology such as (via-hole) couples together unsettled source end or drain terminal.When AlGaN/GaN HEMTs is produced on SiC or sapphire (sapphrie) substrate,, and be difficult to adopt the through-hole interconnection technology because of substrate thinning and etching difficulty.Though the anti-packing technique of chip is having superiority aspect the device heat radiation, neither a kind ofly be suitable for the interconnection technique of large-scale production.And air bridge technology, its technology is simple, be adapted to large-scale production and applied to the interconnection of microwave high power device widely.
2002, people such as the Liu Xunchun of the Chinese Academy of Sciences proposed a kind of method (publication number CN1466189A) for preparing air bridges on substrate.This method is passed through whirl coating repeatedly, develops, and soaks with plasma etching and chlorobenzene and makes trapezoidal sacrifice layer, is coated with two-layer glue again, photoetching upper strata photoresist, and the evaporation deposition metal is peeled off the formation air bridges.Be characterized in to form and the equal-sized slightly arch of design layout air bridges.But using plasma etching and chlorobenzene soak to make and make the complexity that sacrifice layer has increased technology in manufacture process, and adopt the method for evaporation bridge metal, and deposition speed is slow, and using rate of metal is extremely low, is unfavorable for large-scale production.
2004, people such as the Shao Gang of the Chinese Academy of Sciences proposed a kind of compound adhesive and electroplate the method (publication number CN1641837A) of making air bridges.This method adds suitable thickness 9981 glue again by being coated with the very thin PMMA of one deck, through the high-temperature baking round edge, adds the fabrication techniques air bridges of plating again.Its characteristic craft is simple, is suitable for large-scale production, and adopts the thin PMMA glue of one deck, though this method can well solve the wrinkling problem of photoresist in the technical process.But when the high temperature drying glue makes the compound adhesive edge smooth, the very serious problem of photoresist cross-direction shrinkage can occur, make the air bridges span of made much smaller than the layout design parameter.Simultaneously because the longitudinal vertical plane overhang is little, cause when making the high air bridges of bridge floor, must increase the thickness of photoresist, increased certain degree of difficulty to photoetching.
Along with quick raising of the characteristic frequency of third generation wide bandgap semiconductor microwave high power device and power constantly increase, to improving constantly of the requirement of high-speed interconnect line, require a kind of parasitic capacitance of research and development little, resistance is little, and the simple air bridges interconnection technique of technology connects together the various piece of circuit or device.These devices often are used under some extreme environment, in aircraft, communication satellite.Simultaneously, it is very high that its working temperature also can reach, and can reach 700 ℃ as its maximum operating temperature of GaN HEMT.This just requires air bridges that good domes will be arranged, and guarantees that device in all cases can both reliably working.Thereby, must develop the requirement that a kind of new air bridge technology satisfies the device development.
Summary of the invention
The objective of the invention is to overcome the deficiency of above-mentioned prior art, method for producing air bridge in a kind of compound semiconductor microwave high power device is provided, be implemented under the certain situation of spin coating sacrifice layer height, make than prior art bridge arch form height, air bridge structure that longitudinal shrinkage is little, to satisfy various performance requirements based on third generation wide bandgap semiconductor microwave high power device.
Realize that technical scheme of the present invention is: when making the sacrifice layer of decision air bridges shape, the bottom of sacrifice layer be coated with earlier pre-bake temperature high peel off glue, be coated with the low photoresist of pre-bake temperature then, carry out the low-temperature bake of short time at last, form the arch air bridges.Detailed process is as follows:
The high temperature that is coated with pre-bake temperature and is 160 ℃ on Si or GaN substrate is peeled off glue, be coated with pre-bake temperature again and be 85 ℃ photoresist, and the position makes the bridge district by lithography therebetween, and the zone of the electrode on Qiao Qu both sides, makes this bridge district form sacrifice layer;
The substrate that scribbles described two kinds of glue is placed in the baking oven toasts, make the sacrifice layer in bridge district become the neat complete domes of smooth surface, baking temperature: 135 ℃-145 ℃ low temperature, stoving time: 15-25min;
Deposit one deck 80nm-100nm furling plating on sacrifice layer;
Resist coating and make bridge district and electrode zone by lithography on furling plating;
In the cyanide-free electroplate liquid, utilize electroplating technology, in the bridge district that makes by lithography and electrode zone electroplate layer of Au;
Remove mask lithography glue, the Au that removes furling plating and Ti, removal sacrifice layer successively, obtain the arch air bridges.
Technical scheme 2
On the source of having made, drain contact and schottky junctions GaN HEMTs device after touch, coat pre-bake temperature earlier and be 160 ℃ high temperature and peel off glue, be coated with pre-bake temperature again and be 85 ℃ photoresist, and the position makes the bridge district by lithography therebetween, and the electrode zone on Qiao Qu both sides, make this bridge district form sacrifice layer;
The substrate that scribbles described two kinds of glue is placed in the baking oven toasts, make the sacrifice layer in bridge district become the neat complete domes of smooth surface, baking temperature: 135 ℃-145 ℃ low temperature, stoving time: 15-25min;
Deposit one deck 80nm-100nm furling plating on sacrifice layer;
Resist coating and make bridge district and electrode zone by lithography on furling plating;
In the cyanide-free electroplate liquid, utilize electroplating technology, in the bridge district that makes by lithography and electrode zone electroplate layer of Au;
On the plating aspect after electroplating Au, resist coating also makes the electroless coating zone by lithography;
Utilize common process to remove photoresist on the Au of furling plating and Ti, the removal plating aspect successively, remove sacrifice layer, obtain the arch air bridges.
On the GaN of the source of having made, drain contact and Schottky contacts HEMTs device, the high temperature that is coated with pre-bake temperature earlier and is 160 ℃ is peeled off glue, be coated with pre-bake temperature again and be 85 ℃ photoresist, and the position makes the bridge district by lithography therebetween, and the electrode zone on Qiao Qu both sides, make this bridge district form sacrifice layer;
The substrate that scribbles described two kinds of glue is placed in the baking oven toasts, make the sacrifice layer in bridge district become the neat complete domes of smooth surface, baking temperature: 140 ℃ low temperature, stoving time: 20min;
Deposit one deck 100nm furling plating on sacrifice layer;
Resist coating and make bridge district and electrode zone by lithography on furling plating;
In the cyanide-free electroplate liquid, utilize electroplating technology, in the bridge district that makes by lithography and electrode zone electroplate layer of Au;
Utilize routine techniques to remove mask lithography glue, the Au that removes furling plating and Ti, removal sacrifice layer successively, obtain the arch air bridges.
Above-mentioned method for producing air bridge, the thickness proportion of wherein peeling off glue and photoresist is 2:3～5:5.
Above-mentioned method for producing air bridge, wherein the gross thickness of sacrifice layer is at least 2 μ m.
Above-mentioned method for producing air bridge is wherein peeled off glue and is adopted the LOR5A model, and photoresist adopts the EPI622 model.
Above-mentioned method for producing air bridge, wherein furling plating is the Au thin layer that the Ti thin layer of 5nm adds 75nm-95nm.
The present invention has following advantage:
1. the sacrifice layer of making of the present invention exceeds 50-60% before the aspect ratio baking after the baking, makes when making the bridge floor of equal height, is easy to photoetching;
2. with the sacrifice layer of the present invention's making, the width of baking back sacrifice layer has greatly reduced the difficulty of layout design than preceding the dwindling less than 3% of baking;
3. because sacrifice layer adopts the photoresist of two kinds of different in kinds, in the corrosion furling plating, can play the double shielding effect to the metal under the bridge;
4. the arch air bridge floor of making of the present invention is bigger than the arch radian of the arch air bridge floor of existing method making, has high bridge floor, the performance of high reliability.Because the air bridges of pressure ratio horizontal structure that domes can bear or trapezium structure is big, particularly when the high-temperature metal thermal expansion, horizontal bridge and trapezoidal bridge are under the effect of gravity, can expand downwards or subside and reduce the reliability of device, and the domes metal bridge can outwards expand under the effect of power and guarantee the reliability of device.
Description of drawings
Further specify technology contents of the present invention below in conjunction with drawings and Examples
Fig. 1-the 8th, the present invention make the whole process drawing of air bridges, wherein:
Fig. 1 is the production process charts of sacrifice layer;
Fig. 2 is that the baking back forms arch sacrifice layer process figure;
Fig. 3 is a deposit furling plating artwork;
But Fig. 4 is the plating area artwork that makes by lithography behind burnish gilding glue on the furling plating;
Fig. 5 electroplates thickening air-bridge process figure;
Fig. 6 is that electroless coating district mask layer artwork is directly removed in general exposure;
Fig. 7 is resist coating photoetching electroless coating district photoresist process figure again;
Fig. 8 is the complete air-bridge process figure behind the removal furling plating;
Fig. 9 toasts the arch sacrifice layer scanning electron microscope sem technological effect figure that the back forms;
Figure 10 removes air bridges scanning electron microscope sem technological effect figure behind the furling plating with stripping technology;
Figure 11 is the single air bridge structure scanning electron microscope sem technological effect figure that makes on the Si substrate;
Figure 12 is a plurality of air bridge structure scanning electron microscope sem technological effect figure that make on the Si substrate;
Figure 13 is the single air bridge structure scanning electron microscope sem technological effect figure that makes on GaN HEMTs;
Figure 14 is a plurality of air bridge structure scanning electron microscope sem technological effect figure that make on GaN HEMTs.
Embodiment
Backing material selects for use the Si sheet as substrate
At first, on the Si substrate, be coated with one deck 1.5 μ m thick peel off glue LOR5A, in baking oven with 160 ℃ temperature baking 20min; Be coated with the thick photoresist EPI622 of one deck 1.5 μ m again, with 85 ℃ of temperature baking 10min, the ratio of peeling off glue LOR5A and photoresist EPI622 is 5:5; The bridge pier that makes bridge district 6 and Qiao Qu both sides by lithography with first reticle of making air bridges is the zone 3 of electrode then, soak 2min at last in developer solution, and dry up with nitrogen, 6 form 3 μ m sacrifice layers in the bridge district, promptly in the bridge district 6 keep 3 μ m thick peel off glue and photoresist, as shown in Figure 1.Among Fig. 12 is gate electrode, and 8 is the electroless coating zone.
Step 2, low-temperature bake makes the sacrifice layer in bridge district form domes.
To forming the substrate baking 25min of sacrifice layer, make bridge district 6 become the neat domes of smooth surface, as shown in Figure 2 with 135 ℃ low temperature.
Because this baking temperature is lower than 160 ℃ of pre-bake temperatures peeling off glue LOR5A, make that the sacrifice layer width in bridge district is very little in baking after-contraction amount, solve the spanning degree that baking causes and dwindled problem.Simultaneously because this baking temperature is higher than 85 ℃ of the pre-bake temperatures of photoresist EPI622, thereby make photoresist EPI622 after softening, volumetric expansion, under capillary effect, exceed 57% before the bridge district sacrifice layer aspect ratio baking of formation, as shown in Figure 9.
Adopting routine techniques is 1.8 * 10 in vacuum degree
-3Pa, speed is under the 0.3nm/s condition, the furling plating 4 of evaporation deposition one deck 80nm on sacrifice layer, as shown in Figure 3.
This furling plating is made up of one deck 5nm thick Ti and the thick Au thin layer of one deck 75nm.The Ti thin layer can improve source end metal after the annealing and the adhesion strength between the electrogilding, and Au is used for reducing the resistance of conductive layer, makes that the current density of each point is identical when electroplating.
Step 4, resist coating, photoetching bridge and electrode zone.
At first, being coated with a layer thickness on furling plating 4 is the photoresist EPI622 of 2.5 μ m, makes photoresist 7 evenly cover furling plating 4 surfaces, and toasts 10min with 85 ℃ temperature;
Then, on this furling plating 4, make bridge and electrode zone by lithography with second reticle of making air bridges;
At last, in developer solution, soak 2min, dry up with nitrogen, as shown in Figure 4.
Step 5 is electroplated thickening air bridges and electrode zone.
In the cyanide-free electroplate liquid, utilize conventional electroplating technology, on bridge that makes by lithography and electrode zone, electroplate layer of Au, obtain electroplating the bridge of thickening and the metal level 5 of electrode zone, as shown in Figure 5.
Step 6, photoresist is removed in general exposure.
Directly carry out general exposure electroplating Si sheet later, in developer solution, behind the immersion 2min, dry up, can remove photoresist on the electroless coating zone 8, as shown in Figure 6 with nitrogen with mask aligner.
The method of photoresist is removed in this general exposure, soaks the sacrifice layer photoresist in the time of can avoiding removing photoresist with acetone and the furling plating that causes is wrinkling, helps the removal of follow-up furling plating and the protection in electroless coating zone.
Step 7, corrosion furling plating, removal sacrifice layer obtain the arch air bridges.
Since when removing furling plating, can be in edge's appearance furling plating metal residual phenomenon as shown in figure 10, to the certain negative effect of microwave property generation of device.So the present invention when adopting caustic solution to remove furling plating, is that the Si sheet of photoresist is immersed into and corrodes 20s in the liquor kalii iodide removing mask layer earlier, rinses well with clear water, to remove the Au thin layer in the furling plating 4 on the electroless coating zone 8; Corrode 8s with hydrofluoric acid solution again, rinse well with clear water, to remove the Ti thin layer in the furling plating 4 on the electroless coating zone 8, then spend to peel off and soak 5min in the sol solution, to remove the sacrifice layer in bridge district 6, clean up with clear water at last, electroplate on the thickening electrode district at two and form independently air bridges, as shown in Figure 8.Can access the neat more electroplated metal layer in edge with described corroding method, as Figure 11, shown in Figure 12.Because sacrifice layer of the present invention is to make with two kinds of photoresists of different nature, in corrosion process, can play the double shielding effect simultaneously, well protect non-stripping area, improve the rate of finished products of device.
Embodiment 2
The present invention makes based on the air bridges device architecture on the microwave high power GaN HEMT substrate of making source, drain contact and Schottky contacts, i.e. air bridges device architecture on the microwave high power GaN high electron mobility transistor substrate.
At first, on the GaN substrate, be coated with one deck 1.5 μ m thick peel off glue LOR5A, in baking oven with 160 ℃ temperature baking 20min; Be coated with the thick photoresist EPI622 of one deck 2.0 μ m again, with 85 ℃ of temperature baking 10min, this ratio of peeling off glue LOR5A and photoresist EPI622 is 3:4;
The bridge pier that makes bridge district 6 and Qiao Qu both sides by lithography with first reticle of making air bridges is the zone 3 of electrode then, soaks 2min at last in developer solution, and dries up with nitrogen, and 6 form 3.5 μ m sacrifice layers in the bridge district, as shown in Figure 1.
Step 2, low-temperature bake makes the bridge district of sacrifice layer form domes.
To forming the substrate baking 20min of sacrifice layer, make the bridge district become the neat domes of smooth surface, as shown in Figure 2 with 140 ℃ low temperature.
Because this baking temperature is lower than 160 ℃ of pre-bake temperatures peeling off glue LOR5A, make that the sacrifice layer width in bridge district is very little in baking after-contraction amount, solve the spanning degree that baking causes and dwindled problem.Simultaneously because this baking temperature is higher than 85 ℃ of the pre-bake temperatures of photoresist EPI622, thereby make photoresist EPI622 after softening, volumetric expansion, under capillary effect, exceed 60% before the bridge district sacrifice layer aspect ratio baking of formation, as shown in Figure 9.
Adopting routine techniques is 1.8 * 10 in vacuum degree
-3Pa, speed is under the 0.3nm/s condition, the furling plating 4 of evaporation deposition one deck 100nm on sacrifice layer, as shown in Figure 3.
This furling plating 4 is made up of one deck 5nm thick Ti and the thick Au thin layer of one deck 95nm.The Ti thin layer can improve source end metal after the annealing and the adhesion strength between the electrogilding, and Au is used for reducing the resistance of conductive layer, makes that the current density of each point is identical when electroplating.
Step 4, resist coating, photoetching bridge and electrode zone.
At first, 4 are coated with the photoresist EPI622 that a layer thickness is 2.5 μ m on furling plating, make photoresist 7 evenly cover the furling plating surface, and toast 10min with 85 ℃ temperature;
Then, make air bridges and electrode zone by lithography with second reticle of making air bridges;
At last, in developer solution, soak 2min, dry up with nitrogen, as shown in Figure 4.
Step 5 is electroplated thickening air bridges and electrode zone.
In the cyanide-free electroplate liquid, utilize conventional electroplating technology, on bridge that makes by lithography and electrode zone, electroplate layer of Au, obtain electroplating the bridge of thickening and the metal level 5 of electrode zone, as shown in Figure 5.
Step 6, photoresist is removed in general exposure.
Directly carry out general exposure electroplating GaN substrate later, in developer solution, behind the immersion 2min, dry up, can remove the photoresist 7 on the electroless coating zone 8, as shown in Figure 6 with nitrogen with mask aligner.
The method of photoresist is removed in this general exposure, soaks the sacrifice layer photoresist in the time of can avoiding removing photoresist with acetone and the furling plating that causes is wrinkling, helps the removal of follow-up furling plating and the protection in electroless coating zone.
Step 7, corrosion furling plating, removal sacrifice layer obtain the arch air bridges.
Because when removing furling plating, can as shown in figure 10 furling plating metal residual phenomenon appear in edge, and the microwave property of device is produced certain negative effect, and can damage the grizzly bar of device during ultrasonic peeling off and influence device yield.So the present invention when adopting caustic solution to remove furling plating, is that the GaN substrate of photoresist is immersed into and corrodes 26s in the liquor kalii iodide removing mask layer earlier, rinses well with clear water, to remove the Au thin layer in the furling plating 4 on the electroless coating zone 8; Corrode 8s with hydrofluoric acid solution again, rinse well with clear water, to remove the Ti thin layer in the furling plating 4 on the electroless coating zone 8, then spend to peel off and soak 5min in the sol solution, to remove sacrifice layer, clean up with clear water at last, on the electrode that source electrode and the plating of GaNHEMT are thickeied, form independently air bridges, as shown in Figure 8.
Can access the neat more electroplated metal layer in edge with described corroding method, as Figure 13, shown in Figure 14.Because sacrifice layer of the present invention is to make with two kinds of photoresists of different nature, in corrosion process, can play the double shielding effect simultaneously, well protect non-stripping area, improve the rate of finished products of device.
Backing material selects for use GaN as substrate.
At first, on the GaN substrate, be coated with one deck 1.0 μ m thick peel off glue LOR5A, in baking oven with 160 ℃ temperature baking 20min; Be coated with the thick photoresist EPI622 of one deck 1.5 μ m again, with 85 ℃ of temperature baking 10min, the thickness proportion of peeling off glue LOR5A and photoresist EPI622 is 2:3; The bridge pier that makes bridge district 6 and Qiao Qu both sides by lithography with first reticle of making air bridges is the zone 3 of electrode then, soaks 2min at last in developer solution, and dries up with nitrogen, and 6 form 2.5 μ m sacrifice layers in the bridge district, as shown in Figure 1.
Step 2, low-temperature bake makes the sacrifice layer in bridge district form domes.
To forming the substrate baking 15min of sacrifice layer, make the bridge district become the neat domes of smooth surface, as shown in Figure 2 with 145 ℃ low temperature.
Because this baking temperature is lower than 160 ℃ of pre-bake temperatures peeling off glue LOR5A, make that the sacrifice layer width in bridge district is very little in baking after-contraction amount, solve the spanning degree that baking causes and dwindled problem.Simultaneously because this baking temperature is higher than 85 ℃ of the pre-bake temperatures of photoresist EPI622, thereby make photoresist EPI622 after softening, volumetric expansion, under capillary effect, exceed 54% before the bridge district sacrifice layer aspect ratio baking of formation, as shown in Figure 9.
Adopt routine techniques, the vacuum degree of deposition chamber is made as 1.8 * 10
-3Pa, speed is made as 0.3nm/s, and the furling plating 4 of evaporation deposition one deck 90nm is as shown in Figure 3 on sacrifice layer.
This furling plating 4 is made up of one deck 5nm thick Ti and the thick Au thin layer of one deck 85nm.The Ti thin layer can improve source end metal after the annealing and the adhesion strength between the electrogilding, and Au is used for reducing the resistance of conductive layer, makes that the current density of each point is identical when electroplating.
Step 4, resist coating makes bridge and electrode zone by lithography.
At first, being coated with a layer thickness on furling plating 4 is the photoresist EPI622 of 2.5 μ m, makes photoresist evenly cover the furling plating surface, and toasts 10min with 85 ℃ temperature;
Then, make bridge and electrode zone by lithography with second reticle of making air bridges;
At last, in developer solution, soak 2min, dry up with nitrogen, as shown in Figure 4.
Step 5 is electroplated thickening air bridges and electrode zone.
In the cyanide-free electroplate liquid, utilize conventional electroplating technology, on bridge that makes by lithography and electrode zone, electroplate layer of Au, obtain electroplating the thickening bridge with electrode zone metal level 5, as shown in Figure 5.
Step 6, photoresist is removed in general exposure.
Directly carry out general exposure electroplating GaN substrate later, in developer solution, behind the immersion 2min, dry up, can remove the photoresist 7 on the electroless coating zone 8, as shown in Figure 6 with nitrogen with mask aligner.
The method of photoresist is removed in this general exposure, soaks the sacrifice layer photoresist in the time of can avoiding removing photoresist with acetone and the furling plating that causes is wrinkling, helps the removal of follow-up furling plating and the protection in electroless coating zone.
Step 7, corrosion furling plating, removal sacrifice layer obtain the arch air bridges.
Since when removing furling plating, can be in edge's appearance furling plating metal residual phenomenon as shown in figure 10, to the certain negative effect of microwave property generation of device.So the present invention when adopting caustic solution to remove furling plating, is that the GaN sheet of photoresist is immersed into and corrodes 23s in the liquor kalii iodide removing mask layer earlier, rinses well with clear water, to remove the Au thin layer in the furling plating 4 on the electroless coating zone 8; Corrode 8s with hydrofluoric acid solution again, rinse well with clear water, to remove the Ti thin layer in the furling plating 4 on the electroless coating zone 8, then spend to peel off and soak 5min in the sol solution, to remove sacrifice layer, clean up with clear water at last, electroplate on the thickening electrode district at two and form independently air bridges, as shown in Figure 8.
Can access the neat more electroplated metal layer in edge with described corroding method.Because sacrifice layer of the present invention is to make with two kinds of photoresists of different nature, in corrosion process, can play the double shielding effect simultaneously, well protect non-stripping area, improve the rate of finished products of device.
Embodiment 4
The present invention makes based on the air bridges device architecture on the microwave high power GaN HEMTs substrate of making source, drain contact and Schottky contacts.
At first, on the GaN substrate, be coated with one deck 1.0 μ m thick peel off glue LOR5A, in baking oven with 160 ℃ temperature baking 20min; Be coated with the thick photoresist EPI622 of one deck 1.0 μ m again, with 85 ℃ of temperature baking 10min, the thickness proportion of peeling off glue LOR5A and photoresist EPI622 is 5:5; The bridge pier that makes bridge district 6 and Qiao Qu both sides by lithography with first reticle of making air bridges is the zone 3 of electrode then, soaks 2min at last in developer solution, and dries up with nitrogen, and 6 form 2 μ m sacrifice layers in the bridge district, as shown in Figure 1.
Step 2, low-temperature bake makes the bridge district of sacrifice layer form domes.
To forming the substrate baking 25min of sacrifice layer, make the bridge district become the neat domes of smooth surface, as shown in Figure 2 with 140 ℃ low temperature.
Because this baking temperature is lower than 160 ℃ of pre-bake temperatures peeling off glue LOR5A, make that the sacrifice layer width in bridge district is very little in baking after-contraction amount, solve the spanning degree that baking causes and dwindled problem.Simultaneously because this baking temperature is higher than 85 ℃ of the pre-bake temperatures of photoresist EPI622, thereby make photoresist EPI622 after softening, volumetric expansion, under capillary effect, exceed 50% before the bridge district sacrifice layer aspect ratio baking of formation, as shown in Figure 9.
Adopt routine techniques, the vacuum degree of deposition chamber is made as 1.8 * 10
-3Pa, speed is made as 0.3nm/s, the furling plating 4 of evaporation deposition one deck 100nm on sacrifice layer, as shown in Figure 3.
This furling plating 4 is made up of one deck 5nm thick Ti and the thick Au thin layer of one deck 95nm.The Ti thin layer can improve source end metal after the annealing and the adhesion strength between the electrogilding, and Au is used for reducing the resistance of conductive layer, makes that the current density of each point is identical when electroplating.
Step 4, resist coating, photoetching bridge and electrode zone.
At first, being coated with a layer thickness on furling plating 4 is the photoresist EPI622 of 2.5 μ m, makes photoresist evenly cover furling plating 4 surfaces, and toasts 10min with 85 ℃ temperature;
Then, make air bridges and electrode zone by lithography with second reticle of making air bridges;
At last, in developer solution, soak 2min, dry up with nitrogen, as shown in Figure 4.
Step 5 is electroplated thickening air bridges and electrode zone.
In the cyanide-free electroplate liquid, utilize conventional electroplating technology, on bridge that makes by lithography and electrode zone, electroplate layer of Au, obtain electroplating the bridge of thickening and the metal level 5 of electrode zone, as shown in Figure 5.
Step 6, resist coating makes the electroless coating zone by lithography again.
At first, on the metal level 5 of electroplating GaN substrate later, be coated with last layer photoresist EPI622, with 85 ℃ temperature baking 10min;
Then, make electroless coating zone 8 by lithography, keep the photoresist 7 on the metal level 5 with the 3rd reticle of making air bridges;
At last, soak 2min in developer solution, nitrogen dries up, as shown in Figure 7.
Adopt this method, photoresist adds thick metal layers to plating and shields, and in subsequent corrosion removal furling plating process, has avoided KI to electroplating the corrosion of thickening layer.
Step 7, corrosion furling plating, removal sacrifice layer obtain the arch air bridges.
Because when removing furling plating, can as shown in figure 10 furling plating metal residual phenomenon appear in edge, and the microwave property of device is produced certain negative effect, and can damage the grizzly bar of device during ultrasonic peeling off and influence device yield.So the present invention when adopting caustic solution to remove furling plating, is that the GaN substrate of photoresist is immersed into and corrodes 26s in the liquor kalii iodide removing mask layer earlier, rinses well with clear water, to remove the Au thin layer in the furling plating 4 on the electroless coating zone 8; Corrode 8s with hydrofluoric acid solution again, rinse well with clear water, to remove the Ti thin layer in the furling plating 4 on the electroless coating zone 8, then spend to peel off and soak 5min in the sol solution, to remove sacrifice layer, clean up with clear water at last, on the electrode that source electrode and the plating of GaNHEMTs are thickeied, form independently air bridges, as shown in Figure 8.
Can access the neat more electroplated metal layer in edge with described corroding method.Because sacrifice layer of the present invention is to make with two kinds of photoresists of different nature, in corrosion process, can play the double shielding effect simultaneously, well protect non-stripping area, improve the rate of finished products of device.
Embodiment 5
The present invention makes based on the air bridges device architecture on the microwave high power GaN HEMTs substrate of making source, drain contact and Schottky contacts.
Technical process is identical with embodiment 4, and different is: the glue thickness of peeling off of sacrifice layer is 2.0 μ m, and the thickness of photoresist is 2.0 μ m; The sacrifice layer baking temperature is 135 ℃, and stoving time is 15min; The thickness of furling plating is 80nm.
Embodiment 6
The present invention makes based on the air bridges device architecture on the microwave high power GaN HEMTs substrate of making source, drain contact and Schottky contacts.
Technical process is identical with embodiment 4, and different is: the glue thickness of peeling off of sacrifice layer is 1.0 μ m, and the thickness of photoresist is 1.5 μ m; The sacrifice layer baking temperature is 145 ℃, and stoving time is 20min; The thickness of furling plating is 90nm.
Embodiment 7
Backing material selects for use GaN as substrate.
Technical process is identical with embodiment 3, and different is: the glue thickness of peeling off of sacrifice layer is 1.5 μ m, and the thickness of photoresist is 1.5 μ m; The sacrifice layer baking temperature is 138 ℃, and stoving time is 22min; The thickness of furling plating is 80nm.
From adding the air bridge structure electron-microscope scanning SEM design sketch that thick electrode is a bridge pier that Figure 11, Si substrate shown in Figure 12 are made with two, air bridges is the arch bridge of big radian as can be seen, and after electroplating the metal edge process erosion removal furling plating of thickening, electroplate the thickening metal edge and still keep neatly smooth.
From Figure 13, GaN HEMTs device shown in Figure 14 make to add the air bridge structure electron-microscope scanning SEM design sketch that thick electrode and source termination electrode are bridge pier, air bridges is the arch bridge of big radian as can be seen, and the metal edge of electroplating thickening is electroplated the thickening metal and is still kept neatly smooth behind the excessive erosion furling plating.
Backing material of the present invention is selected for use and is not limited to selected Si and GaN material among the embodiment, also can select other compound semiconductor materials for use.Different compound semiconductor materials, only the preceding device making technics of air bridges is made in influence, and does not influence the manufacture craft of air bridges itself.
Claims (10)
1. the method for producing air bridge in the compound semiconductor microwave high power device comprises following process:
The high temperature that is coated with pre-bake temperature and is 160 ℃ on Si or GaN substrate is peeled off glue, is coated with pre-bake temperature again and is 85 ℃ photoresist, and the position makes the electrode zone (3) on bridge district (6) and Qiao Qu both sides by lithography therebetween, makes this bridge district (6) form sacrifice layer;
The substrate that scribbles described two kinds of glue is placed in the baking oven toasts, make the sacrifice layer in bridge district become the neat complete domes of smooth surface, baking temperature: 135 ℃-145 ℃ low temperature, stoving time: 15-25min;
Deposit one deck 80nm-100nm furling plating (4) on sacrifice layer;
Go up resist coating and make bridge district and electrode zone by lithography at furling plating (4);
In the cyanide-free electroplate liquid, utilize electroplating technology, in the bridge district that makes by lithography and electrode zone electroplate layer of Au, form metal level (5);
Utilize the photoresist on the general exposure technology removal electroless coating zone (8), remove furling plating (4), spend and peel off the sacrifice layer that sol solution is removed bridge district (6), obtain the arch air bridges with etching process.
2. method for producing air bridge according to claim 1 is characterized in that peeling off glue and adopts the LOR5A model, and photoresist adopts the EPI622 model, and the thickness proportion of peeling off glue and photoresist is 2:3～5:5.
3. method for producing air bridge according to claim 1 is characterized in that the gross thickness of sacrifice layer is at least 2 μ m.
4. method for producing air bridge according to claim 1 is characterized in that furling plating is the Au thin layer that the Ti thin layer of 5nm adds 75nm-95nm.
5. the method for producing air bridge in the compound semiconductor microwave high power device comprises following process:
On the source of having made, drain contact and schottky junctions GaN HEMTs device after touch, coat pre-bake temperature earlier and be 160 ℃ high temperature and peel off glue, be coated with pre-bake temperature again and be 85 ℃ photoresist, and make the electrode zone (3) on bridge district (6) and Qiao Qu both sides by lithography in the centre position, make this bridge district (6) form sacrifice layer;
The substrate that scribbles described two kinds of glue is placed in the baking oven toasts, make the sacrifice layer in bridge district become the neat complete domes of smooth surface, baking temperature: 135 ℃-145 ℃ low temperature, stoving time: 15-25min;
Deposit one deck 80nm-100nm furling plating (4) on sacrifice layer;
Go up resist coating and make bridge district and electrode zone by lithography at furling plating (4);
In the cyanide-free electroplate liquid, utilize electroplating technology, in the bridge district that makes by lithography and electrode zone electroplate layer of Au and form metal level (5);
Plating aspect after electroplating Au is on the metal level (5), and resist coating also makes electroless coating zone (8) by lithography;
Utilize the furling plating (4) on the etching process removal electroless coating zone (8),, spend and peel off the sacrifice layer that sol solution is removed bridge district (6), obtain the arch air bridges with the photoresist (7) on the general exposure technology removal metal level (5).
6. method for producing air bridge according to claim 5 is characterized in that peeling off glue and adopts the LOR5A model, and photoresist adopts the EPI622 model, and the thickness proportion of peeling off glue and photoresist is 2:3～5:5.
7. method for producing air bridge according to claim 5 is characterized in that the gross thickness of sacrifice layer is at least 2 μ m.
8. method for producing air bridge according to claim 5 is characterized in that furling plating is the Au thin layer that the Ti thin layer of 5nm adds 75nm-95nm.
9. the method for producing air bridge in the compound semiconductor microwave high power device comprises following process:
On the GaN of the source of having made, drain contact and Schottky contacts HEMTs device, the high temperature that is coated with pre-bake temperature earlier and is 160 ℃ is peeled off glue, be coated with pre-bake temperature again and be 85 ℃ photoresist, and the position makes the electrode zone (3) on Qiao Qu and Qiao Qu both sides by lithography therebetween, makes this bridge district (6) form sacrifice layer;
The substrate that scribbles described two kinds of glue is placed in the baking oven toasts, make the sacrifice layer in bridge district become the neat complete domes of smooth surface, baking temperature: 140 ℃ low temperature, stoving time: 20min;
Deposit one deck 100nm furling plating (4) on sacrifice layer;
Resist coating and make bridge district and electrode zone by lithography on furling plating;
In the cyanide-free electroplate liquid, utilize electroplating technology, in the bridge district that makes by lithography and electrode zone electroplate layer of Au, form metal level (5);
Utilize the photoresist on the general exposure technology removal electroless coating zone (8), remove furling plating (4), spend and peel off the sacrifice layer that sol solution is removed bridge district (6), obtain the arch air bridges with etching process.
10. method for producing air bridge according to claim 9 is characterized in that peeling off glue and adopts the LOR5A model, and photoresist adopts the EPI622 model, and the thickness proportion of peeling off glue and photoresist is 2:3～5:5; The gross thickness of sacrifice layer is at least 2 μ m; Furling plating is the Au thin layer that the Ti thin layer of 5nm adds 75nm-95nm.
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| CN101800189B (en) * | 2009-02-11 | 2013-05-01 | 中国科学院微电子研究所 | Method for manufacturing dielectric bridge by using benzocyclobutene |
| CN102375332B (en) * | 2010-08-19 | 2013-07-17 | 中国科学院上海微***与信息技术研究所 | Suspension photoresist planarization technology for MEMS structure |
| JP5578012B2 (en) * | 2010-10-15 | 2014-08-27 | 三菱電機株式会社 | Air bridge manufacturing method |
| CN102479745B (en) * | 2010-11-26 | 2013-12-04 | 中国科学院微电子研究所 | Method for preparing field plate metal suitable for gallium nitride microwave monolithic integrated circuit |
| CN102358613A (en) * | 2011-10-12 | 2012-02-22 | 中国电子科技集团公司第二十四研究所 | Manufacturing method of micro-electromechanical systems (MEMS) arch structure |
| CN102915957B (en) * | 2012-09-17 | 2014-08-06 | 北京大学 | Method for making air bridge and inductance |
| CN106684007B (en) * | 2017-02-21 | 2019-03-15 | 无锡盈芯半导体科技有限公司 | A kind of production method of semiconductor technology air bridges |
| CN109473391A (en) * | 2018-11-12 | 2019-03-15 | 苏州汉骅半导体有限公司 | Air bridges manufacturing method |
| CN109559985B (en) * | 2018-11-23 | 2021-04-23 | 中国工程物理研究院电子工程研究所 | Semiconductor device with air bridge and manufacturing method thereof |
| CN110993561A (en) * | 2019-11-28 | 2020-04-10 | 福建省福联集成电路有限公司 | Method for preventing disconnection of metal connecting wire |
| CN111063657B (en) * | 2019-11-29 | 2022-08-05 | 福建省福联集成电路有限公司 | Air bridge for high current and manufacturing method |
| CN114171669A (en) * | 2021-11-26 | 2022-03-11 | 北京量子信息科学研究院 | Superconducting quantum chip and preparation method and application thereof |
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