A kind of system and method that discharges the MEMS structure by the etch silicon sacrifice layer
Technical field
The present invention relates to MEMS sacrifice layer release tech field, relate in particular to a kind of system and method that discharges the MEMS structure by the etch silicon sacrifice layer.
Background technology
Release process is the technology of often using in the MEMS manufacture process.Release process is divided into wet method release and dry method discharges.Wet method discharges and adopts a large amount of acid-base solutions, has limited the application that is used for the device interconnection metal, and can cause the increase of environmental pollution and cost for wastewater treatment; Discharge etch period and be difficult to control; Slower at thin etch rate with long gap area; The most serious is the bunching that can cause fine structure in dry run, and figure is destroyed.When dry method release using plasma carried out etching, the surperficial microroughness after the etching was big, and etching is incomplete, and residue is arranged; Because the electric charge that inhomogeneous plasma produces can cause the inefficacy of Sensitive Apparatus on the silicon chip, and micro-structural is damaged; Plasma etching equipment price costliness, temperature required higher, the etching selection ratio brings device damage easily, is not suitable for the release of MEMS sacrifice layer of future generation.
XeF
2Be the agent of a kind of silicon etching of isotropism fast, need not plasma source, and many CMOS and semiconductor common used material are had very high selection ratio.One of main application is that the etch silicon sacrifice layer is to discharge the MEMS structure.As dry method release process, XeF
2Etching avoided wet method discharge in since stir or adhesion to the damage of device.XeF
2Extremely low to other semi-conducting material etch rate, this technology guarantees to promote yield, reduces manufacturing cost and improves device performance.Before, for the uniformity that improves the full wafer wafer passes through to reduce gas pressure and flow, or add the method for carrier gas.To influence etch rate and handling capacity yet reduce air pressure and flow, and adding carrier gas meeting lowers efficiency and increases operating cost.Supercritical carbon dioxide has guaranteed crystal column surface high smooth degree as carrier gas, and can not reduce etch rate and efficient.
Summary of the invention
(1) technical problem that will solve
Main purpose of the present invention is to provide a kind of system and method that discharges the MEMS structure by the etch silicon sacrifice layer.
(2) technical scheme
Be an aspect that achieves the above object, the invention provides a kind of system by etch silicon sacrifice layer release MEMS structure, this system comprises:
CO
2The source is used to provide complementary atmospheric carbon dioxide, and silicon chip is carried out the physics auxiliary etch;
XeF
2The source is used to provide xenon difluoride gas, as reactive etch gas;
XeF
2Flow control valve 1 and CO
2 Flow control valve 2 is used to control CO
2And XeF
2Flow, adjustments of gas CO
2And XeF
2Mixing ratio;
High-pressure pump 3 is used for CO
2And XeF
2Mist pressurize, and the mist after will pressurizeing enters in the ballast box 5 by first valve 4;
Ballast box 5 is used to deposit CO
2And XeF
2High pressure mixed gas, this high pressure mixed gas enters in the reaction chamber 8 by second valve 6 and heater strip 7;
Heater strip 7 is used for the CO with high pressure mixed gas
2Gas is heated to more than the critical-temperature;
Reaction chamber 8, the XeF in the high pressure mixed gas
2In reaction chamber 8 sacrificial silicon layer is corroded, the pressure in ballast box 5 and reaction chamber 8 reaches poised state, and the needle valve 9 that is communicated with reaction chamber 8 and spill cavity 10 will be opened, and the mist in the reaction chamber 8 is sent into spill cavity 10;
Spill cavity 10, after the pressure in the reaction chamber 8 surpasses setup pressure value, the mist in the reaction chamber 8 will spill in the spill cavity 10;
Exhaust gas processing device 11 is used for tail gas is handled, and avoids contaminated environment; And
Filter and purification devices 12, be used to realize the separation of gas, liquid, slag and the purifying of carbon dioxide.
In the such scheme, pressure sensor 21, nozzle 22, mask 23, sacrificial silicon layer 24, support 25 and magnetic stirring apparatus 26 are installed in the described reaction chamber 8, wherein:
Pressure sensor 21 is used for measuring the pressure of reaction chamber 8;
Nozzle 22, high pressure mixed gas incides mask 23 on the sacrificial silicon layer 24 through nozzle 22;
Support 25 is used to hold the mask 23 on sacrificial silicon layer to be corroded 24 and the sacrificial silicon layer 24;
Magnetic stirring apparatus 26 is used for accelerated corrosion speed, makes etching more even.
In the such scheme, described mask 23 is silica, photoresist or metal mask.
Be another aspect that achieves the above object, the invention provides a kind of method, it is characterized in that this method comprises by etch silicon sacrifice layer release MEMS structure:
Open XeF
2Flow control valve 1 and CO
2 Flow control valve 2, control CO
2And XeF
2Flow, adjustments of gas CO
2And XeF
2Mixing ratio;
Operation high-pressure pump 3 is to CO
2And XeF
2Mist pressurize, enter in the ballast box 5 by first valve 4;
When ballast box 5 and reaction chamber 8 reach primary condition, second valve 6 is just opened, and allows CO
2And XeF
2Mist enter in the reaction chamber 8;
Pressure in ballast box 5 and reaction chamber 8 reaches poised state, and the needle valve 9 that is communicated with reaction chamber 8 and spill cavity 10 will be opened, and the gas in the reaction chamber 8 is sent in the spill cavity 10, and needle valve 9 was closed when the pressure in reaction chamber 8 was returned to initial pressure;
Gas in the spill cavity 10 enters the filtered pure makeup and puts 12 behind exhaust gas processing device 11, the carbon dioxide that comes out from filter purification devices 12 enters in the carbon dioxide storage tank once more.
In the such scheme, the initial pressure in the ballast box 5 is 11MPa, and initial temperature is 50 ℃; The initial pressure of reaction chamber 8 is 7.6MPa, and initial temperature is 50 ℃.
In the such scheme, at CO
2And XeF
2Mist enter reaction chamber 8 before, the heating by heater strip 7 makes that the carbon dioxide in the mist reaches supercritical temperature in the pipeline; This process lasts till that the pressure in ballast box 5 and the reaction chamber 8 reaches poised state.
In the such scheme, after described carbon dioxide entered in the carbon dioxide storage tank once more, this method also comprised: feed pure CO
2Take out of reaction chamber 8 such as the residue of etching and some particles, when the pressure drop in the reaction chamber 8 to the pressure in 7.6Mpa and the ballast box 5 is increased to 11MPa, repeat above step, after circulating so several times, the dry method of just finishing sacrificial silicon layer discharges.
In the such scheme, work as CO
2And XeF
2Mist when entering in the reaction chamber 8, by pressure sensor 21 pressure in the reaction chamber 8 is maintained 7.6MPa, be blown into silicon substrate 24 as sacrifice layer, XeF by nozzle 22
2Can resolve into the F group, generate volatile fluoride, discharge by needle valve 9 then with pasc reaction; Magnetic stirring apparatus 26 accelerated corrosion speed make corrosion more even, and surface flatness is higher.
(3) beneficial effect
System and method by etch silicon sacrifice layer release MEMS structure provided by the invention, the gas stream that crystal column surface obtains very evenly, concentrates, surface flatness is higher, pure XeF can not occur
2Produce coarse surface during etch silicon.This method etch rate is very fast, efficient height, good uniformity.Supercritical carbon dioxide provides even etching environment, can corrode tiny and long and narrow structure, and be completely to the etching of sacrificial silicon layer, noresidue.This method collection etching and drying and one wet method can not occur and discharge the phenomenon that produces adhesion, can not destroy micro-structural, so productive rate are higher, are fit to produce in enormous quantities in the industry.
Description of drawings
Fig. 1 is the structural representation that discharges the system of MEMS structure by the etch silicon sacrifice layer provided by the invention;
Wherein: 1 is XeF
2Flow control valve, 2 is CO
2Flow control valve II, 3 is high-pressure pump, and 4 is first valve, and 5 is ballast box, and 6 is second valve, and 7 is heater strip, and 8 is reaction chamber, and 9 is needle valve, and 10 is spill cavity, and 11 is exhaust gas processing device, and 12 for filtering purification devices.
Fig. 2 is the structural representation by reaction chamber in the system of etch silicon sacrifice layer release MEMS structure provided by the invention;
Wherein: 21 is pressure sensor, and 22 is nozzle, and 23 is mask material, and 24 is silicon substrate, and 25 is bracing frame, and 26 is magnetic stirring apparatus, and 8 is reaction chamber.
The specific embodiment
For making the purpose, technical solutions and advantages of the present invention clearer, below in conjunction with specific embodiment, and with reference to accompanying drawing, the present invention is described in more detail.
The invention provides a kind of method by etch silicon sacrifice layer release MEMS structure, this method utilizes xenon difluoride as etching reaction gas, and supercritical carbon dioxide discharges sacrificial silicon layer as carrier gas.Carbon dioxide utilizes the distinctive character of its above-critical state to make xenon difluoride more even to the etching of silicon, and the smoothness of corrosion surface is higher, and etching is more complete.Discharge with traditional wet method and plasma discharges and compares, this method for releasing avoided wet method discharge in since stir or adhesion to the damage of device, can improve the uniformity of full wafer wafer, reaction rate is very fast, the efficient height, the time weak point makes XeF
2Etching becomes feasible production in enormous quantities technology.
As shown in Figure 1, Fig. 1 is the structural representation that discharges the system of MEMS structure by the etch silicon sacrifice layer provided by the invention.Wherein: CO
2The source provides complementary atmospheric carbon dioxide, and silicon chip is carried out the physics auxiliary etch, regulates etch rate; The adjustments of gas mixing ratio improves security simultaneously; XeF
2The source provides xenon difluoride gas, as reactive etch gas.XeF
2Flow control valve 1 and CO
2 Flow control valve 2 is used to control CO
2And XeF
2Flow, adjustments of gas CO
2And XeF
2Mixing ratio.High-pressure pump 3 is used for CO
2And XeF
2Mist pressurize, and the mist after will pressurizeing enters in the ballast box 5 by first valve 4.Ballast box 5 is used to deposit CO
2And XeF
2High pressure mixed gas, this high pressure mixed gas enters in the reaction chamber 8 by second valve 6 and heater strip 7.Heater strip 7 is used for the CO with high pressure mixed gas
2Gas is heated to more than the critical-temperature.Reaction chamber 8, the XeF in the high pressure mixed gas
2In reaction chamber 8 sacrificial silicon layer is corroded, the pressure in ballast box 5 and reaction chamber 8 reaches poised state, and the needle valve 9 that is communicated with reaction chamber 8 and spill cavity 10 will be opened, and the mist in the reaction chamber 8 is sent into spill cavity 10.Spill cavity 10, after the pressure in the reaction chamber 8 surpasses setup pressure value, the mist in the reaction chamber 8 will spill in the spill cavity 10.Exhaust gas processing device 11 is used for tail gas is handled, and avoids contaminated environment.Filter and purification devices 12, be used to realize the separation of gas, liquid, slag and the purifying of carbon dioxide.
As shown in Figure 2, Fig. 2 is the structural representation by reaction chamber in the system of etch silicon sacrifice layer release MEMS structure provided by the invention.Pressure sensor 21, nozzle 22, mask 23, sacrificial silicon layer 24, support 25 and magnetic stirring apparatus 26 are installed in the described reaction chamber 8, and wherein: pressure sensor 21 is used for measuring the pressure of reaction chamber 8; Nozzle 22, high pressure mixed gas incides mask 23 on the sacrificial silicon layer 24 through nozzle 22; Support 25 is used to hold the mask 23 on sacrificial silicon layer to be corroded 24 and the sacrificial silicon layer 24; Magnetic stirring apparatus 26 is used for accelerated corrosion speed, makes etching more even.Mask 23 is silica, photoresist or metal mask.
Based on the system by etch silicon sacrifice layer release MEMS structure provided by the invention illustrated in figures 1 and 2, the method by etch silicon sacrifice layer release MEMS structure provided by the invention comprises:
Step 1: open XeF
2Flow control valve 1 and CO
2 Flow control valve 2, control CO
2And XeF
2Flow, adjustments of gas CO
2And XeF
2Mixing ratio;
Step 2: operation high-pressure pump 3, to CO
2And XeF
2Mist pressurize, enter in the ballast box 5 by first valve 4;
Step 3: when ballast box 5 and reaction chamber 8 reach primary condition, second valve 6 is just opened, and allows CO
2And XeF
2Mist enter in the reaction chamber 8;
Step 4: the pressure in ballast box 5 and reaction chamber 8 reaches poised state, the needle valve 9 that is communicated with reaction chamber 8 and spill cavity 10 will be opened, gas in the reaction chamber 8 is sent in the spill cavity 10, and needle valve 9 was closed when the pressure in reaction chamber 8 was returned to initial pressure;
Step 5: the gas in the spill cavity 10 enters the filtered pure makeup and puts 12 behind exhaust gas processing device 11, the carbon dioxide that comes out from filter purification devices 12 enters in the carbon dioxide storage tank once more.
Refer again to Fig. 1, technological process is: open XeF
2Flow control valve 1 and CO
2 Flow control valve 2, control CO
2And XeF
2Flow, adjustments of gas CO
2And XeF
2Mixing ratio; Operation high-pressure pump 3 is to mist CO
2And XeF
2Pressurize, enter in the ballast box 5 by first valve 4.The initial pressure of ballast box is 11MPa, and initial temperature is 50 ℃; The initial pressure of reaction chamber is 7.6MPa, and initial temperature is 50 ℃; When ballast box 5 and reaction chamber 8 reach primary condition, second valve 6 is just opened, and allows CO
2And XeF
2Mist enter in the reaction chamber 8, before entering reaction chamber 8, the heating by heater strip 7 makes that the carbon dioxide in the mist reaches supercritical temperature in the pipeline; This process lasts till that the pressure in ballast box 5 and the reaction chamber 8 reaches poised state; The needle valve 9 that is communicated with reaction chamber 8 and spill cavity 10 afterwards will be opened, and the gas in the reaction chamber 8 is sent in the spill cavity 10, and needle valve 9 was closed when the pressure in reaction chamber 8 was returned to 7.6MPa.Gas in the spill cavity 10 enters the filtered pure makeup and puts 12 behind exhaust gas processing device 11, the carbon dioxide that comes out from filter purification devices 12 enters in the carbon dioxide storage tank once more, and is recycling; Feed pure CO then
2Be used for taking out of reaction chamber 8 such as the residue of etching and some particles; When the pressure drop in the reaction chamber 8 to the pressure in 7.6MPa and the ballast box 5 is increased to 11MPa, repeat above step, after circulating so several times, the dry method of just having finished sacrificial silicon layer discharges.
Refer again to Fig. 2, the process in the reaction chamber is: by pressure sensor 21 pressure in the reaction chamber 8 is maintained 7.6MPa, when mist enters in the reaction chamber 8, be blown into silicon substrate 24 as sacrifice layer, XeF by nozzle 22
2Can resolve into the F group, generate volatile fluoride, discharge by needle valve 9 then with pasc reaction.Magnetic stirring apparatus 26 accelerated corrosion speed make corrosion more even, and surface flatness is higher.
Above-described specific embodiment; purpose of the present invention, technical scheme and beneficial effect are further described; institute is understood that; the above only is specific embodiments of the invention; be not limited to the present invention; within the spirit and principles in the present invention all, any modification of being made, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.