Summary of the invention
The present invention is in order to improve etch rate and effect, and reduces cost, it is provided that a kind of Temperature-controlldeep deep silicon etching method.
The technical solution used in the present invention is to provide a kind of Temperature-controlldeep deep silicon etching method, and for sense coupling machine, the method includes: positive photoresist graphic making step, anisotropic etching step, isotropism depositing step, removes photoresist step;It is characterized in that, the method uses and cools down and use cryogenic liquid as circulating cooling liquid in the many places of described etching machine, thus obtain low temperature, and described anisotropic etching step and isotropism depositing step alternating cyclical etch are to complete under the cryogenic conditions of the plasma etching room of etching machine.
Further, the low temperature of described etching chamber is 0-7 DEG C.
Further, described etching machine includes: main frame, radio-frequency power supply cabinet, electrical control cubicles, gas holder, circulating cooling machine, computer and operating board;Wherein the core component of main frame is plasma source, and it is formed one by plane variable-pitch propeller type inductance coil and high-frequency ceramic medium, and described ceramic dielectric is presented herein below plasma etching room;Between inductively coupled plasma electrode (upper electrode) and radio-frequency electrode (bottom electrode), annular gas flow allotter is installed.
Further, the many places cooling of described etching machine is to arrange cooling line at radio-frequency electrode, etching chamber sidewall, etching gas path pipe.
Further, circulate in described cooling line is cryogenic liquid;Described cryogenic liquid uses ethylene glycol.
Further, between silicon chip and radio-frequency electrode, also put one layer of graphite felt and be beneficial to heat conduction.
Further, the comprising the concrete steps that of described method:
(1) positive photoresist graphic making step:
Be on 400u2 inch silicon wafer at thickness, coat the photoresist of 2 10u, expose, develop after make required figure on a photoresist.
(2) anisotropic etching step:
The described etching chamber that the silicon chip carrying out figure is put on described sense coupling machine alternately etches, and wherein temperature control etching chamber process conditions are temperature: 13 DEG C, pressure: 5 6Pa;Etching gas SF6Flow 130 150sccm, upper electrode power 800 900W, lower electrode power 40 50W, etch period 10 14 seconds;
(3) isotropism depositing step:
Deposited gas C4F8And CHF3, C4F8Flow: 80 90sccm, CHF3Flow: 5 15sccm;Upper electrode power 500 700W, lower electrode power 0 10W, deposition time 8 10 seconds;
Described etch step and depositing step alternate cycles are carried out, and the time is 18 24 seconds, alternate cycles 30 150 times.
(4) photoresist step is removed:
The silicon chip that will have etched, is placed on ultrasonic waves for cleaning in acetone soln, and Wafer Cleaning is clean, dries.
The invention has the beneficial effects as follows that Temperature-controlldeep deep silicon etching method makes the anisotropic etching step in alternately etching extend, isotropism depositing step shortens, thus improves etch rate, and vertical etch is easy to control, and makes the selection ratio of photoresist be greatly improved.
Detailed description of the invention
The method of the present invention uses sense coupling machine to complete, and this etching machine is that domestic ICP equipment enters production line operation the earliest.This etching machine structure includes: main frame, radio-frequency power supply cabinet, electrical control cubicles, gas holder, circulating cooling machine, computer and operating board.Wherein the core component of main frame is plasma source, and it is formed one by plane variable-pitch propeller type inductance coil and high-frequency ceramic medium, and ceramic dielectric is presented herein below plasma etching room.The drum-shaped sidewall of described etching chamber has imbedded intensive cooling line.Etching chamber bottom is the radio-frequency electrode having imbedded cooling line, covers the graphite felt that one layer of heat conduction is good, constitute sample stage on radio-frequency electrode.
Between inductively coupled plasma electrode (upper electrode) and radio-frequency electrode (bottom electrode), annular gas flow allotter is installed.This machine simple in construction performance is excellent.
The technological process of the present invention includes: positive photoresist graphic making step, anisotropic etching step, isotropism depositing step, removes photoresist step.
Wherein anisotropic etching step and isotropism depositing step alternating cyclical etch are the technique completed under the cryogenic conditions of temperature control etching chamber.Cooling line has been imbedded inside temperature control etching chamber sidewall and bottom electrode, the etching gas circuit outer wall outside etching chamber, also it is wrapped cooling line.
In above cooling line, circulation is not water, but cryogenic liquid (ethylene glycol), its feature is not freeze below 0 DEG C, so can obtain low temperature (0 7 DEG C).Its participation makes the anisotropic etching step in alternately etching extend, and isotropism depositing step shortens, thus improves etch rate, and vertical etch is easy to control, and makes the selection ratio of photoresist be greatly improved.
It addition, in order to solve to be etched on silicon chip the heat accumulation produced for a long time, put one layer of graphite felt (Heat Conduction Material) between silicon chip and radio-frequency electrode (bottom electrode).Present invention process is simple and easy to control.Etching surface and sidewall flat smooth.
[embodiment 1]
This embodiment comprises the following steps:
(1) photoetching offset plate figure making step:
It is on 400u2 inch silicon wafer at thickness, coats photoresist, thickness: 2u, with photo-etching machine exposal, development, make required figure on a photoresist;
(2) anisotropic etching step:
The temperature control etching chamber that the silicon chip carrying out figure is put on described sense coupling machine alternately etches, and etching chamber temperature is 2 DEG C, and pressure is 5Pa.Process conditions: upper electrode power 850W, lower electrode power 40W, etching gas SF6Flow 140sccm, etch period 10 seconds.
(3) isotropic plasma depositing step:
This step is used for making sidewall protecting film, its process conditions: deposited gas C4F8Flow be 85sccm and CHF3Flow be 5sccm, upper electrode power 600W, lower electrode power 0W, deposition time 8 seconds.
Step (2) and (3) alternating cyclical etch, alternate cycles 34 times, etching depth 22u;
This embodiment etches without removing photoresist, it is therefore an objective to observe the pattern of glue.As shown in Figure 3;
[embodiment 2], this embodiment comprises the following steps:
(1) photoetching offset plate figure making step:
It is on 400u2 inch silicon wafer at thickness, coats photoresist, thickness: 3.5u, with photo-etching machine exposal, glue is made required figure;
(2) anisotropic etching step:
The temperature control etching chamber that the silicon chip carrying out figure is put on sense coupling machine alternately etches, and etches indoor temperature 2 DEG C, pressure 5.5Pa.Process conditions: upper electrode power 900W, lower electrode power 45W, etching gas SF6, flow 150sccm, etch period 14 seconds.
(3) isotropic plasma deposition step:
This step is used for making sidewall protecting film, its process conditions deposited gas C4F8And CHF3Flow be respectively 80sccm and 10sccm, upper electrode power 700W, lower electrode power 0W, deposition time 10 seconds.
Step (2) and (3) alternating cyclical etch, alternate cycles 125 times.
(4) photoresist step is removed:
The silicon chip alternately etched, putting in acetone soln, ultrasound wave removes photoresist, and Wafer Cleaning is clean, dries.
Measuring etching depth with step instrument is 105u, observes section pattern with SEM.As shown in Figure 4.
Due to the fact that and take above technical scheme, it has the advantage that 1) deep silicon etching perpendicularity is good;2) deep silicon vertical etch control accuracy is high;3) deep silicon vertical etch selects ratio high;4) deep silicon vertical etch depth-to-width ratio is high;5) being applied to home equipment, cost performance is higher.