Summary of the invention
The present invention is in order to improve etch rate and effect, and Cost reduction, provides a kind of temperature control dark silicon etching method.
The technical solution used in the present invention provides the dark silicon etching method of a kind of temperature control, is used for the inductively coupled plasma etching machine, and the method comprises: positive photoresist graphic making step, and the anisotropic etching step, the isotropism depositing step is removed the photoresist step; It is characterized in that, the method adopts in the cooling of the many places of described etching machine and adopts cryogenic liquid as circulating cooling liquid, thereby acquisition low temperature, and described anisotropic etching step and isotropism depositing step alternate cycles etching are to finish under the cryogenic conditions of the plasma etching chamber of etching machine.
Further, the low temperature of described etching chamber is 0-7 ℃.
Further, described etching machine comprises: main frame, radio-frequency power supply cabinet, electrical control cubicles, gas holder, circulating cooling machine, computer and operating desk; Wherein the core component of main frame is plasma source, and it is by plane variable-pitch propeller type inductance coil and high-frequency ceramic medium composition one, is the plasma etching chamber below the described ceramic dielectric; Annular gas flow distributor is installed between inductively coupled plasma electrode (top electrode) and radio-frequency electrode (bottom electrode).
Further, the cooling of the many places of described etching machine is at radio-frequency electrode, etching chamber sidewall, etching gas path pipe cooling line to be set.
What circulate in the described cooling line further, is cryogenic liquid; What described cryogenic liquid adopted is ethylene glycol.
Further, between silicon chip and radio-frequency electrode, also put one deck graphite felt and be beneficial to heat conduction.
Further, the concrete steps of described method are:
(1) positive photoresist graphic making step:
Be on 2 inches silicon chips of 400u at thickness, coat the photoresist of 2-10u, exposure, make required figure at photoresist after developing.
(2) anisotropic etching step:
The described etching chamber that the silicon chip of carrying out figure is put on the described inductively coupled plasma etching machine replaces etching, and wherein temperature control etching chamber process conditions are temperature: 1-3 ℃, and pressure: 5-6Pa; Etching gas SF
6Flow 130-150sccm, upper electrode power 800-900W, lower electrode power 40-50W, etch period 10-14 seconds;
(3) isotropism depositing step:
Deposited gas C
4F
8And CHF
3, C
4F
8Flow: 80-90sccm, CHF
3Flow: 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) remove the photoresist step:
The silicon chip that etching is good is placed on Ultrasonic Cleaning in the acetone soln, and Wafer Cleaning is clean, oven dry.
The invention has the beneficial effects as follows that the dark silicon etching method of temperature control prolongs the anisotropic etching step that replaces in the etching, the isotropism depositing step shortens, thereby improves etch rate, and vertical etching is easy to control, and the selection ratio of photoresist is improved greatly.
The specific embodiment
Method of the present invention uses the inductively coupled plasma etching machine to finish, and this etching machine is that domestic ICP equipment enters the production line operation the earliest.This etching machine structure comprises: main frame, radio-frequency power supply cabinet, electrical control cubicles, gas holder, circulating cooling machine, computer and operating desk.Wherein the core component of main frame is plasma source, and it is by plane variable-pitch propeller type inductance coil and high-frequency ceramic medium composition one, is the plasma etching chamber below the ceramic dielectric.The drum-shaped sidewall of described etching chamber has been imbedded intensive cooling line.The etching chamber bottom is the radio-frequency electrode of having imbedded cooling line, covers the good graphite felt of one deck heat conduction on radio-frequency electrode, has consisted of sample stage.
Annular gas flow distributor is installed between inductively coupled plasma electrode (top electrode) and radio-frequency electrode (bottom electrode).This machine performance simple in structure is good.
Technological process of the present invention comprises: positive photoresist graphic making step, and the anisotropic etching step, the isotropism depositing step is removed the photoresist step.
Wherein anisotropic etching step and isotropism depositing step alternate cycles etching are the technique of finishing under the cryogenic conditions of temperature control etching chamber.Cooling line has been imbedded in temperature control etching chamber sidewall and bottom electrode inside, and the etching gas circuit outer wall that etching chamber is outer is also twining cooling line.
What circulate in above cooling line is not water, but cryogenic liquid (ethylene glycol), its feature is not freeze below 0 ℃, can obtain like this low temperature (0-7 ℃).Its participation prolongs the anisotropic etching step that replaces in the etching, and the isotropism depositing step shortens, thereby improves etch rate, and vertical etching is easy to control, and the selection ratio of photoresist is improved greatly.
In addition, to be etched in for a long time the heat accumulation that produces on the silicon chip in order solving, between silicon chip and radio-frequency electrode (bottom electrode), to put one deck graphite felt (Heat Conduction Material).Technique of the present invention is simple and easy to control.Etching surface and sidewall are smooth smooth.
[Embodiment 1]
This embodiment may further comprise the steps:
(1) photoetching offset plate figure making step:
Be on 2 inches silicon chips of 400u at thickness, coat photoresist, thickness: 2u, use photo-etching machine exposal, develop, make required figure at photoresist;
(2) anisotropic etching step:
The temperature control etching chamber that the silicon chip of carrying out figure is put on the described inductively coupled plasma etching machine replaces etching, and the etching chamber temperature is 2 ℃, and pressure is 5Pa.Process conditions: upper electrode power 850W, lower electrode power 40W, etching gas SF
6Flow 140sccm, etch period 10 seconds.
(3) isotropic plasma depositing step:
This step is used for making sidewall diaphragm, its process conditions: deposited gas C
4F
8Flow be 85sccm and CHF
3Flow be 5sccm, upper electrode power 600W, lower electrode power 0W, deposition time 8 seconds.
Step (2) and (3) alternate cycles etching, alternate cycles 34 times, etching depth 22u;
This embodiment etching is without removing photoresist, and purpose is to observe the pattern of glue.As shown in Figure 3;
[Embodiment 2], this embodiment may further comprise the steps:
(1) photoetching offset plate figure making step:
Be on 2 inches silicon chips of 400u at thickness, coat photoresist, thickness: 3.5 u, use photo-etching machine exposal, make required figure at glue;
(2) anisotropic etching step:
The temperature control etching chamber that the silicon chip of carrying out figure is put on the inductively coupled plasma etching machine replaces etching, 2 ℃ of etching indoor temperatures, pressure 5.5Pa.Process conditions: upper electrode power 900W, lower electrode power 45W, etching gas SF
6, flow 150sccm, etch period 14 seconds.
(3) isotropic plasma deposition step:
This step is used for making sidewall diaphragm, its process conditions deposited gas C
4F
8And CHF
3Flow be respectively 80sccm and 10sccm, upper electrode power 700W, lower electrode power 0W, deposition time 10 seconds.
Step (2) and (3) alternate cycles etching, alternate cycles 125 times.
(4) remove the photoresist step:
Replacing the good silicon chip of etching, to put in the acetone soln, ultrasonic wave removes photoresist, and Wafer Cleaning is clean, oven dry.
Measuring etching depth with step instrument is 105u, observes the section pattern with SEM.As shown in Figure 4.
The present invention is owing to take above technical scheme, and it has the following advantages: 1) dark silicon etching perpendicularity is good; 2) the vertical etching control accuracy of dark silicon is high; 3) the vertical etching selection ratio of dark silicon is high; 4) the vertical etching depth-to-width ratio of dark silicon is high; 5) be applied to home equipment, cost performance is higher.