The lithographic method of the super photonasty photoresist of being altogether unjustifiable of etching
Technical field
The invention belongs to the semiconductor making method in microelectronic chip manufacturing field.
Background technology
For the high-voltage power element; in order to improve its reliability under high-temperature high-pressure work environment; usually need to use very thick photoresist as sealer; guarantee internal components normal operation under extreme condition of work (conducting voltage as above in 6000V is in the 400 lasting operational environments greater than 30min of the above high temperature of degree).For long-time isolated high-voltage breakdown and hot operation, the thickness of photoresist is usually all very thick.Photoresist is typically polyimide (polyimides) herein.
Polyimide is a kind of high-molecular organic material, is divided into two kinds of photonasty and non-photosensitives.Non-photosensitive is directly polyimide precursor (Polyimide Procursor wherein is typically polyamic acid polyamic acid) usually, and generally there is open loop structure in polyimide precursor, and the wet method method liquid of the photoresist that can be etched is removed; The functional group that photonasty is passed through to increase the functional group of light sensitivity on polyimide precursor and suppressed dissolving, thus cause that by photochemical reaction the reaction removal of light sensitivity group suppresses the functional group of dissolving, produces polyimide precursor.
Then imidization by after heating by uniform temperature, occurs in polyimide precursor, forms closed loop, thereby is insoluble to the wet method method liquid of etching photoresist, and forms the resinous materials with certain mechanical/electrical intensity.Typical polyimide precursor molecular formula and imidization can be expressed as:
Usually in the semiconductor technology course of processing, for for simplicity, in actual production factory with photonasty polyimide exposure before, Polyiamic Precursor after exposure; The front Polyiamic Precursor of non-photosensitive polyimid heated polymerizable etc. is commonly referred to as polyimide.
In the actual chips manufacture process, photoresist uses wet etching usually, and this moment is too thick because of photoresist thickness, usually needs etching for a long time, or multiple etching, and its production capacity is very low, causes manufacturing cost very high.
In addition, when the thickness of photoresist greater than to a certain degree the time, as 15um, be difficult to make it complete reaction by normal exposure process, and be removed, therefore need the photoresist of practical non-photosensitive, coordinate simultaneously photoresist to carry out graphically, then with photoresist as mask, the non-photosensitive photoresist is carried out etching, usually all use wet etching.
The normal development technique of photoresist is: exposure, PEB (rear baking) develops, and cleans.Wherein the PEB Main Function spreads for the light acid that auxiliary photoresist produces in exposure process, and makes the photoresist environment higher than its activation energy by heating, and comes the fill-in light chemical reaction to occur.In therefore common technique, the PEB step is necessary.
Summary of the invention
Technical problem to be solved by this invention is to provide the lithographic method of the super photonasty photoresist of being altogether unjustifiable of a kind of etching, and it can reduce the etch period of super thick photoresist, improves production capacity, reduces manufacturing cost.
In order to solve above technical problem, the invention provides a kind of etching process of the super photonasty photoresist of being altogether unjustifiable, comprise the following steps: spin coating non-photosensitive photoresist; The spin coating photoresist; Exposed photoresist, and directly develop; Silicon chip erosion also cleans.
Beneficial effect of the present invention is: reduce the etch period of super thick photoresist, improve production capacity, reduce manufacturing cost.
The wet etching liquid is tetramethyl aqua ammonia TMAH, gamma-butyrolacton GBL, 1-METHYLPYRROLIDONE NMP, propylene glycol monomethyl ether PGME, pure solution or the mixed solution of 1-Methoxy-2-propyl acetate PGMEA.
Thickness>15um after its spin coating of photoresist thickness.
Photoresist is applied to the 400 above high-temperature work environments of degree, high-temperature duration>30 minute.
The concrete technology flow process of the non-photosensitive photoresist in step 1 is:
150 degree~250 degree dehydration preliminary dryings;
The non-sightseeing photoresist of spin coating;
100~130 degree front bakings;
20 degree~30 degree room temperatures are cooling.
Described non-photosensitive photoresist is non-photosensitive polyimide precursor (Polyamic Precursor is typically polyamic acid Polyimide Acid) or non-photosensitive polyimides (Polyimide).
Description of drawings
Below in conjunction with the drawings and specific embodiments, the present invention is described in further detail.
Fig. 1 is the decay of photoresist etching with heating-up temperature/time.
Embodiment
Reduce the etch period of super thick photoresist, improve production capacity, reduce manufacturing cost.The thermal process relation of finding restriction photoresist etch rate and its experience by test is very large, and heating time is longer, and its etch rate descends just more obvious.
Take 2.3%TMAH as the etching liquid as example, the non-photosensitive photoresist is non-photosensitive polyimide, thickness 20um.When heat budget is spent 130,300s, interior its etch rate is 0.2um/s approximately, if but temperature is higher than 135 degree, or total heating time is over 400s, developing rate namely drops to 0.05um/s and tends towards stability, if therefore do according to conventional PEB technique, needs to increase the 80-150 degree, the thermal process of 60s-90s, its etch rate descends very obvious.
This patent is by removing the PEB step, and its developing rate can rise 20%~30%, and the single developing time reduces greatly.
In this example being applied to take 2.3% tetramethyl aqua ammonia TMAH as the etching liquid as example, the photoresist of etching 40um thickness.(the wet etching liquid can use other as gamma-butyrolacton GBL, 1-METHYLPYRROLIDONE NMP, propylene glycol monomethyl ether PGME, pure solution or the mixed solution of 1-Methoxy-2-propyl acetate PGMEA.) described non-photosensitive photoresist can be polyimides polyimide.
At first spin coating non-photosensitive photoresist, its processing step is:
1) 150 degree~250 degree dehydration preliminary dryings;
2) the non-sightseeing photoresist of spin coating;
3) 100~130 degree front bakings;
4) 20 degree~30 degree room temperatures are cooling.
Single material discharge-amount is 3~50ml, and spin coating master rotating speed speed 500-2000rpm can form for two steps, and low speed+at a high speed, the front baking time is 120s-240s, should not surpass 240s.
Next spin coating photoresist, its step and spin coating photoresist are similar, and discharge-amount is 0.5-5ml, spin coating speed 1500-3500rpm, front baking time 45-90s
After exposure imaging, step were completed for exposing, directly entering developing cell developed, without the PEB step.
The present invention is not limited to execution mode discussed above.Above description to embodiment is intended in order to describe and illustrate the technical scheme that the present invention relates to.Based on the apparent conversion of the present invention enlightenment or substitute and also should be considered to fall into protection scope of the present invention.Above embodiment is used for disclosing best implementation method of the present invention, so that those of ordinary skill in the art can use numerous embodiments of the present invention and multiple alternative reaches purpose of the present invention.