CN101740477A - Method for forming through hole and double-embedded structure - Google Patents
Method for forming through hole and double-embedded structure Download PDFInfo
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- CN101740477A CN101740477A CN200810225760A CN200810225760A CN101740477A CN 101740477 A CN101740477 A CN 101740477A CN 200810225760 A CN200810225760 A CN 200810225760A CN 200810225760 A CN200810225760 A CN 200810225760A CN 101740477 A CN101740477 A CN 101740477A
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Abstract
The invention discloses a method for forming a through hole, which comprises the following steps: providing a substrate which is provided with an etching stop layer provided with a dielectric layer; defining a through hole graph on the dielectric layer; performing primary etching to form a through hole opening in the dielectric layer till the etching stop layer is exposed; and performing secondary etching, and removing the etching stop layer from the through hole opening, wherein the gas used in the secondary etching comprises an etching reaction gas and an auxiliary gas, the etching reaction gas comprises a fluorine containing gas, and the auxiliary gas comprises a gas of which the mass is smaller than argon. The invention also discloses a corresponding method for forming a double-embedded structure. The method for forming the through hole and the double-embedded structure avoids the problem that the lower part of the side wall of the through hole is sunken, and improves the forming quality of the through hole or the double-embedded structure.
Description
Technical field
The present invention relates to technical field of manufacturing semiconductors, the formation method of particularly a kind of through hole and dual-damascene structure.
Background technology
The making of semiconductor integrated circuit is extremely complicated process, its purpose is various electronic building bricks and circuit that particular electrical circuit is required, dwindle on the silicon chip that is produced on small size, and each assembly must electrically connect the competence exertion desired function by suitable internal connecting line.Wherein, in order to realize that the electrical connection between multilayer circuit need be made a large amount of through holes on the silicon chip, the quality of these through hole performances is to the overall performance important influence of circuit.
Fig. 1 is the device profile schematic diagram of the existing through hole formation method of explanation to Fig. 4.Wherein, Fig. 1 is the device profile schematic diagram behind the formation dielectric layer in the existing forming process of through hole, as shown in Figure 1, usually before growth is used for the dielectric layer 102 of interlayer electric insulation, meeting is growth etching stop layer 101 on silicon substrate 100, and it can be silicon nitride layer or silicon carbide layer, as, in the following technology node of 65nm, this layer is generally the silicon carbide layer (NDC) of nitrating.The etch rate of this etching stop layer 101 will be starkly lower than dielectric layer 102, can stop at comparatively equably in this etching stop layer 101 when the etching through hole opening guaranteeing.
Fig. 2 is the device profile schematic diagram behind the formation via hole image in the existing forming process of through hole, as shown in Figure 2, utilizes photoetching process to define via hole image 105 on dielectric layer 102 surfaces.
Fig. 3 is the device profile schematic diagram that forms in the existing forming process of through hole behind the via openings, as shown in Figure 3, define via hole image 105 with photoresist after, can utilize dry etching technology in dielectric layer 102, to form via openings 107.Because the etch rate of the etching stop layer 101 of lower floor will be much smaller than the etch rate of dielectric layer 102, this step etching can stop in the etching stop layer 101.
Fig. 4 is the device profile schematic diagram behind the removal etching stop layer in the existing forming process of through hole, as shown in Figure 4, after the dielectric layer etching is finished, also need the etching stop layer that via openings 107 bottoms are residual 101 to remove, to expose the conductive structure of lower floor to the open air, this step can be described as usually and stops layer removal step (LRM, Liner Removal).
In the practical operation, the LRM step in this step normally utilizes dry etch process to realize that its polymer that produces in the time of can utilizing plasma to etching simultaneously carries out isotropic removal.Therefore, easily depression problem (undercut or pull back) appears in the side-walls (being place, through-hole side wall below) at etching stop layer in this step etching process, shown in depression 110 among Fig. 4.Especially in the following technology node of 65nm, this etching stop layer 101 is formed by the carborundum of comparatively weak nitrating usually, and this depression problem is just even more serious.And in a single day such depression problem appears, and will directly have influence on the filling quality of metal in the through hole of back, and then have influence on the electrical connection quality in the integrated circuit, make the performance of device, as aspects such as reliabilities, variation even inefficacy.
The Chinese patent application that disclosed publication number was CN101231968A on July 30th, 2008 discloses a kind of inlaying inner connecting line structure and dual-damascene technics, it utilizes carbon tetrafluoride and nitrogen trifluoride gas bulk plasmon to be the etching gas among the LRM, to solve the problem that forms groove in the layer dielectric layer that causes owing to misalignment in the mosaic texture.But this application does not propose effective solution for the problem that depression appears in place, through-hole side wall below in the above-mentioned LRM step.
Summary of the invention
The invention provides the formation method of a kind of through hole and dual-damascene structure, easily below through-hole side wall, locate the phenomenon that occurs caving in existing through hole or the dual-damascene structure forming process to improve.
For achieving the above object, the formation method of a kind of through hole provided by the invention comprises step:
Substrate is provided, and on described substrate, has etching stop layer, on described etching stop layer, have dielectric layer;
On described dielectric layer, define via hole image;
Carry out first etching, in described dielectric layer, form via openings, to exposing described etching stop layer;
Carry out second etching, remove the etching stop layer in the described via openings, and used gas comprises etching reaction gas and assist gas in described second etching, wherein, etching reaction gas comprises fluoro-gas, and assist gas comprises the gas of quality less than argon gas.
The present invention has the formation method of the another kind of dual-damascene structure of identical or relevant art feature, comprises step:
Substrate is provided, and on described substrate, has lower floor's conductive structure, on described lower floor conductive structure, have etching stop layer, on described etching stop layer, have first dielectric layer;
On described first dielectric layer, define via hole image;
Carry out first etching, in described first dielectric layer, form via openings, to exposing described etching stop layer;
Form second dielectric layer on described first dielectric layer and in the via openings;
On described second dielectric layer, form groove figure;
Carry out second etching, form the groove that links to each other with at least one via openings;
Remove second dielectric layer in the described via openings;
Carry out the 3rd etching, remove the etching stop layer in the described via openings, and used gas comprises etching reaction gas and assist gas in described the 3rd etching, wherein, etching reaction gas comprises fluoro-gas, and assist gas comprises the gas of quality less than argon gas.
Compared with prior art, the present invention has the following advantages:
The formation method of through hole of the present invention and dual-damascene structure, assist gas in the LRM step no longer adopts the heavier argon gas of quality, and the gas of employing lighter weight, as adopt a kind of of nitrogen, helium, oxygen, hydrogen etc. or some kinds, the gas bombardment power of such lighter weight is less, reduced the damage of isotropic physical property bombardment, avoided below through-hole side wall, occurring the problem of depression, improved the formation quality of through hole or dual-damascene structure the etching stop layer sidewall.
Description of drawings
Fig. 1 is the device profile schematic diagram behind the formation dielectric layer in the existing forming process of through hole;
Fig. 2 is the device profile schematic diagram behind the formation via hole image in the existing forming process of through hole;
Fig. 3 is the device profile schematic diagram behind the formation via openings in the existing forming process of through hole;
Fig. 4 is the device profile schematic diagram behind the removal etching stop layer in the existing forming process of through hole;
Fig. 5 is the profile of the dual-damascene structure of employing prior art making;
Fig. 6 is the flow chart of first embodiment of the invention through hole formation method;
The generalized section of the substrate that provides in the first embodiment of the invention is provided Fig. 7;
Fig. 8 is the device profile schematic diagram behind the formation via hole image in the first embodiment of the invention;
Fig. 9 is the device profile schematic diagram behind the formation via openings in the first embodiment of the invention;
Figure 10 is the device profile schematic diagram behind the removal etching stop layer in the first embodiment of the invention;
Figure 11 is the flow chart of second embodiment of the invention dual-damascene structure formation method;
The generalized section of the substrate that provides in the second embodiment of the invention is provided Figure 12;
Figure 13 is the device profile schematic diagram behind the formation via hole image in the second embodiment of the invention;
Figure 14 is the device profile schematic diagram behind the formation via openings in the second embodiment of the invention;
Figure 15 is the device profile schematic diagram behind formation second dielectric layer in the second embodiment of the invention;
Figure 16 is for illustrating the device profile map after the formation groove figure in the second embodiment of the invention;
Figure 17 carries out device profile schematic diagram after second etching in the second embodiment of the invention for explanation;
Figure 18 is for illustrating the device profile schematic diagram behind the formation dual-damascene structure opening in the second embodiment of the invention;
Figure 19 is the device profile schematic diagram behind the removal etching stop layer in the second embodiment of the invention;
Figure 20 is the profile of the dual-damascene structure that forms in the second embodiment of the invention;
Figure 21 adopts NF for the present invention
3The profile of the dual-damascene structure that the back forms;
Figure 22 adopts NF for the present invention
3The resistance characteristic figure of the dual-damascene structure that the back forms.
Embodiment
For above-mentioned purpose of the present invention, feature and advantage can be become apparent more, the specific embodiment of the present invention is described in detail below in conjunction with accompanying drawing.
Processing method of the present invention can be widely used in the every field; and can utilize many suitable material; be to be illustrated below by specific embodiment; certainly the present invention is not limited to this specific embodiment, and the known general replacement of one of ordinary skilled in the art is encompassed in protection scope of the present invention far and away.
Secondly, the present invention utilizes schematic diagram to describe in detail, when the embodiment of the invention is described in detail in detail, for convenience of explanation, the profile of expression device architecture can be disobeyed general ratio and be done local the amplification, should be with this as limitation of the invention, in addition, in the making of reality, should comprise the three dimensions size of length, width and the degree of depth.
In the prior art, when forming through hole and dual-damascene structure, in order to make comparatively uniformity of etching energy, and can not damage lower floor's conductive structure, usually can be under dielectric layer, growth one deck etching stop layer on lower floor's conductive structure.This etching stop layer need be selected the material different with dielectric layer for use, and the etch rate to it is obviously lower under the etching condition that is suitable for the etching dielectric layer, stops at comparatively equably in this etching stop layer with the etching energy of guaranteeing via openings.Afterwards, also need to add again the step (LRM step) of this etching stop layer of step removal, to make lower floor that conductive structure exposes to the open air out.
Yet in this step LRM step, regular meeting the depression problem occurs at the through-hole side wall place.Especially reach 65nm technology node when following when device making technics, for the material with low-k mates better, need usually to adopt comparatively weak nitrogenous carbofrax material, this depression problem just becomes even more serious.
Fig. 5 is the profile of the dual-damascene structure that adopts prior art and make, as shown in Figure 5, locates to have formed depression 501 (among the figure shown in the circle) below the sidewall of the through hole of the dual-damascene structure that forms.Can find that by observing this depression is positioned at etching stop layer, it can only occur in its side-walls when removing etching stop layer as can be known.The appearance of this depression 501 can influence the filling quality of metal in the follow-up through hole, and then has influence on the electrical connection properties of device.
Through a large amount of experimental analyses, the appearance of finding this depression mainly is because added argon gas in the LRM step.The effect that adds argon gas in this step etching mainly contains two, and one is to utilize this argon plasma to remove the polymer that produces in the etching process in etching process, and another is to play diluting effect to etching gas, to regulate etch rate.
Think, because the argon gas quality is heavier, its plasma bombardment power is stronger, and this argon plasma is isotropic to the physical property bombardment of substrate, when etching is removed etching stop layer, when especially selecting the etching stop layer that comparatively weak material makes for use, just easily in its side-walls depression appears.
For this reason, the invention provides a kind of new through hole formation method, comprise step: substrate is provided, and on described substrate, has etching stop layer, on described etching stop layer, have dielectric layer; On described dielectric layer, define via hole image; Carry out first etching, in described dielectric layer, form via openings, to exposing described etching stop layer; Carry out second etching, remove the etching stop layer in the described via openings, and used gas comprises etching reaction gas and assist gas in described second etching, wherein, etching reaction gas comprises fluoro-gas, and assist gas comprises the gas of quality less than argon gas.
Among the present invention, will in etching process, be called etching reaction gas by main gas by chemical reaction removal etching stop layer; Will be mainly by under the high pressure effect, becoming plasma in etching process, utilize physics mode to remove the gas of the polymer that is produced in etching stop layer and the etching process, and the gas that etching reaction gas plays diluting effect will be referred to as assist gas.
Wherein, preferably, described fluoro-gas comprises nitrogen fluoride.Alternatively, described assist gas comprises nitrogen and helium.
Preferably, the flow of described nitrogen fluoride is between 5 to 15sccm.
Preferably, the flow of described nitrogen is between 20 to 100sccm, and the flow of described helium is between 100 to 500sccm.
Alternatively, described second etching is at room temperature carried out, and the chamber pressure in when work is between 20 to 60mTorr, and bias power is between 100 to 500W, and source power is between 50 to 200W.
Alternatively, described assist gas comprises a kind of or its combination in nitrogen, oxygen, helium, the hydrogen.
Wherein, described etching stop layer can be the silicon carbide layer of nitrating.
The present invention also provides a kind of formation method of dual-damascene structure of correspondence, comprise step: provide substrate, and on described substrate, have lower floor's conductive structure, on described lower floor conductive structure, have etching stop layer, on described etching stop layer, have first dielectric layer; On described first dielectric layer, define via hole image; Carry out first etching, in described first dielectric layer, form via openings, to exposing described etching stop layer; Form second dielectric layer on described first dielectric layer and in the via openings; On described second dielectric layer, form groove figure; Carry out second etching, form the groove that links to each other with at least one via openings; Remove second dielectric layer in the described via openings; Carry out the 3rd etching, remove the etching stop layer in the described via openings, and used gas comprises etching reaction gas and assist gas in described the 3rd etching, wherein, etching reaction gas comprises fluoro-gas, and assist gas comprises the gas of quality less than argon gas.
Wherein, preferably, described fluoro-gas comprises nitrogen fluoride.Alternatively, described assist gas comprises nitrogen and helium.
Preferably, the flow of described nitrogen fluoride is between 5 to 15sccm, and the flow of described nitrogen is between 20 to 100sccm, and the flow of described helium is between 100 to 500sccm.
Alternatively, described the 3rd etching is at room temperature carried out, and the chamber pressure in when work is between 20 to 60mTorr, and bias power is between 100 to 500W, and source power is between 50 to 200W.
Alternatively, described assist gas can also comprise a kind of or its combination in nitrogen, oxygen, helium, the hydrogen.
Wherein, described etching stop layer can be the silicon carbide layer of nitrating.
Through hole of the present invention and dual damascene formation method, in the LRM step, utilize the gas of lighter weight to replace traditional argon gas, to reduce the bombardment power of plasma, and then reduced of the damage of this LRM step to the etching stop layer sidewall, prevented the appearance of depression problem.
The formation method of through hole of the present invention and dual-damascene structure has adopted NF
3Be etching gas, the polymer that it is produced in the time of can reducing etching, even guaranteeing to adopt lighter gas such as nitrogen also can remove the polymer that produces in the etching process clean, improve the resistance characteristic of through hole or dual-damascene structure, further improved the formation quality of through hole or dual-damascene structure.
First embodiment:
First embodiment of the invention has illustrated a kind of formation method of through hole, and Fig. 6 is the flow chart of first embodiment of the invention through hole formation method, and Fig. 7 to Figure 10 is for describing the device profile schematic diagram of forming process of through hole in the first embodiment of the invention.Below in conjunction with Fig. 6 to Figure 10 the first embodiment of the present invention is elaborated.
Step 601: substrate is provided, and on described substrate etching stop layer, on described etching stop layer, have dielectric layer.
Fig. 7 as shown in Figure 7, has formed etching stop layer 701 and dielectric layer 702 for the generalized section of the substrate that provides in the first embodiment of the invention on substrate 700.
The consideration of need trading off of the thickness of this etching stop layer 701 promptly can not thin excessively (to prevent over etching, guaranteeing that etching stopping is in this layer), can not blocked up (easy damaged substrate when remove the back), its thickness can be arranged on usually 300 to
Between, as be 300,400 or
The unadulterated silicon oxide layer of dielectric layer 702 in the present embodiment for utilizing chemical gaseous phase depositing process to form, its thickness can be arranged on usually 3500 to
Between, as be 3500,4000 or
Step 602: on described dielectric layer, define via hole image.
Fig. 8 is the device profile schematic diagram behind the formation via hole image in the first embodiment of the invention, as shown in Figure 8, utilizes photoresist to define via hole image 705 on dielectric layer 702.
In addition, in other embodiments of the invention, when the through hole of etching is dark, for guaranteeing that the protective effect of mask is enough in the etching process.Can also form one deck hard mask layer again on dielectric layer 702 before utilizing photoresist to form via hole image 705, its etch rate and dielectric layer 702 differ big (as being silicon nitride layer).Then; utilizing photoresist behind definition via hole image on this hard mask layer, earlier this hard mask layer is carried out etching, via hole image is transferred in this hard mask layer; then, utilize the hard mask of photoresist after this is graphical in the via etch process, to realize mask protection again.
Step 603: carry out first etching, in described dielectric layer, form via openings, to exposing described etching stop layer.
Fig. 9 is the device profile schematic diagram behind the formation via openings in the first embodiment of the invention, as shown in Figure 9, has formed via openings 707 after this step etching in dielectric layer 702.Because the etch rate of the etching stop layer 701 of lower floor will be much smaller than the etch rate of dielectric layer 702, this step etching can stop in the etching stop layer 701 more equably.
In the present embodiment, the process conditions that this first etching technics is used are optimized, to reach etching effect preferably.Process conditions after the optimization comprise: use to comprise C
4F
8And O
2Etching gas, and the flow-rate ratio of the two can be between 4: 1 to 1: 1, as are 2: 1.For example, can be with C
4F
8Flow set at 15sccm, O
2Flow set at 5sccm.
Remove C
4F
8And O
2Outside the etching gas, can also feed CH in first etching technics after the optimization
2F
2And Ar gas, particularly, can be with CH
2F
2Flow set between 5 to 15sccm, as be 5,10 or 15sccm; Between 300 to 600sccm, as is 300,450 or 600sccm with the flow set of Ar.
In the present embodiment, the chamber pressure in this first etching process is arranged between 20 to 80mTorr, as is 20,60 or 80mTorr; The RF power is arranged between 2000 to 2500W, as is 2000,2200 or 2500W.
Step 604: carry out second etching, remove the etching stop layer in the described via openings, and used gas comprises fluoro-gas in described second etching, does not contain argon gas.
Figure 10 is the device profile schematic diagram behind the removal etching stop layer in the first embodiment of the invention, and as shown in figure 10, this goes on foot second etching etching stop layer residual in the via openings 701 etchings are removed.
In order to prevent that this step from depression (shown among Fig. 5 501) occurring during etching below the through-hole side wall, utilize the gas of lighter weight in the present embodiment, as nitrogen, replace traditional argon gas, reduced the bombardment power of plasma to etching stop layer, and then reduced damage to the etching stop layer sidewall, prevented the appearance of depression.
By a large amount of experiments and analysis, comparatively preferred process conditions have been obtained in the present embodiment.For example, can this go on foot second etching and be set at room temperature carry out, and the chamber pressure during work is between 20 to 60mTorr, as 20,40,60mTorr etc., bias power is between 100 to 500W, as 100,200,300,400 or 500W etc., source power is between 50 to 200W, as 50,100,200W etc.
In the present embodiment, the gas that adds in second etching process can have multiple compound mode, as adding etching reaction gas CHF
3, and assist gas N
2And O
2Three kinds of gases, wherein, CHF
3React with the etching stop layer (being nitrogenous silicon carbide layer in the present embodiment) that exposes to the open air in outside the through hole in etching process as etching reaction gas, with its removal; N
2And O
2In etching process, under the high pressure effect, become plasma, be mainly used in and remove the polymer that is produced in the etching process, and etching reaction gas is had certain diluting effect.
In the present embodiment, CHF
3Flow set between 20 to 40sccm, as be 20,30 or 40sccm etc.; O
2Flow set between 10 to 20sccm, as be 10,14,18 or 20sccm etc.; N
2Flow set between 20 to 100sccm, as be 20,40,60 or 100sccm etc.
In another embodiment of the present invention, in second etching process, add CHF
3, N
2With three kinds of gases of He, wherein, CHF
3React with the etching stop layer that exposes to the open air in outside the through hole in etching process as etching reaction gas, with its removal; N as assist gas
2In etching process, under the high pressure effect, become nitrogen plasma, be mainly used in and remove the polymer that is produced in the etching process, and etching reaction gas is had certain diluting effect; He as assist gas then is mainly used in dilution etching reaction gas, simultaneously the polymer that produces in the etching process is also had certain scavenging action.
Among this embodiment, CHF
3Flow set between 10 to 40sccm, as be 10,20,30 or 40sccm etc.; N
2Flow set between 20 to 100sccm, as be 20,40,60 or 100sccm etc., the flow set of He as is 100,200,300,400 or 500sccm etc. between 100 to 500sccm.
In other embodiments of the invention, can also in second etching process, remove adding CHF
3Outward, add and comprise in nitrogen, oxygen, helium, the hydrogen any or its combination as assist gas, it can be used for diluting etching reaction gas, simultaneously the polymer that produces in the etching process is also had certain scavenging action.
Adopt the through hole of the method formation of the invention described above first embodiment, the depression problem of its sidewall below has clear improvement, but finds that the resistance value of the through hole of its formation rises to some extent.Think by analysis, in second etching process, etching reaction gas CHF
3The polymer that produces is more, and in etching process, no longer add the heavier argon gas of quality, after using the gas of other lighter weight instead, its bombardment power descends, cause in the etching process the removal dynamics of the polymer that produces not enough, this makes after second etching in the through hole can the residual fraction polymer, and has caused the problem that the through hole resistance value rises.
For addressing this problem, in another embodiment more of the present invention, in second etching process with etching reaction gas CHF
3Change to NF
3, it is carbon containing not, can obviously reduce the generation of polymer in the etching process, even make and to diminish because of using the bombardment power that produces behind the lighter gas instead, can guarantee that also the interior polymer of through hole is removed clean.
As, can in second etching, feed NF
3, N
2With three kinds of gases of He, wherein, NF
3React with the etching stop layer (being nitrogenous silicon carbide layer in the present embodiment) that exposes to the open air in outside the through hole in etching process as etching reaction gas, with its removal, simultaneously, the polymer of its generation is less; N as assist gas
2In etching process, under the high pressure effect, become nitrogen plasma, be mainly used in and remove the polymer that is produced in the etching process, and etching reaction gas is had certain diluting effect; He as assist gas then is mainly used in dilution etching reaction gas, simultaneously the polymer that produces in the etching process is also had certain scavenging action.
Among this embodiment, can be with NF
3Flow set between 5 to 15sccm, as be 5,10 or 15sccm etc., in this scope, can guarantee the silica of the etch rate of nitrogenous silicon carbide layer far above dielectric layer, as more than 1.5: 1, because of etching stop layer 701 is thinner, this selection is when can realize removing etching stop layer 701, and dielectric layer 702 is injury-free or damage less.
In addition, NF
3Flow etch rate is had considerable influence, when its flow is selected, also to take in this.Constant as other process conditions, if NF
3Flow is 5sccm, and its etch rate exists
About, and work as NF
3When flow was 10sccm, its etch rate existed
Work as NF
3When flow was 15sccm, its etch rate existed
If to NF
3Flow select improperly, can cause selection between etching stop layer and dielectric layer than improper first, the damage dielectric layer; Second may make etch rate too fast or slow excessively, and this layer thickness is little, this will cause this step process wayward.
Among this embodiment, can be with N
2Flow set between 20 to 100sccm, as be 20,40,60 or 100sccm etc.N
2Main effect be to remove polymer, though adopt NF
3After, polymer obviously reduces, but if to N
2It is improper that flow is selected, and it is not thorough can to cause polymer to be removed yet, and the resistance value that shows as each through hole is disperseed.
The flow set of He as is 100,200,300,400 or 500sccm etc. between 100 to 500sccm.He mainly is a diluting effect, and its flow size also can be influential to etch rate, and is constant as other process conditions, and etch rate was 720 when the He flow was 100sccm
Etch rate was when flow was 300sccm
Etch rate was when flow was 500sccm
Therefore, the flow to He also needs to be optimized processing.
In other embodiments of the invention, in second etching process, adopt NF
3During as etching reaction gas, also can add comprise any or its combination in nitrogen, oxygen, helium, the hydrogen gas as assist gas, be used to dilute etching reaction gas, simultaneously the polymer that produces in the etching process also played certain scavenging action.
Adopt NF
3As etching reaction gas, the gas that adds lighter weight simultaneously as assist gas after, not only the depression problem at place, through-hole side wall below is resolved, the resistance characteristic of through hole has also obtained obvious improvement, illustrates that the polymer residue problem in it also solves.
The etching figure that forms in the present embodiment is a through hole, in other embodiments of the invention, also can utilize method of the present invention to form other etching figure, as contact hole etc.
Second embodiment:
Semiconductor process techniques enters after 0.18 micron, the characteristic size of device is further dwindled, the RC of interconnection line postpones to become the principal contradiction that influences circuit speed gradually, for improving this point, begins to adopt the process of being made metal interconnected line structure by metallic copper.Compare with traditional aluminium technology, the advantage of process for copper is that its resistivity is lower, and conductivity is better, by its connecting lead wire of making can keep on an equal basis in addition more do forr a short time under the situation of heavy current bearing capacity, more intensive.In addition, it also has bigger advantage than aluminium technology at aspects such as electromigration, RC delay, reliability and life-spans.Because the copper metal is difficult for etching, the making of copper metal connecting line need adopt the structure of dual damascene to realize, and when making the through hole that forms in the dual-damascene structure in the following technology node of 65nm, equally also exists above-mentioned depression problem.
Second embodiment of the invention has illustrated a kind of formation method of dual-damascene structure, and it can overcome above-mentioned depression problem.Figure 11 is the flow chart of second embodiment of the invention dual-damascene structure formation method, and Figure 12 to Figure 19 is the device profile schematic diagram of dual-damascene structure forming process in the explanation second embodiment of the invention.Below in conjunction with Figure 11 to Figure 19 the second embodiment of the present invention is elaborated.
Step 1101: substrate is provided, and on described substrate, has lower floor's conductive structure, on described lower floor conductive structure, have etching stop layer, on described etching stop layer, have first dielectric layer.
Figure 12 as shown in figure 12, has formed the etching stop layer 1201 and first dielectric layer 1202 for the generalized section of the substrate that provides in the second embodiment of the invention on substrate 1200.Wherein, lower floor's conductive structure is not shown.
In order to improve the etching figure in the uniformity aspect the etching depth, consistency, before forming first dielectric layer on the substrate, meeting is growth one deck etching stop layer earlier usually.In the technology more than 0.13 micron, this layer is general to adopt silicon nitride material, and in the technology below 0.13 micron, for the dielectric material with low k value mates better, this etching stop layer is generally nitrogenous or oxygen containing silicon carbide layer.Etching stop layer 1201 in the present embodiment is the nitrogenous silicon carbide layers that utilize the PECVD deposition to form, the etch rate of first dielectric layer of growing thereon in its etch rate and back 1202 is compared low, when guaranteeing via etch can than uniformity stop in this layer.
The consideration of need trading off of the thickness of this etching stop layer 1201 promptly can not thin excessively (to prevent over etching, guaranteeing that etching stopping is in this layer), can not blocked up (easy damaged substrate when remove the back), its thickness can be arranged on usually 300 to
Between, as be 300,400 or
For high integration, high speed device, for reducing parasitic capacitance, first dielectric layer 1202 must be selected the dielectric layer of low k value, as the silica of mixing fluorine (FSG) that utilizes chemical gaseous phase depositing process to form, the silica of carbon dope (CDO), unadulterated silica (USG) layer perhaps adopts the mode (SOD) of spin coating to utilize porous medium layer that liquid colloidal silica sill forms etc.What select for use in the present embodiment is to have black diamond (BD, the Black Diamond) material that the chemical gaseous phase depositing process of low k value is made.Its thickness can be arranged on 3500 to 8000 usually
Between, as be 3500,4000,6500 or 8000
In addition, in other embodiments of the invention, this first dielectric layer 1202 can also be made up of multilayered medium material, as comprising one deck BD material layer, one deck USG material layer etc.
Step 1102: on described first dielectric layer, define via hole image.
Figure 13 is the device profile schematic diagram behind the formation via hole image in the second embodiment of the invention, as shown in figure 13, utilizes photoresist to define via hole image 1204 on dielectric layer 1202.
In the present embodiment, be to be that mask carries out etching to through hole directly with the photoresist, in other embodiments of the invention, can also on first dielectric layer 1202, form one deck hard mask layer (as the hard mask of one deck silicon nitride layer conduct of can growing) again, earlier this hard mask being carried out graphical treatment, is that mask carries out etching formation via openings to first dielectric layer 1202 under it with it again; Perhaps after this hard mask layer being carried out graphically, carry out the etching of via openings more together as mask with photoresist and this hard mask layer, the existence of this hard mask layer can make the through hole edge shape of formation better.
Step 1103: carry out first etching, in described first dielectric layer, form via openings, to exposing described etching stop layer.
Figure 14 is the device profile schematic diagram behind the formation via openings in the second embodiment of the invention, as shown in figure 14, has formed via openings 1205 after this step etching in first dielectric layer 1202.Because the etch rate of the etching stop layer 1201 of lower floor will be much smaller than the etch rate of first dielectric layer 1202, this step etching can stop in the etching stop layer 1201.
In the present embodiment, the process conditions that this first etching technics is used are optimized, to reach etching effect preferably.Process conditions after the optimization comprise: use to comprise C
4F
8And O
2Etching gas, and the flow-rate ratio of the two can be between 4: 1 to 1: 1, as are 2: 1.For example, can be with C
4F
8Flow set at 15sccm, O
2Flow set at 5sccm.
Remove C
4F
8And O
2Outside the etching gas, can also feed CH in first etching technics after the optimization
2F
2And Ar gas, particularly, can be with CH
2F
2Flow set between 5 to 15sccm, as be 5,10 or 15sccm; Between 300 to 600sccm, as is 300,450 or 600sccm with the flow set of Ar.
In the present embodiment, the chamber pressure in this first etching process is arranged between 20 to 80mTorr, as is 20,60 or 80mTorr; The RF power is arranged between 2000 to 2500W, as is 2000,2200 or 2500W.
Step 1104: form second dielectric layer on first dielectric layer and in the via openings.
Figure 15 is the device profile schematic diagram behind formation second dielectric layer in the second embodiment of the invention, as shown in figure 15, after first etching is finished, removed residual photoresist, then, on first dielectric layer 1202 and in the via openings 1205, covered second dielectric layer 1206.
In the present embodiment, for filling vias 1205 preferably, can obtain comparatively smooth surface simultaneously, this second dielectric layer 1206 has adopted the DUO material layer that utilizes spin coating method to form.
Step 1105: on described second dielectric layer, form groove figure.
Figure 16 is for illustrating the device profile map after the formation groove figure in the second embodiment of the invention, and as shown in figure 16, this step normally utilizes photoetching technique to define the figure 1207 of groove on second dielectric layer 1206.
Step 1106: carry out second etching, form the groove that links to each other with at least one via openings.
Figure 17 carries out device profile schematic diagram after second etching in the second embodiment of the invention for explanation, as shown in figure 17, and second dielectric layer 1206 and part first dielectric layer 1202 that utilize the dry etching technology etching not protected by photoresist.
Step 1107: remove second remaining in the described via openings dielectric layer.
Figure 18 is for illustrating the device profile schematic diagram behind the formation dual-damascene structure opening in the second embodiment of the invention; as shown in figure 18; second dielectric layer 1206 and part first dielectric layer 1202 that utilize the dry etching technology etching not protected by photoresist; second remaining in the via openings 1205 dielectric layer 1206 is removed in formation and the groove 1208 that at least one via openings 1205 links to each other again.Remove again second dielectric layer, 1206 surfaces residual photoresist, just formed the groove 1208 that links to each other with at least one through hole 1205.
The through hole 1205 of groove 1208 belows that form can have one or more, and it is the situation of arranging pairing through hole under each groove according to the function design of circuit, has one usually at least.After forming groove 1208, also need the etching stop layer 1201 that is positioned at via openings 1205 bottoms is removed.
Step 1108: carry out the 3rd etching, remove the etching stop layer in the described via openings, and used gas comprises etching reaction gas and assist gas in described the 3rd etching, wherein, etching reaction gas comprises fluoro-gas, and assist gas comprises the gas of quality less than argon gas.
Figure 19 is the device profile schematic diagram behind the removal etching stop layer in the second embodiment of the invention, and as shown in figure 19, this goes on foot the 3rd etching etching stop layer 1201 etchings residual in the via openings 1205 are removed.
In order to prevent that depression from appearring during etching in this step below through-hole side wall, the gas that utilizes lighter weight in the present embodiment is as assist gas, as nitrogen, replace traditional argon gas, reduced the bombardment power of plasma to etching stop layer, and then reduced damage to the etching stop layer sidewall, prevented the appearance of depression.
By a large amount of experiments and analysis, comparatively preferred process conditions have been obtained in the present embodiment.For example, can this go on foot the 3rd etching and be set at room temperature carry out, and the chamber pressure during work is between 20 to 60mTorr, as 20,40,60mTorr etc., bias power is between 100 to 500W, as 100,200,300,400 or 500W etc., source power is between 50 to 200W, as 50,100,200W etc.
In the present embodiment, the gas that adds in the 3rd etching process can have multiple compound mode, as adding CHF
3, N
2And O
2Three kinds of gases, wherein, CHF
3React with the etching stop layer (being nitrogenous silicon carbide layer in the present embodiment) that exposes to the open air in outside the through hole in etching process as etching reaction gas, with its removal; N
2And O
2In etching process, under the high pressure effect, become plasma as assist gas, be mainly used in and remove the polymer that is produced in the etching process, and etching reaction gas is had certain diluting effect.
In the present embodiment, CHF
3Flow set between 20 to 40sccm, as be 20,30 or 40sccm etc.; O
2Flow set between 10 to 20sccm, as be 10,14,18 or 20sccm etc.; N
2Flow set between 20 to 100sccm, as be 20,40,60 or 100sccm etc.
Figure 20 is the profile of the dual-damascene structure that forms in the second embodiment of the invention, as shown in figure 20, adopts the place, through-hole side wall below of the dual-damascene structure that the second embodiment of the invention method forms to no longer include depression problem (shown in 2001 circle among the figure).
In another embodiment of the present invention, in the 3rd etching process, add CHF
3, N
2With three kinds of gases of He, wherein, CHF
3React with the etching stop layer that exposes to the open air in outside the through hole in etching process as etching reaction gas, with its removal; N as assist gas
2In etching process, under the high pressure effect, become nitrogen plasma, be mainly used in and remove the polymer that is produced in the etching process, and etching reaction gas is had certain diluting effect; He as assist gas then is mainly used in dilution etching reaction gas, simultaneously the polymer that produces in the etching process is also had certain scavenging action.
Among this embodiment, CHF
3Flow set between 10 to 40sccm, as be 10,20,30 or 40sccm etc.; N
2Flow set between 20 to 100sccm, as be 20,40,60 or 100sccm etc., the flow set of He as is 100,200,300,400 or 500sccm etc. between 100 to 500sccm.
In other embodiments of the invention, except in the 3rd etching process, adding CHF
3Outward, can also add comprise any or its combination in nitrogen, oxygen, helium, the hydrogen gas as assist gas, it can be used for diluting etching reaction gas, simultaneously the polymer that produces in the etching process is also had certain scavenging action.
Adopt the dual-damascene structure of the method formation of the invention described above second embodiment, the depression problem of its through-hole side wall below has clear improvement, but finds that the resistance value of the structure of its formation rises to some extent.Think by analysis, in the 3rd etching process, etching reaction gas CHF
3The polymer that produces is more, and in etching process, no longer add the heavier argon gas of quality, after using the assist gas of other lighter weight instead, its bombardment power descends, cause in the etching process the removal dynamics of the polymer that produces not enough, this makes after the 3rd etching in the through hole can the residual fraction polymer, and has caused the problem that the through hole resistance value rises.
For addressing this problem, in another embodiment more of the present invention, in the 3rd etching process with etching reaction gas CHF
3Change to NF
3, it is carbon containing not, can obviously reduce the generation of polymer in the etching process, even make because of adopting the bombardment power that produces behind the lighter assist gas to diminish, can guarantee that also the polymer in the through hole is removed clean.
As, can in the 3rd etching, feed NF
3, N
2With three kinds of gases of He, wherein, NF
3React with the etching stop layer (being nitrogenous silicon carbide layer in the present embodiment) that exposes to the open air in outside the through hole in etching process as etching reaction gas, with its removal, simultaneously, the polymer of its generation is less; N as assist gas
2In etching process, under the high pressure effect, become nitrogen plasma, be mainly used in and remove the polymer that is produced in the etching process, and etching reaction gas is had certain diluting effect; He as assist gas then is mainly used in dilution etching reaction gas, simultaneously the polymer that produces in the etching process is also had certain scavenging action.
Among this embodiment, can be with NF
3Flow set between 5 to 15sccm, as be 5,10 or 15sccm etc., in this scope, can guarantee the silica of the etch rate of nitrogenous silicon carbide layer far above dielectric layer, as more than 1.5: 1, because of etching stop layer 1201 is thinner, this selection dielectric layer 1202 when can realize removing etching stop layer 1201 is injury-free or damage less.
In addition, NF
3Flow etch rate is had considerable influence, when its flow is selected, also to take in this.Constant as other process conditions, if NF
3Flow is 5sccm, and its etch rate exists
About, and work as NF
3When flow was 10sccm, its etch rate existed
Work as NF
3When flow was 15sccm, its etch rate existed
If to NF
3Flow select improperly, can cause selection between etching stop layer and dielectric layer than improper first, the damage dielectric layer; Second may make etch rate too fast or slow excessively, and this layer thickness is little, this will cause this step process wayward.
Among this embodiment, can be with N
2Flow set between 20 to 100sccm, as be 20,40,60 or 100sccm etc.N
2Main effect be to remove polymer, though adopt NF
3After, polymer obviously reduces, but if to N
2It is improper that flow is selected, and it is not thorough can to cause polymer to be removed yet, and the resistance value that shows as each through hole is disperseed.
Among this embodiment, can be between 100 to 500sccm with the flow set of He, as be 100,200,300,400 or 500sccm etc.He mainly is a diluting effect, and its flow size also can be influential to etch rate, and is constant as other process conditions, and etch rate was when the He flow was 100sccm
Etch rate was when flow was 300sccm
Etch rate was when flow was 500sccm
Therefore, the flow to He also needs to be optimized processing.
In other embodiments of the invention, in the 3rd etching process, adopt NF
3During as etching reaction gas, also can add comprise in nitrogen, oxygen, helium, the hydrogen any or its combination gas as assist gas, be used to dilute etching reaction gas, simultaneously the polymer that produces in the etching process also played certain scavenging action.
Adopt NF
3As etching reaction gas, the gas that adds lighter weight simultaneously is as after auxiliary, and not only the depression problem at place, through-hole side wall below is resolved, and the resistance characteristic of through hole has also obtained obvious improvement, illustrates that the polymer residue problem in it also solves.
Then, again via openings 1205 and groove 1208 are carried out metalized, form dual-damascene structure.
Figure 21 adopts NF for the present invention
3The profile of the dual-damascene structure that the back forms, as shown in figure 21, the present invention adopts NF
3The place, through-hole side wall below of the dual-damascene structure that the back forms has also no longer included depression problem (shown in 2101 circle among the figure).
Figure 22 adopts NF for the present invention
3The resistance characteristic figure of the dual-damascene structure that the back forms, as shown in figure 22, abscissa is a nitrogen flow among the figure, ordinate adopts NF for the present invention
3The resistance value of the dual-damascene structure that the back forms, 2201 data that obtain for experiment can be seen, by the adjustment to nitrogen flow, can make the consistency of resistance value of dual-damascene structure of formation comparatively desirable.
Though the present invention with preferred embodiment openly as above; but it is not to be used for limiting the present invention; any those skilled in the art without departing from the spirit and scope of the present invention; can make possible change and modification, so protection scope of the present invention should be as the criterion with the scope that claim of the present invention was defined.
Claims (16)
1. the formation method of a through hole is characterized in that, comprises step:
Substrate is provided, and on described substrate, has etching stop layer, on described etching stop layer, have dielectric layer;
On described dielectric layer, define via hole image;
Carry out first etching, in described dielectric layer, form via openings, to exposing described etching stop layer;
Carry out second etching, remove the etching stop layer in the described via openings, and used gas comprises etching reaction gas and assist gas in described second etching, wherein, etching reaction gas comprises fluoro-gas, and assist gas comprises the gas of quality less than argon gas.
2. formation method as claimed in claim 1 is characterized in that: described fluoro-gas comprises nitrogen fluoride.
3. formation method as claimed in claim 2 is characterized in that: described assist gas comprises nitrogen and helium.
4. formation method as claimed in claim 3 is characterized in that: the flow of described nitrogen fluoride is between 5 to 15sccm.
5. formation method as claimed in claim 4 is characterized in that: the flow of described nitrogen is between 20 to 100sccm, and the flow of described helium is between 100 to 500sccm.
6. as claim 1 or 5 described formation methods, it is characterized in that: described second etching is at room temperature carried out, and the chamber pressure in when work is between 20 to 60mTorr, and bias power is between 100 to 500W, and source power is between 50 to 200W.
7. formation method as claimed in claim 2 is characterized in that: described assist gas comprises a kind of or its combination in nitrogen, oxygen, helium, the hydrogen.
8. formation method as claimed in claim 1 is characterized in that: described etching stop layer is the silicon carbide layer of nitrating.
9. the formation method of a dual-damascene structure is characterized in that, comprises step:
Substrate is provided, and on described substrate, has lower floor's conductive structure, on described lower floor conductive structure, have etching stop layer, on described etching stop layer, have first dielectric layer;
On described first dielectric layer, define via hole image;
Carry out first etching, in described first dielectric layer, form via openings, to exposing described etching stop layer;
Form second dielectric layer on described first dielectric layer and in the via openings;
On described second dielectric layer, form groove figure;
Carry out second etching, form the groove that links to each other with at least one via openings;
Remove second dielectric layer in the described via openings;
Carry out the 3rd etching, remove the etching stop layer in the described via openings, and used gas comprises etching reaction gas and assist gas in described the 3rd etching, wherein, etching reaction gas comprises fluoro-gas, and assist gas comprises the gas of quality less than argon gas.
10. formation method as claimed in claim 9 is characterized in that: described fluoro-gas comprises nitrogen fluoride.
11. formation method as claimed in claim 10 is characterized in that: described assist gas comprises nitrogen and helium.
12. formation method as claimed in claim 11 is characterized in that: the flow of described nitrogen fluoride is between 5 to 15sccm.
13. formation method as claimed in claim 12 is characterized in that: the flow of described nitrogen is between 20 to 100sccm, and the flow of described helium is between 100 to 500sccm.
14. as claim 9 or 13 described formation methods, it is characterized in that: described the 3rd etching is at room temperature carried out, and the chamber pressure in when work is between 20 to 60mTorr, bias power is between 100 to 500W, and source power is between 50 to 200W.
15. formation method as claimed in claim 10 is characterized in that: described assist gas comprises a kind of or its combination in nitrogen, oxygen, helium, the hydrogen.
16. formation method as claimed in claim 9 is characterized in that: described etching stop layer is the silicon carbide layer of nitrating.
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|---|---|---|---|
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| CN101740477B CN101740477B (en) | 2012-02-29 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102569167A (en) * | 2010-12-16 | 2012-07-11 | 中芯国际集成电路制造(北京)有限公司 | Method for forming dual damascene structure |
| CN103199058A (en) * | 2013-04-19 | 2013-07-10 | 中微半导体设备(上海)有限公司 | Method for etching through hole |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3214475B2 (en) * | 1998-12-21 | 2001-10-02 | 日本電気株式会社 | Method of forming dual damascene wiring |
| US6313042B1 (en) * | 1999-09-03 | 2001-11-06 | Applied Materials, Inc. | Cleaning contact with successive fluorine and hydrogen plasmas |
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2008
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102569167A (en) * | 2010-12-16 | 2012-07-11 | 中芯国际集成电路制造(北京)有限公司 | Method for forming dual damascene structure |
| CN103199058A (en) * | 2013-04-19 | 2013-07-10 | 中微半导体设备(上海)有限公司 | Method for etching through hole |
| CN103199058B (en) * | 2013-04-19 | 2015-04-08 | 中微半导体设备(上海)有限公司 | Method for etching through hole |
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