CN102832118B - Method for etching bottom anti-reflective coating in dual damascene structure - Google Patents
Method for etching bottom anti-reflective coating in dual damascene structure Download PDFInfo
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- CN102832118B CN102832118B CN201210335545.9A CN201210335545A CN102832118B CN 102832118 B CN102832118 B CN 102832118B CN 201210335545 A CN201210335545 A CN 201210335545A CN 102832118 B CN102832118 B CN 102832118B
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Abstract
The invention discloses a method for etching a bottom anti-reflective coating (BARC) in a dual damascene structure, which adopts a mixed gas which contains H2, Ar and gases of CxFy series as an etching gas, H2 and Ar are taken as main etching gases, and the gases of the CxFy series are taken as auxiliary etching gases; H2 has higher etching rate to light resistance, and has nearly zero etching rate to a lower oxide layer, and accordingly, the damage to an ultra-low dielectric constant (ULK) insulating layer due to over etching is reduced; moreover, the bombardment function of plasma to the BARC is increased during the etching process through the Ar, so the oxide layer is lossless, and the depth difference which is caused by the etching rate differences of different pattern areas and middle parts and peripheries of the wafer is overcome; and accordingly, the lower oxide layer loss of the whole wafer is greatly reduced, the whole etching depth uniformity is improved, moreover, under the conditions of ensuring that a light-resistant pattern is highly and really transferred to the BARC and no residue is left, the light resistance consumption is reduced, and the reliability of the etching technology is improved.
Description
Technical field
The present invention relates to technical field of manufacturing semiconductors, particularly relate to the lithographic method of bottom antireflective coating in a kind of double damask structure.
Background technology
Along with the development of semiconductor fabrication process, the area of semiconductor chip is more and more less, and meanwhile, the quantity of semiconductor device on a semiconductor chip in a also gets more and more.In order to reduce the RC time delay of circuit, have employed copper and replace aluminium as the metal interconnecting wires of semiconductor rear section (BEOL, Back End OfLine), and the material using dielectric constant little is as metal dielectric layer.
Because copper is difficult to be etched, the lithographic technique therefore connected up for the formation of aluminum metal is traditionally inapplicable for copper.For this reason, the wire laying mode that one is called as dual damascene (DualDamascene) structure is developed.So-called double damask structure technique refers to: now output interconnection channel and through hole in the dielectric layer, and then by plating or electroless copper cement copper in interconnection channel and through hole, recycling chemico-mechanical polishing (CMP) grinds off crossing the copper filled out.
When semiconductor technology enters into the following technology node of 40 nanometer, in back segment one times of design specification double damask structure (1XDD), in order to improve the insulation effect of metal dielectric layer, generally adopt ultralow dielectric (ULK, Ultra Low K) material as metal dielectric layer.Owing to containing a large amount of porous (porous) structure in ULK insulating barrier, therefore in plasma etch process, ULK insulating barrier is easily damaged and causes the unfavorable follow-up fillings such as warpage (bowing)/distortion (kinks), and metal disconnects and the factor of a series of unfavorable electrical and yield such as metal short circuit.This just requires the step selecting little as far as possible injury ULK insulating barrier in etching process, also require that the more stable etching depth uniformity controls simultaneously, while guarantee safety etches remaining (Process Window), reduce the percentage of the over etching (Over etch) after main etching (Main etch), to reduce the damage to ULK insulating barrier.
At dual damascene process, opening bottom antireflective coating (BARC, BottomAnti-Reflective Coating) is a very important step.The plasma etching that what the etching technics opening BARC at present generally adopted is based on CxFy and CxHyFz, this kind of gas makes the etching selection of photoresistance to oxide layer below lower (usually at below 2:1).For overcome due in the middle of different pattern (such as rarefaction (ISO)/compact district (Dense)) and wafer, the difference of periphery etching rate and the depth difference that causes, BARC etches completeness to need necessary over etching to ensure.The etching technics opening BARC at present please refer to Figure 1A and Figure 1B, and in conjunction with 1A and Figure 1B, current BARC etching technics comprises the following steps particularly:
S1: Semiconductor substrate is provided, wherein said Semiconductor substrate prepares from bottom to up successively the first metal layer, etching barrier layer 103, first medium layer 104, second dielectric layer 105, first hard mask layer 106, second hard mask layer 107 and the 3rd hard mask layer 108, wherein in described first hard mask layer 106, second hard mask layer 107 and the 3rd hard mask layer 108, form fluting, and BARC 109 fills described fluting and covers on described 3rd hard mask layer 108, and described BARC 109 is coated with patterned photoresistance 110; Wherein, described the first metal layer comprises metal interlamination medium layer 101 and is arranged in the first metal 102 of described metal interlamination medium layer 101; Described dielectric layer wantonly 104 is ULK insulating barrier, and described second dielectric layer 105 is silicon dioxide layer, and described first hard mask layer 106 is SiN layer, and described second hard mask layer 107 is silicon dioxide layer, and described 3rd hard mask layer 108 is low temperature oxide layer; As shown in Figure 1A;
S2: with described patterned photoresistance 110 for mask, adopt the plasma of CxFy and CxHyFz to etch described BARC 109 and described second dielectric layer 105, and carry out necessary over etching, the device architecture figure after having etched as shown in Figure 1B.
But the oxide layer in the place that the above-mentioned etching technics opening BARC at present makes etching rate fast is too much by overetch, and the slow local overetch of etching rate is fewer, causes etching depth uneven.Concrete etching situation please refer to Fig. 2 A and Fig. 2 B, wherein Fig. 2 A is the current photoresistance opening BARC technique Dense region after BARC opens/BARC residue and oxide layer loss schematic diagram, Fig. 2 B is the current photoresistance opening BARC technique ISO region after BARC opens/BARC residue and oxide layer loss schematic diagram, as shown in Figure 2 A and 2 B, photoresistance/the BARC in Dense region remains 1400 dusts, and oxide layer loses 1060 dusts; Photoresistance/the BARC in ISO region remains 1400 dusts, and oxide layer loses 650 dusts.From Fig. 2 A and Fig. 2 B, adopt current BARC etching technics, the etching depth in Dense region and ISO region is very uneven (differences up to more than 400 dusts)
Therefore, be necessary to improve the etching technics of the existing BARC of opening, to improve the etching effect of BARC.
Summary of the invention
The object of the present invention is to provide the lithographic method of bottom antireflective coating in a kind of double damask structure, to improve the etching effect of BARC.
For solving the problem, the present invention proposes the lithographic method of bottom antireflective coating in a kind of double damask structure, and the etching gas that the method adopts comprises H
2, Ar and CxFy system gas, and wherein said H
2be main etching gas with Ar, described CxFy system gas is auxiliary etch gas.
Optionally, described CxFy system gas comprises CF
4and CHF
3.
Optionally, the flow-rate ratio of etching gas is H
2: CF
4: CHF
3: Ar is 200:25:25:100sscm.
Optionally, the pressure 50mT of this lithographic method.
Optionally, the high frequency power of this lithographic method and the ratio of low frequency power are 1000:500W.
Compared with prior art, the lithographic method of bottom antireflective coating in double damask structure provided by the invention, comprises H by adopting
2, Ar and CxFy system gas mist as etching gas, and described H
2be main etching gas with Ar, described CxFy system gas is auxiliary etch gas; Due to H
2higher etching rate is had to photoresistance, and almost nil to the etching rate of lower floor's oxide layer, thus decrease the damage of over etching to ULK insulating barrier; And because Ar adds the bombardment effect of plasma to BARC in etching process, lossless to oxide layer like this and overcome due in the middle of different pattern (ISO/Dense) and wafer, the difference of periphery rate of etch and the depth difference caused; Thus significantly reduce the loss of the oxide layer of whole wafer lower floor, and significantly improve the uniformity of whole etch depth, and make in the step opening BARC, when ensure photoresistance pattern height be transferred to BARC layer really and noresidue, reduce the consumption of photoresistance and improve the reliability of etch process.
Accompanying drawing explanation
Figure 1A to Figure 1B opens device architecture schematic diagram corresponding to each step of etching technics of BARC at present;
Fig. 2 A is the current photoresistance opening BARC technique Dense region after BARC opens/BARC residue and oxide layer loss schematic diagram;
Fig. 2 B is the current photoresistance opening BARC technique ISO region after BARC opens/BARC residue and oxide layer loss schematic diagram;
Fig. 3 A to Fig. 3 B is device architecture schematic diagram corresponding to each step of etching technics opening BARC provided by the invention;
Fig. 4 A is the device profile map adopting current BARC etching technics to obtain;
Fig. 4 B is the device profile map adopting BARC etching technics provided by the invention to obtain.
Embodiment
In the double damask structure proposed the present invention below in conjunction with the drawings and specific embodiments, the lithographic method of bottom antireflective coating is described in further detail.According to the following describes and claims, advantages and features of the invention will be clearer.It should be noted that, accompanying drawing all adopts the form that simplifies very much and all uses non-ratio accurately, only for object that is convenient, the aid illustration embodiment of the present invention lucidly.
Core concept of the present invention is, provides the lithographic method of bottom antireflective coating in a kind of double damask structure, comprises H by adopting
2, Ar and CxFy system gas mist as etching gas, and described H
2be main etching gas with Ar, described CxFy system gas is auxiliary etch gas; Due to H
2higher etching rate is had to photoresistance, and almost nil to the etching rate of lower floor's oxide layer, thus decrease the damage of over etching to ULK insulating barrier; And because Ar adds the bombardment effect of plasma to BARC in etching process, lossless to oxide layer like this and overcome due in the middle of different pattern (ISO/Dense) and wafer, the difference of periphery rate of etch and the depth difference caused; Thus significantly reduce the loss of the oxide layer of whole wafer lower floor, and significantly improve the uniformity of whole etch depth, and make in the step opening BARC, when ensure photoresistance pattern height be transferred to BARC layer really and noresidue, reduce the consumption of photoresistance and improve the reliability of etch process.
The etching gas that in double damask structure provided by the invention, the lithographic method of bottom antireflective coating adopts comprises H
2, Ar and CxFy system gas, and wherein said H
2be main etching gas with Ar, described CxFy system gas is auxiliary etch gas.
Further, described CxFy system gas comprises CF
4and CHF
3.
Further, the flow-rate ratio of etching gas is H
2: CF
4: CHF
3: Ar is 200:25:25:100sscm.
Further, the pressure 50mT of this lithographic method.
Further, the high frequency power of this lithographic method and the ratio of low frequency power are 1000:500W.
Wherein, described H
2as follows with the reaction equation of BARC:
H2+n-C
xH
y(BARC)→n-C
xH
y+1
BARC etching technics provided by the invention comprises the following steps particularly:
S1: Semiconductor substrate is provided, wherein said Semiconductor substrate prepares from bottom to up successively the first metal layer, etching barrier layer 203, first medium layer 204, second dielectric layer 205, first hard mask layer 206, second hard mask layer 207 and the 3rd hard mask layer 208, wherein in described first hard mask layer 206, second hard mask layer 207 and the 3rd hard mask layer 208, form fluting, and BARC 209 fills described fluting and covers on described 3rd hard mask layer 208, and described BARC 209 is coated with patterned photoresistance 210; Wherein, described the first metal layer comprises metal interlamination medium layer 201 and is arranged in the first metal 202 of described metal interlamination medium layer 201; Described dielectric layer wantonly 204 is ULK insulating barrier, and described second dielectric layer 205 is silicon dioxide layer, and described first hard mask layer 206 is SiN layer, and described second hard mask layer 207 is silicon dioxide layer, and described 3rd hard mask layer 208 is low temperature oxide layer; As shown in Figure 3A;
S2: with described patterned photoresistance 210 for mask, adopts H
2, Ar is main, CxFy system gas is that auxiliary plasma etches described BARC 209 and described second dielectric layer 205, and carries out necessary over etching, and the device architecture figure after having etched is as shown in Figure 3 B.
Through measuring, adopt the lithographic method of bottom antireflective coating in double damask structure provided by the invention photoresistance/BARC in Dense region after BARC opens to remain 1000 dusts, oxide layer loses 100 dusts; And after BARC opens, the photoresistance/BARC in ISO region remains 1050 dusts, and oxide layer loses 110 dusts.It can thus be appreciated that greatly reduce the loss of oxide layer compared to current BARC etching technics.As long as make the over etching of 20% just to ensure safety etching remaining, lower than the over etching requirement of current 30%.
Please continue to refer to Fig. 4 A and Fig. 4 B, wherein Fig. 4 A is the device profile map adopting current BARC etching technics to obtain, Fig. 4 B is the device profile map adopting BARC etching technics provided by the invention to obtain, from Fig. 4 A, the device profile adopting current BARC etching technics to obtain has warpage (bowing)/distortion (kinks) phenomenon; And from Fig. 4 B, the device profile adopting BARC etching technics provided by the invention to obtain does not have warpage (bowing)/distortion (kinks) phenomenon, obtain more satisfactory section, so that follow-up filling, improve electrically and yield requirement.
In sum, the invention provides the lithographic method of bottom antireflective coating in a kind of double damask structure, the method comprises H by employing
2, Ar and CxFy system gas mist as etching gas, and described H
2be main etching gas with Ar, described CxFy system gas is auxiliary etch gas; Due to H
2higher etching rate is had to photoresistance, and almost nil to the etching rate of lower floor's oxide layer, thus decrease the damage of over etching to ULK insulating barrier; And because Ar adds the bombardment effect of plasma to BARC in etching process, lossless to oxide layer like this and overcome due in the middle of different pattern (ISO/Dense) and wafer, the difference of periphery rate of etch and the depth difference caused; Thus significantly reduce the loss of the oxide layer of whole wafer lower floor, and significantly improve the uniformity of whole etch depth, and make in the step opening BARC, when ensure photoresistance pattern height be transferred to BARC layer really and noresidue, reduce the consumption of photoresistance and improve the reliability of etch process.
Obviously, those skilled in the art can carry out various change and modification to invention and not depart from the spirit and scope of the present invention.Like this, if these amendments of the present invention and modification belong within the scope of the claims in the present invention and equivalent technologies thereof, then the present invention is also intended to comprise these change and modification.
Claims (5)
1. the lithographic method of bottom antireflective coating in double damask structure, is characterized in that, the etching gas that the method adopts comprises H
2, Ar and C
xf
ybe gas, and wherein said H
2be main etching gas with Ar, described C
xf
ybe gas be auxiliary etch gas; Concrete steps are as follows:
S1: Semiconductor substrate is provided, wherein said Semiconductor substrate the first metal layer, etching barrier layer, first medium layer, second dielectric layer, the first hard mask layer, the second hard mask layer and the 3rd hard mask layer have been prepared from bottom to up successively, wherein in described first hard mask layer, the second hard mask layer and the 3rd hard mask layer, form fluting, and bottom antireflective coating is filled described fluting and is covered on described 3rd hard mask layer, and described bottom antireflective coating is coated with patterned photoresistance; Wherein, described the first metal layer comprises metal interlamination medium layer and is arranged in the first metal of described metal interlamination medium layer; Described first medium layer is ultralow dielectric insulating barrier, and described second dielectric layer is silicon dioxide layer, and described first hard mask layer is SiN layer, and described second hard mask layer is silicon dioxide layer, and described 3rd hard mask layer is low temperature oxide layer; Wherein, described first medium layer contains a large amount of loose structure;
S2: with described patterned photoresistance for mask, adopts H
2, Ar is main, CxFy system gas is that auxiliary plasma etches or over etching described bottom antireflective coating and described second dielectric layer.
2. the lithographic method of bottom antireflective coating in double damask structure as claimed in claim 1, is characterized in that, described C
xf
ybe that gas comprises CF
4and CHF
3.
3. the lithographic method of bottom antireflective coating in double damask structure as claimed in claim 2, it is characterized in that, the flow-rate ratio of etching gas is H
2: CF
4: CHF
3: Ar is 200:25:25:100sccm.
4. the lithographic method of bottom antireflective coating in double damask structure as claimed in claim 3, is characterized in that, the pressure 50mT of this lithographic method.
5. the lithographic method of bottom antireflective coating in double damask structure as claimed in claim 4, it is characterized in that, the high frequency power of this lithographic method and the ratio of low frequency power are 1000:500W.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1524287A (en) * | 2001-02-12 | 2004-08-25 | 兰姆研究有限公司 | Unique process chemistry for etching organic low-K materials |
| CN101124661A (en) * | 2004-05-11 | 2008-02-13 | 应用材料公司 | Carbon-doped-Si oxide etch using H2 additive in fluorocarbon etch chemistry |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102004017533A1 (en) * | 2003-05-03 | 2005-01-13 | Trikon Technologies Limited, Newport | Method for etching porous dielectric |
| US7538025B2 (en) * | 2003-11-14 | 2009-05-26 | Taiwan Semiconductor Manufacturing Company | Dual damascene process flow for porous low-k materials |
| US7977245B2 (en) * | 2006-03-22 | 2011-07-12 | Applied Materials, Inc. | Methods for etching a dielectric barrier layer with high selectivity |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1524287A (en) * | 2001-02-12 | 2004-08-25 | 兰姆研究有限公司 | Unique process chemistry for etching organic low-K materials |
| CN101124661A (en) * | 2004-05-11 | 2008-02-13 | 应用材料公司 | Carbon-doped-Si oxide etch using H2 additive in fluorocarbon etch chemistry |
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