METHOD OF ETCHING A DIELECTRIC LAYER
A method of etching a dielectric layer includes providing a substrate, which includes a dielectric layer and a metal layer, performing a first etching process on the metal layer, and performing a second etching process on the dielectric layer to form a opening in the dielectric layer. The first etching process and the second etching process are in-situ carried out in the same reaction chamber without a vent. Since the first and second etching processes are not performed in different reaction chambers respectively, the cycle time can therefore be improved in the present invention. Because the first and second etching processes are performed without a vent, the substrate is protected from the pollution existing in surrounding.
1. Field of the Invention
The present invention relates to a method of etching a dielectric layer, and more particularly, to a method of etching a dielectric layer by utilizing a metal hard mask as an etching mask.
2. Description of the Prior Art
Devices in the semiconductor industry need to undergo several complicated processes such as a photolithograph process, a dry or wet etching process, an ion implantation, and a heat treatment, etc. to construct precise integrated circuits in layers. Among those complicated processes, the process control of dielectric layer etching has become a critical factor, particularly in some applications such as a damascene process or an interconnection technique. For example, in a damascene process, a dielectric layer is etched to form patterns comprising trenches or via. Next the trenches or via are filled with copper, and a planarization process is performed to complete formation of the damascene structure. Additionally, to satisfy requirements of low RC delay effects, a low-K material, an ultra low-k (ULK) material, or a porous low-k material is used to be the dielectric layer in the damascene structure.
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Since the process of etching the dielectric layer 18 also causes a great loss of the patterned photoresist 24, the patterned photoresist 24 formed on the dielectric layer 18 must be thick enough for masking the dielectric layer 18. However, when the integrated density of semiconductor devices gets higher, the critical dimension (CD) of etch element becomes smaller, and the aspect ratio of the opening 28 becomes higher. The trend to fabricate semiconductor devices with smaller features, has presented difficulties when attempting to form the opening 28 with a high aspect ratio in the dielectric layer 18. For example, the etching by-products are easily piled up in the opening 28. As a result, the traditional method of etching the dielectric layer by utilizing the patterned photoresist 24 as the only etching mask is insufficient for the micro-miniaturization. Accordingly, it is still an important issue to provide an effective etching method without destroying the patterns of the dielectric layer.
SUMMARY OF THE INVENTIONIt is therefore a primary objective of the present invention to provide a method of etching a dielectric layer to solve the above-mentioned problem.
From one aspect of the present invention, a method of etching a dielectric layer is disclosed. First, a substrate is provided. The substrate includes a base layer, a dielectric layer and a metal layer. The dielectric layer and the metal layer are disposed above the base layer. Subsequently, a first etching process is performed on the metal layer to turn the metal layer into a patterned metal layer. Next, a second etching process is performed on the dielectric layer to form at least one opening in the dielectric layer. The first etching process and the second etching process are performed in a same reaction chamber.
It is an advantage of the present invention that the cycle time can therefore be improved, and the substrate is protected from the pollution existing in the surrounding environment, since the first and second etching process are not performed in different reaction chambers respectively.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings:
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The opening of the patterned photoresist 114 can include a predetermined pattern for the subsequent process, such as a trench pattern, and can expose parts of the BARC layer 112. The base layer 102 can include a dielectric layer and a plurality of conducting lines disposed in the dielectric layer. The detail structure of the base layer 102 can be adjusted according to the product design, so is not shown in the drawings. The metal layer 108 can serve as a hard mask during the follow-up etching processes, and is preferably a titanium nitride (TiN) layer or a tantalum nitride (TaN) layer. The cap layer 106 or the cap layer 110 can include a silicon carbide (SiC), tetra-ethyl-ortho-silicate (TEOS), or silicon oxynitride (SiON). In addition, the dielectric layer 104 can include a low-k material (k≦2.9), such as fluoride silicate glass (FSG), organosilicate (OSG), or ultra low-k (ULK) materials. The liner layer 103 can be applied to a copper (Cu) process to prevent copper from diffusing into the adjacent dielectric layers. In addition, the liner layer 103 can also function as an etching stop layer. The liner layer 103 can include silicon nitride compounds, silicon oxide compounds, or silicon carbide compounds, such as SiC, SiN, SiON, SiCn, or NBLOK.
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It should be noted that the process of etching the metal layer 108, the flash process and the process of etching the dielectric layer 104 are preferably performed in the same reaction chamber continuously and in-situ by simply changing the process recipes, such as the process gases, the process frequencies, or the process pressures. In addition, the process of etching the metal layer 108, the flash process and the process of etching the dielectric layer 104 are preferably performed without a vent (without break the vacuum). Since it is unnecessary for the semiconductor substrate 100 to transfer between different chambers of an equipment for undergoing the process of etching the metal layer 108 and the process of etching the dielectric layer 104, the cycle time of the processes can be effectively reduced, and the throughput can therefore be improved. Furthermore, because the process of etching the metal layer 108 and the process of etching the dielectric layer 104 are performed without a vent, the patterned metal layer 108a can be protected from the external pollutions, such as water, chlorine gas or other chemicals. Thus, the pollutions do not damage the profile and shape of the patterned metal layer 108a, and do not affect the process of etching the dielectric layer 104. As shown in
In other embodiments, the method of etching a dielectric layer can be applied to processes of forming a dual damascene structure. Please refer to
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The method of etching the dielectric layer in the present invention can be applied to various processes of forming openings, such as processes of forming a via hole, processes of forming a contact hole, a via-first process of forming an opening of a dual damascene structure, a trench-first process of forming an opening of a dual damascene structure, a partial-via-first process of forming an opening of a dual damascene structure, or a self-aligned process of forming an opening of a dual damascene structure. Please refer to
The opening of the patterned photoresist 214 can include a predetermined pattern for the subsequent process, such as a contact hole pattern, and can expose parts of the BARC layer 112. The base layer 202 can include a silicon-based substrate and various devices disposed on the silicon-based substrate. The detail structure of the base layer 202 can be adjusted according to the product design, so is not shown in the drawings. The metal layer 208 is preferably a TiN layer or a TaN layer. The dielectric layer 204 can include an inter-level dielectric layer (ILD), and can be made from low-k materials or ULK materials. The liner layer 203 can include stressed SiN.
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It should also be noted that the liner layer 203 can function as the CESL in the process of etching the dielectric layer 204, and is further removed to expose base layer 202 in this embodiment. In other embodiments, the liner layer 203 can be etched together with the dielectric layer 204 by utilizing the patterned photoresist 214, the remaining BARC layer 112, and the patterned metal layer 208a as an etching hard mask, until the base layer 202 is exposed to form the contact hole 216 in the dielectric layer 204.
Thereafter, the patterned metal layer 208a, the BARC layer 112 and the patterned photoresist 214 can be removed from the dielectric layer 204. Next, a conductive structure is formed in the contact hole 216 to complete the fabrication of a contact plug (not shown in the drawings).
In the above-mentioned embodiments, a metal layer can be first etched to form a patterned metal layer, and thereafter a dielectric layer is etched in the same reaction chamber by using the patterned metal layer as an etching mask. However, the present invention should not be limited to these embodiments. It is one aspect of this invention that the process of etching a metal layer and the process of etching a dielectric layer can be performed on a semiconductor substrate in the same reaction chamber. Accordingly, the process of etching a dielectric layer might be performed immediately after the process of etching a metal layer in the same reaction chamber in-situ; the process of etching a metal layer might be performed immediately after the process of etching a dielectric layer in the same reaction chamber in-situ; or other processes, such as a cleaning process or a degas process, can be performed between the process of etching a metal layer and the process of etching a dielectric layer. In some embodiments, the semiconductor substrate can be protected in the same reaction chamber from the outside pollutions during the period between the metal-etching process and the dielectric-etching process without a vent (without breaking the vacuum). In other embodiments, the reaction chamber can be vented (breaking the vacuum), or the semiconductor substrate can be transferred outward from said reaction chamber as required.
In sum, the process of etching a dielectric layer and the process of etching a metal layer can be performed in the same reaction chamber without a vent in this invention to protect the semiconductor structure from external pollutions. Thus, the structures of the subsequently formed metal lines or conductive plugs can be improved. The metal layer is usually more anticorrosive than the photoresist in the process of etching dielectric layer. Thus, the patterned metal layer applied as an etching mask can be thinner than the patterned photoresist, and the aspect ratio of the formed opening can therefore be smaller. Since the metal-etching process and the dielectric-etching process are not performed in different reaction chambers respectively, the cycle time can therefore be improved in the present invention, and an efficient process is provided.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention.
Claims
1. A method of etching a dielectric layer, comprising:
- providing a substrate, the substrate comprising a base layer, a dielectric layer and a metal layer, the dielectric layer and the metal layer being disposed above the base layer;
- performing a first etching process on the metal layer to turn the metal layer into a patterned metal layer; and
- performing a second etching process on the dielectric layer to form at least one opening in the dielectric layer, wherein the first etching process and the second etching process are performed in a same reaction chamber.
2. The method of claim 1, wherein the metal layer comprises titanium nitride (TiN).
3. The method of claim 1, wherein the second etching process utilizes the patterned metal layer as an etching mask to etch the dielectric layer.
4. The method of claim 3, wherein the opening of the dielectric layer comprises a trench, a via hole or an opening of a dual damascene structure.
5. The method of claim 4, further comprising a step of forming a patterned photoresist on the metal layer, wherein the first etching process utilizes the patterned photoresist as an etching mask to etch the metal layer.
6. The method of claim 5, further comprising a step of forming a first cap layer on the metal layer before forming the patterned photoresist.
7. The method of claim 6, further comprising a step of forming a bottom anti-reflection coating layer (BARC layer) on the first cap layer before forming the patterned photoresist, wherein the patterned photoresist exposes parts of the BARC layer.
8. The method of claim 7, further comprising a step of etching the BARC layer and the first cap layer by utilizing the patterned photoresist as an etching mask after forming the patterned photoresist.
9. The method of claim 5, wherein the substrate further comprises a second cap layer disposed between the dielectric layer and the metal layer.
10. The method of claim 9, wherein the second etching process utilizes the patterned metal layer as an etching mask to etch the first cap layer and the dielectric layer.
11. The method of claim 1, wherein the opening of the dielectric layer comprises a contact hole.
12. The method of claim 11, further comprising a step of forming a patterned photoresist on the metal layer, wherein the first etching process utilizes the patterned photoresist as an etching mask to etch the metal layer.
13. The method of claim 12, further comprising a step of forming a bottom anti-reflection coating layer (BARC layer) on the metal layer before forming the patterned photoresist, wherein the patterned photoresist exposes parts of the BARC layer.
14. The method of claim 13, further comprising a step of etching the BARC layer by utilizing the patterned photoresist as an etching mask after forming the patterned photoresist.
15. The method of claim 11, wherein the dielectric layer comprises an inter-level dielectric layer.
16. The method of claim 1, wherein the first etching process and the second etching process comprises a plasma etching process.
17. The method of claim 1, wherein the first etching process comprises sulfur hexafluoride gas or chlorine gas.
18. The method of claim 1, wherein the reaction chamber comprises a protecting layer disposed on an inner surface of the reaction chamber.
19. The method of claim 18, wherein the protecting layer comprises silicon carbide or yttrium oxide compounds.
20. The method of claim 1, wherein the substrate is kept in the reaction chamber during a period between the first etching process and the second etching process.
Type: Application
Filed: Jun 20, 2008
Publication Date: Dec 24, 2009
Inventor: Hong Ma (Singapore)
Application Number: 12/142,799
International Classification: C23F 1/02 (20060101);