JP2005166804A - Process and equipment for forming interconnect line - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a high quality void-free interconnect line having a low resistivity easily on the surface of a substrate even when a relatively wide interconnect line and relatively narrow fine interconnect line exist mixedly on the same plane. <P>SOLUTION: A first plating film 6a is formed by first plating on the surface of a substrate having a trench 4 for forming an interconnect line by filling with an interconnect line metal, the first plating film 6a is heat treated, a second plating film 6b is formed by second plating on the surface of the heat treated first plating film 6a and then the second plating film 6b is heat treated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a wiring forming method and apparatus, and in particular, a wiring metal such as copper or silver is provided in a circuit pattern (recess for wiring) having a fine wiring groove provided on the surface of a substrate such as a semiconductor wafer or a printed wiring board. The present invention relates to a wiring forming method and apparatus used for forming a buried wiring by embedding.

  Conventionally, wiring on a substrate provided with a fine circuit pattern, such as a semiconductor wafer or a printed wiring board, has been mainly formed of aluminum. Copper having low resistance and high electromigration resistance is also being used.

  As this type of wiring formation process, a so-called damascene process in which wiring metal is embedded in wiring grooves and contact holes is used. Specifically, a barrier layer (TiN, TaN, WN, etc.) for preventing diffusion of the wiring metal into the insulating film is formed in the wiring groove or contact hole previously formed in the insulating film (interlayer insulating film). Formed by sputtering or CVD, a seed layer as a power feeding layer is formed on the surface of the barrier layer, and then a wiring metal such as copper or silver is embedded by a method such as plating, and then on the insulating film. The buried metal is formed by removing the excess metal and the barrier layer formed in step 1 by a method such as chemical mechanical polishing (CMP) and flattening.

  In general, a wide wiring having a relatively wide width and a fine wiring having a narrow width are mixed in the same plane. In such a case, when the wiring metal is embedded in the wiring groove by plating, the wiring metal is embedded first around the wiring groove for fine wiring, and subsequently, for the wide wiring. It is generally known from the nature of the plating solution that a wiring metal is embedded in the wiring groove. As a result, the film thickness of the plating film deposited on the fine wiring is considerably thicker than the film thickness of the plating film deposited on the wide wiring, and may reach, for example, the same thickness as the wiring groove depth. is there.

  In addition, after depositing a wiring metal by plating, heat treatment (annealing) is performed on the plating film to promote recrystallization of the wiring metal. In this way, by performing the heat treatment on the plating film, the specific resistance value of the wiring metal can be improved to a value close to the bulk value and can be maintained in a stable state.

  However, when the plating film is thickly deposited on the fine wiring as described above and the plating film is subjected to a heat treatment for crystallization of the wiring metal, voids are formed inside the fine wiring due to a so-called “sucking phenomenon”. Called cavity defects may occur. As described above, when a void is generated inside the wiring, the reliability of the wiring and the manufacturing yield are greatly hindered.

This is thought to be due to the fact that wiring metal such as copper deposited by plating condenses when it is crystallized by heat treatment. In particular, in the case of fine wiring, the condensing power of the thick plating film deposited on the fine wiring sucks up the wiring metal embedded in the narrow and thin wiring grooves, and voids are formed at the bottom of the wiring. It is thought to occur.
In addition, the thick plating film deposited on the fine wiring blocks the escape area of impurities generated from the inside of the plating film due to heat treatment and recrystallization, and the influence of the adhesion between the barrier layer and the plating film It is considered to be part of that factor.

  The present invention has been made in view of the above circumstances, even if a relatively wide wide wiring and a narrow fine wiring are mixed in the same plane, there is no void on the surface of the substrate, In addition, it is an object to provide a wiring forming method and apparatus capable of easily forming a high-quality wiring having a small specific resistance value.

  According to the first aspect of the present invention, a first plating film is formed by first plating on a surface of a substrate having a wiring groove for forming a wiring by embedding a wiring metal, and heat treatment of the first plating film is performed. And forming a second plating film by second plating on the surface of the first plating film after the heat treatment, and performing a heat treatment on the second plating film.

  In this way, the heat treatment (annealing) of the plating film is performed at least once in the state where the restriction of the plating film is removed before the thick plating film is deposited on the fine wiring. The wiring metal that is embedded inside to form fine wiring is securely crystallized so as not to generate voids, and after the plating film is further stacked, heat treatment is performed on the plating film again to form the inside of the wiring groove. By crystallizing the wiring metal including the wiring metal that is embedded to form a wide wiring, it is possible to prevent voids from being generated inside the fine wiring due to the so-called “sucking phenomenon” during heat treatment, High-quality wiring with a small specific resistance value can be formed.

  The invention according to claim 2 is the wiring forming method according to claim 1, wherein the formation of the second plating film by the second plating and the heat treatment of the second plating film are repeated a plurality of times. is there. Thus, the quality of the wiring can be further improved by repeating the formation of the second plating film and the heat treatment of the second plating film a plurality of times.

The invention according to claim 3 is the wiring forming method according to claim 1 or 2, wherein the surface of the substrate on which the plating film is formed is cleaned and / or dried prior to the heat treatment of the plating film. is there.
The invention according to claim 4 is the wiring forming method according to any one of claims 1 to 3, wherein the plating film is made of copper or a copper alloy. As a result, it is possible to form a wiring made of copper or a copper alloy having higher electron migration resistance with an electric resistance lower than that of aluminum.

  The invention according to claim 5 is characterized in that the first plating film formed by the first plating substantially embeds the inside of the wiring groove for fine wiring forming the fine wiring having a relatively narrow width. The wiring forming method according to claim 1. As a result, it is possible to efficiently form wiring that prevents voids from being generated inside.

According to the sixth aspect of the present invention, the first plating film is formed on the surface of the substrate having the wiring groove for forming the wiring by embedding the wiring metal, and the second plating film is formed on the surface of the first plating film. A plating cell to be formed, a heat treatment unit for performing heat treatment of the first plating film, and a heat treatment of the second plating film, and a transport robot for transporting the substrate between the plating cells. This is a wiring forming apparatus.
The first plating film and the second plating film may be formed in the same plating cell, and the heat treatment of the first plating film and the heat treatment of the second plating film may be performed in the same heat treatment unit. .
The invention according to claim 7 is the wiring forming apparatus according to claim 6, further comprising a cleaning / drying unit for cleaning and / or drying the surface of the substrate on which the plating film is formed.

The invention described in claim 8 further includes a plating solution analysis unit that analyzes a plating solution used in the plating cell and / or a plating solution supply unit that supplies the plating solution to the plating cell. The wiring forming apparatus according to 6 or 7.
The invention described in claim 9 further includes a cleaning liquid analyzer that analyzes a cleaning liquid used in the cleaning / drying unit and / or a cleaning liquid supply unit that supplies the cleaning liquid to the cleaning / drying unit. 7. The wiring forming apparatus according to 7.

  The invention according to claim 10 is the wiring forming apparatus according to any one of claims 6 to 9, wherein the heat treatment unit is a single wafer type heat treatment unit. By using, for example, a halogen lamp annealing apparatus useful for performing short-term annealing (Rapid Thermal Annealing: RTA) as the heat treatment unit, the annealing treatment can be performed in a shorter time.

  According to the present invention, it is possible to improve the reliability of wiring formation of a semiconductor device, and to provide a semiconductor device having high-quality embedded wiring that has no void inside and has a small specific resistance value.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a manufacturing example of the copper wiring board W in the order of steps. First, as shown in FIG. 1A, an insulating film (interlayer insulating film) such as an oxide film made of SiO ₂ or a low-k material film on a conductive layer 1a on a semiconductor substrate 1 on which a semiconductor element is formed. 2 is deposited, a contact hole 3 and a wiring groove 4 are formed by lithography / etching technique, a barrier layer 5 made of TaN or the like is formed thereon, and a seed layer 7 is formed thereon as a power feeding layer for electrolytic plating.

  Then, as shown in FIG. 1B, the contact hole 3 and the wiring groove 4 of the substrate W are filled with copper by performing copper plating on the surface of the substrate W, and the copper plating film is formed on the insulating film 2. 6 is deposited. Thereafter, the copper plating film 6, the seed layer 7 and the barrier layer 5 on the insulating film 2 are removed by chemical mechanical polishing (CMP), and the copper plating film 6 filled in the contact hole 3 and the wiring groove 4 is formed. The surface and the surface of the insulating film 2 are substantially flush. Thereby, as shown in FIG.1 (c), the wiring which consists of the copper plating film | membrane 6 is formed.

  FIG. 2 shows an overall layout of the wiring forming apparatus according to the embodiment of the present invention. The wiring forming apparatus includes a load / unload station 12 that carries a board into and out of the main frame 10. Inside the main frame 10, there are a heat treatment unit 14 for performing heat treatment (annealing) on the plating film formed on the surface of the substrate, and two cleaning / cleaning methods for cleaning the surface of the substrate with a cleaning liquid such as a chemical solution or pure water and spin drying. A drying unit 16, a substrate stage 18 for temporarily placing a substrate, and four plating cells 20 are disposed. Further, inside the main frame 10, a movable first transfer robot 22 that transfers a substrate between the loading / unloading station 12 and the substrate stage 18, the substrate stage 18, the heat treatment unit 14, and cleaning / drying are provided. A second transportable robot 24 that transfers substrates between the unit 16 and the plating cell 20 and an intake or exhaust duct 26 that performs intake or exhaust are provided.

  Here, the main frame 10 is subjected to a light shielding process, whereby the following steps in the main frame 10 can be performed in a light-shielded state, that is, without light such as illumination light hitting the wiring. ing. Thus, by preventing light from being applied to the wiring, for example, it is possible to prevent a light potential difference from occurring when light is applied to a wiring made of copper, and the wiring from being corroded by this light potential difference.

  Further, located on the side of the main frame 10, a plating solution analysis unit 28 that analyzes the components of the plating solution used in the plating cell 20, a plating solution supply unit 30 that supplies the plating solution to the plating cell 20, and an electrical control unit 32. A cleaning liquid analyzer (not shown) for analyzing components of a cleaning liquid such as a chemical used in the cleaning / drying unit 16 and a cleaning liquid supply part (not shown) for supplying the cleaning liquid to the cleaning / drying unit 16 are provided. Yes.

Here, in this example, a single-wafer type heat treatment unit is used as the heat treatment unit 14. For example, a halogen lamp annealing apparatus useful for performing rapid thermal annealing (RTA) is used as the heat treatment unit 14, so that the heat treatment (annealing) by the heat treatment unit 14 is performed in a shorter time. be able to.
Note that the plating solution analysis unit 28, the plating solution supply unit 30, the electrical control unit 32, and the like may be built in the main frame 10.

Next, an example of forming a copper wiring with this wiring forming apparatus will be described with further reference to FIGS.
First, as shown in FIG. 1A, a contact hole 3 and a wiring groove 4 are formed in an insulating film 2 deposited on the surface, a barrier layer 5 is formed thereon, and a seed layer 7 is formed thereon as a power feeding layer for electrolytic plating. The formed substrate W is prepared, and a substrate cassette storing the substrate W is mounted on the load / unload station 12. Here, for example, the wiring of a semiconductor device generally includes a large number of relatively wide wide wires and narrow fine wires in the same plane. For this reason, as shown in FIG. In addition, the insulating film 2 deposited on the surface of the substrate W includes a wide wiring wiring groove 4a for forming a wide wiring by embedding a wiring metal therein and a fine wiring wiring groove 4b for forming a fine wiring. The barrier layer 5 and the seed layer 7 are formed thereon.

  Then, one substrate is taken out from the substrate cassette mounted on the load / unload station 12 by the first transfer robot 22 and loaded into the main frame 10, and transferred to the substrate stage 18 to be placed and held (step 1). . The second transport robot 22 transports the substrate placed and held on the substrate stage 18 to any plating cell 20.

  In the plating cell 20, for example, first plating using a first plating solution is performed on the surface of the substrate W (step 2), thereby, as shown in FIG. 4B, the surface of the seed layer 7. Then, a first plating film 6a made of copper is formed. Then, when the first plating film 6a substantially fills the inside of the fine wiring wiring groove 4b, the first plating is finished. At this time, as the first plating solution, for example, when using a copper sulfate plating solution having a composition different from that of the second plating solution for performing the following second plating, the copper sulfate concentration is low, the sulfuric acid concentration is high. When using a plating solution having a composition with excellent throwing power and covering properties, and using a copper sulfate plating solution having the same composition as the second plating solution for performing the following second plating, the current density is lowered. Plating. This makes it possible to reliably fill the inside of the fine wiring wiring groove 4b (see FIG. 4) with a particularly high aspect ratio.

  At this time, the composition of the plating solution supplied to the plating cell 20 and used for plating is analyzed by the plating solution analysis unit 28, and the plating solution having a constant composition is supplied from the plating solution supply unit 30 by replenishing the insufficient components. Supply to the plating cell 20. The same applies to the case where the plating solution is supplied to the plating cell 20 to perform the following second plating.

  Next, the substrate W on which the first plating film 6a is formed is transferred to the cleaning / drying unit 16 by the second transfer robot 24, and the surface of the substrate W is cleaned with a cleaning solution such as a chemical solution or pure water. When spin drying is performed or when the plating cell 20 has a spin drying function, the substrate W is spin-dried (liquid drained) in the plating cell 20 (step 3), and the substrate W after drying is removed. It is conveyed to the heat treatment unit 14.

  At this time, when cleaning using a cleaning liquid such as a chemical solution is performed in the cleaning / drying unit 16, the composition of the cleaning liquid supplied to the cleaning / drying unit 16 and used for cleaning is analyzed by a cleaning liquid analyzer (not shown). Then, by supplying the deficient components, a cleaning liquid having a constant composition is supplied to the cleaning / drying unit 16 from a cleaning liquid supply unit (not shown). The same applies to the case where the cleaning liquid is supplied to the cleaning / drying unit 16 to clean the substrate surface on which the second plating film described below is formed.

  In this heat treatment unit 14, heat treatment (annealing) is performed on the first plating film 6a formed on the surface of the substrate W (step 4), thereby being embedded mainly in the wiring groove 4b for fine wiring and finely processing. The wiring metal (copper) that forms the wiring is crystallized. In this heat treatment (annealing), the substrate is heated to 400 ° C., for example, and the heating is continued for several tens of seconds to 60 seconds, for example. At the same time, if necessary, an antioxidation gas is introduced into the heat treatment unit 14, and this gas is caused to flow along the surface of the substrate W, thereby preventing the first plating film 6a from being oxidized. The heating temperature of the substrate is generally 100 to 600 ° C., preferably 300 to 400 ° C.

  As described above, in a state where the restriction of the plating film is removed before the thick plating film is deposited on the fine wiring, that is, as described below, the second plating film 6b is formed to form the copper film. At the time when the inside of the wiring groove 4b for fine wiring is almost filled with the first plating film 6a before the filling is completed, heat treatment (annealing) of the plating film 6a is performed at least once, mainly for fine wiring. The crystallization of the wiring metal that is buried in the wiring groove 4b to form the fine wiring can be reliably performed without generating voids.

  The substrate W that has been subjected to the heat treatment is transported to one of the plating cells 20 by the second transport robot 24, and a second plating solution that uses, for example, a second plating solution is used on the surface of the substrate W by the plating cell 20. Plating is performed (step 5). As a result, as shown in FIG. 4C, a second plating film 6b made of copper is formed on the surface of the first plating film 6a, and the film thickness of the second plating film 6b is a predetermined value. When this is reached, the plating (copper embedding) is completed. At this time, for example, when using a copper sulfate plating solution having a composition different from that of the first plating solution for performing the first plating as the second plating solution, the copper sulfate concentration is high and the sulfuric acid concentration is low. When using a plating solution having an excellent leveling property and using a copper sulfate plating solution having the same composition as the first plating solution for performing the first plating, the plating is performed at an increased current density. As a result, copper can be filled more flatly in a shorter time, particularly in the interior of the wide wiring trench 4a (see FIG. 4).

  At this time, the composition of the plating solution supplied to the plating cell 20 is analyzed by the plating solution analysis unit 28, and the plating solution having a fixed composition is supplied from the plating solution supply unit 30 to the plating cell 20 as described above.

  Next, the substrate W on which the second plating film 6b is formed and the copper embedding is completed is transported to the cleaning / drying unit 16 by the second transport robot 24, and a chemical solution, pure water or the like on the surface of the substrate W is transported. If the plating cell 20 is provided with a spin drying function, the substrate W is spin-dried (liquid drained) (step 6). The dried substrate W is transported to the heat treatment unit 14.

  At this time, when the cleaning / drying unit 16 performs cleaning using a cleaning liquid such as a chemical, the composition of the cleaning liquid supplied to the cleaning / drying unit 16 is analyzed by a cleaning liquid analyzer (not shown), and the cleaning liquid supply unit The cleaning liquid having a constant composition is supplied from the (not shown) to the cleaning / drying unit as described above.

  In this heat treatment unit 14, heat treatment (annealing) of the second plating film 6b formed on the surface of the substrate W is performed (step 7), thereby being buried mainly in the wide wiring wiring groove 4a. The wiring metal (copper) deposited on the surface of the substrate W is crystallized. In this heat treatment (annealing), as described above, the substrate is heated to 400 ° C., for example, and the heating is continued for several tens of seconds to 60 seconds, for example. An oxidation preventing gas is introduced into the unit 14 to prevent the second plating film 6b from being oxidized. The heating temperature of the substrate is generally 100 to 600 ° C., preferably 300 to 400 ° C.

  In this way, the first plating film 6a is formed, and the first plating film 6a is subjected to heat treatment (annealing) to be buried mainly in the wiring groove 4b for fine wiring to form fine wiring. After the wiring metal is crystallized, a second plating film 6b is formed on the surface of the crystallized first plating film (wiring metal) 6a, and the second plating film 6b is again subjected to heat treatment, By crystallizing the wiring metal including the wiring metal that is buried in the wide wiring groove 4a to form the wide wiring, voids are generated inside the fine wiring due to the so-called “sucking phenomenon” or the like. In addition, it is possible to form a high-quality wiring having a small specific resistance value.

Next, the substrate W after the heat treatment is transported to the substrate stage 18 by the second transport robot 24 and is held, and the substrate W held by the substrate stage 18 is cassette of the load / unload station 12 by the first transport robot 22. (Step 8).
Thereafter, the excess metal and barrier layer formed on the insulating film 2 are removed and planarized by a method such as chemical mechanical polishing (CMP), so that a copper plating film is obtained as shown in FIG. (First plating film 6a and second plating film 6b) A wiring composed of 6 is formed.

The above example shows an example in which the formation of the plating film, the cleaning / drying of the substrate, and the heat treatment of the plating film are repeated twice. As shown by the wavy line in FIG. 3, the second plating film formed by the second plating is used as the first plating film, and the second plating film is formed on the surface of the first plating film (second plating film). (Third plating film) is formed, the surface of the substrate is washed and dried, and then the second plating film (third plating film) is heat treated at least once as necessary. It may be repeated. Thus, a higher quality wiring can be obtained by repeating the formation of the plating film, the cleaning / drying of the substrate, and the heat treatment of the plating film three times.
Moreover, although the example which uses copper as a wiring metal is shown, you may use a copper alloy other than copper.

It is a figure which shows the formation example of copper wiring in order of a process. 1 is a plan layout view of a wiring forming apparatus according to an embodiment of the present invention. FIG. 3 is a block diagram showing a wiring formation method when forming a wiring by the wiring forming apparatus shown in FIG. 2 in order of steps. It is a figure which shows the state which forms the 1st plating film and the 2nd plating film in order on the surface of the board | substrate which has a wiring groove | channel in order of a process.

Explanation of symbols

2 Insulating film 3 Contact hole 4 Wiring groove 4a Wide wiring wiring groove 4b Fine wiring wiring groove 5 Barrier layer 6 Copper plating film 6a First plating film 6b Second plating film 7 Seed layer 10 Main frame 12 Load / Unload Load station 14 Heat treatment unit 16 Cleaning / drying unit 18 Substrate stage 20 Plating cells 22, 24 Transport robot 28 Plating solution analysis unit 30 Plating solution supply unit

Claims (10)

Forming a first plating film by first plating on a surface of a substrate having a wiring groove for forming a wiring by embedding a wiring metal;
Heat-treating the first plating film;
Forming a second plating film by second plating on the surface of the first plating film after the heat treatment;
A wiring forming method, wherein the second plating film is heat-treated.   The wiring formation method according to claim 1, wherein the formation of the second plating film by the second plating and the heat treatment of the second plating film are repeated a plurality of times.   3. The wiring formation method according to claim 1, wherein the surface of the substrate on which the plating film is formed is cleaned and / or dried prior to the heat treatment of the plating film.   The wiring forming method according to claim 1, wherein the plating film is made of copper or a copper alloy.   The first plating film formed by the first plating substantially embeds the inside of a wiring groove for fine wiring forming a relatively narrow fine wiring. The wiring formation method of description. A plating cell for forming a first plating film on a surface of a substrate having a wiring groove for forming wiring by embedding a wiring metal, and a second plating film on the surface of the first plating film;
A heat treatment unit for performing heat treatment of the first plating film and heat treatment of the second plating film;
A wiring forming apparatus comprising a transfer robot for transferring a substrate between the plating cell and the heat treatment unit.   The wiring forming apparatus according to claim 6, further comprising a cleaning / drying unit for cleaning and / or drying a surface of the substrate on which the plating film is formed.   The wiring forming apparatus according to claim 6, further comprising a plating solution analysis unit that analyzes a plating solution used in the plating cell and / or a plating solution supply unit that supplies the plating solution to the plating cell.   8. The wiring forming apparatus according to claim 7, further comprising a cleaning liquid analysis unit that analyzes a cleaning liquid used in the cleaning / drying unit and / or a cleaning liquid supply unit that supplies the cleaning liquid to the cleaning / drying unit.   10. The wiring forming apparatus according to claim 6, wherein the heat treatment unit is a single wafer type heat treatment unit.

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