JP4575401B2 - Plating film forming apparatus and plating film forming method - Google Patents

Description

  The present invention relates to a plating film forming apparatus and a film forming method used for forming a damascene wiring or the like by using a plating method in a semiconductor device manufacturing process.

  In a semiconductor device manufacturing process, as a metal film deposition technique for forming damascene wiring or the like, a method is used in which a metal thin film as a base is formed by sputtering or the like, and a metal film is deposited on the metal thin film by plating. It has been.

  In the plating apparatus for performing this plating film formation, in order to maintain the film formation quality, the concentration of inorganic and organic components contained in the plating solution is periodically measured and monitored using a method such as titration, Based on the result, the chemical solution is replenished or the plating solution is discharged to maintain a constant component concentration.

  However, when the plating film forming process of the substrate to be processed is performed sequentially, organic by-products are derived from the organic components by plating film formation and liquid circulation in addition to the organic components originally contained in the plating solution over time. And this increases. It is considered that the formation of this organic by-product involves the oxidation and decomposition of organic components due to dissolved oxygen in the plating solution.

  From the viewpoint of improving the reproducibility of the plating reaction, it has been studied to maintain the dissolved oxygen concentration in the plating solution constant by a method such as degassing or nitrogen blowing (for example, see Patent Document 1). However, the technique disclosed in Patent Document 1 does not actively reduce the dissolved oxygen concentration of the plating solution, but aims to prevent the concentration from exceeding a predetermined concentration. Generation of by-products cannot be suppressed.

The produced organic by-product is adsorbed on the surface of the film formation substrate and taken into the plating film in the same manner as the organic component useful for plating film formation during plating film formation. For example, in constant current plating that controls the voltage so that the plating current is constant, the characteristics of the plating film growth in the damascene wiring are changed by organic by-products, resulting in a decrease in bottom-up amount. Or a problem that the amount of impurities in the plating film increases, and the electrical characteristics of the plating film vary.
JP 2004-260106 A (paragraphs [0032], [0050], [0126], [0127], etc.)

  An object of the present invention is to provide a plating film forming apparatus and a film forming method that can keep the bottom-up amount in wiring and the amount of impurities contained in the plating film constant by plating film formation.

  The present invention provides, as a first invention, a plating tank for forming a Cu film on the surface of a deposition target substrate, a plating solution tank for retaining a certain amount of plating solution, the plating vessel and the plating solution tank. There is provided a plating film forming apparatus comprising: a plating solution circulation line for circulating a plating solution between them; and a hydrogen supply line for supplying hydrogen to the plating solution flowing through the plating solution circulation line.

As a second invention, the present invention provides plating that flows from the plating tank to the plating solution tank while circulating the plating solution between a plating bath that immerses the substrate to be processed and a plating solution tank that retains a certain amount of plating solution. Provided is a plating film forming method characterized in that hydrogen gas is bubbled and supplied to the solution, and the plating solution flowing from the plating solution tank to the plating tank is degassed .

  According to the present invention, when a damascene wiring or the like is formed by plating, the bottom-up amount in the wiring or the amount of impurities contained in the plating film can be kept constant. Thereby, it is possible to suppress variation in the electrical characteristics of the semiconductor device.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration of a plating film forming apparatus. The plating film forming apparatus 10 retains a sufficient amount of plating solution for immersing the Si wafer W in order to deposit a copper plating film (Cu film) on the surface of the Si wafer W as a substrate to be processed. A plating tank 12, a wafer holding mechanism 14 for holding a plurality of Si wafers W and accessing the plating tank 12, a plating solution tank 16 for retaining a certain amount of plating solution, a plating vessel 12 and a plating solution tank A plating solution circulation line 18 that circulates the plating solution between the plating solution 16, a hydrogen supply line 20 that supplies hydrogen to the plating solution that flows through the plating solution circulation line 18, and a plating solution that analyzes a predetermined component contained in the plating solution. An analysis unit 22, a chemical solution supply unit 24 that replenishes the plating solution tank 16 with various chemical solutions constituting the plating solution, and a control unit 26 for controlling the operation of the plating film forming apparatus 10 are provided. .

  The plating tank 12 is provided with a drain 32 a having a valve for discharging the plating solution in the plating tank 12. The plating solution tank 16 is provided with a drain 32b having a valve for discharging the plating solution in the plating solution tank 16.

  The plating solution circulation line 18 is connected to the first pipe 34a for sending the plating solution from the plating tank 12 to the plating solution tank 16, the second pipe 34b for sending the plating solution from the plating solution tank 16 to the plating tank 12, and the first pipe 34a. A liquid feed pump 36a is provided.

  The hydrogen supply line 20 is attached to the first pipe 34 a and supplies hydrogen gas to the plating solution flowing from the plating tank 12 toward the plating solution tank 16. A porous body 28 is attached to the end of the hydrogen supply line 20 on the first pipe 34a side. The hydrogen gas that has passed through the inside of the porous body 28 blows out from a large number of holes on the surface of the porous body 28, becomes bubbles, is taken into the plating solution, and flows toward the plating solution tank 16.

The hydrogen gas thus taken into the plating solution in the form of bubbles is combined with dissolved oxygen or oxygen ions in the plating solution after being dissolved in the plating solution or in a part of the gas, and the dissolved oxygen concentration in the plating solution And reduce the oxygen ion concentration. Since dissolved oxygen and oxygen ions in the plating solution react with organic components added as useful components to the plating solution and generate organic by-products, dissolved oxygen in the plating solution is used in this way. By reducing the concentration and the oxygen ion concentration, the generation of organic by-products can be suppressed. The dissolved oxygen and oxygen ions contained in the plating solution include those derived from carbon monoxide (CO), carbon dioxide (CO ₂ ) and the like in addition to those derived from oxygen (O ₂ ).

  If the plating solution containing hydrogen gas in the form of bubbles is sent from the plating solution tank 16 to the plating tank 12, there is a possibility that plating defects may locally occur due to the bubbles adhering to the surface of the Si wafer W. is there. Therefore, in order to remove bubbles from the plating solution fed to the plating tank 12, the second pipe 34b has a structure equipped with a degassing mechanism (degasser).

  That is, the second pipe 34b has a double structure including a tube 42 made of a gas-liquid separation membrane and an outer tube 44 surrounding the tube 42 so that a space is formed outside the tube 42. By attaching a deaeration device 46 such as a vacuum pump to the outer tube 44 and depressurizing the outer space of the tube 42, the hydrogen gas contained in the plating solution flowing through the tube 42 was depressurized through the tube 42. Captured into space. Thus, the plating solution can be degassed and degassed. At this time, the dissolved oxygen present without reacting with hydrogen can be degassed to further reduce the dissolved oxygen concentration.

  The supply of hydrogen gas by the hydrogen supply line 20 can be started when a new plating solution is supplied to the plating tank 12 and the plating solution tank 16 and circulation of the plating solution by the plating solution circulation line 18 is started. It is preferable to continue until the plating solution is circulated for discharging the plating solution. However, the hydrogen gas supply is not limited to such a constant supply form, and the bottom-up amount of the Cu film is kept constant even in the intermittent operation form in which the supply and stop of the hydrogen gas are repeated at regular intervals. As long as the effect of holding or the like is recognized as described later, it can be adopted.

  The chemical solution supply unit 24 adds a new plating solution adjusted to a predetermined composition, a copper sulfate basic solution as a basic solution of the plating solution, and a plating solution to promote the growth of the plating film in the trench wiring during the plating film formation. In accordance with a command signal from the control unit 26, a chemical solution necessary for replenishing various organic components including organic components and chemical components necessary for replenishing the organic component, pure water for diluting the plating solution, and the like is supplied to the plating solution tank 16. . The chemical solution supply unit 24 may supply these chemical solutions to the plating tank 12.

  When plating film formation is performed on the Si wafer W, naturally, the Cu ion concentration in the plating solution decreases, and the inorganic components and organic components necessary for the plating film formation also decrease. Therefore, the chemical solution supply unit 24 periodically supplies a certain amount of copper sulfate basic solution and various chemical solutions (hereinafter referred to as “periodic replenisher”) to the plating solution tank 16. On the other hand, the plating solution is periodically discharged from the plating solution tank 16 or the plating tank 12 in order to make the total amount of the plating solution used for plating film formation substantially constant.

  In order to monitor the state of the plating solution, the plating solution analyzing unit 22 collects a certain amount of the plating solution from the plating solution tank 16 by driving the liquid feeding pump 36b in accordance with a command signal from the control unit 26, The component concentration of the predetermined component to be configured is periodically measured by, for example, a titration method. In FIG. 1, the plating solution for analyzing the component concentration is collected from the plating solution tank 16, but this collection may be performed from the plating tank 12.

  The control unit 26 stores an allowable concentration range of various components contained in a plating solution actually used during plating film formation. The control unit 26 manages the quality of the plating solution by adding various chemicals so as to adjust the composition of the plating solution when the concentration of the predetermined component deviates from the allowable concentration range.

  2 derived from organic components added to the plating solution to promote the growth of the plating film when the plating film forming process is performed with the plating film forming conditions such as the plating current value and the substrate rotation number being constant. The relationship between the amount of organic by-products and the bottom-up amount in the trench wiring is shown. A line A in FIG. 2 shows a case where hydrogen is supplied from the hydrogen supply line 20 from the time when a new plating solution is supplied to the plating tank 12 and the plating solution tank 16 and circulation thereof is started. Shows a case where hydrogen supply by the hydrogen supply line 20 is not performed.

  The bottom-up amount is set to 1 as the bottom-up amount in the plating film forming process performed immediately after supply of a new plating solution, and the subsequent bottom-up amount is relatively evaluated. The measurement of the bottom-up amount is performed at points a, b, c, d, and e, and the plating solution usage time at each of these measurement points is a <b <c <d <e. This is because the organic by-product is not contained in the new plating solution and it is difficult to analyze even if it is generated, but the amount of organic by-product is determined when hydrogen gas is not supplied to the plating solution. This is because it is obvious that the plating solution tends to increase as the plating solution usage time elapses, so that the amount of organic by-products can be replaced with the plating solution usage time. However, since the amount of organic by-products generated does not increase only depending on the plating solution use time, the horizontal axis in FIG. 2 is indicated by measurement points.

  As shown in FIG. 2, it was confirmed that when the hydrogen gas was not supplied, the plating solution usage time became longer, that is, the bottom-up amount decreased as the organic by-product increased. On the other hand, when hydrogen gas was supplied, it was confirmed that the bottom-up amount could be kept constant even under the same plating film formation conditions.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to such a form. For example, the hydrogen supply line 20 may be directly attached to the plating solution tank 16. Moreover, what increased the dissolved concentration of hydrogen gas can also be used as a periodic replenisher.

The schematic block diagram of a plating film-forming apparatus. The graph which shows the relationship between plating solution usage time and bottom-up amount.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Plating film-forming apparatus, 12 ... Plating tank, 14 ... Wafer holding mechanism, 16 ... Plating solution tank, 18 ... Plating solution circulation line, 20 ... Hydrogen supply line, 22 ... Plating solution analysis part, 24 ... Chemical solution supply part, 26 ... Control unit, 28 ... Porous body, 32a and 32b ... Drain, 34a ... First piping, 34b ... Second piping, 36a and 36b ... Liquid feeding pump, 42 ... Tube, 44 ... Outer tube, 46 ... Deaeration Equipment, W ... Si wafer.

Claims (4)

A plating tank for forming a Cu film on the surface of the deposition substrate;
A plating solution tank for retaining a certain amount of plating solution;
A plating solution circulation line for circulating the plating solution between the plating tank and the plating solution tank;
And a hydrogen supply line for supplying hydrogen to the plating solution flowing through the plating solution circulation line.   The plating film forming apparatus according to claim 1, wherein the hydrogen supply line has a structure in which hydrogen gas is bubbled and supplied to a plating solution.   The plating film forming apparatus according to claim 2, further comprising a deaeration mechanism for removing bubbles of hydrogen gas supplied to the plating solution. While circulating the plating solution between the plating bath in which the substrate to be treated is immersed and the plating solution tank in which a certain amount of plating solution is retained, hydrogen gas is bubbled into the plating solution flowing from the plating bath to the plating solution tank. The plating film forming method is characterized by degassing the plating solution flowing from the plating solution tank to the plating tank .

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