Silicide film formation method

Abstract

To provide a silicide film forming method capable of forming a uniform metal silicide film on a semiconductor wafer.SOLUTION: A semiconductor wafer containing silicon as a constituent element is placed in a sputtering chamber. After that, the inside of the sputtering chamber is evacuated until the pressure becomes 9×10-5 Pa or less. Thereafter, a metal film is deposited on the semiconductor wafer by introducing sputtering gas into the sputtering chamber and sputtering the target. A laser beam is made incident on a metal film deposited on a semiconductor wafer to cause silicide reaction to form a metal silicide film.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for forming a silicide film. [Background technology]

[0002] A technique for forming a metal silicide film by depositing a metal film on a semiconductor wafer containing silicon, such as a silicon wafer or a silicon carbide (SiC) wafer, and then performing laser annealing is known (Patent Document 1). Ni, Ti, Mo, W, etc. are used as the metal film. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-111686 Summary of the Invention [Problem to be solved by the invention]

[0004] It is desirable to form a uniform metal silicide film over the entire surface of a semiconductor wafer. Various evaluation experiments conducted by the inventors of the present application have confirmed that metal silicide films formed by laser annealing may have uneven appearances. An object of the present invention is to provide a silicide film formation method capable of forming a uniform metal silicide film on a semiconductor wafer. [Means for solving the problem]

[0005] According to one aspect of the present invention, A semiconductor wafer containing silicon as a constituent element is placed in a sputtering chamber; Then the pressure is 9 x 10 -5 The sputtering chamber is evacuated to a pressure of 0.01 Pa or less. Thereafter, a sputtering gas is introduced into the sputtering chamber to sputter the target in the sputtering chamber, thereby forming a film on the semiconductor wafer. , consisting of a metal that undergoes a silicide reaction depositing a metal film; Thereafter, depositing a nickel film on the metal film by sputtering another target in the sputtering chamber; The semiconductor wafer on which the metal film and the nickel film are deposited is A method for forming a silicide film is provided in which a laser beam is applied to cause a silicide reaction to form a metal silicide film. [Effects of the Invention]

[0006] Before introducing the sputtering gas, the pressure was 9×10 -5 By evacuating the sputtering chamber until the pressure is below 100 Pa, the amount of oxygen atoms taken into the metal film is reduced, which in turn makes it possible to suppress the occurrence of unevenness in the appearance of the metal silicide film. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a flowchart showing the procedure of a silicide film forming method according to one embodiment. [Figure 2] 2A to 2C are cross-sectional views of a wafer at intermediate stages up to the formation of a metal silicide film, and FIG. 2D is a cross-sectional view of the wafer on which a metal silicide film has been formed. [Figure 3] FIG. 3 is a schematic diagram of the laser annealing apparatus used in this embodiment. [Figure 4] 4A and 4B are optical microscope photographs of the metal silicide films produced by the methods according to the above-mentioned Example and Comparative Example, respectively. [Figure 5] 5A and 5B are schematic diagrams showing cross sections of metal film-stacked wafers produced by the methods of the above-mentioned Example and Comparative Example, respectively. DETAILED DESCRIPTION OF THE INVENTION

[0008] A method for forming a silicide film according to one embodiment will be described with reference to FIGS. 1 to 5B. Fig. 1 is a flowchart showing the procedure of the silicide film forming method according to this embodiment. Fig. 2A to Fig. 2C are cross-sectional views of a wafer at intermediate stages until a metal silicide film is formed, and Fig. 2D is a cross-sectional view of the wafer on which the metal silicide film has been formed.

[0009] First, a semiconductor wafer 31 (FIG. 2A) is loaded into the sputtering chamber of a sputtering device (step S1). The semiconductor wafer 31 is made of a semiconductor containing silicon. For example, the semiconductor wafer 31 is a silicon wafer, a SiC wafer, or the like. For example, an RF magnetron sputtering device is used as the sputtering device. Metallic molybdenum (Mo) is used as the sputtering target.

[0010] After the semiconductor wafer 31 is loaded, the sputtering chamber is evacuated (step S2). -5 The pressure corresponding to the degree of vacuum in the sputtering chamber before the introduction of sputtering gas is referred to as the ultimate pressure Pm. After the sputtering chamber is evacuated, the introduction of sputtering gas begins (step S3). Furthermore, discharge is initiated in the sputtering chamber to perform sputtering, thereby depositing a molybdenum film 32 (FIG. 2B) on the semiconductor wafer 31, and the target is replaced to deposit a nickel film 33 (FIG. 2B) on the molybdenum film 32 (step S4). A wafer including the semiconductor wafer 31, the molybdenum film 32, and the nickel film 33 is referred to as a metal film-stacked wafer 30.

[0011] After the nickel film 33 is deposited, the introduction of the sputtering gas is stopped (step S5), and then the semiconductor wafer 31 is carried out of the sputtering chamber and into an annealing chamber (step S6).

[0012] 3 is a schematic diagram of the laser annealing apparatus used in this embodiment. A stage 10 is supported by a movement mechanism 11 in an annealing chamber 12. The movement mechanism 11 can move the stage 10 within a horizontal plane in response to a command from a control device 20. A metal film-laminated wafer 30 (FIG. 2B) having a molybdenum film 32 and a nickel film 33 formed thereon is held on the upper surface of the stage 10 with the nickel film 33 facing upward.

[0013] In response to a command from the control device 20, the laser light source 21 outputs a pulsed laser beam for annealing. For example, a laser diode with an oscillation wavelength of approximately 800 nm is used as the laser light source 21. The pulsed laser beam 25 output from the laser light source 21 passes through a transmission optical system 22 and a lens 23, passes through a laser transmission window 13 provided on the top plate of the annealing chamber 12, and is incident on the metal film-laminated wafer 30. The transmission optical system 22 includes, for example, a beam homogenizer, an aperture, a lens, a mirror, etc. The beam homogenizer and the lens 23 shape the beam spot on the surface of the metal film-laminated wafer 30, making the beam profile uniform.

[0014] The control device 20 controls the movement mechanism 11 to move the stage 10 in two-dimensional directions within a horizontal plane. The control device 20 further controls the laser light source 21 to emit a pulsed laser beam 25 based on current position information of the stage 10. For example, the control device 20 controls the movement mechanism 11 and the laser light source 21 to move the beam spot of the pulsed laser beam 25 ( FIG. 2C ) in the main scanning direction and the sub-scanning direction on the surface of the metal film-laminated wafer 30. By repeating the main scanning and the sub-scanning, almost the entire surface of the metal film-laminated wafer 30 can be annealed.

[0015] After step S6, laser annealing is performed on the metal film-laminated wafer 30 to cause a silicide reaction between silicon contained in the semiconductor wafer 31 and the molybdenum film 32, thereby forming a molybdenum silicide film 34 (FIG. 2D) (step S7). The notation "MoSi" shown in FIG. 2 does not mean that the composition ratio of Mo to Si is 1:1. After the laser annealing is completed, the metal film-laminated wafer 30 is carried out of the annealing chamber 12 (FIG. 3) (step S8).

[0016] Next, the excellent effects of the above embodiment will be described with reference to FIGS. 4A and 4B. 4A and 4B are optical microscope photographs of metal silicide films fabricated by the methods of the above-described example and comparative example, respectively. The slightly dark areas in FIGS. 4A and 4B are metal film-laminated wafers 30. The metal film-laminated wafers 30 have a square shape with a side length of 10 mm. In the comparative example shown in FIG. 4B, the ultimate pressure Pm in step S2 (FIG. 1) is set to 5×10 -4 It was named Pa.

[0017] In the method according to the embodiment, a metal silicide film was formed that appeared uniform in appearance, as shown in Figure 4A. In contrast, in the method according to the comparative example, it can be seen that color unevenness (dark gray areas and light gray areas in the photograph) occurred in appearance.

[0018] In this way, by applying the method according to the above embodiment, it is possible to form a uniform molybdenum silicide film 34 (FIG. 2D) that has no unevenness in appearance.

[0019] Next, with reference to FIGS. 5A and 5B, the reason why the molybdenum silicide film produced by the method according to the comparative example had uneven appearance will be described.

[0020] 5A and 5B are schematic diagrams showing the cross section of a metal film-laminated wafer 30 produced by the methods of the above-mentioned Example and Comparative Example, respectively. A molybdenum film 32 is formed on a semiconductor wafer 31, and a nickel film 33 is formed on top of that. When the molybdenum film 32 is deposited by sputtering, oxygen atoms 35 are incorporated into the molybdenum film 32. Evaluation experiments by the inventors of the present application have shown that the higher the ultimate pressure Pm in step S2 (lower the degree of vacuum), the greater the amount of oxygen atoms 35 incorporated into the molybdenum film 32. In the above Example (FIG. 5A), the ultimate pressure Pm was set to 9×10 -5 In the comparative example (FIG. 5B), the ultimate pressure Pm is 5×10 -4 Pa. Therefore, the amount of oxygen taken up by the molybdenum film 32 (FIG. 5B) produced by the method according to the comparative example is greater than the amount of oxygen taken up by the molybdenum film 32 (FIG. 5A) produced by the method according to the above example.

[0021] The oxygen atoms 35 captured in the molybdenum film 32 react with molybdenum during laser annealing (step S7). The oxidation reaction of molybdenum during laser annealing causes the appearance of color unevenness in the molybdenum silicide film 34 (FIG. 2D). The ultimate pressure Pm in step S2 is set to 9×10 -5 By setting the pressure at or below 100 Pa, it is possible to form a uniform molybdenum silicide film 34 (FIG. 2D) without uneven color in appearance.

[0022] Next, a modification of the above embodiment will be described. In the above example, the nickel film 33 (FIG. 2B) is deposited on the molybdenum film 32 (FIG. 2B), but the nickel film 33 can be omitted. In this case, a pulsed laser beam 25 (FIG. 2C) for annealing is irradiated onto the metal film-laminated wafer 30 with the molybdenum film 32 exposed, thereby causing a silicide reaction.

[0023] Furthermore, although the metal film was deposited using RF magnetron sputtering in the above embodiment, other sputtering methods may also be used, such as DC magnetron sputtering.

[0024] Furthermore, in the above embodiment, a molybdenum film 32 (FIG. 2C) is used as the metal film that causes a silicide reaction. However, a film made of a metal other than molybdenum that causes a silicide reaction may also be used. Examples of such metals include nickel, titanium, and tungsten. Even when a metal film other than a molybdenum film is used as the metal film that causes a silicide reaction, if a large amount of oxygen is taken into the metal film, an oxidation reaction of the metal occurs during laser annealing, which can result in uneven color appearance. Therefore, even when a metal film other than a molybdenum film is used as the metal film that causes a silicide reaction, it is necessary to set the ultimate pressure Pm in step S2 to 9×10 -5 It is preferable to evacuate to a pressure of 100 Pa or less.

[0025] Furthermore, in order to avoid an increase in the amount of oxygen taken into the metal film that undergoes a silicide reaction with silicon, it is preferable that the purity of the argon gas used as the sputtering gas be 99.9995% or higher.

[0026] The above-described embodiments are merely illustrative, and it goes without saying that partial substitutions or combinations of the configurations shown in the embodiments and modifications are possible. Similar effects resulting from similar configurations of the embodiments and modifications will not be mentioned for each embodiment and modification. Furthermore, the present invention is not limited to the above-described embodiments and modifications. For example, it will be obvious to those skilled in the art that various modifications, improvements, combinations, etc. are possible. [Explanation of symbols]

[0027] 10 stages 11 Moving mechanism 12 Annealing chamber 13 Laser transmission window 20 Control device 21 Laser light source 22 Transmission Optical System 23 Lens 25 Pulsed laser beam 30 Metal film stacked wafer 31 Semiconductor wafers 32 Molybdenum film 33 Nickel film 34 Molybdenum silicide film 35 oxygen atoms

Claims

1. A semiconductor wafer containing silicon as a constituent element is placed in a sputtering chamber; Then, the pressure is 9 x 10 －５ The sputtering chamber is evacuated to a pressure of 10 Pa or less. Then, a sputtering gas is introduced into the sputtering chamber to sputter a target in the sputtering chamber, thereby depositing a metal film made of a metal that causes a silicide reaction on the semiconductor wafer; Thereafter, depositing a nickel film on the metal film by sputtering another target in the sputtering chamber; a silicide film forming method in which a laser beam is irradiated onto the semiconductor wafer on which the metal film and the nickel film are deposited to cause a silicide reaction and form a metal silicide film;

2. 2. The method for forming a silicide film according to claim 1, wherein the sputtering gas is argon gas having a purity of 99.9995% or more.

3. A method for forming a silicide film according to claim 1, wherein the metal film is formed from one of molybdenum, titanium, and tungsten.

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