JP2005317772A - Method for detecting etching terminal point - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for detecting an etching end point capable of detecting an end point with high precision. <P>SOLUTION: At the time of working a coating formed on a semiconductor substrate by plasma etching, predetermined wavelength in the ultraviolet region of a light emission spectrum due to elements contained in reaction gas in the plasma etching is monitored so that an etching end point can be detected according to the change of the strength of the predetermined wavelength. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for detecting an etching end point, and more particularly to a method for detecting an etching end point with improved end point detection accuracy.

  In general, a light emission monitoring method is used as an etching end point detection technique in a manufacturing process of a semiconductor device. This is to detect the etching end point from the change in the emission intensity of the reaction product produced or the emission intensity of the etching gas during etching. (For example, refer to Patent Document 1).

As shown in FIG. 5, a polysilicon film 104 to be etched and a mask pattern 105 are sequentially formed on a substrate 101 (underlying film 103), and the polysilicon film 104 is patterned by etching. At this time, for example, when 405 nm, which is a strong emission peak wavelength due to a reaction product of Si, is monitored, as shown in FIG. 6, when the polysilicon film 104 is etched and the base film 103 is exposed, as shown in FIG. Since the emission intensity decreases, the point where the emission intensity decreases can be set as the etching end point.
Japanese Unexamined Patent Publication No. 5-90216

  In recent years, with the miniaturization and high density of semiconductor devices, improvement in processing accuracy is required. However, for example, as shown in FIG. 8, when a film 114 is formed on a substrate 111 (underlying film 113) on which a groove 112 is formed and etched back to embed the film in the groove, the surface of the groove 112 at the etching end point Since the film to be etched 114 remains, the change in emission intensity is as small as about 5%, and the end point is difficult to detect. Then, there is a problem that problems such as excessive etching 116 and film residue 117 occur due to erroneous detection of the end point.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for detecting an etching end point that eliminates the conventional problems and can detect the end point with high accuracy.

  According to one aspect of the present invention, when processing a film formed on a semiconductor substrate by plasma etching, a predetermined wavelength in an ultraviolet region of an emission spectrum caused by an element contained in a reaction gas in the plasma etching is monitored, An etching end point detection method is provided, wherein the etching end point is detected from a change in intensity of the predetermined wavelength.

  According to one embodiment of the present invention, the end point can be detected with high accuracy.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows a cross-sectional view of a semiconductor substrate in a manufacturing process of a semiconductor device. As shown in the figure, a recess 2 (groove) is formed in a semiconductor substrate 1, and a polysilicon film 4, which is a film to be etched, is formed on the entire surface via a base film 3. Further, a resist mask 5 formed by ordinary photolithography is formed. At this time, the opening area of the recess 2 is, for example, 50% or more and less than 90% of the area of the etching region (region where the resist mask is not formed).

Such a semiconductor substrate is etched using the etching apparatus shown in FIG. As shown in the figure, a lower electrode 7 is provided at the lower part of the chamber 6, and a semiconductor substrate 1 having a film formed thereon is placed thereon. An upper electrode 8 and an etching gas introduction port 9 are installed in the upper portion of the chamber 6, and the emission spectrum is monitored by the monochromator 11 through the side observation window 10.

In such an etching apparatus, a semiconductor substrate 1 as shown in FIG. 1 is installed, and a mixed gas containing Cl ₂ or HCl as an etching reaction gas is introduced from an etching gas inlet 9 under a predetermined condition, so that the lower electrode 7 Then, a high frequency voltage is applied to the upper electrode 8 to generate plasma. Then, the intensity of the emission peak of, for example, 256 ± 2 nm in the emission spectrum caused by Cl plasma of Cl ₂ or HCl as the etching reaction gas is monitored by the monochromator 11 and the etching of the polysilicon film is advanced.

  Then, as shown in FIG. 3, when the polysilicon film 4 is etched leaving the polysilicon film 4 in the recess 2, the unreacted Cl plasma concentration in the etching reaction gas increases. Thus, the emission intensity at 256 nm increases, the end point is detected, and the etching is completed.

  In the present embodiment, when the recess area is 50% or more of the etching area, the amount of change in emission intensity when monitoring the peak emission wavelength derived from the reaction product in the visible region where emission intensity is strong so far is While only about 5% was obtained, by monitoring the peak emission wavelength derived from the etching reaction gas in the ultraviolet region, the emission intensity decreased slightly, but the amount of change could be increased to about 20%. Become. In addition, by setting the monitor wavelength to the ultraviolet region, it becomes difficult to be influenced by light from outside the chamber, so that it is possible to detect the end point with high accuracy.

In this embodiment, the film to be etched is a polysilicon film. However, the present invention is not limited to this, and other conductive films such as an Al film and an Al alloy film can be used. At this time, a mixed gas containing at least one of Cl ₂ and BCl ₃ can be used as the etching gas, and the end point is detected by monitoring, for example, a wavelength of 256 ± 2 nm caused by the Cl plasma, similarly to the polysilicon film. Is possible. As the base film, an oxide film, a nitride film, or the like, which is appropriately selected depending on the device structure, can be used.

Further, the present invention can also be applied to an insulating film etching process. For example, when etching an oxide film or a nitride film, a mixed gas containing at least one of CHF ₃ , CF ₄ , C ₄ F ₈ , SF ₆ and CO, O _2, etc. can be used as an etching gas. The end point can be detected by monitoring, for example, a wavelength of 246 ± 2 nm resulting from the F plasma of the reaction gas. As the base film, an Al film, an Al alloy film, a polysilicon film, a Si substrate (film), or the like can be used as appropriate depending on the device structure.

  In addition, this invention is not limited to embodiment mentioned above. Various other modifications can be made without departing from the scope of the invention.

4A and 4B illustrate a manufacturing process of a semiconductor device in one embodiment of the present invention. The figure which shows the etching apparatus in 1 aspect of this invention. 4A and 4B illustrate a manufacturing process of a semiconductor device in one embodiment of the present invention. FIG. 6 shows changes in plasma emission intensity in one embodiment of the present invention. The figure which shows the manufacturing process of the conventional semiconductor device. The figure which shows the manufacturing process of the conventional semiconductor device. The figure which shows the change of the conventional plasma emission intensity. The figure which shows the problem at the time of the detection of the conventional etching end point.

Explanation of symbols

1, 1 , 101, 111 Semiconductor substrate 2 , 112 Recess 3 , 103, 113 Base film 4, 104, 114 Polysilicon film 5, 105, 115 Mask pattern 6 Chamber 7 Lower electrode 8 Upper electrode 9 Etching gas inlet 10 Peep Window 11 Monochromator 116 Overetching 117 Film remaining

Claims (4)

  When processing a film formed on a semiconductor substrate by plasma etching, a predetermined wavelength in the ultraviolet region of an emission spectrum caused by an element contained in a reaction gas in the plasma etching is monitored, and etching is performed by changing the intensity of the predetermined wavelength. A method for detecting an etching end point, wherein the end point is detected.   2. The method for detecting an etching end point according to claim 1, wherein the coating is formed on a base film in which a recess is formed, and the coating is left at least in the recess by processing by the plasma etching.   The method of detecting an etching end point according to claim 2, wherein the area of the recess is 50% or more and less than 90% of the area of the film to be etched.   4. The method for detecting an etching end point according to claim 1, wherein the coating is at least one of a polysilicon film, an Al or Al alloy film, an oxide film, and a nitride film.

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