JPH0810687B2 - Method for manufacturing semiconductor device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device by a plasma etching method in which a semiconductor substrate is etched or cleaned using plasma or ions. It relates to a method of performing with high accuracy.

Conventional technology The end point detection of plasma etching is conventionally measured from the intensity change of the emission spectrum of the etching species emitted from the etching gas and the emission spectrum of the product formed by the reaction between the etching gas and the material to be etched. Is customary. A method is also known in which the end point is detected from the intensity change of the emission spectrum from the reaction product of the etching gas and the lower member under the material to be etched.

Problems to be Solved by the Invention The end point detection of plasma etching is easy to detect when the etching area is large or when the emission spectrum to be detected has a sufficiently high intensity as compared with other spectra, but otherwise. , It is difficult to detect the end point. In particular, in the process of opening the window of the interlayer contact of a large amount of electrode wiring, etc., the area to be etched is small, and the etching gas also causes a large difference in the etching rate between the material to be etched and the underlying lower member. It is difficult to detect the end point by the emission spectrum from the reaction product of the material to be etched or the lower member and the etching gas because it is selected as described above. Therefore, the method of terminating the etching by fixing the time is predominant. In this case, abnormalities such as roughness of the lower member and an increase in the opening area due to over-etching or non-etching of the electrode contact due to non-etching and an increase in contact resistance occur, which causes a decrease in yield.

Means for Solving the Problems In order to increase the measurement sensitivity of the emission spectrum intensity of the end point detection, in addition to the first gas for etching the material to be etched, the etching gas is etched in comparison with the plasma reactivity with the material to be etched. By mixing a second etching gas having a higher plasma reactivity with the lower member below the material to increase the etching amount of the lower member and increase the intensity of the emission spectrum of the reactant generated by this reaction. Make endpoint detection easy.

Action Mainly under plasma discharge, plasma etching is performed by mixing the first etching gas that reacts with the material to be etched and the second etching gas that has a higher reactivity with the lower member than the material to be etched. As a result, when the material to be etched is completely etched, a reaction between the lower member and the second etching gas is started, and a strong emission spectrum is generated by the reaction product, and the emission spectrum is measured by a detector. The end point of etching can be detected.

Example An example of the present invention will be described below. In the case of forming the interlayer contact window of each layer electrode wiring, the interlayer insulating film of the material to be etched is usually a silicon oxide film or a silicon nitride film. The lower member is aluminum or aluminum alloy.

Freon-based gases such as CF ₄ and SF ₆ are often used for etching the interlayer insulating film. A chlorine gas that does not react with the interlayer insulating film and reacts with aluminum that is a lower member is mixed with the fluorocarbon gas. After the interlayer insulating film has been etched with CFC gas, the aluminum of the lower member reacts with chlorine gas, and the reaction product, aluminum chloride, can be easily distinguished from the emission spectrum of other CFC reaction products. The emission spectrum (for example, 386 nm; AlCl ₃ ^* ) is measured, the exposure of the aluminum surface that is the lower member is confirmed, and the end point is detected.

EFFECTS OF THE INVENTION As the conventional etching gas, a gas is selected so that the resist as a mask material and the material to be etched and the etching rate ratio between the lower member and the material to be etched can be as large as possible. This is because the etching roughness of the lower member is made as small as possible in order to prevent the lower member from being roughened due to the over-etching in order to avoid the etching remaining in the step portion.
However, according to the etching by the etching gas in which the first etching gas for etching the material to be etched of the present invention and the second etching gas having high plasma reactivity with the base member are mixed, it is possible to reduce Lower member (electrode wiring) in the case of etching contact windows, etc.
Does not have any problem in the device characteristics even if it is etched to some extent. Rather, if the end point of etching is detected more quickly, the lower member will be exposed to plasma for a shorter time, and the effect of reducing plasma damage to the substrate will be reduced. is there. Further, since the end point is detected promptly and surely, it is possible to largely prevent the element yield reduction due to unetching or excessive overetching.

Claims (1)

[Claims] 1. A plasma reactivity between a first etching gas for etching a material to be etched and a lower member below the material to be etched is higher than that of the first etching gas. The material to be etched is etched using an etching gas mixed with a high second etching gas, and an emission spectrum from a reaction product of the second etching gas and the lower member is detected to detect the material to be etched. A method of manufacturing a semiconductor device, which comprises detecting an end point of etching of an etching material.