JP3011018B2 - Plasma etching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma etching method for etching an object to be processed using plasma.

[0002]

2. Description of the Related Art Conventionally, in etching a silicon compound such as silicon oxide or silicon nitride using gas plasma, a fluorocarbon-based gas, a fluorocarbon-based gas, or a mixed gas obtained by adding an argon gas thereto has been used. Various attempts have been made to obtain desired processing characteristics in accordance with the type of the object to be processed.

[0003]

In the manufacture of semiconductor devices, the diameter of a silicon wafer to be used has been increasing in order to improve productivity, and it is important in the manufacturing technique to keep processing characteristics uniform within the wafer surface. Points.

[0004] Various contrivances in the prior art have been made by focusing on the processing speed of the object to be processed and the processed shape obtained after the processing.

[0005] The non-uniformity of the processing characteristics is caused by the non-uniformity of the plasma.
It is caused by various factors such as non-uniformity of reaction product exhaustion and non-uniformity of sputtering due to ions, and there are various countermeasures, one of which is dilution of gas or plasma by adding a rare gas. At this time, the rare gas to be added is Ar
In the case of a gas having a large mass, such as Xe or Kr, the rare gas itself has a large physical sputtering effect, so that it affects not only the desired uniformity but also the selectivity.

An object of the present invention is to provide a plasma etching method capable of improving the uniformity of the above-mentioned processing characteristics.

[0007]

The above object is achieved by adding a large amount of He gas to a fluorocarbon gas or a fluorocarbon gas acting as an etchant of silicon oxide or silicon nitride.

[0008]

In the case of He, since the mass is small, the physical sputterability is small, only the dilution effect by addition is obtained, the diffusion speed increases, and the uniformity can be improved without significantly affecting the selectivity and the like. This effect is remarkable in a fluorocarbon gas or a fluorocarbon gas in which the ionization voltage of the etchant is smaller than the ionization voltage of He.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a plasma etching apparatus to which the present invention is applied. In FIG. 1, a gas supply device (not shown) is provided in a processing chamber including a discharge chamber 10 and a quartz window 20.
, An etching gas is introduced and exhausted by the exhaust device 30 and at the same time adjusted to a desired pressure. This etching gas is oscillated from the magnetron 40 and
The plasma is generated by the synergistic action of the microwave applied to the processing chamber through 0 and the magnetic field formed by the solenoid coil 60. The wafer 70 mounted on the electrode 80 is etched by this plasma. A high frequency power supply 90 is connected to the electrode, and the energy of ions incident on the wafer 70 is controlled by the application of the high frequency. can do.

FIG. 2 shows a C4F in the apparatus shown in FIG.
8 when He is added to the underlayer of the silicon oxide film.
The etching rate of ly-Si is shown. In FIG.
The solid line indicates the maximum value of the etch rate in the wafer, and the broken line indicates the minimum value in the wafer. As can be seen from FIG. 2, when the amount of He added increases, the maximum value in the wafer does not change much and only the minimum value gradually increases, thereby improving the uniformity of the underlying poly-Si etch rate. You can see that there is.

Further, the flow rate of the He gas is 5 times or more and 100 times or less of the flow rate of the gas acting as an etchant, so that the effect of uniformization is increased. If the flow rate ratio of the He gas is too large, the upper limit of the flow rate ratio is determined because the etch rate decreases.

FIG. 3 shows the etching rate of Poly-Si underlying the silicon oxide film when Ar is added to C4F8 as in FIG. As can be seen from FIG. 3, when Ar is added, the etch rate changes due to the sputtering effect of Ar, but the rate of increase at a large etch rate is large, and the uniformity in the wafer is improved. Does not work.

In a process of etching a silicon oxide film or a silicon nitride film in a semiconductor device manufacturing process, Po
ly-Si is one of the base films of a silicon oxide film and a silicon nitride film, and it is preferable that Poly-Si is not etched as much as possible when etching a silicon oxide film or a silicon nitride film. That is, it is desirable to have a process characteristic in which the poly-Si etch rate is small. However, the addition of He can reduce the variation in the poly-Si etch rate within the wafer, which is necessary for improving the productivity of semiconductor devices. Will contribute.

The effect of homogenization by adding He is 2
This is particularly noticeable when a high-density plasma of 10 ¹¹ / cm ³ or more is used under a low pressure of about 0 mTorr or less.

In this embodiment, the case where He is added to C4F8 has been described.
It may be a combination of one or more of fluorocarbon gas and hydrofluorocarbon gas.

In this embodiment, an example of the apparatus shown in FIG. 1 has been described. However, the present invention relates to dilution of a main etching gas or its plasma by adding He.
It does not limit the apparatus configuration / plasma generation method.

[0017]

According to the present invention, the in-wafer uniformity of the etching characteristics of the silicon oxide and silicon nitride film etching steps in the semiconductor device manufacturing process can be improved.
Productivity can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus configuration of an embodiment of a plasma etching apparatus to which the present invention is applied.

FIG. 2 is a diagram illustrating the relationship between the amount of He added and a Poly-Si etch rate.

FIG. 3 is a diagram illustrating the relationship between the amount of Ar added and a Poly-Si etch rate.

[Explanation of symbols]

10: discharge chamber, 20: quartz window, 30: exhaust device,
40 ... magnetron, 50 ... waveguide, 60 ... solenoid coil, 70 ... wafer, 80 ... electrode, 90 ... high frequency power supply.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Koichi Okamura 794, Higashi-Toyoi, Katsumatsu-shi, Yamaguchi Prefecture Inside the Kasado factory of Hitachi, Ltd. 64-61023 (JP, A) JP-A-5-251399 (JP, A) JP-A-5-114584 (JP, A) JP-A-5-55173 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/3065

Claims (1)

(57) [Claims] A gas introduced into a processing chamber is turned into a plasma, and the gas plasma generates a plasma to be processed placed in the processing chamber.
In a plasma etching method for etching a wafer having an underlayer, the object is made of a silicon compound containing silicon oxide or silicon nitride, and a fluorocarbon (CxFy: x = 1 to 1) is used as the gas.
6 y = 4 to 12) or hydrofluorocarbon (C
xHyFz: x = 1 to 6 y = 1 to 12 z = 1 to 1
2) at least one or more processing gases and 5
By using a mixed gas in which He gas is mixed by a factor of 100 times, the uniformity of the etch rate in the surface of the underlying wafer
A plasma etching method characterized by improving the plasma etching.