JPH0277126A - Dry etching - Google Patents

Abstract

PURPOSE:To enable anisotropic etching of a desired trench form with a high aspect ratio, while high selection ratio and high etching rate are maintained, by intermittently adding a gas having a protecting film forming action, during a process wherein main etching gas is introduced and dry etching is executed in a plasma atmosphere. CONSTITUTION:A silicon semiconductor wafer 8 is carried onto a second electrode 3; etching reaction gas, e.g., SF6 gas with a flow rate of 60 SCCM, O2 gas with a flow rate of 40 SCCM and Kr gas with a flow rate of 100 SCCM are supplied in the above vessel 1; the inside of the hermetic vessel 1 is kept at a constant pressure, e.g., 0.6Torr; at this time, from a gas feeding pipe 7, gas having a protecting film forming action, e.g., SiCl4 gas with a flow rate of 1 SCCM is intermittently added, thereby protecting the side wall of the inside of trench. That is, the balance between the etching and the side wall protection can be maintained to the utmost, so that the trench form of trench etching can be controlled in a desirable superior form, without decreasing the etching rate.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a dry etching method.

(Conventional technology) Integrated circuit technology is constantly pursuing higher integration, and IM memory is already commercially available, with 4M and 16M being the focus of development. Silicon trench etching is required as one of the development elements to achieve this ultra-integration. As the degree of integration of ICs increases, silicon trench etching has become an indispensable technique for element isolation or for reducing the two-dimensional area of capacitor cells. It is well known to those skilled in the art that a triode etcher is attracting attention as a means of trench etching. For example, Tokuko Sho 57-44749
It is stated in the issue bulletin etc.

(Problems to be Solved by the Invention) However, when trench etching with a high aspect ratio is performed, there are problems such as occurrence of undercuts and roughness of side walls. Especially when a strongly isotropic etching gas is used as the main etchant.

Undercuts were clearly observed at the bottom of the mask.

As described above, regarding the shape as well, it was necessary to satisfy the desired trench shape by controlling the taper angle and round etching.

The present invention has been made to address the above points, and maintains a high etching rate and high selectivity.

In addition, the present invention provides a dry etching method that allows a good trench etching shape to be achieved.

[Structure of the invention]

(Means for Solving the Problems) This invention is characterized in that during the process of introducing a main etching gas and performing dry etching in a plasma atmosphere, a gas having the effect of forming a protective film is intermittently added. It is something.

(Function) By intermittently adding a gas that has the effect of forming a protective film, the side walls inside the trench are protected.In other words, the balance between etching and side wall protection can be maintained optimally, and the trench shape of trench etching can be changed. It becomes possible to control the shape to a desired desired shape.

In particular, in cases where the effect of a gas that has the effect of forming a protective film has a large effect on the trench shape even with the addition of an ultra-micro flow rate, flow rate control using NFC (mass flow controller) is difficult due to the ultra-micro flow rate. However, this can be effectively achieved by the above-mentioned intermittent addition.

In addition, there is no change in the trench taper angle that occurs when a gas that has the effect of forming a protective film is constantly added to the conventional etching gas type, such as changes in the trench shape from a normal taper to a reverse taper. Changes in the taper angle of the trench can also be prevented by adding a gas that has a generating effect intermittently over time.

(Example) Next, an example in which the method of the present invention is applied to dry etching using a triode etcher will be described with reference to the drawings.

Airtight container (1) For example, an AQ* concentric container is used. The surface of this container (2) is processed, for example, into an alumina (A1220.) surface so that it does not respond to the reaction gas. In such a container (1), three electrodes (1) are placed facing each other in order to generate plasma. That is, a disc-shaped cylinder and a second electrode (2) are provided in the vertical direction, and an intermediate electrode (A) is arranged between these electrode plates (3). The above-mentioned third and intermediate electrodes (10) have a mesh structure, and are structured to allow gas to pass through.

Each of these electrodes (1) is constructed so that an operating voltage is applied from outside the airtight container ω. For example, a high frequency power such as 13
．． 56MHz is applied. This high frequency power is supplied by a high frequency power source (20) connected to the first and second electrodes (2), respectively. Furthermore, a gas introduction pipe (2) is connected to the container (1) so as to supply a gas contributing to etching, a gas having a protective film forming action, etc. between each of these electrodes (1). Also, this gas introduction pipe■
The supplied gas can pass through the mesh-structured first and intermediate electrodes (2) and be supplied to the surface of an object to be processed, such as a semiconductor wafer, placed on the second electrode (WA). Further, an exhaust duct (2) is connected to the container (2) to exhaust gas from this container (2), thereby forming a triode etcher (10).

Further, when the wafer (8) is carried onto the second electrode (1) and taken out from the second electrode (2), it is relatively movable so as to widen the distance between the electrode (2) and the intermediate electrode (A). Furthermore, in order to increase the adhesion rate between the wafer (2) and the surface of the second electric bridge (2), the second electrode (4) may have a structure with a curvature in which the central part of the surface protrudes. Alternatively, a ring-shaped suppression mechanism may be used to press from the opposite direction.

Next, the etching method using a lieode etcher will be explained in detail.

An object to be processed, such as a silicon semiconductor wafer (8), is carried onto the second electrode (1) and placed at a predetermined position. Next, from the gas introduction pipe ■, an etching reaction gas such as SFG gas flow rate of 60SCCM, O□ gas flow -11
t40sccM, and Kr gas flowffi 11005C
C is supplied into the container (1), and the pressure inside the airtight container (1) is maintained at a constant pressure, for example, 0.6 TORR. At this time, the supply gas passes through the first electrode (2) and the intermediate electrode (2) as described above, is supplied to the wafer (8) on the second electrode (3), and is exhausted by the exhaust duct (3). . Also, at this time, a high frequency power of 13.56M11z is applied to the intermediate electrode (A) to the second electrode (3), and a high frequency power of 13.56M11z is applied to the high frequency electrode, for example, 4001 + 1° to the first electrode (2) and 200V to the second electrode (3). 0
Apply from 0. At this time, from the above gas introduction pipe ■,
Gases that have the effect of forming a protective film, such as 5iCj! 4 gas flow rate I SCCM is added intermittently.

FIG. 2 shows the shape of the trench etched due to the effects of this intermittent operation. The figure (a) shows the case where a gas having the effect of forming a protective film, for example, 5iCL, is not added. In other words,
The case of only gas species SF, , O□, Kr is shown, (b
) The figure shows the case where 5iCff is constantly added to ISCCM. (c) Figure shows the case where the operation was repeated with 5iCQ41 SCCM added for 1 min and without addition for 1 min. 6 (d) Figure shows 5iCJ! 41 SCC
By repeating each operation of adding M for 10 sec and not adding M for 0 sec, in the figure (e), 5iC1
241, SCCM was added for 5 seconds.

It shows the change in trench shape when each operation was repeated for 5 seconds without addition. The above figure (a) is
Sin, an undercut occurs under the mask.
At this time, the etching rate is: 1. It was Lm/min. Also, as shown in (b) 5jCQ, ISCCM
If , is constantly added, the undercut as shown in Figure (a) disappears, but the shape of the trench changes significantly from the normal taper shown in Figure (a) to the reverse taper.

Next, when 5iCf24 is added intermittently as shown in (c), no undercut is observed, but as in (b), the trench shape changes and the sidewalls become wavy. Put it away. Therefore, if we shorten the time of addition and non-addition of Sj, C4, we get the result shown in figure (d) and finally figure (e).
There is no undercut, and a good etched shape such as an appropriate positive taper and round etching is obtained. Also, the etching rate in figure (e) is also
As in the figure, the etching rate was 1.8 μm/mjn, and a high etching rate could be maintained without any decrease in the etching rate.

As can be seen from these figures, the trench shape obtained by anisotropic trench etching using low-temperature plasma can be improved by intermittently adding a gas having the effect of forming a protective film.

In the above example, the ratio of addition and non-addition of the gas that has the effect of forming a protective film was 1:1, but the ratio is not limited to this, and may be adapted to various processes such as 2:1, 3:1, etc. , the optimal value can be determined freely.

Further, in the above embodiments, a triode etcher has been described, but the present invention can be applied to either a two-pole etcher or an IECR etcher.

As described above, according to this embodiment, the side walls inside the trench are protected by intermittently adding a gas that has the effect of forming a protective film, which means that the balance between etching and side wall protection can be maintained optimally. It is possible to change the trench shape of trench etching without reducing the etching rate.
It becomes possible to control the shape to a desired desired shape.

In particular, in cases where the effect of a gas that has the effect of forming a protective film has a large effect on the trench shape even with the addition of an ultra-micro flow rate, it is impossible to control the flow rate using NFC due to the ultra-micro flow rate. This can be effectively achieved by the above-mentioned intermittent addition.

In addition, the change in trench taper angle when a gas with a protective film-forming effect is constantly added to the conventional etching gas type,
For example, inconveniences such as a normally tapered trench shape becoming a reverse taper do not occur, and changes in the taper angle of the trench can also be prevented by temporally adding a gas that has the effect of forming a protective film.

〔Effect of the invention〕

As explained above, according to the present invention, high selectivity can be achieved.

It is possible to perform anisotropic etching of a desired trench shape with a high aspect ratio while maintaining a high etching rate.

[Brief explanation of the drawing]

FIG. 1 is a structural diagram of a trench etching machine for explaining one embodiment of the method of the present invention, and FIG. 2 is a diagram for explaining the groove shape of trench etching according to the method of FIG. 1... Container, 2, 3.4... Electrode, 5
．． 6...High frequency power supply, 7...Gas introduction pipe. Patent applicant Tokyo Electron Ltd. (a)
(b) (C) (d) (e
) Figure 2 IR6-

Claims (1)

[Claims] A dry etching method characterized by introducing a main etching gas and intermittently adding a gas having a protective film forming effect during the process of dry etching in a plasma atmosphere.