JPS61147532A - Reactive ion etching method - Google Patents

Abstract

PURPOSE:To satisfy high etching rate, high etching selection ration and preferable etching shape by supplying He at 800SCCM or higher when etching an alloy film which mainly contains aluminum by plasma of chlorine gas. CONSTITUTION:When a member 10 to be etched and coated with an alloy film which mainly contains aluminum or aluminum alloy is etched on the surface by a plasma of chlorine gas in a vacuum chamber 1, He is supplied at 800SCCM or higher into the chamber by a gas intake tube 4. If the supply amount is less than 800SCCM, cooling effect of He is not sufficient, and the deterioration of the resist cannot be effectively suppressed.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a reactive ion etching method, and particularly to a reactive ion etching method for etching two films or an alloy film of Ag, 3i, and Cu on a wafer. Involved.

[Technical background of the invention]

For wiring materials such as integrated circuits, A2 or A2-8 i
, Ag-Cu alloys are widely used. With the increasing density of integrated circuits, wiring with a line width of 3 μm or less has come to be used, and when processing and patterning Afi or Ag alloys, the conventional wet etching method using etching liquid has been replaced with a reactive gas etching method. There is a tendency for reactive ion etching methods to be adopted. As the reactive gas, Cl-based gases such as l+, BCl3, Cl22, etc. are used for CC. Particularly, from the viewpoint of obtaining good etching properties, a mixture of these gases (for example, 80g3+CQ2) is often used instead of using the above gases alone.

[Problems with background technology]

However, in reactive ion etching using only C°C gas, if an attempt is made to increase the etching selectivity with respect to the resist as a mask under the condition of a high etching rate f41, undercuts may occur, resulting in poor processing. It cannot be shaped. On the other hand, attempting to obtain a good processed shape results in significant deterioration of the resist. Also,
When conditions are set to simultaneously satisfy a good processed shape and a high etching selectivity to the resist, there is a problem in that the etching rate becomes low.

[Purpose of the invention]

The present invention is based on AMII! Another object of the present invention is to provide a reactive ion etching method with excellent etching characteristics that satisfies all of the requirements of high etching rate, high etching selectivity to resist, and good processed shape when performing reactive ion etching on Affi alloy films. .

(Summary of the Invention) The present inventors have conducted intensive studies on the causes of resist deterioration when reactive ion etching is performed on a H2 film or a /'1 alloy film using Cλ-based gas plasma. It was determined that this was caused by an increase in the temperature of the etching member.

Therefore, the present inventors conducted further research based on the above findings and found that by supplying a predetermined amount of He to the reactive gas in the vacuum chamber, the material to be etched can be etched without impeding the etching performance. By suppressing the temperature rise, it is possible to obtain a high etching rate and a good processed shape without causing resist deterioration as mentioned above, and further, by supplying He, it is possible to stabilize the plasma and achieve uniform etching. We have discovered a new reactive ion etching method.

That is, in the present invention, when etching a member to be etched whose surface is coated with an Al1 film or an alloy film containing An as a main component using a Cλ-based gas plasma in a vacuum chamber,
The present invention is characterized in that 8008 CCM or more of He is supplied into the chamber.

Examples of the above C2-based gas include CCQ4, BCQa
, CQ2, etc. In particular, from the viewpoint of obtaining good etching properties, instead of using the above gases alone, a mixed gas of these gases (for example, BCffi3+CQ,
2) is preferably used.

As an alloy film mainly composed of the above AQ, for example, Ap
-s 1 alloy film, Ag-CIJ alloy film, Aff-3i
-CLJ alloy film, etc. can be mentioned.

The reason why the amount of He supplied into the vacuum chamber is limited is that if the amount of He supplied is less than 8008 CCM, a sufficient cooling effect cannot be achieved by the He, and resist deterioration cannot be effectively suppressed. Note that the upper limit of He supply is desirably 160,080 CM from the viewpoint of exhaust capacity and the like.

[Embodiments of the invention]

Hereinafter, embodiments of the present invention will be described in detail with reference to FIG.

FIG. 1 is a schematic cross-section of a reactive ion etching apparatus used in an embodiment of the present invention. 1 in the figure is a vacuum chamber. A pair of parallel and opposing electrodes 2.3 are disposed within the chamber 1. The upper electrode 2 is box-shaped, and has a gas outlet (not shown) formed on the surface facing the lower electrode 3, and is connected to a gas introduction pipe 4. There is. A mixed gas of 80 gg and C (12) as the main etching gas and He gas are supplied to this gas introduction pipe 4.The flow rate of these gases can be freely set by mass flow. The electrode 2 is connected to the ground.The lower electrode 3 has a cooling water circulation pipe 5 for cooling the electrode 3.
are connected.

Further, this lower electrode 3 is connected to ground via a matching network 6 and a high frequency power source 7. When a high frequency is input between the pair of electrodes 2.3 from such a high frequency power source 7, the lower electrode 3 due to the difference in mobility between ions and electrons.
A self-bias voltage (VdC) is generated nearby, and accelerated ions collide with the member to be etched on the lower electrode. An exhaust pipe 8 is connected to the lower part of the vacuum chamber 1, and a heater 9 is provided around the outer periphery of the chamber 1.

Next, the etching method of the present invention will be explained using the above-mentioned reactive ion etching apparatus.

First, prepare a silin wafer 10 with an Al film deposited on its surface and a resist pattern formed on the Δρ rise,
This wafer 10 was set on the lower electrode 3 in the vacuum chamber 1. Next, 70SC of mixed gas (4:3) of BCj2q and C9,2 was introduced into the chamber 1 from the gas introduction pipe 4.
While supplying 14008 CCM of CMSHe gas, the gas inside the chamber was exhausted from the exhaust pipe 8, and at the same time, high frequency power was applied from the high frequency power supply (13,56 kHz) 7 to the lower electrode 3 so that the self-bias voltage was 1400 V. Then, the accelerated ions were made to collide with the Al film exposed from the resist pattern of the wafer 10, thereby etching the Al. As a result, it was possible to etch the ρ film at a high etching rate, and to form a highly accurate ρ film without undercuts and faithful to the resist pattern.

In fact, when etching was carried out under the same conditions as in the example except that only a mixed gas (4:3) of BCffi3 and C20 was supplied from the gas inlet pipe, the pressure inside the chamber and the high frequency power were changed (conventional example). ) self-bias voltage (V+
When the relationship between etching rate and etching rate was investigated, the characteristic diagram shown in FIG. 2 was obtained. In addition, in this example, the relationship between the self-bias voltage (Vdc) and the etching rate when etching was performed by changing the pressure inside the chamber and the high-frequency power was investigated, and the characteristic diagram shown in Fig. 3 was obtained. . In addition, in FIGS. 2 and 3, areas where undercuts occur are indicated by diagonal lines B and B' above the diagonal lines.
The upper side indicates areas where resist deterioration occurs.

As is clear from FIG. 2, in the conventional example, the etching rate increases as the self-bias voltage (Vdc) increases;
Undercuts are also less likely to occur (marked with a circle in the figure). However, when the self-bias potential (Vdc) becomes lower than -200V, the resist deteriorates (marked with an x in the figure). In other words, the conditions under which both undercut and resist deterioration do not occur are when VdC is -150V to -200V.
The range of V is very narrow, and the maximum etching rate of A2 cannot be achieved, which is 3500 people and 7ml 1nL. On the other hand, He
In this embodiment, the gas is supplied into the chamber together with the mixed gas, and as shown in FIG.
In order to shift to a higher value of C (diagonal line B- in the figure), Vd
Even if c is set to a low voltage of 1,300 V, resist deterioration does not occur, and Aff etching can be performed at an etching rate of 5,000 people/min or more.

Note that the characteristic diagram shown in FIG. 3 explained in the above embodiment is only an example, and the etching rate and undercut occurrence relative to the self-bias voltage (Vdc) may vary depending on the type of reactive gas, the type of Al-gold alloy to be etched, etc. Although the region and resist deterioration region are changed, in any case, the resist deterioration region is shifted to the lower voltage side of the self-bias voltage (VdC) compared to the conventional method, so the same effect as in the embodiment can be achieved.

[Effects of the Invention] As detailed above, according to the present invention, when performing reactive ion etching on an AI2 film or an AQ alloy film, it is possible to satisfy all of a high etching rate, a high etching selectivity to the resistor, and a good processed shape. Furthermore, it is possible to provide a reactive ion etching method that has remarkable effects such as being able to efficiently form highly accurate A2 or H2 alloy wiring.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing one form of the reactive ion etching apparatus used in the embodiment of the present invention, and FIG. 2 shows the relationship between the self-bias voltage (Vdc) and the etching rate of 8λ in the conventional method. FIG. 3 is a characteristic diagram showing the relationship between the self-bias voltage (Vda) and the etching rate of AQ in this embodiment. DESCRIPTION OF SYMBOLS 1... Vacuum chamber, 2... Upper electrode, 3... Lower electrode, 4... Gas introduction tube, 7... High frequency 'Im,
8...Exhaust pipe, 10...Wafer. Applicant's agent Patent attorney Takehiko Suzue Figure 2 Figure 3

Claims (3)

[Claims] (1) When etching a member to be etched whose surface is coated with an Al film or an alloy film mainly composed of Al by plasma of Cl-based gas in a vacuum chamber, it is recommended to supply 800 SCCM or more of He into the chamber. Characteristic reactive ion etching method. (2) The reactive ion etching method according to claim 1, wherein the Cl-based gas is a mixed gas of BCl_3 and Cl_2. (3) The reactive ion etching method according to claim 1, wherein the member to be etched is a wafer, and the wafer is etched one by one.