JP2782797B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Overview] Regarding a method for forming an aluminum-based wiring layer, the present invention suppresses coarsening of wiring metal crystal grains due to heating for improving step coverage, thereby improving device manufacturing yield and reliability. For this purpose, a method is provided in which, after a wiring layer made of aluminum (Al) or an alloy thereof is deposited on a substrate, the substrate is heated and, at the same time, the surface of the wiring layer is irradiated with ions.

[Industrial applications]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming an aluminum-based wiring layer.

At present, Al or an alloy mainly containing Al (1% Si, 2% Cu, or the like) is mainly used as a wiring material of a semiconductor device, and a sputtering method is often used as a film forming method.

The present invention can be applied as a processing method after forming a wiring layer.

[Conventional technology]

In recent years, because the underlying substrate to be wired has become stricter in shape due to miniaturization of elements and multi-layered wiring structure, it has become difficult to form a wiring having a good step coating.

At present, in order to overcome such problems, by increasing the substrate temperature during sputter deposition, the coatability of the film and the flatness of the substrate are improved.

In addition, a method of improving the step coverage by applying a bias to the substrate, performing deposition and etching at the same time, and depositing while shaving the eaves generated at the step portion is adopted.

However, accurately raising the substrate temperature with good reproducibility during sputtering requires considerable equipment complexity, and it is difficult to accurately know the substrate temperature during sputtering. In many cases, film forming conditions are determined by setting or the like.

Therefore, it has been proposed to solve this problem by depositing an Al or Al alloy wiring layer on a substrate by sputtering or the like, and then heating the substrate to be processed to a high temperature without opening to the atmosphere after film formation. ing.

[Problems to be solved by the invention]

In order to improve the step coverage by the above-mentioned conventional proposal, the wiring layer is often heated to a temperature higher than the recrystallization temperature near the melting point, so that the Al crystal grains become coarse depending on the conditions. On the other hand, it is difficult to control the crystal grain size by setting conditions other than the heating temperature.

When the crystal grains become coarse, they protrude to the surface of the wiring layer, increase the wiring resistance, or lower the reliability of the wiring layer.

SUMMARY OF THE INVENTION It is an object of the present invention to suppress the coarsening of crystal grains of wiring metal due to heating for improving step coverage when forming a wiring layer, and to improve the production yield and reliability of devices.

[Means for solving the problem]

In order to solve the above-mentioned problem, after a wiring layer made of aluminum (Al) or an alloy thereof is deposited on a substrate, the substrate is heated to a temperature lower than the melting point of the wiring layer and higher than 400 ° C. And a step of irradiating at least one ion of rare gas, proton, Si or Ti.

[Action]

According to the present invention, at a temperature near the melting point of the wiring metal, the metal atoms have sufficient energy to diffuse and the mobility increases, so that the surface tension acts to improve the coverage at the step portion and obtain a flat substrate. However, in this case, in order to suppress and control the progress of recrystallization in the metal crystal and the coarsening of the crystal grains, for example, heating the substrate at a high temperature and Applying RF voltage to the substrate in Ar atmosphere
The ion irradiation is performed.

This is due to the effect of suppressing the mobility of Al atoms on the surface by the incidence of Ar ions, and the result is considered to be reflected in the crystal grain size.

Here, the melting point of the wiring metal is as follows. Pure Al 66
The temperature is 0 ° C, the temperature of the Al-1% Si alloy is 600 ° C, and the temperature of the Al-2% Cu alloy is 620 ° C.

Next, data showing the relationship between the incident energy of Ar (or the substrate bias voltage) and the average crystal grain size, which is a gist of the present invention, will be described.

FIG. 3 is a diagram showing the relationship between the average crystal grain size and the substrate bias voltage.

The figure shows an example of data when a substrate bias is applied to an Al-1% Si wiring layer at a heating temperature of 500 ° C., and shows how the average crystal grain size gradually decreases as the substrate bias voltage increases and approaches a constant value.

FIG. 4 is a diagram showing the relationship between the heating temperature and the average crystal grain size.

The figure shows that when the heating temperature exceeds 400 ° C. for the Al-1% Si wiring layer, the crystal grain growth becomes remarkable, and the average crystal grain size increases rapidly.

〔Example〕

FIG. 1 is a sectional view of an RF application type substrate heating apparatus for explaining an embodiment of the present invention.

In the figure, a Si wafer 2 as a substrate to be processed, which has been transferred from a sputtering chamber, is placed on a heating stage 1 and fixed by a fixing jig 3.

The anode 7 and the shield 8 are grounded, and the heating stage 1 is grounded via the matching circuit 11 and the RF power supply 10.

The heating stage 1 is heated by a cartridge heater 9 and moves up and down while maintaining airtightness in the chamber 5. The upper position (the position shown) is the processing position, and the lower position is the transfer position.

The heating stage 1 has a pocket shape and the inside is at atmospheric pressure. A cartridge heater 9 and a heater fixing block, a thermocouple (not shown) are provided, and the outside is on the decompression side.

Ar gas is introduced from the back side of the fixed wafer 2 to uniformly heat the wafer, and the flow rate thereof is controlled by the mass flow controller 12 so that the pressure of the Ar gas on the back surface of the wafer becomes about 1 Torr.

Further, the flow rate of the Ar gas in the chamber 5 from the mass flow controllers 4 and 12 into the chamber 5 and the exhaust speed of the exhaust port 6 are controlled so as to be 3 mTorr.

As described above, the wafer 2 is heated to 550 ° C., and the RF power source 10 applies the RF voltage of 13.56 MHz to 500 V and holds the wafer 2 for 2 minutes.

In the case of heating at 550 ° C., the crystal grain size was 1010 μm when the RF voltage was not applied, but was 〜3 μm in the example where the RF voltage was applied.

Irradiation of Ar ions on the wafer is performed by DC
A voltage may be applied, or an ion beam of Ar or the like by an ion milling gun may be used.

FIG. 2 is a sectional view showing an example of a configuration of a continuous processing apparatus including a sputtering process.

In the figure, the wafer is transported in the direction of the arrow, and is composed of a load lock chamber 21, a sputter processing chamber 22, an RF application type substrate heating device 23 of the embodiment, and a load lock chamber 24 in this order. Numeral 29 is for carrying in the wafer, connecting the chambers, and carrying out the wafer.

With this apparatus, the processing of the present invention can be performed without opening the wafer after the sputtering processing to the atmosphere.

In addition, even if the wafer is once put into the atmosphere, the surface oxide can be removed by ion irradiation by providing a device for RF or ion milling, so that it can be used as a single device.

In the present invention, ions are irradiated in order to suppress the progress of recrystallization in the wiring metal crystal and the coarsening of the crystal grains. Therefore, the irradiation ions are gas ions or metal ions that do not attack the wiring metal. It is considered good.

Therefore, although Ar was used as the ion to be irradiated in the description of the operation and the examples, other inert gas, that is, He, Ne, Kr, Xe, Rn, or proton, could be used instead.
Alternatively, the same effect can be expected by implanting ions such as Si and Ti.

〔The invention's effect〕

As described above, according to the present invention, when forming a wiring layer, coarsening of crystal grains of wiring metal due to heating for improving step coverage can be suppressed, and the device manufacturing yield and reliability are improved. be able to.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of an RF-applied substrate heating apparatus for explaining an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing an example of a configuration of a continuous processing apparatus including a sputtering process. FIG. 3 is a diagram showing the relationship between the average crystal grain size and the substrate bias voltage, and FIG. 4 is a diagram showing the relationship between the average crystal grain size and the heating temperature. In the figure, 1 is a heating stage, 2 is a wafer to be processed, 3 is a fixing jig, 4 is a mass flow controller, 5 is a chamber, 6 is an exhaust port, 7 is an anode, 8 is a shield, 9 is a cartridge heater, 10 Is an RF power supply, 11 is a matching circuit, and 12 is a mass flow controller.

Claims (1)

(57) [Claims] 1. After a wiring layer made of aluminum (Al) or an alloy thereof is deposited on a substrate, the substrate is heated to a temperature lower than the melting point of the wiring layer and higher than 400 ° C. A method for manufacturing a semiconductor device, comprising a step of irradiating at least one kind of ions of a rare gas, proton, Si or Ti.