JP2847549B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a method suitable for manufacturing a semiconductor device having a wiring which is flattened by melting and solidifying a conductive film, and by irradiating a pulsed laser beam to the conductive film. When flattening is performed by melting and solidifying, the purpose is to prevent the conductive film from evaporating by preventing the preheating effect from occurring.
Irradiated with laser light to melt and solidify the irradiated area to flatten it, then irradiate pulsed laser light to the area separated from the flattened area and similarly melt and solidify the irradiated area to flatten After that, the irradiation of the pulsed laser beam to the region separated from the flattened region and the melting and solidification of the irradiated region are repeated, and thereafter, after a time during which heat accumulation for generating the preheating effect is not performed, A step of irradiating the region adjacent to the previous flattened region with pulsed laser light, melting and solidifying the irradiated region to flatten the surface, and thereafter, flattening the entire conductive film in the same manner. Constitute.

[Industrial applications]

The present invention relates to a method suitable for manufacturing a semiconductor device having a wiring which is flattened by melting and solidifying a conductive film.

In today's highly integrated semiconductor devices, the unevenness of the surface is large and the wiring is thin, so disconnections occur due to the steps, and especially in the case of multi-layer, the upper layer As the irregularities become more severe, disconnections are more likely to occur, and it becomes difficult to perform precise photolithography.

Therefore, means for preventing the occurrence of such irregularities is required.

[Conventional technology]

Conventionally, efforts to planarize the surface of a semiconductor device have often been directed to an interlayer insulating film, but at present, this is also in a stalemate state.

Therefore, in recent years, it has been practiced to irradiate a pulsed laser beam to a conductive film such as aluminum, which forms a wiring, to melt and solidify the film. The pulsed laser beam is sequentially moved so that the irradiated regions are connected. Finally, the entire conductive film is melted and solidified to realize flattening.

That is, when the conductive film is irradiated with a pulsed laser beam, it becomes a melt-softened state, viscous flow occurs, and the conductive material flows into a concave portion of the unevenness existing under the conductive film, thereby relaxing the unevenness. .

In the conventional technology, the pulse laser beam irradiation time interval
By shortening it to about 0.01 [second], the through put is improved.

[Problems to be solved by the invention]

When the conventional technique is applied to planarize the conductive film, heat is accumulated in the conductive film or the base every time the pulsed laser light is irradiated, so that a preheating effect occurs, and the pulsed laser light The phenomenon that the temperature reached by irradiation increases as the order of irradiation increases. When such a phenomenon occurs, the annealing state differs for each irradiation position.
For example, in the case where the aluminum film is sequentially melted every time the laser beam is irradiated and a viscous flow is generated to flatten the aluminum film, an aluminum evaporation phenomenon occurs as the irradiation process proceeds.

This is because, even if the irradiation conditions under which the optimal viscous flow is obtained in a state where the preheating effect does not act, the preheating effect appears as the irradiation sequence becomes later, and the excessive irradiation conditions, that is, the ultimate temperature due to irradiation, Becomes higher than the evaporation temperature of aluminum, and evaporation occurs.

An object of the present invention is to suppress evaporation of a conductive film by irradiating the conductive film with a pulsed laser beam so that the conductive film is melted and solidified so as to be planarized so that a preheating effect does not occur.

[Means for solving the problem]

FIG. 1 is an explanatory view of a main part of a conductive film for explaining the principle of the present invention.

In the figure, the square designated by the symbol FR is the irradiation area (flattened area) of the pulsed laser light, and the numbers displayed therein indicate the irradiation order. Note that a square representing the irradiation region FR may be considered as a spot of the pulsed laser light as viewed in a cross section.

In the present invention, when irradiating a pulsed laser beam for melting and solidifying the conductive film, if a certain region is irradiated, the region adjacent thereto is not immediately irradiated,
Irradiation is performed on an area distant from the area, and irradiation is performed on the above-described adjacent area in a state in which the temperature of the first irradiation area and the temperature in the vicinity thereof have no heat accumulation that may cause a preheating effect. .

That is, in the drawing, after irradiating the first region, a region separated by three regions downward from the first region, in other words, a region separated by three spots is defined as a second irradiation region, and the third irradiation region is defined as the second irradiation region. A portion further away from the region by three regions is selected, and then, for the first time, a region adjacent to the first region is selected as a fourth irradiation region.

With this configuration, heat that causes a preheating effect is not accumulated in the conductive film or its base.

For this reason, in the method of manufacturing a semiconductor device according to the present invention, the conductive film, which is a wiring formed in the semiconductor device, is irradiated with pulsed laser light to melt and solidify the irradiated area, thereby flattening. And then irradiating a pulsed laser beam to a region separated from the flattened region, similarly melting and solidifying the irradiated region to flatten it, and thereafter, applying a pulsed laser beam to a region separated from the flattened region. The irradiation of the laser beam and the melting and solidification of the irradiation area are repeated, and then, after a time period in which heat accumulation for generating the preheating effect is not performed, irradiation of the pulse laser light to the area adjacent to the previous flattening area And melting and solidifying the irradiated area to make the irradiated area flat, and thereafter, flattening the entire conductive film in the same manner.

[Action]

By adopting the above-described means, it is possible to prevent the heat generated every time the pulsed laser light is irradiated from being trapped, thereby preventing the effect of preheating the whole, and therefore, the same ultimate temperature can be obtained for each irradiation. Thus, the phenomenon that the temperature reached increases as the irradiation order is later disappears, and no accident such as evaporation of the conductive film occurs.

〔Example〕

Using a silicon semiconductor substrate whose surface is covered with a silicon dioxide film having a thickness of 1 μm, an aluminum wiring having a thickness of 1 μm is formed on the silicon dioxide film, and the aluminum wiring has an energy density of 7 μm. J / cm ² ], a spot size of 2 [mm] × 2 [mm], and an irradiation time interval of 0.01 [second]. The irradiation order is as shown in FIG. And each irradiation area is in the X direction and Y direction.
In each of the directions, an overlapping portion of 0.5 [mm] was provided so as to be connected. The timing of irradiating the irradiation area adjacent to a certain irradiation area may be a time interval, and may be 0.1 [second] or more after the irradiation of the certain irradiation area ends. The irradiation of the pulsed laser beam may be performed in a state where the aluminum wiring is in an aluminum film, that is, in a state before being patterned as a wiring.

In this manner, it was confirmed that even when the irradiation of about 4000 shots necessary for irradiating the entire surface of the wafer having a diameter of about 10 cm (4 inches) was performed, the evaporation phenomenon of the aluminum wiring did not occur.

By the way, in the laser annealing in which the irradiation regions are continuously adjacent to each other at the irradiation time intervals described in the experimental example 1, the evaporation phenomenon occurs from the tenth shot.

〔The invention's effect〕

In the method for manufacturing a semiconductor device according to the present invention, the conductive film is irradiated with a pulsed laser beam to melt and solidify the irradiated area to flatten the area, and the pulsed laser is applied to an area separated from the flattened area. Irradiating light and similarly melting and solidifying the irradiated area to make it flat, and repeating the irradiation of pulsed laser light to the area separated from the flattened area and the melting and solidifying of the irradiated area, the preheating effect is obtained. After a lapse of time during which the heat to be generated is not accumulated, the area adjacent to the flattened area is irradiated with pulsed laser light, and the irradiated area is melted and solidified to be flattened. It is going to be done.

By adopting the above-described configuration, it is possible to avoid that the heat generated every time the pulsed laser beam is radiated is prevented from generating the effect of preheating the entirety. Thus, the phenomenon that the temperature reached increases as the irradiation order is later disappears, and no accident such as evaporation of the conductive film occurs.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a main part of a conductive film for explaining the principle of the present invention. In the figure, FR indicates an irradiation area (flattened area) of the pulsed laser beam, and the numbers displayed therein indicate the irradiation order.

Claims (1)

(57) [Claims] A conductive film formed on a semiconductor device and serving as a wiring is irradiated with a pulsed laser beam to melt and solidify the irradiated area to flatten it, and then to apply a pulse to an area separated from the flattened area. Irradiating laser light and similarly melting and solidifying the irradiated area to flatten it; thereafter, repeating pulsed laser light irradiation and melting and solidification of the irradiated area to an area separated from the flattened area, Thereafter, after a time during which heat accumulation for generating the preheating effect is not performed, irradiation with pulsed laser light to a region adjacent to the previous flattened region and melting and solidification of the irradiated region are performed to be flattened, A method of manufacturing a semiconductor device, comprising a step of flattening the entire conductive film in the same manner as described below.