JP2743396B2 - Method for manufacturing semiconductor device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device having elements such as trench capacitors, and more particularly to a method of heat-treating each of these elements.

[Summary of the Invention]

According to the present invention, in a heat treatment of a semiconductor device in which an element such as a trench capacitor is formed on a substrate, an energy pulse beam is applied to the main surface of the substrate from a plurality of directions, so as to be localized and A uniform heat treatment is performed to increase the degree of integration and reliability of the semiconductor device.

[Conventional technology]

With the miniaturization of VLSI design rules, there is a strong demand for improved heat treatment selectivity and uniformity in semiconductor device manufacturing methods.

For example, in the manufacture of a MOS transistor, for example, an impurity is ion-implanted into a region serving as a source or a drain by a self-alignment technique using a gate electrode as a mask, and then a heat treatment for activating the region is performed. As this heat treatment, besides normal thermal annealing,
Techniques such as rapid thermal annealing using infrared rays have been applied. Furthermore, since a quasi-low temperature process is required to support the future submicron technology and form a shallow junction, technologies such as excimer laser pulse annealing using an excimer laser as a uniform surface beam are required. Has also been proposed.

In the field of DRAM, mega-bit products have already been commercialized, and further integration is progressing. It is important to choose between a planar type and a trench type as the capacitor structure to cope with higher integration.
Assuming a bit-class DRAM, the latter is promising. This trench type capacitor (hereinafter referred to as trench
It is called a capacitor. If it is attempted to increase the storage capacity without increasing the occupied area in (1), the aspect ratio of the trench cut in the semiconductor substrate necessarily increases. To introduce impurities to form a lower electrode layer in the semiconductor substrate along the inner wall of such a trench, the trench must be formed by PS
It is coated with a film containing impurities such as G (phosphorus silicate glass) and AsSG (arsenic silicate glass), and the impurities are diffused from these films toward the inner wall. For example, a method of providing an impurity region on the inner wall is known.

[Problems to be solved by the invention]

By the way, all of the above techniques have some problems to be solved in the heat treatment process.

In the manufacturing process of the MOS transistor, even if ion implantation is performed using the gate electrode as a mask, some ions are distributed so as to circumvent just below the periphery of the gate electrode,
An ion-implanted region is formed so as to partially overlap the gate electrode. Even if such an ion-implanted region is to be annealed using an energy beam such as an excimer laser, this type of beam has a short wavelength (UV light), is excellent in straightness, and is located just below the periphery of the gate electrode. Does not reach. This portion may remain without being activated, which may cause deterioration of transistor characteristics. Further, in the process of forming the trench capacitor, if an attempt is made to diffuse impurities from the film containing the impurities toward the inner wall of the trench, high-temperature annealing is required, and a shallow electrode junction cannot be formed. According to the oblique rotation ion implantation method, such high-temperature annealing is unnecessary, but in reality, the controllability of the ion implantation method itself is still not sufficient.

Therefore, an object of the present invention is to solve the above-described problems and provide a method for manufacturing a highly reliable semiconductor device, particularly a semiconductor device having an element such as a trench capacitor, which can cope with high integration. .

[Means for solving the problem]

The method for manufacturing a semiconductor device according to the present invention is proposed in view of the above-described conventional circumstances, and the method for manufacturing a semiconductor device according to the present invention includes impurities on the main surface side of the base. A semiconductor region having a concave portion covered with a film is formed, and heat treatment is performed by irradiating an energy pulse beam to the main surface of the base from a plurality of directions. Is a diffusion of

Here, as means for irradiating an energy pulse beam from a plurality of directions, an excimer laser
A single light source such as a pulsed beam is used and the substrate and / or
Alternatively, a method of moving a light source may be used. The movement of the light source at this time is only required to change the relative positional relationship between the base and the light source so that the irradiation direction changes. Therefore, a reciprocating motion, a rotating motion, a swinging motion, or a combination of these motions is used. Is selected. An appropriate method may be selected so that the region where the heat treatment is to be performed is locally and uniformly irradiated. Further, the number of light sources is not limited to one, but may be plural.

Further, in the method of the present invention, the energy pulse
The beam is radiated while rotating with the perpendicular to an axis at any point on the substrate.

[Action]

In the method for manufacturing a semiconductor device according to the present invention, an energy pulse beam for performing a heat treatment is applied obliquely to the main surface of the base.

When the present invention is applied to the formation of the lower electrode layer of the trench capacitor, the energy beam reaches the inner wall of the trench even if the aspect ratio of the trench is large, and local and selective heating is possible. Becomes Therefore, unlike the conventional case, it is not necessary to heat-treat the entire substrate, so that unnecessary diffusion can be suppressed and the electrode junction can be made shallow.

In this case as well, the irradiation angle of the energy pulse beam is inclined and the rotation of the light source is combined, so that uniform irradiation inside the trench becomes possible and the inner wall is annealed uniformly.

〔Example〕

Hereinafter, an example in which the method of the present invention is applied to the formation of a trench capacitor of a DRAM will be described.

Hereinafter, an example of the manufacturing method will be described with reference to FIGS.
This will be described with reference to FIG.

First, as shown in FIG. 2 (A), when excimer laser pulse beam (hereinafter, referred to as beam), which will be described later, is irradiated on the semiconductor substrate 11 on which the element isolation region 12 has been formed in advance by selective oxidation. Silicon oxide layer 13 to serve as a mask for
And an aluminum reflective film 14 are laminated in this order, and a photoresist layer 15 is selectively formed on the aluminum reflective film 14.
To form

Next, as shown in FIG.
Trench 16 by dry etching using
Is formed, and the photoresist layer 15 is removed.

Next, as shown in FIG. 2 (C), a PSG layer 17 containing, for example, phosphorus as a film containing impurities is applied and formed on the entire surface of the substrate as described above.

Next, as shown in FIG. 2 (D), a beam is irradiated from an irradiation direction P inclined by an angle φ with respect to a perpendicular O at the center of the trench groove 16, and impurities are transferred from the PSG layer 17 to the inner wall of the trench groove 16 with impurities. A certain phosphorus is diffused to form the lower electrode layer 18. At this time, since the beam reaching the main surface of the base is reflected by the aluminum reflecting film 14, the main surface is not heated, and local annealing can be performed only inside the trench 16.

Furthermore, the beam that has reached the trench 16 from an oblique direction is reflected on the inner wall of the trench 16 and reaches the bottom and the opposing surface, but more uniform annealing is possible by rotating the substrate around the perpendicular O. Becomes

Conventionally, high-temperature annealing has been performed to form the lower electrode layer 18, so it is difficult to keep the junction depth shallow, especially when a plurality of trench capacitors are formed in close proximity. Was a problem. However, according to the present invention, since such a local heat treatment is performed, such a problem does not occur.

〔The invention's effect〕

As is apparent from the above description, when the method for manufacturing a semiconductor device according to the present invention is applied, the energy pulse
Because the beam is irradiated very locally and uniformly,
While the occurrence of junction leakage and the shortening of the effective channel length are effectively prevented, high integration can be achieved. Moreover, in applying the present invention, it is not necessary to drastically change the manufacturing process of the conventional semiconductor device using the energy pulse beam for the heat treatment, so that the present invention is excellent in economy and productivity.

[Brief description of the drawings]

1 (A) to 1 (D) are schematic sectional views showing an example in which the present invention is applied to the formation of a trench capacitor in the order of steps, and FIG. 1 (A) is an element isolation region, FIG. 1 (B) is a process for forming a trench groove by dry etching and a process for removing a photoresist and the like, and FIG. 1 (C) is a process for forming and coating a PSG layer. FIG. 1 (D) is for explaining a step of forming a lower electrode layer by diffusing phosphorus by excimer laser pulse beam irradiation. 11 Semiconductor substrate 12 Device isolation region 13 Silicon oxide layer 14 Aluminum reflective film 15 Photoresist layer 16 Trench groove 17 PSG layer 18 Lower electrode layer

Claims (2)

(57) [Claims] A semiconductor region having a concave portion covered with a film containing impurities is formed on a main surface side of a substrate, and an energy pulse beam is irradiated on the main surface of the substrate from a plurality of directions. Wherein the impurity is diffused into the inner wall of the concave portion by the heat treatment. 2. The semiconductor according to claim 1, wherein said energy pulse beam is emitted while making an angle with a perpendicular at an arbitrary point on said main surface and rotating about said perpendicular. Device manufacturing method.