JPS628012B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device, which includes a step of scanning an adhered layer such as a semiconductor polycrystalline layer on the surface of a semiconductor wafer such as a silicon substrate while irradiating and heating it with a laser beam. .

Conventionally, when using a laser annealing method to lower the resistance of a deposited layer such as a polycrystalline silicon layer deposited on the surface of a semiconductor wafer, a laser beam is applied over the entire surface of the deposited layer such as the polycrystalline silicon layer. After irradiation and heating, resist patterning and etching are performed to form a desired pattern.

However, the base dielectric layer formed under this polycrystalline silicon or other deposited layer, such as a thick oxide film (field), a thin oxide film (gate), and exposed areas of the silicon surface (direct contact), may vary. Since the structure is not uniform in the vertical and horizontal directions, the state of heat conduction is not uniform over the entire surface of the wafer. For this reason, when a deposited layer such as polycrystalline silicon is irradiated and heated with the same laser power, the state change experienced by the deposited layer becomes extremely non-uniform. That is, in FIG. 1, the vertical axis shows the sheet resistance value (Ω/□) of polycrystalline silicon formed on regions with different base oxide film thicknesses, and the horizontal axis shows the laser power (Watts). Note that polycrystalline silicon has a thickness of 5000Å and a voltage of 1× at 100KeV.
10 ¹⁶ As ⁺ /cm ² was implanted, and the annealing conditions using argon laser were T _sub = 400°C,
X _scao = 50 cm/s, Y _step = 16 μm. As shown in FIG. 1, when the oxide film that is the underlying dielectric layer is thick, heat conduction is poorer than when it is thin, so the situation is equivalent to irradiation with a high-power laser beam. A is t _px = 500Å, B is t _px =
These are the characteristics of 7500Å. As described above, in the manufacturing process of a semiconductor device whose underlying structure is not uniform, even if the entire surface of the adhered layer, such as polycrystalline silicon, is irradiated and heated with the same laser power, the state after irradiation is not uniform. This appears as non-uniformity in the etching rate in the subsequent patterning, and therefore, the formation of fine patterns has the disadvantage that a pattern must be formed in advance taking these etching rates into consideration.

Therefore, an object of the present invention is to achieve the same annealing state even if the thickness of the base dielectric layer differs, even if the deposited layer such as a semiconductor polycrystalline layer is scanned while being irradiated and heated with the same laser power. The present invention provides a method for manufacturing a semiconductor device in which uniform etching rate and electrical characteristics can be obtained.

In order to achieve such an object, the present invention forms a thin dielectric layer only on the deposited layer in areas where there is no underlying dielectric layer or in thin areas, and will be described in detail below using Examples. do.

FIGS. 2a to 2c are cross-sectional views showing an embodiment of the method for manufacturing a semiconductor device according to the present invention in the order of manufacturing steps. In the figure, 1 is a thick field oxide film, 2 is a thin gate oxide film, 3 is a direct contact region, 4 is a polycrystalline silicon layer as a semiconductor polycrystalline layer to be annealed with a light beam such as a laser beam, and 5 6 is a silicon substrate, and 6 is a thin oxide film formed on this polycrystalline silicon layer 4 as a thin dielectric layer.

Note that the thick field oxide film 1 is a portion where there is a thick base dielectric layer, and the thin gate oxide film 2
is a portion where there is a thin underlying dielectric layer, and the direct contact region 3 is a portion where there is no underlying dielectric layer.

Next, the manufacturing process of the semiconductor device with the above configuration will be explained. First, as shown in FIG. 2b, a thin oxide film 6 as a thin dielectric layer is formed on a polycrystalline silicon layer 4 as an adhesion layer shown in FIG. 2a. Then, as shown in FIG. 2b, the thin oxide film 6 is patterned using the same mask used for field formation.
The thin oxide film 6 can be removed on the polycrystalline silicon 4 on the region where the underlying dielectric layer is thick. On the other hand, a thin oxide film 6 can be formed on the polycrystalline silicon 4 on a region where there is no base dielectric layer or on a thin region. Therefore, for example, if the thickness of this thin oxide film 6 is set to 800 Å as shown in FIG. The irradiation power received by the polycrystalline silicon 4 is stronger than that of the polycrystalline silicon 4 on other regions where the underlying dielectric layer is thick. Therefore, polycrystalline silicon 4 can be brought into the same annealed state regardless of the thickness of the underlying dielectric layer.

In the above embodiments, it is advantageous in terms of the process flow to form the thin oxide film 6 using a thermal oxide film, but it goes without saying that the oxide film 6 may be formed by any method. Furthermore, although the oxide film 6 is used in the embodiment, it goes without saying that a nitride film can also be used in the same manner. Further, although polycrystalline silicon is used as the semiconductor polycrystalline layer, it is needless to say that the present invention is not limited to this.

As described above in detail, according to the method of manufacturing a semiconductor device according to the present invention, even if the entire surface of the semiconductor wafer is irradiated with the same light beam power and annealed while scanning, the thickness of the underlying dielectric layer will not change. Regardless of the method, the semiconductor polycrystalline layer can be brought to the same annealing state, and there are effects such as uniform etching rate and uniform electrical characteristics.

[Brief explanation of the drawing]

Figure 1 shows the laser power (Watts) dependence of the sheet resistance (Ω/□) of polycrystalline silicon pre-doped with arsenic with different base oxide film thicknesses, and Figure 2 shows the dependence of the sheet resistance (Ω/□) on the laser power (Watts) for the semiconductor according to the present invention. Figure 3 is a cross-sectional view of the manufacturing process order showing an example of the device manufacturing method. FIG. 3 is a diagram showing changes in reflectance with changes in film thickness. DESCRIPTION OF SYMBOLS 1... Field oxide film, 2... Gate oxide film, 3... Direct contact region, 4... Polycrystalline silicon layer, 5... Silicon substrate, 6... Thin oxide film. Note that the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. A semiconductor polycrystalline layer is deposited on a base dielectric layer formed on a main surface of a semiconductor wafer and has a different thickness in the plane direction and is partially missing, and this semiconductor polycrystalline layer is In a method for manufacturing a semiconductor device that includes a step of scanning while irradiating and heating with a laser beam, a thin dielectric layer is formed only on a semiconductor polycrystalline layer in an area where there is no underlying dielectric layer and an area where the underlying dielectric layer is thin. A method for manufacturing a semiconductor device, characterized in that the semiconductor polycrystalline layer is scanned and annealed while being irradiated and heated with the same laser beam power. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the thin dielectric layer is an oxide or nitride of a substance constituting a semiconductor polycrystalline layer. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the thin dielectric layer is formed using a mask used for forming the thick region of the underlying dielectric layer.