JPH0618430A - Surface inspection method for wafer with film - Google Patents

Abstract

PURPOSE:To provide a surface inspection method of a wafer with a film with surface roughness and film thickness unevenness. CONSTITUTION:This method uses an optical system where an angle in laser incidence 1 is less than 45 deg. to a wafer 4a. With this method, a laser scattered section area against surface roughness of a deposited film 4 is reduced to some extent, and any laser interference to be caused between components by a back scattering light out of a foreign substance 3a, a surface of the deposited film 4b and a front scattering light reflected on an interface is reduced as well.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inspection method for detecting defects such as foreign substances attached to the surface of a film-coated wafer on which a vapor-deposited film (hereinafter simply referred to as a film) is deposited.

[0002]

2. Description of the Related Art In the process of manufacturing a semiconductor IC, foreign matter adhering to a wafer in the process of depositing a polycrystalline polysilicon film by a CVD device or an aluminum film by a sputtering device on the surface of a silicon wafer will reduce the product yield. It is the main cause of decrease.

Conventionally, there is no suitable surface inspection method for a film-coated wafer, and a so-called mirror surface wafer surface inspection method before film deposition is applied to the film-coated wafer surface inspection.

An example of the conventional wafer surface inspection apparatus described above will be described below with reference to the drawings.

FIG. 6 shows a detection optical system of a conventional wafer surface inspection apparatus. In FIG. 6, 1 is an incident laser beam, 2 is a projection lens, 4a is a mirror surface wafer, 5
Is a rotary stage, and 6 is an optical fiber.

The operation of the wafer surface inspecting apparatus constructed as above will be described below.

First, the incident laser beam 1 is condensed by the light projecting lens 2 into a spot of about 10 to 100 μm on the wafer surface. When the foreign matter 3a is present on the surface of the wafer, the weak scattered light from the foreign matter is collected by a large number of optical fibers 6 and is converted into an electric signal by a photoelectric element to detect the foreign matter. (For example, "Monthly Semiconductor
Worl "(1992.4) pp. 116-121.

[0008]

However, in the defect detection optical system for the mirror-finished wafer having the above-mentioned structure, the incident angle of the laser is almost perpendicular to the wafer in order to obtain sufficient scattered light intensity from the foreign matter. . Therefore, when it is applied to the surface inspection of a film-coated wafer, erroneous detection of crystal particles and uneven detection sensitivity may occur due to laser scattering due to the crystal particles contained in the film and changes in the laser interference level due to non-uniformity of the film thickness. Therefore, there is a problem in that it is not possible to perform a defect inspection of a highly sensitive film-coated wafer.

In view of the above problems, the present invention provides a highly sensitive surface inspection method for a film-coated wafer having surface roughness and film thickness unevenness.

[0010]

In order to solve the above problems, the surface inspection method for a film-coated wafer of the present invention uses an optical system in which the laser incident angle is an acute angle with respect to the wafer.

[0011]

The present invention has the above-described structure to reduce the laser scattering cross-sectional area against the surface roughness of the vapor deposition film 4b, and the backscattered light from the foreign matter 3a and the forward scattered light reflected on the surface or interface of the vapor deposition film 4b are components. By reducing the laser interference that occurs between the surfaces, the surface inspection of the film-coated wafer having surface roughness and film thickness unevenness can be performed with high sensitivity.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for inspecting a surface of a film-coated wafer according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram of an optical system of a method for inspecting a surface of a film-coated wafer according to an embodiment of the present invention. In FIG. 1, 1 is an incident laser, 2 is a projection lens, 4a is a wafer, 4b is a vapor deposition film, 5 is a rotary table, and 6 is an optical fiber. The surface inspection method for a film-coated wafer constructed as described above The operation will be described below with reference to FIGS. 2 and 3.

First, FIGS. 2a and 2b show the interference of each component of the scattered light by the foreign matter in the conventional example and the present example, respectively. In the conventional example shown in FIG. 2a, the foreign matter 3a
Since the backscattered light 7a, the forward scattered light 7b reflected on the surface of the foreign matter, and the forward scattered light 7c reflected at the interface between the wafer 4a and the wafer 4b have the same central direction,
When the forward scattered light 7c reflected at the interface where the phase shifts due to the film thickness interferes with other components, and the film thickness is uneven within the wafer surface, the in-plane sensitivity is uneven. On the other hand, in the present embodiment shown in FIG. 2B, since the center direction or center position of each scattered light component is different, laser interference between each scattered light component is reduced, and stable sensitivity is obtained within the wafer surface. .

Next, FIGS. 3a and 3b show noise components due to surface roughness in the conventional example and the present example, respectively. In the conventional example of FIG. 3 (a), the foreign matter 3a and the surface roughness 3b have the same scattering area with respect to the incident laser, but in the present embodiment of FIG. 3 (b), the scattering cross-sectional area of only the surface roughness 3b. Is reduced, and only the foreign matter 3a can be detected with high sensitivity.

Further, the effect will be described with reference to FIGS. 4 and 5. FIGS. 4 and 5 show a wafer having unevenness in film thickness and surface roughness, with 0.5 μm P on the left half surface with the OF (orientation flat) facing down.
It is the result of having measured by the surface inspection method of the conventional example FIGS. 4a and 5a and this Example FIG. 4b and FIG.

First, in FIG. 4a, although the film thickness is uneven in the vertical direction of the wafer and the PSL standard particles of 0.5 μm are evenly adhered to the surface of the left half surface, the OF is turned down and the upper left is turned on. The detection sensitivity on one side is reduced. on the other hand,
In FIG. 4b, a uniform detection sensitivity is obtained on the left half surface of the wafer.

Next, in FIG. 5a, there is surface roughness on the entire surface of the wafer, and the PSL standard particles of 0.5 μm adhere to only the left half surface with the OF down, but the surface on the right half surface as well. False detection due to roughness is recognized. On the other hand, in FIG. 5b, there is no erroneous detection on the right half surface of the wafer, and uniform detection sensitivity is obtained only on the left half surface.

As described above, according to the method for inspecting the surface of the film-coated wafer of this embodiment, the film having the surface roughness and the film thickness unevenness is used by using the optical system in which the laser incident angle is 30 ° with respect to the wafer. The surface inspection of the attached wafer can be performed with high sensitivity.

[0020]

INDUSTRIAL APPLICABILITY As described above, the present invention enables highly sensitive surface inspection of a film-coated wafer having surface roughness and film thickness unevenness by using an optical system in which the laser incident angle is an acute angle with respect to the wafer. You can

[Brief description of drawings]

FIG. 1 is a schematic diagram of a surface inspection optical system for a film-coated wafer according to a first embodiment of the present invention.

FIG. 2 is an explanatory view of a laser interference reducing action in the same embodiment.

FIG. 3 is an explanatory diagram of a noise component reducing action due to surface roughness in the example.

FIG. 4 is a diagram showing a film-coated wafer inspection result for explaining a laser interference reducing effect in the example.

FIG. 5 is a diagram showing a film-coated wafer inspection result for explaining a noise component reducing effect due to surface roughness in the example.

FIG. 6 is a schematic diagram of a detection optical system of a conventional mirror surface wafer surface inspection apparatus.

[Explanation of symbols]

 1 Incident laser 2 Projection lens 3a Foreign matter 3b Surface roughness 4a Wafer 4b Evaporated film 5 Rotating table 6 Optical fiber 7a Center direction of backscattered light 7b Center direction of forward scattered light reflected on the surface 7c Front scattered light reflected at the interface Toward the center

Claims (1)

[Claims] 1. A laser incident angle in an inspection of a film-coated wafer for detecting a foreign matter by injecting a laser spot on the surface of the wafer and condensing only scattered light by the foreign matter of the laser spot by an optical fiber. Is a method for inspecting a film-coated wafer surface, which uses an optical system having an acute angle with respect to the wafer.