JPH0634559A - Method of detecting flaw in surface inspecting apparatus - Google Patents

Abstract

PURPOSE:To provide the number of extraneous matters on the surface of a wafer and also to judge as to whether a detected extraneous matter is a flaw or not, by a method wherein when a division adjacent to a detection unit division judged to have an extraneous matter has also an extraneous matter, these extraneous matter are regarded as a new extraneous matter. CONSTITUTION:The surface of a wafer is divided by basic detection divisions and each division is inspected to detect any extraneous matter. When divisions 4 and 5 are judged to have an extraneous matter, the divisions adjacent to the divisions 4, 5 are inspected as to whether or not an extraneous matter exists, and when it exists therein, the two divisions wherein the extraneous matters exist are regarded as one new extraneous matter (a hatched part). When the detection is completed for all of adjacent divisions, the number (a) of divisions occupied by the new extraneous matter is calculated, as 14, for instance. Next, the number (b) of divisions occupied by the minimum rectangle containing the new extraneous matter is calculated, as 36, for instance. Then, a/b is determined and, when the value of a/b is a constant (p) or below set by the user, the new extraneous matter is regarded as a flaw, while it is regarded as a large extraneous matter when the value is larger than the constant (p). When a=b, no flaw nor large extraneous matter is regarded as not existing. The constant (p) is set on the basis of a shape model of the flaw, or the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface inspection apparatus for inspecting the surface of an object to be inspected for foreign matter, and a method for determining whether or not the inspection result is a defect.

[0002]

2. Description of the Related Art FIG. 5 is a diagram showing an example of an inspection result display by a conventional surface inspection apparatus. In the figure, reference numeral 1 is a wafer, and the black portion on the surface of the wafer 1 is "with foreign matter"
It is a category determined to be. 2 is an aggregate consisting of 15 adjacent sections. Reference numeral 3 denotes a foreign substance (dust from the inspection device itself) which is composed of one section.

Next, a conventional flaw discrimination method will be described. In each inspection device, the wafer surface is divided into basic detection units, and the presence or absence of foreign matter is determined for each division. As a result, the section determined to have "foreign matter" is displayed in black, and the number of sections displayed in black is regarded as the number of foreign matter. According to the example shown in FIG. 5, the aggregate 2 of the sections is “15 pieces of foreign matter” even though it shows a large foreign matter or a scratch that extends over 15 sections, and is divided into eight “foreign matter” sections. In addition, "23 foreign matters" are displayed on the entire wafer. Therefore, after the foreign matter is detected, a person looks into the microscope to determine whether each foreign matter is a scratch or a large foreign matter or dust from the inspection apparatus itself by experience.

[0004]

Since the conventional flaw determination method is performed as described above, it is impossible to obtain an accurate number of foreign matters and it is impossible to determine whether or not the foreign matters are scratched. It was necessary for human beings to judge by experience. Therefore, since the exact number of dusts from the inspection device itself cannot be obtained, there is a problem in that the inspection device cannot be cleaned unnecessarily, or the product in the portion having no flaw on the wafer cannot be utilized.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to obtain an accurate number of foreign matters on the wafer surface and to determine whether or not the detected foreign matters are flaws. Aim to get.

[0006]

According to a first flaw judging method of the present invention, a step of judging whether or not there is a foreign matter also in the adjacent section with respect to the "presence of foreign matter" section, the result of the decision Is "existence of foreign matter", two foreign matter in adjacent sections are regarded as the same foreign matter to be a new foreign matter, a step of counting the number of categories occupied by the smallest rectangle including the new foreign matter, and the new foreign matter is It includes a step of calculating a ratio of the number of divisions to the number of divisions occupied by the rectangle, and a step of determining from the ratio whether or not the new foreign matter is a flaw.

The second flaw determination method according to the present invention is
After detecting the new foreign matter, counting the number of adjacent divisions with "foreign matter" for each peripheral division corresponding to the edge of the new foreign matter, ratio of the number of adjacent divisions with "foreign matter" to the total number of adjacent divisions A step of calculating the ratio of the number of adjacent divisions with "foreign matter" to the total number of adjacent divisions for each of the peripheral divisions to a preset constant, the ratio of the number of peripheral divisions satisfying the comparison condition to the total number of peripheral divisions And a step of determining whether or not the new foreign matter is scratched from the ratio.

[0008]

In the first flaw determination method according to the present invention, the section adjacent to the section "with foreign matter" is also "with foreign matter".
If so, those foreign substances are regarded as the same foreign substance, and are regarded as new foreign substances,
Count the exact number of foreign particles on the wafer surface. Furthermore, when the ratio of each new foreign substance in the smallest rectangle that includes the new foreign substance is equal to or smaller than the constant p (specified by the user), it is determined as a flaw.

On the other hand, in the second flaw determination method, attention is paid to the peripheral section corresponding to the edge of the new foreign matter, and the proportion of the section "with foreign matter" in the adjacent sections to the peripheral section is calculated, and this proportion is calculated. When the ratio of the number of peripheral sections that is equal to or larger than the constant q (specified by the user) to the total number of peripheral sections is equal to or smaller than the constant r (specified by the user), it is determined as a flaw.

[0010]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram in which foreign matter on the wafer surface is displayed in a wafer map. In the figure, 4 and 5 are detection unit classifications for detecting “presence of foreign matter”, and other shaded areas are the same. 6 is a detection unit classification of "no foreign matter".

Next, the operation will be described with reference to the flowchart of FIG. First, it is determined whether or not there is a foreign substance in each detection unit category (S1). If there is no foreign substance, the next category is entered (NO in S1). If there is a foreign substance (YES in S1), it is determined whether or not there is a foreign substance also in the adjacent section to that section (S2). If there is a foreign substance also in the adjacent section (when YES in S2), two adjacent foreign substances are present.
Is newly regarded as one foreign matter (new foreign matter) (S
3). When the presence / absence of foreign matter is completed for all the adjacent foreign matters (NO in S2), the number of categories a occupied by the newly detected new foreign matter is calculated (S4). Figure 1
In this example, the number of divisions occupied by the foreign matter detected as a new foreign matter is 14. Next, the number of divisions b occupied by the smallest rectangle containing the new foreign matter is calculated (S5). In the example of FIG. 1, the portion indicated by the dotted line is this rectangle, and the number of occupying sections is 5 × 7 = 35.

Next, the ratio (a / b) of the number of sections occupied by the new foreign matter to the number of sections occupied by the rectangle is determined (S
6). If a / b = 1 (YES in S7), the new foreign matter is a point, a straight line, or a rectangular shape, and since there is no such flaw or large foreign matter, the process ends. a
If / b is not 1 (NO in S7), it is compared with a constant p preset by the user (S8). Generally, scratches have a finer line shape than large foreign matter, so a /
If b is equal to or smaller than the constant p (YES in S8), the new foreign matter is regarded as a flaw, and if larger than the constant p (NO in S8), it is regarded as a large foreign matter. The above constants are set by a flaw shape model or the like. For example, if the constant p is set to 0.5, the ratio is 14/35 = 0.4 <0.5 in the example of FIG. By the above processing, even if there are scratches or large foreign particles on the surface of the wafer, it is possible to obtain an accurate number of foreign particles and also to determine whether or not there are scratches by setting the constant p.

Example 2. In the above embodiment, whether or not there is a scratch is determined by the ratio of the number of divisions occupied by the new foreign matter to the number of divisions occupied by the smallest rectangle encompassing the new foreign matter, but it may be determined by the method described below. . FIG. 3 is a diagram showing the new foreign matter detected by determining the presence / absence of the foreign matter for each detection unit category, similarly to the first embodiment.
The shaded area is the category of "foreign matter", of which "・"
A portion 7 indicated by indicates a peripheral section corresponding to the edge of the new foreign matter.
Next, the operation will be described with reference to the flowchart of FIG. First, as in the first embodiment, the presence or absence of a foreign substance is determined for each detection unit segment, and if there is a foreign substance in an adjacent segment, it is regarded as the same foreign substance and a new foreign substance is detected (T1 to T3). Next, for each of the peripheral section 7 that corresponds to the edge of the new foreign matter,
Among the adjacent sections, the number c of the sections with “foreign matter” is calculated (T4), and the ratio (c / d) of the number of the sections c to the total number of adjacent sections is calculated (T5). After performing the processes of T4 to T5 for all the peripheral sections 7, the initial value of N is set to 0, and when the calculated ratio (c / d) is larger than the constant q preset by the user, N = N + 1 is added. Then, the number N of peripheral divisions in which the ratio (c / d) of all the peripheral divisions is larger than the constant q is obtained (T6 to T9). In this case, q varies depending on the number of adjacent sections, so it is determined for each peripheral section. Next, the ratio N / M of the N to the total number M of peripheral sections is calculated (T10), and the N / M is compared with the constant r set by the user (T11). In general, scratches are sharp and have many sharp edges as compared with large foreign matter, so if N / M is larger than the constant r (when YES in T11), it is regarded as large foreign matter, and if it is small (NO in T11). When) it is regarded as a scratch and the process ends. Note that r in this case is also determined from a flaw shape model or the like. Also in this example, the number of foreign matters can be accurately grasped, and whether or not there is a flaw can be determined by setting the constants q and r.

[0014]

As described above, according to the present invention, it is possible to obtain the accurate number of foreign matters on the wafer surface and to determine whether the detected foreign matters are scratches or large foreign matters. It is possible to obtain an accurate number of foreign substances (dust from the inspection device itself), and the inspection device may be cleaned with the minimum necessary amount. In addition, it is possible to make the most of the product on the wafer where there are no scratches.

[Brief description of drawings]

FIG. 1 is a diagram showing foreign matter on a surface of a wafer which is an inspection target in a first embodiment of the present invention.

FIG. 2 is a flowchart showing a processing flow according to the first embodiment of the present invention.

FIG. 3 is a diagram showing foreign matter on the surface of a wafer which is an inspection target in the second embodiment of the present invention.

FIG. 4 is a flowchart showing the flow of processing according to the second embodiment of the present invention.

FIG. 5 is a diagram showing an example of an inspection result display by a conventional wafer surface inspection device.

[Explanation of symbols]

 1 Wafer 2 Foreign matter 3, 4, 5 Detection unit category considered to be “foreign matter” 6 Detection unit category considered to be “no foreign matter” 7 Peripheral category corresponding to edge of foreign matter

Claims (2)

[Claims] 1. The wafer surface is divided into basic detection units,
In a surface inspection apparatus that determines the presence or absence of foreign matter for each basic detection unit category (hereinafter, abbreviated as category), for the category of "foreign matter", a step of determining whether there is a foreign matter also in the adjacent section, If the result of the determination is "foreign matter present", two foreign matter in adjacent sections are regarded as the same foreign matter to be new foreign matter, a step of counting the number of categories occupied by the smallest rectangle including the new foreign matter, A flaw determination method comprising: a step of calculating a ratio of the number of categories occupied by new foreign matter to the number of categories occupied by the rectangle; and a step of determining whether or not the new foreign matter is flawed from the rate. 2. The surface of the wafer is divided into basic detection units,
In the surface inspection device that determines the presence / absence of foreign matter for each category, the step of determining whether there is any foreign matter in the adjacent category for the category of "foreign matter". , A step of considering two foreign matter in adjacent categories as a new foreign matter as the same foreign matter, and a step of counting the number of adjacent categories with "foreign matter" for each of the peripheral categories corresponding to the edge of the new foreign matter, The step of calculating the ratio of the number of adjacent sections of "foreign matter" to the total number of adjacent sections, the step of comparing the ratio of the number of adjacent sections of "foreign object" to the total number of adjacent sections for each of the peripheral sections with a preset constant, And a step of calculating a ratio of the number of peripheral divisions satisfying the comparison condition to the total number of peripheral divisions, and a step of determining from the ratio whether or not the new foreign matter is a flaw. How to identify scratches.