JPH04131761U - Total internal reflection fluorescent X-ray analyzer - Google Patents

Abstract

(57) [Summary] [Purpose] In a total internal reflection fluorescence X-ray analyzer, the sample surface Ws
Improve analysis accuracy by correcting undulations. [Structure] As shown in FIG. 3(a), a distance detector 20 detects a first measurement distance T1 from a first measurement point a to a reference height H. Next, after slightly moving the sample W in the radial direction r (left side) as shown in FIG. 3(b), the distance detector 20 performs a second measurement from the second measurement point b to the reference height H. Detect distance T2.
After this, the sample W is tilted by an angle corresponding to the difference ΔT between the measurement distances T1 and T2 with respect to the horizontal distance L1 between the two measurement points a and b, that is, the inclination of the sample surface Ws, and ), the sample surface Ws in the measurement range A1 to be analyzed is made horizontal.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This idea irradiates the sample surface with primary X-rays at a small incident angle to This invention relates to a total internal reflection fluorescent X-ray analyzer that analyzes fluorescent X-rays from.

0002

[Conventional technology]

Traditionally, total internal reflection fluorescence X-ray spectrometers have been used, for example, to analyze As a device to detect impurities such as arsenic and stainless steel particles attached to the surface layer. (For example, see Japanese Patent Application Laid-Open No. 63-78056). An example of this type of device is shown in Figure 4.

0003 In FIG. 4, primary X-rays B1 emitted from an X-ray source 51 are converted into parallel rays by a parallel optical system 52. After that, the surface Ws of the sample W consisting of a wafer is exposed to a small incident angle α (for example, 0. 05°). Part of the incident primary X-ray B1 is totally reflected and becomes reflected X-ray B2, and the other part excites the sample W, causing fluorescent X-rays unique to the elements that make up the sample W. Generate B3. Fluorescent X-ray B3 is detected by a fluorescent X-ray detector placed opposite the sample surface Ws. Enter 60. This incident fluorescent X-ray B3 is detected by the fluorescent X-ray detector 60. After the ray intensity is detected, the desired X-ray spectrum is determined by the multiple pulse height analyzer 61. can get.

0004 This type of total internal reflection fluorescent X-ray analyzer is characterized by the fact that the incident angle α of the primary X-ray B1 is minute. Therefore, reflected X-rays B2 and scattered X-rays are difficult to enter the fluorescent X-ray detector 60, and the fluorescent If the noise is small compared to the output level of fluorescent X-ray B3 detected by the radiation detector 60, There is an advantage. In other words, a large signal-to-noise ratio can be obtained, resulting in good analysis accuracy and For example, it has the advantage of being able to detect even minute amounts of impurities.

[0005] In addition, since the incident angle α of the primary X-ray B1 is small, most of the primary X-ray B1 It only reaches the surface Ws layer of the sample W, and it is difficult to enter the inside of the sample W. therefore , since fluorescent X-rays B3 are difficult to generate from inside the sample W, the analysis accuracy of the sample surface Ws is It has the advantage of being good.

[0006]

[Problem that the idea aims to solve]

However, even if the surface Ws of a sample such as a wafer is quite flat, the magnification shown in Fig. 5 may occur. As shown in the diagram, there are microscopic undulations. Therefore, the actual value of primary X-ray B1 is An error occurs in the incident angle α with respect to a preset incident angle (predetermined value). However, Therefore, as shown in this figure, when the actual incident angle α is large, the primary X-ray B1 The fluorescent X-rays and scattered X-rays from internal elements that are not the target of measurement enter the inside of the material W. As a result, accurate analysis of the sample surface Ws becomes impossible.

[0007] This idea was made in view of the conventional problems mentioned above, and it improves the accuracy of analysis of the sample surface. An object of the present invention is to provide a total internal reflection fluorescent X-ray analyzer that can perform

[0008]

[Means to solve the problem]

In order to achieve the above purpose, this device uses two measurement points on the sample surface. Place the sample on a distance detector that detects each vertical distance to the reference height. It includes a drive device for tilting the sample stage and a control device. The above control device Receiving the measurement signal from the distance detector, calculate the vertical distance relative to the horizontal distance between the two measurement points. The driving device is controlled based on the distance difference to set the incident angle to a predetermined value.

[0009]

[Effect]

According to this idea, the lead value for the horizontal distance between two measurement points on the sample surface is The drive device is controlled based on the direct distance difference, that is, the slope of the sample surface, and the sample stage is moved. Since it is tilted at a predetermined angle, the sample surface can be kept horizontal regardless of the waviness of the sample surface. By doing so, the incident angle of the primary X-ray can be kept at a small predetermined angle.

0010

【Example】

An embodiment of this invention will be described below with reference to FIGS. 1 to 3. In FIG. 1, an irradiation device 50 includes an X-ray source 51 and a parallel optical system 52. X-ray The primary X-ray B1 emitted from the source 51 is made into a parallel beam by the parallel optical system 52, and is directed to the sample. The light is irradiated onto W at a small incident angle α. The sample W is, for example, a silicon substrate. It consists of a wafer implanted with impurities such as arsenic, and its surface Ws has gentle undulations. (See FIG. 3(a)) and is placed on the sample stage 40.

[0011] A distance detector 20 is arranged near the fluorescent X-ray detector 60. this distance The detector 20 and the fluorescent X-ray detector 60 are connected to the primary X-ray B1 as shown in the plan view of FIG. It is the irradiation direction and is lined up on the straight line R passing through the diameter of the sample stage 40, as shown in Figure 1. , are arranged facing the sample stage 40. The distance detector 20, as described later, By moving the sample stage 40 in the radial direction r and rotating in the circumferential direction θ (Fig. 2), the sample table Each vertical distance T1 from the two measurement points a and b on the surface Ws to the reference height H, Detects T2 and outputs the respective distances T1 and T2 to the control device 21 as distance signals t1 and t2. It is something. Note that in this embodiment, the distance detector 20, for example, directs light to the sample surface. From a displacement sensor that emits light toward Ws and detects the distance based on the intensity of the reflected light. Become.

0012 The sample stage 40 is rotatably attached to the rotating base 10. The above rotating base The base 10 is provided so as to be able to slide horizontally on the slide base 11, as shown in Fig. 2(a). In addition, the sliding direction r is set to be the same direction as the irradiation direction of the primary X-ray B1. death Therefore, since the sample stage 40 moves in the radial direction r and the circumferential direction θ, as will be described later, , any measurement point A on the sample W is detected by the fluorescent X-ray detector 60 and the distance detector 20 in FIG. is moved below.

[0013] The slide base 11 is tilted at an angle of inclination by a drive device 30 around a central fulcrum 31. The degree can be set arbitrarily. In other words, the drive device 30 is located inside the slide base 11. An elevating section 33 provided at the right end of the slide base 11 is centered around a fulcrum 31 provided at the center. are moved up and down by a motor M to change the inclination angle of the sample stage 40.

[0014] The control device 21 is composed of, for example, a microcomputer, and includes the first and Upon receiving the second measurement signals t1 and t2, the horizontal Based on the difference ΔT between the vertical distances T1 and T2 with respect to the distance L1, the drive device 30 shown in FIG. 1 is controlled. By outputting the control signal d and controlling the drive device 30, the incident angle α is set to a predetermined value. Set to value. The rest of the configuration is the same as the conventional example, and the same or equivalent parts are designated by the same reference numerals. The detailed explanation will be omitted.

[0015] Next, we will explain the operation when analyzing the diagonally shaded measurement area A1 in Figure 2(a). Ru. First, rotate the sample stage 40 in the circumferential direction θ and place the measurement point A1 as shown in Figure 2(b). Move it on straight line R. After this movement, the sample stage 40 is moved in the radial direction r ( left side), and as shown in Figure 3(a), move the first measurement point a within measurement point A1 to the distance Move it directly below the detector 20.

[0016] After this movement, the distance detector 20 performs the first measurement from the first measurement point a to the reference height H. A constant distance T1 is detected and a first measurement signal t1 is output to the control device 21. After this, the sample Move the table 40 (Fig. 1) slightly in the radial direction r (left side) and perform the second measurement as shown in Fig. 3(b). The fixed point b is placed opposite to the distance detector 20 directly below. After this movement, the distance detector 20 Detects the second measurement distance T2 from the measurement point b to the reference height H and controls the measurement signal t2. Output to control device 21.

[0017] The control device 21 that receives both signals t1 and t2 calculates the difference ΔT between both measured distances T1 and T2, and further calculates the difference ΔT between the two measured distances T1 and T2. From the following formula, the lifting distance D of the lifting section 33 in FIG. 1 is approximately determined. D=ΔT・L2/L1 L2: Distance between the lifting part 33 of the drive device 30 and the fulcrum 31 The control device 21 outputs the determined vertical distance D to the drive device 30 as a control signal d. .

[0018] Upon receiving the control signal d, the drive device 30 lowers the elevating section 33 by an elevating distance D. , rotate the sample stage 40 slightly clockwise about the fulcrum 31. With this rotation , the measurement point A1 becomes horizontal as shown in FIG. 3(c). After this, measure point A1 like this. After moving it to the bottom of the fluorescent X-ray detector 60 as shown in the figure, shine and analyze measurement point A1.

[0019] In this way, this idea can be applied to the sample shown in Fig. 1 according to the inclination caused by the waviness of the sample surface Ws. The feeding table 40 can be tilted. Therefore, while keeping the sample surface Ws horizontal, Analysis can be performed by setting the incident angle α to a predetermined value. As a result, the sample W There is no risk of fluorescent X-rays or scattered X-rays entering the fluorescent X-ray detector 60 from inside. This improves the accuracy of analyzing the sample surface Ws.

[0020] In addition, in this embodiment, one distance detection can be performed by moving the sample stage 40. Since vertical distances T1 and T2 at two measurement points a and b are sequentially measured using the instrument 20, expensive Since it is not necessary to install two distance detectors 20, the cost is reduced.

[0021] In the above example, measurement points a and b were any two points within measurement point A, but As shown in 2(d), multiple measurement points a and b are placed in the direction Z perpendicular to the radial direction r within the measurement location A. It may be provided. In this case, the distance difference ΔT (Fig. 3(b)) is the left measurement point a1, a2...an The average value of the first measurement distance at the measurement points b1, b2 ...bn on the right side Calculated by the difference from the average value of a fixed distance.

[0022]

[Effect of the idea]

As explained above, according to this invention, between two measurement points on the sample surface The drive device is based on the difference in vertical distance to horizontal distance, that is, the slope of the sample surface. Since the sample stage is tilted by controlling the can be made horizontal. Therefore, the incident angle of the primary X-ray can be set to a small predetermined angle. Since it can be kept at a certain temperature, fluorescent X-rays and scattered X-rays from inside the sample are prevented. Since this can be prevented, the accuracy of analysis of the sample surface is improved.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a total internal reflection fluorescent X-ray analyzer showing an embodiment of this invention.

[Fig. 2] (a), (b), and (c) are plan views showing a method of moving measurement points, and (d) is a plan view showing measurement points in the measurement range.

FIG. 3 is a process diagram showing a waviness correction method.

FIG. 4 is a schematic configuration diagram of a conventional total internal reflection fluorescent X-ray analyzer.

FIG. 5 is an enlarged view of the sample surface.

[Explanation of symbols]

20...Distance detector, 21...Control device, 30...Drive device, 40...Sample stage, 50...Irradiation device, 60...Fluorescent X-ray detector, a, b...Measurement point, B1...Primary X-ray, B3...Fluorescence X-ray, H...Reference height, L1...
Horizontal distance, T1,T2...Vertical distance, t1,t2...Measurement signal, ΔT
...difference in vertical distance, W...sample, Ws...sample surface, α...incident angle.

Claims (1)

[Scope of utility model registration request] 1. An irradiation device that irradiates a sample surface with primary X-rays at a minute angle of incidence, and a fluorescent X-ray detector that detects fluorescent In a total internal reflection fluorescent X-ray analyzer that analyzes the fluorescent X-rays based on the detection results from the X-ray detector, there are two measurement points on the sample surface located near the fluorescent a distance detector that detects the vertical distance between the two measurement points; a drive device that tilts the sample stage on which the sample is placed; A total internal reflection fluorescent X-ray analyzer comprising: a control device that controls the drive device based on the difference in vertical distance and sets the incident angle to a predetermined value.