JP5338517B2 - Nondestructive single crystal substrate stress measurement method, measurement device, and measurement program - Google Patents

Description

  The present invention relates to a method, apparatus, and program for measuring warpage stress of a semiconductor chip, and more particularly, to a method, apparatus, and program for measuring warpage stress of a semiconductor chip mounted in a package using X-rays without destroying the package. And about.

  In recent years, various LSI chip mounting techniques have been developed in response to demands for downsizing, high functionality, and high performance of electronic components. Many of the elemental technologies for realizing such a so-called advanced mounting technology are concerned about the increase in mechanical stress applied to the LSI chip. For this reason, the importance of the technique which measures the stress and distortion to the mounted LSI chip nondestructively is increasing.

  Conventionally, evaluation of stress and warpage of a mounted semiconductor chip has been performed using a Raman spectroscopy method or a strain gauge method. However, Raman spectroscopy is a destructive inspection in which measurement is performed on the cross section of the package, and stress is relaxed when the cross section is created. Therefore, there is a concern that the measurement result may not reflect the stress of the actual semiconductor chip. Further, although the strain gauge method is a nondestructive inspection, the strain measured by this method is a strain on the package surface, and the strain applied to the semiconductor chip can be obtained only by estimation. There is a need for a method for measuring the warping stress of a semiconductor chip directly and non-destructively.

  Therefore, Patent Document 1 discloses a method for directly measuring the warpage of a packaged semiconductor chip using X-ray diffraction and nondestructively. In the method described in Patent Document 1, first, diffracted X-rays from a semiconductor chip are acquired through a package material, and the sample position dependency of a rocking curve is measured. Next, the shape of the semiconductor chip, that is, the warp is obtained from the sample position dependency of the diffraction peak position obtained as a result.

JP 2008-203212 A

  However, in Patent Document 1, although there is a detailed description of the experimental procedure for obtaining the diffracted X-ray, the warp stress of the semiconductor chip is not required. In order to predict the influence of the warping stress on the device characteristics or to compare the measurement result with the result of the stress simulation, a method for analyzing the warping stress from the diffraction measurement is required.

  The present invention has been made in consideration of the above problems, and provides an analysis method with validity in a method of directly measuring the warpage of a packaged semiconductor chip using X-ray diffraction, In addition, it is an object of the present invention to provide a program for automating a part or all of a series of adjustment work and analysis work including the appropriate analysis method and an apparatus for realizing the program.

  In order to solve the above-described problem, the nondestructive single crystal substrate stress measurement method according to claim 1 includes a step of irradiating a component having a single crystal substrate sealed with a package material with X-rays, A non-destructive single crystal substrate stress measurement method comprising: a detection step of detecting diffracted X-rays through the package material; and an analysis step of obtaining a stress of the single crystal substrate using a result of the detection step. The step is a step of repeatedly performing a step of measuring the rocking curve of the diffracted X-ray and a moving step of moving the component until the measurement position reaches the opposite end from one end of the single crystal substrate, In the analysis step, a diffraction peak angle is obtained from the rocking curve obtained in the detection step, and the difference between the peak angles of two adjacent measurement points is Δω. B, and when the movement distance in the movement step is represented by Δx, the warping stress σ at the position x of the single crystal substrate is obtained using the Young's modulus E of the single crystal substrate and the thickness t of the single crystal substrate. (X)

として算出するステップであることを特徴とする。

It is the step which calculates as, It is characterized by the above-mentioned.

  According to the present invention, X-rays are irradiated to a component in which a single crystal substrate is sealed with a package material, diffracted X-rays from the single crystal substrate are detected through the package material, and a rocking curve of the diffracted X-rays is obtained. Obtained by repeatedly performing from one end of the single crystal substrate to the opposite end, obtaining a diffraction peak angle from the obtained rocking curve, and expressing the difference in peak angle between two adjacent measurement points as ΔωB, When the moving distance in the moving step is expressed as Δx, the warping stress σ (x) at the position x of the single crystal substrate is calculated using the Young's modulus E of the single crystal substrate and the thickness t of the single crystal substrate.

として算出する。

Calculate as

  Therefore, it is possible to easily measure the warping stress of the semiconductor chip in the product in a nondestructive manner.

3. The nondestructive single crystal substrate warpage stress measuring apparatus according to claim 2, wherein means for irradiating X-rays to a component in which the single crystal substrate is sealed with a package material, and diffracted X-rays from the single crystal substrate are used as the package material. A non-destructive single crystal substrate warpage measuring apparatus comprising detection means for detecting over and analysis means for obtaining warpage of the single crystal substrate using a result obtained by the detection means, wherein the detection means includes the Measuring the rocking curve of the diffracted X-ray and moving the moving part until the measurement position reaches the opposite end from the one end of the single crystal substrate; means includes means for obtaining a diffraction peak angle from rocking curve obtained by the detection unit, the difference between the peak angles of the two adjacent measurement points represent the [Delta] [omega _B, the moving step When the kick movement distance expressed as [Delta] x, wherein with the thickness t of the Young's modulus E and the single crystal substrate of a single crystal substrate, warping stress at the position x of the single crystal substrate σ (x) is

として算出する手段であることを特徴とする。

It is a means to calculate as, It is characterized by the above-mentioned.

  The non-destructive single crystal substrate warpage measurement program according to claim 3 is a computer that includes the computer included in the non-destructive single crystal substrate warpage stress measurement device according to claim 2, the means for irradiating the X-ray, the detection means, It functions as an analysis means.

The non-destructive single crystal substrate warpage measurement program according to claim 4 is a computer that includes the computer included in the non-destructive single crystal substrate warpage stress measurement device according to claim 2, the means for irradiating the X-ray, the detection means, The difference between the peak angles of two adjacent measurement points determined from the sample position dependency of the analysis means and the diffraction peak angle is expressed as Δω _B (x), and the moving distance in the moving step is expressed as Δx, Using the Young's modulus E of the single crystal substrate and the thickness t of the single crystal substrate, the warping stress σ (x) at the position x of the single crystal substrate is

として算出する手段、として機能させる。

As a means for calculating as

  As described above, according to the present invention, X-rays are irradiated to a component in which a single crystal substrate is sealed with a package material, and diffracted X-rays from the single crystal substrate are detected through the package material. Since the stress of the single crystal substrate is obtained using the above, the warping stress of the semiconductor chip in the product can be measured easily and nondestructively.

It is a figure explaining the principle of curvature measurement. It is a figure explaining the principle of curvature measurement. It is a figure explaining the principle of curvature measurement. It is a figure explaining the principle of curvature measurement. It is a figure explaining the principle of curvature measurement. It is a schematic diagram of the sample which performed the curvature measurement. It is a schematic diagram of the measurement system which performed the curvature measurement. It is a schematic diagram which shows the positional relationship of the irradiation area | region of an incident X ray, a diffraction X ray, and an X-ray, and a sample. It is explanatory drawing of the measurement procedure of the curvature measurement which concerns on this invention. It is a figure which shows the relationship between the curvature radius of the chip | tip produced by the curvature, and curvature distortion. It is a figure which shows the relationship between a chip | tip curvature radius and the difference (angle which a normal line makes) of the peak angle of two measurement points.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the invention will be described in detail with reference to the accompanying drawings.

  First, the principle of a method for measuring the warpage of a semiconductor chip using diffracted X-rays will be described. FIG. 1 shows the means used in the X-ray diffraction method, which is the basis of the warpage measurement method, its configuration, and an outline of the X-ray ray diagram. FIG. 1 is simplified for the sake of explanation, and may not completely match the actual measurement means and configuration, and the X-ray ray diagram.

Incident X-rays 5 generated by an appropriate X-ray source 4 enter the irradiation region 11 (region A) of the Si chip 10. When the rotation angle ω (measured from the direction of the wave vector 8) of the sample stage 7 is changed while the X-ray detector 6 is fixed, the Bragg condition is satisfied, that is, the incident X-ray 5 with respect to the surface of the region A when taking a particular value alpha _B with the incident angle alpha, the diffracted X-ray 9 in the X-ray detector 6 resulting crystals diffracted X-ray in the region a are detected. Here, ω when diffracted X-rays are detected is represented as ω _B. Further, the value of ω _{B in} the region A is expressed as ω _B (A).

When the single crystal substrate is not warped, the sample stage 7 is moved in the x-axis direction with ω kept at ω _B (A), and as shown in FIG. 2, another irradiation region 12 (region) on the Si chip 10 is obtained. Even if B) is irradiated with X-rays, diffracted X-rays remain detected. This is because the incident angle α of the incident X-ray 5 with respect to the chip surface remains the same as α _{B in} the regions A and B.

On the other hand, consider the case where the Si chip 13 is warped upward as shown in FIGS. First, with attention to FIG. 3, the omega _B when irradiated with X-rays in the illumination area 14 (region C) and omega _{B (C).} At this time, since the diffracted X-ray 9 is detected, α is α _B. Next, with the ω set to ω _B (C), the sample stage is moved in the positive direction of the x-axis parallel to the x-axis, and the irradiation region 15 (region D) is irradiated with X-rays (FIG. 4). In the region D, α is deviated from α _B due to warpage, so that no diffracted X-ray is detected. In order to detect the diffracted X-rays in the region D, the value of ω may be changed so that α becomes α _B (FIG. 5). That is, the value of ω may be adjusted in a direction to cancel the change of α caused by the movement of the measurement point. Quantitatively, when the angle between the surface of region C and the surface of region D is Δθ ≧ 0,

… 式（１）
とすれば、領域Ｄにおけるαがα_Ｂとなり、回折Ｘ線が検出される。以上の説明から、反りにより回折Ｘ線が検出される際のωが変化することが理解される。

... Formula (1)
Then, α in the region D becomes α _B , and diffracted X-rays are detected. From the above description, it is understood that ω when diffracted X-rays are detected due to warping.

  Further, when equation (1) is modified, equation (2) is obtained.

… 式（２）
式（２）は、領域Ｄと領域Ｃとでω_Ｂを測定すれば、その変化から領域Ｃと領域Ｄの表面のなす角、すなわち反りによる表面の角度変化が求められることを示している。

... Formula (2)
Equation (2) shows that if ω _B is measured in the region D and the region C, the angle between the surfaces of the region C and the region D, that is, the change in the surface angle due to the warpage can be obtained from the change.

  Although the case where the single crystal substrate is warped upward has been described above, the change in the angle formed by the warp can be measured by the same principle even when the single crystal substrate is warped downward.

  Next, the measurement actually performed using the above method will be described.

  The sample used for the measurement is shown in FIG. An outline of the X-ray diffractometer used for the measurement is shown in FIG. FIG. 8 shows the relationship between the incident X-ray 5 and the diffracted X-ray 9 and the sample in the vicinity of the sample. In this figure, the mold resin, the printed circuit board, and the like are omitted for explanation, and only the Si chip 19 is shown. The beam shape of the incident X-ray 17 is defined as a rectangle of SW1 × SW2 = 2 mm × 0.2 mm by the slit, but the X-ray irradiation area 20 on the Si chip 19 is approximately W1 × W2 = 2 mm × 0. It becomes an area of 26 mm. This is because incident X-rays are obliquely incident on the Si chip surface.

  The measurement procedure is shown below.

  First, in the measurement system as shown in FIG. 7, the package is placed on the sample stage 7 (so that the center of the semiconductor chip overlaps the X-ray irradiation position). Thereafter, the axis of the X-ray optical system is adjusted by halving adjustment. The halving adjustment is an adjustment performed also in the case of X-ray diffraction measurement of a general thin film sample, and thus description thereof is omitted. Next, to obtain diffracted X-rays, the 2θ axis (detector azimuth angle measured from the direction of the wave vector of incident X-rays) and the ω axis (sample stage rotation angle measured from the direction of the wave vector of incident X-rays). ) And adjust.

In this embodiment, warpage of a semiconductor chip formed from a Si (0 0 1) substrate is converted into Si (0 0) using Mo Kα1 characteristic X-rays (energy: 17.48 keV, wavelength: 7.0926 × 10 ⁻² nm). 12) Since the rocking curve of the reflection is observed, the Bragg angle θ _B is expressed as θ _B = 51.59 ° from the equation (3) using the interplanar spacing d of Si (0 0 12) and the X-ray wavelength λ. Since it is obtained, first, 2θ = 2θ _B = 103.18 ° and ω = 51.59 ° are set.

… 式（３）
そして２θ−ωスキャンを行い回折ピークを探す。このスキャンを行っても回折ピークが得られない場合は、次のいずれかの操作により回折ピークを見出す。イ）２θを２θ_Ｂに固定し、ωをθ_Ｂ付近でスキャン。ロ）ωをθ_Ｂに固定し、２θを２θ_Ｂ付近でスキャン。ハ）χ（ｘ軸周りの試料ステージの回転角）をプラス（あるいはマイナス）０．５°に設定し、上記の２θ−ωスキャンか、イ）あるいはロ）の操作で回折ピークを探す。上記のいずれかの操作により回折ピークが見出される。

... Formula (3)
A 2θ-ω scan is then performed to find a diffraction peak. If a diffraction peak is not obtained by performing this scan, the diffraction peak is found by any of the following operations. _B ) Fix 2θ at 2θ _B and scan ω around θ _B. B) ω is fixed at θ _B , and 2θ is scanned around 2θ _B. C) χ (rotation angle of the sample stage around the x axis) is set to plus (or minus) 0.5 °, and a diffraction peak is searched for by the above-mentioned 2θ-ω scan, a) or b). A diffraction peak is found by any of the above operations.

When a diffraction peak is found by the above operation, adjustment is performed so that the diffraction intensity becomes maximum. The conditions of 2θ, ω, and χ when a diffraction peak is found are expressed as 2θ ₀ , ω ₀ , and χ ₀ , respectively.

First, a) 2θ and ω are fixed to 2θ ₀ and ω ₀ , and χ is scanned around χ ₀ to find a point where the diffraction intensity is maximum, and χ is moved to the point χ ₁ . B) ω and χ are fixed to ω ₀ and χ ₁ , and 2θ is scanned around 2θ ₀ . A point where the diffraction intensity is maximized is searched, and 2θ is moved to the point 2θ ₁ . C) 2θ and χ are fixed to 2θ ₁ and χ ₁ , and ω is scanned around ω ₀ . A point where the diffraction intensity is maximum is searched and ω is moved to the point ω ₁ . Thereafter, the scans a) to c) are repeated until the maximum value of the diffraction intensity obtained in each scan does not change. In the subsequent adjustment and measurement, the value of 2θ is fixed.

  Next, the end of the chip is determined as follows using the diffracted X-rays as a clue. That is, starting from the position where the incident X-rays are reliably irradiated to the Si chip, the operations of “moving the sample stage by a certain distance in the x-axis direction” and “measuring the rocking curve” are repeated, and the diffraction X The position immediately before the position where the line no longer appears is determined as the chip end. In this way, the two chip ends are searched.

  Next, the rocking curves are measured at the two chip ends determined by the above method. The starting point ωs and the ending point ωe of the rocking curve in the following measurement are determined so that the diffraction peak angles at the two points are included.

Subsequently, the sample position is adjusted so that X-rays are irradiated to one chip end (upper left in FIG. 9). Then, a acquired peak angle omega _B at intervals of omega = .omega.e rocking curve 24 from omega = .omega.s, returns the value of omega to an initial value .omega.s (Fig. 9 upper right). Thereafter, the sample stage is translated in the x-axis direction by a certain distance, for example, 0.1 mm (lower left in FIG. 9), and the rocking curve 24 is again acquired at the position from ω = ωs to ω = ωe, and the peak angle ω _B is obtained. Then, the value of ω is returned to the initial value ωs (lower right in FIG. 9). In this way, “a rocking curve is acquired in the section from ω = ωs to ω = ωe, the peak angle ω _B is obtained, and the value of ω is returned to the initial value ωs.”, “The sample stage is moved along the x-axis direction. Are repeated until the measurement position reaches the end of the semiconductor chip opposite to the starting point.

  In the above procedure, the acquired rocking curve may be recorded in association with the measurement point, and the peak angle at the rocking curve at each measurement point may be specified collectively after the measurement is completed.

  If the sample position dependency of the peak angle ωB is obtained in this way, the chip stress can be obtained as follows.

  First, the case where stress is applied from the outside (right side) from the state without stress (left side) will be considered using FIG. 10 showing a part of the chip cross section. The center of the Si chips 27 and 28 is assumed to have a stress of 0 (neutral layer). Then, when stress is applied, it is considered that the upper half from the center receives tensile stress and the lower half from the center receives compressive stress. Then, the distortion of the chip surface caused by warping is calculated by the equation (4), where t is the chip thickness. By multiplying this by the Young's modulus E of the chip, the distortion in the surface tangential direction of the chip surface is calculated. Warpage stress σ is obtained (formula (5)).

… 式（４）

... Formula (4)

… 式（５）
一方、曲率半径ＲはωＢ（ｘ）と次のような関係にある。図１１に示すように、Ｓｉチップ２９上の２点（３０および３１）の表面法線（３２および３３）がなす角をΔθ、２点間の距離をΔｘとすると、曲率１／Ｒは、式（６）によって与えられる。

... Formula (5)
On the other hand, the radius of curvature R has the following relationship with ωB (x). As shown in FIG. 11, when the angle formed by the surface normals (32 and 33) of two points (30 and 31) on the Si chip 29 is Δθ and the distance between the points is Δx, the curvature 1 / R is Is given by equation (6).

… 式（６）
一方、Δθの絶対値は各点でのロッキング曲線におけるピーク角度の差Δω_Ｂの絶対値に等しいので、式（７）を得る。

... Formula (6)
On the other hand, since the absolute value of Δθ is equal to the absolute value of the peak angle difference Δω _B in the rocking curve at each point, Equation (7) is obtained.

… 式（７）
式（５）と式（７）とを用いると反り応力式（８）が得られる。

... Formula (7)
Using equations (5) and (7) yields the warpage stress equation (8).

… 式（８）
なお、Δω_Ｂの符号は測定系や測定位置の順序付けの方法によって変わりうるため、適宜正しい応力の符号が得られる様に修正されるべきである。ここでは、図２に示したような測定系を想定した。以上のように、各測定点でのω_Ｂと測定点間の距離Δｘを用いてチップ表面の反り応力を求めることができる。

... Formula (8)
Since the sign of [Delta] [omega _B is to be varied by the ordering of the method of the measurement system and measurement position, it should be modified so as to code appropriately correct stress is obtained. Here, a measurement system as shown in FIG. 2 was assumed. As described above, the warping stress on the chip surface can be obtained using ω _B at each measurement point and the distance Δx between the measurement points.

  As described above, the nondestructive single crystal substrate stress measurement method includes the steps of irradiating a component having a single crystal substrate sealed with a package material with X-rays, and diffracting X-rays from the single crystal substrate through the package material. A non-destructive single crystal substrate stress measurement method comprising: a detection step for detecting a single crystal substrate using a result of the detection step; and an analysis step for obtaining a stress of the single crystal substrate using the result of the detection step. The step of measuring the rocking curve and the moving step of moving the component are repeated until the measurement position reaches the opposite end from the one end of the single crystal substrate, and the analyzing step is performed by the detecting step. The difference between the peak angle of the diffraction peak angle from the obtained rocking curve and the peak angle between two adjacent measurement points is expressed as ΔωB, and the moving step is The warping stress σ (x) at the position x of the single crystal substrate using the Young's modulus E of the single crystal substrate and the thickness t of the single crystal substrate It calculates by Formula (8).

  Therefore, it is possible to easily measure the warping stress of the semiconductor chip in the product in a nondestructive manner.

DESCRIPTION OF SYMBOLS 1 Printed circuit board 2, 10, 13, 19, 27, 28, 29 Si chip 3 Mold resin 4 X-ray source 5, 17 Incident X-ray 6 X-ray detector 7, 23 Sample stage 8 Wave vector 9 of incident X-ray, 18 Diffraction X-ray 10 Resin substrate 11, 12, 14, 15, 20 Irradiation region 24, 25 Rocking curve 30, 31 Rocking curve measurement point 32, 33 Chip surface normal at each measurement point

Claims (4)

Irradiating a component having a single crystal substrate sealed with a package material with X-rays; and detecting a diffracted X-ray from the single crystal substrate through the package material;
A non-destructive single crystal substrate stress measurement method comprising an analysis step of obtaining a stress of the single crystal substrate using a result of the detection step,
The detecting step is a step of repeatedly performing a step of measuring the rocking curve of the diffracted X-ray and a moving step of moving the component until the measurement position reaches the opposite end from one end of the single crystal substrate. ,
In the analyzing step, the difference between the peak angle of two adjacent measurement points is expressed as Δω _B and the moving distance in the moving step is expressed as Δx, and the step of obtaining the diffraction peak angle from the rocking curve obtained in the detecting step. Then, using the Young's modulus E of the single crystal substrate and the thickness t of the single crystal substrate, the warping stress σ (x) at the position x of the single crystal substrate is

Non-destructive single crystal substrate warpage stress measurement method which is a step to calculate as A means for irradiating a part of a single crystal substrate sealed with a package material with X-rays, a detection means for detecting diffracted X-rays from the single crystal substrate through the package material, and a result obtained by the detection means A non-destructive single crystal substrate warpage measuring apparatus comprising an analyzing means for obtaining warpage of the single crystal substrate, wherein the detecting means is a means for measuring a rocking curve of the diffracted X-ray and a movement for moving the component. Means for repeating the measurement until the measurement position reaches the opposite end from one end of the single crystal substrate, and the analysis means calculates the diffraction peak angle from the rocking curve obtained by the detection means. When the difference between the peak angle of the means for obtaining and the two adjacent measurement points is expressed as Δω _B, and the movement distance in the moving means is expressed as Δx, the Young's modulus E of the single crystal substrate and the The warping stress σ (x) at the position x of the single crystal substrate is calculated using the thickness t of the single crystal substrate.

A non-destructive single crystal substrate warpage stress measuring device, characterized in that: A computer included in the nondestructive single crystal substrate warpage stress measuring device according to claim 2,
Means for irradiating the X-ray;
The detection means;
The analysis means;
Non-destructive single crystal substrate warpage measurement program characterized by functioning as A computer included in the nondestructive single crystal substrate warpage stress measuring device according to claim 2,
Means for irradiating the X-ray;
The detection means;
The analysis means;
When the difference in peak angle between two adjacent measurement points obtained from the sample position dependency of the diffraction peak angle is expressed as Δω _B (x) and the moving distance in the moving step is expressed as Δx, the single crystal substrate Using the Young's modulus E and the thickness t of the single crystal substrate, the warping stress σ (x) at the position x of the single crystal substrate is

Means to calculate as
Non-destructive single crystal substrate warpage stress measurement program characterized by functioning as

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