JP2001284538A - Semiconductor bare chip and semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce unwanted radiations generated from an integrated circuit operating at a high speed, formed on the surface of a semiconductor bare chip or a semiconductor wafer. SOLUTION: In the semiconductor bare chip (17) or the semiconductor wafer (10), each having an integrated circuit on the surface, a magnetic loss film (15) covers the backside of the semiconductor bare chip (17) or the semiconductor wafer (10). The loss film (15) may use a granular magnetic film which may be e.g. a sputtered film formed by sputtering or a vapor deposition film formed by vapor deposition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor bare chip and a semiconductor wafer having an integrated circuit formed on a surface.

[0002]

2. Description of the Related Art In recent years, highly integrated semiconductor elements that operate at high speed have become remarkably popular. For example, random access memory (RAM), read only memory (ROM), microprocessor (MPU), central processing unit (CP)
U) or an image processor arithmetic logic unit (IPAL)
U) and the like. In these active elements, the operation speed and signal processing speed are increasing at a rapid pace, and electric signals propagating through high-speed electronic circuits are accompanied by abrupt changes in voltage and current. It is the main cause of noise.

On the other hand, electronic components and electronic devices are progressing at a rapid pace, as it is not known that the flow of weight reduction, thinning, and miniaturization will stop. Along with that, the degree of integration of semiconductor devices,
The mounting density of electronic components on printed wiring boards has been remarkably increased. Therefore, electronic elements and signal lines that are densely integrated or mounted are extremely close to each other, and high-frequency radiation noise is likely to be induced along with the above-described increase in signal processing speed.

[0004] As is well known, a semiconductor bare chip having an integrated circuit formed on a surface is obtained by cutting a semiconductor wafer.

FIG. 8 shows a conventional semiconductor wafer. FIG.
2A is a plan view, FIG. 2B is an enlarged view of a portion surrounded by a circle in FIG. 2A, and FIG. 2C is a cross-sectional view taken along line AA ′ in FIG.

As shown in FIG. 8, a semiconductor bare chip is
For example, it is made by using well-known wafer manufacturing technology. The semiconductor wafer 10 'has a plurality of chip portions 1 each having an integrated circuit (not shown) formed on each surface.
0a ', each of which has a chip electrode (electrode pad) 11 formed thereon. Although the illustrated chip electrode 11 is formed along the outer peripheral edge of each chip portion 10a ', the chip electrode may be formed in the active region. In general, an aluminum-based alloy is used as a metal forming the chip electrode 11. The semiconductor wafer 10 'then comprises a passivation film 12. More specifically, the entire surface of the semiconductor wafer 10 ′ is covered with the passivation film 12. The passivation film 12 is made of, for example, a polyimide, a silicon nitride film, or a silicon oxide film by using a well-known technique such as spin coating. The thickness of the passivation film 12 is 2
0 μm or less. After the formation of the passivation film 11, the chip electrode 11 is exposed to the atmosphere by exposing the semiconductor wafer 10 'and etching it. As a result, the passivation film 12 has the semiconductor wafer 10 ′ except for the position where the chip electrode 11 is formed.
Cover the entire surface. The chip portions 10a 'are then separated from each other into individual semiconductor bare chips along scribe lines 13. This separation is performed by a well-known dicing technique using a dicing saw. This chip portion 10a 'is a semiconductor bare chip 17'.

[0007]

In such a semiconductor bare chip, a problem of unnecessary radiation from a power supply line has been pointed out, and measures such as inserting a lumped constant component such as a decoupling capacitor into the power supply line have been taken. I have.

However, in a semiconductor bare chip in which a high-speed integrated circuit is formed on the surface, since a generated noise includes a harmonic component, a signal path behaves like a distributed constant. A situation has arisen in which noise countermeasures based on a conventional lumped constant circuit do not work.

Accordingly, an object of the present invention is to effectively reduce unnecessary radiation generated from an integrated circuit in a semiconductor bare chip and a semiconductor wafer having such a high-speed integrated circuit formed on the surface. To provide a semiconductor bare chip and a semiconductor wafer.

[0010]

The present inventors have previously invented a composite magnetic material having a large magnetic loss at a high frequency and arranged it near an unnecessary radiation source, so that the above-described semiconductor element or electronic device can be obtained. A method has been found for effectively suppressing unnecessary radiation generated from a circuit or the like. Recent studies have shown that the mechanism of the unwanted radiation attenuation using such magnetic loss is due to the addition of an equivalent resistance component to the electronic circuit that is the unwanted radiation source. . Here, the magnitude of the equivalent resistance component depends on the magnitude of the magnetic loss term μ ″ of the magnetic material. More specifically, the magnitude of the resistance component equivalently inserted into the electronic circuit is: When the area of the magnetic body is constant, μ ″ is substantially proportional to the thickness of the magnetic body.
Therefore, in order to obtain a desired unnecessary radiation attenuation with a smaller or thinner magnetic body, a larger μ ″ is required. For example, a magnetic loss body is used in a minute area such as the inside of a mold of a semiconductor device. In order to take measures against unnecessary radiation, the magnetic loss term μ ″ needs to be an extremely large value, and a magnetic material having a much larger μ ″ than conventional magnetic loss materials has been required. Has been made in view of the current situation.

In the course of research on a soft magnetic material by a sputtering method or a vapor deposition method, the present inventors have developed a method of forming a granular magnetic material in which minute magnetic metal particles are homogeneously dispersed in a non-magnetic material such as ceramics. Focusing on the excellent permeability characteristics, we studied the microstructure of magnetic metal particles and the surrounding nonmagnetic material, and as a result, when the concentration of magnetic metal particles in the granular magnetic material is in a specific range, in the high frequency region It has been found that excellent magnetic loss characteristics can be obtained. M-
Many studies have been made on a granular magnetic material having a composition of XY (M is a magnetic metal element, Y is O or any of N and F, and X is an element other than M and Y), and many studies have been made so far. Is known to have a large saturation magnetization. In the M-XY granular magnetic material, the magnitude of the saturation magnetization depends on the volume ratio occupied by the M component. Therefore, in order to obtain a large saturation magnetization, it is necessary to increase the ratio of the M component. Therefore, in a general use such as a magnetic core of a high-frequency inductor element or a transformer, the ratio of the M component in the M-XY granular magnetic material is substantially equal to the saturation magnetization of the bulk metal magnetic material including only the M component. It is limited to a range where a saturation magnetization of 80% or more can be obtained.

The present inventors have proposed a granular magnetic material having a composition of M-XY (M is a magnetic metal element, Y is O or any of N and F, and X is an element other than M and Y). As a result of examining the ratio of the components in a wide range, it was found that in any composition system, when the magnetic metal M was in a specific concentration range, a large magnetic loss was exhibited in a high frequency region, and the present invention was reached.

The highest region where the ratio of the M component shows a saturation magnetization of 80% or more with respect to the saturation magnetization of the bulk metal magnetic material composed of only the M component is a high saturation magnetization which has been actively studied conventionally. And is a region of a low loss MXY granular magnetic material. Since the material in this region has a large real part magnetic permeability (μ ′) and a large saturation magnetization, it is used for a high-frequency micro magnetic device such as the above-described high-frequency inductor. , The electrical resistivity is small. Therefore, when the film thickness is increased, the magnetic permeability at a high frequency deteriorates due to the occurrence of eddy current loss in a high frequency region, so that it is not suitable for a relatively thick magnetic film used for noise suppression. The region showing the saturation magnetization where the ratio of the M component is 80% or less and 60% or more of the saturation magnetization of the bulk metal magnetic material composed of only the M component is because the electric resistivity is relatively large, approximately 100 μΩ · cm or more. Even if the thickness of the material is about several μm, the loss due to the eddy current is small, and the magnetic loss is almost a loss due to natural resonance. Therefore, since the frequency dispersion width of the magnetic loss term μ ″ becomes narrow, it is suitable for noise suppression (high-frequency current suppression) in a narrow band frequency range.
60 of saturation magnetization of bulk metal magnetic material consisting only of M component
%, The region exhibiting a saturation magnetization of 35% or more has an electric resistivity of approximately 500 μΩ · cm or more, so that the loss due to the eddy current is extremely small and the magnetic interaction between the M components becomes small. Then, the thermal disturbance of the spin becomes large, and the frequency at which the natural resonance occurs fluctuates, and as a result, the magnetic loss term μ ″ shows a large value in a wide range. Suitable for suppression.

On the other hand, a region where the ratio of the M component is smaller than the region of the present invention becomes superparamagnetic because almost no magnetic interaction occurs between the M components.

A guide for designing a material when a high-frequency current is suppressed by disposing a magnetic loss material in the immediate vicinity of an electronic circuit is given by a product μ ″ · δ of a magnetic loss term μ ″ and a thickness δ of the magnetic loss material. Therefore, in order to obtain effective suppression of a high-frequency current having a frequency of several hundred MHz, it is necessary to roughly set μ ″ · δ ≧ 1000 (μ
m) is required. Therefore, a magnetic loss material of μ ″ = 1000 requires a thickness of 1 μm or more, and a material having low electric resistance that easily causes eddy current loss is not preferable. In the composition system of the present invention, the ratio of the M component shows saturation magnetization in which the saturation magnetization is 80% or less of the saturation magnetization of the bulk metal magnetic material composed of only the M component, and a region where superparamagnetism does not appear, that is, only the M component. A region showing 35% or more of the saturation magnetization of the bulk metal magnetic material is suitable.

The present invention is an application of a magnetic loss film such as the above-mentioned granular magnetic thin film. here,
"Granular magnetic thin film" means several tens of MHz to several GHz.
A magnetic thin film that exhibits a very large magnetic loss at high frequencies and has a fine structure with a fine grain size of several nanometers to several tens of nanometers. In this technical field, it is also called a “microcrystalline thin film”. being called.

That is, according to the present invention, in a semiconductor bare chip having an integrated circuit formed on the front surface, a semiconductor bare chip characterized by providing a magnetic loss film on the back surface of the semiconductor bare chip is obtained.

Further, according to the present invention, there is provided a semiconductor wafer having an integrated circuit formed on a front surface, wherein a magnetic loss film is provided on a back surface of the semiconductor wafer.

In the semiconductor bare chip or semiconductor wafer, a granular magnetic thin film can be used as the magnetic loss film. The granular magnetic thin film may be, for example, a sputtered film formed by a sputtering method or a vapor-deposited film formed by a vapor-deposition method.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

A semiconductor wafer according to one embodiment of the present invention will be described with reference to FIG. In FIG.
(A) is a plan view, (b) is an enlarged view of a circled part of (a), and (c) is a cross-sectional view taken along line BB 'of (b).

The semiconductor wafer 10 shown has the same configuration as the semiconductor wafer 10 'shown in FIG. 8, except that the back surface is covered with a magnetic loss film 15. Components having the same functions as those shown in FIG. 8 are denoted by the same reference numerals, and descriptions thereof will be omitted to avoid redundant description.

The chip portion 10a is a scribe line 13
Along with individual semiconductor bare chips.
This separation is performed by a well-known dicing technique using a dicing saw. This chip portion 10a is a semiconductor bare chip 17.

Here, as the magnetic loss film 15, the present inventors have already filed an application (20 filed on Jan. 24, 2000).
A granular magnetic thin film (hereinafter, referred to as “prior application”) of Japanese Patent Application No. 52507 (2000) can be used.
Such a granular magnetic thin film can be manufactured by a sputtering method, a reactive sputtering method, or an evaporation method as described in the specification of the prior application. In other words, the granular magnetic thin film may be a sputtered film formed by a sputtering method or a reactive sputtering method,
Alternatively, a vapor deposition film formed by a vapor deposition method may be used. When manufacturing a granular magnetic thin film, actually, the sputtered film or the deposited film is heat-treated in a vacuum magnetic field at a predetermined temperature for a predetermined time.

The detailed manufacturing method of the granular magnetic thin film is described in detail in the above-mentioned prior application, so please refer to it.

The granular magnetic thin film thus formed exhibits a very large magnetic loss at a high frequency of several tens of MHz to several GHz even if the thickness is small (for example, 2.0 μm or less). The inventors have already confirmed by experiments.

The present inventors have found that the granular magnetic thin film according to the present invention, which exhibits μ ″ dispersion in the quasi-microwave band,
Experiments have already confirmed that a high-frequency current suppression effect equivalent to that of a composite magnetic sheet having a thickness of about 500 times is exhibited. Therefore, it can be said that the granular magnetic thin film according to the present invention is promising as a material used for EMI measures such as a semiconductor integrated device that operates at a high-speed clock near 1 GHz.

Next, referring to FIG. 2, a sputtering manufacturing apparatus will be described as an example of an apparatus for manufacturing a granular magnetic thin film as the magnetic loss film 15. This sputtering manufacturing apparatus includes a vacuum container (chamber) 18,
A gas supply device 22 and a vacuum pump 23 are connected to the chamber 18. In the champer 18, a substrate 23 and a target 25 are arranged to face each other with a shutter 21 interposed therebetween. The target 25 is composed of the components X, Y, or the components M in which the chips 24 composed of the components X are arranged at predetermined intervals. Chip 24 and target 25
Is connected to one end of an RF power source 26,
The other end of the power supply 26 is grounded.

Next, an example of manufacturing a granular magnetic thin film (sample 1) manufactured using the sputtering manufacturing apparatus having such a configuration will be described.

First, the diameter φ of the target 25 = 10
Size of chip 24 on 0 mm Fe disk = 5 m long
A total of 120 Al ₂ O ₃ chips of mx 5 mm wide x 2 mm thick were provided. Then, the vacuum container 1 is
While keeping the inside of the chamber 8 at a degree of vacuum of about 1.33 × 10 ⁻⁴ Pa, the gas supply device 22 puts A into the vacuum vessel 18.
By supplying r gas, the inside of the vacuum vessel 18 is brought into an Ar gas atmosphere. In this state, high-frequency power is supplied from the RF power supply 26. Under such conditions,
A magnetic thin film was formed on a glass substrate serving as the substrate 23 by a sputtering method. Then, the obtained magnetic thin film was further
By performing a heat treatment in a vacuum magnetic field at a temperature of 2 ° C. for 2 hours, the above-mentioned sample 1 of the granular magnetic thin film was obtained.

When the sample 1 thus obtained was subjected to fluorescent X-ray analysis, the composition of the film was Fe ₇₂ Al ₁₁ O ₁₇ , the film thickness was 2.0 μm, and the DC resistivity was 530 μΩ · c.
m. Further, the anisotropic magnetic field H _k of sample 1 18 (O
a e), the saturation magnetization M _s was 1.68T (tesla). Further, even if the magnetic loss term is “μ” on the complex magnetic permeability characteristic of the sample 1, a frequency band in which 50% or more of the maximum value “μ” _{max is} equivalent to a half width μ corresponding to a half width standardized by its center frequency. ₅₀ was 148%. The ratio {M _s (M _s (M _s (M)) of the saturation magnetization M _s (M-X-Y) of the sample 1 to the saturation magnetization M _s (M) of the metal magnetic material composed only of the composition M was used. MX-
Y) / M _s (M)} × 100% was 72.2%.

In order to verify the magnetic loss characteristics of the sample 1, the magnetic permeability μ characteristics (μ-f characteristics) with respect to the frequency f were examined as follows. That is, the measurement of the μ-f characteristic is as follows.
This was performed by inserting the sample 1 into the detection coil processed into a strip shape and measuring the impedance while applying a bias magnetic field. Based on this result, the frequency characteristic (μ ″ -f characteristic) of the magnetic loss term μ ″ was obtained.

FIG. 3 is a graph showing the μ ″ -f characteristic of the sample 1. In FIG. 3, the horizontal axis represents the frequency f (MHz),
The vertical axis represents the magnetic loss term μ ″. From FIG. 3, the magnetic loss term μ ″ of the sample 1 has a slightly steep variance, a very large peak value, and a resonance frequency of 70 μm.
It can be seen that it is as high as around 0 MHz.

Further, using a high-frequency electromagnetic interference suppressing effect measuring device 30 as shown in FIG. However, the high-frequency electromagnetic interference suppression effect measuring device 30 connects the microstrip line 31 and a network analyzer (HP8753D) (not shown) to both sides in the longitudinal direction of the microstrip line 31 having a line length of 75 mm and a characteristic impedance Zc = 50Ω. And the magnetic sample 33 is arranged just above the sample arrangement portion 31a of the microstrip line 31 so that the transmission characteristics S between the two ports can be improved.
₂₁ can be measured.

This high frequency electromagnetic interference suppression effect measuring device 30
In the case where the high-frequency current is suppressed by applying an equivalent resistance component to the transmission line in which the magnetic loss material is disposed immediately adjacent to the transmission line as in the configuration of This is considered to be substantially proportional to the product μ ″ · δ of the size of the term μ ″ and the thickness δ of the magnetic body.

FIG. 5 shows a high-frequency current suppression effect measuring device 30.
The transmission characteristics S ₂₁ (d) for the frequency f (MHz) showing the result of measuring the high-frequency current suppression effect of the sample magnetic material by
B).

As shown in FIG. 5, the transmission characteristic S ₂₁ of the sample 1 is 10
It can be seen that the frequency decreases from 0 MHz or higher, reaches a minimum value of -10 dB near 2 GHz, and then increases. This result, transmission characteristics S ₂₁ magnetic loss term μ of the magnetic material "as well as dependent on the dispersion of the product μ the size of the inhibitory effect was described above"
・ It turns out that it depends on δ.

By the way, as shown in FIG. 6, it is assumed that the magnetic material such as the sample 1 has a dimension 1 and is configured as a distributed constant line having a magnetic permeability μ and a dielectric constant ε. be able to. In this case, as an equivalent circuit constant per unit length (Δl), a unit inductance ΔL, a unit resistance ΔR in a form of series connection, a unit capacitance ΔC interposed between these and a ground line, a unit ground It has a conductance ΔG. When converted them to sample dimensions based on the transmission characteristic S _21, sample 1, the inductance L, resistance R, and the capacitance C as the equivalent circuit constant,
It can be regarded as an equivalent circuit having the ground conductance G.

As described in the study of the effect of suppressing high-frequency electromagnetic interference, when the antenna is arranged on the microstrip line 31 made of a magnetic material, the change in the transmission characteristic S21 is mainly in series with the inductance L in the equivalent circuit. Added resistance R
Therefore, the value of the resistor R can be obtained and its frequency dependence can be examined.

[0040] Figure 7, the transmission characteristic S ₂₁ shown in FIG. 5 were calculated based on the value of the resistor R to be added in series to the inductance L of the equivalent circuit shown in FIG. 6, the frequency f (MHz 4) shows the characteristics of the resistance value R (Ω) with respect to the above-mentioned values.

From FIG. 7, it can be seen that the resistance value R monotonically increases in the quasi-microwave band region, and becomes several tens of ohms at 3 GHz, and its frequency dependence shows the frequency dispersion of the magnetic loss term μ ″ having a maximum near 1 GHz. It can be understood that this is a result of reflecting that the ratio of the sample size to the wavelength monotonically increases in addition to the above-mentioned product μ ″ · δ.

From the above results, the sample exhibiting the magnetic loss term μ ″ dispersion in the quasi-microwave band exhibits the same high-frequency current suppressing effect as the composite magnetic sheet having a thickness of about 500 times,
It can be said that it is effective to apply to measures for suppressing high-frequency electromagnetic interference at GHz.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications and changes can be made without departing from the spirit of the present invention.
Of course, deformation is possible. For example, in the embodiment of the present invention, only a manufacturing example by a sputtering method has been described as a method of manufacturing a granular magnetic thin film, but other manufacturing methods such as a vacuum evaporation method, an ion beam evaporation method, and a gas deposition method may be used. The manufacturing method is not limited as long as the method can uniformly realize the magnetic loss film according to the present invention.

In the embodiment of the present invention, the heat treatment is performed in a vacuum magnetic field after the film is formed. However, any composition or film forming method that can obtain the performance of the present invention with an as-deposited film can be used. For example, the present invention is not limited to the post-film formation processing described in the embodiment.

Further, in the above-described embodiment, only an example in which the back surface of the semiconductor bare chip 17 (semiconductor wafer 10) is directly covered with the magnetic loss film 15 is described. The formed adhesive tape is connected to the semiconductor bare chip 17 (semiconductor wafer 1).
Needless to say, it may be attached to the back surface of 0). Further, in the above embodiment, the case where the magnetic loss film 15 is a granular magnetic thin film has been described as an example.
The film is not limited thereto, and any film may be used as long as it exhibits a very large magnetic loss at a high frequency of several tens MHz to several GHz.

[0046]

As described above, according to the present invention, since the back surface of the semiconductor bare chip or the semiconductor wafer is covered with the magnetic loss film, unnecessary radiation generated from the integrated circuit formed on the front surface can be effectively prevented. It becomes possible to reduce.

[Brief description of the drawings]

FIGS. 1A and 1B are views showing a semiconductor wafer according to an embodiment of the present invention, wherein FIG. 1A is a plan view, FIG. 1B is an enlarged view of a circled portion of FIG. It is sectional drawing cut | disconnected by the BB 'line of FIG.

FIG. 2 is a schematic cross-sectional view of a sample manufacturing apparatus using a sputtering method.

FIG. 3 is a diagram illustrating an example of frequency dependence of a magnetic loss term μ ″ according to a sample 1 as a magnetic loss film.

FIG. 4 is a perspective view showing a measurement system for observing the suppression effect of a high-frequency current suppressor made of a sample 1 as a magnetic loss film.

FIG. 5 shows the transmission characteristics of sample 1 as a magnetic loss film (S ₂₁ )
FIG. 4 is a diagram showing frequency characteristics of the multiplexed signal;

FIG. 6 is a diagram showing an equivalent circuit of a magnetic body that is a magnetic loss film.

FIG. 7: Transmission characteristics of sample 1 as a magnetic loss film (S ₂₁ )
FIG. 9 is a diagram illustrating frequency characteristics of a resistance value R calculated by the calculation.

8A and 8B are views showing a conventional semiconductor wafer, wherein FIG. 8A is a plan view, FIG. 8B is an enlarged view of a circled portion of FIG.
(C) is a sectional view taken along line AA 'of (b).

[Explanation of symbols]

 Reference Signs List 10 semiconductor wafer 11 chip electrode 12 passivation film 13 scribe line 15 magnetic loss film (granular magnetic thin film)

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yoshio Awakura 7-1 Koriyama, Taishiro-ku, Sendai-shi, Miyagi F-term (reference) 5F038 BH10 BH19 EZ20

Claims (8)

[Claims] 1. A semiconductor bare chip having an integrated circuit formed on a front surface thereof, wherein a magnetic loss film is provided on a back surface of the semiconductor bare chip. 2. The semiconductor bare chip according to claim 1, wherein said magnetic loss film is a granular magnetic thin film. 3. The semiconductor bare chip according to claim 2, wherein said granular magnetic thin film is a sputtered film formed by a sputtering method. 4. The semiconductor bare chip according to claim 2, wherein said granular magnetic thin film is an evaporation film formed by an evaporation method. 5. A semiconductor wafer having an integrated circuit formed on a front surface thereof, wherein a magnetic loss film is provided on a back surface of the semiconductor wafer. 6. The semiconductor wafer according to claim 5, wherein said magnetic loss film is a granular magnetic thin film. 7. The semiconductor wafer according to claim 6, wherein said granular magnetic thin film is a sputtered film formed by a sputtering method. 8. The semiconductor wafer according to claim 6, wherein said granular magnetic thin film is an evaporation film formed by an evaporation method.