JPH03235333A - Semiconductor substrate having improved getter effect, semiconductor device using the substrate and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent occurrence of dust in manufacture and to maintain a high getter effect till a final process by a method wherein a polycrystalline silicon film having a specified thickness or larger is formed at least on the rear side of a semiconductor substrate. CONSTITUTION:A polycrystalline silicon film 4 having a film thickness of 0.8mum or larger is formed continuously on the rear side B and the lateral wall surface 2C of a semiconductor substrate l. A getter effect is obtained by utilizing a crystal defect in this film 4. When the film 4 has the thickness of 0.8mum or above, it remains on the rear side of the substrate 1 till a final process even when a thermal oxidation processing is conducted in manufacturing processes of a semiconductor device. According to this constitution, the occurrence of dust in manufacture is prevented and a high getter effect can be maintained till the final process.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates generally to semiconductor substrates, and more particularly to semiconductor substrates improved to have enhanced getter effects.

The present invention also relates to a semiconductor device using such a semiconductor substrate and a method for manufacturing the same.

[Prior Art] Semiconductor devices are extremely sensitive to unintentional impurities, so techniques for improving device characteristics through gettering are important. Gettering refers to the removal of heavy metals such as (:u, Fe5Au, etc.) from the electrically active region of a semiconductor device.

FIGS. 9A and 9B are process diagrams showing a conventional gettering method, and are shown in cross-sectional views.

Referring to FIG. 9A, a disk-shaped semiconductor substrate 1 having a main surface 2A and a back surface 2B is prepared.

Semiconductor substrate 1 is made, for example, by slicing silicon single crystal. Next, referring to FIG. 9B,
A mechanically strained layer 3 is formed on the back surface 2B of the semiconductor substrate 1 by sandblasting. The sandblasting process is performed by hitting the back surface 2B of the semiconductor substrate 1 with quartz powder.

Next, a semiconductor device is obtained by forming a circuit on main surface 2A of semiconductor substrate 1.

Incidentally, in the process of forming a circuit on the main surface 2A, the semiconductor substrate 1 is subjected to various heat treatments. During this heat treatment, the semiconductor substrate 1 is contaminated with heavy metals. However, the heavy metal introduced into the semiconductor substrate 1 is captured and confined within the mechanically strained layer 3 due to the getter effect. As a result, even if the semiconductor substrate 1 is contaminated with heavy metals, the main surface 2A on which a circuit is formed will not be adversely affected by the heavy metals, and as a result, the characteristics and yield of the semiconductor device will be improved.

[Problems to be Solved by the Invention] The conventional gettering method was configured as described above. Therefore, with reference to FIG. 9B, when unevenness is formed on the back surface 2B of the semiconductor substrate 1 and thereby the mechanically strained layer 3 is formed, there is a situation where the material peels off from the back surface 2B in the form of minute pieces. was occurring. These peeled off microscopic pieces turn into dust and have a negative impact on the semiconductor manufacturing process.
It was a problem.

Furthermore, during heat treatment during the manufacturing process of a semiconductor device, the strain in the mechanically strained layer 3 is relaxed and its gettering ability is lost.

That is, FIG. 10A (before heat treatment) and FIG. 10B (
After heat treatment), stacking faults 4a, which are a type of crystal defect, grown from mechanically strained layer 3 formed on back surface 2B of semiconductor substrate 1 are annealed out and disappear by the heat treatment process. Since the stacking fault 4 is a getter source,
The disappearance of the stacking fault 4a results in the loss of gettering ability,
That was a problem.

In addition, as prior art related to this invention, Japanese Patent Application Laid-Open No. 58
JP-A-138035 discloses a semiconductor device formed using a semiconductor substrate having a polycrystalline silicon layer on the back surface. According to this prior art, the semiconductor substrate has a getter effect because it has a polycrystalline silicon layer on the back surface. However, the getter effect disappears during the semiconductor device manufacturing process because the semiconductor substrate is bent or the polycrystalline silicon film or silicon oxide is consumed during the semiconductor device manufacturing process. There was a problem.

In order to solve the above-mentioned problems, the present applicant has already disclosed in Japanese Unexamined Patent Publication No. 64-53552 a semiconductor substrate having a main surface and a back surface, and a semiconductor substrate provided on at least the back surface of the semiconductor substrate. The present invention discloses a semiconductor substrate comprising a polycrystalline silicon film, in which the concentration of oxygen contained in the semiconductor substrate is controlled to 14×10 17 atoms/cm′ or less according to the old ASTM standard. The present invention is a further improvement of this invention.

The object of the present invention is to have a high getter effect, to obtain it without generating dust during manufacturing, and to obtain it even when subjected to heat treatment.
An object of the present invention is to provide a semiconductor substrate whose getter effect is maintained until the final process of manufacturing a semiconductor device.

Still another object of the present invention is to provide a semiconductor device made using such a semiconductor substrate and a method for manufacturing the same.

[Means for Solving the Problems] In order to achieve the above object, a semiconductor substrate according to a first aspect of the present invention includes a semiconductor substrate having a main surface and a back surface, and a semiconductor substrate provided on at least the back surface of the semiconductor substrate. A polycrystalline silicon film.

The polycrystalline silicon film has a thickness of 0.8 μm or more.

According to a preferred embodiment of the present invention, the concentration of oxygen contained in the semiconductor substrate is 15% according to the old ASTM standard.
．． It is controlled to below 0XIO"atoms/cm'.

A semiconductor device according to a second aspect of the invention includes a semiconductor substrate having a main surface and a back surface, a polycrystalline silicon film provided on at least the back surface of the semiconductor substrate, and an element provided on the main surface of the semiconductor substrate. It is equipped with. The polycrystalline silicon film has a thickness of 0.184 m or more.

According to a preferred embodiment of the present invention, the concentration of oxygen contained in the semiconductor substrate is 15% according to the old ASTM standard.
．． It is controlled to below 0XIO"atoms/cm3.

In the method for manufacturing a semiconductor device according to the third aspect of the invention, first, a semiconductor substrate having a main surface and a back surface is prepared. Next, on at least the back surface of the semiconductor substrate,
A polycrystalline silicon film having a thickness of 0.5 μm or more is formed. Thereafter, elements are formed on the main surface of the semiconductor substrate.

[Operation] According to the first aspect of the invention, since the semiconductor substrate is provided with a polycrystalline silicon film on at least the back surface, a getter effect can be obtained by utilizing crystal defects in the polycrystalline silicon film. . In addition, the polycrystalline silicon film is 0.8
The polycrystalline silicon film remains on the back surface of the semiconductor substrate until the final step of the semiconductor manufacturing process, and its gettering ability is limited by the semiconductor manufacturing process. It is maintained until the final process. In addition, since the semiconductor substrate is not obtained by a method of forming a mechanically strained layer by forming unevenness on the back surface of the semiconductor substrate, dust that deteriorates semiconductor characteristics does not adhere to the semiconductor substrate. I haven't.

According to the second aspect of the invention, since the semiconductor device is formed using the semiconductor substrate having the above characteristics, a semiconductor device with good semiconductor characteristics can be obtained.

According to the third aspect of the invention, since a semiconductor device is formed using a semiconductor substrate having the above characteristics, dust does not adhere to the semiconductor substrate. As a result, a semiconductor device with excellent semiconductor characteristics can be obtained at a high yield.

[Example code] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a semiconductor substrate according to an embodiment of the present invention. The semiconductor substrate 1 has two main surfaces and a back surface 2B. The main surface 2A and the back surface 2B have a plane orientation (or
ientation) This is the surface of 100〉. The back surface 2B and side wall surface 2C of the semiconductor substrate 1 are coated with 0.8-2.
A polycrystalline silicon film 4 having a thickness of 0 μm is continuously formed. Since the polycrystalline silicon film 4 has crystal defects, a getter effect can be obtained by utilizing these crystal defects.

When the plane orientation of the semiconductor substrate 1 is <100>, the main surface 2
When a MO3 field effect transistor is formed in A, the characteristics of the gate oxide film are improved. Note that it is also possible to make the surface orientation of the semiconductor substrate 1 <111>, and in this case, the breakdown voltage of the semiconductor device is improved.

The lower the oxygen concentration in the semiconductor substrate 1, the better in order to improve the characteristics of the semiconductor device to be formed.
8. M standard. OX1017atoms/cm3
Above, 15. It is preferable to control OXIO to 17 atoms/Cm3 or less. The reason for this will be explained with reference to FIG. Oxygen concentration is 8゜0XIO”at oms/
If it is less than cm 3 , the semiconductor substrate 1 will be curved due to heat treatment during the manufacturing process of the semiconductor device. Further, even if the oxygen concentration exceeds 15° OX 1017 atoms/Cm', the semiconductor substrate 1 will curve. Therefore, it is preferable that the oxygen concentration be controlled within the above range.

Further, with reference to FIG. 1, when a semiconductor device is formed using the semiconductor substrate 1 in which the polycrystalline silicon film 4 is formed on the side wall surface 2C of the semiconductor substrate 1, slip lines, which are crystal defects, are formed on the semiconductor substrate 1. This prevents this from occurring on the outer periphery of the area.

Note that the reason why the thickness of the polycrystalline silicon film 4 is controlled to be 0.8 to 2.0 μm will be described later.

Next, a method for manufacturing a semiconductor substrate according to the present invention will be described with reference to FIGS. 3A to 30.

Referring to FIG. 3A, a disk-shaped semiconductor substrate 1 having a main surface 2A and a back surface 2B is prepared.

Semiconductor substrate 1 is made, for example, by slicing silicon single crystal. Note that the oxygen concentration in the semiconductor substrate 1 is controlled by the conditions for pulling the ingot, which is a silicon single crystal.

Next, referring to FIG. 3B, polycrystalline silicon film 4 is deposited over the entire surface of semiconductor substrate 1 by chemical vapor deposition.

Thereafter, with reference to FIG. 3C, main surface 2 of semiconductor substrate 1 is
The polycrystalline silicon film 4 on the side A is removed by mirror polishing. As a result, a semiconductor substrate with an enhanced getter effect as shown in FIG. 1 can be obtained.

According to this method, a polycrystalline silicon film 4 that provides a getter effect is formed by chemical vapor deposition.

Therefore, the situation where dust adheres to the semiconductor substrate does not occur as observed in the conventional sandblasting method. As a result, when a semiconductor device is manufactured using this semiconductor substrate, the semiconductor device has good electrical characteristics.
The effect is that a high yield can be obtained.

Next, an appropriate range of oxygen concentration in the semiconductor substrate will be explained.

FIG. 4 is a diagram showing the relationship between the oxygen concentration in the semiconductor substrate and the density of stacking faults on the surface of the semiconductor substrate. Straight line (
1) shows the results of an experiment conducted using a semiconductor substrate according to the present invention with a polycrystalline silicon film on the back surface, and straight line (2) shows the results of an experiment conducted using a conventional semiconductor substrate with a sandblasting process on the back surface. The results of the experiments conducted are shown.

From Figure 4, the following things became clear. That is, in the case of a conventional semiconductor substrate subjected to sandblasting, the density of stacking faults on the surface of the semiconductor substrate becomes slightly higher as the oxygen concentration decreases.

On the other hand, in the case of a semiconductor substrate having a polycrystalline silicon film on the back surface, the lower the oxygen concentration, the lower the density of stacking faults. Further, the oxygen concentration of the semiconductor substrate is 15. OXIO1
When it becomes less than 7atoms/cm3 (former ASTM),
Compared to semiconductor substrates subjected to conventional sandblasting,
The semiconductor substrate according to the present invention has lower stacking and defect densities. From the above results, in the semiconductor substrate according to the present invention, the oxygen concentration is 15.0×10”atoms/cm.
It is preferable to set it to 3 (old ASTM) or less. The lower limit of oxygen concentration is 8. OXIO17atoms/cm' (old AS
TM). This is because, as shown in FIG. 2, when the oxygen concentration falls below this value, the semiconductor substrate will curve.

Next, the preferred thickness of the polycrystalline silicon film will be explained. Since the polycrystalline silicon film is a getter source, the polycrystalline silicon film must remain on the back surface of the semiconductor substrate until the end of the semiconductor device manufacturing process. Therefore, in order to find out how thick the polycrystalline silicon film is required to remain on the back surface of the semiconductor substrate until the end of the semiconductor device manufacturing process, we tested various types of polycrystalline silicon films. Film thickness (1.5 μm, 1.0 μm, 0°6 μm
A semiconductor substrate having one of three film thicknesses (m) was prepared. These semiconductor substrates were then passed through the entire process of manufacturing semiconductor devices.

FIG. 5 is an X-ray analysis diagram showing a polycrystalline silicon film present on the back surface of a semiconductor substrate that has gone through all the processes of manufacturing a semiconductor device. Curve (10) initially
The figure shows the case of a semiconductor substrate on which a polycrystalline silicon film was deposited to a thickness of 1.5 μm. Curve (11
) initially had a polycrystalline silicon film of 1.0 μm on its back surface.
The figure shows the case of a semiconductor substrate deposited with a film thickness of .

Curve (12) shows the case of a semiconductor substrate on which a polycrystalline silicon film was initially deposited to a thickness of 1.5 μm on its back surface. In the figure, the peak indicated by reference number 13 is the X-ray analysis peak of the <111> crystal of polycrystalline silicon, and the peak indicated by reference number 14 is the X-ray analysis peak of the <100> crystal of the semiconductor substrate.

In general, a polycrystalline silicon film deposited on the back surface of a semiconductor substrate becomes silicon oxide from its surface and is consumed over time during a thermal oxidation treatment step and an oxide film removal step in the manufacturing process of a semiconductor device. Referring to curve (12) in FIG. 5, whether the film thickness of the polycrystalline silicon film is 0.
In the case where the thickness is 6 μm, after the semiconductor substrate passes through the entire process of manufacturing a semiconductor device, no polycrystalline silicon film remains on the back surface of the semiconductor substrate. This is because the peak 13 of polycrystalline silicon has disappeared. In other words, this means that the thickness of the polycrystalline silicon film is 0.6μ.
If it is m, it indicates that the getter effect disappears at a certain point in the entire process of manufacturing the semiconductor device.

On the other hand, the thickness of the polycrystalline silicon film is 1.0 μm or 1 μm.
．． In the case of 5 μm, curves (10) and (
11), there is a peak 13 of polycrystalline silicon. This means that the film thickness is 1.0 μm or 1.5 μm.
If it is .mu.m, it means that the polycrystalline silicon film, which is a getter source, remains on the back surface of the semiconductor substrate. That is, if the thickness of the polycrystalline silicon film formed on the back surface of the semiconductor substrate is 1.0 μm or more, the gettering ability is reliably maintained until the final step of the semiconductor device manufacturing process.

Additionally, in another experiment, when a semiconductor substrate with a polycrystalline silicon film on the back side was passed through the entire process of manufacturing a semiconductor device, the polycrystalline silicon film disappeared as an oxide film by a thickness of 0.8 μm. is empirically confirmed. Therefore, the preferred minimum thickness of the polycrystalline silicon film is 0.8 μm. Further, the preferred maximum thickness of polycrystalline silicon is 2.0 μm, because it has been empirically recognized that if the film thickness exceeds this value, the semiconductor substrate will curve.

Next, application examples of the semiconductor substrate according to the present invention will be described.

6A and 6B are cross-sectional views showing the process of manufacturing a stacked capacitor cell, which is a type of dynamic RAM, using the semiconductor substrate according to the present invention.

Referring to FIG. 6A, polycrystalline silicon film 4 is formed on back surface 2B of semiconductor substrate 1. Referring to FIG. Next, a transistor and a capacitor are formed on the main surface of semiconductor substrate 1. The transistor includes a gate electrode 5 formed on the main surface of semiconductor substrate 1 and a pair of source/drain regions 6.6 formed on the main surface of semiconductor substrate 1. The capacitor includes a storage node 7 provided in electrical contact with one source/drain region 6, a dielectric pair film 8 provided on the storage node 7, and a dielectric pair film 8 provided on the dielectric pair film 8. and a select plate electrode 9.

After that, an interlayer insulating film 10 is formed on the entire surface of the semiconductor substrate,
Next, a contact hole 11 is provided in this interlayer insulating film 10, and a bit line 12 is connected to the other source/drain region 6 through this contact hole 11.

In the entire process of manufacturing semiconductor devices as described above,
Since the crystal defects in the polycrystalline silicon film 4 act as a getter source, a semiconductor device with excellent electrical characteristics can be obtained.

Continuing with reference to FIG. 6B, the back surface 2B of the semiconductor substrate 1
When polycrystalline silicon film 4 is removed from the semiconductor device, the semiconductor device is completed.

Next, we varied the thickness of the polycrystalline silicon film in order to investigate the relationship between the refresh (record-holding operation) defect rate and the thickness of the polycrystalline silicon film formed on the back surface of the semiconductor substrate. Thus, a semiconductor memory device shown in FIG. 6A was manufactured.

FIG. 7 is a diagram showing the relationship between the refresh failure rate and the thickness of the polycrystalline silicon film. In the figure, the horizontal axis indicates the thickness of the polycrystalline silicon film formed on the back surface of the semiconductor substrate. In addition, the vertical axis shows the refresh failure rate of a semiconductor memory device made using a conventional semiconductor substrate (wafer) whose back side has been subjected to sandblasting treatment, which is 100.
3 shows the refresh failure rate of a semiconductor memory device made using a semiconductor substrate (wafer) according to the present invention. In the figure, a straight line 13a indicated by a dotted line indicates the level of the refresh failure rate of a semiconductor memory element manufactured using a conventional semiconductor substrate whose back surface is sandblasted. Note that the black circles indicate cases where the oxygen concentration of the silicon single crystal wafer is 9.0 to 11.
0 [X1017a toms/cm3 (old ASTM
) When using a semiconductor substrate, the white circle indicates that the oxygen concentration of the silicon single crystal wafer is 12.0 to 13.5
17ato/cm3 (former ASTM)] is used.

As is clear from Figure 7, the oxygen concentration in the semiconductor substrate is 13.5X1017 atoms/am3 (former ASTM).
In the case below, the refresh failure rate decreases as the thickness of the polycrystalline silicon film increases. When the thickness of the polycrystalline silicon film exceeds 0.8 μm, the refresh failure rate of the semiconductor memory device made using the semiconductor substrate according to the present invention is lower than that of the semiconductor memory device made using the conventional sandblasting semiconductor substrate. This is lower than the refresh failure rate of semiconductor devices. This result also shows that the thickness of the polycrystalline silicon film is required to be 0.8 μm or more.

Further, when using a conventional semiconductor substrate subjected to sandblasting treatment, a problem of "dust generation" occurred, but when the semiconductor substrate according to the present invention is used, such a problem does not occur. This will be explained in more detail below.

FIGS. 8A and 8B are histograms of the number of dust particles (per semiconductor substrate) attached to the surface of a semiconductor substrate. FIG. 8A shows a case where the semiconductor substrate of the present invention is used, and FIG. 8B shows a case where a conventional semiconductor substrate subjected to sandblasting treatment is used. In these figures, the class value represents the number of dust particles having a size of 0.5 μm or more. The frequency represents the number of semiconductor substrates belonging to the class value. Next, we will explain how to read these tables. For example, at number 2 in FIG. 8A, 0.
It is shown that there were 4 out of 24 semiconductor substrates (n) with 2 to 4 pieces of dust having a size of 5 μm or more.

As is clear from a comparison of FIGS. 8A and 8B, the semiconductor substrate according to the present invention generates less dust than the conventional semiconductor substrate subjected to sandblasting.

In the above embodiment, the semiconductor substrate according to the present invention is used in a dynamic RAM, but the present invention is not limited to this, and may be used in other semiconductor memory devices, and may also have a switching function. The present invention may be used in a semiconductor logic circuit device including a transistor having the following characteristics.

The present invention can be summarized as follows.

(1) The semiconductor substrate according to claim 1, wherein the polycrystalline silicon film has a thickness of 0°8 μm or more.
, 0 μm or less.

(2. The semiconductor substrate according to claim 1, wherein the polycrystalline silicon film is continuously formed on the back surface and side wall surface of the semiconductor substrate.

(3) The semiconductor substrate according to claim 1, wherein the concentration of oxygen contained in the semiconductor substrate is
15 according to TM standard. It is controlled to OX1017atoms/cm3 or less.

(4) The semiconductor substrate according to (3) above, wherein the concentration of oxygen contained in the semiconductor substrate is
8 in TM standard. OxOx1017ato/cm3 or more,
15. It is controlled to OX1017atoms/cm3 or less.

(5) The semiconductor substrate according to claim 1, wherein the semiconductor substrate has a plane orientation of <100>.

(6) The semiconductor device according to claim 2, wherein the polycrystalline silicon film has a thickness of 0. 8 μm or more, 2.
It is 0 μm or less.

(7) The semiconductor device according to claim 2, wherein the concentration of oxygen contained in the semiconductor substrate is
15 according to TM standard. It is controlled to OX1017atoms/Cm3 or less.

(8) In the semiconductor device according to (7) above, the concentration of oxygen contained in the semiconductor substrate is
According to the TM standard, 8. OX1017atoms/cm' or more, 15. It is controlled to OX1017atoms/cm3 or less.

(9) The semiconductor device according to claim 2, wherein the element includes a transistor.

(10) The semiconductor device according to claim 2, wherein the element includes a transistor and a capacitor.

(11) The semiconductor device according to (10) above, wherein the transistor includes an MO5 field effect transistor.

[Effects of the Invention] As explained above, according to the semiconductor substrate according to the first aspect of the present invention, at least the back surface of the semiconductor substrate is provided with a polycrystalline silicon film, so crystal defects in the polycrystalline silicon film can be eliminated. By using this, a getter effect can be obtained. Further, the film thickness of the polycrystalline silicon film was set to 0. Since the thickness is 8 μm or more, even if thermal oxidation treatment is performed in the semiconductor device manufacturing process, the polycrystalline silicon film will remain until the final step of the semiconductor manufacturing process, and the gettering ability will be reduced until the final step of the semiconductor device manufacturing process. will be maintained until Further, according to the present invention, unlike a semiconductor substrate obtained by the conventional sand-plus method, dust that deteriorates electrical characteristics does not adhere to the semiconductor substrate.

According to the second aspect of the invention, since a semiconductor device is formed using a semiconductor substrate having the above-mentioned characteristics, dust does not adhere to the semiconductor substrate, and as a result, the semiconductor substrate has good electrical characteristics. A semiconductor device is obtained.

According to the third aspect of the invention, since a semiconductor device is formed using a semiconductor substrate having the above characteristics, dust does not adhere to the semiconductor substrate. As a result, it is possible to obtain semiconductor devices with excellent electrical characteristics at a high yield.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a semiconductor substrate according to an embodiment of the present invention. FIG. 2 is a diagram showing the relationship between the oxygen concentration in a semiconductor substrate and the warpage of the substrate. FIGS. 3A to 3C are process diagrams showing a method for manufacturing a semiconductor substrate according to an embodiment of the present invention, and are shown in cross-sectional views. FIG. 4 is a diagram showing the relationship between the oxygen concentration in the semiconductor substrate and the density of stacking faults on the surface of the semiconductor substrate. FIG. 5 is an X-ray analysis diagram of the back surface of a semiconductor substrate that has gone through all the processes of manufacturing a semiconductor device. FIGS. 6A and 6B are process diagrams showing a method for manufacturing a semiconductor memory device using a semiconductor substrate according to the present invention, and are shown in cross-sectional views. FIG. 7 is a diagram showing the relationship between the refresh failure rate and the thickness of the polycrystalline silicon film. FIG. 8A is a histogram of the number of dust particles adhering to the surface of a semiconductor substrate according to the present invention. FIG. 8B is a histogram of the number of dust particles adhering to the surface of a conventional semiconductor substrate subjected to sandblasting. FIGS. 9A and 9B are process diagrams showing a method for forming a mechanically strained layer on the back surface of a semiconductor substrate by sandblasting, and are shown in cross-sectional views. FIG. 10A is a diagram showing stacking faults appearing on the back side of a conventional semiconductor substrate subjected to sandblasting treatment, and FIG. 10B is a diagram showing the state of stacking faults appearing on the back side of a conventional semiconductor substrate subjected to sandblasting treatment. , is a diagram showing the back side. In the figure, 1 is a semiconductor substrate, 2A is a main surface, 2B is a back surface, and 4 is a polycrystalline silicon film. High School 10 1: Heisei 4 Rei Rim 2s 2 Main entry 114:5
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Claims (3)

[Claims] (1) A semiconductor substrate having a main surface and a back surface, and a polycrystalline silicon film provided on at least the back surface of the semiconductor substrate, the polycrystalline silicon film having a thickness of 0.8 μm or more. A semiconductor substrate with enhanced getter effect. (2) A semiconductor substrate having a main surface and a back surface, a polycrystalline silicon film provided on at least the back surface of the semiconductor substrate, and an element provided on the main surface of the semiconductor substrate, the polycrystalline silicon A semiconductor device in which the film has a thickness of 0.8 μm or more. (3) preparing a semiconductor substrate having a main surface and a back surface; forming a polycrystalline silicon film having a thickness of 0.8 μm or more on at least the back surface of the semiconductor substrate; and the semiconductor substrate A method for manufacturing a semiconductor device, comprising: forming an element on the main surface of the semiconductor device.