JPH1055940A - Semiconductor substrate and method of manufacturing semiconductor device - Google Patents

Abstract

(57) [Summary] [Problem] To make warpage as small as possible. SOLUTION: The substrate, a diffusion layer formed by diffusing an element having an atomic radius smaller than the atomic radius of the element constituting the substrate to one surface of the substrate, and the diffusion layer formed on the diffusion layer. A first film made of a material having a smaller coefficient of thermal expansion than the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Generally, an individual semiconductor device has phosphorus on one side,
A thin semiconductor substrate in which impurities such as boron are diffused at a high concentration is often used. This is because an individual semiconductor device often causes a current to flow in the thickness direction of the substrate, and a high-concentration diffusion layer is required to reduce the series resistance at that time. For example, when the individual semiconductor device is N as shown in FIG.
In the case of a PN transistor, an N-type diffusion layer 24 serving as a collector layer is formed on one surface of an N-type semiconductor substrate 22, and a P-type diffusion layer 22 serving as a base layer is formed on the other surface. N-type diffusion layer 28 serving as an emitter layer in layer 22
Is formed. Then, the collector layer 24, the base layer 26,
Electrodes 30, 32, and 34 are provided on the emitter layer 28, respectively. In the case of this transistor, current flows from the collector layer 24 to the emitter layer 28.

In order to reduce the series resistance, it is effective to reduce the thickness of the substrate. Generally, a thin film diffusion wafer is used for an individual semiconductor device.

A conventional method for manufacturing a diffusion wafer (semiconductor substrate) will be described with reference to FIG. First, high-concentration phosphorus is diffused from the front and back surfaces of the N-type silicon substrate 42 shown in FIG. 3A to form a high-concentration N-type diffusion layer 44 (see FIG. 3B). Thereafter, the diffusion surface on one side is removed by polishing, or the wafer after diffusion is divided into two parts in the thickness direction and then polished to form a diffusion wafer 46 (see FIG. 3C).

[0005]

In the diffusion wafer thus obtained, the atomic radius of the diffusion impurity is generally smaller than the atomic radius of silicon (= 0.117 nm). For example, the atomic radii of phosphorus and boron are each 0.110 nm,
0.088 nm. As a result, the diffusion wafer 46 shown in FIG.
In this case, the warpage is generally formed such that the diffusion surface side 44a is concave.

Conventionally, as a semiconductor substrate of an individual semiconductor device, a diffusion wafer having a diameter (diameter) of 75 mm to 125 mm is mainly used. The warpage of the wafer after diffusion was about 150 μm when it was large for a wafer having a diameter of 125 mm, but no particular problem occurred. Also, there is no major problem in manufacturing due to warpage occurring when a semiconductor element is manufactured using a wafer, and the design rule of the element is loose, and it is not necessary to control the warpage of the diffusion wafer.

As a matter of course, a diffusion wafer having a diameter smaller than 125 mm has a smaller warpage,
There was no problem. However, as the diameter of the wafer becomes larger and the design rules become stricter, the wafer whose warpage is not controlled becomes a major cause of transport troubles and lowering of the yield in the manufacturing process.

The present invention has been made in consideration of the above circumstances, and has as its object to provide a semiconductor substrate and a method of manufacturing a semiconductor device which can minimize warpage.

[0009]

According to a first aspect of the present invention, there is provided a semiconductor substrate, wherein an element having an atomic radius smaller than the atomic radius of an element constituting the substrate is diffused to one surface of the substrate. And a first film made of a material having a smaller coefficient of thermal expansion than the substrate formed on the diffusion layer.

According to a second aspect of the semiconductor substrate according to the present invention, there is provided a semiconductor device comprising: a substrate; and a diffusion layer formed by diffusing an element having an atomic radius smaller than an atomic radius of an element constituting the substrate onto one surface of the substrate. A second film formed on a surface of the substrate opposite to the surface on which the diffusion layer is formed, the second film being made of a material having a larger coefficient of thermal expansion than the substrate. And

In a third aspect of the semiconductor substrate according to the present invention, there is provided a silicon substrate having a diffusion layer formed on the main surface and having a thickness of tsi, and a silicon dioxide having a thickness of t _SiO2 formed on the diffusion layer. And a film, wherein the diameter of the silicon substrate is a,
When the warpage of the silicon substrate is R0 and the desired warpage when the silicon dioxide film is formed on the silicon substrate is R, k = (0.5 to 2.5) × 10 ³ , the silicon dioxide film The thickness tsio ₂ is t _SiO2 = k × (R
−Ro) × (T _Si / a) ² .

According to a method of manufacturing a semiconductor device according to the present invention, when manufacturing a semiconductor device using the semiconductor substrate according to any one of the first to third aspects, one side of the semiconductor substrate is formed during the manufacturing process. A film of a material having a different thermal expansion coefficient from that of the semiconductor substrate is formed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a semiconductor substrate according to the present invention will be described with reference to FIG. The semiconductor substrate of this embodiment is formed as follows. If the plane orientation is (10
0), a 0.7 mm thick silicon wafer (also referred to as a substrate) 2 is subjected to a heat treatment at 1200 ° C. for 120 minutes using phosphorus oxychloride (POCl ₃ ) to form a phosphorus glass layer 4 on the front and back surfaces of the substrate 2. Then, a phosphorus diffusion layer 5 is formed (see FIG. 1A).

Subsequently, after removing the phosphorus glass layer 4, a heat treatment is performed at 1285 ° C. for 180 hours in a mixed gas atmosphere of nitrogen and oxygen to diffuse phosphorus deeply in the depth direction of the substrate 2 (FIG. 1 (b)). At this time, FIG.
As shown in (b), the SiO ₂ film 6 is formed on the front and back surfaces of the substrate 2.

[0015] Then the SiO ₂ film 6 as shown in FIG. 1 (c)
Then, the substrate is heat-treated in steam at 1200 ° C. for 50 minutes to form an SiO ₂ film 8 having a thickness of 0.7 μm on the front and back surfaces of the substrate 2 (see FIG. 1D). Subsequently, one side of the substrate 2 is ground and mirror-polished to form a semiconductor substrate 10 having a thickness of 300 μm (FIG. 1E).
reference).

The semiconductor substrate 10 formed as described above
Warpage occurs on the diffusion surface side (the surface side on which the SiO ₂ film 8 is formed).
Was concave and 15 μm. Incidentally, when the SiO ₂ film 8 was not formed, the warpage was 250 μm with the diffusion surface side being concave.

The semiconductor substrate 10 of this embodiment is made of Si
The difference in thermal expansion coefficient between the O ₂ film 8 and the silicon substrate 2 (for example,
Silicon is about 3 × 10 ^-6 / ° C and SiO ₂ is about 5 × 10 ^-7
/ ° C.), and at high temperature, the silicon substrate 2 and the SiO ₂ film 8 which are in an equilibrium state in terms of stress are reduced in temperature and the silicon substrate 2 side shrinks more than the SiO ₂ film 8 side. , With reduced warpage.

In the above embodiment, the SiO ₂ film 8 is formed on the surface of the substrate 2 on which the diffusion layer 5 is formed, but a film made of a material having a smaller thermal expansion coefficient than the material forming the substrate 2 is used. It goes without saying that the same effect can be obtained even if it is formed on the surface of the substrate 2 on which the diffusion layer 5 is formed.

The same effect can be obtained even if a film made of a material having a larger thermal expansion coefficient than the material constituting the substrate 2 is formed on the surface of the substrate 2 opposite to the surface on which the diffusion layer 5 is formed. Needless to say.

Further, even if the film to be formed is a composite film, if the thermal expansion coefficient of the entire composite film has the same tendency, it is needless to say that the same effect on warpage can be obtained.

Next, a description will be given of a second embodiment of the semiconductor substrate according to the present invention. The semiconductor substrate of this embodiment is shown in FIG.
In the semiconductor substrate 10 of the first embodiment shown in FIG. 1E, the thickness of the SiO ₂ film 8 is changed from 0.7 μm to 1.0 μm. The warpage of the semiconductor substrate 10 of this embodiment was 155 μm. In addition, this film thickness of 1.0 μm S
The iO ₂ film 8 is formed by performing a heat treatment (oxidation treatment) at 1200 ° C. for 90 minutes in steam.

In general, the warpage generated during the device manufacturing process is large, and the warpage of the diffusion wafer does not necessarily need to be “0” before the device process is introduced, and the warpage is controlled to a certain size according to the device manufacturing process to be used. It is better to do.

The silicon dioxide film 8 is applied to the silicon wafer 2
In general, the warpage when applied to one surface of the silicon wafer is given _assuming that the silicon dioxide film thickness is t _SiO2 , the silicon wafer thickness is t _Si , the warpage is r, and the wafer diameter is a.

[0024]

(Equation 1) It is expressed as Here, K is a proportional constant. Therefore, when the warpage caused by the diffusion (corresponding to the warpage without the silicon dioxide film 8 shown in FIG. 1E) is R ₀ , the warpage R of the wafer (semiconductor substrate 10) on which the silicon dioxide film 8 is formed Is positive when the diffusion surface is convex

[0025]

(Equation 2) The thickness t _{SiO2 of the} silicon dioxide film for obtaining the target warpage is given by the equation (2).

[0026]

(Equation 3) Is obtained. Here, k is a proportional constant, which varies depending on the conditions for forming the silicon dioxide film. As a result of various studies, k = (0.5 to 2.5) × 10 ³ was found practically.

If the thickness of the SiO ₂ film is determined as described above and the SiO ₂ film is formed on the diffusion surface side of the silicon substrate 2, a desired warpage can be obtained.

Next, an embodiment of a method of manufacturing a semiconductor device according to the present invention will be described. In the manufacturing method of this embodiment, a semiconductor substrate (diffusion wafer) 10 is first formed as shown in FIG.

Thereafter, the diffusion wafer is put into a manufacturing process of a semiconductor device. At the intermediate stage of the device process, the warpage of the wafer is
It was found that the film was warped by 00 μm, and a 0.65 μm SiO ₂ film was formed on the diffusion surface side by normal pressure CVD. Subsequently, after the wafer was washed, the wafer was subjected to a heat treatment at 1000 ° C. for 20 minutes in a nitrogen atmosphere. As a result, the warpage was greatly reduced to 10 μm with the diffusion surface side protruding.

The control of warpage by forming a thin film as described above is very effective for a large-diameter diffused wafer.
It is clear from the description of the above embodiments that the magnitude of the warpage can be freely controlled depending on the type of the film and whether the film is formed on the front surface or the back surface of the wafer.

When the manufacturing method according to the above-described embodiment is used, troubles that occur during the device manufacturing process during wafer transfer have been reduced.

The wafer cracking due to transport trouble is 10 to
In addition to the reduction from about 15% to 1% or less, the maintenance of the apparatus was greatly reduced by 2 hours.

Further, when the yield in the lithography step (circuit printing step) is not reduced due to the warpage, and the chip yield per wafer is set at 1.0, the manufacturing method of the present embodiment is used. To 1.05 to 1.1 times.

Incidentally, in the above embodiment,
A diffusion wafer having a high-concentration N-type diffusion layer formed on an N-type substrate has been described. However, a diffusion wafer having a high-concentration P-type diffusion layer formed on a P-type substrate. It goes without saying that a similar effect can be obtained by using a wafer or a diffusion wafer in which a P-type diffusion layer is formed on an N-type substrate.

[0035]

As described above, according to the present invention, warpage can be reduced as much as possible.

[Brief description of the drawings]

FIG. 1 is a process sectional view showing a process for manufacturing a semiconductor substrate according to the present invention.

FIG. 2 is a cross-sectional view illustrating an example of a conventional individual semiconductor device.

FIG. 3 is a process cross-sectional view showing a conventional process for manufacturing a semiconductor substrate.

[Explanation of symbols]

Reference Signs List 2 silicon substrate 4 phosphorus glass layer 5 diffusion layer 6 SiO ₂ film 8 SiO ₂ film 10 semiconductor substrate (diffusion wafer) 22 N-type silicon substrate 24 collector (N-type diffusion layer) 26 base (P-type diffusion layer) 28 emitter (N Diffusion layer) 42 N-type silicon substrate 44 N-type diffusion layer 44 Diffusion surface side 46 Semiconductor substrate (diffusion wafer)

Claims (4)

[Claims] 1. A substrate, a diffusion layer formed by diffusing an element having an atomic radius smaller than an atomic radius of an element constituting the substrate into one surface of the substrate, and a diffusion layer formed on the diffusion layer. And a first film made of a material having a smaller thermal expansion coefficient than the substrate. 2. A substrate, a diffusion layer formed by diffusing an element having an atomic radius smaller than an atomic radius of an element constituting the substrate into one surface of the substrate, and a diffusion layer formed on the substrate. A second film formed of a material having a larger thermal expansion coefficient than that of the substrate, the second film being formed on a surface opposite to the formed surface. 3. A silicon substrate having a diffusion layer formed on the main surface and having a thickness of t _{si, and} a silicon dioxide film having a thickness of t _Sio2 formed on the diffusion layer. The diameter is a, the warpage of the silicon substrate is Ro, and the desired warpage when the silicon dioxide film is formed on the silicon substrate is R, k = (0.5-2.
5) A semiconductor substrate characterized in that the thickness t _Sio2 of the silicon dioxide film satisfies t _Sio2 = k × (R−Ro) × (T _si / a) ² when × 10 ³ . 4. When a semiconductor device is manufactured using the semiconductor substrate according to claim 1, a material having a different thermal expansion coefficient from that of the semiconductor substrate is provided on one surface of the semiconductor substrate during a manufacturing process. A method of manufacturing a semiconductor device, comprising: forming a film.