JPH07307258A - Temperature compensation member for heat treatment, heat treatment method of wafer employing the temperature compensation member and apparatus for the same - Google Patents

Abstract

PURPOSE:To provide a temperature compensation member for a heat treatment which makes the temperature uniform on the surface of a wafer. CONSTITUTION:A first dummy wafer 10a is composed of a wafer-shaped substrate 11a and an impurity layer 12 provided on the one side surface of the substrate 11a. The substrate 11a may be a semiconductor wafer made of silicon, gallium arsenite, germanium, etc., or an insulating wafer made of quarts. The impurity of the impurity layer 12 is highest at the center part of the substrate 11a and is reduced gradually in a radial direction.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to the heat treatment of semiconductor wafers.

[0002]

2. Description of the Related Art A heat treatment process is indispensable for manufacturing a semiconductor device. Due to the recent increase in the diameter of wafers and the miniaturization of individual semiconductor chips formed on the wafer, a high technology is required for the heat treatment process. Is required. For example, it is required to increase the rate of temperature rise during the heat treatment process or to make the in-plane temperature of the wafer uniform during temperature rise and during steady state. It is necessary to increase the temperature rising rate for both economical and technical reasons, and it is necessary to make the temperature within the wafer uniform to eliminate the variation among the semiconductor chips. Particularly in the case of processing time of the second order, it is very important to keep the wafer in-plane temperature uniform even when the temperature is raised.

However, increasing the rate of temperature rise and increasing the diameter of the wafer increase the non-uniformity of the in-plane temperature of the wafer. Normally, when the temperature rises, the temperature at the center of the wafer is the lowest, and the temperature gradually increases toward the edge,
The temperature at the periphery becomes the highest, and the opposite temperature distribution is obtained during cooling. Therefore, thermal distortion may cause crystal defects or warpage of the wafer. In order to prevent crystal defects or warpage of the wafer, for example, in the case of a silicon wafer having a diameter of 200 mm, the heating rate is set to 10 at a heat treatment temperature of 800 ° C. or lower.
C./min., And at 800.degree. C. or higher, about 5.degree. C./min. However, lowering the temperature raising rate leads to an increase in the total processing time.

On the other hand, in heat treatment of a batch type diffusion furnace, a rapid heat treatment technique has been proposed in which the temperature rising / falling rate is about 100 ° C./min. However, in order to perform heat treatment at this heating rate, a new method is required to reduce the non-uniformity of the in-plane temperature of the wafer to a threshold value or less which causes crystal defects or warpage of the wafer. One of them is to use a wafer boat having a ring-shaped dish placed under each wafer. The ring-shaped dish is made of quartz or SiC. The effect of the ring is that heat is taken from the peripheral edge of the wafer when the temperature rises, and heat is supplied to the peripheral edge when cooling, so that the temperature change in the peripheral area having a large temperature change rate is made equal to that in the central portion having a small temperature change rate. It is to lower. The ring can improve the non-uniformity of the temperature within the wafer surface.
Even at a temperature rising rate of about ° C / min, crystal defects on the wafer can be prevented.

However, since the ring has a relatively large heat capacity with respect to the wafer, the rate of temperature rise decreases around the processing temperature of the wafer. Also, because of the shape of the ring, the temperature at its inner edge becomes a local extreme as a function of radial distance from the center of the wafer. Further, generally, the thickness of the ring is about several millimeters, so that the stacking density of wafers is significantly reduced, and the productivity is deteriorated.

[0006]

As described above, there is a method of decreasing the temperature rising rate in order to keep the wafer in-plane temperature uniform during the heat treatment, but the processing time increases. Even if the heating rate is increased and the processing time is shortened, the temperature in the wafer surface can be kept uniform by using a ring-shaped dish, but the stacking density of wafers is reduced and the wafer temperature at the inner edge of the ring is reduced. Is an extreme value, which is a problem.

Therefore, the present invention provides a temperature compensating member for heat treatment, a method for heat treating a wafer using the temperature compensating member, and a heat treating apparatus having the temperature compensating member in order to make the in-plane temperature of the wafer during the heat treating uniform. The purpose is to provide.

[0008]

A first temperature compensation member for heat treatment according to the present invention comprises a semiconductor or insulating wafer and an impurity layer provided on one side or both sides of the wafer. Is formed such that the impurity concentration is highest in the central portion of the wafer and the impurity concentration is lower as the distance from the central portion increases in the radial direction.

The second temperature compensating member comprises a semiconductor or insulating wafer and a coating layer for coating one side or both sides of the wafer. When the coating layer is formed of a material having a lower emissivity or absorptivity of radiation than the wafer, the thickness of the coating layer is the thinnest in the central portion of the wafer, and the radial distance from the central portion is accordingly increased. Get thicker. On the contrary, when the coating layer is formed of a material having a higher emissivity or absorptivity of radiation than that of the wafer, the thickness of the coating layer is thickest in the central portion of the wafer and is radial from the central portion. As you move away, you get thinner.

In the heat treatment method using the temperature compensating member, the temperature compensating member and the wafer to be heat treated are arranged so as to be adjacent to each other and the heat treatment is performed. It is also possible to alternately arrange the temperature compensation member and the wafer to be heat treated,
A plurality of wafers to be heat-treated as one group,
The temperature compensating member may be arranged so as to sandwich the group.

As a heat treatment apparatus having the temperature compensating member, the temperature compensating member is provided on a wafer board holding a wafer to be heat treated. That is, the temperature compensation member is formed integrally with the wafer board.

[0012]

In the first temperature compensation member, the impurity layer has the highest emissivity (absorptivity) in the central portion,
The emissivity (absorptivity) decreases as the distance from the central portion increases in the radial direction. In the second temperature compensation member, the emissivity (absorption rate) depends on the material and shape of the coating layer.
Changes.

These temperature compensating members have a high emissivity (absorptivity) in the central portion, and decrease the emissivity (absorptivity) as they move away in the radial direction. As a result, the cooling rate is high in the central portion, and the cooling rate decreases in accordance with the emissivity curve as the distance increases in the radial direction. When a material to which Kirchhoff's law is almost applied is used, the emissivity and the absorptance of radiation are equal, and the absorptivity of radiation at a temperature rise is higher in the central portion than in the peripheral portion. Therefore, it is compensated that the region close to the central axis has a smaller rate of temperature change than the region far from the central axis at both the time of increasing the heat treatment temperature and the case of cooling, and the temperature is maintained over the entire surface. Can be kept uniform.

According to the heat treatment method using the temperature compensating member, the temperature compensating member has a uniform temperature over the entire surface, and the wafer to be heat treated is entirely covered by radiation exchange with the temperature compensating member. Can be kept uniform.

[0015]

Embodiments of the present invention will be described with reference to the drawings. First, the temperature compensating member (dummy wafer) for heat treatment according to the present invention will be described. The dummy wafer according to the present invention is roughly classified into two types. The first-type dummy wafer 10 has a structure including a wafer-shaped substrate and impurities that are non-uniformly added to the substrate, and the second-type dummy wafer 20 is a wafer-shaped substrate made of any material. It is a structure to be used and covered.

According to FIG. 1 (a), a first type dummy
The wafer 10a includes a wafer-shaped substrate 11a and the substrate 11a.
and an impurity layer 12 provided on one surface of a. Board 1
Reference numeral 1a is a semiconductor wafer such as silicon, gallium arsenide and germanium, or an insulating wafer such as quartz. The impurity concentration of the impurity layer 12 is the highest in the central portion of the substrate 11a and becomes lower as the distance from the center is increased in the radial direction. Further, according to FIG. 1B, the first type dummy wafer 1
Reference numeral 0a 'includes a wafer-shaped substrate 11a and two impurity layers 12 provided on both surfaces of the substrate 11a.

For example, the substrate 11a has a diameter of 200 m.
m, when using a 0.75 μm thick silicon wafer,
The impurity layer 12 is made of arsenic (As), boron (B), phosphorus (P).
It can be formed by using any of the impurities. The impurity concentration is 1.0 × 10 ²¹ c in the central portion of the substrate 11a.
m ^-3 .

Such dummy wafers 10a, 10a '
Then, the impurity concentration of the impurity layer 12 is formed with a gradient. The higher the impurity concentration, the higher the emissivity or absorption of radiation. Therefore, only the substrates 11a and 11b are damaged.
When a wafer is used, the temperature profile is non-uniform in the radial direction, but in the case of the dummy wafers 10a and 10a 'of the present invention, the non-uniform temperature profile is improved by the impurity layer 12 to provide a uniform temperature profile over the entire surface. Obtainable.

These dummy wafers 10a and 10a 'are
It is preferably used when the heat treatment temperature is low, for example, 800 ° C. or lower. As the processing temperature rises, redistribution of impurities may occur, and especially when the substrate 11 is made of a semiconductor material, the emissivity continuously decreases.

Therefore, the first type dummy wafer 10b which can be used even in the heat treatment at 800 ° C. or higher will be described. According to FIG. 2, the dummy wafer 10b is a wafer-shaped substrate 11b made of an insulating material containing inclusions (impurities) 13 (shown by circles) that emit (absorb) radiation. The inclusions 13 are contained not in the vicinity of the front surface and the back surface of the substrate 11b but in the whole. The concentration of inclusions 13 is highest in the central region and decreases with distance from the center along the radial direction. If the dummy wafer 10b,
Even if the heat treatment temperature is high, redistribution of the inclusions 13 does not occur, so that a uniform temperature profile can be obtained. Note that, for example, the substrate 11b can be formed using SiO ₂ and the inclusions 13 can be formed using Si.

Next, the second type dummy wafer 20 will be described. This type is effective not only for low-temperature heat treatment, but also for high-temperature heat treatment at 1000 ° C. or higher which is often used for manufacturing semiconductor devices.

According to FIG. 3 (a), a second type dummy
The wafer 20a includes a wafer-shaped substrate 21 and a coating layer 22a provided on one surface of the substrate 21. Further, as shown in FIG. 3B, the second type dummy wafer 20a 'is composed of a wafer-shaped substrate 21 and two coating layers 22a provided on both surfaces of the substrate 21, respectively. The substrate 21 is a semiconductor wafer made of silicon, gallium arsenide, germanium, or the like, or an insulating wafer such as quartz. Coating layer 22a
Is a terraced multilayer structure, and the number of layers is the largest in the central portion of the substrate 21 and decreases as the distance from the center is increased in the radial direction. The coating layer 22a is formed of a material (or a plurality of materials) having a higher emissivity (absorption rate) than the substrate 21. These dummy wafers 20
In a and 20a ', the non-uniform temperature profile of the substrate 21 is corrected by the coating layer 22a, and a uniform temperature profile is obtained over the entire surface.

According to FIG. 4 (a), the second type dummy
The wafer 20b includes a wafer-shaped substrate 21 and a coating layer 22b provided on one surface of the substrate 21. Further, as shown in FIG. 2B, the second type dummy wafer 20b 'is composed of a wafer-shaped substrate 21 and two coating layers 22b provided on both surfaces of the substrate 21, respectively. Coating layer 22b
Is a terrace-shaped multilayer structure, and the number of layers is the substrate 21.
It is the least in the central part of and increases as it moves away from the center in the radial direction. The coating layer 22b is formed of a material (or a plurality of materials) having an emissivity (absorption rate) lower than that of the substrate 21. In these dummy wafers 20b and 20b ', the non-uniform temperature profile of the substrate 21 is corrected by the coating layer 22b, and a uniform temperature profile is obtained over the entire surface.

Referring to FIG. 5, the second type dummy wafer 20c includes a substrate 21, a coating layer 22a provided on a central portion of one surface of the substrate 21, and a coating layer 22a on the same surface as the coating layer 22a. It is composed of a coating layer 22b provided around the periphery.
Further, according to FIG. 2B, the second type dummy wafer 2
Reference numeral 0c ′ includes a wafer-shaped substrate 21, and coating layers 22a and 22b provided on both surfaces of the substrate 21. The coating layer 22a is formed of a material having an emissivity (absorption rate) higher than that of the substrate 21, and conversely, the coating layer 22b is formed of a material having an emissivity (absorption rate) lower than that of the substrate 21. The dummy wafer 20c is a combination of the dummy wafer 20a and the dummy wafer 20b.
The same applies to 0c '. Therefore, the dummy wafers 20c, 2
At 0c ', the non-uniform temperature profile of the substrate 21 is corrected with higher accuracy, and the temperature profile becomes uniform over the entire surface.

The case where the coating layer has a terrace-shaped multilayer structure has been described above, but the coating layer may be a single layer as shown in FIG. Since the single layer is formed of the same material as the case of the multi-layer, the structure is clear by simply showing the corresponding relationship below. Dummy wafer 2
0x (FIG. 6 (a)) and the dummy wafer 20x '(FIG. 6).
(B) is a dummy wafer 20a, 20a 'shown in FIG.
Respectively correspond to. Dummy wafer 20y (Fig. 6
(C)) and the dummy wafer 20y ′ (FIG. 6 (d))
It corresponds to the dummy wafers 20b and 20b 'shown in FIG. 4, respectively. Dummy wafer 20z (FIG. 6 (e)) and dummy
The wafer 20z '(FIG. 6 (f)) corresponds to the dummy wafers 20a and 20a' shown in FIG. 3, respectively.

Further, another embodiment of the second type dummy wafer will be described with reference to FIG. As shown in FIG. 3A, the dummy wafer 20d includes a wafer-shaped substrate 21 and a coating layer 23a provided on one surface of the substrate 21. Further, according to FIG. 2B, the dummy wafer 20d 'is composed of a wafer-shaped substrate 21 and two coating layers 23a respectively provided on both surfaces of the substrate 21. The coating layer 23a has the thickest layer thickness in the central portion of the substrate 21, is a single layer whose thickness monotonically decreases as the distance from the central portion increases in the radial direction, and has a shape like a convex mirror. In addition, the coating layer 2
3a is formed of a material (or a plurality of materials) having a higher emissivity (absorption rate) than the substrate 21. The dummy wafers 20d and 20d 'have a uniform temperature profile due to the coating layer 23a.

As shown in FIG. 3C, the dummy wafer 20e.
Is composed of a wafer-shaped substrate 21 and a coating layer 23b provided on one surface of the substrate 21. Further, according to FIG.
The dummy wafer 20e 'is composed of the wafer-shaped substrate 21 and the substrate 2
It is composed of two coating layers 23b respectively provided on both sides of 1. The coating layer 23b has the thinnest layer thickness in the central portion of the substrate 21, is a single layer in which the layer thickness increases monotonically with the radial distance from the central portion, and has a shape like a concave mirror. The coating layer 23b is formed of a material (or a plurality of materials) having a lower emissivity (absorption rate) than the substrate 21. These dummy wafers 20e, 20e '
Has a uniform temperature profile due to the coating layer 23b.

The second type dummy wafer 20 described above.
Is composed of a substrate 21 and a coating layer 22 or a coating layer 23 that covers the surface of the substrate 21. For example, if the substrate 21 has a diameter of 20
When a silicon wafer of 0 mm is used, the coating layers 22a, 2
3a can be formed of SiC, SiO ₂ , Si ₃ N ₄ , and the coating layers 22b and 23b can be formed of tungsten and gold. However, when using tungsten, gold, or the like, it is necessary to provide a transparent coating layer, for example, a coating layer made of quartz, on the surface in order to avoid contamination.

The above-mentioned dummy wafer is different from the wafer to be heat-treated. However, when the impurity layer is provided only on one side or the coating layer is provided only on one side, the impurity layer or the coating layer can be provided on the back surface of the wafer to be heat treated, that is, the wafer itself on which the semiconductor chip is formed. Further, when providing the coating layer on both sides of the substrate, it is not necessary to provide the coating layer of the same shape on both sides, the front surface may be covered with a single layer, the back surface may be covered with multiple layers, the surface may be covered with multiple layers, The back surface may be covered with a single layer.

Next, a heat treatment method using a dummy wafer according to the present invention will be described with reference to FIG. As a first heat treatment method, as shown in FIG. 4A, a wafer 40 and a dummy wafer 50 to be heat treated (hatched in the drawing).
And are placed alternately. Further, as a second heat treatment method, as shown in FIG.
The wafer 50 is placed. How the dummy wafer 50 is arranged is determined based on the required temperature uniformity of the wafer 40 to be heat-treated. Dummy wafer 5 during heat treatment
0 is a uniform temperature over the entire surface, and the uneven temperature profile in the radial direction of the wafer 40 is compensated for, and the uniformity can be maintained. The dummy wafer 50 can be used regardless of batch type heat treatment or single wafer type heat treatment.

Further, an example of a heat treatment apparatus having a dummy wafer according to the present invention will be described with reference to FIG. The heat treatment apparatus includes a processing tube 91, a heater 92 provided around the processing tube 91, a wafer boat 93 made of quartz or SiC, and a predetermined processing gas blown into the processing tube 91. It comprises an inlet 94 and an outlet 95 of the injector. The wafer board 93 has a plurality of, for example, four support rods, and accommodates a wafer to be heat-treated and a dummy wafer. The dummy wafer may be removable like the wafer to be heat-treated, or may be integrally formed with the wafer board 93. If the dummy wafer is removable, depending on the temperature uniformity required for the wafer to be heat treated,
The arrangement of the dummy wafer can be easily changed.

If a dummy wafer having a coating layer provided on only one surface of the substrate is used, the stacking density of wafers to be heat-treated can be increased. Furthermore, when a coating layer is provided on the back surface of the wafer itself to be heat-treated, the stacking density can be further increased.

[0033]

The dummy wafer according to the present invention has a uniform temperature on the entire surface due to the impurity layer or the coating layer. Therefore, it is possible to easily compensate for the non-uniform temperature profile of the wafer to be heat-treated adjacent to the dummy wafer to obtain a uniform temperature profile. With the conventional heat treatment method using a ring, an extreme value occurs somewhere from the center to the periphery of the wafer to be heat treated, but with the method using the dummy wafer, the temperature curve in the radial direction is made uniform. be able to. Further, since the in-plane temperature of the wafer to be heat-treated by the dummy wafer uniformly rises at the time of raising the temperature after holding the dummy wafer and the wafer to be heat-treated in the heat treatment apparatus, the temperature rise time becomes short and the temperature rises. It becomes faster and economically effective.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first type temperature compensating member according to the present invention, where (a) shows a case where an impurity layer is provided on only one side, and (b) shows a case where an impurity layer is provided on both sides.

FIG. 2 is a cross-sectional view showing another example of the first type temperature compensating member according to the present invention.

FIG. 3 is a cross-sectional view showing a second type temperature compensating member according to the present invention in the first case in which the coating layer is a terrace-shaped multilayer structure, and (a) shows the coating layer provided on only one surface. In this case, (b) shows the case where the coating layers are provided on both sides.

FIG. 4 is a sectional view showing a second type temperature compensating member according to the present invention in a second case where the coating layer is a terrace-shaped multilayer structure, and (a) shows the coating layer provided on only one surface. In this case, (b) shows the case where the coating layers are provided on both sides.

FIG. 5 is a sectional view showing a second type temperature compensating member according to the present invention in a third case in which the coating layer is a terrace-shaped multilayer structure, and FIG. 5 (a) shows the coating layer provided on only one surface. In this case, (b) shows the case where the coating layers are provided on both sides.

FIG. 6 shows a second type temperature compensating member according to the present invention, in the case where the coating layer is a single layer, (a) to (f).
Corresponds to FIGS. 3 to 5.

FIG. 7 is a cross-sectional view showing a second type temperature compensation member according to the present invention, where (a) is a single layer and a coating layer having a shape like a convex mirror is provided on only one side, and (b) is (a). ) Shows a case where a coating layer similar to the above is provided on both sides, and (c) shows a case where a single layer and a coating layer having a shape like a concave mirror are provided on only one side
(D) shows the case where the same coating layer as in (c) is provided on both sides.

FIG. 8 is a sectional view showing a heat treatment method using a temperature compensation member according to the present invention, FIG. 8A shows a case where wafers to be heat treated and temperature compensation members (hatched portions) are alternately arranged, b) shows a case where the temperature compensating member is arranged so as to sandwich a plurality of wafers to be heat-treated.

FIG. 9 is a schematic view showing an example of a heat treatment apparatus having a temperature compensation member according to the present invention.

[Explanation of Codes] 10 ... First type dummy wafer, 11 ... Wafer-shaped substrate 12 ... Impurity layer, 13 ... Inclusion, 20 ... Second type dummy wafer 21 ... Wafer-shaped substrate, 22, 23 ... coating layer 40 ... wafer to be heat treated, 50 ... dummy wafer 91 ... processing tube, 92 ... heater, 93 ... wafer boat 94 ... introduction port, 95 ... discharge port

Claims (9)

[Claims] 1. A temperature compensating member for heat treatment, which is a disc-shaped member, wherein the central part of the disc has the largest emissivity, and the emissivity decreases with increasing distance from the center. 2. A semiconductor or insulating wafer, and at least one of the front surface and the back surface of the wafer, wherein the central portion of the wafer has a high impurity concentration and the impurity concentration increases in a radial direction away from the central portion. A temperature compensation member for heat treatment, comprising a lower impurity layer. 3. An insulative wafer containing impurities that radiate or absorb radiation, wherein the impurities are provided on the entire surface of the wafer, and the concentration of the impurities in the central portion of the wafer is high and the impurity is in the radial direction from the central portion. A temperature compensating member for heat treatment, characterized in that the content concentration decreases with increasing distance. 4. A temperature compensating member for heat treatment, comprising a semiconductor or insulating wafer and a coating layer for coating at least one of the front surface and the back surface of the wafer. 5. The coating layer is formed of a material having a lower emissivity or absorptivity of radiation than that of the wafer, has a thinnest thickness in a central portion of the wafer, and is separated from the central portion in a radial direction. The temperature compensating member for heat treatment according to claim 4, wherein the thickness is increased. 6. The coating layer is formed of a material having a higher emissivity or absorptivity of radiation than that of the wafer, has a thickest thickness in a central portion of the wafer, and is separated from the central portion in a radial direction. The temperature compensating member for heat treatment according to claim 4, wherein the thickness is reduced. 7. The temperature compensating member for heat treatment according to claim 4, wherein the coating layer is a single layer or a terrace-like multilayer. 8. A semiconductor chip is formed by using a semiconductor or insulating wafer and a temperature compensation member for heat treatment for providing an impurity layer or a coating layer on the wafer to make the in-plane temperature of the wafer uniform. A method for heat treatment, characterized in that, when heat-treating a true wafer, the temperature compensating member and the true wafer are arranged adjacent to each other and heat-treated. 9. A heat treatment apparatus for heat-treating a plurality of semiconductor wafers, a treatment chamber for treating the semiconductor wafers and introducing a predetermined gas, a heater provided around the treatment chamber, and the treatment chamber. And a wafer board for holding the semiconductor wafer, the wafer board having a temperature compensation for heat treatment including an impurity layer or a coating layer for making the in-plane temperature of the semiconductor wafer uniform. A heat treatment apparatus having a member.