JPS6323313A - Heat-treatment of semiconductor wafer - Google Patents

Abstract

PURPOSE:To reduce the variations in the element characteristics among two or more wafers and inside each wafer and to reduce the size of the title device, by a method wherein two or more semiconductor wafers are arranged inside a jig so that the wafers are held at fixed intervals and at two or more positions on their peripheries by making contact with the jig and the wafers are heat-treated without making contact with the inside wall of a furnace while the jig is rotated and moved upward and downward. CONSTITUTION:Two or more wafers 11 are held inside a wafer-holding jig 12. The jig containing the wafers 11 is set upright and is then inserted into a vertical-type diffusion furnace 13 in such a way that the jig 12 is rotated by 90 deg. and suspended with a jig holder 16 and that the wafers 11 are arranged horizontally. For the diffusion treatment, the wafers 11 are heated with a heater 14 at a predetermined temperature while the wafer-holding jig 12 suspended with the jig holder 16 is kept without making contact with the inside wall of the furnace. By making use of this contactless arrangement the jig holder 16 is then moved upward and downward as shown by an arrow UL and is also rotated as shown by an arrow R so that the wafers 11 can be moved upward and downward and can be rotated. Because the heat from the heater 14 and the impurities contained in a gas 15 can be applied to the wafers 11 in a uniform manner, it is made possible to reduce the variations in the element characteristics among each of the wafers and inside each wafer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method of subjecting a semiconductor wafer to heat treatment such as impurity diffusion.

[Background Art] Conventionally, when diffusing acceptor impurities or donor impurities into semiconductor wafers, as shown in FIG. Generally, the carrier is held and inserted into a horizontal diffusion furnace 3 as shown in FIG. Gas (02, T-I2. N2
etc.) 5 was normally used. An example of a horizontal diffusion furnace is JP-A-49-104570.

However, according to such conventional techniques, when a wafer is inserted into a furnace, the inner wall of the furnace body and the wafer jig tend to come into contact with each other, resulting in the generation of foreign matter. In addition, due to uneven temperature distribution in the furnace, uneven gas flow velocity distribution, or turbulent flow, considerable variations in device characteristics occur within a wafer or between wafers. There is.

In other words, when the wafer is held in the furnace, the wafer jig comes into contact with the wall of the furnace, so heat transfer from this contact surface may cause a difference in temperature distribution between the wafer jig and the wafer, or the wafer may be introduced into the furnace. This causes problems such as differences in the density of the reactant gases at the top and bottom of the furnace body due to the influence of gravity, and variations within wafers.

In addition, it is necessary to stand the wafers one by one on a jig, which is not suitable for automation. Another disadvantage is that the device occupies a considerable amount of space.

[Object of the Invention] An object of the present invention is to provide a novel heat treatment method for semiconductor wafers that eliminates the above-mentioned drawbacks.

[Summary of the Invention] A typical outline of the present invention is as follows. In other words, when heat treating a plurality of semiconductor wafers in a furnace body in which a cylindrical space exists almost vertically, the plurality of semiconductor wafers are attached to a semiconductor wafer holding jig, and each of the semiconductor wafers is attached to a plurality of periphery portions of the semiconductor wafer. The plurality of semiconductor wafers are arranged in a jig at a certain point while maintaining a predetermined interval, and the plurality of semiconductor wafers are arranged in a furnace from one side of the furnace body without coming into contact with the inner wall of the furnace, and the plurality of semiconductor wafers are It is characterized by heat treatment while rotating and moving it up and down.

With such a configuration, the inner wall of the furnace and the wafer (wafer jig) can be made non-contact, and the generation of foreign matter can be reduced. In addition, since the wafer is held almost horizontally, it is easy to transfer the wafer from one jig to another in a batch, making it compatible with automation and also compatible with larger diameter wafers.

It also saves space and energy, and is resistant to thermal deformation.

Furthermore, since the wafers are rotated and moved up and down during the heat treatment, the gas uniformly spreads to each wafer and within the wafer.

[Embodiment] FIG. 3 shows a wafer holding jig used in an embodiment of the present invention, in which a large number of semiconductor wafers 11 are held at approximately equal intervals between a pair of holding members 12A below.

They are arranged in a holding jig 12 consisting of 12B. The holding members 12A and '2I3 have the same configuration as each other, and as shown in the figure, when stacked one on top of the other, they form a cylindrical part each having an inner diameter corresponding to the outer diameter of the wafer, and a total of six rod-shaped parts 12X, three each. It looks like this.

Then, the wafer 1 of each rod-shaped portion 12X. A groove with a width corresponding to the wafer thickness is cut in the part to be engaged with l.
As will be described later, even if the wafer 11 is held horizontally, the wafer does not fall.

A large number of wafers 11 held in the wafer holding jig 12 as shown in FIG.
By rotating it by 0° and holding it in the jig holder 16, it is inserted into the vertical diffusion furnace (heat treatment furnace) 13 in a substantially horizontal state. The diffusion kp 13 has a heater 1lI and is adapted to introduce a carrier gas 15 containing impurities from below.

In the diffusion process, a gas 15 is introduced into the furnace 13 and the wafer 11 is heated to a predetermined temperature by the heater 14. On the other hand, the wafer holding jig 12 is held using a jig boulder 16 without contacting the inner wall of the furnace. In this example, we use this non-contact feature to create a jig holder! 6, then arrow UL
By moving the wafer 11 up and down as shown in FIG. 2 and rotating it as shown by arrow R, the wafer 11 is given vertical movement and rotational motion. In this way, the heat of the heater 14 and the impurities in the gas XS can be uniformly applied to the wafer 11, so that variations in device characteristics within a wafer and between wafers can be significantly reduced.

5 and 6 show that when a large number of diffused transistors are formed on each wafer in the processing batch of FIG. 4,
Figure 2 shows the variation in the current amplification factor hFE of transistors within a wafer or in a failed wafer in comparison with the conventional method.

According to FIG. 5, it is clear that the variation in hFE along the Y direction within one wafer is much smaller in the case of the present invention shown by the solid line B than in the case of the conventional method shown by the broken line A. . Furthermore, according to FIG. 6, it is clear that the variation in hFE among wafers 11 within the same processing batch is much smaller in the case of the present invention shown by the solid line B than in the conventional case shown by the broken line and . be.

[Effects] (1) According to the present invention, the wafer holding means located in the furnace body space holds a plurality of wafers facing each other substantially horizontally at a predetermined interval in the longitudinal direction, and rotates the wafers within the horizontal plane. Moreover, since the device is configured to be able to move up and down, the reduction in variations in device characteristics between wafers and within a wafer and the miniaturization of the device are more remarkable as described below.

(2) According to the present invention, since the wafer is placed almost horizontally and rotated within the horizontal plane, the diameter of the furnace body can be reduced, that is, the distance from the heater to the center of the furnace body can be shortened. Temperature non-uniformity within the wafer becomes smaller and heating approaches uniformity.

(3) Rotation in the horizontal plane causes a gentle gas turbulence, and the gas flows uniformly between and within each wafer.

(4) Since the wafers are held facing each other almost horizontally, the gas flow does not directly hit the wafer surface, reducing the gas concentration.

The effect of variation in quantity is small. Therefore, the variation between lots is also small.

(5) Since the wafer is rotated while being held almost horizontally, uniform rotation is possible without placing any burden on the rotation of the wafer jig means. Therefore, the wafer holding jig can be supported on a cantilever as shown in FIG. 4, and the generation of foreign matter can be prevented.

(6) Since the wafer rotates in a horizontal plane, there is no wobbling of the wafer, and foreign matter is less likely to come out.

(7) The diameter of the furnace body is reduced, making it possible to increase gas efficiency and further save space.

(8) Since the wafers are held facing each other, it is easy to transfer the jig and it is possible to charge a large amount of wafers.

(9) In a horizontal furnace, if the furnace body is kept at a high temperature for a long time, deformation such as the center part of the quartz tube sagging downwards due to the influence of gravity tends to occur, but in a vertical furnace, the quartz tube is originally in the direction of the weight. (Vertical direction), so there is less worry about deformation such as sagging.

[Application field] The present invention provides uniform processing for multiple semiconductor wafers.

[Brief explanation of drawings]

FIG. 1 is a side view showing how a wafer is held in a conventional technique, FIG. 2 is a sectional view of a furnace body showing a diffusion method in a conventional technique, and FIG. 3 is a wafer used in an embodiment of the present invention. FIG. 4 is a perspective view showing a holding jig, FIG. 4 is a sectional view of a furnace body showing a diffusion method according to an embodiment of the present invention, and FIGS. 5 and 6 compare the effects of this invention with those of the prior art. This is a graph showing 11... Semiconductor wafer, 12... Wafer holding jig,
13... Vertical diffusion furnace, 16... Jig holder. Pin Figure 1 Figure 2 Figure 6 Figure 6 17 people

Claims (1)

[Claims] 1. When heat-treating a plurality of semiconductor wafers in a furnace body in which a cylindrical space exists almost vertically, the plurality of semiconductor wafers are attached to a semiconductor wafer holding jig, and each of the semiconductor wafers is attached to a plurality of peripheral edges of the semiconductor wafer. The plurality of semiconductor wafers are held in contact with each other at certain points and arranged on a jig at a predetermined interval, and the plurality of semiconductor wafers are placed into the furnace from one side of the furnace body without contacting the inner wall of the furnace, and the plurality of semiconductor wafers are A method for heat treatment of semiconductor wafers, characterized by performing heat treatment while rotating and moving up and down.