JPS633446B2 - - Google Patents

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 wafer is held at a wafer and inserted into a horizontal diffusion furnace 3 as shown in FIG. Usually, a carrier gas (O ₂ , H ₂ , N _{2 ,} etc.) 5 was introduced. An example of a horizontal diffusion furnace is JP-A-49-104570.

However, according to such conventional technology, 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. Additionally, due to non-uniform temperature distribution in the furnace, non-uniform gas flow velocity distribution or turbulent flow, there is considerable variation in device characteristics within a wafer or between wafers. There are drawbacks that arise.

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 causes a difference in temperature distribution between the wafer jig and the wafer, and The density of the introduced reactant gas varies between the upper and lower parts of the furnace body due to the influence of gravity, resulting in variations within a single wafer.

Furthermore, 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 tube in which a cylindrical space exists along a substantially vertical direction, each of the plurality of semiconductor wafers is placed against a semiconductor wafer holding jig, and the peripheral edge of the semiconductor wafer is The jig is held in contact with the inner wall of the furnace tube at a plurality of locations, and is placed at predetermined intervals along the longitudinal direction of the jig, so that the jig can be held in contact with the inner wall of the furnace tube within the furnace tube that exists along the vertical direction. The jig is characterized by being supported at one end in the longitudinal direction and subjected to heat treatment.

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. Further, since the wafer is held almost horizontally, it is easy to transfer the wafer from one jig to another in a batch, which makes it compatible with automation, and can also accommodate larger diameter wafers.

Furthermore, space and energy savings can be achieved.
Resistant to heat deformation.

Further, since the wafers are subjected to rotational motion 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 by a pair of upper and lower holding members 12 at approximately equal intervals.
They are arranged in a holding jig 12 consisting of A and 12B. The holding members 12A and 12B have similar configurations, and as shown in the figure, when stacked one on top of the other, they form a cylindrical part having an inner diameter corresponding to the outer diameter of the wafer, with a total of six rod-shaped parts 12X, three each. It's getting old. A groove with a width corresponding to the thickness of the wafer is cut in the portion of each rod-shaped portion 12X that should engage the wafer 11, so that the wafer does not fall even when the wafer 11 is held horizontally as described later. It's getting old.

A large number of wafers 11 held in the wafer holding jig 12 as shown in FIG. In this state, it is inserted into a vertical diffusion furnace (heat treatment furnace) 13 made up of a quartz tube extending in the vertical direction. The diffusion furnace 13 has a heater 14, and a carrier gas 15 containing impurities is introduced from below.

During the diffusion process, gas 15 is introduced into furnace 13 and wafer 11 is heated to a predetermined temperature by heater 14 . On the other hand, the wafer holding jig 12 is held using a jig holder 16 without contacting the inner wall of the furnace. In this embodiment, by utilizing this non-contact, the jig holder 16 is further moved up and down as shown by the arrow UL and rotated as shown by the arrow R, thereby imparting vertical and rotational movement to the wafer 11. In this way, the heat from the heater 14 and the impurities in the gas 15 can be uniformly applied to the wafer 11, so variations in device characteristics within a wafer and between wafers can be significantly reduced.

FIGS. 5 and 6 show the current amplification factor h _FE of transistors within one wafer or between multiple wafers when a large number of diffused transistors are formed on each wafer in the processing batch shown in FIG. The variation is shown in comparison with the case using the conventional method.
According to FIG. 5, Y within one wafer 11
It is clear that the variation in h _FE along the direction is much smaller in the case of the invention shown by the solid line B than in the case of the conventional method shown by the dashed line A. Furthermore, according to FIG. 6, it is clear that the variation in hFE between wafers 11 within the same processing batch is sufficiently smaller in the case according to the present invention shown by the solid line B than in the conventional case shown by the broken line A.

[Effects] (1) According to the present invention, since a plurality of semiconductor wafers are heat-treated in a furnace tube in which a cylindrical space exists almost vertically, that is, in order to utilize the vertical space, , it is more space efficient than the conventional horizontal diffusion furnace and can save space.

(2) According to the present invention, since each of a plurality of semiconductor wafers is held in contact with the semiconductor wafer holding jig at a plurality of locations on the peripheral edge of the semiconductor wafer, the semiconductor wafer holding jig itself The wafer can be made lightweight and a large amount of wafer yardage is possible.

(3) As mentioned above, the semiconductor wafer holding jig itself can be made lightweight, so the semiconductor wafer holding jig can be held inside the furnace tube without coming into contact with the inner wall of the furnace tube, as shown in Figure 4. Heat treatment can be performed by supporting only one longitudinal end of the semiconductor wafer holding jig with the tool holder 16. That is, the semiconductor wafer holding jig can be supported in a cantilevered manner.

(4) If the semiconductor wafer holding jig is supported on one side, it is natural that the generation of foreign matter will be reduced compared to when it is supported on both sides. That is, according to the present invention,
As shown in FIG. 4, since the other end of the semiconductor wafer holding jig in the longitudinal direction is floated, there is no contact friction within the furnace tube, and as a result, the generation of foreign matter is reduced.

(5) According to the present invention, semiconductor wafer holding jigs are arranged at predetermined intervals along the longitudinal direction, and the jigs are maintained in the furnace tube that exists along the vertical direction without contacting the inner wall thereof. Since the diameter of the furnace body can be reduced, in other words,
Since the distance from the heater to the center of the furnace body can be shortened, temperature non-uniformity within the wafer is reduced, and heating becomes closer to uniformity.

(6) According to the present invention, since the wafers are held substantially horizontally facing each other, the gas flow does not directly hit the wafer surface, and the influence of variations in gas concentration and amount is small. Therefore, the variation between lots is also small.

(7) According to the present invention, since the plurality of semiconductor wafers are placed almost horizontally as in the embodiment and the wafers are rotated within the horizontal plane, gas turbulence is generated softly; Gas spreads uniformly between and within each wafer.

(8) According to the present invention, since a plurality of semiconductor wafers are rotated almost horizontally and the wafers are rotated within a horizontal plane as in the embodiment, the rotation of the wafer rotation means is not burdened and the rotation is uniform. Rotation is possible.

As described above, according to the present invention, variations in device characteristics within and between wafers can be significantly reduced without complicating the furnace structure or the jigs used, and various semiconductor devices can be improved. The effect of manufacturing in terms of yield is significant.

[Brief explanation of the drawing]

FIG. 1 is a side view showing how a wafer is held in a conventional technique (horizontal diffusion), FIG. 2 is a sectional view of a furnace body used in the conventional technique, and FIG. 3 is an embodiment of the present invention. FIG. 4 is a perspective view showing a wafer holding jig used, FIG. 4 is a sectional view of a furnace body showing a diffusion method according to an embodiment of the present invention, and FIGS. This is a graph showing a quantitative comparison with the above. 11...Semiconductor wafer, 12...Wafer holding jig, 13...Vertical diffusion furnace, 16...Jig holder.

Claims (1)

[Claims] 1. When heat-treating a plurality of semiconductor wafers in a furnace tube in which a cylindrical space exists along a substantially vertical direction, each of the plurality of semiconductor wafers is placed against a semiconductor wafer holding jig, and each of the semiconductor wafers is The jig is held in contact with the wafer at multiple points around the periphery of the wafer, and is placed at predetermined intervals along the longitudinal direction of the wafer. A method for heat treatment of a semiconductor wafer, characterized in that the heat treatment is carried out by supporting the jig at one longitudinal end of the jig without contacting the wafer. 2. The method of heat processing a semiconductor wafer according to claim 1, wherein the wafer holding jig is rotated during the heat treatment.