JPH03273620A - Heat treating method of semiconductor wafer - Google Patents

Abstract

PURPOSE:To improve space efficiency and to prevent the entrainment of contamination sources when a jig is inserted into a furnace by engaging a plurality of holding jigs with grooves, holding semiconductor wafers at a plurality of places at the peripheral part, inserting the jig in the reverse direction with respect to the introducing direction of gas into a furnace tube, and performing heat treatment such as impurity diffusion. CONSTITUTION:Many semiconductor wafers 11 are aligned in a holding jig 12 comprising a pair of upper and lower holding members 12A and 12B at an approximately equal interval. A cylindrical part having the inner diameter corresponding to the outer diameter of the wafer when they are overlapped is formed of total of six rod-shaped parts 12X at every three pieces. A groove having the width corresponding to the thickness of the wafer is cut at a part which is engaged with the wafer 11 in each rod-shaped part 12X. Many wafers 11 in the wafer holding jig 12 are inserted into a vertical diffusing furnace (heat treating furnace) 13 by rotating the jig 12 and holding the jig with a jig holder 16. The furnace 13 is composed of a quartz pipes which are extending in the vertical direction in the approximately horizontal state. In diffusing, gas 15 is introduced into the furnace 13, and the wafers 11 are heated to specified temperature with a heater 14. Meanwhile, the wafer holding jig 12 is held under the non-contact state with the inner wall of the furnace by using the jig holder 16. The jig holder 16 is vertically moved and rotated by utilizing the non-contact state.

Description

[Detailed description of the invention]

[0001]

[Industrial application field]

The present invention relates to a method of subjecting a semiconductor wafer to heat treatment such as impurity diffusion. [0002]

[Conventional technology]

Conventionally, when diffusing acceptor impurities or donor impurities into semiconductor wafers, a large number of wafers 1 are held upright and parallel in a jig 2 made of quartz or silicon as shown in FIG. The wafer is generally inserted into a horizontal diffusion furnace 3, which has a heater 4 and a carrier gas (02, H2, N2, etc.) containing impurities from the end opposite to the wafer insertion opening. ) 5 was normally allowed to flow in. The horizontal diffusion furnace is disclosed, for example, in Japanese Patent Application Laid-open No. 104570/1983. [0003]

[Problem to be solved by the invention]

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. Additionally, in combination with the non-uniform temperature distribution in the furnace, non-uniform gas flow velocity distribution or turbulence can cause considerable variation in device characteristics within a wafer or between wafers. There are drawbacks that arise. [0004] That is, 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 furnace There is a problem in that the density of the reactant gas introduced into the body differs between the upper and lower parts of the furnace body due to the influence of gravity, and variations occur within a single wafer. [0005] Furthermore, it is necessary to stand up 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. [0006] An object of the present invention is to provide a novel method for heat treatment of semiconductor wafers that eliminates the above-described drawbacks. In particular, it is an object of the present invention to provide a heat treatment method that avoids complicating the apparatus and eliminates the entrainment of contamination sources into the furnace tube. [0007]

[Means to solve the problem]

The present invention is characterized in that when a plurality of semiconductor wafers are heat-treated in a furnace tube in which a cylindrical space exists along a substantially vertical direction, one longitudinal end of the furnace tube is inserted into the plurality of semiconductor wafers. A cylindrical type is used, which has an open end and a closed end having a gas inlet at the other end on the opposite side in the longitudinal direction, and the plurality of semiconductor wafers are spaced at predetermined intervals in the longitudinal direction. A semiconductor wafer holding jig comprising a plurality of rod-like members each having a groove of a predetermined width into which a semiconductor wafer is engaged while maintaining the distance between the rod-like members and a member supporting both ends of the rod-like members so as to maintain a predetermined distance between the rod-like members. The tools are engaged with the grooves at a plurality of locations on the peripheral edge of the semiconductor wafer so that a predetermined interval is maintained in the longitudinal direction and the semiconductor wafers face each other, and Insert the jig into the furnace tube from the open end of the furnace tube along the
Heat treatment is performed by introducing gas into the furnace tube from the gas inlet of the furnace tube without bringing the jig into contact with the inner wall of the furnace tube.[0008]

[Effect]

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 wafers are held almost horizontally, it is easy to transfer them all at once from one jig to another, making it compatible with automation.
It can also accommodate larger diameter wafers. It also saves space and energy, and is resistant to thermal deformation. [0009] In particular, since the gas is introduced from the opposite direction to the direction in which the wafer is inserted, the structure of the apparatus, that is, the furnace tube, is not complicated, and the entanglement of contamination sources into the metal body in the furnace tube when the semiconductor wafer is inserted is avoided. This can be prevented by gas inflow from the side [0010]

【Example】

FIG. 1 is a sectional view showing the overall configuration of a diffusion treatment method according to an embodiment of the present invention. FIG. 2 shows a wafer holding jig used in an embodiment of the invention. [0011] First, in FIG. 2, a large number of semiconductor wafers 11 are arranged at approximately equal intervals in a holding jig 12 consisting of a pair of upper and lower holding members 12A and 12B. Holding member 12A. 12B have the same configuration as each other, and as shown in the figure, when stacked together, three cylindrical portions each having an inner diameter corresponding to the outer diameter of the wafer are formed by a total of six rod-shaped portions 12X. . A groove with a width corresponding to the wafer thickness is cut in the portion of each rod-like 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 has become. [0012] A large number of wafers 11 held in the wafer holding jig 12 as shown in FIG.
By rotating it and holding it in a jig holder 16, it is inserted in a substantially horizontal state into a vertical diffusion furnace (heat treatment furnace) 13 made up of a quartz tube extending vertically. The diffusion furnace 13 has a heater 14, and a carrier gas 15 containing impurities is introduced from below on the opposite side from where the wafer is inserted. [0013] In 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
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 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. [0014] FIGS. 3 and 4 show variations in current amplification factor hFE of transistors within one wafer or between multiple wafers when a large number of diffused transistors are formed for each wafer in the processing batch of FIG. 1. This is shown in comparison with the case using the conventional method. According to FIG. 3, it is clear that the variation in hFE along the Y direction within one wafer 11 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. 4, hF between wafers 11 within the same processing batch
It is clear that the variation in E is also 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. [0015]

【Effect of the invention】

(1) According to the present invention, a plurality of semiconductor wafers are heat-treated in a furnace tube in which a cylindrical space exists along a substantially vertical direction. It is more space efficient than a horizontal diffusion furnace and can save space. [0016] (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 is The jig itself can be made lightweight, and a large amount of wafers can be charged. [0017] (3) As mentioned above, the semiconductor wafer holding jig itself can be made lightweight, so the semiconductor wafer holding jig can be brought into contact with the inner wall of the furnace tube within the furnace tube as shown in FIG. Instead, heat treatment can be performed by supporting only one longitudinal end of the semiconductor wafer holding jig with the jig holder 16. That is, the semiconductor wafer holding jig can be supported in a cantilever manner. [0018] (4) If the semiconductor wafer holding jig is supported on a cantilever, it is natural that the generation of foreign matter is reduced compared to when it is supported on both sides. That is, as shown in FIG. 1, since the other longitudinal end of the semiconductor wafer holding jig is floated, there is no contact friction within the furnace tube, and therefore the generation of foreign matter is reduced. [0019] (5) According to the present invention, semiconductor wafer holding jigs are arranged at predetermined intervals along the longitudinal direction, and the jigs are placed in a furnace tube existing along the vertical direction and in contact with the inner wall thereof. Since the temperature can be maintained without heating, 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, so that temperature non-uniformity within the wafer is reduced, and heating becomes closer to uniformity. [00203 (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;
The influence of variations in gas concentration and amount is small. Therefore, the variation between lofts is also small. [0021] (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 softly generated. This allows the gas to spread uniformly between and within each wafer. [0022] (8) According to the present invention, since the plurality of semiconductor wafers are rotated almost horizontally in the horizontal plane as in the embodiment, no burden is placed on the rotation of the wafer rotation means. Uniform rotation is possible. [0023] (9) As shown in FIG. 1, since the gas flows in from the direction opposite to the support side of the semiconductor wafer holding jig, the factors that induce gas disturbance near the gas inlet are reduced, and the Uniform gas distribution between each wafer and within the wafer can be achieved. [0024] As described above, according to the present invention, variations in device characteristics within a wafer and between wafers can be significantly reduced without complicating the furnace structure or the jigs used.
The effect of being able to manufacture various semiconductor devices at high yields is the key.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a furnace body showing a diffusion method according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a wafer holding jig used in an embodiment of the present invention.

FIG. 3 is a graph showing variations in current amplification factors in a predetermined direction of a wafer, comparing the effects of the present invention with those of the prior art.

FIG. 4 is a graph showing variations in current amplification factors at wafer positions within the same processing batch, comparing the effects of the present invention with those of the prior art.

FIG. 5 is a side view showing a state in which a wafer is held in a conventional technique.

FIG. 6 is a sectional view of the entire furnace body used in the diffusion method according to the prior art.

[Explanation of symbols]

11 Semiconductor wafer 12 Wafer holding jig 13 Vertical diffusion furnace 16 Jig holder

[Document person]

drawing

[Figure 1]

[Figure 2]

[Figure 3]

[Figure 4] 1-1. phantom Y° direction

[Figure 5]

[Figure 6]

Claims (2)

[Claims] 1. In a furnace tube in which a cylindrical space exists along a substantially vertical direction, when a plurality of semiconductor wafers are heat-treated while introducing gas into the furnace tube, the plurality of semiconductor wafers are placed at a predetermined interval in the longitudinal direction. A semiconductor wafer holding jig comprising a plurality of rod-shaped members each provided with a groove of a predetermined width into which a semiconductor wafer is engaged, and a member that supports both ends of the rod-shaped members so as to maintain a predetermined distance between the rod-shaped members. In contrast, by engaging each of the grooves with the grooves, the semiconductor wafer is engaged and held at multiple locations on the periphery of the semiconductor wafer, and the jig is arranged at predetermined intervals along the longitudinal direction of the jig. The jig is inserted into a furnace tube existing along the vertical direction from a direction opposite to the direction in which gas is introduced into the furnace tube, and one longitudinal end of the jig is inserted without contacting the inner wall of the furnace tube. A method for heat treatment of semiconductor wafers, characterized in that the heat treatment is performed while supporting only on the sides. 2. 2. The method of heat treating a semiconductor wafer according to claim 1, wherein the wafer holding jig is rotated during the heat treatment.