JPS6122856B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat treatment method for impurity diffusion, oxidation, etc. of a semiconductor substrate (semiconductor wafer).

FIG. 1 shows an apparatus used in a conventional general semiconductor wafer heat treatment method. 1 is a boat, 2 is a wafer, and 3 is a diffusion furnace. A wafer 2 is placed in a groove of a boat 1, inserted into a furnace 3, and subjected to diffusion or oxidation for a predetermined period of time. That is, in this apparatus, a boat 1 with wafers 2 held upright is inserted into a furnace tube 3, and diffusion and oxidation are performed.

In this apparatus, there is no problem if the heat treatment time is under one condition, but it becomes a problem when it is necessary to perform the heat treatment under several conditions. For example, it may be possible to observe changes in sheet resistance and diffusion depth by varying the drive-in time after depositing impurities, or to observe changes in oxide film thickness by varying the oxidation time. Normally, when conducting various heat treatment experiments, the heat treatment time is often varied.

In such experiments, for example, heat treatment time is
If it is necessary to perform three conditions of 60 minutes, 120 minutes, and 240 minutes, if each condition is performed separately, a total time of 420 minutes is required. This takes time, so all wafers for each condition are placed in one boat, inserted into the furnace, and after 60 minutes have elapsed, the boat is pulled out and the wafers for 60 minutes are taken out.
There is a method of repeatedly inserting the remaining part, heat-treating it for the remaining time, and then taking it out. In this case, the heat treatment time can be reduced to 240 minutes under the third condition, but all the wafers are placed on one boat, and when the boat is pulled out, the wafers other than those to be taken out are moved to the low temperature part of the furnace. In the end, heating and cooling at high temperatures are two
Since the wafer under the first condition is subjected to 4 times, and the wafer under the third condition is subjected to 6 times, defects due to thermal distortion are likely to enter the wafer. Furthermore, at high temperatures of 1100° C. or higher, gradual cooling is usually performed using an automatic insertion device, etc., which has the disadvantage of increasing time errors, and also increases errors in the diffusion depth of impurities.

On the other hand, if there are three conditions, for example, the most preferable method would be to prepare three boats as shown in Figure 1, place wafers in each of the three boats, insert them at the same time, and take them out separately and sequentially. . However, if this method is carried out using boats shaped like 1 in Figure 1, the connections between the boats are extremely poor, and if each boat tilts during insertion and the wafer comes into contact with the furnace wall, it will break and become impractical. This method is not possible with the apparatus of FIG.

The present invention was made as a result of consideration of such problems in heat treatment. That is, in the present invention, fitting portions, such as recesses and protrusions, are formed at the front and rear of a heat treatment boat, and a plurality of boats are connected by the fitting portions, and when they are inserted into a diffusion furnace at the same time and taken out, It is characterized by a heat treatment method in which the parts are separated from the fitting part and pulled out individually.

FIG. 2 is a perspective view showing a heat treatment boat used in a method according to an embodiment of the present invention. The material of the boat 10 is, for example, quartz glass, and the lower support member 11
An upper wafer holding member 12 is connected to the top of the wafer holding member 12 via a short support 13. Wafer 18 has groove 17
held by. For example, cylindrical recesses 14, 14' are formed at the front end of the lower support member 12, and cylindrical convex parts 15, 14' are formed at the rear end.
15' is formed. These are fitting parts between the boats, and the convex part of the boat of the same shape adjacent to the front part fits into the concave parts 14 and 14', and the concave part of the boat adjacent to the rear part has the convex part 15. , 15' are inserted and fitted. 16 is a handle for pulling out the boat. It is preferable that the handle portion is shorter than the fitting portion. Furthermore, as shown in Figure 2, if the upper wafer holding member is installed offset to the rear with respect to the lower support member, the pull-out rod will easily enter the handle when pulling out the boat, and the fitting of the boat adjacent to the rear will be difficult. The holding member 12 overlaps the handle part and the handle part, and when connected, it is possible to arrange a large number of wafers close to each other in a state similar to one boat, which is convenient for uniform diffusion.

FIG. 3A is a diagram showing the boat inserted into the diffusion furnace, in which 10a, 10b, 10c are boats according to the present invention, 18 is a wafer, 19 is a furnace tube, 20 is an insertion rod, 11a, 11b, 11c. are supporting members of each boat, and 12a, 12b, and 12c are wafer holding members of each boat. In this apparatus, when performing heat treatment for three different times, for example, three boats 10a, 10b, and 10c, each carrying a wafer 18, are connected by fitting the uneven portions, and are simultaneously inserted into the furnace using the insertion rod 20. insert. At this time, three boats 10a, 10b, 10
c are connected to each other, so they can be easily inserted without tilting. When the shortest heat treatment is completed, the boat 10a in front is pulled out using the pull-out rod as shown in FIG. 3B. The boat 10a is easily separated and pulled out from the fitting portion. Thereafter, the boats 10b and 10c can be sequentially pulled out at the end of each heat treatment time.

As explained above, according to the present invention, a plurality of boats having fitting portions are connected and simultaneously inserted into a diffusion furnace while preventing the boats from tilting, and each boat is connected to the fitting portion when being pulled out. Since it is possible to separate the samples and draw them out sequentially, a simple experiment on heat treatment time does not require the total time for each individual, and only the longer heat treatment time is required, so the time required for the experiment can be greatly shortened. Therefore, each boat only needs to be inserted and pulled out once each, minimizing the effects of defects on wafers due to high temperature heating and cooling. However, it is also possible to use an automatic dethermal insertion device. In the above embodiments, the shape of the fitting part is described as a cylindrical shape and a columnar uneven part, but the shape is not limited to this, and any shape that allows adjacent boats to be fitted to each other may be used. Although the holder has been described as a wafer upright type, it can also be applied to a flat plate type or a boat on which wafers can be placed. In addition, although quartz glass has been described as the material of the boat, the present invention is also applicable to boats made of graphite, other heat-resistant materials, and other reaction-resistant gas materials.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a conventional heat treatment method using a boat, FIG. 2 is a perspective view showing a heat treatment boat used in a heat treatment method according to an embodiment of the present invention, and FIGS. FIG. 3 is a cross-sectional view showing the state of the heat treatment method. 10... Heat treatment boat, 11... Lower support member, 12... Upper wafer holding member, 14, 1
4'... Front cylindrical recess, 15, 15'... Rear cylindrical convex part, 16... Handle, 18... Wafer, 1
9...Diffusion furnace, 20...Insertion, pull-out rod.

Claims (1)

[Claims] 1. Forming fitting parts at the front and rear of a heat treatment boat on which semiconductor substrates are placed, connecting a plurality of boats by the fitting parts, and placing the plurality of boats into a diffusion furnace at the same time after installing the semiconductor substrates. 1. A method of heat treatment of a semiconductor substrate, which comprises inserting the boat, separating the boat from the fitting portion after undergoing a predetermined heat treatment, and sequentially pulling out the boat.