JPS6224937B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a heat treatment furnace used for surface oxidation, annealing, impurity diffusion, etc. of semiconductor wafers during semiconductor manufacturing.

(2) Conventional technology and problems Most of the heat treatment furnaces that have been used in the past have been standardized as horizontal furnaces, in which a large number of semiconductor wafers to be processed are stored in a quartz boat and the boat is It is processed by charging it into a heated quartz tube by manual operation. As an example, Figure 1 shows
A schematic cross-sectional structure of a high-temperature oxidation treatment furnace is shown.
is a semiconductor wafer, 2 is a quartz boat, 3 is a quartz tube, 4 is a quartz cap, 5 is an insertion rod, and 6 is a heating element, humidified oxygen gas is introduced from the inlet 7 of the quartz tube, and is perpendicular to the quartz boat 2. Silicon dioxide (SiO ₂ ) is generated on the silicon (Si) surface of the semiconductor wafer 1 held upright. In this case, loading or unloading of the quartz boat is done manually.
It is a construction that is extremely difficult to automate this operation. For example, if the quartz boat is mounted on a paddle (truck) with a pull-out rod, the processing time in the furnace is determined, and an automatic charging or pull-out mechanism is provided (this mechanism is publicly known), the quartz boat can be mounted on a paddle (carriage) with a pull-out rod. I have to rely on manual work to put it on top. This is because quartz is fragile and semiconductor wafers are also fragile, so they must be handled with great care, and if a robot moves in three-dimensional space, there is a high probability of breakage.

However, in semiconductor manufacturing, not only the assembly process but also the chemical processing process, many of the processes are now automated and automated.
Such unmanned operation is extremely effective in reducing the adhesion of dirt and dust to semiconductor materials, and also has the advantage of greatly contributing to quality improvement.

(3) Purpose of the invention Therefore, the purpose of the present invention is to automate the heat treatment process, which is the most difficult to automate, and to propose a heat treatment furnace.

(4) Structure of the Invention The features of the present invention include a vertical heating furnace for storing and heating baskets in which a plurality of semiconductor wafers are stacked horizontally, and a plurality of baskets for storing the baskets before and after the heat treatment. and an insertion stage for placing the baskets in and out of the heating furnace. This is a heat treatment furnace that is equipped with a transport mechanism for transporting materials.

(5) Embodiment of the Invention FIG. 2 is a cross-sectional structural diagram of an embodiment of the present invention, and FIG. 3 shows a cross section AA' in FIG. 2. 1
0 is a vertical heating furnace, and the quartz tube 11 has a diameter of 2000 mmφ.
The length of the furnace is short, about 1 m, and it provides sufficient soaking length. The heating body 12 is divided into three blocks, each of which is temperature controlled, and the inflow gas is supplied from the inlet 13 at the top of the quartz tube 11.

In such a vertical heating furnace, the container for holding semiconductor wafers is not a boat type but a basket type. The structure is shown in FIG. 4, which is a side view of the stacked semiconductor wafers 1. The entire basket 20 is made of quartz and has a shape with three studs 22 erected on a circular base 21 with legs.
3 to form a semiconductor wafer 1 and a ring 23.
Stack them alternately. Compared to conventional boats, this type of basket has the effect of reducing crystal defects induced in semiconductor wafers, and this is because in a boat, when the semiconductor wafer is upright, gravity is applied to several points at the bottom of the wafer, so the fulcrum is However, this is thought to be because the stress is reduced because the basket is supported around the wafer by gravity on a ring-shaped surface or line.

As shown in FIG. 2, this basket 20 is automatically inserted from the lower part of the heating furnace and pulled out. In order to do this, an insertion stage 14 is located directly below the heating furnace 10, and a basket is placed on the insertion stage 14 and moved up and down by a motor from outside the dustproof box 15. Furthermore, a quartz lid is provided at the bottom of the insertion stage, and it moves up and down simultaneously with the insertion stage.

Placing on or removal from the insertion stage 14 is performed by operating a transport mechanism 16 provided on the side. The transport mechanism 16 puts out a fork, inserts it into the lower part of the circular stand 21 of the basket 20, lifts it up, and rotates it 180 degrees. Then, basket 2
0 reaches the rotary storage chamber 17, the fork can then be lowered, the basket 20 placed in that position and the fork retracted. The transport mechanism 16 is used to automatically communicate between the storage chamber 17 and the insertion stage 14 through such an operation.

In conjunction with this, the rotary storage chamber 17 rotates,
Heat treatment is performed automatically in sequence, and the entire operation is controlled by a computer. That is, after the processing of one basket is completed, (1) the storage chamber 17 rotates;
(2) The transport mechanism operates, (3) the insertion stage moves up, (4) heat treatment, (5) the insertion stage moves down, (6) the transport mechanism operates, and each operation is controlled by a computer. Therefore, the control is automatic and directed, and the basket is always in a dust-proof box and does not become contaminated.

In the above example diagram, there are only four storage rooms 17, but if this number is increased, the storage room 17 can be automatically operated for about 10 hours. For example, to describe a simple surface oxidation process, the inflow gas is humidified oxygen gas, the heating temperature is 1000-1100°C, and the time it is kept in the furnace is about 50 minutes. The temperature of the heating furnace is similarly controlled by a computer and is raised and lowered from 500°C to 1100°C and then lowered to 500°C in synchronization with the insertion and delivery of the baskets, and then the insertion stage is moved down. However, without immediately activating the transport mechanism, the material is left to cool naturally to 100 to 200 degrees Celsius for several minutes. Therefore, to process one basket, approximately 1
It takes time, and with 10 baskets, you don't need any manpower to operate it in a day.

(6) Effects of the invention Although the above is just one example, automatic processing under computer control becomes extremely easy by using a vertical heating furnace, and in addition to surface oxidation treatment, chemical vapor deposition It can be easily used in the heat treatment (annealing) process after implanting impurity atoms. Therefore, the present invention not only has the effect of reducing the number of processing steps by automatically performing the heat treatment process, but also helps improve the quality of semiconductor devices.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional heat treatment furnace, FIGS. 2 and 3 are sectional views of a heat treatment furnace according to the present invention, and FIG. 4 is a sectional view of a basket. In the figure, 1 is a semiconductor wafer, 2 is a boat, 3,
11 is a quartz tube, 10 is a vertical heating furnace, 6 and 12 are heating elements, 7 and 13 are gas inlets, 14 is an insertion stage, 15 is a dustproof box, 16 is a transport mechanism, 17
2 indicates a rotating storage room, and 20 indicates a basket.

Claims (1)

[Claims] 1. A vertical heating furnace for storing and heating baskets in which a plurality of semiconductor wafers are stacked horizontally, and a plurality of rotating storage chambers for storing a plurality of baskets before and after heat treatment; A transport mechanism is provided, which comprises an insertion stage for installing the baskets and taking them in and out of the heating furnace, and automatically transports the plurality of baskets while rotating between the insertion stage and the plurality of rotating storage chambers. A heat treatment furnace for semiconductors characterized by: