JPH0220831Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a wafer boat for a diffusion furnace used in the diffusion process of semiconductor device manufacturing.

[Prior Art] In the wafer process of the semiconductor device manufacturing process, a gas containing boron or phosphorus is supplied in a high-temperature diffusion furnace, and glass containing impurities that serve as a diffusion source is once formed on the wafer surface. A predetermined amount of impurity is diffused into the wafer by forming a layer and then further maintaining it at high temperature.

In the first process of forming a glass layer containing impurities (called primary diffusion), the gas needs to spread evenly in the diffusion furnace, so wafers can be arranged at regular intervals as shown in Figure 4. A wafer boat 4 for a primary diffusion furnace made of quartz and having grooves 5 cut therein is usually used.

However, in the next step of diffusing impurities from the glass layer into the wafer (referred to as secondary diffusion), in order to increase productivity, the wafers are loaded so that they are in contact with each other, as shown in Figure 3. A wafer boat 1 made of quartz without grooves is used.

[Problem that the invention aims to solve] This softening of ordinary quartz boats on the market is 1100
It is said that the process starts at about ℃, and under diffusion conditions higher than this temperature, the boat naturally softens. Therefore, if a boat full of wafers is exposed to a high diffusion temperature for several days, the boat will adhere to the wafers in the portions that support the weight of the wafers. This tendency is especially noticeable the newer the boat.

If such an adhesion phenomenon occurs, when the wafers are unloaded from the boat again after the diffusion process is completed, the wafers will be chipped due to adhesion to the boat, and in extreme cases, more than half of the loaded wafers may be wasted.

This adhesion phenomenon gradually disappears with repeated use, so conventionally this has been relied upon exclusively.

[Means for Solving the Problems] The present invention provides a boat that does not cause the above-mentioned adhesion phenomenon even in a new state, and therefore does not cause chipping of wafers. A quartz wafer boat for a diffusion furnace used in the subsequent diffusion is characterized in that its inner wall is roughened and sandblasted with #20 to #2000 abrasive.

[Function] In the present invention, since the inner wall surface of the boat is roughened, contact with the wafer is made not through the surface but at many points. Therefore, even if the boat softens, it will not adhere firmly to the wafer.

[Example 1] A new quartz wafer boat for a diffusion furnace made by Company T,
Diameter 76 with phosphorus glass layer formed on the surface by primary diffusion
Loaded with 900 mmφ semiconductor silicon wafers,
Phosphorus diffusion was performed at 1300°C for 90 hours.

After dispersion, the wafers were unloaded from the boat, but 433 of them were chipped or chipped due to adhesion to the boat.
It was damaged and became a defective product.

In other words, the yield of non-defective products was 52%.

[Example 2] A new T with the same specifications as that used in Example 1
The inner wall of a quartz wafer boat for use in a diffusion furnace manufactured by the company was sandblasted using an abrasive with a grain size of #400.
This is shown in FIGS. 1 and 2.

In this example, as can be seen in Fig. 2,
The surface roughening process is performed in a band-like manner on the contact portion with the wafer, and is not performed on other surfaces as it is unnecessary.

That is, as shown in FIG. 5, since the curvature of the wafer boat inner wall surface 2 is smaller than the curvature of the wafer 6, contact between the wafer and the boat is limited to a portion of the bottom surface of the boat.

As in Example 1, this wafer boat had a diameter of 76 mmφ with a phosphor glass layer formed on its surface by primary diffusion.
Loaded with 900 semiconductor silicon wafers, 1300
Phosphorus diffusion was carried out at ℃ for 90 hours.

After diffusion, the wafers were unloaded from the boat, but there were no chips or scratches due to adhesion of the boat, and the yield of non-defective products was 100%.

In addition to the above examples, the inner wall surface was made with grain size #16.
Similar experiments were carried out on wafers sandblasted with #2500 abrasive, and some adhesion to the wafer was observed in both cases.
It was suggested that the effect is not sufficient if it is less than or exceeds #2000.

[Effects] As mentioned above, according to the present invention, the inner wall surface of the boat is roughened by sandblasting with an abrasive material with a grain size of #20 to #2000, so that contact with the wafer is not made on the surface as in the conventional case. It depends on many things, even if the boat is in new condition.
No adhesion of boats to the wafer occurs.

Therefore, naturally, wafer chips do not occur, the yield of products increases, and productivity is greatly improved.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a wafer boat that is an embodiment of the present invention, and FIG. 2 is a plan view of a wafer boat that is an embodiment of the present invention. FIG. 3 is a perspective view of a conventional wafer boat. FIG. 4 is a perspective view of a wafer boat for a primary diffusion furnace. FIG. 5 is a front sectional view of a wafer boat loaded with wafers. DESCRIPTION OF SYMBOLS 1... Wafer boat, 2... Wafer boat inner wall surface, 3... Surface roughened surface, 4... Wafer boat for primary diffusion furnace, 5... Groove, 6... Wafer.

Claims (1)

[Scope of utility model registration request] A wafer boat for a diffusion furnace, wherein the inner wall surface of the boat is sandblasted with an abrasive of #20 to #2000.