JPH0414218A - Manufacture of semiconductor element - Google Patents

Abstract

PURPOSE:To prevent the generation of boron particles of a large crystalline form by a method wherein a semiconductor substrate is left to stand in a nitrogen atmosphere for prescribed hours or longer after a doping process. CONSTITUTION:A silicon wafer 1 is erected on a groove in a quartz boat, is heated at about 750 deg.C in carrier gas, such as N2 gas or the like, along with a PBN plate to perform a doping process and a high-concentration boron glass layer 4 is adhered on the surface of the wafer. The wafer is stored in an atmosphere, in which N2 gas is made to flow at a flow rate of 10l/minute, for 1.5 hours or longer along with the boat. The wafer is detached from the boat under a clean booth of 30% of lower of a humidity and is erected on a groove in another boat. This boat is moved to a diffusion furnace, in which such carrier gas an N2 gas or the like is made to flow, and a drive process at 1000 deg.C or higher is performed to form a p-type region 5 of a prescribed depth. It may be though that in case boron glass comes into contact to a moisture containing atmosphere and there is a boron crystal in the vicinity of the boron glass, the boron glass is adhered on the crystal to recrystallize and large crystal grains are generated. Accordingly, when the wafer is left to stand in the nitrogen atmosphere for 1.5 hours after the doping process, a large crystallization of the wafer due to the reaction of the wafer to water is prevented from being generated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device, which includes a step of forming a boron glass layer on the surface of a semiconductor substrate and then diffusing boron into the interior of the substrate by heat treatment.

C. Prior Art] In a wafer process for manufacturing semiconductor devices,
When forming a p-type diffusion region with a depth of 40 tna or more, a diffusion method that increases the impurity concentration and prevents a decrease in lifetime is performed with good reproducibility.
Pyrolitenoch BN (asexual BN) abbreviated as PBN
It is considered best to use this as a diffusion source. Diffusion processes can be broadly divided into doping and driving. P when doping
8.03 flies toward the wafer from the BN plate, and boron is diffused into the wafer from the area not covered by the oxide film mask on the wafer surface, and at the same time a boron glass layer with a high boron concentration is formed on the wafer surface. During driving, the wafer having a boron glass layer on its surface is directly heat-treated to diffuse boron to a predetermined depth. If the boron glass layer on the wafer is removed by water washing or chemical treatment, it is not possible to obtain a deep p-type region with high concentration, so diffusion is performed as is.

[Problem to be solved by the invention]

When boron is diffused by the method described above, crystalline boron grains with a grain size of about 20 to 100 tera are seen to be generated on the wafer surface before the drive process.

If these grains are present, boron during the drive process penetrates through the masked part of the oxide film patterned by photolithography, creating a p-type head region in unnecessary parts. As a result, the resistance value of the n-type region becomes abnormal. Furthermore, if grains are generated on a fine pattern of the mask, they will electrically short-circuit the p-type head regions on both sides produced in the drive process.

The occurrence of such large crystalline boron grains causes a decrease in the yield rate of semiconductor devices during the manufacturing process. Crystalline boron particles generated after doping can be easily removed by washing with water. However, at the same time, as mentioned above, the high concentration boron glass layer is also removed, so washing with water cannot be performed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a semiconductor device in which doping is performed while preventing the formation of large crystalline boron grains as a fundamental measure to solve the above-mentioned problems.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a doping process in which a semiconductor substrate is heated in an atmosphere containing boron oxide to deposit a boron glass layer on the surface of the semiconductor substrate, and a boron glass layer is deposited on the surface of the semiconductor substrate. In a method of manufacturing a semiconductor device, which includes a drive step of heating a semiconductor substrate to which a glass layer is attached to diffuse boron into the substrate, the semiconductor substrate is left in a nitrogen atmosphere for 1.5 hours or more after the doping step, and then Let's move on to the drive process.

[Effect]

When boron glass comes into contact with an atmosphere containing moisture, B2O3
+HtO-2HB (h) reaction is known to occur, and if there is a lot of water, it will become an aqueous solution, but if there is a boron crystal nearby, it will attach to the crystal and recrystallize, producing large crystal grains. According to actual observation results, small boron grains were not observed near large crystallized boron grains.After the doping process, when left in a nitrogen atmosphere for 1.5 hours, the reaction with water occurred. It was confirmed that large crystallization caused by the above was prevented and the generation of large crystal grains could be suppressed by 100%.

〔Example〕

Figure 1 fat~(C1 conceptually shows the p-type region forming step in one embodiment of the present invention. First, oxide #2 is formed on the entire surface of the n-type silicon wafer 1, and then photolithography is performed. I buttered it and opened opening 3.
(Fig. δ)) Next, these multiple wafers are placed in the groove of a quartz boat, and a doping process is performed by heating them together with a PBN plate to about 750°C in a carrier gas such as N2, to coat the surface with a high concentration. A boron glass layer 4 was deposited (Fig.
Store in a gas atmosphere for at least 1.5 hours. Thereafter, the wafers are removed from the boat in a clean booth with a humidity of 30 Vo or less, and placed in a groove in another boat. Transfer this boat to a diffusion furnace that flows a carrier gas such as N2,
The p-type region 5 with a predetermined depth is formed by performing a drive process at a temperature of 1000°C or higher (see Figure 1). No formation of a p-type head region was observed in positions where no p-type head was present.

〔Effect of the invention〕

According to the present invention, the generation of large crystalline boron grains from the boron glass layer formed in the doping process is suppressed by leaving the semiconductor substrate in a nitrogen atmosphere after the doping process, and the generation of large crystalline boron grains due to diffusion through the mask is suppressed. It was possible to prevent the formation of no boron diffusion process. This results in
The occurrence of defective products during the boron diffusion process has been significantly reduced, making it possible to maintain a high rate of non-defective products.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view conceptually showing the boron diffusion process according to an embodiment of the present invention in the order of fat or C1. ■ = silicon wafer, 2: #I film, 4: boron glass layer, 5: p-type head area. Daij! Personal patent attorney Iwao Yamaguchi

Claims (1)

[Claims] 1) A doping process in which the semiconductor substrate is heated in an atmosphere containing boron oxide to deposit a boron glass layer on the surface of the semiconductor substrate, and a drive process in which the semiconductor substrate with the boron glass layer attached is heated to diffuse boron into the substrate. 1. A method for manufacturing a semiconductor device, comprising: leaving the semiconductor substrate in a nitrogen atmosphere for 1.5 hours or more after the doping step, and then proceeding to a drive step.