JPS62198118A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve the reliability of a semiconductor element and to manufacture a semiconductor device having high yield by uniformizing thermal energy applied to wafers after finishing two steps of forming a thin polycrystalline film by a reduced pressure CVD method and adding an impurity to the thin polycrystalline film by a vapor diffusing method. CONSTITUTION:In the steps of forming a conductive layer, the total C of ther mal energy distributions A, B of a furnace 1 applied to wafers 2 after finishing two steps of forming a thin polycrystalline film and adding an impurity while holding the uniformity of the film thickness in the forming step and the uniform ity of resistors in the adding step. As a result, the diameters of the particles on the many wafers 2 after finishing vapor diffusing step can be fallen within the range approx. 2,000-3,000Angstrom , and the irregularity becomes very small. There fore, the diameter of the particles, the thickness and the resistances of thin polycrystalline film after finishing the two steps all become uniform among the wafers 2, and the reflectively and the oxidizing velocity of the film all become uniform among the wafers 2.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a semiconductor device, and particularly to a method for manufacturing a high-yield, highly reliable semiconductor device having a conductive layer.

Conventional technology Low pressure CV is one of the methods for forming conductive layers in semiconductor devices.
There is a method in which a polycrystalline thin film such as polysilicon is formed by the D method, and then an impurity such as phosphorus is added to the polycrystalline thin film by a vapor phase diffusion method to lower the resistance of the polycrystalline thin film.

FIG. 2 shows an example of the thermal energy distribution of each process furnace according to the conventional technique of this method. Since the thermal energy given to each wafer is given by the product of temperature and time, this thermal energy distribution is determined by the temperature distribution set in each furnace.

FIG. 2a schematically shows a large number of wafers inserted into a low-pressure CVD furnace and a diffusion furnace.
The reaction gas 4 is sent while the is placed on the boat 3.

Figure 1 and Figure C show the thermal energy distribution set in the reduced pressure CVN furnace and diffusion furnace, respectively. It shows. Note that the broken line in d of the same figure shows the distribution of FIG. 1 and C of the same figure as is.

The position on the horizontal axis in b-c in FIG. 4 corresponds to the wafer position in FIG. 4.

Generally, in a process of forming a polycrystalline thin film using a low pressure CVD method, the temperature distribution of the low pressure CVD furnace is determined so that the thickness of the polycrystalline thin film is the same on a large number of wafers inserted into the low pressure CVD furnace. Similarly, when adding impurities to a polycrystalline thin film using the vapor phase diffusion method, the temperature distribution of the furnace is determined so that the resistance of the polycrystalline thin film is the same on a large number of wafers inserted into the diffusion furnace. Therefore, since the temperature distribution of each house is determined independently, the thermal energy applied to the wafers after the completion of the two steps described above is non-uniform among the wafers, as shown in FIG. 2d.

Problems to be Solved by the Invention As mentioned above, after the completion of the above two steps, there is non-uniformity in the thermal energy applied to each wafer. The particle size of
unevenness between the two.

For example, in the process of growing a polysilicon film with a thickness of 4,000 using the reduced pressure CT/D method, if a temperature difference of 30°C is set between the entrance and the back of the furnace, the grain size of the polysilicon after growth will be The numbers vary between 500 and 3,000 people at the top of Unino in the back. Furthermore, by adding a heat treatment of about 100° C. in the next step of adding impurities using a vapor-phase diffusion method, the crystal grains grow two to three times, and the range of variation becomes even larger. The variation in crystal grain size after the completion of the gas phase diffusion step is as much as 500% or more.

As a result, for example, the reflectance of a polycrystalline thin film becomes non-uniform,
Non-uniform resist dimensions may occur during resist exposure in the subsequent mask alignment process, or non-uniform oxide film thickness may occur due to differences in oxidation speed when forming an interlayer insulating film by thermally oxidizing the upper layer of a polycrystalline thin film. Problems such as this occur.

Means for Solving the Problems In order to solve the above-mentioned problems, in the method of manufacturing a semiconductor device according to the present invention, the thermal energy applied to each wafer is made uniform after the completion of the above-mentioned two steps. In other words, while maintaining the uniformity of film thickness and resistance in each process, the temperature distribution of each unit is set so that the total thermal energy given to the wafer in the two processes is equal between the two processes. It is possible to make the grain size of the polycrystalline thin film uniform after the process is completed.

Effect: According to the method of manufacturing a semiconductor device according to the present invention, the grain size of the polycrystalline thin film after the completion of the two steps is uniform;
The reflectance of the polycrystalline thin film is uniform between wafers, and it is possible to reduce variations in resist dimensions in subsequent mask steps.

Furthermore, even when the upper layer of the polycrystalline thin film is thermally oxidized to form the glabellar insulating film, the oxidation rate is uniform, so there is no unevenness in the oxide film thickness, improving device reliability and increasing yield. It is possible to manufacture semiconductor devices with high performance.

Embodiment FIG. 1 shows an example of the thermal energy distribution for each house in the conductive layer forming process according to the present invention.

Figure 1a schematically shows a large number of wafers inserted into a vacuum CVD furnace and a diffusion furnace, which have the same configuration as the conventional one.
The thermal energy distribution set in the D furnace and the diffusion furnace, the solid line d in the same figure shows the distribution that is the sum of the thermal energy distributions shown in the same figure and in the same figure C. Note that the broken line in d in the same figure shows the distributions in d and c in the same figure as they are.

As shown in Figure 1d, the thermal energy given to the sea urchins in the two steps is uniform. In this example, the uniformity of the film thickness in the polycrystalline thin film formation process and the uniformity of resistance in the impurity addition process are maintained, while the thermal energy applied to the unino after the completion of the above two processes is made uniform. By setting the temperature distribution of each house, many combinations are possible.

As a result, the particle size on a large number of sea urchins after the vapor phase diffusion process can be kept to about 2000 to 30008, and the variation is 60%, which is less than one-tenth of the conventional value, which is extremely small.

Therefore, the grain size, film thickness, and resistance of the polycrystalline thin film after the above two steps are all uniform between wafers. As a result, the reflectance and oxidation rate of the polycrystalline thin film are uniform across all wafers, making it possible to manufacture semiconductor devices with high reliability and yield.

Effects of the Invention As is clear from the above embodiments, according to the method of manufacturing a semiconductor device of the present invention, it is possible to manufacture a highly reliable semiconductor device at a high yield.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram and a thermal energy distribution diagram of an embodiment showing the method of manufacturing a semiconductor device according to the present invention, and FIG. 2 is a schematic diagram and a thermal energy distribution diagram of a conventional example. 1...Furnace, 2...Wafer, 3...
...Boat, 4...Reactant gas. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure /- Furnace wafer position sea urchin △ position 亙 sea urchin 8th place!

Claims (3)

[Claims] (1) Includes a step of forming a polycrystalline thin film by a low pressure CVD method and a step of adding impurities to the polycrystalline thin film by a vapor phase diffusion method, and includes a low pressure CVD furnace temperature distribution in the polycrystalline thin film forming step and diffusion in the impurity addition step. A method for manufacturing a semiconductor device, characterized in that the furnace temperature distribution is set so that the thermal energy applied to each of a large number of wafers inserted into the two furnaces is the same after the two steps are completed. (2) The semiconductor device according to claim 1, wherein the temperature distribution of the low pressure CVD furnace is set so that the thickness of the polycrystalline thin film formed on a large number of wafers inserted into the low pressure CVD furnace is the same. manufacturing method. (3) The temperature distribution of the diffusion furnace is set so that the resistance of the polycrystalline thin film formed on a large number of wafers inserted into the diffusion furnace is the same. A method for manufacturing a semiconductor device.