JPH0982654A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To diffuse the concentration of impurities, which are diffused in semiconductor wafers, in a high concentration uniformly from the surfaces of the wafers to the deep regions to enhance the gettering effect of contamination by a method wherein before diffused layers are respectively formed in the semiconductor substrates by an impurity thermal diffusion method, thin oxide films are respectively formed on the surfaces of the semiconductor substrates. SOLUTION: A quartz tube 3 is filled with oxygen gas by its introduction and a wafer mount boat 4 is inserted in the tube 4. While the oxygen gas is introduced in the tube 3, the interior of the tube 3 is heated by heating heaters 2 and after the interior of the tube 3 is made to heat up to a prescribed temperature, nitrogen gas and source gas are introduced in the tube 3 in addition to oxygen gas. A prescribed time of a heat treatment is performed in an atmosphere with these gases introduced therein and the heating of the interior of the tube 3 is stopped. By such an impurity thermal diffusion method, an oxygen gas atmosphere is made before impurities are diffused in semiconductor wafers and oxide films are respectively formed on the surfaces of the wafers. Thereby, a high impurity concentration can be diffused to the deep regions in the wafers in an even manner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly to improvement of a method of forming an impurity diffusion layer.

[0002]

2. Description of the Related Art In general, when an impurity diffusion layer is formed by thermally diffusing impurities in a semiconductor substrate (semiconductor wafer), a thermal diffusion device having a structure as shown in FIG. 2 is used. In this heat diffusion device, the quartz tube 3 serving as a reaction chamber, and the quartz tube 3
A vacuum chamber is formed with the cap / elevator 7 that matches the opening of the. On the cap / elevator 7, a boat support and heat retention cylinder 6 and a wafer mounting boat 4 for loading a plurality of semiconductor wafers are provided.

This vacuum chamber is covered with a heater 2 on the outside, is further provided with a gas inlet 8 and a gas exhaust port 9, and an exhaust system composed of an exhaust pump (not shown) is provided on the gas exhaust port 9 side. It is provided.

Further, the gas introduction port 8 is connected to a gas introduction system including a mass flow controller 11 for introducing a process gas of three systems for thermally diffusing impurities, a valve 10 and a gas pipe. The gas system used is, for example, an inert gas (nitrogen gas: N ₂ ) for the gas G1, an oxidizing gas (oxygen gas: O ₂ ) for the gas G2, and phosphorus oxychloride or the like for the gas G3. A bottle 1 is provided in the gas path, and a source gas in which phosphorus gas or the like is mixed with a source carrier gas (N ₂ ) is used.

Diffusion of impurities by such a thermal diffusion device is carried out in the sequence shown in FIG. In this step, the semiconductor wafer loaded in the boat 3 is fitted by raising the cap / elevator 7 and inserting it into the quartz tube 3. After that, only the nitrogen gas (gas G1) is introduced into the quartz tube 3 to fill it (t1). In this nitrogen gas atmosphere, the heater 2 is heated to raise the temperature inside the quartz tube 3 to a predetermined temperature (900 to 1100 ° C.) (t2). After that, thermal diffusion of impurities is performed in an atmosphere in which oxygen gas (gas G2) and phosphorus gas (gas G3) serving as a source gas are introduced in addition to nitrogen gas.

By such a sequence, a phosphorus diffusion layer is formed on the semiconductor wafer. For example, as shown in FIG. 7, when a ring getter is applied to a P-type substrate (or P-type layer), impurities are diffused from the surface of the P-type substrate by a thermal diffusion device to form an impurity diffusion layer, and a heavy metal or the like is formed. And the upper part including the impurity diffusion layer is removed.

[0007]

The profile of the impurity concentration in the depth direction of the diffusion layer formed by the above-described conventional forming method is shown by the plot of X mark in FIG. FIG.
Indicates the relationship between the impurity concentration and the depth,
The conventional forming method (marked with X) has a characteristic that the concentration of the substrate surface is high, but the impurity concentration is gradually lowered in the depth direction. That is, since the impurity concentration in the deep region is low, there is a problem that the getter effect such as heavy metal contamination is weak and the lifetime is short.

Therefore, the conventional impurity diffusion cannot sufficiently remove heavy metals and the like. Therefore, it is an object of the present invention to provide a method for manufacturing a semiconductor device in which a high impurity concentration is uniformly diffused to a deep region and a getter effect of contamination is enhanced.

[0009]

In order to achieve the above object, the present invention is a semiconductor device in which a diffusion layer of a second type conductor is formed on a semiconductor substrate made of a first type conductor which is mounted in a reaction chamber. In the manufacturing method of the above, an oxidizing gas or a mixed gas of an oxidizing gas and an inert gas having an arbitrary mixing ratio is introduced into the reaction chamber, and the reaction chamber is placed in an atmosphere of the oxidizing gas or the mixed gas. The semiconductor substrate is inserted and 5 × 1 is formed on the surface of the semiconductor substrate until the impurities are diffused.
Provided is a method for manufacturing a semiconductor device in which an oxide film having a thickness of 0 ⁻² μm or less is formed and an impurity concentration of a second type diffusion layer has a uniform profile in the depth direction.

According to the method of manufacturing a semiconductor device having the above-described structure, a thin oxide film is formed on the surface of the semiconductor substrate before the diffusion layer is formed by thermal diffusion of impurities, so that the impurities diffused in the semiconductor wafer are formed. Is uniformly diffused from the surface to a deep region at a high concentration, and the high concentration diffusion layer enhances the gettering effect of heavy metal contamination and removes heavy metals and the like.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of thermal diffusion of impurities by the method for manufacturing a semiconductor device of the present invention will be described below with reference to the drawings. In carrying out the first embodiment, the heat diffusion device shown in FIG. 2 having the same configuration as the conventional one is used. Thermal diffusion of impurities by this thermal diffusion device Fig. 1
It will be described with reference to the sequence of manufacturing steps shown in FIG.

The gas used as the process gas of the three systems for thermally diffusing the impurities is, for example, an inert gas (nitrogen gas: N ₂ ) for the gas G1 and an oxidizing gas (oxygen gas) for the gas G2. : O _2), and oxychloride Aer Lingus and carrier gas (N ₂₎ gas G3.

First, oxygen gas (gas G2) is introduced into the quartz tube 3 serving as a reaction chamber to fill it (t11), and thereafter,
A wafer mounting boat 4 loaded with a semiconductor substrate (semiconductor wafer) is inserted. That is, the cap is lowered and the quartz tube 3
Is released (atmospheric state), oxygen gas is introduced to bring the inside of the quartz tube 3 into an oxygen gas atmosphere state.

Then, while introducing oxygen gas, the inside of the quartz tube 3 is heated by the heater 2 to a predetermined temperature (900-1).
After the temperature is raised to 100 ° C. (t12), in addition to oxygen gas, nitrogen gas of gas G1 and source gas (phosphorus) of gas G3 are introduced.

In the atmosphere in which these gases are introduced, heat treatment is performed for a predetermined time (t13) and heating is stopped. At the same time, the introduction of source gas and oxygen gas is stopped. Then, the semiconductor wafer is cooled in a nitrogen gas atmosphere, cooled to a predetermined temperature, and then taken out (t14).

By such a thermal diffusion method of impurities, an oxygen gas atmosphere is created before the impurities are diffused to form an oxide film on the surface of the semiconductor wafer. This oxide film has a film thickness of 5 × 10 ^-2 μm or less, and 1 × 10 ^-2 μm
About m is preferable.

Therefore, it suffices that the thickness of the oxide film be formed, and the flow rate of oxygen gas and the above-mentioned steps (t11) and (t1).
The time between 2) and may be set arbitrarily. The semiconductor wafer manufactured by this thermal diffusion method of impurities has a relationship of the impurity concentration with respect to the depth as shown by a circle in FIG. 3, and the impurity concentration on the substrate surface is 1 × 10 ¹⁹ (atoms / cm ³ ) level. At a concentration, impurities are diffused uniformly (box-like profile) to a depth of about 2.5 μm.

Further, as shown in FIG. 4, the lifetime was about 100 μsec in the conventional manufacturing method, but it was 220 μm by using the manufacturing method of the present invention.
It has been improved to about sec.

Next, the second embodiment will be described with reference to the sequence of manufacturing steps as shown in FIG. In the second embodiment, the same heat diffusion device as the configuration of the first embodiment is used.

First, the wafer mounting boat 4 loaded with semiconductor wafers is inserted into the quartz tube 3 of the reaction chamber. Then, while exhausting the inside of the quartz tube 3, nitrogen gas (gas G1) and oxygen gas (gas G2) are introduced and filled (t21). The mixing ratio of nitrogen gas and oxygen gas is preferably about 90:10.

Then, while introducing nitrogen gas and oxygen gas, the inside of the quartz tube 3 is heated by the heater 2 to raise the temperature to a predetermined temperature (900 to 1100 ° C.) (t22).
In addition to nitrogen gas and oxygen gas, phosphorus gas (gas G3) serving as a source gas is introduced. Heat treatment is performed for a predetermined time in an atmosphere in which these gases are introduced, and heating is stopped (t23). At the same time, the introduction of source gas and oxygen gas is stopped. Then, the semiconductor wafer is cooled in a nitrogen gas atmosphere, cooled to a predetermined temperature, and then taken out (t24).

The oxide film formed before the impurity diffusion according to the second embodiment preferably has the same film thickness as that of the first embodiment. Therefore, it is sufficient that the oxide film has a desired film thickness, and the conditions for forming the oxide film are the time between the steps (t21) and (t22) described above and the mixture of nitrogen gas and oxygen gas. The ratio may be set arbitrarily.

According to the second embodiment as described above, the same effect as that of the first embodiment can be obtained. Next, a third embodiment will be described.

In the above-described first and second embodiments, after mounting on the heat diffusion device, an oxygen gas atmosphere was created in the quartz tube 2 of the heat diffusion device to form an oxide film.
In the embodiment, the above-mentioned 5 × 10 5 before being attached to the heat diffusion device.
Form an oxide film of ^-2 μm or less.

Therefore, the semiconductor wafer having the oxide film formed on the surface thereof is mounted in a thermal diffusion apparatus, and impurities are diffused by the conventional thermal diffusion method shown in FIG. That is,
The heater 2 is heated to a predetermined temperature in a nitrogen gas atmosphere, and the impurity diffusion step is performed. According to the third embodiment, the same effect as that of the first embodiment can be obtained.

As described above, by using the impurity thermal diffusion method according to the semiconductor manufacturing method of the present invention,
The impurity concentration diffused in the semiconductor wafer is uniformly diffused from the surface to the deep region at a high concentration.

Therefore, the gettering effect such as heavy metal contamination is enhanced by the uniform high-concentration diffusion layer down to the deep region,
Heavy metals and the like can be removed sufficiently, and the lifetime can be doubled or longer than before.

[0028]

As described in detail above, according to the present invention, it is possible to provide a method for manufacturing a semiconductor device in which a high impurity concentration is uniformly diffused into a deep region to enhance the gettering effect of contamination.

[Brief description of drawings]

FIG. 1 is a diagram showing an impurity diffusion process of the present invention by a thermal diffusion device as a first embodiment.

FIG. 2 is a diagram showing a configuration of a thermal diffusion device that thermally diffuses impurities to form an impurity layer.

FIG. 3 is a diagram showing a relationship between a depth of an impurity diffusion layer formed on a semiconductor wafer and an impurity concentration.

FIG. 4 is a diagram for comparing the lifetimes of the conventional manufacturing method and the manufacturing method of the present invention.

FIG. 5 is a diagram showing an impurity diffusion process of the present invention by a thermal diffusion device as a second embodiment.

FIG. 6 is a diagram showing a conventional impurity diffusion process using a thermal diffusion device.

FIG. 7 is a view showing a cross section of a semiconductor wafer on which an impurity diffusion layer is formed by a thermal diffusion device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Bottle, 2 ... Heater, 3 ... Quartz tube, 4 ... Wafer mounting boat, 5 ..., 6 ... Boat support and heat insulation cylinder, 7 ... Cap and elevator, 8 ... Gas inlet, 9 ... Gas exhaust,
Gas G1 ... inert gas (nitrogen gas: N _2), gas G2 ...
Oxidizing gas (oxygen gas: O ₂ ), gas G3 ... Source carrier gas (N ₂ ).

Claims (3)

[Claims] 1. A method of manufacturing a semiconductor device, wherein a diffusion layer of a second type conductor is formed on a semiconductor substrate made of a first type conductor mounted in a reaction chamber, wherein an oxidizing gas is introduced into the reaction chamber. The semiconductor substrate is inserted into the reaction chamber in an oxidizing gas atmosphere, an oxide film is formed on the surface of the semiconductor substrate until impurities are diffused, and the impurity concentration of the second type diffusion layer is A method for manufacturing a semiconductor device, which has a uniform profile in the depth direction. 2. A method of manufacturing a semiconductor device in which a second type diffusion layer is formed on a first type semiconductor substrate mounted in a reaction chamber, wherein an oxidizing gas and an inert gas are mixed in the reaction chamber at an arbitrary mixing ratio. Is introduced into the reaction chamber, and the semiconductor substrate is inserted into the reaction chamber in a mixed gas atmosphere, and an oxide film is formed on the surface of the semiconductor substrate until impurities are diffused. The method for manufacturing a semiconductor device, wherein the impurity concentration of the diffusion layer has a uniform profile in the depth direction. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the oxide film formed on the semiconductor substrate has a thickness of 5 × 10 ⁻² μm or less.