JP2003100759A - Method for manufacturing epitaxial silicon wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an epitaxial silicon wafer having a sufficient gettering effect without affected by the temperatures during the device process in a p/p+type epitaxial wafer using a substrate with low concentration of oxygen, in order to solve the problem that the gettering perfor mance becomes insufficient when the initial concentration of oxygen of the epitaxial silicon wafer substrate is low because the formation of BMD's (Bulk Micro Defect) is insufficient during the device process and to cope with the recent outstanding trend toward lower temperatures in the process. SOLUTION: After an epitaxial layer is formed on a p/p+type silicon wafer having a medium to low concentration of oxygen and a low resistivity, that is, an interstitial oxygen concentration of less than 13×10<17> (atoms/cm<3> ) and a specific resistance of 0.005 to 0.05 Ω/cm, it is raised in temperature to higher than 1,150 deg.C in an non-oxidizing atmosphere or preferably in the presence of an inert gas such as an argon gas, and after the same temperature is maintained for a few seconds, a process is applied in which it is lowered in temperature to 900 deg.C at a temperature lowering speed of more than 20 deg.C/sec, and if desired, a heating process is applied for depositing oxygen.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention uses a so-called medium to low oxygen concentration base silicon wafer (hereinafter referred to as a substrate wafer) having an interstitial oxygen concentration of 13 × 10 ¹⁷ (atoms / cm ³ ) or less. The present invention relates to a method for manufacturing an epitaxial silicon wafer having a sufficient gettering effect even in various temperature regions encountered during a device process in the epitaxial wafer.

[0002]

2. Description of the Related Art As a method for improving the gettering effect of a silicon wafer, many methods have been proposed. For example, high-temperature heat treatment at 1100 ° C. or higher is performed in advance to outwardly diffuse interstitial oxygen in the surface layer of the silicon semiconductor substrate to form a defect-free layer, and then heat treatment is performed at a relatively low temperature condition to allow the supersaturated oxygen remaining inside. By forming and growing precipitation nuclei of Cu, defects (Bu
lk Micro Defect: Hereinafter referred to as BMD. )
There is known a method of obtaining a wafer on which a film is formed.

[0003]

In recent semiconductor devices, the cell size and wiring width have become smaller due to further miniaturization, and at the same time, the junction depth has become smaller. For this reason,
The maximum temperature of the process, which was around 1200 ° C. in the past, has fallen to about 1050 ° C., and the heat treatment time is shortened. Under such a low temperature and short time process, BMD is difficult to grow and the gettering ability is deteriorated.

In addition, up to now, several millimeters to several hundreds of milliΩ ·
A so-called p / p in which an epitaxial layer having a resistivity of several to several tens Ω is laminated on a wafer substrate having a low resistivity of cm.
+ Epiwafers have been widely used. This type of wafer has been considered to have a strong gettering ability because a high concentration of boron in the substrate forms a compound with Fe. However, in recent research, metal impurities other than Fe,
In particular, it has been found that Ni and Cu do not have this effect. In order to getter such metal impurities, it is necessary to control oxygen precipitation even at p / p + to ensure gettering of the strain field of BMD.

Generally, BMD formation on an epi-wafer is determined by the interstitial oxygen concentration and process heat treatment conditions. Since the process conditions are determined by the requirements of the device structure and cannot be changed, so-called natural intrinsic gettering (hereinafter referred to as NI, which controls the oxygen concentration of the crystal and causes precipitation nucleation and growth to occur naturally during the process).
It is called G. ) Is used. The amount of BMD depends on the oxygen concentration, and if it is too small, the gettering ability is insufficient, and if it is too large, it causes a decrease in the wafer strength and the occurrence of slip. Therefore, it is a target tuned for each process and a crystal with a narrow oxygen concentration range. Need to be raised. It is difficult to control the oxygen concentration in the head and tail of the crystal, and the crystal yield is sacrificed or the device must absorb the deviation from the ideal wafer.

[0006]

Means for Solving the Problems That is, as a result of various studies for achieving the above-mentioned object, the present inventor has found that the interstitial oxygen concentration is 13 × 10 ¹⁷ (atoms / cm ³ ) or less, so-called medium to low. With oxygen concentration, specific resistance is 0.005
After forming an epitaxial layer on a 0.05 Ω · cm substrate wafer, this is heated to 1150 ° C. or higher in a non-oxidizing atmosphere, preferably in the presence of an inert gas such as argon gas, and kept at the same temperature. The present invention has been completed by finding that an epitaxial wafer having a strong gettering effect can be obtained by holding it for several seconds and then cooling it to 900 ° C at a temperature lowering rate of 20 ° C / sec or more. Is.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the substrate wafer used is not suitable as an epitaxial wafer having N-IG as a gettering site.
It is a low to medium oxygen concentration product of 3 × 10 ¹⁷ (atoms / cm ³ ) or less and has a specific resistance of 0.005 to 0.05 Ω · c.
m substrate. Even with such an oxygen concentration,
By performing the heat treatment under the above conditions, a strong gettering effect is exhibited.

The manufacturing method according to the present invention will be described below. The manufacturing method according to the present invention is preferably performed in a non-oxidizing atmosphere, preferably in an argon atmosphere, after forming the epitaxial layer on the substrate wafer. In this case, the oxygen concentration in the same atmosphere is preferably strictly controlled, and is preferably 10,000 ppma or less, more preferably 5000 ppma or less, still more preferably 1000 ppma or less. The rate of temperature rise is not necessarily limited, and a rate that can be achieved by using a commercially available rapid heating annealing furnace is sufficient. The temperature is usually 1150 ° C. or higher, and does not necessarily need to significantly exceed 1200 ° C. Preferably, it is 1150 ° C or higher and lower than 1200 ° C. When the desired temperature, for example, 1150 ° C. is reached, the same temperature is maintained for several seconds, preferably 3 seconds or more and less than 5 seconds. The holding time need not exceed 10 seconds in any case.

Immediately after maintaining the same temperature, the temperature inside the furnace is lowered. The rate of decrease of the temperature in the furnace is 20 ° C./sec or more, preferably 50 ° C./sec or more, more preferably 100 ° C./sec or more. The temperature inside the furnace was lowered to 9
The rapid cooling operation may be stopped when the temperature reaches 00 ° C., and then natural cooling may be performed.

If the gettering ability is desired from the initial stage of the device process, a heat treatment for stabilizing oxygen precipitates may be added after the above heat treatment. For example, 70
0 ° C to 800 ° C for at least 2 hours + 900 ° C to 100
By performing a two-step heat treatment for at least 2 hours at 0 ° C,
It can grow to BMD and exert a strong gettering action. The combination of each of the low temperature and the high temperature and each processing time may be set in consideration of the interstitial oxygen concentration, and may be set after performing a preliminary test as necessary. This makes it possible to obtain an epitaxial wafer that is not affected by the thermal history in the subsequent device processing steps.

[0011]

EXAMPLES The present invention will be described below with reference to examples, but of course the present invention is not limited to these examples.

The plane orientation (10
0), the interstitial oxygen concentration is about 10.90 × 10 ¹⁷ (ato
ms / cm ³ ), specific resistance of 0.007 Ω · cm of 200
After using a silicon wafer with an outer diameter of mm as a substrate wafer to form an epitaxial layer by a conventional method, the atmosphere in each leaf rapid heating annealing furnace is an argon atmosphere and the oxygen concentration in the furnace is 3000 pp.
As ma, the temperature was raised to 1200 ° C. and held for about 3 seconds, and then a heat treatment of cooling to 900 ° C. at a temperature decrease rate of 100 ° C./second was performed. In addition, a sample not subjected to the heat treatment was prepared as a comparative example for confirming the effect.

(Gettering Ability Evaluation 1) Using the epitaxial silicon wafers with the rapid heating / cooling heat treatment obtained in the above embodiment, various simulated process heat treatments including the low temperature device process shown in Table 1 were performed, The wafer was cleaved, the BMD was made visible by selective etching with a light solution, etc., and its density was obtained by using a differential interference microscope.

(Evaluation of Gettering Ability 2) The gettering ability during the process was evaluated by actually contaminating the metal. Gettering ability test method (test sample): Epitaxial silicon wafers subjected to the rapid heating / cooling heat treatment obtained in the example and subjected to various simulated process heat treatments including the low temperature device process shown in Table 1 were used. . (Metal used): As the used metal, Ni that does not form a compound with boron was used. Ni was applied to the back surface of each sample at the following concentrations as shown in FIG. (Ni concentration): 1 × 10 ¹² , 1 × 10 ¹³ , 1 × 10 ¹⁴ ,
And 1 × 10 ¹⁵ (each atom / cm ² ). (Diffusion treatment condition): The sample is heated at 950 ° C. for 10 minutes,
Ni was diffused from the back surface into the inside of the wafer. (Determination of gettering effect): Each sample after heat treatment was washed with dilute hydrochloric acid and ammonia water + hydrogen peroxide solution + ultrapure mixed solution to remove dust, and then BMD in wafer
Ni diffused from the back to the front without gettering
Particle Counter LS6000 (manufactured by Hitachi Deco)
Was measured as haze.

[0015]

[Table 1]

Table 2 shows the measurement results of the BMD density of capability evaluation 1 below. Regarding the Ni gettering effect of the performance evaluation 2, good ones are shown by ◯, and bad ones are shown by x. An example of what is judged to be good is shown in FIG. 2, and an example of what is judged to be bad is shown in FIG.

[0017]

[Table 2]

The interstitial oxygen concentration of the silicon semiconductor substrate is a so-called low to medium concentration product of 13 × 10 ¹⁷ (atoms).
/ Cm ³ ) or less, by performing rapid heating / cooling heat treatment, even if the above-mentioned low temperature / short time device process heat treatment is performed, 3.0 × 1 inside the silicon substrate is obtained.
A BMD of 0 ^{7 to} 7.6 × 10 ⁷ (pieces / cm ⁻³ ) was obtained. Further, a consistent correlation was found between the BMD density and the gettering ability of Ni.

[0019]

According to the present invention, after forming an epitaxial layer on a silicon semiconductor substrate, a high temperature short time heat treatment of rapid heating and rapid cooling is performed in a non-oxidizing atmosphere, and further, if necessary, oxygen precipitation is performed. By performing the heat treatment for the purpose, an epitaxial silicon wafer having a strong gettering effect can be manufactured.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the position and concentration of intentional Ni contamination.

FIG. 2 shows an epitaxial wafer treated according to the method of the present invention in accordance with gettering ability evaluation 2 as shown in Table 1.
3 is a photograph showing a haze map showing the surface state of a wafer that had a gettering effect among the wafers intentionally contaminated with Ni after the process simulated heat treatment of FIG.

FIG. 3 shows an epitaxial wafer treated according to the method of the present invention in accordance with gettering ability evaluation 2 in Table 1.
5 is a photograph showing a haze map showing the surface state of a wafer that was intentionally contaminated with Ni after the process simulated heat treatment of No. 1 was not added and had no gettering effect.

Claims (4)

[Claims] 1. An epitaxial silicon wafer is heated to 1150 ° C. or higher in a non-oxidizing atmosphere, held at the same temperature for several seconds, and then cooled to 900 ° C. at a temperature lowering rate of 10 ° C./second or higher. A method for manufacturing an epitaxial silicon wafer having high gettering ability. 2. The oxygen concentration contained in the base silicon wafer used for manufacturing the epitaxial silicon wafer is 13 × 10 ¹⁷ (atoms / cm ³ ASTM F121).
-76 standard) The so-called medium to low oxygen concentration of the following or less, The manufacturing method of Claim 1 characterized by the above-mentioned. 3. The manufacturing method according to claim 1, wherein the non-oxidizing atmosphere is an argon atmosphere. 4. The concentration of oxygen in a non-oxidizing atmosphere is 100.
It is below 100 ppma, It is characterized by the above-mentioned.
The manufacturing method according to any one of 1.