JP2001345321A - Oxidation treatment method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that the uniformity in film thickness becomes poor when a treatment temperature is reduced in the so called dry oxidation method for obtaining a silicon oxide film, by supplying oxygen and hydrogen chloride gases into the reaction tube of, for example, a vertical heat-treating device and oxidizing the silicon layer of a semiconductor wafer. SOLUTION: A heater part is provided in the middle of the gas supply tube outside the vertical heat-treating device, thus heating the mixed gas of the hydrogen and hydrogen chloride gases before supplying into the reaction tube. For example, when the treatment temperature of the reaction tube is equal to 800 deg.C, the mixed gas is heated to approximately 1,000 deg.C, thus generating a small amount of moisture by allowing both gases to react each other. Although the moisture increases the film of the silicon oxide film, the change in the amount of generation of moisture depending on a position in a surface can be avoided when flowing from the peripheral of the wafer to a center, and the uniformity in the surface of the film thickness can be improved by generating moisture, for example, in nearly balanced state in advance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxidizing method for forming a silicon oxide film and an apparatus therefor.

[0002]

2. Description of the Related Art A large number of semiconductor wafers (hereinafter referred to as "wafers") are loaded into a batch furnace, and a silicon oxide film (SiO2 film) is formed by oxidizing a silicon film on the wafer to form a silicon oxide film (SiO2 film). And a dry oxidation method using hydrogen chloride (HCl) gas, a wet oxidation method in which oxygen gas and hydrogen (H2) gas are burned outside to generate steam, and the steam and oxygen gas are introduced into the reaction tube. It is known, and an oxidation method is selected according to a target film quality.

[0003] Among these oxidation methods, the dry oxidation method includes:
While the silicon film is oxidized by oxygen gas, impurities on the surface are removed by the gettering effect of chlorine. Specifically, for example, a large number of wafers are held in a boat in a shelf shape, loaded into a vertical reaction tube, and a processing atmosphere is heated by a heater surrounding the reaction tube, and then an oxygen gas and a hydrogen chloride gas are heated. Is supplied into the reaction tube from the ceiling of the reaction tube at room temperature and exhausted from the lower side.

[0004]

By the way, the higher the process temperature is, the more easily a defect called a slip is generated on the wafer, and in order to avoid the influence of heat on the film deposited on the underlayer, it is also necessary to save energy. Therefore, lowering the process temperature is being studied.

However, when the process temperature is lowered,
Along with the increase in the diameter of the wafer, the uniformity of the film thickness within the surface of the wafer deteriorates, and the wafer-to-wafer (between the surfaces)
The variation in the film thickness also increases.

Examining the relationship between the mounting position of the wafer on the boat and the film thickness, the uniformity of the film thickness tends to be worse as it is located on the upper side of the boat. The present inventors presume the reason for this as follows. FIG.
(A), (b), and (c) schematically show the gas flow on the wafer W, the temperature and the film thickness of the wafer W, respectively. The oxygen gas and the hydrogen chloride gas flow from the periphery (edge) of the wafer W toward the center, and silicon on the wafer is oxidized by the oxygen gas. However, since the heat of the wafer W is radiated from the periphery, the temperature is set at the center. It gets higher as you go. For this reason, since the oxidation reaction is promoted at the center, even when the film thickness uniformity is high, the film thickness tends to be originally larger at the center than at the periphery.

On the other hand, hydrogen generated by the decomposition of hydrogen chloride reacts with oxygen to produce a small amount of water vapor. Since the gas is not sufficiently heated on the upper side of the boat, the amount of water vapor generated increases as the gas is heated from the peripheral edge to the center of the wafer W. This water vapor has the effect of increasing the thickness of the oxide film, and the difference in the amount of generated water vapor has a great effect on the film thickness. As a result, the film thickness distribution becomes a so-called mountain-shaped distribution in which the film thickness at the central portion of the wafer W is large, and the uniformity is deteriorated. Then, since the gas is heated toward the lower side of the reaction tube, the reaction of generating water vapor is substantially in an equilibrium state on the lower side of the boat, and the wafer W
Water vapor has already been generated and exhausted before the gas flows along. Therefore, when the processing gas flows from the peripheral edge of the wafer W toward the center, the amount of water vapor hardly changes regardless of the position of the wafer W, so that the uniformity of the film thickness is improved. From these facts, it is considered that the uniformity of the film thickness on the upper stage side of the boat is considerably poor, and the difference in the film thickness between the upper and lower wafers is large. As a result, it is currently difficult to lower the process temperature.

The present invention has been made under such circumstances, and it is an object of the present invention to provide a so-called dry oxidation treatment for an object to be processed, whereby a high uniformity of an oxide film thickness can be obtained. It is an object of the present invention to provide a technology capable of contributing to lowering the temperature.

[0009]

According to the present invention, an object to be processed having a silicon layer formed on at least a surface thereof is carried into a reaction vessel, and the inside of the reaction vessel is heated to a predetermined processing temperature, and hydrogen and chlorine are removed. In a method of supplying a processing gas containing a gas containing a compound containing oxygen and an oxygen gas into a reaction vessel to oxidize the silicon layer to form a silicon oxide film, the processing gas is supplied into the reaction vessel. The method is characterized in that a small amount of water is generated by applying energy to the processing gas.

The step of applying energy to the processing gas is, for example, a step of generating water to such an extent that the generation of water is not further promoted at the processing temperature in the reaction vessel. This step is a step of heating the processing gas by, for example, a heating unit provided in a gas supply pipe. In this case, the heating temperature is preferably higher than the processing temperature in the reaction vessel. The gas composed of a compound containing hydrogen and chlorine is, for example, hydrogen chloride gas.

As an example of an oxidation treatment apparatus for carrying out this method, an object to be treated is carried into a reaction vessel, and the inside of the reaction vessel is heated to a predetermined treatment temperature to produce a gas containing a compound containing hydrogen and chlorine. , An oxygen gas, and a heat treatment apparatus that supplies a processing gas containing the gas into the reaction vessel to oxidize the object to be processed, a gas supply pipe that supplies the processing gas into the reaction vessel, and the gas supply pipe. And a heating section for heating the processing gas before supplying the processing gas into the reaction vessel to generate a trace amount of water. As a heat treatment apparatus, for example, a large number of objects to be processed are held in a holder in a shelf shape, carried into a vertical reaction vessel, and heated inside the reaction vessel to a predetermined processing temperature by a heater surrounding the reaction vessel. A mold heat treatment device is used.

Further, the heating section is provided with a ventilation resistor, a heating chamber for heating the processing gas, and a heating chamber provided around the heating chamber and containing a small amount of metal impurities, such as a high-purity carbon material. It is preferable to provide a heater having a heater portion sealed in ceramics such as quartz.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing an example of an oxidation treatment apparatus used to carry out the oxidation treatment method of the present invention. The oxidation treatment apparatus includes a vertical heat treatment apparatus 1 and a heating unit 2 for heating the treatment gas before introducing the treatment gas into the vertical heat treatment apparatus 1. The structure of the vertical heat treatment apparatus 1 will be described.
As shown in FIGS. 1 and 2, a vertical heat treatment furnace 3, a wafer boat 4 as a holder, a boat elevator 40 for raising and lowering the wafer boat 4, and a heat treatment furnace 3 are connected. A gas supply pipe 5 and an exhaust pipe 30.

The vertical heat treatment furnace 3 includes a reaction tube 31 which is a reaction vessel made of, for example, quartz, a heater 32 which is a heating means provided with a resistance heating element provided around the reaction tube 31, and the like. A heat equalizing container 33 provided between the reaction tube 31 and the heater 32 and supported by a heat insulator 34. The reaction tube 31 has an open lower end,
A gas diffusion plate 31c having a large number of gas holes 31b is provided slightly below the upper surface 31a. The gas supply pipe 5
Is piped through the heat insulator 34 from the outside, bent in an L-shape inside the heat insulator 34 and vertically raised between the reaction tube 31 and the soaking container 33, The projection 31 protrudes into the space between the upper surface 31a and the gas diffusion plate 31c.

The wafer boat 4 is provided with a plurality of columns 43, for example, between a top plate 41 and a bottom plate 42 in FIG. 1, and inserts and holds the peripheral edge of the wafer W in a groove formed in the column 43 in the vertical direction. It is configured to be. The wafer boat 4 has a lid 44 for opening and closing the opening 35 at the lower end of the reaction tube 31.
It is placed on the top via a heat insulation section, for example, a heat insulation cylinder 45. The heat retaining cylinder 45 is mounted on a turntable 46 and can be rotated via a rotary shaft 47 by a driving section M provided on the boat elevator 40. The lid 44 is provided on the boat elevator 40, and the wafer boat 4 is carried into and out of the heat treatment furnace 3 by moving the boat elevator 40 up and down.

The heating section 2 is provided outside the vertical heat treatment apparatus 1 and in the middle of the gas supply pipe 5 as shown in FIG. The heating unit 2 includes a heating tube 21 made of, for example, transparent quartz, which forms a heating chamber, a heater 22 spirally formed outside the heating tube 21, a heating tube 21 and a heater 22. A cooling water passage 24 for allowing a coolant, such as cooling water, to flow therethrough. In the heating tube 21,
For example, a number of transparent quartz glass beads 2 which are ventilation resistors
Many 0s are filled. By providing the ventilation resistor, the residence time of the gas is prolonged, and the gas is heated efficiently by heating the ventilation resistor and flowing while contacting the gas.

The heater portion 22 is formed by knitting a plurality of fiber bundles made of, for example, a metal having a small amount of metal impurities, for example, a high-purity carbon fiber to form a string. Are formed in a spiral shape by being enclosed in a box, and generate heat when energized by the power supply line 25. Reference numeral 26 denotes a temperature sensor composed of a thermocouple.

The gas supply pipe 5 is branched downstream of the heating section 2 through a valve V0, and branched pipes 51 and 52.
Are connected to an oxygen gas source 53 and a hydrogen chloride gas source 54, respectively. V1 and V2 are valves, and MF1 and MF2 are mass flow controllers which are gas flow sections. The heating section 2 is preferably provided as close as possible to the heat treatment furnace 3 in order to prevent the heated gas from cooling before entering the heat treatment furnace 3.

Next, the operation of the above embodiment will be described. First, a large number of wafers W to be processed, for example, 60 wafers each having a silicon layer formed on the surface thereof, are held in a shelf shape on a wafer boat 4, and are heated to a predetermined temperature by a heater 32 in advance. The boat 35 is carried into the interior 31 by a boat elevator 40, and the opening 35 serving as a furnace port is airtightly closed by a lid 44 (the state shown in FIG. 1). Subsequently, a predetermined processing temperature, for example, 800
The inside of the reaction tube 31 is heated up to ° C. In the step of loading the wafer W and the step of raising the temperature inside the reaction tube 31, for example, a nitrogen gas mixed with a slight amount of oxygen gas is supplied into the reaction tube 31 from a gas supply pipe not visible in the drawing. Tube 3
When the inside of the reaction tube 1 reaches the processing temperature, the supply of gas is stopped, and the inside of the reaction tube 31 is slightly depressurized by exhausting the inside of the reaction tube 31 through an exhaust pipe 30 by an exhaust means (not shown). After stabilizing, an oxidation treatment is performed.

On the other hand, in the heating section 2 provided outside the vertical heat treatment apparatus 1, the inside of the heating pipe 21 is heated to, for example, 1000 ° C.
, And the valve V0 is opened to allow a processing gas composed of oxygen gas and hydrogen chloride gas to flow through the heating pipe 21. The processing gas flows out through the gaps while contacting the transparent quartz glass beads 20 in the heating tube 21,
While passing here, it is heated to around 1000 ° C. As a result, it is considered that the oxygen gas and the hydrogen chloride gas react as shown in the following formula to generate a minute amount of water vapor, for example, on the order of several hundred ppm. 2HCl → H2 + Cl2 H2 + 1 / 2O2 → H2 0 The processing gas thus heated enters the heat treatment furnace 3, rises while being heated through the inside of the soaking tube 33, and flows into the upper part of the reaction tube 31. Further, the processing gas is supplied to the gas holes 31.
b to the processing area in the reaction tube 31, and is exhausted from the lower exhaust pipe 30. At this time, the processing gas enters between the wafers W stacked on the shelf, and the wafer W
The silicon layer on the surface is oxidized to form a silicon oxide film. As described above, the processing gas contains a trace amount of water vapor, and the water vapor increases the oxide film.

According to this embodiment, the uniformity of the film thickness in the plane of the wafer W is high and the uniformity of the film thickness between the wafers W is high, as can be seen from the results of the examples described later. . The reason is considered as follows. Processing gas (mixed gas of oxygen gas and hydrogen chloride gas)
Is heated in the heating unit 2 to, for example, around 1000 ° C., and after the steam is generated, it cools down a little while flowing through the gas supply pipe 5 on the secondary side. Since the equilibrium of the reaction in which water vapor is generated from oxygen and hydrogen in the above chemical formula does not shift to the product side, water vapor is generated at a temperature higher than the processing temperature in the reaction tube 31. If so, the processing gas does not generate any more steam in the reaction tube 31.

Therefore, when the processing gas enters between the wafers W stacked on the wafer boat 4, the steam is generated and exhausted, so to speak, is included in the processing gas flowing from the peripheral edge to the center of the wafer W. The amount of water vapor is almost the same at every position. As a result, the wafer boat 4
Also in the wafer W positioned at the upper stage, the degree of film-increasing action by water vapor in the plane is almost the same, so that the in-plane uniformity of the film thickness is increased. In the prior art, since the generation of water vapor progresses toward the lower side of the wafer boat 4, the uniformity of the film thickness is poor on the upper side, and the uniformity of the film thickness is higher on the lower side. In this case, it can be said that the lower gas atmosphere is generated on the upper side, and the variation in the film thickness distribution among the wafers W is reduced, that is, the uniformity of the film thickness between the surfaces is increased.

Strictly speaking, since the water vapor contributes to the increase in the film thickness, it is considered that the amount of water decreases somewhat toward the center of the wafer W. Is higher, and the film thickness at the center originally tends to be larger.Therefore, by increasing the thickness of the film at the periphery, the effect of raising the film thickness at the periphery acts, thereby increasing the uniformity of the film thickness. It can be said that there is.

The phenomenon in which the generation of water vapor proceeds in the reaction tube 3 has a greater effect on the in-plane uniformity and the inter-plane uniformity of the film thickness at lower temperatures. It can greatly contribute.

In the above description, the compound gas containing hydrogen and chlorine used in the present invention is not limited to hydrogen chloride gas, but may be, for example, dichlorosilane (SiH 2 Cl 2) gas. Further, the step of applying energy to the processing gas to generate moisture is not limited to heating by the heating unit 2, and is performed by activating the gas by applying energy such as microwave power or laser light. It may be a process or the like. In this case, it is preferable to generate steam in advance to such an extent that no more steam is generated when the processing gas is introduced into the reaction tube. Further, the apparatus for oxidizing the wafer in the reaction vessel is not limited to the apparatus for performing batch processing, but may be, for example, a single-wafer heat treatment apparatus.

[0026]

EXAMPLES The results of tests performed using the apparatus according to the above-described embodiment will be described.

(Example 1) Under the following processing conditions, 20c
A silicon oxide film was formed on the surface of the m-size wafer.

Temperature in reaction tube: 800 ° C. Gas flow rate: O 2 /HCl=10/0.5 (slm) Processing time: 90 minutes Temperature of heating section: 1000 ° C. Number of wafers mounted: 100 Pressure in reaction tube: − 49 Pa (−5 mmH 2 O) The thickness of the silicon oxide film of the wafers located on the upper, middle, and lower stages of the wafer boat is measured, and the in-plane uniformity of each wafer is checked, and the same is performed with the heater of the heating unit turned off. As a result, the results shown in FIG. 4 were obtained. The in-plane uniformity is a value expressed by 2 × in-plane average value / (maximum value−minimum value) of the film thickness.

From these results, it was found that the in-plane film thickness uniformity from the upper stage to the middle stage was improved by supplying the processing gas into the reaction tube after heating it in the heating section. It can be seen that the film thicknesses are uniform even between wafers.

(Embodiment 2) Under the following processing conditions, 20c
A silicon oxide film was formed on the surface of the m-size wafer.

Temperature in reaction tube: 800 ° C. Gas flow rate: O 2 /HCl=10/0.3 (slm) Temperature of heating section: 1000 ° C. Number of wafers mounted: 100 Pressure in reaction tube: −49 Pa (−5 mmH 2 O) The length of the oxidation treatment time was set to four times of 2 minutes, 15 minutes, 30 minutes, and 60 minutes. In each case, the uniformity of the in-plane film thickness of the middle wafer was examined, and the uniformity of the film thickness between the surfaces was also determined. Upon examination, the results shown in FIG. 5 were obtained. However, the inter-surface uniformity means that the average value of the film thickness of each wafer (actually, a predetermined number of monitor wafers) on the boat is determined, and the difference between the maximum value and the minimum value of the average values is A, Assuming that the average value of the average film thickness of each wafer is B, it is a value represented by 2 × B / A.

As can be seen from the results, the longer the oxidation treatment time, that is, the thicker the film, the greater the effect of improving the in-plane and inter-plane uniformity. Also has the effect of improving uniformity.

(Embodiment 3) A wafer boat is carried into a reaction tube without mounting a wafer, and the temperature in the reaction tube is set to 80
0 ° C. and the gas flow rate was O2 / HCl = 10/1 (s
lm), and the hydrogen concentration in the gas exhausted from the exhaust pipe was examined when the temperature of the heating unit was set to 1000 ° C. and when the temperature was turned off.

The results are as shown in FIG. Note that the analysis start time is the elapsed time from the start of gas flow.
From this result, it can be seen that when the heating unit is turned on, the hydrogen concentration is low, but it is presumed that the H2 (hydrogen) concentration is low because the reaction of H2 + 1 / 2O2 → H2O is progressing. Also, when the heating unit is turned off, this reaction does not proceed as compared with the case where the heating unit is turned on, so H2
It is considered that the concentration is high.

[0035]

As described above, according to the present invention, when performing so-called dry oxidation on an object to be processed, high uniformity of the thickness of the oxide film can be obtained, which contributes to lowering the process temperature. it can.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view showing an example of an oxidation treatment apparatus used in an oxidation treatment method of the present invention.

FIG. 2 is an external view of a vertical heat treatment apparatus used in the oxidation treatment apparatus of FIG.

FIG. 3 is a cross-sectional view showing a heating unit used in the oxidation treatment apparatus of FIG.

FIG. 4 is a characteristic diagram showing a result of examining film thickness uniformity depending on a position of a wafer boat.

FIG. 5 is a characteristic diagram showing a result of examining a relationship between an oxidation treatment time and film thickness uniformity.

FIG. 6 is an explanatory diagram showing the measurement results of the hydrogen concentration on the exhaust port side of the reaction tube when the processing gas is heated by the heating unit and when it is not heated.

FIG. 7 is an explanatory diagram for explaining a problem of a conventional oxidation treatment method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vertical heat treatment apparatus 2 Heating part W Semiconductor wafer 20 Transparent quartz glass bead 21 Heating tube 22 Heater part 23 Heat insulator 3 Heat treatment furnace 31 Reaction tube 32 Heater part 4 Wafer boat 40 Boat elevator 44 Lid 5 Gas supply pipe 53 Oxygen gas source 54 Hydrogen chloride gas source

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[Procedure amendment]

[Submission date] January 17, 2001 (2001.1.1)
7)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Katsushi Ishii 1-2-4, Machiya, Shiroyama-cho, Tsukui-gun, Kanagawa Prefecture Inside the Sagami Office of Tokyo Electron Tohoku Co., Ltd. (72) Inventor Kazutoshi Miura Shiroyama-cho, Tsukui-gun, Kanagawa Prefecture 1-241 Machiya Tokyo Electron Tohoku Co., Ltd. Sagami Office F-term (reference) 5F045 AA20 AB32 AC11 AC13 BB02 BB03 DP19 EE07 EK06 EK09 5F058 BA20 BC02 BF55 BF62 BG02 BJ01

Claims (12)

[Claims] 1. A gas comprising a compound containing hydrogen and chlorine, wherein the object to be processed having a silicon layer formed at least on its surface is carried into a reaction vessel and the inside of the reaction vessel is heated to a predetermined processing temperature. A method of supplying a processing gas containing oxygen gas into a reaction vessel to oxidize the silicon layer to form a silicon oxide film, wherein the processing gas is supplied with energy before the processing gas is supplied into the reaction vessel. 2. An oxidation treatment method according to claim 1, wherein a small amount of water is generated by applying the water. 2. The step of applying energy to the processing gas comprises:
2. The method according to claim 1, wherein the water is generated to such an extent that the generation of the water is not further promoted at the processing temperature in the reaction vessel.
The oxidation treatment method described in the above. 3. The step of applying energy to the processing gas comprises:
2. The oxidation treatment method according to claim 1, wherein the treatment gas is heated. 4. The oxidation treatment method according to claim 3, wherein the temperature at which the processing gas is heated before being supplied into the reaction vessel is higher than the processing temperature within the reaction vessel. 5. The step of heating the processing gas before supplying the gas into the reaction vessel is performed in a heating section provided in a gas supply pipe for supplying the gas into the reaction vessel. 5. The oxidation treatment method according to 3 or 4. 6. The oxidation treatment method according to claim 1, wherein the gas comprising a compound containing hydrogen and chlorine is hydrogen chloride gas. 7. The method according to claim 1, wherein the step of forming the silicon oxide film is performed by holding a large number of objects to be processed in shelves and carrying them into a vertical reaction tube. The oxidation treatment method according to any one of the above. 8. An oxidation treatment apparatus for oxidizing a silicon layer on a surface portion of an object to form a silicon oxide film, wherein the object is carried into a reaction vessel and the inside of the reaction vessel is heated to a predetermined processing temperature. A heat treatment apparatus for heating and supplying a processing gas containing a gas containing a compound containing hydrogen and chlorine and an oxygen gas to the inside of the reaction vessel to oxidize the object to be processed; A gas supply pipe for supplying a gas, and a heating unit provided on the gas supply pipe for heating the processing gas and generating a small amount of moisture before supplying the processing gas into the reaction vessel. An oxidation treatment apparatus characterized by the above-mentioned. 9. A heat treatment apparatus holds a large number of objects to be processed in a holding device in a shelf shape and carries them into a vertical reaction vessel, and heats the inside of the reaction vessel to a predetermined processing temperature by heating means surrounding the reaction vessel. 9. The oxidation treatment apparatus according to claim 8, wherein the oxidation treatment apparatus is a vertical heat treatment apparatus for heating. 10. A heating section is provided with a ventilation resistor, a heating chamber for heating a processing gas, and a resistance heating element provided so as to surround the heating chamber and containing few metallic impurities in ceramics. The oxidation treatment apparatus according to claim 8 or 9, further comprising a heater portion formed as described above. 11. The oxidation treatment apparatus according to claim 10, wherein the resistance heating element is made of a high-purity carbon material. 12. The oxidation treatment apparatus according to claim 10, wherein the ceramic is quartz.