JPH07268627A - Heat treating method - Google Patents

Abstract

PURPOSE:To rapidly raise the temp. of the body to be treated such as a semicon ductor wafer to a prescribed temp., furthermore executing heat treatment at a stable temp. and therefore subjecting the wafer to uniform heat treatment at the time of executing oxidizing treatment and diffusing treatment thereto. CONSTITUTION:A heat controlling sheet 3 provided in the upper direction of a reaction tube 1 is heated by a heating means 22 to form a primary heating area in which temp. is substantially uniform to the change of the position of the height on the upper part of the reaction tube and a secondary heating area in which temp. is mildly decreased as it proceeds to the lower direction. After the temp. of a wafer W is rapidly increased to the primary heating area, it is mildly decreased within the secondary heating area, and in the meantime, heat treatment is executed.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a heat treatment method.

[0002]

2. Description of the Related Art As semiconductor devices become finer and more highly integrated, the thickness of each layer of the device is becoming thinner, while semiconductor wafers (hereinafter referred to as "wafers") are also changed from 6-inch size to 8-inch or 12-inch size. Therefore, the development of ultra-thin film technology for large areas has become an important issue. In addition, for example, in the oxide film of the capacitor insulating film, the formation of the gate oxide film, or the diffusion process of impurity ions, the film quality, the film thickness, and the diffusion depth are greatly affected by the thermal budget (thermal history). It is necessary to suppress the heat treatment.

Here, in the vertical heat treatment, which is one of the conventional batch heat treatment apparatuses, the heat treatment is carried out by carrying in a reaction vessel surrounded by heaters, a holder in which a large number of wafers are stacked in a rack shape. However, since the wafer is heated by the heater arranged on the side of the reaction tube, a large temperature gradient is generated between the central portion and the peripheral portion of the wafer when the wafer is heated rapidly. A large difference occurs in the thermal budget between the wafer that first enters the reaction tube and the wafer that finally enters the reaction tube, and it is difficult to perform a process with a uniform thermal budget even in the same batch.

From the above, the present inventor has improved the heat treatment furnace of the vertical heat treatment apparatus so that, for example, one wafer is placed on the holder in the reaction tube and carried into the set position, and then the temperature of the heating source is changed. We are studying a method of controlling the temperature of the wafer by changing the temperature. According to this method, it is possible to obtain high uniformity in the in-plane temperature of the wafer, but on the other hand, it is difficult to rapidly raise and lower the temperature of the wafer because the reaction tube and the heating furnace surrounding it are large. There is a drawback that the heat history becomes large and high throughput cannot be obtained.

Therefore, the inventor of the present invention arranges a heating source on one end side of the reaction tube, places one wafer on a holder, and moves it from the other end side of the reaction tube to a predetermined heating region on the one end side for heat treatment. Are considering how to do. According to this method, the temperature of the wafer can be rapidly raised and lowered,
There is an advantage that the heat history can be kept small.

[0006]

However, if the wafer is allowed to reach a predetermined heating region in the reaction tube, there is an unstable time zone around the set temperature before the temperature of the wafer settles down to the set temperature. This temperature instability time period is not so long and the temperature variation range is narrow. However, when forming an ultrathin oxide film of 50 angstroms, for example, a film thickness variation of several angstroms becomes a problem. Therefore, the intended oxide film cannot be formed by the method of merely reaching the predetermined heating region of the wafer. Therefore, when using a single-wafer type heat treatment apparatus using a reaction tube, one of the important issues is how to obtain a good wafer temperature profile.

The present invention has been made under these circumstances, and stabilizes the temperature of the object to be processed in a short time,
This is to provide a heat treatment method capable of performing heat treatment with high in-plane uniformity.

[0008]

According to a first aspect of the present invention, there is provided a first heating region on one end side of a reaction tube in which a temperature is substantially uniform with respect to a position in a longitudinal direction of the reaction tube, and A second heating region that is continuous with the first heating region and has a temperature gradient in which the temperature gradually decreases toward the other end side of the reaction tube is formed, and the object to be treated is connected to the other end side of the reaction tube. The heat treatment is performed by moving the inside of the second heating region to the other end side of the reaction tube while moving the inside of the second heating region slowly.

According to the second aspect of the present invention, a heating region having a temperature gradient in which the temperature gradually decreases toward the other end of the reaction tube is formed at one end of the reaction tube, and the object to be treated is set to the reaction tube. It is characterized in that it is moved from the other end side to be positioned in the heating region, and then heat treatment is carried out while gradually moving inside this heating region to the other end side of the reaction tube.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the reaction tube is surrounded by a heat insulator, and a heat control plate is provided outside one end of the reaction tube and is orthogonal to the length direction of the reaction tube. Is provided, and the inside of the reaction tube is heated by the heating means via the heat regulation plate.

The invention of claim 4 is the invention of claim 1, 2 or 3.
In the invention, the average temperature gradient in the heating region in which the object to be processed moves toward the other end of the reaction tube is 20 ° C./cm or less.

[0012]

When the object to be processed reaches a predetermined position in the first heating area, the temperature of the object to be processed increases according to the heat history up to that position. Then, the temperature of the object to be processed further rises, but since the object to be processed moves toward the lower temperature, the thermal energy received is gradually decreased, and thus the temperature of the object to be processed is quickly increased. Stabilizes to a predetermined temperature. As a result, heat treatment with high in-plane uniformity, for example, an ultrathin oxide film can be formed or impurities can be diffused. However, the object may be moved to the other end of the reaction tube after reaching the predetermined position in the second heating area without reaching the first heating area. Regarding the first or second heating region, for example, by using a heat control plate, this radiates radiant heat directed in the length direction of the reaction tube as a heating source on one end side of the reaction tube and is uniform in the cross section of the reaction tube. A heated area is formed.

[0013]

1 is a sectional view showing a heat treatment apparatus used in an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a bottomed cylindrical reaction tube made of quartz, and the reaction tube 1 is arranged in a cylindrical heat insulator 21 with its open end facing downward. A heating means 22, for example, a resistance heating element is provided on the upper side of the reaction tube 1. The resistance heating element is, for example, molybdenum disilicide (MoSi ₂ ), Kanthal (an alloy wire of iron, chromium and aluminum). Product name) Composed of resistance heating elements such as wires.

A heat control plate 3 made of, for example, silicon carbide (SiC) is arranged between the reaction tube 1 and the heating means 22 so as to face a wafer W described later. The heat control plate 3 transfers the radiant heat from the heating means 22 to the wafer W.
In order to make the wafer W uniformly incident on the surface to be processed, it is preferable that the outer diameter of the wafer W is twice or more that of the wafer W in order to uniformly heat the entire surface of the wafer W.

At the lower end of the heat insulating body 21, there is provided a cooling means 11 which forms a refrigerant flow path through which a refrigerant such as water flows, and a flange portion at the lower end of the reaction tube 1 is provided below the cooling means 11. It is installed. Further, a metal manifold 12 is provided below the reaction tube 1, and a gas supply pipe 41 and an exhaust pipe 42 are connected to the manifold 12. The inner end side of the gas supply pipe 41 extends upward in the reaction pipe 1, and the supply port is located diagonally above the wafer W. Further, the manifold 12 has a wafer loading / unloading port (not shown) which is opened and closed by a shutter. At the lower end side of the manifold 12, a lid 13 that hermetically seals the processing space is provided.

A wafer holder 5 is provided in the reaction tube 1 at the top of an elevating shaft 61. This wafer holder 5
Is made of, for example, silicon carbide (SiC), and has, for example, 3 to 4 holding projections for holding the wafer W formed at the peripheral edge portion. The elevating shaft 61 penetrates the lid 13 airtightly, for example, via the magnetic seal portion 14 so as to rotate and elevate freely, and the lower end of the elevating shaft 61 is connected to a rotating mechanism 63 provided on the elevating arm 62. Has been done. The lifting arm 62
Is screwed into a ball screw 64 driven by a motor 65, and is configured to be able to move up and down while being guided by a guide rod (not shown) by the rotation of the ball screw 64. The motor 65 is controlled by the controller 60 so that the wafer W moves in a movement pattern described later.

Next, an embodiment of the method of the present invention which is carried out by using the above apparatus will be described. First, in the reaction tube 1, for example, O
₂ gas and N ₂ gas are allowed to flow, the wafer holder 5 is positioned below the reaction tube 1 as shown by a chain line, and the wafer W, which is the object to be processed, is loaded from the wafer loading / unloading port of the manifold 12. Then, it is placed on the wafer holder 5.
After the wafer loading / unloading port is closed, for example, O ₂ gas and HCl gas are supplied from the gas supply pipe 41 to form an oxide film on the surface of the wafer W at 900 SCCM and 100 SC, respectively.
It is supplied into the reaction tube 1 at a flow rate of CM, and the inside of the reaction tube 1 is maintained at normal pressure while being exhausted from the exhaust tube 42.

On the other hand, the inside of the reaction tube 1 is heated by the heating means 22 via the heat control plate 3, whereby a heating region having a temperature profile as shown in FIG. 2 is formed in the reaction tube 1. That is, in the upper region of the reaction tube 1, a first heating region in which the temperature does not substantially change with respect to a change in height position, and in a lower side of the first heating region, the temperature is continuously increased downward. Is gradually lowered, for example, a second heating region having a temperature gradient of about 2 to 5 ° C./cm is formed.

Then, the motor 65 is driven to raise the elevating shaft 61 via the ball screw 64 to move the wafer W to the upper region of the reaction tube 1. The solid line in FIG. 3 is an example of the movement pattern of the wafer W. First, the wafer W is raised to the position P1 in the first heating region at a speed of, for example, 50 mm / sec. In this case, the wafer W may be raised at a constant speed, but the speed may be changed midway, or the wafer W may be stopped at a predetermined position to be raised intermittently. It should be raised in a way that takes into account the impact.

Immediately after the wafer W reaches the position P1, the wafer W is gently lowered to the position P2 in the second heating area. This descending speed is set to, for example, 0.1 mm / sec, and the height difference between P1 and P2 is set to, for example, 6 mm. Thereafter, the wafer W is moved from the position P2 to, for example, 100
It descends to the position indicated by the chain line in FIG. 1 at a speed of mm / sec.

By moving the wafer W in such a movement pattern, the surface temperature profile of the wafer W becomes as shown by the dotted line in FIG. That is, by rapidly raising the wafer W to the position P1 as indicated by the solid line, the temperature of the wafer W rises later than the temperature profile in the reaction tube 1 in the moving path of the wafer W. When the wafer W reaches the position P1, the temperature of the wafer W is lower than the temperature of the position P1 in the temperature profile shown in FIG. 2, and if the height position of the wafer W is fixed to P1, the temperature of the wafer W becomes , The temperature continues to rise toward the temperature corresponding to the position P1, but the wafer W gradually falls and enters the second heating region, and goes to the lower temperature, so the temperature rise is suppressed,
It stabilizes at a predetermined temperature corresponding to the balance of heat energy balance, for example, 1000 ° C. Thus, an oxide film having a film thickness of 50 Å is formed on the surface of the wafer W.

When the temperature profile of the wafer W is enlarged, when the wafer W reaches the position P1 and then begins to descend, there is a region where the temperature becomes slightly unstable as shown in FIG. 4 (a). To do. In this unstable region, the temperature at each point on the wafer surface is within the range indicated by the diagonal lines, but within this range there is temperature variation within the surface.
However, the temperature unstable region is very short, for example, about 2 seconds, and the temperature is stable after passing through the unstable region, so that it becomes uniform in the plane of the wafer W. Therefore, the thermal history is substantially the same in the plane of the wafers W, so that the film thickness of the oxide film is uniform and, of course, it is uniform between the wafers W.

The upper limit position of the wafer W is not limited to the first heating region but may be the second heating region. The upper limit position may be set at any point, or after the wafer W reaches the upper limit position. Whether it is immediately lowered or slightly stopped may be appropriately set according to the rising speed of the wafer W, the processing time, and the like. In the region where the wafer moves slowly, in this example, in the heating region from P1 to P2, if the temperature gradient is too large, it becomes difficult to control the temperature of the wafer with high accuracy. It is preferably not more than cm.

As a comparative example to be compared with the above-described embodiment, the same apparatus is used and a wafer W is used as shown by the solid line in FIG.
Wafer W in the case where a movement pattern is taken to stop the position P1 as it is after reaching the position P1
When the temperature (surface temperature) of is examined, the temperature profile is as shown by the dotted line. That is, the temperature of the wafer W is
As shown in FIG. 4B, an unstable region (hatched portion) exists, but since the temperature width of this unstable region is large and its time zone is long, for example, 30 seconds, the thermal history in the plane of the wafer W is large. Is large, and the temperature of the wafer W is gradually increasing, and it takes, for example, 300 seconds to stabilize the temperature at a constant value. Therefore, it is difficult to control the thickness of the oxide film and the in-plane uniformity is high. Is much lower than that of the embodiment.

For example, when the oxidation treatment is performed at a temperature of 1000 ° C., a difference of 0.5 ° C. causes a film thickness difference of 1 angstrom, and the movement pattern greatly affects the in-plane uniformity of the wafer when forming an extremely thin film. It is understood that the method of the embodiment is very effective for forming an ultrathin film. Further, according to the method of the embodiment, the temperature of the wafer can be rapidly raised to the target temperature and the temperature can be rapidly lowered after the heat treatment, so that the thermal history is small and the throughput is high.

In the above, the results of the formation of the ultra-thin oxide film such as the gate oxide film and the capacitor insulating film by the oxidation treatment and the diffusion treatment of the impurity ions depend almost on the temperature control of the wafer. Although it is suitable for heat treatment, it can be applied to other heat treatments such as CVD treatment, annealing treatment, and ashing treatment. In that case, the movement pattern of the wafer may be appropriately set according to each process. For example, when performing the diffusion process, the wafer is raised intermittently (stepwise in the movement pattern with respect to time) as shown in FIG.
An important temperature range T1 to T2 for controlling the diffusion length of impurities
In the meantime, it is possible to control the temperature rising rate of the wafer.

The heat treatment apparatus used in the present invention is not limited to the above-mentioned configuration, and for example, a resistance heating element may be provided not only on the upper side of the heat control plate but also on the side peripheral surface of the reaction tube. The heat control plate corresponds to a heating source when viewed from the wafer, and is preferable because it uniformly radiates radiant heat to the wafer, but the heating source may have another configuration.

[0028]

As described above, according to the present invention, since the object to be processed can be rapidly heated to a predetermined temperature and heat-treated at a stable temperature, the object is uniformly heat-treated. be able to.

[Brief description of drawings]

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

FIG. 2 is a characteristic diagram showing a temperature profile of an upper portion in a reaction tube.

FIG. 3 is a characteristic diagram showing an example of a movement pattern of a wafer and a temperature change in the method of the embodiment.

FIG. 4 is an explanatory diagram showing an enlarged temperature change of a wafer in a method according to an example and a comparative example.

FIG. 5 is a characteristic diagram showing a wafer movement pattern and a temperature change in the method of the comparative example.

FIG. 6 is a characteristic diagram showing another example of the movement pattern of the wafer and a temperature change.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction tube 21 Insulator 22 Heating means 3 Thermal control plate 41 Gas supply pipe 42 Exhaust pipe 5 Wafer holder W Wafer 60 Control part 61 Elevating shaft

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Wataru Okase 1-24-141, Machiya, Shiroyama-cho, Tsukui-gun, Kanagawa Prefecture Tokyo Electron Tohoku Co., Ltd. Sagami Business Office

Claims (4)

[Claims] 1. A first heating region on one end side of the reaction tube where the temperature is substantially uniform with respect to a position in the lengthwise direction of the reaction tube, and a reaction tube which is continuous with the first heating region. A second heating region having a temperature gradient in which the temperature gradually decreases toward the other end side of the reaction tube, and the object to be treated is moved from the other end side of the reaction tube to the first heating region. A heat treatment method, characterized in that the heat treatment is carried out while being positioned and then slowly moving inside the second heating region to the other end side of the reaction tube. 2. A heating region having a temperature gradient in which the temperature gradually decreases toward the other end of the reaction tube is formed at one end of the reaction tube, and the object to be treated is provided from the other end of the reaction tube. A heat treatment method, characterized in that the heat treatment is carried out by moving it to the heating region, and then gradually moving inside the heating region to the other end side of the reaction tube. 3. The reaction tube is surrounded by a heat insulator, and a heat control plate which is orthogonal to the length direction of the reaction tube is provided outside one end of the reaction tube, and the heat control plate is interposed by a heating means. The heat treatment method according to claim 1 or 2, wherein the inside of the reaction tube is heated. 4. The average temperature gradient of the heating region in which the object to be processed moves toward the other end side of the reaction tube is 20 ° C./cm or less, and the average temperature gradient is 20 ° C./cm or less. Heat treatment method.