JPH08316222A - Method and apparatus for heat treatment - Google Patents

Abstract

PURPOSE: To stabilize a substrate, to be treated, quickly to a prescribed temperature and to perform a uniform heat treatment when the substrate to be treated is carried into a reaction container so as to be heat-treated. CONSTITUTION: The absorptivity of heat rays differs according to their angle of incidence when the temperature of a wafer W is, e.g. near 500 deg.C, and the absorptivity is small when the heat rays are vertically incident. When a wafer holding implement 3 is raised, a wafer holding plate 31 is pushed up by, e.g. a thrust pin, and the wafer holding plate 31 is held in a state that it is tilted from a horizontal plane. Then, the heat rays which are reached directly from a heating source 24 are obliquely incident on the wafer W at a prescribed angle of incidence, the heat rays can be absorbed with a large absorptivity, and temperature rises in respective positions of the wafer W become uniform. Consequently, the temperature of the wafer W is stabilized quickly to a prescribed temperature, and, as a result, a heat treatment whose in-plane uniformity is high can be executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment method and an apparatus therefor.

[0002]

2. Description of the Related Art During the manufacturing process of semiconductor devices,
Oxidation treatment to oxidize the surface of silicon at high temperature to obtain an oxide film (insulating film), or diffusion treatment to heat the silicon layer with an impurity layer formed on the surface and thereby diffuse impurities into the silicon layer. and so on.

A batch type vertical heat treatment apparatus is known as a heat treatment apparatus for performing this kind of oxidation and diffusion. For example, in forming an oxide film or a gate oxide film of a capacitor insulating film or diffusing treatment of impurity ions, When obtaining an extremely thin film or shallow junction, the film quality, film thickness, and diffusion depth are greatly affected by the thermal budget (thermal history), and in batch type heat treatment equipment, the wafer previously loaded into the reaction tube and the last There is a large difference in thermal budget from the wafer loaded in one direction.

Therefore, studies are being made on a single-wafer type heat treatment apparatus in which the above-mentioned heat treatment furnace is improved so that wafers are loaded one by one onto a holder at a set position in a reaction tube and then rapidly heated. Such a single-wafer-type heat treatment apparatus will be described with reference to the schematic diagram shown in FIG. 8A. 1 is a vertical reaction vessel, and a portion including a heat treatment region is surrounded by a heat insulator 10. . The reaction container 1 is provided with a processing gas supply pipe 11 and an exhaust pipe 12 so that the processing gas flows from top to bottom.

A wafer holder 13 for holding the wafer W horizontally is provided in the reaction vessel 1. The wafer holder 13 is shown in a transfer chamber (not shown) below the reaction vessel 1. One wafer W is placed by the transfer means, and the wafer W is raised to a predetermined position. On the other hand, the wafer W is heated to a predetermined heat treatment temperature by the heating unit 15 composed of the resistance heating element 15a and the heat equalizing element 15b, and the processing gas is supplied from the processing gas supply pipe 11 to oxidize in a normal pressure atmosphere, for example. .

[0006]

In the above-mentioned heat treatment apparatus, the wafer W is carried into the heat treatment area in the reaction vessel 1 while being held horizontally by the wafer holder 13, but the wafer holder 13 rises. The inter-wafer W receives the heat rays directly incident in the vertical direction from the heating portion 15 as shown by solid arrows in FIG. 9B, and is reflected obliquely by the heat insulator 10 as shown by dotted arrows. It also receives heat rays (secondary radiant heat). As described above, heat rays having different incident angles are incident on the wafer W from the heating unit 15. However, when the incident angles are different, the transmittance and the reflectance of the heat rays are different, and the amount of heat rays absorbed by the wafer W is also changed. come.

When the temperature of the wafer W is as low as about 600 ° C. when preheating the inside of the reaction vessel 1, the surface of the wafer W is a mirror surface and has a short wavelength, for example, 0.9 μm.
Since a part of the heat ray of about 3 μm is transmitted and reflected, the rate of transmission and reflection of the heat ray is largely different depending on the incident angle. With heat rays, the absorptance is very small, for example, about 0.1.

Therefore, when the wafer W is held horizontally, when the wafer W is heated, the influence of obliquely incident heat rays having a relatively high absorptivity is large, but the amount of obliquely incident heat rays is large. Since the angle of incidence is different at each position and the incident angle is also different, and the amount of heat ray absorbed is also different accordingly, the temperature rise varies at each position. Therefore, when the temperature of the wafer W is raised to the heat treatment region, it takes a long time for the temperature of the wafer W to be stabilized at the heat treatment temperature over the entire surface. As a result, the heat treatment rate, for example, the growth rate of the oxide film varies. ,
There is a problem that the in-plane uniformity of the film thickness becomes low.

When the wafer W is held horizontally and carried into the heat treatment area, the surface area of the wafer W is large, so that the wafer W is subjected to a large resistance (wind pressure), and the area immediately behind the wafer W becomes negative pressure. There is also a problem that a pressure difference occurs between the pressure on the front surface side and the pressure on the back surface side of the wafer W, and the flow of the processing gas is disturbed.

The present invention has been made under the above circumstances, and an object thereof is to stabilize the temperature of a substrate to be processed in a short time, thereby enabling a heat treatment with high in-plane uniformity. And to provide the device.

[0011]

According to the first aspect of the invention, the substrate to be processed is held in a substantially horizontal state by a holder and is carried into the reaction vessel from below, and the heating is provided outside the reaction vessel. In the heat treatment method of performing heat treatment by radiant heat from a source, the substrate to be processed is raised to a heat treatment region in a reaction container in a tilted state.

According to the second aspect of the present invention, the substrate to be processed is held by the holding tool in a substantially horizontal state and carried into the reaction vessel from below, and is heat-treated by radiant heat from a heating source provided outside the reaction vessel. In the heat treatment method, the upper end position of the substrate to be processed moves in the circumferential direction with time,
It is characterized in that the substrate to be processed is raised to a heat treatment region in a reaction container in a tilted state.

According to a third aspect of the present invention, the substrate to be processed is held by a holder in a substantially horizontal state, carried into the reaction vessel from below, and heat-treated by radiant heat from a heating source provided outside the reaction vessel. In the above heat treatment apparatus, a mechanism for tilting the substrate to be processed is provided in combination with the holder.

[0014]

For example, if a heat source is provided above the reaction vessel and a heat insulating material is provided around the reaction vessel so as to surround it,
While the heat rays from the heat source are directly incident on the surface to be treated of the substrate to be treated in the vertical direction, the heat rays reflected by the heat insulating material are also incident, but while the substrate to be treated is inclined with respect to the horizontal plane, When the temperature is increased to the heat treatment area, the heat rays directly incident from the heating source are incident on the surface to be treated obliquely.

Here, when the substrate to be processed is at a low temperature of, for example, about 500 ° C., the rate of transmission or reflection of heat rays greatly differs depending on the incident angle. There is a large difference in absorptivity between the incident light and the incident light. In addition, the heat rays that are directly incident from the heating source are
Since the amount of heat rays is larger than that of heat rays reflected by the heat insulating material and incident, if this direct heat ray is made incident obliquely, the heat ray can be absorbed with a large absorptivity, and at each position on the surface to be treated. The temperature rise will also come together. Therefore, the temperature of the object to be processed is quickly stabilized at a predetermined temperature, and as a result, heat treatment with high in-plane uniformity can be performed.

When the substrate to be processed is tilted and moved up to the heat treatment region in the reaction vessel so that the upper end position of the substrate to be processed moves in the circumferential direction with time,
At each position of the substrate to be processed, the portion close to the heating source changes with time, so that variations in the intensity of heat rays received from the heating source are suppressed, and heat treatment with higher in-plane uniformity can be performed.

[0017]

1 is a sectional view showing a heat treatment apparatus for carrying out a heat treatment method according to an embodiment of the present invention. 2 in FIG.
Is a tubular reaction container made of, for example, quartz and having an open lower end, and this reaction container 2 constitutes a processing chamber for performing heat treatment on a substrate to be processed, for example, a semiconductor wafer W. The reaction vessel 2 is arranged in a heating furnace 20, which is provided, for example, with silicon carbide (S) so as to cover the periphery and the upper surface of the reaction vessel 2 with a gap.
The heat equalizing member 21 made of iC) is provided.

Further, on the outside of the heat equalizing member 21, a heat insulating body 22 and an exterior body 23 having a water cooling jacket 23a are provided. A heating source 24 composed of a resistance heating element is arranged between the upper surface of the heat equalizing member 21 and the heat insulating body 22.
Further, the reaction container 2 is provided with a processing gas supply pipe 25 so as to supply a processing gas from a processing gas supply source (not shown) to the wafer W on the wafer holder 3 described later, and the reaction container 2 An exhaust pipe 26 for exhausting the inside is connected.

A wafer holder 3, which is a holder for a substrate to be processed, is provided in the reaction container 2. The wafer holder 3 is a wafer on which a wafer is placed as shown in FIGS. 2 and 3. The holding plate 31 is configured to be supported by the support portion 32. For example, as shown in FIG. 2, the wafer holding plate 31 has a step 30 formed in the bottom surface from the peripheral edge to the center so that the transfer arm 30a can be horizontally inserted and removed, and the wafer W can be removed. In order to prevent it, the periphery is set up.

The support portion 32 has, for example, a columnar shape, and a support rod 33 is projectingly provided at the center of the upper surface thereof. The wafer holding plate 31 is supported by the support rod 33 via a ball joint portion 34 so as to be rotatable about both a vertical axis and a horizontal axis. Further, in the support portion 32, as one set of push-up pins P, P provided at positions facing each other in the radial direction with the support rod 33 sandwiched therebetween, four sets are provided at positions equally divided into n, for example, 8 in the circumferential direction. Pins P1 to
P4 (one set of pins is given the same reference numeral) is arranged. The upper end of each pin P is formed in a flat plate shape having an arc shape, for example, to ensure the support of the wafer holding plate 31.

The pair of push-up pins P, P are configured to move in the vertical direction at the same time, for example, and when horizontally supporting the wafer holding plate 31, as shown in FIG. In addition, the set of push-up pins P, P is raised by the length L which is the distance between the lower surface of the wafer holding plate 31 and the upper surface of the support member 32 to support the set of push-up pins P and P. Part 3
The wafer holding plate 31 is supported by 6. When the wafer holding plate 31 is tilted and supported from the horizontal plane, as shown in FIG. 3B, one of the push-up pins P moves up from the position of the length L by ΔL and the other Of the ball joint portion 3 is lowered from the position of the length L by ΔL, and the set of the push-up pins P, P and the support rod 33 causes the ball joint portion 3 to move.
The wafer holding plate 31 is supported via 4 so as to be inclined from the horizontal plane.

At this time, ΔL is determined according to the angle of inclination of the wafer holding plate 31 from the horizontal plane, and this angle of inclination has a high absorption rate for the direct heat ray H from the heating source 24, as will be described later. The angle is set to a predetermined angle according to the incident angle of the heat ray H required for absorption by. For example, ΔL is set so that the wafer holding plate 31 is inclined within a range of, for example, 30 degrees from the horizontal plane. In this embodiment, the support portion 32, the push-up pin P, the support rod 33, and the ball joint portion 34 constitute a tilting mechanism for tilting the wafer holding plate 31.

The wafer holder 3 is attached to the top of an elevating shaft 42 via a rotary table 41, and the elevating shaft 42 is a cylindrical body below the reaction container 2 as shown in FIG. Lifting mechanism 43 including a ball screw, etc. at the lower end of 5.
It is configured so that it can be raised and lowered by. A rotary shaft 44 is provided in the lift shaft 42 via a bearing 42a, and the rotary shaft 44 is rotated by the motor M, so that the wafer holder 3 can be rotated via the rotary table 41. It has become.

On the lower side of the reaction vessel 2, there is provided a tubular body 5 having a water cooling jacket, the upper end of which is hermetically connected to the lower end of the reaction vessel 2 and the inner space of which is continuous with the space inside the reaction vessel 2. It is arranged. A transfer chamber 51 for transferring a wafer between the wafer holder 3 and the outside is formed in the cylindrical body 5, and a side wall of the transfer chamber 51 is opened and closed by a gate valve. A loading / unloading port 52 for the wafer W to be formed is formed. Shutters S1 and S for blocking radiant heat from the reaction container side are provided on both sides of the upper portion of the transfer chamber 51.
2 is provided, and the shutter S is also provided on both sides of the lower part of the transfer chamber 51 so as to block the bottom side of the tubular body 5.
3 and S4 are provided, and the shutters S3 and S4 each have a semicircular cutout formed at the tip thereof when the shutters S3 and S4 surround the lift shaft 42. Reference numerals 53, 54, 55 and 56 are shutter waiting chambers.

Next, the operation of the above embodiment will be described. First, the wafer holder 3 is positioned in the transfer chamber 51 as shown by a chain line, the wafer W to be processed is loaded from the loading / unloading port 52 and placed on the wafer holding plate 31. At this time, the wafer holding plate 31 is horizontally supported by a pair of push-up pins P and a supporting portion 36, as shown in FIG. 4A, and the transfer arm 30a (see FIG. 2) is the wafer W. With the
The wafer W is lowered so as to be accommodated in the step portion 30, the wafer W is placed on the wafer holding plate 31, and then taken out.

On the other hand, the radiant heat from the heating source 24 is applied to the heat equalizer 21.
The reaction gas enters the reaction vessel 2 through the above, and a soaking region of a predetermined temperature is formed, and a processing gas, for example, a mixed gas of O ₂ gas and HCl gas is supplied into the reaction vessel 2 from the processing gas supply pipe 25. At this time, the shutters S1, S2, and S
3 and S4 are closed, and the radiant heat from the reaction tube 2 is blocked by the shutters S1 and S2.

Next, after opening the shutters (S1, S2), the wafer holder 3 is raised by the elevating shaft 42 while rotating it through the rotating shaft 44 and the rotating table 41. At this time, the push-up member 35 is used. As a result, a set of push-up pins P sequentially moves in the vertical direction in the circumferential direction, whereby the wafer holding plate 31 is tilted at a predetermined angle, for example, 0 to 30 degrees from the horizontal plane, and the position of its upper end moves in the circumferential direction with time. While rising.

That is, first, as described above, a set of push-up pins P is provided.
1 and P1 both rise by the length L to support the wafer holding plate 31, and then one push-up pin P1 rises by ΔL and the other push-up pin P1 descends by ΔL to hold the wafer. The plate 31 is supported by tilting it from the horizontal plane. Thereafter, the push-up pins P1 are returned to their original positions (positions L) again to support the wafer holding plate 31 horizontally, and the push-up pins P1 are also returned.
1, a pair of push-up pins P2, P2 adjacent to each other in the circumferential direction rise by the length L to horizontally support the wafer holding plate 31,
On the other hand, the pair of push-up pins P1 and P1 both move down. Then, the push-up pin P2 is moved similarly to the push-up pin P1 to tilt and support the wafer holding plate 31 from the horizontal plane, and then the push-up pin P3 and the push-up pin P4 are sequentially moved in the vertical direction.

In this way, as shown in FIGS. 4B and 4C, the wafer holding plate 31 is pushed up by the push-up pins P1, P2, P.
3 and P4, the wafer holding plate 31 is tilted and supported so that its upper end position moves with time, and the reaction container 2 is moved as shown in FIG.
To a predetermined position inside. As a result, the temperature of the wafer W is raised to a predetermined temperature, for example, 1100 ° C. Then, the wafer holder 3 is stopped at this height position for a predetermined time to form an oxide film having a thickness of, for example, 50 Å on the surface of the wafer W, and then the wafer holding plate 31 is tilted with respect to a horizontal plane, for example. , FIG. 4 (c), (b),
The wafer holder 3 is lowered in the order of (a).

When the wafer holder 3 is lifted in this manner, the heat rays H directly incident on the surface to be processed of the wafer W from the heating source 24 are obliquely incident on the wafer W as shown in FIG. Here, if the incident angle is different, the transmittance and the reflectance of the heat ray H are different, and the absorptance of the heat ray H becomes lower as the heat ray H enters vertically. This tendency becomes larger as the temperature becomes lower, and the absorptance is considerably small when the wafer W is around 500 ° C., for example.

On the other hand, the surface to be processed of the wafer W receives the heat ray H directly incident from the heating source 24 and the heat ray H (secondary radiant heat) reflected by the heat insulator 22 and incident.
The amount of the heat ray H that is directly incident is overwhelmingly larger, and the heat ray H is incident on the entire surface of the wafer W at substantially the same angle.

If the wafer W is tilted when it is lifted from the transfer chamber 51, the heat ray H directly from the heating source 24 is obliquely incident on the surface to be processed of the wafer W and is absorbed at a high absorption rate. To be done. On the other hand, the secondary heat rays reflected and incident on the heat insulating body 22 have various ways of reflection, and the incident angle differs depending on the incident position on the surface to be processed, and the heat absorption amount also differs.

Therefore, regarding the influence of the secondary heat ray, although the heat absorption amount varies depending on the position of the surface to be processed, the heat ray directly incident from the heating source 24 has a large heat absorption amount, and thus the secondary heat ray H Less affected by variations in heat absorption,
The temperature rise at each position of the wafer W is uniform. Therefore, since the in-plane temperature stabilizes at a predetermined temperature, for example, 1100 ° C. in a short time, the variation in thermal history due to the temperature near the heat treatment temperature that influences the growth of the oxide film is reduced, and thus the in-plane uniformity of the film thickness of the oxide film is reduced. Get higher

When the wafer W is raised while being inclined so that its upper end position moves with time, the portions near the heating source 24 at each position of the wafer W change with time, so the heat rays received from the heating source 24. The variation in the strength of H is suppressed, and the heat treatment can be performed with higher in-plane uniformity.

Here, in FIG. 6A, as in the above-mentioned embodiment,
FIG. 6B shows a change with time in the in-plane temperature when the wafer W is raised, and FIG. 6B shows a change in the in-plane temperature with respect to the case where the wafer holder 3 is raised with the wafer W held horizontally. It's a change. As shown in this figure, the in-plane temperature is 11
Times T1 and T2 until stabilization at 00 ° C. are shorter when the wafer is tilted than when it is horizontal (T1 <T2),
The in-plane temperature difference when the in-plane temperature converges to 1100 ° C is also small.

Further, when the wafer holding plate 31 is tilted and supported from the horizontal plane when the wafer holder 3 is moved up and down, the resistance (wind pressure) received by the wafer W is reduced, and when the wafer W is raised, the resistance of the wafer W is increased. Negative pressure is generated on the back surface side and on the front surface side of the wafer W when descending, but the degree of the negative pressure is small, and therefore the difference in pressure between the front surface side and the back surface side of the wafer W is also small. Therefore, the turbulence of the air flow in the reaction vessel 2 is suppressed, and as a result, the processing gas is almost uniformly distributed on the wafer
Since it flows to the surface of the oxide film, the disorder of the growth of the oxide film is reduced, and it is possible to obtain an advantage that a high in-plane uniformity can be obtained.

Further, the heat treatment apparatus for carrying out the present invention is not limited to the above-mentioned constitution, but may be constituted by combining the wafer holder with the seesaw mechanism 6 as shown in FIG. 8, for example. That is, in the see-saw mechanism 6, a first see-saw portion 63 in which the movable plate 62 moves in a seesaw motion by the shaft portion 61, and a second sheath in which the movable plate 65 moves in a seesaw motion by the shaft portion 64.
The saw portion 64 is vertically stacked so as to be orthogonal to each other.

In such a structure, when the wafer holder 3 is raised, the wafer holding plate 31 first moves the first seesaw portion 6 first.
A part of it is lifted by 3 and supported in a state of being inclined from the horizontal plane, and then the seesaw portion of this seesaw portion 63.
1 in the circumferential direction from the previously lifted position according to the movement
The position moved by 80 degrees is lifted. After this, the second sea
The saw portion 66 lifts the position that is moved 90 degrees in the circumferential direction from the position, and further moves 1 position in the circumferential direction from the position.
The position moved by 80 degrees is lifted. Therefore, also in such an example, the wafer W rises to the heat treatment region while being supported in a state of being inclined from the horizontal plane, and the upper end position of the wafer W changes by 90 degrees with time.

As described above, in the present invention, the wafer may be tilted even while the wafer reaches the heat treatment area and then stops at that position to perform the heat treatment. Further, the present invention is not limited to the single-wafer type heat treatment apparatus as in the above-described embodiment, but a batch type heat treatment in which a plurality of wafers are arranged in a holder and arranged in a shelf shape, and these wafers are collectively heat-treated. It may be applied to the device. The present invention can be applied not only to the formation of an oxide film, but also to other heat treatments such as impurity ion diffusion treatment, CVD treatment, and annealing treatment.

[0040]

As described above, according to the present invention, since the substrate to be processed is raised to the heat treatment region in a tilted state, the substrate to be processed can be quickly stabilized at a predetermined temperature to achieve in-plane uniformity. High heat treatment can be performed.

[Brief description of drawings]

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

FIG. 2 is a perspective view showing a wafer holding plate and a supporting portion used in one embodiment of the method of the present invention.

FIG. 3 is a cross-sectional view showing a supporting portion used in an embodiment of the method of the present invention.

FIG. 4 is an explanatory view showing the operation of the method of the present invention.

FIG. 5 is an explanatory view showing steps of one embodiment of the method of the present invention.

FIG. 6 is a characteristic diagram showing a change with time of in-plane temperature of a wafer.

FIG. 7 is a seesaw used in another embodiment of the method of the present invention.
It is a perspective view showing a mechanism.

FIG. 8 is a schematic sectional view showing a conventional heat treatment apparatus.

[Explanation of symbols]

 2 Reaction Container 20 Heating Furnace 22 Heat Insulator 24 Heat Source 3 Wafer Holding Tool 31 Wafer Holding Plate 32 Supporting Part 33 Supporting Rod 34 Ball Joint Part P (P1 to P4) Push-up Pin 41 Rotating Table H Heat Wire W Wafer

Claims (3)

[Claims] 1. A heat treatment method in which a substrate to be processed is held by a holder in a substantially horizontal state, carried into a reaction vessel from below, and heat-treated by radiant heat from a heating source provided outside the reaction vessel, A heat treatment method comprising raising the substrate to be treated to a heat treatment region in a reaction container in a tilted state. 2. A heat treatment method in which a substrate to be processed is held by a holder in a substantially horizontal state, carried into a reaction vessel from below, and heat-treated by radiant heat from a heating source provided outside the reaction vessel, A heat treatment method, wherein the substrate to be processed is raised to a heat treatment region in a reaction container while being tilted so that the upper end position of the substrate to be processed moves in the circumferential direction with time. 3. A heat treatment apparatus in which a substrate to be processed is held by a holder in a substantially horizontal state, loaded into a reaction vessel from below, and heat-treated by radiant heat from a heating source provided outside the reaction vessel, A heat treatment apparatus comprising a mechanism for inclining a substrate to be processed in combination with the holder.