Method for manufacturing a composite structure

FIELD OF INVENTION

2The present invention relates to a method of manufacturing a composite structure. The invention also relates to a composite structure.

BACKGROUND OF THE INVENTION

4The method shown in FIG. 1 for manufacturing a composite structure comprising, in a direction from its rear surface to its front surface, a carrier substrate 1, a cover layer 2, at least one dielectric layer 3 and a working layer 4 and known from the previous layer (see, for example, document EP 1780794), includes the following steps:

5a) obtaining a donor substrate 5 and a carrier substrate 1;

6b) forming at least a dielectric layer 3, comprising:

7a first surface contacting the donor substrate 5,

8a second surface opposite the first surface,

9- a peripheral surface connecting the first and second surfaces together;

10the dielectric layer 3 has a contour Cz;

11c) forming a cover layer 2 positioned so that it covers the second surface of the dielectric layer 3;

12d) forming a weakened zone 6 in a donor substrate 5 bounding the working layer 4 in contact with the first surface of the dielectric layer 3;

13e) assembling the carrier substrate 1 and the donor substrate 5, so that the carrier substrate 1 and the cover layer 2 contact along the contact surface 7 having the contour Cs;

14e) the donor substrate 5 rupture along the weakened zone 6.

15Next, the assembly formed by the working layer 4, the dielectric layer 3 and the cover layer 2 will be referred to as the stack of layers 8.

16At the end of step e), the stack of layers is transferred to the carrier substrate 1 to form a composite structure.

17As shown in FIG. 2, the composite structure has a peripheral ring 9.

18This peripheral ring 9 is located in the peripheral region of the carrier substrate 1, in which, in the absence of sufficient adhesion between the carrier substrate 1 and the donor substrate 5, the stacking of the layers 8 does not occur.

19Thus, the stage is observed at the boundary separating the peripheral ring from the stack of transferred layers.

20In addition, the side surfaces of the cover layer 2 and the dielectric layer 3 are open at this stage and therefore are not protected from any chemical influences.

21Consequently, the chemical action can generate particles through the delamination of the working layer 4.

22This step also takes place when only a dielectric layer 3 or a cover layer 2 is formed, for example a dielectric layer 3. The plastic deformation of the working layer 4 is typically performed so as to cover or seal the dielectric layer 3 in the step.

23However, the Applicant has found that, in the presence of a cover layer 2 and at least one dielectric layer 3, the fracture stage at the edge of the substrate is atypical. Thus, Figure 3 shows the steps obtained on such a substrate after the fracture stage e).

24If there are several intermediate layers, the fault stage does not lead to a single stage, but, on the contrary, to several stages. In fact, it turns out that the fault propagates along the periphery of the substrate, not along the weakened zone, but at the interface between the dielectric layer 3 and the cover layer 2.

25The main disadvantage of this manufacturing method is that it leads to an atypical fault at the edge of the substrate.

26This is the case, in particular, when the composite structure, in the direction from its rear surface to its front surface, includes a silicon substrate, a silicon dioxide layer, a silicon nitride layer, a silicon dioxide layer and a silicon layer.

27In addition, the presence of several steps makes it impossible to plastic deform the working layer 4 by heat treating the working layer 4 to protect the cover layer 2 and the dielectric layer 3 in the step.

28This is due to the fact that during the thermal treatment, the working layer 4 is dried, rather than plastic deformation.

29One of the objectives of the present invention is thus to provide a method for manufacturing a composite substrate that makes it possible to perform the step of plastic deformation of the working layer 4 so as to cover the exposed surface of the cover layer 2 and the dielectric layer 3 in a step.

SUMMARY OF THE INVENTION

31The present invention is directed to eliminating the above disadvantages and relates to a method for manufacturing a composite structure comprising, in the direction from its rear surface to its front surface, a carrier substrate, a cover layer, at least one dielectric layer and a working layer comprising the following steps:

32a) obtaining a donor substrate and a carrier substrate;

33b) forming at least a dielectric layer including:

34- the first surface contacting the donor substrate,

35a second surface opposite the first surface,

36- a peripheral surface connecting the first and second surfaces together;

37the dielectric layer has a contour;

38c) forming a cover layer arranged so as to cover the second surface of the dielectric layer;

39d) formation of a weakened zone in the donor substrate bounding the working layer contacting the first surface of the dielectric layer;

40e) assembling the carrier substrate and the donor substrate, such that the carrier substrate and the cover layer are contacted along a contact surface having a contour;

41f) the donor substrate gap over the weakened zone; notably, characterized in that steps b) and e) are performed

42in such a way that the dielectric layer contour fits into the contour of the contact surface, and step c) is performed so that the coating layer covers the peripheral surface of the dielectric layer.

43Thus, after the transfer step e), the stack of layers is transferred to a carrier substrate.

44A stack of portable layers includes a central portion and a peripheral portion.

45The central part of the stack includes a working layer, a dielectric layer and a cover layer.

46The peripheral part includes only the working layer and the cover layer.

47In this case, a simple step is achieved. The peripheral part corresponds to the transferred stack, which includes one intermediate layer.

48Thus, the fault stage leads to a single step on the peripheral ring.

49As a result, the resulting composite structure allows plastic deformation of the working layer by performing heat treatment, for example, so as to seal the coating layer, in particular, in one step.

50According to one embodiment of the invention, the carrier substrate includes:

51- the upper surface on which the cover layer, the dielectric layer and the working layer are transferred;

52- the lower surface opposite the upper surface;

53- a peripheral zone connecting the lower surface and the upper surface;

54the contour of the contact surface and the peripheral region of the support substrate define a substantially annular surface of width L, and steps b) and e) are performed such that the dielectric layer contour and the peripheral region of the carrier substrate define a substantially annular surface with a width of 105% to 150%, preferably from 110% to 140%, even more preferably from 115% to 130%, of the width L.

55According to one embodiment of the invention, the dielectric layer is formed in 2 steps b1) and b2):

56b1) deposition of a layer of a dielectric material onto a donor substrate;

57b2) the partial removal of the layer of the dielectric material in such a way that the residual layer of the dielectric material forms a dielectric layer.

58According to one embodiment of the invention, the dielectric layer comprises silicon nitride to a thickness in the range of 10 to 80 nm.

59According to one embodiment of the invention, the coating layer comprises silica to a thickness greater than 80 nm.

60According to one embodiment of the invention, the donor substrate includes at least one of the following materials: silicon, germanium, silicon and germanium alloy.

61According to one embodiment of the invention, after step e), a heat treatment step is carried out to seal the cover layer and the dielectric layer with the working layer.

62According to one embodiment of the invention, the donor substrate includes an additional layer in contact with the dielectric layer and having the same chemical composition as the cover layer.

63According to one embodiment of the invention, the donor substrate includes silicon, the further layer comprises silicon dioxide, the dielectric layer includes silicon nitride and the coating layer comprises silicon dioxide.

64The invention also relates to a composite structure comprising, from the rear surface to its front surface, a carrier substrate, a cover layer, at least one dielectric layer, and a working layer, wherein the dielectric layer has:

65- the first surface contacting the working layer;

66a second surface contacting the cover layer;

67a peripheral surface connecting the first surface and the second surface, said composite structure being remarkable in that the cover layer covers the entire peripheral surface of the dielectric layer such that the working layer and the cover layer seal the dielectric layer.

68A portable stack of layers includes a central portion and a peripheral portion.

69The central part of the stack includes a working layer, a dielectric layer and a cover layer.

70The peripheral part includes only the working layer and the cover layer.

71Thus, there is a simple step, and the peripheral part corresponds to a stack including one intermediate layer.

72Therefore, the resulting composite structure allows plastic deformation of the working layer by performing heat treatment, for example, so as to seal the coating layer in one step.

73According to one embodiment of the invention, the working layer includes at least one of the following materials: silicon, germanium, silicon and germanium alloy.

74According to one embodiment of the invention, the working layer includes a single crystal material.

75According to one embodiment of the invention, the coating layer comprises silicon dioxide.

76According to one embodiment of the invention, the dielectric layer includes silicon nitride.

77According to one embodiment of the invention, the cover layer has:

78- a first surface contacting the carrier substrate,

79a second surface contacting the dielectric layer,

80- a peripheral surface connecting the first and second surfaces of the cover layer,

81The working layer covering the peripheral surface of the coating layer.

82According to one embodiment of the invention, the additional layer is disposed between the working layer and the dielectric layer, the additional layer having the same chemical composition as the cover layer.

83According to one embodiment of the invention, the working layer includes monocrystalline silicon, the additional layer includes thermal silica, the dielectric layer includes silicon nitride and the cover layer comprises silicon dioxide.

BRIEF DESCRIPTION OF THE DRAWINGS

85Other features and advantages will become apparent from the following description of embodiments of the manufacturing method of the invention, which are given by way of non-limiting examples with reference to the accompanying drawings, in which:

86FIG. 1 is a schematic view of a manufacturing method according to a prior art method;

87- FIG. 2 is a front surface view of a composite structure obtained by a manufacturing method according to a known method from the prior art;

88FIG. 3 is a cross-sectional view of a substrate used in a manufacturing method according to a known method of the prior art; FIG.

89- Figures 4a and 4b are schematic representations of a first embodiment of the invention;

90FIG. 5 is a cross-sectional view of a composite structure obtained according to the manufacturing method of the present invention and subjected to a sealing treatment; FIG.

91- Figures 6a and 6b are schematic representations of a second embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

93In order to simplify the description, for the various embodiments of the invention, the same references will be used for the same elements or elements performing the same functions.

94The method shown in Figures 4a and 4b is a method of manufacturing a composite structure comprising, from the rear surface to its front surface, a carrier substrate 10, a cover layer 20, at least one dielectric layer 30 and a working layer 40 comprising the following stages:

95a) providing a donor substrate 50 and a carrier substrate 10;

96b) forming at least a dielectric layer 30 including:

97- the first surface contacting the donor substrate,

98a second surface opposite the first surface,

99- a peripheral surface connecting the first and second surfaces together;

100the dielectric layer 30 has a Cz contour;

101c) forming a cover layer 20 disposed to cover the second surface of the dielectric layer 30;

102d) forming a weakened zone 60 in the donor substrate 50 bounding the working layer 40 in contact with the first surface of the dielectric layer 30;

103e) assembling the carrier substrate 10 and the donor substrate 50, such that the carrier substrate 10 and the cover layer 20 are contacted along the contact surface 70 having the contour Cs;

104e) the donor substrate 50 fracture along the attenuated zone 60.

105Steps b) and e) are performed in such a way that the contour Cz of the dielectric layer 30 fits into the contour Cs of the contact surface 70, and step c) is performed such that the cover layer 20 covers the peripheral surface of the dielectric layer 30.

106Before carrying out the manufacturing method according to the invention, the step of determining the contour Cs of the contact surface can be performed.

107This step of determining the contour Cs is particularly effective when it comes to implementing a method for manufacturing a plurality of composite structures.

108This is due to the fact that, in the context of fabricating a plurality of composite structures, the plurality of donor substrates 50 and the plurality of carrier substrates 10 are selected such that the contact surface contour Cs substantially remains equivalent (or even identical) from a single composite structure to another.

109Subsequently, donor substrates 50 in a plurality of donor substrates 50 are selected so that their geometric characteristics are substantially equivalent or even equal.

110Then, the carrier substrates 10 in the plurality of carrier substrates 10 are selected so that their geometric characteristics are substantially equivalent or even equal.

111Geometrical characteristics of the substrate mean, but are not limited to, its thickness at any point of the surface, the deviation of its thickness and its shape.

112Thus, it is sufficient to define the contour Cs for the fabrication of the structure and apply the result to the production of a plurality of composite structures.

113The definition of the contour Cs can include the following steps:

114- assembly of the carrier substrate 10 and the donor substrate 50;

115- use of a scanning acoustic microscope to obtain an image of the contour Cs of the contact surface 70.

116Another solution may be, when implementing the method for manufacturing a composite structure, in excluding the formation of the dielectric layer 30 and measuring the width of the peripheral ring at all points on the edge of the carrier substrate.

117The appearance of the peripheral ring on the composite structure is limited by the edge of the carrier substrate and the contour Cs of the contact surface 70. Then, the definition of the contour Cs is carried out directly.

118For example, the Applicant has found that the manufacture of a composite structure comprising the cover layer 20 results in the formation of a 0.8 mm wide peripheral ring.

119A carrier substrate (10) is particularly preferred, which includes:

120an upper surface on which the cover layer (20) is transferred, a dielectric layer (30) and a working layer (40);

121- the lower surface opposite the upper surface;

122- a peripheral zone connecting the lower surface and the upper surface;

123a contour (Cs) of the contact surface (70) and a peripheral region of the carrier substrate (10) defining a substantially annular surface of width L, and steps b) and e) are made so that the dielectric layer (Cz) loop (Cz) and the peripheral layer the region of the carrier substrate (10) defines a substantially annular surface with a width that is 105% to 150%, preferably 110% to 140%, even more preferably 115% to 130%, of the width L.

124Thus, in the context of the method for manufacturing a plurality of composite structures, a plurality of donor substrates 50 and a plurality of carrier substrates 10 may have a certain variation in their geometric characteristics.

125The donor substrate 10 that is supplied in step a) may include one of materials selected from: silicon, silicon and germanium alloy, germanium.

126The carrier substrate 30 that is supplied in step a) can consist of all materials that are commonly used in microelectronics, optical, optoelectronic and photovoltaic industries.

127In particular, the carrier substrate 10 includes at least one of materials selected from the following group: silicon, silicon carbide, silicon-germanium, glass, ceramic or metal alloy.

128At least one dielectric layer 30 is formed on a donor substrate.

129The cover layer 20 is formed so that it covers the dielectric layer 30.

130The formation of the cover layer 20 and the dielectric layer 30 will be described in detail below when describing various embodiments of the invention.

131Next, step d) forming a weakened zone 60 in the donor substrate 50 is performed.

132The weakened zone 60 limits the working layer 40 in the donor substrate 50, the working layer in contact with the dielectric layer 30.

133The working layer 40 is intended to be transferred to the carrier substrate 10.

134A weakened zone 60 can be created by implanting atomic particles in a donor substrate 50.

135By atomic particles are meant atomic, molecular or ionic particles.

136The introduced particles can include at least one of the following particles: hydrogen, helium.

137Hydrogen can be introduced with energy in the range of 10 to 210 keV at a dose in the range of 7 × 10¹⁵ up to 1 × 10^17th at / cm².

138The assembly step e) may be a molecular binding step.

139The fracture stage e), preferably, can be thermal annealing, which is performed at a temperature in the range of 300 ° to 600 ° C.

140At the last step e), a composite structure is obtained.

141The composite structure includes, from its front surface to its rear surface, a working layer 40, a dielectric layer 30, a cover layer 20 and a carrier substrate 10.

142First Embodiment of the Invention

143A first embodiment of the invention is shown in Figures 4a and 4b.

144Formation of the dielectric layer 30

145The dielectric layer 30 can be formed in two steps:

146b1) forming a layer of the dielectric material of the donor substrate 10;

147b2) the partial removal of the layer of the dielectric material, such that the residual layer of the dielectric material forms a dielectric layer 20.

148Step b1) can be a vapor deposition operation, a low-pressure vapor deposition or plasma-induced vapor deposition onto a donor substrate 50. It can also be a high-temperature treatment in a selected atmosphere (nitriding, oxidation, and the like).

149The thickness of the layer of the dielectric material can be in the range of 10 nm to 80 nm, for example 50 nm.

150After step b1), step b2) is carried out, which includes partial removal of the layer of dielectric material. The partial removal is performed such that the remaining or residual portion of the dielectric material layer is included in the dielectric layer 30.

151In other words, the partial removal of the dielectric material layer is performed on the peripheral surface of the donor substrate 50 bounded by the edge of the donor substrate 50 and the contour Cz.

152Thus, the residual portion of the dielectric layer material forms a dielectric layer 30.

153The peripheral surface of the donor substrate 50 may have the form of an annular surface.

154Step b2), preferably, can be carried out with a chemical pickling solution.

155It is particularly advantageous that a plurality of dielectric layers 30 can be successfully formed.

156For example, one dielectric layer 30 comprising silicon nitride and another dielectric layer 30 comprising silicon dioxide.

157In the case of a dielectric layer 30 comprising silicon nitride (Si₃N₄), the chemical pickling solution can be a solution of phosphoric acid (H₃PO₄), heated to a temperature above 50 ° C.

158The chemical pickling solution can be distributed by the nozzle onto the edge of the donor substrate 50 during rotation so that the dielectric layer 30 is etched only on the peripheral surface of the donor substrate 50 bounded by the edge of the donor substrate 10 and the contour Cz.

159Formation of a cover layer 20

160The cover layer 20 can be formed by vapor deposition, low-pressure vapor deposition or plasma-induced vapor deposition.

161The cover layer covers the second surface and the peripheral surface of the dielectric layer 30 completely.

162The cover layer 20 may include a material different from the materials of the dielectric layer 30, selected from the following materials: silicon oxide, silicon nitride or oxynitride, aluminum nitride, aluminum oxide, polycrystalline silicon, and amorphous silicon.

163It is particularly preferred that the cover layer 20 comprises silicon oxide and its thickness is greater than 80 nm, for example 100 nm.

164At the end of step e), a composite structure is obtained.

165The composite structure includes, in the direction from its rear surface to its front surface, a carrier substrate 10, a cover layer 20, at least one dielectric layer 30 and a working layer 40, wherein the dielectric layer 30 has:

166a first surface contacting the working layer 40;

167a second surface contacting the cover layer 20;

168a peripheral surface connecting the first surface and the second surface,

169the cover layer 20 covers the completely peripheral surface of the dielectric layer 30, so that the working layer 40 and the cover layer 30 seal the dielectric layer 30.

170Thus, after the transfer step, the dielectric layer 30 of the contour Cz is placed vertically on the line with the central surface 80 of the contour Cp of the carrier of the substrate 10.

171Thus, the surface bounded by the contour Cs of the contact surface 70 and the contour Cp of the central surface 80 is positioned opposite the stack of layers comprising only the working layer 40 and the cover layer 20.

172In addition, the central surface 80 of the carrier substrate 10 faces a stack of layers including the working layer 40, the dielectric layer 30 and the cover layer 20.

173Thus, there is a single stage at the edge of the substrate.

174Consequently, the execution of a single step allows the cover layer 20 and the dielectric layer 30 to be sealed by the working layer 40. The sealing is performed by heat treatment, without any drying of the working layer 40, as shown in FIG.

175In this connection, any person skilled in the art will find a technical description of the sealing of the insulator layer by means of the working layer 40 in the published application FR 2852143 A1 (E.NEYRET) dated September 10, 2004 (September 10, 2004) on page 10, lines 3-28 .

176In a particular configuration of this first embodiment of the invention, the cover layer 20 is made of polycrystalline silicon or amorphous silicon, and its thickness is in the range of several nm to several thousand nm, for example 2000 nm. The dielectric layer 30 is made of silicon oxide, and the working layer 40 is made of silicon. Thus, composite silicon is formed on an insulating structure having a hidden layer of polycrystalline silicon or amorphous silicon under the insulating layer. This type of composite structure is particularly suitable for the manufacture of semiconductor devices that find application in the radio frequency domain.

177Second Embodiment of the Invention

178The second embodiment of the invention shown in Figures 6a and 6b differs from the first embodiment of the invention in that the donor substrate 50 comprises an additional layer 90, the additional layer 90 being contacted with the dielectric layer 30 and the further layer 90 has the same layer chemical composition, as well as a cover layer 20.

179For example, an additional layer 90 and a cover layer 20 include silicon oxide.

180The additional layer 90 is formed directly on the donor substrate 50 before the dielectric layer 30.

181The additional layer 90 may include a material different from the materials of the dielectric layer 30 selected from the following materials: silicon oxide, silicon nitride or oxynitride, aluminum nitride, aluminum oxide, polycrystalline silicon, and amorphous silicon.

182Preferably, the additional layer 90 is made of silicon oxide and its thickness is in the range of 2 to 20 nm, for example, 7 nm.

183When the donor substrate 50 is made of silicon, an additional silicon oxide layer 90 can be obtained by thermal oxidation of this donor substrate and thus an additional layer 90 is formed from thermal silica.

184At the end of step e), a composite structure is obtained.

185The composite structure includes, from its front surface to its rear surface, a working layer 40, an additional layer 90, a dielectric layer 30, a cover layer 20 and a carrier substrate 10.

186Thus, after the transfer step, the dielectric layer 30 of the contour Cz is arranged along a vertical line with the central surface 80 of the contour Cp of the carrier substrate 10.

187As a consequence, the surface bounded by the contour Cs of the contact surface 70 and the contour Cp of the central surface 80 is located opposite the stack of layers comprising only the working layer 40, the additional layer 90, and the cover layer 20.

188In addition, the central surface 80 of the carrier substrate 10 is positioned opposite the stack of layers including the working layer 40, the dielectric layer 30, and the cover layer 20.

189Then, the stack of the cover layer 20 and the additional layer 90, which have the same chemical composition, are spliced ​​with one layer of dielectric material.

190Thus, a single step is carried out at the edge of the substrate.

191Consequently, the execution of a single step allows the cover layer 20, the dielectric layer 30 and the additional layer 90 to be sealed by the working layer 40. The sealing is performed by heat treatment without any drying of the working layer 40.

192The additional layer 90 preferably includes silicon dioxide. Thus, a composite structure is formed, generally referred to as SOI ONO (silicon on silicon dioxide, on silicon nitride and on silicon dioxide).

193Accordingly, the invention is preferably intended for the manufacture of composite SOI ONO substrates or for the production of SOI (SOI) substrates for use in radio frequency domains.